C. G. Willson

Measurement of Thin‐Film Dissolution Kinetics Using a Quartz Crystal Microbalance

A new general method for measuring the dissolution kinetics of thin films is described. In this technique, the film is cast on a piezoelectric quartz crystal. The mass of the dissolving film is determined as a function of time by monitoring the characteristic oscillation frequency of the crystal. Frequency shifts exhibited by the crystal are shown to be linearly related to the mass of the cast film. The method allows determination of the dissolution kinetics of films knowing only their density and the characteristic oscillation frequency of the uncoated quartz crystal. The technique has several advantages over alternative in situ methods based on optical interferometry or capacitance. It can be used to measure very high dissolution rates and to study thick or opaque films that otherwise could not be studied.

Use Of A Quartz Crystal Microbalance Rate Monitor To Examine Photoproduct Effects On Resist Dissolution

A new general method for measuring dissolution kinetics of thin films has been developed. This technique employs a quartz crystal microbalance to measure the mass of the dissolving thin film. The method allows the measurement of very rapid dissolution rates, and can also be used to study the dissolution kinetics of thick or opaque films. The technique has several advantages over alternative in situ methods based on optical interferometry or capacitance. This instrument has been used to examine the effects of photoproducts on the dissolution kinetics of positive photoresist. The influence of photolytically generated carboxylic acid, and the nitrogen byproduct entrapped in the film, have been independently assessed by comparing the solubility of films of novolac resin, and films of resin plus carboxylic acid photoproduct, with that of exposed photoresist. Our results indicate that the acid does not significantly influence the solubility of the resin, and that entrapped gaseous photoproducts exert a rate-enhancing effect.

Inorganic Photoinitiators for Photolithographic Applications

Photolithography is used extensively in the microelectronics industry to generate three-dimensional patterns in a solid substrate such as single crystal silicon (Willson 1983; Bowden 1984). Figure 1 illustrates the sequence of steps that comprise the typical photolithographic process. The substrate initially is coated with a thin layer of a photosensitive material, termed a resist, and then exposed to light through a mask containing transparent and opaque areas that define the desired pattern. The transparent areas transmit light which causes a photochemical reaction in the resist, thereby affording a means of differentiating the exposed and unexposed regions. Preferential dissolution of the unexposed resist in a suitable developing solvent, for example, creates a negative tone image of the mask on the substrate surface (a positive tone image results if the exposed resist dissolves preferentially in the developer). This image, in turn, can be transferred into the substrate via a chemical and/or physical etching process in which the areas not protected by the resist are attacked by the etchant. The final step involves stripping away the resist to yield a negative tone relief image in the substrate that replicates the pattern of the mask.

Poly(alkylnylstannanes). A new class of main chain organotin polymers

SummaryThe synthesis of poly(alkynylstannanes) was achieved by the step-growth polymerization of bisaminostannanes and α,ω-diynes. This is a new class of organotin polymers containing tin-alkyne linkages in the polymer backbone. The polymers were obtained in good yield, albeit with relatively low molecular weight. The polymers underwent crosslinking on standing to give insoluble material and required stabilization with radical inhibitors. The thermal properties of these materials, and the influence of the group pendent to tin are discussed.