JPH10111203A - Capacitive semiconductor sensor and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of a distance between electrodes and stabilize a sensor property by forming an oxide film having a notch part in the central part on a silicon base plate, and forming a silicon film on the oxide film. SOLUTION: A SiO2 oxide film 12 having a circular notch part in the central part is formed on a silicon base plate 11. A silicon film 14 is laminated on the oxide film 12 which is formed in the notch part witch a cavity 13. Also, electrodes 15, 16 are respectively formed on the rear surface of the silicon base plate 11 and the silicon film 14 to measure the electrostatic capacity between the silicon film 14 and silicon base plate 11. While the electrostatic capacity is determined by the thickness of the oxide film 12, since the oxide film 12 is formed by the thermal oxidation of a silicon wafer, the thickness of the film can be controlled with high accuracy. Thus, an interval of the cavity 13 can be controlled with high accuracy. Further, since a region between the silicon film 14 and the base plate 11 opposed to each other is determined as the region not intercepted by the oxide film 12, the positional shear between electrodes 15, 16 is not produced and a sensor property is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type semiconductor sensor such as a capacitance type acceleration sensor and a pressure sensor, and a method of manufacturing the same. The present invention relates to a capacitance-type semiconductor sensor that can be formed without using it, and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional capacitance type semiconductor pressure sensor. The lower surface of the silicon substrate 1 has its central portion etched by an etchant such as KOH to form a concave portion 3, and the diaphragm 2 having a predetermined thickness is formed at the lower central portion. On the other hand, the glass substrate 4 is etched by an etchant to form a concave portion 5 in the center of the lower surface. An electrode 7 is formed in the concave portion 5 on the lower surface of the glass substrate 4, and a diffusion layer 6 is formed on the upper surface of the diaphragm 2. Then, the glass substrate 4 and the silicon substrate 1 are anodically bonded to each other to assemble a capacitance type semiconductor pressure sensor. The electrode 7 and the diffusion layer 6 are led out to an external electric circuit by wiring formed on the glass substrate 4 and the silicon substrate 1.

In this capacitance type semiconductor pressure sensor, when the pressure changes from normal pressure, the distance between the electrode 7 on the glass substrate 4 and the diffusion layer 6 on the silicon substrate 1 changes. , The capacitance between the electrode 7 and the diffusion layer 6 changes. This change in capacitance is extracted as an electric signal.

[0004]

However, in the above-mentioned conventional capacitance type semiconductor pressure sensor, since it is assembled by bonding the glass substrate 4 and the silicon substrate 1, the electrode 7 and the diffusion layer 6 are formed. It is easy to cause misalignment. Further, since the concave portion 5 is formed by etching the glass substrate 4 and the electrode 7 is formed on the inner surface of the concave portion, the distance between the electrode 7 and the diffusion layer 6 is determined by the etching depth. For this reason, there is a disadvantage that the distance between the electrodes fluctuates due to variations in etching, and the pressure sensor characteristics fluctuate due to etching accuracy.

In the conventional method of manufacturing a semiconductor pressure sensor, the recesses 3 and 5 are formed in the silicon substrate 1 and the glass substrate 4 by wet etching using an alkaline etching solution. The process cannot be mixed with the manufacturing process of the semiconductor device, and it is necessary to use a dedicated device. In addition, since it is formed by wet etching using an alkaline solution, it is difficult to form a fine integrated circuit or the like on a chip in terms of yield, and there is a limit to miniaturization of the chip.

The present invention has been made in view of the above problems, and has high accuracy in the distance between the electrodes, stable sensor characteristics, and can share a general semiconductor device manufacturing apparatus. Further, it is an object of the present invention to provide a capacitance-type semiconductor sensor in which a fine integrated circuit can be formed on a sensor chip and the chip can be downsized, and a method for manufacturing the same.

[0007]

A capacitive semiconductor sensor according to the present invention has a silicon substrate, an oxide film formed on the silicon substrate by removing a central portion, and an oxide film formed on the oxide film. And a void is formed between the silicon substrate and the silicon film at a portion where the oxide film is missing.

In this capacitive semiconductor sensor,
The resistance value of the silicon substrate and the silicon film is 0.1Ωc.
m or less.

In another capacitance type semiconductor sensor according to the present invention, an impurity concentration (boron, phosphorus, etc.) of 1 × 10 ¹⁸ atom is provided on a surface of the silicon substrate facing the silicon film.
It has a high concentration diffusion layer of ms · cm ⁻³ or more.

[0010] A method of manufacturing a capacitance type semiconductor sensor according to the present invention comprises the steps of: oxidizing a silicon substrate to form an oxide layer on the surface; and etching the oxide layer by photolithographic etching to remove a predetermined portion. A step of forming a film, a step of bonding another silicon substrate on the oxide film, and a step of polishing the other silicon substrate to form a silicon film having a predetermined thickness. I do.

