Back-illuminated image sensor chip and manufacturing method thereof

Abstract

The embodiment of the present application provides a back-illuminated image sensor chip and a method for making the same. The method for making the back-illuminated image sensor chip includes: providing a substrate, the substrate having a front side and a back side opposite to the front side, an interconnection structure formed on the front side of the substrate, a metal grid located in the device area, an opening located in the peripheral area and exposing the interconnection structure, and a metal connection extending from the device area to the peripheral area and filling the opening and electrically connected to the interconnection structure formed on the back side of the substrate; using ethyl silicate gas and oxygen to react to generate a layer of silicon oxide film, the silicon oxide film at least covers the metal grid and the metal connection line; performing plasma surface treatment on the silicon oxide film to form a waterproof protective film on the metal grid and the metal connection line. The method for making the back-illuminated image sensor chip can effectively reduce the distance between the molecules of each component of the waterproof protective film, so that the waterproof protective film has good waterproof performance, thereby effectively ensuring the final performance and service life of the image sensor.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a back-illuminated image sensor chip and a manufacturing method thereof. Background Art

[0002] The back-illuminated CMOS image sensor chip forms an image sensor on the front side of the substrate, and sets a color filter and a micro lens on the back side of the substrate so that the incident light enters the image sensor from the back side of the substrate.

[0003] Among them, the back-illuminated image sensor chip includes several image sensors. In order to reduce the optical crosstalk of light received by different image sensors, a metal grid is generally provided on the back of the substrate to isolate the light. However, when tungsten deposited by chemical vapor deposition (CVD) is used as the metal grid on the back, the surface of the CVD tungsten is oxidized during the moisture and heat resistance test, forming a protective layer defect on the side wall of the metal grid, allowing water vapor molecules to pass through the defect layer and contact the metal interconnect structure, affecting the final performance and service life of the image sensor. Summary of the invention

[0004] The present application provides a back-illuminated image sensor chip and a method for manufacturing the same, aiming to solve the problem of existing back-illuminated image sensor chips, in which water vapor molecules pass through the protective layer defects formed by the side walls of the metal grid, thereby contacting the metal interconnect structure, affecting the ultimate performance and service life of the image sensor.

[0005] In order to solve the above technical problems, a technical solution adopted by the present application is: to provide a method for manufacturing a back-illuminated image sensor chip. The manufacturing method includes: providing a substrate, the substrate having a front side and a back side opposite to the front side, the front side of the substrate forming an interconnection structure, the back side of the substrate forming a metal grid located in the device area, an opening located in the peripheral area and exposing the interconnection structure, and a metal connection extending from the device area to the peripheral area and filling the opening and electrically connecting the interconnection structure; using ethyl silicate gas and oxygen to react to generate a layer of silicon oxide film, the silicon oxide film at least covering the metal grid and the metal connection line; performing plasma surface treatment on the silicon oxide film to form a waterproof protective film on the metal grid and the metal connection line.

[0006] Wherein, the plasma is nitrogen plasma.

[0007] Wherein, the components of the waterproof protective film include Si x O y H z , wherein the Si x O y H zThere is nitrogen plasma physically adsorbed between molecules, x, y, and z are all natural numbers greater than zero; and / or, the components of the waterproof protective film include Si a O b N c H d , where a, b, c, and d are all natural numbers greater than zero, and a <x,b<y,d<z。

[0008] When the nitrogen plasma surface treatment is performed, the flow rate of the nitrogen plasma introduced is in the range of 5000-10000 m / s, so that the components of the waterproof protective film include Si x O y H z , and the Si x O y H z There is nitrogen plasma physically adsorbed between molecules.

[0009] When the nitrogen plasma surface treatment is performed, the flow rate of the nitrogen plasma introduced is in the range of 10000-20000 m / s, so that the components of the waterproof protective film include Si a O b N c H d .

[0010] Wherein, the waterproof protective film at least covers the side walls of the metal grid.

