JPH0513783A - Integrated pressure sensor - Google Patents

Abstract

PURPOSE:To provide an integrated pressure sensor wherein a stylus-pressure stress is hardly propagated to a piezoresistance layer by means of a new structure. CONSTITUTION:A thin diaphragm 2 is formed in the central part of a square silicon chip 1. Piezoresistance layers 3a, 3b, 3c, 3d by an impurity diffusion operation are formed on the diaphragm 2. A signal processing circuit provided with a thin-film resistor for adjustment use is formed in the peripheral part of the silicon chip 1. Two each of pads 6, for probing use, which are used to adjust the resistance value of the thin-film resistor for adjustment use are arranged at four corners of the silicon chip 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated pressure sensor in which a signal processing circuit is integrated.

[0002]

2. Description of the Related Art In an integrated pressure sensor in which a signal processing circuit is integrated, as shown in FIG.
A thin diaphragm 21 is formed in a part of 0, and a piezoresistive layer 22 is arranged in the diaphragm portion.
Further, a signal processing circuit is formed in the peripheral portion of the silicon chip 20, and the signal processing circuit is provided with an adjusting thin film resistor. Then, the output of the sensor is adjusted by adjusting the resistance value of the adjusting thin-film resistor while the prober is pressed against the probing pad (electrode) 23.

At the time of trimming the thin film resistor for adjustment,
Probing stylus stress propagates to the piezoresistive layer 22,
The sensor output fluctuates greatly due to the influence of the stress. Therefore, in Japanese Patent Laid-Open No. 1-236659, a groove is formed between the diaphragm and the probing pad 23, and this groove reduces the propagation of the surface stress generated during probing to the diaphragm.

[0004]

However, when this structure is adopted, the number of steps for forming the groove is increased, and at the same time,
Since the groove is provided, the chip area becomes large.

An object of the present invention is to provide an integrated pressure sensor having a novel structure in which stylus stress is less likely to propagate to the piezoresistive layer.

[0006]

According to a first aspect of the present invention, a thin diaphragm is formed in a central portion of a rectangular silicon chip, a piezoresistive layer is arranged on the diaphragm, and a peripheral portion of the silicon chip is used for adjustment. In an integrated pressure sensor formed with a signal processing circuit having a thin film resistor,
The gist is an integrated pressure sensor in which probing pads for adjusting the resistance value of the adjusting thin-film resistor are arranged only at the corners of the silicon chip.

According to a second aspect of the present invention, a thin diaphragm is formed in a central portion of a rectangular silicon chip, a piezoresistive layer is arranged on the diaphragm, and a signal having an adjusting thin film resistor in the peripheral portion of the silicon chip. In an integrated pressure sensor having a processing circuit, a probing pad for adjusting the resistance value of the adjusting thin film resistor,
The gist is an integrated pressure sensor arranged on a scribe line in the minor axis direction of the piezoresistive layer on a silicon wafer to be a silicon chip.

[0008]

In the first aspect of the invention, stylus pressure is applied to the probing pad during probing, but since the probing pad is arranged only at the corner of the silicon chip, the stress propagates to the piezoresistive layer. Hard to do. As a result, the sensor has uniform characteristics.

According to the second aspect of the present invention, stylus pressure is applied to the probing pad during probing, but the probing pad is arranged on the scribe line in the minor axis direction of the piezoresistive layer on the silicon wafer. The stress is less likely to propagate to the resistance layer. As a result, the sensor has uniform characteristics.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a perspective view of the integrated pressure sensor of this embodiment, and FIG. 1 is a plan view of the integrated pressure sensor. A thin diaphragm 2 is formed in the central portion of a rectangular silicon chip 1, and the diaphragm 2 has a square shape. On the diaphragm 2, four piezoresistive layers 3a, 3b, 3c and 3d formed by impurity diffusion are arranged. A Wheatstone bridge circuit is formed by the piezoresistive layers 3a, 3b, 3c and 3d.

Further, as shown in FIG. 2, the silicon chip 1
A signal processing circuit 4 is integrated and formed in the peripheral part of the signal processing circuit 4. The signal processing circuit 4 has an adjusting thin film resistor 5.
The signal processing circuit 4 includes piezoresistive layers 3a, 3b, 3c and 3d.
It processes (amplifies) the resulting signal.

Also, as shown in FIG. 1, a silicon chip 1
2 probing pads 6 in each corner
Are arranged. The probing pad 6 is electrically connected to the signal processing circuit 4, and the piezoresistive layer 3 is provided.
It is for taking out signals generated from a, 3b, 3c and 3d to the outside. That is, the extraction pad (electrode) for adjusting the resistance value of the adjustment thin film resistor 5 by probing (contacting) with the prober 7 shown in FIG.
Is.

By doing so, the stylus stress generated during probing causes the piezoresistive layers 3a, 3b, 3
Propagation to c and 3d is prevented, and an output adjustment error due to stylus pressure is reduced as compared with the sensor shown in FIG.

