JP2013064698A - Manufacturing method of dynamic quantity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a dynamic quantity sensor for forming an airtight space having high airtightness reliability even when surface roughness or dust is present in a joining interface of a sensor wafer and a package wafer.SOLUTION: The manufacturing method executes a step of forming a plurality of sensing units 1 on the sensor wafer 100 and forming a recess 2 on one wafer of the sensor wafer 100 and the package wafer 200, a step of arranging a sealing material 30 on a side face of the recess 2, a step of joining the sensor wafer 100 and the package wafer 200, a step of heating and melting the sealing material 30 and flowing the melted sealing material 30 to an end of the joining interface of the sensor wafer 100 and the package wafer 200, and a step of curing the sealing material 30 to seal the end of the joining interface of the sensor wafer 100 and the package wafer 200 with the sealing material 30.

Description

  The present invention relates to a method of manufacturing a mechanical quantity sensor that detects a mechanical quantity.

  22 and 23 are sectional views of conventional mechanical quantity sensors. Conventionally, some mechanical quantity sensors have an airtight space adjacent to a sensing unit as shown in FIGS.

  The mechanical quantity sensor shown in FIG. 22 is an acceleration sensor, and includes a sensor substrate 10 having a sensing unit 1 that detects acceleration as a mechanical quantity, and a recess 2 for forming an airtight space 23 adjacent to the sensing unit 1. The package substrate 20 is provided, and the sensor substrate 10 and the package substrate 20 are joined to form an airtight space 23 between the recess 2 and the sensor substrate 10.

  The mechanical quantity sensor shown in FIG. 23 is a pressure sensor, and includes a sensing substrate 1 that detects pressure as a mechanical quantity and a sensor substrate 110 that has a recess 2 for forming an airtight space 112 adjacent to the sensing section 1. A package substrate 210 that closes the recess 2 is provided, and the airtight space 112 is formed between the recess 2 and the package substrate 210 by joining the sensor substrate 110 and the package substrate 210.

  As a method of manufacturing such a mechanical quantity sensor, as disclosed in Patent Document 1, there is a method using WLP (Wafer Level Packaging) technology in which a sensor wafer and a package wafer are packaged at a wafer level.

  Specifically, the method described in Patent Document 1 includes a sensor wafer in which a plurality of sensor bodies having a sensing unit are formed, and a package wafer in which a recess for forming a space for hermetically sealing the sensing unit is formed. When bonding at the wafer level, each bonding surface of a plurality of frame-shaped sealing bonding layers provided in multiple regions corresponding to the sensor main body on the mutually facing surfaces is activated and then bonded at room temperature, thereby A hermetic space is formed between the recess and the recess. Thereafter, the bonded sensor wafer and package wafer are divided for each chip. In this method, the airtight reliability of the airtight space is improved by providing a plurality of frame-like sealing bonding layers.

Japanese Patent No. 3938198

  However, even when multiple frame-shaped sealing bonding layers are provided as in the method described in Patent Document 1 described above, if surface roughness, dust, or the like exists on each bonding surface of the frame-shaped sealing bonding layer, There is a high possibility that a space is formed at the joint interface, and an airtight leak may start from there.

  In view of the above points, the present invention has an object to provide a method for manufacturing a mechanical quantity sensor capable of forming an airtight space with high airtight reliability even when surface roughness or dust is present at the bonding interface between a sensor wafer and a package wafer. And

In order to achieve the above object, in the invention described in claim 1,
Forming a plurality of sensing portions (1) on the sensor wafer (100) and forming a plurality of recesses (2) constituting the airtight spaces (23, 112) on one of the sensor wafer (100) and the package wafer (200); When,
Sealing for covering and sealing the end (3a) of the bonding interface (3) between the sensor wafer (100) and the package wafer (200) with respect to either the sensor wafer (100) or the package wafer (200) Arranging the material (30) at a site that reaches the end (3a) of the bonding interface (3) when the sealing material (30) melts and flows;
The sensor wafer (100) and the package wafer (200) are bonded together, and the recess (2) formed in one of the sensor wafer (100) and the package wafer (200) is closed with the other wafer, whereby the airtight space (23 112),
Heating and melting the sealing material (30), and flowing the melted sealing material (30) to the end (3a) of the bonding interface (3) between the sensor wafer (100) and the package wafer (200); ,
Curing the sealing material (30) and covering the end (3a) of the bonding interface (3) with the sealing material (30);
And a step of dividing the bonded sensor wafer (100) and package wafer (200) into chips.

  As described above, according to the present invention, the edge portion of the bonding interface between the sensor wafer and the package wafer is covered with the sealing material at the stage of the wafer state before being divided into chips. Therefore, according to the present invention, since the end portion of the bonding interface is covered with the sealing material, even if surface roughness or dust exists at the bonding interface between the sensor wafer and the package wafer, an airtight space with high airtight reliability is formed. can do.

The invention according to claim 2 is the invention according to claim 1,
The process of joining the sensor wafer (100) and the package wafer (200) is to perform heat treatment on the superimposed sensor wafer (100) and package wafer (200),
In the step of disposing the sealing material (30), a material that melts and flows at the temperature of the heat treatment is disposed as the sealing material (30),
The step of heating and melting the sealing material (30) is performed simultaneously with the step of bonding the sensor wafer (100) and the package wafer (200).

  Thus, if a material that melts and flows at the heat treatment temperature in the joining step is used as the sealing material, the sealing material (30) can be heated and melted by the heat treatment in the joining step.

  Moreover, in the invention according to claim 1 or 2, the location of the sealing material in the step of arranging the sealing material (30) is, for example, a concave portion (as in the invention according to claim 3). It can be at least the side surface (2a) of 2). In this case, in the process of melting the sealing material (30) by heating, one of the sensor wafer (100) and the package wafer (200) in which the recess (2) is formed is set to the top, and the other wafer is set to the bottom. By setting it as the state made into, it can be made to flow the melt | dissolved sealing material to the edge part of a joining interface.

  Furthermore, in the case where the sealing material is disposed on at least the side surface (2a) of the recess (2), for example, as in the invention according to claim 4, the sealing material melted with respect to the surface of the other wafer It is preferable to form a groove (102, 202) for storing the material (30). Thus, in the step of heating and melting the sealing material (30), the melted sealing material (30) is stored in the groove portions (102, 202), thereby the end portion (3a) of the bonding interface (3). Can be kept in a position to cover.

  Moreover, in the case where the sealing material is disposed on at least the side surface (2a) of the recess (2), for example, as in the invention according to claim 5, the sealing material melted with respect to the surface of the other wafer It is preferable to form protrusions (103, 203) for blocking the material (30). Thereby, in the process of heating and melting the sealing material (30), the melted sealing material (30) is dammed up by the protruding portions (103, 203), so that the end portion of the bonding interface (3) ( The sealing material (30) can be fastened in a position covering 3a).

  Further, in the case where solder as a sealing material is disposed on at least the side surface (2a) of the recess (2), as in the invention according to claim 6, the melted sealing with respect to the surface of the other wafer It is preferable to form a metal film (104, 204) for storing the material for use (30). Accordingly, in the step of heating and melting the sealing material (30), the molten sealing material (30) is accumulated on the surface of the metal film (104, 204) having high wettability, so that the bonding interface ( The sealing material (30) can be fastened to a position covering the end (3a) of 3).

  Moreover, in the invention according to claim 1 or 2, the location of the sealing material in the step of arranging the sealing material (30) is, for example, a concave portion (as in the invention according to claim 7). Among the other wafers in which 2) is not formed, it was previously provided at a position facing the upper end corner (2c) of the recess (2) when the sensor wafer (100) and the package wafer (200) were joined. It can be inside the groove (105). In this case, in the process of melting the sealing material (30) by heating, one of the sensor wafer (100) and the package wafer (200) in which the concave portion (2) is formed is placed on the bottom, and the other wafer is placed on the top. In this state, by melting the sealing material (30), the melted sealing material can be flowed to the end portion of the bonding interface.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is sectional drawing of the acceleration sensor in 1st Embodiment. It is sectional drawing which shows the manufacturing process of the acceleration sensor in 1st Embodiment. It is sectional drawing which shows the manufacturing process of the acceleration sensor in 1st Embodiment. It is sectional drawing which shows the manufacturing process of the acceleration sensor in 1st Embodiment. It is a figure which shows the manufacturing process of the acceleration sensor in 1st Embodiment, (a), (b) is the top view and side view of the sensor wafer and package wafer after joining, respectively. FIG. 5 is an enlarged view of a region A2 surrounded by a broken line in FIG. 4B after the bonding heat treatment. It is a fragmentary sectional view of the acceleration sensor at the time of heat processing for junction in a 2nd embodiment. It is a fragmentary sectional view of the acceleration sensor at the time of heat processing for junction in a 3rd embodiment. It is a fragmentary sectional view of the acceleration sensor at the time of heat processing for junction in a 4th embodiment. It is a fragmentary sectional view of the acceleration sensor at the time of heat processing for junction in a 5th embodiment. (A), (b) is an enlarged view of area | region A3 enclosed with the broken line in FIG. 10, respectively before and after the sealing material 30 melt | dissolves. It is sectional drawing of the pressure sensor in 6th Embodiment. It is sectional drawing which shows the manufacturing process of the acceleration sensor in 6th Embodiment. It is sectional drawing which shows the manufacturing process of the acceleration sensor in 6th Embodiment. It is sectional drawing which shows the manufacturing process of the acceleration sensor in 6th Embodiment. It is an enlarged view of area | region B1 enclosed with the broken line in FIG.15 (b) at the time of the heat processing for joining. It is a fragmentary sectional view of the acceleration sensor at the time of heat processing for junction in the modification of a 6th embodiment. It is a fragmentary sectional view of the acceleration sensor at the time of heat processing for junction in the modification of a 6th embodiment. It is a fragmentary sectional view of the acceleration sensor at the time of heat processing for junction in the modification of a 6th embodiment. It is sectional drawing of the pressure sensor at the time of the heat processing for joining in 7th Embodiment. (A), (b) is an enlarged view of the area | region B2 enclosed with the broken line in FIG. 20, respectively before and after the sealing material 30 melt | dissolves. It is sectional drawing of the conventional mechanical quantity sensor. It is sectional drawing of the conventional mechanical quantity sensor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings in order to simplify the description.

(First embodiment)
FIG. 1 shows a cross-sectional view of an acceleration sensor as a mechanical quantity sensor in the present embodiment. As shown in FIG. 1, the acceleration sensor according to the present embodiment includes a sensor substrate 10 having a sensing unit 1 that detects acceleration, and a package substrate 20 having a recess 2 that forms an airtight space adjacent to the sensing unit 1. ing.

  The sensor substrate 10 includes a support substrate 11 made of silicon, a buried insulating film 12 made of a silicon oxide film disposed on the surface of the support substrate 11, and an opposite side of the support substrate 11 across the buried insulating film 12. An SOI substrate having a semiconductor layer 13 made of silicon is disposed.

  The semiconductor layer 13 is formed with a movable electrode 14 that can be displaced in a direction parallel to the substrate surface in response to application of acceleration, and a fixed electrode 15 that is disposed opposite to the movable electrode 14 as the sensing unit 1. . The movable electrode 14 and the fixed electrode 15 are separated by a groove 16 formed in the semiconductor layer 13. Further, portions of the buried insulating film 12 facing the movable electrode 14 and the fixed electrode 15 are removed.

  The package substrate 20 includes a semiconductor substrate 21 made of silicon and an insulating film 22 made of a silicon oxide film formed on the surface of the semiconductor substrate 21 on the sensor substrate 10 side. The package substrate 20 is bonded to the semiconductor layer 13 of the sensor substrate 10 via an insulating film 22 formed on the surface on the sensor substrate 10 side.

