KR0135553B1 - Semiconductor type acceleration detecting device - Google Patents

Abstract

The present invention relates to a semiconductor acceleration detection apparatus which can reduce the sensitivity to a direction other than the acceleration direction to be measured while simplifying the manufacturing process. The semiconductor acceleration device of the present invention includes a semiconductor substrate 10, a rectangular mass portion 20 for converting acceleration into a force, a beam 30 supporting each corner of the mass portion 20, and each beam ( Piezoresistors R13-R16 formed at the edges of 30 and converting the stress applied to the respective beams 30 into resistance values, and two fixed resistors having a predetermined resistance value in place of the semiconductor substrate 10. Each of the series connected piezoresistors having diagonally opposed piezores (R13, R16; R14, R15) connected in series and facing each other diagonally and facing each of the fixed resistors (2R; 2R) diagonally; It is connected to R13, R16; R14, R15 to form a half bridge circuit, and the output (V1, R1, R16; R14, R15) and the output at the connection point of each of the fixed resistors (2R; 2R) It is characterized by drawing out V2).

Description

Semiconductor Acceleration Detection Device

1 is a plan view according to an embodiment of a conventional semiconductor acceleration detection apparatus

2 is an equivalent circuit diagram of the semiconductor acceleration detection device shown in FIG.

3 is a plan view according to another embodiment of the conventional semiconductor acceleration detection apparatus

4 is an equivalent circuit diagram of the semiconductor acceleration detection device shown in FIG.

5 is a plan view of a semiconductor acceleration detection apparatus according to the present invention.

6 is a cross-sectional view taken along line I-I in FIG.

FIG. 7 is an equivalent circuit diagram of the semiconductor acceleration detection device shown in FIG.

* Description of the symbols for the main parts of the drawings *

1,1 ', 10 ... silicone substrate 2,2', 20 ... mass part

3,3 ', 30 ... beam 2R ... fixed resistance

R1, R4 ... Vertical voltage resistorsR2, R3, R5-R16 ... Horizontal voltage resistors

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration detection device, and more particularly, to a semiconductor acceleration detection device capable of reducing a sensitivity to a direction other than the acceleration direction to be measured while simplifying a manufacturing process.

Acceleration detection device is actively used to perform the necessary control in the electronic control suspension system (Electronic Control Suspension System) of the vehicle or to determine the operation time of the air-bag (Air-Bag).

Such acceleration detection apparatuses are roughly classified into mechanical and semiconductor types, and semiconductor types are classified into cantilever types and bridge types. As is well known, when a resistor is formed by diffusing impurities into a single crystal semiconductor and stress deformation is applied to the resistor thus formed, the magnetic resistance value changes. This phenomenon is referred to as a piezo-resistive effect. All types of acceleration sensors are manufactured by applying such piezoresistive effect.

1 is a plan view according to an embodiment of a conventional semiconductor acceleration detection device, FIG. 2 is an equivalent circuit diagram of the semiconductor acceleration detection device shown in FIG. 1, and FIG. 3 is another diagram of a conventional semiconductor acceleration detection device. 4 is an equivalent circuit diagram of the semiconductor acceleration detection apparatus shown in FIG.

