JPH07201691A - Electrostatic junction method - Google Patents

Abstract

PURPOSE:To resolve problems that a curve, a crack, a separation, or the like occurs when plates composed of a material different in thermal expansivity are electrostatic-connected to each other. CONSTITUTION:When both plates are superimposed on each other and a DC voltage is applied in a vacuum to electrostatic-connect, a surface of a plate having small thermal expansivity is heated. Thus, as a difference in a temperature occurs between both plates to decrease a difference in a thermal expansion amount, a curve, a crack, a separation, or the like does not occur when cooling. As a result, as for a plate coupling with a silicon plate, a plate of low-priced material like a soda lime glass can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic joining method used for joining a semiconductor plate and a glass plate, such as joining a displacement detecting element of a semiconductor pressure sensor and a pedestal.

[0002]

2. Description of the Related Art A displacement detecting element used in a semiconductor pressure sensor or the like utilizes the piezoresistive effect of silicon, and as a pedestal for connecting a pressure guiding pipe, the coefficient of thermal expansion generally matches that of Si. Borosilicate glass is used. FIG. 2 shows a structural example of the semiconductor pressure sensor. Generally, a diaphragm portion 11 formed by plasma etching or the like has a diffusion strain gauge for converting displacement into an electric signal and is covered with a surface coating layer 2 including an insulating layer, a wiring protection layer, and the like. The silicon pressure sensitive chip 10 is provided with a through hole 31 at a portion corresponding to the diaphragm.
Glass pedestal 3 combined with borosilicate glass plate 3 having
The pressure guiding pipe 4 and the pressure guiding pipe 4 are integrated by soldering. Such a structure is manufactured by electrostatically bonding the silicon plate 1 that has undergone the IC process to the glass plate 4 having the through holes 41 as shown in FIG.

[0003]

Electrostatic bonding is a direct bonding of a conductor such as aluminum or a semiconductor such as silicon, which is easily oxidized, to an alkali-containing glass containing mobile ions or an insulator such as β-alumina. It is one method, and it is mainly done by heating glass and applying voltage,
This is a bonding method using electrostatic attraction generated by the movement of alkali ions in the glass. By the transfer of electrons when the electrostatic attractive force is generated, the metal-glass interface is covalently bonded without an intervening substance, and the bonding force is very strong. Since the bonding is performed at a high temperature where the ions in the glass move, if the thermal expansion coefficients of the objects to be bonded differ from each other, thermal stress will occur during cooling, causing problems such as warping at normal temperature, cracking, and peeling. Become. Therefore, matching the coefficients of thermal expansion of the materials to be joined is an indispensable condition, which is a major limitation in selecting materials. For example, as mentioned above, expensive borosilicate glass must be used.

In view of the above points, an object of the present invention is to provide an electrostatic bonding method which can bond materials having different thermal expansion coefficients, is simple, and is effective in reducing the cost of the device. To do.

[0005]

In order to achieve the above-mentioned object, the present invention is designed so that plates made of materials having different thermal expansion coefficients are superposed on each other in a vacuum, and a DC voltage is applied between the plates to cause electrostatic discharge. When performing the joining, heating is performed from the front surface side of the plate made of a material having a small thermal expansion coefficient. It is effective that the material having a large coefficient of thermal expansion is glass and the material having a small coefficient of thermal expansion is silicon. The glass is soda lime glass, and the surface temperature of the glass plate during heating is about 400 ° C.
Good to be.

[0006]

When the surface of a plate made of a material having a small coefficient of thermal expansion such as silicon is heated during electrostatic bonding, a temperature difference is generated between the plates made of a material having a large coefficient of thermal expansion such as soda lime glass. As a result, the expansion of the plate made of a material having a small coefficient of thermal expansion increases, so that the difference in the amount of thermal expansion between the two plates decreases. As a result, problems such as warpage, cracking, and peeling after cooling do not occur.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the electrostatic bonding work of a silicon plate 1 and a glass plate 3 according to one embodiment of the present invention. The material of the glass plate 3 is
It is soda-lime glass, and the dimensions and coefficient of thermal expansion of both plates are as shown in Table 1.

[0008]

[Table 1] As shown in FIG. 1, the electrostatic bonding is performed by stacking a silicon plate 1 and a glass plate 3 on a carbon plate 7 serving as a lead placed on a hot plate 6 in a vacuum chamber 5, and After bringing the anode 8 into contact with the glass plate 3 and the cathode 9 into contact with the glass plate 3, the inside of the chamber 5 was evacuated to a vacuum, and a DC voltage was applied. The conditions for electrostatic bonding are as shown in Table 2.

[0009]

[Table 2] Under the above conditions, when the silicon plate 1 and the soda-lime glass plate 3 are superposed and heated from the silicon plate 1 side in a vacuum, when the temperature on the heating side is 400 ° C.
A temperature difference of 00 ° C. or more occurred, the difference in elongation due to thermal expansion was reduced, and electrostatic bonding became possible, and no defects such as cracking or peeling were observed even after cooling. Similarly, by setting an appropriate one-sided heating temperature and heating direction, it was possible to join a soda-lime glass plate and an aluminum plate having a larger coefficient of thermal expansion.

[0010]

As described above, according to the present invention, when two plates made of materials having different thermal expansion coefficients are electrostatically bonded to each other, the bonding atmosphere is set to a vacuum without heat conduction, and one surface of the sample is stacked. By heating from above, the temperature difference between the materials at the time of joining increases and the difference in the amount of thermal expansion decreases,
It became possible to join without defects such as warpage, cracking, and peeling during cooling. As a result, it is not necessary to use an expensive material for the glass pedestal connected to the silicon chip of the semiconductor pressure sensor, and the cost reduction is achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an electrostatic bonding work according to an embodiment of the present invention.

FIG. 2 is a sectional view of a displacement detection element of a semiconductor pressure sensor embodying the present invention during manufacture.

3 is a cross-sectional view of an electrostatic bonding material for manufacturing the displacement detection element of FIG.

[Explanation of symbols]

 1 Silicon Plate 3 Glass Plate 5 Vacuum Chamber 6 Heat Plate 7 Carbon Plate 8 Anode 9 Cathode

Claims (3)

[Claims] 1. When plates made of materials having different coefficients of thermal expansion are superposed on each other in a vacuum, and a DC voltage is applied between the plates to perform electrostatic bonding, plates made of materials having a small coefficient of thermal expansion are used. An electrostatic bonding method characterized by heating from the surface side. 2. A material having a large coefficient of thermal expansion is glass,
The electrostatic bonding method according to claim 1, wherein the material having a small thermal expansion coefficient is silicon. 3. The electrostatic bonding method according to claim 2, wherein the glass is soda lime glass, and the surface temperature of the glass plate during heating is about 400 ° C.