Manufacturing method of wafer

Abstract

To provide a manufacturing method of a wafer in which a loss of an oxide film on a lower substrate is suppressed.SOLUTION: A manufacturing method of a wafer includes a preparation step, a coating formation step, and an etching step. In the preparation step, a substrate joint body comprising a lower substrate, an upper substrate which is adjacent to the lower substrate in a thickness direction of the lower substrate, and an oxide film. The oxide film includes: an inner film part between the lower substrate and the upper substrate; a lower film part covering an outer surface of the lower substrate; and an upper film part covering an outer surface of the upper substrate and connected to the lower film part. In the coating formation step, an annular coating is formed which covers at least a portion of the lower film part, a portion of the upper film part, and an annular connection part of the lower film part and the upper film part. In the etching step, the upper film part is etched by an etchant which dissolves the oxide film.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a wafer including two stacked substrates.

Background Art

[0002] Conventionally, as a method for manufacturing this type of wafer, for example, the method described in Patent Document 1 is known. In the manufacturing method described in Patent Document 1, a base wafer (hereinafter referred to as a lower substrate) and a bond wafer (hereinafter referred to as an upper substrate) are prepared. An oxide film is formed on the surface of the upper substrate. Next, the lower substrate and the upper substrate are joined by heat treatment to form a bonded wafer. When the heat treatment is performed in an atmosphere containing oxygen, an oxide film is also formed on the surface of the lower substrate. Hereinafter, a bonded wafer having an oxide film also formed on the surface of the lower substrate is referred to as a substrate assembly.

[0003] Next, the outer peripheral portion of the upper substrate is ground to a depth that does not reach the lower substrate in the thickness direction of the wafer. As a result, a portion of the oxide film formed on the ground portion of the upper substrate is removed. The unground portion of the outer peripheral portion of the upper substrate is etched with an etching solution that corrodes the substrate. At this time, the oxide film on the unground portion remains on the wafer without being etched. The remaining oxide film on the unground portion is etched with an etching solution that corrodes the oxide film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method for manufacturing a wafer described in Patent Document 1, when the oxide film on the unground portion is etched, the etching solution may reach the vicinity of the upper substrate of the oxide film on the lower substrate, and the oxide film on the lower substrate may be etched. From the viewpoint of suppressing defects due to etching of the oxide film on the lower substrate, there is still room for improvement in the method for manufacturing a wafer.

[0006] Therefore, an object of the present invention is to solve the above problems and provide a method for manufacturing a wafer in which defects in the oxide film on the lower substrate are suppressed.

Means for Solving the Problems

[0007] To achieve the above object, a method for manufacturing a wafer according to an aspect of the present invention includes: a preparation step of preparing a substrate assembly including a lower substrate, an upper substrate adjacent to the lower substrate in the thickness direction of the lower substrate, an inner film portion between the lower substrate and the upper substrate, a lower film portion covering the outer surface of the lower substrate, and an oxide film having an upper film portion covering the outer surface of the upper substrate and connected to the lower film portion; a covering portion forming step of forming an annular covering portion covering at least a part of the lower film portion, a part of the upper film portion, and an annular connection portion between the lower film portion and the upper film portion; an etching step of etching the upper film portion with an etching solution that dissolves the oxide film; and includes.

Effects of the Invention

[0008] According to the present invention, it is possible to manufacture a wafer in which defects in the oxide film on the lower substrate are suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0010] The method for manufacturing a wafer according to one aspect of the present invention is as follows: A preparation step of preparing a substrate bonded body including a lower substrate, an upper substrate adjacent to the lower substrate in the thickness direction of the lower substrate, an inner film portion between the lower substrate and the upper substrate, a lower film portion covering the outer surface of the lower substrate, and an oxide film having an upper film portion covering the outer surface of the upper substrate and connected to the lower film portion; A covering portion forming step of forming an annular covering portion covering at least a part of the lower film portion, a part of the upper film portion, and an annular connecting portion between the lower film portion and the upper film portion; An etching step of etching the upper film portion of the oxide film with an etching solution that dissolves the oxide film; and includes.

[0011] When the upper film portion of the oxide film is etched, there is a possibility that the etching solution reaches the vicinity portion of the lower film portion with respect to the upper film portion, and at least a part of the lower film portion may be etched together with the upper film portion. On the other hand, according to the above manufacturing method, at least a part of the lower film portion is covered by the covering portion in the etching step, and thus is protected from the etching solution.

