Photoresist, types negative resist

There are two types of photoresists negative and positive photoresists. The negative resist reacts upon exposure to hght to form an insoluble form of the photoresist. Addition of developer then dissolves the unexposed regions of the resist. A positive resist reacts when irradiated to produce a soluble form of the resist that is then washed away by the developer. 

The resists employed for wet etching adhesion experiments were typical commercially available azide initiated/cyclized isoprene type negative photoresists. 

Etch resists can be of the photoresist or galvanoresist type. Photoresists react chemically to UV energy input, and galvanoresists are removed by laser energy. Photoresists can be further categorized as positive or negative. A positive photoresist is soluble after exposure and washes off, whereas exposure decreases a negative resist s solubility (Fig. 3.9). 

Photoirradiation of this stacked film causes the Ag to diffuse into the Se-Ge film in a process referred to as Ag-photodoping. This diffusion, which is characteristic of amorphous chalcogenide materials, causes the Se-Ge film to become insoluble in alkaline solutions and the resist thus functions as a negative-type photoresist. The photodoped regions also are resistant to fluorine-based plasmas enabling dry development of the resist (7). Dry development has also been achieved using a reactive-ion etching (RIE) technique and is discussed later. 

The type of photoresist being used (e.g., positive-tone resist, negative-tone resist, diazonaphthoquinone-novolac resist, chemically amplified resist, single-layer resist, bilayer resist, etc.)... 

There is a variety of photoresist materials on the market. Some of these photosensitive materials are negative types and some are positive. Both wet and dry resist materials may be used. It is beyond the scope of this section to discuss the advantages and disadvantages of each. The reader is directed to the references for additional information on the subject [20-22]. 

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