Exposure control apparatus and method

• US 5,627,627 A
• Filed: 09/29/1995
• Issued: 05/06/1997
• Est. Priority Date: 02/24/1993
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Suzuki, Kazuaki
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): MALLEY, DANIEL PATRICK
• Application Number:
  US08/536,468
• Time in Patent Office: 585 Days
• Field of Search: 355/53, 355/67, 355/68, 355/71
• US Class Current: 355/68
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• CPC Class Codes: G03F 7/70091 Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA]
• CPC Class Codes: G03F 7/70358 Scanning exposure, i.e. relative movement of patterned beam and workpiece during imaging
• CPC Class Codes: G03F 7/70558 Dose control, i.e. achievement of a desired dose
• CPC Class Codes: G03F 7/70566 Polarisation control
• CPC Class Codes: G03F 7/70583 Speckle reduction, e.g. coherence control or amplitude/wavefront splitting

Abstract

An apparatus has a pulse light source for emitting light pulses with varying light quantities, an illumination optical system for radiating the light pulses from the source onto a predetermined illumination region on a mask on which a transfer pattern is formed, and a projection optical system for projecting an image of the pattern onto a predetermined exposure region on a substrate, and which synchronously scans the mask and the substrate during the projection. The apparatus includes a measuring device for detecting intensities of the light pulses radiated onto the substrate during the scanning and measuring an integrated light quantity on each of a plurality of partial regions in the exposure region on the substrate on the basis of a detection signal of the intensities, wherein the partial regions are defined by a scanning speed of the photosensitive substrate and an oscillation interval of the light pulses. The apparatus further includes an adjusting device for adjusting an intensity of the next light pulse to be radiated onto the mask on the basis of a difference between a target integrated light quantity and the measured integrated light quantity on each of the partial regions when some light pulses are radiated onto the mask.

Claims

1. A scanning exposure apparatus comprising:

an illumination system for illuminating a mask with light pulses;

a projection optical system receiving light pulses from said mask and having an image field which is smaller than an exposure region on a photosensitive substrate, in which region an image of a pattern on said mask is to be formed by light pulses radiated from said projection optical system;

a scanning system which synchronously scans said mask and said substrate relative to said projection optical system for scanning exposure;

a measurement system which measures, during the scanning exposure, individual integrated light quantities radiated on each of a plurality of partial regions, respectively in said exposure region, within the image field to be irradiated with a next light pulse, based on intensities of light pulses radiated on said substrate; and

an adjusting system which adjusts an intensity of said next light pulse based on the measured integrated light quantities.

2. An apparatus according to claim 1, wherein said illumination system has a light source which radiates said light pulses, and said adjusting system includes a device which adjusts a voltage applied to said light source to vary intensity of the light pulses.

3. An apparatus according to claim 1, wherein said measurement system includes a photoelectric detector for receiving a portion of each light pulse and a calculator for calculating individual integrated light quantities radiated each of said plurality of partial regions, respectively based on a signal from said photoelectric detector and for determining the intensity of said next pulse based on the calculated integrated light quantities.

4. An apparatus according to claim 3, wherein said illumination system includes an optical integrator for reducing non-uniformity in illuminance of each light pulse on said mask and an optical member for guiding a portion of each light pulse from said optical integrator to said photoelectric detector.

5. An apparatus according to claim 1, further comprising a controller which detects a difference between at least one of said integrated light quantities and a target exposure dose corresponding thereto, the controller suspending said scanning exposure when said difference exceeds a predetermined value.

6. A scanning exposure apparatus comprising:

an illumination system for illuminating a mask with light pulses;

a projection optical system receiving light pulses from said mask and having an image field which is smaller than an exposure region on a photosensitive substrate, in which region an image of a pattern on said mask is to be formed by light pulses radiated from said projection optical system;

a scanning system which synchronously scans said mask and said substrate relative to said projection optical system for scanning exposure; and

a measurement system which measures, during the scanning exposure, individual integrated light quantities radiated on each of a plurality of partial regions, respectively, in said exposure region, within the image field to be irradiated with a next light pulse, based on intensities of light pulses radiated on said substrate;

wherein an intensity of said next light pulse is determined based on the measured integrated light quantities.

7. A scanning exposure apparatus comprising:

an illumination system for illuminating a mask with light pulses;

a scanning system which synchronously scans said mask and a substrate for scanning exposure; and

a measurement system, including a photoelectric detector which receives a portion of each light pulse and which measures, each time a predetermined number of pulses are radiated on the mask during the scanning exposure, individual integrated light quantities radiated on each of a plurality of partial regions in an exposure region, respectively, on the substrate on which an image of a pattern on the mask is formed by light pulses from the mask, based on a signal from said photoelectric detector.

8. An apparatus according to claim 7, further comprising an adjusting system for adjusting, during the scanning exposure, intensity of a light pulse based on the measured integrated light quantities.

