Direct writing electron beam lithography

A quasi-shaped-beam method to enhance the throughput of a vector scan electron-beam lithography system using a circular spot with Gaussian shaped current density distribution was developed. Spot diameter is switched by varying the condenser currents. Exposure spot movements caused by mean size switching are prevented using an adapted control of the electron source alignment coils. An ultrahigh vacuum sealed anode chamber was built to use LaB6 cathodes. A part of its emitted light is reflected to a specially developed quotient pyrometer to measure the cathode tip temperature. A modified correlation method enables use of process induced topographical markers for wafer alignment. Necessary short detection time is achieved by pipelining and parallel processing techniques using microprocesser controlled signal processing hardware. The underetching of the marker generating process is measured with the position detection.