With the progress of mask writer technology, 50 KV electron beam writers always perform with better pattern fidelity
and critical dimension (CD) control than traditional laser raster-scan writers because laser spot size is confined by the
laser longer wavelength relative to electron beam. As far as Optical Proximity Correction (OPC) pattern fidelity is
concerned, critical masks with OPC process have to choose Variable-Shape-Beam (VSB) electron beam writer presently.
However, the over-aggressive OPC fragmentation induces data volume abrupt explosion, longer writing time, higher
mask cost and even mask quality degradation <sup>1</sup>.
Micronic Sigma7500 laser writer introduces a novel imaging system combining partial coherent light and DUV spatial
light modulation (SLM) to generate a high-quality pattern image <sup>2</sup>. The benefit of raster-scan laser writer is high
throughput with consistent writing time regardless of pattern geometry, complexity and data size. However, pattern CD
accuracy still needs improvement. This study is to evaluate jog CD control capability of Sigma7500 on OPC typical
line-and-space test patterns with different orientations of 0°, 90°, 45° and 135°. In addition, mask CD uniformity and
OPC jog height linearity will also be demonstrated.
DRAM intra-field CD uniformity (CDU) demand becomes more crucial with pattern size shrink and wafer die or
memory size expanding. Intra-field CDU error mainly comes from mask CD error, scanner exposure and wafer process.
This study makes use of a method to extract systematic CDU error from multi-field CDU results. Based on the
information of the systematic CDU error, localized mask transmittance modulation is implemented to compensate the
intra-field systematic CDU error on wafer. A focused ultrafast laser beam forms shading elements in mask quartz
substrate. Mask transmittance modulation is controlled by the shading element density variation. This study will
demonstrate the intra-field CDU improvement result, CD modulation calibration validity, CD proximity variation result
and mask inspection result etc.
The purpose of paper is to investigate the impact of mask blank flatness on critical
dimension uniformity (CDU) and depth of focus (DOF) in the wafer printing process
with a test pattern designed for 65nm node technology. In this experiment we use 3
test masks with different flatness (0.3T, 0.5T and 1T), and the same test pattern array.
The mask flatness was measured with a Tropel® UltraFlat<sup>TM</sup> 200, and the focus error
is extracted from the CD data of the focus and energy matrix (FEM) analysis.
The goal of the study is to quantify the mask flatness influence on the high-numerical
aperture (NA) lithographic process.