Solid-state imaging device, electronic device, and method for manufacturing solid-state imaging device

Abstract

In a configuration including a package structure, the present invention prevents damage caused by, for example, cracking of component elements and peeling between elements due to an increase in the internal pressure of a cavity during reflow. The package structure has a cavity (5) between a solid-state imaging element (2) and a lid element (3). The solid-state imaging device (1) includes: a solid-state imaging element including a semiconductor substrate (6) and having one plate surface side of the semiconductor substrate as a light-receiving side (2a); a light-transmitting lid element provided at a predetermined distance from the solid-state imaging element on the light-receiving side of the solid-state imaging element; and a support portion (4) provided on the light-receiving side of the solid-state imaging element, supporting the lid element with respect to the solid-state imaging element, and forming a cavity between the solid-state imaging element and the lid element. The semiconductor substrate has a recess (20) formed on the other plate surface side (2b) thereof and partially reduces the thickness of the semiconductor substrate.

Description

Technical Field

[0001] The present technology relates to a solid-state imaging device, an electronic device, and a method for manufacturing a solid-state imaging device. Specifically, the present technology relates to a solid-state imaging device and a method for manufacturing a solid-state imaging device, the solid-state imaging device including a solid-state imaging element including a semiconductor substrate, a light-transmitting cover element made of, for example, glass, and a support member made of, for example, resin, the solid-state imaging device having a package structure in which a plurality of light-receiving elements are formed on the solid-state imaging element on one plate surface side of the semiconductor substrate, the cover element is provided on the solid-state imaging element through the support member, and a cavity is included between the solid-state imaging element and the cover element. Background Art

[0002] An image sensor that converts light from an object into an electrical signal to record an image is incorporated as a solid-state imaging element in the main body of digital cameras and video cameras that have been rapidly developed in recent years. Examples of image sensors include complementary metal oxide semiconductor (CMOS) type and charge-coupled device (CCD) type image sensors. An image sensor is a chip in which a plurality of light-receiving elements are formed on one plate surface side of a semiconductor substrate.

[0003] Generally, a solid-state imaging device including an image sensor has a package structure in which a light-transmitting cover element made of, for example, glass is mounted on the image sensor through a support member made of, for example, resin, and a cavity is included between the image sensor and the cover element. In this configuration, the cover element is supported on the image sensor through the support member provided on the light-receiving surface side of the image sensor such that the cover element faces the light-receiving surface, and a portion surrounding the space between the image sensor and the cover element is sealed with the support member to form a cavity between the image sensor and the cover element (for example, refer to Patent Document 1). In a solid-state imaging device having such a configuration, light transmitted through the cover element passes through the cavity and is detected by being received by light-receiving elements forming each pixel provided on the light-receiving surface of the image sensor.

[0004] In recent years, image sensors have often been adopted in small devices such as smartphones, and it has been required to make the package structure of the image sensor smaller in size and shorter in height. Therefore, a structure called wafer-level chip scale (or size) package (WCSP) has been widely used as a configuration of an image sensor. WCSP greatly contributes to reducing the size because WCSP is not a structure obtained by performing dicing to obtain separated chips and then performing packaging, but a structure obtained by creating a package in a wafer state and finally performing dicing to obtain chips having the original size.

[0005] The solid-state imaging device having the above-described package structure is subjected to reflow to melt solder used for bonding, for example, when the solid-state imaging device is mounted on a substrate. During reflow, the solid-state imaging device is exposed to an environment at a temperature of, for example, about 250°C. Therefore, the gas (water vapor) containing moisture in the cavity is heated, and the internal pressure (vapor pressure) in the cavity increases. Here, when the support member that supports the cover element on the image sensor is made of resin, there is moisture in the cavity that passes through the support member.

[0006] The increase in the internal pressure in the cavity may cause damage, for example, cracking of structural elements of the solid-state imaging device, such as a semiconductor substrate, a cover element, or a support member that supports the cover element, included in the image sensor; and detachment of bonded structural elements. When such damage occurs, moisture, dust, etc. enter the cavity from the damaged part, which results in a decrease in the performance of the device. The techniques described below can be used as countermeasures to solve such problems.

[0007] First, there is a technique that includes an element that deforms according to the internal pressure in the cavity as an element forming the cavity, and due to the deformation of the included element, the internal pressure in the cavity is prevented from increasing excessively (for example, refer to Patent Document 2). Patent Document 2 discloses a configuration in which a cap portion is included as an element that deforms according to the internal pressure in the cavity, and the cap portion forms a cavity with an insulating substrate or the like. The cap portion is a plate-like element made of metal (for example, copper), and has a thin bending portion that deforms according to the internal pressure in the cavity.

[0008] In addition, there is a technique for preventing an increase in the internal pressure of the cavity by providing an air passage in an element forming the cavity, the air passage leading from the inside of the cavity to the outside (for example, refer to Patent Document 3). Patent Document 3 discloses a configuration in which an optical element is placed in a recess of a package, the recess is covered with a transparent element to form a hollow structure, and an air passage that communicates the inside of the recess with the outside of the package is formed in the package.

[0009] In addition, there is a technique for reducing moisture in the cavity and preventing an increase in the internal pressure in the cavity by providing a moisture-absorbing element or a moisture-proof element that captures moisture inside or outside the cavity (for example, refer to Patent Document 4). Patent Document 4 discloses a configuration in which a moisture absorbent obtained by mixing a granular moisture-absorbing substance and a paste resin as a viscous substance is applied to, for example, the inside of an element forming the cavity.

[0010] Citation List

[0011] Patent Document

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-296453

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 9-129767

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 2011-77170

[0015] Patent Document 4: Japanese Patent Application Laid-Open No. 7-321251. Summary of the Invention

[0016] Technical Problem

[0017] The above technologies have the following problems. First, the technology in which components are deformed according to the internal pressure in the cavity is provided separately, and the technology of providing a moisture-absorbing element or the like inside or outside the cavity causes a problem that the package structure has a large external size. Such a problem is particularly obvious in the WCSP for achieving the above-mentioned size reduction. In addition, when an independent element (e.g., a moisture-absorbing element) is provided inside the cavity, a failure may occur in the device, or the device may exhibit poor characteristics due to the detachment of the independent component. In addition, the technology of providing an air passage leading from the inside of the cavity to the outside may cause an influence on the image due to dust or the like entering the cavity from the air passage.

[0018] In addition, all technologies result in a complex manufacturing method and an increased production cost. Therefore, the price of the final product including the solid-state imaging device having the above package structure may increase. As described above, a new solution is needed to solve the problems caused by, for example, an increase in the internal pressure force in the cavity during reflow.

[0019] An object of the present technology is to provide a solid-state imaging device, an electronic device, and a method for manufacturing a solid-state imaging device having a package structure including a cavity between a solid-state imaging element and a cover element, the package structure enabling prevention of damage caused by an increase in the internal pressure in the cavity during, for example, reflow, such as cracking of the structural elements of the solid-state imaging device and detachment of the bonded structural elements.

[0020] Solution to the Problem

[0021] The solid-state imaging device according to the present technology includes: a solid-state imaging element including a semiconductor substrate, and a light-receiving side thereof being one plate surface side of the semiconductor substrate; a light-transmitting cover element provided on the light-receiving side of the solid-state imaging element and spaced apart from the solid-state imaging element at a specific interval; and a support member provided on the light-receiving side of the solid-state imaging element and supporting the cover element on the solid-state imaging element to form a cavity between the solid-state imaging element and the cover element, the semiconductor substrate including a recess formed on the other plate surface of the semiconductor substrate, and the semiconductor substrate having a thickness partially reduced due to the formation of the recess.

[0022] In addition, in another aspect of the solid-state imaging device according to the present technology, the solid-state imaging device further includes a filling resin portion, which is made of a thermoplastic resin and is configured to be filled into the recess, and the filling resin portion deforms as the semiconductor substrate deforms.

[0023] In addition, in another aspect of the solid-state imaging device according to the present technology, the solid-state imaging device further includes a solder portion, which is provided on the surface side of the filling resin portion and is used for mounting the solid-state imaging element.

[0024] In addition, in another aspect of the solid-state imaging device according to the present technology, the thermoplastic resin is a paste composition containing one of a polyetherimide resin, a polyetheramide resin, and a polyetheramide-imide resin as a main component.

[0025] In addition, in another aspect of the solid-state imaging device according to the present technology, in the solid-state imaging device, the thermoplastic resin is a paste composition obtained by adding a plastic segment to one of a polyimide resin, a polyamide resin, and a polyamide-imide resin.

[0026] In addition, in another aspect of the solid-state imaging device according to the present technology, in the solid-state imaging device, the thermoplastic resin is a paste composition containing one of a polyimide resin, a polyamide resin, and a polyamide-imide resin as a main component, and further contains thermoplastic resin particles.

[0027] In addition, in another aspect of the solid-state imaging device according to the present technology, in the solid-state imaging device, the recess includes a bottom surface portion substantially parallel to the plate surface of the semiconductor substrate and a side surface portion forming the inner surface of the recess; and the side surface portion includes a first inclined surface and a second inclined surface, the first inclined surface is inclined in a specific direction with respect to the plate surface of the semiconductor substrate, and the second inclined surface forms a curved shape with the first inclined surface in the cross-sectional view of the semiconductor substrate.

[0028] In addition, in another aspect of the solid-state imaging device according to the present technology, in the solid-state imaging device, the recess includes a bottom surface portion substantially parallel to the plate surface of the semiconductor substrate and a side surface portion forming the inner surface of the recess; and the side surface portion includes the (111) plane or an equivalent crystal plane of the semiconductor substrate.

[0029] In addition, in another aspect of the solid-state imaging device according to the present technology, the solid-state imaging device further includes a solder portion, which is provided on the other plate surface of the semiconductor substrate and is used for mounting the solid-state imaging element; and the internal pressure in the cavity at a specific peak temperature during reflow for melting the solder portion is less than the internal pressure that causes cracking of the element forming the cavity or detachment of the bonding element forming the cavity.

[0030] An electronic device according to the present technology includes: a solid-state imaging device including a solid-state imaging element, the solid-state imaging element including a semiconductor substrate, and a light-receiving side of the solid-state imaging element being one plate surface side of the semiconductor substrate; a light-transmitting cover element disposed on the light-receiving side of the solid-state imaging element and spaced apart from the solid-state imaging element at a specific interval; and a support member disposed on the light-receiving side of the solid-state imaging element and supporting the cover element on the solid-state imaging element to form a cavity between the solid-state imaging element and the cover element, the semiconductor substrate including a recess formed on the other plate surface of the semiconductor substrate, and the semiconductor substrate having a thickness partially reduced due to the formation of the recess.

[0031] A method for manufacturing a solid-state imaging device according to the present technology includes: providing a light-transmitting plate material on one plate surface side of a semiconductor wafer through a wall and spaced apart from the semiconductor wafer at a specific interval, the semiconductor wafer being a semiconductor wafer on which a group of pixels is formed on one plate surface side, the semiconductor wafer being a semiconductor wafer in which a plurality of portions each being a solid-state imaging element are formed in a specific arrangement, the wall being formed along the specific arrangement to surround the pixel group; forming a recess on the other plate surface of the semiconductor wafer corresponding to the solid-state imaging element, the semiconductor wafer having a thickness partially reduced due to the formation of the recess; and cutting a group of the semiconductor wafers, the wall, and the plate material into pieces such that the group of the semiconductor wafers, the wall, and the plate material are divided along the specific arrangement into portions corresponding to respective solid-state imaging elements.

[0032] In addition, in another aspect of the method for manufacturing a solid-state imaging device according to the present technology, in the method for manufacturing a solid-state imaging device, forming the recess includes: performing a first etching including forming a semi-recess by removing a portion corresponding to the recess from the semiconductor wafer using dry etching; and performing a second etching including etching the semi-recess downward using anisotropic etching after the first etching to form the recess.

[0033] In addition, in another aspect of the method for manufacturing a solid-state imaging device according to the present technology, the method for manufacturing a solid-state imaging device further includes forming a filled resin portion in the recess by filling the recess with a thermoplastic resin before cutting the group of the semiconductor wafers, the wall, and the plate material into pieces, the filled resin portion being deformed as the semiconductor substrate forming the solid-state imaging element.

[0034] In addition, in another aspect of the method for manufacturing a solid-state imaging device according to the present technology, the method for manufacturing a solid-state imaging device further includes placing a solder portion on a surface side of the filled resin portion before cutting the group of the semiconductor wafers, the wall, and the plate material into pieces, the solder portion being for mounting the solid-state imaging element.

[0035] Advantageous effects of the invention

[0036] The present technology provides a configuration with a packaging structure, the packaging structure including a cavity between a solid-state imaging element and a cover element, the packaging structure enabling prevention of damage caused by an increase in internal pressure in the cavity during, for example, reflow, such as cracking of structural elements and detachment of bonded structural elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a cross-sectional view showing the configuration of a solid-state imaging device according to a first embodiment of the present technology;

[0038] Figure 2 shows the back side of a semiconductor substrate according to a first embodiment of the present technology;

[0039] Figure 3 is a view for describing a method of manufacturing a solid-state imaging device according to a first embodiment of the present technology;

[0040] Figure 4 is a view for describing a method of manufacturing a solid-state imaging device according to a first embodiment of the present technology;

[0041] Figure 5 is a view for describing a method of manufacturing a solid-state imaging device according to a first embodiment of the present technology;

[0042] Figure 6 is a view for describing a method of manufacturing a solid-state imaging device according to a first embodiment of the present technology;

[0043] Figure 7 is a view for describing a method of manufacturing a solid-state imaging device according to a first embodiment of the present technology;

[0044] Figure 8 shows a recess included in a solid-state imaging device according to a first embodiment of the present technology;

[0045] Figure 9 shows the configuration of a solid-state imaging device of a comparative example compared with the present technology;

[0046] Figure 10 is a view for describing the operation in a solid-state imaging device according to a first embodiment of the present technology;

[0047] Figure 11 is a set of cross-sectional views, each cross-sectional view showing a modified configuration of a solid-state imaging device according to a first embodiment of the present technology;

[0048] Figure 12 is a cross-sectional view showing the configuration of a solid-state imaging device according to a second embodiment of the present technology;

[0049] Figure 13Shows the back side of a semiconductor substrate according to a second embodiment of the present technology;

[0050] Figure 14 Is a diagram for describing a method of manufacturing a solid-state imaging device according to a second embodiment of the present technology;

[0051] Figure 15 Is a diagram for describing a method of manufacturing a solid-state imaging device according to a second embodiment of the present technology;

[0052] Figure 16 Is a diagram for describing operations in a solid-state imaging device according to a second embodiment of the present technology;

[0053] Figure 17 Is a diagram for describing a modification of a method of manufacturing a solid-state imaging device according to a second embodiment of the present technology;

[0054] Figure 18 Is a diagram for describing a modification of a method of manufacturing a solid-state imaging device according to a second embodiment of the present technology;

[0055] Figure 19 Is a diagram for describing a modification of a method of manufacturing a solid-state imaging device according to a second embodiment of the present technology;

[0056] Figure 20 Is a cross-sectional view showing the configuration of a solid-state imaging device according to a third embodiment of the present technology;

[0057] Figure 21 Shows the back side of a semiconductor substrate according to a third embodiment of the present technology;

[0058] Figure 22 Is a diagram for describing a method of manufacturing a solid-state imaging device according to a third embodiment of the present technology;

[0059] Figure 23 Is a diagram for describing a method of manufacturing a solid-state imaging device according to a third embodiment of the present technology;

[0060] Figure 24 Is a diagram for describing operations in a solid-state imaging device according to a third embodiment of the present technology;

[0061] Figure 25 Is a block diagram showing a configuration example of an electronic device including a solid-state imaging device according to an embodiment of the present technology. Detailed Description

[0062] In a configuration where a cover element is provided on a solid-state imaging element via a support member and a cavity is provided between the solid-state imaging element and the cover element, the present technology prevents damage caused by an increase in pressure in the cavity by designing, for example, the shape of a semiconductor substrate included in the solid-state imaging element.