In this method of manufacturing a capacitance type semiconductor sensor, a metal wiring layer can be further formed on the silicon film.

In the present invention, the silicon substrate and the silicon film are stacked using the oxide film as a spacer, and a gap between the silicon substrate and the silicon film is formed in a portion where the oxide film is missing. When a potential between the silicon substrate and the silicon film is applied and the capacitance between the two is detected, the silicon film is deformed when pressure is applied, and the capacitance between the silicon substrate and the silicon film changes. . The pressure or the pressure change is detected by electrically detecting the capacitance change.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a capacitance type semiconductor pressure sensor according to an embodiment of the present invention, and FIG. 2 is a plan view thereof. FIG. 1 is the same as FIG.
FIG. 3 is a sectional view taken along line AA of FIG. SiO ₂ oxide film 12 having a circular notch at the center on silicon substrate 11
Are formed. Then, a silicon film 14 is laminated on the oxide film 12, and a void 13 is formed in a missing portion of the oxide film 12 so as to be surrounded by the oxide film 12 and sandwiched between the silicon substrate 11 and the silicon film 14. . An electrode 15 is formed on the back surface of the silicon substrate 11, and an electrode 16 is formed on the silicon film 14. The silicon substrate 11 and the silicon film 14 have a resistance of 0.1 Ω · cm.
It is as follows. Thereby, the silicon substrate 11 and the silicon film 14 have sufficiently high conductivity.

Next, a method of manufacturing the above-described capacitance type semiconductor pressure sensor will be described. FIG. 3 is a sectional view showing the manufacturing method of this embodiment in the order of steps. As shown in FIG. 3A, a silicon substrate (silicon wafer) 11 is oxidized,
Oxide layers 21 and 22 are formed on both front and back surfaces.

Next, as shown in FIG. 3B, a resist 23 having a pattern having a circular notch at the center as shown in FIG. Immerse in an acid-based etching solution. Thus, the oxide film 22 on the back surface of the silicon substrate 11 and the portion of the oxide film 21 not covered with the resist 23 are etched and removed. As a result, the oxide film 12 having a circular cutout 25 at the center as shown in FIG. 4B is formed in the portion where the oxide film 21 was present.

After that, as shown in FIG. 3C, after removing the resist 23, another silicon substrate 24 is
2. Paste on top. This is done by stacking the oxide film 12 and the silicon substrate 24 and heating them to about 1000 ° C. for 2 hours in a nitrogen atmosphere while sandwiching them with an appropriate load.
Oxide film 12 and silicon layer 24 are joined.

Next, as shown in FIG. 3D, the surface of the silicon layer 24 is polished to form a silicon film 14 having a predetermined thickness. Thereby, the silicon film 1
4. Void 1 surrounded by silicon substrate 11 and oxide film 12
3 is formed.

Thereafter, an aluminum electrode 16 is formed on the silicon film 14, and an aluminum electrode 15 is formed on the back surface of the silicon substrate 11. Thus, the capacitance type semiconductor pressure sensor is manufactured. The electrodes 15 and 16 are led out, and the capacitance between the silicon film 14 and the silicon substrate 11 is measured.

In the capacitance type semiconductor pressure sensor configured as described above, when the pressure acts on the silicon film 14 to deform the silicon film 14, the distance between the silicon film 14 and the silicon substrate 11 changes. Changes during the period. This change in capacitance is detected via the electrodes 15 and 16, and pressure or a change in pressure is detected.

In the present embodiment, the capacitance between the silicon film 14 and the silicon substrate 11 is determined by the thickness of the oxide film 12, but since the oxide film 12 is formed by thermal oxidation of the silicon wafer, The film thickness can be controlled with high accuracy. For this reason, the space between the gaps can be controlled with high accuracy. Further, the silicon film 14 and the silicon substrate 11
Is determined as a region that is not blocked by the oxide film 12, so that no positional displacement between the electrodes occurs. Therefore, the characteristics of the pressure sensor are stable. Further, in this embodiment, the sensor of this embodiment can be manufactured without using a hydrofluoric acid-based etchant for etching the oxide film and using an alkali-based etchant. The manufacturing apparatus can be used as it is. For this reason, the sensor of this embodiment can be manufactured without using a dedicated device.

As shown in FIG. 4A, the oxide film 12 is not limited to the one having the circular cutout 25, and as shown in FIG. By forming a shape having a straight portion extending from the missing portion to one edge, the gap 13 formed in the step of FIG.
Is not sealed and communicates with the outside. Thus, a differential pressure type sensor can be obtained.

