JP3399164B2 - Acceleration sensor and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor formed by joining first and second semiconductor substrates and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as an acceleration sensor formed by using a semiconductor processing technique, as shown in FIG. 11A, a weight portion 30 is cantilevered by a thin cantilever beam portion 31 so as to be swingable. Beam method and weight 30 as shown in FIG.
There is a doubly supported beam system in which a thin doubly supported beam part 32 is swingably supported. As a method of detecting acceleration by both of these methods, a method of detecting mechanical strain as a change in electric resistance, There is a detection method based on a change in capacitance. For example, in the former detection method, when acceleration is applied to the weight portion 30 that is swingably supported by the cantilever beam portion 31, the mechanical strain generated in the beam portion due to the swing of the weight portion 30 is reduced. This is detected as a change in electric resistance of a piezoresistive element (not shown) formed on the cantilever portion 31.

Here, the acceleration sensor as described above is manufactured by utilizing a bonding technique of silicon substrates, that is, a so-called SOI technique. Hereinafter, the manufacturing process of the conventional acceleration sensor will be described with reference to FIGS. 12
A first semiconductor substrate 10 having a weight portion 1 as shown in (a) is prepared. Here, one main surface of the first semiconductor substrate 10 (a main surface on the side not bonded to the second semiconductor substrate 11; hereinafter, this surface is referred to as a “rear surface”) is the first semiconductor substrate 10 and the first semiconductor substrate 10. Since the weight portion 1 is formed by etching after joining the second semiconductor substrate 11 to each other, it is necessary to form a mask capable of withstanding etching for a long time. Generally, a silicon nitride film is used in an alkaline etching solution such as an aqueous potassium hydroxide solution (hereinafter KOH). Therefore, on the back surface of the first semiconductor substrate 10, the silicon nitride film 33 that serves as a mask for etching when the weight portion 1 is formed.
Are formed (see FIG. 2B). The silicon nitride film 33 is also formed on the main surface of the first semiconductor substrate 10 on the side to be bonded (hereinafter, this surface is referred to as the “front surface”). Next, the silicon nitride films 33 on both front and back surfaces of the first semiconductor substrate 10 are removed along a predetermined pattern (see FIG. 6C), and the first semiconductor substrate of the portion where the silicon nitride film 33 is removed is removed. Predetermined recesses 14 are formed on both main surfaces by etching 10 (see FIG. 3D).
Then, the first semiconductor substrate 10 and the second semiconductor substrate 11
And Si are bonded by Si-Si bonding, the silicon nitride film 33 on the bonding surface (front surface) is removed by etching, leaving only the silicon nitride film 33 on the back surface of the first semiconductor substrate 10 (see FIG. 8E). , The first semiconductor substrate 10 and the second semiconductor substrate 11 are joined and bonded by fusion bonding (silicon fusion bond: SFB) by high-temperature treatment (see FIG. 6F), and The beam portion 2 is formed by mechanically grinding the semiconductor substrate 11 into a thin film (see FIG. 7G).

Next, the thinned second semiconductor substrate 11 is formed.
A contact layer 15 and a resistance element (piezoresistor) 16 are formed by diffusing impurities on the surface of the beam 2 (see FIG. 13).
(See (a) and (b)), and further, a metal wiring 18 connected to the contact layer 15 and the piezoresistor 16 and a protective film 19 for protecting the metal wiring 18 are formed (FIGS. See d)). After that, the first semiconductor substrate 10 is etched from the recess 14 on the back surface side thereof until it reaches the recess 14 on the front surface side (see (e) in the same figure), and further, the second semiconductor substrate 11 thinned is formed. By forming the slit 20 and partially separating it, the beam portion 2 and the weight portion 1 swingably supported by the beam portion 2 are formed to complete a chip-shaped acceleration sensor (see FIG. 2 (f)). ).