[0012] Furthermore, in the above manufacturing method, the covering portion straddles the connection portion between the lower film portion and the upper film portion in the thickness direction. By this, the above-mentioned vicinity portion of the lower film portion is more reliably protected from the etching solution as compared with a method in which the covering portion does not straddle the connection portion. Therefore, it is possible to suppress the defect of the lower film portion due to the etching of the lower film portion together with the upper film portion.

[0013] Also, the covering portion may cover the entire surface of the lower film portion.

[0014] According to this manufacturing method, since the entire surface of the lower film portion is protected from the etching solution by the covering portion, the defect due to the etching of the lower film portion can be further suppressed as compared with a method in which the covering portion covers only a part of the surface of the lower film portion.

[0015] Also, according to the above manufacturing method, in the etching step, dipping etching can be performed in which the substrate assembly is dipped in the etching solution. By this, the manufacturing efficiency of the wafer can be improved as compared with a method of adopting an etching technique for processing the substrate assemblies one by one such as spin etching.

[0016] Also, the upper substrate may have a protruding portion that protrudes outward of the connection portion when viewed along the thickness direction. The surface of the upper film portion may have a downward region having a downward component. The surface of the lower film portion may have an overlapping region that overlaps the upper film portion and is connected to the downward region of the upper film portion when viewed along the thickness direction. The covering portion forming step may include a coating step in which a photosensitive resin that is solubilized in a developer by exposure is applied across the overlapping region of the lower film portion and the downward region of the upper film portion, an exposure step in which light that exposes the photosensitive resin is irradiated downward along the thickness direction with respect to the substrate assembly, and a developing step in which the exposed portion of the photosensitive resin is dissolved by the developer to form the covering portion.

[0017] According to this manufacturing method, the light that exposes the photosensitive resin is irradiated downward onto the substrate assembly. As a result, the photosensitive resin applied to the upward region having an upward component on the surface of the upper film portion is solubilized and dissolved by the developer. Therefore, in the etching step, the upward region of the upper film portion can be exposed from the covering portion and brought into contact with the etching solution.

[0018] Also, according to this manufacturing method, since the upper substrate and the upper film portion block the light irradiated downward, the photosensitive resin applied to the downward region of the upper film portion and the overlapping region of the lower film portion remains without being exposed to light and solubilized. As a result, a covering portion that straddles the connection portion between the lower film portion and the upper film portion in the thickness direction can be formed without using a coating technique that requires high precision.

[0019] In the coating step, the photosensitive resin may be poured onto the upper film portion and spin-coated on the entire surface of the upper film portion and the overlapping region of the lower film portion. In the etching step, the upper film portion may be spin-etched from above.

[0020] According to this manufacturing method, the upper film portion is spin-etched. In this case, since it is difficult for the etching solution to reach the downward region having a downward component on the surface of the lower film portion, there is little need to form a covering portion in the downward region of the lower film portion. Therefore, compared with a method in which the etching of the upper film portion is performed by a method other than spin etching, the covering portion can be made smaller, and the amount of photosensitive resin used in the manufacture of the wafer can be reduced.

[0021] In the coating step, the substrate assembly may be immersed in the photosensitive resin.

[0022] According to this manufacturing method, photosensitive resin can also be applied to the downward region of the lower film portion. Since the photosensitive resin applied to the downward region of the lower film portion is not exposed to the light irradiated downward, it remains without being photosensitized and solubilized. As a result, since the downward region of the lower film portion is covered by the covering portion, compared with a method in which the downward region is not covered by the covering portion, it is possible to suppress the defect of the lower film portion due to etching of the lower film portion together with the upper film portion.

[0023] Further, when the photosensitive resin applied to the surface of the lower film portion is not exposed to the above light, the entire surface of the lower film portion is protected from the etching solution by the covering portion. As a result, in the etching step, immersion etching in which the substrate assembly is immersed in the etching solution can be performed. Therefore, the manufacturing efficiency of the wafer can be improved as compared with the case of adopting an etching method for processing the substrate assemblies one by one such as spin etching.

[0024] Further, the upper substrate may have a protruding portion that protrudes outward from the connecting portion when viewed along the thickness direction. The surface of the upper film portion may have a downward region having a downward component. In the covering portion forming step, the resin constituting the covering portion may be poured onto the lower film portion and spin-coated on the entire surface of the lower film portion and the downward region of the upper film portion.

