Design and synthesis of functional polymers for nanoscale electronics

The progression towards smaller critical dimensions in the semiconductor industry will require the routine and rapid patterning of nanometer scale features over large areas in the near future. In order to facilitate the patterning of features on the nanometer scale, the materials being used should be no larger than the desired pixel size. In this instance, the resolution is limited only by the ability to address the individual molecules. Herein, the successful implementation of dendrimers, hyperbranched polymers, and star polymers as resist materials for nanometer scale imaging is described. The application of self-assembled monolayers (SAMs) of dendrimers on silicon and titanium substrates for patterning by atomic force microscopy (AFM) is first described. This is followed by examples of chemically amplified resist materials based on dendrimers, hyperbranched polymers, and star polymers that have been imaged by deep-UV (DUV) and electron-beam (e-beam) irradiation. The application of these highly branched polymers represents a paradigm shift in the architecture of polymers used in the semiconductor industry.; Following a brief summary of recent efforts at patterning on the nanometer scale (Chapter 1), the application of SAMs of dendrimers as resist materials is discussed in Chapters 2, 3, and 4. Generation three, poly(benzyl ether) dendrimers were synthesized, followed by assembly onto silicon and titanium substrates through the use of covalent, ionic, and coordination attachments. A SAM of dendrimers was first patterned by AFM, resulting in a pattern that was removed via an aqueous etch process using the dendrimer monolayer as the etch mask. This resulted in a positive tone image, demonstrating the first example of pattern transfer using a single layer of dendrimers as the etch mask. In contrast, the labile nature of the ionic linkage enabled the patterning of negative tone features with improved aspect ratios through the removal of the unexposed regions following patterning by AFM. Through the application of the labile ionic binding moiety, positive tone pixels 35 nm in diameter were patterned. An elucidation of the factors controlling line width and heighth in AFM lithography is presented in Chapter 5. Several efforts have also been made to apply branched polymers (dendrimers, hyperbranched polymers, and star polymers) to conventional chemically amplified resist systems (Chapters 6, 7, and 8). A poly(aryl ether-ester) dendrimer and a poly(phenyl ester) hyperbranched polymer were modified with tert-butyl carbonate ( t-BOC) groups on the periphery in order to impart imaging capabilities to these polymers. Resist formulations of these polymers exhibited good sensitivity to DUV and e-beam irradiation. In order to image the star polymers, they were prepared with arms of poly(t-butyl acrylate). Patterning results of these branched polymers indicate that the branched architecture has a large impact on the resist performance, and is able to pattern features on the nanometer scale.