Chemical amplification in resist design

Abstract

The remarkable advancement of the microelectronics technology we have witnessed in the past decade are the direct result of the increase in the number of components per chip, which has been made possible by decreasing the minimum feature size on the chip. The feature size continues to shrink, placing stringent demands on resist materials that are used to fabricate minute integrated circuit devices. Reduction of the feature size to <0.5 μm will require the introduction of new lithographic technologies that employ short wavelength radiations such as deep UV (<300 nm), electron beams and X-rays. However, these high resolution lithographic technologies demand extremely high resist sensitivities for their economical operation. The concept of 'chemical amplification' was proposed in 1982 to dramatically boost the sensitivity through incorporation of a gain mechanism in imaging chemistries. In this scheme, photochemically generated acids are used as catalyst to induce a cascade of subsequent chemical reactions in the resist film. The use of photochemical acid generators has not only provided high sensitivities but also offered high contrast and resolution, allowing the design of a whole new family of advanced resist systems, which are reviewed in this paper with emphasis placed on the chemistry responsible for imaging.