Imec’s new post-exposure bake method speeds up EUV chipmaking tools, boosting production for the most advanced chips — 20% gain in photoresist improvement from

Imec's new post-exposure bake method speeds up EUV chipmaking tools, boosting production for the most advanced chips — 20% gain in photoresist improvement from

New 1.4nm nanoimprint lithography template could reduce the need for EUV steps in advanced process nodes

It should be noted that post-exposure bake is one of the most sensitive steps in the entire lithography flow. PEB activates and drives reactions triggered by photons during the exposure, so small variations of temperature, heating ramp rate, bake time, and atmosphere can have drastic effects on critical dimension (CD), line-edge roughness (LER), and stochastic defect levels, which means that one combination of settings can lead to yield improvement, another can be a yield killer. Changing gas composition inside the PEB module is a big deal not only from the pure semiconductor manufacturing flow point of view, but also from such points of view as long-term material stability, tool oxidation, and safety considerations, just to mention a few.

In standard EUV production environments, wafers are exposed in a vacuum and then transferred to a bake module operating under normal cleanroom air containing 21% of oxygen. So, to conduct its experiments, Imec developed a special tool called BEFORCE*, which isolates wafer handling and baking from the surrounding fab environment. The system integrates gas injection and blending capabilities along with built-in photo-speed metrology, which enabled researchers to regulate oxygen contents in the chamber while controlling photoresist performance. To put Imec's discovery into use, foundries will have to ask their fab tool makers to replicate what BEFORCE does during the PEB step.

"This is just a first result from the BEFORCE tool: the controlled gas composition provides an additional knob to study the origins of environmental effects on the lithographic variability of MOR materials," said Ivan Pollentier, Senior Researcher at imec. "Equipment manufacturers can use these insights as a guideline to adapt their tools for improved EUV lithography throughput and stability."

*Bake and EUV system with FTIR and Outgas measurement for Resist evaluation in Controlled Environment.

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