Lithographic processes optical lithography

OpticalUthography. Optical lithography uses visible or ultraviolet light as the exposure media, and is the dominant lithographic process used for patterning IC wafers. The linewidth limit is near 0.4 tm, although some narrower features may be possible (34). The masks typically are made from patterned, opaque chromium films on glass. 

Optical Lithography. Lithographic processes can be classified according to the energy used to expose the resists and the equipment necessary to accomplish the process. Image quality depends on the exposure method, hardware, and resist material. In optical lithography, the resist is exposed to radiation within the near- to deep-UV region (200-450 nm). 

In recent years, an ever increasing number of lithographic techniques have emerged to complement optical lithography, which is still the work horse for practically all pattern replication processes. These developments are driven not only by the need for methods for the replication of sub-100 nm patterns (where conventional lithography is expected to meet its limits), but also by the invention of new high performance, low cost technologies, for example all-polymer based electronics, displays or photovoltaic devices. 

This discussion will be limited to those lithography methods that utihze the application of external radiation (i. e. optical exposure, e-beam exposure, or x-ray exposure) and will not include imprint lithography techniques such as hot embossing. Thick film lithography is generally used to refer to lithographic processes that utilize photoresist film thicknesses greater than 5 x in thickness. 

Defects in ArF lithography, as in other optical lithographic technologies, can be categorized into three broad categories, namely, (i) intrinsic defects, (ii) particle defects, and (iii) process (coat, bake, and develop unit operations)-induced defects. While process-induced and intrinsic defects make up the bulk of the... 

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