IPC Definitions - January 01, 2012
G03F 1/26 - Definition
This group covers:
Subject matter of main group G03F 1/00 in which the radiation modifying products are either patterned phase shift masks (PSM’s), PSM blanks therefor, or specialized substrates for preparing such patterned PSM’s; and the processes of preparing are directed to preparation of such patterned PSM’s, preparation of PSM blanks therefor, or preparation of specialized substrates therefor.
(1) Note. In this subgroup, the phase shift mask (PSM) has a phase shift (PS) transmissive or reflective region that provides a different effective optical path length for illumination exiting the PS region than that of another (usually adjacent non-PS) region, so that exiting illumination from these separate regions are at different phases from each other. When the phase difference between adjacent PS and non-PS regions is 180 degrees, destructive interference is maximized for the exiting illumination between these regions, causing minimum combined diffracted light intensity, which results in a darkened projected light intensity that improves resolution when exposing a photosensitive layer (such as a photoresist).
(2) Note. For a transmissive PSM, the phase shift (PS) region is usually produced by selective addition of a transparent PS layer that increases the effective thickness of a transmissive substrate or by selective etching to create a recess that decreases the thickness of the transmissive substrate, each of which provides exiting illumination that differs in phase from illumination exiting another unchanged region of the transmissive substrate. However, the difference in phase at the phase shifting region can also be produced by selective doping or implantation of particular ions into the transmissive substrate to selectively change the refractive index or other optical characteristic of the transparent substrate, altering the passage of illuminated light exiting from the phase shifting region relative to light exiting from another (non-PS) region of the transmissive substrate for the PSM.