US 5,690,785 A · Lithography control on uneven surface

Abstract

A reticle pattern is transferred to a semiconductor wafer with a coated resist film by using a reduction (demagnification) exposure system having a focus sensor and an autofocus mechanism operating in response to an output of the focus sensor. An average level of a plurality of autofocus points in a chip area is calculated while the semiconductor wafer is mounted on a stage. The semiconductor wafer is scanned and levels of the surface in the chip area are sampled. From the distributions of sampled surface levels, a stepped surface level to be focussed is derived. An offset value between the average level and the stepped surface level to be focussed is derived and an autofocus point is corrected by the offset value to expose the chip area of the semiconductor wafer. A method of exposing a semiconductor wafer is provided which can perform an exposure most suitable for each process, by identifying a stepped surface level to be automatically focussed.

Claims10

Dependent claims

A method of exposing a semiconductor wafer in which a reticle pattern is transferred to the semiconductor wafer with a coated resist film by a reduction exposure system having a focus sensor and an autofocus mechanism operating in response to an output of the focus sensor, the method comprising the steps of:

calculating an average level of a plurality of autofocus points in a chip area of the semiconductor wafer mounted on a stage;
scanning the semiconductor wafer and sampling levels of the surface in the chip area;
deriving a stepped surface level to be focussed in accordance with distributions of sampled surface levels;
calculating an offset value between the average level and the stepped surface level to be focussed;
and
correcting an autofocus point by the offset value and exposing the chip area of the semiconductor wafer.

3 more elements

A method of manufacturing a semiconductor device comprising the steps of:

forming a field oxide film on a semiconductor wafer, said field oxide film defining an active region;
forming a gate insulating film on said active region;
forming a gate electrode layer over said gate insulating film and said field oxide film;
measuring an average level of the surface of the semiconductor wafer with said gate electrode layer, a level of the surface above the active region, and a level of the surface above another region;
correcting an exposure system adapted to adjust a focus in accordance with said average level in accordance with a difference between said average level and said level of the surface above the active region, and obtaining a resist pattern through photolithography;
and
etching said gate electrode layer to form a gate electrode by using said resist pattern as a mask.

4 more elements

Dependencies are inferred from the claim text.

Lithography control on uneven surface

Life of this patent

Lithography control on uneven surface

Life of this patent

Abstract

Claims10