Inspection apparatus and its focus adjustment method

Patent metadata

Field	Value
Publication number	US-2017256045-A1
Application number	US-201715441633-A
Country	US
Kind code	A1
Filing date	Feb 24, 2017
Priority date	Mar 2, 2016
Publication date	Sep 7, 2017
Grant date	—

Abstract

An inspection apparatus according to an aspect of the present invention includes an EUV light source 11 , an illumination optical system 10 provided to apply the EUV light to an EUV mask 60 , a concave mirror and a convex mirror 22 configured to reflect the EUV light reflected on the EUV mask 60 , a camera 32 configured to detect EUV light reflected on the convex mirror 22 and thereby take an image of the EUV mask 60 , an AF light source 16 configured to generate AF light having a wavelength of 450 nm to 650 nm, first and second detectors 27 and 30 configured to detect the AF light reflected on the EUV mask 60 through the concave mirror with the hole 21 and the convex mirror 22 , and an processing device 31 configured to adjust a focus point of the EUV light on the EUV mask 60.

First claim

1 . An inspection apparatus comprising:
an EUV (Extremely Ultraviolet) light source configured to generate EUV light; an illumination optical system provided to apply the EUV light to an EUV mask comprising a multilayer reflection film and an absorption film; a concave mirror with a hole formed therein, the concave mirror with the hole being configured to reflect the EUV light reflected on the EUV mask; a convex mirror configured to reflect the EUV light reflected on the concave mirror with the hole toward the hole of the concave mirror with the hole; an image pickup device configured to detect the EUV light reflected on the convex mirror and thereby take an image of the EUV mask; an AF light source configured to generate AF light having a wavelength of 450 nm to 650 nm; an AF photodetector configured to detect the AF light reflected on the EUV mask through the concave mirror with the hole and the convex mirror; and an adjustment unit configured to adjust a focus point of the EUV light on the EUV mask based on a detection result of the AF photodetector.

2 . The inspection apparatus according to claim 1 , wherein the AF light is incident on an outer side of an incident place of the EUV light on a reflection surface of the concave mirror with the hole.

3 . The inspection apparatus according to claim 1 , wherein
the illumination optical system comprises a dropping mirror disposed directly above the EUV mask, the dropping mirror being configured to reflect the EUV light emitted from the EUV light source toward the EUV mask, and the AF light is reflected on the dropping mirror and then incident on the EUV mask.

4 . The inspection apparatus according to claim 3 , wherein
a stop is disposed in a place conjugate with the EUV mask in the illumination optical system, and the AF light source is disposed on a rear side of the stop.

5 . The inspection apparatus according to claim 1 , wherein
the illumination optical system comprises a dropping mirror disposed directly above the EUV mask, the dropping mirror being configured to reflect the EUV light emitted from the EUV light source toward the EUV mask, and the AF light is incident on the EUV mask from outside of the dropping mirror.

6 . The inspection apparatus according to claim 5 , wherein an incident place of the AF light coincides with the incident place of the EUV light on the EUV mask.

7 . The inspection apparatus according to claim 1 , wherein an incident place of the AF light is deviated from the incident place of the EUV light on the EUV mask.

8 . The inspection apparatus according to claim 1 , wherein a pellicle formed of a material containing silicon is provided on the EUV mask.

9 . A focus adjustment method for an inspection apparatus,
the inspection apparatus comprising: an EUV light source configured to generate EUV light; an illumination optical system provided to apply the EUV light to an EUV mask comprising a multilayer reflection film and an absorption film; a concave mirror with a hole formed therein, the concave mirror with the hole being configured to reflect the EUV light reflected on the EUV mask; a convex mirror configured to reflect the EUV light reflected on the concave mirror with the hole toward the hole of the concave mirror with the hole; an image pickup device configured to detect the EUV light reflected on the convex mirror and thereby take an image of the EUV mask; and an AF light source configured to generate AF light having a wavelength of 450 nm to 650 nm, the focus adjustment method comprising: a step of detecting the AF light reflected on the EUV mask through the concave mirror with the hole and the convex mirror; and a step of adjusting a focus point of the EUV light on the EUV mask based on a detection result of the AF photodetector.

10 . The focus adjustment method according to claim 9 , wherein the AF light is incident on an outer side of an incident place of the EUV light on a reflection surface of the concave mirror with the hole.

11 . The focus adjustment method according to claim 9 , wherein
the illumination optical system comprises a dropping mirror disposed directly above the EUV mask, the dropping mirror being configured to reflect the EUV light emitted from the EUV light source toward the EUV mask, and the AF light is reflected on the dropping mirror and then incident on the EUV mask.

12 . The focus adjustment method according to claim 11 , wherein
a stop is disposed in a place conjugate with the EUV mask in the illumination optical system, and the AF light source is disposed on a rear side of the stop.

13 . The focus adjustment method according to claim 9 , wherein
the illumination optical system comprises a dropping mirror disposed directly above the EUV mask, the dropping mirror being configured to reflect the EUV light emitted from the EUV light source toward the EUV mask, and the AF light is incident on the EUV mask from outside of the dropping mirror.

14 . The focus adjustment method according to claim 13 , wherein an incident place of the AF light coincides with the incident place of the EUV light on the EUV mask.

15 . The focus adjustment method according to claim 9 , wherein an incident place of the AF light is deviated from the incident place of the EUV light on the EUV mask.

16 . The focus adjustment method according to claim 9 , wherein a pellicle formed of a material containing silicon is provided on the EUV mask.

Assignees

• Lasertec Corp

Inventors

• Miyai Hiroki
• Takehisa Kiwamu

Classifications

• H04N23/56

  provided with illuminating means · CPC title

• G01N21/8806

  Specially adapted optical and illumination features · CPC title

• G06T2207/30148

  Semiconductor; IC; Wafer · CPC title

• G06T2207/10148

  Varying focus · CPC title

• H04N5/2256

  Electricity · mapped topic