Focusing method

• US 5,323,016 A
• Filed: 06/28/1993
• Issued: 06/21/1994
• Est. Priority Date: 02/09/1990
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kataoka, Yoshiharu, Kubo, Hiroyoshi, Yamada, Yuichi, Kawashima, Haruna
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): HANIG, RICHARD E
• Application Number:
  US08/082,159
• Time in Patent Office: 358 Days
• Field of Search: 250/561, 250/548, 356/400, 356/401
• US Class Current: 250/559.3
• CPC Class Codes: G03F 9/70 for microlithography measuring printed patterns for monitoring overlay G03F7/70633 or focus G03F7/70641; projection system adjustment G03F7/70258; position control G03F7/70775

Abstract

A method of bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of the detection of the deviation of the wafer surface from a reference plane of a deviation detecting sensor, includes the steps of: moving the wafer surface along an optical axis of the projection optical system, to a position close to the reference plane; detecting a deviation of the wafer surface from the reference plane; and moving the wafer surface on the basis of the detection, to be brought into coincidence with the image plane of the projection optical system.

Claims

1. A method of bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of a deviation of the wafer surface from a reference plane of a deviation detecting sensor, comprising the steps of:

moving the wafer surface to a position close to the reference plane;

detecting a deviation of the wafer surface from the reference plane;

correcting any inclination of the wafer surface in accordance with the detected deviation; and

moving, after said correcting step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

2. A method according to claim 1, wherein said correcting step comprises the step of bringing the wafer surface into substantial coincidence with the reference plane.

3. A method used in manufacturing semiconductor devices by bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of a deviation of the wafer surface from a reference plane of a deviation detecting sensor and by projecting an image of a pattern upon the wafer through the projection optical system, comprising the steps of:

moving the wafer surface to a position close to the reference plane;

detecting a deviation of the wafer surface from the reference plane;

correcting any inclination of the wafer surface in accordance with the detected deviation; and

moving, after said correcting step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

4. A method according to claim 3, further comprising the step of, before attainment of coincidence of the wafer surface with the image plane, bringing the wafer surface into substantial coincidence with the reference plane.

5. A method of bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of deviations of the wafer surface, at different points thereon, from a focal plane of a deviation detecting optical sensor, comprising the steps of:

moving the wafer surface to a position close to the focal plane of the optical sensor;

detecting deviations at the different points of the wafer surface from the focal plane;

correcting any inclination of the wafer surface in accordance with the detected deviations; and

moving, after said correcting step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the focal plane of the optical sensor.

6. A method according to claim 5, wherein said correcting step comprises the step of bringing the wafer surface into substantial coincidence with the reference plane.

7. A method used in manufacturing semiconductor devices by bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of deviations of the wafer surface, at different points thereon, from a focal plane of a deviation detecting optical sensor, and by projecting an image of a pattern upon the wafer surface through the projection optical system, comprising the steps of:

moving the wafer surface to a position close to the focal plane of the optical sensor;

detecting deviations at the different points of the wafer surface from the focal plane;

correcting any inclination of the wafer surface in accordance with the detected deviations; and

moving, after said correcting step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the focal plane of the optical sensor.

8. A method according to claim 7, further comprising the step of, before attainment of coincidence of the wafer surface with the image plane, bringing the wafer surface into substantial coincidence with the reference plane.

9. A method of bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of a deviation of the wafer surface from a reference plane of a deviation detecting sensor, comprising the steps of:

moving the wafer surface along an optical axis of the projection optical system, to a position close to the reference plane;

detecting a deviation of the wafer surface from the reference plane;

moving the wafer surface on the basis of the detection, to be brought into coincidence with the reference plane of the deviation detecting sensor; and

moving, after said second moving step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

10. A method according to claim 9, further comprising the step of, for attainment of the coincidence, correcting any inclination of the wafer surface with respect to the reference plane in accordance with the detected deviation.

11. A method according to claim 9, wherein, an initial state, the wafer surface is between the image plane and the reference plane or at a side of the image plane remote from the reference plane.

