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Energy Research and Development Div is ion FINAL PROJECT REPORT
ADVANCED EPI TOOLS FOR GALLIUM NITRIDE LIGHT EMITTING DIODE DEVICES
DECEMBER 2012CEC ‐500 ‐2013 ‐027
Prepared for: California Energy Commission Prepared by: Applied Materials, Inc.
Prepared by: Primary Author(s): Nag Patibandla, Ph.D. Applied Materials, Inc. 3050 Bowers Avenue P. O. Box 58039 Santa Clara, CA 95054-3299 408-563-5224 Contract Number: PIR-10-055 Prepared for: California Energy Commission Dustin Davis Contract Manager Virginia Lew Office Manager Energy Efficiency Research Office Laurie ten Hope Deputy Director ENERGY RESEARCH AND DEVELOPMENT DIVISION Robert P. Oglesby Executive Director
DISCLAIMER This report was prepared as the result of work sponsored by the California Energy Commission. It does not necessarily represent the views of the Energy Commission, its employees or the State of California. The Energy Commission, the State of California, its employees, contractors and subcontractors make no warranty, express or implied, and assume no legal liability for the information in this report; nor does any party represent that the uses of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the California Energy Commission nor has the California Energy Commission passed upon the accuracy or adequacy of the information in this report.
1
ACKNOWLEDGEMENTS
This material is based upon work supported by the United States Department of Energy (DOE) under Award Number DE‐EE0003331 and by the California Energy Commission (Energy Commission), agreement PIR‐10‐055.
The project team gratefully acknowledges the hard work of the DOE and Energy Commission in developing and managing this important project. The project team extends thanks to project managers, Brian Dotson of DOE’s National Energy Technology Laboratory (NETL) and Dustin Davis of the Energy Commission, who helped guide this work.
Also, the project team thanks Jim Brodrick, the solid‐state lighting portfolio manager in DOEʹs Office of Energy Efficiency and Renewable Energy. His vision for solid state lighting and manufacturing were very helpful to successfully execute this project.
FINALLY, THE TEAM THANKS SEAN EVANS, WHO WAS THE INITIAL PROGRAM MANAGER AT NETL
2
PREFACE
The California Energy Commission Energy Research and Development Division supports public interest energy research and development that will help improve the quality of life in California by bringing environmentally safe, affordable, and reliable energy services and products to the marketplace.
The Energy Research and Development Division conducts public interest research, development, and demonstration (RD&D) projects to benefit California.
The Energy Research and Development Division strives to conduct the most promising public interest energy research by partnering with RD&D entities, including individuals, businesses, utilities, and public or private research institutions.
Energy Research and Development Division funding efforts are focused on the following RD&D program areas:
• Buildings End‐Use Energy Efficiency
• Energy Innovations Small Grants
• Energy‐Related Environmental Research
• Energy Systems Integration
• Environmentally Preferred Advanced Generation
• Industrial/Agricultural/Water End‐Use Energy Efficiency
• Renewable Energy Technologies
• Transportation
Advanced EPI Tools for Gallium Nitride Light Emitting Diode Devices is the final report for the grant, PIR‐10‐055, conducted by Applied Materials Incorporated. The information from this project contributes to Energy Research and Development Division’s Buildings End‐Use Energy Efficiency Program.
For more information about the Energy Research and Development Division, please visit the Energy Commission’s website at www.energy.ca.gov/research/ or contact the Energy Commission at 916‐327‐1551.
