Model-based hot spot monitoring

Patent metadata

Field	Value
Publication number	US-10030965-B2
Application number	US-201615148116-A
Country	US
Kind code	B2
Filing date	May 6, 2016
Priority date	May 8, 2015
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

Methods and systems for monitoring parameters characterizing a set of hot spot structures fabricated at different locations on a semiconductor wafer are presented herein. The hot spot structures are device structures that exhibit sensitivity to process variations and give rise to limitations on permissible process variations that must be enforced to prevent device failures and low yield. A trained hot spot measurement model is employed to receive measurement data generated by one or more metrology systems at one or more metrology targets and directly determine values of one or more hot spot parameters. The hot spot measurement model is trained to establish a functional relationship between one or more characteristics of a hot spot structure under consideration and corresponding measurement data associated with measurements of at least one metrology target on the same wafer. A fabrication process parameter is adjusted based on the value of a measured hot spot parameter.

First claim

What is claimed is:

1. A measurement system comprising:
an illumination source configured to illuminate each of a plurality of metrology targets disposed a first plurality of locations on a wafer, the wafer also including a plurality of hot spot structures at a second plurality of locations on the wafer that are different from the first plurality of locations, the wafer being illuminated by the illumination source after an intermediate process step of a semiconductor wafer fabrication sequence;
a detector configured to detect an amount of light from each of the plurality of metrology targets in response to the illuminating of each of the plurality of metrology targets and generate an amount of measurement data based on the detected amounts of light; and
a computing system configured to:
determine a value of at least one parameter characterizing a hot spot structure of the plurality of hot spot structures based on the amount of measurement data and a trained hot spot measurement model; and
communicate a signal to a process tool that causes the process tool to adjust a process parameter associated with a fabrication process step of the semiconductor wafer fabrication sequence based on the value of the at least one parameter characterizing the hot spot structure.

2. The measurement system of claim 1 , wherein the computing system is further configured to:
receive an indication of the plurality of hot spot structures at the second plurality of locations on the wafer;
receive an indication of the plurality of metrology targets at the first plurality of locations on the wafer;
receive an indication of a process window associated with one or more process parameters associated with any process step prior to and including the intermediate process step;
estimate a value of the at least one parameter characterizing the hot spot structure at each of a plurality of process points within the process window;
determine an amount of measurement data associated with a measurement of each of the plurality of metrology targets at each of the plurality of process points within the process window; and
train the hot spot measurement model based on the estimated value of the at least one parameter characterizing the hot spot structure at each of a plurality of process points within the process window and the amount of measurement data.

3. The measurement system of claim 2 , wherein the estimating of the value of the at least one parameter characterizing the hot spot structure involves a simulation of a semiconductor fabrication model calibrated for the hot spot structure.

4. The measurement system of claim 2 , wherein the estimating of the value of the at least one parameter characterizing the hot spot structure involves a measurement by a reference metrology system of the at least one parameter characterizing the hot spot structure repeatedly fabricated at each of a plurality of process points within the process window.

5. The measurement system of claim 2 , wherein the one or more process parameters associated with the intermediate process step include lithography focus and lithography dosage.

6. The measurement system of claim 2 , wherein the determining of the amount of measurement data associated with the measurement of each of the plurality of metrology targets involves a measurement of the plurality of metrology targets repeatedly fabricated at each of the plurality of process points within the process window.

7. The measurement system of claim 2 , further comprising:
estimating a value of one or more parameters characterizing each of the plurality of metrology targets at each of the plurality of process points within the process window by a simulation of a semiconductor fabrication model, and wherein the determining the amount of measurement data associated with the measurement of each of the plurality of metrology targets is based on a simulation of a metrology target measurement model characterizing the measurement of each of the plurality of metrology targets by the measurement system at the value of the one or more parameters characterizing each of the plurality of metrology targets.

8. The measurement system of claim 1 , wherein the plurality of hot spot structures include relatively dense structures and relatively isolated structures.

9. The measurement system of claim 1 , wherein at least one of the plurality of metrology targets is an actual device structure.

10. The measurement system of claim 9 , wherein the plurality of metrology targets includes any of a line-space grating, a FinFET structure, a SRAM device structure, a Flash structure, and a DRAM memory structure.

11. The measurement system of claim 1 , wherein the hot spot measurement model is any of a linear model, a non-linear model, a polynomial model, a neural network model, a support vector machines model, a decision tree model, and a random forest model.

12. The measurement system of claim 1 , wherein the plurality of metrology targets and the plurality of hot spot targets are the same type of structure.

13. The measurement system of claim 1 , wherein the illuminating of each of the plurality of metrology targets and the detecting of the amount of light from each of the plurality of metrology targets includes measurements acquired by a plurality of different metrology techniques.

14. A measurement system comprising:
an illumination source configured to illuminate each of a plurality of metrology targets disposed a first plurality of locations on a wafer, the wafer also including a plurality of hot spot structures at a second plurality of locations on the wafer that are different from the first plurality of locations, the wafer being illuminated by the illumination source after an intermediate process step of a semiconductor wafer fabrication sequence;
a detector configured to detect an amount of light from each of the plurality of metrology targets in response to the illuminating of each of the plurality of metrology targets and generate an amount of measurement data based on the detected amounts of light; and
a non-transitory computer readable medium storing an amount of program code that when executed by a computing system causes the computing system to:
determine a value of at least one parameter characterizing a hot spot structure of the plurality of hot spot structures based on the amount of measurement data and a trained hot spot measurement model; and
communicate a signal to a process tool that causes the process tool to adjust a process parameter associated with a fabrication process step of the semiconductor wafer fabrication sequence based on the value of the at least one parameter characterizing the hot spot structure.

15. The measurement system of claim 14 , wherein the amount of program code further causes the computing system to:
receive an indication of the plurality of hot spot structures at the second plurality of locations on the wafer;
receive an indication of the plurality of metrology targets at the first plurality of locations on the wafer;
receive an indication of a process window associated with one or more process parameters associated with any process step prior to and including the intermediate process step;
estimate a value of the at least one parameter characterizing the hot spot structure at each of a plurality of process points within the process window;
determine an amount of measurement data associated with a measurement of each of the plurality of metrology targets at each of the plurality of process points within the process window; and
train the hot spot measurement model based on the estimated value of the

Assignees

• Kla Tencor Corp

Inventors

• Pandev Stilian Ivanov
• Kapasi Sanjay
• Smith Mark D
• Levy Ady

Classifications

• H10P74/203 Primary

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

• H10P74/23

  characterised by multiple measurements, corrections, marking or sorting processes · CPC title

• G01B11/00 Primary

  Measuring arrangements characterised by the use of optical techniques · CPC title

• H01L22/12

  Electricity · mapped topic

• H01L22/20

  Electricity · mapped topic