JPH075060A - Semiconductor pressure sensor - Google Patents

Abstract

(57) [Summary] [Purpose] Pressure can be detected accurately under conditions where vibrations occur, and it does not cost much. [Structure] A diaphragm 21 is formed by recessing a lower surface (corresponding to one surface side) of a semiconductor substrate 20, and a gauge resistor 2 is provided on an upper surface side (corresponding to the other surface side) of the diaphragm 21.
2 is provided, the lower surface side of the diaphragm 21 is flat, and a recess 24 is formed on the upper surface side of the diaphragm 21 leaving a continuous protruding portion 23. The gauge resistance 22 is formed in a direction corresponding to the crystal orientation of the semiconductor substrate 20.

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 for automobiles, industrial measurement and the like.

[0002]

2. Description of the Related Art Various proposals have been made to improve the pressure detection sensitivity of conventional semiconductor pressure sensors. Generally, in order to increase the pressure detection sensitivity of the semiconductor pressure sensor, it is necessary to reduce the thickness of the diaphragm. However, if the diaphragm thickness is simply reduced,
As shown in FIG. 1, the linearity of the sensor output with respect to the pressure deteriorates. This is because when the diaphragm is made thin, the influence of the balloon effect becomes large, and as shown in FIG. 11, the sensor output is saturated with an increase in pressure and the nonlinearity becomes remarkable.

In order to improve such non-linearity, a structure in which a part of the diaphragm is thickened (referred to as a boss structure) has been conventionally used. In a semiconductor pressure sensor having a normal structure, for example, as shown in FIG. 12A, a thin portion formed by forming a recess 11 from a lower surface of a sensor chip 10 made of a semiconductor serves as a diaphragm 12, but the sensor having the boss structure described above. In the chip, as shown in FIG. 12B, a thick boss portion 13 is provided on a part of the lower surface side of the diaphragm 12, and a gauge resistance for pressure detection (due to pressure) is provided on the upper surface of the diaphragm 12. Detecting distortion change) is provided. According to this type of semiconductor pressure sensor, since the boss structure suppresses the expansion of the diaphragm 12 due to the pressure, it is said that the balloon effect is reduced and the nonlinearity can be improved.

[0004]

However, in the semiconductor pressure sensor of the type described above, since the boss portion 13 has a certain weight, the boss portion 13 becomes a weight and operates as an acceleration sensor under the condition where vibration or acceleration is applied to the sensor. However, there is a problem in that the vibration or the like may be detected as noise of pressure measurement.

Further, as shown in FIG. 13, the conventional semiconductor pressure sensor is used by fixing the sensor chip 10 on a pedestal 14 made of glass or the like. In that case, the upper surface of the pedestal 14 is etched to provide a margin 15 for preventing the boss portion 13 and the pedestal 14 from interfering with each other with respect to the movement of the boss portion 13 (mainly in the diaphragm thickness direction). There is a problem that it is necessary to process and form the dent, and the number of processing steps increases and the cost is high. In FIG. 13, reference numeral 16 is a hole that communicates the outside of the sensor with the space surrounded by the upper surface of the pedestal 14 and the lower surface of the chip 10. A measurement medium is introduced into the space through this hole 16 or the space is opened to the atmosphere.

Incidentally, the semiconductor pressure sensor has a detection characteristic such as a pressure range according to the purpose of use. The conventional pressure sensor corresponds to various pressure ranges by changing the setting of the diaphragm thickness, and as a matter of course, the diaphragm thickness is reduced as the pressure range to be measured becomes smaller. That is, in the conventional semiconductor pressure sensor, the parameter to be controlled corresponding to the pressure range is only the diaphragm thickness.

However, a semiconductor (n-type silicon or p-type silicon) layer of another species (second type) is epitaxially grown on a certain type (first type) semiconductor (for example, p-type silicon or n-type silicon) plate. When a diaphragm is formed by chemical etching using the wafers laminated by, the first type semiconductor plate is removed to form a recess, and the second type semiconductor layer becomes a diaphragm. Semiconductor substrate (material wafer) having a second type (n-type silicon or p-type silicon) layer of thickness
Need to be prepared, and there is a problem in terms of cost (increasing cost) and process control (the line must correspond to various wafers).

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a semiconductor pressure sensor which can accurately detect pressure under conditions where vibration or the like occurs and which is inexpensive. Is to provide. Also,
It is an object of the present invention to provide a semiconductor pressure sensor that does not require preparation of semiconductor substrates having various layer thicknesses for each pressure detection characteristic such as a pressure range.

