A phase shift mask having transmission properties that are dependent at least in part on an intensity of an incident light beam. The phase shift mask has a mask substrate that is substantially transparent to the incident light beam. A first phase shift layer is disposed on the mask substrate. The first...http://www.google.com.hk/patents/US6841308?utm_source=gb-gplus-share專利 US6841308 - Adjustable transmission phase shift mask
