Patent DE-10359991-A1 (DE)
Title: Phase shift mask for the projection of pattern of structure elements formed on mask into substrate includes first structure elements formed as elevated ridges and second structure elements formed by trenches or ridges
Inventor: NOELSCHER CHRISTOPH
IPC: G03F1/00
Filed: 2003-12-19
Abstract: A phase shift mask for the projection of a pattern of structure elements (14, 16, 18, 50-55) formed on the mask into a substrate includes first structure elements formed as elevated ridges made from semitransparent, phase-shifting material; and second structure elements formed by trenches with closely adjacent trench edges in the planar surface of the mask substrate (58). A phase shift mask for the projection of a pattern of structure elements (14, 16, 18, 50-55) formed on the mask into a substrate, comprises a first portion of the pattern, and a second portion of the pattern. The first structure elements are formed as elevated ridges made from a semitransparent, phase-shifting material, which is arranged on a planar surface of a transparent mask substrate (58) the of the phase shift mask. The second structure elements are formed by trenches with closely adjacent trench edges in the planar surface of the mask substrate with a depth, or ridges with closely adjacent ridge edges within a surface etched with the depth into the surface of the mask substrate, such that a light beam transmitted through the mask substrate within the trenches or ridges experiences a phase shift of 180 +- 20[deg] with respect to a light beam transmitted through the mask substrate on the planar surface outside the trenches. An independent claim is also included for a method for forming the pattern on the phase shift mask, comprising providing a mask blank with a mask substrate, a semitransparent, phase-shifting layer, an absorber layer, and a photosensitive resist. The resist is exposed and developed so that bright regions to be formed by the first portion and bright and dark regions to be formed by the second portion are opened in the resist. The bright regions of the first portion for forming the first structure elements and the bright and dark regions of the second portion of the pattern are transferred into the absorber layer. The resist and renewed application of a second resist are removed. The second resist is exposed and developed for covering openings formed by the transferred bright regions of the first portion in the absorber layer and the semitransparent layer and for opening the dark regions to be formed on the mask, or the bright regions to be formed on the mask of the second portion of the pattern in the resist. The openings formed by the dark regions or by the bright regions of the second portion are transferred from the resist into the mask substrate as far as a depth representing a phase difference of 180 +- 20[deg] of the light beams passing through compared with mask regions without an absorber which have not undergone mask substrate etching for the formation of the second structure elements. The second structure elements are formed as ridge (mesa) in the case of the transferred bright regions, or as trench in the case of the transferred dark regions with adjacent ridge or trench walls. The further resist is removed. The absorber layer is removed to uncover the semitransparent, elevated ridges of the first structure elements.