JPH09329519A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor which is improved so that a zero-shift signal or span-shift signal becomes minimum. SOLUTION: This sensor is provided with a square single-crystal semiconductor chip 12 on one side of which a pair of radial stress sensors 13 and 14 with pressure-sensing characteristics and a pair of circumferential stress sensors 15 and 16 with pressure-sensing characteristics are formed and on the other side of which a square hollowed part 17 is formed. It is also provided with a cuboid-shaped insulating base 19 in the center of which a communication hole 18 with a circular cross section is formed. The hole 18 is communicated to the above-mentioned square hollowed part 17 formed on the semiconductor chip 12. A square frame 22, which is made of the same single-crystal material as the semiconductor chip 12 and with an opening part 23 communicated to the hollowed part 17 formed on the semiconductor chip 12 and the communication hole 18 formed in the insulating base 19, is inserted between the insulating base 19 and the semiconductor chip 12. And the semiconductor chip 12 and the base 19 are integrally joined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor, and more particularly to a pressure sensor using a square semiconductor chip.

[0002]

2. Description of the Related Art In a conventional semiconductor pressure sensor, a semiconductor chip having a pair of radial stress sensors and a pair of circumferential stress sensors formed on one surface is used. A diaphragm structure is employed to respond to the pressure differential across the other surface. That is, a cavity is formed on the other surface of the semiconductor chip, and one end of a cylindrical pedestal is coupled to the other surface of the chip so as to cover the cavity.

Thus, a semiconductor pressure sensor originally employs a circular diaphragm with a circular semiconductor chip and a cylindrical pedestal, so that the entire sensor has a common axis with respect to the chip, cavity and pedestal. The structure was symmetrical in the xy plane perpendicular to the axis. However, recently, it has become common to use a square semiconductor chip by cutting a crystal wafer, and
Anisotropic etching is also used to form the cavity in the semiconductor chip, and the pedestal that covers the cavity is also a rectangular parallelepiped pedestal made of a material different from that of the semiconductor chip. Has come to be adopted. Therefore, in such a rectangular diaphragm structure, the xy axis is common to the semiconductor chip and the pedestal of the rectangular parallelepiped joined to the semiconductor chip.
The symmetry in the plane is no longer shown, and the symmetry also disappears in the z-axis (axis) direction. 1A and 1B are views showing an example of a conventional semiconductor pressure sensor having a rectangular diaphragm structure. FIG. 1A is a top view and FIG. 1B is a side sectional view. The semiconductor pressure sensor 11 includes a thin square semiconductor chip 12. The semiconductor chip 12 is made of a single crystal semiconductor material such as silicon. On the first surface of the semiconductor chip 12, the radial stress sensors 13, 1
4 are arranged. That is, these stress sensors 1
3 and 14 are oriented such that their longitudinal directions are along the radial direction of the cylindrical coordinates with the center of the semiconductor chip 12 shown in FIG. 1 as the origin. On the first surface of the semiconductor chip 12 also circumferential stress sensors 15, 16 are arranged. That is, these stress sensors 15 and 16 are oriented such that their longitudinal directions are along the circumferential direction of the cylindrical coordinates. These stress sensors 13, 14, 15,
16 is formed by implanting and diffusing an impurity such as boron into a predetermined region on the surface of the semiconductor chip 12 according to a predetermined shape, for example, by an ion implantation technique. Each of these sensors 13, 14, 15, 16 exhibits a pressure-sensitive resistance characteristic, and the resistance value of each sensor changes according to the pressure applied to those sensors.

A rectangular cavity 17 is shown in phantom in FIG.
Are formed on the second surface (lower surface) of the semiconductor chip 12. As shown in FIG. 1 (B), a pedestal 19 having a rectangular cross section in which a communication hole 18 having a circular cross section is formed in the center is arranged so as to cover the cavity 17 from the lower surface of the semiconductor chip 12, and The upper surface is bonded to the second surface of the semiconductor chip 12 by high temperature treatment. The pedestal 19 functions to transmit the pressure to be detected to the cavity 17. When the pressure is transmitted to the cavity 19, the portion of the semiconductor chip 12 located above the cavity 17 forms the diaphragm 20. The stress caused inside the diaphragm 20 is related to the difference between the pressure transmitted by the pedestal 19 and the pressure applied to the first surface of the semiconductor chip 12. Also, pedestal 1
9 and the semiconductor chip 12 are different from each other in the diaphragm 2 due to the difference in compressibility at the time of cooling after the high temperature treatment.
Stress is generated at 0. For example, when the pedestal 19 has a higher compression rate than the semiconductor chip 12, the first
Tension is generated on the surface, which causes a change in static pressure.

