Method and system for simultaneous tilt and height control of a substrate surface in an inspection system

Patent metadata

Field	Value
Publication number	US-9810619-B2
Application number	US-201314022305-A
Country	US
Kind code	B2
Filing date	Sep 10, 2013
Priority date	Sep 12, 2012
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

A system for substrate tilt and focus control in an inspection system includes a dynamically actuatable substrate stage assembly including a substrate stage for securing a substrate; a tilt-height detection system including: a height detection sub-system and a tilt detection sub-system. The system further includes a first actuator configured to selectably actuate the substrate along a direction perpendicular to the surface of the substrate at a location of the substrate stage assembly; and an additional actuator configured to selectably actuate the substrate along a direction substantially perpendicular to the surface of the substrate at an additional location of the substrate stage assembly; and a MIMO tilt-focus controller communicatively coupled to the height detection sub-system, the tilt detection sub-system, the first actuator and the additional actuator.

First claim

What is claimed:

1. A system for tilt and focus control in an inspection system, comprising:
a dynamically actuatable substrate stage assembly including a substrate stage for securing a substrate;
a laser source configured to generate a light beam;
a tilt-height detection system including:
a height detection sub-system comprising: an optical assembly; and a height sensor, wherein the height sensor comprises one or more optical sensors configured to measure height of a surface of the substrate at a position of inspection of the substrate surface; and
a differential interference contrast tilt detection sub-system configured to measure tilt of the substrate disposed on the substrate stage, wherein the differential interference contrast tilt detection sub-system comprises an oblique differential interferometer optical assembly, wherein the oblique differential interferometer optical assembly comprises a first optical sensor and a second optical sensor;

a first actuator operably coupled to the substrate stage assembly at a first location of the substrate stage assembly and configured to selectively actuate the substrate along a direction substantially perpendicular to the surface of the substrate at the first location of the substrate stage assembly;
an additional actuator operably coupled to the substrate stage assembly at an additional location of the substrate stage assembly and configured to selectively actuate the substrate along a direction substantially perpendicular to the surface of the substrate at the additional location of the substrate stage assembly; and
a tilt-focus controller including one or more processors configured to execute a set of program instructions stored in memory, the tilt-focus controller communicatively coupled to at least the height detection sub-system, the tilt detection sub-system, the first actuator and the additional actuator, wherein the set of program instructions are configured to cause the one or more processors to:
receive one or more height measurements from the height detection sub-system;
receive one or more tilt measurements from the tilt detection sub-system; and
responsive to the measured one or more height measurements and the one or more tilt measurements, selectively adjust an actuation state of at least one of the first actuator and the additional actuator in order to control at least one of a tilt of the substrate surface and a height of the substrate surface at the position of inspection in order to maintain the substrate surface substantially at an imaging plane of a detector of the inspection system or a focus of illumination of the inspection system within a selected tolerance level.

2. The system of claim 1 , wherein the substrate stage is configured to secure a semiconductor wafer.

3. The system of claim 1 , wherein the substrate stage assembly comprises:
a substrate stage platform; and
a substrate chuck configured to secure the substrate, wherein the first actuator is operably coupled to the substrate stage platform at a first location and the additional actuator is operably coupled to the substrate stage platform at an additional location.

4. The system of claim 1 , wherein the optical assembly of the height detection sub-system is configured to direct the light beam onto the surface of the substrate at substantially the position of inspection of the inspection system; and
the one or more optical sensors of the height sensor are configured to detect a relative position of the light beam reflected from the surface of the substrate, wherein the tilt-focus controller is configured to determine a height value of the surface of the substrate based on the measured relative position of the light beam at the sensor.

5. The system of claim 4 , wherein the one or more optical sensors of the height sensor comprises:
one or more bicell sensors.

6. The system of claim 4 , wherein the one or more optical sensors of the height sensor comprises:
at least one of one or more line CCD sensors and one or more line CMOS sensors.

7. The system of claim 1 , wherein the oblique differential interferometer optical assembly comprises:
an optical element configured to separate the light beam from the laser source into a first beam and a second beam and direct the first beam and the second beam onto the substrate at the position of inspection of the inspection system, wherein the first beam and the second beam are orthogonally polarized and transversely separated;
a reflection-transmission flat is configured to reflect back a portion of the first beam and the second beam from the substrate surface back to the optical element, wherein the optical element is configured to recombine the reflected back portion of the first beam and the second beam into a recombined beam;
wherein the first sensor is configured to detect light of at least a first polarization of the recombined beam; and
wherein the second sensor is configured to detect light of at least a second polarization of the recombined beam, wherein the tilt-focus controller is further configured to compare the light of the first polarization detected by the first sensor and the light of the second polarization detected by the second sensor in a differential interference detection process in order to determine a tilt of the substrate surface.

8. The system of claim 7 , further comprising:
a polarized beam splitter configured to direct light of the first polarization of the combined beam to the first detector and light of the second polarization of the combined beam to a second detector.

9. The system of claim 7 , wherein at least one of the first sensor and the second sensor is a photodiode.

10. The system of claim 7 , wherein the height detection sub-system comprises:
a height sensor comprising one or more optical sensors configured for substrate height detection, wherein the first beam is directed to the height sensor for substrate height detection by a portion of the oblique differential interferometer optical assembly, wherein the tilt-focus controller is configured to determine a height value of the surface of the substrate based on the measured relative position of the first light beam at the height sensor.

11. The system of claim 7 , wherein the optical element is a Wollaston prism.

12. The system of claim 1 , wherein the oblique differential interferometer optical assembly comprises:
a first optical element configured to separate the light beam from the laser source into a first beam and a second beam and direct the first beam and the second beam onto the substrate at the position of inspection of the inspection system, wherein the first beam and the second beam are orthogonally polarized and transversely separated;
a second optical element configured to form a recombined beam by combining the first beam and the second beam upon reflection from the substrate surface;
wherein the first sensor configured to detect light of at least a first polarization of the recombined beam; and
wherein the second sensor configured to detect light of at least a second polarization of the recombined beam, wherein the tilt-focus controller is further configured to compare the light of the first polarization detected by the first detector and light of the second polarization detected by the second detector in a differential interference detection process in order to determine a tilt of the substrate surface.

13. The system of claim 12 , further comprising:
a polarized beam splitter configured to direct light of the first polarization of the combined beam to the first detector and light of the second polarization of the combined beam to a second detector.

Assignees

• Kla Tencor Corp

Inventors

• Cai Zhongping
• Xiong Jingyi
• Trytko Tyler
• Slobodov Alexander
• Doyle Paul
• Romanovsky Anatoly

Classifications

• G01N21/01 Primary

  Arrangements or apparatus for facilitating the optical investigation · CPC title

• G01N21/956 Primary

  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

• G01B5/0004

  Supports (G01B5/025 takes precedence) · CPC title