[0025] According to this manufacturing method, since the resin is poured onto the lower film portion and spin-coated, it is difficult to reach the upward region of the upper film portion. Therefore, in the etching step, the upward region of the upper film portion can be more reliably exposed from the covering portion as compared with other coating methods. Therefore, the upper film portion can be etched more reliably.

[0026] Further, according to the above manufacturing method, a step of removing the resin from the surface of the upper film portion to expose the upper film portion (for example, photosensitization and removal of the photosensitive resin) is not required. Therefore, the number of steps in wafer manufacturing can be reduced as compared with a method in which such a step is required. Therefore, the manufacturing efficiency of the wafer can be improved.

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that these embodiments do not limit the present invention. Also, in the drawings, substantially the same members are denoted by the same reference numerals, and the description thereof will be omitted.

[0028] Hereinafter, for convenience of explanation, terms indicating directions such as "upper" and "lower" are used, but these terms do not limit the method for manufacturing a wafer according to the present invention or the usage state of the wafer manufactured by the manufacturing method.

[0029] <Embodiment> With reference to FIGS. 1 to 5, a first example of a method for manufacturing a wafer according to the present invention and a wafer manufactured by the manufacturing method will be described. FIG. 1 is a plan view showing a first example of a method for manufacturing a wafer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view corresponding to line III-III in FIG. 1 of a wafer manufactured by the method for manufacturing a wafer according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a cross-sectional view showing a process subsequent to FIG. 3. FIG. 5 is a cross-sectional view showing a process subsequent to FIG. 4. FIG. 6 is an enlarged cross-sectional view showing the process shown in FIG. 5.

[0030] As shown in FIG. 2, the wafer 1 includes a lower substrate 20 covered with an oxide film 40 and an upper substrate 30 bonded to the lower substrate 20 via the oxide film 40 in the thickness direction of the lower substrate 20. The thickness direction of the lower substrate 20 is also the thickness direction of the upper substrate 30. Hereinafter, the thickness direction of the lower substrate 20 and the upper substrate 30 will be simply referred to as the thickness direction. In this specification and the claims, the thickness direction corresponds to the vertical direction. In the example shown in FIG. 2, each of the lower substrate 20 and the upper substrate 30 is a silicon substrate.

[0031] When the lower substrate 20 and the upper substrate 30 are silicon substrates, the oxide film 40 contains silicon oxide. The oxide film 40 has an inner film portion 41 sandwiched between the lower substrate 20 and the upper substrate 30 in the thickness direction, and a lower film portion 42 covering the outer surface of the lower substrate 20. In this specification and the claims, the outer surface of the lower substrate 20 refers to the region of the surface of the lower substrate 20 excluding the bonding region bonded to the upper substrate 30 via the oxide film 40. That is, the lower film portion 42 is the portion of the portion of the oxide film 40 covering the lower substrate 20 excluding the inner film portion 41.

[0032] On the other hand, the outer surface of the upper substrate 30 is not covered by the oxide film. In this specification and the claims, the outer surface of the upper substrate 30 refers to the region of the surface of the upper substrate 30 excluding the bonding region bonded to the upper substrate 30 via the oxide film 40.

[0033] A first example of a method for manufacturing a wafer according to an embodiment of the present invention will be described. In FIGS. 1 to 5, the thickness of the oxide film 40 is exaggeratedly shown in order to clearly show the arrangement of the oxide film 40. Also, in each figure, the lower substrate 20 and the upper substrate 30 are shown to have the same thickness, but they may have different thicknesses.

[0034] (Preparation step) First, as shown in FIG. 3, in the preparation step, a substrate assembly 10 for manufacturing a wafer 1 is prepared.

[0035] The substrate assembly 10 has a lower substrate 20 and an upper substrate 30 bonded to the lower substrate 20 via the inner film portion 41 of the oxide film 40 in the thickness direction. The oxide film 40 covers each of the lower substrate 20 and the upper substrate 30. The oxide film 40 has an upper film portion 43 covering the outer surface of the upper substrate 30 in addition to the inner film portion 41 and the lower film portion 42.

[0036] The lower substrate 20 and the upper substrate 30 are circular in shape with the same diameter when viewed in a plan view along the thickness direction. Hereinafter, the plan view along the thickness direction will be simply referred to as the plan view. Note that the lower substrate 20 and the upper substrate 30 may have a shape other than circular in the plan view. Also, the diameter of the lower substrate 20 and the diameter of the upper substrate 30 may be different. In the present embodiment, in the plan view, the center of the lower substrate 20 and the center of the upper substrate 30 overlap each other.

