screen printing – the proven, low risk, fast path to se … · 2011. 9. 28. · screens yield...

Applied Materials External Use

SELECTIVE EMITTER (SE) TECHNOLOGY WEBCAST

Screen Printing – The Proven, Low Risk, Fast Path to SE Implementation

Wednesday, Sept 28, 2011


Selective Emitter – Increasing CellEfficiency to Drive Down Cost Per Watt

Charlie GayPresident – Solar


Solar PV MissionLowering the Cost of Electricity

To accelerate global PV adoption by delivering cost effective solutions that integrate technology, equipment and

materials which improve factory productivityand increase cell efficiency.

Increasing Efficiency

ReducingMaterial Cost

Improving Productivity

InstalledCost Per Watt

MfgCost Per

Area

WattsPer

Area

From productivity

=

SYSTEMSYSTEM MODULEMODULE BOSBOS

+ BOSOther

Balance of System

Cost PerArea +WattsPer

Area

From efficiency From efficiency

3


100

110010-110-210-310-4 101 102 103

Cumulative Installations (GW)

Aver

age

Mod

ule

Sale

s Pr

ice

($/W

)

Avg. Module PricePV Learning CurveBOSSystem Price

10

Efficiency increase and cost reduction must now happen simultaneously

Scale is No Longer Enough

4

Source: Navigant Consulting


Crystalline Silicon Technology Roadmap

Conventional Cell

20112010

Screens

Yield

Precision Screens

DoublePrint (DP)

Selective Emitter (SE)

Shallow Emitter

MAP™ Yield Metrology

Front / Back Contact

2-Side Passivation

Optimal Light

Trapping

Back Contact

2012E

GEN 1 GEN 1.5 GEN 2

Mod

ule

Effic

ienc

y (%

)

5

Source: Applied Materials


What is Selective Emitter?

Homogeneous emitter region requires compromise

Good junction performance

Low resistance to the front silver grid

6

Standard Cell Selective Emitter Cell

Si

N+

P-type

SiNAg

N+SiN

Ag

SiP-type

N++

Selective emitter decouples the regions

Lower dopant concentrations of the field region help reduce recombination

Higher dopant concentration emitter improves ohmic contact


Selective Emitter Modeling

7

V oc

* Jsc

(mW

/cm

2 )

Electrically Active Surface Dopant

Cel

l Effi

cien

cy

Ns (cm-3)

SE Design Space

65

80

95

110

Rsheet (Ω/)

0.4 to 0.7%

Conventional Cell

Practical Efficiency Gain

Between 0.4 – 0.7% Achievable

Source: Applied Solar R&D

Diffused emitter conventional cell with peak doping Ns at surface

23

23.1

23.2

23.3

23.4

23.5

23.6

23.7

0.0E+00 5.0E+19 1.0E+20 1.5E+20 2.0E+20 2.5E+20 3.0E+20 3.5E+20


Selective Emitter Formation

Hari PonnekantiVice President Solar Product Development


Selective Emitter Formation: Approaches

9

New SE Steps

Conventional Cell Steps

Printed SE

P-Diffusion

PSG Etch

Passivation

Front Metal

Back Metal

Co-Firing

SCREEN PRINTED SE

Mask Formation

PSG Etch

Passivation

Front Metal

Back Metal

Co-Firing

PSG & Emitter Etch Back

Strip

P-Diffusion

ETCH BACK

Laser Doping

P-Diffusion

PSG Etch

Passivation

Front Metal

Back Metal

Co-Firing

LASERDOPING

Masked Implantation

Passivation

Front Metal

Back Metal

Co-Firing

Oxidation Anneal

Blanket Implantation

IONIMPLANTATION

PSG – Phosphorous Silicate Glass


Why Screen Printing?

Production proven

Availability of standard equipment

Low risk

Quick and easy implementation

Minimal number of additional steps

Upgrade available for existing lines

High accuracy metallization

10


Straight forward Implementation

with Proven Screen Printing

Technology

Printed SE: Process Approach

11

Single step diffusion process

SE region formed

Screen printed

on wafer

P-Glass removal and anti-reflective coating deposited

Wafer ready for metallization


Applied Baccini® Screen Printers for SE Low wafer breakage

Low metal contamination pre-diffusion solutions

Extendable and upgradableflexible platform

Adaptable to mono- and multi-crystalline silicon

Common platform design for SE formation and metallization reduces variables for optimal cell performance and binning

12

Excellence in Screen Printing

High Precision Printing and Soft Handling for Advanced Cells


Printable SE Solution: Hardware Applied Baccini Soft Line printer for screen printing SE paste

– Non-metal screen– Precision squeegee and flood bar prevent SE paste contamination– Soft wafer handling with <0.1% breakage rate generates greater cost savings

Soft Line oven with non-metal contact for drying SE paste

Extendable and flexible platform – easy conversion to metallization or future applications

13

Add one printer & dryer to existing line

Standard Equipment, Simple Integration


Integration Requirements for Implementation

14

Compatibility with customer line Optimization of cell design and processes

Emitter

Passivation

Metallization

Cell Design

SE Integration Services from Applied Materials


SE Implementation: Device Design

15

Grid Design • Finger spacing for optimum FF and reduced shading• Number of fingers optimized for high emitter Rsheet

EmitterEngineering

• N++ for low contact resistance • N+ deep diffusion for improved blue response

SE Line Width • Line width for alignment tolerances and minimum shading losses• Screen opening optimization for printed SE line width

SiNAg

Si

N++N+

Ag

N++

SE line width≤ 250 µmP-type

Si

Finger Spacing1.9-2.3mm

Ag Line ≤ 100 µm

Selective Emitter

Cell Design


Failure to optimize diffusion for field emitter as well as the selective emitter results in low cell efficiency

SE Implementation: Diffusion

16

Emitter diffusion is crucial for high efficiency cell manufacturing

Optimization for blue response– Low surface concentration– Approximately 100 Ω/sq.

