Contrast-enhanced lithography layer

Contrast enhancement lithography is a clever procedure which uses a bleachable contrast enhancing layer to restore the distorted aerial image of the mask which has been blurred by diffraction effects into a sharp image at the underlying photoresist surface. The process is too complicated to explain in detail here and the interested reader is referred to the cited literature (60,61). Suffice it to say that the large extinction coefficients of most polysilane derivatives coupled with their ready bleachability make them ideally suited for such purposes and we have demonstrated this application at 313 nm (16,18). 

Contrast-Enhanced Lithography. Contrast-enhanced lithography is a clever technique that uses a thin layer of a bleachable contrast-enhancing layer coated over a conventional photoresist to sharpen the mask image. 

The principle of contrast enhancement by photobleachable layers has been known in photography for quite a long time. New formulations were developed for application in lithography and used for the production of cathode ray tubes More recently, a family of arylnitrones have been investigated and described as effective contrast-enhancing materials (CEM) for use in IC-lithography The photochemical reaction which occurs is a cyclization reaction ... 

In the last decade, several techniques have been developed in order to improve the resolution that can be obtained with optical lithography. This review describes a number of these techniques. Some techniques make use of a photosensitive layer on top of the photoresist, which results in enhancement of the contrast of the aerial image (Sects. 3.1.1 and 3.1.2). Other techniques use the possibility of slope control during development (Sects. 3.1.3 and 3.1.4). Also discussed are some techniques involving anisotropic plasma etching. 

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