Optical lithography systems

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 1.25 Optical lithography system of lenses (Canon).31...

The two principal modes of operation of electron-beam exposure systems include the maskless direct-write electron-beam machines and the mask-based electron-beam machines. Direct-write electron-beam machines operate directly from design data and are capable of extremely high resolution. Mask-based electron-beam systems utilize masks in their imaging process. The implementation of electron-beam lithography in mix-and-match mode with optical lithography in a manufacturing environment has been demonstrated. 

S. S. Miura, C.F. Lyons, and T.A. Brunner, Reduction of linewdith variation over reflective topo graphy, Proc. SPIE 1674, 147 156 (1992) H. Yoshino, T. Ohfuji, and N. Aizaki, Process window analysis of the ARC and TAR systems for quarter micron optical lithography, Proc. SPIE 2195, 236 245 (1994). 

There are six basic elements of optical lithography, i.e., (i) an exposure source, (ii) an illumination optics system, (iii) a photomask or reticle and its pellicle, (iv) a projection optics system, (v) a wafer stage, and (vi) a photoresist-coated wafer. As shown in Fig. 13.3, the source provides the exposure radiation that, with the aid of the illumination optics, illuminates the photomask and transfers... 

The key operational parameters of exciplex and excimer lasers used in optical lithographic applications include exposure-dose-related parameters comprising average power, pulse energy, repetition rate, and pulse width temporal coherence spatial coherence including beam dimensions, beam divergence, and beam uniformity and maintenance and reliability. Table 13.2 lists some of the key operational parameters of KrF, ArF, and F2 laser systems used in optical lithography. 

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