Larry Rhodes, Chun Chang, Cheryl Burns, Dennis Barnes, Brian Bennett, Larry Seger, Xiaoming Wu, Andy Sobek, Mike Mishak, Craig Peterson, Leah Langsdorf, Hideo Hada, Hiroaki Shimizu, Kazuhito Sasaki
Of all candidate 193 nm photoresist binder resins, transition metal catalyzed vinyl addition cyclic olefin (i.e., norbornene) polymers (PCO) hold the promise of high transparency and excellent etch resistance. In order to access lower molecular weight polymers, which are typically used in photoresists, α-olefin chain transfer agents (CTAs) are used in synthesizing vinyl addition poly(norbornenes). For example, HFANB (α,α-bis(trifluoromethyl)bicyclo
[2.2.1]hept-5-ene-2-ethanol) homopolymers (p(HFANB)) with molecular weights (Mn) less than 5000 have been synthesized using such chain transfer agents. However, the optical density (OD) at 193 nm of these materials was found to rise as their molecular weights decreased consistent with a polymer end group effect. Extensive NMR and MS analysis of these polymers revealed that olefinic end groups derived from the chain transfer agent were responsible for the deleterious rise in OD. Chemical modification of these end groups by epoxidation, hydrogenation, hydrosilation, etc. lowers the OD of the polymer by removing the olefinic chromophore, however, it does require a second synthetic step. Thus a new class of non-olefinic chain transfer agents has been developed at Promerus that allow for excellent control of vinyl addition cyclic olefin polymer molecular weight and low optical density without the need of a post-polymerization chemical modification. Low molecular weight homopolymers of HFANB have been synthesized using these chain transfer agents that exhibit ODs ≤ 0.07 absorbance units per micron. This molecular weight control technology has been applied to both positive tone and negative tone vinyl addition cyclic olefin binder resins. Lithographic and etch performance of positive tone photoresists based on these binder resins will be presented.
Alicyclic polymers, such as substituted polynorbornenes, are one potential material solution for providing photoresist polymer resins with high transparency backbones for photolithography at 193 nm and 157 nm wavelengths. In addition, the bis-trifluoromethyl carbinol functional group has been identified as a highly transparent base soluble group that can be used for producing photoresist resins from polynorbornene materials for 157 nm lithography. In this work, the interactions between commercial photoacid generators (PAGs) and bis-trifluoromethyl carbinol substituted polynorbornene (HFAPNB) are examined. It was found that photoacid generators can act as strong dissolution inhibitors for bis-trifluoromethyl carbinol substituted polynorbornene homopolymers. More importantly, it was found that a variety of photoacid generators can act as photoswitchable dissolution inhibitors for these materials, with exposure of the photoacid generator resulting in a reduction in the dissolution inhibition (i.e. increased dissolution rate) of the functionalized polynorbornene. The complete inhibition of unexposed HFAPNB polymers by iodonium photoacid generators allows for the formulation of photodefinable materials using a simple two component system consisting only of PAG and the HFAPNB polymer.
As features shrink below 100 nm, new exposure technologies such as 157 nm lithography are being developed. One of the critical challenges in developing these new lithographic tools and processes is the development of appropriate resist materials that can be used at these lower exposure wavelengths. Creating organic resist polymer resins for 157 nm exposure is a particularly challenging issue since many organic functional groups absorb at this wavelength. It has been previously shown that fluorinated polymers may offer the required low optical absorbance needed to serve as resist resins for 157 nm lithography. In particular, there has been interest in bis-trifluoromethyl carbinol substituted polynorbornenes (HFAPNB) and similar materials for use in photoresists. The bis-trifluoromethyl carbinol group offers a base soluble group that is sufficiently transparent to be used at 157 nm. This work has focused on the dissolution behavior and other characteristics of bis-trifluoromethyl carbinol substituted polynorbornenes. In particular, it was found that the dissolution behavior of the HFAPNB homopolymer is strongly controlled by its ability to hydrogen bond with both neighboring chains and also other small molecule additives such as dissolution inhibitors and photoacid generators. A detailed molecular level explanation for these effects is presented. The interaction of a series of commercial photoacid generators with HFAPNB polymers are presented. The use of such information for the rational design of advanced resist materials using these polymers will be discussed.
Fluorinated diesters were synthesized and evaluated as dissolution inhibitors (DIs) for 157 nm lithography. The results of dissolution rate measurements, exposure studies, and etching experiments on blends of fluorinated polymers containing these dissolution inhibitors are reported. It was shown that the DIs effectively slow the dissolution rate of the matrix polymer, poly(hexafluorohydroxyisopropyl styrene) (PHFHIPS). Etching studies show that they enhance the plasma etch resistance of poly(methyl methacrylate) using tetrafluoromethane plasma. Addition of the best performing dissolution inhibitor, cyclohexane-1,4-dicarboxylic acid bis-(1-cyclohexyl-2,2,2-trifluoro-1-methyl-ethyl) ester) (FCDE1) to candidate 157 nm photoresist polymers, Duvcor and poly(hexafluorohydroxyisopropyl styrene)-co-poly(t-butyl methacrylate) [pPHFHIPS-co-pt-BMA], improves the imaging behavior of these polymers. Our attempts to elucidate the mechanism of dissolution inhibition for this series of compounds will be discussed. Fourier Transform Infrared (FTIR) studies in conjunction with dissolution rate measurements performed on a series of DI analogues suggest a mechanism based on hydrogen bonding.
Stephen Hill, Pavi Sandhu, C. Buhler, Shinya Uji, James Brooks, Larry Seger, M. Boonman, A. Wittlin, J. A. Perenboom, Philippe Goy, R. Kato, H. Sawa, S. Aonuma
We will discuss the unique high field millimeter-wave spectroscopic capabilities which we have developed at the National High Magnetic Field Laboratory. The main purpose of this effort is to investigate the electrodynamic response of novel conducting materials in very strong magnetic fields. The paper is organized as follows: we begin by discussing the motivation for these studies, followed by an overview of the experimental techniques; the remainder of the paper focuses on a number of recent experimental studies.
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