Photosensitive and Etched Patterned Materials

Microtechnology refers to a field of development concerning tiny components for a variety of applications. The developments are concentrated on reducing the products to the smallest possible size. Special procedures are 

The base glasses for these glass-ceramics are derived from the Si02—Li20 system. The base glasses contains Ce - and Ag -ions. The compositions are shown in Table 4-1. During exposure to UV light, photoelectrons cause the oxidation of Ce to Ce. As a result, Ag is reduced to Ag(0). 

This metallic silver is the nucleating agent for the lithium metasilicate Li2Si03 phase. As a result, this crystal phase can be precipitated by controlled crystallization at 600 C (Beall 1993). The lithium metasilicate crystals are easily etched with dilute hydrofluoric acid (HF). Thus, defined structures can be etched into the finished products. These specially structured glassy bodies 

If UV exposure and heat treatment are conducted a second time, approximately 40 wt% of the main crystal phase lithium disilicate is produced along with (X-quartz with a total crystal content of approximately 60%. This product called Fotoceram was also manufactured by Corning Glass Works, USA. The chemical composition of Fotoform /Fotoceram is shown in Table 4-1. Selected properties are listed in Table 4-2 (Beall 1992). 

The exposure to UV light of the base glass can be precisely controlled with specially tailored patterns that permit high-precision components to be fabricated (Fig. 4-1). The accuracy (Table 4-3) of these parts is higher than that which could have been achieved using mechanical or even laser procedures, although less accurate than photolithographic techniques used to pattern silicon and certain metals. 

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