JPH0688762A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a pressure resistance and high sensitivity, suppress the volumetric changes in pressure-transmitting medium due to temperature changes, and keep the back-up effect stable while excessive differential pressure is impressed in a peeling-off direction of semiconductor epitaxial layer by making one layer of diaphragm section thin. CONSTITUTION:The title is provided with an epitaxial layer 2 in an upper part of a semiconductor board 1 having a first pressure-transmitting passage 3 and a recessed pressure receiving part 4 which is larger than an inner diameter of the passage 3 on a face part of the layer facing the semiconductor board 1. A recessed pressure receiving part 5 is formed on a face part of the layer 2 on the opposite side of the board 1 to constitute a diaphragm part 6 between the part 4 and the part 5. A pressure-transmitting base 10 in which a second pressure-transmitting passage 9 has a smaller diameter than that of the part 5 is prepared on the face part of the layer 2 of the part 5 side.

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 used in a differential pressure transmitter or the like, and more particularly to a semiconductor pressure sensor having a structure effective in realizing high pressure resistance and ultra-miniaturization.

[0002]

2. Description of the Related Art Conventionally known semiconductor pressure sensors have focused on the excellent elastic characteristics of single crystal silicon itself, and use the single crystal silicon to form a thin film silicon diaphragm (hereinafter referred to as a diaphragm). ) Is formed on the one surface side of the diaphragm, a stress sensor that causes a change in piezoresistive characteristics in response to a stress change that changes in response to a difference in pressure applied to both sides of the diaphragm is arranged. A circular concave portion is formed on the other surface side to realize a thin film in order to enhance the original function of the diaphragm, and constitutes a single crystal semiconductor chip as a whole.

By the way, it has been found that the size of a single crystal semiconductor chip is high in pressure resistance because the flexibility of the diaphragm is increased as the size of the single crystal semiconductor chip is reduced. Therefore, in order to realize the downsizing of the sensor chip, a technique for making the diaphragm thinner is necessary. The structure of the conventional semiconductor pressure sensor and the thin film manufacturing process will be described below with reference to FIGS.

First, as shown in FIG. 3A, a first N type epitaxial layer 1 is formed on a high resistance P type silicon substrate 101.
02, a thermal oxide film 103 and a low resistance N
^{A ++} type epitaxial layer 104 is formed. After that, FIG.
A second layer is formed on the first N type epitaxial layer 102 and a low resistance N ⁺⁺ type epitaxial layer 104 as shown in FIG.
Of the second N-type epitaxial layer 105
A piezoresistive portion 107 as a stress sensor is arranged on the surface of the mold epitaxial layer 105 that functions as a diaphragm, while a hole pattern 108 for etching is formed in the thermal oxide film 103.

Further, as shown in FIG. 3C, the second N
After the surface of the type epitaxial layer 105 is protected by applying wax or the like, the P type silicon substrate 101 is etched by using an anisotropic etching solution, and the N ⁺⁺ type epitaxial layer 1 is formed.
Etching holes 109 reaching 04 are formed. Subsequently, as shown in FIG. 3D, the N ⁺⁺ type epitaxial layer 104 is etched using an isotropic etching solution to form a concave pressure receiving portion 110 and remove the thermal oxide film 103.

Thereafter, the lead wire is taken out through the electrode on the piezoresistive portion 107, while the second N-type epitaxial layer 105 adjacent to the pressure receiving portion 110 serves as a diaphragm. Therefore, the function of this diaphragm is obtained. After joining to the pedestal so as to make the most of it, it is installed in an envelope that outputs the measured pressure appropriately. Therefore, by taking the structure and manufacturing process as described above, the diaphragm 106
Can be thinned.

[0007]

However, in the semiconductor pressure sensor having the above-described structure and manufacturing process, since all the electrodes and the lead wires are installed in the pressure medium having a large volume, pressure fluctuation is not a little involved. Affected, and even if the diaphragm 106 is made thinner,
When the volume of the pressure transmitting medium having a large volume changes due to the temperature change, the changed amount is applied as the diaphragm pressure, which causes a measurement error. This naturally limits the miniaturization of the sensor.

