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US 5,477,058 AGranted
Attenuated phase-shifting mask with opaque reticle alignment marks
AssigneeKabushiki Kaisha Toshiba
InventorTakashi Sato
Life of this patent
Estimating the term…
Abstract
An attenuated phase-shifting mask has a circuit pattern formed of a layer of halftone phase-shifting material, e.g., SiNx, which inherently appears substantially transparent to the visible light utilized to align the mask with a wafer. The reticle alignment marks of the mask are made of a separate substantially opaque layer in order to ensure that the reticle alignment marks will be visible to the mask/wafer alignment equipment.
Claims16
An attenuated phase-shifting mask for use in the production of an integrated circuit chip, said mask comprising:
- a light transmissive substrate;
- a mask pattern formed on said substrate, said mask pattern (a) defining a circuit pattern to be projected onto an integrated circuit chip, (b) including a first layer of material that attenuates electromagnetic radiation passing therethrough, and which appears substantially transparent to visible light, and (c) serving to effect a phase-shift to electromagnetic radiation transmitted therethrough;
- and
- at least one reticle alignment mark formed on said substrate, said alignment mark being formed of a second layer of material that is substantially opaque to visible light.
1 more element
A method of projecting a circuit pattern onto a semi-conductor wafer, comprising:
- aligning in an exposure tool an attenuated phase-shift mask and a semi-conductor wafer, said alignment step being performed by detecting with an alignment light a reticle alignment mark on the mask formed of a first layer of material that is substantially opaque to the alignment light;
- then
- projecting onto the semiconductor wafer electromagnetic radiation passed through a mask pattern formed on said mask, said mask pattern (a) defining a circuit pattern to be projected onto said wafer, (b) including a second layer of material that attenuates the electromagnetic radiation passed therethrough, and which appears substantially transparent to the alignment light, and (c) serving to effect a phase-shift to said electromagnetic radiation passed therethrough.
Dependencies are inferred from the claim text.