JPH1140820A - Manufacture of semiconductor dynamic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a first semiconductor substrate on a recess uniform in thickness, when a second substrate is bonded on the first semiconductor substrate provided with a recess, so as to form a semiconductor dynamic sensor composed of a diaphragm and others on the recess. SOLUTION: An epxitaxial Si layer 2 is formed on an SIMOX substrate 1, a mask aligning trench (first recess) 3 is formed by a trench processing, an insulating film 4 is filled up into the trench 3, and another trench (second recess) 5 is formed through the trench processing. An Si substrate 6 as a second semiconductor substrate is pasted on the SIMOX substrate 1. Thereafter, the surface of the SIMOX substrate 1, opposite to its surface bonded on the Si substrate 6, is subjected to etching, whereby an Si substrate 1a and an insulating film 1b are removed by etching. Through this setup, a diaphragm is formed on a reference pressure chamber 7, and than a pressure detector is formed on the diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor dynamic quantity sensor such as a pressure sensor and an acceleration sensor.

[0002]

2. Description of the Related Art Conventionally, a method for manufacturing a semiconductor pressure sensor is disclosed in Japanese Patent Application Laid-Open No. Hei 8-236788. FIG. 8 shows an outline of a method of manufacturing this. First, as shown in FIG. 8A, a concave portion 102 for a diaphragm and a concave portion 102 are formed on one surface of a first semiconductor substrate 100.
A concave portion 101 for deeper mask alignment is formed, and the inside of the concave portion 101 is filled with an insulating film 103. And FIG.
As shown in FIG. 8B, a second semiconductor substrate 104 is attached to one surface of the first semiconductor substrate 100, and thereafter, FIG.
As shown in (c), the other surface of the first semiconductor substrate 100 is polished until the concave portion 101 for mask alignment is exposed. Thereafter, the pressure detecting element is formed at a position corresponding to the diaphragm concave portion 102 with reference to the exposed position of the mask aligning concave portion 101.

[0003]

However, in this case, since the polishing is performed until the concave portion 101 for mask alignment is exposed, over-polishing is required.
Since the concave portion 102 for the diaphragm exists, the first semiconductor substrate 100 on the concave portion 102 suffers polishing drooling. That is, since the first semiconductor substrate 100 on the concave portion 102 is polished while being bent during polishing,
As shown in (c), in the first semiconductor substrate 100 on the recess 102, the thickness is thick at the center of the recess and thin at the periphery of the recess, the thickness becomes uneven, and the sensor accuracy is deteriorated.

The present invention has been made in view of the above problems.
It is an object of the present invention to make the thickness of the first semiconductor substrate over the recess uniform when manufacturing the semiconductor physical quantity sensor using the bonding of the second semiconductor substrate.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, as the first semiconductor substrate (1, 2, 41, 42), an insulating film (1b, 41) is used.
b) using a silicon film (1c, 2, 41c, 42) on the first concave portion (5, 5'45) of a depth not reaching the insulating film in the silicon film of the first semiconductor substrate; )
And a second concave portion (3, 43) having a depth reaching the insulating film. Thereafter, the first semiconductor substrate is bonded to the second semiconductor substrate (6, 20). The surface of the first semiconductor substrate on the opposite side is removed by etching until the second concave portion is exposed, and the silicon film on the first concave portion is formed into a structure that receives a mechanical amount and is displaced.

By using the etching process as described above, the thickness of the first semiconductor substrate on the second concave portion can be made uniform. In this case, since the first semiconductor substrate having a silicon film on the insulating film is used,
By etching and removing the second concave portion until the second concave portion is exposed, that is, the insulating film is removed, the thickness of the first semiconductor substrate on the first concave portion can be set to a desired thickness.

In the case where a semiconductor substrate having an insulating film inside is used as the first semiconductor substrate, the first semiconductor substrate is removed by etching to the insulating film as an etching step. By using the first step of performing etching and the second step of etching and removing the insulating film, the thickness of the first semiconductor substrate on the first concave portion can be easily set to a desired thickness.

