Measurement system optimization for X-ray based metrology

Patent metadata

Field	Value
Publication number	US-10324050-B2
Application number	US-201614994817-A
Country	US
Kind code	B2
Filing date	Jan 13, 2016
Priority date	Jan 14, 2015
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

Methods and systems for optimizing measurement system parameter settings of an x-ray based metrology system are presented. X-ray based metrology systems employing an optimized set of measurement system parameters are used to measure structural, material, and process characteristics associated with different semiconductor fabrication processes with greater precision and accuracy. In one aspect, a set of values of one or more machine parameters that specify a measurement scenario is refined based at least in part on a sensitivity of measurement data to a previous set of values of the one or more machine parameters. The refinement of the values of the machine parameters is performed to maximize precision, maximize accuracy, minimize correlation between parameters of interest, or any combination thereof. Refinement of the machine parameter values that specify a measurement scenario can be used to optimize the measurement recipe to reduce measurement time and increase measurement precision and accuracy.

First claim

What is claimed is:

1. A method comprising:
providing a first amount of x-ray radiation to one or more target structures on a surface of a semiconductor wafer from an x-ray illumination source of an x-ray based metrology system;
detecting an amount of radiation from each of the one or more target structures in response to the first amount of x-ray radiation on a detector of the x-ray based metrology system;
generating a first amount of x-ray measurement data based on the detected amount of x-ray radiation, wherein the first amount of x-ray measurement data is associated with measurements performed by the x-ray based metrology system in a first measurement configuration characterized by a first set of values of one or more machine parameters;
determining a second set of values of the one or more machine parameters based at least in part on a parametric sensitivity and noise characteristics of the first amount of measurement data associated with the measurements of the one or more target structures by the x-ray based metrology system at the first set of values of the one or more machine parameters; and communicating the second set of values of the one or more machine parameters to the x-ray based metrology system: and
adjusting the x-ray based metrology system from the first measurement configuration to a second measurement configuration based on the second set of values of the one or more machine parameters;
wherein rotational and linear actuators are configured to measure a location of one or more targets over any number of angular increments with respect to a normal orientation of the one or more targets.

2. The method of claim 1 , further comprising:
receiving a second amount of x-ray measurement data associated with measurements of the one or more target structures by the x-ray based metrology system in the second measurement configuration including the second set of values of the one or more machine parameters;
determining a third set of values of the one or more machine parameters based at least in part on a sensitivity of the second amount of measurement data associated with measurements of the target structure by the x-ray based metrology system on the second set of values of one or more machine parameters; and
communicating the third set of values of the one or more machine parameters to the x-ray based metrology system.

3. The method of claim 1 , further comprising:
determining a measurement model of the one or more target structures that relates values of one or more parameters of interest and the first set of values of the one or more machine parameters to the first amount of x-ray measurement data;
performing a regression of the first amount of measurement data on the measurement model to determine estimated values of the one or more parameters of interest;
receiving an indication of reference values of the one or more parameters of interest;
determining a difference between the estimated values of the one or more parameter values and the reference values of the one or more parameters of interest exceeds a threshold value; and
storing the first set of values of the one or more machine parameters in a memory if the difference between the estimated values of the one or more parameter values and the reference values of the one or more parameters of interest does not exceed a predetermined threshold value.

4. The method of claim 1 , wherein the first set of parameters includes at least one of an angle of incidence, an azimuth angle, a beam photon energy, a measurement duration, a beam divergence, an illumination spot size, and a detector location.

5. The method of claim 1 , wherein the determining of the second set of values of the one or more machine parameters involves:
determining a measurement model of the one or more target structures that relates values of one or more parameters of interest and the first set of values of the one or more machine parameters to the first amount of x-ray measurement data; and
determining the second set of values of the one or more machine parameters based on an optimization that involves a minimization of a statistical measure of the values of the one or more parameters of interest subject to a constraint on measurement duration.

6. The method of claim 5 , wherein the statistical measure is indicative of the variance or covariance of the values of the one or more parameters of interest.

7. The method of claim 2 , wherein the determining of the second set of values of the one or more machine parameters involves:
determining a model that relates the first set of values of the one or more machine parameters to the first amount of measurement data; and
determining the second set of values of the one or more machine parameters such that one or more signals of the second amount of measurement data converges toward a minimum or maximum value.

8. The method of claim 7 , wherein the model that relates the first set of values of the one or more machine parameters to the first amount of measurement data is a stoichastic filter.

9. The method of claim 1 , wherein the first amount of x-ray measurement data associated with measurements of the one or more target structures by the x-ray based metrology system is generated by simulation.

10. The method of claim 5 , further comprising:
reducing a number of floating parameters of the measurement model of the one or more target structures that relates values of the one or more parameters of interest and the first set of values of the one or more machine parameters to the first amount of x-ray measurement data.

11. The method of claim 10 , wherein the reducing the number of floating parameters involves any of a constraint equation defining a relationship between two or more parameters, a correlation matrix defining the relationship between two or more parameters, and a set of expected profiles selected by a user.

12. An x-ray based metrology system, comprising:
an x-ray illumination source providing x-ray illumination incident onto a specimen under measurement;
an x-ray detector collecting an amount of x-ray radiation diffracted or scattered from the specimen in response to the incident x-ray illumination; and a computing system configured to:
receive a first amount of x-ray measurement data associated with measurements of one or more target structures on the specimen by the x-ray based metrology system in a first measurement configuration characterized by a first set of values of one or more machine parameters;
determine a second set of values of the one or more machine parameters based at least in part on a parametric sensitivity and noise characteristics of the first amount of measurement data associated with measurements of the target structure by the x-ray based metrology system on the first set of values of one or more machine parameters: and
communicate the second set of values of the one or more machine parameters to the x-ray based metrology system, wherein the x-ray based metrology system adjusts from the first measurement configuration to a second measurement configuration based on the second set of values of the one or more machine parameters;
wherein rotational and linear actuators are configured to measure a location of the specimen over any number of angular increments with respect to a normal orientation of the specimen.

13. The x-ray based metrology system of claim 12 , wherein the computing system is further configured to:
receive a second amount of x-ray measurement data associated with measurements of the one or more target structures by the x-ray based metrology system in a second measurement configuration including the second set of valu

Assignees

• Kla Tencor Corp

Inventors

• Hench John J
• Shchegrov Andrei V
• Bakeman Michael S

Classifications

• G01N23/20008 Primary

  Constructional details of analysers, e.g. characterised by X-ray source, detector or optical system; Accessories therefor; Preparing specimens therefor (monochromators for X- rays using crystals G21K1/06) · CPC title

• G01N2021/0137

  with PC or the like · CPC title

• G01N21/01

  Arrangements or apparatus for facilitating the optical investigation · CPC title