12. A method used in manufacturing semiconductor devices by detecting deviations of different surface zones of a wafer from a reference plane of a sensor and by projecting an image of a pattern sequentially onto the surface zones of the wafer through a projection optical system while sequentially bringing the surface zones of the wafer into coincidence with an image plane of the projection optical system in accordance with the detected deviations, wherein a first surface zone of the wafer is brought into coincidence with the image plane of the projection optical system and then the image of the circuit pattern is projected upon the first surface zone through the projection optical system, comprising the steps of:

after the image projection to the first surface zone, moving a second surface zone of the wafer, adjacent to the first surface zone, to a position close to the reference plane of the sensor;

detecting a deviation of the second surface zone from the reference plane; and

bringing the second surface zone into coincidence with the reference plane of the sensor, on the basis of the detection; and

moving, after said bringing step, the second surface zone along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the sensor.

13. A method according to claim 12, further comprising the step of, for attainment of the coincidence of the second surface zone with the image plane, correcting any inclination of the second surface zone with respect to the image plane.

14. A method according to claim 13, wherein said bringing step comprises the step of moving the wafer along an optical axis of the projection optical system to displace the surface of the wafer.

15. A method according to claim 14, wherein said bringing step further comprises the step of moving the wafer along an optical axis of the projection optical system to displace the surface of the wafer, while correcting the inclination of the second surface zone.

16. A method according to claim 14, wherein said bringing step comprises the step of first bringing the second surface zone into coincidence with the reference plane of the sensor and then displacing the second surface zone along the optical axis of the projection optical system.

17. A method according to any one of claims 13-16, wherein, after the image projection onto the second surface zone, said method comprises the step of repeating the process of detecting deviation with respect to the reference plane, coincidence attainment, and image projection for the remaining surface zones of the wafer sequentially.

18. A method according to any one of claims 13-16, further comprising the steps of using the sensor to detect the deviation optically, and using a focal plane of the sensor as the reference plane.

19. A semiconductor device manufactured by a method wherein a surface of a wafer is brought into coincidence with an image plane of a projection optical system on the basis of detection of a deviation of the wafer surface from a reference plane of a deviation detecting sensor and wherein an image of a pattern is projected on the wafer through the projection optical system, said method comprising the steps of:

moving the wafer surface to a position close to the reference plane;

detecting a deviation of the wafer surface from the reference plane;

correcting any inclination of the wafer surface in accordance with the detected deviation; and

moving, after said correcting step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

20. A semiconductor device manufactured by a method, wherein a surface of a wafer is brought into coincidence with an image plane of a projection optical system on the basis of detection of deviations of the wafer surface, at different points thereon, from a focal plane of a deviation detecting optical sensor and wherein an image of a pattern is projected on the wafer surface through the projection optical system, said method comprising the steps of:

moving the wafer surface to a position close to the focal plane of the optical sensor;

detecting deviations at the difference points of the wafer surface from the focal plane;

correcting any inclination of the wafer surface in accordance with the detected deviations; and

moving, after said correcting step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the focal plane of the optical sensor.

21. A semiconductor device manufactured by a method wherein deviations of different surface zones of a wafer from a reference plane of a sensor are detected, wherein an image of a pattern is projected onto the surface zones of the wafer sequentially through a projection optical system while sequentially bringing the surface zones of the wafer into coincidence with an image plane of the projection optical system in accordance with the detected deviations, and wherein a first surface zone of the wafer is brought into coincidence with the image plane of the projection optical system and then the image of the circuit pattern is projected upon the first surface zone through the projection optical system, said method comprising the steps of:

after the image projection to the first surface zone, moving a second surface zone of the wafer, adjacent to the first surface zone, to a position close to the reference plane of the sensor;

detecting a deviation of the second surface zone from the reference plane;

bringing the second surface zone into coincidence with the reference plane of the sensor, on the basis of the detection; and

moving, after said bringing step, the second surface zone along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the sensor.

22. A method of bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of the deviation of the wafer surface from a reference plane of a deviation detecting sensor, comprising:

a first moving step for moving the wafer surface to a position close to the reference plane;

a detecting step for detecting the deviation of the wafer surface from the reference plane; and

a second moving step for moving the wafer surface along an optical axis of the projection optical system on the basis of the detected deviation by an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

23. A method according to claim 22, wherein said second moving step comprises the step of correcting any inclination of the wafer surface in accordance with the detected deviation after said detecting step.

