Wafer CD variation for random units of track and polarization

Guo, Ningqun; Ackmann, Paul; Richter, Frank; Kurth, Karin; Maelzer, Stephanie; Hsieh, Michael; Schurack, Frank; Gn, Fang Hong

doi:10.1117/12.917622

Cited by 1 publication

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“…The most temperature sensitive step in the lithography sequence is the postexposure bake step. Requirements call for the temperature to be controlled within 0.1 °C across the wafer at temperatures between 70 and 150 °C. , A number of recent investigations also showed the importance of proper bake plate operation, both in steady-state and transient, on CD control. ,− Two approaches exist in addressing this issue in industry. The first approach involves the development of less temperature sensitive photoresist.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Real-Time Control of Multizone Thermal Processing System for Photoresist Processing

Tay

Chua

Wang

et al. 2013

Ind. Eng. Chem. Res.

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We present a real time, in situ method to control the spatial temperature uniformity of a semiconductor substrate during the various bake steps in the lithography sequence. Significantly, the wafer temperature settles down to steady state within 50 s under closed-loop control. The corresponding maximum temperature nonuniformity during transient is less than 1 °C and the steady state temperature nonuniformity is less than 0.1 °C. Specifically, we have developed a complete thermal diffusion model for the entire bake plate-and-wafer system, so that the transient thermal behavior is accurately captured during the baking process. By monitoring the bake plate temperature and fitting the data into the model, an updated model can be estimated and the desired wafer temperature can then be calculated and controlled in real time. Experimental results confirm the efficacy of the approach and its superiority over traditional run-to-run control techniques.

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