Thomas John Markley

Grafting reactions of vinyl acetate onto poly[(vinyl alcohol)-co- (vinyl acetate)]

The grafting preference of vinyl acetate onto the methine carbon of poly(vinyl alcohol) (PVOH) versus the acetate group of poly(vinyl acetate) (PVAc) was determined as part of an attempt to prepare novel branched PVOH from partially hydrolyzed PVAc. The results showed long chain grafting on the acetate groups of the PVAc units rather than the methine carbons of the PVOH or PVAc units. Decreasing the monomer or initiator concentration decreased the molecular weight of the graft copolymer formed. Of the initiators studied, ammonium persulfate gave the largest increase in copolymer molecular weight. Both hydrolysis and reacetylation combined with gel permeation chromatography (GPC) and 13C-NMR of the fully hydrolyzed material were used to estimate the number and location of grafts.

Solid state cyanocobaltates that reversibly bind dioxygen: synthesis, structure and reactivity relationships

New pentacyanocobaltate compositions, Li 3 Co(CN) 5 . 1.42DMF . 0.48DMAC (3) (DMF = N,N-dimethylformamide, DMAC = N,N-dimethylacetamide) and Mg 1.5 Co(CN) 5 . 2DMF (4) were prepared and as solids were found to reversibly bind dioxygen. Compound 3 was found to be more stable to repeated cycling between O 2 and N 2 atmospheres than the previously reported Li 3 Co(CN) 5 . 2DMF (2). The cyanide stretching frequencies of 3 and 4 are significantly higher than for (Et 4 N) 3 Co(CN) 5 , an irreversible O 2 sorbent. This is ascribed to a loss of electron density from cobalt due to interaction of cyanide with the cations Li(1 +) and Mg(2 +) resulting in reversible O 2 binding.

Hexafluoroisopropyl and trifluoromethyl carbinols in an acrylate platform for 157-nm chemically amplified resists

Electromagnetic radiation in the vacuum-ultraviolet (VUV) region is needed for imaging of very fine features at the 65 nm and 45 nm nodes. Photolithography using 157-nm radiation, emitted from an F2 excimer laser, is a candidate for next generation lithography. Only chemically amplified resists containing fluorinated hydrocarbons and siloxanes have the required transparency at this wavelength. We have identified hexafluoroisopropanol units as a building block for our 157-nm resist polymers. This paper reports our progress on the most recent research development for this platform. The hexafluoroisopropanol functionality, which has a pKa similar to phenol, has been used to increase the transparency of 157-nm single-layer acrylate-based resists. Our recent effort has been focused on the syntheses of new acrylate monomers with highly transparent building blocks based on trifluoroacetone. The first example, a homopolymer derived from trifluoroacetone bearing a fluorinated hemiacetal unit, has moderate transparency at 157 nm (A = 1.9 μm-1). We have also introduced a new acrylate monomer containing a trimer based on trifluoroacetone, where the 6-hydroxy group in the hemiacetal unit is substituted by a fluorine atom, with an acceptable transparency at 157 nm (A = 2.1 μm-1). Copolymers of the former monomer, derived from trifluoroacetone, and tert-butyl α-fluoroacrylate have also been prepared and showed good 248-nm lithographic performance suggesting suitability for 157-nm lithography. This paper will discuss the transparency, etch resistance and chemical properties of several fluorinated acrylate-based resists, synthesized from groups containing pendent hexafluoroisopropanol units and trimers derived from trifluoroacetone.

Wetting and dissolution studies of fluoropolymers used in 157 nm photolithography applications

Photolithography using the F2 excimer laser at 157 nm, a technology to bridge traditional optical lithography and next generation lithographies, promises to enable ultralarge scale integrated devices with sub-70 nm design rules. Chemically amplified resists based on fluoropolymers have previously been shown to be good candidates for 157 nm microlithography. In our research, hexafluoroisopropyl alcohol (HFIPA) groups have been incorporated into polymers to improve the base solubility and to increase the transparency needed for new photoresists at 157 nm. These new polymers have absorbance values at 157 nm ranging from 1.7 to 3.9 μm−1. The introduction of fluorine groups increases their hydrophobicity and makes these polymers more difficult to wet at the surface. We have studied the effect of fluorine content on hydrophobicity of fluorinated polymers by measuring contact angle data over short time intervals. The ability to combine fluoropolymer synthesis with extensive contact angle studies has proven to be...

