JPH0233975A - Semiconductor pressure measuring device - Google Patents

Abstract

PURPOSE:To simplify an offset regulating circuit by an unbalance and to form a pressure detector having high sensitivity by disposing one P-N junction diode at the maximum stress on a silicon semiconductor single crystalline diaphragm. CONSTITUTION:A silicon single crystal is thinly formed on the inner rear face of a broken line circle 12, and a diaphragm is formed. A P-N junction diode 13 is formed near in inner contact with the periphery of the diaphragm. The diode 13 is partly extended out of the diaphragm, and a connecting aluminum electrode pad 14 is formed thereat. When a reverse current is measured, a pressure detector having high sensitivity is very simply formed. Thus, an offset regulating circuit by an unbalance is simplified, the detector having high sensitivity is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor pressure measuring device that can easily measure the pressure of gas or liquid with high sensitivity and that can easily correct the zero point of the output.

Conventional pressure measurement devices include one in which a strain gauge is attached to a metal diaphragm, and one in which a piezoresistive element is formed on the surface of a semiconductor diaphragm using an impurity diffusion method.In recent years, semiconductor pressure sensors have become particularly popular due to their simplicity and small size. is remarkable.

However, since this semiconductor pressure sensor uses a diffused resistance bridge, the balance of each gauge resistance built into the bridge is extremely important. If each bridge resistor is not balanced, the output cannot be maintained at zero when no pressure is applied, and in order to use it as a gauge, some kind of compensation must be done in an external circuit. The output of the bridge when no pressure is applied is called the offset voltage, but it is extremely difficult to correct this offset voltage even if the ambient temperature changes if it is corrected using an external circuit. It is. Therefore, various methods are employed to reduce this offset voltage as much as possible so that there is no need for correction using an external circuit. For example, in order to form a pattern for a bridge resistor, ultra-high precision pattern forming technology is used to minimize deviations in the pattern width dimensions of each gauge resistor. In addition, P-type impurities (such as boron) are implanted and diffused by ion implantation to reduce the variation in concentration of P-type impurities that are diffused through the silicon oxide film mask thus formed. However, as a result, it is necessary to form a well-balanced bridge.These ultra-high precision pattern forming techniques and ion implantation techniques use sophisticated and expensive equipment and require a high degree of skill.

Problems to be Solved by the Invention As mentioned earlier, conventional semiconductor pressure sensors utilize the piezoresistive effect of four well-balanced diffusion gauge resistors fabricated on the surface of a semiconductor single crystal, but offset It is very difficult to create a small voltage. This invention easily solves this problem.

Means for Solving the Problems The present invention consists of a silicon single-crystal diaphragm that deforms under pressure, and a PN junction placed at the part of the diaphragm surface where maximum strain occurs, and the reverse current of the PN junction changes depending on the pressure. This paper proposes a pressure detection device that can detect pressure and easily reduce offset to zero.

According to the present invention, a PN junction is provided on a silicon single crystal diaphragm that is deformed by pressure, and pressure can be detected by a change in reverse current of the PN junction.

Embodiment A semiconductor diaphragm type pressure sensing device according to the present invention will be explained with reference to FIGS. 1 and 2. FIG.

FIG. 1 is a schematic cross-sectional view of a semiconductor single-crystal diaphragm type pressure detection device of the present invention.

1 is a cap of the pressure sensor and has a vent hole 2.

Reference numeral 3 denotes a thin metal wire for connection, such as a gold wire or an aluminum wire, for extracting an electric signal from the semiconductor single crystal diaphragm. 4 is a semiconductor single crystal diaphragm, which is the main part of the present invention. 5 is a pedestal, and 6 is a lead wire connected by a connecting gold wire or aluminum wire for taking out a signal to the outside of the package. 7 is a header, 8 is a glass for insulating the header 7 and the lead wires, and 9 is a pressure introduction tube through which pressure is introduced through an opening 10 and applied to the back surface of the semiconductor single crystal diaphragm.

Next, FIG. 2 will be explained. FIG. 2 is a pattern diagram of a PN junction arranged on the surface of the semiconductor single crystal diaphragm 4. Reference numeral 11 indicates a silicon semiconductor single crystal chip. On the inside back surface of the black line circle 12, silicon single crystal is processed into a thin layer to form a diaphragm. A PN junction 13 is formed very close to and inscribed around this diaphragm.

A part of this PN junction 13 is extended to the outside of the diaphragm, and an aluminum electrode pad 14 for connection is formed there. This electrode operates as the P-type side electrode of the PN junction. Further, 15 is formed as an N-type side electrode of a PN junction. As mentioned above, it can be seen that a highly sensitive pressure detection device can be formed very easily by forming a PN junction diode having the structure shown in FIG. 2 and measuring its reverse current. Furthermore, since only one PN junction diode element is used, it can be seen that pressure can be easily detected without offset due to unbalance.

The saturation current of the PN junction is expressed by the following equation.

Here, q represents the electron charge, Do and D represent the diffusion coefficients of electrons and holes, respectively, and np and plJ represent the minority carrier (electron, hole) density in the P-type region and the N-type region, respectively. Matari. , Lp is a minority carrier (electron).

hole) is the diffusion distance. The reverse current is expressed by the following formula (%) where k is Boltzmann's constant, T is the absolute temperature, q is the electron charge, and ■ is the applied voltage, which indicates the color value in the case of the reverse direction. Further, e is the base of natural logarithm. Since V in equation (2) is negative, if the reverse voltage becomes a large value, the reverse current becomes equal to the saturation current. Therefore, -Is becomes a reverse current.

By the way, it is known that minority carriers increase significantly when pressure is applied. For example, FIG. 3 shows the relationship between pressure and the number of minority carriers. From this figure, the minority carriers are reduced to about iooo due to pressure application.

It can be seen that the number increases by double. Furthermore, it can be seen that the sensitivity is about 10 times greater for compressive stress than for tensile stress.

On the other hand, when pressure is applied to a circular silicon diaphragm from one direction, the magnitude of stress in each part of the diaphragm takes on values as shown in FIG. This figure shows that the stress in the radial direction shows a large value at the center and periphery of the diaphragm, and in particular, the absolute value of the stress in the periphery direction is larger than that at the center. Also, since the number is negative, it can be seen that if a tensile stress is applied to the center, a compressive stress is applied to the periphery. From this, it can be seen that the following structure is necessary to realize a highly sensitive pressure detection device that utilizes changes in the reverse current of the PN junction.

A pressure sensor has been proposed in which the pressure receiving surface is from the back side of a silicon single crystal diaphragm and a PN junction is arranged around the surface of the diaphragm.

Effects of the Invention As described in the embodiment, by arranging one PN junction diode at the location where the stress is greatest on the silicon semiconductor single crystal diaphragm, the offset adjustment circuit due to unbalance can be simplified, and a very inexpensive, It has become possible to create a highly sensitive pressure detection device.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of an apparatus according to an embodiment of the present invention, Fig. 2 is a plan view of a semiconductor chip used in the same embodiment, and Fig. 3 shows the relationship between stress and the increase ratio of minority carriers in a semiconductor single crystal. FIG. 4 is a characteristic diagram showing the relationship between the radial position and stress of a circular silicon single crystal diaphragm. 1...Cap, 2...Outside air intake port,
3... Thin metal wire for connection, 4... Silicon chip, 5... Pedestal, 6... Lead wire, 7... Header, 8...Glass (
insulator), 9...pressure introduction pipe, 10...
...Pressure inlet. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 1 Figure 3 Figure 2 Personality

Claims (1)

[Claims] It has a diaphragm part made of thinly processed semiconductor single crystal,
A semiconductor pressure measuring device having a PN junction on its main surface, the PN junction being arranged at the maximum strain area on the diaphragm surface.