[0011] Before the step of using ethyl silicate gas and oxygen to react to form a silicon oxide film, the method further includes: forming a color filter and / or a microlens between the metal grids; and the waterproof protective film further covers the surface of the color filter and / or the microlens on one side away from the substrate and the side wall of the color filter and / or the microlens.

[0012] In order to solve the above technical problems, another technical solution adopted by the present application is: to provide a back-illuminated chip. The back-illuminated image sensor chip includes: a substrate having a front side and a back side opposite to each other; a plurality of interconnection structures formed on the front side of the substrate; wherein the substrate is formed with an opening located in the peripheral area and exposing the interconnection structure; a metal grid formed in the device area on the back side of the substrate; a metal connection line extending from the device area to the peripheral area and filling the opening, and electrically connected to the interconnection structure; a waterproof protective film at least covering the metal grid and the metal connection line; wherein the waterproof protective film is a layer of silicon oxide film after plasma surface treatment.

[0013] The silicon oxide film is formed by reacting ethyl silicate gas with oxygen.

[0014] Wherein, the plasma is nitrogen plasma; the components of the waterproof protective film include Si x O y H z , wherein the Si x O y H z There is nitrogen plasma physically adsorbed between molecules, x, y, and z are all natural numbers greater than zero; and / or, the components of the waterproof protective film include Si a O b N c H d , where a, b, c, and d are all natural numbers greater than zero, and a <x,b<y,d<z。

[0015] Among them, it further includes: a color filter and / or a microlens, which is arranged between the metal grids; wherein the waterproof protective film covers the surface of the metal grid, the metal wiring, the color filter and / or the microlens away from the substrate, and covers the side walls of the metal grid, the metal wiring, the color filter and / or the microlens.

[0016] The beneficial effects of the present application are as follows: Different from the prior art, the back-illuminated chip and the manufacturing method thereof provided in the embodiment of the present application provide a substrate, and form an interconnection structure on the front side of the substrate, and form a metal grid located in the device area, an opening located in the peripheral area and exposing the interconnection structure, and a metal connection line extending from the device area to the peripheral area and filling the opening and electrically connected to the interconnection structure on the back side of the substrate; then, ethyl silicate gas and oxygen are reacted to generate a layer of silicon oxide film, and the silicon oxide film at least covers the metal grid and the metal connection line; then, the silicon oxide film is subjected to plasma surface treatment to form a waterproof protective film on the metal grid and the metal connection line; wherein, by further subjecting the silicon oxide film to plasma surface treatment to form a waterproof protective film, the spacing between the molecules of each component of the waterproof protective film can be effectively reduced, and a good blocking effect is played on the water vapor molecules penetrating into the gaps between the molecules of each component of the waterproof protective film, thereby effectively improving the waterproof performance of the waterproof protective film, and reducing the probability of water vapor molecules passing through the waterproof protective film to enter the front side of the substrate and contact the interconnection structure, affecting the final performance and service life of the image sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0018] Figure 1A flowchart of a method for manufacturing a back-illuminated image sensor chip provided in one embodiment of the present application;

[0019] Figure 2 A schematic diagram of the structure of a back-illuminated image sensor chip provided in one embodiment of the present application;

[0020] Figure 3 A schematic diagram of the spacing between the molecules of various components of the existing protective waterproof membrane;

[0021] Figure 4 For Si x O y H z Schematic diagram of nitrogen plasma adsorbed between molecules;

[0022] Figure 5 Nitrogen plasma and Si x O y H z Schematic diagram of the distance between the molecules of each component of the waterproof protective film after the molecules react;

[0023] Figure 6 for Figure 5 Schematic diagram showing nitrogen plasma adsorbed between the molecules of each component of the waterproof protective film. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] The terms "first", "second", "third" in this application are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second", "third" can expressly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the embodiments of this application, all directional indications (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the steps or units listed, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] The present application is described in detail below with reference to the accompanying drawings and embodiments.

