JP5912048B2 - Manufacturing method of semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor element obtained by joining the substrates together, more particularly to a method of manufacturing a semiconductor device obtained by bonding the silicon substrate to each other.

  An acceleration sensor, an impact sensor, a pressure sensor, and a vibration type are formed by bonding a sensor substrate made of a silicon base material having an SOI (Silicon on Insulator) layer and a wiring substrate made of a silicon base material supporting the sensor substrate. A semiconductor element such as a gyro or a variable capacitor is manufactured.

  Patent Document 1 discloses a piezoresistive semiconductor pressure sensor. As shown in FIG. 9, the pressure sensor is formed by joining a first silicon substrate 300 having a movable diaphragm 300a and a second silicon substrate 310 serving as a base.

  For this bonding, a diffusion prevention layer 301 for preventing the diffusion of Au and an Au bonding layer 302 are laminated in this order on the surface of the first silicon substrate 300, and Au on the surface of the second silicon substrate 310. A diffusion preventing layer 311 for preventing diffusion and an Au bonding layer 312 are laminated in this order.

  Then, the Au bonding layers 302 and 312 of the first and second silicon substrates 300 and 310 are overlapped with each other, a predetermined load is applied at a predetermined temperature, and the Au bonding layers 302 and 312 of both the silicon substrates 300 and 310 are applied. Join each other. The diffusion prevention layers 301 and 311 are formed of a metal thin film such as Ti, Ni, Cr, W, or Al, a silicon oxide film, a silicon nitride film, or a glass thin film.

JP 2001-150398 A

  In a semiconductor element obtained by bonding a sensor substrate made of a silicon base material having an SOI layer and a wiring substrate made of a silicon base material that supports the sensor substrate, the sensor substrate and the wiring board, A bonding electrode layer used for bonding is formed.

  In the sensor substrate, the bonding electrode layer is formed on the surface of the sensor substrate by sputtering or the like, and the bonding electrode layer is patterned by a semiconductor microfabrication technique.

  Then, using the patterned resist layer as a mask, a groove reaching the silicon oxide layer is formed in the silicon layer by ion etching means such as reactive ion etching. Then, an etching agent containing hydrogen fluoride is infiltrated into the groove formed in the silicon layer, and a part of the silicon oxide layer is removed by etching.

However, in the piezoresistive semiconductor pressure sensor disclosed in Patent Document 1, a diffusion prevention layer 301 and an Au bonding layer 302 are laminated in this order as the bonding electrode layer on the surface of the first silicon substrate 300 as a sensor substrate. Is done. The diffusion prevention layer 301 is formed of a metal thin film such as Ti, Ni, Cr, W, or Al, a silicon oxide film (SiO ₂ ), a silicon nitride film (Si ₃ N ₄ ), or a glass thin film.

  By the way, when an etchant containing hydrogen fluoride is used in the configuration as in Patent Document 1, Ti, Ni, Cr, W, Al, a silicon oxide film, or a glass thin film is affected by the etchant. Can not be used to melt, or.

  In the combination of the silicon nitride film and the Au bonding layer 302, it is necessary to form a connection hole penetrating the insulating silicon nitride film in order to obtain conductivity. In such an aspect, since the first silicon substrate 300 and the Au bonding layer 302 are in direct contact, the silicon nitride film cannot exhibit the function of preventing diffusion.

  In order to obtain a strong bond between the Au bonding layers 302 and 312, it is known to clean the surfaces of the Au bonding layers 302 and 312 with sulfuric acid / hydrogen peroxide (mixed solution of sulfuric acid and hydrogen peroxide). However, Ni, W, and Al cannot be used when washed with sulfuric acid / hydrogen peroxide because they are affected or dissolved by sulfuric acid / hydrogen peroxide.

  As shown in FIG. 9, in the piezoresistive semiconductor pressure sensor disclosed in Patent Document 1, the silicon layer is exposed at the interface between the first silicon substrate 300 and the diffusion prevention layer 301. It is known that a natural oxide film is formed on the front and back surfaces of the silicon layer, and that the thicker the natural oxide film is, the higher the impurity concentration of the silicon layer is.

  Therefore, when an etchant containing hydrogen fluoride is used in the configuration as in Patent Document 1, it is formed on the surface of the first silicon substrate 300 at the interface between the first silicon substrate 300 and the diffusion prevention layer 301. When the natural oxide film is etched, etching proceeds in a cut shape at the interface. Due to this cutting, the diffusion prevention layer 301 is cracked or voided, and in some cases, the diffusion prevention layer 301 or the Au bonding layer 302 is peeled off, resulting in poor conduction.

An object of the present invention has been made in unto this problem is to provide a method for manufacturing a semiconductor element having a high-quality joint.

The method for manufacturing a semiconductor element of the present invention includes a first base, a second base, a movable part, and a joint electrically connected to the movable part, and the first base and the The movable portion is configured to include a functional portion disposed between the second base material and a first insulating layer made of an oxide between the joint portion and the first base material. parts are in the manufacturing method of the semiconductor element provided to be displaceable between said second substrate and said first substrate,
A step (a) of forming an adhesion layer made of aluminum oxide or nitride on the side of the joining portion facing the second base material, and patterning the adhesion layer; (B) forming a first underlayer and a first bonding layer made of Au in this order, and patterning the first underlayer and the first bonding layer, and patterning the functional portion Forming and etching away a part of the first insulating layer between the functional part and the first substrate; and the first bonding layer of the second substrate. Including a step (d) of patterning a second bonding layer made of Au at a position opposite to and a step (e) of bonding the first bonding layer and the second bonding layer. Features.

  In the steps (a) to (b), the bonding portion that outputs the physical quantity detected by the movable portion to the outside is a stack of the adhesion layer, the first base layer, and the first bonding layer. Formed with a structure.

  In the step (c), the functional part including the movable part and the joint part is formed. And the said movable part is provided displaceably by the said 1st insulating layer between the said movable part and the said 1st base material being etched away.

  In step (c), the first insulating layer between the movable part and the first base material is etched away with an etchant containing hydrogen fluoride. At that time, the adhesion layer, the first base layer, and the first bonding layer have corrosion resistance to the etching agent.

  In the step (e), when the first bonding layer and the second bonding layer are bonded, the first bonding layer is disposed to be laminated on the first base layer. The first underlayer functions as a diffusion preventing layer for the first bonding layer.

  In addition, bonding the first bonding layer and the second bonding layer in the step (e) has a structure in which the first base layer and the first bonding layer are stacked on the adhesion layer. By having it, cracks, voids, film peeling, and the like are not generated in the joint portion.

  Therefore, according to the present invention, it is possible to provide a method for manufacturing a semiconductor element having a high-quality junction.

  The first base material, the second base material, and the functional part are made of silicon, the first insulating layer is made of silicon oxide, and a part of the first insulating layer contains hydrogen fluoride. It is preferable to be removed by etching with an etching agent.

  If it is such an aspect, since the silicon is not etched and the silicon oxide is removed by etching with the etching agent, the first oxide made of oxide is formed between the joint and the first base material. A semiconductor element having an insulating layer and removing the first insulating layer between the movable part and the first base material to displace the movable part can be manufactured.

When the first insulating layer between the movable portion and the first base material is removed by the etching agent containing hydrogen fluoride, the bonding portion includes the adhesion layer, the first underlayer, and the first bonding. It is composed of layers, and these layers are corrosion resistant to the etchant. In addition, since the first underlayer has a structure laminated on the adhesion layer, when the first insulating layer is removed by the etchant, cracks, voids, film peeling, etc. are formed at the joint. Will not occur.
Therefore, according to the present invention, it is possible to provide a method for manufacturing a semiconductor element having a high-quality joint.

2 is a schematic plan view of a functional unit in the semiconductor element of the first embodiment. FIG. 2 is a schematic cross-sectional view of a semiconductor element taken along line AA in FIG. 1 and viewed from the direction of an arrow. 1 is a schematic perspective view showing a state where a semiconductor element of a first embodiment is stationary under zero gravity. 1 is a schematic perspective view showing a state in which the semiconductor element of the first embodiment is operating. It is a manufacturing process explanatory view of the semiconductor element in a 1st embodiment. It is a section schematic diagram of a semiconductor device in a 2nd embodiment. It is a microscope picture of a defective example. It is a microscope picture of a non-defective example. 1 is a schematic cross-sectional view of a piezoresistive semiconductor pressure sensor disclosed in Patent Document 1.

<First Embodiment>
Regarding the semiconductor elements shown in the drawings, the Y direction is the left-right direction, the Y1 direction is the left direction, the Y2 direction is the right direction, the X direction is the front-rear direction, the X1 direction is the front direction, and the X2 direction is the rear direction. . In addition, the direction orthogonal to both the X direction and the Y direction is the Z direction, which is the vertical direction, the Z2 direction is the upward direction, and the Z1 direction is the downward direction. In the drawings, the dimensions are appropriately changed for easy viewing.

  In the first embodiment, the semiconductor element is an acceleration sensor. The semiconductor element is not limited to an acceleration sensor, and an impact sensor, a pressure sensor, a vibration gyroscope, a variable capacitor, and the like are also possible.

