Method and apparatus for projection exposure
First Claim
1. A projection exposure method wherein a mask formed with a pattern for transfer is illuminated with illuminating light for exposure, and an image of said mask pattern is projected onto a photosensitive substrate through a projection optical system, said method comprising the steps of:
- using a phase plate which is disposed on a Fourier transform plane of said projection optical system or on a plane near said Fourier transform plane, said phase plate including a circular region of radius r2 which is centered at an optical axis of said projection optical system and which allows said illuminating light to pass therethrough;
dividing said circular region into a central circular region of radius r1 (r1<
r2) which is centered at the optical axis of said projection optical system, and a peripheral annular region which lies between a circle of radius r1 and a circle of radius r2, which are centered at said optical axis;
setting not only a ratio t (=t1/t2) of an amplitude transmittance t1 of illuminating light passing through said central circular region to an amplitude transmittance t2 of illuminating light passing through said peripheral annular region, at a value which is not larger than zero, but also a ratio r1/r2 of said radius r1 to said radius r2, at a value which is determined according to said amplitude transmittance ratio t;
when the pattern image of said mask is to be transferred onto said substrate by successively carrying out three divided exposure operations such that a position of said substrate relative to a position of an image-forming plane of said projection optical system is successively changed in the optical axis direction of said projection optical system by a distance d at a time, setting said distance d at a value which is determined according to a numerical aperture NA of said projection optical system and a wavelength λ
of said illuminating light;
setting two amounts of exposure for two of said three divided exposure operations which are carried out at two opposite extremity positions of an exposure range in said optical axis direction such that said two amounts of exposure become substantially equal to each other; and
setting one amount of exposure for one of said three divided exposure operations which is carried out at an intermediate position in said optical axis direction, at a value which is determined according to said distance d.
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Accused Products
Abstract
A projection exposure method wherein a mask (R) is illuminated with illuminating light (ILB) for exposure, and an image of the mask pattern is projected onto a photosensitive substrate (W) through a projection optical system (PL). A phase plate is disposed on a Fourier transform plane (FTP) of the projection optical system (PL) or on a plane near the Fourier transform plane. The circular region of the phase plate of radius r2 is divided into a central circular region (FA) and a peripheral annular region (FB) when the pattern image of the mask (R) is to be transferred onto the substrate (W) by successively carrying out three divided exposure operations such that the position of the substrate (W) relative to the position of the image-forming plane of the projection optical system (PL) is changed in the optical axis direction by a distance d at a time, the distance d is set at a value which is determined according to the numerical aperture of the projection optical system (PL) and the wavelength of the illuminating light. Moreover, the amounts of exposure for two of the three divided exposure operations which are carried out at two opposite extremity positions of the exposure range in the optical axis direction are set substantially equal to each other, and the amount of exposure for one of the three divided exposure operations which is carried out at an intermediate position in the optical axis direction is set according to the distance d.
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Citations
14 Claims
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1. A projection exposure method wherein a mask formed with a pattern for transfer is illuminated with illuminating light for exposure, and an image of said mask pattern is projected onto a photosensitive substrate through a projection optical system, said method comprising the steps of:
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using a phase plate which is disposed on a Fourier transform plane of said projection optical system or on a plane near said Fourier transform plane, said phase plate including a circular region of radius r2 which is centered at an optical axis of said projection optical system and which allows said illuminating light to pass therethrough; dividing said circular region into a central circular region of radius r1 (r1<
r2) which is centered at the optical axis of said projection optical system, and a peripheral annular region which lies between a circle of radius r1 and a circle of radius r2, which are centered at said optical axis;setting not only a ratio t (=t1/t2) of an amplitude transmittance t1 of illuminating light passing through said central circular region to an amplitude transmittance t2 of illuminating light passing through said peripheral annular region, at a value which is not larger than zero, but also a ratio r1/r2 of said radius r1 to said radius r2, at a value which is determined according to said amplitude transmittance ratio t; when the pattern image of said mask is to be transferred onto said substrate by successively carrying out three divided exposure operations such that a position of said substrate relative to a position of an image-forming plane of said projection optical system is successively changed in the optical axis direction of said projection optical system by a distance d at a time, setting said distance d at a value which is determined according to a numerical aperture NA of said projection optical system and a wavelength λ