[0037] The lower film portion 42 and the upper film portion 43 are connected to each other at the connection portion 44 which is the edge portion of the inner film portion 41. As shown in FIG. 1, the connection portion 44 is annular in the plan view. That is, the lower film portion 42 and the upper film portion 43 are connected to each other over the entire circumference of the edge portion of the inner film portion 41. Note that the connection portion 44 has a shape corresponding to the shapes of the lower substrate 20 and the upper substrate 30. For example, when the lower substrate 20 and the upper substrate 30 are polygonal, the connection portion 44 is polygonal in the plan view. That is, the term "annular" is not limited to a circular ring shape.

[0038] As shown in FIGS. 1 and 3, the upper substrate 30 has an upper protruding portion 31 that protrudes outward from the annular connection portion 44 in the plan view. The upper protruding portion 31 corresponds to the "protruding portion" in the present invention. In the example shown in FIG. 3, the upper protruding portion 31 has a shape that bulges in a direction orthogonal to the thickness direction.

[0039] As shown in FIG. 3, in the present embodiment, the lower substrate 20 has a lower protruding portion 21 that protrudes outward from the annular connection portion 44 in the plan view. The lower protruding portion 21 has a shape that bulges in a direction orthogonal to the thickness direction.

[0040] The thickness of each of the lower film portion 42 and the upper film portion 43 is constant or substantially constant, but it may not be constant or substantially constant. When the thickness of each of the lower film portion 42 and the upper film portion 43 is constant or substantially constant, each of the surface 42a of the lower film portion 42 and the surface 43a of the upper film portion 43 has a shape along the outer surface of the lower substrate 20 or the outer surface of the upper substrate 30. The surface 42a of the lower film portion 42 has a downward region 42b having a downward component in the thickness direction and an upward region 42c having an upward component. The surface 43a of the upper film portion 43 has a downward region 43b having a downward component in the thickness direction and an upward region 43c having an upward component.

[0041] In other words, on the surface 42a of the lower film portion 42, the downward region 42b of the lower film portion 42 is a region below the most protruding portion of the lower protrusion 21. The upward region 42c of the lower film portion 42 is a region above the most protruding portion of the lower protrusion 21. Similarly, on the surface 43a of the upper film portion 43, the downward region 43b of the upper film portion 43 is a region below the most protruding portion of the upper protrusion 31. The upward region 43c of the upper film portion 43 is a region above the most protruding portion of the upper protrusion 31.

[0042] The surface 42a of the lower film portion 42 has an overlapping region that overlaps the upper film portion 43 in plan view and is connected to the downward region 43b of the upper film portion 43. In the present embodiment, the entire surface of the surface 42a of the lower film portion 42 is the overlapping region.

[0043] Such a substrate bonded body 10 can be manufactured, for example, as follows. First, an oxide film 40 is formed on at least one surface of the lower substrate 20 and the upper substrate 30. The oxide film 40 can be formed, for example, by thermal oxidation such as dry oxidation, wet oxidation, or steam oxidation, sputtering, or chemical vapor deposition (CVD). In the present embodiment, it is described assuming that the oxide film 40 is formed only on the surface of the lower substrate 20. Next, the lower substrate 20 and the upper substrate 30 are heat-treated and bonded in a state where they are overlapped in the thickness direction with the oxide film 40 interposed therebetween. At this time, when the heat treatment is performed in an atmosphere containing oxygen, an oxide film 40 is also formed on the outer surface of the upper substrate 30. Thus, the substrate bonded body 10 as shown in FIG. 3 is completed.

[0044] (Coating portion forming step) Next, in the coating portion forming step, as shown in FIG. 4, an annular coating portion 50 is formed to cover at least a part of the lower film portion 42, a part of the upper film portion 43, and the annular connecting portion 44. In the present embodiment, the coating portion 50 straddles all portions of the connecting portion 44 in the thickness direction in the thickness direction. In the example shown in FIG. 4, the coating portion 50 covers the upward region 42c of the lower film portion 42 and the downward region 43b of the upper film portion 43.

[0045] Such a coating portion 50 can be formed, for example, by the coating step, exposure step, and development step described below.

[0046] (Coating step) First, in the coating step, a photosensitive resin is applied to at least the downward region 43b of the surface 43a of the upper film portion 43 and at least the upward region 42c of the surface 42a of the lower film portion 42. The photosensitive resin is solubilized in a developer described later by causing a chemical or structural change by light having a specific wavelength. As the photosensitive resin, for example, a positive photoresist such as OFPR-5000 manufactured by Tokyo Ohka Kogyo Co., Ltd. can be used.

