Shape measuring method, shape measuring apparatus, program, recording medium, method of manufacturing optical element, and optical element

Patent metadata

Field	Value
Publication number	US-2016238482-A1
Application number	US-201615018933-A
Country	US
Kind code	A1
Filing date	Feb 9, 2016
Priority date	Feb 16, 2015
Publication date	Aug 18, 2016
Grant date	—

Abstract

A rotary stage is controlled to two measurement positions along a rotational direction in which an object surface is moved when detecting a wavefront of reflected light from partial regions by a detecting unit, to move the object surface. Respective placement errors in a trajectory of the object surface at the two measurement positions are measured based on wavefronts detected by the detecting unit in states in which the rotary stage is controlled to each of the two measurement positions. For the remaining measurement positions among the measurement positions, respective placement errors with respect to the trajectory of the object surface are estimated based on the placement errors measured. Before measurement of each item of partial shape data, the rotary stage is controlled to a measurement position and stages are controlled to a position that cancels a placement error at the measurement position to align the object surface.

First claim

What is claimed is:

1 . A shape measuring method for measuring a shape of an object surface of an object by: controlling, by means of a controlling unit, a first stage that scans the object having the object surface in a drive direction and a second stage that moves the object in a direction that is different from the drive direction of the first stage, to thereby move the object surface along a trajectory that is previously set; irradiating a measuring beam sequentially onto a plurality of partial regions of the object surface; detecting wavefronts of reflected light from each of the plurality of partial regions by a detecting unit; and using the controlling unit to calculate partial shape data of the plurality of partial regions based on the wavefronts, and stitch the partial shape data;
the shape measuring method comprising: moving in which the controlling unit controls the first stage to move the object surface to at least two positions along the drive direction that are less than a number of a plurality of measurement positions along the drive directions to which the object surface is moved when detecting a wavefront of reflected light of each of the plurality of partial regions by means of the detecting unit; actual measuring in which the controlling unit actually measures respective placement errors with respect to the trajectory of the object surface at the at least two positions based on wavefronts detected by the detecting unit in states in which the first stage is controlled to each of the at least two positions; estimating in which the controlling unit estimates respective placement errors with respect to the trajectory of the object surface with regard to positions of the first stage other than the at least two positions among the plurality of measurement positions based on the placement errors that are actually measured by the actual measuring; and aligning in which, before each detection at a time of detecting respective wavefronts of reflected light from the plurality of partial regions by means of the detecting unit for calculating the partial shape data, the controlling unit controls the first stage to the measurement position and controls the second stage to a position that cancels out a placement error at the measurement position, to thereby align the object surface.

2 . The shape measuring method according to claim 1 , wherein:
the object surface has symmetry; and in the estimating, the controlling unit determines an axial misalignment quantity of an axis of symmetry of the object surface with respect to a driving axis of the first stage based on a placement error with respect to the trajectory of the object surface at the at least two positions of the first stage, and calculates respective placement errors with respect to the trajectory of the object surface at positions of the first stage other than the at least two positions based on the axial misalignment quantity.

3 . The shape measuring method according to claim 1 , wherein the at least two positions are included in the plurality of measurement positions.

4 . The shape measuring method according to claim 1 , wherein:
the object surface has revolution symmetry; and the first stage is a rotary stage that scans the object in a rotational direction as the drive direction.

5 . The shape measuring method according to claim 4 wherein, the at least two positions include a first position, and a second position that is reached by rotating by π [rad] in the rotational direction around a driving axis of the first stage relative to the first position.

6 . The shape measuring method according to claim 1 , wherein:
the object surface has translation symmetry; and the first stage is a linear stage that scans the object in a linear direction as the drive direction.

7 . The shape measuring method according to claim 1 , wherein the detecting unit is a Shack-Hartmann sensor.

8 . The shape measuring method according to claim 1 , wherein an error component in a perpendicular direction to a travelling direction of the measuring beam is included in the placement errors of the object surface with respect to the trajectory.

9 . The shape measuring method according to claim 1 , wherein an error component that is parallel to a travelling direction of the measuring beam is included in the placement errors of the object surface with respect to the trajectory.

10 . The shape measuring method according to claim 1 , wherein an inclination error component of an axis of symmetry of the object surface is included in the placement errors of the object surface with respect to the trajectory.

11 . The shape measuring method according to claim 1 , wherein a reference object having a reference surface of a shape that serves as a reference for the object surface is placed on the first stage, further comprising:
error measuring in which the controlling unit actually measures a placement error with respect to a design position of the reference surface based on a wavefront of reflected light from the reference surface that is detected by the detecting unit; reference surface aligning in which the controlling unit controls the second stage to a position that cancels out the placement error that is actually measured in the error measuring, to thereby align the reference surface; systematic error calculating in which, after the reference surface aligning, the controlling unit determines shape data based on a wavefront of reflected light from the reference surface that is detected with the detecting unit, and determines a systematic error based on the shape data; and partial shape data calculating in which the controlling unit calculates the partial shape data in which the systematic error is corrected.

12 . The shape measuring method according to claim 1 , further comprising:
measuring a position of a guidepost placed on the first stage while driving the first stage by the controlling unit to acquire the driving error of the first stage; and controlling the second stage onto a position to cancel the driving error by the controlling unit, for an alignment of the object surface.

13 . The shape measuring method according to claim 12 , wherein
in the measuring, the controlling unit calculates the position of the guidepost, based on a wavefront of a light reflected from a surface of the guidepost detected by the detecting unit.

14 . The shape measuring method according to claim 1 , wherein:
in the aligning, the controlling unit repeatedly performs control of the second stage that moves the second stage to a position that cancels out a placement error of the object surface, until the controlling unit determines a placement error of the object surface that is based on a wavefront detected by the detecting unit and the placement error is less than a previously set threshold.

15 . A shape measuring apparatus for measuring a shape of an object surface of an object, comprising:
a light source for irradiating a measuring beam onto an object surface of an object; a first stage that scans the object with respect to the measuring beam; a second stage that moves the object in a direction that is different to a drive direction of the first stage; a detecting unit that detects a wavefront of reflected light from the object surface; and a controlling unit configured to control the first stage and the second stage to measure a shape of the object surface, wherein the object surface is moved along a trajectory that is previously set, the light source irradiates a measuring beam sequentially onto a plurality of partial regions of the object surface, the

Assignees

• Canon Kk

Inventors

• Maeda Atsushi

Classifications

• G01B11/24 Primary

  for measuring contours or curvatures · CPC title

• G01J9/00

  Measuring optical phase difference (devices or arrangements for controlling the phase of light beams G02F1/01); Determining degree of coherence; Measuring optical wavelength (spectrometry G01J3/00) · CPC title

• G01M11/08 Primary

  Testing mechanical properties {(G01M11/005 takes precedence)} · CPC title

• G01B2210/52

  Combining or merging partially overlapping images to an overall image · CPC title

• G01M11/0257

  by analyzing the image formed by the object to be tested · CPC title