US 6,856,385 B2Granted

Spatial averaging technique for ellipsometry and reflectometry

AssigneeTherma-Wave, Inc.

InventorsLanhua Wei, Hanyou Chu, Jon Opsal

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Abstract

This invention relates to optical metrology tools that are used to evaluate small measurement areas on a semiconductor wafer, where the measurement area is surrounded by a material different from the measurement area. In one embodiment, a probe beam is scanned over the measurement area and the surrounding material as data is taken at multiple locations. A processor determines the characteristics of the measurement area by identifying an extremum value of the measurements which represents the center of the measurement area. In another embodiment, the processor determines the characteristics of the sample using a combination of light measured from within and without the measurement area. The measured data is treated as a combination of light from both regions and mathematically modeled to account for both the contribution of the light reflected from the measurement area and the light reflected from the surrounding material.

Claims8

Dependent claims

An apparatus for evaluating the characteristics of a sample wherein the sample includes a measurement area defined by a region having characteristics different from the surrounding region, comprising:

a laser for generating a probe beam of radiation which is directed to illuminate a spot on the surface of the sample wherein the size of the probe beam spot is similar to the size of the measurement area;
an optical detector for monitoring the probe beam after reflection from the sample;
a polarizer positioned in the probe beam path between the laser and the detector;
an analyzer positioned in the probe beam path between the laser and the detector;
a movable stage for supporting the sample in a manner to translate the sample with respect to the probe beam such that the probe beam spot strikes the sample at a location substantially in the center of the measurement area and at locations on either side thereof allowing optical measurements with the optical detector to be made at a plurality of the locations;
and
a processor for determining the change in polarization state of the probe beam induced by interaction with the sample and computing the characteristics of the sample for each of the measurement locations and for determining an extremum in the computed characteristics to identify the measurement location best corresponding to the center of the measurement area.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/400,369Filed 27 Mar 2003 · continuation
Priority: 15 Sep 1999
Published: US 2003/0214654 A120 Nov 2003
Granted: 15 Feb 2005
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G01N 21/211
Polarisation-affecting properties: ellipsometry
G01B 11/065
With measurement of polarization: using one or more discrete wavelengths
G01N 21/9501
Characterised by the material or shape of the object to be examined: semiconductor wafers
H10P 74/203
Characterised by the properties tested or measured, e.g. structural or electrical properties: structural properties, e.g. testing or measuring…

Family

Application60/153,932Us provisional application · filed 15 Sep 1999
Application09/658,812Parent of this division · filed 11 Sep 2000
Application09/871,220Parent of this continuation · filed 31 May 2001
US 2003/0214654 A1Pre-grant publication · published 20 Nov 2003
US 6,577,384 B2Parent of this continuation
US 6,281,027 B1Parent of this division
Application09/871,220Parent of this division
US 2002/0012123 A1Published application
US 6,856,385 B2This patent

From the US filing history. Foreign family members aren’t listed.