Method and system for combined photothermal modulated reflectance and photothermal IR radiometric system

• US 6,917,039 B2
• Filed: 12/10/2002
• Issued: 07/12/2005
• Est. Priority Date: 02/13/2002
• Status: Active Grant

• Current Assignee: The Therma-Wave Incorporated (KLA Corporation)
• Original Assignee: The Therma-Wave Incorporated (KLA Corporation)
• Inventors: Salnik, Alex, Nicolaides, Lena
• Primary Examiner(s): Gabor, Otilia
• Application Number:
  US10/315,588
• Publication Number:
  US 20030150993A1
• Time in Patent Office: 945 Days
• Field of Search: 250/341.1, 250/339.11, 250/359.1, 250/338.1, 250/358.1, 250/360.1, 250/340, 250/225, 356/364, 356/365, 356/366, 356/367, 356/369
• US Class Current: 250/341.1
• CPC Class Codes: G01N 21/171 with calorimetric detection, e.g. with thermal lens detection
• CPC Class Codes: G01N 21/1717 with a modulation of one or more physical properties of the sample during the optical investigation, e.g. electro-reflectance
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

A method and apparatus for evaluating a semiconductor wafer. A combination of a photothermal modulated reflectance method and system with a photothermal IR radiometry system and method is utilized to provide information which can be used to determine properties of semiconductor wafers being evaluated. The system and method can provide for utilizing a common probe source and a common intensity modulated energy source. The system and method further provide an infrared detector for monitoring changes in infrared radiation emitted from a sample, and photodetector for monitoring changes in beam reflected from the sample.

Claims

1. An apparatus for evaluating characteristics of a sample comprising:

a probe source which emits a probe beam of radiation which is incident upon the sample, and reflected off the sample;

an intensity modulated energy source which supplies intensity modulated energy to the sample, wherein in response to the intensity modulated energy a reflectivity of the sample changes, and wherein in response to the intensity modulated energy infrared radiation emitted by the sample changes;

a photodetector which detects changes in said reflected probe beam, where changes in the reflected probe beam result from the variations in the reflectivity of the sample;

an infrared detector which detects the changes in the infrared radiation emitted from the sample; and

a processor system coupled to the photodetector for analyzing changes in the reflected probe beam to evaluate characteristics of the sample, and the processor system coupled to the infrared detector, wherein the processor system analyzes the changes in the infrared radiation to evaluate characteristics of the sample.

2. The apparatus of claim 1, further including a reflective objective which focuses the intensity modulated energy and the probe beam on the sample, and collects infrared radiation emitted from the sample.

3. The apparatus of claim 1 further including:

a window having reflective and transmissive properties, which transmits infrared radiation emitted from the sample and reflects the probe beam reflected off the sample; and

a reflective objective which focuses infrared radiation onto the infrared detector after it has been transmitted through the window.

4. The apparatus of claim 1, wherein the intensity modulated energy source is operable such that a modulation frequency of the intensity modulated energy source can be varied between at least a first frequency and a second frequency wherein when operating at the first frequency the processor system operates to analyze the reflectivity of the sample, and wherein at the second frequency the processor system operates to analyze the infrared radiation detected by the infrared radiation detector.

5. The apparatus of claim 4, further including:

a first reflective objective which focuses the intensity modulated energy and the probe beam on the sample;

a window having reflective and transmissive properties, which transmits infrared radiation emitted from the sample and reflects the probe beam and the intensity modulated energy; and

a second reflective objective which focuses infrared radiation onto the infrared detector after it has been transmitted through the window.

6. The apparatus of claim 1, wherein the intensity modulated energy source is operable such that a modulation frequency of the intensity modulated energy source can be varied between at least a first frequency and a second frequency, wherein the first frequency is greater than 1 MHz, and the second frequency is less than 1 MHz, wherein when operating at the first frequency the processor system operates to analyze the reflectivity of the sample, and wherein at the second frequency the processor system operates to analyze the infrared radiation detected by the infrared radiation detector.

7. The apparatus of claim 1, wherein the apparatus further includes a memory system coupled to the processor system, wherein memory system includes reflectivity data for samples of known composition, and includes infrared radiation data for samples of known composition, wherein the processor is operative to analyze infrared radiation detected by the infrared radiation detector relative to the infrared radiation data stored in the memory system to determine characteristics of the sample, and the processor is operative to analyze changes in the reflected probe beam, detected by the detector, relative to the reflectivity data stored in the memory system to determine characteristics of the sample.

8. The apparatus of claim 1, further including:

a reflective objective which focuses the intensity modulated energy and the probe beam on the sample;

a window having reflective and transmissive properties, which transmits infrared radiation emitted from the sample and reflects the probe beam and the intensity modulated energy; and

a reflective objective which focuses infrared radiation onto the infrared detector after it has been transmitted through the window.

9. The apparatus of claim 1, wherein the processor operates to combine the analyzing of changes of the reflected probe beam, and the changes in the infrared radiation emitted from the sample, and based on this combined analysis makes determinations as to characteristics of the sample.

10. A method for evaluating characteristics of a semiconductor sample comprising:

generating intensity modulated energy from an intensity modulated energy source;

directing the intensity modulated energy from the intensity modulated energy source to the surface of the sample, wherein the intensity modulated energy causes changes in an infrared radiation emitted from the sample, and changes in a reflectivity of the sample;

directing a probe beam from a probe source such that it is incident upon the sample, and reflected off the sample;

monitoring changes in the reflected probe beam resulting from the changes in the reflectivity of the sample;

analyzing the monitored changes of the reflected probe beam to evaluate the sample;

monitoring the changes in the infrared radiation emitted from the sample; and

analyzing the monitored changes in the infrared radiation emitted by the sample to evaluate the sample.

11. The method as recited in claim 10, wherein during said analyzing of the changes of the reflected probe beam, the changes in the reflected probe beam are compared with predetermined changes of a probe beam associated with a known reference sample, whereby characteristics of the sample can be determined, and wherein during said analyzing the monitored changes in the infrared radiation, the changes are compared with predetermined changes in infrared radiation associated with a known reference sample, whereby characteristics of the sample can be determined.

12. The method of claim 10, further wherein the generating of the intensity modulated energy is such that a modulation frequency of the intensity modulated energy can be at two different frequencies, wherein at a first frequency the analyzing the monitored changes in the reflected probe beam is done, and wherein at a second frequency the analyzing the monitored changes in the infrared radiation emitted by the sample is done.

13. The method of claim 10, wherein the directing the intensity modulated energy and the directing the probe beam to the sample, includes directing the intensity modulated energy and the probe beam such that intensity modulated energy and the probe beam are reflected of a window toward the sample, and further including transmitting infrared radiation emitted from the sample through the window and toward an infrared detector.

14. The method of claim 10, wherein the analyzing of the monitored changes in the reflected probe beam, and the analyzing of the monitored changes in the infrared radiation emitted by sample are combined, and based on this combined analysis, determining characteristics of the sample.