US-12625381-B2 - Illumination apparatus and illumination method

Abstract

Provided are an illumination apparatus and an illumination method capable of uniformly illuminating a visual field region detected by a detector. The present disclosure provides an illumination apparatus including: a drive unit configured to drive an optical member such that illumination light scans, in one direction, a visual field region that is a region extending in the one direction on a sample; and a control unit configured to control the drive unit to cause the illumination light to scan in synchronization with a transfer of a sensor that receives light from the visual field region illuminated by the illumination light.

Inventors

• Keitaro HAYASHIDA
• Shinji Tanaka
• Masaki KOICHI
• Haruhiko Kusunose

Assignees

• LASERTEC CORPORATION

Dates

Publication Date

20260512

Application Date

20240308

Priority Date

20230309

Claims (20)

1. 1 . An illumination apparatus comprising: a drive unit configured to drive an optical member such that illumination light has a moving component that scans, in one direction, a visual field region that is a region extending in the one direction on a sample; and a control unit configured to control the drive unit to cause the illumination light having the moving component in one direction to scan in synchronization with an integration cycle of a TDI sensor that receives light from the visual field region illuminated by the illumination light, wherein the sample is an object for which images are acquired by the TDI sensor.
2. 2 . The illumination apparatus according to claim 1 , wherein the illumination light contains EUV light generated from plasma generated by irradiation of a target with laser light, the optical member defines an irradiation position of the laser light onto the target, and the drive unit causes the illumination light to have the moving component that scans in the one direction by driving the optical member such that the laser light has a laser light moving component that scans the target in a predetermined direction.
3. 3 . The illumination apparatus according to claim 2 , wherein the drive unit drives the optical member such that a relationship between a position of the laser light on the target and time involves a triangular wave.
4. 4 . The illumination apparatus according to claim 2 , wherein the drive unit drives the optical member such that a relationship between a position of the laser light on the target and time involves at least one of the three waveforms: triangular wave, sine wave, rectangular wave, or a combined and overlapped waveform of any of those three waveforms.
5. 5 . The illumination apparatus according to claim 1 , wherein the illumination light contains EUV light generated from plasma, and the optical member defines a position, at which the EUV light is irradiated onto the sample, on an optical path from a generation position of the plasma to the sample.
6. 6 . The illumination apparatus according to claim 1 , wherein a spot of the illumination light in the visual field region has a circular shape.
7. 7 . The illumination apparatus according to claim 1 , wherein a spot of the illumination light in the visual field region has an ellipse shape with a major axis extending in another direction orthogonal to the one direction.
8. 8 . The illumination apparatus according to claim 1 , wherein the optical member includes at least one of a mirror that reflects the illumination light onto the sample, a beam shifter that shifts an illumination position of the illumination light, an acousto-optical element that shifts an illumination position of the illumination light, and an electro-optical element, and the drive unit drives the optical member such that the illumination light scans the visual field region in the one direction.
9. 9 . The illumination apparatus according to claim 1 , wherein the TDI sensor includes a plurality of image sensor arrays having a plurality of image sensors, and transfers information between the image sensors belonging to the same image sensor array, and the one direction is substantially equal to a direction in which the image sensor arrays are arranged.
10. 10 . The illumination apparatus according to claim 1 , wherein the control unit controls the drive unit to set the number of times of execution of round-trip scanning including the moving component on one side in the one direction and the moving component on another side in the one direction of the illumination light in one cycle of the integration cycle of the TDI sensor, to an integer.
11. 11 . The illumination apparatus according to claim 1 , further comprising a light source control unit configured to change an intensity of the illumination light in synchronization with the integration cycle of the TDI sensor.
12. 12 . An illumination apparatus comprising: a drive unit configured to drive an optical member such that illumination light has a moving component that scans, in one direction, a visual field region that is a region extending in the one direction on a sample; and a control unit configured to control the drive unit to cause the illumination light to scan in the one direction more than a predetermined number of times in one cycle of an integration cycle of the TDI sensor that receives light from the visual field region illuminated by the illumination light, wherein the sample is an object for which images are acquired by the TDI sensor.
13. 13 . An illumination method comprising steps of: driving an optical member such that illumination light has a moving component that scans, in one direction, a visual field region that is a region extending in the one direction on a sample; and causing the illumination light having the moving component in the one direction to scan in synchronization with an integration cycle of a TDI sensor that receives light from the visual field region illuminated by the illumination light, wherein the sample is an object for which images are acquired by the TDI sensor.
14. 14 . The illumination method according to claim 13 , wherein the illumination light contains EUV light generated from plasma generated by irradiation of a target with laser light, the optical member defines an irradiation position of the laser light onto the target, and the step of driving the optical member includes causing the illumination light to have the moving component that scans in the one direction by driving the optical member such that the laser light has a laser light moving component that scans the target in a predetermined direction.
15. 15 . The illumination method according to claim 14 , wherein the step of driving the optical member includes driving the optical member such that a relationship between a position of the laser light on the target and time involves a triangular wave.
16. 16 . The illumination method according to claim 14 , wherein the step of driving the optical member includes driving the optical member such that a relationship between a position of the laser light on the target and time involves at least one of the three waveforms: triangular wave, sine wave, rectangular wave, or a combined and overlapped waveform of any of those three waveforms.
17. 17 . The illumination method according to claim 13 , wherein the illumination light contains EUV light generated from plasma, and the optical member defines a position, at which the EUV light is irradiated onto the sample, on an optical path from a generation position of the plasma to the sample.
18. 18 . The illumination method according to claim 13 , wherein a spot of the illumination light in the visual field region has a circular shape.
19. 19 . The illumination method according to claim 13 , wherein a spot of the illumination light in the visual field region has an ellipse shape with a major axis extending in another direction orthogonal to the one direction.
20. 20 . The illumination method according to claim 13 , wherein the optical member includes at least one of a mirror that reflects the illumination light onto the sample, a beam shifter that shifts an illumination position of the illumination light, an acousto-optical element that shifts an illumination position of the illumination light, and an electro-optical element, and the step of driving the optical member includes driving the optical member such that the illumination light scans the visual field region in the one direction.