[0028] Image sensors are core components of mobile phones, computers and other camera devices. They realize image capture by converting optical signals into electrical signals. For example, for mobile phones, taking photos is just an additional function of the phone. Camera phones have lower requirements for color quality and exposure time, but higher requirements for power consumption and price. Therefore, CMOS image sensors have become the first choice for mobile phones. With the advancement of technology, CMOS continues to develop towards high resolution, digitization, multi-function and miniaturization, making the CMOS camera phone market more competitive. However, in addition to functions, power consumption and cost, product life has also become a part of the competition.

[0029] As an electronic product, whether it can withstand high temperature and high pressure is a basic means of testing its service life. Moisture resistance and waterproofness have gradually become a major selling point for manufacturers' products to compete in the market. The conventional moisture resistance and waterproofness method is to protect the entire structure by covering it with silicon nitride and thick silicon oxide films to form a water vapor barrier layer. However, for back-illuminated CMOS image sensors, a grid-like metal grid is formed on the back of the substrate during the pixel period, and a filter is formed between the metal grids. The protection scheme using silicon nitride and thick silicon oxide will affect the filtering and increase the product cost. Moreover, when tungsten deposited by CVD is used as the metal grid on the back, the surface of the CVD tungsten is oxidized during the moisture resistance and heat resistance test, and a protective layer defect is formed on the side wall of the metal grid, allowing water vapor molecules to pass through the defect layer and contact the metal interconnect structure, thereby affecting the final performance and service life of the image sensor.

[0030] The embodiment of the present application provides a back-illuminated image sensor chip and a method for manufacturing the same. The back-illuminated CMOS image sensor chip is widely used in the fields of mobile phone cameras, webcams, computer cameras, etc. The back-illuminated image sensor chip and the method for manufacturing the same can provide good waterproof performance, greatly reducing the probability of water vapor molecules entering the front side of the substrate and contacting the interconnection structure, affecting the final performance and service life of the image sensor.

[0031] See also Figure 1 and Figure 2 , Figure 1 A flowchart of a method for manufacturing a back-illuminated image sensor chip provided in one embodiment of the present application; Figure 2 Schematic diagram of the structure of a back-illuminated image sensor chip provided in one embodiment of the present application; Figure 1 As shown, the method for manufacturing the back-illuminated image sensor chip specifically includes:

[0032] Step S1: providing a substrate.

[0033] The substrate 11 may be a crystalline silicon substrate or may be formed of other semiconductor materials. Figure 2 As shown, the substrate 11 has a front side A and a back side B opposite to the front side A. The front side A of the substrate 11 is formed with an interconnection structure 14 to be electrically connected to an image sensor formed in the substrate 11. The image sensor is configured to convert an optical signal (photon) into an electrical signal, and it may be a photosensitive metal oxide semiconductor (MOS) transistor or a photosensitive diode. The specific structure and function of the interconnection structure 14 are the same or similar to the metal interconnection structure of the prior art, and will not be described in detail here.

[0034] Furthermore, a metal grid 12 located in the device region is formed on the back side B of the substrate 11. The metal grid 12 may be formed by depositing a metal layer by chemical vapor deposition (CVD), physical vapor deposition (PVD), etc., and then etching the metal layer by an anisotropic etching method (e.g., dry etching) to form the metal grid 12. The metal layer includes a metal or a metal alloy, wherein the metal in the metal layer may include tungsten, aluminum, copper, and / or the like. Specifically, the specific implementation process of forming the metal grid 12 may refer to the specific implementation method of forming the metal grid 12 in the back-illuminated CMOS image sensor chip in the prior art, and the same or similar technical effects may be achieved, which will not be described in detail herein.

[0035] Furthermore, the back side B of the substrate 11 is also formed with an opening located in the peripheral area and exposing the interconnection structure 14, and a metal connection 15 extending from the device area to the peripheral area and filling the opening and electrically connecting to the interconnection structure 14, wherein the metal connection 15 and the metal grid 12 can be formed using the same material in the same process step.

[0036] Step S2: using ethyl silicate gas and oxygen to react to form a silicon oxide film, wherein the silicon oxide film at least covers the metal grid and the metal wiring.

