Resist optimization for SOR x-ray lithography using an orthogonal experimental design

Abstract

A positive tone chemically amplified resist is optimized for SOR x-ray lithography using an orthogonal response surface experimental design. Seven factors are manipulated in the matrix, including two resist chemistry factors and five process factors. Electrically probed linewidths are analyzed for statistical significance of main effects and interactions. The resist chemistry and process are coupled and advanced lithographic work must consider both together if optimized performance is desired. The shape and size of the Exposure-Gap tree for +/- 10% linewidth control is influenced strongly by resist chemical and process changes and is not just a function of the aerial image. Dose latitude is not correlated with resist sensitivity indicating stochastic effects don't affect the image quality significantly in acid catalyzed resist processing. There is >+/- 10% dose latitude available for quarter micron imaging over a 5 micron gap range. The work shows that a formulation and process exist which is compatible with quarter micron lithography with relatively wide process latitude and straight resist profiles were obtained with good sensitivity.