A pattern-recognition and encoding system has been developed for a biochip platform using shaped hydrogel sensors batch produced via photolithography. Each sensor shape is fashioned with a unique pattern of dots that makes it identifiable to a pattern recognition system. By linking the sensor's function to its shape, "random" arrays can be created (i.e., arrays that do not require sensors to be located at specific positions). Random arraying can be quickly and cost-effectively achieved via self-assembly methods. Pattern-recognition software was written to perform automated recognition of micrographs exhibiting fluorescing sensors. As a test of the recognition process, an array of shape-encoded DNA sensors was fabricated using lithography. Fluorescent micrographs were taken of a DNA-sensing experiment, and then processed with the pattern-recognition software. The results show that this process is quite viable with 98% recognition accuracy of the nondefective sensors in both images.
In immersion lithography a fluid with a high refractive index is used to enable increases in the numerical aperture (NA) of the imaging system and therefore decrease the minimum feature size that can be patterned. Water has been used in first generation immersion lithography at 193 nm for the 45 nm node. To generate still smaller features, fluids with a higher index than water are needed. Both saturated hydrocarbons and a new class of salts with incorporated alkane groups have been studied. Both of these types of fluids possess the "adjustable" absorbance edge behavior needed to provide a fluid with a high index and low absorbance at 193 nm. Since alkanes have physical properties that are difficult to integrate into current fluid handling systems, the aqueous solutions are particularly attractive as more semiconductor-friendly fluids. A full characterization of the optical properties of these fluids will be reported, as well as physical property results and confirmation of the feasibility of 32 nm l/s imaging with 1.5 NA using the salt solutions.
ArF immersion lithography using water as a fluid medium enables production of 45 nm features. Extending immersion lithography to 32 nm or below requires increases in the refractive indices of the lens material, the immersion fluid, and the resist material. However, a material with a high refractive index generally also has high absorbance. In attempt to design a resist with high refractive index and low absorbance, we studied several types of sulfur-containing polymers and determined which sulfur groups increase the refractive index without increasing the absorbance at 193 nm. We describe new thioester and sulfone structures that enable high index with low absorbance. This chemistry has been exploited to produce polymers with a refractive index of 1.8 at 193 nm and an absorbance less than 1.4 &mgr;m-1. The compatibility of the sulfur functionality with chemically amplified imaging chemistry was demonstrated by printing at 193 nm.
Immersion lithography at 193nm has rapidly evolved from a novel technology to the top contender for the 45nm device node. The likelihood of immersion implementation in semiconductor manufacturing has raised interest in expanding its capabilities. Extending resolution requires immersion fluids with higher refractive indices than those currently available. We have therefore sought substances which, when added to water, increase the refractive index at 193nm without increasing the absorbance and viscosity beyond acceptable limits. This work explores the relationship between index of refraction and absorbance, with specific focus on the identification of fluids that have a high index and low absorbance. The majority of the fluids studied either have prohibitively high absorbance values or material properties that would be incompatible with current fluid handling systems. However, a class of methylsulfonate salts was identified with optical and material properties approaching the target values. Fluid testing and imaging is included to confirm the resolution enhancing capability of these new high index fluids.