[0037] Specifically, tetraethyl orthosilicate (TEOS) gas and oxygen may be used to form a silicon oxide film by chemical vapor deposition (CVD) or high aspect ratio process (HARP) process. The spacing between the molecules of each component of the silicon oxide film formed in step S2 can be seen in Figure 3 , Figure 3 The distances between the molecules of the silicon oxide film are different, and water vapor molecules can easily enter the chip through the gaps between the molecules of the silicon oxide film and contact the interconnection structure 14, thereby affecting the final performance and service life of the image sensor. The tetraethyl orthosilicate (TEOS) can be specifically ethyl orthosilicate.

[0038] Step S3: performing plasma surface treatment on the silicon oxide film to form a waterproof protective film on the metal grid and the metal wiring.

[0039] The plasma is nitrogen plasma; of course, the plasma can also be argon plasma. Figure 3 As shown in FIG. 1 , since TEOS is an organic macromolecular structure and the deposition rate of the TEOS silicon oxide film is relatively fast, some TEOS in the formed silicon oxide film is not completely decomposed into silicon dioxide; that is, the formed silicon oxide film still has Si x O y H zCompound molecules, such as H2SiO3, H4SiO4, H2Si2O5 and other molecules, still exist, which makes the distances between the components of the silicon oxide film different in size. Water vapor molecules can easily enter the chip through the gaps between the components of the silicon oxide film and contact the interconnection structure 14, thereby affecting the ultimate performance and service life of the image sensor.

[0040] To this end, in an embodiment of the present application, the silicon oxide film is further subjected to nitrogen plasma surface treatment, that is, nitrogen is introduced into the silicon oxide film using a plasma device to form a waterproof protective film 13; thereby reducing the distance between the components of the formed waterproof protective film 13, improving the waterproof performance of the waterproof protective film 13, and avoiding affecting the image sensor.

[0041] In one embodiment, when nitrogen plasma surface treatment is performed, the flow rate of the introduced nitrogen plasma is in the range of 5000-10000 m / s. Figure 4 , Figure 4 For Si x O y H z Schematic diagram of nitrogen plasma adsorbed between molecules; nitrogen plasma is adsorbed between the molecules of each component of the waterproof protective film 13, so that the nitrogen plasma can be used to fill the partial gaps between the molecules of each component of the waterproof protective film 13, thereby effectively reducing the distance between the molecules of each component on the waterproof protective film 13. Figure 3 The corresponding solution, since the distance between the molecules of each component on the waterproof protective film 13 is reduced, can to a certain extent block the water vapor molecules from penetrating into the gaps between the molecules of each component of the waterproof protective film 13, so as to reduce the amount of water vapor molecules entering the interconnection structure 14 through the gaps, thereby achieving better waterproof performance and avoiding water vapor molecules from entering the front side A of the substrate 11 and contacting the interconnection structure 14, which affects the final performance of the image sensor and the probability of service life.

[0042] Specifically, in this embodiment, the components of the waterproof protective film 13 after nitrogen plasma surface treatment include Si x O y H z , where x, y, and z are all natural numbers greater than zero. It can be understood that in this embodiment, the nitrogen plasma is mainly adsorbed between the components of the waterproof protective film 13 by physical adsorption; of course, specific experiments have shown that when the flow rate of the nitrogen plasma is not less than 7000 m / s, the nitrogen plasma will be adsorbed between the Si in the waterproof protective film 13. x O y H zThe compound reacts. Therefore, at this time, the components of the waterproof protective film 13 after nitrogen plasma surface treatment may also include some Si a O b N c H d ; where a, b, c, and d are all natural numbers greater than zero, and a < x, b < y, d < z. In a preferred embodiment, while reducing the spacing between the molecules of each component on the waterproof protective film 13, to further save energy, the flow rate of the introduced nitrogen plasma can be in the range of 5000 - 70000 m / s.