[0047] The photosensitive resin is applied, for example, by spin coating. In the example shown in FIG. 4, the photosensitive resin is poured into the upward region 43c of the upper film portion 43, and by the rotation of the substrate assembly 10, it is spread over the entire surface 43a of the upper film portion 43 and the upward region 42c of the lower film portion 42. On the other hand, since the photosensitive resin is scattered away from the lower film portion 42 by the centrifugal force caused by the rotation of the substrate assembly 10, it is not applied to the downward region 42b of the lower film portion 42.

[0048] Note that the method for applying the photosensitive resin is not limited to spin coating as long as the photosensitive resin can be applied to at least the portion where the covering portion 50 is formed on the surface 42a of the lower film portion 42 and the surface 43a of the upper film portion 43. For example, the photosensitive resin may be applied to the entire surface 42a of the lower film portion 42 and the entire surface 43a of the upper film portion 43 by immersing the entire substrate assembly 10 in the photosensitive resin. Also, for example, the photosensitive resin may be spray-coated.

[0049] (Exposure process) In the exposure process after the coating process, the light that exposes the photosensitive resin is irradiated downward along the thickness direction with respect to the substrate assembly 10, as indicated by the arrow in FIG. 4. The photosensitive resin applied to the upward region 43c of the upper film portion 43 (shown by the broken line in FIG. 4) is exposed to the downward-irradiated light and is exposed. On the other hand, the photosensitive resin applied to the downward region 43b of the upper film portion 43 and the downward region 42b of the lower film portion 42 is not exposed to the light and does not become exposed.

[0050] The downward-irradiated light is blocked by the upper substrate 30 and the upper film portion 43. Therefore, the photosensitive resin applied to the overlapping region in the upward region 42c of the lower film portion 42 is not exposed to the light and does not become exposed. On the other hand, if there is a non-overlapping region in the upward region 42c of the lower film portion 42 that does not overlap with the upper film portion 43 in plan view, the photosensitive resin applied to the non-overlapping region is exposed to the light and becomes exposed.

[0051] Note that in the exposure process, the portion of the applied photosensitive resin that constitutes the covering portion 50 may be masked in order to more reliably prevent exposure and solubilization.

[0052] (Development process) In the development process after the exposure process, the exposed portions of the applied photosensitive resin are dissolved by the developer. The developer dissolves the exposed portions of the photosensitive resin while not dissolving the unexposed portions. The developer is, for example, an alkaline developer. In the example shown in FIG. 4, the photosensitive resin (shown by a broken line in FIG. 4) applied to the upward region 43c of the upper film portion 43 is dissolved by the developer and removed from the substrate assembly 10. As a result, the upward region 43c of the upper film portion 43 is exposed to the outside of the covering portion 50.

[0053] By the above-described coating process, exposure process, and development process, a covering portion 50 composed of the unexposed portions of the applied photosensitive resin is formed.

[0054] (Etching process) Next, in the etching process, as shown in FIG. 5, the upper film portion 43 (shown by a broken line in FIG. 5) is etched by an etching solution that dissolves the oxide film 40. The etching solution has a corrosive action on the oxide film 40. For example, when the oxide film 40 contains silicon oxide, the etching solution is diluted hydrofluoric acid (DHF) or buffered hydrofluoric acid (BHF).

[0055] The etching of the upper film portion 43 is performed, for example, by spin etching. In the case of spin etching, the etching solution is poured into the upward region 43c of the upper film portion 43 and acts while spreading over the upward region 43c by the rotation of the substrate assembly 10.

[0056] As the etching of the upper film portion 43 progresses, as shown in FIG. 6, a gap D is formed between the upper substrate 30 and the covering portion 50 due to the dissolution of the upper film portion 43. At least a part of the etching solution that has spread along the outer surface of the upper substrate 30 enters the gap D. The etching solution that has entered the gap D advances along the gap D without dripping away from the outer surface of the upper substrate 30 or scattering due to the rotation of the substrate assembly 10, and dissolves the upper film portion 43 that constitutes the bottom of the gap D. Therefore, according to this method, compared with the method in which the downward region 43b of the upper film portion 43 is not covered by the covering portion 50, the portion of the upper film portion 43 that constitutes the downward region 43b can be more reliably dissolved.

