Photoresist

photoresist

A film used in photolithography that temporarily holds the pattern of a circuit path or microscopic element of a chip. When exposed to light, it hardens and is resistant to the acid bath that washes away the unexposed areas. Not to be confused with photoresistor.

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photoresist [′fōd·ō·ri‚zist]

(graphic arts)

A light-sensitive coating that is applied to a substrate or board, exposed, and developed prior to chemical etching; the exposed areas serve as a mask for selective etching.

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Photoresist 

a photosensitive polymer coating applied to the surface of a semiconductor plate with an oxide film. Photoresists are used in semiconductor electronics and microelectronics to produce areas of a specific configuration that permit access of an etching agent onto the plate.

The properties of a photoresist are altered on exposure to ultraviolet light or an electron beam through a glass template of the required configuration applied to the photoresist. Either the solubility of the photoresist is sharply reduced (in the case of a negative photoresist), or the photoresist is decomposed and may be easily removed (in the case of a positive photoresist). Subsequent treatment with a solvent forms the access areas in the nonirradiated segments of a negative photoresist or in the irradiated segments of a positive photoresist. Negative photoresists consist of layers of polyvinyl alcohol with chromates or cinnamic acid esters and layers of cyclized rubber with additives that produce crosslinking of the macromolecules under the action of light. Positive photoresists consist of a phenol-formaldehyde or cresol-formal-dehyde resin with ortho-naphthoquinone diazide.

REFERENCES

Fotolitografiia i optika. Moscow-Berlin, 1974.
Mazel’, E. Z., and F. P. Press. Planarnaia tekhnologiia kremnievykh priborov. Moscow, 1974.