[0063] Embodiments for implementing the present technology (hereinafter referred to as "embodiments") will be described with reference to the accompanying drawings. Note that the embodiments will be described in the following order.

[0064] 1. Configuration example of a solid-state imaging device according to the first embodiment

[0065] 2. Method for manufacturing a solid-state imaging device according to the first embodiment

[0066] 3. Modification of the solid-state imaging device according to the first embodiment

[0067] 4. Configuration example of a solid-state imaging device according to the second embodiment

[0068] 5. Manufacturing method of a solid-state imaging device according to the second embodiment

[0069] 6. Modification of the method for manufacturing a solid-state imaging device according to the second embodiment

[0070] 7. Configuration example of a solid-state imaging device according to the third embodiment

[0071] 8. Method for manufacturing a solid-state imaging device according to the third embodiment

[0072] 9. Configuration example of an electronic device

[0073] <Configuration example of a solid-state imaging device according to the first embodiment>

[0074] Reference Figure 1 and Figure 2 The configuration of a solid-state imaging device 1 according to the first embodiment of the present technology will be described. As Figure 1 shown, the solid-state imaging device 1 includes an image sensor 2 as a solid-state imaging element, a glass 3 as a light-transmitting cover element, and a partition wall 4 as a support member that supports the glass 3 on the image sensor 2.

[0075] The solid-state imaging device 1 has a package structure in which the glass 3 is mounted on the image sensor 2 through the partition wall 4, and the cavity 5 is included between the image sensor 2 and the glass 3. In the solid-state imaging device 1, the glass 3 is supported on the image sensor 2 by the partition wall 4 provided on the front surface 2a, which is the light-receiving side surface of the image sensor 2, such that the glass 3 faces the front surface 2a. The portion surrounding the space between the image sensor 2 and the glass 3 is sealed with the partition wall 4 to form the cavity 5 between the image sensor 2 and the glass 3. The solid-state imaging device 1 according to the present embodiment is a solid-state imaging device that applies the so-called WCSP structure as the package structure.

[0076] The image sensor 2 includes a silicon-based semiconductor substrate 6, which is made of silicon (Si) and is an example of a semiconductor, and the light-receiving side of the image sensor 2 is the front surface 2a side ( Figure 1 the upper side in ) corresponding to one plate surface of the semiconductor substrate 6. The image sensor 2 is a rectangular plate-shaped chip and includes a plurality of light-receiving elements formed on the front surface 2a, and the glass 3 is placed on the image sensor 2 through the partition wall 4 provided on the light-receiving side of the semiconductor substrate 6. The image sensor 2 according to the present embodiment is a CMOS image sensor. However, the image sensor 2 may be a CCD image sensor.

[0077] Most of the image sensor 2 is formed by the semiconductor substrate 6. Image sensor elements are formed on the front surface of the semiconductor substrate 6. In other words, the image sensor 2 includes a pixel region 8 on the front surface 2a as a light-receiving portion, and the pixel region 8 is a light-receiving region including, for example, a plurality of pixels 7 formed in a specific arrangement (e.g., Bayer arrangement). The image sensor 2 includes, on the front surface 2a, a region surrounding the pixel region 8, which is a peripheral region. The pixel region 8 includes an effective pixel region for generating, amplifying, and reading signal charges through photoelectric conversion performed in each pixel 7.

[0078] The pixel 7 includes a photodiode and a plurality of pixel transistors. The photodiode is a photoelectric converter including a photoelectric conversion function. The photodiode includes a light-receiving surface that receives light entering from the front surface 2a of the image sensor 2 and generates a certain amount of signal charges according to the amount (intensity) of the light entering the light-receiving surface. Each of the plurality of pixel transistors includes a MOS transistor, and each MOS transistor is used to amplify, transfer, select, or reset the signal charges generated by the photodiode. Note that the plurality of pixels 7 may have a pixel-sharing structure in which the photodiodes and transfer transistors forming the plurality of pixels in units share other individual pixel transistors.

[0079] On the front 2a side of the image sensor 2, a color filter and an on-chip lens are formed corresponding to each pixel 7 on the semiconductor substrate 6 through an antireflection film formed of, for example, an oxide film or a planarization film made of an organic material. The light entering the on-chip lens is received by a photodiode through the color filter and the planarization film or the like.

[0080] The following are representative examples of the structure of the image sensor 2 to which the present technology can be applied. In other words, the examples include: a front-illuminated image sensor in which a pixel region 8 is formed on the front side of the semiconductor substrate 6; a back-illuminated image sensor in which a photodiode or the like is arranged in the reverse order so that the back side of the semiconductor substrate 6 is the light-receiving surface side to improve the light transmittance; and an image sensor in a single-chip form obtained by stacking peripheral circuits of a group of pixels. However, the image sensor 2 according to the present technology is not limited to an image sensor having these structures.

[0081] Glass 3 is provided on the light-receiving side of the image sensor 2 at a specific interval from the image sensor 2. Glass 3 is an example of a cover element and is a rectangular plate-like element having substantially the same size as the image sensor 2. Glass 3 is arranged such that the outer shape of glass 3 substantially coincides with the outer shape of the image sensor 2 in a plan view and is arranged parallel to the image sensor 2. Glass 3 includes a lower surface 3b and an upper surface 3a. The lower surface 3b is the plate surface facing the image sensor 2 side, and the upper surface 3a is the surface opposite to the lower surface 3b. The light passing through glass 3 enters the light-receiving surface of the image sensor 2.

[0082] Various lights entering from an optical system (for example, a lens usually located above glass 3) are transmitted through glass 3, and glass 3 transmits various lights through the cavity 5 to the light-receiving surface of the image sensor 2 facing glass 3. Glass 3 includes a function of protecting the light-receiving surface side of the image sensor 2 and includes a function of blocking moisture (water vapor), dust, etc. from entering the cavity 5 from the outside together with the partition wall 4.

[0083] According to the present technology, in addition to a glass plate, for example, a plastic plate, a silicon plate that transmits only infrared light, etc. can be used as the cover element. Note that, for example, considering the situation when the image sensor 2 is used, any type of wavelength filter film is formed on the surface of glass 3, or glass 3 having any type of wavelength filter film formed thereon can be coated with an antireflection film for preventing reflection inside or outside the cavity 5.

[0084] The partition wall 4 is provided on the light-receiving side of the image sensor 2 and supports glass 3 on the image sensor 2 to form a cavity 5 between the image sensor 2 and glass 3. The partition wall 4 is provided in the peripheral region on the front 2a of the image sensor 2 to surround the pixel region 8, which is a region obtained by excluding the pixel region 8 from the front 2a.

[0085] The partition wall 4 is located between the front surface 2a of the image sensor 2 and the lower surface 3b of the glass 3, and serves as a sealing portion for sealing the image sensor 2 and the glass 3. In other words, the partition wall 4 and the glass 3 together block moisture, dust, etc. from entering the cavity 5 from the outside.

[0086] The partition wall 4 is formed on a part surrounding the glass 3 along the outer shape of the glass 3, and is arranged in a rectangular frame shape in a plan view. In the plan view, the partition wall 4 is arranged along the outer edge of the glass 3 within the range of the outer shape of the glass 3. For example, the partition wall 4 is arranged such that the outer surface 4c of the partition wall 4 is substantially flush with the outer surface 3c of the glass 3.

[0087] The material of the partition wall 4 is, for example, a photosensitive adhesive, which is made of, for example, a UV (ultraviolet) curable resin as an acrylic resin, a thermosetting resin such as an epoxy resin, or a mixture thereof. The partition wall 4 is formed on the front surface 2a of the image sensor 2 by, for example, coating using a dispenser or patterning using a photolithography technique. A photosensitive resin that can generally freely form a pattern is advantageously used as the material of the partition wall 4.

[0088] When the partition wall 4 is made of a resin material, the partition wall 4 serves as an adhesive for bonding the image sensor 2 and the glass 3 in a state where the image sensor 2 and the glass 3 are separated from each other. However, the partition wall 4 is not limited to being made of resin. For example, the partition wall 4 may be a structure made of ceramics (e.g., glass) or inorganic materials (e.g., metal or silicon), and is attached to the image sensor 2 and the glass 3 using, for example, an adhesive. The partition wall 4 as a structure made of glass or the like can be expected to provide an effect of preventing moisture penetration.

[0089] The cavity 5 is a flat rectangular space portion located between the image sensor 2 and the glass 3. Specifically, the cavity 5 is formed by the front surface 2a of the image sensor 2, the lower surface 3b of the glass 3, and the inner surface 4a of the partition wall 4. The inside of the cavity 5 is a space portion on the image sensor 2 that is completely isolated from the outside and protected.

[0090] Once the incident angle of light entering the glass 3 is affected by the refractive index of the material of the glass 3, it will change. However, with respect to the light entering the on-chip lens formed in the pixel 7, since the cavity 5 is a space with a refractive index of 1, the original incident angle of the light entering the glass 3 is replicated.

[0091] In addition, the solid-state imaging device 1 includes a plurality of electrode pads 11 formed on the front surface 2a side of the image sensor 2. The plurality of electrode pads 11 are terminals for transmitting signals to the outside / receiving signals from the outside. For example, a material such as aluminum is used as the material of the electrode pads 11. In addition, the image sensor 2 includes a set of solder balls 12, each solder ball 12 corresponding to a solder portion for mounting the image sensor 2, and provided on the back surface 2b side of the other plate surface (the surface opposite to the front surface 2a) of the semiconductor substrate 6. The electrode pads 11 are electrically connected to the solder balls 12. Note that the image sensor 2 is mounted on a substrate (e.g., an insertion substrate) in a product, for example.

[0092] The electrode pads 11 are formed in a portion directly below the partition wall 4 on the front surface 2a side of the image sensor 2. In addition, the electrode pads 11 are connected to the solder balls 12 through a wiring layer 14 extending to be embedded in a through hole (through-silicon via: TSV), which is formed from the back surface 2b side of the image sensor 2.

[0093] The through hole 13 is formed by embedding an in-hole wiring portion 14a in the inner surface of the hole. The in-hole wiring portion 14a forms the wiring layer 14, and the hole is formed to penetrate the semiconductor substrate 6. The in-hole wiring portion 14a forms the wiring layer 14, where a planar wiring portion 14b is formed on the back surface 2b side of the semiconductor substrate 6, and the planar wiring portion 14b is connected to the solder ball 12. For example, the through hole 13 is formed using deep reactive ion etching (DRIE), which is a process for semiconductor devices and enables the formation of a narrow deep opening (i.e., a hole with a so-called high aspect ratio).

[0094] This electrical connection enables the signal quality to be maintained in a short connection path. However, for example, the electrode pads 11 can be connected to the solder balls 12 from the front surface 2a side of the image sensor 2 through bonding wires. In this configuration, for example, the electrode pads 11 are formed outside the partition wall 4 on the front surface 2a side of the image sensor 2.

[0095] For example, the wiring layer 14 is made of a low-resistance metal material such as copper (Cu), which has a low resistance value and is favorable for the transmission of high-speed signals. Note that in addition to copper (Cu), the wiring layer 14 can be made of tungsten (W), titanium (Ti), tantalum (Ta), titanium-tungsten alloy (TiW), polysilicon, etc. The portion of the image sensor 2 where the wiring layer 14 is formed is covered with an insulating film 15, which is made of, for example, an oxide film or a nitride film. The insulating film 15 is formed in the form of a liner for the wiring layer 14 so that the wiring layer 14 does not come into direct contact with the semiconductor substrate 6. In other words, the insulating film 15 is located between the wiring layer 14 and the semiconductor substrate 6.

[0096] In addition, a solder resist (solder resist layer) 16 made of an insulating resin is formed on the back surface 2b side of the image sensor 2 to cover the entire back surface 2b. The solder resist 16 includes an opening 16a, and by using this opening 16a, only the portion where the solder balls 12 are in contact with the wiring layer 14 is opened. The solder resist 16 also embeds the through holes 13 and is formed to cover the in-hole wiring portion 14a and the planar wiring portion 14b of the wiring layer 14. The solder resist 16 defines the contact area between the wiring layer 14 and the solder balls 12 and includes a function of preventing short circuits from occurring between adjacent solder balls 12. In addition, the wiring layer 14 is disposed inside the solder resist 16 on the back surface 2b side of the image sensor 2. This enables reliable coverage of the wiring and prevents, for example, wiring short circuits due to conductive foreign matter.

[0097] The plurality of solder balls 12 are portions that serve as external terminals and are appropriately set according to, for example, the number of signals of the image sensor 2 or the substrate of the product. In the present embodiment, this set of solder balls 12 is disposed on the back surface 2b side of the image sensor 2 along the outer shape of the rectangular chip of the image sensor 2 (refer to Figure 2 ).

[0098] In consideration of recent environmental problems, lead-free materials are often used as the material of the solder balls 12. Its material composition is appropriately selected according to the purpose of use of the product, the necessary cost, etc. The following processes are used as the processes for providing the solder balls 12: a process including placing the solder balls 12 in the opening 16a of the solder resist 16 with a high positional accuracy, and the solder balls 12 having a uniform size in a state where a solder flux is applied to the solder balls 12; or a process including printing a solder paste on the opening 16a of the solder resist 16 using a printing technique and then performing reflow to form the solder into a spherical shape.

[0099] As described above, by forming electrodes using the through holes 13 passing through the front surface 2a and the back surface 2b of the image sensor 2, the solid-state imaging device 1 having a WCSP structure has a configuration in which wiring is not performed by wire bonding. In other words, in the solid-state imaging device 1, the wiring layer 14 extending through the through hole 13 from the electrode pad 11 is connected to the solder balls 12 on the back surface 2b side of the image sensor 2, the electrode pad 11 is the signal connection end of the image sensor 2, and the through hole 13 passes through the front surface 2a and the back surface 2b of the image sensor 2.

[0100] Compared with a chip-on-board (COB) package structure that requires a connection area for wire bonding around the chip of the image sensor 2, since a connection area for wire bonding is not required, this configuration enables size reduction and cost reduction. In addition, the WCSP structure enables assembly to be performed using a so-called wafer process in a clean room. Therefore, it is desirable to achieve a dust-free state, and this helps to improve the performance of the image sensor 2.

[0101] The following are examples of the dimensions of the respective components in the solid-state imaging device 1 according to the present embodiment. The thickness of the image sensor 2 is from 300 μm to 600 μm. The thickness of the glass 3 is from 100 μm to 500 μm. The thickness (height) of the partition wall 4 is from 10 μm to 50 μm. The thickness of the solder resist 16 is from 10 μm to 30 μm. Note that these dimensions are merely examples, and appropriate dimensions according to the device structure, pixel size, etc. of the solid-state imaging device 1 are used as the dimensions of the respective components.

[0102] For example, when the solid-state imaging device 1 is mounted on the substrate of a product, the solid-state imaging device 1 according to the present embodiment having the above configuration is subjected to reflow to melt the solder balls 12 for bonding. During the reflow, the solid-state imaging device 1 is exposed to an environment at a temperature of, for example, about 250°C. Therefore, the gas containing moisture (water vapor) in the cavity 5 is heated, and the internal pressure (vapor pressure) in the cavity 5 increases. Here, when the partition wall 4 that supports the glass 3 on the image sensor 2 is made of resin, there is moisture passing through the glass 3 in the cavity 5.

[0103] The increase in the internal pressure in the cavity 5 may cause damage, for example, cracking of the structural elements of the solid-state imaging device 1 (for example, the semiconductor substrate 6 included in the image sensor 2, the glass 3, or the partition wall 4 that supports the glass 3); and detachment of the bonded structural elements. When such damage occurs, moisture, dust, etc. enter the cavity 5 from the damaged part, which results in a reduction in the device performance. Therefore, the solid-state imaging device 1 according to the present embodiment has the following configuration.

