Phase shift mask

Abstract

The present disclosure provides a phase shift mask. The phase shift mask includes a transparent substrate; an etch stop layer disposed on the substrate; and a tunable transparent material layer disposed on the etch stop layer and patterned to have an opening, wherein the tunable transparent material layer is designed to provide phase shift and has a transmittance greater than 90%.

Description

technical field [0001] Embodiments of the present invention relate to a method for forming a semiconductor structure, and more particularly relate to a phase shift photomask used therefor. Background technique [0002] In semiconductor technology, optical interference and other effects often cause variations in critical dimensions. As such, the photomask error parameters would be unacceptably high for the size of the smaller structures in sub-wavelength patterning, especially contact holes. Various techniques have been used to improve photomask error parameters, such as using phase-shift photomasks (eg, chrome-free phase-shift photomasks) to define circuit patterns. In the chrome-free phase-shift photomask, the circuit structure is defined in the light-transmitting photomask, and there is a phase shift between adjacent light-transmitting regions of the transparent photomask. As such, when imaged onto a semiconductor substrate, destructive interference will produce dark str...

AI Technical Summary

Problems solved by technology

However, existing chromium-free phase-shift photomasks are limited in their flexibility to improve image quality and other issues, such as the tolerance of the etch process relative to the expected phase shift

In addition, the existing chromium-free phase-shift photomasks have limited protection for the light-transmitting substrate when forming and using the photomask.

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