SOI substrate, method for manufacturing an SOI substrate, and transducer

Abstract

To provide an SOI substrate with improved reliability of the bond between the support substrate and the element substrate. [Solution] The SOI substrate 4 comprises a support substrate 1 having a first surface 11 and a recess 13c having a second surface 12 recessed from the first surface 11, an element substrate 3 that forms a cavity 6 with the recess 13c, and an oxide film 2 provided between the support substrate 1 and the element substrate 3. The support substrate 1 has a protrusion 14p on the edge of the recess 13c, and either the support substrate 1 or the element substrate 3 is provided so as to overlap with the protrusion 14p in a plan view and has a counterbore portion 15c as a second recess that is deeper than the height 14h of the protrusion 14p.

Description

Technical Field

[0001] The present invention relates to a SOI substrate, a method for manufacturing the SOI substrate, and a transducer.

Background Art

[0002] Patent Document 1 describes an example in which a semiconductor device including a SOI (Silicon on Insulator) substrate is applied to an acceleration sensor. The SOI substrate includes a silicon substrate, a support substrate having a recess, an insulating film provided on the support substrate, and a semiconductor layer made of a silicon substrate and joined to the insulating film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the study by the inventors, in the manufacturing process of the transducer, when the support substrate is placed in a high-temperature environment, swelling may occur along the edge of the recess of the support substrate. When swelling occurs at the edge of the recess of the support substrate, there is a risk that the bonding between the element substrate and the support substrate becomes unstable.

[0005] This problem becomes particularly prominent when the manufacturing process of the transducer includes a step of forming a recess in a support substrate made of a silicon substrate and then forming an oxide film on the surface of the support substrate including the recess by a thermal oxidation method.

Means for Solving the Problems

[0007] A method for manufacturing an SOI substrate according to one aspect of the present application includes the steps of: forming a first recess on a first surface of a first semiconductor substrate that is recessed from the first surface; forming a second recess on the edge of the first recess on the first surface of the first semiconductor substrate; forming an oxide film on the first surface of the first semiconductor substrate and forming a protrusion in the second recess that is lower than the depth of the second recess; and joining the first semiconductor substrate and the second semiconductor substrate.

[0008] A method for manufacturing an SOI substrate according to one aspect of the present application comprises the steps of: forming a first recess on a first surface of a first semiconductor substrate that is recessed from the first surface; forming an oxide film on the first surface of the first semiconductor substrate and forming a protrusion on the edge of the first recess on the first surface; forming a second recess on a third surface of a second semiconductor substrate at a position that overlaps with the protrusion in a plan view, the second recess being deeper than the height of the protrusion and wider than the width of the protrusion; and joining the first semiconductor substrate and the second semiconductor substrate.

[0009] A transducer according to one aspect of the present application comprises the SOI substrate. [Brief explanation of the drawing]

[0010] [Figure 1] A plan view of a transducer equipped with an SOI substrate according to Embodiment 1. [Figure 2] Cross-sectional view of the transducer along line AA in Figure 1. [Figure 3] Enlarged cross-sectional view of area C in Figure 2. [Figure 4] Flowchart showing a method for manufacturing a transducer including a method for manufacturing a SOI substrate. [Figure 5] Flowchart showing details of the support substrate preparation step of FIG. 4. [Figure 6A] Cross-sectional view showing one aspect of the manufacturing process. [Figure 6B] Cross-sectional view showing one aspect of the manufacturing process. [Figure 6C] Cross-sectional view showing one aspect of the manufacturing process. [Figure 6D] Cross-sectional view showing one aspect of the manufacturing process. [Figure 6E] Cross-sectional view showing one aspect of the manufacturing process. [Figure 6F] Cross-sectional view showing one aspect of the manufacturing process. [Figure 7] Enlarged cross-sectional view of the range C of FIG. 2 of the transducer according to Embodiment 2. [Figure 8A] Flowchart showing details of the support substrate preparation step of FIG. 4. [[ID=3l]] [Figure 8B] Flowchart showing details of the element substrate preparation step of FIG. 4. [Figure 9A] Cross-sectional view showing one aspect of the manufacturing process. [Figure 9B] Cross-sectional view showing one aspect of the manufacturing process. [Figure 9C] Cross-sectional view showing one aspect of the manufacturing process. [Figure 9D] Cross-sectional view showing one aspect of the manufacturing process. [Figure 9E] Cross-sectional view showing one aspect of the manufacturing process. [Figure 10] Plan view of a transducer provided with a SOI substrate according to Embodiment 3. [[ID=Sl]] [Figure 11] Cross-sectional view of the transducer along the line D-D of FIG. 10.

MODE FOR CARRYING OUT THE INVENTION

[0011] In the embodiments of the present invention, the components shown in each drawing may be shown with different dimensional scales for ease of viewing. The drawings may illustrate three axes, an X-axis, a Y-axis, and a Z-axis, which are perpendicular to each other.

[0012] In the following description, the tip side of the arrow of the three axes may be described as the "plus side" and the base end side of the arrow may be described as the "minus side". A direction parallel to the X-axis may be described as the "X-axis direction", a direction parallel to the Y-axis may be described as the "Y-axis direction", and a direction parallel to the Z-axis may be described as the "Z-axis direction".