Furthermore, as the diaphragm becomes thinner, it becomes possible to measure the differential pressure with high sensitivity. On the contrary, when the differential pressure is excessive, the risk of the diaphragm breaking tends to increase more and more. In that sense as well, a backup plate for limiting the central displacement of the diaphragm is required to improve the pressure resistance.

Therefore, in the prior art, although the P-type silicon substrate 101 itself functions as a backup plate against the excessive differential pressure applied from the piezoresistive portion side to the sensor chip side, the opposite N It does not have a backup plate function against excessive pressure in the direction of peeling the ⁺⁺ type epitaxial layer.

The present invention has been made in view of the above circumstances, and realizes further thinning of the diaphragm to achieve pressure resistance and high sensitivity, and to minimize the volume change of the pressure transmission medium with respect to the temperature change. It is an object of the present invention to provide a semiconductor pressure sensor that stably maintains a backup effect when an excessive differential pressure is applied in the semiconductor epitaxial layer peeling direction.

[0011]

In order to solve the above problems, the invention according to claim 1 forms a semiconductor epitaxial layer on one surface portion of a single crystal semiconductor substrate, and
A first pressure receiver having a diameter larger than the diameter of the first pressure guiding path, which penetrates through the semiconductor substrate through the first pressure guiding path and which faces the semiconductor substrate. In a semiconductor pressure sensor having a portion, a concave second pressure receiving portion that forms a diaphragm portion with the first pressure receiving portion is formed on a surface portion of the semiconductor epitaxial layer opposite to the semiconductor substrate. In addition, a stress sensor is arranged at a predetermined position of the diaphragm portion on the side of the second pressure receiving portion, and the stress sensor is arranged on the surface portion of the semiconductor epitaxial layer on the side of the second pressure receiving portion from the diameter of the second pressure receiving portion. Is a semiconductor pressure sensor provided with a pressure guiding base having a second pressure guiding path having a small diameter.

The first and second pressure receiving portions provided on both sides of the semiconductor epitaxial layer are based on the measurement sensitivity, the volume change of the pressure transmission medium due to temperature change, and the pressure resistance at the time of excessive differential pressure. The diameter of the concave portion of the pressure receiving portion, the step of the concave portion and the thickness of the diaphragm portion are appropriately selected.

[0013]

Therefore, according to the inventions corresponding to claims 1 and 2, by taking the above-mentioned means, the concave pressure receiving portions are formed on both surfaces of the semiconductor epitaxial layer, so that a further thin film of the diaphragm portion is formed. The pressure sensor can be downsized and the measurement sensitivity of the diaphragm can be significantly improved. Moreover, a concave first pressure receiving portion having a diameter larger than the diameter of the first pressure guiding path is provided on the surface portion of the semiconductor epitaxial layer facing the semiconductor substrate, and in addition to this, the concave first pressure receiving portion is further provided on the side opposite to the semiconductor substrate. Since the concave second pressure receiving portion having a diameter larger than the diameter of the second pressure guiding passage is provided on the surface portion of the semiconductor epitaxial layer, the volume of the pressure transmitting medium is the sum of these pressure guiding passages and the pressure receiving portion. Only volume,
The volume of the pressure transmission medium can be greatly reduced compared to the past,
The amount of influence due to temperature change can be reduced.

Further, the excessive differential pressure applied from the piezoresistive portion side to the sensor chip is such that the semiconductor substrate itself serves as a backup plate, but the excessive differential pressure in the semiconductor epitaxial layer peeling direction is further influenced by the second pressure guiding path. The pressure guiding table with the above structure exerts a backup effect and can greatly improve the pressure resistance performance, and moreover, it is possible to connect the pressure guiding pipes in both positive pressure and negative pressure directions.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view showing a structural example of a semiconductor pressure sensor including a pedestal, and FIG. 2 is a cross-sectional view as seen from an oblique direction cut in a positional relationship in which connection patterning is desired.

