Method of determining position offset of a pattern

• US 5,671,165 A
• Filed: 03/14/1996
• Issued: 09/23/1997
• Est. Priority Date: 09/18/1995
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Tomimatu, Yoshikatu
• Primary Examiner(s): Trammell, James P.
• Assistant Examiner(s): Pipala, Edward
• Application Number:
  US08/615,764
• Time in Patent Office: 558 Days
• Field of Search: 364/488, 364/489, 364/490, 364/491, 364/559, 364/560, 364/571.01, 356/375, 356/399, 356/400, 356/401, 382/144, 382/145, 382/151
• US Class Current: 702/94
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching

Abstract

A method of determining position offset is obtained which allows accurate determination of the magnitude of position offset even though the magnitudes of position offset of the outermost shots are not actually measured. According to the method of determining position offset, magnitudes of offset of the designated shots on the surface of a wafer other than the outermost shots are actually measured, and based on the measured magnitudes of offset, the magnitudes of position offset of the outermost shots are calculated and magnitudes of offset are calculated finally taking into consideration the magnitudes of position offset of the outermost shots. As a result, accurate error data can be derived even without actually measuring the magnitudes of offset of the outermost shots.

Claims

1. A method of determining position offset of a substrate to be processed having a plurality of unit patterns arranged on a main surface thereof, comprising the steps of:

measuring position offset data at a plurality of predetermined unit patterns other than the unit patterns located outermost on said processed substrate among the unit patterns of said processed substrate;

calculating a predetermined error parameter based on said position offset data measured;

calculating a first linear error component of the unit pattern for which said position offset data is measured based on said error parameter;

calculating a first random error component of the unit pattern for which said position offset data is measured by subtracting said measured first linear component from said position offset data measured corresponding thereto;

calculating a second linear error component of the unit pattern located outermost on said processed substrate based on said error parameter;

calculating a second random error component corresponding to said second linear error component based on said first random error; and

calculating error data by adding each said second linear error component and said second random error component corresponding thereto.

2. The method of determining position offset according to claim 1, wherein the plurality of unit patterns for which said position offset data is measured are arranged symmetrically with respect to the center of said substrate to be processed.

3. The method of determining position offset according to claim 1, wherein

said error parameter includes

an X offset error which is a displacement in a direction of an X axis of said processed substrate having X and Y axes perpendicular to each other,

a Y offset error which is a displacement in a direction of a Y axis of said processed substrate having the X and Y axes perpendicular to each other,

an X expansion and shrinkage error which is a displacement due to expansion and shrinkage in the direction of the X axis of said processed substrate,

a Y expansion and shrinkage error which is a displacement due to expansion and shrinkage in the direction of the X axis of said processed substrate,

an X rotation error which is a displacement due to rotation of the X axis of said processed substrate, and

Y rotation error which is a displacement due to rotation of the Y axis of said processed substrate;

and

said six error parameters are calculated by least squares method based on said position offset data measured.

4. The method of determining position offset according to claim 1, wherein said second random error component is calculated by multiplying by a predetermined number a variation range of said first random error component so that the variation range which is a difference between the maximum value and the minimum value of said first random error component is 6 ×

standard deviation and making a correspondence of random digit to distributed data of said first random error component in the variation range.

5. The method of determining position offset according to claim 1, further comprising the steps of obtaining an average magnitude of offset by taking an average of said error data and dividing by 2 said variation range which is a difference between the maximum value and the minimum value of said error data to obtain 3 ×

standard deviation of magnitudes of offset.

6. A method of determining position offset of a substrate to be processed having a plurality of unit patterns arranged on a main surface thereof, comprising steps of:

measuring position offset data at a plurality of predetermined unit patterns other than the unit pattern located outermost on said processed substrate among the unit patterns on said processed substrate;

calculating a predetermined error parameter based on said position offset data measured;

calculating a first linear error component of the unit pattern for which said position offset data is measured based on said error parameter; and

calculating a first random error component of the unit pattern for which position offset data is measured by subtracting each said first linear error component calculated from said position offset data measured corresponding thereto;

calculating a second linear component of each of the all unit patterns of said processed substrate based on said error parameter;

calculating a second random error component corresponding to said second linear error component based on said first random error of the unit pattern for which said position offset data is measured; and

calculating error data of said all unit patterns by adding each said second linear error component of said all unit patterns and said random error component corresponding thereto.

7. The method of determining position offset according to claim 6, wherein the plurality of unit patterns for which said position offset data is measured are arranged symmetrically with respect to the center of said substrate to be processed.

8. The method of determining position offset according to claim 6, wherein

said error parameter includes

an X offset error which is a displacement in a direction of an X axis of said processed substrate having X and Y axes perpendicular to each other,

a Y offset error which is a displacement in a direction of the Y axis of said processed substrate having the X and Y axes perpendicular to each other,

an X expansion and shrinkage error which is a displacement due to expansion and shrinkage of said processed substrate in the direction of the X axis,

an Y expansion and shrinkage error which is a displacement due to expansion and shrinkage of said processed substrate in the direction of the Y axis,

an X rotation error which is a displacement due to rotation of the X axis of said processed substrate, and

a Y rotation error which is a displacement due to rotation of the Y axis of said processed substrate;

and

said six error parameters are calculated by least squares method based on said position offset data measured.

9. The method of determining position offset according to claim 6, wherein said second random error component is calculated by multiplying by a predetermined number a variation range of said first random error component so that the variation range which is a difference between the maximum value and the minimum value of said first random error component is 6 ×

standard deviation and making correspondence between random digit and distributed data of said first random error component in the variation range.

10. The method of determining position offset according to claim 6, further comprising the step of obtaining an average magnitude of offset by taking an average of error data of said all unit patterns and calculating standard deviation of magnitudes of offset based on the error data of said all unit patterns.