Water-soluble chromophore containing copolymers for bottom antireflection coating applications in lithography

Regulatory concerns in the semiconductor industry from both VOC emissions a nd solvent handling have prompted the desire to introduce water-based formu lations in spin-coating fabrication processes. As resolution demands for i- line lithography are driven to finer feature size and architecture, the nee d for antireflection coatings as a means of eliminating feature distortions from back reflected light is increasing. Common image irregularities, such as reflective notching and standing wave effects, can be effectively elimi nated through application of an antireflection coating of optimal thickness between the resist layer and substrate. This work describes the design and development of novel side-chain methacrylate copolymers for use in water-b ased antireflection coating formulations. A pendant chromophore is incorpor ated into the polymer structure to allow optimization of the critical coati ng optical properties, refractive index, and absorption coefficient. The po lymer solubility parameter and crosslinking density can be tailored by inco rporation of appropriate functionality to allow compatibility with the devi ce fabrication process. Terpolymers were designed, which were water-soluble , had a thermally activated crosslinking mechanism, and contained a keto-es ter azobenzene chromophore that was highly absorbing at i-line wavelength. Optical properties of polymer films were collected by spectroscopic elipsom etry and utilized in the design process to identify the optimum chromophore structure. Lithographic images, fabricated utilizing these coatings, were of excellent quality, allowing critical dimension resolutions of less than 0.3 mu m (C) 1999 John Wiley & Sons, Inc.