Pattern detecting method, pattern detecting apparatus, projection exposing apparatus using the same and exposure system

• US 5,684,565 A
• Filed: 09/12/1994
• Issued: 11/04/1997
• Est. Priority Date: 09/10/1993
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Shibata, Yukihiro, Iwata, Hisafumi, Yoshida, Minoru, Yoshitake, Yasuhiro, Oshida, Yoshitada
• Primary Examiner(s): Grimley, Arthur T.
• Assistant Examiner(s): Kerner, Herbert
• Application Number:
  US08/304,586
• Time in Patent Office: 1,149 Days
• Field of Search: 250/548, 356/400, 356/401, 355/53, 355/67, 355/71
• US Class Current: 355/53
• CPC Class Codes: G03F 9/7065 Production of alignment light, e.g. light source, control of coherence, polarization, pulse length, wavelength

Abstract

A method and apparatus is disclosed for detecting a pattern image of each of a plurality of patterns on the surface of an object. Light emitted from either a light source including a wide wavelength or a light source including a plurality of monowavelengths is applied to the object. The object includes a layered structure having a plurality of layers, wherein at least a part of an uppermost layer of the object is optically transparent. Spectral illumination intensity characteristics of the light emitted from the light source is varied, depending on information about both the layered structure of the object, and a material of the object to obtain a desired spectral illumination intensity, and a pattern image of each of patterns is detected as either a one-dimensional or a two-dimensional image based on light reflected from the object.

Claims

1. A method of detecting a pattern image of each of a plurality of patterns on the surface of an object, comprising the steps of:

applying light emitted from either a light source including a wide wavelength or a light source including a plurality of monowavelengths to said object, said object having a layered structure which includes a plurality of layers, wherein at least a part of the uppermost layer of said object is optically transparent;

effectively varying spectral illumination intensity characteristics of the light emitted from said light source depending on information about both the layered structure of said object and a material of said object to obtain a desired spectral illumination intensity; and

detecting a pattern image of each of said patterns as either a one-dimensional or a two-dimensional image based on light reflected from said object.

2. A method as claimed in claim 1, wherein the light emitted from said light source is set such that a traveling direction of the light is varied for each wavelength by a light separator and said spectral illumination intensity characteristics are thereafter effectively varied by inserting, into optical paths separated by said light separator, a spatial light transmittance modulator for making light transmittances different from each other at each location where the light of each wavelength passes therethrough.

3. A method as claimed in claim 1, wherein when, the pattern image of said object irradiated with the light at said desired spectral illumination intensity is detected as either the one-dimensional or the two-dimensional image, a spectral transmittance variable filter for varying a transmittance for each wavelength of the light reflected from said object is inserted into an optical path of each light reflected from said object to thereby effectively vary the spectral illumination intensity characteristics of the light emitted from said light source.

4. A method as claimed in claim 1, wherein when, the pattern image of said object irradiated with the light at said desired spectral illumination intensity is detected as either the one-dimensional or the two-dimensional image, numerical apertures used for detection of the pattern image are made different from each other every wavelength of the light reflected from said object.

5. A method as claimed in claim 4, wherein each wavelength of the light emitted from the light source is caused to have directivity so as to reach a partial coherence of illumination having a predetermined ratio with respect to each of said numerical apertures.

6. A method as claimed in claim 1, wherein a multiple interference intensity at each wavelength of the detected image pattern, which is caused by the layer structure, is calculated based on the information about both the layered structure of said object and the material of said object and the spectral illumination intensity characteristics of the light emitted from said light source are effectively varied depending on said information so as to produce a waveform of a detected signal capable of reflecting the structure of each pattern with fidelity.

7. A method of detecting a pattern image of each of a plurality of patterns on a surface of an object, comprising the steps of:

applying light emitted from either a light source including a wide wavelength or a light source including a plurality of monowavelengths to said object, said object having a layered structure which includes a plurality of patterns, wherein at least a part of an uppermost layer of said object is optically transparent;

substantially focusing the light emitted from said light source and reflected from said object on a light separator so as to spectrally separate the light in a predetermined spectral direction;

focusing light reflected from said object through said light separator on a detector so as to form an image in a pattern detecting direction orthogonal to said predetermined spectral direction in which the patterns separated by said light separator are spectrally separated; and

detecting, by said detector, the spectrally separated patterns as spectral one-dimensional images.

8. A method as claimed in claim 7, wherein a correction about a chromatic aberration included in a detection optical system is effected on respective signals in a pattern detecting direction, which correspond to respective spectral wavelengths of spectral one-dimensional images and respective signals subjected to the chromatic aberration correction are thereafter synthesized to produce a synthesized signal, thereby detecting each pattern image based on a synthesized signal.

9. A method as claimed in claim 7, wherein respective signals existing in the pattern detecting direction are multiplied by constants different from each other every wavelength over the entirety of the signals having their corresponding wavelengths and the wavelengths of the signals are thereafter combined into one, thereby detecting each pattern based on the combined wavelength.

10. A method as claimed in claim 7, wherein respective signals are multiplied every wavelength by constants different from each other depending on locations of the signals having their corresponding wavelengths and respective wavelengths of the signals are combined into one, thereby detecting each pattern based on the combined wavelength.

11. A device for detecting a pattern image of each of a plurality of patterns on the surface of an object, comprising:

a light source for emitting one of a light including a wide wavelength and a light effectively including a plurality of monowavelengths;

an illuminating device for irradiating said object using light emitted from said light source, said object having a layered structure which includes a plurality of layers, wherein at least a part of the uppermost layer of said object is optically transparent to light emitted from said light source;

a pattern detector for detecting each pattern on the surface of said object using the light reflected from said object;

apparatus for varying spectral illumination intensity characteristics of the light emitted from said light source depending on information about both the layered structure of said object and a material of said object to thereby obtain a desired spectral illumination intensity; and

an image-forming optical system for detecting a pattern image of said object irradiated with the light at said desired illumination intensity as either a one-dimensional or a two-dimensional image.

12. A device as claimed in claim 11, wherein said varying apparatus comprises:

a light separator, disposed in the optical path of the light emitted from said light source, for varying the direction of traveling of the light for each wavelength; and

a spatial light transmittance modulator, disposed in each optical path of the light separated by said light separator, for making light transmittances different from each other at each location where the light of each wavelength passes therethrough.

13. A device as claimed in claim 11, wherein said varying apparatus comprises:

a spectral transmittance variable filter, disposed in an optical path of the light reflected from the object irradiated with the light at said desired spectral illumination intensity, for varying a transmittance for each wavelength of the reflected light.

14. A device as claimed in claim 11, wherein said image-forming optical system includes apparatus for varying a numerical aperture thereof according to each wavelength of the light reflected from the object.

15. A device as claimed in claim 11, further comprising:

apparatus for causing each wavelength of the light to have directivity so as to reach a partial coherence of illumination having a predetermined ratio with respect to each numerical aperture for pattern detection made for each wavelength.

16. A device as claimed in claim 11, further comprising:

means for inputting information about both said layered structure of said object and said material of said object;

means for calculating a multiple interference intensity at each wavelength of the detected light, which is caused by the layered structure, based on the information about both the layered structure of said object and the material of said object; and

means for calculating the spectral illumination intensity characteristics of the light emitted from said light source, which are capable of obtaining a waveform of each detected signal reflecting the structure of each pattern with fidelity.

17. A device for detecting a pattern image of each of a plurality of patterns on the surface of an object, comprising:

a light source for emitting one of a light including a wide wavelength and a light effectively including a plurality of monowavelengths;

an illuminating device for irradiating said object with light emitted from said light source;

a pattern detector for detecting each pattern on the surface of said object using light reflected from said object;

an optical system for focusing light reflected from said object on a light separator;

said light separator, which includes a diffraction grating and is disposed in a position between said object and said optical system, separates light reflected from said object;

a non-rotation symmetry image-focusing system for focusing each of said patterns formed by light reflected from said object through said light separator with respect to a pattern detecting direction orthogonal to each of directions in which the patterns separated by said light separator are spectrally separated and for setting each pattern to a state in which said object subjected to the spectral process has been non-imaged, with respect to the light separating direction;

a two-dimensional image sensor for detecting spectral one-dimensional images based on patterns focused by said non-rotation symmetry image-focusing system; and

a processing circuit for electrically processing the images obtained by said two-dimensional image sensing device.

18. A device as claimed in claim 17, wherein said processing circuit effects a correction about a chromatic aberration included in respective signals existing in the pattern detecting direction, said respective signals corresponding to respective spectral wavelengths of the one-dimensional images, combines the respective signals subjected to the chromatic aberration correction into one and detects each pattern based on the combined signal.

19. A device as claimed in claim 17, wherein said processing circuit multiplies respective signals existing in the pattern detecting direction by constants different from each other every wavelength over all of the signals, said respective signals corresponding to wavelengths of the one-dimensional images, combines the wavelengths of the signals into one and detects each pattern based on the combined wavelength.

20. A device as claimed in claim 17, wherein said processing circuit multiplies respective signals every wavelength by constants different from each other depending on locations of the signals, said respective signal corresponding to wavelengths of the one-dimensional images, combines the respective wavelengths of the signals into one and detects each pattern based on the combined wavelength.

21. A projection exposing device comprising:

a mask for an original image;

an exposure illumination system for applying illumination to a pattern drawn on said mask;

a projection optical system illuminated by said exposure illumination system and for projecting light transmitted through said mask onto an object to be exposed and exposing the object to said light;

a movable stage having the object mounted thereon;

a pattern detecting unit for detecting a position of a pattern on the object;

alignment apparatus for aligning said mask relative to the object depending on the detected position of said pattern on said object;

a light source for emitting a light including a wide wavelength or effectively including a plurality of monowavelengths;

illuminating apparatus for irradiating an alignment pattern on said object with the light emitted from said light source, said object is comprised of a layered structure having a plurality of layers, wherein an uppermost layer of said object has at least an optically-transparent part;

pattern detecting apparatus for detecting the alignment pattern on the surface of said object using light reflected from said alignment pattern;

means for effectively varying spectral illumination intensity characteristics of the light emitted from said light source depending on information about both the layered structure of said object and a material of said object to thereby obtain a desired spectral illumination intensity; and

an image-forming optical system, disposed in an optical path of the light, for detecting a pattern image of said object irradiated with the light at said desired illumination intensity as either a one-dimensional or a two-dimensional image.

