JPH11326095A - Manufacture of electrostatic capacity type pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrostatic capacity type pressure sensor decreasing the dispersion of the thickness of a diaphragm and reducing the roughness of a silicon surface in the manufacturing process of the diaphragm section of an electrostatic capacity type pressure sensor chip. SOLUTION: P<+> boron is diffused at the manufacturing portion for a diaphragm section, etching is applied for 6 hr at 90 deg.C with a 22%- tetramethylammonium hydroxide(TMAH) etching solution, it is then washed with water and dried, etching is again applied for 1 hr at 90 deg.C with a 5%-TMAH etching solution, and the diaphragm section is manufactured by utilizing a P<+> etch stop effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a sensor having a sensor chip in which an electrode formed on one substrate and a diaphragm formed on the other substrate have a gap to form a cavity. The present invention relates to a method for manufacturing a capacitance type pressure sensor that detects pressure based on a change in capacitance.

[0002]

2. Description of the Related Art FIG. 3 shows an external perspective view of a capacitance type pressure sensor. FIG. 4 shows an example of a cross-sectional view along the line AA 'of the capacitance type pressure sensor of FIG.

The pressure sensor shown in FIG. 4 is a capacitance type pressure sensor, in which a silicon substrate 11 is provided with a diaphragm 13 which is deformed in response to pressure, and a glass substrate 1 is provided.
On the second 2, a fixed electrode 16 is formed. The silicon substrate 11 and the glass substrate 12 are partially joined to each other, whereby a cavity 14 is formed below the diaphragm 13. The silicon substrate 11 and the glass substrate 12 form a sensor chip 15, and the sensor chip 15 is adhered on the pedestal 23 by the glass substrate 12. Further, through holes 19 and 20 in the sensor chip for introducing atmospheric pressure or for introducing a pressure to be compared with the measured pressure into the glass substrate 12 constituting the sensor chip 15 and the pedestal 23 on which the sensor chip 15 is disposed. Are formed. On the pedestal 23, a lead terminal 24 formed together during molding is arranged, and the lead terminal 24 and the fixed electrode 1 are formed.
6 is electrically connected by a lead wire 18.

The sensor chip 15 is provided with a lateral hole,
As a result, the fixed electrode 16 is drawn out.
The lateral hole is sealed with a sealant 17 to isolate the cavity 14 from the area outside the sensor chip. Then, the pedestal 23 and the pressure introducing hole 21 for introducing the pressure to be measured are provided.
Part 2 of a molding material as a cover member provided with
2 is sealed by ultrasonic welding.

FIG. 2 shows a process of manufacturing a sensor chip.
A process chart from the anodic bonding of a silicon substrate and a glass substrate is shown. In the sensor chip, a silicon substrate and a glass substrate are integrated by anodic bonding, and then the silicon substrate is etched to form a diaphragm on the silicon substrate, thereby completing the sensor chip structure.

[0006] In the manufacturing process of the silicon substrate, the diaphragm portion is formed by adding P
⁺ Boron is diffused by 3.5 μm, and a 22% tetramethylammonium hydroxide (TMAH) etching solution is etched at 90 ° C. for 7H using a P ⁺ etch stop effect.
Then, a diaphragm portion is manufactured. After the etching, washing with water and drying in a vacuum oven are repeated to sufficiently clean the inside of the cavity. Thereafter, the integrated wafer is stuck on a dicing tape, diced, and cut into individual sensor chips. After dicing, the sensor chip is completed by washing with water and drying in a vacuum oven.

In the illustrated capacitance type pressure sensor, when pressure is applied to the diaphragm 13, the diaphragm 13 constituting the movable electrode is deformed according to the magnitude of the pressure difference from the pressure in the cavity. Due to the deformation of the diaphragm 13, the gap between the diaphragm 13 and the fixed electrode 16 changes. Here, the diaphragm unit 1
3 and the fixed electrode 16 have a relationship c = ζ (A / d). Here, c is the capacitance, Δ is the dielectric constant of air, A is the electrode area, and d is the gap width between the electrodes. Therefore, the capacitance changes due to the change in the gap width,
Further, since there is a certain correlation between the force and the gap, the pressure can be known by detecting the capacitance.

[0008]

In the case of the above-mentioned capacitance type pressure sensor, a silicon substrate and a glass substrate are integrated by anodic bonding, and then the silicon substrate is etched by using an etching solution, thereby forming a diaphragm portion. To complete the sensor chip structure.However, in the etching of the diaphragm part manufacturing process, in order to finish the silicon etching while leaving the set diaphragm thickness, in the previous silicon substrate manufacturing process, the diaphragm part was formed. Attempts were made to diffuse the P ⁺ boron into the fabricated part and to control the diaphragm thickness using the P ⁺ etch stop effect.

However, if etching is performed with a conventional concentration of one type of etching solution, the P ⁺ etch stop effect is not sufficiently observed, and if the thickness of the diaphragm is controlled only by time, the thickness of the diaphragm greatly affects the variation characteristics. There's a problem. Further, when etching is performed with one type of etching solution concentration while changing the concentration of the etching solution, P
^{+ Although an} etch stop effect can be seen, there is a problem that the surface of the diaphragm becomes rough, which greatly affects the characteristics.

The present invention has been made to solve such a problem, and its technical problem is that in the manufacturing process of the diaphragm portion of the sensor chip, the P ⁺ etch stop effect is utilized and the silicon surface is removed. An object of the present invention is to provide a manufacturing method for preventing roughening and stably providing a capacitance type pressure sensor having good characteristics.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides the following method of manufacturing a capacitance type pressure sensor.