[0104] As Figure 1 and Figure 2 shown, in the solid-state imaging device 1 according to the present embodiment, the semiconductor substrate 6 includes a recess 20 formed on the back surface 2b side of the semiconductor substrate 6, and the thickness of the semiconductor substrate 6 is partially reduced due to the formation of the recess 20. The recess 20 is a recess formed in the image sensor 2 that is a rectangular plate-shaped chip, such that the recess opens on the back surface 2b side.

[0105] The recess 20 includes a bottom surface portion 21 that is substantially parallel to the plate surface of the semiconductor substrate 6 and side surface portions 22 that form the inner surface of the recess 20. The bottom surface portion 21 is the portion in the image sensor 2 that forms the bottom surface 23, and the bottom surface 23 is a horizontal surface opposite to the front surface 2a. The side surface portions 22 are surface portions formed between the bottom surface portion 21 and the back surface 2b.

[0106] The recess 20 has a shape along the outer shape of the image sensor 2 in a bottom view. Therefore, the recess 20 is a rectangular recess (refer to Figure 2)。Therefore, in the recess 20, the bottom surface portion 21 is formed in a rectangular shape along the outer shape of the image sensor 2, and the side surface portion 22 is formed along the four side surfaces of the bottom surface portion 21. The semiconductor substrate 6 including such a recess 20 has a frame shape, and the opening side of the semiconductor substrate 6 is the back surface 2b side.

[0107] The range of the region where the recess 20 is formed is, for example, a range including the pixel region 8. Further, the recess 20 is formed to be within, for example, the range where the cavity 5 is formed, that is, within the region inside the partition wall 4.

[0108] Due to the recess 20, a part of the image sensor 2 where the recess 20 is formed becomes thinner and forms a diaphragm-like part. The part where the recess 20 is formed is the image sensor 2 excluding the peripheral part of the image sensor 2. Specifically, the image sensor 2 includes a thin plate portion 24 and a thick plate portion 25 in the semiconductor substrate 6. The thin plate portion 24 is formed in a rectangular shape corresponding to the range where the recess 20 is formed, and the thick plate portion 25 is formed in a frame shape to surround the outer periphery of the thin plate portion 24. On the back surface 2b side, the thick plate portion 25 is thicker than the thin plate portion 24.

[0109] Corresponding to the range where the recess 20 is formed, the thick plate portion 25 includes linear portions respectively along the four sides of the rectangle. Due to the linear portions, the thick plate portion 25 has a rectangular frame shape in a plan view. The thickness of the thin plate portion 24 obtained due to the recess 20 is, for example, about 1 / 3 to 1 / 4 of the thickness of the thick plate portion 25 having the normal thickness of the semiconductor substrate 6. Further, in the configuration including the recess 20, the lower surface of the thick plate portion 25 surrounding the recess 20 is the back surface 2b of the image sensor 2.

[0110] In principle, the recess 20 is formed by etching. However, the method for forming the recess 20 is not limited to etching, and any method capable of partially removing the semiconductor substrate 6 can be used. Note that the method for forming the recess 20 will be described later.

[0111] The side surface portion 22 of the recess 20 is described. In the present embodiment, the side surface portion 22 includes, in a cross-sectional view of the semiconductor substrate 6, a first inclined surface 31 inclined in a specific direction with respect to the plate surface of the semiconductor substrate 6, and a second inclined surface 32 formed in a curved shape with the first inclined surface 31.

[0112] As Figure 1As shown, the first inclined surface 31 is the surface forming the part located on the back surface 2b side (hereinafter also referred to as the "lower side") of the side surface portion 22, and the second inclined surface 32 is the surface forming the front surface 2a side (hereinafter also referred to as the "upper side") of the side surface portion 22. Due to the first inclined surface 31 and the second inclined surface 32, the side surface portion 22 has a surface that is bent to form a substantially laterally V-shaped surface in the cross-sectional view of the solid-state imaging device 1, and this surface has convex portions on the outer sides ( Figure 1 the outer sides on the left and right in

[0113] In other words, with respect to the direction perpendicular to the plate surface of the semiconductor substrate 6 ( Figure 1 the up-and-down direction in

[0114] ), the first inclined surface 31 is inclined from the inner side to the outer side in the left-and-right direction from the lower side to the upper side. The second inclined surface 32 is inclined from the outer side to the inner side in the left-and-right direction from the lower side to the upper side with respect to the vertical direction. In addition, the upper end of the second inclined surface 32 is connected to the bottom surface 23 of the bottom surface portion 21 to form an obtuse-angle portion with the bottom surface 23.

[0115] In the above-described side surface portion 22 having a curved surface portion due to the first inclined surface 31 and the second inclined surface 32, both the first inclined surface 31 and the second inclined surface 32 form acute angles with the horizontal direction O1 parallel to the plate surface of the semiconductor substrate 6. In other words, both the angle α1 formed by the first inclined surface 31 and the horizontal direction O1 and the angle α2 formed by the second inclined surface 32 and the horizontal direction O1 are acute angles.

[0116] In the present embodiment, the side surface portion 22 of the recess 20 includes the (111) plane or an equivalent crystal plane of the semiconductor substrate 6 (hereinafter collectively referred to as the {111} plane). The semiconductor substrate 6 is a silicon substrate. The {111} plane is based on the crystal structure of silicon and is a crystal plane formed by anisotropic etching performed on the silicon substrate.

[0117] In the present embodiment, both the first inclined surface 31 and the second inclined surface 32 forming the side surface portion 22 of the recess 20 have the {111} plane. In other words, both the first inclined surface 31 and the second inclined surface 32 have crystal planes formed by anisotropic etching. When both the first inclined surface 31 and the second inclined surface 32 are surfaces formed by anisotropic etching as described above, the angle α1 and the angle α2 with respect to the horizontal direction O1 are both approximately 55° (54.7°) and are substantially the same as each other.

[0118] Anisotropic etching is a wet etching and is a commonly used technique in the process of manufacturing microelectromechanical systems (MEMS). In this technique, a desired opening pattern is formed on a target processing surface of a semiconductor substrate (e.g., a silicon substrate) using, for example, an oxide film, a nitride film, or an alkali-resistant resist, and the semiconductor substrate is immersed in a strong alkali solution (e.g., potassium hydroxide (KOH)) using this pattern as a mask to perform etching. According to anisotropic etching, the shape of the opening is uniquely determined in a state where the {111} plane is exposed due to the crystal orientation of the semiconductor substrate. Usually, a single-crystalline silicon substrate having a (100) surface orientation is generally used as the semiconductor for forming an image sensor. In this case, when a rectangular hole mask of an oxide film, a nitride film, or a resist is formed on the back surface of the silicon substrate, an opening having an etched shape is formed, and the etched shape gradually widens or narrows in the depth direction at an inclination of approximately 55° from the opening.

[0119] The solid-state imaging device 1 according to the present embodiment described above is formed in a WCSP structure having the following configuration. In other words, the solid-state imaging device 1 includes a semiconductor substrate 6, a wiring layer 14, solder balls 12, a partition wall 4, and glass 3. A recess 20 is formed on the back side of the semiconductor substrate 6, and an image sensor element is formed on the front side of the semiconductor substrate 6. The wiring layer 14 is formed on a flat portion located outside the recess 20 of the semiconductor substrate 6. The wiring layer 14 is connected to an electrode pad 11 and is provided to extend. The solder balls 12 are formed on the wiring layer 14 through a pad portion (not shown). The partition wall 4 is formed to surround the image sensor element of the semiconductor substrate 6, and isolates the space located above the portion where the image sensor element is formed from the outside and serves as a cavity 5. The glass 3 is bonded to the partition wall 4.

[0120] <2. Method for Manufacturing the Solid-State Imaging Device According to the First Embodiment>

[0121] Refer to Figures 3 to 7 An example of a method for manufacturing the solid-state imaging device 1 according to the first embodiment of the present technology is described.

[0122] In the process of manufacturing the solid-state imaging device 1, first, a silicon wafer 40 on which pixels 7 are formed is provided, as shown in A of Figure 3 The silicon wafer 40 is a silicon wafer on which various processes for forming the image sensor 2 have been performed. In other words, the silicon wafer 40 is a semiconductor wafer on which a group of pixels 7 are formed on one plate surface side of the semiconductor wafer, and each of them is a plurality of parts of the image sensor 2 formed in the silicon wafer 40 in a specific setting. In recent years, 8-inch wafers or 12-inch wafers are mainly used as the silicon wafer 40.

[0123] A wall 44 corresponding to the partition wall 4 is formed on the silicon wafer 40, and a glass plate 43 corresponding to the glass 3 is attached to the silicon wafer 40. Here, the wall 44 may be formed on the front surface 40a of the silicon wafer 40, and then the glass plate 43 is attached to the wall 44. In addition, the wall 44 that has been pre-formed on the glass plate 43 may be attached to the front surface 40a of the silicon wafer 40.

[0124] The glass plate 43 is an example of a light-transmitting plate material. The wall 44 is formed along a specific setting of a plurality of image sensors 2 to surround a set of pixels 7. In other words, corresponding to the rectangular region that will finally form the solid-state imaging device 1, the wall 44 is formed in a grid pattern in a plan view.

[0125] For example, patterning using photolithography techniques, screen printing, etching, coating using a dispenser, etc. are used as methods for forming the wall 44. By bonding the silicon wafer 40 and the glass plate 43 through the wall 44, a cavity 45 corresponding to the cavity 5 is formed in each solid-state imaging device 1.

[0126] Note that when the partition wall 4 is a structure made of, for example, glass or metal, the structure formed in a grid pattern is attached to the silicon wafer 40 and the glass plate 43 using a specific adhesive. In this case, it is advantageous to perform the process of attaching the structure in a clean room with high cleanliness so that dust does not enter the cavity 45.

[0127] As described above, in the method for manufacturing the solid-state imaging device 1 according to the present embodiment, a process of setting the glass plate 43 at a specific interval on the front surface 40a side of the silicon wafer 40 through the wall 44 is performed. The front surface 40a side is one plate surface side of the silicon wafer 40, and the wall 44 is formed in a grid pattern to surround a set of pixels 7.

[0128] As described above, after setting the cavity 45 (5) corresponding to each solid-state imaging device 1 in the wafer state by performing separation using the wall 44, a protective sheet 50 is attached to the front surface 43a of the glass plate 43, as Figure 3 shown in A. The protective sheet 50 is used to protect the front surface 43a of the glass plate 43 from being processed in the process of scraping the silicon wafer 40 from the back surface 40b side of the silicon wafer 40.

[0129] Generally, various thin films formed in various processes performed previously are stacked on the back surface 40b of the silicon wafer 40. In addition, due to the processing performed in the process, fine scratches and dust may adhere to the back surface 40b. Therefore, in some cases, the stacked thin films are removed to expose the silicon surface. In addition, in recent years, there has been a great demand for thinner and smaller smartphones and digital cameras, so it is necessary to make the sensor device itself as thin as possible.

[0130] Therefore, a back grinding (BG) process of scraping the back side 40b of the silicon wafer 40 is performed so that, in the wafer state, the silicon wafer 40 has a desired thickness that does not affect the device characteristics, as Figure 3 shown in B of. In this process, the front side 43a of the glass plate 43 is protected from being processed by using a protective sheet 50. In the BG process, for example, a back grinding foil 58 such as a diamond foil is used to polish the silicon wafer 40. Due to the BG process, the thickness of the silicon wafer 40 changes from the original thickness T1 to a desired thickness T2 that is thinner than the original thickness T1.

[0131] The protective sheet 50 is attached to the entire front side 43a of the glass plate 43 by using a device such as a laminator. Regarding the removal of the protective sheet 50, for example, a type of protective sheet whose adhesion strength is weakened by irradiating with ultraviolet light, a type of protective sheet whose adhesion strength is weakened by heating, etc. are used as the protective sheet 50. In addition, in order to increase the surface roughness of the back side 40b of the silicon wafer 40, a mirror polishing process such as chemical polishing or dry polishing can be performed after the BG process.

[0132] Next, a process of forming a first insulating film 52 (for example, a nitride film made of, for example, Si 3 N 4 or an oxide film made of, for example, SiO 2 ) on the back side 40b of the silicon wafer 40 is performed, as Figure 3 shown in C of. Advantageously, in order to form the first insulating film 52, plasma enhanced chemical vapor deposition (PECVD) that can form a film at a low temperature is generally used. However, the film formation method is not limited to this, and high frequency sputtering for forming an insulating film or another method for forming a film can be used.

[0133] In the process of forming the first insulating film 52, the first insulating film 52 can be formed in a state where the protective sheet 50 used in the previous process remains attached to protect the glass plate 43 from scratches generated during the process and various reaction gas environments in the PECVD process. Alternatively, another protective sheet replacing the protective sheet 50 can be attached. In addition, when a device that provides an environment where there is no need to worry about, for example, damage to the glass plate 43 caused during the process or contamination of the glass plate 43 caused during the PECVD is available, the first insulating film 52 can be formed without the protective sheet 50.

[0134] Next, patterning is performed on the first insulating film 52, as Figure 4As shown in A. That is, patterning is performed on the first insulating film 52 formed in the previous process to form a desired pattern, and a photolithography process (lithography process) for exposing the underlying silicon wafer 40 is performed. In this process, a technique such as reactive ion etching (RIE) is used to partially remove the first insulating film 52, so that openings 52a and 52b of a fine pattern are formed in the first insulating film 52. The opening 52a is used for the perforation 40c (refer to Figure 4 B) for opening the through hole 13. The through hole 13 is formed to pass through the silicon wafer 40 from the back side 40b of the silicon wafer 40 to the electrode pad 11. The opening 52b is used to thin the silicon wafer 40 to form the recess 20.

[0135] Regarding the patterning performed on the first insulating film 52, patterning is performed using a photoresist 53 made of a specific photosensitive material, and after the first insulating film 52 is partially removed by, for example, RIE, the photoresist 53 is removed. Specifically, as the patterning process, the following processes are sequentially performed. That is, the patterning process includes: for example, applying the photoresist 53 as a mask and drying the applied photoresist 53, exposing the mask to perform patterning, using a developer to remove the portions of the mask corresponding to the openings 52a and 52b, performing plasma cleaning using argon or oxygen as needed to remove the residues remaining in the removed portions, etching the openings of the mask by RIE, removing the unnecessary photoresist 53, and performing plasma cleaning using argon or oxygen as needed to remove the residues remaining in the removed portions.

[0136] Next, a process for forming the perforation 40c for the through hole 13 is performed, as shown in Figure 4 B. In this process, first, patterning is performed using photolithography technology to form a photoresist 54 on the first insulating film 52 formed in the previous process, so that the portion of the photoresist 54 corresponding to the opening 52a is opened. In other words, the photoresist 54 includes an opening 54a continuous with the opening 52a of the first insulating film 52.

[0137] Thereafter, etching is performed to form the perforation 40c in the silicon wafer 40 through the opening 52a of the first insulating film 52 and the opening 54a of the photoresist 54. Here, the process of forming the perforation 40c is a process of forming a perforation having a so-called high aspect ratio. Therefore, for example, DRIE using an etching process showing higher directionality than ordinary RIE is used to form the perforation 40c. Compared with the case of ordinary RIE, high-density plasma is used for DRIE. Therefore, a photoresist 54 having a higher impedance to plasma is used. After the perforation 40c is formed, the photoresist 54 is removed.

[0138] Next, a second insulating film 55 is formed to cover the entire surface including the inner surface of the through-hole 40c. Figure 4 By covering the inner surface of the through-hole 40c with the second insulating film 55, problems regarding device operation, such as current leakage due to the exposure of the silicon surface of the silicon wafer 40, are solved.