24. A method used in manufacturing semiconductor devices by bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of the deviation of the wafer surface from a reference plane of a deviation detecting sensor and by projecting an image of a pattern upon the wafer through the projection optical system, comprising:

a first step of moving the wafer surface to a position close to the reference plane and detecting the deviation of the wafer surface from the reference plane; and

a second step of moving the wafer surface along an optical axis of the projection optical system in accordance with the detected deviation by an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

25. A method according to claim 24, wherein said second moving step comprises the step of correcting any inclination of the wafer surface in accordance with the detected deviation after said detecting step.

26. A method of bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of the detection of deviations of the wafer surface, at different points thereon, from a reference plane of a deviation detecting optical sensor, comprising:

a first moving step for moving the wafer surface to a position close to the reference plane of the optical sensor;

a detecting step for detecting deviations at the different points of the wafer surface from the reference plane; and

a second moving step for moving the wafer surface along an optical axis of the projection optical system in accordance with the detected deviation by an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

27. A method according to claim 26, wherein said second moving step comprises the step of correcting any inclination of the wafer surface in accordance with the detected deviation after said detecting step.

28. A method according to claim 26, wherein, in an initial state, the wafer surface is between the image plane and the reference plane or at a side of the image plane remote from the reference plane.

29. A method used in manufacturing semiconductor devices by bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of deviations of the wafer surface, at different points thereon, from a reference plane of a deviation detecting optical sensor, and by projecting an image of a pattern upon the wafer surface through the projection optical system, comprising:

a first moving step for moving the wafer surface to a position close to the reference plane of the optical sensor;

a detecting step for detecting deviations at the different points of the wafer surface from the reference plane; and

a second moving step for moving the wafer surface along an optical axis of the projection optical system in accordance with the detected deviation by an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

30. A method according to claim 29, wherein said second moving step comprises the step of correcting any inclination of the wafer surface in accordance with the detected deviation after said detecting step.

31. A method used in manufacturing semiconductor devices by detecting deviations of different surface zones of a wafer from a reference plane of a sensor and by projecting an image of a pattern sequentially onto the surface zones of the wafer through a projection optical system while sequentially bringing the surface zones of the wafer into coincidence with an image plane of the projection optical system in accordance with the detected deviations, wherein a first surface zone of the wafer is brought into coincidence with the image plane of the projection optical system and then the image of the circuit pattern is projected upon the first surface zone through the projection optical system, said method comprising the steps of:

after the image projection to the first surface zone, moving a second surface zone of the wafer, adjacent to the first surface zone, to a position close to the reference plane of the sensor;

detecting a deviation of the second surface zone from the reference plane; and

moving the second surface zone along an optical axis of the projection optical system in accordance with the detected deviation by an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

32. A method according to claim 31, wherein, after the image projection onto the second surface zone, said method comprises the step of sequentially repeating said moving, detecting, coincidence attainment, and image projection steps for the remaining surface zones of the wafer.

33. A method according to claim 31, further comprising the steps of using the sensor to detect the deviation optically, and using a focal plane of the sensor as the reference plane.

34. A semiconductor device manufactured by a method wherein a surface of a wafer is brought into coincidence with an image plane of a projection optical system on the basis of the detection of the deviation of the wafer surface from a reference plane of a deviation detecting sensor and wherein an image of a pattern is projected on the wafer through the projection optical system, said method comprising the steps of:

moving the wafer surface to a position close to the reference plane and detecting the deviation of the wafer surface from the reference plane; and

moving the wafer surface along an optical axis of the projection optical system in accordance with the detected deviation by an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detection sensor.

35. A semiconductor device manufactured by a method, wherein a surface of a wafer is brought into coincidence with an image plane of a projection optical system on the basis of the detection of deviations of the wafer surface, at different points thereon, from a reference plane of a deviation detecting optical sensor and wherein an image of a pattern is projected on the wafer surface through the projection optical system, said method comprising the steps of:

moving the wafer surface to a position close to the reference plane and detecting the deviation of the wafer surface from the reference plane; and

moving the wafer surface along an optical axis of the projection optical system in accordance with the detected deviation by an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.