Optical module for optical height measurement

Patent metadata

Field	Value
Publication number	US-10724845-B2
Application number	US-201816168972-A
Country	US
Kind code	B2
Filing date	Oct 24, 2018
Priority date	Mar 23, 2018
Publication date	Jul 28, 2020
Grant date	Jul 28, 2020

Abstract

The optical module for optical height measurement includes a laser light source, an irradiation optical system, a detection optical system, and a detector. The laser light source is configured to irradiate the layer-structured specimen with a light beam. The irradiation optical system includes an objective lens. The objective lens is located to be approximately perpendicular to the layer-structured specimen. The detection optical system is configured to guide a reflected light reflected by the layer-structured specimen and a light passing through the objective lens and an aperture-restrictor-for-return to the detector. The aperture-restrictor-for-return is located immediately after the objective lens. The aperture-restrictor-for-return is configured to restrict the reflected light and cause only a light in a high NA region to pass through. The detector is configured to convert an entered light into a light detection signal. The detector includes a multi-divided detector array.

First claim

What is claimed is:

1. An optical module for optical height measurement that optically measures a surface height of a layer-structured specimen including a transparent or semi-transparent thin film, comprising:
a laser light source configured to irradiate the layer-structured specimen with a light beam;
an irradiation optical system that includes an objective lens, the objective lens being disposed approximately perpendicular to the layer-structured specimen;
a detection optical system including an aperture element and a detector,
wherein the aperture element is disposed immediately after the objective lens with respect to a path of reflected light reflected by the layer-structured specimen,
wherein the aperture element includes a first aperture, through which the light beam incident on the layer-structured specimen passes through and a second aperture, having a smaller aperture size than the first aperture, through which the reflected light passes after passing through the objective lens,
wherein the second aperture is configured to restrict the reflected light and cause only a light in a high NA region to pass through, and
wherein the detector is configured to convert light entered into the detector into a light detection signal,
wherein the detector includes a multi-divided detector array, and
wherein the reflected light reflected by the layer-structured specimen includes a surface reflected light from the layer-structured specimen and a deep surface reflected light from a deep layer other than the surface reflected light,
wherein the surface reflected light and the deep surface reflected light are separated and detected on the detector.

2. The optical module for optical height measurement according to claim 1 , wherein the aperture element has a rectangular shape.

3. The optical module for optical height measurement according to claim 1 , wherein a light beam with which the layer-structured specimen is irradiated by the objective lens is a light beam containing only an approximately S-polarized component entering the surface of the layer-structured specimen.

4. The optical module for optical height measurement according to claim 1 ,
wherein Δs and parameters of Formula (2), Formula (3), and Formula (4) are configured such that a spot diameter Δs where the surface reflected light and the deep surface reflected light from the layer-structured specimen converge on the detector and a spot interval Δα as an interval between a spot position of the surface reflected light on the detector and a spot position of the deep surface reflected light on the detector satisfy the following Formula (1):

⁢

[

Formula
⁢

⁢
1

]

⁢

Δα
≧

Δ
⁢

⁢
s

(
1
)

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[

Formula
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⁢
2

]

⁢

Δα
=

Δ
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⁢
Rout

-

Δ
⁢

⁢
Rin

2
⁢

Na
cl

(
2
)

⁢

[

Formula
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⁢
3

]

Δ
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Rout

=

f
obj

-

2
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z
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1
-

NAout
2

NAout

+

Assignees

• Hitachi Lg Data Storage Inc

Inventors

• Tomita Daisuke
• Suenaga Hideo
• Kurokawa Takahiro
• Morimoto Yoshitaka

Classifications

• G11B7/131 Primary

  Arrangement of detectors in a multiple array · CPC title

• G11B7/127

  Lasers; Multiple laser arrays {(lasers per se H01S)} · CPC title

• G11B7/09

  with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following · CPC title

• G01B11/0616 Primary

  of coating · CPC title

• G02B27/0955

  Lenses (lenses per se G02B3/00) · CPC title