  FIG. 1 is a schematic plan view of the functional unit 2 viewed from the first base material 21 side through the first base material 21. FIG. 2 is a schematic cross-sectional view of the semiconductor element 1 cut along the line AA in FIG. 1 and viewed from the direction of the arrow. 3 and 4 are perspective views of the functional unit 2 seen through the first base material 21, and the frame body unit 5 is omitted.

  As shown in FIGS. 1 and 2, the semiconductor element 1 includes a functional part in an SOI layer 27 (see FIG. 5A) provided on a first base material (silicon) 21 via a first insulating layer (silicon oxide) 22. 2 is formed. That is, a planar resist layer corresponding to the shape of each part is patterned on the SOI layer 27 made of conductive silicon, and the SOI layer 27 is ionized by reactive ion etching or the like in a part where the resist layer does not exist. Each part is separated by cutting with an etching means. Therefore, each part formed in the functional part 2 of the semiconductor element 1 is configured within the range of the SOI layer 27 and the electrode layer formed in the SOI layer 27. When the semiconductor element 1 is in a stationary state under zero gravity, as shown in FIG. 3, the movable portion 3 is a portion in which the entire front surface and the entire back surface are located on the same surface and protrudes from the front surface and the back surface. There is no. Since the actual semiconductor element 1 is used on the earth, the movable part 3 is slightly displaced by the influence of the earth's gravity even when it is stationary.

  As shown in FIG. 1, the functional unit 2 constituting the semiconductor element 1 has a movable part 3, joint parts 10-12, and a frame part 5 around the movable part 3 and the joint parts 10-12. It is configured.

  As shown in FIGS. 1 and 3, the movable part 3 includes a weight part 4 that is displaced in parallel in the vertical direction (Z), and rotation support parts 6, 7, 8, 9 provided inside the weight part 4. It is comprised.

  As shown in FIG. 1, the first rotation support portion 6 is integrally formed with a connecting arm 6 a extending in the front direction (X1) and a leg portion 6 b extending in the rear direction (X2). Further, as shown in FIG. 1, the second rotation support portion 7 is integrally formed with a connecting arm 7a extending in the rear direction (X2) and a leg portion 7b extending in the front direction (X1).

  Further, a central joint 10, a left joint 11, and a right joint 12 are provided inside the movable part 3. Each joining part 10-12 is provided at predetermined intervals in the left-right direction (Y). The width dimensions in the front-rear direction (X) of the central joint 10, the left joint 11, and the right joint 12 are substantially the same.

  The connecting arms 6a and 7a and the leg portions 6b and 7b are formed in a shape that extends in a predetermined width dimension in a direction away from each of the joint portions 10 to 12 and parallel to the front-rear direction (X).

  FIG. 2 is a schematic cross-sectional view taken along the line AA shown in FIG. 1 and viewed from the arrow direction. As shown in FIG. 2, the center joint portion 10 is fixedly supported on the first base material 21 via the first insulating layer 22 made of silicon oxide. The frame body portion 5 provided around the movable portion 3 is fixedly supported on the first base material 21 via the first insulating layer 22 made of silicon oxide.

  And the junction parts 10-12 are each comprised with the fixing | fixed part 10a-12a, the contact | adherence layer 23, the 1st base layer 24, and the 1st junction layer 25. The central joint 10 is also provided with a connection hole 26. The frame body portion 5 includes a frame body fixing portion 5a, an adhesion layer 23, a first base layer 24, and a first bonding layer 25. However, the left joint 11 and the right joint 12 are not shown.

  As shown in FIG. 1, the distal end portion of the connecting arm 6 a of the first rotation support portion 6 and the weight portion 4 are rotatably connected by a connection portion 40 a, and the second rotation support portion 7 The distal end portion of the connecting arm 7a and the weight portion 4 are rotatably connected by a connecting portion 40b.

  The connection arm 6a of the first rotation support portion 6 is rotatably connected by the left joint portion 11 and the support connection portion 50b, and by the central joint portion 10 and the support connection portion 50a. The connecting arm 7a of the second rotation support portion 7 is rotatably connected by the right joint portion 12 and the support connection portion 51b, and by the central joint portion 10 and the support connection portion 51a.

  A third rotation support portion 8 formed separately from the weight portion 4 and the left joint portion 11 is provided in the rear direction (X2) of the left joint portion 11, and in the forward direction (X1) of the right joint portion 12. A fourth rotation support portion 9 formed separately from the weight portion 4 and the right joint portion 12 is provided.

  The tip end portion of the third rotation support portion 8 and the weight portion 4 are rotatably connected by a connecting portion 41a. Moreover, the front-end | tip part of the 4th rotation support part 9 and the weight part 4 are connected rotatably by the connection part 41b.

  The 3rd rotation support part 8 and the left side junction part 11 are connected rotatably by the support connection part 52a. Moreover, the 4th rotation support part 9 and the right side junction part 12 are connected rotatably by the support connection part 52b.