In the semiconductor pressure sensor thus constructed, the stress generated inside the semiconductor chip 12 is detected by the stress sensors 13, 14, 15 and 16. The resistance of these sensors varies with the stress applied to each sensor, which is represented by the vector σ described in relation to the axis of the semiconductor pressure sensor. The unit of the stress vector σ is Newton / square meter. That is, the stress caused along the longitudinal direction of the sensors 13 and 14 oriented in the radial direction is called the radial stress σr, and the longitudinal stress of the sensors 15 and 16 is the circumferential stress (tangential line). Also called directional stress)
It is called σc.

Four stress sensors 13, 14, 15, 16
Although not shown, the pressure is measured by an output signal generated when electrically connected in a constant current Wheatstone bridge. The output signal voltage generated by the constant current Wheatstone bridge circuit is given by the following equation.

E = (1/2) iBRπ ₄₄ (σr−σc) (1) where i is the current supplied to the bridge, and the product Rπ ₄₄ is a constant that changes only in relation to the temperature of the semiconductor pressure sensor. is there. In the case of a perfectly pressure-sensitive semiconductor pressure sensor,
If the semiconductor chip 12 and the pedestal 19 are made of different materials, it is possible to prevent the zero shift signal from being generated under a constant static pressure. That is, in this case, since the stress generated on the surface of the semiconductor chip 12 of the diaphragm 20 is uniform and does not relate to the direction, (σr−σc) in the above equation (1) becomes zero, and the output of the bridge Does not occur. However, when the semiconductor chip 12 is not a circle but a square, the cavity 17 of the diaphragm 20 is also a square, and the pedestal 19 with a circular hole is joined to the rectangular parallelepiped, it lacks in axial symmetry. Furthermore, since the chip material is a semiconductor single crystal and the pedestal material is made of a material different from that of the chip, symmetry is also lacking in the z-axis direction, so even if axial symmetry, compressive stress is applied to the diaphragm under static pressure. It works, and the diaphragm is deformed to be convex upward as shown in FIG.

[0008]

In such a conventional semiconductor pressure sensor, since there is no axial symmetry and the semiconductor chip and the pedestal are different materials, the pressure applied to the pressure sensor or the sensitivity of the pressure sensor is low. Because of the change, a false signal, termed the zero shift signal or span shift signal, results. Here, the zero shift signal means a signal generated when the pressure difference applied to both surfaces of the diaphragm constituting the pressure sensor is zero, or a change thereof. Further, the span shift signal means a signal generated by a change in the hardness of the diaphragm forming the pressure sensor and a change in the sensitivity of the stress sensor in response to the pressure difference applied to both sides of the semiconductor chip.

That is, the above equation (1) shows that the stress difference between the radial direction and the circumferential direction directly affects the zero shift signal. Furthermore, it is shown that when such a stress difference exists, the temperature change affecting (Rπ44) also contributes to the zero shift signal. However, the above equation shows that the zero shift signal can be minimized or eliminated by making σr and σc equal. Typically, the stress sensor is oriented parallel or perpendicular to the edges of the square semiconductor chip 12, as shown in FIG. Theoretically, if the sensor is placed in such an orientation, the stresses σr and σc will be equal. However, when the output signal of a pressure sensor having a silicon chip and a pedestal made of glass was observed under different static pressure conditions, it was observed that the stress signal increased in response to static pressure. This is because the diaphragm receives compressive stress due to the difference in compressibility between the tip and pedestal materials due to static pressure, and the diaphragm is deformed in the same way as pressure is applied from the pedestal side. Was found to be the cause. This is similar to the effect of residual strain due to the difference in thermal expansion coefficient between the semiconductor chip and the pedestal. As a method of solving this, there is a method of compensating by using a signal from a sensor that can separately measure static pressure. However, this method is not the best method in terms of cost and reliability because the signal processing is complicated.

Accordingly, it is an object of the present invention to provide an improved semiconductor pressure sensor such that the zero shift signal or span shift signal is minimized.

[0011]

According to the present invention, a pair of radial stress sensors and a pair of circumferential response sensors having pressure sensitive characteristics are formed on one surface and a square shape is formed on the other surface. And a rectangular single crystal semiconductor chip in which the cavity is formed, and a rectangular parallelepiped in which the semiconductor chip is fixed, and a communication hole having a circular cross section which communicates with the square cavity formed in the semiconductor chip is formed in the central portion. A shaped insulating pedestal, formed between the insulating pedestal and the semiconductor chip, made of the same single crystal material as the semiconductor chip, and formed in the cavity formed in the semiconductor chip at the center and the insulating pedestal A semiconductor pressure sensor having a rectangular frame having an opening communicating with each of the communication holes is provided.

Further, according to the present invention, the opening portion of the rectangular frame is configured such that the opening area is small at the central portion in the thickness direction of the rectangular frame and gradually increases toward the upper and lower surfaces. The semiconductor pressure sensor characterized by the above is obtained.

