Physical quantity sensor
View Patent ↗A highly accurate physical quantity sensor which can ensure reliability in strength and reduce resistance changes caused by stresses. Assuming, with respect to stress σ imposed on a substrate in a predetermined direction (e.g., direction in which maximum stress is imposed), a parallel direction to be a horizontal direction and a perpendicular direction to be a vertical direction, each of resistors of the sensor has a horizontal resistance component Rl and a vertical resistance component Rt. When a ratio of a piezoresistance coefficient πl of the horizontal resistance component Rl, which is provided when the stress imposed on the substrate is applied to the horizontal resistance component Rl, to a piezoresistance coefficient πt of the vertical resistance component Rt, which is provided when the stress is applied to the vertical resistance component Rt, is πl:πt=−n:1 (n:integer), a resistance value ratio of the vertical resistance component Rt to the horizontal resistance component Rl is set substantially equal to the ratio of the piezoresistance coefficient πl to πt.
1. A physical quantity sensor, comprising:
a substrate;
a rectangular diaphragm formed in said substrate; and
resistors for measuring a physical quantity constituting a voltage generated on said resistors, said resistors being formed on an electric insulating film on said diaphragm in a pattern of strips, said resistors including a horizontal resistor component and a vertical resistor component, and said horizontal resistor component and said vertical resistor component being orthogonal with each other,
wherein a ratio of a piezoresistance coefficient of the vertical resistor component to a piezoresistance coefficient of the horizontal resistor component is substantially equal to a resistance value ratio of the resistance value of the vertical resistor component to a resistance value of the horizontal resistor component, said piezoresistance coefficient of said vertical resistor component being obtained by imposing a stress to said vertical resistor component in a vertical direction, said piezoresistance coefficient of the horizontal resistor component is obtained by imposing a stress to said horizontal resistor component in a horizontal direction.
2. The physical quantity sensor according to claim 1 , wherein said horizontal resistor component and said vertical resistor component are made of polycrystalline silicon doped with impurities, and the resistance value ratio of the horizontal resistor component to the vertical resistor component is equal to 3.
3. The physical quantity sensor according to claim 1 , wherein said horizontal resistor component and said vertical resistor component are extended in interdigitated relation in parallel with each other.
4. The physical quantity sensor according to claim 1 , wherein said resistors comprise a heating resistor and a temperature sensitive resistor, each having a power-supply side terminal and a ground side terminal which are branched to at least four terminals.
5. The physical quantity sensor according to claim 1 , wherein the measured generated voltage is representative of air flow.
6. The physical quantity sensor according to claim 1 , wherein the measured generated voltage is representative of acceleration.
7. A physical quantity sensor comprising:
a substrate;
a rectangular diaphragm formed in said substrate; and
resistors for measuring a physical quantity consisting of voltage generated on said resistors, said resistors being formed on an electric insulating film on said diaphragm in a pattern of strips, said resistors including a horizontal resistor component and a vertical resistor component, said horizontal resistor component and said vertical resistor component being orthogonal with each other,
wherein a ratio of the resistance value of the horizontal resistor component to a resistance value of the vertical resistor component is 0.5 times to 1.5 times a ratio of a piezoresistance coefficient of the horizontal resistor component to a piezoresistance coefficient of the vertical resistor component, said piezoresistance coefficient of the vertical resistor component being obtained by imposing a stress to said vertical resistor component in a vertical direction, and said piezoresistance coefficient of the horizontal resistor component is obtained by imposing a stress to said horizontal resistor component in a horizontal direction.
8. The physical quantity sensor according to claim 7 , wherein said horizontal resistor component and said vertical resistor component are made of polycrystalline silicon doped with impurities, and the resistance value ratio of the horizontal resistor component to the vertical resistor component is equal to 3.
9. The physical quantity sensor according to claim 7 , wherein said horizontal resistor component and said vertical resistor component are extended in interdigitated relation in parallel with each other.
10. The physical quantity sensor according to claim 7 , wherein said resistors comprise a heating resistor and a temperature sensitive resistor, each having a power-supply side terminal and a ground side terminal which are branched to at least four terminals.