Dry etching of silicon is an essential process step for the fabrication of Micro electromechancal system (MEMS). The AZ7220 positive photo-resist was used as the etching mask and silicon micro-trenches were fabricated...Dry etching of silicon is an essential process step for the fabrication of Micro electromechancal system (MEMS). The AZ7220 positive photo-resist was used as the etching mask and silicon micro-trenches were fabricated with a multiplexed indu ctively coupled plasma (ICP) etcher. The influence of resist pattern profile, an d etch condition on sidewall roughness were investigated detail. The results sho w that the sidewall roughness of micro-trench depends on profiles of photo-resis t pattern, the initial interface between the resist bottom surface and silicon s urface heavily. The relationship between roughness and process optimization para meters are presented in the paper. The roughness of the sidewall has been decrea sed to a 20-50nm with this experiment.展开更多
The comb capacitances fabricated by deep reactive ion etching （RIE） process have high aspect ratio which is usually smaller than 30 ： 1 for the complicated process factors, and the combs are usually not parallel du...The comb capacitances fabricated by deep reactive ion etching （RIE） process have high aspect ratio which is usually smaller than 30 ： 1 for the complicated process factors, and the combs are usually not parallel due to the well-known micro-loading effect and other process factors, which restricts the increase of the seismic mass by increasing the thickness of comb to reduce the thermal mechanical noise and the decrease of the gap of the comb capacitances for increasing the sensitive capacitance to reduce the electrical noise. Aiming at the disadvantage of the deep RIE, a novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances is developed. One part of sensing of inertial signal of the micro-accelerometer is by the grid strip capacitances whose overlapping area is variable and which do not have the non-parallel plate＇s effect caused by the deep RIE process. Another part is by the sensing gap alterable capacitances whose gap between combs can be reduced by the actuators. The designed initial gap of the alterable comb capacitances is relatively large to depress the effect of the maximum aspect ratio （30 ： 1） of deep RIE process. The initial gap of the capacitance of the actuator is smaller than the one of the comb capacitances. The difference between the two gaps is the initial gap of the sensitive capacitor. The designed structure depresses greatly the requirement of deep RIE process. The effects of non-parallel combs on the accelerometer are also analyzed. The characteristics of the micro-accelerometer are discussed by field emission microscopy （FEM） tool ANSYS. The tested devices based on slide-film damping effect are fabricated, and the tested quality factor is 514, which shows that grid strip capacitance design can partly improve the resolution and also prove the feasibility of the designed silicon-glass anodically bonding process.展开更多
文摘Dry etching of silicon is an essential process step for the fabrication of Micro electromechancal system (MEMS). The AZ7220 positive photo-resist was used as the etching mask and silicon micro-trenches were fabricated with a multiplexed indu ctively coupled plasma (ICP) etcher. The influence of resist pattern profile, an d etch condition on sidewall roughness were investigated detail. The results sho w that the sidewall roughness of micro-trench depends on profiles of photo-resis t pattern, the initial interface between the resist bottom surface and silicon s urface heavily. The relationship between roughness and process optimization para meters are presented in the paper. The roughness of the sidewall has been decrea sed to a 20-50nm with this experiment.
基金supported by the National Natural Science Foundation of China (No. 60506015)the Zhejiang Provincial Natural ScienceFoundation of China (No.Y107105).
文摘The comb capacitances fabricated by deep reactive ion etching （RIE） process have high aspect ratio which is usually smaller than 30 ： 1 for the complicated process factors, and the combs are usually not parallel due to the well-known micro-loading effect and other process factors, which restricts the increase of the seismic mass by increasing the thickness of comb to reduce the thermal mechanical noise and the decrease of the gap of the comb capacitances for increasing the sensitive capacitance to reduce the electrical noise. Aiming at the disadvantage of the deep RIE, a novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances is developed. One part of sensing of inertial signal of the micro-accelerometer is by the grid strip capacitances whose overlapping area is variable and which do not have the non-parallel plate＇s effect caused by the deep RIE process. Another part is by the sensing gap alterable capacitances whose gap between combs can be reduced by the actuators. The designed initial gap of the alterable comb capacitances is relatively large to depress the effect of the maximum aspect ratio （30 ： 1） of deep RIE process. The initial gap of the capacitance of the actuator is smaller than the one of the comb capacitances. The difference between the two gaps is the initial gap of the sensitive capacitor. The designed structure depresses greatly the requirement of deep RIE process. The effects of non-parallel combs on the accelerometer are also analyzed. The characteristics of the micro-accelerometer are discussed by field emission microscopy （FEM） tool ANSYS. The tested devices based on slide-film damping effect are fabricated, and the tested quality factor is 514, which shows that grid strip capacitance design can partly improve the resolution and also prove the feasibility of the designed silicon-glass anodically bonding process.