  The concave portion 2 is formed at a position facing the sensing portion 1 on the surface of the package substrate 20 on the sensor substrate 10 side. The recess 2 is configured by forming an insulating film 22 on the surface of the recess formed in the semiconductor substrate 21. The recess 2 and the sensor substrate 10 (support substrate 11) form an airtight space 23 in a vacuum state, and the sensing unit 1 is hermetically sealed.

  In this embodiment, a sealing material 30 for covering the bonding interface between the sensor substrate 10 and the package substrate 20 is attached to the surface of the recess 2. Details of the sealing material 30 will be described later.

  A through hole 24 is formed in the package substrate 20 so as to penetrate from the surface on the sensor substrate 10 side to the surface on the opposite side. Insulating films 25 and 26 are formed on the wall surface of the through hole 24 and the surface of the package substrate 20 opposite to the sensor substrate 10 side. A metal wiring layer 27 made of Al, Cu, or the like electrically connected to the sensor substrate 10 is formed in the through hole 24 and on the surface of the package substrate 20 opposite to the sensor substrate 10 side. . A plurality of metal wiring layers 27 are formed, and each metal wiring layer 27 is electrically connected to the movable electrode 14, the fixed electrode 15, and the like.

  In the acceleration sensor, when an acceleration is applied in a direction parallel to the substrate surface, the distance between the movable electrode 14 and the fixed electrode 15 changes with the application of the acceleration, and the capacitance between both electrodes generated by the change in the distance. Acceleration is detected based on the change.

  Next, the manufacturing method of the acceleration sensor of this embodiment is demonstrated.

  2 to 4 show the manufacturing process of the acceleration sensor of this embodiment. 2 to 4 correspond to a portion of a region A1 surrounded by a broken line in FIG.

  First, by performing the steps shown in FIGS. 2A to 2E, a plurality of sensor substrates 10 having the sensing unit 1 are formed on one sensor wafer 100. 2A to 2E, only a portion corresponding to one sensor substrate 10 in the sensor wafer 100 is shown.

  Specifically, as shown in FIG. 2A, an SOI substrate in which a buried insulating film 12 and a semiconductor layer 13 are sequentially stacked on the surface of a support substrate 11 is prepared as the sensor wafer 100. Subsequently, as shown in FIG. 2B, a photolithography process is performed to form a resist 41 having a desired pattern on the surface of the semiconductor layer 13, and then, as shown in FIG. The groove 16 is formed so as to demarcate the patterns of the movable electrode 14 and the fixed electrode 15 by performing an etching process using the resist 41 as a mask.

  Subsequently, as shown in FIG. 2D, by performing an etching process on the buried insulating film 12 through the groove 16, a portion of the buried insulating film 12 facing the movable electrode 14 and the fixed electrode 15 is formed. The cavity 42 is formed by etching away. Thereafter, the resist is removed as shown in FIG. In this way, a plurality of sensor substrates 10 having the sensing unit 1 are formed on one sensor wafer 100.

  On the other hand, by performing the steps shown in FIGS. 3A to 3H, a plurality of package substrates 20 having the recesses 2 are formed on one package wafer 200. 3A to 3H, only a portion corresponding to one package substrate 20 in the package wafer 200 is shown.

  Specifically, as shown in FIG. 3A, a semiconductor wafer (semiconductor substrate 21) is prepared as the package wafer 200. Then, as shown in FIG. 3B, a photolithography process is performed to form a resist 43 having a desired pattern on one surface of the semiconductor substrate 21. Subsequently, as shown in FIG. 3C, an etching process using the resist 43 as a mask is performed to form a recess 21a on one surface side of the semiconductor substrate 21, and then, as shown in FIG. 43 is removed. Subsequently, as shown in FIG. 3E, an insulating film 22 is formed on the surface of the semiconductor substrate 21 by a CVD method or the like. Thereby, the recess 2 is formed in the package wafer 200. At this time, the insulating film 26 is also formed on the surface of the semiconductor substrate 21 opposite to the surface where the recess 2 is formed.

  Subsequently, as shown in FIG. 3F, a photolithography process is performed to form a resist 44 on one surface of the package wafer 200 excluding the recess 2. Subsequently, as shown in FIG. 3G, a sealing material 30 is applied or deposited on one surface of the package wafer 200 including the inside of the recess 2. As the sealing material 30, a material that melts and flows at the temperature of the heat treatment for bonding described later is used. For example, BPSG and low-melting glass can be used, organic materials such as vinyl and vinyl chloride can be used, and low-melting metals such as solder can be used.

  Thereafter, as shown in FIG. 3 (h), the sealing material 30 located outside the inside of the recess 2 is removed together with the resist 44. Thereby, the sealing material 30 is disposed on the side surface 2a and the bottom surface 2b of the recess 2. At this time, it can be said that the sealing material 30 is arrange | positioned at all the side surfaces 2a of the recessed part 2, and the sealing material 30 arrange | positioned at the side surface 2a is continuing cyclically | annularly. In the present embodiment, the steps shown in FIG. 3F to FIG. 3H are steps for disposing the sealing material 30.

  Before the step shown in FIG. 3E, the through hole 24 is formed by etching the semiconductor substrate 21, and in the step shown in FIG. 3E, the insulating layer 25 is formed on the inner surface of the through hole 24. After the formation, the metal wiring layer 27 is formed before the step shown in FIG. 3F or after the step shown in FIG.

  In this way, a plurality of package substrates 20 having the recesses 2 are formed on one package wafer 200.

  Thereafter, the sensor wafer 100 and the package wafer 200 are bonded to each other, and the recess 2 formed in the package wafer 200 is closed with the sensor wafer 100 to form the hermetic space 23.

