1. Process Recipe Optimization using Calibrated Simulation Engine
SFR Workshop
November 8, 1999
Junwei Bao, Nickhil Jakatdar, Costas Spanos
Berkeley, CA
The goal of this work is to calibrate the lithography simulation engine by accurately extracting the model parameters, and optimize process recipe to obtain a maximum yield.
2/28/2019

2. Motivation
Current lithography simulators are parameter limited as opposed to model limited.
Importance of predictive capabilities is increasing with increasing development costs and time-to-market pressures.
Process recipe needs to be optimized considering the effect of parameter variations.
2/28/2019

3. Moving the Process Development from Real World to Virtual World
(Lithography
Equipment)
Process Inputs
(temp.,time,dose)
Process
Output
Process Inputs
Virtual World
(Process
Models)
Model
Coefficients
Simulated
Output
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4. Parameter Extraction and Recipe Optimization Framework
Experiment
Data
Spatial
variation filter
Param. & op.
point variance
Param. mean
values
Calibrated
Sim. Eng.
Target Specs.
of features
Recipe of
max. yield
In-line sensor
measurement
Maximization of overlapping area
2/28/2019

5. Parameter Extraction -- Unpatterned Experiments1 .5
Deprotection
140C
135C
120C
110C
Exposure
+ PEB
Parameters
Exposure Dose (mJ/cm2)
3000
2000
Develop
Parameters
Develop Rate in A/sec
1000
Normalized concentration of unreacted sites
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6. Parameter Extraction -- Patterned Experiments
Mask 1
Mask 2
Mask 3
Mask 4
Mask 5
Mask 6
Mask 7
Mask 8
Mask 9
Mask 10
Masks 1-10 differ in
the line-space ratios
0.25 micron process
technology
OPC assisted masks
-1 Focus +1
-1 Focus +1
AFM vs Simulation
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7. Recipe Optimization Framework
Process
Inputs
Calibrated
Lithography
Simulator
Simulated
Output
Target Profile + -
RECIPE
OPTIMIZER
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8. Recipe Optimization 2/28/2019 Resist Th : 655 nm
Exposure : 18.3 mJ/cm2
Focus : mm
PEB temp : 126oC
PEB time : 80 secs
Develop time : 80 secs
2/28/2019

9. Future Work -- Recipe Optimization with Variations
Parameter
distributions
In-die spatial
variation
Simulated
Output distributions
Profiles
within spec.
Calibrated
Lithography
Simulator
Operating Point
distributions + -
Overlapping to get yield
RECIPE
OPTIMIZER
2/28/2019