22. A projection exposing device as claimed in claim 21, wherein said varying apparatus comprises:

light separating means, disposed in an optical path of the light emitted from said light source, for varying the direction of travel of the light for each wavelength; and

a spatial light transmittance modulator, disposed in each optical path of the light separated by said light separating means, for making light transmittances different from each other at each location where the light having each wavelength passes therethrough.

23. A projection exposing device as claimed in claim 21, wherein said varying apparatus comprises:

a spectral transmittance variable filter, disposed in an optical path of the light reflected from the object irradiated with the light at said desired spectral illumination intensity, for varying a transmittance for each wavelength of the reflected light.

24. A projection exposing device as claimed in claim 21, wherein said image-forming optical system comprises:

means for varying a numerical aperture thereof according to each wavelength of the light reflected from the object.

25. A projection exposing device as claimed in claim 21, further comprising:

means for causing each wavelength of the illuminating light to have directivity so as to reach a partial coherence of illumination having a predetermined ratio with respect to each numerical aperture for pattern detection made for each wavelength.

26. A projection exposing device as claimed in claim 21, further comprising:

means for inputting information about the layered structure of said object and the material of the object;

means for calculating a multiple interference intensity at each wavelength of detected light, caused by the layered structure of said object, based on the information about both the layered structure of said object and the material of the object; and

means for calculating the spectral illumination intensity characteristics of the light emitted from said light source, which are capable of obtaining a waveform of each detected signal reflecting the structure of each pattern with fidelity.

27. A projection exposing device as claimed in claim 21, wherein said pattern detecting unit comprises:

said illuminating apparatus constructed in such a manner that the light emitted from said light source is transmitted through said projection optical system and applied to said object; and

said pattern detecting means for detecting the alignment pattern on the object.

28. A projection exposing device as claimed in claim 21, wherein said pattern detecting means comprises:

means apparatus for correcting a chromatic aberration developed when the light emitted from the light source and reflected from the alignment pattern passes through said projection optical system.

29. A projection exposing device as claimed in claim 28, wherein said pattern detecting means is provided in a pair each constructed so as to detect each of two alignment patterns disposed on the surface of said object and orthogonal to each other and to detect a sagittal image of said projection optical system and said chromatic aberration correcting apparatus effects a color correction on said sagittal image.

30. A projection exposing device as claimed in claim 29, wherein a main ray of detected light of the light reflected from one of the two alignment patterns falls within a plane including the direction of the alignment pattern and a normal line to the object and serves to vary the angle of reflection for each wavelength.

31. An exposing system comprising:

a projection exposing device which includes;

an exposure illumination system for applying illumination to a pattern drawn on an original-image mask;

a projection optical system illuminated by said exposure illumination system and for projecting light transmitted through said mask onto an object to be exposed and exposing the object to said light,

a movable stage having the object mounted thereon,

a pattern detection system for detecting a position of a pattern on the object, and

alignment apparatus for aligning said mask relative to the object depending on the position of said pattern on the object;

a pattern detecting unit for setting an object, before and after being exposed to the light by said projection exposing device, as said object, irradiating said object with the light emitted from either a light source including a wide wavelength or a light source effectively including a plurality of monowavelengths and detecting a pattern on the surface of said object using the light reflected from said object;

a device for forming a light-sensitive layer on said object to be exposed;

a unit for developing the light-sensitive layer exposed to the light by said projection exposing device;

a device for etching said developed light-sensitive layer on said object; and

a control device for feeding back pattern position information about alignment, which has been detected by said pattern detecting unit, to said light-sensitive layer forming device or said developing unit or said etching device, or feeding back or feeding forward pattern position information to said projection exposing device.

32. An exposing system as claimed in claim 31, wherein when the position of the pattern such as an alignment pattern on the object is detected by said pattern detecting unit before said projection exposing device effects an exposure process on the object, optical conditions of said pattern detecting unit are varied to thereby detect the alignment pattern at an illumination of the pattern detection system to obtain first pattern position information and second pattern position information, and a difference between the first pattern position information and the second pattern position information is determined and fed forward to said projection exposing device as an alignment offset value when said projection exposing device effects the exposure process on the object.

33. An exposing system as claimed in claim 31, wherein the light-sensitive layer on said object exposed to light by said exposing device is developed by said developing unit, the position of the alignment pattern on the object is detected by said pattern detecting unit to thereby determine an error in position at superposition exposure, and the error is fed back to a next exposure as an alignment offset for an object to be next exposed.