Roller Screws Research Articles

High speed flat guide ceramic stage for electron-beam lithography system

A high speed precision ceramic x–y stage has been developed for a high throughput submicron e-beam lithography system. This stage gives beam exposure during high speed continuous stage movement and shortens the step-and-repeat overhead time. In this exposure method the eddy current on the stage surface caused by high speed stage movement in a magnetic leakage field from the objective lens deteriorates the patterning accuracy. To reduce the eddy current, the stage has no metal bulk parts and the major components are made of a fine ceramic material which is of light weight and low thermal expansion. In order to prevent charge-up phenomenon, electric conductivity of the ceramic has been controlled by adding a small amount of nonmagnetic metal and the nonconductive parts are coated with a thin metal layer. A plate structure with flat guide is used to lighten the stage for achieving both constant velocity movement and high speed step-and-repeat performance. A unique separation mechanism between stage and drive bar with piezoelectric elements has been developed for x–y independent movements avoiding vibration from the driving mechanism. The major stage components and specimen chamber are designed by using dynamic vibration simulation. The stage drive mechanism, which is comprised of roller screws and dc motors, operates with a velocity and position controller. The maximum velocity of 160 mm/s, positioning time of 150 ms/10 mm, and yawing accuracy of ±3 μrad, is achieved. This stage has a direct wafer holding mechanism, operating with an automated wafer loader system which can handle 100 wafers/h.