High-sensitivity z-axis vibration sensor and method of fabricating the same
First Claim
1. A method of fabricating a high-sensitivity MEMS-type z-axis vibration sensor, comprising:
- providing a silicon on insulator (SOI) substrate comprising an upper silicon layer disposed over a thermal oxide layer, and a silicon wafer disposed under the thermal oxide layer;
doping the upper silicon layer with impurities to form a lower electrode;
forming a silicon dummy ring in the doped upper silicon layer to define a center mass region of the doped upper silicon layer;
forming a second upper oxide layer to a predetermined thickness and a polysilicon layer over the doped upper silicon layer;
doping the polysilicon layer with impurities to form a center ground electrode;
forming a sacrificial oxide layer and an upper electrode over the doped polysilicon layer;
etching a lower surface of the silicon wafer to isolate the center mass region of the doped upper silicon layer; and
etching the sacrificial oxide layer and the second upper oxide layer through an upper surface of the upper electrode, and forming a vibration space in which the doped polysilicon layer is capable of vibrating in a z-axis direction.
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Abstract
Provided is a high-sensitivity MEMS-type z-axis vibration sensor, which may sense z-axis vibration by differentially shifting an electric capacitance between a doped upper silicon layer and an upper electrode from positive to negative or vice versa when center mass of a doped polysilicon layer is moved due to z-axis vibration. Particularly, since a part of the doped upper silicon layer is additionally connected to the center mass of the doped polysilicon layer, and thus an error made by the center mass of the doped polysilicon layer is minimized, it may sensitively respond to weak vibration of low frequency such as seismic waves. Accordingly, since the high-sensitivity MEMS-type z-axis vibration sensor sensitively responds to a small amount of vibration in a low frequency band, it can be applied to a seismograph sensing seismic waves of low frequency which have a very small amount of vibration and a low vibration speed. Moreover, since the high-sensitivity MEMS-type z-axis vibration sensor has a higher vibration sensibility than MEMS-type z-axis vibration sensor of the same size, it can be useful in electronic devices which are gradually decreasing in size.
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Citations
8 Claims
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1. A method of fabricating a high-sensitivity MEMS-type z-axis vibration sensor, comprising:
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providing a silicon on insulator (SOI) substrate comprising an upper silicon layer disposed over a thermal oxide layer, and a silicon wafer disposed under the thermal oxide layer; doping the upper silicon layer with impurities to form a lower electrode; forming a silicon dummy ring in the doped upper silicon layer to define a center mass region of the doped upper silicon layer; forming a second upper oxide layer to a predetermined thickness and a polysilicon layer over the doped upper silicon layer; doping the polysilicon layer with impurities to form a center ground electrode; forming a sacrificial oxide layer and an upper electrode over the doped polysilicon layer; etching a lower surface of the silicon wafer to isolate the center mass region of the doped upper silicon layer; and etching the sacrificial oxide layer and the second upper oxide layer through an upper surface of the upper electrode, and forming a vibration space in which the doped polysilicon layer is capable of vibrating in a z-axis direction. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification