JPH0413866B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention provides a semiconductor pressure sensor in which gauge resistors of different conductivity types formed on a thin part of a semiconductor substrate of one conductivity type are bridge-connected, and an output voltage is obtained by changing the gauge resistance due to a force applied to the thin part. Regarding.

[Prior art and its problems]

FIG. 2 shows a conventional semiconductor pressure sensor by a in a plan view, b in a sectional view taken along line B-B' of a, and n
Gauge resistors 3 and 4 made of p-type regions provided on the diaphragm portion 2 of the silicon substrate 1 are
The gauge resistors 3 and 4 are bridge-connected by a wiring layer 5 insulated by an insulating film 7, and the output voltage is based on the imbalance in the resistance values of the gauge resistors 3 and 4 that occurs when pressure is applied to the diaphragm portion 2. Detect pressure value. Although the wiring layer 5 is made of Al, there is a large difference in the coefficient of thermal expansion between the semiconductor substrate 1 and the Al wiring layer 5, and the temperature accuracy of the sensor deteriorates because it is subjected to compressive and tensile forces due to temperature changes. It is known. As a solution to this problem, a method has been adopted in which the temperature characteristics are improved by using Mo, W, or their silicides, which have a coefficient of thermal expansion close to that of the semiconductor substrate, for wiring. However, in such a sensor, the pad part 6 provided at the end of the wiring layer 5 for connection to an external terminal has a wire that can be bonded to an Al wire or an Au wire.
It is necessary to apply a film of Al or Au, and the wiring material
Mo, W or its silicide and pad material
The laminated structure of Al and Au tends to cause delamination, which has the disadvantage of reducing reliability.

[Purpose of the invention]

The present invention has a terminal pad part in which a gauge resistor is connected by a wiring made of a material having a coefficient of thermal expansion similar to that of a semiconductor substrate, and which can be easily bonded to a conductive wire, and is based on a laminated structure of the wiring and the pad part. The purpose of the present invention is to provide a semiconductor pressure sensor that is free from delamination, has high temperature accuracy, and is highly reliable.

[Key points of the invention]

A semiconductor pressure sensor according to the present invention includes a wiring made of a material having a coefficient of thermal expansion similar to that of the semiconductor material on a semiconductor substrate, and a terminal pad part made of a material that allows easy bonding between the end of the wiring and a conductive wire spaced apart. The above objective is achieved by eliminating the laminated structure by electrically connecting the end of the wiring and the pad part with a low resistance diffusion layer of a different conductivity type formed from the substrate surface. do.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention, in which a is a plan view of a substrate, and b is a sectional view taken along line A-A' of a, where parts common to FIG. 2 are given the same reference numerals. . n-type
A wiring layer 5 made of Mo, W, or a silicide thereof having a coefficient of thermal expansion close to that of the Si substrate is used for bridge connection of the p-type gauge resistors 3 and 4 provided on the diaphragm portion 2 of the Si substrate 1. In addition, the pad metal layer 6
Apply a film of Al or its alloy or Au, and connect to external terminals with Al wire or Au wire. There is a gap 9 with a width of several μm between the wiring 5 and the pad metal layer 6.
A desired internal wiring is obtained by connecting the wiring layer 5 and the pad metal layer 6 via the p-type low resistance layer 8 in which impurities are diffused at a high concentration. It has been confirmed that if the resistance caused by the gap 9 between the wiring layer 5 and the pad metal layer 6 is less than 1/1000 of the gauge resistance, the effect on the accuracy of the pressure sensor can be ignored in practice. The formation of the low-resistance layer 8 necessary to obtain this resistance and the photolithography for forming the gap portion 9 can be sufficiently performed using conventional process techniques. With this configuration, there is no laminated structure of the wiring and the pad portion, and there is an advantage that there is no delamination between layers, and there is also an advantage that stress applied from the wiring 5 to the gauge resistors 3 and 4 during temperature changes is small. FIG. 3 shows another embodiment, which differs from FIG. 1 in that a low resistance diffusion layer 8 is extended under the wiring layer 5 and the pad metal layer 6.
As can be seen from Figure b, there is no step due to the insulating film 7 in the direction of current flow, and the wiring layer 5 and pad metal layer 6
Since it is provided on the plane above the low resistance diffusion layer 8, it has the advantage that internal wiring will not be disconnected.

【Effect of the invention】

According to the present invention, stress in the gauge resistors caused by temperature changes is reduced by using a material with a coefficient of thermal expansion similar to that of the substrate material for connecting gauge resistors formed in thin parts of a semiconductor substrate and to terminals. The pad part is made of a metal that has high temperature accuracy and is easy to bond to the conductor, and is formed separately from the wiring, and is connected with a low-resistance diffusion layer in the substrate, thereby eliminating the need for a laminated structure and achieving reliability without delamination. It is possible to obtain a semiconductor pressure sensor with high performance.

[Brief explanation of drawings]

FIG. 1 shows a semiconductor substrate according to an embodiment of the present invention, a is a plan view, b is a sectional view taken along line A-A' of a, and FIG. 2 is a semiconductor substrate of a conventional semiconductor pressure sensor, where a is FIG. 3 shows a semiconductor substrate according to another embodiment of the present invention,
FIG. 3A is a plan view and b is a sectional view taken along line C-C' of a. 1: Si substrate, 2: Diaphragm part, 3, 4: Gauge resistor, 5: Wiring layer, 6: Pad part metal layer,
8: Low resistance diffusion layer, 9: Gap.

Claims (1)

[Claims] 1. In a device in which gauge resistors of different conductivity types formed on a thin part of a semiconductor substrate of one conductivity type are connected to each other and to terminals and wiring, a material having a coefficient of thermal expansion similar to that of the semiconductor material is used on the semiconductor substrate. and a terminal pad part made of a material that facilitates bonding of a conductive wire at a distance from the end of the wiring. A semiconductor pressure sensor characterized in that it is electrically connected by a diffusion layer.