[0057] If at least a part of the upper film portion 43 remains without being etched, the remaining portion of the upper film portion 43 may later come off the substrate assembly 10 and become fragments. Such fragments may interfere with later processes such as grinding and polishing of the upper substrate 30, or may cause damage such as cracks to the upper substrate 30. On the other hand, when the spin etching described above is performed, since the portion of the upper film portion 43 that constitutes the downward region 43b can be more reliably dissolved, the possibility of the generation of fragments of the upper film portion 43 can be reduced. Therefore, it is possible to suppress obstacles in processes such as grinding and polishing of the upper substrate 30 and damage to the upper substrate 30.

[0058] Also, the etching solution that has entered the gap D does not contact the lower film portion 42 until the upper film portion 43 between the upper substrate 30 and the covering portion 50 is etched. That is, the etching of the lower film portion 42 is not started until the upper film portion 43 is etched. Therefore, it is possible to suppress the loss of the lower film portion 42 due to the etching of the lower film portion 42 together with the upper film portion 43.

[0059] Note that the method of etching the upper film portion 43 is not limited to spin etching. For example, when the entire surface 42a of the lower film portion 42 is covered by the covering portion 50, immersion etching in which the entire substrate assembly 10 is immersed in the etching solution may be performed.

[0060] (Coating Removal Step) Next, the coating portion 50 is removed from the substrate assembly 10, and the wafer 1 is manufactured. For example, the coating portion 50 is removed by immersion in a remover, ashing, or the like.

[0061] After the coating removal step, the upper substrate 30 may be processed according to the use of the wafer 1. For example, the upper substrate 30 may be ground downward along the thickness direction by a grinding wheel. In this case, in the wafer 1 manufactured by the above manufacturing method, since the upper film portion 43 is removed, it is possible to suppress the consumption of the grinding wheel by grinding the upper film portion 43 harder than the upper substrate 30. Further, since fragments of the upper film portion 43 are less likely to occur during grinding, it is possible to reduce the possibility of hindrance to the processing of the upper substrate 30 and damage to the upper substrate 30 caused by the fragments.

[0062] A second example of a wafer manufacturing method will be described with reference to FIGS. 7 and 8. FIG. 7 is a cross-sectional view showing a second example of a wafer manufacturing method according to an embodiment of the present invention, corresponding to the line III-III in FIG. 1. FIG. 8 is a cross-sectional view showing the steps following FIG. 7. The difference between the second example of the wafer manufacturing method and the first example of the wafer manufacturing method is that in the coating formation step, the exposure step and the development step are not required. Therefore, the resin constituting the coating portion 50 is not limited to a photosensitive resin, and for example, a heat-shrinkable resin resistant to hydrofluoric acid can be used. In the second example of the wafer manufacturing method, the description of the same steps as in the first example will be omitted below.

[0063] In the coating formation step, as shown in FIG. 7, the substrate assembly 10 is placed in an upside-down posture, that is, a posture in which the lower substrate 20 is positioned above the upper substrate 30. Hereinafter, the names of the respective components will be used for explanation regardless of the posture of the substrate assembly 10.

[0064] The resin is spin-coated onto the substrate assembly 10. More specifically, the resin is poured into the downward region 42b of the lower film portion 42 and spread over the entire surface 42a of the lower film portion 42 and the downward region 43b of the upper film portion 43 by the rotation of the substrate assembly 10. On the other hand, since the resin is scattered away from the upper film portion 43 by the centrifugal force caused by the rotation of the substrate assembly 10, it is not applied to the upward region 43c of the upper film portion 43. The applied resin hardens to form the covering portion 50.

[0065] Next, in the etching process, as shown in FIG. 8, the upper film portion 43 is etched. In FIG. 8, the substrate assembly 10 is shown in its original posture, that is, the same posture as the substrate assembly 10 shown in FIG. 5. Since the entire surface 42a of the lower film portion 42 is covered by the covering portion 50, the upper film portion 43 can be etched by immersion etching. Note that the etching method of the upper film portion 43 is not particularly limited, and for example, the above-mentioned spin etching may be used.

[0066] When the upper film portion 43 of the oxide film 40 is etched, the etching solution may reach the vicinity portion of the lower film portion 42 with respect to the upper film portion 43, and at least a part of the lower film portion 42 may be etched together with the upper film portion 43. On the other hand, according to the above manufacturing method, at least a part of the lower film portion 42 is covered by the covering portion 50 in the etching process, and thus is protected from the etching solution.

