Projection printing

Bowden, The lithographic process the physics, in Introduction to Microlithography, L.F. Thompson, C.G. Willson, and M.J. Bowden, Eds., pp. 24, American Chemical Society, Washington, DC (1994). 

Germany) that could pattern a maximum square field of 10 mm x 10 mm. It could achieve overlay of 0.7 p.m and a resolution of 1.25 p.m. The development of the DSW4800, it should he pointed out, was preceded hy systems designed and huilt hy several semiconductor companies, including Philips, Thomson CSF, and who huilt steppers for their own use and did not sell them commercially, although the Philips stepper technology was eventually commercialized hy ASM Lithography.  

Another approach that has been adopted in the IC industry for mitigating the effects of aberration, particularly chromatic aberration, is line narrowing of the incident radiation. The basis of this approach derives from the realization that an illumination radiation with extremely narrow spectral bandwidth is associated with very low chromatic aberration, obviating the need for color correction of the refractive elements associated with such a system. The required degree of spectral purity increases with increasing NA. For instance, KrF (248-nm) exposure systems with NA 0.7 require spectral bandwidth on the order of a picometer 

Bouwer, G. Bouwhuis, H. Van Heek, and S. Wittkoek, The sihcon repeater, Philips Tech. Rev. 37(11/12), 330 333 S. Wittkoek, Optical aspects of the silicon repeater, Philips Tech. Rev. 41, 268 (1983/84) H. Binder and M. Lacomhat, Step and repeat projection printing for VLSI circuit fahrication, IEEE Trans. Electron Dev. ED-26(4), 698 704 (1979) J. Wilcyncski, Optical step and repeat camera with dark field automatic alignment, J. Vac. Sci. Technol. 16,1929 1933 (1979). 

Levinson, Principles of Lithography, 2nd ed., p. 141, SPIE Press, Bellingham, WA (2005). i Microlithography mask making, VLSI Research Inc. Report (1992). 

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The spectral irradiance of a typical mercury xenon lamp is shown in Figure 45. There is a characteristic high intensity mercury emission at 313 nm and a low intensity emission at 334 nm The MUV projection printing tools isolate these two lines through insertion of band-pass filter sets into the optical path, such that little or no light to the blue of 300 nm or to the red of 350 nm is transmitted to the resist surface. The transmission of a filter set of this sort for the Perkin Elmer Micralign 500 is shown in Figure 46. 

Dubroeucz, G. M. Zahorsky, D. "KrF Excimer Laser as a Future Deep UV Source for Projection Printing," International Conference on Microlithography, Grenoble, France, Oct. 1982. 

Figure 18. SEM photomicrographs of Geo /Se0 9/HPR 206 bilevel patterns generated by projection printing over the poly silicon level of a 16K MOS RPM wafer. (Reproduced with permission from Ref. 111.)...

Figure 9. Poly silane bilayer resist, top layer 0.25 am experimental polysilane, bottom layer 1.0 am of hardbaked photoresist, projection printed at 313 nm with 02-RIE image transfer.

Bromide Emulsions. Bromide emulsions are very sensitive and fast. They are used for projection printing exclusively,... 

Chlor-Bromide Emulsions. In chlor-broirude emulsions the amount of silver chloride is greater than that of silver bromide, These emulsions are somewhat faster than chloride emulsions and used for contact or slow projection printing, Chlur-bruiiiide emulsions produce warni-tuued silver linages with a brown or brown-black color,... 

In equation 1, bmin is the minimum feature size transferable, A is the wavelength of light, s is the separation between the mask and the substrate, and d is the thickness of the resist layer. In projection printing, a series of undulating maxima and minima are produced. Because of mutual interference, the dark region is never completely dark, and the maximum brightness does not correspond to 100% transmission. The quality of transfer can be conveniently indicated by the modulation index, M, which is defined as follows ... 

Even though projection optics embodies the inherent limitation of pattern transfer just mentioned, this technique has become a dominant approach in high-resolution work. A key reason for this success is the ability of projection printing to use reduction refraction optics with high numerical apertures. The resolving power of projection systems can be approximated by ... 

Moreau and Schmidt (7) demonstrated the sensitivity of poly(methyl methacrylate) (PMMA) to DUV radiation in 1970 and described most of the features of DUV lithography. The main objective of their work was to employ DUV radiation to allow larger mask-to-wafer separation at constant resolution in proximity printing. Their work demonstrated the utility of PMMA as a DUV resist, and they predicted that DUV radiation would be employed with an acrylate polymer of some type in future projection printing systems that should allow reliable printing of submicrometer features. 

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