The first semiconductor substrate may be a SIMOX substrate (1, 41).
If an epitaxial layer (2, 42) is formed thereon, the thickness of the first semiconductor substrate on the first recess is adjusted to a desired thickness by using an insulating film formed inside the SIMOX substrate. Can be set easily.

[Detailed Description of the Invention]

[0010]

(First Embodiment) FIG. 1 shows a method of manufacturing a semiconductor pressure sensor according to a first embodiment of the present invention. First, as shown in FIG. 1A, SIMOX (Se) is used as a first semiconductor substrate.
partion by Implemented Oxge
n) A substrate 1 is prepared. This SIMOX substrate 1 forms an oxide film in a silicon (Si) substrate by ion-implanting oxygen into a silicon (Si) substrate at a high concentration and then performing heat treatment.
It has an SOI structure. As shown in FIG.
a, an oxide film 1b as an insulating film, and an ultra-thin Si layer 1c on the oxide film 1b.

[0011] Then, as shown in FIG.
An epitaxial Si layer 2 is formed on an ultra-thin Si layer 1c of an OX substrate 1, and thereafter, as shown in FIG. 1C, a trench groove (first concave portion) 3 for mask alignment is formed by trench processing. I do. In this case, the trench 3 has a depth reaching the oxide film 1b through the epitaxial Si layer 2. Then, as shown in FIG. 1D, the trench groove 3 is back-filled with the insulating film 4 and flattened by flattening polishing. When the trench 3 is filled with the insulating film 4, the trench may be filled with polysilicon after thermal oxidation.

Further, as shown in FIG. 1E, a trench groove (second concave portion) 5 is formed by trench processing.
Next, an Si substrate 6 as a second semiconductor substrate is prepared,
As shown in FIG. 1F, the Si substrate 6 is bonded to the surface of the SIMOX substrate 1 where the trench 5 is formed.
By this bonding, a reference pressure chamber 7 is formed between the Si substrate 6 and the SIMOX substrate 1 in a region where the trench 5 is formed.

Thereafter, as shown in FIG.
The surface of the OX substrate 1 opposite to the bonding surface is etched. In this etching, first, the silicon substrate 1a is etched and removed using KOH, and then the insulating film 1b is etched and removed using hydrofluoric acid. As a result, a diaphragm is formed on the reference pressure chamber 7. In addition, the insulating film 4 in the trench 3 is exposed by this etching process. With the position of the insulating film 4 in the exposed trench groove 3 as a reference, mask alignment in the following steps is performed.

After the above-described etching step, as shown in FIG. 2B, a diffusion gauge (strain gauge) 8 is formed on the diaphragm (or around the diaphragm) as an element for detecting pressure. Next, as shown in FIG. 2C, an insulating film 9 is formed, a contact window is opened on the diffusion gauge 8, and as shown in FIG. Is formed and patterned. Then, as shown in FIG. 2E, a passivation film 11 is formed, and a window for a pad is opened. Thus, a semiconductor pressure sensor is manufactured.

In the embodiment described above, the trench for forming the reference pressure chamber is formed by using the trench processing. However, the groove for forming the reference pressure chamber may be formed by etching. Good. The manufacturing process in this case is shown in FIG. First, as shown in FIG.
An X substrate 1 is prepared, and then, as shown in FIG.
On the ultra-thin Si layer 1c of the IMOX substrate 1, a p-type epitaxial Si layer 2a and an n-type epitaxial Si layer 2b are stacked. Thereafter, as shown in FIG. 3C, a trench 3 is formed, and as shown in FIG. 3D, the trench 3 is back-filled with an insulating film 4 and flattened.

