Contact photolithography

Figure 2.12 Schematic representation of rapid prototyping. A system of channels is designed in a CAD program, (a) Transparency used as a photomask in contact photolithography to produce a master, (b) liquid PDMS pre-polymer poured over the master and cured for 1 h at 70°C, (c) PDMS replica peeled from the master, and (d) the replica sealed to a flat surface to enclose the channels [6].

In the given case it should be noted, that the edges of the lower layer elements defining the picture (topology) of photomask are not subjected to friction at contact photolithography (as they are protected by the elements of the upper layer), that increases percentage of IC output. 

The existence of gaps between transparent sections of the photomask substrate and the surface of exposing photoresist, as well as the of channels between the upper elements of the photomask, solving the problems of contact photolithography (1.3). 

At the contact photolithography the common problem is the capture photoresist of a by photomask and the swelling of the photoresist. 

At the contact photolithography in which quinonediazide resists are widely used unforeseen separation of photomask from IC plate is observed in some cases due to pressure of nitrogen evolved during resist exposure. 

The developed construction and new technological processes of making photomasks withh submicron size elements solve problems of contact photolithography and have a number of advantages over the technologies existing so far. 

A microfuel processor with trench-refilled thick silicon dioxide for thermal isolation fabricated by water-immersion contact photolithography, J. Micromech. Microeng. 

Details of building specific types of microelectronic devices are well described by Grovenor15 as an illustration, we consider only the chemical techniques involved in making a metallic contact to a silicon wafer surface. Preparation of a wafer of Si or other material and application of epitaxial layers of semiconducting or insulating materials, if required, were outlined in Section 19.2.1. The construction of shaped features on the wafer is usually done by photolithography, or ion- or electron-beam variants thereof. 

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