Resist process optimization for a DUV laser pattern generator

Abstract

For many years, laser patter generation has been printing on i-line resists. As features sizes continue to shrink, laser pattern generation is moving to DUV laser wavelengths, and a production worthy resist process is needed. Characteristics such as standing waves, resist foot and CD drift during and after the exposure have previously challenged efforts to migrate to 248nm stepper chemically amplified resists (CARs) to mask making applications. In this study the performance of a commercially available 248nm laser/e-beam resist solution is examined on the Sigma7000 series laser patter generators.To achieve virtually no resists foot as well as tight CD control, the optimum process conditions for optical laser applications were sought. Cross-sectional and top-down scanning electron microscopy was performed to evaluate the resist and dry etch processes. A comparison is made with the resist DX1100P, used in initial stages for DUV laser pattern generators development. The new resist also benefit from being well established in mask making with e-beam mask writers.

Managing effects in CD control from PED and PEB in advanced DUV photomask manufacturing using FEP-171 resist

“…We also found that commercially coated blanks are rather insensitive to PEB temperature variations. Earlier investigations using in-house coated blanks [1] showed larger dependence on PEB temperature with respect to the final lithographic performance. Thus for optimal process performance, PEB conditions can not be considered separately from post-apply bake.…”

“…Based on previous work [1] Table 1 is from the moment the resist surface reaches the setpoint temperature (after 4 minutes) until end of bake. For the process window evaluation, the dose range used was 70-130% (10% steps) and the focus range was ±0.4µm (0.1µm steps).…”

“…The lithographic performance of advanced chemically amplified resists (CAR) is to large degree determined by control of the acid diffusion and acid quencher (base). The photoacid diffusion and the influence of the baking steps post-apply bake (PAB) and PEB on diffusion phenomena has been well documented [1][2][3][4]. Higher post apply bake temperatures lead to reduction of remaining solvent inside the resist film thus densification of the resist film and thereby a reduction of acid mobility.…”

High performance FEP-171 resist process in combination with NTAR7 and NTAR5 chrome and the Sigma7300 DUV mask writer

“…Category Paper title Conference [1] Resist screening and PAB/PEB tuning In Part One of this paper the development process for binary masks is fine tuned one step further with respect to lithographic performance on mask, especially CD linearity and clear-field/dark-field variation. Design of Experiment (DOE) was used to generate a new fine tuned development recipe.…”

“…The recent introduction of high-productivity DUV laser mask writers has been facilitated by a relatively straight forward adaptability to the standard materials and processes used for 50 keV VSB. This adaptation has been described for binary masks in a series of papers [1][2][3] for the SLM-based DUV (248 nm) Sigma7300 mask writer [4][5], papers that have also suggested possible optimizations of the materials and processes for the Sigma7300. An overview of the Sigma7300 process papers is found in Table 1.…”