3
ABSTRACT
For light emitting diodes (LEDs) to realize its potential in lowering energy consumption and becoming the standard for general lighting needs, it is generally agreed that costs to the consumer must come down significantly. When Applied Materials Incorporated (Applied Materials) conducted a comprehensive review of the value chain of the LED bulb, it was clear that Gallium Nitride (GaN) deposition costs were a significant driver in the final cost of the bulb. The costs not only include tool cost, but the yield and performance of the chips out of the tool. The overall goal of this project was to develop, build, and demonstrate an improved manufacturing system for GaN power devices such as LEDs. Applied Materials designed, demonstrated and validated the system performance of the full LED Epitaxy (epi) process. The project accomplished its goals and resulted in successfully building a world‐class, epi system that produces high quality LEDs at a lower cost which is now commercially available. Keywords: LEDs, Light Emitting Diodes, Applied Materials, solid state lighting, GaN LED manufacturing
Please use the following citation for this report:
Patibandla, Nag (Applied Materials, Inc.). 2012. Advanced EPI Tools for Gallium Nitride Light Emitting Diode Device. California Energy Commission. Publication Number: CEC‐500‐2013‐027
4
TABLE OF CONTENTS
Acknowledgements .................................................................................................................................. 1
PREFACE .................................................................................................................................................... 2
ABSTRACT ................................................................................................................................................ 3
TABLE OF CONTENTS ........................................................................................................................... 4
EXECUTIVE SUMMARY ........................................................................................................................ 5
Introduction ............................................................................................................................................ 5
APPENDIX A: Applied Materials Report to U.S. Department of Energy .................................. A‐1
5
EXECUTIVE SUMMARY
Introduction The California Energy Commission (Energy Commission) provided cost share funding to supplement Applied Materials, Incorporated’s (Applied Materials) American Recovery and Reinvestment Act of 2009 (ARRA) award. The purpose of the project was to conduct research and development of a new, more cost effective process for manufacturing Gallium Nitride (GaN) power devices such as Light Emitting Diodes (LEDs). The Energy Commission’s cost share assisted in the design and development of a new method to produce high quality light emitting diodes at a lower cost.
The project resulted in the demonstration of a prototype tool that can deposit high‐quality GaN materials on at least two different substrate materials. This new advanced system will enable LED manufacturers to fabricate higher‐quality LED devices at a lower cost, and help address a major obstacle to widespread adoption of high quality and more energy efficient LEDs. This project accomplished the goals of designing, validating and developing improved GaN manufacturing process equipment that is now commercially available.
Wide spread adoption of LEDs could significantly reduce energy use associated with lighting. The LED technology is an efficient light source over other technologies such as incandescent. Incandescent lighting produces up to 18 lumens of light output for every watt of energy it consumes while LEDs produce up to 100 lumens for every watt.
Energy Commission funding was critical to retain jobs during a down economy at Applied Materials’ Research and Development facility in Santa Clara, California. By 2015, Applied Materials estimates that 350 employees will be assigned to the product that resulted from this project. About one‐half of the employees will be in Santa Clara, California. These employees will work in engineering, manufacturing, service and maintenance, technology, marketing, administration, and critical support functions such as finance, human resources, and legal counsel.
Appendix A contains a copy of the final report, Advanced Epi Tools for Gallium Nitride Light Emitting Diode Devices, prepared by Applied Materials for the U. S. Department of Energy under grant DE – EE0003331.
A‐1
APPENDIX A: Applied Materials Report to U.S. Department of Energy Submitted to the U. S. Department of Energy, Agreement DE‐EE0003331, December 7, 2012
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2
Disclaimer:
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof."