[0009]

The present invention has the following constitution in order to achieve the above object. According to the present invention, a diaphragm is formed by recessing one side of a semiconductor substrate, and
In a semiconductor pressure sensor in which a gauge resistance is provided on the other surface side of the diaphragm, the one surface side of the diaphragm is flat, and the other surface side of the diaphragm is continuous in a direction corresponding to a crystal orientation of a semiconductor substrate. The semiconductor pressure sensor is characterized in that a recess is formed while leaving the protruding portion, and a gauge resistance is formed in the protruding portion.

Further, according to the present invention, in a semiconductor pressure sensor in which a diaphragm is formed by recessing one side of a semiconductor substrate, and a gauge resistor is provided on the other side of the diaphragm, the one side of the diaphragm is provided. The side is flat, a recess is formed on the other surface side of the diaphragm leaving a continuous protruding portion in a direction corresponding to the crystal orientation of the semiconductor substrate, and the protruding portion corresponding to the pressure detection characteristic is formed. Ratio W ₀ / W ₁ of the width W ₀ of the recess and the width W ₁ of the recess, or the ratio t ₀ / t ₁ of the thickness t _{0 of the} protrusion and the thickness t ₁ of the recess.
And a gauge resistance is formed on the protruding portion, which is a semiconductor pressure sensor.

[0011]

In the semiconductor pressure sensor of the present invention, since one side of the diaphragm is flat, the boss portion is not provided unlike the prior art. Therefore, in a situation where vibration is applied, the acceleration sensor does not operate, and the vibration does not become noise.

Further, a recess is formed on the other surface side of the diaphragm, leaving a continuous protrusion in a direction corresponding to the crystal orientation of the semiconductor substrate, and a gauge resistance is formed on the protrusion. Therefore, even if the recess is formed, the portion having the gauge resistance is not thinned, so that the balloon effect is reduced and the non-linearity of the sensor output with respect to the pressure is prevented from being deteriorated.

Further, the ratio W ₀ / the width W _{0 of the} protrusion and the width W ₁ of the recess is determined according to the pressure detection characteristic, for example, the pressure range.
The diaphragm is formed with W ₁ , or the ratio t ₀ / t ₁ of the thickness t _{0 of the} protrusion and the thickness t ₁ of the recess. Therefore, a semiconductor substrate in which a conductive semiconductor (for example, p-type silicon) plate of a certain type (first type) and a conductive semiconductor (for example, n-type silicon) of another type (second type) are stacked by epitaxial growth or the like. When a (material wafer) is used, the first-conductivity-type semiconductor plate is removed by chemical etching, and the diaphragm is formed by the second-conductivity-type layer. It is not necessary to prepare a semiconductor substrate having a second conductivity type layer having various thicknesses. Therefore, it is possible to manufacture semiconductor pressure sensors corresponding to various pressure detection characteristics without preparing semiconductor substrates (material wafers) having various layer thicknesses. Further, when a semiconductor substrate made of a single conductivity type semiconductor is used and a diaphragm is formed by denting a predetermined depth from one surface, it is necessary to prepare semiconductor substrates having various dent depths. Absent.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. The embodiment of the present invention is the chip-shaped semiconductor pressure sensor shown in FIG. FIG. 1A is a plan configuration diagram of the chip, and FIG. 1B is a side sectional configuration diagram of the chip taken along the line I-I of FIG.

As shown in FIG. 1, in the semiconductor pressure sensor of the embodiment, the diaphragm 21 is formed by denting the lower surface side (corresponding to one surface side) of the semiconductor substrate 20, and the upper surface side of the diaphragm 21 ( Gauge resistance 2 on the other side)
2 is provided, the lower surface side of the diaphragm 21 is flat, and a recess 24 is formed on the upper surface side of the diaphragm 21 leaving a continuous protruding portion 23. The gauge resistance 22 is formed in a direction corresponding to the crystal orientation of the semiconductor substrate 20.

The semiconductor substrate 20 of the embodiment is shown in FIG.
As shown in FIG. 3, a diaphragm forming portion 26 made of an n-type silicon layer is laminated on the base portion 25 of the p-type silicon layer, and this p-type silicon substrate is formed by etching from below to the lower limit of the diaphragm forming portion 26. It is a thing.
Further, the lower surface side of the diaphragm 21 is formed flat by this etching, and a thick portion such as the boss portion of the conventional semiconductor pressure sensor is not formed.