[0139] The second insulating film 55 is formed over the entire surface, and thus the inner surface of the through-hole 40c and the portion of the opening 52b of the first insulating film 52 are part of a single-layer insulating film formed by the second insulating film 55. In addition, the portion where the first insulating film 52 exists is part of an insulating film having a two-layer structure formed by the first insulating film 52 and the second insulating film 55, and this enables excellent insulating performance to be obtained. As described above, the insulating film structure including the single-layer portion formed by the second insulating film 55 and the two-layer portion formed by the first insulating film 52 and the second insulating film 55 is the insulating film 15 in the solid-state imaging device 1. Note that the illustration of the first insulating film 52 is omitted in Figure 4 C of.

[0140] The second insulating film 55 is formed to cover the contact portion on the back surface of the electrode pad 11 facing the upper portion of the through-hole 40c and the portion of the silicon wafer 40 where the recess 20 is formed. Therefore, patterning is performed using a lithography technique to remove from the second insulating film 55 the portions corresponding to the contact portion on the back surface of the electrode pad 11 and the portion where the recess 20 is formed, as Figure 4 shown in C of. Thus, a contact hole 55a for exposing the back surface of the electrode pad 11 and an opening 55b for forming the recess 20 are formed in the second insulating film 55.

[0141] In the process of partially removing the second insulating film 55, first, a coating is formed on the second insulating film 55 by, for example, applying a resist to the second insulating film 55 including the portion located in the through-hole 40c. Here, it is necessary to adjust the viscosity of the resist and the coating method so that the resist does not enter only the deep through-hole 40c. In addition, regarding the process of exposing the resist, an exposure apparatus capable of expanding the depth of focus is used, or a method of performing two exposures on the bottom and other portions of the through-hole 40c is used according to the use.

[0142] Next, a copper wiring layer 56 corresponding to the wiring layer 14 in the solid-state imaging device 1 is formed on the back surface 40b side of the silicon wafer 40, as Figure 5 shown in A of. The copper wiring layer 56 is used to form solder balls 12 on the back surface 40b side of the silicon wafer 40 in the WCSP structure. The copper wiring layer 56 extends from the back surface of the electrode pad 11 to pass through the through-hole 40c, and the solder ball 12 is connected to the extended portion of the copper wiring layer 56. The copper wiring layer 56 includes an in-hole wiring portion 56a corresponding to the in-hole wiring portion 14a (refer to Figure 1) and a planar wiring portion 56b formed along the back surface 40b and corresponding to the planar wiring portion 14b (see Figure 1 ).

[0143] Before forming the copper wiring layer 56, a seed layer is pre-formed by a film-forming method such as sputtering. The seed layer is a thin film made of, for example, titanium (Ti) or copper (Cu). The seed layer serves as an electrode used when the copper wiring layer 56 is embedded in the vias 40c by electroplating. Note that before forming the copper wiring layer 56, a barrier metal film made of, for example, tantalum (Ta) or titanium (Ti) can be formed by sputtering, for example, to prevent the diffusion of the in-hole wiring portion 56a.

[0144] Patterning is performed by a photolithography process to form a resist pattern corresponding to the wiring pattern in a specified area on the seed layer. Thereafter, the copper wiring layer 56 is formed in the portions of the seed layer exposed by performing patterning by electroplating using the seed layer as an electrode. Thus, the in-hole wiring portion 56a and the planar wiring portion 56b of the via 13 are formed.

[0145] The copper wiring layer 56 is generally formed to have a thickness of about 10 μm. However, the thickness of the copper wiring layer 56 is appropriately increased or decreased according to, for example, the signal type of the solid-state imaging device 1 or the number of signals of the solid-state imaging device 1. In addition, after forming the copper wiring layer 56 by electroplating, unnecessary resist patterns are removed using, for example, a dedicated removal solution or a rinsing agent, and the seed layer is removed by, for example, wet etching.

[0146] Next, a process of forming the solder resist 57 is performed, as shown in Figure 5 B of. The solder resist 57 is formed to prevent short circuits in the wiring of the copper wiring layer 56 and to define the positions where the solder balls 12 are placed. In the solder resist 57, pad openings 57a exposing the copper wiring layer 56 are formed in the portions where the solder balls 12 are placed, such that the pad openings 57a fit the size of the solder balls 12.

[0147] For example, a photosensitive resin using, for example, an epoxy resin as a base resin is used as the solder resist 57. This enables the use of a photomask used in the photolithography process to freely design the pad openings 57a. As the photolithography process, the following processes are sequentially performed. That is, the photolithography process includes: for example, applying the solder resist 57 and drying the applied solder resist 57, exposing a mask corresponding to the pad openings 57a to perform patterning, removing a part of the solder resist 57 corresponding to the pad openings 57a using a developer, and performing plasma cleaning using argon or oxygen as needed to remove residues remaining in the removed portion.

[0148] The formed pattern of the solder resist 57 has a shape that does not cause the solder resist 57 to interfere with the portion where the solder balls 12 are placed and the portion where the recess 20 is formed. In addition, the solder resist 57 is embedded in the through hole 40c, and the in-hole wiring portion 56a is formed in the through hole 40c.

[0149] Next, a process of forming the recess 20 corresponding to each image sensor 2 is performed on the back surface 40b side, which is the other plate surface of the silicon wafer 40. In the back surface 40b, the thickness of the silicon wafer 40 is partially reduced due to the formation of the recess 20. In other words, the recess 20 corresponding to each solid-state imaging device 1 is formed by partially removing a part of the silicon wafer 40 corresponding to the image sensor 2 from the back surface 40b side.

[0150] In the present embodiment, the process of forming the recess 20 includes a first etching process and a second etching process, and the recess 20 is formed by a two-stage etching process. The process of forming the recess 20 will be described in detail below.

[0151] First, when performing the etching for forming the recess 20, a process of forming a photoresist 61 on the back surface 40b side of the silicon wafer 40 is performed so that the photoresist 61 covers the portion other than the portion where the recess 20 is formed, as Figure 5 shown in C. The photoresist 61 is formed by the above-described photolithography process. In other words, the photoresist 61 is applied and the applied photoresist 61 is dried. The photoresist 61 is exposed to perform patterning. A part of the rectangular or square opening 61a corresponding to the portion where the recess 20 is formed is removed using a developer, and cleaning is performed as needed to remove the residue remaining in the removed portion.

[0152] The photoresist 61 covers the solder resist 57 and covers the planar wiring portion 56b of the copper wiring layer 56 exposed from the pad opening 57a. The photoresist 61 can be the same type of resist as the above-described photoresists 53 and 54, or can be another type of resist having a viscosity and physical properties different from those of the photoresists 53 and 54. However, it is advantageous for the photoresist 61 to have strong alkali resistance because a strong alkali solution is used when forming the recess 20. This will be described later.

[0153] After forming the photoresist 61, a first etching process of forming a semi-recess 20X by removing the portion corresponding to the recess 20 from the silicon wafer 40 by dry etching is performed.

[0154] As Figure 6 shown in A, in the first etching process, etching is performed on the silicon portion to a desired depth using RIE (a type of dry etching), and the silicon portion is exposed from the opening 61a of the photoresist 61 on the back surface 40b side of the silicon wafer 40. Thus, the semi-recess 20X is formed.

[0155] The semi-recessed portion 20X has a rectangular or square shape in the bottom view. The semi-recessed portion 20X includes a bottom surface 20Xa that is substantially parallel to the front surface 40a, and side surfaces 20Xb that are substantially perpendicular to the bottom surface 20Xa, as the etched surfaces. In other words, due to the bottom surface 20Xa and the side surfaces 20Xb surrounding the bottom surface 20Xa, the semi-recessed portion 20X has a generally square shape in the side cross-sectional view and a rectangular, flat recessed shape in the plan view. As described above, the first etching process creates holes in the depth direction (longitudinal direction) perpendicular to the plate surface of the silicon wafer 40.

[0156] The depth of the semi-recessed portion 20X affects the substantially lateral V-shaped bending form of the side surface portion 22 of the final recess 20 in the cross-sectional view. Therefore, the depth of the semi-recessed portion 20X is determined according to the desired shape of the side surface portion 22 of the recess 20.

[0157] After the first etching process, a second etching process is performed to form the recess 20 by anisotropically etching the semi-recessed portion 20X downward, as Figure 6 shown in B.

[0158] In the second etching process, the silicon wafer 40 on which the semi-recessed portion 20X is formed by RIE is placed in a strong alkaline solution (e.g., potassium hydroxide (KOH)), and anisotropic etching is performed on the silicon. Before placing the silicon wafer 40 in the strong alkaline solution, a protective sheet 62 is attached to the front surface 43a of the glass plate 43 using dedicated equipment to protect the front surface 43a of the glass plate 43.

[0159] In the anisotropic etching, for example, a so-called batch wet etching equipment that processes multiple silicon wafers 40 at a time is used. According to this wet etching equipment, the wafers are placed in a KOH solution heated to about 60 °C to 80 °C, and etching is performed for a specific period while rotating and swinging the wafers so that etching is uniformly performed on the wafer surface. The etching period and the temperature of the KOH solution are precisely controlled, and this enables obtaining the desired etching amount. Note that examples of the solution used when performing anisotropic etching include tetramethylammonium hydroxide (TMAH) and ethylenediamine pyrocatechol (EDP) in addition to KOH.

[0160] After performing the anisotropic etching, unnecessary portions of the photoresist 61 are removed, as Figure 6 shown in C. Here, cleaning is performed as needed to remove residues remaining in the removed portions of the photoresist 61, and this cleaning is performed by, for example, plasma cleaning. Note that after performing the anisotropic etching, the alkaline solution can be washed away by a method such as quick dump rinse (QDR), and then water drying can be performed as needed.

[0161] When the second etching process is performed as described above, the recess 20 is formed, the silicon wafer 40 is partially thinned from the back surface 40b side at portions corresponding to each image sensor 2, and a diaphragm shape is formed through the recess 20.

[0162] Here, the correlation between the depth of the semi-recess 20X and the shape of the side surface portion 22 of the recess 20 is described. When anisotropic etching is performed on a (100) plane-oriented silicon substrate widely used in manufacturing an image sensor or LSI, the etching performed on the (100) plane proceeds until the (111) plane is exposed, and the (111) plane forms an angle of approximately 55° with the end plane in the plane direction. Therefore, if the depth of the etching performed to form the semi-recess 20X is deeper, the dog-leg shape (lateral V shape) formed in the (111) plane orientation is larger in the cross-sectional view. In other words, if the depth of the semi-recess 20X is deeper, the region size A1 of the first inclined surface 31 and the region size A2 of the second inclined surface 32 are proportionally closer in the depth direction of the recess 20 (refer to Figure 1 ).

[0163] Specifically, as shown in A and B of Figure 8 , when the depth of the recess 20 is a constant depth D1, if the etching depth of the semi-recess 20X (D2, D3) is deeper, the area ratio of the first inclined surface 31 in the surface of the side surface portion 22 of the recess 20 formed is larger (the area ratio of the second inclined surface 32 is smaller). In other words, if the depth of the semi-recess 20X is deeper, the region size A1 of the first inclined surface 31 in the depth direction is larger. Note that in A and B of Figure 8 , the rectangular shaded portion B1 surrounded by the dotted line represents the region portion removed to form the semi-recess 20X in the silicon wafer 40.

[0164] Compared with the case where the depth of the semi-recess 20X shown in A of Figure 8 is the shallower depth D2, when the depth of the semi-recess 20X is the deeper depth D3, the recess 20 has a larger width in the lateral direction, as shown in B of Figure 8 . In other words, when the depth of the semi-recess 20X is the deep depth D3, the width dimension W3 in the lateral direction is larger than the width dimension W2 in the lateral direction when the depth of the semi-recess 20X is the shallow depth D2, as shown in A of Figure 8 . Here, the width dimension (W2, W3) in the lateral direction is the dimension between the position P1 and the position P2. In the cross-sectional view of the silicon wafer 40, the position P1 is each of the left end and the right end of the semi-recess 20X in the direction parallel to the plate surface of the silicon wafer 40 (the left-right direction in A and B of Figure 8 ). The position P2 is the vertex of the corner formed by the first inclined surface 31 and the second inclined surface 32 of the side surface portion 22 of the recess 20.

[0165] As described above, in the second etching process of performing anisotropic etching to form the recess 20, the etching depth of the semi-recess 20X preformed by the first etching process enables control of the curved shape formed by the first inclined surface 31 and the second inclined surface 32 of the side surface 22 of the final recess 20. Thus, for example, when it is necessary to make the curved shape of the side surface 22 of the recess 20 relatively large, as shown in Figure 8 B of, it is sufficient to form the semi-recess 20X deeper in the first etching process.

[0166] For example, the size of the thin plate portion 24 having the diaphragm structure required for the image sensor 2 is a factor for determining the depth of the semi-recess 20X. In other words, if the etching depth of the semi-recess 20X is deeper, then when performing anisotropic etching, the width in the lateral direction is larger, and the area of the thin plate portion 24 is closer to the area of the opening located at the lower end of the recess 20. Regarding the thin plate portion 24, there is a possibility of generating a stress difference between the pixels 7 due to deformation of the thin plate portion 24. Therefore, it is advantageous that the recess 20 is formed such that the entire pixel region 8 is within the range of the thin plate portion 24 corresponding to the curved portion.

[0167] Now, return to the description of the method for manufacturing the solid-state imaging device 1. Next, solder balls 12 are formed on the lower side of the solder resist 57 ( Figure 7 the upper side in A of), as shown in Figure 7 A of. The solder balls 12 are formed to be electrically connected to the planar wiring portion 56b of the copper wiring layer 56 through the pad opening 57a of the solder resist 57.

[0168] The following are two examples of the method for forming the solder balls 12. One example method includes using a method such as printing to selectively transfer a solder flux to the pad opening 57a of the solder resist 57; using a dedicated placement device to precisely place the solder balls 12 formed to a desired size; performing reflow at about 250°C to 260°C; and connecting the solder balls 12 to the copper wiring layer 56 through the pad opening 57a. Another example method includes using a method such as printing to selectively transfer a solder paste containing a solder flux to the pad opening 57a; performing reflow at about 250°C to 260°C to form the solder into a spherical shape; and connecting the solder used as the solder balls 12 to the copper wiring layer 56 through the pad opening 57a. In both methods, after forming the solder balls 12, cleaning is performed as needed to remove the solder flux.

[0169] After performing the above processes, cutting is performed along the designated cutting line L1. In other words, the process of cutting a set of silicon wafers 40, walls 44, and glass plates 43 into blocks such that the set of silicon wafers 40, walls 44, and glass plates 43 are divided into portions corresponding to the respective image sensors 2 along a specific setting.

[0170] By performing dicing, a group of silicon wafers 40 corresponding to the image sensor 2, glass plates 43 corresponding to the glass 3, walls 44 corresponding to the partition walls 4, etc. are divided. Using, for example, dedicated equipment, a plurality of chips (solid-state imaging devices 1) generated by performing dicing are picked up from the protective sheet 62. This makes it possible to obtain a plurality of solid-state imaging devices 1, each solid-state imaging device 1 having a package structure that includes an image sensor 2, glass 3, a partition wall 4, and a cavity 5 between the image sensor 2 and the glass 3, and the image sensor 2 includes a recess 20 formed on the back surface 2b side, as Figure 7 shown in B of

[0171] Note that in the above method for the solid-state imaging device 1, a method of forming the recess 20 in the silicon wafer 40 after the glass plate 43 is attached to the silicon wafer 40 is employed. However, the recess 20 can be formed before the glass plate 43 is attached to the silicon wafer 40. In this case, when performing anisotropic etching to form the recess 20, it is necessary to protect the pixel surface of the silicon wafer 40 with, for example, an alkali-resistant resist or film so that the pixel surface is not affected.

