US 5,489,986 A · Position detecting apparatus

Abstract

In a position detecting apparatus having an object optical system, two beams are generated for irradiating a diffraction grating formed on an object from two directions at a predetermined intersect angle for forming an interference fringe, the beams passing through a pupil plane of the object optical system spaced apart a predetermined distance from each other. An opto-electric detector receives diffracted light from the grating via the object optical system and outputs a detection signal, and the position of the object is determined on the basis of the detection signal. An adjustable optical member provided in a light path between an optical source and the object changes incident angles at which the two beams are incident on the grating while keeping the intersect angle between the two beams substantially constant.

Drawings

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Drawings

Claims8

Dependent claims

A projection type exposure apparatus including,

a projection optical system for projecting a pattern formed on a mask;
a substrate stage member for holding a photosensitive substrate onto which the pattern is projected, and movable in a two dimensional X-Y plane substantially perpendicular to an optical axis of said projection optical axis and further movable in a Z direction along the optical axis;
and
a pattern position detecting device for radiating two beams, each of which intersects the other on said photosensitive substrate and has a frequency which is different from that of the other, and for optoelectrically detecting and converting beat light caused by interference between at least two diffracted beams generated along the same direction from a grating pattern on said photosensitive substrate, into a signal, and for determining a position of the grating pattern along a pitch direction thereof based on phase of the signal, thereby detecting the grating pattern formed on said photosensitive substrate or an alignment;
said apparatus comprising:
(a) a reference plate provided on said substrate stage member and having a reference grating pattern which is substantially the same as the grating pattern on said photosensitive substrate;
(b) a first stage control system for positioning said substrate stage member in the X-Y plane so that the reference grating pattern is irradiated by the two beams from said pattern position detecting device;
(c) a second stage control system for controlling movement of said substrate stage member along the Z direction go that said reference grating pattern is moved parallel to the optical axis of said projection optical system within a range where the two beams intersect;
(d) a monitoring device to monitor the phase of the signal optoelectrically detected and converted from the beat light generated from the reference grating pattern by said pattern position detecting device at each predetermined change in position of said reference plate on said substrate stage member along the Z direction;
(e) a calculating device to calculate an inclination of an imaginary line bisecting an intersect angle formed between the two beams at the grating pattern, based on a characteristic of a change in the phase of the signal with respect to a change in said position along the Z direction;
and
an optical element to compensate the incident angle of each of the two beams at the grating pattern so that the imaginary line is maintained substantially perpendicular to the pitch direction of said grating pattern.

9 more elements

A projection type exposure apparatus including,

a projection optical system for projecting a pattern formed on a mask;
a substrate stage member for holding a photosensitive substrate onto which the pattern is projected, and movable in a two dimensional X-Y plane substantially perpendicular to an optical axis of said projection optical axis and further movable in a Z direction along the optical axis;
and
a pattern position detecting device for radiating two beams, each of which intersects the other on said photosensitive substrate and has a frequency which is different from that of the other, and for optoelectrically detecting and converting beat light caused by interference between at least two diffracted beams generated along the same direction from a grating pattern on said photosensitive substrate, into a signal, and for determining a position of the grating pattern along a pitch direction thereof based on phase of the signal, thereby detecting the grating pattern formed on said photosensitive substrate for an alignment;
said apparatus comprising:
(a) a reference plate provided on said substrate stage member and having a reference grating pattern which is substantially the same as the grating pattern on said photosensitive substrate;
(b) a first stage control system for positioning said substrate stage member in the X-Y plane so that the reference grating pattern is irradiated by the two beams from said pattern position detecting device, and for servo-controlling said substrate stage member so that the phase of the signal optoelectrically detected and converted from the beat light generated from the reference grating pattern by said pattern position detecting device is held in a predetermined state;
(c) a second stage control system for controlling said substrate stage member under the servo-control of said first stage control system so that said reference grating pattern is moved along the Z direction parallel to the optical axis of said projection optical system within a range where the two beams intersect;
(d) a measuring device for detecting a displacement amount of said substrate stage member in the X-Y plane, which occurs as said substrate stage member is moved along the Z direction by said second stage control system;
(e) a calculating device to calculate an inclination of an imaginary line bisecting an intersect angle formed between the two beams at the grating pattern, based on change in position of said substrate stage member along the Z direction and the detected displacement amount thereof in the X-Y plane;
and
an optical compensating device to change the incident angle of each of the two beams at the grating pattern based on the calculated inclination so that the imaginary line is maintained substantially perpendicular to the pitch direction of said grating pattern.

