Combination optical and electrical metrology apparatus

• US 20020186036A1
• Filed: 07/26/2002
• Published: 12/12/2002
• Est. Priority Date: 03/15/1999
• Status: Active Grant

• Current Assignee: Walter Lee Smith
• Original Assignee: Walter Lee Smith
• Inventors: Smith, Walter Lee
• Granted Patent: US 6,791,310 B2
• Time in Patent Office: Days
• US Class Current: 324/765
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence

Abstract

A combination metrology tool is disclosed for analyzing samples, and in particular semiconductor samples. The device includes a first measurement module for determining electrical characteristics of the sample. In general, such a measurement module will monitor voltage or capacitance characteristics to derive information such as carrier lifetimes, diffusion lengths and surface doping. The device also includes a second measurement module for determining compositional characteristics such as layer thickness, index of refraction and extinction coefficient. The second measurement module will include a light source for generating a probe beam which interacts with the sample. A detection system is provided for monitoring either the change in magnitude or polarization state of the probe beam. The output signals from both measurement modules are combined by a processor to more accurately evaluate the sample.

Claims

1. A method of evaluating a sample comprising the steps of:

measuring the electrical characteristics of the sample and generating first output signals corresponding thereto;

measuring the composition characteristics of the sample and generating second output signals responsive thereto; and

evaluating the sample based on a combination of the first and second output signals.

4. A method as recited in claims 1, 2 or 3 wherein said step of evaluating the sample includes using one of the first or second output signals to characterize one parameter of the sample and wherein the remaining output signals are used to further characterize the sample wherein said one parameter is treated as a known parameter.

5. A method as recited in claims 1, 2 or 3 wherein said step of evaluating the sample includes using the first and second output signals in a fitting algorithm to evaluate both the electrical and the composition characteristics of the sample.

6. A method as recited in claims 1, 2 or 3 wherein said first measurements are performed using a technique selected from the group consisting of oxide surface potential, surface photovoltage, contact potential difference, Kelvin probe and corona charge measurements.

7. A method as recited in claim 6 wherein said electrical characteristics include at least one selected from the group consisting of minority carrier diffusion length, minority carrier lifetime, metal concentration, surface recombination velocity, minority carrier recovery time, surface barrier voltage, oxide voltage, surface space charge, dielectric capacitance, electrical oxide thickness, surface doping,

8. A method as recited in claims 1, 2 or 3 wherein said composition characteristics include at least one selected from the group consisting of layer thickness, index of refraction and extinction coefficient.

2. A method of evaluating a sample comprising the steps of:

measuring the electrical characteristics of the sample at a predetermined region thereof in a non-contact manner and generating first output signals corresponding thereto;

measuring the composition characteristics at said region of the sample in a non-contact manner and generating second output signals responsive thereto; and

evaluating said region of the sample based on a combination of the first and second output signals.

3. A method of evaluating a sample comprising the steps of:

measuring the voltage or capacitance of the sample at a predetermined region thereof in a non-contact manner and generating first output signals corresponding thereto;

directing a probe beam of light to reflect off said region of the sample;

measuring either the change in magnitude or polarization state of the probe beam induced by the interaction with the sample and generating second output signals responsive thereto;

evaluating said region of the sample based on a combination of the first and second output signals.

9. An apparatus for evaluating a sample comprising:

a first measurement module for obtaining measurements of the sample corresponding to electrical characteristics and generating first output signals responsive thereto;

a second measurement module for obtaining measurements of the sample corresponding to composition characteristics of the sample and generating second output signals responsive thereto; and

a processor for evaluating the sample based on a combination of said first and second output signals.

10. An apparatus for evaluating a semiconductor sample comprising:

a first measurement module for performing non-contact measurements of either the voltage or capacitance of the sample in a predetermined region thereof and generating first output signals responsive thereto;

a second measurement module for performing non-contact optical measurements of the sample, said module including at least one light source for generating a probe beam directed to reflect off the sample in said predetermined region thereof, said second measurement module further including a detector for monitoring either the change in magnitude or polarization state of the probe beam induced by the sample and generating second output signals responsive thereto; and

a processor for evaluating the sample based upon a combination of the first and second output signals.

11. An apparatus as recited in claims 9 or 10 wherein the processor evaluates the sample using one of the first or second output signals to characterize one parameter of the sample and wherein the remaining output signals are used to further characterize the sample wherein said one parameter is treated as a known parameter.

12. An apparatus as recited in claims 9 or 10 wherein the processor evaluates the sample using the first and second output signals in a fitting algorithm to evaluate both the electrical and the composition characteristics of the sample.

13. An apparatus as recited in claims 9 or 10 wherein said first measurement module operates using a technique selected from the group consisting of oxide surface potential, surface photovoltage, contact potential difference, Kelvin probe and corona charge measurements.

14. An apparatus as recited in claim 13 wherein the measurements made by the first measurement module are used to evaluate at least one parameter selected from the group consisting of minority carrier diffusion length, minority carrier lifetime, metal concentration, surface recombination velocity, minority carrier recovery time, surface barrier voltage, oxide voltage, surface space charge, dielectric capacitance, electrical oxide thickness, surface doping,

15. An apparatus as recited in claims 9 or 10 wherein the measurements made by the second measurement module are used to evaluate at least one parameter selected from the group consisting of layer thickness, index of refraction and extinction coefficient.