JPS6286734A - Method for chip mounting - Google Patents

Abstract

PURPOSE:To reduce the temperature dependence of the offset in a silicon diaphragm type pressure sensor by bonding the structure to a semiconductor element in a point contact manner. CONSTITUTION:A diaphragm 2 is formed on a first main surface of a silicon chip 1 by recessing part of the first main surface and an electronic circuit is integrated on a second main surface. A pedestal 3 consists of pyrex having a roughly equal thermal expansion coefficient to that of silicon and the pedestal 3 and the silicon chip 1 are bonded by an electrostatic bonding method in a vacuum. The bonding of the pedestal 3 and a structure 7 is bonded by a method wherein an epoxy silver paste with a fine area is applied on the pedestal by a screen printing method and so on and the pedestal is bonded on the structure 7 in a point contact manner. As the bonded part of the pedestal 3 and the structure 7 is bonded in a point contact manner in such a manner, the contact area becomes smaller and the effect of thermal expansion of the structure 7 becomes harder to conduct to the pedestal 3. Accordingly, the effect of thermal expansion of the structure 7, which exerts on the diaphragm 2 formed on the silicon chip 1, can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for mounting a chip on a silicon diaphragm pressure sensor, and more particularly to a method for mounting a chip on a silicon diaphragm pressure sensor that measures absolute pressure.

[Conventional technology]

In recent years, silicon diaphragm pressure sensors have come into the spotlight due to semiconductor technology. This sensor is unique in that silicon is used not only as a base material for electrical elements, but also as a highly rigid mechanical element.

A silicon diaphragm pressure sensor has a large number of unit cells arranged in a silicon wafer, and a part of the first main surface is indented by anisotropic etching, machining, etc., and the second main surface is pressure-sensitive. It is manufactured by integrating electronic circuits such as the r-di resistor 1, which becomes the element, and then dividing it into unit cells, and making the unit cells into pieces. This die is adhered to a structure that becomes a package for the pressure sensor, and the pressure sensor is realized by applying desired electrical wiring. When bonding the die, it is known that a pedestal is interposed between the structure and the goo in order to prevent thermal strain effects caused by the difference in thermal expansion coefficient between the structure and silicon, which is the material of the die. ing. As the pedestal, for example, Pyrex glass, which has a coefficient of thermal expansion similar to that of silicon wafer, is used.

For absolute pressure silicon diaphragm pressure sensors,
The glass and the goo are bonded together by electrostatic bonding in a vacuum, and true nitrogen pressure is sealed in the silicon diaphragm portion.

Electrostatic adhesion is a technology in which glass and silicon are completely bonded and bonded in an atmosphere of high temperature and high electric field, and is particularly effective in reducing costs because it can be bonded wafer by wafer during the process before separation.

The structure and the glass are bonded together by applying a jepoxy adhesive to the entire surface of the glass by screen printing or the like.

The prior art will be fully explained below with reference to the drawings.

FIG. 2 is a sectional view showing the structure of a silicon diaphragm type pressure sensor mounted on a chip by a conventional method.

In FIG. 2, a silicon chip 11 has a first main surface (the surface facing the pedestal) partially recessed to form a diaphragm 12, and an electronic circuit is integrated on the second main surface. Pedestal 13
The pedestal 13 and the silicon chip 11 are bonded to each other by electrostatic adhesion. Gepoxy silver paste 15 is entirely printed on the entire surface of this pedestal 13 by a screen printing method and adhered to the structure 17, and further, 20 tons of wireboring/7' ing is applied between the silicon chip 11 and the stem 18.
The structural unit 17 is completed by sealing with a cap 19.

[Problem that the invention seeks to solve]

However, in the silicon diaphragm pressure sensor obtained in this way, the entire surface of the pedestal 13 is bonded to the structure 17, so the thermal expansion of the structure 17 is directly transmitted to the pedestal 13. The influence of thermal expansion of the structure 17 on the silicon chip 11 could not be completely blocked, causing distortion in the diaphragm 12 of the silicon chip 11 due to temperature changes, causing the offset to change depending on the temperature.

An object of the present invention is to provide a silicon diaphragm type pressure sensor whose offset is less dependent on temperature.

[Means for solving problems]

The present invention is a method for mounting a semiconductor element on a structure, which is characterized in that the structure is bonded to the semiconductor element in a point-contact manner.

[Effect]

According to the present invention, the semiconductor element is set in the structure by adhering it to the pedestal, but since the area of the bonded part between the pedestal and the structure is small, the influence of thermal expansion of the structure is not easily transmitted to the pedestal. Therefore, changes in offset due to changes in temperature are reduced.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a pressure sensor using a silicon diaphragm chip-mounted by the method of the present invention. In FIG. 1, a silicon chip 1 has a diaphragm 2 formed by recessing a part of its first main surface (the surface facing the pedestal).
is formed, and an electronic circuit is integrated on the second main surface.

The pedestal 3 is made of Pyrex glass, which has a coefficient of thermal expansion approximately equal to that of silicon, and the pedestal 3 and the silicon chip 1 are bonded together in a vacuum by electrostatic adhesion.

The above is exactly the same as the conventional method. The present invention
The pedestal 3 and the structure 7 are bonded together by applying a small area of epoxy steel paste (1) to the pedestal 3 using a printing method or the like, and adhering it to the structure 7 in a point contact manner. This is what I did.

Further, as in the conventional case, a wire zapping 10 is applied between the silicon tip 1 and the stem 8, and the structure 7 is connected to the cap 9.
It is completed by sealing with.

According to the method of the present invention, since the adhesive portion between the pedestal 3 and the structure 7 is in point contact, the contact area is small and the influence of thermal expansion of the structure 7 is not easily transmitted to the pedestal 3. Structure 7 that acts on the diaphragm 2 formed on the chip 1
The effect of thermal expansion is reduced.

[Effects of the Invention] As explained above, the method of the present invention has the effect of providing a silicon diaphragm type pressure sensor with less temperature dependence of offset.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a silicon diaphragm type pressure sensor showing an embodiment of the present invention, and FIG. 2 is a sectional view of a silicon diaphragm type pressure sensor chip-mounted by a conventional method. 1... Silicon chip, 2... Diaphragm, 3.
... Pedestal, 5... Epoxy silver paste, 7... Structure. 8...Stem, 9...Can 7', 10...
bonding wire.

Claims (1)

[Claims] (1) A chip mounting method for mounting a semiconductor element on a structure, the method comprising bonding the semiconductor element to the structure in a point-contact manner.