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

Abstract

Regulatory concerns in the semiconductor industry from both VOC emissions and solvent handling have prompted the desire to introduce water-based formulations in spin-coating fabrication processes. As resolution demands for i-line lithography are driven to finer feature size and architecture, the need 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 eliminated 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-based antireflection coating formulations. A pendant chromophore is incorporated into the polymer structure to allow optimization of the critical coating optical properties, refractive index, and absorption coefficient. The polymer solubility parameter and crosslinking density can be tailored by incorporation of appropriate functionality to allow compatibility with the device fabrication process. Terpolymers were designed, which were water-soluble, had a thermally activated crosslinking mechanism, and contained a keto-ester azobenzene chromophore that was highly absorbing at i-line wavelength. Optical properties of polymer films were collected by spectroscopic elipsometry 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 m.

Synthesis of a photo‐patternable cross‐linked epoxy system containing photodegradable carbonate units for deep UV lithography

“…Because these values have been known to impart effective antireflective properties to the polymer materials, 20 mol % of AMMA was used in this study. 15 MAA was introduced into the polymer because it can impart dual functions such as cross-linking with the oxirane groups of BOCA to generate a stable cross-linked epoxy film and increasing the solubility of the decomposed film (third structure in Fig. 1) in the basic developer, tetramethyl ammonium hydroxide (TMAH) 2.38% aqueous solution.…”

“…4). Because these values have been known to impart effective antireflective properties to the polymer materials, 20 mol % of AMMA was used in this study 15…”

Understanding deviations in lithographic patterns near interfaces: Characterization of bottom anti-reflective coatings (BARC) and the BARC–resist interface

“…Bottom anti-reflective coatings (BARCs) are used extensively in photolithography to improve processing performance by minimizing standing waves, thin film interference effects, and reflective notching from reflecting substrates [18][19][20][21][22][23]. The photoresist is spun cast onto the BARC, which is typically a cross-linked polymer network, loaded with a dye that absorbs the UV exposure radiation, limiting reflections from the substrate.…”