Description

INCORPORATION BY REFERENCE This application is based upon and claims the benefit of priority from Japanese patent applications No. 2023-036152, filed on Mar. 9, 2023, and No. 2024-022288, filed on Feb. 16, 2024, the disclosure of which is incorporated herein in its entirety by reference. BACKGROUND The present disclosure relates to an illumination apparatus and an illumination method. In Published Japanese Translation of PCT International Publication for Patent Application, No. 2016-534341, Japanese Unexamined Patent Application Publication No. 2010-236966, and Japanese Unexamined Patent Application Publication No. H11-072905, inspection apparatuses for defects occurring in semiconductor substrates and photomasks are disclosed. SUMMARY In inspection for mask defects using extreme ultra violet (EUV) light, it is necessary to uniformly and efficiently illuminate an inspection region of a sample. When a laser produced plasma (LPP) method is used for an EUV light source that generates EUV light and an illumination optics system has a critical illumination configuration, a focusing profile of laser light is directly reflected in an illumination profile. For example, intensity distribution of a cross section orthogonal to an optical axis of laser light exciting a target in the LPP method has a Gaussian profile. For this reason, in order to uniformly illuminate a visual field region on a sample detected by a horizontally long sensor plane of a sensor such as a camera with illumination light having a horizontally long and flat profile, it is necessary to construct a complex optical system. For example, it is also possible to form illumination light having a nearly flat illumination profile by expanding or splitting a single focused beam with beam expanding or splitting using a cylindrical lens, a crystal plate, or the like. Thereby, the illumination light can be formed into a shape that covers the visual field region. However, the optical system becomes complicated and the quantity of light emitting out of the visual field region increases, resulting in inefficiency. In Japanese Unexamined Patent Application Publication No. 2019-158431, since there is a disadvantage that illumination NA distribution varies depending on a position, a method of scanning on a light source side is preferable. An object of the present disclosure is to solve such problems, and to provide an illumination apparatus and an illumination method that can uniformly illuminate a visual field region detected by a detector. An illumination apparatus according to the present disclosure includes: a drive unit configured to drive an optical member such that illumination light scans, in one direction, a visual field region that is a region extending in the one direction on a sample; and a control unit configured to control the drive unit to cause the illumination light to scan in synchronization with an integration cycle of a TDI sensor that receives light from the visual field region illuminated by the illumination light. In the illumination apparatus, the illumination light may contain EUV light generated from plasma generated by irradiation of a target with laser light, the optical member may include a mirror that reflects the laser light onto the target, and the drive unit may cause the illumination light to scan the visual field region in the one direction by driving the optical member such that the laser light scans the target in a predetermined direction. In the illumination apparatus, the drive unit may drive the optical member such that a relationship between a position of the laser light on the target and time involves a triangular wave. In the illumination apparatus, the drive unit may drive the optical member such that a relationship between a position of the laser light on the target and time involves at least one of the three waveforms: triangular wave, sine wave, rectangular wave, or a combined and overlapped waveform of any of those three waveforms. In the illumination apparatus, a spot of the illumination light in the visual field region may have a circular shape. In the illumination apparatus, a spot of the illumination light in the visual field region may have an ellipse shape with a major axis extending in another direction orthogonal to the one direction. In the illumination apparatus, the optical member may include at least one of a mirror that reflects the illumination light onto the sample, a beam shifter that shifts an illumination position of the illumination light, and an acousto-optical element that shifts an illumination position of the illumination light, and the drive unit may drive the optical member such that the illumination light scans the visual field region in the one direction. An illumination apparatus according to the present disclosure includes: a drive unit configured to drive an optical member such that illumination light scans, in one direction, a visual field region that is a region extending in the one dir