Exposure tools

The resist must have suitable radiation sensitivity. Today s exposure tools are so costiy that tool throughput is a key measure of performance. The overall time to expose a resist film is the sum of the times to load and position the substrate in the exposure tool, to align the substrate and the mask, to irradiate the film, and to unload the complete part. In the optimum case the resist exhibits sufficient radiation sensitivity so that the fraction of the overall cycle apportioned to irradiate the film does not limit the number of substrates exposed in a given period of time. 

Three approaches have been identified that reduce susceptibility of CA resists to airborne contamination. In the first, process engineering changes such as the addition of special activated carbon filters to the environmental chambers surrounding the exposure tools (76,79), overcoating the resist with a soluble protective film to isolate the resist from the environment (77,80,81), or modifications of the process flow to minimize the time interval between exposure and post-exposure bake have been shown to improve CA resist processibibty. 

Fig. 40. Schematic of an euv exposure tool. Key features are the excimer laser-driven x-ray source and the redective optical elements (including the mask) in...

It is predicted that CEM techniques will extend resolution to feature sizes as small as 0.4X/NA, or -0.6 (tm for currently available exposure tools operating at 405 and 436 nm (91). The currently available materials afford improved resolution and yield, and increased process latitude (92). Further developments to achieve practical, water soluble systems plus a better match with the absorption characteristics of the resist would be desirable. 

Of the several competing strategics for obtaining 0.5 micrometer resolution necessary for 4 megabit static RAM devices (I), use of deep-uv exposure tools is the l... 

This study will show an approach to materials which have many of the desirable features of the poly(phthaladehyde)-onium salt imaging system but do not suffer from the problem of spontaneous gaseous material evolution upon irradiation. The new polyformal-based imaging systems all have a "built-in" thermal activation requirement which allows for image self-development outside of the exposure tool. 

Because the available photon flux and photon energy distribution for the various x-ray sources vary widely, the type of x-ray source utilized in an XRL exposure tool has a significant impact on resist selection. For this reason, it is appropriate to begin a report on resist design with a short summary describing the types of x-ray sources which are currently, or soon to be, available. A comparison... 

Clearly, the sensitivity of a resist should be commensurate with machine design parameters to allow optimized throughput. For example, an electron beam exposure system writing at a modulation rate of 20 MHz (dwell time of 50 nsec), a beam current of 5 x 10-8 amps at 10 kV, and an address structure (spot size) of 0.25 2 would require a resist with a sensitivity of 10 6 C/cm2 (1 / 2) or better in order to write the maximum number of wafers per hour of which it is capable. The same argument also applies to other exposure tools. 

Exposure tools Gamma radiation from 60Co source Flood exposure to 50 keV electrons Pattern exposure to 20 keV electrons... 

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