Method and apparatus for manufacturing a diffraction grating zone plate

• US 5,623,473 A
• Filed: 06/29/1995
• Issued: 04/22/1997
• Est. Priority Date: 06/30/1994
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Ichihara, Yutaka
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): CHU, KIM KWOK
• Application Number:
  US08/496,554
• Time in Patent Office: 663 Days
• Field of Search: 369/116, 369/112, 430/321, 430/299, 359/575, 359/566
• US Class Current: 430/321
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/043 along the beam path, i.e. alignment of laser beam axis relative to laser beam apparatus
• CPC Class Codes: G02B 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08

Abstract

An apparatus of this invention has an objective lens for guiding an exposure beam emitted by a light source toward a first region on a rotary table, a lighting light source for irradiating lighting light in the direction of the first region via the objective lens, an image pickup device for picking up an image from the first region obtained via the objective lens, modulation means for changing the propagating direction of the exposure beam, and a controller for controlling the modulation means on the basis of a signal input from the image pickup device.

Claims

1. An apparatus for drawing concentric circular patterns on a photoresist coated on a substrate placed on a rotary table by irradiating an exposure beam emitted by a light source onto the photoresist, comprising:

(a) an objective lens for guiding the exposure beam emitted by the light source toward a first region on the photoresist coated on the substrate;

(b) a lighting light source for irradiating lighting light in a direction of the first region via said objective lens;

(c) an image pickup device for picking up an image from the first region obtained via said objective lens;

(d) a deflector for changing a propagating direction of the exposure beam; and

(e) a controller for controlling said deflector on the basis of a signal input from said image pickup device.

2. An apparatus according to claim 1, further comprising a motor for rotating the rotary table.

3. An apparatus according to claim 1, wherein said deflector comprises an acoustooptic modulator arranged in an optical passage of the exposure beam which propagates from the light source to said objective lens.

4. An apparatus according to claim 1, further comprising:

a) a mirror for reflecting the exposure beam emitted by the light source in a direction of said objective lens;

b) a beam splitter arranged in an optical passage of the exposure beam which passes between said objective lens and said mirror, the exposure beam which is guided to said beam splitter from a direction of said mirror being transmitted or deflected through said beam splitter and being incident onto said objective lens, the lighting light emitted by said lighting light source being deflected or transmitted by said beam splitter and being incident onto said objective lens, the lighting light which is incident onto said beam splitter from a direction of the rotary table via said objective lens being deflected or transmitted by said beam splitter and being irradiated onto said image pickup device;

c) a movable head which is fixed to said objective lens, said mirror, and said beam splitter, and is movable relative to the rotary table, and

d) an actuator for moving said movable head.

5. An apparatus according to claim 4, further comprising:

a) a laser distance measuring unit for detecting a position of said head; and

b) an actuator controller for controlling said actuator on the basis of an output from said laser distance measuring unit.

6. An apparatus according to claim 1, wherein the image is an image of an edge of a step portion formed on a surface of the substrate, and

said controller controls said deflector, so that the exposure beam is irradiated onto a photoresist portion coated on a predetermined region, adjacent to the edge, of the substrate.

7. An apparatus according to claim 1, further comprising:

a) a focal point detector for measuring a distance between said objective lens and the photoresist;

b) an actuator which can move said objective lens along a direction normal to the surface of the rotary table; and

c) an auto focal point position controller for controlling said actuator on the basis of an output from said focal point detector.

8. An apparatus according to claim 1, further comprising a filter which is inserted in an optical passage of the lighting light between said lighting light source and said objective lens, and shields light in a wavelength range to which the photoresist is exposed.

9. An apparatus according to claim 1, wherein the image is an image of an edge of a step portion formed on a surface of the substrate, and

said controller comprises a position calculator for calculating a position of the edge on the basis of an output from said image pickup device.

10. An apparatus according to claim 1, wherein

a) the image is an image of an edge of a step portion formed on a surface of the substrate,

b) said deflector comprises an acoustooptic modulator arranged in an optical passage of the exposure beam which propagates from the light source to said objective lens, and

c) said controller comprises:

a position calculator for calculating a position of the edge on the basis of an output from said image pickup device; and

an AOM controller for controlling said acoustooptic modulator on the basis of an output from said position calculator, so that the exposure beam is irradiated onto a photoresist portion coated on a predetermined region, adjacent to the edge, of the substrate.

11. An apparatus according to claim 10, further comprising a memory for storing data of the position of the edge calculated by said position calculator.

