Fine Pattern Fabrication below 100 nm with 70 kV Cell Projection Electron Beam Lithography

Cell projection electron beam lithography has been developed to achieve high throughput, and this system is now available commercially. However, the cell projection method uses a beam current that is much higher than that of the variable shaped beam method, and the Coulomb interaction caused by electrical repulsion (the coulomb effect) is thus much stronger. It is important to control the Coulomb effect in fine pattern fabrication because it causes beam blur that degrades resolution. This paper describes the effects of the acceleration voltage on the resolution of fine patterns below 100 nm as determined through experiments and simulations. Using an electron beam (EB) lithography system with 70 kV acceleration, we made 120 nm pitch lines and spaces (L&S) patterns by the cell projection method. Throughput was improved by using an acceleration voltage higher than the usual 50 kV acceleration. Because the Coulomb effect under 70 kV acceleration is weaker, we could use a higher beam current density or a larger cell projection size. The 70 kV acceleration is particularly useful for fine patterns and enables throughput twice that possible with 50 kV acceleration for 70 nm L&S pattern delineation.