3
3
ContentsExecutiveSummary..............................................................................................................................4
ProgramGoalsandAccomplishments...........................................................................................5
Overview ................................................................................................................................. 5
Program Goals ........................................................................................................................ 5
ProjectActivitySummary.................................................................................................................27
Original hypotheses .............................................................................................................. 27
Approaches used ................................................................................................................... 29
Problems encountered ........................................................................................................... 30
Productsdevelopedundertheaward.........................................................................................31
Networks or collaborations fostered ..................................................................................... 31
Technologies/Techniques ..................................................................................................... 31
Inventions/Patent Applications ............................................................................................. 31
Summary................................................................................................................................................32
Acknowledgements............................................................................................................................33
4
ExecutiveSummary
Over the course of this program, Applied Materials, Inc., with generous support from the United States Department of Energy, developed a world-class three chamber III-Nitride epi cluster tool for low-cost, high volume GaN growth for the solid state lighting industry. One of the major achievements of the program was to design, build, and demonstrate the world’s largest wafer capacity HVPE chamber suitable for repeatable high volume III-Nitride template and device manufacturing. Applied Materials’ experience in developing deposition chambers for the silicon chip industry over many decades resulted in many orders of magnitude reductions in the price of transistors. That experience and understanding was used in developing this GaN epi deposition tool. The multi-chamber approach, which continues to be unique in the ability of the each chamber to deposit a section of the full device structure, unlike other cluster tools, allows for extreme flexibility in the manufacturing process. This robust architecture is suitable for not just the LED industry, but GaN power devices as well, both horizontal and vertical designs. The new HVPE technology developed allows GaN to be grown at a rate unheard of with MOCVD, up to 20x the typical MOCVD rates of 3m per hour, with bulk crystal quality better than the highest-quality commercial GaN films grown by MOCVD at a much cheaper overall cost. This is a unique development as the HVPE process has been known for decades, but never successfully commercially developed for high volume manufacturing. This research shows the potential of the first commercial-grade HVPE chamber, an elusive goal for III-V researchers and those wanting to capitalize on the promise of HVPE. Additionally, in the course of this program, Applied Materials built two MOCVD chambers, in addition to the HVPE chamber, and a robot that moves wafers between them. The MOCVD chambers demonstrated industry-leading wavelength yield for GaN based LED wafers and industry-leading uptime enabled in part by a novel in-situ cleaning process developed in this program. The Department of Energy was a great supporter of this leading-edge technology that can benefit U.S. industry and keep GaN manufacturing competitive in the United States. We gratefully acknowledge their role in advancing the state-of-the-art.
5
ProgramGoalsandAccomplishments
Overview For solid state lighting to realize its potential in lowering energy consumption for the nation and becoming the standard for general lighting needs, it is generally agreed that costs to the consumer must come down significantly. When Applied Materials did a comprehensive review of the value chain of the LED bulb, it was clear that GaN deposition costs were a significant driver in the final cost of the bulb. The costs not only include tool cost, but the yield and performance of the chips out of the tool. The overall goal of this program was to develop, build, and demonstrate a low-cost manufacturing system for GaN LED manufacturing. Not only did we design a system, but validate the system by developing a full LED epi process. We set this high bar of actually demonstrating world-class device performance because of the reputation Applied Materials has built over many decades as the leader in high volume nano-scale manufacturing. Without developing a process, and given the fact that Applied Materials was new to this market, we could not validate the world-class nature of our system. We are happy to report that we accomplished the goals we set out to accomplish in this successful program, building a world-class, low-cost epi system for GaN LEDs that has shipped to customers world-wide. We describe our achievements in more detail below. Our approach was fundamentally different than the standard approach in two ways. First, Applied Materials would use the cluster approach that it has successfully implemented in the silicon industry, driving down manufacturing costs by orders of magnitude and enabling the information age. Secondly, we would develop the world’s first manufacturing-grade HVPE chamber to increase the rate of GaN deposition by over an order of magnitude, further driving down epi manufacturing costs for the LED industry.
ProgramGoals There were five milestones proposed at the start of this program in 2010. We are happy to report that we exceeded expectations for all of them. This program was unique in that Applied Materials not only designed new epi chamber architectures, but developed GaN process and GaN devices to show the viability of the tool design. This feedback loop was a key to the success of the program and sometimes not recognized as a necessary requirement. The key achievements for each milestone are highlighted below.