  The connection arm 6a of the first rotation support part 6 and the third rotation support part 8 are connected via a connection part 42a. Further, the connecting arm 7a of the second rotation support part 7 and the fourth rotation support part 9 are connected via a connection part 42b.

  Each connecting portion 40a, 40b, 41a, 41b, 42a, 42b and each supporting connecting portion 50a, 50b, 51a, 51b, 52a, 52b have spring properties by cutting the SOI layer 27 into a thin plate by etching. It consists of a torsion bar (spring part).

  The first insulating layer 22 is not provided at a position facing the rotation support parts 6 to 9 and the weight part 4. However, FIG. 2 shows only the leg portion 6 b of the first rotation support portion 6, the leg portion 7 b of the second rotation support portion 7, and the weight portion 4.

  The functional unit 2 includes the movable unit 3, the bonding units 10 to 12, and the frame body unit 5, and is formed from the SOI layer 27. In the joint portions 10 to 12 and the frame portion 5, the adhesion layer 23, the first base layer 24, and the first joint layer 25 are formed on the surfaces of the fixing portions 10 a, 11 a, 12 a, and 5 a made of the SOI layer 27. These layers are also included in the functional unit 2. The sensor substrate 20 includes a first base material 21, a functional unit 2, and a first insulating layer 22.

  The movable part 3 includes a weight part 4, rotation support parts 6 to 9, connection parts 40 to 42, and support connection parts 50 to 52.

  As shown in FIG. 2, the semiconductor element 1 is provided with a first base member 21 on one side separated from the movable part 3 in the vertical direction (Z) and a second base member 31 on the other side. In the wiring substrate 30, the second insulating layer 32 is formed on the surface of the second base material 31 facing the first base material 21, and the fixed electrode layer 36 is formed on the surface of the second insulating layer 32. Configured. The fixed electrode layer 36 is formed on the surface of the second insulating layer 32 by using a conductive metal material by sputtering or plating. The fixed electrode layer 36, the movable part 3, and the weight part 4 together constitute a detection part.

  The semiconductor element 1 is elastically restored by the torsion bars (spring portions) provided in the respective support connection portions 50 to 52 and the connection portions 40 to 42 when no force (acceleration or the like) is applied from the outside under weightlessness. With the force, as shown in FIG. 3, the surface of all the parts is maintained in the same plane. When the semiconductor element 1 is actually used, the semiconductor element 1 is slightly displaced due to the gravity of the earth.

  When, for example, acceleration is applied to the semiconductor element 1 from the outside, the acceleration acts on the rotation support portions 6 to 9, the weight portion 4, the joint portions 10 to 12, and the like. At this time, the respective constituent members move relatively due to the difference in inertia force caused by the magnitude of the mass of the respective constituent members. As a result, the joint portions 10 to 12 connected to the first base material 21 and the second base material 31 try to stay in the absolute space, and the weight portion 4 relatively moves in the direction in which the acceleration acts. Therefore, the weight portion 4 is displaced downward (Z1) about the support connecting portions 51a and 50b so that the weight portion 4 is displaced upward (Z2) from the stationary state position in FIG. ), The second rotation support portion 7 rotates downward (Z1) around the support connection portions 50a and 51b, and the third rotation support portion 8 centers around the support connection portion 52a. It rotates downward (Z1), and the fourth rotation support portion 9 rotates downward (Z1) about the support connecting portion 52b. As a result, each component member is displaced as shown in FIG. (However, only a part of the constituent members is shown in FIG. 4.) During this turning operation, the torsion bars provided in the connecting portions 40 to 42 and the support connecting portions 50 to 52 are twisted and deformed.

  FIG. 5 is a process chart showing a method for manufacturing the semiconductor element 1. Each figure is a schematic cross-sectional view during the manufacturing process.

  In the step shown in FIG. 5A, an adhesion layer 23 made of aluminum oxide or nitride is formed on the surface of the SOI layer 27 provided on the first base 21 via the first insulating layer 22 by sputtering or the like. The film is formed by a CVD (Chemical Vapor Deposition) method.

  Subsequently, a resist layer in which holes corresponding to the connection holes 26 are formed on the adhesion layer 23 is patterned by a photolithographic technique. Then, the adhesion layer 23 in the portion of the connection hole 26 is removed by ion etching means such as ion milling or reactive ion etching.

  In the step shown in FIG. 5B, the first underlayer 24 made of a platinum group element and the first bonding layer 25 made of Au are formed by sputtering, plating, or the like. A resist layer is formed to cover the region where the adhesion layer 23, the first underlayer 24, and the first bonding layer 25 are left, and the adhesion layer 23, the first adhesion layer 23, and the first adhesion layer 23 are formed by ion etching means such as ion milling or reactive ion etching. The first underlayer 24 and the first bonding layer 25 are removed.