[0013] In the following, "plan view" means looking at an object from the plus side in the Z-axis direction of the object or from the minus side in the Z-axis direction of the object. The plus side in the Z-axis direction may be described as "above", and the minus side in the Z-axis direction may be described as "below".

[0014] The description of the upper surface of a certain configuration refers to the surface on the plus side in the Z-axis direction of the said configuration. For example, the "upper surface of the substrate" indicates the surface on the plus side in the Z-axis direction of the substrate. The description of the lower surface of a certain configuration refers to the surface on the minus side in the Z-axis direction of the said configuration. For example, the "lower surface of the substrate" indicates the surface on the minus side in the Z-axis direction of the substrate.

[0015] Hereinafter, as a specific example of the transducer 100 provided with the SOI substrate 4 of the present embodiment, examples of an acceleration sensor 110 provided with the SOI substrate 4 and a vibrator 130 provided with the SOI substrate will be described. Note that the transducer 100 is not limited to the acceleration sensor 110 and the vibrator 130. Generally, a transducer refers to a converter that converts a certain physical quantity into another physical quantity, and there are transducers by electromechanical conversion, transducers by acoustic-electric conversion, transducers by opto-electric conversion, and the like. The transducer 100 according to one aspect of the present application may be a transducer 100 formed using the SOI substrate 4. For example, the transducer 100 provided with the SOI substrate 4 may be a physical quantity sensor such as a vibration power generation device provided with the SOI substrate 4, a gyro sensor provided with the SOI substrate 4, or other MEMS (Micro Electro Mechanical System) devices provided with the SOI substrate 4.

[0016] 1. Embodiment 1 In Embodiment 1, an acceleration sensor 110 equipped with an SOI substrate 4 will be described based on the drawings as an example of a transducer 100 equipped with an SOI substrate 4.

[0017] 1.1. Accelerometer with SOI substrate Figure 1 is a plan view of an acceleration sensor 110 equipped with an SOI substrate 4 according to Embodiment 1, in which the cover 5 is made transparent. Figure 2 is a cross-sectional view of the acceleration sensor 110 along line AA in Figure 1.

[0018] As shown in Figure 1, the acceleration sensor 110 is a Si-MEMS sensor manufactured using silicon MEMS technology. The acceleration sensor 110 detects changes in physical quantities due to the displacement of the roughly inverted U-shaped movable frame 31 as changes in capacitance. In Embodiment 1, the acceleration sensor 110 is a Z-axis acceleration sensor that measures acceleration in the Z-axis direction based on the displacement of the movable frame 31. However, the acceleration sensor 110 is not limited to a Z-axis acceleration sensor. For example, it may be a sensor that detects acceleration in the X-axis direction and / or the Y-axis direction.

[0019] The acceleration sensor 110 may include electronic circuits (not shown). In other words, the acceleration sensor 110 may include electronic circuits. In this case, the electronic circuits are mounted on a semiconductor chip, for example, and electrically connected to the acceleration sensor 110. The electronic circuits are, for example, a conversion circuit and an output circuit. The conversion circuit converts the displacement of the movable frame 31 into an electrical signal, and the output circuit outputs the converted electrical signal as a detection signal. The acceleration sensor 110 does not have to include electronic circuits. In other words, the acceleration sensor 110 does not have to include electronic circuits. The acceleration sensor 110 may also be housed in a package (not shown).

[0020] As shown in Figure 2, the acceleration sensor 110 comprises an SOI substrate 4 and a cover 5. The SOI substrate 4 comprises a support substrate 1, an element substrate 3, and an oxide film 2 provided between the support substrate 1 and the element substrate 3.

[0021] The support substrate 1 and the element substrate 3 are each composed of silicon substrates. In Embodiment 1, the support substrate 1 is an example of a first semiconductor substrate, and the element substrate 3 is an example of a second semiconductor substrate.

[0022] The oxide film 2 is an insulator made of a silicon oxide film formed by thermal oxidation treatment of the support substrate 1 using a thermal oxidation method. In Embodiment 1, since the oxide film 2 is formed after the recess 13c is formed in the support substrate 1, it is formed on the surface of the support substrate 1, including the inside of the recess 13c. The oxide film 2 may be formed by the CVD method, but it is more preferable to form the oxide film 2 by the thermal oxidation method. This is because an oxide film formed by the thermal oxidation method has better flatness and uniformity of film thickness than an oxide film formed by the CVD method.

[0023] The support substrate 1 has a first surface 11 and a recess 13c having a second surface 12 that is recessed from the first surface 11. In Embodiment 1, the recess 13c is an example of a first recess. The element substrate 3 is bonded to the first surface 11. A portion of the first surface 11 constitutes the mounting portion 16. The mounting portion 16 is a base on which the first fixing frame 36a, the second fixing frame 36b, and the fixing portion 38 of the element substrate 3 are placed.

[0024] The recess 13c is bonded to the first surface 11 by the element substrate 3, thereby forming a cavity 6 between the recess 13c and the element substrate 3. The second surface 12 is the bottom surface of the recess 13c. A projection 17 is provided on the second surface 12. The projection 17 is a stopper that suppresses excessive vibration of the first comb-tooth movable electrode 32a and the second comb-tooth movable electrode 32b of the element substrate 3. The projection 17 is also provided on the recess 5c of the lid 5.

