Inspection method for plate-shaped objects

Abstract

To provide a method for inspecting a tabular object, capable of simply inspecting a tabular object without contaminating the tabular object.SOLUTION: A method for inspecting a tabular object whose surface is formed as a mirror surface by using a light source and an imaging unit provided in the vicinity of the light source, includes irradiation step 102 of irradiating the surface of the tabular object with light at a predetermined incidence angle from the light source, projection step 103 of projecting reflected light of the light with which the surface of the tabular object is irradiated in the irradiation step 102, on a projection surface to form a projection image reflecting unevenness generated on the surface of the tabular object, and imaging step 104 of imaging the projection image projected in the projection step 103 with the imaging unit through the surface of the tabular object formed as the mirror surface.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for inspecting a plate-like object.

Background Art

[0002] In recent years, with the progress of miniaturization and thinning of semiconductor devices, a technology has been developed to increase the three-dimensional integration degree by bonding semiconductor devices to each other without using bonding wires. Among them, a method called WoW (Wafer on Wafer), in which a plurality of wafers are bonded and laminated, has an advantage of excellent productivity because wafers can be processed in a batch.

[0003] However, when wafers are bonded to each other, so-called voids such as the inclusion of bubbles and particles may occur (see, for example, Patent Document 1). Since the devices at the locations where voids occur become defective products, it is necessary to perform inspection during bonding, and inspection by SAT (Scanning Acoustic Tomography) has been proposed (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the inspection described in Patent Document 2 is an observation in water, so there has been a concern about contamination of the wafer, which is a plate-like object. Also, in an inspection using a catoptric system that does not contaminate the wafer, a large-scale apparatus is required due to a long optical path length, and thus a method for more simply performing inspection has been desired.

[0006] The present invention has been made in view of the above facts, and its purpose is to provide a method for inspecting plate-like objects that allows for simple inspection of plate-like objects without contaminating them. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a method for inspecting a plate-shaped object, comprising a light source and an imaging unit disposed near the light source, wherein the plate-shaped object has a mirror-like surface, the method comprising: an irradiation step of irradiating the surface of the plate-shaped object with light from the light source at a predetermined incident angle; a projection step of projecting the reflected light of the light irradiated onto the surface of the plate-shaped object in the irradiation step onto a projection surface to form a projection image that reflects the irregularities that have occurred on the surface of the plate-shaped object; and an imaging step of capturing the projection image projected in the projection step with the imaging unit via the mirror-like surface of the plate-shaped object.

[0008] In the method for inspecting the plate-like object, the light source and the imaging unit may be included in electronic equipment. [Effects of the Invention]

[0009] This invention has the effect of enabling simple inspection of plate-like objects without contaminating them. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a plate-shaped object to be inspected by the inspection method for plate-shaped objects according to Embodiment 1. [Figure 2] Figure 2 is a schematic cross-sectional view showing an enlarged view of part II in Figure 1. [Figure 3] Figure 3 is a schematic diagram showing the electronic equipment, plate-shaped object, and projection surface used in the inspection method for plate-shaped objects according to Embodiment 1. [Figure 4] Figure 4 is a flowchart showing the flow of the inspection method for plate-shaped objects according to Embodiment 1. [Figure 5]Figure 5 schematically shows the projected image projected onto the projection surface during the projection step of the inspection method for plate-shaped objects shown in Figure 4. [Figure 6] Figure 6 is a schematic cross-sectional view showing a modified example of the plate-like material shown in Figure 1. [Figure 7] Figure 7 is a schematic diagram showing the electronic equipment, plate-like object, and projection surface shown in Figure 3. [Modes for carrying out the invention]

[0011] Embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by those skilled in the art, and those that are substantially the same. In addition, the components described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the present invention.

[0012] [Embodiment 1] A method for inspecting a plate-like object according to Embodiment 1 of the present invention will be described based on the drawings. Figure 1 is a schematic cross-sectional view showing an example of a plate-like object to be inspected in the inspection method for plate-like objects according to Embodiment 1. Figure 2 is a schematic cross-sectional view showing an enlarged view of part II in Figure 1. Figure 3 is a schematic diagram showing the electronic equipment, plate-like object, and projection surface used in the inspection method for plate-like objects according to Embodiment 1. Figure 4 is a flowchart showing the flow of the inspection method for plate-like objects according to Embodiment 1.