[0172] According to the solid-state imaging device 1 and the method for manufacturing the solid-state imaging device 1 according to the present embodiment as described above, the package structure having the cavity 5 between the image sensor 2 and the glass 3 makes it possible to prevent damage such as cracking of structural elements and detachment of bonded structural elements due to an increase in the internal pressure in the cavity 5 during, for example, reflow. Specifically, the following are the effects provided by the solid-state imaging device 1 and the method for manufacturing the solid-state imaging device 1 according to the present embodiment.

[0173] Here, as Figure 9 shown, a configuration in which the recess 20 is not formed in the semiconductor substrate 6 is assumed to be a configuration of a comparative example as compared with the solid-state imaging device 1 according to the present embodiment. In the configuration of the comparative example, the back surface 2b of the image sensor 2 is a flat surface that is completely parallel to the front surface 2a, and the image sensor 2 has a substantially uniform thickness.

[0174] In the configuration of the comparative example, due to the reflow performed for the solder balls 12, the internal pressure in the cavity 5 increases. This leads to the possibility that stress will concentrate on the weaker parts of the package structure, resulting in damage. Examples of the weaker parts include the joints of the partition wall 4 with the image sensor 2 and the glass 3, and the partition wall 4 itself. The following are the modes of damage to the package structure.

[0175] First, there is a mode in which the partition wall 4 detaches at the joint of the partition wall 4 with the image sensor 2 or the glass 3, that is, for example, in Figure 9detach from the portions indicated by the reference numerals M1 and M2 in []. A resin material is generally used as the material of the partition wall 4. Therefore, the image sensor 2 having the front surface 2a made of an inorganic film such as SiN or SiO 2 and the partition wall 4 detach from each other at their interface, or the glass 3 and the partition wall 4 detach from each other at their interface. When the partition wall 4 detaches, the internal pressure (reference numerals Q1 and Q2) in the cavity 5 is released from the detached portion.

[0176] In addition, there is a mode in which, for example, in the portion indicated by the reference numeral R1 in []. Figure 9 a crack 4X is generated in the partition wall 4. For example, when the partition wall 4 is made of a resin material, the material itself becomes brittle due to moisture absorption and high temperature, and cohesive failure occurs in the partition wall 4 itself due to the stress caused by the increase in the internal pressure in the cavity 5. If a crack 4X is generated in the partition wall 4, the internal pressure in the cavity 5 is released from the cracked portion (reference numeral S1). In addition, as a mode of damage, there may also be a mode obtained by combining the above-described detachment mode and the above-described mode of generating cracks.

[0177] If breakage occurs in the above mode, a gap connecting the cavity 5 to the outside will be generated, and this may cause moisture, dust, etc. to enter the cavity 5 through this gap. The moisture, dust, etc. that have entered the cavity 5 may cause a decrease in the image quality and performance of the solid-state imaging device 1. In addition, regarding the influence caused by the increase in the internal pressure in the cavity 5, the glass 3 may separate due to the breakage of the partition wall 4, or components themselves such as the image sensor 2 or the glass 3 may break. This may cause serious problems in terms of the reliability of the solid-state imaging device 1 itself.

[0178] Here, the phenomenon related to the increase in the internal pressure in the cavity 5 is described. In principle, in the manufacturing process, dry air is encapsulated in the cavity 5. Water vapor in the atmosphere before placing the glass plate 43, or water vapor that passes through the wall 44 itself after forming (sealing) the cavity 5, or water vapor that passes through the adhesive for bonding the wall 44 to the silicon wafer 40 and the glass plate 43, enters the cavity 5 at the same time.

[0179] It is known that the internal pressure P of the cavity 5 at normal room temperature 0 (hereinafter referred to as "the internal cavity pressure") is the sum of the dry air pressure P at room temperature A0 and the water vapor partial pressure P B0 , where P 0 = P A0 + P B0 (Dalton's law of partial pressures). It has been confirmed that when the temperature rises, according to the relationship regarding P A0the Boyle-Charles law and according to the Tetens law (Tetens equation) regarding P B0 generate different partial pressures at corresponding temperatures.

[0180] In Figure 9 the configuration of the comparative example shown, when the temperature (peak temperature T P : 240 °C to 260 °C) during reflow performed on, for example, a mother board increases, the respective partial pressures increase. Therefore, the internal pressure P P inside the cavity at the peak temperature T P may be greater than the damage limit pressure P D of the package structure. In this case, as described above, stress concentrates in the relatively weak part of the package structure and causes damage.

[0181] Specifically, the dry air pressure P A0 is inversely proportional to the volume of the cavity 5 (hereinafter referred to as "cavity volume") at each temperature. Therefore, when the temperature rises, the internal pressure P P inside the cavity is greater than the damage limit pressure P D , unless the cavity volume increases according to the temperature. In addition, according to the Tetens law, the water vapor partial pressure P B0 also tends to increase rapidly as the temperature rises. This accelerates the increase in the internal pressure of the cavity corresponding to the sum of P A0 and P B0 .

[0182] The solid-state imaging device 1 according to the present embodiment includes a package structure in the form of a diaphragm, and the package structure includes a recess 20 in the image sensor 2. This enables the cavity volume to increase due to the bending of the semiconductor substrate 6 when the internal pressure of the cavity increases. This makes it possible to suppress an excessive increase in the internal pressure of the cavity and thus prevent damage caused during reflow, such as cracking of components around the cavity 5 and detachment of bonded components.

[0183] Specifically, when the internal pressure of the cavity increases during reflow, pressure is applied to the front 2a side of the image sensor 2, as Figure 10 shown (reference arrow C1). The thin plate portion 24 formed due to the recess 20 is the main deforming portion in the image sensor 2, and due to the applied pressure, the thin plate portion 24 elastically deforms in a bent shape and expands outward (on the back 2b side). In other words, in the image sensor 2, the thin plate portion 24 is the main portion serving as a diaphragm portion having a restoring force, and this portion bends outward as the internal pressure of the cavity increases.

[0184] Since the image sensor 2 is deformed as described above to expand outward, the cavity volume can be increased as the internal pressure in the cavity increases during reflow. This makes it possible to suppress an excessive increase in the internal pressure of the cavity and thus prevent damage such as cracking of the structural elements of the solid-state imaging device 1 and detachment of the bonded structural elements. Therefore, a degradation in the performance of the solid-state imaging device 1 can be prevented.

[0185] In addition, in the solid-state imaging device 1 according to the present embodiment, the recess 20 is formed to have a rectangular shape in a plan view, and the image sensor 2 is formed to have a frame structure due to the recess 20. Compared with the case where the entire silicon substrate is simply thinned, this configuration makes it possible to define a portion that deforms and bends as the internal pressure of the cavity increases and maintain the strength of the structure. In addition, the original external dimensions of the image sensor 2 can be maintained, thereby preventing the external dimensions of the package structure from becoming larger.

[0186] Specifically, when the entire silicon substrate is simply thinned, the external terminals in the image sensor 2 are likely to move, and this may cause the structure to be unstable. In addition, there is also a problem that it is difficult to replace the existing structure. Therefore, a structure such as the solid-state imaging device 1 in which the silicon substrate is partially thinned due to the recess 20 according to the present embodiment can ensure structural stability. In addition, in this structure, there is a portion having the original thickness of the silicon substrate. Therefore, the existing structure can be easily replaced.

[0187] In addition, the thin plate portion 24, which is the main deformed portion in the image sensor 2, is an inward portion located in the peripheral portion where the solder balls 12 are provided. Therefore, for example, the contact portion for the solder balls 12 can be less affected by the deformation of the image sensor 2 due to an increase in the internal pressure of the cavity. This brings an advantage when, for example, the increase in the internal pressure of the cavity becomes larger than usual due to a large amount of moisture being sucked into the cavity 5, because it allows the thin plate portion 24 to bend and deform to a large extent.

[0188] In addition, in the solid-state imaging device 1 according to the present embodiment, there is no need to provide a portion communicating with the outside to the cavity 5 to prevent an increase in the internal pressure of the cavity. This makes it possible to prevent dust and the like from entering the cavity 5 as much as possible, thereby preventing performance degradation due to the influence of dust and the like on the image quality.

[0189] In addition, in the solid-state imaging device 1 according to the present embodiment, there is no need to change the structure in the cavity 5 to prevent an increase in the internal pressure of the cavity. Therefore, it is possible to prevent device failures or poor characteristics of the device due to detachment of a separate element such as a moisture absorption element in the cavity. In a configuration where a separate element is provided in the cavity, the device may malfunction or the device may exhibit poor characteristics.

[0190] Regarding the internal pressure of the cavity, the solid-state imaging device 1 according to the present embodiment is configured to satisfy the following conditions. In other words, the solid-state imaging device 1 is configured such that when performing reflow for the solder balls 12, the internal pressure P of the cavity at a specific peak temperature T P is less than the internal pressure, that is, the damage limit pressure P that causes cracking of the elements forming the cavity 5 or detachment of the bonding elements forming the cavity 5 P . D .

[0191] In other words, regarding the solid-state imaging device 1, the following conditions are satisfied. When the internal pressure of the cavity reaches the internal pressure P of the cavity at the peak temperature T P in the image sensor 2, the thin plate portion 24 formed by the concave portion 20 is deformed and bent due to the deformation, and the deformation causes an increase in the cavity volume. When V P represents the increased volume, and V 1 represents the original cavity volume (at room temperature), the cavity volume V 0 at the peak temperature T P is represented by V 2 +V 0 (V 1 =V 2 +V 0 ). In addition, the solid-state imaging device 1 is configured such that when the cavity volume reaches V 1 , the internal pressure P 2 of the cavity is less than the internal pressure of the cavity that causes any damage to the cavity structure at the temperature T 2 , that is, the damage limit pressure P D (P D <P 2 <P D ). As described above, the solid-state imaging device 1 is configured such that the effect of reducing the internal pressure of the cavity is provided by the semiconductor substrate 6 bent due to the concave portion 20

[0192] In addition, in the solid-state imaging device 1 according to the present embodiment, the concave portion 20 includes a bottom surface portion 21 and a side surface portion 22, and the side surface portion 22 has a curved shape formed by a first inclined surface 31 and a second inclined surface 32. The curved shape has a convex portion on the outside of the concave portion 20, and the curved shape is located on the left and right. This configuration enables the image sensor 2 to be stably deformed and bent while maintaining the strength of the image sensor 2 when the internal pressure of the cavity increases

[0193] In addition, in the solid-state imaging device 1 according to the present embodiment, the side surface portion 22 of the concave portion 20 is formed by the {111} plane in the silicon substrate. In other words, both the first inclined surface 31 and the second inclined surface 32 forming the side surface portion 22 have the {111} plane. This configuration enables the image sensor 2 to be stably deformed and bent while maintaining the strength of the image sensor 2 when the internal pressure of the cavity increases. In addition, the concave portion 20 can be easily formed, for example, by anisotropic etching using the crystal structure of the semiconductor substrate 6.

[0194] In addition, in the method for manufacturing the solid-state imaging device 1 according to the present embodiment, a two-stage etching process including a first etching process using dry etching and a second etching process using anisotropic etching is used as a method for forming the concave portion 20. This method enables precise control of, for example, the etching time in each etching process, the temperature of the etching solution in anisotropic etching, and the method of holding and swinging the substrate in the etching equipment, to obtain an accurate etching depth, that is, the accurate thickness of the target portion to be removed from the semiconductor substrate 6. In addition, as described above, by adjusting the depth of the semi-concave portion 20X formed by the first etching process, the bending shape formed by the first inclined surface 31 and the second inclined surface 32 included in the side surface portion 22 of the concave portion 20 can be controlled.

[0195] <3. Modification of the solid-state imaging device according to the first embodiment>

[0196] A modification of the solid-state imaging device 1 is described. The modification described below is a modification of the shape of the concave portion 20 in the cross-sectional view.

[0197] (First modification)

[0198] In the first modification, the concave portion 20A includes an opening shape along a rectangular shape in the side sectional view, as shown in A of Figure 11 In other words, the concave portion 20A of the first modification includes an inner surface 31A as a surface perpendicular to the bottom surface 23 of the bottom surface portion 21, as the surface forming the side surface portion 22. The upper end of the inner surface 31A is connected to the bottom surface 23 of the bottom surface portion 21 to form a right angle with the bottom surface 23. As described above, the concave portion 20A of the first modification is formed by a rectangular bottom surface 23 and inner surfaces 31A formed on each side of the bottom surface 23. For example, like in the above first etching process, the concave portion 20A of the first modification is formed by dry etching (e.g., RIE).

[0199] (Second modification)

[0200] In the second modification, the concave portion 20B includes an opening shape along a trapezoidal shape in the side sectional view, as shown in Figure 11As shown in FIG. B. In other words, the second modified recess 20B includes an inclined surface 31B as the surface forming the side surface portion 22, and the inclined surface 31B is a surface that is inclined in the left - right direction from the lower side to the upper side with respect to the vertical direction from the outside to the inside. The upper end of the inclined surface 31B is connected to the bottom surface 23 of the bottom surface portion 21 to form an obtuse - angled corner with the bottom surface 23. As described above, the second modified recess 20B is formed by a rectangular bottom surface 23 and inclined surfaces 31B formed on each side of the bottom surface 23. For example, as in the above - mentioned second etching process, the second modified recess 20B is formed by anisotropic etching utilizing the crystal structure of silicon.

[0201] These modified configurations can also prevent damage caused by an increase in the internal pressure of the cavity, such as cracking of structural elements and detachment of bonded structural elements. In other words, the shape of the recess 20 is not particularly limited. It is sufficient if the image sensor 2 can have a diaphragm structure including a portion that deforms and bends as the internal pressure of the cavity increases to prevent, for example, an excessive increase in the internal pressure of the cavity during reflow. In addition, each of the above - mentioned modified configurations enables the recesses 20A and 20B to be formed relatively easily by a single etching process.

[0202] <Configuration example of a solid - state imaging device according to the second embodiment>

[0203] The second embodiment of the present technology is described. Note that the same structural elements as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and their descriptions are appropriately omitted.

[0204] As Figure 12 and Figure 13 shown, the solid - state imaging device 51 according to the present embodiment includes a filling resin portion 70, which is a sealing resin portion provided in a state of being held in the recess 20. The filling resin portion 70 is provided so as to fill the recess 20 and is made of a thermoplastic resin. As described above, the filling resin portion 70 is a portion that deforms along with the semiconductor substrate 6 when the internal pressure of the cavity increases, for example, during reflow.

[0205] The filling resin portion 70 is formed to fill the recess 20 and includes a bottom surface 70a flush with the back surface 2b, and the bottom surface 70a is a flat portion located outside the recess 20 of the image sensor 2. In other words, the bottom surface 70a of the filling resin portion 70 faces the opening of the recess 20 on the back - surface 2b side of the image sensor 2 (refer to Figure 13 ).

[0206] Therefore, the filling resin portion 70 has an external shape that conforms to the surface shapes of the bottom surface portion 21 and the side surface portion 22 that form the concave portion 20, and has an overall external shape in the form of a flat plate. In other words, in the formation of the concave portion 20, in the form of a flat plate with a substantially constant thickness, the filling resin portion 70 has a shape that conforms to the portion removed from the image sensor 2 by etching.

[0207] Specifically, in addition to the bottom surface 70a, the filling resin portion 70 further includes an upper surface 71 that is the surface in contact with the bottom surface 23 of the concave portion 20, an upper inclined surface 72 that is the surface in contact with the second inclined surface 32, and a lower inclined surface 73 that is the surface in contact with the first inclined surface 31. Due to the filling resin portion 70 being embedded in the concave portion 20, the image sensor 2 and the filling resin portion 70 form an integrated plate-like body having a substantially constant thickness.

