US 9,810,619 B2
Method and system for simultaneous tilt and height control of a substrate surface in an inspection system
Zhongping Cai, Fremont, CA (US); Jingyi Xiong, Sunnyvale, CA (US); Tyler Trytko, Sunnyvale, CA (US); Alexander Slobodov, San Jose, CA (US); Paul Doyle, San Jose, CA (US); and Anatoly Romanovsky, Palo Alto, CA (US)
Assigned to KLA-Tencor Corporation, Milpitas, CA (US)
Filed by KLA-Tencor Corporation, Milpitas, CA (US)
Filed on Sep. 10, 2013, as Appl. No. 14/22,305.
Claims priority of provisional application 61/700,251, filed on Sep. 12, 2012.
Prior Publication US 2014/0071457 A1, Mar. 13, 2014
Int. Cl. G01N 21/01 (2006.01); G01N 21/956 (2006.01); G01B 5/00 (2006.01)
CPC G01N 21/01 (2013.01) [G01B 5/0004 (2013.01); G01N 21/956 (2013.01)] 45 Claims
OG exemplary drawing
 
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.