Pressure sensor element and method of manufacturing the same

Abstract

To prevent metal deposited for joining from accumulating on a bottom surface of a diaphragm.SOLUTION: An opening adjustment plate 105 is provided between a support substrate 101 and a first semiconductor layer 102. The opening adjustment plate 105 has a second through-hole 113 having a diameter φ2 smaller than a diameter φ1 of an opening 112 of the first semiconductor layer 102. The second through-hole 113 is located within an area of the opening 112. The opening adjustment plate 105 and the support substrate 101 are joined together via a metal layer 106.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure sensor element and a manufacturing method thereof. [Background technology]

[0002] For example, pressure sensors that output a pressure value from the amount of deflection, or displacement, of a diaphragm subjected to pressure are widely used in industrial applications, including semiconductor equipment. This type of pressure sensor includes a pressure sensor element that uses a strain element that uses the piezoresistance effect to detect the displacement of the diaphragm as stress and outputs a pressure value from the detected stress. In this type of pressure sensor element, the strain element is formed in the semiconductor layer on which the diaphragm is formed (Patent Document 1).

[0003] This pressure sensor element is mounted on a meter body. To insulate and separate the element section made of a semiconductor from the meter body, it is bonded to a support substrate made of an insulator such as glass. In order to fix the semiconductor layer to the support substrate such as glass in this way, a metal layer is formed at the bonding interface between them to improve bonding strength, and the metal layers are then bonded together. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-171318 Summary of the Invention [Problem to be solved by the invention]

[0005] In forming the metal layer described above, the metal is generally deposited from the bottom side of the semiconductor layer by a deposition method such as vacuum evaporation or sputtering. As a result, the metal is also deposited on the bottom surface of the diaphragm exposed in the opening of the semiconductor layer, forming a metal layer. When heat is applied in a later process, the thin metal film formed on the bottom surface of the diaphragm diffuses through the diaphragm (semiconductor layer) and reaches the strain element, creating a current leakage path and affecting the operation of the strain element.

[0006] The present invention has been made to solve the above problems, and has as its object to prevent metal from being deposited on the bottom surface of the diaphragm for bonding. [Means for solving the problem]

[0007] The pressure sensor element of the present invention comprises a support substrate having a first through hole, a first semiconductor layer having an opening and formed on the support substrate, a second semiconductor layer formed on the first semiconductor layer to cover the opening and having a diaphragm with the area of ​​the opening as a pressure receiving portion, a strain element formed in the second semiconductor layer to measure the strain of the diaphragm, and an opening adjustment plate arranged between the support substrate and the first semiconductor layer, having a second through hole that is narrower than the opening of the first semiconductor layer and is positioned within the area of ​​the opening, and joined to the support substrate via a metal layer.

[0008] In one configuration example of the pressure sensor element, the opening adjustment plate is bonded to the first semiconductor layer.

[0009] The method for manufacturing a pressure sensor element according to the present invention includes a first step of preparing a support substrate having a first through-hole, and forming an element portion including a first semiconductor layer having an opening, a second semiconductor layer formed on the first semiconductor layer to cover the opening and having a diaphragm with the area of ​​the opening as a pressure-receiving portion, and a strain element formed in the second semiconductor layer to measure the strain of the diaphragm; a second step of attaching an opening adjustment plate having a second through-hole to the underside of the first semiconductor layer; a third step of forming a metal layer on the surface of the opening adjustment plate that will be the bonding surface with the support substrate, and forming a metal layer on the bonding surface of the support substrate; and a fourth step of abutting the metal layer-forming surface of the opening adjustment plate against the metal layer-forming surface of the support substrate to bond them together.

[0010] In one configuration example of the method for manufacturing the pressure sensor element, the third step forms a metal layer by depositing metal.

