Phase difference specifying method
View Patent ↗A phase shift mask comprises first and second mask patterns. The first mask pattern is a backing film enabling a first optical image to be formed on a substrate. The first optical image forms a resist pattern having a width that changes depending on the distance between the phase shift mask and the substrate. The second mask pattern is a semi-transmissive film enabling a second optical image to be formed on the substrate. The second optical image can form a resist pattern having a width that changes depending on the distance between the phase shift mask and the substrate and on a thickness of the semi-transmissive film. The duty ratio of the second mask is set so that the rate at which the width of the first optical image varies will be the same as the rate at which the width of the second optical image varies.
1. A phase difference specifying method comprising:
preparing a phase shift mask having a first mask pattern and a second mask pattern, the first mask pattern comprising a backing film having a first shape which enables a first optical image to be formed on a predetermined substrate that is a target of exposure, the first optical image capable of forming a first resist pattern having a first width that changes depending on a distance from the predetermined substrate, the second mask pattern comprising a semi-transmissive film having a second shape which enables a second optical image to be formed on the predetermined substrate, the second optical image capable of forming a second resist pattern having a second width that changes depending on a distance from the predetermined substrate and on a thickness of the semi-transmissive film, the first mask pattern and the second mask pattern being separated from each other by a first interval;
forming the first and second resist patterns on the predetermined substrate by exposing the predetermined substrate to light through the phase shift mask, the phase shift mask being arranged at a first position on a predetermined optical axis separated from the predetermined substrate by a first distance;
obtaining the difference between the first width of the first resist pattern and the second width of the second resist pattern; and
obtaining the difference between the phases of a first light passing through the phase shift mask except for regions where the first and second mask patterns are formed, and a second light passing through the second mask pattern, based on the width difference between the first resist pattern and the second resist pattern.
2. The phase difference specifying method according to claim 1 , wherein
the first position is a position on the predetermined optical axis separated from a second position by a second distance, the second position being a position where the first and second optical images are formed on the predetermined substrate in focus.
3. The phase difference specifying method according to claim 1 , wherein
the phase difference between the first light and the second light is specified by using a correspondence relationship between the width difference and the phase difference which is registered in advance.
4. The phase difference specifying method according to claim 1 , wherein
at least two combinations of the first and second resist patterns are formed on the predetermined substrate, a width direction of the first resist patterns being the same as a width direction of the second resist patterns, and
the width difference is calculated based on the center between an exterior edge of one first resist pattern and an exterior edge of one second resist pattern and the center between an interior edge of the other first resist pattern and an interior edge of the other second resist pattern, one first resist pattern being located at one external side in the width direction, the other first resist pattern being located at an internal side in the width direction, one second resist pattern being located at the other external side in the width direction, and the other second resist pattern located at an internal side in the width direction.
5. The phase difference specifying method according to claim 1 , wherein
the phase shift mask has at least two combinations of the first and second mask patterns, the combinations having a second interval therebetween, and
the width direction of the first and second mask patterns in one combination is the same as the width direction of the first and second mask patterns in the other combination.
6. The phase difference specifying method according to claim 1 , wherein
the first and second shapes are line-and-space patterns.
7. The phase difference specifying method according to claim 1 , wherein
a duty ratio of the second shape is set so that a change in the width of the first optical image with respect to the first distance will be equal to a change in the width of the second optical image with respect to the change of the first distance when the thickness of the semi-transmissive film is set so that the phase difference becomes 180°.
8. The phase difference specifying method according to claim 1 , wherein
the backing film is made of chrome.
9. The phase difference specifying method according to claim 1 , wherein
the semi-transmissive film is a chromium oxide film, a molybdenum silicide oxide film, or a multilayer film including at least one of a chromium oxide film and a molybdenum silicide oxide film.
10. The phase difference specifying method according to claim 1 , wherein
the second mask pattern is a Levenson type phase shift mask.
11. A phase difference specifying method comprising:
preparing a phase shift mask having a mask pattern comprising a semi-transmissive film having a shape which enables an optical image to be formed on a predetermined substrate that is a target of exposure, the optical image capable of forming a resist pattern having a width that changes depending on a distance from the predetermined substrate;
forming a first resist pattern on the predetermined substrate by exposing the predetermined substrate through the phase shift mask, the phase shift mask being arranged at a first position on a predetermined optical axis separated from the predetermined substrate by a first distance;
forming a second resist pattern on the predetermined substrate by exposing the predetermined substrate through the phase shift mask, the phase shift mask being arranged at a second position which is separated from the predetermined optical axis by a first interval in a direction perpendicular to the predetermined optical axis and from the predetermined substrate by a second distance;
obtaining the difference between the first width of the first resist pattern and the second width of the second resist pattern; and
obtaining the difference between the phases of a first light passing through the phase shift mask except for regions where the mask pattern is formed and a second light passing through the mask pattern, based on the width difference between the first resist pattern and the second resist pattern.
12. The phase difference specifying method according to claim 11 , wherein
the first position is a position on the predetermined optical axis separated from a third position by a third distance, the third position being a position where the optical images are formed on the predetermined substrate in focus, and
the second position is a position on the predetermined optical axis separated from the third position by the third distance, the third position existing between the first and second positions.
13. The phase difference specifying method according to claim 11 , wherein
the phase difference between the first light and the second light is specified by using a correspondence relationship between the width difference and the phase difference which is registered in advance.
14. The phase difference specifying method according to claim 11 , wherein
at least two combinations of the first and second resist pattern are formed on the predetermined substrate, a width direction of the first resist patterns being the same as a width direction of the second resist patterns, and
the width difference is calculated based on the center between an exterior edge of one first resist pattern and an exterior edge of one second resist pattern and the center between an interior edge of the other first resist pattern and an interior edge of the other second resist pattern, one first resist pattern being located at one external side in the width direction, the other first resist pattern being located at an internal side in the width direction, one second resist pattern being located at the other external side in the width direction, and the other second resist pattern located at an internal side in the width direction.
15. The phase difference specifying method according to claim 11 , wherein
the phase shift mask has at least two mask patterns which have a second interval therebetween, and
a width direction of one mask pattern is the same as a width direction of the other mask pattern.
16. The phase difference specifying method according to claim 11 , wherein
the shape of the mask pattern is a line-and-space pattern.
17. The phase difference specifying method according to claim 11 , wherein
the semi-transmissive film is a chromium oxide film, a molybdenum silicide oxide film, or a multilayer film including at least one of a chromium oxide film and a molybdenum silicide oxide film.
18. The phase difference specifying method according to claim 11 , wherein
the phase shift mask has a backing film which is larger than the mask pattern formed on a position separated from the mask pattern by the first interval in a direction perpendicular to the predetermined optical axis, and
the shadow of the backing film covers the first resist pattern formed on the predetermined substrate when forming the second resist pattern.
19. The phase difference specifying method according to claim 18 , wherein
the backing film is made of chrome.
20. The phase difference specifying method according to claim 11 , wherein
the mask pattern is a Levenson type phase shift mask.