6
Mileston
GoalIncrease phase epias an MO
AccomplTable 1 scapacity with oper
Key adva
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ancements in
ast GaN depUnique in-situExcellent u-Gor (002) of 9
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9
Mileston
GoalDecreaseHVPE+Mquantum each waf
Accompl
DeviceP Validatiothe advanmanufactthe LED in additio Figures 3chamber clearly shVolume M
ne2:HVPE
e cycle time MOCVD sys
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11
Figure 5: Awavelengt The handsystems aseasoningvarious M HighQu Another flow andlayer whiof the sys
A key achieveth uniformity
ds-off 12- coand the frequg, and epi re
Milestones th
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Figure 6
rogram: 60 anng of the cham
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ments. This he program.
i-chamber prring MQW gh gas flows aradiant heati
6: MQW SEM
nd 120 continumber.
or improvemanual cleanincapability w
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nal
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12
PLResu Figure 7 examine nm bin arfor LED min-max
ults
shows the wcumulative round the tarmanufacture
x variation of
wavelength uPL performargeted 450nmers. Figure 8f 12.5nm.
Figu
uniformity france. The rem value, cle
8 shows the w
ure 7: Distribu
rom a series esults showe
early demonswavelength u
ution of PL fo
of runs withed 86.9% of strating exceuniformity w
or Wavelength
h a number oall points w
eptional binnwithin a sing
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of wafers to were located ining capabiligle carrier an
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13
Fig Bow
Typicallywafer benduring gris especiaMOCVDInGaN M
In order ton waveltemperatu
The stresmanagedbow wastemperatusitu opticmultiple profile acGaN/n-G
gure 8: Full ca
y, lattice misnding, defecrowth is the ally importan
D growth is kMQW growth
to verify thelength uniforure bow for
ss during HVd by changin
also managure convex bcal bow meaquantum wecross the 2”
GaN templat
arrier mappin
smatch and tct formation,change of thnt for indium
known to be h conditions
impact of wrmity, we ussubsequent
VPE growth g of HVPE ped by changbow height wsurements at
ell test structwafer for Intes.
ng of waveleng
thermally ind, or even filmhermal contam-containingvery temperis required f
wafer curvatused HVPE u-MOCVD In
(and as a resprocess para
ging of u-GaNwas used- 8 t room tempture growth.
nGaN multip
gth showing ex
duced stress m cracking. Aact between tg compoundrature sensitifor good in w
ure during ou-GaN/n-GaN
nGaN multip
sult, the bowameters durinN/n-GaN thto 60 m. Th
perature and Table 2 shole quantum w
xceptional mi
during MOCAn importanthe wafer ans, since indiuive. Therefowafer wavel
ur HVPE+MN templates wple quantum
w of u-GaN/nng in-situ buhickness andhe templatestransferred t
ows the PL mwell structur
in-max binnin
CVD LED gnt impact of nd the substrum incorpor
ore, wafer bolength unifor
MOCVD intewith differenwell structur
n-GaN tempuffer steps. Ind a range of rs were charato the MOCV
mapping andres grown on
ng of 12.5nm
growth resulwafer bendiate holder. Tration duringow control atrmity.
egration grownt room re growth.
plates) was n some runsroom acterized by VD chamber
d wavelengthn HVPE u-
lts in ing This g t
wth
s the
ex r for
h line
14
Table 2: Pwell struct
Three HVsubsequetemplatesbow (9 STD (3.5result, th The conscenter) caAssuminInGaN Mwavelengacross th So, with distributiuniformit
To verifyMOCVDwere placdepositioHVPE testructurewaveleng
PL mapping antures grown o
VPE u-GaN/ent InGaN ms revealed dim) template57 nm) the we wavelengt
siderable conan be correla
ng that the waMQW growthgth profile cae wafer) at I
stress controion across thty.