FIG. 5 is a sectional view showing a capacitance type semiconductor pressure sensor according to a second embodiment of the present invention. Between the silicon film 34 and the silicon substrate 31, an oxide film 32 having a missing portion in the center is formed. Then, high-concentration diffusion layers 35 and 36 are formed on the mutually facing surfaces of the silicon substrate 31 and the silicon film 34, respectively. Further, a lead portion 37 which is connected to the high-concentration diffusion layer 35 and is a high-concentration diffusion layer penetrating the silicon substrate 31 in the thickness direction is formed on the silicon substrate 31, and the silicon film 34 is formed from the high-concentration diffusion layer 36. A lead portion 38 extending in the thickness direction is formed on the silicon film 34. Note that the diffusion layers 35 and 36 and the leads 37 and 38 have a high impurity (boron, phosphorus, etc.) doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more. Thereby, the diffusion layers 35 and 36 and the leads 37 and 38 have sufficiently high conductivity.

In the capacitance type semiconductor pressure sensor thus configured, the capacitance between the diffusion layers 35 and 36 is measured via the leads 37 and 38. Also in this embodiment, similarly to the embodiment shown in FIG. 1, a pressure change can be measured by a change in capacitance.

The pressure sensor of this embodiment can also be manufactured by the thin film forming technique shown in FIG. 3, and the accuracy of the capacitance value is high.

FIG. 6 is a sectional view showing a device incorporating the above-described pressure sensor of this embodiment. The mold 41 has a bottom part 42 and an intermediate step part 43, and the pressure sensor chip 4
0 is located on the bottom 42. And the chip 40
The electrode on the upper surface of the chip 40 is connected to the wiring layer 45 formed on the intermediate step 43 of the mold 41 via the bonding wire 46, and the electrode on the lower surface of the chip 40 is
1 and is directly connected to and connected to a wiring layer 44 formed on the bottom 42. Thus, each electrode of the chip 40 is led out to the outside via the wiring layers 44 and 45.

Each of the above embodiments applies the present invention to a pressure sensor for measuring an absolute pressure. As described above, by changing the shape of the air gap as shown in FIG. Differential pressure can also be measured. Further, the present invention can be applied to semiconductor sensors other than pressure sensors such as acceleration sensors.

[0027]

As described above, according to the present invention,
The accuracy of the space between the gaps is determined by the accuracy of the thickness of the oxide film, and the distance of the space in the direction orthogonal to this space, that is, the accuracy of the size of the counter electrode is determined by the accuracy of photolithography. An extremely high semiconductor sensor with stable characteristics can be obtained.

In the manufacturing process, KOH
Since an alkaline etching solution such as that described above is not used, an ordinary semiconductor device manufacturing apparatus can be used in common, and a dedicated apparatus is not required, so that no new capital investment is required.
Also, since no alkaline etching solution is used, LS
Similarly to I, an integrated circuit or the like that does not like contamination by alkali ions can be mounted on the sensor chip. In addition, since anisotropic etching of the silicon substrate is not performed, a thick wafer can be used, so that breakage during the movement of the process is suppressed, the yield can be improved, and the chip can be downsized. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a capacitance type semiconductor pressure sensor according to an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a sectional view showing the manufacturing method in the order of steps.

FIG. 4 is a plan view of one step in the same manufacturing method.

FIG. 5 is a sectional view showing a capacitance type semiconductor pressure sensor according to another embodiment of the present invention.

FIG. 6 is a diagram showing an apparatus incorporating a pressure sensor according to an embodiment of the present invention.

FIG. 7 is a sectional view showing a conventional capacitance type semiconductor pressure sensor.

[Explanation of symbols]

 11, 31: Silicon substrate 12, 32: Oxide film 13, 33: Void 14, 34: Silicon film 15, 16: Electrode 35, 36: High concentration diffusion layer 37, 38: Lead

Claims (5)

[Claims] 1. A semiconductor device comprising: a silicon substrate; an oxide film formed on the silicon substrate without a central portion; and a silicon film formed on the oxide film. An electrostatic capacitance type semiconductor sensor, wherein a gap is formed between a silicon substrate and a silicon film. 2. The silicon substrate and the silicon film have a resistance of 0.1 Ωcm or less.
The capacitance-type semiconductor sensor according to 1. 3. An impurity concentration of 1 × 10 ¹⁸ atom on a surface of the silicon substrate facing the silicon substrate.
2. The capacitance type semiconductor sensor according to claim 1, wherein the capacitance type semiconductor sensor has a high concentration diffusion layer of s · cm ⁻³ or more. 4. A step of oxidizing a silicon substrate to form an oxide layer on the surface, a step of etching the oxide layer by photolithographic etching to form an oxide film having a predetermined portion missing, and a step of forming another oxide film on the oxide film. Bonding a silicon substrate and polishing another silicon substrate to form a silicon film having a predetermined thickness. 5. A step of oxidizing a silicon substrate to form an oxide layer on the surface, a step of etching the oxide layer by photolithographic etching to form an oxide film having a predetermined portion missing, and a step of forming a predetermined oxide film on the oxide film. Bonding a silicon film having a thickness of 3 mm.