of said illuminating light;setting two amounts of exposure for two of said three divided exposure operations which are carried out at two opposite extremity positions of an exposure range in said optical axis direction such that said two amounts of exposure become substantially equal to each other; and setting one amount of exposure for one of said three divided exposure operations which is carried out at an intermediate position in said optical axis direction, at a value which is determined according to said distance d. - View Dependent Claims (2)
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3. A projection exposure apparatus wherein a mask formed with a pattern for transfer is illuminated with illuminating light for exposure, and an image of said mask pattern is projected onto a photosensitive substrate through a projection optical system, said apparatus comprising:
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a phase plate which is disposed on a Fourier transform plane of said projection optical system or on a plane near said Fourier transform plane, said phase plate including a circular region of radius r2 which is centered at an optical axis of said projection optical system and which allows said illuminating light to pass therethrough, said circular region being divided into a central circular region of radius r1 (r1<
r2) which is centered at the optical axis of said projection optical system, and a peripheral annular region which lies between a circle of radius r1 and a circle of radius r2, which are centered at said optical axis, wherein a ratio t (=t1/t2) of an amplitude transmittance t1 of illuminating light passing through said central circular region to an amplitude transmittance t2 of illuminating light passing through said peripheral annular region is set at a value which is not larger than zero, and a ratio r1/r2 of said radius r1 to said radius r2 is set at a value which is determined according to said amplitude transmittance ratio t;a relative height control mechanism for moving said substrate and an image-forming plane of said projection optical system relative to each other in said optical axis direction; and an exposure control system for controlling an amount of exposure by which said substrate is exposed to said illuminating light; wherein, when the pattern image of said mask is to be transferred onto said substrate by successively carrying out three divided exposure operations such that a position of said substrate relative to a position of the image-forming plane of said projection optical system is successively changed in said optical axis direction by a distance d at a time through said relative height control mechanism, said distance d is set at a value which is determined according to a numerical aperture NA of said projection optical system and a wavelength λ
of said illuminating light; andtwo amounts of exposure for two of said three divided exposure operations which are carried out at two opposite extremity positions of an exposure range in said optical axis direction are set substantially equal to each other through said exposure control system, and an amount of exposure for one of said three divided exposure operations which is carried out at an intermediate position in said optical axis direction is set at a value which is determined according to said distance d through said exposure control system. - View Dependent Claims (4, 5)
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6. A projection exposure method wherein a mask formed with a pattern is irradiated with illuminating light, and an image of said mask pattern is projected onto a photo-sensitive substrate through a projection optical system, said method comprising the steps of:
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disposing an optical filter on a Fourier transform plane in said projection optical system or on a plane near said Fourier transform plane, said optical filter having a central circular region which is centered at an optical axis of said projection optical axis, and an outer region which is provided outwardly of said central circular region so that an amplitude transmittance t1 of light passing through said central circular region is different from an amplitude transmittance t2 of light passing through said outer region; and projecting said pattern image onto said substrate by carrying out exposure when said substrate is successively rearranged at three different positions spaced in the optical axis direction of said projection optical system, such that amounts of exposure at two opposite extremity positions of said three positions in said optical axis direction are approximately equal to each other. - View Dependent Claims (7, 8, 9)
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10. A projection exposure apparatus comprising:
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an illumination system for irradiating a mask with illuminating light; a projection optical system for projecting an image of a pattern on said mask onto a photosensitive substrate; an optical filter which is disposed on a Fourier transform plane in said projection optical system or on a plane near said Fourier transform plane, said optical filter having central circular region which is centered at an optical axis of said projection optical system, and an outer region which is provided outwardly of said central circular region so that an amplitude transmittance t1 of light passing through said circular region is different from an amplitude transmittance t2 of light passing through said outer region; a driving system for stepwisely moving said substrate in said optical axis direction of said projection optical system for projecting said pattern image when said substrate is successively rearranged at three different positions spaced in said optical axis direction; and a member for controlling an amount of exposure by which said mask is irradiated with said illuminating light so that amounts of exposure which are applied to said substrate by projection of said pattern image at two opposite extremity exposure positions in said optical axis direction are approximately equal to each other. - View Dependent Claims (11, 12, 13, 14)
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Specification