Measuring semiconductor device features using stepwise optical metrology

Patent metadata

Field	Value
Publication number	US-9482519-B2
Application number	US-201414560518-A
Country	US
Kind code	B2
Filing date	Dec 4, 2014
Priority date	Dec 4, 2014
Publication date	Nov 1, 2016
Grant date	Nov 1, 2016

Abstract

The present invention relates generally to metrology, and more particularly, to an apparatus and method of measuring multiple parameters of a structure or feature of a semiconductor device using a combination of stepwise optical metrology and a linear system of equations to generate an output as function of position. In an embodiment, a light beam having a width greater than the features to be measured may be shined on a first area of the semiconductor device to calculate a first average. The light beam may then be shined on a second area that overlaps the first area by at least one individual feature to calculate a second average. The averages may be entered into a system of linear equations which may then be solved to calculate an overall average.

First claim

What is claimed is:

1. A method of measuring an average characteristic of features on a semiconductor structure comprising:
projecting a light beam onto the features in a first area;
collecting a first reflected light beam from the first area, wherein the first reflected light beam is the projected light beam after it has reflected off the features in the first area;
converting the first reflected light beam into first data;
projecting the light beam onto the features in a second area, wherein the second area overlaps with the first area by at least one individual feature;
collecting a second reflected light beam from the second area, wherein the second reflected light beam is the projected light beam after it has reflected off the features in the second area;
converting the second reflected light beam into second data;
performing analysis of the first data and second data to determine an overall average value;
comparing the overall average value to a predetermined desired value; and
discarding the semiconductor structure if the overall value differs from the desired value by a predetermined amount.

2. The method of claim 1 , wherein the light beam has a width that is larger than a width of the individual features.

3. The method of claim 1 , wherein the analysis comprises:
setting up a first linear equation comprising a first weighted average of the characteristic of the features in each of the first area;
setting up a second linear equation comprising a second weighted average of the characteristic of the features in each of the first area;
combining the first linear equation and the second linear equation into a system of equations; and
solving the system of equations.

4. The method of claim 3 , wherein the system of equations comprises a linear equation Ax=y, wherein A∈R (m*n) , m is the number of areas, n=p+m−1, p is the number of pitches overall, x is a vector with the characteristic in each area, y is the weighted average in each area, and A is a semi-circulant matrix with only p unique elements,

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)

.

5. The method of claim 1 , wherein the projecting the light beam onto the features in the second area comprises moving the light beam by approximately 1 pitch of the features.

6. The method of claim 1 , wherein the projecting the light beam onto the features in the second area comprises moving the semiconductor structure by approximately 1 pitch of the features.

7. A non-transitory computer program product for measuring an average characteristic of features on a semiconductor structure, the computer program product comprising a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising:
projecting a light beam onto the features in a first area;
collecting a first reflected light beam from the first area, wherein the first reflected light beam is the projected light beam after it has reflected off the features in the first area;
converting the first reflected light beam into first data;
projecting the light beam onto the features in a second area, wherein the second area overlaps with the first area by at least one individual feature;
collecting a second reflected light beam from the second area, wherein the second reflected light beam is the light beam after it has reflected off the features in the second area;
converting the second reflected light beam into second data;
performing analysis of the first data and second data to determine an overall average value;
comparing the overall average value to a predetermined desired value; and
discarding the semiconductor structure if the overall value differs from the desired value by a predetermined amount.

8. The non-transitory computer program product of claim 7 , wherein the light beam has a width that is larger than a width of the individual features.

9. The non-transitory computer program product of claim 7 , wherein the analysis comprises:
setting up a first linear equation comprising a first weighted average of the characteristic of the features in each of the first area;
setting up a second linear equation comprising a second weighted average of the characteristic of the features in each of the first area;
combining the first linear equation and the second linear equation into a system of equations; and
solving the system of equations.

10. The non-transitory computer program product of claim 9 , wherein the system of equations comprises a linear equation Ax=y, wherein A∈R (m*n) , m is the number of areas, n=p+m−1, p is the number of pitches overall, x is a vector with the characteristic in each area, y is the weighted average in each area, and A is a semi-circulant matrix with only p unique elements,

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Assignees

• IBM
• Globalfoundries Inc

Inventors

• Zhang Yunlin

Classifications

• H10P74/203

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

• G01N21/4738

  Diffuse reflection (precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration), e.g. also for testing fluids, fibrous materials · CPC title

• G01N2201/12

  Circuits of general importance; Signal processing · CPC title

• G01B11/14 Primary

  for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) · CPC title

• G01B11/02 Primary

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