[0013] (Plate-like object) The inspection method for a plate-shaped object according to Embodiment 1 is a method for inspecting a plate-shaped object 1 shown in Figure 1. The plate-shaped object 1 to be processed by the inspection method for a plate-shaped object according to Embodiment 1 is composed of multiple wafers 2 bonded together, as shown in Figures 1 and 2. The wafers 2 are disc-shaped semiconductor wafers, optical device wafers, etc., with silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), or silicon carbide (SiC) as the substrate. On the wafers 2, for example, multiple devices are formed in regions demarcated by multiple intersecting division lines, each device having electrode pads and through electrodes connected to the electrode pads.

[0014] The plate-shaped object 1 to be inspected in the inspection method for plate-shaped objects according to Embodiment 1 is constructed by attaching a second wafer 2 (hereinafter referred to as 2-2) to one wafer 2 (hereinafter referred to as 2-1) with an adhesive layer 3, and then thinning the second wafer 2 by grinding and polishing the surface of the second wafer 2-2, and then attaching a third wafer 2 (hereinafter referred to as 2-3) to the second wafer 2-2 with an adhesive layer 3, and then thinning the third wafer 2-3 by grinding and polishing, in particular CMP (Chemical Mechanical Polishing) processing, and forming the surface 4 of the third wafer 2-3 (corresponding to the surface of the plate-shaped object 1) to a mirror finish.

[0015] The adhesive layer 3 may be composed of a liquid resin adhesive, or it may be composed of a resin sheet-like adhesive having adhesive layers on both sides. In Embodiment 1, the thickness of wafer 2-1 and the thickness of the second wafer 2-2 are approximately 400 μm, and the thickness of the third wafer 2-3 is 20 μm. In Embodiment 1, the second wafer 2-2 is provided with a through hole 7 for accommodating a chip 6 sealed with molding resin 5. The surfaces of the molding resin 5 and the chip 6 are formed flat along both surfaces of the second wafer 2-2. Thus, in Embodiment 1, the plate-like object 1 is a three-layer plate-like object in which wafer 2-1, the second wafer 2-2, and the third wafer 2-3 are sequentially laminated with the adhesive layer 3 in between.

[0016] As shown in FIG. 2, in the plate-shaped object 1 having the above-described configuration, voids 8 may occur in the adhesive layer 3, or minute steps may occur between the surfaces of the molded resin 5 and the chip 6 sealed in the through-hole 7 and the surface of the second wafer 2-2. When voids 8 occur in the adhesive layer 3 of the plate-shaped object 1, or minute steps occur between the surfaces of the molded resin 5 and the chip 6 sealed in the through-hole 7 and the surface of the second wafer 2-2, minute irregularities will occur on the surface 4.

[0017] The inspection method for the plate-shaped object according to Embodiment 1 is a method for inspecting the presence or absence of the above-described minute irregularities on the surface 4 of the plate-shaped object 1. The inspection method for the plate-shaped object according to Embodiment 1 uses the electronic device 10 shown in FIG. 3.

[0018] (Electronic device) As shown in FIG. 3, the electronic device 10 includes a light source 11 and an imaging unit 12 disposed in the vicinity of the light source 11. That is, the light source 11 and the imaging unit 12 are included in the electronic device 10. The electronic device 10 includes, for example, a tablet-type terminal, a smartphone, a mobile phone, a portable personal computer, a head-mounted display, a digital camera, a media player, an e-book reader, a navigator, a wearable device, or a game machine, etc., but is not limited thereto. In Embodiment 1, the electronic device 10 is a smartphone.

[0019] In Embodiment 1, as shown in FIG. 3, the electronic device 10 further includes a control unit 13, a display unit 14, and a housing 15 that houses the light source 11, the imaging unit 12, the control unit 13, and the display unit 14. The light source 11 irradiates the surface 4 of the plate-shaped object 1 with light 111. The light 111 irradiated from the light source 11 may be parallel light or non-parallel light. When the light 111 is parallel light, it is preferable to combine an optical element such as a lens with the light source 11. When the light 111 is non-parallel light, it is preferable that the light source 11 has a small emission region and can be regarded as a point light source. In Embodiment 1, the light source 11 includes an LED (Light-Emitting Diode) or the like.