y the w-to-wD runs was coced on 31x2
on in HVPE emplates (locs were depogth uniformi
nd wavelengthon HVPE u-Ga
/n-GaN tempmultiple quan
ifferent behae exhibits a cwavelength p
h STD is low
ncave waveleated to the cafer center ih conditions)an be correlaInGaN MQW
ol during HVhe wafer duri
w and run-to-onducted in ” carrier andchamber at ocated across sited in MOity data for th
h profile acrosaN/n-GaN tem
plates had dintum well stravior in termconsiderableprofile for higw (0.95 nm)
ength profileonvex wafers cooler than) a higher inated to a flat
W growth co
VPE growth,ing MOCVD
run wavelenAMAT clus
d transferredoptimized (fthe carrier) wCVD chambhree MOCV
ss the 2” sappmplates
ifferent convructure depo
ms of wavelen concave wagh convex bfor this tem
e (or red shifr shape at Inn the wafer e
ndium concent wafer shapenditions.
, we were abD GaInN MQ
ngth uniformster tool. Sixd to HVPE chfor stress conwas transfer
ber and charaVD runs are p
hire substrate
vex bow heigosition on thength uniformavelength prbow (51 m)
mplate.
ft of the PL nGaN MQW edges in the ntration can e (and unifo
ble to optimiQW growth a
mity asequencx 2 inch sapphamber. Aftentrol) conditrred to MOCacterized bypresented at
e for InGaN m
ght: 9, 26 ane top of HVPmity. While tofile and hig
) template is
wavelength growth concase of convbe expectedrm temperat
ize the tempeand achieve
ce of three Hphire substrater 6 m thictions, the carCVD chambey ex-situ PL.
Table 3.
multiple quant
nd 51 m. AfPE templatesthe low convgh wavelengnearly flat. A
in the waferditions. vex bowing d. The flat ture distribut
erature high wavele
HVPE and thtes for each
ck u-GaN/n-Grrier with sixer. The test LThe PL
tum
fter s, all vex
gth As a
r
(at
tion
ength
hree run GaN x LED
15
Table 3: The PL wavelength uniformity data from LED structures grown on HVPE u-GaN/n-GaN templates in three MOCVD runs
The average data for PL wavelength uniformity are presented at Table 4. The within wafer uniformity and run-to-run uniformity have achieved the target. The wafer-to-wafer uniformity is close to the target and can be improved by additional tuning.
Table 4:Average data for PL wavelength uniformity of integrated HVPE/MOCVD runs
A quick EL apparatus is used to measure the EL wavelength at 5 points across the wafer and the wavelength STD is calculated. Table 4 is an example of EL measurement of a wafer from the integrated HVPE/MOCVD run. It shows the EL STD of HVPE and MOCVD can achieve 1.15 nm which exceeds the target of 1.5 nm.
Table 5: EL and PL wavelength measurement
Run ID 6MA079 Run ID 6MA080 Run ID 6MA081
Waf
er
ID Wavelength
(nm) STD (nm)
Wavelength (nm)
STD (nm)
Wavelength (nm)
STD (nm)
2 448 1.11 446 1.23 447.9 1.58 14 445.6 1.05 444.7 1.22 445.8 1.42 25 445.5 1.32 444.1 1.6 444.1 1.9 27 444.8 1.16 444.8 1.68 444 1.93 17 446.4 1.13 445.9 1.08 444.6 1.23 5 447.6 1.85 448.6 1.8 448.3 1.15
Average 446.32 1.27 445.68 1.44 445.78 1.54 W-to-W uniformity (nm) 1.26 1.61 1.91
Uniformity Within Wafer Wafer-to-Wafer Run-to-Run Result (nm) 1.41 1.59 0.34
Target (nm) 1.5 1.0 1.4
PL WLD (nm)
PL WLD u% (nm)
EL WLD @10mW (nm)
EL WLD STD 5pts (nm)
449.2 0.856 448.8 1.15
16
In summary, the impact of wafer curvature during growth of a LED test structure on wavelength uniformity across the wafer was demonstrated. With stress control during HVPE growth, we were able to optimize the temperature distribution across the wafer during MOCVD InGaN MQW growth and reach specification target for PL wavelength uniformity.