[0067] Furthermore, in the above manufacturing method, the covering portion 50 straddles the connection portion 44 between the lower film portion 42 and the upper film portion 43 in the thickness direction. Thus, the above-mentioned vicinity portion of the lower film portion 42 is more reliably protected from the etching solution as compared with a method in which the covering portion 50 does not straddle the connection portion 44. Therefore, it is possible to suppress the loss of the lower film portion 42 due to the etching of the lower film portion 42 together with the upper film portion 43.

[0068] When the lower film portion 42 is partially etched, the thickness variation of the lower film portion 42 becomes large, and interference fringes are likely to occur on the surface of the lower film portion 42. Such interference fringes can cause misrecognition and malfunction of an apparatus that recognizes the outer shape of the wafer 1 and performs handling or processing of the wafer 1. On the other hand, according to the above method, since at least a part of the lower film portion 42 is protected from the etching solution, it is possible to suppress an increase in the thickness variation of the lower film portion 42. As a result, interference fringes are less likely to occur on the surface of the lower film portion 42, so that the above misrecognition and malfunction can be suppressed. Further, in the portion of the lower film portion 42 protected by the covering portion 50, since the thickness variation of the lower film portion 42 is small, patterning of the wafer 1 can be performed using the lower film portion 42.

[0069] Further, according to this manufacturing method, since the entire surface 42a of the lower film portion 42 is protected from the etching solution by the covering portion 50, compared with a method in which the covering portion 50 covers only a part of the surface 42a of the lower film portion 42, it is possible to further suppress defects due to etching of the lower film portion 42.

[0070] Further, according to the above manufacturing method, in the etching step, immersion etching can be performed in which the substrate assembly 10 is immersed in the etching solution. As a result, compared with a method of adopting an etching technique for processing the substrate assemblies 10 one by one, such as spin etching, the manufacturing efficiency of the wafer 1 can be improved.

[0071] Further, according to this manufacturing method, the light that exposes the photosensitive resin is irradiated downward with respect to the substrate assembly 10. As a result, the photosensitive resin applied to the upward region 43c of the upper film portion 43 is solubilized and dissolved by the developer. Therefore, in the etching step, the upward region 43c of the upper film portion 43 can be exposed from the covering portion 50 and brought into contact with the etching solution.

[0072] Also, according to this manufacturing method, since the upper substrate 30 and the upper film portion 43 block the light irradiated downward, the photosensitive resin applied to the downward region 43b of the upper film portion 43 and the overlapping region of the lower film portion 42 remains without being photosensitized and solubilized. As a result, the covering portion 50 that straddles the connection portion 44 between the lower film portion 42 and the upper film portion 43 in the thickness direction can be formed without using a coating method that requires high precision.

[0073] Also, according to this manufacturing method, the upper film portion 43 is spin-etched. In this case, since it is difficult for the etching solution to reach the downward region 42b of the lower film portion 42, the necessity of forming the covering portion 50 in the downward region 42b of the lower film portion 42 is low. Therefore, compared with a method in which the etching of the upper film portion 43 is performed by a method other than spin etching, the covering portion 50 can be made smaller, and the amount of the photosensitive resin used in the manufacture of the wafer 1 can be reduced.

[0074] Also, according to this manufacturing method, the photosensitive resin can be applied to the downward region 42b of the lower film portion 42. Since the photosensitive resin applied to the downward region 42b of the lower film portion 42 is not exposed to the light irradiated downward, it remains without being photosensitized and solubilized. As a result, since the downward region 42b of the lower film portion 42 is covered by the covering portion 50, compared with a method in which the downward region 42b is not covered by the covering portion 50, it is possible to suppress the defect of the lower film portion 42 due to the etching of the lower film portion 42 together with the upper film portion 43.

[0075] Also, when the photosensitive resin applied to the surface 42a of the lower film portion 42 is not exposed to the above-mentioned light, the entire surface of the surface 42a of the lower film portion 42 is protected from the etching solution by the covering portion 50. As a result, in the etching step, immersion etching in which the substrate assembly 10 is immersed in the etching solution can be performed. Therefore, compared with the case of adopting an etching method of processing the substrate assemblies 10 one by one such as spin etching, the manufacturing efficiency of the wafer 1 can be improved.

