Topcoat process to prevent image collapse

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is made to the figure to illustrate selected embodiments and preferred modes of carrying out the invention.
It is to be understood that the invention is not hereby limited to those aspects depicted in the figure.
Moreover, a preferred embodiment is described comprising a positive resist, developed in aqueous-based solutions.
However, the invention may be embodied as a negative resist and may be embodied as a resist developed in organic-based solutions.
Turning now to the FIGURE, a wafer 10, coated with a layer of photoresist material 12 is shown.
A photomask 11 is used to screen an image (arrows) that may be comprised of light of the desired UV frequency or of electrons.
The wafer 10 supporting the exposed resist 12 is immersed in an aqueous solution of a tetraalkylammonium hydroxide 13, preferably 0.
263 normal tetramethylammonium hydroxide.
In the embodiment depicted, the exposed resist material is insoluble in such solutions.
The figure indicates that the resist image 12 has a high aspect ratio (height/width).
If exposed to high surface tension forces experienced during the drying process, the image may tend to collapse.
While still immersed, the bathing fluid 14 is changed to distilled water to rinse the wafer and then an overcoat 15 is applied.
The topcoat can be applied from an aqueous based fluid or a co-solvent mixture as long as the "inert" solvent or topcoat does not distort the resist image by swelling, extraction, or collapsing the image.
The stabilizers have to be soluble in the topcoat solvent as well as being able to be removed in liquefied CO.
sub.
2 or supercritical fluid of CO.
sub.
2 and/or inert co-solvents.
Polymers or even low molecular film forming substances such as Fluorad (a trademark of 3M) such as FC-430 fluorinated surfactants can be used to overcoat the resist image.
The coated resist image is temporarily stabilized prior to removal of the stabilizer by a low surface tension liquid such as CO.
sub.
2.
The thickness of the stabilizing coating should be as sufficient as necessary to planarize or partially planarize the resist image sufficiently to prevent image distortion