Under the finger higher doping to give lower sheet resistance – Approximately 65 Ω/sq.

Selective Emitter Cell

N+SiN

Ag

SiP-type

N++

65Ω/sq. 100Ω/sq

Target Jo 50-70 fA/cm2

Emitter saturation current density after

development of diffusion


Diffusion Challenges

17

Emitter diffusion is crucial for high efficiency cell manufacturing– Limited thermal budget

on multi c-Si

Optimization of the field emitter– Tuned to maximize blue response– Address needs of the highly

doped emitter region• Achieve ohmic contact• High fill factor

50

60

70

80

90

100

110

300 400 500 600 700 800 900 1000 1100

Baseline

Selective Emitter Diff. 1

Selective Emitter Diff. 2

Wavelength, nm

IQE,

%

Internal Quantum Efficiency

Source: Applied Solar R&D, Mono c-Si

Failure to optimize diffusionresults in low current and voltage with poor fill factor


SE Implementation: Front Side SiN

18

Low reflectivity is a critical requirement to maximize cell efficiency

SE gains for Isc and Vocwill be less if passivation is not optimized

Optimized passivation thickness

– Thin for fill factor and ohmic contact

Refractive index 2.05-2.10

Average Weighted Reflectivity

0

5

10

15

20

25

30

360 560 760 960

Refle

ctivity, %

Wavelength, nm

Opt SiNxUnopt SiNx

Failure to optimize passivation for reflectivity results in lack of full SE gain in integrated cell.

Source: Applied Solar R&D, Mono c-Si


Selective Emitter MetallizationAndrea MorettoGlobal Product ManagerApplied Baccini Cell Systems


Metallization Criteria Precise alignment is critical to maximize efficiency gains from SE Sub-optimal alignment can cause high contact resistance and poor

shunting behavior Challenges to high accuracy metallization

– Difficult to see / invisible SE patterns after anti-reflection coating– Perfect alignment and printing on top of SE pattern– Fine line printing

20

Pattern-based Alignment for Very High Accuracy and Alignment Repeatability

Advanced vision system detects

SE patternSoftware algorithms translate SE position

Metal is printed accurately and precisely

over SE region


Applied Baccini® Esatto Technology™Difficult to see SE As seen by Esatto

21

Advanced Vision System for Pattern Detection


Laser Doping Mono c-Si Laser Doping Mono c-Si

Etch BackMulti c-SiEtch BackMulti c-Si

Honeywell PasteMulti c-Si

Honeywell PasteMulti c-Si

InnovalightInkMono c-Si

InnovalightInkMono c-Si

Screen Printed SE

Esatto Technology in Action

22

Esatto Technology for metallization is proven on all selective emitter formation methods for both mono- and multi-crystalline silicon.


Intrinsicsystem

repeatability:+/-15µm

SE printingrepeatability:

+/-35µm

Alignment Results

23


Screen Printing – The Proven, Low Risk, Fast Path to SE Implementation

Results from the Field

Hari PonnekantiVice President Solar Product Development


Screen Printed SE Validation

Parameter ValueVoc (V) 0.643Isc (A) 8.86Jsc (mA/cm2) 37.54Fill Factor (%) 78.4Rshunt est (Ω cm2) 9120Voc slope (Ω cm2) 1.15Efficiency (%) 18.91

156mm Mono c-Si, Honeywell PasteBaccini screen printed SE and metallization

8.7

8.8

8.9

9.0

9.1

9.2

Cel

l Effi

cien

cy, %

I sc, A

mps

17.0%

17.5%

18.0%

18.5%

19.0%

Avg. Efficiency 18.5%

Pilot Cell EfficiencyPrinted SE Champion CellIV Curve

Current

SE CellStandard Cell

SE CellStandard Cell

Avg. Efficiency 17.9%

Avg. Isc 9.94 Amps

Avg. Isc 9.84 Amps

25


Screen Printed SESi Ink SECIUM™ Mass Production Results

26

Production with Silicon Ink technology since Q1 2010 4 lines in production today Efficiencies up to 19.2% in production Solar modules certified

Source: SNEC 2011 – DuPont Innovalight

SECIUM is a trademark of JA Solar Holdings Co., Ltd.

Applied Materials External Use27

EVA and glass

Minimized current loss by optimizing cell SiNx

6% module gain due to screen printed Silicon Ink

Module Power

Selective Emitter 229 W

Homogeneous Emitter 216 W156mm x 156mm, 54-cell module

Screen Printed SECell Efficiency Gain Maintained at Module

Source: SNEC 2011 – DuPont Innovalight


Xi’an Solar Technology Center

State-of-the-Art

R&D Capabilities

Customer Collaboration

New Applications and Product Development

Equipment and Process

SupportProduct Training

Process Validation &

Demos

28

One of the world’s largest solar R&D centers

Comprehensive capabilities for:WaferingCell TechnologyAdvanced Module TechnologyModule Reliability Testing

Easy customer access


Applied Materials’ Selective Emitter Solutions

29

Best-in-class screen printers and dryers from Applied Baccini Cell Systems,

ideally suited for SE formation –

easy integration, low cost, low risk.

Esatto Technology for high accuracy SE metallization –supporting all SE methods on both mono and multi.

Qualified consumables –

paste and screen recommendations.

Technology transfer and integration

support.

Equipment Solutions

Service Solutions

Applied Materials External Use30

screen printing – the proven, low risk, fast path to se … · 2011. 9. 28. · screens yield...

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