The semiconductor substrate 20 of the embodiment is composed of a wafer whose crystal orientation is (110). In the case of this semiconductor substrate 20, two rectangular recesses 24 (indicated by diagonal lines in FIG. 1) are formed on the upper surface of the substrate 20 by etching, leaving the peripheral portion 20a of the substrate 20,
In addition, between these two recesses 24, a protrusion 23 that is substantially linearly continuous is formed along the <110> direction.

Gauge resistors 22 are arranged on the upper surface side of the protrusion 23 along the <110> direction, and at both ends of the protrusion 23 near the substrate peripheral portion 20a. One gauge resistor 22 is arranged, and two gauge resistors 22 are arranged in parallel at the center of the protrusion 23.

As described above, in this embodiment, the protrusion 23
Forming direction and the disposing direction of the gauge resistor 22 are the same.
However, the present invention is not limited to this, and if the gauge resistance is arranged in a direction detectable with respect to the crystal orientation of the wafer, it may be arranged in other states (other places, other numbers). it can. Regarding the gauge resistance 22 and the crystal orientation, there is, for example, Fujikura Electric Wire Technical Report No. 66 (issued in September 1983). Further, a semiconductor substrate in which a p-type layer is laminated on an n-type substrate, or a substrate consisting of n-type or p-type is also within the scope of the present invention.

Further, in the structure according to the present invention as in the embodiment, the pressure sensitivity is increased without deteriorating the non-linearity. This is for the following reason. FIG. 2 is an enlarged view of a cross section of the protruding portion 23 in the longitudinal direction around the gauge resistor 22.

As shown in FIG. 2, the upper surface of the substrate (gauge resistance 2
By etching the second formation side), a recess 24 is formed in a portion other than the protrusion 23 to form the thin film portion 21a. When pressure is applied, the diaphragm 21 bends,
The neutral surface of the diaphragm 21 (the surface that does not expand or contract during bending) is substantially indicated by the symbol e in FIG.
In this case, the neutral surface e moves below the neutral surface f of the diaphragm 21 in the original state where the thin film portion 21a is not formed, and becomes far from the gauge resistance 22. This is similar to the fact that the fulcrum of the lever has just moved, so that the stress on the gauge resistance 22 when the diaphragm 21 bends naturally increases.

That is, the sensitivity of the sensor can be increased without reducing the thickness of the diaphragm 21 in the portion where the gauge resistor 22 is present. Further, since the thickness of the diaphragm 21 of the protrusion 23 having the gauge resistance 22 is thick and not thin,
The stretch of that part is small, the balloon effect etc. are hard to occur,
Non-linearity does not deteriorate. Further, when the sensor chip of this embodiment is mounted and fixed on the pedestal made of glass, it is not necessary to etch the pedestal 14 unlike the sensor chip 10 shown in FIG. 13, and the manufacturing cost is reduced. To do.

Next, an example of the manufacturing process of the sensor chip of the embodiment will be described. 3 (a) to 3 (e) show a chip at each stage of the manufacturing process, and FIG. 4 shows an explanatory view thereof. First, as shown in FIG. 3A, the starting wafer is a p-type semiconductor wafer 28. In this case, the crystal orientation is (110).
After that, the n-type semiconductor layer 28a is formed on the upper surface of the wafer 28 by epitaxial growth or the like.

Next, the wafer 28 is thermally oxidized to form a SiO ₂ film 29 on the upper and lower surfaces. After that, the SiO ₂ film 29 at the location where the gauge resistor 22 is to be formed is selectively removed by etching using a photomask and a photoresist, and a window is formed. Diffusion is performed after the window is exposed, and the silicon at the window opening is changed from n-type to p ⁺ . The diffusion layer changed to p ⁺ becomes the gauge resistance 22. The cross-sectional structure of the wafer with the gauge resistor 22 thus formed is as shown in FIG. 3B (cross-sectional view taken along the line III-III of FIG. 4A), and the planar structure is shown in FIG. As shown.

Then, as shown in FIG. 3C, the wafer 28 is etched from the lower surface to the upper surface to form the diaphragm 21. In this case, either a method of etching the p-type semiconductor by etching stop and leaving the n-type semiconductor layer 28a, or a method of determining the thickness of the diaphragm 21 by the etching time of the p-type semiconductor may be used.

