Focused beam scatterometry apparatus and method

Patent metadata

Field	Value
Publication number	US-9793178-B2
Application number	US-201514833540-A
Country	US
Kind code	B2
Filing date	Aug 24, 2015
Priority date	Aug 28, 2014
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

The capacity to measure nanoscale features rapidly and accurately is of central importance for the monitoring of manufacturing processes in the production of computer integrated circuits. It is known that far-field scattered light requires a priori sample information in order to reconstruct nanoscale information such as is required in semiconductor metrology. Parameters of interest include, for example, trench depth, duty cycle, wall angle and oxide layer thickness. We describe a scatterometry apparatus and method that uses unconventional polarization states in the pupil of a high NA objective lens, and refer to this as focused beam scatterometry, in which the illumination consists of a focused field with a suitably tailored, spatially-varying polarization distribution. We describe how four or more parameters can be measured and distinguished with an accuracy consistent with the needs laid out in the semiconductor roadmap.

First claim

We claim:

1. A focused beam scatterometry method for characterizing an object having a periodic or quasi-periodic structure and one or more process errors, comprising:
selecting a predictive scattering model for a perfectly specified test target of the object for providing predictive data;
identifying one or more process error parameters of the object to be characterized;
providing a focused light field input having at least a spatially varying polarization distribution over the field that will yield a particular functional form output for a respective one of the process errors, given a known polarization output analyzer;
illuminating the object or a test target of the object with the input light field;
collecting light scattered/reflected from the object or the test target of the object as measured data; and
characterizing each of the identified one or more process error parameters in a single measurement by comparing the measured data with the predictive data.

2. The method of claim 1 , wherein the one or more process error parameters include a process error and a measurement range.

3. The method of claim 1 , further comprising selecting the spatially varying polarization distribution of the input light field that will yield a particular functional form output for at least two respective ones of the process errors.

4. The method of claim 1 , further comprising selecting the spatially varying polarization of the input light field that will yield a particular functional form output for at least four respective ones of the process errors.

5. The method of claim 1 , wherein the one or more process error parameters are selected from a group consisting of an etch depth, a side wall angle, a coating thickness, a coating composition, a line edge roughness, and a critical dimension of the object.

6. The method of claim 1 , wherein at least one of the one or more process error parameters has a scale less than 1000 nanometers.

7. The method of claim 6 , wherein the at least one of the one or more process error parameters has a scale less than 22 nanometers.

8. The method of claim 1 , wherein the input light field is in the form of a single focused beam comprising an ensemble of plane waves.

9. The method of claim 8 , wherein each of the plane waves has an intensity, a polarization, and a phase characteristic, further wherein at least some of the waves' characteristics are different than at least some others of the waves' characteristics.

10. The method of claim 1 , wherein collecting the light scattered/reflected from the object or the test target of the object comprises measuring an irradiance distribution of the scattered/reflected light over an exit pupil of a measurement system used for the measurement.

11. The method of claim 1 , wherein the object is a semiconductor fabrication.

12. The method of claim 11 , wherein the object is a Fin FET device.

13. The method of claim 1 , further comprising collecting the measured data using an off-null methodology.

14. The method of claim 13 , wherein the off-nulling conditions for the parameters are varied over the pupil of the system, such that the final irradiance distributions have shapes from which the error parameters can be inferred.

15. A focused beam scatterometry system for characterizing an object having a periodic or quasi-periodic structure and one or more process errors, comprising:
an input light field polarization coding component;
a focusing component for focusing the input light field on an object to be characterized, disposed in an optical path of the polarization coding component;
a polarization analyzer component disposed to receive the input light field scattered/reflected from the object to be characterized; and
a detector disposed to receive an output from the polarization analyzer.

16. The system of claim 15 , wherein the input light field polarization coding component is a spatial light modulator (SLM).

17. The system of claim 15 , wherein the polarization analyzer component is one of a linear polarizer and a circular polarizer.

18. The system of claim 15 , comprising an off-null configuration.

Assignees

• Alonso Miguel A
• Head Stephen
• Theisen Michael
• Brown Thomas
• Univ Rochester

Inventors

• Alonso Miguel A
• Head Stephen
• Theisen Michael
• Brown Thomas

Classifications

• H10P74/203 Primary

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• G01B2210/56

  Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth · CPC title

• G03F7/70625

  Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness · CPC title

• G01N21/21

  Polarisation-affecting properties (G01N21/19 takes precedence) · CPC title

• G01B11/02

  for measuring length, width or thickness (G01B11/08 takes precedence) · CPC title