[0005]

In the above-mentioned conventional acceleration sensor, the first semiconductor substrate 10 has the second semiconductor substrate 1
Since the silicon nitride film 33 is formed only on the back surface side at the time of joining with the first semiconductor substrate 1, the internal stress of the silicon nitride film 33 warps the first semiconductor substrate 10, and the first and second semiconductor substrates 10 are warped.
However, there is a problem that the two semiconductor substrates 10 and 11 cannot be stably joined and bonded to each other, and the yield is deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an acceleration sensor which does not warp and which can improve the yield, and a manufacturing method thereof.

[0007]

In order to achieve the above object, the invention of claim 1 bonds a second semiconductor substrate to one main surface of the first semiconductor substrate on which at least a weight portion is formed. An acceleration sensor comprising a beam portion for swingably supporting a weight portion on the second semiconductor substrate, wherein buffer layers for buffering internal stress are formed on both main surfaces of the first semiconductor substrate .
And the other main surface which is the anti-bonding surface of the first semiconductor substrate.
It is characterized in that a silicon nitride film is formed on the surface buffer layer .

[0008]

In order to achieve the above object, the invention of claim 2 comprises the step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate, and one main surface of the first semiconductor substrate. Bonding a second semiconductor substrate to the surface via a buffer layer, processing the first semiconductor substrate to form a weight portion, and processing the second semiconductor substrate to form a beam portion And having.

[0010]

In order to achieve the above-mentioned object, the invention of claim 3 comprises the step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate, and one main surface of the first semiconductor substrate. Bonding the second semiconductor substrate to the surface via a buffer layer, forming a silicon nitride film on the buffer layer on the other main surface which is the non-bonded surface of the first semiconductor substrate, and the silicon nitride film. The method has a step of processing the first semiconductor substrate to form a weight portion using the film as a mask and a step of processing the second semiconductor substrate to form a beam portion.

[0012]

[0013]

According to a fourth aspect of the present invention, in order to achieve the above object, a step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate, and joining of the second semiconductor substrate. A step of forming a buffer layer made of a silicon oxide film on the side main surface, and a step of joining one main surface of the first semiconductor substrate on which the buffer layer is formed and the main surface of the second semiconductor substrate, The method is characterized by including a step of processing the first semiconductor substrate to form a weight portion and a step of processing the second semiconductor substrate to form a beam portion.

[0015]

According to the first aspect of the invention, the second semiconductor substrate is bonded to one main surface of the first semiconductor substrate on which at least the weight portion is formed, and the weight portion is shaken on the second semiconductor substrate. An acceleration sensor formed by forming a beam portion that supports movably, wherein buffer layers for buffering internal stress are formed on both main surfaces of a first semiconductor substrate, and an anti-bonding surface of the first semiconductor substrate is formed.
Since the silicon nitride film is formed on the buffer layer on the other main surface, the buffer layer alleviates the internal stress applied to the first semiconductor substrate and reduces the warp of the first semiconductor substrate due to the internal stress.

[0016]

According to the second aspect of the present invention, the step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate and the step of forming the buffer layer on one main surface of the first semiconductor substrate are performed. And the step of joining the second semiconductor substrate to each other, the step of processing the first semiconductor substrate to form the weight portion, and the step of processing the second semiconductor substrate to form the beam portion. 1
The buffer layers formed on both main surfaces of the semiconductor substrate relax the internal stress applied to the first semiconductor substrate, reduce the warpage of the first semiconductor substrate during manufacturing, and reduce the stress between the first semiconductor substrate and the first semiconductor substrate. The minute irregularities on the bonding surface of the second semiconductor substrate are absorbed by the buffer layer, the matching at the time of bonding can be enhanced, and the buffer layer is used as an etching mask when etching the first semiconductor substrate. be able to.

