JP2000286429A - 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, which has little dispersion in its sensor sensitivity characteristics for a sensor chip. SOLUTION: In an etching process for forming a diaphragm, an etching device having an etching solution stirring mechanism (stirrer) 8 and a circulating mechanism (pump) 7 is used, and cleaning of the diaphragm using warm water is executed, whereby dispersion in the thicknesses of the diaphragm is lessened and an electrostatic capacity type pressure sensor, which has little dispersion in its sensor sensitivity characteristics, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a capacitance type pressure sensor, and more particularly to a method for manufacturing a capacitance type pressure sensor, in which electrodes are formed on a silicon substrate and a glass substrate, respectively. The present invention relates to a method for manufacturing a capacitance type pressure sensor in which substrates are bonded.

[0002]

2. Description of the Related Art A conventional manufacturing method will be described with reference to FIGS. FIG. 2 is a manufacturing process diagram of the sensor chip,
FIG. 3 is an external view showing an example of a capacitance type pressure sensor, and FIG. 4 is a sectional view thereof (AA ′ in FIG. 3). FIG. 5 is a schematic sectional view of a conventional etching apparatus.

In FIG. 4, a capacitance type pressure sensor is:
A fixed electrode 16 is formed on a glass substrate 12 which is a first substrate, and a diaphragm 13 which is deformed in response to pressure is formed on a silicon substrate 11 which is a second substrate.
The silicon substrate 11 and the glass substrate 12 are joined at a part thereof, whereby the diaphragm 1
3, a cavity portion 14 is formed. 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, the glass substrate 12 and the sensor chip 1
Through holes 19 and 20 for introducing atmospheric pressure or for introducing a pressure to be compared with the pressure to be measured are formed in the pedestal 23 on which 5 is disposed. On the pedestal 23, there are arranged lead terminals 24 produced together during molding.
The lead terminal 24 and the fixed electrode 16 are electrically connected by the lead wire 18.

[0005] A lateral hole (not shown) is formed in the sensor chip 15.
Is provided, whereby the fixed electrode 16 is electrically drawn to the outside. Diaphragm 13 also serving as movable electrode
Is pressed through a silicon substrate 11 with a movable electrode pad (not shown) provided on a glass substrate 12, and is taken out of the cavity portion 14 as an electrode.

Thereafter, the lateral hole is sealed with a sealing material 17 in order to isolate the cavity 14 from the area outside the sensor chip. Then, the cap 23 of the molding material provided with the pedestal 23 and the pressure introducing hole 21 for introducing the pressure to be measured is sealed by ultrasonic welding or the like.

Referring to the manufacturing process of FIG. 2, the protective film on the surface of the silicon substrate 11 to be bonded to the glass substrate 12 is etched and integrated with the glass substrate 12 by anodic bonding.

The integrated wafer 9 is placed in a rack 6 and inserted into an etching apparatus containing hydrazine as shown in FIG. 5 to perform etching. Here, 1 is a heater for heating, and 5 is a bubbler (bubbler) using nitrogen gas for stirring the etching solution. Also,
Reference numeral 4 denotes a cooler in which water is circulated, which aims to reduce a change in concentration due to evaporation of the etching solution.

The etching conditions depend on the thickness of the diaphragm, but the hydrazine solution temperature is 70.degree.
The diaphragm portion 13 was formed by performing the time etching.

After the formation of the diaphragm 13, washing with water and drying in a vacuum oven are repeated to sufficiently clean the cavity 14.

Next, the wafer 9 is put on an adhesive resin sheet, diced, and divided into individual sensor chips, which are also washed and dried to complete the sensor chips.

The principle of operation of the capacitance type pressure sensor is that when pressure is applied to the diaphragm 13 which also serves as a movable electrode, the diaphragm 13 constituting the movable electrode is deformed. Due to the deformation of the diaphragm 13, the gap between the diaphragm 13 and the fixed electrode 16 changes.
Here, there is a relationship of c = ζ (A / d) between the diaphragm 13 and the fixed electrode 16 and the capacitance c therebetween. Ζ is the dielectric constant of air, A is the electrode area, and d is the gap size between the electrodes. Therefore, the capacitance c changes due to the change in the gap size d, and since there is a certain correlation between the pressure and the gap size, it is necessary to measure the pressure from the change in the capacitance. Can be.

[0013]

In a conventional method of manufacturing a capacitance type pressure sensor, a silicon substrate and a glass substrate are integrated by anodic bonding, and then the silicon substrate is etched to form a diaphragm, and the sensor chip is mounted. Although completed, it was necessary to perform etching for a long time to perform silicon etching while leaving a predetermined diaphragm thickness, and control of the etching rate, in other words, control of the temperature and concentration of the etching solution was important. . In the conventional stirring method using a bubbler apparatus, evaporation is remarkable even when a lid provided with a cooler for preventing evaporation is provided, the concentration of hydrazine changes, and the thickness of the diaphragm varies with the change in etching rate. The variation in the thickness of the diaphragm eventually affects the sensitivity characteristics of the sensor chip, and the variation increases.

Further, there is a problem that the etching solution in the cavity is not easily dropped due to the adhesion of the etching solution only by the conventional washing with water after the etching.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a technical problem of the present invention is to prevent a change in an etching rate in a process of forming a diaphragm portion of a sensor chip, and to reduce a thickness of the diaphragm. Reduce variability,
An object of the present invention is to provide a method of manufacturing a capacitance type pressure sensor having a small variation in sensor sensitivity characteristics.