  Specifically, first, surface activation treatment is performed on each of the surface on the sensing unit 1 side of the sensor wafer 100 and the surface on the concave portion 2 side of the package wafer 200. As this surface activation treatment, for example, an energy treatment such as plasma irradiation or a wet treatment immersed in a liquid such as a chemical can be employed.

  Subsequently, as shown in FIGS. 4A and 4B, the sensor wafer 100 and the package wafer 200 are overlapped with each other so that the sensing portion 1 of the sensor wafer 100 and the recess 2 of the package wafer 200 face each other under vacuum. After that, a heat treatment for bonding is performed. In this heat treatment for bonding, the sensor wafer 100 is positioned below and the package wafer 200 is positioned above. Further, the heat treatment temperature at this time is set to a temperature lower than the melting point of the metal wiring layer 27, for example, 300 ° C. so that the metal wiring layer 27 formed on the package wafer 200 does not melt.

  By this heat treatment for bonding, as shown in FIGS. 5A and 5B, the surfaces of the sensor wafer 100 and the package wafer 200 are covalently bonded, and the sensor wafer 100 and the package wafer 200 are directly bonded. 5A and 5B are a plan view and a side view in a state where the sensor wafer 100 and the package wafer 200 are joined, respectively, and one square surrounded by a broken line in FIG. 5A. Corresponds to one sensor substrate 10 and one package substrate 20.

  Then, after performing the bonding heat treatment, a process of cooling the bonded sensor wafer 100 and package wafer 200 is performed. For example, the sensor wafer 100 and the package wafer 200 after the bonding heat treatment are naturally cooled.

  After that, the acceleration sensor of this embodiment is manufactured through a process of dicing the bonded sensor wafer 100 and the package wafer 200 and dividing them into chips. The parts divided from the sensor wafer 100 and the package wafer 200 for each chip constitute the sensor substrate 10 and the package substrate 20.

  Here, FIG. 6 shows an enlarged view of a region A2 surrounded by a broken line in FIG. 4B after the bonding heat treatment. In this embodiment, as the sealing material 30, a material that melts at a temperature at the time of the heat treatment for bonding and flows in a viscous flow is adopted. Therefore, as shown in FIG. The sealing material 30 applied to the bottom surface 2 b is heated and melted, and the melted sealing material 30 flows to the end 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200. Then, the sealing material 30 is cured by natural cooling after the heat treatment for bonding, and the end portion 3 a of the bonding interface 3 is covered with the sealing material 30.

  As described above, according to the present embodiment, the sealing material 30 covers the end portion 3a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200 from the inside of the concave portion 2, so that the surface roughness and dust are the sensor wafer 100 and the package wafer. Even if it exists in the junction interface 3 with 200, the airtight space 23 with high airtight reliability can be formed.

  In the present embodiment, the step of bonding the sensor wafer 100 and the package wafer 200 also serves as the step of heating and melting the sealing material 30, that is, simultaneously with the step of bonding the sensor wafer 100 and the package wafer 200. The process of heating and melting the sealing material 30 is performed. The process of cooling the bonded sensor wafer 100 and package wafer 200 corresponds to the process of curing the sealing material 30.

(Second Embodiment)
FIG. 7 shows a partial cross-sectional view of the acceleration sensor during the heat treatment for bonding in the present embodiment. FIG. 7 is a diagram corresponding to FIG. Only the differences from the first embodiment will be described below.

  In the present embodiment, a groove 102 for storing the sealing material 30 melted during the bonding heat treatment is provided in advance on the surface 101 of the sensor wafer 100 on the package wafer 200 side.

  The groove 102 is adjacent to the end 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200, and has an annular shape so as to surround the end 3 a of the bonding interface 3 with the package wafer 200 from the inside on the surface 101 of the sensor wafer 100. Are arranged in succession.

  Further, the groove 102 is formed before the step of bonding the sensor wafer 100 and the package wafer 200. For example, the groove portion 102 can be formed together with the groove 16 by etching the semiconductor layer 13 in the steps shown in FIGS.

  According to the present embodiment, the sealing material 30 is accumulated in the groove 102 during the heat treatment for bonding, so that the sealing material is disposed at a position covering the end portion 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200. 30 can be securely fastened. Further, it is possible to prevent the melted sealing material 30 from adhering to the sensing unit 1 and adversely affecting the sensing unit 1.

(Third embodiment)
FIG. 8 shows a partial cross-sectional view of the acceleration sensor during the heat treatment for bonding in the present embodiment. FIG. 8 corresponds to FIG. Only the differences from the first embodiment will be described below.

  In this embodiment, instead of the groove portion 102 of the second embodiment, a protrusion 103 for damming the sealing material 30 melted during the heat treatment for bonding is provided on the surface 101 of the sensor wafer 100 on the package wafer 200 side. Provided.

  The protruding portion 103 is a portion protruding from the surface 101 of the sensor wafer 100 as compared to the region other than the protruding portion 103, and is spaced inward from the end portion 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200. The sensor wafer 100 is continuously arranged in an annular shape so as to surround the end portion 3a of the bonding interface 3 with the package wafer 200 from the inside on the surface 101 of the sensor wafer 100.

  Further, the protrusion 103 is formed before the process of bonding the sensor wafer 100 and the package wafer 200. For example, after removing the resist 41 in the step shown in FIG. 2E, a semiconductor, a metal, and an insulator are deposited to form the protruding portion 103, or the region other than the region where the protruding portion 103 is to be formed is removed by etching. The protrusion 103 can be formed.

  According to the present embodiment, during the heat treatment for bonding, the melted sealing material 30 is dammed up by the protruding portion 103, thereby sealing at a position covering the end 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200. The material 30 can be securely fastened. Further, it is possible to prevent the melted sealing material 30 from adhering to the sensing unit 1 and adversely affecting the sensing unit 1.

  In this embodiment, the protruding portion 103 is provided instead of the groove portion 102 of the second embodiment. However, as shown by a broken line in FIG. 8, both the groove portion 102 of the second embodiment and the protruding portion 103 are provided. May be provided on the surface 101 of the sensor wafer 100.

