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Virtual metrology for chemical mechanical planarization of semiconductor wafers

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Abstract

Chemical mechanical planarization (CMP) is an important operation for surface modification of wafers in semiconductor manufacturing. Productivity and quality of wafers depends strongly on the efficiency of CMP and virtual metrology (VM) is a promising tool not only to facilitate wafer-to-wafer control but also to reduce cycle time. Development of VM tools for CMP is still not a reality due to the complexity of CMP and unavailability of critical process measurements such as slurry temperature and abrasive particle size distribution in real-time. To overcome these challenges, a novel hybrid modeling framework is proposed for creating a VM solution for CMP. Physics-based models are utilized for estimating slurry temperature and mean abrasive particle size (MAPS) from sensor data. They supplement other sensor data for developing soft sensors to predict slurry temperature, MAPS, and the material removal rate (MRR). This hybrid framework is tested with about 3000 sets of published industrial sensor data. Exploratory analysis indicated two distinct regimes of operation, low and high MRR, and a strong relationship of MRR with slurry temperature and MAPS. Several machine learning (ML) algorithms such as random forest, Lasso regression and support vector machine are explored and XGBoost is found to be the best amongst them. The optimum operating conditions are determined through model-based optimization using the hybrid modeling framework and particle swarm optimization. These results suggested CMP to be carried out at the smallest MAPS to maximize MRR. This framework would be useful for building a digital twin system of CMP.

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Data availability

The raw data of the CMP process used for analysis, model development and process optimization are provided by the PHM data challenge, 2016 (PHM Society, 2016). This data is in public domain (PHM Society, 2016). The preprocessed or the clean data is available with the authors and can be made available to the requestor based on qualified request.

Abbreviations

abs max :

Maximum value of particle size (µm)

abs min :

Minimum value of particle size (µm)

abs n :

Normalized MAPS

AI:

Artificial intelligence

AUC:

Area under curve

BEOL:

Back end of line

CFD:

Computational fluid dynamics

CLC:

Closed loop control

d j :

Disturbance variable

DBN:

Deep belief networks

DDMs:

Data driven models

DEM:

Discrete element method

E comb :

Combined activation energy (J/mol)

ERT:

Extremely Randomized trees

f :

Function of decision/disturbance variable

FEOL:

Front end of line

GBT:

Gradient boosting trees

IMM:

Integrated metrology module

k :

Thermal independent constant

KNN:

K-nearest neighbors

KPI:

Key performance indicators

L2L:

Lot to lot

l i :

Lower bounds of decision variable

LSTM:

Long short-term memory

MAE:

Mean absolute error

MAPS:

Mean absolute particle size

ML:

Machine learning

MRR:

Material removal rate

MSE:

Mean square error

MTGP:

Multi task gaussian process

n i :

Number of feature selection methods that selected ith feature

P :

Pressure applied on the wafer (Pa)

PBMs:

Physics based models

PSO:

Particle swarm optimization

R :

Universal gas constant (J/mol. K)

R2 :

Coefficient of regression

R i ,k :

Rank of the feature i

RMSE:

Root means square error

SAM:

Stand-alone metrology module

SVM:

Support vector machines

t :

Number of dimensional spaces

T :

Slurry temperature (K)

T max :

Maximum temperature (K)

T min :

Minimum temperature (K)

T n :

Normalized temperature

u i :

Upper bounds of decision variable

U :

Relative velocity (m/s)

v j :

Velocity of the particle

VM:

Virtual metrology

W2W:

Wafer to wafer

x i :

Decision variable

x j :

Position of the particle

References

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Acknowledgements

The authors thank the management of Tata Consultancy Services for the permission to publish this paper, and Mr. K. Ananth Krishnan, Dr. Harrick Vin and Dr. Gautam Shroff for their encouragement and support.

Funding

This study was funded by the Tata Consultancy Services Limited.

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Authors and Affiliations

Authors

Contributions

Conceptualization: NKVN, VR; Data curation: BD; Formal Analysis and Investigation: BD, VSM; Methodology: VSM, NKVN; Supervision: VR; Validation: BD, VSM; Visualization: BD, VSM; Writing – original draft: BD; Writing – review & editing: VSM, NKVN, VR.

Corresponding author

Correspondence to Venkataramana Runkana.

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All authors declare that there are no competing financial or non-financial interests.

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Deivendran, B., Masampally, V.S., Nadimpalli, N.R.V. et al. Virtual metrology for chemical mechanical planarization of semiconductor wafers. J Intell Manuf (2024). https://doi.org/10.1007/s10845-024-02335-0

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  • DOI: https://doi.org/10.1007/s10845-024-02335-0

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