Hans-Thomas Schacht

Discriminatory protein binding by a library of 96 new affinity resins: A novel dye-affinity chromatography tool-kit

Initial acceptance of Cibacron Blue 3G-A based matrices has made dye-ligand affinity chromatography an attractive proposition. This prompted the synthesis and search for new dye structures. A systematic library of 96 affinity resins was generated using novel analogs of Cibacron Blue 3G-A and also by varying spacer lengths for immobilization. The library was tested in a batch binding and elution mode using seven different proteins--four Aspergillus enzymes namely, NADP-glutamate dehydrogenase, laccase, glutamine synthetase and arginase, bovine pancreatic trypsin and the two serum proteins human serum albumin and immunoglobulin G. Unique binding patterns were observed for each of them indicating that the library displayed discriminatory interactions. The significance of spacer length in the interaction with proteins was discernable. Trypsin interacted best with affinity resins that had no spacer. It was possible to resolve IgG and HSA from a mixture using a combination of resins. There was a good spread of HSA binding capacity in the 96 affinity resins. While some showed better HSA binding capacity than the commercial CB3GA-based matrix, a few with lower capacity were also observed. Subsequent to an initial screen, one affinity resin (CR-017) could be used to enrich Aspergillus terreus NADP-GDH from crude cell extracts. The efficacy of this dye-affinity resin was rationalized by characterizing NADP-GDH inhibition kinetics with the corresponding free dye ligand. In the sum, the library provides a set of dye-ligand affinity matrices with a potential for use in high throughput screening for protein purification.

Structural design of ketal and acetal blocking groups in two-component chemically amplified positive DUV resists

In the present study, protecting groups of moderate stability, such as acetals and ketals, were investigated as pendant blocking groups in polyvinyl phenols. Polymers were obtained by reacting enol ethers with the phenolic side groups to form acetal or ketal blocked phenols. Decomposition temperatures, glass transition temperatures, and molecular weights of the resulting polymers were monitored and correlated with the protecting group structure. Stability of the protecting groups can be explained by protonation occurring at either of the two oxygen sites, making two cleavage routes possible. Secondary reactions of the released protecting groups in the resist film were investigated and discussed. The structure of the protecting group was designed in order to meet basic resist properties such as resolution/linearity, DOF, post exposure delay latitude and thermal stability. A Canon FPA 4500 (NA equals 0.37) and a GCA XLS exposure tool (NA equals 0.53) were used for the optimization process. A preoptimized resist formulation based on the above criteria exhibits 0.23 micrometers line/space resolution, 0.8 micrometers focus latitude at 0.25 micrometers resolution and approximately two hours post exposure delay latitude.

Overview of photoacid generator design for acetal resist systems

An overview is given of how the design of photoacid generators (PAGs) is critical to tuning both the lithographic and thermal properties of chemically amplified resist systems. The importance of PAG chemistry is illustrated with an ARCH resist system that contains acetal protecting groups removable with low activation energies. We detail the effect of PAG on the resists resolution, depth of focus and thermal decomposition temperature.

Design and process of a new DUV ARCH3 resist

A new concept for polymer design is described which can extend the utility of acetal chemistry in the development of advanced chemically amplified deep-UV resists for KrF excimer lasers. Many acetal blocked polymers only impart marginal thermal flow properties to the photoresist matrix. This polymer design concept can overcome this thermal flow deficiency and also improve photoresist contrast and resolution. This concept involves the formation of crosslinked acetal polymers from linear acetal blocked polymers via acid labile crosslinks. The resulting branched polymers have increased Tg and therefore impart improved thermal flow properties to the resist. Furthermore, the acid lability of the crosslinks results in a large molecular weight differential between exposed and unexposed areas of the resist leading to larger dissolution rate discrimination between exposed and unexposed regions. The ultimate result is improved resolution capability of the resist system. This design concept has been incorporated into the ARCH3 resist series.

Deep-UV resists based on methacrylamide copolymers

The present paper describes chemically amplified positive tone Deep-UV resists based on N-hydroxybenzyl methacrylamide (HBMAA) copolymers. HBMAAs were found to be attractive comonomers, due to their facile synthesis and their beneficial impact on the physical properties of the copolymers and the photoresists prepared from them. For example, good adhesion was provided to the silicon substrate and high glass transition temperatures were achieved which confer an appreciable thermal flow stability to the resist. HBMAA/4-tetrahydropyranyl vinyl phenol/methacrylic acid terpolymers were synthesized by radical polymerization which proceeds in a statistical manner. This allows for the monomers to be combined in the appropriate ratios, thus, tailoring the polymer properties, such as the glass transition and the dissolution rate. Two and three component resist formulations based on these terpolymrs exhibit linear resolution to 0.35 micrometers (NA 0.37). Thermal flow stability of the resists exceeded 130 degree(s)C. No auto decomposition was observed. Resists were applied without top coat and have a post exposure delay latitude of more than one hour.

Advanced positive photoresists for practical deep-UV lithography

New positive tone deep UV resists with enhanced post-exposure delay (PED) latitude and process latitude are presented. Additives and functionalized sulfone terpolymers are tailored to optimize the dissolution properties and process stability. Adjustment of the dissolution rate is used as a design criterion for optimizing the resist performance. RX 165 resist, optimized using the above criteria, exhibits 0.25 micron line/space resolution, 0.8 micrometers focus latitude at 0.275 micrometers resolution, and 1 hour post exposure delay latitude.