[0020] The imaging unit 12 acquires an image by imaging the surface 4 of the plate-shaped object 1, which is illuminated by light 111 from the light source 11. The imaging unit 12 includes, for example, a digital camera that combines an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) with an optical element such as a lens. The imaging unit 12 outputs the image acquired by imaging within the field of view 121 to the control unit 13.

[0021] In Embodiment 1, the light source 11 and the imaging unit 12 are arranged adjacent to each other such that their optical axes 112 and 122 are parallel or parallel to each other. Thus, in the present invention, the light source 11 and the imaging unit 12 are arranged adjacent to each other such that the direction in which the light source 11 emits light 111 and the direction of the field of view 121 captured by the imaging unit 12 are the same. In Embodiment 1, the light source 11 and the imaging unit 12 are arranged 1 cm apart from each other such that their optical axes 112 and 122 are parallel to each other.

[0022] The control unit 13 controls each of the aforementioned components of the electronic device 10. The control unit 13 is a computer that includes, for example, an arithmetic processing unit as an arithmetic means including a microprocessor such as a CPU (Central Processing Unit), a storage device as a storage means having memory such as ROM (Read Only Memory) or RAM (Random Access Memory), and an input / output interface device as a communication means.

[0023] The display unit 14 is connected to the control unit 13 and displays images captured and acquired by the imaging unit 12. In Embodiment 1, the display unit 14 comprises a display and a touchscreen that are stacked on top of each other. The display includes a display device such as a liquid crystal display (LCD), an organic electro-luminescence display (OELD), or an inorganic electro-luminescence display (IELD). The touchscreen detects contact from a finger, pen, or stylus pen using any method such as a capacitive method, a resistive method, a surface acoustic wave method (or ultrasonic method), an infrared method, an electromagnetic induction method, or a load detection method.

[0024] (Inspection method for plate-like objects) Next, a method for inspecting a plate-shaped object according to Embodiment 1 will be described. The method for inspecting a plate-shaped object according to Embodiment 1 is a method for inspecting a plate-shaped object 1 whose surface 4 is formed to be mirror-like, using a light source 11 and an imaging unit 12, i.e., an electronic device 10, and is a method for inspecting whether or not there are minute irregularities on the surface 4 of the plate-shaped object 1. As shown in Figure 4, the method for inspecting a plate-shaped object according to Embodiment 1 comprises a preparation step 101, an irradiation step 102, a projection step 103, and an imaging step 104.

[0025] (Preparation Steps) Preparation step 101 is the step of arranging the plate-shaped object 1 and the electronic device 10 in the relative positional relationship shown below. In Embodiment 1, in preparation step 101, as shown in Figure 3, the light source 11, i.e., the electronic device 10 and the plate-shaped object 1 are positioned so that light 111 is irradiated onto the entire surface 4 of the plate-shaped object 1, and the reflected light 113 reflected from the surface 4 of the plate-shaped object 1 is projected onto the projection surface 20. The projection surface 20 is, for example, a surface formed of a light color such as white, such as a light-colored wall surface of a structure or a light-colored screen. In Embodiment 1, the projection surface 20 is formed of a light color such as white, but in the present invention, it is not limited to white. Also, in Embodiment 1, the projection surface 20 is a wall surface parallel to the vertical direction.

[0026] Furthermore, in Embodiment 1, in preparation step 101, as shown in Figure 3, the imaging unit 12, i.e., the electronic device 10, and the plate-like object 1 are positioned so that the entire surface 4 of the plate-like object 1 is included within the field of view 121 of the imaging unit 12, and a projected image 21 reflected on the mirror surface 4 of the plate-like object 1 can be captured. The projected image 21 is an image consisting of reflected light 113 projected onto the projection surface 20, and is an image showing minute irregularities reflected on the surface 4 of the plate-like object 1. In Embodiment 1, the electronic device 10 and the plate-like object 1 are positioned so that the angle θ (corresponding to the angle of incidence) of the optical axis 112 of the light source 11 with respect to the surface 4 of the plate-like object 1 is 45 degrees. However, in the present invention, the angle θ is not limited to 45 degrees as long as it is less than 90 degrees. Also, in the present invention, the relative positional relationship between the plate-like object 1 and the electronic device 10 is not limited to the positional relationship shown in Figure 3.