(Fourth embodiment)
FIG. 9 shows a partial cross-sectional view of the acceleration sensor during the heat treatment for bonding in this embodiment. FIG. 9 corresponds to FIG. Only the differences from the first embodiment will be described below.

  In the present embodiment, solder is used as the sealing material 30 and, instead of the grooves 102 in the second embodiment, the melted solder is accumulated on the surface 101 on the package wafer 200 side of the sensor wafer 100 during the heat treatment for bonding. A metal film 104 is provided.

  The metal film 104 is located on the inner side (left side in FIG. 9) of the end portion 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200, and the end portion of the bonding interface 3 with the package wafer 200 on the surface 101 of the sensor wafer 100. It is continuously arranged in an annular shape so as to surround 3a from the inside.

  The metal film 104 is formed before the process of bonding the sensor wafer 100 and the package wafer 200. For example, after removing the resist 41 in the step shown in FIG. 2E, the metal film 104 can be formed by sputtering, CVD, or the like.

  According to the present embodiment, since the metal film 104 having higher solder wettability than the surface of the sensor wafer 100 is provided on the surface 101 of the sensor wafer 100 on the package wafer 200 side, the melted solder 30 during the heat treatment for bonding is provided. Can be collected on the surface of the metal film 104, and the sealing material 30 can be securely fastened at a position covering the end 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200. Further, it is possible to prevent the melted sealing material 30 from adhering to the sensing unit 1 and adversely affecting the sensing unit 1.

  In this embodiment, the metal film 104 is provided instead of the groove 102 of the second embodiment. However, the groove 102 of the second embodiment is provided on the surface 101 of the sensor wafer 100 and further on the surface of the groove 102. A metal film 104 may be provided. Further, the protrusion 103 according to the third embodiment may be provided on the surface 101 of the sensor wafer 100, and further, the metal film 104 may be provided between the surface of the protrusion 103 and the end 3 a of the bonding interface 3. Further, both the groove portion 102 of the second embodiment and the protruding portion 103 of the third embodiment are provided on the surface 101 of the sensor wafer 100, and the metal film 104 is provided between the surface of the protruding portion 103 and the end portion 3 a of the bonding interface 3. May be provided.

(Fifth embodiment)
FIG. 10 shows a cross-sectional view of the mechanical quantity sensor at the time of heat treatment for bonding in the present embodiment, and FIGS. 11A and 11B show enlarged views of a region A3 surrounded by a broken line in FIG. FIGS. 11A and 11B show the states before and after the sealing material 30 is melted, respectively.

  In the present embodiment, as shown in FIG. 10, the sensor wafer 100 is positioned on the upper side and the package wafer 200 is positioned on the lower side during the heat treatment for bonding.

  At this time, as shown in FIG. 11A, a groove portion 105 for placing the sealing material 30 is provided in advance on the surface 101 of the sensor wafer 100 on the package wafer 200 side, and the groove portion 105 is sealed. Stop material 30 is arranged in advance.

  The groove 105 is arranged at a position facing the upper end corner 2c of the recess 2 of the package wafer 200 when the sensor wafer 100 and the package wafer 200 are bonded. More specifically, the side surface on the outer side (right side in FIG. 11) of the groove portion 105 is positioned outside the side surface 2b of the concave portion 2, and the side surface on the inner side (left side in FIG. 11) of the groove portion 105 is the concave portion 2. It is located inside the side surface 2b. Thus, the groove 105 is disposed across the upper end corner 2c in a direction parallel to the surface of the sensor wafer 100 so that the groove 105 is not completely blocked by the package wafer 200 and a gap continuous to the recess 2 is formed. Has been.

  The position of the end 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200 is determined by the position of the outer side surface of the groove 105. The reason why the side surface on the inner side of the groove portion 105 is positioned on the inner side of the side surface 2b of the concave portion 2 to form the gap is to allow the melted sealing material 30 to flow. However, the gap is preferably as small as possible so that the melted sealing material 30 does not drip from the gap.

  The groove 105 is continuously arranged in an annular shape so as to surround the recess 2 when the sensor wafer 100 and the package wafer 200 are bonded.

  The groove 105 is formed before the process of bonding the sensor wafer 100 and the package wafer 200. For example, after removing the resist 41 in the step shown in FIG. 2E, the semiconductor layer 13 is etched to form the groove 105, and then the sealing material 30 is applied to the groove 105. In the present embodiment, the step of applying the sealing material 30 after forming the groove 105 is the step of disposing the sealing material 30.

  Then, as shown in FIG. 11B, during the bonding heat treatment, the sealing material 30 arranged in the groove 105 is heated and melted, and the melted sealing material 30 is packaged with the sensor wafer 100 and the package. It flows to the end 3 a of the bonding interface 3 of the wafer 200. The sealing material 30 is cured by natural cooling after the heat treatment for bonding, and the end portion 3 a of the bonding interface 3 is covered with the sealing material 30.

  Therefore, also in the present embodiment, since the end portion 3a of the bonding interface 3 is covered with the sealing material 30, the airtight space 23 with high airtight reliability can be formed as in the first embodiment.

(Sixth embodiment)
FIG. 12 shows a cross-sectional view of a pressure sensor as a mechanical quantity sensor in the present embodiment. As shown in FIG. 12, the pressure sensor according to the present embodiment is joined to the sensor substrate 110 having a sensing unit 1 that detects pressure and a recess 2 that forms an airtight space 112 adjacent to the sensing unit 1. And a package substrate 210 that closes the recess 2.

  The sensor substrate 110 is a semiconductor substrate made of silicon having one surface and the other surface on the opposite side, and is formed on the one surface side (the package substrate 210 side) by the recess 2 provided on the other surface side (the surface on the package substrate 210 side). Diaphragm 111 is formed on the opposite surface.