  Subsequently, the SOI layer 27 is shaved by ion etching means such as reactive ion etching using the same resist layer, and the fixing portions 10a to 12a and the frame body fixing portion 5a are formed to protrude. However, the left side fixing part 11a and the right side fixing part 12a are not shown.

  In the present embodiment, the fixing portions 10a to 12a and the frame body fixing portion 5a are projected to secure a gap in which the movable portion 3 is movable, but the present invention is not limited to this. For example, even if the gap is secured only by the protrusion provided on the second base material 31 side, or by the adhesion layer 23, the first base layer 24, the first bonding layer 25, the second bonding layer 35, and the like. good.

  In the step shown in FIG. 5C, a resist layer having a planar shape corresponding to the shape of each of the weight portion 4 and the rotation support portions 6, 7, 8, 9 is formed, and the SOI layer exposed from the resist layer. The portion 27 is removed by ion etching means such as reactive ion etching until the first insulating layer 22 is reached. In this way, the weight portion 4 and the rotation support portions 6, 7, 8, and 9 are separated, and a groove is formed therebetween. However, only the leg portion 6b of the first rotation support portion 6 and the leg portion 7b of the second rotation support portion 7 are illustrated.

  After the resist layer is removed, the sensor substrate 20 is washed with sulfuric acid / hydrogen peroxide so that the second bonding layer 35 to be described later can be bonded satisfactorily. To be cleaned.

  Subsequently, a mixed gas, which is an etchant containing anhydrous hydrogen fluoride gas, is infiltrated into the groove separating the weight portion 4 and the rotation support portions 6, 7, 8, 9, and the first insulating layer 22 A part of is removed by etching. As a result, the first insulating layer 22 between the movable portion 3 including the weight portion 4 and the rotation support portions 6, 7, 8, 9, and the first base material 21 is removed by etching, and the joint portions 10 to 10 are removed. 12, and the first insulating layer 22 is left between the frame 5 and the first base material 21. In this way, the sensor substrate 20 is manufactured.

  In the first embodiment, a mixed gas that is an etchant containing anhydrous hydrogen fluoride gas is used. However, the present invention is not limited to this. It is also possible to use an etching agent containing a hydrofluoric acid aqueous solution.

  The thickness dimension of the first base material 21 is about 0.2 to 0.7 mm, the thickness dimension of the functional unit 2 composed of the movable part 3, the joint parts 10 to 12 and the frame part is about 10 to 30 μm, The thickness dimension of the first insulating layer 22 is about 1 to 3 μm.

  As described above, since the thickness dimension of the functional unit 2 is as very thin as about 10 to 30 μm, after the first insulating layer 22 is removed by etching with the etching agent, the adhesion layer 23, the first underlayer 24, and It is very difficult to form the first bonding layer 25 to form a pattern.

  As shown in FIG. 5D, the wiring board 30 is formed. A second insulating layer 32 is formed on the surface of the second base material 31 constituting the wiring substrate 30 so as to face the first bonding layer 25 formed on the bonding portions 10 to 12 and the frame body portion 5. Then, the second base layer 34 and the second bonding layer 35 are formed on the surface of the second insulating layer 32.

The second base material 31 is a silicon substrate having a thickness dimension of about 0.2 to 0.7 mm. The second insulating layer 32 is made of silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), or the like, and is formed by a sputtering method, a CVD method, or the like.

  The wiring board 30 is washed with sulfuric acid / hydrogen peroxide to clean the surface to which the second bonding layer 35 is bonded. The sensor substrate 20 and the wiring substrate 30 are inserted into a vacuum container in a state of being adjusted to face each other, heated to a predetermined temperature (about 150 to 300 ° C.) while being evacuated, and a predetermined load (6500). About 7500 N). Thereby, as shown in FIG.5 (e), the 1st joining layer 25 and the 2nd joining layer 35 are joined firmly.

  The physical quantity detected by the movable portion 3 is output to the outside via the central joint portion 10, the second joint layer 35, the second base layer 34, and the wiring layer 37. For this reason, the central joint portion 10 is provided with a connection hole 26 that electrically connects the movable portion 3, that is, the fixed portion 10 a and the first base layer 24. Since the physical quantity detected by the movable part 3 is not output to the outside via the left joint part 11 and the right joint part 12, no connection hole 26 is provided in the left joint part 11 and the right joint part 12.