17
Milestone3:SecondSubstrateDemonstration
GoalAssure the industrial relevance of the three-chamber MOCVD / HVPE system developed for Milestone 2 by developing processes that allow it to deposit high-quality LED structures on the most promising alternate substrate material.
Accomplishments Over the course of this program, we investigated a variety of alternate substrates in addition to standard two-inch planar sapphire substrates. GrowthofHPVEGaNonPSS We started the investigation of u-GaN deposition on 2” PSS in the HVPE chamber to validate the feasibility for LED customers. Three different in situ HVPE buffer concepts were investigated and Table 6 shows XRD rocking curves for (002) and (102).
Table 6:XRD data of u-GaN grown on PSS using HVPE
The results show how the crystal quality can be engineered to extremely low values, among the best in the industry and the deposition rate for PSS was also demonstrated to be 60um/hour. Table 7 shows the excellent flat 2-D morphology of u-GaN layers grown in single deposition runs on PSS with high GaN growth rate (about 60 m/hour).
(002) (102)
A RB33 6 196.8 185.6
B RB34 9.7 306.9 199.9
C RB47 7.6 221.3 138.7
Rocking Curves
(XRD arcsec)Buffer type Runs ID
GaN
Thickness
(um)
18
GaNon As we hadevelopmwafers on
Ta
PSS4”Sap
ave discussedment over othn a platter in
Figur
ble 7: Optical
pphire
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re 9: WL unifo
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ost interest ie to fit eightshown in Fig
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19
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20
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afers
21
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22
Mileston
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23
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24
Mileston
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Accompl We wereteam of DFigure 18described
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25
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26
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PE (2 hrs)
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27
ProjectActivitySummary
Originalhypotheses The original Statement of Program Objectives (SOPO) is listed below.
OBJECTIVESTHE RECIPIENT proposes to develop a multi-chamber system such as a two MOCVD chambers, one HVPE chamber, lamp heating, and automated in situ cleaning. The system shall be capable of growing high-quality LEDs on substrate materials currently in commercial use or under consideration. It shall contain a 300-mm or larger platter that holds 28 two-inch wafers. THE RECIPIENT shall build it on the successful Centura (TM) platform, the standard for growing low-cost, high-quality epitaxial wafers in the integrated circuit industry. The proposed system shall decrease operating costs through a combination of decreasing cycle time, increasing throughput, using in-situ cleaning, and decreasing the cost of chemicals. It shall increase the internal quantum efficiency of LEDs by reducing the density of extended defects and point defects. It shall improve binning yields by improving the uniformity of wavelength and output power within the wafer, from wafer to wafer, and from run to run. TASKSTOBEPERFORMED
ProjectManagement andPlanningTHE RECIPIENT shall develop and maintain a Project Management Plan (PMP) throughout the course of the project. The initial PMP shall be submitted to the DOE Project Officer within 60 days of award. The Recipient shall review and update the PMP at the end of each Budget Period and resubmit as a part of the budget period continuation application. The PMP shall also be modified on an ad hoc basis to reflect significant changes or deviations of planning. Multi‐WaferHVPEEpiChamberTHE RECIPIENT shall design and assemble a multi-wafer nitride HVPE system for high volume production. The goal shall be to identify a chamber design and compatible process conditions that can deposit high-quality GaN at a growth rate of several microns per hour. THE RECIPIENT shall test multiple approaches to injecting reagents into the reactor chamber to optimize mixing and uniform distribution of reagent gases. THE RECIPIENT shall optimize growth parameters such as temperature, pressure, V:III ratio, carrier flow rate, and total gas flow. u-GaN and MQW layer thickness uniformities shall be monitored both within wafer (w-i-w) and wafer to wafer (w-2-w) across a multi-wafer carrier. The recipient shall have the goal of controlling GaN layer thickness uniformity with a standard deviation below 2%. THE RECIPIENT shall optimize the chamber design for the requisite temperature control. The HVPE system shall have a goal of achieving contaminant levels below 1016 atoms/cm3 for chlorine and oxygen. The HVPE