  Although not shown, the diaphragm 111 is formed with a gauge diffusion resistor (strain gauge) that generates an electric signal based on the strain of the diaphragm 111 so as to constitute a bridge circuit. A space 112 between the diaphragm 111 and the package substrate 210 is hermetically sealed, and is configured as, for example, a vacuum chamber as a reference pressure chamber.

  In this embodiment, as in the first embodiment, the sealing material 30 for covering the bonding interface between the sensor substrate 110 and the package substrate 210 is attached to the side surface 2a and the bottom surface 2b of the recess 2. Yes.

  The package substrate 210 includes a semiconductor substrate 211 made of silicon, and the semiconductor substrate 211 is a sensor substrate through an insulating film 212 made of a silicon oxide film formed on one surface of the semiconductor substrate 211 (the surface on the sensor substrate 110 side). 110 is joined. In this embodiment, the insulating film 212 is formed not only on one surface of the semiconductor substrate 211 but also on the other surface (the surface opposite to the sensor substrate 110 side) and the side surface. The film 212 may not be formed.

  In this pressure sensor, when pressure is applied from the surface side of the diaphragm 111, the diaphragm 111 is distorted, the resistance value of the gauge diffusion resistance is changed based on the distortion of the diaphragm 111, and the voltage value in the bridge circuit is changed. . The applied pressure is detected based on the changed voltage value. In the pressure sensor of this embodiment, the pressure difference between the pressure applied to the surface of the diaphragm 111 and the inside of the vacuum chamber 112, that is, the absolute pressure is detected.

  Next, the manufacturing method of the pressure sensor of this embodiment is demonstrated.

  13 to 15 show the manufacturing process of the pressure sensor of this embodiment.

  First, a plurality of sensor substrates 110 having the sensing unit 1 are formed on one sensor wafer 100 by performing the steps shown in FIGS. In FIGS. 13A to 13E, only a portion corresponding to one sensor substrate 110 in the sensor wafer 100 is shown.

  Specifically, as shown in FIG. 13A, a sensor wafer 100 made of silicon is prepared. In the sensor wafer 100, a gauge diffusion resistor or the like is formed at a position where the diaphragm 111 is to be formed on one surface (the lower surface in FIG. 3) of the sensor wafer 100.

  Then, as shown in FIG. 13B, a photolithography process is performed to form a resist 51 having a desired pattern on the other surface of the sensor wafer 100 (upper surface in FIG. 13). Subsequently, as illustrated in FIG. 13C, an etching process using the resist 51 as a mask is performed to form the recess 2 on the other surface of the sensor wafer 100. As a result, the diaphragm 111 is formed as the bottom of the recess 2.

  Subsequently, as shown in FIG. 13D, the sealing material 30 is applied to the other surface of the sensor wafer 100 including the inside of the recess 2 as in the first embodiment. Thereafter, as shown in FIG. 13E, the sealing material 30 located outside the inside of the recess 2 is removed together with the resist 51. Thereby, the sealing material 30 is provided on the side surface 2 a and the bottom surface 2 b of the recess 2. In the present embodiment, the steps shown in FIGS. 13D and 13E are steps for disposing the sealing material 30.

  In this way, a plurality of sensor substrates 110 having the recesses 2 constituting the sensing unit 1 and the airtight space 112 are formed on one sensor wafer 100.

  On the other hand, a package wafer 200 (semiconductor substrate 211) made of silicon is prepared as shown in FIG. 14A, and an insulating film 212 is formed on the surface of the semiconductor substrate 211 as shown in FIG. Thereby, a plurality of package substrates 210 are formed on one package wafer 200.

  Thereafter, the sensor wafer 100 and the package wafer 200 are bonded together, and the recess 2 formed in the sensor wafer 100 is closed with the package wafer 200, thereby forming a hermetic space 112.

  Specifically, first, surface activation treatment is performed on each of the surface of the sensor wafer 100 on the concave portion 2 side and the surface of the package wafer 200 in the same manner as in the first embodiment. Subsequently, as shown in FIGS. 15A and 15B, the sensor wafer 100 and the package wafer 200 are overlapped with each other while the concave portion 2 of the sensor wafer 100 and the package wafer 200 are opposed to each other in a vacuum. As in the first embodiment, heat treatment for bonding is performed. At this time, the sensor wafer 100 is on the upper side and the package wafer 200 is on the lower side. Thereby, the sensor wafer 100 and the package wafer 200 are directly bonded.

  Then, the pressure sensor of this embodiment is manufactured by performing the process of cooling the sensor wafer 100 and the package wafer 200 which were joined, and performing the process of dicing for every chip | tip.

  Here, FIG. 16 shows an enlarged view of a region B1 surrounded by a broken line in FIG. 15B during the heat treatment for bonding. Also in the present embodiment, as shown in FIG. 16, during the heat treatment for bonding, the sealing material 30 applied to the side surface 2 a of the recess 2 is heated and melted, and the melted sealing material 30 becomes the sensor wafer 100. And flow to the end 3 a of the bonding interface 3 of the package wafer 200. Then, the sealing material 30 is cured by natural cooling after the heat treatment for bonding, and the end portion 3 a of the bonding interface 3 is covered with the sealing material 30.

  Therefore, also in this embodiment, since the sealing material 30 covers the bonding interface 3 between the sensor wafer 100 and the package wafer 200 from the inside of the recess 2, surface roughness and dust are formed on the bonding interface 3 between the sensor wafer 100 and the package wafer 200. Even if it exists, the airtight space 112 with high airtight reliability can be formed.

  In the present embodiment, the process of bonding the sensor wafer 100 and the package wafer 200 also serves as the process of heating and melting the sealing material 30, and the process of cooling the bonded sensor wafer 100 and package wafer 200 is sealed. This corresponds to the step of curing the material 30.

  Moreover, it is also possible to combine 2nd-4th embodiment with respect to this embodiment as follows. 17 to 19 show modifications of the present embodiment, respectively.