[0025] The element substrate 3 has an element portion 3e and a peripheral portion 34 formed by MEMS processing technology. The element portion 3e and the peripheral portion 34 are electrically insulated from each other. A cover 5 is joined to the peripheral portion 34, forming a housing space S between the support substrate 1 and the cover 5. The element portion 3e is housed in the housing space S. The housing space S is maintained in a desired atmosphere. For example, the housing space S is filled with an inert gas such as nitrogen, helium, or argon, and at the operating temperature (approximately -40°C to 80°C), the atmosphere is approximately atmospheric pressure.

[0026] The element section 3e includes a movable frame 31, a fixed frame 36, a fixed section 38, and a beam section 39. The movable frame 31 has a first extending portion 31a and a second extending portion 31b that extend in the Y-axis direction, a connecting portion 31c that connects one end of the first extending portion 31a and one end of the second extending portion 31b, and a first comb-tooth movable electrode 32a and a second comb-tooth movable electrode 32b provided on the connecting portion 31c.

[0027] The other end of the first extension 31a and the other end of the second extension 31b are fixed to the fixing part 38 via the beam part 39. The beam part 39 is a torsion bar, and together with the movable frame 31, forms a structure called a one-sided seesaw structure. As a result, the movable frame 31 is held to swing freely in the Z-axis direction with the beam part 39 as the axis of rotation in the housing space S.

[0028] The fixed frame 36 includes a first fixed frame 36a, a second fixed frame 36b, a first comb-tooth fixed electrode 37a provided on the first fixed frame 36a, and a second comb-tooth fixed electrode 37b provided on the second fixed frame 36b.

[0029] The element unit 3e constitutes a detection unit Z for detecting acceleration in the Z-axis direction. The detection unit Z includes a first detection unit ZA composed of a first comb-tooth movable electrode 32a and a first comb-tooth fixed electrode 37a, and a second comb-tooth movable electrode 32b and a second comb-tooth fixed electrode 37b.

[0030] The first comb-tooth movable electrode 32a has a recess R1. The recess R1 is a portion of the first comb-tooth movable electrode 32a that is recessed in the Z-axis direction. The second comb-tooth fixed electrode 37b has a recess R2. The recess R2 is a portion of the second comb-tooth fixed electrode 37b that is recessed in the Z-axis direction.

[0031] By having recesses R1 and R2, the acceleration sensor 110 can detect acceleration in both the positive and negative directions along the Z-axis. When acceleration occurs in the positive direction along the Z-axis, the opposing area between the first comb-tooth movable electrode 32a and the first comb-tooth fixed electrode 37a decreases in the first detection unit ZA. When acceleration occurs in the negative direction along the Z-axis, the opposing area between the second comb-tooth movable electrode 32b and the second comb-tooth fixed electrode 37b decreases in the second detection unit ZB. Therefore, the acceleration sensor 110 can detect the decrease in the opposing area in the detection units ZA and ZB as a change in capacitance.

[0032] The connecting portion 31c has a recess R3. The recess R3 is provided to eliminate the non-uniformity of mass in the X-axis direction of the connecting portion 31c of the movable frame 31 caused by the recess R1. Therefore, the wobble of the movable frame 31 can be suppressed.

[0033] The first comb-tooth fixed electrode 37a is electrically connected to the electrode pad 71 via wiring 74. The second comb-tooth fixed electrode 37b is electrically connected to the electrode pad 73 via wiring 76. The first comb-tooth movable electrode 32a and the second comb-tooth movable electrode 32b are electrically connected to the electrode pad 72 via wiring 75. The electrode pads 71, 72, and 73 are electrically connected to the electronic circuit described above.

[0034] 1.2. Configuration for stabilizing the connection between the support substrate and the element substrate Next, a configuration for stabilizing the bond between the support substrate 1 and the element substrate 3 will be explained based on Figure 3. Figure 3 is an enlarged cross-sectional view of area C in Figure 2.

[0035] The support substrate 1 has a protrusion 14p on the edge of the recess 13c. The protrusion 14p is the part of the edge of the recess 13c of the support substrate 1 that has risen due to being placed in a high-temperature environment during the oxide film formation process S13 described later. The protrusion 14p is formed along the periphery of the recess 13c.

[0036] According to the inventors' studies, the silicon wafer used in the support substrate 1 has a crystal orientation, <100> When a wafer with a flat surface is used, the protrusion 14p is the edge of the recess 13c, <111> By sliding along surface Cp, it is clear that this is a raised area.

[0037] <100> surface and <111> The angle with surface Cp is approximately 54°. Therefore, the width 14w of the protrusion 14p formed by placing the support substrate 1 in a high-temperature environment is <100> Surface and <111> It is possible to predict this from the angle formed by the surface Cp and the depth 13d of the recess 13c. Also, the height 14h of the convex portion 14p is about 1 / 100th of the depth 13d of the recess 13c.

[0038] For example, if the depth 13d of the recess 13c is approximately 30 μm, and the inner wall of the recess 13c is approximately vertical, then the width 14w of the protrusion 14p is approximately 20 μm, and the height 14h of the protrusion 14p is approximately 0.2 μm. The thickness of the oxide film 2 is approximately 2 μm.

