Use of chromeless phase shift masks to pattern contacts

Abstract

Method for using chromeless phase shift lithography (CPL) masks to pattern contacts corresponding CPL masks. The method for patterning contacts includes illuminating a CPL mask comprising a reticle having plurality of phase-shifting features interspersed with non-phase-shifting areas with a short wavelength light source, wherein the phase-shifting features are configured in a pattern corresponding to a target pattern of the contacts on the semiconductor substrate. Phase-shifted and non-phase-shifted light passing through the reticle is the projected as an aerial image onto a layer of a negative tone resist applied over the semiconductor substrate to pattern the contacts in the resist. The phase-shifting features may comprise recesses or mesas, and cause light passing therethrough to be phase-shifted in phase approximately 180° from light passing through non-phase-shifting areas of the mask.

1 . A chromeless phase shift lithography (CPL) mask comprising:
 a reticle having a plurality of phase-shifting features interspersed with non-phase-shifting areas, said phase-shifting features configured in a pattern corresponding to a target contact pattern to be formed in a semiconductor substrate and causing light passing therethough to be shifted in phase relative to light passing through the non-phase-shifting areas of the CPL mask not occupied by the phase-shifting features.   
   
   
       2 . The CPL mask of  claim 1 , wherein the plurality of phase-shifting features comprise a plurality of recesses formed in a quartz substrate. 
   
   
       3 . The CPL mask of  claim 1 , wherein the plurality of phase-shifting features comprise a plurality of mesas extending upward from a quartz substrate. 
   
   
       4 . The CPL mask of  claim 1 , wherein the phase-shifting features are arranged in a pattern to produce an array of contacts having a pitch of approximately 200 nanometers or less. 
   
   
       5 . The CPL mask of  claim 1 , wherein the phase-shifting features are arranged in a pattern to produce contact holes having a critical dimension of approximately 100 nanometers or less. 
   
   
       6 . The CPL mask of  claim 1 , wherein the plurality of phase-shifting features are substantially square in shape. 
   
   
       7 . The CPL mask of  claim 1 , wherein light passing through the phase-shifting features is shifted in phase 180° relative to light passing through the non-phase-shifting areas.