Post on 10-Jan-2017
Mountain View, California
Beaverton, Oregon
High-Speed Quantum Efficiency Measurements in Research and Manufacturing
Quantum EfficiencyQuantum Efficiency
ARC
Si
ARC thicknessFront Surface QualityBulk LifetimeBack Surface Quality
Silicon
ZnO
CdS
CIGS
Same Info, plus:
CdS thicknessCIGS bandgap
CIGS
( ) ( ) λλλ dSQEitop •= ∫ ∫= ...bottomi=?
Same Info, plus:
Cell Current Matching
Multijunction
Traditional QE Machines
1 in 100,000
$$$$
.
Filter Wheel Brightness Filter Degradation
Monochromator
Strength Weakness
Resolution Brightness
1:100,000
Typical measurement time: ~5 minutes
4
FlashQE Development History
Young et al
Prototype
2005 2008 2011 2014
Commercial Dev
Tau Science
FlashQE- Technology
• All wavelengths measured simultaneously• Solid State lightsource >20,000 hr lifetime• Active feedback
Typical Measurement Time: ~1 second~1 second~1 second~1 secondTypical Measurement Time: ~1 second~1 second~1 second~1 second
Cell Current = f(λ1, λ2, …)Cell Current = f(λ1, λ2, …)Cell Current = f(λ1, λ2, …)Solid State Lightsource:
FlashQE Configurations: Mapping
•Small Spot Configuration•Throughput:
•40 sites/minute
•Chuck:•Cell•Mini-module
•Options:•Light Bias•Reflectance•Transmittance
R&D Applications
FlashQE Configurations: Full Cell
Module for In-Line Integration
•Cell sort•Spectral Binning•Eliminate Spectral Mismatch Correction•SPC
•Emitter•BSF•ARC•BARC…
Example: Stability Test on c-Si
Measurement Time: 9 hours– 32,000 Repeats
6-σ <1%
Full Cell
Example: Temperature Coeff: QE(λ,Τ)
As Temp rises…Bandgap narrows (Varshni Equation)
�QE increases near gapλ (IR)
∆QE/∆T
λ (IR)(UV )
Result (1st order):
+More complex behaviorSurf Recomb, Trapping
λ (UV)
Overlayer (Nitride) absorption redshifts�QE decreases in UV
Example: QE Temp Coefficient
60 second measurement: warm sample from 25-43C
Example: Light Induced Degradation, c-Si
EQE #1 EQE #21 sec 6 hr 1 sec
Depth info
Si
Light Soak
: #2- #1=∆EQE
∆E
QE
(%
)
λ=390 nm
QE Mapping: c-Si Cell
In UV, ~7% QE Enhancement at wafer edge
Absorption Depth: 0.1 micron
PixELTM
13
Near Term Challenges (1-3 yrs)
Improve Metrology “Time to Information”
R&D, QA labs• Shorten turnaround time of standard
techniques.LBIC, QE, Impurity Imaging…
• Workflow optimization
Manufacturing• Detect specific defect types
Hotspots, µ−cracks • SPC info to improve η
Higher Speed is Needed
Problem: Wafer handling bottleneck in R&D, QA labs
QE
LBIC
Hot-spot
PL
EL
Hours
Minutes
Minutes
10’s of Minutes
…Hours of elapsed time…
Minutes
Tau Science
Solution: Multipurpose Tools
Tau Science
Hotspot: 400ms PL: 100ms
MP LBIC: Minutes FlashQE: 1sec
Complete in seconds-minutes.
16
Long Term Challenges (>3 yrs)
Continuing challenge of “Time to Information”>3000 wph…
Machine Interface Standardization• Mechanical• FA / MES communication protocols
Balance Complexity vs. Cost
Tau Science
Tau Science