  As shown in FIG. 17, a groove 202 for storing the melted sealing material 30 can be provided on the surface 201 of the package wafer 200 on the sensor wafer 100 side, as in the second embodiment. The groove 202 is the same as the groove 102 of the second embodiment.

  Further, as shown in FIG. 18, a protrusion 203 for damming the melted sealing material 30 is provided on the surface 201 of the package wafer 200 on the sensor wafer 100 side, as in the third embodiment. be able to. The protrusion 203 is the same as the protrusion 103 of the third embodiment. Note that both the groove 202 and the protrusion 203 may be provided on the surface 201 of the package wafer 200 as indicated by a broken line in FIG.

  Further, in the case where solder is used as the sealing material 30, as shown in FIG. 19, in order to increase the wettability of the solder on the surface 201 of the package wafer 200 on the sensor wafer 100 side, as in the fourth embodiment. A metal film 204 can be provided on the substrate. This metal film 204 is the same as the metal film 104 of the fourth embodiment. In addition, as shown in FIG. 17, the groove part 202 is provided, the metal film 204 is provided on the surface of the groove part 202, or the protrusion part 203 is provided as shown in FIG. The metal film 204 is provided up to 3a, or both the groove 202 and the projection 203 are provided as shown by the broken line in FIG. 18, and the metal is formed between the surface of the projection 203 and the end 3a of the bonding interface 3. A film 204 may be provided.

  By doing in this way, the sealing material 30 can be reliably fastened to a position covering the end portion 3 a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200.

(Seventh embodiment)
FIG. 20 shows a cross-sectional view of the pressure sensor at the time of heat treatment for bonding in the present embodiment, and FIGS. 21A and 21B show enlarged views of a region B2 surrounded by a broken line in FIG. FIGS. 11A and 11B show the states before and after the sealing material 30 is melted, respectively.

  In the present embodiment, as shown in FIG. 20, the sensor wafer 100 is positioned below and the package wafer 200 is positioned above during the bonding heat treatment.

  At this time, as shown in FIG. 21A, a groove 205 for placing the sealing material 30 is provided in advance on the surface 201 of the package wafer 200 on the sensor wafer 100 side. A stopping material 30 is applied in advance.

  The groove portion 205 corresponds to the groove portion 105 of the fifth embodiment. Similarly to the fifth embodiment, when the sensor wafer 100 and the package wafer 200 are joined, the upper end corner portion 2c of the concave portion 2 of the sensor wafer 100 is obtained. It is arrange | positioned in the position facing.

  The groove 205 is formed before the step of bonding the sensor wafer 100 and the package wafer 200. For example, after the insulating film 212 is formed in the step shown in FIG. 14B, the semiconductor substrate 211 and the insulating film 212 are etched to form the groove 205, and then the sealing material is formed in the groove 205. 30 is applied. In the present embodiment, the step of applying the sealing material 30 after forming the groove 205 is the step of disposing the sealing material 30.

  Then, as shown in FIG. 21B, during the bonding heat treatment, the sealing material 30 disposed in the groove 205 is heated and melted, and the melted sealing material 30 is packaged with the sensor wafer 100 and the package. It flows to the end 3 a of the bonding interface 3 of the wafer 200. The sealing material 30 is cured by natural cooling after the heat treatment for bonding, and the end portion 3 a of the bonding interface 3 is covered with the sealing material 30.

  Therefore, also in the present embodiment, the end portion 3a of the bonding interface 3 is covered with the sealing material 30, so that the airtight space 112 with high airtight reliability can be formed as in the sixth embodiment.

  By the way, when providing the recessed part 2 in the sensor wafer 100 like 6th, 7th embodiment, this embodiment is more preferable than 6th Embodiment. The reason is as follows. In the sixth embodiment, as shown in FIG. 12, the sealing material 30 adheres to the sensing unit 1 because the sealing material 30 is disposed in the recess 2 of the sensor wafer 100. Although the pressure can be detected even if the sealing material 30 is attached to the sensing unit 1, the detection accuracy may be reduced as compared with the case where the sealing material 30 is not attached to the sensing unit 1. is there. On the other hand, according to the present embodiment, since the sealing material 30 is disposed on the package wafer 200, the sealing material 30 can be prevented from adhering to the sensing unit 1.

(Other embodiments)
(1) In the first to fourth and sixth embodiments, the sealing material 30 is disposed on the side surface 2a and the bottom surface 2b of the recess 2; however, the sealing material 30 is disposed only on the side surface 2a of the side surface 2a and the bottom surface 2b of the recess 2. May be.

  Further, in the fifth and seventh embodiments, the grooves 105 and 205 in which the sealing material 30 is disposed are disposed adjacent to the recess 2 by disposing the grooves 105 and 205 at positions facing the upper end corner 2 c of the recess 2. However, the grooves 105 and 205 may be disposed at a position away from the recess 2. That is, the sealing material 30 may be disposed at a position away from the recess 2. At this time, if the grooves 105 and 205 are positioned inside the chip with respect to the end surface of the chip formed by dicing, the recess 2 can be hermetically sealed from the inside of the chip.

  In short, the sealing member 30 is a part away from the end 3a of the bonding interface 3 between the sensor wafer 100 and the package wafer 200 with respect to either the sensor wafer 100 or the package wafer 200. What is necessary is just to arrange | position to the site | part which reaches | attains the edge part 3a of the joining interface 3 when it melt | dissolves and flows, ie, the surface continuous to the joining interface 3 of the sensor wafer 100 and the package wafer 200.

  (2) In each of the above-described embodiments, the bonding heat treatment temperature is set to 300 ° C., but can be changed to other temperatures.

  For example, when the bonding process between the sensor wafer 100 and the package wafer 200 is performed, if the metal wiring layer is not formed on the sensor wafer 100 and the package wafer 200, the bonding heat treatment temperature may be higher than 300 ° C. it can. In this case, as the sealing material 30, a material that melts at this heat treatment temperature may be used.

