High Resolution Cell Projection

Inhalt:
The ever more demanding requirements in the semiconductor manufacturing sector together with the increasing mask making costs and cycle times call for new lithographic solutions. Electron beam lithography has shown its superior performance and flexibility in advanced patterning applications. It enables already today process and technology developments ahead of the ITRS roadmap, which addresses currently the 32nm and 22nm node or even below. Thus electron beam direct write (EBDW) can avoid the high costs and delay times related to the advanced masks required for critical layers. On the other side EBDW faces the concerns regarding its throughput, which bases upon the inherited sequential exposure method. A solution to improve the throughput performance offers the implementation of the cell projection method as already materialized in the Vistec SB3055 tool. In addition to the variable shape beam technology, which can project regular structures (rectangles, slants and triangles) only, cell projection is able to image complex structures. Thus, structures that would have required a multiple of regular shots are now projected in one single shot. Thanks to this approach not only the shot count is noticeably reduced, but also the overall throughput is increased. First experimental and simulation results show an improvement of a factor of about 3X. Nevertheless, the final throughput gain strongly depends on the pattern and data structure itself. Combining high resolution variable shape beam technology with the cell projection feature allows advanced R&D and small volume and prototyping applications to be performed with one system. The Vistec SB3055 features the high resolution capability of variable shape beam lithography and incorporates the advantages of the cell projection technology. Owing to this new option we are able to improve the throughput for standard design features while maintaining the required high accuracy of our exposure system. Beside this, the combination of cell projection and standard shape beam technology still offers a high degree of flexibility as the key advantage of EBDW. On the Vistec SB3055 system we have performed different resolution tests serving as comparison between cell projection and standard shape beam. In this paper we will present the resolution capability obtained with cell projection on test structures as well as the general accuracy achieved for real patterns.