Next, as shown in FIG. 3E, only the n-type epitaxial Si layer 2b is etched by concentration difference etching or electrochemical etching to form a groove (second concave portion) 5 '. . A reference pressure chamber is formed by the groove 5 '. Thereafter, the same steps as those in FIG. In this embodiment, since the grooves 5 are formed by concentration difference etching or electrochemical etching, the accuracy of the film thickness of the diaphragm can be increased.

The semiconductor pressure sensor described above is not limited to a sensor for detecting an absolute pressure, but may be configured to detect a relative pressure. (Second Embodiment) In the second embodiment, a semiconductor dynamic quantity sensor is applied to a semiconductor acceleration sensor.

FIG. 4 shows a perspective configuration of the semiconductor acceleration sensor. As shown in the figure, a semiconductor substrate 21 is bonded to an upper surface of a semiconductor substrate 20, and a beam structure (movable structure) 22 and fixed electrodes 23 and 24 are formed on the semiconductor substrate 21. The beam structure 22 includes four anchor portions 25 projecting from the substrate 20 side, and mass portions supported by the anchor portions 25 via the beam portions 26 and arranged at predetermined intervals on the upper surface of the substrate 20. (Mass part) 27
And movable electrodes 28 and 29 provided on the mass portion 27.

The fixed electrodes 23 and 24 are fixed on the substrate 20 and have a comb shape facing the movable electrodes 28 and 29. In addition, the fixed electrode 23 is electrically connected to the pad 31 by the wiring 30 formed on the substrate 20, and the fixed electrode 24 is also electrically connected to the pad 33 by the wiring 32 formed on the substrate 20. I have. Further, the anchor portion 25 is electrically connected to the pad 35 by the wiring 34 formed on the substrate 20. Although not shown in FIG. 4, a lower electrode is formed on the substrate 20 immediately below the beam structure 22.

In the above configuration, when the mass 27 receives acceleration in the direction perpendicular to the beam 26 in the plane of the semiconductor substrate 21, the mass 27 is displaced in the direction in which the acceleration is applied. Movable electrodes 28, 29 disposed
And fixed electrodes 23, 2 fixed to the semiconductor substrate 21.
The distance between the four changes. Since the movable electrodes 28 and 29 and the fixed electrodes 23 and 24 form a capacitor, when the capacitor receives an acceleration, the capacitor changes as a result and is converted into an acceleration by a conventional detection circuit.

Next, a method of manufacturing the above-described semiconductor acceleration sensor will be described with reference to FIG. First, as shown in FIG. 5A, a SIMOX substrate 41 as a first semiconductor substrate
Prepare The SIMOX substrate 41 is a Si substrate 41
a, an oxide film 41b as an insulating film, and an ultra-thin Si layer 41c on the oxide film 41b. And FIG.
As shown in FIG. 5B, an epitaxial Si layer 42 is formed on the ultra-thin Si layer 41c of the SIMOX substrate 41, and thereafter, as shown in FIG. The recess 43 is formed by trench processing. In this case, the trench 43 is formed by epitaxial Si
The depth reaches the oxide film 41b through the layer 42. Then, as shown in FIG. 5D, the trench 3 is back-filled with the insulating film 4 and flattened by flattening polishing.

Further, as shown in FIG. 5E, a trench groove (second concave portion) 45 is formed by trench processing. Next, a second semiconductor substrate 20 for bonding is prepared. In this case, first, as shown in FIG.
An insulating film 52 is formed on a substrate 51. Next, as shown in FIG. 6B, the wirings 30, 32, and the lower electrode are formed, and the anchor portions 23 and the fixed electrodes 23, 24 are formed on the substrate. A polysilicon thin film 53 for fixing on the substrate 20 is formed and patterned. Further, FIG.
As shown in (c), an insulating film 54 for bonding is formed, and is polished for flattening. Thus, the second semiconductor substrate 20 is formed. The second semiconductor substrate 20 is to be the substrate 20 shown in FIG.

