Contrast enhancement materials

Watanabe S, Ishihara T, Itoh KI. Alkali-Soluble Nitrone Compounds and Contrast Enhanced Material Comprising the Same, US Patent No. 5310620, May 10, 1994. 

Scheme IV, Photobleaching of a diarylnitrone to an oxaziridine in contrast-enhancement materials.

We have also demonstrated other lithographic uses for polysilanes as nonimageable O2-RIE barrier layers (9), as short wavelength contrast enhancing materials (26) and more recently as sensitive, positive e-beam resists (36). 

Evaluation of Witer-Soluble Diazonium Salts as Contrast-Enhancement Materials Using a g-Line Stepper... 

An aqueous solution of diazoniun salt and polyvinyl pyrrolidone is used as a contrast enhancement material. An improved resist profile is obtained with this CEL material when a g-line stepper is used. Resist contrast is discussed in terms of such optical characteristics as the quantun yield of bleaching and the molar absorption coefficient for the materials. 

The contrast enhancement materials reported so far can be classified into three categories, namely nitronesd,2,3), polysilanes(4), and a diazoniun salt(5). However, the use of nitrone and polysilane in the CEL process presents a problem, because organic solvents are required in the film forming and... 

Because of their desirable properties and radiation sensitivity, polysilanes have been used in a variety of microlithographic applications as (1) mid-UV contrast-enhancing materials, (2) imaging layers in a variety of bilayer lithographic processes, and (3) new resist materials for ionizing radiation. 

Chart 2.3. Various dyes used as contrast-enhancement materials. The poly-silanes are useful in the mid-UV region (308-313 nm), the other materials are designed for use in the near-UV region (365- 36 nm). 

Ding, Y, Hu,Y, et al. Polymer-assisted nanoparticulate contrast-enhancing materials. ScienceChina Chemistiy,53(3), 479-486 (2010). 

The principle of contrast enhancement by photobleachable layers has been known in photography for quite a long time. New formulations were developed for application in lithography and used for the production of cathode ray tubes More recently, a family of arylnitrones have been investigated and described as effective contrast-enhancing materials (CEM) for use in IC-lithography The photochemical reaction which occurs is a cyclization reaction ... 

The amount of contrast material required for CTA is comparable to that used for conventional contrast-enhanced CT imaging. The amount of scanning time required for a CTA examination of the head and neck, such as is usually performed for acute... 

To date, we have exercised these materials in basically three types of multilayer lithographic applications (1) as short wavelength contrast enhancing layers, (2) as imagable 02-RIE resistant materials in bilayer processes and (3) as radiation sensitive materials for multilayer, e-beam processes. 

A rapidly increasing number of publications on polysilanes documents current interest in these polymers (JJ. Polysilanes are potentially applicable in microlithography as high resolution UV-resists (2J, imageable etch barriers ), or contrast enhancement layers (4). They have been successfully used as precursors to Si-C fibers (5J and ceramic reinforcing agents ((L). Polysilanes have also initiated polymerization of vinyl monomers (J ). Doping of polysilanes have increased their conductivity to the level of semiconductors (8). Very recently polysilanes were used as photoconductors (9) and non-linear optical materials (10b... 

Abstract Raman spectroscopy can potentially offer a non-invasive, information rich biochemical snap-shot of living human cells, tissues or material-cell tissue constructs rapidly (seconds-minutes), without the need of labels or contrast enhancers. This chapter details the exciting potential and challenges associated with the use of this analytical technique in tissue engineering (TE). The use of Raman spectroscopy in three intricately linked areas of TE will be considered (1) the characterisation of the various scaffolds and smart materials, (2) the biochemical analysis of cellular behaviour important in TE (e.g. differentiation) and (3) the use of Raman spectroscopy for the analysis of tissue/extra-cellular matrix (ECM) formation in vitro or possibly in vivo. 

Figure 2.5. The intensity function or aerial image of a mask is ideally a square wave. However, projection optics operating near their diffraction limit degrade this square wave into a sinusoid with a small direct current dc) term. When this intensity function is imposed on the contrast-enhancement lithographic material, bleaching occurs most rapidly in the high-intensity areas such that the transmitted intensity function that exposes the resist is modified and thus leads to improved contrast.

---