Phase-shifting lithographic masks having phase-shifting layers o

Details Phase-shifting lithographic masks having phase-shifting layers o Phase-shifting lithographic masks having phase-shifting layers o

1993-12-08

1995-04-11

Chapman, Mark A.

Radiation imagery chemistry: process, composition, or product th

Radiation modifying product or process of making

Radiation mask

430320, 430321, G03C 500

Patent

active

054057213

ABSTRACT:
A phase-shifting lithographic mask, for use in conjunction with optical radiation of wavelength .lambda., has a transparent substrate upon which are successively located a bottom (2m+1).pi. radian phase-shifting layer and a patterned top (2n+1).pi. radian phase-shifting layer each having at least approximately the same refractive index at the wavelength .lambda. as that of the substrate. A more finely patterned, opaque chromium layer is located on the patterned top phase-shifting layer. The bottom phase-shifting layer is chemically different from both the substrate and the top layer, in order to provide either etch-stopping or end-point etch detection during subsequent dry ion beam millings--as with gallium ions--of either or both of the layers, for the purpose of mask repair. For example, the substrate is quartz (silicon dioxide), the bottom phase-shifting layer is calcium fluoride, and the top phase-shifting layer is silicon dioxide. Remnants of the gallium then can be removed from both the exposed portions of the substrate and of the bottom layer--by means of successive etchings, for example, with HF and HCl, respectively, for respective prescribed time intervals having a ratio such that the relative phase shifts of the substrate and both phase-shifting layers are not disturbed by the respective etchings.

REFERENCES:
patent: 5144362 (1992-09-01), Kamon et al.
patent: 5147763 (1992-09-01), Kamitakahara
Hasegawa, N. et al., "Submicron Photolithography Using Phase-Shifting Mask," Fourth Hoya Photomask Symposium, Japan. 1991.

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