Position detecting apparatus

• US 5,489,986 A
• Filed: 04/25/1994
• Issued: 02/06/1996
• Est. Priority Date: 02/28/1989
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Magome, Nobutaka, Mizutani, Hideo, Ota, Kazuya, Komatsu, Kouichiro
• Primary Examiner(s): Rosenberger, Richard A.
• Assistant Examiner(s): HANTIS, KAREN
• Application Number:
  US08/233,081
• Time in Patent Office: 652 Days
• Field of Search: 356/399-401, 356/349, 356/356, 356/363, 355/43, 355/53, 250/548
• US Class Current: 356/401
• CPC Class Codes: G03F 9/70 for microlithography measuring printed patterns for monitoring overlay G03F7/70633 or focus G03F7/70641; projection system adjustment G03F7/70258; position control G03F7/70775

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.

Claims

1. 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.

2. 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.

3. 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.

4. A position detecting apparatus including,

a light source of coherent light;

a divider for dividing a beam from said light source into two beams;

an objective optical system for receiving the two beams and making the two beams intersect each other on a diffraction grating pattern of an object, the position of which is to be detected; and

an optoelectric detector for receiving at least two diffracted beams generated along the same direction from said diffraction grating pattern;

said apparatus comprising;

(a) two optical modulators for shifting frequencies of incident beams in response to high frequency drive signals, and generating two diffracted beams with diffraction angles in response to the frequency of said drive signals in order to make a predetermined frequency difference between the two beams;

(b) a drive signal generator for generating high frequency drive signals respectively applied to said two optical modulators;

(c) an optical lens system for substantially conjugating each diffracting point of said optical modulators, with respect to the object through said objective optical system; and

(d) a frequency changing circuit for changing frequencies of the high frequency drive signals respectively applied to said optical modulators by said drive signal generator while maintaining constant the frequency difference therebetween, thereby changing diffracting angles of the incident beams generated by said optical modulators, in order to adjust the incident angles of the two beams radiated to the object from said objective optical system.

5. 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. A position detecting apparatus according to claim 5, wherein said adjusting member comprises a mechanism for finely moving said detector holding member with respect to said interference light path.

7. A position detecting apparatus according to claim 5, wherein said adjusting member comprises a tiltable parallel plane glass disposed in front of said detector holding member for shifting said interference light path with respect to said detector holding member.

8. 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 Δ

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 Δ

Z satisfying the following inequality,

space="preserve" listing-type="equation">Δ

Z<

(λ

-f.sup.2)/(Dr-Pr)

wherein,

f;

a focal distance of said objective lens system

λ

;

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.