  Further, as in Patent Document 1, the sensor wafer 100 and the package wafer 200 may be bonded at room temperature. In this case, a process of melting the sealing material 30 and a process of curing the sealing material 30 are performed separately from the bonding process and the cooling process of the sensor wafer 100 and the package wafer 200. Thus, the joining step and the step of melting the sealing material 30 can be performed separately.

  (3) In the first to fifth embodiments, the present invention is applied to a method for manufacturing an acceleration sensor, and in the sixth and seventh embodiments, the present invention is applied to a method for manufacturing a pressure sensor. The present invention can also be applied to a manufacturing method of a quantity sensor.

  Further, in each of the embodiments described above, the semiconductor layer of the sensor wafer 100 and the insulating film of the package wafer 200 are bonded. However, the materials constituting the bonding surfaces of the sensor wafer 100 and the package wafer 200 are arbitrarily changed. Is possible. For example, metal films formed on the respective surfaces of the sensor wafer 100 and the package wafer 200 may be bonded together. Further, Si (single crystal, polycrystalline bulk) or the like is adopted as the semiconductor layer, SiO, SiN or the like is adopted as the insulating film, or Al, Cu, Fe, W, Ti or the like is adopted as the metal film. be able to.

  In each of the above-described embodiments, the airtight spaces 23 and 112 are vacuumed. However, if the airtight spaces 23 and 112 are airtight, the airtight spaces 23 and 112 may not be vacuumed. Also good.

DESCRIPTION OF SYMBOLS 1 Sensing part 2 Recessed part 2c Upper end corner part of recessed part 3 Bonding interface 3a End part of bonded interface 10 Sensor substrate 20 Package substrate 23 Airtight space 30 Sealing material 100 Sensor wafer 110 Sensor substrate 112 Airtight space 200 Package wafer 210 Package substrate

Claims (7)

A sensing unit (1) for detecting a mechanical quantity;
In the manufacturing method of the mechanical quantity sensor comprising an airtight space (23, 112) adjacent to the sensing unit (1),
A plurality of the sensing portions (1) are formed on the sensor wafer (100), and a concave portion (2) constituting the airtight space (23, 112) is formed on one of the sensor wafer (100) and the package wafer (200). A step of forming a plurality,
Either the sensor wafer (100) or the package wafer (200) is sealed by covering the end (3a) of the bonding interface (3) between the sensor wafer (100) and the package wafer (200). A sealing material (30) for disposing the sealing material (30) at a site that reaches the end (3a) of the bonding interface (3) when the sealing material (30) melts and flows;
The sensor wafer (100) and the package wafer (200) are bonded together, and the recess (2) formed in the one wafer of the sensor wafer (100) and the package wafer (200) is closed with the other wafer. And forming the airtight space (23, 112),
The sealing material (30) is heated and melted, and the melted sealing material (30) flows to the end (3a) of the bonding interface (3) between the sensor wafer (100) and the package wafer (200). A process of
Curing the sealing material (30) and covering the end portion (3a) of the bonding interface (3) with the sealing material (30);
A method of manufacturing a mechanical quantity sensor, comprising the step of dividing the bonded sensor wafer (100) and the package wafer (200) into chips. The step of bonding the sensor wafer (100) and the package wafer (200) is to heat-treat the superimposed sensor wafer (100) and the package wafer (200),
In the step of disposing the sealing material (30), as the sealing material (30), a material that melts and flows at the temperature of the heat treatment is disposed.
The mechanical quantity sensor according to claim 1, wherein the step of heating and melting the sealing material (30) is performed simultaneously with the step of bonding the sensor wafer (100) and the package wafer (200). Manufacturing method. In the step of disposing the sealing material (30), the sealing material (30) is disposed on at least the side surface (2a) of the recess (2),
In the step of melting the sealing material (30) by heating, one of the sensor wafer (100) and the package wafer (200) in which the concave portion (2) is formed is used as the upper wafer, The method for manufacturing a mechanical quantity sensor according to claim 1, wherein the sealing material (30) is melted in a state of being below. Prior to the step of bonding the sensor wafer (100) and the package wafer (200), grooves (102, 202) for accumulating the melted sealing material (30) with respect to the surface of the other wafer. )
In the step of melting the sealing material (30) by heating, the melted sealing material (30) is stored in the groove portions (102, 202), so that the end portion (3a) of the bonding interface (3) is collected. The method of manufacturing a mechanical quantity sensor according to claim 3, wherein: Prior to the step of bonding the sensor wafer (100) and the package wafer (200), a protrusion (103) for damming the melted sealing material (30) to the surface of the other wafer. , 203),
In the step of melting the sealing material (30) by heating, the melted sealing material (30) is dammed up by the protrusions (103, 203), so that the end of the bonding interface (3) The method for manufacturing a mechanical quantity sensor according to claim 3 or 4, wherein the sealing material (30) is fastened at a position covering (3a). Using solder as the sealing material (30),
Prior to the step of bonding the sensor wafer (100) and the package wafer (200), a metal film (104, 104) for storing the melted sealing material (30) on the surface of the other wafer. 204) forming,
In the step of melting the sealing material (30) by heating, the melted sealing material (30) is accumulated on the surface of the metal film (104, 204), so that the bonding interface (3) The method for manufacturing a mechanical quantity sensor according to any one of claims 3 to 5, wherein the sealing material (30) is fastened to a position covering the end (3a). In the step of disposing the sealing material (30), the sensor wafer (100) is compared with the other wafer of the sensor wafer (100) and the package wafer (200) in which the recess (2) is not formed. ) And the package wafer (200) are bonded to the sealing material (30) in a groove (105) previously provided at a position facing the upper end corner (2c) of the recess (2). )
In the step of melting the sealing material (30) by heating, one of the sensor wafer (100) and the package wafer (200) in which the concave portion (2) is formed is set as the lower wafer. The method for manufacturing a mechanical quantity sensor according to claim 1, wherein the sealing material (30) is melted in a state where the surface is facing up.

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