Immersion lithography at 193nm has rapidly evolved from a novel technology to the top contender for the 45nm device node. The likelihood of immersion implementation in semiconductor manufacturing has raised interest in expanding its capabilities. Extending resolution requires immersion fluids with higher refractive indices than those currently available. We have therefore sought substances which, when added to water, increase the refractive index at 193nm without increasing the absorbance and viscosity beyond acceptable limits. This work explores the relationship between index of refraction and absorbance, with specific focus on the identification of fluids that have a high index and low absorbance. The majority of the fluids studied either have prohibitively high absorbance values or material properties that would be incompatible with current fluid handling systems. However, a class of methylsulfonate salts was identified with optical and material properties approaching the target values. Fluid testing and imaging is included to confirm the resolution enhancing capability of these new high index fluids.
The design of 157 nm photoresists is a daunting task since air, water, and most organic compounds are opaque at this wavelength. Spectroscopic studies 1 led to the observation that fluorinated hydrocarbons and siloxanes offer the best hope for the transparency that is necessary for the design of an effective 157nm photoresist, and these classes of materials have quickly become the prominent platforms for a variety of research activities in this field. There have been a number of authors that have suggested that negative resists have unique attributes for specific device applications. 2 Numerous authors have discussed negative photoresists over the years. There are many uses for such materials at various levels in a semiconductor device 2 . One such use is with complementary phase shift mask thus eliminating the need for a second exposure step. This paper reports our recent progress toward developing a negative 157nm resist materials based on fluoropolymers with crosslinkers that are transparent at 157nm. The authors will report on the synthesis of the polymers used in this work along with the crosslinkers and other additives used in the formulation of the photoresist. Imaging experiments at practical film thicknesses at 157nm with binary and strong phase shifting masks will be shown demonstrating imaging capabilities. Spectroscopic data demonstrating chemical mechanisms and material absorbance will be shown along with other process related information.
In this paper we review the design and performance of ArF resists developed from various polymer platforms. Inadequate etch performance of early ArF acrylate platforms necessitated the development of new etch resistant platforms, in terms of both etch rate and etch uniformity. Two resist platforms were developed to address etch resistance: 1) alternating copolymers of cyclic olefins and maleic anhydride (COMA); and 2) polycycloolefin polymers (CO). Improvements have been made in the imaging performance of these resists, such that they now approach the lithographic performance of acrylate based resists. Recently, a third platform based on polymerization of vinyl ethers with maleic anhydride (VEMA), which has excellent etch performance, was developed by Samsung. Here we will focus our discussion on acrylate, COMA and VEMA based resists.
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