  In order to ensure a stable electrical connection, it is necessary that the bonding between the first bonding layer 25 and the second bonding layer 35 be strong. As shown in FIG. 2 and FIG. 6, since the connecting hole 26 is provided in the central joint portion 10, the surface of the first joining layer 25 corresponding to the connecting hole 26 is likely to be lower than other portions. . Therefore, the portion corresponding to the connection hole 26 tends to be inferior in bonding strength to other portions. Therefore, in order to ensure strong bonding of the central bonding portion 10, it is necessary to increase the bonding area between the first bonding layer 25 and the second bonding layer 35 with respect to the area of the connection hole 26. is there.

In the present embodiment, the area of the connection hole 26 is about 450 to 550 μm ² , the bonding area of the first bonding layer 25 and the second bonding layer 35 is about 2950 to 3050 μm ² , and the ratio is about 6 Is double.

  The semiconductor element 1 is formed by forming an adhesion layer 23, a first underlayer 24, and a first bonding layer 25 on the fixing portions 10a to 12a and the frame body fixing portion 5a, and then an etching agent made of anhydrous hydrogen fluoride gas. Exposed to. In addition, before the sensor substrate 20 and the wiring substrate 30 are joined, sulfuric acid / hydrogen peroxide cleaning is performed. Therefore, the fixing portions 10a to 12a, the frame body fixing portion 5a, the adhesion layer 23, the first base layer 24, and the first bonding layer 25 are the bonding portions 10 to 12 and the frame body portion 5, respectively. An anhydrous hydrogen fluoride gas, a hydrofluoric acid aqueous solution, and a sulfuric acid / hydrogen peroxide aqueous solution are made of a material that is corrosion resistant.

  Since the physical quantity detected by the movable unit 3 is output to the outside through the fixed unit 10a, the fixed unit 10a, that is, the SOI layer 27 is made of conductive silicon. It is known that a natural oxide film is formed on the surface of conductive silicon. However, the joint portions 10 to 12 and the frame body portion 5 of the semiconductor element 1 of the present embodiment are formed on the fixing portions 10a to 12a and the frame body fixing portion 5a, respectively, made of conductive silicon. In this structure, the first base layer 24 and the first bonding layer 25 are stacked.

  Therefore, the first base layer 24 is not directly in contact with the conductive silicon, but is firmly bonded via the adhesion layer 23. Therefore, when exposed to an etchant containing anhydrous hydrogen fluoride gas, the notch-like etching that occurs when the natural oxide film on the surface of the conductive silicon is etched is the interface between the conductive silicon and the adhesion layer 23. Proceed to. That is, the cut etching does not occur at the interface between the adhesion layer 23 and the first underlayer 24.

  However, when the sensor substrate 20 and the wiring substrate 30 are heated and pressure-bonded, the metal layer composed of the first base layer 24 and the first bonding layer 25 is compressed to generate residual stress. Therefore, if there is a cut at the interface between the conductive silicon and the first underlayer 24, the first underlayer 24 may be cracked or voided due to the stress relaxation phenomenon of the residual stress starting from this notch. As a result, the first base layer 24 and the first bonding layer 25 may be peeled off, resulting in poor conduction. In order to prevent this, in this embodiment, the adhesion layer 23 is inserted between the conductive silicon and the first base layer 24.

  Cracks and voids generated in the first underlayer 24 and film peeling of the first underlayer 24 and the first bonding layer 25 are observed with a metal microscope, a scanning electron microscope, or the like. Is possible.

  Since the adhesion layer 23 is made of a material harder than the metal layer composed of the first underlayer 24 and the first bonding layer 25, it hardly deforms when heated and pressure-bonded. Therefore, the residual stress generated in the adhesion layer 23 is very small, and even if there is a cut at the interface between the conductive silicon and the adhesion layer 23, the adhesion layer 23, the first underlayer 24, and the first bonding layer 25 There are no problems such as cracks, voids, or film peeling.

Therefore, according to this embodiment, while providing the movable part 3, the base material is joined, and the semiconductor element which has the high quality joining parts 10, 11, 12, and the frame part 5 is provided. Can do. Further, the movable part 3 and the joint portion 10, 11 and 12, since the hermetically sealed by a frame portion 5 surrounding the periphery and the second bonding layer 35, the semi-conductor elements, precisely detecting a physical quantity Is possible.

  The thickness of the first bonding layer 25 is preferably 0.05 to 0.2 μm. The first bonding layer 25 and the second bonding layer 35 are bonded by heating and pressure bonding. At this time, if the flatness of the contact surface of the first bonding layer 25 is poor, only the initially protruding portion is crimped, and the other portion is crimped as this portion is crushed. For this reason, since the crimping proceeds unevenly within the contacting surface, an insufficient bonding portion is likely to occur, and the residual stress caused by the crimping is uneven within the film, thereby obtaining an appropriate bonding strength. There was nothing.