[0208] The filling resin portion 70 has the property of high elasticity at room temperature and enhances the strength of the image sensor 2 including the concave portion 20. In addition, since the filling resin portion 70 is thermoplastic, the filling resin portion 70 has the property of less elasticity at high temperatures (e.g., during reflow) and deforms along with the deformation of the image sensor 2 (e.g., the bending deformation of the thin plate portion 24) to avoid interfering with the deformation of the image sensor 2. Advantageously, for example, a thermoplastic resin that exhibits a Young's modulus of about 500 MPa to 1 GPa at room temperature and a Young's modulus of about 10 MPa to 100 MPa at high temperatures (e.g., during reflow) is used as the material for the filling resin portion 70 having the above properties.

[0209] Describe the material of the filling resin portion 70. As described above, a material having the property of maintaining strength when highly elastic at room temperature and having less elasticity at high temperatures to avoid deformation of the silicon substrate is used as the material for the filling resin portion 70. In addition, a paste material is used as the material for the filling resin portion 70 so that a printing process is applicable. Specifically, the following materials are used.

[0210] Advantageously, a paste composition containing one of a polyetherimide resin, a polyetheramide resin, and a polyetheramide-imide resin as a main component is used as the thermoplastic resin for the material of the filling resin portion 70.

[0211] Polyetherimide resins, polyetheramide resins, and polyetheramide-imide resins are materials obtained by adding the characteristics of flexible polyethers to thermoplastic resins (e.g., imide resins, amide resins, and amide-imide resins), and are widely used in, for example, parts subjected to thermal stress or connection parts of elements with different linear expansions. Advantageously, for example, the polyetheramide resin "HIMAL (trade name)" manufactured by Hitachi Chemical Co., Ltd. or a paste resin based on HIMAL is used as the thermoplastic resin for forming the filled resin portion 70.

[0212] In addition, the thermoplastic resin for forming the filled resin portion 70 may be a paste composition obtained by adding a plastic segment to one of a polyimide resin, a polyamide resin, and a polyamide-imide resin.

[0213] Specifically, for example, a material obtained by adding a soft segment of siloxane imide to a hard segment of an imide resin (aromatic polyimide) is used as the material for the filled resin portion 70. The hard segment has a structure with high elasticity and high heat resistance, and the soft segment has a structure with flexibility and low elasticity. Therefore, when the material obtained by adding siloxane imide to the imide resin is used as the material for the filled resin portion 70, as described above, it is possible to obtain a filled resin portion 70 having high elasticity, high heat resistance, flexibility, and low elasticity.

[0214] In addition, the thermoplastic resin for forming the filled resin portion 70 may be a paste composition that contains one of a polyimide resin, a polyamide resin, and a polyamide-imide resin as a main component and also contains thermoplastic resin particles.

[0215] Regarding such a paste composition, a resin filler having the property of being insoluble in a solvent at room temperature but soluble by heating is used to obtain a material in a paste form. Specifically, a material obtained by kneading a polyetheramide resin used as a matrix resin with a resin filler having a regulated elastic modulus can be used as the material for the filled resin portion 70. Such a material is used as a matrix paste, and for example, low-elasticity rubber particles are added as resin particles to the obtained material. The amount of the added low-elasticity rubber is adjusted so that the elastic modulus of the paste composition can be controlled. Here, advantageously, for example, the polyetheramide resin "HIMAL (trade name)" manufactured by Hitachi Chemical Co., Ltd. is used as the matrix resin.

[0216] In addition, a material obtained by adding a thermoplastic material (e.g., a polyamide silicone copolymer or a polyamide-imide silicone copolymer) or a material obtained by combining the obtained material with another material can be used as the material for the filled resin portion 70.

[0217] <5. Method for Manufacturing Solid-State Imaging Device of Second Embodiment>

[0218] Refer to Figure 14 and Figure 15 and describe an example of a method for manufacturing the solid-state imaging device 51 according to the second embodiment of the present technology. The method for manufacturing the solid-state imaging device 51 according to the present embodiment is different from the method for manufacturing the solid-state imaging device 1 according to the first embodiment in that it includes a process of forming a filled resin portion 70.

[0219] In other words, the method for manufacturing the solid-state imaging device 51 according to the present embodiment is a method obtained by including, in the above-described method for manufacturing the solid-state imaging device 1, a process of forming a filled resin portion 70 in the recess 20 by filling the recess 20 with a sealing resin 75 that is a thermoplastic resin. The filled resin portion 70 deforms as the semiconductor substrate 6 of the image sensor 2 is formed, and the process of forming the filled resin portion 70 is performed before the process of performing dicing to obtain individual chips.

[0220] Specifically, in the process of manufacturing the solid-state imaging device 51 according to the present embodiment, after performing the process of forming the recess 20 (refer to Figure 6 C), the process of forming the filled resin portion 70 is performed, as shown in Figure 14 A and B.

[0221] In this process, first, the sealing resin 75, which is the material of the filled resin portion 70, is printed using a printing machine including a squeegee 76, as shown in Figure 14 A. The sealing resin 75 is initially in a paste state and thus can be printed. For example, when the sealing resin 75 is printed using a printing machine, a template 77 made of a nickel alloy is used as a printing mask. A patterned opening 77a that coincides with the opening of the recess 20 is formed in the template 77.

[0222] In a state where each patterned opening 77a is aligned to coincide with a corresponding one of the recesses 20, the template 77 is set on the solder resist 57. When the squeegee 76 moves on the set template 77, the sealing resin 75 is filled into the recess 20 through the patterned opening 77a, and the surface of the sealing resin 75 is smoothed. Thereafter, the template 77 is removed, and then the printing of the sealing resin 75 is completed. Note that the method for printing the sealing resin 75 is not particularly limited, and any other method can be appropriately used.

[0223] After printing the sealing resin 75, baking is performed under specific temperature conditions so that the solvent evaporates from the paste-like sealing resin 75 and the sealing resin 75 is cured. The temperature for baking is appropriately set according to the sealing resin 75 and the solvent contained in the sealing resin 75. Further, for example, a hot plate or an oven is appropriately selected and used as a baking device as needed. When baking is performed, the sealing resin 75 in the recess 20 is cured and a filled resin portion 70 is formed, as shown in B of Figure 14 Note that the method for forming the filled resin portion 70 may be a method other than printing.

[0224] Thereafter, as in the first embodiment, solder balls 12 are formed on the lower side of the solder resist 57 (on the upper side of A of Figure 15 ), as shown in A of Figure 15 Then, cutting is performed along the designated cutting line L2. This makes it possible to obtain a plurality of solid-state imaging devices 51, each solid-state imaging device 51 having a package structure including an image sensor 2, a glass 3, a partition wall 4, and a cavity 5 between the image sensor 2 and the glass 3, and further including a filled resin portion 70 in the recess 20, the image sensor 2 including a recess 20 formed on the back surface 2b side, as shown in B of Figure 15 Note that the method for forming the filled resin portion 70 may be a method other than printing.

[0225] In addition to the effects provided by the solid-state imaging device 1 according to the first embodiment and the method for manufacturing the solid-state imaging device 1, the solid-state imaging device 51 according to the present embodiment and the method for manufacturing the solid-state imaging device 51 as described above provide the following effects.

[0226] In other words, since the solid-state imaging device 51 according to the present embodiment includes a filled resin portion 70 made of a thermoplastic resin in the recess 20, the stiffness of the package structure including the image sensor 2 thinned due to the recess 20 can be enhanced at room temperature, and an excessive increase in the internal pressure of the cavity at high temperature during reflow, for example, can be suppressed without disturbing the bending deformation of the image sensor 2 caused by the recess 20. This makes it possible to prevent damage to the package structure.

[0227] Specifically, when the internal pressure of the cavity increases during reflow, pressure is applied to the front surface 2a side of the image sensor 2, as shown in Figure 16 (reference arrow C2). In the image sensor 2, the thin plate portion 24 is the main portion serving as a diaphragm portion, and this portion bends outward as the internal pressure of the cavity increases due to the applied pressure.

[0228] Here, the filling resin portion 70 has thermoplasticity. Accordingly, the elastic modulus of the filling resin portion 70 decreases as the temperature rises, and the filling resin portion 70 deforms as the image sensor 2 deforms. In other words, the filling resin portion 70 does not interfere with the deformation of the image sensor 2. Therefore, as the image sensor 2 deforms and expands outward, the cavity volume can be increased, and thus an excessive increase in the internal pressure of the cavity that may cause damage to the package structure can be suppressed.

[0229] In addition, regarding the bending deformation of the image sensor 2 at high temperatures, the filling resin portion 70 serves as a buffer to receive the bending deformation of the image sensor 2. Accordingly, the stress applied to the thin plate portion 24 by the internal pressure of the cavity is released, and this makes it possible to suppress, for example, breakage such as cracking generated in the thin plate portion 24 or the partition wall 4 falling off.

[0230] In addition, even when the image sensor 2 is thinned by forming the recess 20 and processed into a diaphragm shape, sufficient impact resistance can be ensured due to the strong relative strength of silicon itself. However, in the case of a high-vibration environment in use or the like, the thin plate portion 24 vibrates due to the influence of vibration, and this may affect the imaging characteristics. The filling resin portion 70 is a portion that supports the thin plate portion 24 (thin portion) from the back side of the thin plate portion 24. Accordingly, the filling resin portion 70 makes it possible to suppress the vibration of the thin plate portion 24. This makes it possible to effectively maintain the imaging characteristics. In addition, the filling resin portion 70 makes it possible to prevent an external force applied to the thin plate portion 24 or an impact applied from the outside, thereby protecting the thin plate portion 24. In other words, the filling resin portion 70 makes it possible to improve the impact resistance of the thin plate portion 24.

[0231] However, since the filling resin portion 70 is provided in the recess 20, the original external dimensions of the image sensor 2 can be maintained, thereby preventing the external dimensions of the package structure from becoming large.

[0232] In addition, as in the case of the solid-state imaging device 1 according to the first embodiment, in the solid-state imaging device 51 according to the present embodiment, when performing reflow for the molten solder balls 12, the internal pressure P of the cavity at a specific peak temperature T P is less than the damage limit pressure P P which causes cracking of the elements forming the cavity 5 or the bonded elements forming the cavity 5 to fall off. D

[0233] In addition, in the solid-state imaging device 51 according to the present embodiment, since the bent shape of the side surface portion 22 formed by the first inclined surface 31 and the second inclined surface 32 is adopted as the shape of the concave portion 20, the side surface portion 22 serves as a stopper. This makes it possible to prevent the filling resin portion 70 from falling off or detaching. In other words, according to the concave portion 20 including the side surface portion 22 having a bent shape, the portion of the side surface portion 22 that forms a lateral V shape in the cross-sectional view (specifically, the inwardly protruding portion formed by the first inclined surface 31 and the back surface 2b and included in the edge of the opening) serves as a portion for locking the filling resin portion 70, and thus the filling resin portion 70 is held in the concave portion 20. This makes it possible to effectively prevent the filling resin portion 70 from falling off or separating from the concave portion 20.

[0234] In addition, in the present embodiment, in addition to the size of the thin plate portion 24 in the first embodiment, the degree of risk that the filling resin portion 70 may fall off or detach is a factor necessary for determining the etching depth of the semi-concave portion 20X formed by the first etching process in order to control the bent shape of the side surface portion 22 of the concave portion 20 formed by anisotropic etching. In other words, if the etching depth of the semi-concave portion 20X is deeper, when anisotropic etching is performed, the width in the lateral direction is larger (the lateral V shape in the cross-sectional view is larger). This makes it less likely that the filling resin portion 70 will fall off or detach.

[0235] In addition, in the solid-state imaging device 51 according to the present embodiment, laser marking can be performed on the filling resin portion 70.

[0236] <6. Modification of the method for manufacturing the solid-state imaging device according to the second embodiment>

[0237] Refer to Figures 17 to 19 A modification of the method for manufacturing the solid-state imaging device 51 is described. The manufacturing method according to the following modification is different from the above manufacturing method in that, first, the concave portion 20 and the filling resin portion 70 are formed, and then the copper wiring layer 56 of the through hole 13 and the like are formed.

[0238] Therefore, as in the above manufacturing method, in the manufacturing method according to this modification, first, the wall 44 corresponding to the partition wall 4 is formed on the silicon wafer 40 on which the pixels 7 are formed, and the glass plate 43 corresponding to the glass 3 is attached to the silicon wafer 40 (refer to Figure 3 A). Next, the protective sheet 50 is attached to the front surface 43a of the glass plate 43, and then the BG process of scraping the silicon wafer 40 from the back surface 40b side using the back grinding foil 58 is performed (refer to Figure 3 B). Then, the process of forming the first insulating film 52 such as a nitride film or an oxide film on the back surface 40b of the silicon wafer 40 is performed (refer to Figure 3 C). The subsequent processes are different from the above manufacturing method.

[0239] In the following process, first, patterning is performed on the first insulating film 52 by a photolithography process, as shown in A of Figure 17 . In this process, a photoresist 153 is used for patterning. A technique such as RIE is used to partially remove the first insulating film 52 so that an opening 52b for thinning the silicon wafer 40 to form the recess 20 is formed in the first insulating film 52. As described above, in the patterning process, the following processes are performed in a specific order: applying the photoresist 153 and drying the applied photoresist 153, performing partial removal, performing plasma cleaning, etc. Here, with respect to the photoresist 153, a part of the opening 153a corresponding to the part where the recess 20 is formed is removed. Note that it is advantageous for the photoresist 153 to have strong alkali resistance because a strong alkali solution is used when forming the recess 20.

[0240] Next, in the same manner as the above manufacturing method, a process of forming the recess 20 on the back side 40b of the silicon wafer 40 is performed by a two-stage etching process including a first etching process and a second etching process.

[0241] In other words, a semi-recess 20X is formed by dry etching (e.g., RIE), as shown in B of Figure 17 . Thereafter, a protective sheet 62 is attached to the front surface 43a of the glass plate 43, as shown in C of Figure 17 , and the recess 20 is formed by anisotropic etching using a strong alkali solution (e.g., KOH). After performing the anisotropic etching, unnecessary portions of the photoresist 153 are removed.

[0242] Next, in the same manner as the above manufacturing method, a process of forming the filled resin portion 70 is performed. In other words, first, using a template 77 including a patterned opening 77a, a paste-like sealing resin 75 is printed using a printing press including a squeegee 76, as shown in A of Figure 18 . Here, for example, the template 77 is set to be slightly away from the first insulating film 52 in order to protect the first insulating film 52. After printing the sealing resin 75, baking is performed to form the filled resin portion 70 in the recess 20, as shown in B of Figure 18 .

[0243] Next, patterning is performed on the first insulating film 52 by a photolithography process, as shown in B of Figure 18 . In this process, a photoresist 154 is used for patterning. A technique such as RIE is used to partially remove the first insulating film 52 so that an opening 52a for a fine pattern is formed in the first insulating film 52, and the opening 52a is for opening the perforation 40c of the through hole 13 (refer to Figure 18In C), the through hole 13 is formed to pass through the silicon wafer 40 from the back surface 40b side of the silicon wafer 40 to reach the electrode pad 11. In other words, in this process, patterning is performed using photolithography technology to form a photoresist 154 on the first insulating film 52, so that an opening 154a continuous with the opening 52a is formed.

[0244] After that, etching is performed to form a perforation 40c in the silicon wafer 40 through the opening 52a of the first insulating film 52 and the opening 154a of the photoresist 154, as Figure 18 shown in C of. Here, DRIE is used for etching as described above. Therefore, a photoresist 154 having a high impedance to plasma is used. After the perforation 40c is formed, the photoresist 154 is removed.

[0245] Next, in the same manner as the above manufacturing method, a second insulating film 55 corresponding to the insulating film 15 in the solid-state imaging device 51, a copper wiring layer 56 corresponding to the wiring layer 14 in the solid-state imaging device 51, and a solder resist 57 for providing the solder ball 12 are sequentially formed.

