JPH04194635A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To simplify a gage diffusion resistant region by forming the gage diffusion resistant region oppositely to an end of a diaphragm which has been formed by etching a second silicon oxide film. CONSTITUTION:A silicon substrate 1 is processed by thermal oxidation and a silicon oxide film 2 is formed on its principal surface, while a silicon substrate 3 is adhered on it. Then a periphery of the substrate 3 is etched to form a gage diffusion resistor forming portion and a gage peripheral silicon oxide film 4 is formed at the etched portion and also a silicon oxide film 6 is formed over an entire surface. Then a window is opened on the oxide film 6, impurities such as boron are implanted, and a gage diffusion resistant region 5 enclosed by the oxide films 2,4 is formed. A silicon oxide film 11 is formed on the region 5, a metal electrode 7 for wiring the region 5 is formed via a window on the oxide film 11, and an entire surface is covered by a glass coat 8. Further an etching mask 9 is formed on a rear face of the substrate 1 to form a diaphragm 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device and a method for manufacturing the same, and particularly to a semiconductor device suitable for use in, for example, a semiconductor pressure sensor with an SOI structure used in an automobile, etc., and a method for manufacturing the same. It is about the method.

[Prior Art] FIG. 14 is a sectional view showing a conventional semiconductor device, for example, a semiconductor pressure sensor having an SOI structure. In the figure, (3) is a silicon substrate, (2) is a first silicon oxide film formed in the silicon substrate (3), and (5) is a gauge formed on the first silicon oxide film (2). The diffusion resistance region is provided so as to face the end of the diaphragm (10).

(6) is a silicon substrate (3), a first silicon oxide film (
2) and a second silicon oxide film provided to cover the gauge diffused resistance region (5), (7) is formed by partially removing this second silicon oxide film (6) and covering the gauge diffused resistance region (5).
), (8) is this metal electrode (7)
A second silicon oxide film (6
), and (9) is an etching mask used when forming the diaphragm (10).

Next, the operation of the conventional semiconductor pressure sensor shown in FIG. 14 will be explained. When the pressure changes, the diaphragm (10) of the silicon thin film section is distorted.

The gauge diffused resistance region (5) assembled in the bridge faces the end of the diaphragm (10).
10) is distorted, the resistivity changes due to the piezoresistive effect. When the resistivity of the gauge diffused resistance region (5) changes, the bridge of the gauge diffused resistor loses its balance and outputs a voltage. Since the output voltage is proportional to the magnitude of strain, and the magnitude of strain is proportional to the magnitude of pressure, changes in pressure can be detected by changes in voltage. In addition, by adopting the S01 structure in which the periphery of the gauge diffused resistance region (5) is covered with the first silicon oxide film (2), the second silicon oxide film (6), and the glass coat (8), it can be used at high temperatures. It is a semiconductor pressure sensor.

Next, this conventional semiconductor pressure sensor manufacturing method will be described in the 15th section.
This will be explained with reference to FIGS. The explanation will be made in comparison with the left half of the cross-sectional view of FIG. 14. In FIG. 15, a silicon substrate (3) is prepared, and in FIG. 16, a predetermined portion of the silicon substrate (3) is etched. In FIG. 17, a silicon oxide M (11) and a silicon desaturation film (12) are formed on the unetched portion of the silicon substrate (3). In FIG. 18, a first silicon oxide film (2) is formed (LOCO3 oxidation).

In FIG. 19, the entire surface of the first silicon oxide film (2) is etched and planarized. In Figure 20, polysilicon (3) is deposited and silicon nitride II is used as a reflector.
I (12) is formed to match the silicon oxide film (2).

Next, in FIG. 21, Ar laser is irradiated. The beam is focused to 50 μmφ, 10 to 100 cm/
The polysilicon (13) is recrystallized by scanning over the wafer surface at a speed of about 1.5 seconds to form single crystal silicon (14) as shown in FIG. 22, thereby obtaining an SOI structure. In FIG. 23, only the silicon single crystal is left on the first silicon oxide film (2) where the gauge diffused resistance region (5) is to be formed.

In FIG. 24, an impurity such as boron is implanted or debossed into a silicon single crystal of a required size so as to obtain the required resistivity, and a gauge diffused resistance region is formed by annealing or drive heat treatment.