  The first bonding layer 25 made of Au is formed by sputtering or plating. It is known that the flatness of the surface of a film formed by a sputtering method, a plating method or the like deteriorates as the thickness increases. Therefore, in order to maintain good flatness of the first bonding layer 25 and have strong bonding strength, the upper limit is 0.2 μm, and more preferably 0.1 μm or less.

  When heating and pressure bonding, the first bonding layer 25 is pressure-bonded and crushed. Therefore, if it is too thin, there may be a disappearance portion partially free of Au. For this reason, an appropriate bonding strength may not be obtained, and a good contact resistance may not be obtained. Therefore, in order to suppress such problems and stably have a strong bonding strength, a thickness of 0.05 μm is the lower limit.

  Further, when such a bonding failure occurs in the bonded portion of the frame body portion 5, the functional unit 2 is not hermetically sealed by the frame body portion 5, so that the physical quantity cannot be detected accurately. Therefore, it is necessary to have an appropriate bonding strength from the hermetic sealing.

The thickness of the adhesion layer 23 is preferably 0.02 to 0.2 μm. The adhesion layer 23 made of aluminum oxide (Al ₂ O ₃ ) or nitride is formed by sputtering or CVD. It is known that the film formed by sputtering or CVD has poor surface flatness as the thickness increases. When the flatness of the adhesion layer 23 is deteriorated, the flatness of the first bonding layer 25 laminated on the adhesion layer 23 is also deteriorated. Therefore, in order to maintain good flatness of the first bonding layer 25 and have strong bonding strength, the upper limit of the thickness of the adhesion layer 23 is 0.2 μm, and is 0.1 μm or less. Is more preferable.

  As the thickness of the adhesion layer 23 decreases, the strength deteriorates. Therefore, when the thickness of the adhesion layer 23 is 0.02 μm or less when heated and pressure-bonded, the adhesion layer 23 is cracked and damaged. Therefore, in order to stably have strong bonding strength, the lower limit of the thickness of the adhesion layer 23 is 0.02 μm.

  The first underlayer 24 is preferably made of at least one metal selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum, or an alloy thereof.

  If it is such an aspect, it has corrosion resistance with respect to the etching agent containing anhydrous hydrogen fluoride gas and hydrofluoric acid aqueous solution, and sulfuric acid perwater solution.

  Further, when the first bonding layer 25 made of Au and the fixing portions 10a to 12a made of silicon and the frame fixing portion 5a are in direct contact with each other, Au and silicon easily react when heated and pressed. Diffuses into the silicon. As a result, the bonding between the first bonding layer 25 and the second bonding layer 35 is deteriorated. Therefore, it is necessary to provide a diffusion preventing layer between the first bonding layer 25 and the fixing portions 10a to 12a and the frame fixing portion 5a. The first underlayer 24 is made of at least one metal selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum, or an alloy thereof, so that the first underlayer 24 is a diffusion preventing layer. can do.

  It is preferable that the first base material 21 and the second base material 31 are made of silicon, and the first insulating layer 22 is made of silicon oxide.

  With such a structure, silicon is not etched and silicon oxide is removed by etching with an etchant composed of anhydrous hydrogen fluoride gas or hydrofluoric acid aqueous solution. Therefore, the joint portions 10 to 12 and the first base material 21 are removed. It is possible to have the first insulating layer 22 made of oxide between and the movable portion 3 and the first base member 21 without the first insulating layer 22.

  In the first embodiment, the first base material 21 is made of silicon and the first insulating layer 22 is made of silicon oxide. However, the present invention is not limited to this. The first base material 21 is made of, for example, a metal material that is corrosion-resistant to an etchant made of anhydrous hydrogen fluoride gas or an aqueous hydrofluoric acid solution, and the first insulating layer 22 is etched by the etchant. It can also be an oxide.

The adhesion layer 23 is preferably made of aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), or aluminum nitride (AlN). With such an embodiment, an adhesive layer 23 having corrosion resistance to an etchant containing anhydrous hydrogen fluoride gas or an aqueous hydrofluoric acid solution and an aqueous sulfuric acid / hydrogen peroxide solution is possible.

  The connection hole 26 that penetrates the adhesion layer 23 is provided to electrically connect the fixing portion 10 a and the first base layer 24. The connection hole 26 is preferably covered with the first base layer 24 and the first bonding layer 25 so that the surface of the fixing portion 10 a is not exposed in the connection hole 26.

  In such an embodiment, since the interface between the fixed portion 10a and the first base layer 24 is not exposed in the connection hole 26, the natural oxide film on this interface is not etched, so that high quality is achieved. It is possible to form a simple joint.

