US 5,493,403 A · Method and apparatus for the alignment of a substrate

Abstract

Method comprises a process for obtaining a photoelectric signal with a waveform have a pair of extremal values at respective positions corresponding to a pair of edge portions of an alignment mark by photoelectrically detecting the reflected light from the alignment mark on a substrate; a first determination process for determining the position of the alignment mark on the basis of a pair of slope portions existing inside the pair of extremal values of the photoelectric signal waveform; a second determination process for determining the position of the alignment mark on the basis of a pair of slope portions existing outside the pair of extremal values of the photoelectric signal waveform; a third determination process for determining the position of the alignment mark on the basis of both a pair of slope portions existing inside said pair of extremal values of the photoelectric signal waveform and a pair of slope portions existing outside; and a process for selecting any one of the first determination process, second determination process, or third determination process in accordance with the objective alignment accuracy of the substrate.

Claims15

Dependent claims

A method of aligning a substrate wherein an alignment mark formed on the substrate is irradiated with light and the position of the substrate is determined by detecting the position of the alignment mark with respect to a predetermined direction on the basis of light information from the alignment mark, said method comprising:

a process for obtaining a photoelectric signal having a waveform with a pair of extremal values corresponding to a pair of mark edge portions which define the width in said predetermined direction of said alignment mark, said photoelectric signal being obtained by detecting said light information from said alignment mark photoelectrically and said photoelectric signal changing its intensity in time-series with respect to said predetermined direction;
a first determination process for determining the position of said alignment mark on the basis of a pair of slope portions existing inside said pair of extremal values of said photoelectric signal waveform;
a second determination process for determining the position of said alignment mark on the basis of a pair of slope portions existing outside said pair of extremal values of said photoelectric signal waveform;
a third determination process for determining the position of said alignment mark on the basis of both a pair of slope portions existing inside said pair of extremal values of said photoelectric signal waveform and a pair of slope portions existing outside;
a process for selecting any one of said first determination process, second determination process, or third determination process in accordance with the objective alignment accuracy of said substrate;
and,
a process for moving said substrate relative to a predetermined reference position in accordance with the alignment mark position determined by the selected determination process.

4 more elements

An apparatus for aligning a substrate provided with an alignment mark formed at a predetermined position thereon, the mark composed of a pattern which includes a plurality of mark elements aligned with a predetermined spacing in a predetermined detecting direction, the mark elements have predetermined width with respect to the detecting direction, the apparatus comprising:

(a) an illumination system for radiating a light beam onto said pattern;
(b) a photoelectric detecting device whose detecting area is of a constant length in said detecting direction, the device outputting, when said pattern falls within a part of the detecting area, a photoelectric signal with a waveform representing an optical profile of said pattern with respect to said detecting direction;
(c) slope extraction means for extracting up-slope portions and down-slope portions, which appear at positions corresponding to the edges of said mark elements defining said width, within the waveform of said photoelectric signal for each of said edges of the mark elements;
(d) means for obtaining first waveform positions which interiorly divide a shoulder level and an extreme value level of each slope portion with a predetermined ratio for each of said slope portions extracted by said slope extraction means;
(e) selection means for selecting at least one of a set of said first waveform positions obtained for two slope portions which is situated internally of a pair of said edges defining said width of said mark elements and a set of said first waveform positions obtained for two slope portions which is situated externally of said edges;
and
(f) calculation means for calculating a center position of said pattern within said detecting area by averaging a plurality of said first waveform positions included in said at least one set of the first waveform positions selected by said selection means;
and,
(g) moving means for positioning the substrate in accordance with the calculated position of said pattern by said calculation means.

6 more elements

An apparatus for aligning a substrate provided with an alignment mark pattern formed at a predetermined position thereon, the mark pattern composed of one or a plurality of mark elements having a predetermined width with respect to a predetermined detecting direction, the apparatus having an objective optical system for radiating illumination light onto a local area on said substrate and receiving light reflected from the local area, the size of the local area being such that the local area can contain said mark pattern, and a photoelectric detecting device which outputs, when said mark pattern falls within a part of said local area, a photoelectric signal having a waveform representing an optical profile of said mark pattern, the apparatus comprising:

(a) means including a memory which performs digital sampling of level of said photoelectric signal so as to store digital waveform data corresponding to an optical profile of said mark pattern;
(b) a first means which detects a plurality of up-slope and down-slope portions, within said digital waveform data, whose contrast is above a predetermined value;
(c) a second means which detects, among the slope portions detected by said first means, a number of up-slope portion--down-slope portion pairs in which the up-slope portion and the down-slope portion are within a predetermined distance;
(d) a third means which, when said number of pairs corresponds to the number of all edges of said one or plurality of mark elements in said mark pattern, allows execution of position determination according to one of the following three position determination modes:
a first mode in which only two slope portions situated internally of a pair of edges which define the width of said mark element are used;
a second mode in which only two slope portions situated externally of a pair of edges which define the width of said mark element are used;
and a third mode in which four slope portions which appear for said pair of edges are used;
(e) a fourth means which, when said number of pairs is substantially different from the number of all edges of said one or plurality of mark elements, prohibits execution of said second and third position determination modes;
and,
a movable stage for moving said substrate in accordance with the position determined by said one of three position determination modes.

7 more elements

An apparatus for positioning a substrate held on a stage movable along a predetermined coordinate system, wherein the substrate is provided with a mark at a predetermined position on its surface, the mark being defined by at least two parallel linear edges, and wherein the apparatus positions the substrate with respect to a direction transverse to said linear edges, the apparatus comprising:

(a) a scanning image pick-up device which has a detection area positioned at a predetermined position within said coordinate system and which picks up, within said detection area, an image of a portion of the surface of said substrate including said mark, wherein, when the image pick-up device scans the image in the direction transverse to said linear edges of the mark, said image pick-up device generates an image signal which changes its level at least at positions of each of the linear edges;
(b) an interferometer measuring a coordinate position of said stage;
(c) means for designating a coordinate position of said substrate at which said mark appears within said detection area;
(d) first waveform processing means for processing a pair of the portions of a waveform of the image signal from said image pick-up device including an up-slope form corresponding to one of the two linear edges of said mark and a down-slope form corresponding to the other of the two linear edges of said mark so as to determine a center position of said mark within said detection area;
(e) second waveform processing means for processing portions of a waveform of the image signal from said image pick-up device including an up-slope--down-slope pair corresponding to one of the two edges of said mark and an up-slope - down-slope pair corresponding to the other of the two edges of said mark so as to determine a center position of said mark within said detection area;
and
(f) control means for controlling movement of said stage based on said center position of said mark determined by either one of said first and second waveform processing means and a coordinate position measured by said interferometer.

4 more elements

An apparatus for positioning a substrate held on a stage movable along a predetermined coordinate system, wherein the substrate is provided with a mark which includes N mark elements at predetermined positions on its surface, N being a positive integer, the mark elements being arranged parallel to each other with a predetermined spacing and each of the mark elements being defined by two parallel linear edges, and wherein the apparatus positions the substrate with respect to a direction transverse to the linear edges, the apparatus comprising:

(a) a scanning image pick-up device which has a detection area positioned at a predetermined position within said coordinate system and which picks up, within said detection area, an image of a portion of the surface of said substrate including said mark, wherein, when the image pickup device scans the image of 2N linear edges of the mark, 2N being two times N, said image pick-up device generates an image signal which changes its level at least at positions of each of the 2N linear edges;
(b) means for designating a coordinate position of said substrate at which an image of said mark on the substrate appears within said detection area;
(c) first waveform processing means for processing N pairs of portions of a waveform of the image signal from said image pick-up device, where each pair includes an up-slope form corresponding to one of the linear edges of a mark element and a down-slope form corresponding to the other linear edge of the mark element, so as to determine a center position of said mark within said detection area;
(d) second waveform processing means for processing 2N up-slope--down-slope pair portions of a waveform of the image signal from said image pick-up device corresponding to each of the edges of said mark elements so as to determine a center position of said mark within said detection area;
(e) means for designating in advance which of said first waveform processing means or said second waveform processing means is to be used, in accordance with a waveform of said image signal;
and
(f) control means for controlling movement of said stage based on said center position of said mark determined by the designated waveform processing means.

4 more elements

Dependencies are inferred from the claim text.

Method and apparatus for the alignment of a substrate

Life of this patent

Method and apparatus for the alignment of a substrate

Life of this patent

Abstract

Claims15