9 more elements

A projection type exposure apparatus including,

a projection optical system for projecting a pattern formed on am ask;
a substrate stage member for holding a photosensitive substrate onto which the pattern is projected, and movable in a two dimensional X-Y plane substantially perpendicular to an optical axis of said projection optical axis and further movable in a Z direction along the optical axis;
and
a pattern position detecting device for radiating two beams, each of which intersects the other on said photosensitive substrate and has a frequency which is different from that of the other, and for optoelectrically detecting and converting beat light caused by interference between at least two diffracted beams generated along the same direction from a grating pattern on said photosensitive substrate, into a signal, and for determining a position of the grating pattern along a pitch direction thereof based on phase of the signal, thereby detecting the grating pattern formed on said photosensitive substrate for an alignment;
said apparatus comprising:
(a) a reference plate provided on said substrate stage member and having a reference grating pattern which is substantially the same as the grating pattern on said photosensitive substrate;
(b) a first stage control system for positioning said substrate stage member in the X-Y plane so that the reference grating pattern is irradiated by the two beans from said pattern position detecting device;
(c) a second stage control system for controlling movement of said substrate stage member along the Z direction so that said reference grating pattern is moved parallel to the optical axis of said projection optical system within a predetermined range where the two beams intersect;
(d) an indicating device for indicating a beat signal waveform or Lissajous's figure of the signal optoelectrically detected and converted from the beat light generated from the reference grating pattern by said pattern position detecting device;
and
(e) an adjusting device to change incident angles of the two beams with respect to said reference plate while maintaining constant an intersect angle between the two beams as said reference grating pattern is moved along the Z direction within the predetermined range by said second stage control system, until the signal waveform or the Lissajous's figure indicated by said indicating device represents a substantially constant phase state.

8 more elements

A position detecting apparatus including,

a light source of coherent light;
a divider for dividing a beam from said light source into two radiated beams;
an objective optical system for receiving the two radiated beams and making the two radiated beams intersect each other on a diffraction grating pattern of an object;
and
a first optoelectric detector positioned at a pupil space or a conjugated space thereof of said objective optical system for receiving interference light between two beams generated coaxially along the same direction from said diffraction grating pattern and passing through said objective optical system;
said apparatus detecting the object position based on a signal from said optoelectric detector, the apparatus comprising:
(a) a detector holding member holding said first optoelectric detector and holding second and third optoelectric detectors with light receiving planes thereof at said pupil space or the conjugated space thereof, said second and third optoelectric detectors being located at opposite sides of said first optoelectric detector along a pitch direction of the diffraction grating pattern;
and
(b) an adjusting member to adjust a relative positional relation between said detector holding member and the received interference light path in a plane perpendicular to an optical axis of said objective optical system based on signals obtained by said second and third optoelectric detectors which respectively receive two light beams generated from the object differently from said interference light.

6 more elements

An exposure apparatus including,

an exposure light illuminating system for exposing a pattern of a mask onto a photosensitive substrate;
an objective optical system positioned in a space above the mask and movable in accordance with a position of a first diffraction grating mark on the mask for detecting a relative positional deviation between said first diffraction grating mark on said mask and a second diffraction grating mark formed on said photosensitive substrate, said objective optical system comprising an objective lens system having an optical axis substantially perpendicular to a surface of the mask, and a reflection member movable with said objective lens system and bending the optical axis perpendicularly at a portion thereof, said exposure apparatus detecting the first and second diffraction grating marks through said objective optical system, and comprising:
(a) a beam generating system for directing two beams into said objective optical system so as to form beam waists at each of two positions in a pupil space of said objective lens system, which are symmetrically separated from the optical axis by a predetermined distance, thereby to radiate two parallel flux beams intersecting with a predetermined angle on said first diffraction grating mark of the mask;
(b) a driving device for driving said objective optical system along a direction of the beam radiation from said beam generating system, in accordance with location of said first diffraction grating mark on the mask;
and
(c) an optoelectric detector for optoelectrically detecting diffracted light generated parallel to the optical axis of said objective lens system from said first diffraction grating mark, within the pupil space of said objective lens system or a conjugated space thereof, through said objective optical system;
said driving device driving said objective optical system within a predetermined range along the optical axis, and the predetermined range being limited to a distance .DELTA.Z between the beam waist positions of the two beams radiated from said beam generating system and a pupil plane of said objective lens system, the distance .DELTA.Z satisfying the following inequality,
.DELTA.Z<(.lambda.-f.sup.2)/(Dr-Pr)
wherein,
f:
a focal distance of said objective lens system
.lambda.:
a wavelength of the two beams
Dr:
an irradiation width of the two beams intersecting on said first diffraction grating mark, along a pitch direction on said mark
Pr:
a pitch of said diffraction grating mark.