[0018]

According to the third aspect of the present invention, the step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate and the step of forming the buffer layer on one main surface of the first semiconductor substrate are performed. Bonding the second semiconductor substrate with each other, forming a silicon nitride film on the buffer layer on the other main surface which is the anti-bonding surface of the first semiconductor substrate, and using the silicon nitride film as a mask. Since the method includes the step of processing the first semiconductor substrate to form the weight portion and the step of processing the second semiconductor substrate to form the beam portion, long-time etching can be performed by using the silicon nitride film as a mask. It becomes possible, and the shape of the weight portion can be precisely formed.

[0020]

[0021]

According to the invention of claim 4 , the step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate, and the step of forming silicon on the main surface of the second semiconductor substrate on the bonding side. A step of forming a buffer layer made of an oxide film, a step of joining one main surface of the first semiconductor substrate on which the buffer layer is formed and a main surface of the second semiconductor substrate, and the first semiconductor substrate Since the step of processing to form the weight portion and the step of processing the second semiconductor substrate to form the beam portion are included, the first semiconductor substrate and the second semiconductor substrate are bonded to each other using buffer layers. It suffices to join them, and it becomes possible to join them at a relatively low temperature, and the manufacturing process can be simplified.

[0023]

【Example】

(Embodiment 1) FIG. 1 is a diagram showing a first embodiment of the present invention. The acceleration sensor according to the present embodiment is a double-supported beam type sensor described in the related art, and has x-axis and y-axis
It is a so-called triaxial acceleration sensor having sensitivity in the axial and z-axis directions. Such an acceleration sensor is generally widely used in automobiles, airplanes, home electric appliances and the like.

In this acceleration sensor, a first semiconductor substrate 10 on which a weight portion 1 is formed and a thin second semiconductor substrate 11 on which a beam portion 2 is formed include a buffer layer 12 made of a silicon nitride film. Are formed by bonding and pasting together, and a buffer layer 12 also made of a silicon nitride film is formed on the anti-bonding surface of the first semiconductor substrate 10.

Next, a method of manufacturing the acceleration sensor of this embodiment will be described with reference to FIGS. A silicon nitride film 13 serving as an etching mask is formed on both main surfaces of the first semiconductor substrate 10 made of a silicon substrate as shown in FIG. 2A by a method such as plasma CVD or low pressure CVD (FIG. 2B). reference). The silicon nitride film 13 formed on both main surfaces of the first semiconductor substrate 10 is patterned by photolithography (see FIG. 3C). That is,
The remaining silicon nitride film 13 becomes the buffer layers 12 on both main surfaces of the first semiconductor substrate 10, respectively.

Then, both main surfaces of the first semiconductor substrate 10 are anisotropically etched with an aqueous solution of potassium hydroxide (KOH), EDP (ethylene diamine pyrocatechol) or the like using the silicon nitride film 13 (buffer layer 12) as a mask. Then, both main surfaces are dug at the same time by about 10 μm to form a recess 14 (see FIG. 3D). Then, the second semiconductor substrate 11 is bonded and bonded to one main surface of the first semiconductor substrate 10 (see FIG. 8E). At this time, in the conventional manufacturing method, the silicon nitride film 13 formed on the bonding surface of the first semiconductor substrate 10 was removed and bonded, but in the present invention, the silicon nitride film 13 is bonded without being removed. Then, the silicon nitride film 13 is interposed between the first and second semiconductor substrates 10 and 11 to form the buffer layer 12. Here, the step of joining the two semiconductor substrates 10 and 11 is 10
Since the heat treatment at a high temperature of 00 ° C. or higher is performed, when the silicon nitride film for the mask is formed only on one main surface of the first semiconductor substrate 10 as in the conventional case, the first stress is generated by the internal stress of the silicon nitride film. However, the silicon nitride film 13 on the bonding surface side of the first semiconductor substrate 10 is not removed as in the present invention, and silicon nitride is formed on both main surfaces of the first semiconductor substrate 10. If the high temperature treatment is performed with the film 13 formed, the silicon nitride film 13 serves as the buffer layer 12 to relieve the internal stress and reduce the warpage of the first semiconductor substrate 10. The yield in the step of bonding can be improved. Further, in this embodiment, since the masking silicon nitride film 13 for forming the recess 14 in the first semiconductor substrate 10 is used as the buffer layer 12, it is not necessary to newly form the buffer layer. Moreover, the step of removing the silicon nitride film 13 on the bonding surface of the first semiconductor substrate 10 is not necessary, and the manufacturing process can be simplified.

