JPH0281477A - Semiconductor acceleration sensor and its manufacture - Google Patents

Abstract

PURPOSE:To form a stopper during a wafer process by a method wherein a plurality of first protruding parts formed in a weight part and a plurality of second protruding parts formed in a support part are piled up via prescribed gaps in such a way that, for one part, the first protruding parts are situated at the upper part in a vertical direction and that, for the remaining part, the second protruding parts are situated at the upper part. CONSTITUTION:An Si support part 11, an Si weight part 12, an Si cantilever 13, first protruding parts 15 and second protruding parts 16 are formed during a wafer process. When an acceleration is applied to this sensor, the Si weight part 12 is displaced to an alpha1 direction or an alpha2 direction. When an excessive acceleration is applied, the first protruding parts hit the second protruding parts 16 if a displacement exceeds a prescribed value; thereby, the displacement is stopped. For example, when an ABC cross section is viewed, the first protruding parts 15 are stopped by the second protruding parts 16 for an excessive displacement in the alpha2 direction; when an AB'C' cross section is viewed, the first protruding parts 15 aye stopped also by the second protruding parts 16 for the excessive displacement in the alpha1 direction. Accordingly, even when the excessive acceleration is applied, it is possible to prevent the Si cantilever 13 from being damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a semiconductor acceleration sensor having a stopper structure that can be formed by batch processing.

[Prior art]

As a conventional semiconductor acceleration sensor, for example, IE Electron Devices
Electron Devices, vol, E
D-26°No, 12. p, 1911. Dec,
1979 A Batch Fabricate
d5ilicon Accelerometer”
) are listed.

FIG. 2 is a perspective view and a sectional view along A-A'B-B' of the above device.

In FIG. 2, 21 is a Si substrate, 22 is a Si cantilever,
23 is a Si weight, 24 is a gap, and 25 is a piezoresistor.

In the semiconductor acceleration sensor shown in FIG.

When acceleration is applied, the SL weight 23 is displaced, thereby causing strain in the Si cantilever 22. A piezoresistance 25 is formed on the surface of this Si cantilever 22, and a Si
When strain is generated in the cantilever beam 22, the resistance value of the piezoresistor 25 changes due to the piezoresistance effect. Acceleration can be detected by detecting this change in resistance value.

Moreover, as a mounting structure of the above-mentioned sensor chip, a structure as shown in FIG. 3 (a perspective view and a sectional view taken along the line xx') is shown. This is a structure to prevent the cantilever beam from breaking due to excessive acceleration such as falling, and the Si substrate 21 having the Si cantilever beam 22 and the Sl weight 23 is sandwiched between two stoppers, a lower stopper 26 and an upper stopper 27. It has a built-in structure.

[Problem that the invention seeks to solve]

However, the acceleration sensor having the above structure has the following problems.

First of all, in the above structure, there is no function to suppress the displacement of the weight between the formation of the beam and the formation of the stopper, so it is necessary to pay great attention to the handling of the chip. If the quality is poor, there is a problem that the beam will be destroyed and the yield will be lowered.

Second, there is a problem that the stopper forming process becomes complicated and the cost increases. That is, one of the purposes of forming an acceleration sensor using a semiconductor is to reduce the cost per chip through batch processing. ! As is clear from the 2-piece construction, products with stable quality and low cost can be produced by making a large number of chips on a wafer and processing them simultaneously. If the structure is formed using the same method, the cost will increase significantly.

Thirdly, there is the problem of difficulty in forming the stopper.

That is, in the structure shown in FIG. 3, depending on the beam design, the distance between the stopper and the weight must be controlled with an accuracy of several μm to several tens of μm, and high precision is required for forming the stopper and adhering it to the chip. This requires advanced stopper manufacturing technology and stopper adhesion technology, which poses a problem in that the mounting cost also increases.