14 more elements

Dependencies are inferred from the claim text.

Description40,206 words

Summary8,135 words

#1. Field of the Invention

#The present invention relates to a position detecting apparatus using a diffraction grating formed on an object such as a semiconductor device, and more particularly to an apparatus which is used in alignment of exposure equipment for lithography to detect the relative positional relationship between a mask having an original pattern and an object onto which the original pattern is transferred.

#The present invention further relates to a position detecting apparatus of the grating interference type, and more particularly to a position detecting apparatus suitable for high-precision aligners used in positioning wafers, masks, etc. in semiconductor manufacture apparatus and so forth.

Brief description of the drawings45 figures

#FIG. 1 is a diagrammatic view showing the configuration of a stepper according to a first embodiment of the present invention;

#FIG. 2 is a principle view of the present invention for explaining the state of an interference fringe and a diffraction grating:

#FIG. 3 is a view depicting in more detail a main section of an optical system shown in FIG. 1;

Detailed description31,212 words

#Hereinafter, the configuration of a projection type exposure equipment (stepper), in which a position detecting apparatus according to a first embodiment of the present invention is incorporated, will be described with reference to FIGS. 1, 3, 4, 5, 6 and 7. The basic configuration is similar to that disclosed in the above-cited Japanese Patent Laid-Open No. 63-283129.

#In FIG. 1, a reticle 1 having a predetermined circuit pattern and a grating mark for alignment thereon is held on a reticle stage 2 movable two-dimensionally. Each pattern on the reticle 1 is imaged with an exposure light on a wafer 4 through a projection lens 3 which is tele-centric on both sides. Here, the projection lens 3 is satisfactorily corrected in color aberration with respect to the wavelength of the illumination light (e.g., g line or i line) for exposure, and the reticle 1 and the wafer 4 are arranged in conjugate relation to each other for the wavelength of the exposure light. A grating mark similar to that formed on the reticle 1 is formed on the wafer 4 as well. The wafer 4 is held under suction on a stage 5 which is not only two-dimensionally movable in the x- and y-directions using the step and repeat technique, but also finely movable in the z-direction. When transfer exposure of the reticle 1 to one shot region on the wafer 4 has been completed, the wafer 4 is stepped to a next shot position. Fixed to a portion of the reticle stage 2 is a movable mirror 6 for reflecting a laser beam from laser beams interference type length gauge (hereinafter referred to an interferometer) 43 adapted to detect a relevant position in the horizontal plane of the reticle 1 in the x-, y- and rotating (.theta.-) directions. Although the interferometer 43 has three laser beams for length measurement to detect the position in the x-, y- and .theta.-directions independently of each other, a part of the laser beams is omitted on the drawing for simplicity of explanation. The reticle stage 2 has a moving stroke less than several millimeters, and the interferometer 43 is set to have detecting resolution on the order of 0.01 .mu.m, for example. On the other hand, fixed to a portion of the wafer stage 5 is a movable mirror 7 for reflecting laser beams from an interferometer 45 adapted to detect a relevant position in the horizontal plane of the wafer 4 in the x- and y-directions. Likewise, although the interferometer 45 has two laser beams for length measurement to detect the position in the x- and y-directions independently of each other, a part of the laser beams is omitted on the drawing for simplicity of explanation. The reticle stage 2 is driven by a drive motor 42 in the x-, y- and .theta.-directions, while the wafer stage 5 is moved by a drive motor 46 in the two-dimensional directions and in the z-direction.

#An illumination system for exposure comprises a mercury lamp 30, an ellipsoidal lens 31, an input lens group 32 including a condensing lens, an interference filter and others, an optical integrator (fly's-eye lens) 33, a mirror 34, a main condenser lens 35, a dichroic mirror 22, etc. The dichroic mirror 22 is obliquely disposed above the reticle 1 at an inclined angle of 45.degree. so that the exposure light passing through the condenser lens 35 is reflected by the dichroic mirror 22 vertically downward to uniformly irradiate the reticle 1. The dichroic mirror 22 has reflectivity over 90% for the wavelength of the exposure light and transmissivity over 50% for the wavelength of an illumination light (longer than that of the exposure light) for alignment. PG,45

Facts

Application

08/233,081Filed 25 Apr 1994 · continuation

Priority

JP 1-4829328 Feb 1989

Granted

6 Feb 1996

Term ended

6 Feb 2013

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification2 codes

G03F 9/70
Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically: for…
G03F
Photomechanical production of textured or patterned surfaces

Position detecting apparatus

Life of this patent

Position detecting apparatus

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims8

Description40,206 words

Drawings

Classification2 codes

Life of this patent

Description40,206 words