After the bonding, the second semiconductor substrate 11 is thinned down to about 10 μm by the chemical etching method (see FIG. 7F). Note that this step can be performed by time control or a method of using a wafer having an epitaxial layer on the second semiconductor substrate 11 and leaving only the epitaxial layer by electrolytic etching. then,
Impurities such as boron are diffused or ion-implanted into the main surface of the thinned second semiconductor substrate 11 to form a contact layer 15 made of a high-concentration impurity layer (FIG. 3A).
reference). Similarly, a piezoresistor 16 formed of a high-concentration impurity layer is formed by diffusing or ion-implanting impurities such as boron into the main surface of the portion of the second semiconductor substrate 11 that will be the beam portion 2 (see FIG. 2B). ). In addition, this piezoresistor 16
The impurity concentration in may be lower than that of the contact layer 15. Then, after forming an insulating layer 17 on the main surface of the second semiconductor substrate 11 so as to cover the piezoresistors 16 and the contact layers 15, a contact window is provided in the insulating layer 17 to provide each contact layer 15 and the piezoresistors 16 with each other. The metal wiring 18 electrically connected to is formed (see FIG. 11C). It is desirable to use gold for the metal wiring 18, but when gold is used, it is desirable to form a chromium layer between the gold and the semiconductor substrate in order to enhance the adhesion to the substrate. Further, the metal wiring 18 may be formed not only by gold but also by using aluminum, chromium or the like. Here, a protective film 19 of a silicon nitride film is formed in order to protect the metal wiring 18 from anisotropic etching in a later process (see FIG. 3D).

Then, the first semiconductor substrate 10 is anisotropically etched from the back surface (main surface on the side opposite to the bonding surface) by using the silicon nitride film 13 as the buffer layer 12 as a mask with a strong alkaline solution such as KOH. The first semiconductor substrate 10 is separated to form the weight portion 1 supported by the second semiconductor substrate 11 (see FIG. 8E). Finally, the beam portion 2 is formed by forming the slit 20 in the second semiconductor substrate 11 by dry etching such as RIE (reactive dry etching) and partially separating it (see (f) in the figure). An acceleration sensor having a structure in which the portion 1 is supported only by the thin beam portion 2 is completed.

According to the manufacturing method of this embodiment described above, since the buffer layers 12 made of the silicon nitride film 13 are formed on both main surfaces of the first semiconductor substrate 10, the first semiconductor substrate is relaxed by stress relaxation. The warp of 10 is reduced, and the first and second
The semiconductor substrates 10 and 11 can be stably bonded (bonded) to each other, thereby improving the yield in the bonding process. Further, the buffer layer 12 formed on the bonding surface allows the first and second semiconductor substrates 10, 1 to be formed.
The minute irregularities on the joining surface of No. 1 are filled and absorbed, and the consistency at the time of joining can be improved. Moreover,
Since the masking silicon nitride film 13 of the first semiconductor substrate 10 is used as the buffer layer 12, it is not necessary to increase the number of steps for newly forming the buffer layer 12, and the silicon nitride film 13 on the bonding surface is removed. It is also possible to simplify the manufacturing process by eliminating the process. The buffer layer 12 formed on the main surface of the first semiconductor substrate 10 on the side opposite to the bonding surface is
It can be used as an etching mask when forming the weight portion 1 as in the conventional case.