[0039] In Figure 3, the depth 13d of the recess 13c is the length from the top surface of the oxide film 2 on the first surface 11 to the top surface of the oxide film 2 on the second surface 12. Alternatively, the depth 13d of the recess 13c may be the length from the first surface 11 to the second surface 12. The height 14h of the protrusion 14p is the length from the top surface of the portion of the counterbore 15c that does not overlap with the protrusion 14p to the top surface of the protrusion 14p. Alternatively, the height 14h of the protrusion 14p may be the length from the top surface of the portion of the oxide film 2 on the counterbore 15c that does not overlap with the protrusion 14p to the top surface of the oxide film 2 at the top of the protrusion 14p. Furthermore, the depth 15d of the counterbore 15c is the length from the top surface of the oxide film 2 on the first surface 11 to the top surface of the portion of the oxide film 2 on the counterbore 15c that does not overlap with the protrusion 14p. The depth 15d of the counterbore portion 15c may be the length from the top surface of the first surface 11 to the top surface of the portion of the counterbore portion 15c that does not overlap with the protrusion 14p.

[0040] The protrusion 14p is formed in the counterbore 15c provided around the recess 13c, along the edge of the recess 13c on the first surface 11. In other words, the counterbore 15c is provided so as to overlap with the position where the protrusion 14p is formed in a plan view. The counterbore 15c is the portion on the first surface 11 that has been removed by etching or the like, including the edge of the recess 13c, before the oxide film 2 is formed.

[0041] The counterbore portion 15c is formed such that its width 15w is greater than the width 14w of the protrusion 14p, and its depth 15d is greater than the height 14h of the protrusion 14p. Therefore, even when the support substrate 1 on which the protrusion 14p is formed and the element substrate 3 are joined via the oxide film 2, the protrusion 14p does not come into contact with the element substrate 3, thus preventing the joint between the support substrate 1 and the element substrate 3 from becoming unstable due to the protrusion 14p. In Embodiment 1, the counterbore portion 15c is an example of a second recess.

[0042] 1.3. Method for manufacturing an SOI substrate and a method for manufacturing an acceleration sensor equipped with an SOI substrate Next, the manufacturing method of the SOI substrate 4 and the manufacturing method of the acceleration sensor 110 equipped with the SOI substrate 4 will be described with reference to Figures 4 to 6F. Figure 4 is a flowchart showing the manufacturing method of the acceleration sensor 110 equipped with the SOI substrate 4, including the manufacturing method of the SOI substrate 4. Figure 5 is a flowchart showing the details of the support substrate preparation step S1 in Figure 4. Figures 6A to 6F are cross-sectional views showing one aspect of the manufacturing process, and Figures 6A to 6F show the cross-section at the position corresponding to the BB line in Figure 1.

[0043] As shown in Figure 4, the manufacturing method for the acceleration sensor 110 equipped with the SOI substrate 4 includes a support substrate preparation step S1, an element substrate preparation step S2, a lid preparation step S3, a first bonding step S4, an etching step S5, a second bonding step S6, and a sealing step S7. In the flowchart of Figure 4, the manufacturing method for the SOI substrate 4 includes the support substrate preparation step S1, the element substrate preparation step S2, and the first bonding step S4.

[0044] As shown in Figure 5, the support substrate preparation step S1 includes a recess formation step S11, a counterbore processing step S12, and an oxide film formation step S13. In the recess formation process S11, as shown in Figure 6A, a mask (not shown) is formed on a part of the first surface 11 of the prepared support substrate 1, and dry etching or the like is performed to form a recess 13c having a second surface 12 that is recessed from the first surface 11. The depth 13d of the recess 13c is formed to a desired depth according to the movable range of the movable frame 31 of the element part 3e. A part of the first surface 11 is made into a mounting part 16. Note that the support substrate 1 and element substrate 3 shown in Figures 6A to 6F represent a part of a wafer. The acceleration sensor 110 is formed in a wafer state in the flowcharts of Figures 4 and 5, and is divided into individual pieces in a subsequent process.

[0045] In the counterboring process S12, as shown in Figure 6B, a counterbored portion 15c is formed around the recess 13c of the first surface 11. The counterbored portion 15c is the part of the edge of the recess 13c of the first surface 11 that has been removed by etching or the like.

[0046] The depth 15d of the counterbore portion 15c is formed to be deeper than the height 14h of the protrusion 14p, and the width 15w of the counterbore portion 15c is formed to be wider than the width 14w of the protrusion 14p.

[0047] In the oxide film formation step S13, as shown in Figure 6C, an oxide film 2 is formed on the support substrate 1 by thermal oxidation. At this time, a protrusion 14p is formed in the counterbore portion 15c along the edge of the recess 13c. The height 14h of the formed protrusion 14p is lower than the depth 15d of the counterbore portion 15c. Therefore, the top of the protrusion 14p does not protrude beyond the first surface 11 of the support substrate 1 in the positive Z-axis direction.

[0048] In the first bonding step S4, as shown in Figure 6D, the element substrate 3 is bonded to the support substrate 1 via the oxide film 2, forming a cavity 6 between the support substrate 1 and the element substrate 3, which is composed of a recess 13c and the element substrate 3. Although Figure 3 was an enlarged cross-sectional view of area C in Figure 2, the area around the recess 13c in Figure 6D has a similar structure to that in Figure 3.