Furthermore, in the above-mentioned acceleration sensor, a weight such as metal is sometimes added to the top surface of the Sl weight 23 in order to reduce sensitivity to other axes, but the thickness of such metal weight inevitably varies. Therefore, it is difficult to accurately set the distance between the weight and the stopper (the distance between the metal weight formed on the top surface of the SL weight 23 and the -F section stopper 27 in Fig. 3), and therefore a high precision effect can be obtained. Another problem is that it is difficult to implement a stopper.

The present invention has been made in order to solve various problems of the prior art as described above, and it is possible to form a stopper during sensor chip formation, that is, during wafer processing.
The purpose of the present invention is to provide a semiconductor acceleration sensor that has stable and uniform performance, is inexpensive, and is suitable for mass production.

[Means to solve the problem]

In order to achieve the above object, the semiconductor acceleration sensor of the present invention includes a plurality of first protrusions provided on a portion of the weight portion facing the support portion, and a plurality of first protrusions provided on the portion of the support portion facing the weight portion. a plurality of second protrusions formed at positions that partially overlap the first protrusions in the vertical direction, and
Among the plurality of first and second protrusions, some of the plurality of protrusions have the first protrusion on top in the vertical direction, and others have the second protrusion on top and are mutually connected to each other. They are configured to overlap with each other with a predetermined gap in between. The vertical relationship between the first and second protrusions is set so that, for example, one is on top and the other is on bottom, which is alternately repeated.

The manufacturing method of the present invention also includes the step of forming a high concentration n-type diffusion layer at a predetermined position on the surface of the Si substrate to serve as a gap between the first protrusion and the second protrusion. , forming a Si layer on the surface of the Si substrate; forming a high concentration p-type diffusion layer at a predetermined position of the Si layer so as to be in contact with at least the high concentration n-type diffusion layer;
After forming a film to serve as a Si etching mask at a predetermined position on the back surface of the i-substrate, electrochemical etching is performed from the back surface to form one or more beam portions and a single layer provided at the end of the beam portion. a step of forming a weight portion and a support portion connected to the other end of the beam portion and formed so as to surround the outer periphery of the weight portion; a step of removing the high concentration p-type diffusion layer; and a step of removing the electrochemical forming a gap between the first protrusion and the second protrusion by removing the high concentration n-type diffusion layer exposed by etching by electrolytic etching, and separating the Si weight part from the support part; It is configured to have the following.

[Effect]

With the above configuration, in the semiconductor acceleration sensor of the present invention, when excessive acceleration is applied and the mutual positional displacement between the weight part and the support part becomes large, the first protrusion The part and the second protrusion come into contact and prevent further displacement.

In addition, the first protrusion and the second protrusion overlap so that in some cases the first protrusion is on top and in others the second protrusion is on top. No matter which direction acceleration is applied, excessive displacement can be reliably prevented, and the beam portion can be effectively protected from damage.

In addition, in the manufacturing method of the present invention, a stopper (protrusion) can be formed in the urchin hub.
Yield is improved, and since there is no need to form a stopper later, mounting costs can be reduced.

Further, a high concentration n-type diffusion layer is formed at a predetermined position on the surface of the Si substrate to serve as a gap between the first protrusion and the second protrusion, and is later removed by electrolytic etching. Since the gap is formed between the first and second protrusions, the gap size can be formed with high precision, and the protection characteristics provided by the stopper can be made uniform.

In addition, the formation of the high concentration n-type diffusion layer which will become the above-mentioned void portion can be performed at the same time as the formation process of the buried WI (high concentration n-type diffusion layer) in the signal processing circuit of the acceleration sensor. Simplify.

Cost can be reduced.

【Example〕

FIG. 1 shows an embodiment of the present invention, in which (a) is a plan view;
(b) is a cross-sectional view taken along line A-B-C in (a), and (c) is a cross-sectional view taken along line A-B'-G' in (a).

First, to explain the structure, a Si cantilever 13 having an SL weight part 12 at one end is fixed to a Si support part 11.
A piezoresistor I4 is formed on the surface of the Si cantilever I3. The process up to this point is the same as the conventional example shown in FIG.