[0011] In one configuration example of the above-described method for manufacturing the pressure sensor element, the second step bonds the opening adjustment plate to the first semiconductor layer by joining the opening adjustment plate to the first semiconductor layer. [Effects of the Invention]

[0012] As described above, according to the present invention, an opening adjustment plate having a second through hole is used between the support substrate and the first semiconductor layer, thereby preventing metal deposited for bonding from accumulating on the bottom surface of the diaphragm. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of a pressure sensor element according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing a partial configuration of the pressure sensor element according to the embodiment of the present invention. [Figure 3A] FIG. 3A is a cross-sectional view illustrating a state of the pressure sensor element in the middle of a process, for illustrating a method for manufacturing the pressure sensor element according to the embodiment of the present invention. [Figure 3B]FIG. 3B is a cross-sectional view showing a state of the pressure sensor element in the middle of a process, for illustrating the method of manufacturing the pressure sensor element according to the embodiment of the present invention. [Figure 3C] FIG. 3C is a cross-sectional view showing a state of the pressure sensor element in the middle of a process, for explaining the method of manufacturing the pressure sensor element according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] A pressure sensor element according to an embodiment of the present invention will be described below with reference to Figures 1 and 2. This pressure sensor element includes a support substrate 101, a first semiconductor layer 102, a second semiconductor layer 103, a strain element 104, and an aperture adjustment plate 105.

[0015] The support substrate 101 has a first through hole 111. The support substrate 101 can be made of an insulating material such as glass (heat-resistant glass), quartz, or sapphire. The support substrate 101 can also be made of gold, aluminum, copper, GaAs, or the like. The support substrate 101 is made of a different material from the first semiconductor layer 102 described below. The first semiconductor layer 102 is formed on the support substrate 101. The first semiconductor layer 102 has an opening 112. The first semiconductor layer 102 can be made of silicon, for example.

[0016] The second semiconductor layer 103 is formed on the first semiconductor layer 102, covering the opening 112. The second semiconductor layer 103 also has a diaphragm 121 formed thereon, with the region of the opening 112 serving as a pressure-receiving portion. As illustrated in FIG. 2, the opening 112 may have a rectangular (square) shape in plan view when viewed from the normal direction to the plane of the second semiconductor layer 103. In this case, the shape of the diaphragm 121 in plan view is rectangular (square). The opening 112 may also have a circular shape in plan view. In this case, the shape of the diaphragm 121 in plan view is circular. The second semiconductor layer 103 may be made of single-crystal silicon whose main surface is a (100) plane.

[0017] The strain elements 104 are formed on the second semiconductor layer 103 and measure the strain of the diaphragm 121. For example, as illustrated in Fig. 2, the strain elements 104 can be arranged at four locations at equal intervals around the circumference of the diaphragm 121. When the shape of the diaphragm 121 in a plan view is square, the strain elements 104 can be arranged near the center of each of the four sides.

[0018] The strain element 104 can be, for example, a piezo-strain element that uses the piezo-resistance effect to measure the strain of the diaphragm 121. For example, the piezo-strain element can be configured by a piezo-resistance region formed from a p-type region by introducing boron (B), which is a p-type impurity, into a predetermined location of the diaphragm 121 made of single crystal silicon.

[0019] Furthermore, strain element 104 can be made of a material whose resistance value changes with strain and can be used to measure the strain of diaphragm 121. The strain element includes a detection layer whose resistance value changes with strain and a reference layer that serves as a reference for the detection layer, and measures the strain of diaphragm 121 by comparing the change in resistance between the detection layer and the reference layer. The reference layer is, for example, a layer whose deformation due to pressure is fixed, and whose resistance value does not change with strain.

[0020] The aperture adjustment plate 105 is disposed between the support substrate 101 and the first semiconductor layer 102. The aperture adjustment plate 105 has a second through hole 113 with a diameter φ2 narrower than the diameter φ1 of the aperture 112 in the first semiconductor layer 102. The second through hole 113 is disposed within the region of the aperture 112. The aperture adjustment plate 105 and the support substrate 101 are bonded together via a metal layer 106. The aperture adjustment plate 105 may be bonded to the first semiconductor layer 102.