In FIG. 25, the wafer surface is covered with a second silicon oxide film (6), and in FIG. 26, a window is opened in the second silicon oxide film (6), and metal electrodes (7) are wired.

Then, the front surface is covered with a glass coat (8), and an etching mask (9) is formed on the back surface. In FIG. 27, the diaphragm (1o) is controlled to the required thickness by etching from the back side.

[Problems to be Solved by the Invention] Since the conventional semiconductor device and its manufacturing method are configured as described above, the process of forming a single crystal silicon, that is, an SOI structure, on a silicon oxide film is complicated and requires a lot of effort. However, there have been problems in that it is difficult to control the Guiaflam thickness after surface pattern formation, and it is difficult to obtain highly accurate semiconductor devices due to variations in wafer thickness and etching rate.

This invention was made in order to solve the above-mentioned problems, and it is possible to easily form an SOI structure and automatically stop the control of diaphragm etching, thereby easily producing a high-precision semiconductor device and its manufacturing method. The purpose is to obtain.

[Means for Solving the Problems] A semiconductor device according to the present invention includes first and second silicon substrates bonded together via a first silicon oxide film,
A gauge diffused resistance region formed in a part of the first silicon substrate, a second silicon oxide film covering the gauge diffused resistance region, and a part of the second silicon oxide film are removed to remove the gauge diffused resistance region. a metal electrode connected to a diffused resistance region; and an insulating film that partially exposes the metal electrode and covers the second silicon oxide film, and the gauge diffused resistance region etches the second silicon oxide film. The diaphragm is formed so as to face the end of the diaphragm.

[Operations] In this invention, by using silicon substrates bonded together via a silicon oxide film, the gauge diffused resistance region can be easily constructed into an S○ tank structure, and the interfacial silicon oxide film can be used as a diaphragm etching stopper. Therefore, the diaphragm thickness can be controlled by grinding the front side silicon substrate.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a sectional view showing an embodiment of the present invention, and parts corresponding to those in FIG. 14 will be described with the same reference numerals. In FIG. 1, (1) is the first silicon substrate, (2) is the first silicon substrate, and (2) is the first silicon substrate.
A first silicon oxide film is formed at the bonding interface by thermal oxidation on the silicon substrate (1), and (3) is a second silicon oxide film bonded to the first silicon substrate (1) via the first silicon oxide film. (4) is a silicon oxide film around the gauge to surround the gauge diffused resistance region (5). This gauge diffusion resistor (5) is formed in a bridge configuration at the end of the diaphragm (10) to detect pressure. (
6) is the second silicon oxide film, (7) is the metal electrode for wiring the gauge diffused resistance region (5), (8) is the glass coat as an insulating film, and (9) is the first silicon substrate (
This is an etching mask for etching 1) to form a diaphragm (10). In addition, the diaphragm (1
0) is a silicon thin film portion because it generates distortion when pressure is applied. <11) is the third silicon oxide film.

The operation of the embodiment of the present invention shown in FIG. 1 is exactly the same as that shown in FIG. 14, so a description thereof will be omitted.

Next, the manufacturing method of this example will be explained with reference to FIGS. 2 to 13. The explanation will be made in comparison with the left half of the sectional view of FIG. A first silicon substrate (1) and a second silicon substrate (3) are prepared as shown in FIGS. 2 and 3, respectively.

In FIG. 4, a first silicon substrate is treated by thermal oxidation to form a first silicon oxide film (2) at the bonding interface on at least its main surface.

In FIG. 5, silicon oxidation 11! The first silicon substrate (1) on which (2) is formed is bonded to the second silicon substrate (3) made of silicon single crystal. The bonding method will be explained below. Both substrates are cleaned without particles, and the bonding surfaces are treated to make them hydrophilic and hydroxyl groups are attached. Align the crystal axes of both substrates and overlap them. In this state, both substrates are in close contact due to hydrogen bonding. Heat treatment is performed after stacking. A dehydration condensation reaction is caused at 500 to 1000°C.

Further, heat treatment is performed at 1000°C or higher to diffuse oxygen at the bonding interface. This provides the same bonding strength as a single wafer.