[0043] In another embodiment, refer to Figure 5 , Figure 5 It is a schematic diagram of the spacing between the molecules of each component of the waterproof protective film 13 after the reaction of nitrogen plasma with Si x O y H z molecules; when performing nitrogen plasma surface treatment, the flow rate of the introduced nitrogen plasma is in the range of 10000 - 20000 m / s, so that the nitrogen plasma reacts with Si x O y H z compounds in the waterproof protective film 13, so that the components of the formed waterproof protective film 13 include more Si a O b N c H d compounds; where a, b, c, and d are all natural numbers greater than zero, and a < x, b < y, d < z. In this embodiment, Figure 3 and Figure 5 can be compared and referred to simultaneously. Since a < x, b < y, d < z, therefore, the Si a O b N c H d compound molecules are smaller than the Si x O y H z compound molecules. Therefore, in a certain space, the spacing between the Si a O b N c H d compound molecules is smaller than the spacing between the Si x O y H z compound molecules. Therefore, in a certain space and when the other components in the waterproof protective film 13 are the same, after nitrogen plasma treatment, Si a O b N c H dThe density of the waterproof protective film 13(m) of the compound molecules is greater than that of the Si x O y H z The density of the waterproof protective film 13 (n) of the compound molecules; that is, the distance between the molecules of each component of the waterproof protective film 13 (m) is smaller than the distance between the molecules of each component of the waterproof protective film 13 (n); compared to Figure 3 The corresponding solution can reduce the amount of water vapor molecules entering the waterproof protective film 13, thereby achieving a better waterproof effect and preventing water vapor molecules from entering the front surface A of the substrate 11 and contacting the interconnection structure 14, thereby affecting the final performance and service life of the image sensor. Figure 4 In the corresponding solution, the reaction completeness of the compound of the deposited waterproof protective film 13 is optimized, and the distance between molecules is further reduced, which is beneficial to improving the waterproof performance.

[0044] It is understood that in order to accelerate the reaction or to make more nitrogen plasma react with the Si in the waterproof protective film 13, x O y H z The nitrogen plasma may react with the Si in the waterproof protective film 13, and the flow rate of the nitrogen plasma may be greater than 20000 m / s, which is not limited in the present application. x O y H z The compound is not completely reacted, and the components of the waterproof protective film 13 further include Si x O y H z Meanwhile, in this embodiment, refer to Figure 6 , Figure 6 for Figure 5 The schematic diagram of the nitrogen plasma adsorbed between the molecules of each component of the waterproof protective film 13 is shown; the nitrogen plasma can also be physically adsorbed in the gaps between the molecules of each component of the waterproof protective film 13. For example, physically adsorbed on Si a O b N c H d The gap between compound molecules, Si x O y H z The gap between compound molecules, Si a O b N c H d Compound molecules and Si x O y H z The space between molecules of a compound.

[0045] In a specific embodiment, the waterproof protective film 13 at least covers the surface of the metal grid 12 and the metal connection 15 away from the substrate 11 and covers the side walls of the metal grid 12 and the metal connection 15, so as to protect each surface of the metal grid 12 and the metal connection 15 and prevent water vapor molecules from entering the front side A of the substrate 11 from the surface of the metal grid 12 and the metal connection 15 away from the substrate 11 and / or from the side walls of the metal grid 12 and the metal connection 15 and contacting the interconnection structure 14.

[0046] In the specific implementation process, before step S2, a color filter and / or microlens is formed between the metal grids 12; wherein the waterproof protective film 13 further covers the surface of the color filter and / or microlens on one side away from the substrate 11 and the side wall of the color filter and / or microlens. In this way, the possibility that water vapor molecules will not enter the front side A of the substrate 11 from the back side B of the substrate 11 and contact the interconnection structure 14 can be reduced as much as possible, thereby effectively ensuring the waterproof performance of the prepared back-illuminated image sensor chip. Among them, the specific implementation process of forming the color filter and / or microlens is the same or similar to the specific implementation process of forming the color filter and / or microlens in the existing preparation of the back-illuminated image sensor chip, and the same or similar technical effects can be achieved. For details, please refer to the prior art and will not be repeated here.

