Exposure optics system

The exposure optics system comprises the set of optics (mirrors and lenses) that delivers the aerial image of the mask to the resist-coated wafer on the exposure stage. There are two categories of such systems. Contact and proximity optics systems are the simplest and the least expensive of the systems, but are not well suited for high-volume IC manufacture because of their high level of defectivity. The other system, the projection optics system, is predominantly used in modern semiconductor manufacturing. Both systems rely on the entire mask, or at least a portion of it, to be imaged simultaneously. 

The use of optical hthography in silicon IC device fabrication dates back to the mid-1950s when Andrus employed it at Bell Laboratories to define precise 

Grenon, C. Peters, K. Battacharyya, and W. Volk, Formation and detection of sub peUicle defects by exposure to DUV systems illumination, Proc. SPIE 3873, 162 176 (1999) B.J. Grenon, C. Peters, K. Battacharyya, W. Volk, and A. Poock, Reticle surface con taminants and their relationship to sub pellicle particle formation, Proc. SPIE 5256, 1103 1110 (2003). 

Levinson, Principles of Lithography, 2nd ed., p. 267, SPIE Press, Bellingham, WA (2005). G. Rider, Estimation of the field induced damage thresholds in reticles, Semicond. Manuf, pp. 80 94 (Feb., 2004). 

3 UV Photochemistry in the Exposure Chamber Environment of Opticai Lithographic Toois 

---

For resist exposure, the resolution limit will be set by the range over which the ions interact with the resist. As with electron beam exposure, ions create secondary electrons up to several nanometers away from the beam, and these electrons can travel further before their energy is absorbed. Ultimate resolution will probably be about 10-20 nm, as it is with electrons. At present this limit is beyond the capabilities of the ion optical systems. 

Exposure by an optical system to form the latent image,... 

The exposure of the coated wafers is done through a complicated optical system. The size of the features is given by the Rayleigh equation, and is directly proportional to the exposure wavelength (X) and inversely proportional to the numerical aperture (NA), while k is a constant that depends on the equipment used (with values between 0.4 and 1.0)... 

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... 

While the original pattern-generation tools of the early 1970s were optical systems, in 1974, AT T BeU Laboratories introduced an electron-beam direct exposure mask-making system called MEBES," which was subsequently licensed to ETEC for commercialization. By 1980, electron-beam mask writers became... 

---