[0027] (Irradiation step) The irradiation step 102 is the step of irradiating the surface 4 of the plate-shaped object 1 with light 111 from the light source 11 at the angle θ described above. In Embodiment 1, in the irradiation step 102, the area around the plate-shaped object 1, the electronic device 10, and the projection surface 20 is darkened, and the electronic device 10 irradiates the entire surface 4 of the plate-shaped object 1 with light 111 from the light source 11. In this invention, in the irradiation step 102, the room lighting may be turned off to darken the area around the plate-shaped object 1, the electronic device 10, and the projection surface 20. Alternatively, a box-shaped jig that darkens the inside may be prepared to darken the area around the plate-shaped object 1, the electronic device 10, and the projection surface 20.

[0028] (Projection step) Figure 5 is a schematic diagram showing the projected image projected onto the projection surface in the projection step of the inspection method for plate-like objects shown in Figure 4. The projection step 103 is a step in which the reflected light 113, which is reflected from the surface 4 of the plate-like object 1 that was irradiated onto the surface 4 in the irradiation step 102, is projected onto the projection surface 20 to form a projected image 21 that reflects the irregularities that have occurred on the surface 4 of the plate-like object 1.

[0029] In Embodiment 1, during the projection step 103, light 111 irradiated onto the surface 4 of the plate-like object 1 is reflected by the surface 4 of the plate-like object 1, and the reflected light 113 of light 111 is projected onto the projection surface 20, forming a projected image 21 consisting of the reflected light 113 on the projection surface 20. As a result, the light 111 irradiated from the light source 11 is scattered in the convex parts of the minute irregularities on the surface 4 of the plate-like object 1, and converges in the concave parts. Therefore, in the projected image 21, the convex parts 41 (shown by parallel diagonal lines in Figure 5) of the minute irregularities on the surface 4 of the plate-like object 1 become darker, and the concave parts 42 (shown by parallel diagonal lines in Figure 5) become brighter. Thus, in Embodiment 1, during the projection step 103, as shown in Figure 5, a pattern corresponding to the minute irregularities on the surface 4 of the plate-like object 1, i.e., a pattern that reflects the irregularities, is generated in the projected image 21 by the so-called magic mirror principle.

[0030] Furthermore, the projection image 21 shown in Figure 5 illustrates an example where a void 8 is generated below the thickness direction of the convex portion 41 of the minute irregularities on the surface 4 of the plate-like object 1, and the mold resin 5 below the thickness direction of the concave portion 42 is recessed compared to the surface of the second wafer 2-2.

[0031] (Imaging step) The imaging step 104 is a step in which the imaging unit 12 captures the projected image 21 projected in the projection step 103 via the surface 4 of the plate-like object 1 which is formed on a mirror surface. In the projection step 103, the projected image 21 projected onto the projection surface 20 is reflected on the surface 4 of the plate-like object 1. In Embodiment 1, in the imaging step 104, the electronic device 10 captures the projected image 21 reflected on the surface 4 of the plate-like object 1 with the imaging unit 12. After that, an operator or the like checks for the presence or absence of minute irregularities on the surface 4 of the plate-like object 1 in the captured projected image 21, that is, the presence or absence of minute steps between the surfaces of the void 8, mold resin 5, and chip 6 and the surface of the second wafer 2-2.

[0032] In the plate-shaped object inspection method according to Embodiment 1 described above, in the projection step 103, the reflected light 113 of the light 111 irradiated onto the surface 4 of the plate-shaped object 1 is projected onto the projection surface 20 to form a projected image 21 that reflects the irregularities on the surface 4 of the plate-shaped object 1, and in the imaging step 104, the imaging unit 12 captures the projected image 21 projected onto the surface 4 of the plate-shaped object 1. Therefore, the plate-shaped object 1 can be inspected without immersing it in water, and thus contamination of the plate-shaped object 1 can be prevented.

[0033] Furthermore, the inspection method for a plate-shaped object according to Embodiment 1 involves darkening the area around the plate-shaped object 1, the electronic device 10, and the projection surface 20, and without using complex optical systems such as lenses, projecting the reflected light 113 of the light 111 irradiated onto the surface 4 of the plate-shaped object 1 onto the projection surface 20 in the projection step 103. This forms a projected image 21 that reflects the irregularities on the surface 4 of the plate-shaped object 1, using the principle of a so-called magic mirror. Thus, the surface 4 of the plate-shaped object 1 can be easily inspected.