[0047] It should be noted that the nitrogen plasma in this application specification is not limited to being adsorbed on Si a O b N c H d The gap between compound molecules, Si x O y H z The gap between compound molecules, Si a O b N c H d Compound molecules and Si x O y H z The gaps between the compound molecules can also be adsorbed between other components of the waterproof protective film 13, as long as the gaps between the molecules of each component can be reduced.

[0048] The method for manufacturing a back-illuminated image sensor chip provided in an embodiment of the present application comprises providing a substrate 11, and forming an interconnection structure 14 on the front side A of the substrate 11, and forming a metal grid 12 located in the device area, an opening located in the peripheral area and exposing the interconnection structure 14, and a metal connection line 15 extending from the device area to the peripheral area and filling the opening and electrically connected to the interconnection structure 14 on the back side B of the substrate 11; then using ethyl silicate gas and oxygen to react to generate a layer of silicon oxide film, the silicon oxide film at least covering the metal grid 12 and the metal connection line 15; then performing plasma surface treatment on the silicon oxide film to form a metal grid 12 on the metal grid 12. and forming a waterproof protective film 13 on the metal connection 15; wherein, by further performing plasma surface treatment on the silicon oxide film to form the waterproof protective film 13, the spacing between the components of the waterproof protective film 13 can be effectively reduced, and the water vapor molecules can be effectively blocked from penetrating into the gaps between the components of the waterproof protective film 13, thereby effectively improving the waterproof performance of the waterproof protective film 13, and reducing the probability of water vapor molecules passing through the waterproof protective film 13 from the back side B of the substrate 11 to the front side A of the substrate 11 and contacting the interconnection structure 14, affecting the final performance and service life of the image sensor. At the same time, this method does not affect the structural design and filtering effect of the back-illuminated image sensor chip, and can also save costs.

[0049] In this embodiment, if Figure 2 As shown, a back-illuminated image sensor chip manufactured by the above-mentioned back-illuminated image sensor chip manufacturing method is also provided. The back-illuminated image sensor chip includes: a substrate 11, a metal grid 12, a waterproof protective film 13, a plurality of interconnection structures 14, metal wirings 15 and a plurality of image sensors (not shown).

[0050] The substrate 11 has a front side A and a back side B opposite to each other; and the substrate 11 is formed with an opening located in the peripheral area and exposing the interconnection structure 14; the substrate 11 may be a crystalline silicon substrate or formed of other semiconductor materials. A plurality of image sensors and the interconnection structure 14 are both arranged on the front side A of the substrate 11; the plurality of image sensors are configured to convert light signals (photons) into electrical signals, and they may be photosensitive metal oxide semiconductor (MOS) transistors or photosensitive diodes. The interconnection structure 14 is used to electrically connect the plurality of image sensors. The metal wiring 15 extends from the device area to the peripheral area and fills the opening, and is electrically connected to the interconnection structure 14.

[0051] The metal grid 12 is disposed on the back surface B of the substrate 11 to reduce the optical crosstalk of the light received by different image sensors. Specifically, the metal grids 12 can be provided in one-to-one correspondence with a plurality of image sensors. For other specific structures and functions of the metal grid 12, reference can be made to the specific structures and functions of the metal grid 12 in the prior art, and the same or similar technical effects can be achieved. For details, reference can be made to the prior art and will not be elaborated here.

[0052] The waterproof protective film 13 covers the metal grid 12 and the metal connection 15. Among them, the waterproof protective film 13 is a layer of silicon oxide film after plasma surface treatment. Among them, the silicon oxide film is formed by reacting tetraethyl orthosilicate gas with oxygen. The plasma is nitrogen plasma.