28
system shall be suitable for a cluster deposition system that also incorporates MOCVD chambers. At the end of Task 2, THE RECIPIENT shall test the system for the following criteria:
Growth of 4-micron GaN layer Temperature uniformity across the carrier GaN thickness uniformity within the wafer GaN thickness uniformity wafer-to-wafer GaN crystalline quality (threading dislocations per cm2) Contaminant levels for Oxygen and Chlorine
EpiToolwithmultiChamberSplitProcessTHE RECIPIENT shall design and build a multi-chamber, split-process Epi tool that with the goal of increasing throughput and minimizing PL wavelength drift. The system shall have the ability to grow HT-GaN template in one chamber and MQW layers in another chamber. THE RECIPIENT shall have a target both w-i-w and w-2-w PL wavelength uniformity of 2 nm or better. THE RECIPIENT shall integrate precise multi-zone temperature controls and process gas flow controls into the production ready Epi tool. THE RECIPIENT shall develop a process recipe with the goal of optimizing the multi-chamber system such as a MOCVD / HVPE (2+1) system described above to be capable of fabricating LEDs with internal quantum efficiency up to 75%. THE RECIPIENT shall test the multi-chamber MOCVD / HVPE system for the following properties:
EL Uniformity Within the Wafer PL Uniformity Within the Wafer PL Uniformity Wafer-to-Wafer PL Uniformity Run-to-Run Run-to-Run Std. Dev. IQE
ProcessforGrowingLow‐Defect,High‐QualityLEDStructuresontheMostIndustriallyRelevantSubstratesTHE RECIPIENT shall have the goal of demonstrating that the multi-chamber, split-process Epi prototype developed in Task 3 can deposit high-quality GaN material (including ternary and quaternary alloys) on at least two substrates. The process development shall focus on optimizing crystal quality and uniformity, and exploring process parameters with a goal of elucidating GaN, GaInN, and AlInGaN epitaxial growth mechanisms.
In‐SituCleaningProcessTHE RECIPIENT shall develop an in situ cleaning process for the MOCVD chamber using halogen-based etching gases, with the goal of delivering a clean showerhead, with minimal residual GaCl3, that does not adversely affect the crystal quality of the GaN layers in a subsequent run. THE RECIPIENT shall demonstrate in situ cleaning time with a goal of reaching 1 hour clean time. THE RECIPIENT shall have a goal that the in situ cleaning makes it possible to complete at least 5 MOCVD chamber runs without breaking vacuum and without
29
affecting the crystal quality of LED structures created in the next run or in succeeding runs.
Optimizedmulti‐ChamberEpiToolTHE RECIPIENT shall assemble an optimized multi-chamber system such as a MOCVD / HVPE (2+1) system capable of growing high quality HB-LEDs with low defect densities on multi-wafer carriers. THE RECIPIENT shall equip the MOCVD process chambers with in situ cleaning capability for enhanced throughput, high binning yield, and minimal deviations in PL/EL/thickness uniformity.
Approachesused Key aspects to our technical approach are itemized below.
1. Validate our baseline approach for low-cost split process GaN growth: focus on each layer and then on integration
a. u-GaN/n-GaN (Si-doped) b. MQW c. p-GaN (Mg-doped)
2. Create a multi-chamber MOCVD / HVPE system (2 MOCVD +1 HVPE). 3. Create a novel subsystem for automated in situ cleaning of the deposition chambers. 4. Control the growth temperature with precision high-speed lamp heating. 5. Reduce material defects by taking advantage of the flexible configuration of Applied
Material’s CenturaTM deposition chambers.
The multi-chamber architecture enabled an innovative approach to growing the hetero-epitaxial layer by using dedicated chambers for each of the major segments in the epi stack: u-GaN/n-GaN, MQW, and p-GaN.