In addition, a first protrusion 15 is provided on the SL weight side in a predetermined area around the Si sink portion 12 and on the Si weight portion 12 side of the Si support portion 11, respectively. A second protrusion 16 is formed on the Si support portion side as follows. That is, the first protrusion 15 and the second protrusion 16 are formed so as to partially overlap with each other with a predetermined gap 17 in between. There are two ways of overlapping: one in which the first protrusion 15 is on top of the second protrusion 16 as shown in the ABC section of FIG. As shown in cross section C', there is an overlapping manner in which the second protrusion 16 is on top of the first protrusion 15, and the structure has both overlapping manners.

The vertical relationship between the first and second projections is as follows.

For example, the relationship is set so that one side is above and the other is below. That is, if the first protrusion is on top at a location, the second protrusion may be on top next to it.

Next, the action will be explained.

In the sensor shown in FIG. 1, the Si support portion 11, the SL weight portion 12, the Si cantilever 13, the first protrusion 15, and the second protrusion 16 are formed during the wafer process.

When acceleration is applied to this sensor, the Si weight part 12
is displaced in the α1 direction or α2 direction in FIG. If excessive acceleration is applied, the displacement increases, but if the displacement exceeds a predetermined value, the first protrusion 15 and the second protrusion 15
The displacement is stopped by the contact with the protrusion 16.

For example, when looking at the ABC section in FIG.
If you look at the AB'C' cross section in (c),
For excessive displacement in the α1 direction, the first protrusion 15 is still stopped by the second protrusion 16. Therefore, even when excessive acceleration is applied, excessive stress is not applied to the Si cantilever beam 13, and the Si cantilever beam 13
damage can be prevented.

In addition, since it is possible to form a protrusion that serves as a stopper to prevent the Si cantilever from breaking during the wafer process, the stopper can be formed with high precision, and the yield of acceleration sensor manufacturing is improved. Since there is no need to do this, implementation costs are reduced.

Next, FIG. 4 is a diagram showing a second embodiment of the present invention, and shows a plan view of an acceleration sensor having a double-supported beam structure.

In this embodiment, Si beams 1 are provided at both ends of the Si weight portion 12.
This figure shows a case where the present invention is applied to an acceleration sensor having a so-called double-supported beam structure, which has 31 and 132 beams. It can be applied to

Next, a method for manufacturing the acceleration sensor shown in FIG. 1 will be explained based on FIG. 5.

First, in (a), the <111> plane P-type Si substrate 4
P+ or the like is introduced at a high concentration into a predetermined position on the main surface of 1 by ion implantation or the like, and is thermally diffused to produce a high concentration n-type wave dispersion Jf! Form J42.

Next, in (b), by epitaxial growth method,
On the main surface of the p-type Si substrate 41, an n-type upper Si layer 43 into which n-type impurities are introduced at a low concentration is formed.

Next, in (c), a p-type impurity (such as B+) is introduced at a high concentration on the upper Si layer 43 so as to be in contact with the high concentration n-type wave dispersion layer 42 by ion implantation. It is diffused to form a p-type wave dispersion H144.

Next, in (d), after forming the piezoresistor 14 at a predetermined position that will become the beam of the acceleration sensor using a thermal diffusion method,
Sio2 and SiN, which serve as a mask for Si etching, are placed at predetermined positions on the back surface of the p-type Si substrate 41.

Forms a film. Next, using an electrochemical etching method using an alkaline etching solution with the n-type upper Si layer 43 as an anode, the p-type wave scattering layer formed in a predetermined region of the p-type Si substrate 41 and in the upper Si layer 43 is etched. 44. The electrochemical etching method is described in detail in JP-A-61-97572 (Method for manufacturing semiconductor acceleration sensor). Finally, by etching the high concentration n-type wave 1142 using 5% HF'@ and deetching, the first protrusion 15 and the second protrusion 16 are separated and a stopper is formed. Moreover, by this wafer process, the Si support portion 11. The Si weight portion 12 and the Si cantilever beam 13 are formed at the same time.

