Asher Klatchko

Describing thin-film imaging with a Gaussian beam as potential flow

It is shown that patterning with a Gaussian beam on thin films is congruent to a diffusion process. In particular, the acuity of the image patterned is tied to a steady state (Laplace equation). For a small spot size, pattern acuity improves locally when the Laplacian approaches zero at the said region. However, when the spot size (blur) of the patterning beams is of the order of the critical dimensions of the geometry, the diffusion equation gives rise to a global steady state. As a corollary, a conformal mapping of the type w=z2 is applied, transforming a 45∘ rotated cross into a contact hole. We discuss the relevance of conformal mapping to corner rounding seen on raster beam pattern generators.

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.

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.

Conformal mapping in microlithography

We show that a conformal mapping of the type, W = z π/α, describes how a shape of a 45° rotated cross transforms into a contact hole. We discuss its relevance to corner rounding seen on raster beam pattern generators.