Extreme ultra-violet (euv) inspection systems

Patent metadata

Field	Value
Publication number	US-2015192459-A1
Application number	US-201514589902-A
Country	US
Kind code	A1
Filing date	Jan 5, 2015
Priority date	Jan 8, 2014
Publication date	Jul 9, 2015
Grant date	—

Abstract

Disclosed are methods and apparatus for reflecting, towards a sensor, extreme ultra-violet (EUV) light that is reflected from a target substrate. The system includes a first mirror arranged to receive and reflect the EUV light that is reflected from the target substrate, a second mirror arranged to receive and reflect the EUV light that is reflected by the first mirror, a third mirror arranged to receive and reflect the EUV light that is reflected by the second mirror, and a fourth mirror arranged to receive and reflect the EUV light that is reflected by the third mirror. The first mirror has an aspherical surface. The second, third, and fourth mirrors each have a spherical surface.

First claim

What is claimed is:

1 . An apparatus for reflecting, towards a sensor, extreme ultra-violet (EUV) light that is reflected from a target substrate, the apparatus comprising:
an illumination source for generating EUV light that illuminates a target substrate; objective optics for receiving and reflecting EUV light that is reflected from the target substrate; and a sensor for detecting EUV light that is reflected by the objective optics, wherein the objective optics comprises
a first mirror arranged to receive and reflect EUV light that is reflected from the target substrate,
a second mirror arranged to receive and reflect EUV light that is reflected by the first mirror,
a third mirror arranged to receive and reflect EUV light that is reflected by the second mirror, and
a fourth mirror arranged to receive and reflect EUV light that is reflected by the third mirror,
wherein the first mirror has an aspherical surface, and wherein the second, third, and fourth mirrors each has a spherical surface.

2 . The apparatus of claim 1 , wherein the target substrate is an EUV photolithography mask.

3 . The apparatus of claim 1 , wherein the first and fourth mirrors each have a size that is equal to or greater than about 200 mm, and wherein the second and third mirrors each have a size that is less than or equal to about 50 mm.

4 . The apparatus of claim 1 , wherein the second mirror partially obscures the first mirror from EUV light that is reflected from the target substrate, and wherein the first mirror includes an opening through which the EUV light that is reflected from the second mirror passes and is received by the third mirror.

5 . The apparatus of claim 1 , wherein a numerical aperture (NA) of the objective optics is equal to or lower than 0.20.

6 . The apparatus of claim 5 , wherein a numerical aperture (NA) of the objective optics is between about 0.14 and 0.18.

7 . The apparatus of claim 6 , wherein a magnification of the objective optics has a range between about 300× and 1000×.

8 . The apparatus of claim 1 , wherein a field of view of the objective optics is at least 10,000 square microns.

9 . The apparatus of claim 1 , wherein a field of view of the objective optics is at least 100,000 square microns.

10 . The apparatus of claim 1 , wherein the objective optics are associated with a wavefront error that is less than or equal to about 100 milliwaves.

11 . The apparatus of claim 10 , wherein the objective optics are associated with a wavefront error that is less than or equal to about 20 milliwaves.

12 . The apparatus of claim 10 , wherein the objective optics are associated with a target blur of an image of an object of the target substrate that is less than a quarter of a diffraction limited point spread function.

13 . The apparatus of claim 1 , wherein the objective optics has a working distance that is at least 100 mm.

14 . The apparatus of claim 1 , wherein the objective optics is sized to have a total track distance from the target substrate to the sensor that is less than about 1.5 m.

15 . An objective optics system for reflecting extreme ultra-violet (EUV) light that is reflected from a target substrate, the system comprises:
a first mirror arranged to receive and reflect EUV light that is reflected from the target substrate, a second mirror arranged to receive and reflect EUV light that is reflected by the first mirror, a third mirror arranged to receive and reflect EUV light that is reflected by the second mirror, and a fourth mirror arranged to receive and reflect EUV light that is reflected by the third mirror, wherein the first mirror has an aspherical surface, wherein the second, third, and fourth mirrors each have a spherical surface.

16 . The system of claim 15 , wherein a numerical aperture (NA) of the objective optics system is equal to or less than 0.20.

17 . The system of claim 15 , wherein a field of view of the objective optics system is at least 10,000 square microns.

18 . The system of claim 15 , wherein the objective optics system is associated with a wavefront error that is less than or equal to about 100 milliwaves.

19 . The system of claim 15 , wherein the objective optics system has a working distance that is at least 100 mm.

20 . A method of reflecting extreme-ultraviolet (EUV) light that is reflected from an EUV reticle towards a sensor, comprising:
at a first aspherical mirror, receiving and reflecting EUV light that is reflected from the EUV reticle; at a second spherical mirror, receiving and reflecting EUV light that is reflected from the first aspherical mirror; at a third spherical mirror, receiving and reflecting EUV light that is reflected from the second spherical mirror; and at a fourth spherical mirror, receiving and reflecting EUV light that is reflected from the third spherical mirror towards the sensor.

Assignees

• Kla Tencor Corp

Inventors

• Kvamme Damon F

Classifications

• G01N21/956

  Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} · CPC title

• G01J1/0411 Primary

  using focussing or collimating elements, i.e. lenses or mirrors; Aberration correction · CPC title

• G01N2201/0636

  Reflectors · CPC title

• G03F1/84

  Inspecting · CPC title

• G02B17/0657

  off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry · CPC title