[0021] According to the above-described embodiment, the provision of opening adjustment plate 105 having second through-hole 113 narrower than opening 112 in first semiconductor layer 102 suppresses the amount of metal deposited to bond support substrate 101 penetrating into first semiconductor layer 102. As a result, the amount of metal deposited that reaches the bottom surface of diaphragm 121 can be reduced.

[0022] Next, a method for manufacturing the pressure sensor element according to the embodiment will be described with reference to FIGS. 3A, 3B, and 3C.

[0023] 3A, an element section is fabricated which includes a frame-shaped first semiconductor layer 102 having an opening 112, a second semiconductor layer 103 on which a diaphragm 121 is formed, and a strain element 104 formed on the second semiconductor layer 103. The element section can be fabricated by bonding together the first semiconductor layer 102, which is formed by processing a silicon substrate, and the second semiconductor layer 103, which is formed by processing another silicon substrate. Furthermore, although not shown, a support substrate 101 having a first through hole 111 formed therein is prepared (first step).

[0024] For example, an n-type silicon substrate is prepared, and a mask pattern having openings in areas that will become strain elements 104 is formed on the silicon substrate using a known photolithography technique. Next, a p-type impurity such as boron is introduced into the silicon substrate exposed through the openings in the mask pattern using a known ion implantation method to form piezoresistance elements that will become strain elements 104.

[0025] Next, after removing the mask pattern, a mask pattern having openings in regions to be lead-out wiring portions connected to the strain element 104 is formed on the silicon substrate again. Next, by a known ion implantation method, impurities are introduced at a higher concentration into the silicon substrate exposed through the openings of the mask pattern to form a lead-out wiring structure.

[0026] Next, after removing the mask pattern, the second semiconductor layer 103 is thinned by known chemical mechanical polishing (CMP) or dry etching techniques to form the strain element 104 using the piezoresistance element described above.

[0027] Meanwhile, another silicon substrate is prepared, and a mask layer having an opening corresponding to the region where the opening 112 will be formed is formed thereon by a known photolithography technique. Next, the silicon substrate is etched using the mask layer as a mask in a state of high vertical anisotropy by well-known reactive ion etching, thereby forming the first semiconductor layer 102 having the opening 112. The second semiconductor layer 103 and the first semiconductor layer 102 formed as described above are bonded together to form the element portion.

[0028] Alternatively, the element portion can be formed using a well-known SOI (Silicon on Insulator) substrate. For example, a mask pattern having openings in areas to be the strain element 104 is formed on the surface silicon layer of the SOI substrate by known photolithography. Next, a p-type impurity such as boron is introduced by known ion implantation into the surface silicon layer exposed through the openings of the mask pattern to form a piezoresistance element, which is the strain element 104.

[0029] Next, after removing the mask pattern, a mask pattern having openings in regions to be lead-out wiring portions connected to the strain element 104 is formed on the surface silicon layer again. Next, by a known ion implantation method, impurities are introduced at a higher concentration into the surface silicon layer exposed through the openings of the mask pattern to form a lead-out wiring structure.

[0030] Meanwhile, a mask layer having an opening corresponding to the region to be the opening 112 is formed on the back surface of the SOI substrate by known photolithography. Next, the silicon substrate and the buried oxide layer are etched with high vertical anisotropy by well-known reactive ion etching using the mask layer as a mask, thereby forming the first semiconductor layer 102 having the opening 112.

[0031] In this etching process, first, conditions are applied that etch silicon but not silicon oxide, causing the buried oxide layer to function as an etching stop layer and forming an opening 112 in the silicon substrate. Next, conditions are applied that etch silicon oxide but not silicon, causing the surface silicon layer to function as an etching stop layer and forming an opening 112 in the buried oxide layer.

[0032] In this way, an element portion can be formed in which the second semiconductor layer 103 is formed on the first semiconductor layer 102. In this case, a buried insulating layer (not shown) remains between the upper surface of the first semiconductor layer 102, which is formed in a frame shape with the opening 112, and the lower surface of the second semiconductor layer 103.

