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A microgyroscope, which vibrates in two orthogonal axes on the substrate plane, is designed and fabricated. The shuttle mass of the vibrating gyroscope consists of two parts. The one is outer shuttle mass which vibrates in driving mode guided by four folded springs attached to anchors. And the other is inner shuttle mass which vibrates in driving mode as the outer frame does and also can vibrate in sensing mode guided by four folded springs attached to the outer shuffle mass. Due to the directions of vibrating modes, it is possible to fabricate the gyroscope with simplified process by using polysilicon on insulator structure. Fabrication processes of the microgyroscope are composed of amsotropic silicon etching by PIE, gasphase etching (GPE) of the buried sacrificial oxide layer, metal electrode fonnation. An electromechanical model of the vibrating mierogyroscope was modeled and bandWidth characteristics of the gyroscope were analyzed firstly. The analyzed characteristics ofthe gyroscope were evaluated by experiment. The gyroscope operates at DC 4V and AC 0. 1V in a vacuum chamber of lOOmtorr. The detection circuit consists of a discrete sense amplifier and a noise canceling circuit. Using the evaluated electromechanical model, an operating condition for high performance ofthe gyroscope is obtained

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One of the limiting factors in fabrication of surface micromachined structures is the residual stress formed in the film during deposition. In order to fabricate the microsiructure using the polysilicon layers deposited in a conventional LPCVD furnace, we used the multi-stacked polysilicon films and reported a method of stress control in that films. In the multi-stacked polysilicon film there exist the polysilicon/polysilicon interfaces, at which oxidized layers are formed during film stacking and dopant atoms are segregated. These facts made the multi-stacked film difficult to be used as structural layers for microstructure fabrication. In order to control the stress profile, we investigated the. effects of dopant distribution and oxidized layers on the stress profile in the multi-stacked film using micromachined test structures. The stress profile could be modified considerably by multi-steps doping process and the residual stress was reduced to 15MPa for 5pm thick film. The contribution ofthe oxidized layer to the stress profile was also studied extensively and we could reduce the effect of the oxidized layer by the symmetrical stacking of films. Using the simple model, the dopant-induced stress profile was calculated theoretically from the dopant concentration profile and it suggested an improved method for estimating the stress profile of doped polysilicon films. Using the method developed in this study, the microstructure made ofthe multi-stacked polysilicon film was successfully fabricated with a low stress gradient of O.5MPa/pim.. The conventional LPCVD equipment without any modification can fabricate the polysilicon structural layer for the microstructure fabrication by the multi-stacking process, which offered the convenient method of stress control.