Further, according to the present invention, a pair of radial stress sensors and a pair of circumferential stress sensors having pressure-sensitive characteristics are formed on one surface, and a rectangular cavity is formed on the other surface. Rectangular shaped single crystal semiconductor chip, and a rectangular parallelepiped insulating pedestal in which the semiconductor chip is fixed and a communication hole having a circular cross section which communicates with the rectangular cavity formed in the semiconductor chip is formed in the central portion. And a rectangular frame having a square frame having an opening at the center, which is laminated and arranged on the semiconductor chip on the side opposite to the insulating pedestal, made of the same material as the insulating pedestal. Is obtained.

Further, according to the present invention, the semiconductor pressure sensor can be obtained in which the insulating pedestal is made of glass.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the semiconductor pressure sensor of the present invention will be described below with reference to FIG. FIG. 2 is a side sectional view of the semiconductor pressure sensor of the present invention. In this embodiment, the semiconductor pressure sensor 21 is the conventional semiconductor shown in FIG. 1 except that a square frame 22 is interposed between a semiconductor chip 12 and a pedestal 19 made of a different material. Since the structure is the same as that of the chip 12, corresponding parts are designated by the same reference numerals, and detailed description thereof will be omitted.

The rectangular frame 22 is made of the same material as the semiconductor chip, preferably made of a semiconductor material having the same crystal orientation. The opening portion 23 of the rectangular frame 22 is configured such that the opening area is small in the central portion in the thickness direction of the rectangular frame 22 and gradually increases toward the upper and lower surfaces.

As described above, by interposing the rectangular frame 22 made of the same material as the semiconductor chip 12 and having the same crystallographic direction between the semiconductor chip 12 and the pedestal 19 made of a different material, the semiconductor chip 12 is formed. It is possible to reduce the difference in compressibility between the glass 12 and the glass pedestal 19 during cooling from a high temperature state, and bring (σr−σc) close to zero.

FIG. 3 is a side sectional view of a semiconductor pressure sensor showing still another embodiment of the present invention. In this embodiment, the semiconductor pressure sensor 21 has a rectangular frame 31 made of the same glass material as the pedestal 19 stacked on the semiconductor chip 12 opposite to the glass pedestal 19. Square frame 31
An opening 32 is formed in the center of the.

With such a configuration, the semiconductor chip 12
Rectangular frame 31 made of the same material as the pedestal 19 having a larger elastic modulus than
By disposing and fixing on the first surface side of the semiconductor chip 12, it is possible to reduce or eliminate the amount of strain that deforms on the first surface side in the semiconductor chip 12.

[0020]

According to the present invention described above, since the radial and circumferential stress changes in the diaphragm caused by temperature changes or static pressure changes are approximately equal,
The zero shift signal caused by temperature or pressure changes is very small. In other words, the tension generated in the diaphragm due to the difference in compressibility of different materials due to the static pressure change is eliminated, and the tension caused by the deformation generated from the different materials on the package side is also relaxed by the rectangular frame of the same material provided on the cavity side of the semiconductor chip. Therefore, the span shift becomes very small.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a conventional semiconductor pressure sensor.

FIG. 2 is an immediate sectional view showing an embodiment of the present invention.

FIG. 3 is an immediate sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 11 Semiconductor Pressure Sensor 12 Semiconductor Chip 13 Radial Stress Sensor 14 Radial Stress Sensor 15 Circumferential Stress Sensor 16 Circumferential Stress Sensor 17 Square Cavity 18 Communication Hole 19 Pedestal 20 Diaphragm 21 Semiconductor Pressure Sensor 22 Square Frame 23 Opening 31 Square frame 32 Opening

Claims (4)

[Claims] 1. A rectangular unit having a pair of radial stress sensors and a pair of circumferential stress sensors having pressure-sensitive characteristics on one surface and a rectangular cavity formed on the other surface. The crystalline semiconductor chip and this semiconductor chip are fixed,
A rectangular parallelepiped insulating pedestal in which a communication hole having a circular cross section is formed in the center, which communicates with the rectangular cavity formed in the semiconductor chip, and is inserted between the insulating pedestal and the semiconductor chip. A single frame made of the same single crystal material as that of the chip, and provided with a rectangular frame having a central part having a cavity formed in the semiconductor chip and an opening communicating with the communication hole formed in the insulating pedestal, respectively. Semiconductor pressure sensor. 2. The opening portion of the rectangular frame is configured such that the opening area is small at the central portion in the thickness direction of the rectangular frame and gradually increases toward the upper and lower surfaces. 1. The semiconductor pressure sensor according to 1. 3. A rectangular unit having a pair of radial stress sensors and a pair of circumferential stress sensors having pressure-sensitive characteristics formed on one surface and a rectangular cavity formed on the other surface. The crystalline semiconductor chip and this semiconductor chip are fixed,
A rectangular parallelepiped insulating pedestal in which a communication hole having a circular cross section that communicates with the rectangular cavity formed in this semiconductor chip is formed in the center, and a stacked arrangement on the semiconductor chip on the opposite side of this insulating pedestal. And a square frame made of the same material as the insulating pedestal and having an opening in the center thereof. 4. The semiconductor pressure sensor according to claim 1, wherein the insulating pedestal is made of glass.