The FEM analysis results for the above are shown in FIGS.
Shown in. In this analysis, as shown in FIG. 3, the piezoresistive layers 3a and 3b are arranged in the central part of the diaphragm 2 in the silicon chip 1 on the (110) plane, and the piezoresistive layers 3c and 3d are arranged in the peripheral part. , C, D and E points are applied. Piezoresistive layers 3a and 3b in the central portion
Stress σ _r-centet generated in the radial direction (r direction) and stress σ generated in the r direction of the peripheral piezoresistive layers 3c and 3d.
_{The r-side} stress difference (= σ _{r-centet −σ r-side} ) is the result shown in FIG. From the results of points A, B, and C, it is found that the piezo portion generated stress difference (= σ _{r-centet −σ r-side} ) is greater when the point where the force is applied is farther from the piezoresistive layers 3a, 3b, 3c, and 3d. It turns out that it becomes smaller. Further, from the results of the points C and E, the piezo portion generated stress difference is smaller at the point E where a force is applied in the direction of the piezoresistive coefficient 0 (t direction). Further, at point D, it is considered that the above-mentioned two effects are overlapped with each other, resulting in the smallest piezo portion generated stress difference.

Therefore, since the output adjustment error is proportional to the stress difference generated in the gauge portion, the output adjustment error is minimized when the probing pads 6 are arranged at the four corners of the silicon chip 1.

On the (110) plane, the piezoresistive force is more exerted in the direction (t direction) perpendicular to the radial direction than in the radial direction (r direction). It is considered that the stress that affects the piezo portion is reduced due to the crystal orientation dependence of the coefficient. Further, it is considered that the stress applied to the piezo portion is reduced when the stress is propagated on the silicon surface when the point where the force is applied is separated from the piezo portion by the probing.

As described above, in this embodiment, the thin diaphragm 2 is formed in the central portion of the rectangular silicon chip 1, and the piezoresistive layers 3a, 3b, 3c, 3 are formed on the diaphragm 2.
The signal processing circuit 4 having the adjusting thin film resistor 5 was formed in the peripheral portion of the silicon chip 1 while the d was arranged.
Then, the probing pad 6 for adjusting the resistance value of the adjusting thin-film resistor 5 was arranged only at the corner of the silicon chip 1. Therefore, stylus pressure is applied to the probing pad 6 at the time of probing, but since the probing pad 6 is arranged only at the corner of the silicon chip 1, the piezoresistive layers 3a, 3b, 3c, 3d are not affected. It becomes difficult for stress to propagate. As a result, unlike a conventional sensor, a groove having no groove is provided between the diaphragm and the probing pad, and a stylus stress is less likely to propagate to the piezoresistive layer with a new structure, so that the sensor has uniform characteristics. You can

As an application example of this embodiment, (10
Also in the (0) plane, even if the probing pad 6 is arranged only at the corner of the chip in the direction of the piezoresistance coefficient of 0,
The same effect as described above can be obtained. (Second Embodiment) Next, only the difference between the second embodiment and the first embodiment will be described.

As shown in FIG. 5, the piezoresistive layers 3a, 3b, 3 at the scribe lines 9 orthogonal to each other in the silicon wafer 8 which becomes the silicon chip 1 on the (110) plane.
Probing pads 6 are arranged on scribe lines 9a in the minor axis directions of c and 3d.

As described above, in this embodiment, the probing pad 6 for adjusting the resistance value of the adjusting thin film resistor 5 is used.
Is arranged on the scribe line 9a in the short axis direction of the piezoresistive layers 3a, 3b, 3c, 3d on the silicon wafer 8 to be the silicon chip 1, so that stylus pressure is applied to the probing pad 6 during probing. , The probing pad 6 is a piezoresistive layer 3a on the silicon wafer 8,
The piezoresistive layers 3a, 3b, 3c, 3b, 3c, 3d are arranged on the scribe line 9a in the minor axis direction.
It becomes difficult for the stress to propagate to 3d. As a result, the sensor has uniform characteristics.

[0022]

As described in detail above, according to the present invention, it is possible to provide an integrated pressure sensor having a novel structure in which stylus pressure stress is less likely to propagate to the piezoresistive layer.

[Brief description of drawings]

FIG. 1 is a plan view of a sensor according to a first embodiment.

FIG. 2 is a perspective view of a sensor.

FIG. 3 is a plan view of a sensor for explaining measurement points.

FIG. 4 is a diagram showing a difference in stress generated at each measurement point.

FIG. 5 is a plan view of the sensor of the second embodiment.

FIG. 6 is a plan view of a conventional integrated pressure sensor.

[Explanation of symbols]

1 Silicon chip 2 diaphragm 3a, 3b, 3c, 3d piezoresistive layer 4 Signal processing circuit 5 Thin film resistor for adjustment 6 Probing pad 8 Silicon wafer 9a scribe line

Claims (2)

[Claims] 1. A rectangular silicon chip is formed with a thin diaphragm in a central portion thereof, a piezoresistive layer is arranged on the diaphragm, and a signal processing circuit having a thin film resistor for adjustment is formed in the peripheral portion of the silicon chip. In the integrated pressure sensor described above, a probing pad for adjusting the resistance value of the adjusting thin film resistor is arranged only at a corner of the silicon chip. 2. A thin diaphragm is formed in the central portion of a rectangular silicon chip, a piezoresistive layer is arranged on the diaphragm, and a signal processing circuit having a thin film resistor for adjustment is formed in the peripheral portion of the silicon chip. In the integrated pressure sensor, the probing pad for adjusting the resistance value of the adjusting thin film resistor is arranged on the scribe line in the minor axis direction of the piezoresistive layer on the silicon wafer that becomes the silicon chip. A featured integrated pressure sensor.