FABRICATION LIMITS OF ELECTRON-BEAM LITHOGRAPHY AND OF UV, X-RAY AND ION-BEAM LITHOGRAPHIES

The paper discusses and compares the lithography methods being develop ed for the fabrication of future generations of silicon integrated cir cuits. The smallest features in today's circuits are about 0.3 mu m in size and this will be reduced to 0.1 mu m within the next ten years. The methods discussed include optical (ultraviolet light) projection, which is used predominantly at present, projection printing at wavelen gths between the X-ray and ultraviolet regions, X-ray proximity printi ng, and scanning and projection with electrons and ions. There are sev ere problems to be overcome with all of the methods before they can sa tisfy future needs. The difficulties are not just connected with obtai ning adequate resolution. The more challenging requirements are those associated with the elimination of distortion in the highly complex tr illion pixel images and of achieving an exposure rate of about one per second with a system of acceptable cost, that is less than about $10M . The various approaches for correcting distortion and obtaining adequ ate throughput are described, as are the factors limiting resolution. Finally, the ultimate capabilities of electron beam methods for fabric ating structures and devices with dimensions down to 1 nm are describe d.