JPH0577307B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an anodic bonding method used for bonding metal, silicon, etc. to the surface of an insulating material such as ceramics or glass.

(Prior Art) For example, in the manufacturing process of semiconductor pressure sensors and the like, anodic bonding is performed to bond a silicon wafer or the like to the surface of an insulating material such as glass.
As shown in U.S. Patent No. 3,397,278, etc., this anodic bonding method involves contacting the metal or silicon wafer to be bonded to one side of an insulating material such as glass as an anode, and the other side of the insulating material. A metal cathode is brought into contact with the surface of the
This is a method of bonding an anode and an insulating material by applying a DC voltage under a temperature condition of . However, no matter how smooth the bonding surface between the anode and the insulating material is polished, the entire surface will not be in close contact with each other at the same time, and current conduction between the two starts from several contact points, so it is difficult to use an anode with a large wafer-like area. When bonding to an insulator, the bond starts from multiple locations distributed on the bonding surface and the bond gradually expands around the bonded area, causing air bubbles to form at the bonding interface that remains between these bonded areas until the end. There was a problem with being locked up. These bubbles are compressed as the bonding progresses, and in some cases may cause enough strain to destroy the anode or insulating material.

(Problems to be solved by the invention) The present invention solves the conventional problems as described above,
This method was developed with the aim of creating an anodic bonding method that does not generate bubbles on the bonding surface even when bonding a wafer-like anode with a large area to an insulating material.

(Means for Solving the Problems) The present invention uses a liquid as the cathode in an anodic bonding method in which an anode and a cathode are brought into contact with both surfaces of an insulating material and a DC voltage is applied to bond the insulating material and the anode. By applying a DC voltage while sequentially expanding the diameter of the contact surface between the surface of the insulating material and the liquid, the bonding interface between the anode and the insulating material is moved outward from the center and the bonding is performed. This is a characteristic feature.

(Embodiments) Next, the present invention will be explained in more detail with reference to the illustrated embodiments. Reference numeral 1 is an insulating material such as glass or ceramics, and 2 is an anode that is in contact with one side of the insulating material 1. In the case of manufacturing a semiconductor pressure sensor, the insulating material 1 is glass and the anode 2 is a silicon wafer.
It is connected to the positive side of the DC power supply 4 of ~2000V. 5 is a metal flat plate held at a position slightly apart from the opposite surface of the insulating material 1;
A liquid 7 which acts as a cathode is supplied from a pipe 6 connected to the central hole. When performing anodic bonding, the entire body is heated to 300 to 400°C by the heater 8, so the liquid used here is a liquid that is stable at this temperature and has excellent electrical conductivity. For example,
It is preferable to use an alkali salt such as KNO ₃ or NaNO ₃ .

To carry out anodic bonding by the method of the present invention, the whole is heated to about 300 to 400° C., and then liquid 7 is first supplied near the center of flat plate 5. As a result, a DC voltage is applied only to the central part of the insulating material 1, and inside this part of the insulating material 1, positive ions such as Li ⁺ , Na ⁺ , K ^+, etc. face the cathode 5 side, and O ^2- , etc. Negative ions are anode 2
A polarization phenomenon toward the side occurs, and this O ^2- ion chemically bonds with, for example, Si ⁺ ions of the anode 2, and the insulating material 1
The anode 2 is joined at the center of the . If the liquid 7 is continued to be supplied while performing anodic bonding in this way, the contact surface between the surface of the insulating material 1 and the liquid 7 will gradually expand, so that the outer part where the anodic bonding was first performed will Similarly, the anodic bonding progresses, and the bonding interface between the insulating material 1 and the anode 2 moves outward from the center. In this way, by applying a DC voltage while continuing to supply the liquid 7, the bonding interface between the anode 2 and the insulating material 1 gradually moves outward and the entire bonding is performed, so that the anode 2 and the insulating material 1
There is no risk of a portion surrounded by the bonding interface occurring between the two. Therefore, according to the present invention, anodic bonding can be performed without producing bubbles on the bonding surfaces. In the above embodiment, the liquid 7 was supplied using the flat plate 5, but it is not necessarily necessary to use the flat plate 5 if the orientation is reversed from that in FIG.

(Effects of the Invention) As is clear from the above description, the present invention uses a liquid as a cathode and gradually expands the diameter of the contact surface between the insulating material and the liquid, thereby moving the bonding interface outward from the center. Since the bonding can be performed while the bonding process is being performed, the anodic bonding can be completed without the risk of creating bubbles on the bonding surfaces. Therefore, the present invention is particularly suitable for bonding a wafer-like wide-area anode to an insulating material, and will greatly contribute to the industry.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating the anodic bonding method of the present invention, and FIG. 2 is a bottom view thereof. 1: Insulating material, 2: Anode, 7: Liquid.

Claims (1)

[Claims] 1 In an anodic bonding method in which an anode and a cathode are brought into contact with both surfaces of an insulating material and a DC voltage is applied to join the insulating material and the anode, a liquid is used as the cathode, and the surface of the insulating material 1 is brought into contact with the liquid 7. An anodic bonding method characterized by performing bonding while moving the bonding interface between the anode 2 and the insulating material 1 outward from the center by applying a DC voltage while sequentially expanding the diameter of the surface.