Contact angles and structure/surface property relationships of immersion materials

Abstract

Surface properties of materials are an important, even vital, consideration in immersion lithography. Many investigations have shown that sessile drop static contact angles are not entirely useful in the design of high performance immersion lithography surfaces. We have synthesized and characterized a broad family of "hydrophobic" materials and this paper will share information on the role of molecular structure on contact angles and hysteresis of these immersion materials. Insight into the relationship between structure and contact angles for future immersion materials will be presented.

Novel topcoat materials with improved receding angles and dissolution properties for ArF immersion lithography

“…Increasing fluorine-content in the polymer is the most widely used approach to increase contact angle, which reflects hydrophobicity. However, it was reported that after a certain point (more than 5 fluorocarbon groups), advancing contact angle (ACA) stops increasing [3]. RCA is also dependant on fluorine-content.…”

“…Reported by Honda et. al., the increasing effect on RCA by increasing fluorine content rapidly diminishes after 6 or more fluorine atoms [3]. Therefore, the possibility of reaching target contact angles by controlling adequate fluorine content was realized.…”

Advances in Patterning Materials for 193 nm Immersion Lithography

“…To study the fundamental interaction of water with immersion surfaces, contact angle measurements are made using commercially available systems. − In the tilting sessile drop method shown in Figure , for example, a droplet of water is placed on a coated substrated that is tilted until the droplet begins to slide. The static advancing contact angle (SACA, θ s,a ) and static receding contact angle (SRCA, θ s,r ) are determined just before the drop begins to slide.…”

“…Unfortunately, most of these base-solubilizing groups are hydrophilic, lower receding water contact angles, and increase contact angle hysteresis. Fluoroalcohols and trifluoromethanesulfonamides are particularly well-suited for use in alkali-soluble immersion materials because the fluoroalkyl groups in these moieties make them considerably more hydrophobic . Hexafluoroalcohol-based materials in particular exhibit good water contact angles, acceptable dissolution rates in TMAH developer, and high solubility in alcoholic casting solvents.…”

“…The water contact angles of side-chain fluorinated acrylic polymers are strongly dependent upon the length of the fluorinated segment. , For example, the dynamic contact angles of water droplets on poly(fluoroalkyl acrylate) polymers (i.e., −[CH 2 CH(CO 2 (CH) x (CF 2 ) y −1 CF 3 )] n −, wherein x = 1 for y = 1−2, and x = 2 for y = 4−10) are shown in Figure as a function of the length of the perfluorinated side-chain length ( y ) . Takahara et al attributed the very high receding contact angles of polymers having long ( y > 8) perfluorinated segments to ordered, crystalline structures of the fluorinated side-chains at the surface.…”