Novel negative tone photodefinable low dielectric constant hybrid films

Multifunctional films have the potential to reduce the number of processing steps to prepare various complex electronic devices and thereby reduce the cost of manufacturing the device and increase the throughput of the process. By combining low dielectric thin film and photoresist technologies into one material, such an advantage could be provided to electronics device markets. Air Products and Chemicals has discovered negative tone photodefinable films having dielectric constant values less than 3.0 that are developable in water and/or aqueous TMAH solutions. The low dielectric films produced via a novel reaction pathway involving the use of photoacid generators (PAGs) provides a versatile link to various feature sizes depending on the choice of radiation source and PAG used. Specific examples of film properties and processing latitude will be presented for these developmental materials.

Novel reactions of quadricyclane: a new route to monomers for low-absorbing polymers in 157-nm photoresists

Norbornene monomers with fluorinated substituents are often used in copolymers targeted for photoresist applications at 157 nm. Homopolymers of these norbornene monomers typically exhibit an absorption coefficient greater than 1.5 μm-1. Comonomers, which are often perfluoroolefins, are needed to meet the transparency requirement for 157 nm lithography, namely an absorption coefficient less than 1.0 μm-1. Clearly, a norbornene monomer that gives a homopolymer with an optical density less than 1.0 μm-1 would require less, if any, perfluoroolefin comonomer, providing a distinct advantage in the production of the base resin. Research in Air Products and Chemicals’ labs has led to the discovery that fluorinated hydroxyalkyl ether derivatives of norbornene ring systems with suitable substitution patterns can give homopolymers with absorption coefficients of less than 1 μm-1. The monomers are produced via a novel reaction pathway involving quadricyclane. This pathway provides a versatile and rich synthetic chemistry, and the potential for eliminating, or at least substantially decreasing, perfluoroolefin incorporation into 157 nm photoresists. Specific examples of these reactions are discussed here, along with VUV-VASE and etch resistance data for a series of polymers derived from quadricyclane reactions.

Impact of surfactant in developer on CD performance

Surfactant-formulated developers were utilized to enhance the CD performance for 365nm (I-line), 248nm (DUV) and 193nm resist processing. From one generation to the next, the resist surface becomes more and more hydrophobic, creating the need for enhanced surface wetting. Contact angle measurement of surfactant-formulated developers on different generations of resist surfaces, from 365nm to 157nm resist surfaces, indicated improved wetting. On-wafer testing showed significant improvement on CD uniformity with surfactant-formulated developers for 365nm, 248nm and 193nm processing. Faster development rates were also observed for chemically amplified resist systems, including 248nm, 193nm and 157nm.

New Metal Complex Oxygen Absorbents for the Recovery of Oxygen

Emerging non-cryogenic technologies for the separation of air use zeolites and microporous “molecular sieve” carbons as moderately selective nitrogen and oxygen adsorbents, respectively.1,2 While the zeolites have a thermodynamic affinity for N2, use of carbons relies on a kinetic selectivity for the passage of oxygen into the micropores. It is well known that certain coordination compounds of cobalt and iron reversibly react with oxygen under near ambient conditions.3,4 Since this is a chemical rather than a physical interaction as is seen with zeolites and carbons, it should be possible to use such metal complexes as O2 equilibrium sorbents for air separation. We have been conducting a long term research effort to prepare such metal complex oxygen carriers for use in future generation non-cryogenic air separation devices.5 The primary interest in such complexes is in their use in pressure or temperature swing processes for the production of inert gas (N2,Ar) and oxygen.6,7 For these applications, the oxygen complex could either be used as a circulating liquid or as a solid sorbent. In order to be useful in a commercial process an oxygen complex has to satisfy several requirements. It must (a) bind O2 rapidly and reversibly, (b) have a high stability (>1 year lifetime), and (c) be accessible via simple synthetic techniques at minimal cost.