9. An apparatus according to claim 8, wherein said illumination system has a light source which radiates said light pulses, and said adjusting system includes a device which adjusts a voltage applied to said light source to vary intensity of a light pulse.

10. An apparatus according to claim 7, further comprising a projection optical system receiving light pulses from the mask for projecting the image of the pattern of the mask onto said substrate, the projection optical system having a rectangular image field which is smaller than a size of said exposure region.

11. An apparatus according to claim 7, further comprising a controller which detects a difference between at least one of the measured integrated light quantities and a target exposure dose corresponding thereto, the controller suspending said scanning exposure when said difference exceeds a predetermined value.

12. A scanning exposure apparatus comprising:

an illumination system for irradiating a mask with light pulses;

a scanning system which synchronously scans the mask and a photosensitive substrate for scanning exposure, so that an image of a pattern on the mask is formed by light pulses from the mask on a plurality of small regions in an exposure region on the photosensitive substrate during the scanning exposure, wherein, during said scanning exposure individual integrated light quantities radiated on each of said plurality of small regions vary among said plurality of small regions; and

a measurement system which measures, each time a predetermined number of pulses are radiated on the mask during the scanning exposure, each of the individual integrated light quantities radiated on said plurality of small regions, respectively.

13. A scanning exposure apparatus

comprising:

an illumination system for illuminating a mask with light pulses;

a projection optical system receiving light pulses from said mask and having an image field which is smaller than a size of an exposure region on a photosensitive substrate, in which region an image of a pattern on said mask is to be formed by light pulses radiated from said projection optical system;

a scanning system which synchronously scans said mask and said substrate relative to said projection optical system for scanning exposure, wherein, during said scanning exposure, individual integrated light quantities radiated on each of a plurality if small regions in said exposure region within said image field vary among said plurality of small regions; and

an adjusting system which adjusts intensity of said light pulses in accordance with the individual integrated light quantities radiated on each of the plurality of small regions, respectively.

14. A method for scanningly exposing an exposure region on a photosensitive substrate with an image of a pattern on a mask, utilizing light pulses irradiating the mask and projected from the mask to the substrate by a projection optical system, the exposure region being larger than an image field of the projection optical system, comprising the steps of:

synchronously scanning said mask and said substrate relative to said projection optical system for scanning exposure, wherein, during said scanning exposure, individual integrated light quantities radiated on each of a plurality of small regions is said exposure region within said image field vary among said plurality of small regions;

measuring, each time a predetermined number of pulses are radiated on the mask during the scanning exposure, each of the individual integrated light quantities radiated on said plurality of small regions, respectively; and

adjusting an energy amount of a next light pulse to be radiated on the substrate based on measured integrated light quantities.

15. A method according to claim 14, wherein a voltage applied to a light source which radiates aid light pulses is adjusted so that an energy amount of a light pulse is varied.

16. A method according to claim 14, further comprising the step of:

suspending said scanning exposure, when a difference between at least one of said integrated light quantities and a target exposure dose corresponding thereto exceeds a predetermined value.

17. A scanning exposure method comprising the steps of:

synchronously scanning a mask and a substrate relative to a projection optical system so to scanningly expose an exposure region on the substrate with an image of a pattern on a mask, utilizing light pulses irradiating the mask, the exposure region being larger than an image field of the projection optical system, wherein, during a scanning exposure, individual integrated light quantities radiated on a plurality of small regions in said exposure region within said image field vary among said plurality of small regions; and

measuring, each time a predetermined number of pulses are radiated on the mask during the scanning exposure, each of the individual integrated light quantities radiated on said plurality of small regions, respectively.

18. A method according to claim 17, further comprising the step of:

adjusting an energy amount of a next light pulse to be radiated onto said substrate, when a difference between at least one of said integrated light quantities and a target integrated light quantity corresponding thereto exceeds a predetermined value.

19. A method according to claim 17, further comprising the step of:

suspending said scanning exposure, when a difference between at least one of said integrated light quantities and a target exposure dose corresponding thereto exceeds a predetermined value.

20. A method according to claim 17, further comprising the step of:

determining intensity of a next light pulse for irradiating said mask in accordance with differences between the individual measured integrated light radiated quantities on each of said plurality of small regions and target integrated light quantities respectively corresponding thereto.

21. A scanning exposure method comprising the steps of:

synchronously scanning a mask and a substrate relative to a projection optical system so as to scanningly expose an exposure region on the substrate with an image of a pattern on the mask, utilizing light pulses irradiating the mask during a scanning exposure, the exposure region being larger than an image field of the projection optical system,; and

adjusting an energy amount of a next light pulse to be radiated onto said substrate in accordance with individual integrated light quantities radiated on each of a plurality of small regions, respectively, in said exposure region within said image field during the scanning exposure.