Although the buffer layer 12 is formed of the silicon nitride film in the manufacturing method of this embodiment, the invention is not limited to this. For example, the main surface of the first semiconductor substrate 10 on the junction side is thermally oxidized. A silicon oxide film may be formed and this silicon oxide film may be used as the buffer layer. That is, the first and second semiconductor substrates 10 and 11 are joined not by joining the silicon substrate and the silicon nitride film, but by joining the silicon substrate and the silicon oxide film. Here, in the step of anisotropically etching the first semiconductor substrate 10 after bonding, the silicon oxide film is generally etched by a long-time etching with KOH.
It is desirable to use such as an etchant.

In the acceleration sensor manufactured as described above, the weight portion 1 is formed by the four beam portions 2 formed by being partially separated from the second semiconductor substrate 11 by the slit 20.
Is swingably supported. As shown in FIGS. 4A and 4B, the bending direction and amount of each beam portion 2 change depending on the direction of the applied acceleration. X is obtained by extracting the amount of change as a change in the resistance value of the piezoresistor 16.
It is possible to detect acceleration in the three axial directions of the axes, the y-axis, and the z-axis. It should be noted that the acceleration can be detected by changing the resistance value of the piezoresistor 16 by using a known method such as a method of forming a bridge circuit by the piezoresistor 16, and detailed description thereof will be omitted.

In the configuration of this embodiment, the first semiconductor substrate 1
Since the buffer layer 12 made of the silicon nitride film 13 is formed on both main surfaces of No. 0, warpage of the first semiconductor substrate 10 due to internal stress can be reduced. (Embodiment 2) FIGS. 5 and 6 are views for explaining a manufacturing method in a second embodiment of the present invention. The manufacturing method of this embodiment will be described below with reference to FIGS. The same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

First, the steps of forming and patterning the silicon oxide film 21 on both main surfaces of the first semiconductor substrate 10 made of a silicon substrate (see FIGS. 5A to 5C) are almost the same as those of the first embodiment. It is common. Next, in this embodiment, only the main surface, which is the bonding surface of the first semiconductor substrate 10, is anisotropically etched using the silicon oxide film 21 as a mask to form a recess 14 by engraving about 10 μm. (Refer to the same figure (d)). Thus, in this embodiment, the first semiconductor substrate 10 is
Since only one main surface (bonding surface) is anisotropically etched, the other main surface which is not etched is protected by a resist or the like. The first semiconductor substrate 10
The silicon oxide film 21 formed on both main surfaces of the above becomes the buffer layer 22 in the case of the present embodiment.

Then, the second semiconductor substrate 11 is bonded and bonded to one main surface of the first semiconductor substrate 10 by heat treatment at 1000 ° C. or higher (see FIG. 8E). After that, a silicon nitride film 23 for a mask is formed on substantially the entire main surface, which is an anti-bonding surface of the first semiconductor substrate 10 (see FIG. 6F), and the second semiconductor substrate 11 is chemically formed. The thickness is reduced to about 10 μm by the etching method (see FIG. 7G).

Next, the thinned second semiconductor substrate 11 is formed.
Impurities such as boron are diffused or ion-implanted into the main surface of the contact layer 15 to form the contact layer 15 and the piezoresistor 16 made of a high-concentration impurity layer (see FIGS. 6A and 6B). Then, after forming an insulating layer 17 on the main surface of the second semiconductor substrate 11 so as to cover the piezoresistors 16 and the contact layers 15, a contact window is provided in the insulating layer 17 to provide each contact layer 15 and the piezoresistors 16 with each other. A metal wiring 18 electrically connected to is formed. Then, patterning by photolithography is performed to align the silicon nitride film 23 with the silicon oxide film 21,
The silicon nitride film 23 on the back surface (anti-bonding surface) of the first semiconductor substrate 10 is removed (see FIG. 7C). Further, a protective film 19 of a silicon nitride film is formed in order to protect the metal wiring 18 from anisotropic etching in a later process (see FIG. 3D). Then, the first semiconductor substrate 10 is anisotropically etched (about 390 μm) from the back surface (anti-bonding surface) by using a strong alkaline solution such as KOH with the silicon nitride film 23 as a mask, and the first semiconductor substrate 10 is separated. Then, the weight portion 1 supported by the second semiconductor substrate 11 is formed (see FIG. 8E). That is, in this embodiment, the silicon nitride film 2
3 is used as a mask when anisotropically etching the first semiconductor substrate 10 from the back surface (anti-bonding surface) side. As described above, the silicon nitride film 23 is used as a mask instead of the silicon oxide film 21, because the buffer layer 22 of the silicon oxide film 21 cannot perform a sufficient mask function for an etchant such as KOH. This is because. There is also a method of applying a resist on the buffer layer 22 of the silicon oxide film 21 instead of the silicon nitride film 23 and masking it. However, the buffer layer 22 of the silicon oxide film 21 having a step of about 10 μm after being patterned is formed. There is a drawback that it is difficult to apply the resist uniformly, and when the silicon nitride film 23 is used as a mask as in the present embodiment, there is an advantage that patterning can be performed accurately by photolithography.