[0076] Also, according to this manufacturing method, since the resin is poured into the lower film portion 42 and spin-coated, it is difficult to reach the upward region 43c of the upper film portion 43. Therefore, in the etching process, the upward region 43c of the upper film portion 43 can be more reliably exposed from the covering portion 50 compared with other coating methods. Thus, the upper film portion 43 can be etched more reliably.

[0077] Further, according to the above manufacturing method, a step of removing the resin from the surface 43a of the upper film portion 43 to expose the upper film portion 43 (for example, exposure and removal of a photosensitive resin) is not required. Therefore, the number of steps in the manufacture of the wafer 1 can be reduced compared with the method that requires such a step. Thus, the manufacturing efficiency of the wafer 1 can be improved.

[0078] Note that the present invention is not limited to the above-described embodiments and can be implemented in various other modes. For example, in the above, each of the lower substrate 20 and the upper substrate 30 is assumed to be a silicon substrate, but the present invention is not limited thereto. Each of the lower substrate 20 and the upper substrate 30 may be composed of a material capable of forming the oxide film 40 on their surfaces. For example, each of the lower substrate 20 and the upper substrate 30 may be a silicon substrate doped with impurities such as phosphorus or boron.

[0079] Also, in the above, in the preparation step, the upper substrate 30 and the lower substrate 20 covered with the oxide film 40 are joined, but the present invention is not limited thereto. The substrate assembly 10 may be produced, for example, by joining the lower substrate 20 and the upper substrate 30 covered with the oxide film 40, or may be produced by joining the lower substrate 20 and the upper substrate 30 both covered with the oxide film 40.

[0080] The present invention is fully described in connection with preferred embodiments with reference to the accompanying drawings, but various modifications and variations will be apparent to those skilled in the art. Such modifications and variations are to be understood as being included therein as long as they do not depart from the scope of the present invention as defined by the appended claims.

Industrial Applicability

[0081] Since the present invention can suppress the defect of the oxide film on the lower substrate, it is useful for a method of manufacturing a wafer in which a plurality of substrates are bonded.

Explanation of Reference Numerals

[0082] 1 Wafer 10 Substrate assembly 20 Lower substrate 30 Upper substrate 31 Upper protrusion 40 Oxide film 42 Lower film portion 42a Surface 43 Upper film portion 43a Surface 43b Downward region 44 Connection portion 50 Coating portion

Claims

1. A preparation step of preparing a substrate assembly including a lower substrate, an upper substrate adjacent to the lower substrate in the thickness direction of the lower substrate, an inner film portion between the lower substrate and the upper substrate, a lower film portion covering the outer surface of the lower substrate, and an oxide film having an upper film portion covering the outer surface of the upper substrate and connecting to the lower film portion; A covering portion forming step of forming an annular covering portion covering at least a part of the lower film portion, a part of the upper film portion, and an annular connection portion between the lower film portion and the upper film portion; An etching step of etching the upper film portion with an etching solution that dissolves the oxide film; Including A method for manufacturing a wafer.

2. The method for manufacturing a wafer according to claim 1, wherein the covering portion covers the entire surface of the lower film portion.

3. The upper substrate has a protruding portion protruding outward from the connection portion when viewed along the thickness direction, The surface of the upper film portion has a downward region having a downward component, The surface of the lower film portion has a overlapping region that overlaps the upper film portion and connects to the downward region of the upper film portion when viewed along the thickness direction, The covering portion forming step includes A coating step of coating a photosensitive resin that is solubilized in a developer by exposure across the overlapping region of the lower film portion and the downward region of the upper film portion; An exposure step of irradiating light that exposes the photosensitive resin downward along the thickness direction with respect to the substrate assembly; A developing step of dissolving the exposed portion of the photosensitive resin with a developer to form the covering portion; Including The method for manufacturing a wafer according to claim 1 or 2.

4. In the coating step, the photosensitive resin is poured onto the upper film portion and spin-coated on the entire surface of the upper film portion and the overlapping region of the lower film portion, In the etching step, the upper film portion is spin-etched from above, The method for manufacturing a wafer according to claim 3.

5. The method for manufacturing a wafer according to claim 3, wherein in the coating step, the substrate assembly is immersed in the photosensitive resin.

6. The upper substrate has a protruding portion protruding outward from the connection portion when viewed along the thickness direction, The surface of the upper film portion has a downward region having a downward component, In the covering portion forming step, the resin constituting the covering portion is poured onto the lower film portion and spin-coated on the entire surface of the lower film portion and the downward region of the upper film portion, The method for manufacturing a wafer according to claim 2.

Images