[0034] Furthermore, the inspection method for plate-shaped objects according to Embodiment 1 has the effect of allowing the defect of the plate-shaped object 1 to be confirmed on the actual plate-shaped object 1, since the imaging unit 12 captures the projected image 21 formed on the projection surface 20 projected onto the surface 4 of the plate-shaped object 1 in the imaging step 104.

[0035] As a result, the inspection method for plate-like objects according to Embodiment 1 has the effect of enabling simple inspection of plate-like objects 1 without contaminating them.

[0036] Next, the inventors of the present invention confirmed the effectiveness of the inspection method for plate-shaped objects according to Embodiment 1. For this confirmation, the plate-shaped object 1, the electronic device 10, and the projection surface 20 were positioned in the relative positions shown in Figure 3, the surroundings were darkened, and light 111 was irradiated from the light source 11. The projected image 21 of the present invention obtained by imaging was compared with an image of a comparative example obtained by imaging without darkening the surroundings or irradiating with light 111 from the light source 11.

[0037] In the comparative example image, the areas reflecting the unevenness of the surface 4 of the plate-like object 1 were not visible. In contrast to this comparative example image, the projected image 21 of the present invention showed a pattern reflecting the minute step difference between the surface of the mold resin 5 and chip 6 and the surface of the second wafer 2-2.

[0038] Therefore, in the projection step 103, the reflected light 113 of the light 111 irradiated onto the surface 4 of the plate-like object 1 is projected onto the projection surface 20 to form a projection image 21 that reflects the irregularities on the surface 4 of the plate-like object 1. In the imaging step 104, the imaging unit 12 captures the projection image 21 projected onto the surface 4 of the plate-like object 1, making it possible to confirm the presence or absence of minute steps between the surfaces of the voids 8, mold resin 5, and chips 6 and the surface of the second wafer 2-2, as well as their positions.

[0039] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core of the present invention. For example, in the present invention, the plate-shaped object 1 to be inspected is not limited to a so-called three-layer structure having three wafers 2-1, 2-2, and 2-3, but may also be a so-called two-layer structure having two wafers 2-1 and 2-2 as shown in Figure 6, or it may have four or more wafers 2-1, 2-2, and 2-3. Figure 6 is a schematic cross-sectional view showing a modified example of the plate-shaped object shown in Figure 1. In Figure 6, the same reference numerals are used for the same parts as in Embodiment 1, and their descriptions are omitted. In the case of the plate-shaped object 1 shown in Figure 6, for example, the second wafer 2-2 is inspected.

[0040] Furthermore, in this invention, the plate-shaped object 1 to be inspected is not limited to a bonded wafer, but may also be a wafer that has undergone internal processing (for example, a modified layer or cracks formed inside).

[0041] Furthermore, in the present invention, the projection surface 20 does not have to be a wall surface parallel to the vertical direction. For example, as shown in Figure 7, it may be a screen or the like that is inclined with respect to the vertical direction so that it gradually approaches the surface 4 of the plate-like object 1 in the horizontal direction as it goes upward. Figure 7 is a schematic diagram showing the electronic equipment, plate-like object, and projection surface shown in Figure 3. Note that in Figure 7, the same reference numerals are used for the same parts as in Embodiment 1, and their descriptions are omitted. [Explanation of Symbols]

[0042] 1. Plate-like object 4 surface 10 Electronic equipment 11 Light source 12 Imaging Unit 20 Projection plane 21 Projection Image 102 Irradiation Step 103 Projection Step 104 imaging steps 111 light 113 Reflected light θ Angle (a given angle of incidence)

Claims

1. A method for inspecting a plate-shaped object whose surface is formed to be mirror-like, using a light source and an imaging unit disposed near the light source, An irradiation step in which light is irradiated onto the surface of the plate-shaped object from the light source at a predetermined angle of incidence, A projection step involves projecting the reflected light from the light irradiated onto the surface of the plate-like object in the irradiation step onto a projection surface to form a projected image that reflects the irregularities created on the surface of the plate-like object, An imaging step in which the projected image projected in the projection step is captured by the imaging unit through the surface of the plate-like object formed on a mirror surface, A method for inspecting plate-shaped objects, characterized by comprising the following features.

2. The method for inspecting a plate-shaped object according to claim 1, characterized in that the light source and the imaging unit are included in an electronic device.

Images