Next, an electrode 30 made of aluminum or the like for the wafer 28 is formed. The cross-sectional structure of the wafer 28 with the electrodes 30 formed is shown in FIG. 3D (IV- in FIG. 4B).
As shown in FIG. 4B, the plan configuration is as shown in FIG. 4B.

Next, the wafer 28 is etched from the upper surface to leave the protrusions 23 and the thin film portion 21 of the diaphragm 21.
a is formed. The semiconductor chip of the embodiment is manufactured as described above.

Next, in the semiconductor pressure sensor of the embodiment,
End W ₀ of the protrusion 23, two recessed width W ₁ and the projecting portion 23 the thickness t ₀ recess 24 dimensioned thickness t ₁ for the will be described. As in the chip-shaped semiconductor pressure sensor shown in FIG. 5, the widths W ₀ and W ₁ and the thicknesses t ₀ and t ₁ are defined. 5A is a sectional view taken along line VV of FIG. 5B of the chip,
(B) is a plan view of the chip.

In the semiconductor pressure sensor in this case,
The diaphragm 21 has a ratio W of the width W ₀ of the protrusion 23 and the width of the two recesses 24 (width between inner surfaces of the two recesses) W ₁ according to the pressure range required for the semiconductor sensor. ₀ / W ₁ or a ratio t ₀ / t ₁ of the thickness t ₀ of the protrusion 23 and the thickness t ₁ of the recess 24, and the gauge resistance 22 is formed in the protrusion 23. Are formed.
The manufacturing process of the semiconductor pressure sensor chip in this case is performed in the same manner as in FIG. 3, and only the setting of the recess 24 is changed, and therefore the description thereof is omitted.

Thus, the ratio of the widths W ₀ and W ₁ W ₀ /
The sensitivity to pressure can be changed by changing W ₁ or the ratio t ₀ / t ₁ of the thicknesses t ₀ and t ₁ . This makes it possible to construct a pressure sensor according to the required pressure range (in a normal semiconductor pressure sensor, the ratio W ₀ / W ₁ = 1 of the widths W ₀ and W _{1 and} the thickness t ₀ ). The ratio of t ₁ is t ₀ / t ₁ = 1). That is, it is possible to configure a pressure sensor corresponding to various pressure ranges without changing the specifications of the wafer that is the material and changing the manufacturing conditions to almost the same.

[0031] Here, for explaining the principle of dimensioning the above, and those provided with a recess in the chip upper surface, and the width W ₀ and W ratio W ₀ / W ₁ or the thickness t ₀ of ₁ ratio of t ₁ t
_A description will be given of a survey example of semiconductor chips having various configurations by changing ₀ / t ₁ . First, the case of changing the ratio W ₀ / W ₁ of the width W ₀ and W _1.

In this case, as shown in FIGS. 6 (a) to 6 (c) (in this figure, a configuration of crossing at 1/2 of the <110> direction is shown), a model of a semiconductor chip having a (110) orientation: model 1 , Model 2 and model 3 were used. The model 1 is one in which the diaphragm is not provided with a recess from above, the model 2 is provided with a recess 24 and is provided with an elongated continuous projection 23 in the center of the diaphragm 21, and the model 3 is in the center of the diaphragm 21. A relatively wide protrusion 23 is provided.

Further, FIGS. 7A and 7B show a plan view and a side view of a 1/4 model obtained by further dividing the semiconductor chip from the center in the width direction, and FIG.
FIG. 7 shows a model diaphragm. As shown in FIG. 7, a half width of the protrusion from the center line is A, a half width of the diaphragm is B, a depth of the depression is C, and a protrusion is C. The data examples of the sizes A to D of the models 1 to 3 and the thicknesses D to C where the thickness of the cylindrical portion is D and the thickness of the thin film portion of the diaphragm is D to C are If the distance from the edge to the center of the chip is set to 1, the ratio is as shown in FIG.

With respect to these models 1 to 3, simulation was carried out on bending stress when pressure was applied using the finite element method. The result is shown in FIG. Figure 9
Shows the strain distribution in the longitudinal direction of the protrusion from the chip center, that is, in the <110> direction of the chip of FIG. 7, detected from the chip edge to the chip center.