  <Second Embodiment>

  FIG. 6 is a schematic cross-sectional view of the semiconductor device of the second embodiment. In the present embodiment, the outer periphery of the adhesion layer 23 is located outside the outer periphery of the first base layer 24. That is, the pattern of the adhesion layer 23 is larger than the pattern of the first underlayer 24 and the first bonding layer 25 in a plan view. Regarding the residual stress generated by heating and press-bonding, a force obtained by summing up the residual stress in the pattern is generated in the first underlayer 24 and the first bonding layer 25. Therefore, it is advantageous to reduce the pattern. .

  However, when the pattern of the first underlayer 24 and the first bonding layer 25 is reduced, the area ratio of the cuts generated at the interface between the conductive silicon and the first underlayer 24 is increased. Therefore, when exposed to an etchant made of anhydrous hydrogen fluoride gas, the first underlayer 24 and the first bonding layer 25 are affected by the film stress of the first underlayer 24 and the first bonding layer 25. Problems such as cracks, voids, or film peeling may occur.

  Therefore, in the present embodiment, the adhesion layer 23 is inserted between the conductive silicon and the first foundation layer 24, and the pattern of the adhesion layer 23 is changed to the first foundation layer 24 and the first bonding layer in a plan view. The pattern is larger than 25 patterns. As a result, even if there is a cut at the interface between the conductive silicon and the adhesion layer 23, the area ratio of the cut can be reduced, so that the adhesion layer 23, the first underlayer 24, and the first bonding layer 25 are cracked, There are no problems such as voids or film peeling.

FIG. 7 shows a metal micrograph of a defective example. In this defective example, the first underlayer 24 (ruthenium) is formed and patterned on conductive silicon, and then etched with an etchant containing anhydrous hydrogen fluoride gas. In this case, a crack-like defect occurred in the first underlayer 24. FIG. 8 shows a metal micrograph of a good product example. In this non-defective example, an adhesion layer 23 (Al ₂ O ₃ ) having an area larger than the area of the first underlayer 24 in plan view is formed between the conductive silicon and the first underlayer 24 (ruthenium). And then etched with an etchant containing anhydrous hydrogen fluoride gas. In this case, no crack-like defect occurred in the first underlayer 24.

  In the present embodiment, the fixed portions 10 a, 11 a, 12 a and the frame body fixing portion 5 a do not protrude and are provided with the same height (Z) dimension as the movable portion 3.

Table 1 below shows the half-conductor devices, after immersion in water, by infrared microscopy (Infrared Microscope) or the like is transmitted through the first substrate, the result of observation of the presence or absence of flooding. Further, the surface roughness (RMS: root mean square surface roughness) of the first bonding layer is evaluated by an atomic force microscope, and this result is also shown. As shown in Table 1, it can be seen that as the thickness of the first bonding layer increases, the surface roughness of the first bonding layer increases. It can also be seen that the first bonding layer is not immersed when the thickness is 0.2 μm or less, but is immersed when the thickness is 0.3 μm or more. Therefore, it is understood that the water immersion starts when the thickness of the first bonding layer is between 0.2 μm and 0.3 μm.

DESCRIPTION OF SYMBOLS 1 Semiconductor element 2 Function part 3 Movable part 4 Weight part 5 Frame body part 5a Frame body fixing | fixed part 6, 7, 8, 9 Rotation support part 10, 11, 12 Junction part 10a, 11a, 12a Fixed part 20 Sensor substrate 21 First base material 22 First insulating layer 23 Adhesion layer 24 First underlayer 25 First bonding layer 26 Connection hole 27 SOI layer 30 Wiring substrate 31 Second base material 32 Second insulating layer 34 Second Base layer 35 Second bonding layer 36 Fixed electrode layer 37 Wiring layers 40, 41, 42 Connection portions 50, 51, 52 Support connection portions

Claims (2)

A first base material; a second base material; a movable portion; and a joint portion electrically connected to the movable portion, wherein the first base material is disposed between the first base material and the second base material. And a first insulating layer made of an oxide between the bonding portion and the first base material, and the movable portion includes the first base material and the first base material. In the manufacturing method of the semiconductor element provided to be displaceable between the second base material,
A step (a) of forming an adhesion layer made of aluminum oxide or nitride on the side of the bonding portion facing the second base material, and patterning the adhesion layer;
A step (b) of forming a first underlayer made of a platinum group element and a first bonding layer made of Au in this order and patterning the first underlayer and the first bonding layer; ,
Patterning the functional part and etching away a part of the first insulating layer between the functional part and the first substrate (c);
Patterning a second bonding layer made of Au at a position facing the first bonding layer of the second substrate (d);
A step (e) of bonding the first bonding layer and the second bonding layer. The first base material, the second base material, and the functional part are made of silicon, the first insulating layer is made of silicon oxide, and a part of the first insulating layer is made of hydrofluoric acid. The method for manufacturing a semiconductor device according to claim 1 , wherein the semiconductor element is removed by etching with an etchant.