Finally, the second semiconductor substrate 11 is formed by dry etching such as RIE (reactive dry etching).
A beam portion 2 is formed by forming a slit 20 in the groove and partially separating it, and an acceleration sensor having a structure in which the weight portion 1 is supported only by the thin beam portion 2 is completed (see (f) in the figure). . According to the present embodiment, the silicon oxide film 21 formed on both main surfaces of the first semiconductor substrate 10 is used as the buffer layer 22 to reduce the warp of the substrate and to etch the first semiconductor substrate 10. Since the silicon nitride film 23 is used for the mask in this case, not only the yield in the bonding process can be improved, but also the detection sensitivity can be improved by forming the shape of the weight portion 1 faithfully on the mask, and further, the first semiconductor KOH can be used instead of EDP as an etchant in the anisotropic etching of the substrate 10,
The manufacturing process can be simplified and the cost can be reduced. Although the silicon oxide film 21 is used as the buffer layer 22 in this embodiment,
A silicon nitride film may be formed on both main surfaces of the first semiconductor substrate 10 and used as a buffer layer.

(Embodiment 3) FIGS. 7 and 8 show the third embodiment of the present invention.
FIG. 8 is a diagram for explaining a manufacturing method in the example of FIG.
Hereinafter, the manufacturing method of this embodiment will be described with reference to FIGS. 7 and 8. Since the structure and the manufacturing method of this embodiment are substantially the same as those of the first embodiment, the common parts are designated by the same reference numerals and the description thereof will be omitted. Only the characteristic parts of this embodiment will be described. To do.

In this embodiment, the silicon nitride film 13 serving as the buffer layer 12 is formed on both main surfaces of the first semiconductor substrate 10, and the silicon nitride film 24 is formed on both main surfaces of the second semiconductor substrate 11 as well. The feature is that the buffer layer 25 is formed. That is, in the step of bonding and bonding the first semiconductor substrate 10 and the second semiconductor substrate 11 as shown in FIG. 7E, the silicon nitride film of the first semiconductor substrate 10 in the case of the first embodiment. 13 and the second semiconductor substrate 11 (silicon) are required to be bonded by a high temperature treatment of 1000 ° C. or higher, whereas in the present embodiment, silicon nitride of the first and second semiconductor substrates 10 and 11 is used. Since the films 13 and 24 are bonded to each other, bonding can be performed at a low temperature of about 400 ° C. Further, in the case of bonding (bonding) different materials such as silicon and a silicon nitride film as in Example 1, voids are likely to occur at the bonding interface due to the difference in atomic distance between the surfaces, but in this Example, silicon nitride is used. The same kind of bonding (bonding) between the films 13 and 24 can reduce the occurrence of voids. The other steps shown in FIGS. 7 and 8 are the same as those in the first embodiment, and the description thereof will be omitted.