[0033] Next, as shown in FIG. 3B, an aperture adjustment plate 105 is attached to the lower surface of the first semiconductor layer 102 (second process). For example, a silicon substrate is prepared, and a mask layer having an opening in an area to be the second through-hole 113 is formed thereon by a known photolithography technique. Next, the silicon substrate is etched using the mask layer as a mask, thereby forming the aperture adjustment plate 105 having the second through-hole 113. The aperture adjustment plate 105 thus formed is attached to the lower surface of the first semiconductor layer 102. For example, the two can be attached by well-known direct bonding.

[0034] Next, as shown in FIG. 3C , a metal layer 106 is formed on the surface of the aperture adjusting plate 105, which will be the bonding surface with the support substrate 101 (third step). Although not shown in FIG. 3C , the metal layer 106 is also formed on the bonding surface of the prepared support substrate 101. For example, the metal layer 106 can be formed by depositing a predetermined metal by sputtering or vacuum deposition. According to the embodiment, since the metal layer 106 is formed on the surface of the aperture adjusting plate 105, the metal that reaches the back surface of the second semiconductor layer 103 (diaphragm 121) is limited to that which passes through the second through-hole 113, which has a reduced opening diameter. As a result, the metal layer formed on the bottom surface of the diaphragm 121 is very small, and problems with the distortion element 104 due to diffusion from this metal layer can be suppressed.

[0035] Thereafter, the metal layer forming surface of the opening adjusting plate 105 and the metal layer forming surface of the support substrate 101 are brought into contact with each other, and the two are bonded together (fourth step).

[0036] As described above, according to the embodiment of the present invention, an opening adjustment plate having a second through hole is used between the support substrate and the first semiconductor layer, thereby making it possible to prevent metal deposited for bonding from accumulating on the bottom surface of the diaphragm.

[0037] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0038] 101...support substrate, 102...first semiconductor layer, 103...second semiconductor layer, 104...strain element, 105...aperture adjustment plate, 106...metal layer, 111...first through hole, 112...aperture, 113...second through hole, 121...diaphragm.

Claims

1. a support substrate having a first through hole; a first semiconductor layer formed on the support substrate and having an opening; a second semiconductor layer on which a diaphragm is formed, the second semiconductor layer covering the opening and using the opening region as a pressure receiving portion; a strain element formed on the second semiconductor layer for measuring strain of the diaphragm; an opening adjustment plate that is disposed between the support substrate and the first semiconductor layer, has a second through-hole that is narrower than the opening of the first semiconductor layer and is disposed within the area of ​​the opening, and is bonded to the support substrate via a metal layer; A pressure sensor element comprising:

2. 2. The pressure sensor element according to claim 1, The aperture adjustment plate is a pressure sensor element bonded to the first semiconductor layer.

3. a first step of forming an element portion including a first semiconductor layer having an opening, a second semiconductor layer formed on the first semiconductor layer to cover the opening and having a diaphragm formed thereon, the diaphragm having a region of the opening as a pressure receiving portion, and a strain element formed on the second semiconductor layer to measure strain of the diaphragm, and preparing a support substrate having a first through-hole; a second step of attaching an aperture adjustment plate having a second through hole to a lower surface of the first semiconductor layer; a third step of forming a metal layer on the surface of the opening adjustment plate that will be the bonding surface with the support substrate, and forming a metal layer on the bonding surface of the support substrate; a fourth step of contacting the metal layer-formed surface of the opening adjustment plate and the metal layer-formed surface of the support substrate to bond them together; A method for manufacturing a pressure sensor element comprising:

4. 4. The method for manufacturing a pressure sensor element according to claim 3, The third step is a method of manufacturing a pressure sensor element, in which a metal layer is formed by depositing a metal.

5. 5. The method for manufacturing a pressure sensor element according to claim 3, further comprising the steps of: The second step is a method for manufacturing a pressure sensor element, in which the opening adjustment plate is bonded to the first semiconductor layer, thereby attaching the opening adjustment plate to the first semiconductor layer.

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