JPH09304206A - Semiconductor pressure transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor pressure transducer which minimizes a zero shaft and its irregularity due to a temperature and to a static pressure. SOLUTION: A square diaphragm 3 is formed in the center of a square semiconductor chip 2 so as to be tilted at about 45 deg. with reference to the semiconductor chip 2. The semiconductor chip 2 is anodically bonded to a pedestal 4. The whole rear of a thick part 2a at the semiconductor chip 2 is not bonded to the pedestal 4, every corner part is separated from the pedestal 4 by forming a step part 10, and a non-bonded part 13 is formed. The size of the non-bonded part 13 is formed in such a way that a stress σr, in the direction of diagonal lines of the semiconductor chip 2 (a direction perpendicular to sides of the diaphragm), which is generated in diffusion resistances 6a to 6d is equal to a stress σθ in a direction perpendicular to the diagonal lines of the chip (a direction parallel to the sides of the diaphragm).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure transducer for detecting a differential pressure or a pressure, and more particularly to a polygonal semiconductor chip having a polygonal diaphragm formed so that its diagonal line is orthogonal to the diagonal line of the semiconductor chip. The present invention relates to a semiconductor pressure converter.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor pressure converter for detecting a differential pressure or pressure, one using a Si (silicon) semiconductor diaphragm is known. This Si diaphragm type semiconductor pressure transducer forms a gauge (diffusion resistance) acting as a piezoresistive region on the surface of a substrate made of a semiconductor crystal by an impurity diffusion or ion implantation technique, and also forms a lead by vapor deposition of Al or the like. Then
By removing a part of the back surface by etching, a thin portion having a thickness of about 20 μm to 60 μm, that is, a diaphragm is formed. When measuring the differential pressure or liquid level, the high pressure side and the low pressure side are applied to the front and back sides of the diaphragm respectively, and the stress generated in the diaphragm changes depending on the pressure difference, so the resistance of the diffusion resistance The value changes due to the stress generated in the diaphragm, the output voltage accompanying the resistance change at this time is detected, and the differential pressure or the pressure is measured.

As a semiconductor chip, a circular chip having a circular diaphragm was originally generally used.
Recently, it is possible to easily obtain a plurality of square chips by cutting a crystal wafer, and therefore, a square one having a circular diaphragm (eg, JP-A-59-11).
No. 4874) and a square chip having a square diaphragm are becoming common. In particular, when the shape of the diaphragm is square, side etching does not occur when etching the square recessed portion on the back surface side of the chip, so dimension control is easy, and anisotropic etching that can be downsized should be performed. You can

10 and 11 are a plan view and a sectional view showing a conventional example of a semiconductor pressure converter. In this semiconductor pressure converter 1, a square diaphragm 3 is formed in the center of a square semiconductor chip 2 so that its diagonal lines a, a are orthogonal to the diagonal lines b, b of the semiconductor chip.
Is anodically bonded to the base 4. For this reason, the diaphragm 3 is formed with an inclination of 45 ° with respect to the semiconductor chip 2. The semiconductor chip 2 is made of p-type single crystal Si having a crystal plane orientation of (100) plane, a recess 5 is formed on the back surface side by the formation of the diaphragm 3 by etching, and a peripheral portion forms a thick portion 2a to form a pedestal. It is joined to 4.

In the vicinity of the edge of the surface of the diaphragm 3, four diffusion resistors 6a to 6d, which act as a piezo region and detect a differential pressure or pressure, are provided on the diagonal line b of the semiconductor chip 2.
It is formed on b. Further, the four diffusion resistors 6a to 6d have the crystal plane orientation (100) of the semiconductor chip 2.
In parallel with the <110> crystal axis direction where the piezoresistive coefficient is maximum in. Such diffused resistors 6a-
6d is formed by a diffusion or ion implantation method and is connected to a wheelstone bridge to differentially output a differential pressure signal of the low pressure and high pressure side pressures P1 and P2 applied to the front and back surfaces of the diaphragm 3. The resistance change rate at this time is represented by the following equation. ΔR / R = π ₄₄ (σr−σθ) / 2 (1) where π ₄₄ is the piezoresistance coefficient, σr is the stress perpendicular to the side of the diaphragm, and σθ is the stress parallel to the side of the diaphragm. is there.

