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