[0049] Even when the support substrate 1 and the element substrate 3 are joined, the protrusion 14p does not come into contact with the element substrate 3. Therefore, the joining of the support substrate 1 and the element substrate 3 is not hindered by the protrusion 14p, enabling a good bond. As a result, bonding defects due to void formation and other issues are avoided, and improvements in yield and product reliability can be expected. Furthermore, since residual stress on the element substrate 3 is eliminated at the edge of the cavity 6, impact resistance can be improved.

[0050] The support substrate 1 and the element substrate 3 are joined, for example, by directly bonding the oxide film 2 and the element substrate 3. Alternatively, the support substrate 1 and the element substrate 3 may be joined using other bonding techniques, such as anodic bonding, intermediate layer bonding, or fusion bonding. Furthermore, after bonding, high-temperature annealing may be performed to improve the bonding quality between the oxide film 2 and the element substrate 3. The SOI substrate 4 is formed through the above process.

[0051] In etching step S5, as shown in Figure 6E, dry etching is performed on the element substrate 3 to form the element portion 3e and the peripheral portion 34. Alternatively, before etching step S5, the element substrate 3 may be ground and polished to a desired thickness.

[0052] The area around the recess 13c in Figure 6E is the same as in Figure 3, and the SOI substrate 4 has the structure of Figure 3. That is, the SOI substrate 4 comprises a support substrate 1 as a first semiconductor substrate having a first surface 11 and a recess 13c as a first recess having a second surface 12 recessed from the first surface 11, an element substrate 3 as a second semiconductor substrate that forms a cavity 6 with the recess 13c, and an oxide film 2 provided between the support substrate 1 and the element substrate 3. The support substrate 1 has a protrusion 14p on the edge of the recess 13c, and either the support substrate 1 or the element substrate 3 is provided so as to overlap with the protrusion 14p in a plan view and has a counterbore portion 15c as a second recess that is deeper than the height 14h of the protrusion 14p.

[0053] In the second bonding step S6, the lid 5 is bonded to the SOI substrate 4, as shown in Figure 6F. In sealing step S7, the containment space S is brought to a desired atmosphere using a through-hole (not shown) provided in the lid 5, and then the through-hole is sealed. The acceleration sensor 110 is formed by the above steps. The manufacturing process of the acceleration sensor 110 may also include steps such as forming the aforementioned electronic circuit on the acceleration sensor 110, electrically connecting a semiconductor chip equipped with the electronic circuit to the acceleration sensor 110, and housing the acceleration sensor 110 in a package. The area around the recess 13c in Figure 6E is the same as in Figure 3. In this way, the acceleration sensor 110, as a specific example of the transducer 100, has the structure shown in Figure 3. In other words, the transducer 100 comprises a support substrate 1 as a first semiconductor substrate having a first surface 11 and a recess 13c as a first recess having a second surface 12 recessed from the first surface 11, an element substrate 3 as a second semiconductor substrate that forms a cavity 6 with the recess 13c, and an oxide film 2 provided between the support substrate 1 and the element substrate 3. The support substrate 1 has a protrusion 14p on the edge of the recess 13c, and either the support substrate 1 or the element substrate 3 is provided so as to overlap with the protrusion 14p in a plan view and has a counterbore portion 15c as a second recess that is deeper than the height 14h of the protrusion 14p.

[0054] As described above, the SOI substrate 4 of Embodiment 1, the method for manufacturing the SOI substrate 4, and the acceleration sensor 110 equipped with the SOI substrate 4 provide the following effects.

[0055] The SOI substrate 4 of Embodiment 1 comprises a support substrate 1 as a first semiconductor substrate having a first surface 11 and a recess 13c as a first recess having a second surface 12 recessed from the first surface 11, an element substrate 3 as a second semiconductor substrate that forms a cavity 6 with the recess 13c, and an oxide film 2 provided between the support substrate 1 and the element substrate 3. The support substrate 1 has a protrusion 14p on the edge of the recess 13c, and either the support substrate 1 or the element substrate 3 is provided so as to overlap with the protrusion 14p in a plan view and has a counterbore portion 15c as a second recess that is deeper than the height 14h of the protrusion 14p.

[0056] Therefore, according to the SOI substrate 4 of Embodiment 1, even when the support substrate 1 and the element substrate 3 are joined, the protrusions 14p do not come into contact with the element substrate 3, thus preventing the joint between the support substrate 1 and the element substrate 3 from becoming unstable due to the protrusions 14p. Thus, joint defects due to void formation and the like are avoided, and an SOI substrate 4 and / or an acceleration sensor 110 equipped with the SOI substrate 4 can be realized, which have high industrial value and can be expected to improve yield and product reliability.

[0057] In the SOI substrate 4 of Embodiment 1, the counterbore portion 15c, which serves as the second recess, is provided in the support substrate 1, which serves as the first semiconductor substrate. As described above, since the counterbore portion 15c is provided on the support substrate 1, the alignment of the counterbore portion 15c and the protrusion portion 14p can be easily performed. Therefore, it is possible to reliably avoid instability in the joint between the support substrate 1 and the element substrate 3.