Thereafter, as shown in FIG. 7A, the second semiconductor substrate 20 is inserted into the trench 45 of the SIMOX substrate 41.
Is bonded to the surface on which is formed. And FIG.
As shown in (b), the SIMOX substrate 4 is turned upside down.
1 is etched on the side opposite to the bonding surface. In this etching, first, KOH is used to form S
The portions up to the i-substrate 41a are removed by etching, and then the portions up to the insulating film 41b are removed by etching using hydrofluoric acid. By this etching step, the insulating film 44 in the trench 43 is formed.
Is exposed. The insulating film 4 in the exposed trench groove 43
With reference to No. 4, mask alignment in the following steps is performed.

Next, as shown in FIG. 7C, an Al electrode 60 for wiring is formed and patterned. And FIG.
As shown in (d), the ultra-thin Si layer 41c and the epitaxial Si layer 42 of the SIMOX substrate 41 are trench-etched to form a groove 61 for defining the beam structure 22 and the fixed electrodes 23 and 24. Thus, the semiconductor acceleration sensor shown in FIG. 4 is manufactured.

In the first and second embodiments described above, the order of forming the grooves 3 and 43 as the first concave portions and the grooves 5 and 45 as the second concave portions may be reversed. The first semiconductor substrate may be any substrate having an Si film on an insulating film. In addition to the substrate using the SIMOX substrate 1, for example, SOS (Silicon On Sapphire) may be used.
ire) Substrates or Si / CaF ₂ / Si substrates can be used.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing a semiconductor pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a manufacturing process following FIG. 1;

FIG. 3 is a process chart showing another method for manufacturing the semiconductor pressure sensor according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a perspective configuration of a semiconductor acceleration sensor manufactured according to a second embodiment of the present invention.

FIG. 5 is a process chart showing a process until a trench 45 is formed in a first semiconductor substrate in the method of manufacturing the semiconductor acceleration sensor shown in FIG. 4;

FIG. 6 is a process chart showing a step of preparing a second semiconductor substrate in the method of manufacturing the semiconductor acceleration sensor shown in FIG.

FIG. 7 is a process diagram showing a process after bonding the first and second semiconductor substrates in the method for manufacturing the semiconductor acceleration sensor shown in FIG. 4;

FIG. 8 is a process chart showing a method for manufacturing a conventional semiconductor pressure sensor.

[Explanation of symbols]

1, 41: SIMOX substrate, 2, 42: epitaxial Si layer, 3, 43: trench groove, 4, 44: buried insulating film, 5, 45: trench groove, 6, 20: second semiconductor substrate, 8: diffusion gauge.

Claims (3)

[Claims] 1. A step of preparing a first semiconductor substrate (1, 2, 41, 42) having a silicon film (1c, 2, 41c, 42) on an insulating film (1b, 41b); The first concave portion (5, 5 ′, 45) having a depth not reaching the insulating film and the second concave portion having a depth reaching the insulating film.
Forming a concave portion (3, 43) of the first semiconductor substrate, the surface of the silicon film of the first semiconductor substrate having the first and second concave portions formed thereon, and a second semiconductor substrate (6, 2).
0) bonding, and a step of etching and removing the surface of the first semiconductor substrate opposite to the bonding surface until the second concave portion is exposed, wherein a silicon film on the first concave portion is provided. A method of manufacturing a semiconductor dynamic quantity sensor, characterized in that: is a structure that is displaced by receiving a dynamic quantity. 2. The method according to claim 1, wherein the first semiconductor substrate is a semiconductor substrate having the insulating film therein, wherein the etching includes etching the first semiconductor substrate to the insulating film. The method according to claim 1, further comprising a second step of etching and removing the insulating film. 3. The first semiconductor substrate, wherein an epitaxial layer (2, 42) is formed on a SIMOX substrate (1, 41) having the insulating film therein, and wherein the first concave portion is formed. 3. The method according to claim 2, wherein the second concave portion is formed in the epitaxial layer, and the second concave portion is formed at a depth reaching the insulating film through the epitaxial layer. 4.