[0246] In other words, first, a second insulating film 55 covering the inner surface of the perforation 40c and including a contact hole 55a and an opening 55b corresponding to the opening of the recess 20 is formed, as Figure 19 shown in A of. Next, a copper wiring layer 56 including an in-hole wiring portion 56a and a planar wiring portion 56b formed along the back surface 40b is formed by electroplating, as Figure 19 shown in B of. Next, a solder resist 57 including a pad opening 57a is formed, as Figure 19 shown in C of.

[0247] Then, in the same manner as the above manufacturing method, the solder ball 12 is formed, and then cutting is performed along a specified cutting line L2 (refer to Figure 15 A of). This forms the recess 20 in the solid-state imaging device 51, and a plurality of solid-state imaging devices 51 are obtained, each solid-state imaging device 51 including a filled resin portion 70 in the recess 20 (refer to Figure 15 B of).

[0248] <7. Configuration example of the solid-state imaging device according to the third embodiment>

[0249] The third embodiment of the present technology is described. Note that structural elements identical to those in the first and second embodiments are denoted by the same reference numerals as in the first and second embodiments, and their descriptions are appropriately omitted.

[0250] As Figure 20 and Figure 21As shown, the solid-state imaging device 81 according to the present embodiment includes a plurality of solder balls 82 provided on the bottom surface 70a side of the surface of the filling resin portion 70. The solder balls 82 are solder portions for mounting the image sensor 2.

[0251] In the present embodiment, the plurality of solder balls 82 are two-dimensionally arranged in an array on the bottom surface 70a side of the filling resin portion 70. In other words, compared with the solid-state imaging device 51 according to the second embodiment, the solid-state imaging device 81 according to the present embodiment includes a plurality of solder balls 82 arranged in an array on the surface side of the filling resin portion 70, rather than a plurality of solder balls 12 provided in the peripheral portion on the back surface 2b side of the image sensor 2. However, the plurality of solder balls 82 may be provided together with the plurality of solder balls 12. In addition, Figure 21 The arrangement of the solder balls 82 is schematically shown, and in Figure 21 the example shown, the solder balls 82 are arranged in a matrix with a four-row and four-column arrangement.

[0252] In order to provide the solder balls 82 on the bottom surface 70a side of the filling resin portion 70, it is necessary to form a wiring layer 14 led out from the electrode pad 11, a pad portion for placing the solder balls 82, and a solder resist 16 for defining the placement position of the solder balls 12 on the filling resin portion 70, as in the case of the substrate portion of the semiconductor substrate 6. In addition, when the solder balls 12 are provided on the surface of the semiconductor substrate 6, it is necessary to form an insulating film 15 (e.g., an oxide film or a nitride film) so that the wiring layer 14 does not directly contact the silicon substrate. Since the thermoplastic resin for manufacturing the filling resin portion 70 naturally has good insulating properties, the wiring layer 14 can be directly formed on the filling resin portion 70.

[0253] Therefore, in the solid-state imaging device 81 according to the present embodiment, a resin-on-wiring portion 14c is provided on the bottom surface 70a of the filling resin portion 70 as a part of the wiring layer 14. The resin-on-wiring portion 14c is directly formed on the filling resin portion 70 without an insulating film such as an oxide film or a nitride film. For example, the resin-on-wiring portion 14c is formed in a grid pattern corresponding to the layout of the solder balls 82 arranged in an array. Specifically, in Figure 20 the cross-sectional view shown, the solid-state imaging device 81 includes solder balls 82A and 82B as the solder balls 82. The solder ball 82A is provided on an extension portion 14d where the planar wiring portion 14b extends to be provided on the filling resin portion 70, and in the cross-sectional view, the solder ball 82B is provided on the resin-on-wiring portion 14c existing on the filling resin portion 70 as an independent portion.

[0254] In addition, the solid-state imaging device 81 according to the present embodiment includes a resin covering portion 16c in the solder resist 16, and the resin covering portion 16c is formed to cover the bottom surface 70a of the filling resin portion 70.

[0255] The solid-state imaging device 81 according to the present embodiment is formed into a WCSP structure having the following configuration. In other words, the solid-state imaging device 81 includes a semiconductor substrate 6, a filling resin portion 70, a wiring layer 14, solder balls 82, a partition wall 4, and glass 3. A recess 20 is formed on the back side of the semiconductor substrate 6, and an image sensor element is formed on the front side of the semiconductor substrate 6. The filling resin portion 70 is filled into the recess 20 and formed flush with the back surface 2b. Due to the formation of the filling resin portion 70, the semiconductor substrate 6 has the same dimensions as its original external dimensions. The wiring layer 14 is connected to the electrode pad 11 and is provided to extend onto the filling resin portion 70. On the filling resin portion 70, the solder balls 82 are formed on the wiring layer 14 through a pad portion (not shown). The partition wall 4 is formed to surround the image sensor element of the semiconductor substrate 6 and isolates the space above the portion where the image sensor element is formed from the outside and serves as a cavity 5. The glass 3 is bonded to the partition wall 4.

[0256] <8. Method for manufacturing a solid-state imaging device according to the third embodiment>

[0257] Refer to Figure 22 and Figure 23 An example of a method for manufacturing the solid-state imaging device 81 according to the third embodiment of the present disclosure is described. The method for manufacturing the solid-state imaging device 81 according to the present embodiment is different from the above-described modification of the method for manufacturing the solid-state imaging device 51 according to the second embodiment in that it includes a process of providing the solder balls 82 on the filling resin portion 70.

[0258] In other words, the method for manufacturing the solid-state imaging device 81 according to the present embodiment includes a process of placing the solder balls 82 on the surface side (bottom surface 70a side) of the filling resin portion 70, the solder balls 82 being for mounting the image sensor 2, and the process of placing the solder balls 82 is performed before the process of performing dicing to obtain individual chips.

[0259] Regarding the process before the process of forming the second insulating film 55 that covers the inner surface of the through-hole 40c and includes the contact hole 55a and the opening 55b corresponding to the recess 20, the method for manufacturing the solid-state imaging device 81 according to the present embodiment is the same as the modification of the method for manufacturing the solid-state imaging device 51 according to the second embodiment described above.

[0260] After forming the second insulating film 55, a copper wiring layer 56 corresponding to the wiring layer 14 in the solid-state imaging device 81 is formed on the back side 40b of the silicon wafer 40, as Figure 22 shown in A. The copper wiring layer 56 is for forming the solder balls 82 on the back side 40b of the silicon wafer 40 in the WCSP structure.

[0261] In other words, in the solid-state imaging device 81 according to the present embodiment, the copper wiring layer 56 extends from the back surface of the electrode pad 11 to pass through the through hole 40c, and the solder ball 82 is connected to the extended portion of the copper wiring layer 56. The copper wiring layer 56 includes an in-hole wiring portion 56a corresponding to the in-hole wiring portion 14a (refer to Figure 20 ), a planar wiring portion 56b formed along the back surface 40b and corresponding to the planar wiring portion 14b including the extended portion 14d (refer to Figure 20 ), and a resin-on wiring portion 56c corresponding to the resin-on wiring portion 14c (refer to Figure 20 ), so that the solder ball 82 is provided on the lower side of the resin filling portion 70. The copper wiring layer 56 is formed by, for example, electroplating as described above.

[0262] Next, a process of forming the solder resist 57 including the pad opening 57a is performed, as shown in B of Figure 22 . The solder resist 57 is formed to prevent a short circuit from occurring in the wiring of the copper wiring layer 56 and to define the position where the solder ball 82 is placed. In the solder resist 57, the pad opening 57a exposing the copper wiring layer 56 is formed in the portion where the solder ball 82 is placed, so that the pad opening 57a fits the size of the solder ball 82.

[0263] In the present embodiment, the solder resist 57 is also formed on the bottom surface 70a of the resin filling portion 70, thereby forming a portion corresponding to the resin covering portion 16c in the solder resist 16 of the solid-state imaging device 81. The pad opening 57a is formed at a position corresponding to each resin-on wiring portion 56c.

[0264] Thereafter, corresponding to the planar wiring portion 56b and the resin-on wiring portion 56c, the solder balls 82 are formed in the region on the resin filling portion 70 located on the lower side of the solder resist 57 (the upper side in A of Figure 23 ), as shown in A of Figure 23 . The solder balls 82 are formed in a manner similar to the solder balls 12 in the above manufacturing method.

[0265] After the solder balls 82 are formed, cutting is performed along the designated cutting line L3. This results in obtaining a plurality of solid-state imaging devices 81, each solid-state imaging device 81 having a package structure including the image sensor 2, the glass 3, the partition wall 4, and the cavity 5 between the image sensor 2 and the glass 3, and further including the resin filling portion 70 in which the solder balls 82 are placed in the recess 20. The image sensor 2 includes the recess 20 formed on the back surface 2b side, as shown in B of Figure 23 .

[0266] In addition to the effects provided by the solid-state imaging device 1 according to the first embodiment and the method for manufacturing the solid-state imaging device 1, the solid-state imaging device 81 according to the present embodiment and the method for manufacturing the solid-state imaging device 81 as described above provide the following effects.

[0267] In other words, since the solid-state imaging device 81 according to the present embodiment includes the filling resin portion 70 made of a thermoplastic resin in the recess 20, the encapsulation structure can be strengthened at room temperature and an excessive increase in the internal pressure of the cavity at high temperatures can be suppressed, as in the case of the solid-state imaging device 51 according to the second embodiment.

[0268] Specifically, when the internal pressure of the cavity increases during reflow, the pressure is applied to the front surface 2a side of the image sensor 2 (refer to arrow C3), and in the image sensor 2, the thin plate portion 24 is the main portion that bends outward as the internal pressure of the cavity increases, as Figure 24 shown. Here, the thermoplasticity of the filling resin portion 70 enables an increase in the cavity volume without disturbing the deformation of the image sensor 2, thereby suppressing an excessive increase in the internal pressure of the cavity that may cause damage to the encapsulation structure.

[0269] Furthermore, in the solid-state imaging device 81 according to the present embodiment, as in the case of the solid-state imaging device 1 according to the first embodiment, when performing reflow for melting the solder balls 82, the internal pressure P P of the cavity at a specific peak temperature T P is less than the damage limit pressure P D that causes cracking of the elements forming the cavity 5 or detachment of the bonding elements forming the cavity 5.

[0270] In addition, due to the fact that the speed of signals has become faster and signals have multiple functions, recent image sensors tend to process a large number of signals. The solid-state imaging device 81 according to the present embodiment enables, for example, arranging the solder balls 82 in an array on the filling resin portion 70, and thus it is easy to ensure the number of solder balls 82.

[0271] Furthermore, since the solder balls 82 are provided on the filling resin portion 70 formed of a thermoplastic resin, the solid-state imaging device 81 according to the present embodiment enables reducing the pressure caused by temperature cycling associated with mounting the solid-state imaging device 81 on a substrate. This enables preventing fatigue failure of the solder balls 82 and suppressing connection failure caused in the region around the solder balls 82. In other words, since the filling resin portion 70 serves as a pressure buffer layer under temperature cycling, an effect of extending the life of the joints produced using the solder balls 82 is expected, and this enables improving the reliability regarding the mounting of the solid-state imaging device 81.

[0272] Generally, the pressure buffer layer is formed of a pressure buffer layer having a thickness, for example, of about 50 μm to 80 μm overlapping the chip of the image sensor 2. This results in an increase in the thickness of the package structure, thereby preventing the package structure from thinning. In this regard, the solid-state imaging device 81 according to the present embodiment enables the filling resin portion 70 to be used as a pressure buffer layer to which pressure is applied to the solder balls 82 without increasing the thickness of the image sensor 2.

[0273] Reference Figure 24 A detailed description of the improvement in mounting reliability provided by the solid-state imaging device 81 according to the present embodiment is given below. The following are the phenomena that may occur under temperature cycling: Thermal strain caused by the difference in the linear expansion coefficients between the package structure of the solid-state imaging device 81 and the mounting substrate 90 on which the solid-state imaging device 81 is mounted using the solder balls 82 is concentrated on the solder balls 82, and this may cause fatigue failure at the joints formed using the solder balls 82. Here, the mounting substrate 90 is made of an organic material such as plastic, ceramic, etc., for example. Specifically, for example, the mounting substrate 90 has a structure in which copper wiring is provided to glass epoxy resin.

[0274] First, during reflow, the linear expansion coefficient of the package itself of the solid-state imaging device 81 is considered to be constant. On the other hand, generally, the linear expansion coefficient of the mounting substrate 90 is greater than that of silicon, and the mounting substrate 90 expands greatly at high temperatures because the mounting substrate 90 is made of an organic material.

[0275] After the solid-state imaging device 81 is mounted on the mounting substrate 90, the mounting substrate 90 attempts to return to its original state. Therefore, a residual pressure is generated in the direction in which the mounting substrate 90 contracts (refer to arrow U1). Here, the pressure applied to the area around the solder balls 82 is partially absorbed and reduced by the filling resin portion 70 serving as a pressure buffer layer.

[0276] In addition, the mounting substrate 90 attempts to further contract in the mounted state in a low-temperature environment. Therefore, the residual pressure increases. In this case, the pressure is also absorbed by the filling resin portion 70 serving as a pressure buffer layer. On the other hand, the mounting substrate 90 attempts to expand in the mounted state in a high-temperature environment. Therefore, the residual pressure decreases.

[0277] As described above, the pressure applied to the area around the solder balls 82 in each state is mainly the residual pressure caused by the package itself of the solid-state imaging device 81 and the mounting substrate 90. In the solid-state imaging device 81 according to the present embodiment, the pressure caused under temperature cycling is propagated from the mounting substrate 90 to the filling resin portion 70 through the solder balls 82 and the pad portions, and is finally absorbed by the filling resin portion 70. Therefore, fatigue failure of the solder balls 82 can be prevented, and the mounting reliability of the solid-state imaging device 81 can be improved.

[0278] <9. Configuration Example of Electronic Device>

[0279] Use Figure 25 An example of applying the solid-state imaging device according to the above-described embodiment to an electronic device is described. Note that, here, an example of applying the solid-state imaging device 1 according to the first embodiment is described.

[0280] The solid-state imaging device 1 can generally be applied to an electronic device that uses a solid-state imaging element for an image-capturing section (photoelectric converter), such as an image-capturing device such as a digital camera or a video camera, a portable terminal device including an imaging function, and a copying machine that uses a solid-state imaging element for an image reader. The solid-state imaging element can be formed as a single chip, or can have a form of a module that includes an imaging function and in which an imaging section and a signal processor or an optical system are packaged together.

[0281] As Figure 25 shown, an image-capturing device 200 as an electronic device includes an optical section 202, a solid-state imaging device 1, a digital signal processor (DSP) circuit 203 as a camera signal processing circuit, a frame memory 204, a display section 205, a recording section 206, an operation section 207, and a power supply section 208. The DSP circuit 203, the frame memory 204, the display section 205, the recording section 206, the operation section 207, and the power supply section 208 are interconnected via a bus.

[0282] The optical section 202 includes a plurality of lenses and captures incident light (image light) from an object to form an image of the incident light on the imaging surface of the solid-state imaging device 1. The solid-state imaging device 1 converts the amount of incident light of the image formed on the imaging surface by the optical section 202 into an electrical signal in units of pixels and outputs the electrical signal as a pixel signal.

[0283] The display section 205 is, for example, a panel display device such as a liquid crystal panel or an organic electroluminescence (EL) panel, and displays a moving image or a still image captured by the solid-state imaging device 1 thereon. The recording section 206 records a moving image or a still image captured by the solid-state imaging device 1 on a recording medium such as a hard disk or a semiconductor memory.

[0284] The operation section 207 issues operation commands for various functions of the image-capturing device 200 in response to operations performed by a user. The power supply section 208 supplies power to each of the DSP circuit 203, the frame memory 204, the display section 205, the recording section 206, and the operation section 207 as needed, and the supplied power is used to operate these power supply targets.