[0058] The manufacturing method for the SOI substrate 4 of Embodiment 1 includes a recess formation step S11, which is the step of forming a recess 13c as a first recess that is recessed from the first surface 11 of the support substrate 1 as a first semiconductor substrate; a counterbore processing step S12, which is the step of forming a counterbore portion 15c as a second recess at the edge of the recess 13c on the first surface 11 of the support substrate 1; an oxide film formation step S13, which is the step of forming an oxide film 2 on the first surface 11 of the support substrate 1 and forming a protrusion 14p in the counterbore portion 15c that is lower than the depth 15d of the counterbore portion 15c; and a first joining step S4, which is the step of joining the support substrate 1 and the element substrate 3.

[0059] Therefore, according to the manufacturing method of the SOI substrate 4 of Embodiment 1, even when the support substrate 1, on which the protrusions 14p are formed by the oxide film formation step S13, is joined to the element substrate 3, the protrusions 14p do not come into contact with the element substrate 3. Thus, the instability of the joint between the support substrate 1 and the element substrate 3 due to the protrusions 14p is avoided. As a result, bonding defects due to void formation and the like are avoided, and a manufacturing method for the SOI substrate 4 with high industrial value that can be expected to improve yield and product reliability can be realized.

[0060] The acceleration sensor 110, which serves as the transducer 100 in Embodiment 1, includes the SOI substrate 4 described above. Therefore, a highly reliable acceleration sensor 110 can be realized.

[0061] 2. Embodiment 2 Embodiment 2 describes another form of the acceleration sensor 110 of Embodiment 1 with reference to the drawings. Figure 7 is an enlarged cross-sectional view of the area C in Figure 2 of the acceleration sensor 110 according to Embodiment 2. Figure 8A is a flowchart detailing the support substrate preparation process S1 in Figure 4. Figure 8B is a flowchart detailing the element substrate preparation process S2 in Figure 4. Figures 9A to 9E are cross-sectional views showing one aspect of the manufacturing process.

[0062] Embodiment 2 differs from Embodiment 1 in that a recessed portion 35c corresponding to the recessed portion 15c of Embodiment 1 is provided on the element substrate 3. Note that components identical to those in Embodiment 1 are denoted by the same reference numerals, and their descriptions may be omitted.

[0063] 2.1. Configuration for stabilizing the bond between the support substrate and the element substrate As shown in Figure 7, a recessed portion 35c is provided on the third surface 33 of the element substrate 3 at a position overlapping with the protrusion 14p. The third surface 33 is the lower surface of the element substrate 3 and is the bonding surface with the support substrate 1.

[0064] The counterbore portion 35c is formed such that its width 35w is greater than the width 14w of the protrusion 14p, and its depth 35d is greater than the height 14h of the protrusion 14p. Therefore, even when the support substrate 1 on which the protrusion 14p is formed and the element substrate 3 are joined via the oxide film 2, the protrusion 14p does not come into contact with the element substrate 3, thus preventing the joint between the support substrate 1 and the element substrate 3 from becoming unstable due to the protrusion 14p. In Embodiment 2, the counterbore portion 35c is an example of a second recess.

[0065] 2.2. Method for manufacturing an SOI substrate and a method for manufacturing an acceleration sensor equipped with an SOI substrate In Embodiment 2, the SOI substrate 4 is manufactured based on the follow chart shown in Figure 4. In the manufacturing method of the SOI substrate 4 of Embodiment 2, the support substrate preparation step S1 includes a recess formation step S11 and an oxide film formation step S13, as shown in Figure 8A.

[0066] In the recess formation step S11, as shown in Figure 9A, a mask (not shown) is formed on a part of the first surface 11 of the prepared support substrate 1, and dry etching or the like is performed to form a recess 13c having a second surface 12 that is recessed from the first surface 11.

[0067] In the oxide film formation step S13, as shown in Figure 9B, an oxide film 2 is formed on the support substrate 1 by thermal oxidation. At this time, the edge of the recess 13c rises, forming a convex portion 14p.

[0068] As shown in Figure 8B, in Embodiment 2, the element substrate preparation step S2 includes the counterboring step S21.

[0069] In the counterboring process S21, as shown in Figure 9C, a counterbored portion 35c is formed on the third surface 33 of the element substrate 3. The counterbored portion 35c is the part of the third surface 33 that has been removed by etching or the like, and is provided in a position that overlaps with the protrusion 14p when joined to the support substrate 1.

[0070] The depth 35d of the counterbore portion 35c is formed to be deeper than the height 14h of the protrusion 14p, and the width 35w of the counterbore portion 35c is formed to be wider than the width 14w of the protrusion 14p.

[0071] In the first bonding step S4, as shown in Figure 9D, the element substrate 3 is bonded to the support substrate 1 via the oxide film 2, forming a cavity 6 between the support substrate 1 and the element substrate 3, which is composed of a recess 13c and the element substrate 3.

[0072] Even when the support substrate 1 and the element substrate 3 are joined, the protrusion 14p does not come into contact with the element substrate 3. Therefore, the joining of the support substrate 1 and the element substrate 3 is not hindered by the protrusion 14p, enabling a good bond. As a result, bonding defects due to void formation and other issues are avoided, and improvements in yield and product reliability can be expected. Furthermore, since residual stress on the element substrate 3 is eliminated at the edge of the cavity 6, impact resistance can be improved.