In these figures, reference numeral 1 denotes a high resistance P-type silicon substrate, and a low resistance N-type epitaxial layer 2 having a required thickness is provided on the upper surface of the silicon substrate 1.
Further, a first pressure guide path 3 having a diameter that gradually decreases from, for example, a substantially central portion of the lower surface of the silicon substrate 1 to an upper surface portion directly above is provided. This first
The pressure guiding path 3 is formed under the etching process using an anisotropic etching solution.

Then, the surface of the N-type epitaxial layer 2 facing the P-type silicon substrate 1 is etched by using an isotropic etching solution so that the diameter of the upper side of the first pressure guiding path 3 becomes smaller than that of the first pressure guiding path 3. Also has a concave first pressure receiving portion 4 having a sufficiently large diameter, and isotropic similarly on the upper surface side of the N-type epitaxial layer 2 which is a side surface opposite to the first pressure receiving portion 4. A concave second pressure receiving portion 5 having the same size as the first pressure receiving portion 4 is formed by using an etching solution, and these two pressure receiving portions 4, 5 are formed.
The silicon thin film portion sandwiched between the two constitutes a diaphragm portion 6 of thin film silicon.

Further, a piezoresistive portion 7 as a stress sensor is formed on the surface portion of the second pressure receiving portion 5 located on the upper surface portion of the N-type epitaxial layer 2 and relatively near the peripheral portion. , And these piezoresistive parts 7 to N
A wiring patterning 8 is formed so as to extend outward through the die epitaxial layer 2.

On the upper surface of the N-type epitaxial layer 2, a pressure is introduced so that the diaphragm 6 is sandwiched between the P-type silicon substrate 1 and the first pressure guide path 3. Pressure guide 1 having a second pressure guide path 9 having a shape
0 is joined. As a material of the pressure guide table 10,
It is preferable to use a silicon compound such as Pyrex glass, which is easily anodically bonded to the sensor chip.

The ratio of the diameter of the concave pressure receiving portions 4 and 5 formed on the upper and lower surfaces of the N-type epitaxial layer 2, the step of the concave portion and the thickness of the diaphragm portion 6 can be arbitrarily selected. Is selected from the standpoint of obtaining a desired measurement sensitivity, reducing the volume change of the pressure transmission medium due to temperature change, and the like, and further, when the excessive differential pressure is applied, the deformation amount of the diaphragm portion 6 is a concave portion. The size is appropriately selected in consideration of the size that is restricted by the step, that is, the high pressure resistance is secured by closing the small diameter portions of the pressure guiding paths 3 and 9 by the deformation of the diaphragm portion 6.

Then, the P type silicon substrate 1 side is butt-joined so as to cover the insulating pedestal 11 from the pressure guiding table 10 side so as to cover the insulating pedestal 12, and the semiconductor pressure sensor main body is packaged as shown in the figure.

Therefore, according to the semiconductor pressure sensor of the above embodiment, by forming the concave pressure receiving portions 4 and 5 on both surfaces of the N-type epitaxial layer 2, the diaphragm portion 6 having a film thickness of several microns is formed. This can be realized, and further thinning can be achieved as compared with the conventional case. As a result, the semiconductor pressure sensor can be downsized and the measurement sensitivity of the diaphragm part 6 can be significantly improved with the downsizing of the diaphragm part 6.

Moreover, in the conventional pressure sensor, the ratio of the film thickness is larger than the diameter of the diaphragm portion 6, and only the unnecessary self-pressure resistance is provided, and the measurement sensitivity of the diaphragm portion 6 is greatly restricted. Will be. On the other hand, in the pressure sensor of the present invention, a desired measurement sensitivity can be obtained from the diameter of the diaphragm portion 6 and the ratio of the film thickness, and various structural improvements, that is, a small-diameter pressure guiding type having a diaphragm type. By using the diaphragm portion 6 having a diameter larger than the diameters of the passages 3 and 9 and their diameters, the self-pressure resistance performance can be sufficiently enhanced.

