Samuel C. Howells

DUV ALTA system aerial image enhancement for improved pattern fidelity

The ALTA 4300 system has been used to successfully write many advanced design layers previously only feasible with 50kV vector shaped beam tools. In order to further enlarge the application space of this high productivity an aerial image enhancement technique has been developed to deliver mask patterns that more closely match pattern data for corners and jogs. This image enhancement is done in real time in the ALTA system’s rasterizer by modifying the gray level mapping of pixels near the corner vertexes. SEM measurements of corner rounding with standard rasterization and the enhanced rasterization show an improvement of corner rounding radius from ~205 to ~132 nm. A direct comparison of SEM micrographs show no qualitative difference between vector scan mask features and those written with aerial image enhancement. This convincingly demonstrates that the ALTA 4300 system with the new image enhancement can write many layers requiring vector scan corner acuity.

Evolution of dopants and defects in silicon under various annealing sequences

Several decades of research into understanding the mechanisms responsible for diffusion and activation of group-III acceptor and group-V donor impurities in silicon has been driven by the technological need for creating electrical junctions in the S/D and extensions of transistors in semiconductor integrated circuits. It is now conclusively known that anomalous diffusion of implanted impurities during annealing results from their interaction with the non-conservative evolution of excess point-defect damage created by the original implantation, and the effect annealing ambients, co-impurities, interfaces and surfaces have on that evolution [1–8]. Early experiments shown in Ref. [2] conclusively proved this by etching away the surface region containing implant damage before annealing, and demonstrating that the anomalous behavior disappeared. Starting from the as-implanted damage, the nucleation, growth and dissolution of a sequence of larger defects at the expense of smaller ones during the anneal, sets the point defect flux and super-saturation levels (the ratio of point defect concentration to its temperature equilibrium value), which then determine the magnitude and durations of the various phases of anomalous diffusion [9].

DUV ALTA system aerial image enhancement for improved pattern fidelity: phase II

The ALTA 4300 system has been used to successfully write many advanced designs previously only possible with 50kV VSB systems. In order to further enlarge the application space of this high productivity system, an aerial image enhancement technique has been developed to deliver mask patterns that more closely match the pattern data for corners and jogs. This image enhancement is done in real time in the ALTA systems rasterizer by modifying the gray level mapping of pixels near the corner vertexes. SEM measurements of corner rounding with standard rasterization and the enhanced rasterization show a 35% improvement of corner rounding radius from ~205 to ~132 nm. A direct comparison of SEM micrographs show little qualitative difference between vector scan mask features and those written with aerial image enhancement. This convincingly demonstrates that the ALTA 4300 system with the new image enhancement can write many layers requiring vector scan corner acuity.