Method for estimating optimum position of a wafer for forming image patterns thereon
AssigneeOki Electric Industry Co., Ltd.
InventorAkira Watanabe
Life of this patent
Estimating the term…
Abstract
Apparatus for determining the optimum position of an object with respect to a focal point of a focused beam of radiation. The apparatus has a resolution limit and includes a radiation source, a lens for focusing the beam of radiation on the object, and a reticle interposed between the radiation source and the lens. A focusing pattern, formed on the reticle, when projected onto the object by the focusing means, produces a projected focusing pattern which is not resolvable, the resolution of the projected focusing pattern being not greater than the resolution limit of the apparatus.
Claims11
In combination with an apparatus for manufacturing a semiconductor device, said apparatus having a radiation source, means for supporting a semiconductor wafer, and a reticle interposed between said radiation source and said wafer, a method of determining the optimum position of said wafer with respect to a focal point thereof, comprising the steps of:
- forming a reticle pattern on said reticle, said reticle pattern having a plurality of elements each separated from adjacent elements by a distance which is not greater than a resolution limit;
- changing in successive increments and/or decrements the distance between the wafer and the reticle;
- projecting radiation from said radiation source through said reticle pattern to form transferred reticle patterns on the wafer at each of said incremental and/or decremental distances, each of said transferred reticle patterns having first and second spaced end portions;
- measuring the spacing between the first and second end portions of said transferred reticle patterns at each of said distances;
- selecting one of said measured distances;
- and
- setting the wafer at the position corresponding to the selected distance.
In combination with an apparatus for manufacturing a semiconductor device, said apparatus having a radiation source, means for supporting a wafer, and a reticle interposed between said radiation source and said wafer, a method of determining the optimum position of said wafer with respect to a focal point thereof, comprising the steps of:
- forming a reticle pattern on said reticle, said reticle pattern having a plurality of serrate portions at an end thereof, each of said serrate portions being separated from each other at a distance which is not greater than a resolution limit;
- changing in successive increments and/or decrements the distance between the wafer and the reticle;
- projecting radiation from said radiation source through said reticle pattern to form transferred reticle patterns on the wafer at each of said incremental and/or decremental distances, each of said transferred reticle patterns having first and second spaced end portions;
- measuring the spacing between the first and second end portions of said transferred reticle patterns at each of said distances;
- selecting one of said measured distances;
- and
- setting the wafer at the position corresponding to the selected distance.
A method of determining the optimum position of a wafer comprising the steps of
- forming a reticle pattern on a reticle having a plurality of elements, each of said elements being separated from adjacent elements by a distance which is not greater than a resolution limit;
- changing in successive increments and/or decrements the distance between the wafer and said reticle;
- projecting radiation from a radiation source through said reticle pattern to form transferred reticle patterns having spaced end portions on the wafer at each of the incremental and/or decremental distances;
- measuring the spacing between said end portions of said transferred reticle patterns at each of said distances;
- selecting one of said measured distances;
- and
- setting the wafer at the position corresponding to the selected distance.
Dependencies are inferred from the claim text.