On the other hand, with the progress of thinning of the diaphragm portion 6, there is a possibility that the destruction of the sensor chip will increase more and more when the excessive differential pressure is applied. For that purpose, the backup plate becomes indispensable. . In this respect, in the conventional technique, the back-up plate is formed only on one side, and it is not possible to sufficiently deal with the excessive differential pressure. However, in the case of the pressure sensor of the present invention, the pressure guiding paths 3, 3 of small diameter are provided.
9 and the diaphragm portion 6 having a larger diameter than that, while suppressing the excessive pressure, the pressure guide table 10 can serve as a backup plate especially against the excessive differential pressure in the peeling direction of the N-type epitaxial layer 2. The pressure resistance performance can be greatly improved, and moreover, the pressure guiding tubes can be connected in both positive and negative pressure directions, so that the semiconductor pressure sensor of the absolute pressure gauge has flexibility.

Further, since the total volume of the pressure transmitting medium is limited to the total volume of both pressure guiding paths 3 and 9 and the pressure receiving portions 4 and 5 of the diaphragm portion 6, the medium volume is remarkably reduced as compared with the conventional case. This can significantly reduce the change in medium volume due to temperature changes and reduce measurement errors.
As a result, it greatly contributes to the improvement of measurement accuracy.

Further, while the piezoresistive portion 7 is formed at a portion relatively close to the peripheral edge of the diaphragm portion 6, the piezoresistive portion 7 is connected to the external electrode by the connection patterning 8 formed on the N-type epitaxial layer 2. Therefore, it is possible to maintain the airtightness at the time of joining the sensor chip and the pressure guiding table 10 without being affected by the volume change of the pressure transmitting medium. The present invention can be variously modified and implemented without departing from the scope of the invention.

[0027]

As described above, according to the present invention, it is possible to realize a further thin film of the diaphragm, thereby achieving pressure resistance and high sensitivity, and further, the volume of the pressure transmission medium due to temperature change. It is possible to provide a semiconductor pressure sensor that can minimize the change and can stably maintain the backup effect when an excessive differential pressure is applied in the semiconductor epitaxial layer peeling direction.

[Brief description of drawings]

FIG. 1 is a structural sectional view showing an embodiment of a semiconductor pressure sensor according to the present invention.

FIG. 2 is a cross-sectional view of the semiconductor pressure sensor shown in FIG. 1 as seen from an oblique direction cut in a positional relationship such that connection patterning is desired.

FIG. 3 is a diagram illustrating a structure and a manufacturing process of a conventional semiconductor pressure sensor.

[Explanation of symbols]

1 ... P-type silicon substrate, 2 ... N-type epitaxial layer, 3
... 1st pressure guide path, 4 ... 1st pressure receiving part, 5 ... 2nd pressure receiving part, 6 ... Diaphragm part, 7 ... Piezoresistive part, 9
... second pressure guiding path, 10 ... pressure guiding base.

Claims (2)

[Claims] 1. A surface portion of the semiconductor epitaxial layer, which has a semiconductor epitaxial layer formed on one surface portion of the single crystal semiconductor substrate, penetrates the first pressure guiding path in the semiconductor substrate, and faces the semiconductor substrate. In the semiconductor pressure sensor having a concave first pressure receiving portion having a diameter larger than the diameter of the first pressure guiding path, the first portion is formed on the surface portion of the semiconductor epitaxial layer opposite to the semiconductor substrate. A concave second pressure receiving portion that forms a diaphragm portion is formed between the pressure receiving portion and a stress sensor at a predetermined position of the diaphragm portion on the side of the second pressure receiving portion. A semiconductor pressure sensor characterized in that a pressure guiding base having a second pressure guiding passage having a diameter smaller than that of the second pressure receiving portion is provided on a surface portion of the semiconductor epitaxial layer on the pressure receiving portion side. . 2. The first and second pressure receiving portions provided on both sides of the semiconductor epitaxial layer are based on the measurement sensitivity, the volume change of the pressure transmission medium due to temperature change, the pressure resistance at the time of excessive differential pressure, and the like. The semiconductor pressure sensor according to claim 1, wherein the diameter of the concave portion of the pressure receiving portion, the step of the concave portion, and the thickness of the diaphragm portion are appropriately selected.