(Embodiment 4) FIGS. 9 and 10 are views for explaining a manufacturing method in a fourth embodiment of the present invention. Hereinafter, the manufacturing method of this embodiment will be described with reference to FIGS. 9 and 10. Since the structure and manufacturing method of this embodiment are substantially the same as those of the second embodiment, common parts are designated by the same reference numerals and description thereof will be omitted, and only the characteristic parts of this embodiment will be described. To do.

In this embodiment, the silicon oxide film 21 serving as the buffer layer 22 is formed on both main surfaces of the first semiconductor substrate 10, and the silicon oxide film 26 is formed on both main surfaces of the second semiconductor substrate 11 as well. The feature is that the buffer layer 27 is formed. That is, in the step of bonding and bonding the first semiconductor substrate 10 and the second semiconductor substrate 11 as shown in FIG. 9E, the silicon oxide film of the first semiconductor substrate 10 in the case of the second embodiment. 21 and the second semiconductor substrate 11 (silicon) are required to be joined by a high temperature treatment of 1000 ° C. or higher, whereas in the present embodiment, silicon oxidation of the first and second semiconductor substrates 10 and 11 is performed. Since the films 21 and 26 are bonded to each other, bonding can be performed at a low temperature as compared with the case of the second embodiment. Further, in the case of bonding (bonding) different kinds of materials such as silicon and a silicon oxide film as in Example 2, voids are likely to occur at the bonding interface due to the difference in atomic distance between the surfaces, but in this Example, silicon oxide is used. Membrane 21, 26
It is possible to reduce the occurrence of voids due to the same type of bonding (bonding). The other steps shown in FIGS. 9 and 10 are the same as those in the second embodiment, and thus the description thereof will be omitted.

[0041]

According to the first aspect of the present invention, the second semiconductor substrate is bonded to one main surface of the first semiconductor substrate on which at least the weight portion is formed, and the weight portion is shaken on the second semiconductor substrate. An acceleration sensor formed by forming a beam portion movably supported, wherein a buffer layer for buffering internal stress is formed on both main surfaces of a first semiconductor substrate and an anti-bonding surface of the first semiconductor substrate.
Since the silicon nitride film is formed on the buffer layer on the other main surface, the buffer layer relieves the internal stress applied to the first semiconductor substrate, and thus the warp of the first semiconductor substrate due to the internal stress can be reduced. is there.

[0042]

According to a second aspect of the present invention, a step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate, and a step of forming the buffer layer on one main surface of the first semiconductor substrate via the buffer layers are provided. Since it has a step of joining the second semiconductor substrates, a step of processing the first semiconductor substrate to form a weight portion, and a step of processing the second semiconductor substrate to form a beam portion, The buffer layers formed on both main surfaces of the semiconductor substrate alleviate the internal stress applied to the first semiconductor substrate, reduce the warpage of the first semiconductor substrate during manufacturing, and reduce the warp of the first semiconductor substrate and the second semiconductor substrate. The minute irregularities on the bonding surface of the semiconductor substrate are absorbed by the buffer layer, the matching at the time of bonding can be enhanced, and the yield at the time of manufacturing can be improved. Moreover, the buffer layer can be used as an etching mask when etching the first semiconductor substrate, and the manufacturing process can be simplified.

[0044]

According to a third aspect of the present invention, a step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate and a step of forming the buffer layer on one main surface of the first semiconductor substrate via the buffer layers are provided. The step of joining the second semiconductor substrate, the step of forming a silicon nitride film on the buffer layer on the other main surface which is the anti-joint surface of the first semiconductor substrate, and the first step using the silicon nitride film as a mask. A step of processing the semiconductor substrate of to form a weight portion,
Since the step of processing the second semiconductor substrate to form the beam portion is included, it is possible to perform etching for a long time by using the silicon nitride film as a mask, and it is possible to precisely form the shape of the weight portion. There is an effect that the yield at the time of manufacture can be improved and the acceleration detection sensitivity can be improved at the same time.