[0016]

According to the present invention, there is provided a first substrate on which a fixed electrode is formed, and a second substrate on which a diaphragm portion which is deformed in response to pressure is formed. Manufacturing method of a capacitive pressure sensor including a sensor chip in which a first substrate and a second substrate are joined to form a cavity so that a portion and an electrode portion face each other with a gap therebetween. At

(1) In the step of forming a diaphragm on the second substrate by etching, an etching apparatus provided with an etching solution stirring mechanism and an etching solution circulation mechanism is used.

(2) The method is characterized in that warm water is used for cleaning after the etching step.

(3) Further, the etching solution in the present invention is TMAH [tetramethylammonium hydroxide:
(CH ₃ ) ₄ NOH]. The problem can be solved by the above means.

[0020]

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

FIG. 1 is a schematic sectional view of a silicon etching apparatus for a capacitance type pressure sensor according to the present invention.

In FIG. 1, the silicon substrate has an n-type (1
First, a thermal oxide film (Si)
O ₂ ) is formed, and the cavity 14 is patterned by photolithography. Thereafter, the silicon is etched using the TMAH solution to form a gap between the silicon and the fixed electrode.

Next, the thermal oxide film on the bonding surface was removed with dilute hydrofluoric acid or the like, and the silicon substrate and the glass substrate were integrated by anodic bonding.

Thereafter, the integrated wafer 9 is placed in the rack 6
And inserted into the etching apparatus of FIG. 1 to form the diaphragm portion 13. The etching solution is 90 ° C TMAH
And heated by the heater 2 with a stirrer. The etching solution was stirred by a stirrer 8, and the etching solution was circulated using a pump 7 having a corrosion-resistant diaphragm. Furthermore, the lid was covered with the cooler 4 in which water was circulating, and etching was performed for 6.0 hours while preventing the concentration change due to evaporation of TMAH, thereby forming the diaphragm portion 13.

After the etching, the substrate was washed with warm water at 80 ° C., and then repeatedly washed with water, dried in a vacuum oven, and the inside of the cavity portion 14 was sufficiently washed.

Thereafter, the wafer 9 was attached to an adhesive resin sheet, diced, divided into single chips, washed and dried to complete the sensor chip 15.

Hereinafter, as shown in FIG.
5 is adhered to the pedestal 23, each electrode and the lead terminal 24 are electrically connected by the lead wire 18, and finally, the cap portion 22 of the molding material is sealed by ultrasonic welding to complete the capacitance type pressure sensor. Was.

The pressure sensor obtained as described above is
Variations in the thickness of the diaphragm portion are reduced, mass productivity is improved, and a characteristically stable and highly reliable capacitive pressure sensor with small variations in sensor sensitivity characteristics is obtained.

[0029]

As described above, according to the present invention, in the etching process for forming the diaphragm portion, the etching device having an agitating and circulating mechanism for the etching solution is used. Variations in thickness can be reduced, and a capacitance type pressure sensor with small variations in sensor sensitivity characteristics can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a silicon etching apparatus of the present invention.

FIG. 2 shows a process of manufacturing a sensor chip of a conventional capacitance type pressure sensor.

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

FIG. 4 is a cross-sectional view of the capacitance type pressure sensor (A-
A ').

FIG. 5 is a schematic sectional view of a conventional silicon etching apparatus.

[Explanation of symbols]

 Reference Signs List 1 heater 2 heater with stirrer 3 etching vessel 4 cooler 5 bubble generator (bubbler) 6 rack 7 circulation mechanism (pump) 8 stirring mechanism (stirrer) 9 wafer 11 silicon substrate 12 glass substrate 13 diaphragm section 14 cavity section 15 sensor chip Reference Signs List 16 fixed electrode 17 sealing material 18 lead wire 19, 20 through hole 21 pressure introducing hole 22 cap portion 23 pedestal 24 lead terminal

Claims (4)

[Claims] A first substrate on which a fixed electrode is formed; and a second substrate on which a diaphragm that deforms in response to pressure is formed, wherein the diaphragm and the electrode are interposed via a gap. The first substrate and the second substrate are bonded to each other so as to face each other, and a method of manufacturing a capacitance type pressure sensor including a sensor chip forming a cavity portion, wherein the diaphragm of the second substrate is A method for manufacturing a capacitance-type pressure sensor, wherein an etching device having an etching solution stirring mechanism is used when it is formed by etching. 2. A semiconductor device comprising: a first substrate on which a fixed electrode is formed; and a second substrate on which a diaphragm portion deformable in response to pressure is formed, wherein the diaphragm portion and the electrode portion are connected via a gap. The first substrate and the second substrate are bonded to each other so as to face each other, and a method of manufacturing a capacitance type pressure sensor including a sensor chip forming a cavity portion, wherein the diaphragm of the second substrate is A method for manufacturing a capacitance-type pressure sensor, comprising using an etching apparatus having an etching solution circulation mechanism when forming by etching. 3. The method for manufacturing a capacitance type pressure sensor according to claim 1, wherein hot water is used for cleaning after said etching step. 4. The capacitance type pressure sensor according to claim 1, wherein the etching solution is made of TMAH [tetramethylammonium hydroxide; (CH ₃ ) ₄ NOH]. Production method.