That is, the present invention comprises a first substrate on which an electrode portion is formed, and a second substrate on which a diaphragm portion that is deformed in response to pressure is formed, wherein the diaphragm portion, the electrode portion, A sensor chip in which the first and the second substrates are joined by providing a cavity portion such that the cavity portion faces each other with a gap therebetween, and a gap between the diaphragm portion and the electrode portion is provided. In a method of manufacturing a capacitance-type pressure sensor in which the pressure difference is detected by a change in capacitance, the capacitance is formed by performing an etching process using the plurality of etching solutions having different concentrations of the etching solution. This is a method for manufacturing a pressure sensor.

Further, the present invention provides the above-mentioned etching solution,
This is a method for producing the above-mentioned capacitance type pressure sensor comprising tetramethylammonium hydroxide; (CH ₃ ) ₄ NOH.

Thus, it is possible to stably provide a capacitance type pressure sensor having a constant diaphragm thickness of the diaphragm portion of the sensor chip, a small surface roughness of the diaphragm, and excellent characteristics.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a capacitance type pressure sensor according to the present invention will be described below with reference to the drawings.

FIG. 1 is a process chart showing one example of a process of manufacturing a sensor chip in a method of manufacturing a capacitance type pressure sensor according to the present invention, starting from anodic bonding of a silicon substrate and a glass substrate.

FIG. 4 is a diagram showing an A-capacity type pressure sensor in FIG.
It is A 'sectional drawing. The sensor chip 15 integrates the silicon substrate 11 and the glass substrate 12 by anodic bonding, and then etches the silicon substrate 11,
The diaphragm 13 is formed on the silicon substrate 11 to complete the sensor chip structure.

The fabrication of the diaphragm is performed by adding P ⁺ to the diaphragm fabrication portion in the manufacturing process of the silicon substrate.
Boron is diffused by 3.5 μm and a 22% tetramethylammonium hydroxide (TMAH) etching solution 90 ° C.
6Hr etching, followed by washing and drying, and again 5% TMAH etching solution at 90 ° C. for 1H
r-etching is performed, and a diaphragm portion is manufactured using the P ⁺ etch stop effect. Also, in some cases,
Etching may be performed again for a short time using a 22% TMAH etching solution.

After etching, the interior of the cavity is sufficiently washed by repeating washing with water and drying in a vacuum oven.
After that, the integrated wafer is put on dicing tape,
Dicing is performed to separate each sensor chip. After dicing, the sensor chip is completed by washing with water and drying with a vacuum oven.

As a result, it is possible to stably provide a capacitance-type pressure sensor having a constant diaphragm thickness of the diaphragm portion of the sensor chip and good characteristics with less roughness on the diaphragm surface.

The capacitance type pressure sensor according to the embodiment of the present invention performs two-stage etching using a plurality of etching solutions having different concentrations of the etching solution in the process of manufacturing the diaphragm portion of the bonded sensor chip. By doing so, it is possible to stably provide a capacitance pressure sensor having a constant diaphragm thickness of the diaphragm portion of the sensor chip, a small surface roughness of the diaphragm, and excellent characteristics.

The conventional diaphragm thickness variation (standard deviation) of 2.3 μm is reduced to 0.07 μm by the present invention,
Also, the roughness of the diaphragm surface was able to be reduced from the average roughness of 5000 Å to 750 Å by the present invention.

[0023]

As described above, in the present invention, in the manufacturing process of the diaphragm portion of the bonded sensor chip, etching is performed using a plurality of etching solutions having different concentrations of the etching solution. As a result, it was possible to stably provide a capacitance type pressure sensor having a constant diaphragm thickness of the diaphragm portion of the sensor chip and good characteristics with less surface roughness of the diaphragm.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a process table from the bonding and integration of a silicon substrate and a glass substrate in a process of manufacturing a sensor chip in a process of manufacturing a capacitive pressure sensor according to the present invention.

FIG. 2 is a diagram showing an example of a process table from the bonding and integration of a silicon substrate and a glass substrate in a process of manufacturing a sensor chip in a process of manufacturing a conventional capacitive pressure sensor.

FIG. 3 is an external perspective view showing an example of a capacitance type pressure sensor.

FIG. 4 is a sectional view taken along line AA ′ of the capacitive pressure sensor of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Silicon substrate 12 Glass substrate 13 Diaphragm part 14 Cavity part 15 Sensor chip 16 Fixed electrode 17 Sealing material 18 Lead wire 19 Through hole in sensor chip 20 Through hole 21 Pressure introduction hole 22 Cap part 23 Pedestal 24 Lead terminal 25 Electrostatic Capacitive pressure sensor

Claims (2)

[Claims] A first substrate on which an electrode portion is formed; and a second substrate on which a diaphragm portion deformed in response to pressure is formed, wherein the diaphragm portion and the electrode portion have a gap. And a sensor chip in which the first and second substrates are joined by providing a cavity portion in such a relationship as to face each other, and the capacitance of the capacitance between the diaphragm portion and the electrode portion is provided. In a method of manufacturing a capacitance type pressure sensor wherein the pressure difference is detected by a change, the diaphragm is manufactured by an etching process using a plurality of etching solutions having different etching solution concentrations. Manufacturing method of capacitive pressure sensor. 2. The method according to claim 1, wherein the etching solution comprises tetramethylammonium hydroxide; (CH ₃ ) ₄ NOH.