The pedestal 4 is formed of Pyrex glass, ceramics, or the like having a thermal expansion coefficient similar to that of the semiconductor chip 2, and the back surface of the diaphragm 3 is provided in the center with a recess 5 formed on the back surface side of the semiconductor chip 2. A through hole 7 is formed on the side for guiding the low pressure side pressure P1 to be measured.

[0007]

In the above-mentioned conventional semiconductor pressure converter 1, the material of the semiconductor chip 2 is silicon, and the pedestal 4 is made of Pyrex glass, ceramics or the like in consideration of the influence of thermal expansion. However,
Even if the difference between the pressures P1 and P2 applied to both sides of the diaphragm 3 is zero, if the temperature or static pressure changes, σr-σθ in the above equation (1) does not become zero and an output is generated due to the difference in material and shape. Therefore, there is a problem that the zero point shifts. In particular, regarding the shape of the semiconductor chip 2, in the case of a circular chip having a circular diaphragm, there is no problem because it has symmetry with respect to the axis of the semiconductor chip, but in the case of a square, the axial symmetry is lost, so there is a change in temperature or Due to static pressure, σr ≠ σθ, and the resistance value changes. Therefore, zero shift occurs, the differential pressure cannot be detected with high accuracy, and it is necessary to take measures to electronically compensate the signal.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to minimize the zero shift and its variation due to temperature or static pressure, and to convert the semiconductor pressure with good temperature characteristics. To provide a container.

[0009]

In order to solve the above-mentioned problems, the present invention forms a polygonal diaphragm in the center of a polygonal semiconductor chip with an inclination of about 45 ° with respect to the semiconductor chip, and forms an edge portion of the diaphragm. A diffusion resistance is provided on a diagonal line of the semiconductor chip in the vicinity, and in a semiconductor pressure converter in which a thick portion of the semiconductor chip is joined to a pedestal, a stress in a diagonal direction of the semiconductor chip generated in the diffusion resistance and a perpendicular to the diagonal line. It is characterized in that a non-bonding portion is provided between the corner portion of the semiconductor chip and the pedestal so that the stress in the directions becomes equal. Further, the present invention is characterized in that a step portion that forms a non-bonded portion is provided on at least one of the semiconductor chip and the pedestal.

Since a polygonal semiconductor chip having a polygonal diaphragm does not exhibit axial symmetry with respect to the axis of the semiconductor chip, when the pedestal is bonded to the entire back surface of the semiconductor chip, stress at the position where the diffusion resistance is formed is generated. Indicates that the stress σr toward the center of the diaphragm is larger than the stress σθ in the direction perpendicular thereto, and σr> σθ.
When the number of joints between the pedestal and the semiconductor chip is reduced, conversely, the stress σ in the direction perpendicular to the center direction of the diaphragm is
θ increases, and σr <σθ. Therefore, if a non-bonding part is provided between the semiconductor chip and the pedestal and the ratio of the length of the non-bonding part and the length of the bonding part is optimized, σr = σθ
The resistance change rate is theoretically zero.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. 1 is a plan view showing an embodiment of a semiconductor pressure converter according to the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG. The same components as those shown in the section of the prior art are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. In these figures,
The square semiconductor chip 2 has a square diaphragm 3 formed at an angle of approximately 45 °, and the thick portion 2 a is anodically bonded onto the pedestal 4. In this case, the entire back surface of the thick portion 2a is not joined to the pedestal 4, but each corner portion is formed by the step portion 1
By forming 0, the non-bonded portion 13 is formed by being separated from the pedestal 4. The size of the step portion 10, that is, the size of the non-joint portion 13 is determined by the stress σr generated in the diffusion resistors 6a to 6d in the diagonal direction of the semiconductor chip (direction perpendicular to the side of the diaphragm) and the direction perpendicular to the diagonal line (diaphragm It is formed so that the stress σθ in the direction parallel to the side) becomes equal. In other words, σr = σθ is set by optimizing the ratio A / B of the length A of the non-bonded portion 13 and the length B of the bonded portion 13A. Other configurations are the same as those of the conventional semiconductor pressure converter described above.