30
Problemsencountered HVPE uniformity from wafer to wafer was a challenge that we overcame, but took longer than expected to validate. The challenges and progress in our HVPE development was reported monthly to our program manager. The main unforeseen issue for this program, however, was the market condition for LED GaN epi tools after early 2011. The so-called “crash” in tool sales for the LED industry was unexpected in its severity and suddenness. Additionally, since Applied was new to the market, customers demanded that we demonstrate world class LEDs and process controls before purchasing agreements could be completed. This caused understandable delays and although we were able to demonstrate world-class results as described above, the market collapse limited the sales in 2012. The future of the tool developed, however, is especially bright for GaN on silicon manufacturing given the ability to separate processes as well as cost-effective large diameter (>12”) thick GaN templates with GaN thickness greater than 20um.
31
Productsdevelopedundertheaward
Networksorcollaborationsfostered Strong partnerships were fostered with academia, national labs, and other companies through this program. We found the DOESSL Workshops very helpful in making contacts and fostering discussions. One particularly strong collaboration was with Sandia National Labs for third party validation of our GaN process and metrology we were not able to perform, which was particularly helpful to Applied Materials.
Technologies/Techniques A number of key technologies as shown by the inventions below were developed during the course of this program which helped Applied Materials develop key technologies for the GaN epi market. In addition, jobs were created and saved in Santa Clara, California
Inventions/PatentApplications Five patent applications were submitted through this program thanks to the support of the DOE:
32
Summary Over the course of this program, Applied Materials, Inc., with generous support from the United States Department of Energy, developed a world-class three chamber III-Nitride epi cluster tool for low-cost, high volume GaN growth for the solid state lighting industry. One of the major achievements of the program was to design, build, and demonstrate the world’s largest wafer capacity HVPE chamber suitable for repeatable high volume III-Nitride template and device manufacturing. Applied Materials’ experience in developing deposition chambers for the silicon chip industry over many decades resulted in many orders of magnitude reductions in the price of transistors. That experience and understanding was used in developing this GaN epi deposition tool. The multi-chamber approach, which continues to be unique in the ability of the each chamber to deposit a section of the full device structure, unlike other cluster tools, allows for extreme flexibility in the manufacturing process. This robust architecture is suitable for not just the LED industry, but GaN power devices as well, both horizontal and vertical designs. The new HVPE technology developed allows GaN to be grown at a rate unheard of with MOCVD, up to 20x the typical MOCVD rates of 3m per hour, with bulk crystal quality as better than the highest-quality commercial GaN films grown by MOCVD at a much cheaper overall cost. This is a unique development as the HVPE process has been known for decades, but never successfully commercially developed for high volume manufacturing. This research shows the potential of the first commercial-grade HVPE chamber, an elusive goal for III-V researchers and those wanting to capitalize on the promise of HVPE. Additionally, in the course of this program, Applied Materials built two MOCVD chambers, in addition to the HVPE chamber, and a robot that moves wafers between them. The MOCVD chambers demonstrated industry-leading wavelength yield for GaN based LED wafers and industry-leading uptime enabled in part by a novel in-situ cleaning process developed in this program. The Department of Energy was a great supporter of this leading-edge technology that can benefit U.S. industry and keep GaN manufacturing competitive in the United States. We gratefully acknowledge their role in advancing the state-of-the-art.
33
Acknowledgements "This material is based upon work supported by the Department of Energy under Award Number DE-EE0003331." We gratefully acknowledge the hard work of the DOE in developing and managing this important program. We particularly are grateful to or program manager, Brian Dotson of NETL, who has guided us and provided very helpful advice.
Also, we wish to thank Jim Brodrick, the solid-state lighting (SSL) portfolio manager in the DOE's Office of Energy Efficiency and Renewable Energy. His vision for solid state lighting and manufacturing helped to successfully execute programs like ours which are key in providing the investment in driving technology forward.
Finally, we wish to thank Sean Evans, our initial program manager at NETL.