[0053] In a specific embodiment, the components of the waterproof protective film 13 after nitrogen plasma surface treatment include Si x O y H z , where x, y, and z are all natural numbers greater than zero. In this specific embodiment, as Figure 4 shown, nitrogen plasma is physically adsorbed between the Si x O y H z molecules, that is, nitrogen plasma is physically filled between the Si x O y H z molecules. In this way, the nitrogen plasma can be used to fill some of the intermolecular gaps of each component of the waterproof protective film 13, thereby effectively reducing the intermolecular distance between the components of the waterproof protective film 13. Compared with the Figure 3 corresponding solution, since the intermolecular distance between the components of the waterproof protective film 13 is reduced, to a certain extent, water vapor molecules can be blocked from entering the gaps between the components of the waterproof protective film 13, so as to reduce the amount of water vapor molecules entering the front surface A of the substrate 11 through the gap and contacting the interconnection structure 14, and further achieve better waterproof performance, and avoid the occurrence probability that water vapor molecules enter the front surface A of the substrate 11 and contact the interconnection structure 14, affecting the final performance and service life of the image sensor.

[0054] In another specific embodiment, as Figure 5 shown, the components of the waterproof protective film 13 after nitrogen plasma surface treatment include Si a O b N c H d , where a, b, c, and d are all natural numbers greater than zero, and a < x, b < y, d < z. Compared with the first specific embodiment above, since a < x, b < y, d < z, therefore, Si a O b N cH d Compound molecules compared to Si x O y H z The compound molecules are small, so within a certain space, Si a O b N c H d The distance between the molecules of the compound is compared to Si x O y H z The distance between the compound molecules should be small. Therefore, in a certain space and under the condition that the other components in the waterproof protective film 13 are the same, the Si a O b N c H d The density of the waterproof protective film 13m of the compound molecules is greater than that of the Si x O y H z The density of the waterproof protective film 13n of the compound molecules; that is, the distance between the molecules of each component of the waterproof protective film 13m is smaller than the distance between the molecules of each component of the waterproof protective film 13n; compared to Figure 3 The corresponding solution can reduce the amount of water vapor molecules entering the waterproof protective film 13, thereby achieving a better waterproof effect and preventing water vapor molecules from entering the front surface A of the substrate 11 and contacting the interconnection structure 14, thereby affecting the final performance and service life of the image sensor.

[0055] Of course, in this specific embodiment, if Figure 6 As shown, the nitrogen plasma can also be physically adsorbed in the gaps between the molecules of each component of the waterproof protective film 13. For details, please refer to the above related description. Of course, in its specific embodiment, the components of the waterproof protective film 13 after the nitrogen plasma surface treatment also include Si x O y H z and Si a O b N c H d In addition, the nitrogen plasma may also be physically adsorbed in the gaps between the molecules of each component of the waterproof protective film 13 to further reduce the distance between the molecules of each component of the waterproof protective film 13 .

[0056] Specifically, the waterproof protective film 13 at least covers the surface of the metal grid 12 and the metal connection 15 away from the substrate 11 and the side walls of the metal grid 12 and the metal connection 15, so as to protect each surface of the metal grid 12 and prevent water vapor molecules from entering the front side A of the substrate 11 from the surface of the metal grid 12 and the metal connection 15 away from the substrate 11 and / or the side walls of the metal grid 12 and the metal connection 15 and contacting the interconnection structure 14.

[0057] Furthermore, the back-illuminated chip further includes a color filter and / or a microlens disposed between the metal grids 12. In a specific embodiment, the waterproof protective film 13 further covers the surface of the color filter and / or the microlens away from the substrate 11 and the sidewalls of the color filter and / or the microlens. This can minimize the possibility that water vapor molecules will not enter the front side A of the substrate 11 from the back side B of the substrate 11 and contact the interconnection structure 14, thereby effectively ensuring the waterproof performance of the back-illuminated image sensor chip and reducing the probability of water vapor molecules passing through the waterproof protective film 13 and the metal grid 12 to enter the interior of the chip.

[0058] Among them, the specific structure and function of the color filter and / or microlens are the same or similar to the specific structure and function of the color filter and / or microlens in the existing back-illuminated chip, and can achieve the same or similar technical effects. For details, please refer to the existing technology and will not be repeated here.