The joint surface between the semiconductor chip 2 and the pedestal 4 is related to the deformation of the diaphragm 3, and when the square diaphragm 3 is inclined 45 ° so that the diagonal lines are orthogonal to each other with respect to the square semiconductor chip 2, the semiconductor chip is formed. Of the two bonding surfaces, the length of the diagonal bonding surface is long. Therefore, when the entire back surface of the thick portion 2a is bonded, the stress σr perpendicular to the side of the diaphragm 3 is parallel to the side of the diaphragm 3 and the stress σθ.
Get bigger.

Therefore, when the non-joint portion 13 is provided by forming the step portion 10 and the length of the diagonal joint surface of the semiconductor chip 2 is reduced, the stress σr perpendicular to the side of the diaphragm 3 gradually decreases. Therefore, the stress σθ parallel to the side of the diaphragm 3 increases. Therefore, when the step portion 10 is formed to have an optimum size, the stress σr perpendicular to the side of the diaphragm 3 and the stress σθ parallel to the side of the diaphragm 3 can be equalized. As a result, the rate of resistance change becomes zero, and the zero shift of the output due to temperature, static pressure, etc. can be reduced.

FIG. 3 is a plan view showing another embodiment of the present invention, and FIG. 4 is a sectional view taken along the line IV-IV of FIG. In this embodiment, an annular step portion 14 is formed on the outer peripheral surface of the upper surface of the pedestal 4 made of a cylindrical body, and the back surface corner portion of the semiconductor chip 2 is separated from the pedestal 4 to form the non-bonded portion 13. Even in such a structure, since the non-bonding portion 13 is provided, σr−σθ can be made zero, and zero shift can be eliminated.

FIG. 5 is a plan view showing still another embodiment of the present invention, and FIG. 6 is a sectional view taken along line VI-VI of FIG. In this embodiment, one diffusion resistance 6 is formed on the diaphragm 3, and the corner portion of the back surface on the diffusion resistance 6 side is formed as the non-bonding portion 13 by forming the step portion 10. The diffused resistor 6 is connected to an external resistor to form a wheelstone bridge circuit. Also in such a structure, σr−σθ can be set to zero as in the above-described embodiment, and zero shift can be eliminated.

FIG. 7 is a plan view showing still another embodiment of the present invention, and FIG. 8 is a sectional view taken along line VIII-VIII of FIG. In this embodiment, two diffused resistors 6a and 6c are formed in the vicinity of two adjacent sides of the diaphragm 3, and the back surface corners on the side of these diffused resistors 6a and 6c are not formed by forming the step portion 10. The joint 13 is formed. The two diffused resistors 6a and 6c form a half-wheelstone bridge circuit whose circuit configuration is easy. Even in such a structure, since the back surface sides of the two corner portions facing the diffused resistors 6a and 6c are formed as the non-joint portion 13 by forming the step portion 10, the same effect as that of the above-described embodiment can be obtained.

[0017]

EXAMPLE The result of the experiment conducted to confirm the effect of the present invention is shown in FIG. The semiconductor pressure transducer used in the experiment was a square semiconductor chip made of silicon, to which a pedestal of a prismatic body made of Pyrex glass was bonded by anodic bonding, and three types of dimensions were confirmed. The vertical axis of FIG. 9 is the stress (σr−σθ), the horizontal axis is the ratio (A / B) of the lengths of the non-bonded portion A and the bonded portion B (see FIG. 1) on the diagonal line, and the three types of curves are Also crosses σr−σθ = 0, and A,
It is clear that the value of B can eliminate the zero shift.