[0073] The SOI substrate 4 is formed by the above process. Specifically, the SOI substrate 4 comprises a support substrate 1 as a first semiconductor substrate having a first surface 11 and a recess 13c as a first recess having a second surface 12 recessed from the first surface 11, an element substrate 3 as a second semiconductor substrate that forms a cavity 6 with the recess 13c, and an oxide film 2 provided between the support substrate 1 and the element substrate 3. The support substrate 1 has a protrusion 14p on the edge of the recess 13c, and either the support substrate 1 or the element substrate 3 is provided so as to overlap with the protrusion 14p in a plan view and has a counterbore portion 35c as a second recess that is deeper than the height 14h of the protrusion 14p.

[0074] In etching step S5, as shown in Figure 9E, dry etching is performed on the element substrate 3 to form the element portion 3e and the peripheral portion 34. Subsequently, as described above, the lid 5 is joined to the SOI substrate 4, sealing the housing space and thus forming the acceleration sensor 110. Specifically, the transducer 100 comprises a support substrate 1 as a first semiconductor substrate having a first surface 11 and a recess 13c as a first recess having a second surface 12 recessed from the first surface 11, an element substrate 3 as a second semiconductor substrate that forms a cavity 6 with the recess 13c, and an oxide film 2 provided between the support substrate 1 and the element substrate 3. The support substrate 1 has a protrusion 14p on the edge of the recess 13c, and either the support substrate 1 or the element substrate 3 is provided so as to overlap with the protrusion 14p in a plan view and has a counterbore 35c as a second recess that is deeper than the height 14h of the protrusion 14p.

[0075] As described above, the SOI substrate 4 of Embodiment 2, the method for manufacturing the SOI substrate 4, and the acceleration sensor 110 equipped with the SOI substrate 4 provide the following effects in addition to the effects of Embodiment 1.

[0076] In the SOI substrate 4 of Embodiment 2, the counterbore portion 35c, which serves as the second recess, is provided in the element substrate 3, which serves as the second semiconductor substrate. The counterbore portion 35c is provided so as to overlap with the protrusion 14p. Therefore, the counterbore portion 35c can be used as an alignment mark. Thus, good bonding between the support substrate 1 and the element substrate 3 can be achieved.

[0077] The manufacturing method for the SOI substrate 4 of Embodiment 2 includes a recess formation step S11, which is the step of forming a recess 13c as a first recess that is recessed from the first surface 11 of the support substrate 1 as a first semiconductor substrate; an oxide film formation step S13, which is the step of forming an oxide film 2 on the first surface 11 of the support substrate 1 and forming a protrusion 14p on the edge of the recess 13c of the first surface 11; a counterbore processing step S21, which is the step of forming a counterbore portion 35c as a second recess that is deeper than the height 14h of the protrusion 14p and wider than the width 14w of the protrusion 14p on the third surface 33 of the element substrate 3 as a second semiconductor substrate at a position that overlaps with the protrusion 14p in a plan view; and a first joining step S4, which is the step of joining the support substrate 1 and the element substrate 3.

[0078] Therefore, according to the manufacturing method of the SOI substrate 4 of Embodiment 2, even when the support substrate 1, on which the protrusions 14p are formed by the oxide film formation step S13, is joined to the element substrate 3, the protrusions 14p do not come into contact with the element substrate 3. Thus, the instability of the joint between the support substrate 1 and the element substrate 3 due to the protrusions 14p is avoided. As a result, bonding defects due to void formation and the like are avoided, and a manufacturing method for the SOI substrate 4 with high industrial value that can be expected to improve yield and product reliability can be realized.

[0079] The acceleration sensor 110, which serves as the transducer 100 in Embodiment 2, includes the SOI substrate 4 described above. Therefore, a highly reliable acceleration sensor 110 can be realized.

[0080] 3. Embodiment 3 In Embodiment 3, as an example of a transducer 100 equipped with an SOI substrate 4, a resonator 130 equipped with an SOI substrate 4 will be described based on the drawings. Figure 10 is a plan view of the transducer 130 equipped with the SOI substrate 4 according to Embodiment 3, in which the cover 5 is made transparent. Figure 11 is a cross-sectional view of the transducer 130 along the DD line in Figure 10.

[0081] As shown in Figures 10 and 11, the oscillator 130 is a Si-MEMS timing device manufactured using silicon MEMS technology. Note that components identical to those in the embodiments described above are denoted by the same reference numerals, and their descriptions may be omitted.

[0082] The oscillator 130 comprises an SOI substrate 4 and a cover 5. The SOI substrate 4 comprises a support substrate 1, an element substrate 3, and an oxide film 2 provided between the support substrate 1 and the element substrate 3.

[0083] The support substrate 1 has a recessed portion 15c, and a protrusion 14p is formed in the recessed portion 15c. Therefore, even when the support substrate 1 and the element substrate 3 are joined, the protrusion 14p does not come into contact with the element substrate 3, thus preventing the joint between the support substrate 1 and the element substrate 3 from becoming unstable due to the protrusion 14p. Thus, joint defects due to void formation and the like are avoided, and it is possible to realize an industrially valuable SOI substrate 4 and / or an oscillator 130 equipped with the SOI substrate 4 that can be expected to improve yield and product reliability. The counterbore portion 15c may be formed on the element substrate 3 in the same manner as the counterbore portion 35c shown in Embodiment 2.