[0046]

[0047]

According to a fourth aspect of the invention, a step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate, and a silicon oxide film on the main surface of the second semiconductor substrate on the side to be joined. A step of forming a buffer layer consisting of, a step of joining one main surface of the first semiconductor substrate on which the buffer layer is formed and a main surface of the second semiconductor substrate, and processing the first semiconductor substrate. Since the step of forming the weight portion and the step of forming the beam portion by processing the second semiconductor substrate are performed, the first semiconductor substrate and the second semiconductor substrate are bonded to each other by connecting the respective buffer layers. This is advantageous in that the joining can be performed at a relatively low temperature, the yield at the time of manufacturing can be further improved, and the manufacturing process can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram showing Example 1, (a) is a plan view,
(B) is a side sectional view taken along the line AA ′ of FIG. (A), and (c) is a side sectional view taken along the line BB ′ of FIG.

FIG. 2 is a view for explaining the manufacturing process same as above.

FIG. 3 is a view for explaining the manufacturing process same as above.

FIG. 4A and FIG. 4B are diagrams for explaining the operation of the same.

FIG. 5 is a drawing for explaining the manufacturing process in the second embodiment.

FIG. 6 is a view for explaining the manufacturing process same as above.

FIG. 7 is a drawing for explaining the manufacturing process in the third embodiment.

FIG. 8 is a view for explaining the manufacturing process same as above.

FIG. 9 is a drawing for explaining the manufacturing process in the fourth embodiment.

FIG. 10 is a diagram illustrating the manufacturing process same as above.

11A and 11B are diagrams for explaining the operation of a general acceleration sensor.

FIG. 12 is a diagram for explaining a manufacturing process of a conventional example.

FIG. 13 is a view for explaining the manufacturing process same as above.

[Explanation of symbols]

1 Weight section 2 beams 10 First semiconductor substrate 11 Second semiconductor substrate 12 Buffer layer 13 Silicon nitride film 20 slits

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-283419 (JP, A) JP-A-8-274349 (JP, A) JP-A-7-92187 (JP, A) JP-A-1- 167673 (JP, A) JP-A-6-50986 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01P 15/02-15/12 H01L 29/84

Claims (4)

(57) [Claims] 1. A beam portion for joining a second semiconductor substrate to one main surface of a first semiconductor substrate on which at least a weight portion is formed and swingably supporting the weight portion on the second semiconductor substrate. a acceleration sensor formed by forming, forming then together the buffer layer for the internal stress buffering on both main surfaces of the first semiconductor substrate
The buffer of the other main surface which is the anti-bonding surface of the first semiconductor substrate
An acceleration sensor characterized in that a silicon nitride film is formed on the layer . 2. Silicon acid is formed on both main surfaces of the first semiconductor substrate.
Step and a step of joining a second semiconductor substrate through a buffer layer on one main surface of the first semiconductor substrate, the weight portion by processing the first semiconductor substrate forming a buffer layer made of monolayer And a step of forming a beam portion by processing the second semiconductor substrate. 3. A step of forming a buffer layer made of a silicon oxide film on both main surfaces of the first semiconductor substrate, and a step of forming a second semiconductor substrate on one main surface of the first semiconductor substrate via the buffer layer. The step of joining and the other side which is the anti-joining surface of the first semiconductor substrate
A step of forming a silicon nitride film on the buffer layer on the main surface of
First silicon substrate using this silicon nitride film as a mask
And a step of forming a weight portion and a step of forming a beam portion by processing the second semiconductor substrate. 4. A silicon oxide is formed on both main surfaces of the first semiconductor substrate.
A step of forming a buffer layer made of a phosphide film and a second semiconductor substrate
A buffer made of silicon oxide film on the main surface of the plate to be joined
Layer forming step and first semiconductor having a buffer layer formed thereon
Bonding one main surface of the substrate and the main surface of the second semiconductor substrate
And the step of processing the first semiconductor substrate to form the weight portion.
And a step of processing the second semiconductor substrate to form a beam portion
A method of manufacturing an acceleration sensor , the method including:
Law.