The present invention is not limited to the above embodiment, but the shape of each part of the semiconductor pressure transducer,
The structure and the like can be appropriately modified and changed. For example, the pedestal 4 is formed in a cylindrical body, but it may be formed in the same prismatic body as the square semiconductor chip 2. In that case, the non-bonded portion 13
The stepped portion 14 constituting the above may be formed only on the upper surface of the pedestal 4, or may be formed in the entire length in the height direction of the corner portion to form an octagon. Further, the square semiconductor chip 2 may also be composed of two silicon plates, and the effect is exerted by being applied to the joint portion of the silicon plates. Further, in each of the above-described embodiments and examples, an example in which a square diaphragm is formed on a square semiconductor chip is shown, but the present invention is not limited to this, and an octagonal semiconductor chip has a square shape. The diaphragm may be formed, or an octagonal diaphragm may be formed on a square semiconductor chip.

[0019]

As described above, in the semiconductor pressure transducer according to the present invention, a polygonal diaphragm is formed in the center of the polygonal semiconductor chip with an inclination of about 45 ° with respect to the semiconductor chip, and the edge portion of the diaphragm is formed. A diffusion resistance is provided on a diagonal line of the semiconductor chip in the vicinity, and in a semiconductor pressure converter in which a thick portion of the semiconductor chip is joined to a pedestal, a stress in a diagonal direction of the semiconductor chip generated in the diffusion resistance and a perpendicular to the diagonal line. Since a non-joint portion is provided between the corner portion of the semiconductor chip and the pedestal so that the stress in the directions becomes equal, zero shift due to temperature or static pressure does not occur, and a semiconductor pressure converter with good temperature characteristics is provided. Can be provided. Further, since the diaphragm is formed in a square shape, it is possible to easily control the dimensions when forming the step portion and perform anisotropic etching, so that the size can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a semiconductor pressure converter according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a plan view showing another embodiment of the present invention.

4 is a sectional view taken along line IV-IV of FIG.

FIG. 5 is a plan view showing still another embodiment of the present invention.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a plan view showing still another embodiment of the present invention.

8 is a sectional view taken along line VIII-VIII in FIG.

FIG. 9 is a graph showing the relationship between the ratio of the non-bonded portion to the bonded portion, the difference between the stress perpendicular to the side and the stress parallel to the side.

FIG. 10 is a plan view showing a conventional example of a semiconductor pressure converter.

FIG. 11 is a cross-sectional view of the converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor pressure converter, 2 ... Semiconductor chip, 3 ... Diaphragm, 4 ... Base, 5 ... Recessed part, 6, 6a-6d ... Diffusion resistance, 10 ... Step part, 13 ... Non-joint part, 14 ... Step part .

Claims (2)

[Claims] 1. A polygonal diaphragm is formed at a center of a polygonal semiconductor chip with an inclination of about 45 ° with respect to the semiconductor chip, and a diffusion resistance is provided on a diagonal line of the semiconductor chip near an edge of the diaphragm. In a semiconductor pressure converter in which a thick portion of a semiconductor chip is joined to a pedestal, the diagonal portion of the semiconductor chip and the corner portion of the semiconductor chip are equalized so that the stress in the diagonal direction of the semiconductor chip generated in the diffusion resistance is equal to the stress in the direction perpendicular to the diagonal line. A semiconductor pressure converter, wherein a non-bonding portion is provided between the base and the pedestal. 2. The semiconductor pressure converter according to claim 1, wherein a stepped portion that forms a non-bonded portion is provided on at least one of the semiconductor chip and the pedestal.