In addition, in the current manufacturing method of bipolar transistors, in order to reduce the collector resistance of n p n transistors, a high concentration n type dispersion layer, a so-called buried layer, is formed at a predetermined position of a p type Si substrate. After forming this buried layer, an n-type epitaxial layer is grown, and impurity diffusion layers such as an emitter, base, and collector constituting a transistor circuit are formed in this portion.

Therefore, in the manufacturing method of the present invention, FIG.
) The formation of the high concentration n-type wave diffusion layer 42 shown in ) can be performed at the same time as the formation process of the above-mentioned buried layer (high concentration n-type diffusion layer) in the signal processing circuit of the acceleration sensor, etc.
The manufacturing process can be simplified and costs can be reduced.

As described above, the present invention requires fewer manufacturing steps than the acceleration sensor described in Japanese Patent Application No. 62-318752 already filed by the same applicant, thereby improving yield and reducing costs.

〔Effect of the invention〕

With the above configuration, in the present invention,
If excessive acceleration is applied and the displacement of the relative positions of the weight part and the support part becomes large, the protrusions will come into contact with each other and prevent further displacement, thus preventing damage to the beam part. can be effectively protected.

Further, since a protrusion serving as a stopper can be formed during the wafer process, the yield can be improved, and since there is no need to form a stopper later, the mounting cost can be reduced.

Furthermore, since the precision of the gap between the protrusions is determined by the thickness of the high concentration n-type wave scattering [42] formed during the wafer process, it is possible to form the gap with very high precision.

Therefore, according to the present invention, a stopper that prevents the beam from breaking during the manufacturing process and the mounting process, and also prevents the beam from breaking due to application of excessive acceleration or vibration near the resonant frequency after completion, can be created by batch processing. , can be realized with high accuracy and low cis 1-, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a plan view and a sectional view of a semiconductor acceleration sensor of the present invention, FIG. 2 is a perspective view and a sectional view of an example of a conventional semiconductor acceleration sensor, and FIG. 3 is a perspective view showing an example of mounting a conventional semiconductor acceleration sensor. 4 is a plan view of another embodiment of the present invention, and FIG. 5 is a sectional view showing the manufacturing method of the present invention. <Explanation of symbols> 11...Si support part 12...SL weight part 3...S1 cantilever 4...Piezo resistor 5...First protrusion 6...Second protrusion 7 ...Gap between protrusions 31.132...SL beam

Claims (2)

[Claims] 1. one or more beams that are distorted when acceleration is applied; a single weight portion connected to one end of the beam portion; In a semiconductor acceleration sensor formed on a semiconductor substrate, a supporting portion formed to open and surround the beam portion and a piezoresistive portion formed on the beam portion are arranged so that the acceleration detection direction, that is, the direction in which the beam portion is distorted, is perpendicular to the direction in which the beam portion is distorted. In this case,
A plurality of first protrusions provided on a portion of the weight portion facing the support portion, and a portion of the first protrusion portion of the support portion facing the weight portion overlap in a vertical direction. a plurality of second protrusions formed therein, and among the plurality of first and second protrusions, some of the plurality of protrusions have the first protrusions on top in the vertical direction; A semiconductor acceleration sensor characterized in that the second protrusion is on top and overlaps each other with a predetermined gap in between. 2. forming a high concentration n-type diffusion layer at a predetermined position on the surface of the Si substrate to form a gap between the first protrusion and the second protrusion; and forming a Si layer on the surface of the Si substrate. forming a high concentration p-type diffusion layer at a predetermined position of the Si layer so as to be in contact with at least the high concentration n-type diffusion layer;
After forming a film to serve as an etching mask, electrochemical etching is applied from the back side to one or more beams, a single weight provided at the end of the beam, and the other end of the beam. a step of forming a supporting portion connected to the weight portion and surrounding the outer periphery of the weight portion; a step of removing the high concentration p-type diffusion layer; and a step of removing the high concentration n-type diffusion layer exposed by the electrochemical etching. manufacturing a semiconductor acceleration sensor, comprising: forming a gap between the first protrusion and the second protrusion by removing the layer by electrolytic etching, and separating the Si weight part from the support part; Method.