As shown in FIG. 1 and FIG. 2, the structure of the conventional semiconductor acceleration detection device has a silicon substrate 1, a mass part 2 for converting the acceleration into a force, and the mass part 2 It consists of a beam (3) where deformation occurs by a force applied to it and piezo resistors (R1-R4) located at the edge of the beam (3) to convert stress into a resistance value. Two of the piezo resistors R1-R4 facing diagonally (R1, R4) is a vertical pressure resistor that the resistance value decreases with respect to the tensile stress and the other two horizontal pressure resistor (R2) the resistance value increases with respect to the tensile stress , R3). In the conventional semiconductor detection apparatus having the above-described structure, when an external acceleration is applied to the mass portion 2, a force is generated in proportion thereto, and the generated force is a piezoresistor formed at its edge via the beam 3 ( By acting as a stress on R1-R4), the resistance value of the piezoresistor R1-R4 is changed. On the other hand, the acceleration detection device should detect only the acceleration in one direction, for example, Z-axis direction, the stress is also generated in the acceleration in the other axis direction, that is, the X-axis direction and Y-axis direction in the structure of the mass portion 2, the piezoresistor R1 Change the resistance of R4). In more detail with reference to FIG. 2, for the acceleration in the Z-axis direction, the resistance values of the horizontal pressure resistors R2-R3 increase, and the resistance values of the vertical pressure resistors R1, R4 decrease. The potential difference between the output terminals V1 and V2 is induced, and the acceleration can be detected based on this potential difference. As for the acceleration in the X-axis direction, tensile stress is applied to the piezoelectric resistors R1 and R3 on the left side, and compressive stress is applied to the piezoelectric resistors R2 and R4 on the right side. The resistance value decreases and the resistance values of the lower piezoresistors R3 and R4 increase. As a result, there is no potential difference between the output terminals V1 and V2, and the acceleration component in the X-axis direction is automatically canceled out. As for the acceleration in the Y-axis direction, tensile stress is applied to the piezoelectric resistors R3 and R4 on the lower side, and compressive stress is applied to the piezoelectric resistors R1 and R2 on the upper side. The resistance value increases, and the resistance values of the piezo resistors R2 and R4 on the right side decrease. As a result, there is no potential difference between the output terminals V1 and V2, and the acceleration component in the Y-axis direction is also automatically canceled.

However, the acceleration detection device of the above structure has a disadvantage in that the sensitivity is inferior because the width of the beam must be increased in order to form the vertical resistance resistors R1 and R4, and the vertical resistance resistors R1 and R4 and the horizontal resistance resistor are reduced. Due to the difference in piezoelectric resistance coefficient between (R2, R3), the output characteristic is nonlinear, and there is a problem that an offset phenomenon is caused. To improve this, as shown in FIG. 3, four horizontal piezoresistors R6, R7, R10, and R11 are formed on the mass portion 2 'with respect to each beam 3', and the substrate 1 'is formed. A structure in which four other horizontal pressure resistors R5, R8, R9, and R12 are formed on the side of the circuit is proposed. The acceleration detection device having the above-described structure constitutes a bridge circuit using only the horizontal pressure resistors R6, R7, R10, and R11 on the mass portion 2 'side for acceleration in the Z-axis direction, and detects the acceleration. In the X-axis direction and the Y-axis direction, acceleration is detected by making a bridge circuit as shown in FIG. 4 using only four horizontal pressure resistors R9-R12 on the lower side. This reduces the width of the beam and provides good compensation for acceleration in the other axis. However, since the stress is applied to the metal lead drawn from the piezoresistive element on the mass side to the pad (not shown) formed on the semiconductor substrate, the disconnection is caused. There is a concern that there is a problem that the beam width as much as the width of the conductor is required. Furthermore, it is difficult to select a position such that the stresses applied to the piezoresistors on the substrate side and the mass portion side are exactly opposite, thereby causing nonlinear output characteristics and offset phenomenon.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object thereof is to provide a semiconductor acceleration detection device capable of reducing the sensitivity to a direction other than the acceleration direction to be measured while simplifying the manufacturing process.

The semiconductor acceleration detection device of the present invention for achieving the above object is formed on a semiconductor substrate, a rectangular mass portion for converting the acceleration into a force, a beam supporting each corner of the mass portion, the edge of each beam A piezo resistor for converting the stress applied to each beam into a resistance value and a fixed resistor formed in place of the semiconductor substrate and having a predetermined resistance value, the diagonally opposite piezo resistors connected in series and then diagonally Opposed and connected to each of the series connected piezoresistors so as to face each of the fixed resistors diagonally to form a half-bridge circuit and to draw the output at the connection point of the piezoresistor and the fixed resistors.

In the semiconductor type acceleration detection apparatus of the present invention having the above-described structure, it is preferable that each piezoresistor is formed of a horizontal piezoresistor whose resistance value increases with respect to tensile stress.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration according to a preferred embodiment of the semiconductor acceleration detection apparatus of the present invention.

FIG. 5 is a plan view of a semiconductor acceleration detection apparatus according to the present invention, and FIG. 6 is a sectional view taken along line I-I in FIG.