In FIG. 6, the second silicon substrate (3) is processed by grinding to a required diaphragm thickness. In Figure 7,
The periphery of the second silicon substrate (3) is etched to provide a location for forming a gauge diffused resistor. In FIG. 8, a silicon oxide film (4) around the gauge is formed on the etched portion, and a second silicon oxide film (6) is formed on the entire surface. In FIG. 9, a window is opened in the second silicon oxide film (6), and an impurity such as boron is implanted or deposited through this window to form a gauge surrounded by silicon oxide M (2), (4). A diffused resistance region (5) is formed. In FIG. 10, oxidation is performed simultaneously with annealing or driving to form a third silicon oxide film (11) on the gauge diffused resistance region (5).
) to form. In FIG. 11, a window is opened in the third silicon oxide film (11). In FIG. 12, a metal electrode f for wiring a gauge diffused resistance region (5) through a window is shown.
! (7) is formed, and the entire surface is covered with a glass coat (8) so that a part of this metal electrode (7) is exposed, and a diaphragm area is required on the back surface of the first silicon substrate (1). An etching mask <9> is formed in accordance with the above. In FIG. 13, etching is performed from the back surface of the first silicon substrate (1) to form a diamond slum (10). In this case, all diaphragms (
10) is etched until the first silicon oxide M(2) is exposed at the bonding interface. In other words, the first bonding interface
The silicon oxide M(2) acts as a diaphragm etching stopper.

In the above embodiment, a semiconductor pressure sensor with an SOT structure has been described, but it is not limited to this. For example, all semiconductor acceleration sensors with an SOI structure that utilize the piezoresistance effect of a diffused resistor that forms a diaphragm and is assembled in a bridge can be used. Applicable to semiconductors.

[Effects of the Invention] As described above, according to the present invention, the first and second silicon substrates bonded together via the first silicon oxide film, and the silicon substrate formed on a part of the first silicon substrate, a second silicon oxide film covering the gauge diffused resistance region; a metal electrode connected to the gauge diffused resistance region by removing a portion of the second silicon oxide film; an insulating film covering the second silicon oxide film with a part of the metal electrode exposed, the gauge diffused resistance region facing an end of a diaphragm formed by etching the second silicon oxide film. Since the gauge diffusion resistance region of the Sol structure can be easily formed, the bonding interface silicon oxide film is used as a diaphragm etching stopper, and the diaphragm thickness is controlled by grinding, so high precision and High performance semiconductor device!
For example, there is an effect that a semiconductor pressure sensor having an sOI structure can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIGS. 2 to 13 are process diagrams showing a manufacturing method thereof, FIG. 14 is a sectional view showing a conventional semiconductor pressure sensor, and FIGS. FIG. 27 is a process diagram showing the manufacturing method. In the figure, (1) is the first silicon substrate, (2) is the bonding interface first silicon oxide film, (3) is the second silicon substrate, (5) is the gauge diffused resistance region, and (6) is the The second silicon oxide film, (7) is a metal electrode, (8) is a glass coat, (1o) is a diaphragm, and (11) is a third silicon oxide film. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) first and second silicon substrates bonded together via a first silicon oxide film, a gauge diffused resistance region formed in a part of the first silicon substrate, and the gauge diffused resistance region a second silicon oxide film covering the second silicon oxide film; a metal electrode connected to the gauge diffused resistance region by removing a portion of the second silicon oxide film; and a metal electrode connected to the gauge diffused resistance region by partially exposing the metal electrode; an insulating film covering an oxide film, and the gauge diffused resistance region is formed to face an end of a diaphragm formed by etching the second silicon oxide film. . (2) a first silicon substrate on at least one main surface of the first silicon substrate;
a step of forming a silicon oxide film, a step of bonding a second silicon substrate to the first silicon substrate via the first silicon oxide film, and a step of forming the first silicon substrate to a predetermined thickness. forming a second silicon oxide film on the silicon substrate including the gauge diffused resistance forming location; and forming a second silicon oxide film on the silicon substrate including the gauge diffused resistance forming location. forming a third silicon oxide film in the gauge diffused resistance region, and forming a third silicon oxide film in the gauge diffused resistance region; forming a metal electrode to be removed and connected to the gauge diffused resistance region, and etching the second silicon substrate by a predetermined amount using the first silicon oxide film as a stopper, so that the end portion of the second silicon substrate becomes the gauge diffused resistor region. 1. A method of manufacturing a semiconductor device, comprising the step of forming a diaphragm facing the region.