Proceedings PaperX-Ray Lithography Applied To The Fabrication Of 1 Âµm N-Channel Metal Oxide Semiconductor (NMOS) Circuits
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A full field X-ray exposure system has been developed and utilized in the fabrication of 1pm high performance NMOS logic circuits of various complexities from simple ring oscillators to large-scale custom devices. The exposure system is based on a 4 kW stationary palladium source emitting the 4.37Å Lα; line from a 3mm effective spot diameter. A special shadow mask consisting of 0.6pm gold features on a 6μm boron nitride membrane is used to transfer features into a chlorine based X-ray resist sensitive to the 4.37Å radiation. Pattern transfer to the silicon surface is faithfully reproduced through the use of a tri-level resist structure and anisotropic reactive sputter etching. Alignment of various levels is accomplished optically through the use of a bifocal, split field microscope at high magnification and the use of dark field edge sensing. Linewidth control and registration data are presented for various NMOS circuit designs fabricated in the 1pm dimensional region and some circuit performance characterization is reviewed.