From FIGS. 9A and 9B, in any of the models 1 to 3, the maximum tensile strain is generated near the point where the periphery of the chip changes to the diaphragm (diaphragm edge, 1/2 point from the chip edge). Model 2 and model 3 in which the above-mentioned dent is formed from model 1 in which no dent is formed
Is more distorted. This shows that if a recess is provided in the upper part of the diaphragm, the strain increases, the pressure detection sensitivity increases, and it is possible to detect pressure in a low range. Further, comparing model 2 and model 3, the distortion of model 2 is large. This means that if the width W ₁ of the recess in the upper part of the diaphragm is set to be larger or the width W _{0 of the} protrusion is set to be smaller, the strain becomes larger, the pressure detection sensitivity becomes higher, and the pressure detection sensitivity becomes higher. It shows that the range can be lowered further.

Furthermore, the case of changing the ratio t ₀ / t ₁ of the thickness t ₀ and t _1. In this case, the thickness D-C of the thin film portion shown in FIG. 7 is changed, and the models 2 and 5 shown in FIG. 8 have different thicknesses D-C. FIG. 10 shows the distortion detection results of all models.

From FIG. 10, the strain is larger in the models 4 and 5 than in the model 2, and therefore, the detection sensitivity is increased by making the recess on the upper portion of the diaphragm deeper and making the thin film portion of the diaphragm thinner. It shows that the detection range becomes low. In the above-mentioned embodiment, the diaphragm having a square planar shape is taken as an example, but a diaphragm having a round shape or other shapes can also obtain the effect within the scope of the present invention.

[0038]

As described above, according to the present invention, the pressure can be accurately detected under the condition that vibration or the like occurs, and the cost can be reduced because the pedestal need not be processed. Further, it is not necessary to prepare semiconductor substrates having various layer thicknesses for each measurement range. Further, even if only one type of material wafer is used, it is possible to configure pressure sensors having various pressure detection characteristics without changing manufacturing conditions. Thereby, the process control is easy and the yield is good. Further, since it is sufficient to purchase one type of material, the cost can be reduced. Also,
If necessary, chips with different pressure ranges can be obtained in the same wafer under the same manufacturing conditions.

[Brief description of drawings]

1A and 1B are a plan view and a side sectional view of a semiconductor pressure sensor chip according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a main part of the sensor chip of FIG.

3A to 3E are cross-sectional views showing a manufacturing process of a semiconductor pressure sensor.

4A and 4B are plan views illustrating a manufacturing process.

5 (a) and 5 (b) are side sectional views for explaining the dimension setting of the semiconductor pressure sensor chip of the embodiment of the present invention,
It is a top view.

6 (a) to 6 (c) are model explanatory views of a semiconductor pressure sensor chip for explaining the principle of the present invention.

7 (a) to 7 (c) are size explanatory diagrams of each part of each model of the semiconductor pressure sensor chip for explaining the principle of the present invention.

FIG. 8 is a size explanatory diagram of each part of each model of the semiconductor pressure sensor chip for explaining the principle of the present invention.

FIG. 9 is an explanatory diagram of an example of measurement results of model distortions.

FIG. 10 is an explanatory diagram of an example of each model distortion measurement result.

FIG. 11 is an example of a pressure detection result of a conventional sensor.

12A and 12B are examples of a conventional pressure sensor chip having a normal structure and a pressure sensor chip having a boss.

FIG. 13 is an example of a conventional pressure sensor chip mounted on a pedestal.

[Explanation of symbols]

 20 Semiconductor Substrate 21 Diaphragm 22 Gauge Resistance 23 Projection 24 Depression

Claims (2)

[Claims] 1. A semiconductor pressure sensor in which a diaphragm is formed by denting one side of a semiconductor substrate, and a gauge resistor is provided on the other side of the diaphragm, wherein the one side of the diaphragm is flat. And a recess is formed on the other surface side of the diaphragm leaving a continuous protrusion in a direction corresponding to the crystal orientation of the semiconductor substrate, and the protrusion has a gauge resistance. Semiconductor pressure sensor. 2. A semiconductor pressure sensor in which a diaphragm is formed by denting one side of a semiconductor substrate, and a gauge resistor is provided on the other side of the diaphragm, wherein the one side of the diaphragm is flat. And a recess W is formed on the other surface side of the diaphragm leaving a continuous protrusion in a direction corresponding to the crystal orientation of the semiconductor substrate, and the width W _{0 of the} protrusion corresponding to the pressure detection characteristic.
And the width W ₁ of the recess is W ₀ / W ₁ , or the ratio t ₀ / t ₁ of the thickness t _{0 of the} protrusion and the thickness t ₁ of the recess is formed to form a diaphragm, A semiconductor pressure sensor characterized in that a gauge resistance is formed on the protrusion.