Shape measuring apparatus and method for manufacturing target object to be coated

• US 10,704,898 B2
• Filed: 01/10/2017
• Issued: 07/07/2020
• Est. Priority Date: 02/08/2016
• Status: Active Grant

• Current Assignee: NTN Corporation
• Original Assignee: NTN Corporation
• Inventors: Ohba, Hiroaki
• Primary Examiner(s): Lyons, Michael A
• Application Number:
  US16/076,311
• Publication Number:
  US 20190049236A1
• Time in Patent Office: 1,274 Days
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 11/2441 using interferometry
• CPC Class Codes: G01B 9/0203 With imaging systems
• CPC Class Codes: G01B 9/0209 Low-coherence interferometers
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 7/38 measured at different points on the optical axis , e.g. focussing on two or more planes and comparing image data
• CPC Class Codes: G06T 2207/10061 from scanning electron microscope
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/13 Edge detection
• CPC Class Codes: G06T 7/571 from focus
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

A shape measuring apparatus includes: a light source; a two-beam interference objective lens; an imaging device; an observation optical system; a positioning device; and a control device. The control device calculates, for each unit region in the plurality of images obtained by the imaging device, as a focus position of the unit region, a position of the two-beam interference objective lens at which a luminance-based evaluation value is maximized over the plurality of images, and the control device measures a shape of a target object based on the focus position of each unit region in the plurality of images. The control device uses, as the evaluation value, a luminance of each unit region in the plurality of images as well as a value correlated with a difference between the luminance of the unit region and luminances of a plurality of unit regions adjacent to the unit region.

Claims

1. A shape measuring apparatus configured to measure a shape of a target object by applying white light to the target object and using reflected light from the target object, the shape measuring apparatus comprising:

a light source configured to output the white light;

a two-beam interference objective lens configured to divide the white light into two light beams, apply one of the two light beams to the target object and the other light beam to a reference surface, and cause interference between the reflected light from the target object and reflected light from the reference surface to output interference light;

an imaging plane configured to obtain an image of the interference light output from the two-beam interference objective lens;

an observation optical system comprising at least one optical element configured to redirect and guide the white light output from the light source to a surface of the target object through the two-beam interference objective lens and to guide the reflected light from the surface to the imaging plane after the reflected light has passed through the two-beam interference objective lens;

a Z stage configured to move the two-beam interference objective lens relative to the target object; and

a control computer configured to operate an imaging device comprising the imaging plane to obtain a plurality of images while operating the Z stage to change a distance between the target object and the two-beam interference objective lens in an optical axis direction of the two-beam interference objective lens, and configured to measure the shape of the target object using the plurality of images,

the control device computer being further configured to

for each unit region in the plurality of images, calculate, as a focus position of the unit region, a position of the two-beam interference objective lens at which a luminance-based evaluation value is maximized over the plurality of images, and measure the shape of the target object based on the focus position of each unit region in the plurality of images,

use, as the evaluation value, a luminance of each unit region in the plurality of images as well as a value correlated with a difference between the luminance of the unit region and luminances of a plurality of unit regions adjacent to the unit region,

use the luminance as the evaluation value when a maximum value of the luminance of each unit region in the plurality of images is greater than a threshold value, and

use the value correlated with the difference as the evaluation value when the maximum value is smaller than the threshold value.

2. The shape measuring apparatus according to claim 1, wherein

the evaluation value is a variance value of the luminance of each unit region in the plurality of images and the luminances of the plurality of unit regions adjacent to the unit region.

3. The shape measuring apparatus according to claim 1, wherein

the evaluation value is a sum of absolute values of luminance gradients between unit regions adjacent to each unit region in the plurality of images.

4. The shape measuring apparatus according to claim 1, wherein

the evaluation value is a sum of absolute values of differences in luminance gradient between each unit region in the plurality of images and the plurality of unit regions adjacent to the unit region.

5. A method for manufacturing a target object to be coated, the method comprising measuring a shape of the target object to be coated by:

generating white light from a light source;

dividing, with a two-beam interference objective lens, the white light into two light beams;

applying one of the two light beams to the target object by guiding the one of the two light beams of white light output from the light source to a surface of the target object through the two-beam interference objective lens;

applying the other light beam to a reference surface;

causing interference between reflected light from the target object and reflected light from the reference surface to output interference light from the two-beam interference objective lens;

guiding the interference light output from the two-beam interference objective lens to an imaging device;

moving the two-beam interference objective lens relative to the target object to change a distance between the target object and the two-beam interference objective lens in an optical axis direction of the two-beam interference objective lens;

obtaining a plurality of images of the interference light while changing the distance between the target object and the two-beam interference objective lens in the optical axis direction of the two-beam interference objective lens;

calculating, for each unit region in the plurality of images, as a focus position of the unit region, a position of the two-beam interference objective lens at which a luminance-based evaluation value is maximized over the plurality of images, wherein calculating the focus position of each unit region includes using, as the evaluation value, a luminance of each unit region in the plurality of images as well as a value correlated with a difference between the luminance of the unit region and luminances of a plurality of unit regions adjacent to the unit region;

measuring the shape of the target object based on the focus position of each unit region in the plurality of images;

utilizing the luminance as the evaluation value when a maximum value of the luminance of each unit region in the plurality of images is greater than a threshold value; and

utilizing the value correlated with the difference as the evaluation value when the maximum value is smaller than the threshold value.