[0059] The back-illuminated image sensor chip provided in this embodiment absorbs nitrogen plasma in the waterproof protective film 13 and / or allows nitrogen plasma to react with Si x O y H z Compounds react to form Si a O b N c H d , which can effectively reduce the distance between the molecules of each component of the waterproof protective film 13, thereby being able to block water vapor molecules from penetrating into the gaps between the molecules of each component of the waterproof protective film 13 to a certain extent, so as to reduce the amount of water vapor molecules that enter the front side A of the substrate 11 through the gaps and contact the interconnection structure 14, thereby making the back-illuminated image sensor chip have better waterproof performance, effectively ensuring the ultimate performance and service life of the image sensor.

[0060] The above are only implementation methods of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for manufacturing a back-illuminated image sensor chip, characterized in that: include: A substrate is provided, wherein the substrate has a front side and a back side opposite to the front side, an interconnection structure is formed on the front side of the substrate, and a metal grid located in a device area, an opening located in a peripheral area and exposing the interconnection structure, and a metal connection line extending from the device area to the peripheral area and filling the opening and electrically connected to the interconnection structure is formed on the back side of the substrate; Using ethyl silicate gas and oxygen to react to generate a silicon oxide film, wherein the silicon oxide film at least covers the metal grid and the metal connection line; Performing plasma surface treatment on the silicon oxide film to form a waterproof protective film on the metal grid and the metal wiring; the plasma is nitrogen plasma; When the nitrogen plasma surface treatment is performed, the flow rate of the nitrogen plasma introduced is in the range of 5000-10000 m / s, so that the components of the waterproof protective film include Si x O y H z , and the Si x O y H z There is nitrogen plasma physically adsorbed between molecules; or, The flow rate of the nitrogen plasma introduced is in the range of 10000-20000 m / s, so that the components of the waterproof protective film include Si a O b N c H d ; Before the step of using ethyl silicate gas and oxygen to react to form a silicon oxide film, the method further includes: A color filter and / or a microlens is formed between the metal grids; wherein the waterproof protective film further covers a surface of the color filter and / or the microlens away from the substrate and a side wall of the color filter and / or the microlens.

2. The method according to claim 1, characterized in that The components of the waterproof protective film include Si x O y H z , wherein the Si x O y H z There is nitrogen plasma physically adsorbed between molecules, and x, y, and z are all natural numbers greater than zero; and / or, The components of the waterproof protective film include Si a O b N c H d , where a, b, c, and d are all natural numbers greater than zero, and a <x,b<y,d<z。 3. The method according to claim 1, characterized in that The waterproof protective film covers at least the side walls of the metal grid.

4. A back-illuminated image sensor chip, characterized in that: include: a substrate having opposing front and back surfaces; A plurality of interconnect structures are formed on the front surface of the substrate; wherein the substrate is formed with openings located in the peripheral area and exposing the interconnect structures; A metal grid formed in a device region on the back side of the substrate; a metal connection line extending from the device region to the peripheral region and filling the opening and electrically connected to the interconnect structure; A waterproof protective film, at least covering the metal grid and the metal connection line; wherein the waterproof protective film is a layer of silicon oxide film after plasma surface treatment; The plasma is nitrogen plasma; The components of the waterproof protective film include Si x O y H z , wherein the Si x O y H z There is nitrogen plasma physically adsorbed between molecules, and x, y, and z are all natural numbers greater than zero; and / or, The components of the waterproof protective film include Si a O b N c H d , where a, b, c, and d are all natural numbers greater than zero, and a <x,b<y,d<z; Further comprising: a color filter and / or a microlens, arranged between the metal grids; The waterproof protective film covers the surface of the metal grid, the metal wiring, the color filter and / or the microlens away from the substrate, and covers the side walls of the metal grid, the metal wiring, the color filter and / or the microlens.

5. The back-illuminated image sensor chip according to claim 4, characterized in that: The silicon oxide thin film is formed by reacting ethyl silicate gas with oxygen.

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