Measurement method, exposure method, exposure apparatus, and device fabrication method
A method for measuring a synchronization error between a first stage and a second stage in a scanning exposure apparatus including the first stage which supports a reticle, the second stage which supports a substrate, and a projection optical system which projects a pattern of the reticle onto the substrate, the method comprises the steps of measuring, using a measurement unit, a light intensity distribution formed by a measurement pattern while synchronously scanning a measurement mask which has the measurement pattern and is arranged on the first stage, and the measurement unit arranged on the second stage, and calculating the synchronization error between the first stage and the second stage based on a time change in the light intensity distribution measured in the measuring step.
1. A method for measuring a synchronization error between a first stage and a second stage in a scanning exposure apparatus including the first stage which supports a reticle, the second stage which supports a substrate, and a projection optical system which projects a pattern of the reticle onto the substrate, the method comprising the steps of:
measuring, using a measurement unit, a light intensity distribution formed by a measurement pattern while synchronously scanning a measurement mask which has the measurement pattern and is arranged on the first stage, and the measurement unit arranged on the second stage; and
calculating the synchronization error between the first stage and the second stage based on a time change in the light intensity distribution measured in the measuring step.
2. The method according to claim 1 , wherein the measurement mask and the measurement unit are optically conjugate to each other via the projection optical system.
3. The method according to claim 1 , wherein in the calculating step, a function describing the light intensity distribution is differentiated with respect to time to calculate a direction of synchronization shift between the first stage and the second stage is shifted.
4. The method according to claim 1 , wherein in the calculating step, a function describing the light intensity distribution is differentiated with respect to time to calculate an amount of synchronization shift between the first stage and the second stage.
5. The method according to claim 1 , wherein the measurement unit includes a light-shielding board in which an opening is formed, and a photoelectric conversion device configured to receive light having passed through the opening, and
the measurement unit is arranged such that the opening is located at a position at which a light intensity takes a maximum value in a light intensity distribution formed by the measurement pattern while the measurement mask is at rest.
6. The method according to claim 1 , wherein the measurement unit includes a light-shielding board in which an opening is formed, and a photoelectric conversion device configured to receive light having passed through the opening, and
the measurement unit is arranged such that the opening is located at a position at which a light intensity becomes zero in a light intensity distribution formed by the measurement pattern while the measurement mask is at rest.
7. The method according to claim 1 , wherein the measurement pattern includes a periodic pattern with a period p,
the measurement unit includes a light-shielding board in which an opening is formed, and a photoelectric conversion device configured to receive light having passed through the opening, and
the measurement unit is arranged such that the opening is located at a position shifted by p/4 from a position at which a light intensity takes a maximum value in a light intensity distribution formed by the measurement pattern while the measurement mask is at rest.
8. The method according to claim 5 , wherein the opening is a slit or a pinhole.
9. The method according to claim 1 , wherein
the measurement pattern includes a periodic pattern with a period p, and
p/2 is normalized into a value less than 0.5 by (λ/NA), where λ is an exposure wavelength of the exposure apparatus, and NA is a numerical aperture of the projection optical system.
10. An exposure method for projecting a pattern of a reticle onto a substrate while scanning a first stage which supports the reticle and a second stage which supports the substrate, the method comprising the steps of:
measuring the synchronization error using a measurement method according to claim 1 ;
correcting the measured synchronization error; and
projecting the pattern of the reticle onto the substrate while scanning the first stage and the second stage having undergone the correction of the synchronization error.
11. A device fabrication method comprising the steps of:
exposing a substrate using an exposure method according to claim 10 ; and
performing a development process for the exposed substrate.
12. A scanning exposure apparatus including a first stage which supports a reticle, a second stage which supports a substrate, and a projection optical system which projects a pattern of the reticle onto the substrate, the apparatus comprising:
a measurement mask which is arranged on the first stage and has a measurement pattern;
a measurement unit which is arranged on the second stage and configured to measure a light intensity distribution formed by the measurement pattern, while being scanned in synchronism with the measurement pattern; and
a control unit configured to calculate a synchronization error between the first stage and the second stage based on a time change in the light intensity distribution measured by said measurement unit.