12. An apparatus according to claim 1, wherein

a) the image is an image of an edge of a step portion formed on a surface of the substrate,

b) said deflector comprises an acoustooptic modulator arranged in an optical passage of the exposure beam which propagates from the light source to said objective lens, and

c) said controller comprises:

a position calculator for calculating a position of the edge on the basis of an output from said image pickup device;

a memory for accumulating an output from said position calculator from time 2π

/ω

sec to time 4π

/ω

sec; and

an AOM controller for controlling said acoustooptic modulator, so that the exposure beam is irradiated at a position obtained by adding a half diameter of the exposure beam to data of the position of the edge accumulated on the memory during an interval from time 2(n+1)π

/ω

sec to time 2(n+2)π

/ω

sec,

where

ω

;

the rotational speed rad/sec of the rotary table,

π

;

the ratio of circumference of circle to its diameter, and

n;

an integer.

13. A method of manufacturing a zone plate, comprising the steps of:

(a) forming a concentric circular diffraction grating constituted by a plurality of step portions on a surface of a substrate;

(b) coating a photoresist on the diffraction grating;

(c) observing, using an image pickup device, an edge of each of the Plurality of step portions on the substrate via the photoresist while rotating the substrate;

(d) calculating a position of the edge on the basis of an output from the image pickup device; and

(e) irradiating an exposure beam onto a portion, on a region neighboring the edge position, of the resist while rotating the substrate.

14. A method according to claim 13, further comprising the steps of:

(f) removing a portion of the photoresist from the substrate by dipping the substrate in an organic solvent while applying an ultrasonic wave to the substrate after the step (e); and

(g) washing the substrate with water after the step (f).

15. A method according to claim 14, further comprising the step of irradiating Ar ions onto the substrate coated with the photoresist after the step (g).

16. A method according to claim 14, further comprising the step of etching an exposed portion of the substrate by arranging the substrate between opposing electrodes, arranging the substrate in a reactive gas, and applying a high frequency across the electrodes.

17. A method according to claim 16, wherein the reactive gas contains C₃ H₈.

18. A method according to claim 17, wherein the reactive gas contains CCl₄.

19. A method according to claim 14, wherein an exposed portion of the substrate is etched using a reactive ion etching method after the step (g).

20. An apparatus for irradiating an exposure beam emitted by a light source onto a photoresist coated on a substrate, which is placed on a rotary table, via an objective lens, comprising:

(a) a beam expander which is arranged in an optical passage of the exposure beam which propagates from the light source to the objective lens, and expands a diameter of the exposure beam incident thereon; and

(b) an element which is arranged in an optical passage of the exposure beam which propagates from said beam expander to the objective lens, and has an aperture with a variable size, the exposure beam passing through the aperture.

21. An apparatus according to claim 20, wherein said element comprises:

a first plate which is movable in a first direction perpendicular to a direction of thickness thereof; and

a second plate which is movable in a direction perpendicular to a direction of thickness thereof and the first direction, and

the diameter of the exposure beam is limited by said first and second plates.

22. An apparatus according to claim 21, wherein said element further comprises:

a first actuator for moving said first plate; and

a second actuator for moving said second plate.

23. An apparatus according to claim 20, wherein said element comprises four plates for defining the aperture, and each of said plates is movable in a direction perpendicular to a direction of thickness thereof.

24. An apparatus according to claim 20, wherein said element comprises:

a substrate having an aperture;

a first plate which is movable in a first direction perpendicular to a direction of thickness thereof, and covers a portion of the aperture of said substrate;

a second plate which crosses on said first plate, is movable in a direction perpendicular to both a direction of thickness thereof and the first direction, and covers a portion of the aperture of said substrate.

25. An apparatus according to claim 20, wherein said element comprises:

a substrate having an aperture;

a first plate which is movable in a first direction perpendicular to d direction of thickness thereof, and covers a portion of the aperture of said substrate;

a second plate which crosses on said first plate, is movable in a second direction perpendicular to both a direction of thickness thereof and the first direction, and covers a portion of the aperture of said substrate;

a first actuator which is fixed to said substrate and moves said first plate; and

a second actuator which is fixed to said substrate and moves said second plate.

26. An apparatus according to claim 25, wherein a first guide groove extending in the first direction and a second guide groove extending in the second direction are formed on said substrate,

said first plate has a first projection which is slideably fitted in the first guide groove, and

said second plate has a second projection which is slideably fitted in the second guide groove.