Step-and-scan systems

Levinson, Principles of Lithography, 2nd ed., p. 162, SPIE Press, Bellingham, WA (2005). Software is often used to compensate for the effects of lens heating, see for example, P. van Oorshot, B. Kock, J. van der Spek, E. Stuiver, H. Franken, H. Bother, and R. Garreis, Performance of an I line step and scan system for suh 0.25 p,m mix and match apphcation, Proc. SPIE 3334, 423 436(1998). 

In 1989, Perkin-Elmer introduced the first step-and-scan system (a hybrid between a stepper and scanning projection system) to address the ever-increasing chip size problem and the ever-more stringent dimension control requirements. These issues were mitigated in the step-and-scan tool through the reduction of the exposure area. Developed under the auspices of a joint venture between IBM and Perkin-Elmer in the mid-1980s, the tool was sold under the brand... 

The year 1972 witnessed the invention of proximity x-ray lithography by Hank Smith at Massachusetts Institute of Technology. Many companies (IBM, Canon, Nikon), universities (MIT and the University of Wisconsin), and governments (United States and Japan) spent well over a billion dollars on its development. The first attempts at production of x-ray aligners were made in the mid-1970s by AT T and MIT, and in the early 1980s by Micronix Partners, Hampshire Instruments, Nikon, and Karl Suss. X-ray step-and-repeat and step-and-scan systems were eventually made commercially available. ... 

Figure 3.73. Step-and-scan principle. The wafer is exposed by synchronously scanning the mask and each wafer subfield through the illuminated zone of a ring-field imaging system. Reproduced with permission from reference 19. Copyright 1984 Technical Publishing.)...

On the other hand, steppers and step-and-scan exposure systems, with monochromatic, all-refractive optics, require a very narrow laser bandwidth, typically line narrowing of up to two orders of magnitude relative to the free-running exciplex and excimer lasers. Several methods that have been reported to be effective in narrowing laser bandwidth include gratings. 

Figure 3. Schematic of present and potential future optical lithography systems (a) Perkin Elmer Micralign (10), (b) Bell Labs printer (11), (c) reduction step-and-repeat (Censor, Electromask, GCA, Optimetrix, Philips), (d) IX step-and-repeat (Ultratech), (e) IX stripe scan, and (f) reduction step-scan, R indicates object and image orientations. Lenses are indicated only schematically. (Reproduced with permission from Ref. 30)...

Figure 40. Operating modes for electron beam systems left — raster scan coupled with continuous table motion right — vector scan, step and repeat.

Several other successful machines have also been reported using raster scanning. The IBM EL-1 is a step-and-repeat type system that exposes a 5 mm x 5 mm field. These small fields are then stitched together to form the complete circuit. The EL-1 systems use a 2.5 /im x 2.5 fim square beam and are used to manufacture custom circuits. 

The next level beyond the step-and-shoot method is the helical-scan approach. The conveyor belt of a heftcal-scan system moves continuously at a uniform speed and is synchronized with the rotating disk that holds the X-ray source and detectors. The synchronization ensures that by the time a bag has advanced by... 

A typical DNA array fabrication and application process involves three major steps. First, nucleic acids (the capture sequences or probes) are immobilized at discrete positions on surface activated substrates. Secondly, the resulting array is hybridized with a complex mixture of fluorescently labelled nucleic acids (the target), and thirdly subsequent to hybridization, the fluorescent markers are detected using a high-resolution scanning laser that quantifies the interaction. This chapter focuses on the first of these processes and provides the reader with an overview of substrates, surface activation methods and dehvery systems available for nucleic acid immobilization. 

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