[0285] The above-described image capturing device 200 enables prevention of damage in the solid-state imaging device 1 due to, for example, an increase in the internal pressure of the cavity during reflow, such as cracking of structural elements and detachment of bonded structural elements. This enables acquisition of high-quality captured images.

[0286] The description of the above embodiments is an example of the present technology, and the present technology is not limited to the above embodiments. Therefore, of course, even in the case of an embodiment different from the above embodiments, various modifications can be made according to the design, etc., without departing from the technical idea according to the present disclosure. In addition, the effects described in the present disclosure are not restrictive but merely illustrative, and other effects can be provided. Further, the modifications described in the above respective embodiments can be appropriately combined in an embodiment different from the above respective embodiments.

[0287] In the above embodiment, the package structure including the image sensor 2 has been described as an example. However, the present technology is applicable to any configuration having a hollow package structure. In other words, applying the present technology to a device configuration having a hollow package structure enables acquisition of an inexpensive and highly reliable package structure without changing the original package size.

[0288] Note that the present technology can adopt the following configuration.

[0289] (1) A solid-state imaging device, comprising:

[0290] A solid-state imaging element including a semiconductor substrate, and a light-receiving side of the solid-state imaging element is one plate surface side of the semiconductor substrate;

[0291] A light-transmitting cover element provided on the light-receiving side of the solid-state imaging element at a specific interval from the solid-state imaging element; and

[0292] A support member provided on the light-receiving side of the solid-state imaging element and supporting the cover element on the solid-state imaging element to form a cavity between the solid-state imaging element and the cover element, the semiconductor substrate including a recess formed on the other plate surface of the semiconductor substrate, and the semiconductor substrate having a thickness partially reduced due to the formation of the recess.

[0293] (2) The solid-state imaging device according to (1), further comprising

[0294] A filling resin portion made of a thermoplastic resin and provided to be filled into the recess, the filling resin portion deforming along with the semiconductor substrate.

[0295] (3) The solid-state imaging device according to (2), further comprising

[0296] A solder portion provided on the surface side of the filling resin portion and used for mounting the solid-state imaging element.

[0297] (4) The solid-state imaging device according to (2) or (3), wherein,

[0298] The thermoplastic resin is a paste composition containing, as a main component, one of a polyetherimide resin, a polyetheramide resin, and a polyetheramide-imide resin.

[0299] (5) The solid-state imaging device according to (2) or (3), wherein,

[0300] The thermoplastic resin is a paste composition obtained by adding a plastic segment to one of a polyimide resin, a polyamide resin, and a polyamide-imide resin.

[0301] (6) The solid-state imaging device according to (2) or (3), wherein,

[0302] The thermoplastic resin is a paste composition containing, as a main component, one of a polyimide resin, a polyamide resin, and a polyamide-imide resin, and further containing thermoplastic resin particles.

[0303] (7) The solid-state imaging device according to any one of (1) to (6), wherein,

[0304] The recess includes a bottom face portion substantially parallel to the plate surface of the semiconductor substrate and a side face portion forming the inner surface of the recess, and

[0305] The side face portion includes a first inclined surface and a second inclined surface. The first inclined surface is inclined in a specific direction with respect to the plate surface of the semiconductor substrate, and the second inclined surface forms a curved shape with the first inclined surface in a cross-sectional view of the semiconductor substrate.

[0306] (8) The solid-state imaging device according to any one of (1) to (6), wherein,

[0307] The recess includes a bottom face portion substantially parallel to the plate surface of the semiconductor substrate and a side face portion forming the inner surface of the recess, and

[0308] The side face portion includes the (111) plane or an equivalent crystal plane of the semiconductor substrate.

[0309] (9) The solid-state imaging device according to any one of (1) to (8), further comprising

[0310] A solder portion provided on the other plate surface of the semiconductor substrate and used for mounting the solid-state imaging element, wherein,

[0311] When performing reflow for melting the solder portion, at a specific peak temperature, the internal pressure inside the cavity is less than the internal pressure that causes cracking of the element forming the cavity or detachment of the bonding element forming the cavity.

[0312] (10) An electronic device, comprising

[0313] A solid-state imaging device, comprising

[0314] a solid-state imaging element including a semiconductor substrate, and a light-receiving side of the solid-state imaging element being one plate surface side of the semiconductor substrate;

[0315] a light-transmitting cover element provided on the light-receiving side of the solid-state imaging element and spaced apart from the solid-state imaging element by a specific interval; and

[0316] a support member provided on the light-receiving side of the solid-state imaging element and supporting the cover element on the solid-state imaging element to form a cavity between the solid-state imaging element and the cover element, the semiconductor substrate including a recess formed on the other plate surface of the semiconductor substrate, and the semiconductor substrate having a thickness partially reduced due to the formation of the recess.

[0317] (11) A method of manufacturing a solid-state imaging device, the method comprising:

[0318] providing a light-transmitting plate material on one plate surface side of a semiconductor wafer through a wall and spaced apart from the semiconductor wafer by a specific interval, the semiconductor wafer being a semiconductor wafer on which a set of pixels is formed on one plate surface side, the semiconductor wafer being a semiconductor wafer in which a plurality of portions each being a solid-state imaging element are formed in a specific arrangement, and the wall being formed along the specific arrangement to surround the pixel group;

[0319] forming a recess on the other plate surface of the semiconductor wafer corresponding to the solid-state imaging element, the semiconductor wafer having a thickness partially reduced due to the formation of the recess; and

[0320] cutting a set of semiconductor wafers, the wall, and the plate material into blocks such that the set of semiconductor wafers, the wall, and the plate material are divided along the specific arrangement into portions corresponding to respective solid-state imaging elements.

[0321] (12) The method of manufacturing a solid-state imaging device according to (11), wherein

[0322] forming the recess includes

[0323] performing a first etching including forming a semi-recess by removing a portion corresponding to the recess from the semiconductor wafer using dry etching, and

[0324] performing a second etching including, after the first etching, etching the semi-recess downward using anisotropic etching to form the recess.

[0325] (13) The method of manufacturing a solid-state imaging device according to (11) or (12), further comprising

[0326] Before cutting the group of semiconductor wafers, walls, and plate materials into pieces, a filling resin portion is formed in the recesses by filling the recesses with a thermoplastic resin, and the filling resin portion is deformed as the semiconductor substrate on which the solid-state imaging device is formed.

[0327] (14) The method of manufacturing a solid-state imaging device according to (13) further includes

[0328] Before cutting the group of semiconductor wafers, walls, and plate materials into pieces, a solder portion is placed on the surface side of the filling resin portion, and the solder portion is used for mounting the solid-state imaging device.

[0329] List of reference numerals

[0330] 1 Solid-state imaging device

[0331] 2 Image sensor (solid-state imaging device)

[0332] 2a Front side

[0333] 2b Back side

[0334] 3 Glass (cover element)

[0335] 4 Partition wall (support)

[0336] 5 Cavity

[0337] 6 Semiconductor substrate

[0338] 7 Pixel

[0339] 8 Pixel area

[0340] 14 Wiring layer

[0341] 20 Recess

[0342] 20X Semi-recess

[0343] 21 Bottom surface portion

[0344] 22 Side surface portion

[0345] 31 First inclined surface

[0346] 32 Second inclined surface

[0347] 40 Silicon wafer (semiconductor wafer)

[0348] 43 Glass plate (plate material)

[0349] 44 Wall

[0350] 51 Solid-state imaging device

[0351] 70 Filling resin portion

[0352] 70a bottom surface

[0353] 75 Sealing resin

[0354] 81 Solid-state imaging device

[0355] 82 Solder ball (solder portion)

[0356] 200 Image capturing device (electronic device).

Claims

1. A solid-state imaging device, comprising: a solid-state imaging element including a semiconductor substrate, and a light-receiving side of the solid-state imaging element being one plate surface side of the semiconductor substrate; a light-transmitting cover element disposed on the light-receiving side of the solid-state imaging element at a specific interval from the solid-state imaging element; and a support member disposed on the light-receiving side of the solid-state imaging element and supporting the cover element on the solid-state imaging element to form a cavity between the solid-state imaging element and the cover element, the semiconductor substrate including a recess formed on the other plate surface of the semiconductor substrate, and a thickness of the semiconductor substrate being partially reduced due to the formation of the recess; the recess having a thin plate portion that bends outward as an internal pressure of the cavity increases; a filling resin portion made of a thermoplastic resin, and the filling resin portion being disposed to fill the recess, wherein a bottom surface of the filling resin portion is flush with the other plate surface of the semiconductor substrate, has an external shape that conforms to a surface shape of a bottom surface portion and a side surface portion of the recess, and the filling resin portion deforms along with the semiconductor substrate; a plurality of solder portions arranged in an array on a bottom surface side of the filling resin portion and for mounting the solid-state imaging element, rather than disposing the plurality of solder portions at a peripheral portion of the recess on the other plate surface of the semiconductor substrate; when performing reflow for melting the solder portions, an internal pressure of the cavity at a specific peak temperature is less than an internal pressure that causes cracking of an element forming the cavity or detachment of a bonding element forming the cavity; wherein forming the recess includes: performing a first etching, including forming a semi-recess having a square shape with a predetermined etching depth by removing a portion corresponding to the recess from the semiconductor substrate using dry etching, a depth of the semi-recess being determined according to a desired shape of a side surface portion of the recess, and performing a second etching, including etching the semi-recess downward using anisotropic etching after the first etching to form the recess, wherein by immersing a wafer on which the semi-recess is formed in a strong alkali solution and etching for a specific period of time while rotating and swinging the wafer so that etching is uniformly performed on a wafer surface, etching is inclined inward from a bottom of the semi-recess to form a first inclined surface and a second inclined surface having a specific inclination angle, so that a shape and dimensions of the recess are controlled.

2. The solid-state imaging device according to claim 1, wherein, the thermoplastic resin is a paste composition, and the paste composition contains one of a polyetherimide resin, a polyetheramide resin, and a polyetheramide-imide resin as a main component.

3. The solid-state imaging device according to claim 1, wherein, the thermoplastic resin is a paste composition obtained by adding a plasticizable segment to one of a polyimide resin, a polyamide resin, and a polyamide-imide resin.

4. The solid-state imaging device according to claim 1, wherein, The thermoplastic resin is a paste composition, which contains one of a polyimide resin, a polyamide resin, and a polyamide-imide resin as a main component, and also contains thermoplastic resin particles.

5. The solid-state imaging device according to claim 1, wherein, the recess includes a bottom surface portion parallel to the plate surface of the semiconductor substrate and a side surface portion forming the inner surface of the recess, and the side surface portion includes a first inclined surface and a second inclined surface. The first inclined surface is inclined in a specific direction with respect to the plate surface of the semiconductor substrate, and the second inclined surface forms a curved shape with the first inclined surface in a cross-sectional view of the semiconductor substrate.

6. The solid-state imaging device according to claim 1, wherein, the recess includes a bottom surface portion parallel to the plate surface of the semiconductor substrate and a side surface portion forming the inner surface of the recess, and the side surface portion includes the (111) plane or an equivalent crystal plane of the semiconductor substrate.

7. An electronic device, comprising a solid-state imaging device, including: a solid-state imaging element including a semiconductor substrate, and a light-receiving side of the solid-state imaging element being one plate surface side of the semiconductor substrate; a light-transmitting cover element provided on the light-receiving side of the solid-state imaging element at a specific interval from the solid-state imaging element; and a support member provided on the light-receiving side of the solid-state imaging element and supporting the cover element on the solid-state imaging element to form a cavity between the solid-state imaging element and the cover element. The semiconductor substrate includes a recess formed on the other plate surface of the semiconductor substrate, and the thickness of the semiconductor substrate is partially reduced due to the formation of the recess; the recess has a thin plate portion that bends outward as the internal pressure of the cavity increases; a filling resin portion made of a thermoplastic resin, and the filling resin portion is provided to fill the recess. Wherein, the bottom surface of the filling resin portion is flush with the other plate surface of the semiconductor substrate and has an external shape consistent with the surface shapes of the bottom surface portion and the side surface portion forming the recess, and the filling resin portion deforms along with the semiconductor substrate; a plurality of solder portions arranged in an array on the bottom surface side of the filling resin portion and used for mounting the solid-state imaging element, rather than arranging the plurality of solder portions at the peripheral portion of the recess on the other plate surface of the semiconductor substrate; when performing reflow for melting the solder portions, the internal pressure of the cavity at a specific peak temperature is less than the internal pressure that causes cracking of the elements forming the cavity or detachment of the bonding elements forming the cavity; wherein, forming the recess includes: performing a first etching, including forming a semi-recess having a square shape with a predetermined etching depth by removing a portion corresponding to the recess from the semiconductor substrate using dry etching. The depth of the semi-recess is determined according to the desired shape of the side surface portion of the recess, and Perform a second etching, including forming the recess by anisotropically etching downward the semi-recess after the first etching, wherein, by immersing the wafer on which the semi-recess is formed in a strong alkali solution and rotating and swinging the wafer so that etching is uniformly performed on the wafer surface, etching is performed for a specific period of time, etching is inclined inward from the bottom of the semi-recess to form a first inclined surface and a second inclined surface having a specific inclination angle, so that the shape and size of the recess are controlled.

8. A method of manufacturing a solid-state imaging device, the method comprising: Providing a light-transmitting plate material on one plate surface side of a semiconductor wafer through a wall, at a specific interval from the semiconductor wafer, the semiconductor wafer being a semiconductor wafer on which a set of pixels is formed on one plate surface side, the semiconductor wafer being a semiconductor wafer formed by arranging a plurality of parts each being a solid-state imaging element in a specific arrangement, the wall being formed along the specific arrangement to surround the set of pixels; Forming a recess on the other plate surface of the semiconductor wafer corresponding to the solid-state imaging element, the thickness of the semiconductor wafer being partially reduced due to the formation of the recess; and Cutting the whole of the semiconductor wafer, the wall, and the plate material into pieces, so that the whole is divided along the specific arrangement into parts corresponding to respective solid-state imaging elements; Providing solder portions in openings of a solder resist on the other plate surface of the semiconductor wafer and for mounting the solid-state imaging element, wherein the recess has a thin plate portion that bends outward as the internal pressure of the cavity of the semiconductor wafer increases; Before cutting the whole into pieces, filling the recess with a thermoplastic resin to form a filled resin portion in the recess, wherein the bottom surface of the filled resin portion is flush with the other plate surface of the semiconductor wafer, has an external shape consistent with the surface shape of the bottom surface portion and the side surface portion forming the recess, and the filled resin portion deforms with the semiconductor wafer; Before cutting the whole into pieces, placing a plurality of solder portions in an array on the bottom surface side of the filled resin portion, the solder portions being for mounting the solid-state imaging element, instead of providing the plurality of solder portions at the peripheral portion of the recess on the other plate surface of the semiconductor substrate; When performing reflow for melting the solder portions, the internal pressure of the cavity at a specific peak temperature is less than the internal pressure that causes cracking of the element forming the cavity or detachment of the bonding element forming the cavity; wherein forming the recess includes: Performing a first etching, including forming a semi-recess having a square shape with a predetermined etching depth by removing a portion corresponding to the recess from the semiconductor wafer by using dry etching, the depth of the semi-recess being determined according to the desired shape of the side surface portion of the recess, and Perform a second etching, including forming the recess by anisotropically etching downward the semi-recess after the first etching, wherein, by immersing the wafer on which the semi-recess is formed in a strong alkali solution and rotating and swinging the wafer so as to perform etching uniformly on the wafer surface, etching is performed for a specific period of time, and etching is inclined inward from the bottom of the semi-recess to form a first inclined surface and a second inclined surface having a specific inclination angle, so that the shape and size of the recess are controlled.

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