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Area selective atomic layer deposition ͑ALD͒ of titanium dioxide using polymer films as masking layers has been investigated. A number of factors which must be considered while designing a successful area selective ALD process have been determined and are briefly discussed. Reactivity of the polymer with the ALD precursor species, diffusion of ALD precursors through the polymer mask, and remnant precursor content in the masking film during ALD cycling are key factors. This article investigates the effect of different precursor chemistries in view of the above mentioned factors. Titanium tetrachloride and titanium isopropoxide have been used as two different metal precursors in conjunction with poly͑methyl methacrylate͒ films as photodefinable masking layers. Processing problems arising from factors such as diffusion of precursors through the masking layer can be solved through careful choice of ALD precursors.

An approach to area-selective atomic layer deposition techniques based on the use of a lithographically definable polymeric masking layer has been reported. Successful direct patterned deposition of TiO 2 is demonstrated using a poly͑methyl methacrylate͒ masking layer that has been patterned using deep-UV lithography. A number of factors which must be considered in designing patternable polymeric masking materials and processes have been determined and are briefly discussed, including reactivity of the polymer with the atomic layer deposited ͑ALD͒ precursor species, diffusion of ALD precursors through the polymer mask, and remnant precursor content in the masking film during ALD cycling.Atomic layer deposition ͑ALD͒ is gaining significant attention as an alternative technique for depositing high-quality, ultrathin films. 1,2 This method is particularly useful for producing extremely thin, high-quality, conformal films with thicknesses in the 3-10 nm range where other deposition techniques such as chemical vapor deposition ͑CVD͒ have significant limitations. During ALD, film growth depends critically on the chemistry of the surface upon which deposition occurs. Thus, it should be possible to chemically tailor a surface to achieve area-selective deposition. Selective ALD requires that designated areas of the surface be masked or "protected" to prevent the ALD reaction from occurring in those selected areas, thus ensuring that the ALD film nucleates and grows only on the desired unprotected regions. One obvious advantage of such an additive, area-selective deposition process is the ability to perform direct patterned growth, thereby eliminating the need for etching and the associated subsequent cleaning steps. Elimination of these steps can greatly simplify the overall deposition and patterning process, reduce unintended damage to substrates and devices which result from the use of energetic plasma etch processes, and aid in the integration and patterning of new materials which are difficult to etch.The critical challenge in achieving area-selective ALD is devising materials and methods for modifying selected regions of a substrate surface to prevent ALD reactions from occurring, thus preventing film growth. One way to modify a surface is to chemically bond a molecule directly to the surface. Such an approach blocks reactive sites that are present and thereby prevents reactions between precursor molecules and the surface. Alkyl silanes, which contain long hydrocarbon chains terminated with a reactive silane end group, are a well-known surface-modifying agent. In the case of alkyl silanes, the hydrocarbon chains are relatively unreactive and thus provide a good protective or passivating coating for the surface. For example, octadecyltrichlorosilane ͑OTS͒ forms a densely packed, self-assembled monolayer ͑SAM͒ and has been widely investigated as a surface-modifying agent to block nucleation and growth of a variety of inorganic films such as HfO 2 , ZnO, TiO 2 , ZrO 2 . 3-5 Previous studies 3,4 have demonstrated direct ...

The function of common, positive tone photoresist materials is based on radiation-induced modulation of the dissolution rate of phenolic polymer films in aqueous base. The process through which novolac and other low molecular weight phenolic polymers undergo dissolution is examined from a new perspective in which the “average degree of ionization” of the polymer is regarded as the principal factor that determines the rate of dissolution rather than a diffusive, transport process. This perspective has been coupled with a probabilistic model that provides an explanation for the dependence of the dissolution rate on molecular weight, base concentration, added salts, residual casting solvent, and the addition of “dissolution inhibitors”. It predicts the observed minimum base concentration below which dissolution is no longer observed, and it predicts a molecular weight dependence of that phenomenon. A series of experiments was designed to test this predicted molecular weight response. The results of these experiments are in good agreement with the predicted response.