Alignment method, projection exposure method, and projection exposure apparatus

An exposure method for transferring a pattern formed on a mask onto a photosensitive substrate through a projection optical system, comprising:

• a first step of radiating a light beam having a first wavelength characteristic onto a first fiducial member formed on a mask holder for holding the mask thereon, radiating the light beam having the first wavelength characteristic through the projection optical system onto a second fiducial member installed at the same position as that of the photosensitive substrate in the direction of the optical axis of the projection optical system and corresponding to the first fiducial member, and detecting optical information from the first and second fiducial members to obtain a positional relationship between the first and second fiducial members under the light beam having the first wavelength characteristic;
• a second step of radiating a light beam having a second wavelength characteristic different from the first wavelength characteristic onto the first fiducial member, radiating the light beam having the second wavelength characteristic through the projection optical system onto the second fiducial member, and detecting optical information from the first and second fiducial members to obtain a positional relationship between the first and second fiducial members under the light beam having the second wavelength characteristic;
• a third step of determining a difference between the positional relationships caused by the difference in wavelength between the light beam having the first wavelength characteristic and the light beam having the second wavelength characteristic on the basis of results of the detection in the first and second steps.

A projection exposure apparatus for transferring a pattern formed on a mask onto a photosensitive substrate, comprising:

• a projection optical system, disposed between the mask and the photosensitive substrate, that projects an image of a pattern of the mask onto the photosensitive substrate;
• a mask stage for placing the mask thereon;
• a photosensitive substrate stage, provided with a fiducial plate, for placing the photosensitive substrate thereon;
• a first energy source that radiates a light beam having a first wavelength characteristic and a light beam having a second wavelength characteristic different from the first wavelength characteristic through the projection optical system onto a first mark area including a fiducial mark formed on the fiducial plate;
• a first detector that detects optical information from the first mark area to obtain a position of the fiducial mark under the light beam having the first wavelength characteristic;
• a second detector that detects optical information from the first mark area to obtain a position of the fiducial mark under the light beam having the second wavelength characteristic;
• and
• a calculator that calculates a positional discrepancy of the fiducial mark caused by imaging errors of the projection optical system resulted from the difference in wavelength between the light beam having the first wavelength characteristic and the light beam having the second wavelength characteristic on the basis of results of the detection by the first and second detectors;
• whereby positional alignment for the photosensitive substrate is performed prior to actual exposure on the basis of the positional discrepancy calculated by the calculator.

A projection exposure apparatus for transferring a pattern formed on a mask onto a photosensitive substrate, comprising:

• a projection optical system, disposed between the mask and the photosensitive substrate, that projects an image of a pattern of the mask onto the photosensitive substrate;
• a mask stage, provided with a first fiducial member, for placing the mask thereon;
• a photosensitive substrate stage, provided with a second fiducial member, for placing the photosensitive substrate thereon;
• a first energy source that radiates a light beam having a first wavelength characteristic onto a first fiducial member, and radiates the light beam having the first wavelength characteristic through the projection optical system onto the second fiducial member;
• a first detector that detects optical information from the first and second fiducial members to obtain a correlative positional discrepancy between the first and second fiducial members under the light beam having the first wavelength characteristic;
• a second energy source that radiates a light beam having a second wavelength characteristic different from the first wavelength characteristic onto the first fiducial member, and radiates the light beam having the second wavelength characteristic through the projection optical system onto the second fiducial member;
• a second detector that detects optical information from the first and second fiducial members to obtain a correlative positional discrepancy between the first and second fiducial members under the light beam having the second wavelength characteristic;
• and
• a calculator that calculates a difference between the positional discrepancies caused by the difference in wavelength between the light beam having the first wavelength characteristic and the light beam having the second wavelength characteristic on the basis of results of the detection by the first and second detectors.

A method for making an exposure apparatus which exposes a substrate with a pattern formed on a mask, comprising:

• providing a projection optical system between the mask and the substrate, the projection optical system projecting an image of the pattern of the mask onto the substrate;
• providing a mask stage which holds the mask thereon;
• providing a substrate stage which holds the substrate thereon and comprises a first fiducial mark;
• providing an energy source that radiates a light beam having a first wavelength characteristic and a light beam having a second wavelength characteristic through the projection optical system onto the first fiducial mark;
• providing a detector that detects optical information from the first fiducial mark to obtain positions thereof by using the light beam having the first wavelength characteristic and the light beam having the second wavelength characteristic, respectively;
• and
• providing a calculator that calculates a positional discrepancy caused by the difference in wavelength between the light beam having the first wavelength characteristic and the light beam having the second wavelength characteristic on the basis of results of the detection by the detector.