[0084] The element substrate 3 has a vibrating element 8. The vibrating element 8 has a base portion 81 and a movable portion 82 extending from the base portion 81. The vibrating element 8 of Embodiment 3 has three movable portions 82. Although not shown in the diagram, the base portion 81 is fixed to the first surface 11 of the support substrate 1 and is provided in a cantilevered configuration.

[0085] The cover 5 has an electronic circuit 92. The electronic circuit 92 includes an oscillator circuit, an output circuit, a temperature compensation circuit, and a PLL (Phase Locked Loop) circuit. By connecting the vibrating element 8 to the oscillator circuit, the vibrating element 8 oscillates at a frequency based on the resonant frequency of the movable part 82. The output circuit outputs the generated reference signal. The electronic circuit 92 may be provided on the support substrate 1.

[0086] In Embodiment 3, the oscillator 130 is equipped with an electronic circuit 92, but the electronic circuit 92 does not have to be mounted on the oscillator 130. In other words, in Embodiment 3, the oscillator 130 includes an electronic circuit 92, but the oscillator 130 does not have to include an electronic circuit 92. In this case, the electronic circuit 92 is mounted on a semiconductor chip and electrically connected to the oscillator 130. The oscillator 130 may also be housed in a package (not shown).

[0087] The external electrode 94 is placed on the insulating layer 93. The external electrode 94 is electrically connected to the electronic circuit 92, the through electrode 91, and the vibrating element 8.

[0088] As described above, the oscillator 130 equipped with the SOI substrate 4 of Embodiment 3 provides the following effects in addition to the effects of Embodiment 1 and / or Embodiment 2.

[0089] The transducer 130 in Embodiment 3, which serves as the transducer 100, includes the SOI substrate 4 described above. Therefore, a highly reliable transducer 130 can be realized.

[0090] Although preferred embodiments have been described above, the present invention is not limited to the embodiments described above. The configuration of each part of the present invention can be replaced with any configuration that performs a similar function to the embodiments described above, and any configuration can be added. [Explanation of Symbols]

[0091] 1...Support substrate, 11...First surface, 12...Second surface, 13c...Recess, 13d...Depth, 14p...Convex part, 14w...Width, 14h...Height, 15c...Counterbore part, 15w...Width, 15d...Depth, 16...Mounting part, 17...Protrusion, 2...Oxide film, 3...Element substrate, 3e...Element part, 31...Movable frame, 31a...First extension part, 31b...Second extension part, 31c...Connecting part, 32a...First comb-tooth movable electrode, 32b...Second comb-tooth movable electrode, 33...Third surface, 34...Peripheral part, 35c...Counterbore part, 35w...Width, 35d...Depth, 36...Fixed frame, 36a...First fixed frame, 3 6b…Second fixed frame, 37a…First comb-tooth fixed electrode, 37b…Second comb-tooth fixed electrode, 38…Fixed part, 39…Beam part, 4…SOI substrate, 5…Lid, 5c…Recess, 6…Cavity, 71,72,73…Electrode pads, 74,75,76…Wiring, 8…Vibration element, 81…Base, 82…Movable part, 91…Through electrode, 92…Electronic circuit, 93…Insulating layer, 94…External electrode, 100…Transducer, 110…Accelerometer, 130…Vibrator, R1,R2,R3…Recess, S…Housing space, Z…Detection part, ZA…First detection part, ZB…Second detection part, Cp… <111> surface.

Claims

1. A first semiconductor substrate comprising a first surface and a first recess having a second surface recessed from the first surface, A second semiconductor substrate bonded to the first semiconductor substrate and forming a cavity with the first recess, The device comprises an oxide film provided between the first semiconductor substrate and the second semiconductor substrate, The first semiconductor substrate has a protrusion on the edge of the first recess, Either the first semiconductor substrate or the second semiconductor substrate is provided so as to overlap with the protrusion and has a second recess that is deeper than the height of the protrusion. SOI substrate.

2. The second recess is provided in the first semiconductor substrate, The SOI substrate according to claim 1.

3. The second recess is provided in the second semiconductor substrate, The SOI substrate according to claim 1.

4. A step of forming a first recess on the first surface of the first semiconductor substrate, which is recessed from the first surface, A step of forming a second recess on the edge of the first recess on the first surface of the first semiconductor substrate, A step of forming an oxide film on the first surface of the first semiconductor substrate, and forming a protrusion in the second recess that is lower than the depth of the second recess, The process includes a step of joining the first semiconductor substrate and the second semiconductor substrate, A method for manufacturing SOI substrates.

5. A step of forming a first recess on the first surface of the first semiconductor substrate, which is recessed from the first surface, A step of forming an oxide film on the first surface of the first semiconductor substrate, and forming a protrusion on the edge of the first recess on the first surface, A step of forming a second recess on the third surface of the second semiconductor substrate at a position that overlaps with the protrusion in a plan view, the recess being deeper than the height of the protrusion and wider than the width of the protrusion, The process includes a step of joining the first semiconductor substrate and the second semiconductor substrate, A method for manufacturing SOI substrates.

6. A transducer comprising an SOI substrate according to claims 1 to 3.

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