Study of Base Additives for Use in a Single Layer 193nm Resist Based Upon Poly(norbornene/maleic anhydride/acrylic acid/tert-buty Acrylate).

Abstract

We report on a study of the chemical and lithographic behavior in a 193 nm single layer resist of two types of base additives, aminosulfonates opium and tetrabutylammonium carboxylate salts. These additives were examined because of their low potential for undesirable reaction with maleic anhydride or acrylic acid repeat units in norbonene/maleic anhydride/acrylate based 193 nm resins. For ammonium carboxylate additives it will be shown that using these gives comparable lithographic performance to a standard formulation containing an amine additive. For aminosulfonate onium salts a study was done of the relationship between chemical structure of these additives and their thermal stability and the lithographic performance imparted by these to a 193 nm single layer resist system. It will be shown that the decomposition temperature is a function of the basicity (nucleophilicity) of the counter anion decreasing with increasing basicity but can be improved by going from an iodonium to a sulfonium chromophore. Cyclamate and cysteate opium salts will be shown to provide good lithographic performance with good post-exposure bake delay latitude.

Influence of base additives on the reaction-diffusion front of model chemically amplified photoresists

“…11 The reaction-diffusion process 5,12 that leads to image spreading or blurring 13 has been identified as one factor for feature quality control. 23,24 Base quencher additives have been used commercially in photoresist formulations in attempts to improve performance by limiting diffusion of the photoacid catalyst into unexposed regions. In particular, the mobility of the photoacid is significantly reduced upon deprotection of the resist due to changes in the local composition, [17][18][19][20][21] which can lead to a self-limiting front.…”

“…[14][15][16] However, there are several factors that affect the transport properties of the acid catalyst and alter the shape of the deprotection front. 5, 24,25 The influence of these neutralizing species on the reaction-diffusion process is complex. 22 Additives to the photoresist can be used to further control the spatial extent of the deprotection front.…”

The Multifunctional Role of Base Quenchers in Chemically Amplified Photoresists

“…Some additives may promote adhesion, increase mechanical strength, or inhibit the dissolution of unexposed resist. Strong bases, referred to as base quenchers, are often added to enhance pattern resolution. , The addition of base improves resist contrast and line width control by (i) neutralizing acid that is generated in the dark regions of the pattern by diffraction effects (or by the intensity threshold for X-ray or phase shifted masks) and (ii) eliminating excessive diffusion of photoacid from the exposed regions into the unexposed regions. Some amount of acid diffusion is undoubtedly necessary for chemical amplification; however, excessive acid diffusion blurs the image of the printed feature.…”