As shown in FIGS. 5 and 6, the structure of the semiconductor type acceleration detection apparatus of the present invention is a silicon substrate 10, a rectangular mass portion 20 for converting the acceleration into a force, and a mass portion ( 20 to support each corner of the beam 30 is deformed by the force applied to the mass portion 20, and the stress applied to each beam 30 is located at the edge of the beam 30 to the resistance value It consists of two high-voltage resistors (not shown) formed in place of the piezo resistors R13-R16 and the semiconductor substrate 10 to be converted. Although not shown, circuit wirings are formed on the semiconductor substrate 10 to connect the respective piezoresistors and the fixed resistors as will be described later.

FIG. 7 is an equivalent circuit diagram of the semiconductor acceleration detection device shown in FIG. As shown in FIG. 7, the equivalent circuit of the semiconductor acceleration detection apparatus of the present invention connects the piezoresistors R13, R16, R14, and R15 that are diagonally opposed in series, and each of the fixed resistors 2R; 2R) is also connected to the piezo resistor pairs R13, R16; R14, and R15 connected in series to face diagonally, so as to form a half bridge as a whole. Furthermore, the output terminals V1 and V2 can be drawn out at the connection point of each piezoresistor pair R13, R16; R14, R15 and each fixed resistor 2R; 2R. In the above configuration, each piezoresistor R13-R16 is implemented as a horizontal piezoresistor whose resistance value increases with respect to the tensile stress, and is formed to have the same value in a state where no stress is applied. Furthermore, each of the fixed resistors 2R and 2R is formed to have a value twice the resistance of each piezoresistor R13 to R16 in a state where no stress is applied.

Hereinafter, the operation of the semiconductor acceleration detection apparatus of the present invention will be described in detail.

First, the acceleration component in the Z-axis direction, the compressive stress is applied to all the horizontal pressure resistor (R13-R16) to reduce the resistance value by the same magnitude, accordingly the acceleration between the output terminals (V1, V2) A proportional potential difference is generated.

On the other hand, with respect to the acceleration component in the X-axis direction, tensile stress is applied to the piezoelectric resistors R13 and R15 on the left side, and compressive stress is applied to the piezoelectric resistors R14 and R16 on the right side. The resistance value of R15) increases and the resistance values of the piezo resistors R14 and R16 on the right side decrease. As a result, in the half bridge circuit of FIG. 7, the increase / decrease of the resistance value of the piezo resistors R13 and R16 connected in series is canceled out, so that the overall resistance value does not change, and the increase / decrease of the resistance values of the remaining piezor resistors R14 and R15 is not changed. Offset the overall resistance value does not change. As a result, there is no potential difference between the output terminals V1 and V2. For the acceleration component in the Y-axis direction, tensile stress is applied to the piezoelectric resistors R15 and R16 on the lower side, and compressive stress is applied to the piezoelectric resistors R13 and R14 on the upper side. The resistance value of increases and the resistance values of the piezo resistors R13 and R14 on the upper side decrease. As a result, in the half bridge circuit of FIG. 7, the increase / decrease of the resistance value of the piezo resistors R13 and R16 connected in series is canceled out, so that the overall resistance value does not change, and the increase / decrease of the resistance values of the remaining piezor resistors R14 and R15 is not changed. Offset the overall resistance value does not change. As a result, there is no potential difference between the output terminals V1 and V2.

As described above, according to the semiconductor vehicle speed detecting apparatus of the present invention, there is an effect of effectively reducing the acceleration component in a direction other than the direction to be measured. Furthermore, by using only the horizontal piezoresistor and placing the piezoresistors toward the semiconductor substrate, it is possible to minimize the width of the beam and to easily form the metal conductors.

Claims (2)

Semiconductor substrate 10, A rectangular mass part 20 for converting the acceleration into a force, A beam 30 supporting each corner of the mass portion 20, Piezores (R13-R16) formed at the edge of each beam 30 to convert the stress applied to each beam 30 to a resistance value and Two fixed resistors are formed in place on the semiconductor substrate 10 and have a predetermined resistance value. A pair of piezoresistors R13 and R16 connected in series so as to face diagonally and diagonally oppose each of the fixed resistors 2R and 2R after connecting the piezo resistors R13 and R16; A half bridge circuit is connected to R14 and R15 to draw outputs V1 and V2 at connection points of each piezoresistor R13, R16; R14 and R15 and each of the fixed resistors 2R and 2R0. A semiconductor acceleration detection device, characterized in that. The method of claim 1, Each piezoresistor (R13-R16) is formed of a horizontal piezoresistor whose resistance value increases with respect to tensile stress.