Method for developing negative photoresists

DETAILED DESCRIPTION OF THE INVENTION The process of the invention for developing exposed negative photoresists on substrates comprises treating the photoresist with a mixture comprising trichloroethane and from about 5 weight % up to about 17 weight % of a short chain aliphatic alcohol.
The alcohol is present in an amount equal to or less than the azeotropic (constant boiling) composition.
The trichloroethane is preferably 1,1,1-trichloroethane (methyl chloroform), and preferably includes stabilizing agents, as is well-known in the use of this compound.
Such stabilizers, of which one or more may be present, inhibit metal-induced decomposition or hydrolysis of the 1,1,1,-trichloroethane resulting from its use in the degreasing equipment.
Any of the conventional stabilizers may be employed, such as dioxane, nitromethane, butylene oxide, amines and methyl isopropyl ketone.
Other suitable stabilizers are disclosed in U.
S.
Pat.
No.
4,018,837.
Such stabilizers, however, do not form a part of this invention.
The alcohol employed is a short chain aliphatic compound, preferably having from 1 to 4 carbon atoms.
Examples include methanol, isopropanol and tert-butanol.
Of these, isopropanol and tert-butanol are preferred, with isopropanol being most preferred.
The alcohol is present in an amount equal to or less than the azeotropic composition.
In the case of trichloroethane/isopropanol, the azeotropic composition is about 17 weight % isopropanol.
In the processing of semiconductor wafers or printed circuit (PC) boards (plastic or ceramic) to fabricate devices and circuits thereon, there are several stages at which a layer, e.
g.
, an oxide or metal, must be patterned.
This is generally accomplished by applying a coating of a photoresist, exposing the photoresist to electromagnetic radiation, such as the visible region, and, in the case of negative photoresists, removing the regions unexposed to the radiation by means of a solvent called a developer.
Removal of such selected portions of the photoresist exposes portions of the underlying layer (oxide or metal), which may be removed by treating the so-exposed portions with an etchant that removes the exposed portions of the layer without attacking the remaining photoresist