EFFECT OF DISLOCATIONS ON GALLIUM ARSENIDE FETsij(

0) R&D Status Report No. 2 for the Periodq40 November 1, 1984 to February 1, 1985NN\ Office of Naval Research/

In Defense Advanced Research Projects AgencyU) Contract No. N00014-84-C-0632

D. L. Barrett, S. Mc~uigan, C. W. Eldridge,B. W. Swanson, and R. N. Thomas

February 15, 1985

131 BelhRa

Pittburg. Pensylania1523

EFFECT OF DISLOCATIONS ON GALLIUM ARSENIDE FETs

R&D Status Report No. 2 for the Period

November 1, 1984 to February 1, 1985

office of Naval Research/Defense Advanced Research Projects AgencyContract No. N00014-84-C-0632

D. L. Barrett, S. Mc~uigan, G. W. Eldridge,B. W. Swanson, and R. N. Thomas

February 15, 1985

0

tic

Code

,Avail anid/or

Westinghouse Rau Center pia

1310 Beulah RoadPittsburgh, Pennsylvania W~35

SECURITY CLASSIFICATION OF THIS PAGE (Wl,.n Dat. HFrie-d)

READ INSTRUCTIONSREPORT DOCUMENTATION PAGE FFORE COMPLEFTINC. FORMIREPORT NUMBER 2. GOVT ACC SSSION N*O. 3 R IPIENT'S CATALOG NUMBER

A'Q A~ 5C TITLE (and Subtitle) 5 TYPE OF REPORT & PERIOD COVERED

EFFECT OF DISLOCATIONS ON GALLIUM ARSENIDE FETs Nov. 1 to Feb. 1, 1985 0

R&D tatu Reprt N. 26 PERFORMING ORG. REPORT NUMBER85-9F7-LODIS-Rl

7 AUTHOR(., 8. CONTRACT OR GRANT NuMBER(o)

1). L.. Barrett, S. McGuigan, G. W. El~dridge,B. W. Swanson, and R. N. Thomas N00014-84-C-0632 0

9 PERFORMING ORGANIZATION NAME AND ADDRESS 10 PROGRAM ELEMENT. PROJECT, TASK

Westinghouse R&D Center AREA & WORK UNIT NUMBERS1310) Beulah RoadPittsburgh, PA 15235

1 1 CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE SOffice of Naval Research Feb. 15, 1985Defense Advanced Research Projects Agency 13 NUM13ER OF PAGES800 N. Qu incy St., Arlington, VA 222171

14, MONITORING AGENCY NAME A ADDRESS(il dilferen, from Controling Office) IS. SECURITY CLASS. (of il rep-t)3

ISO DECLASSIFICATION DOWNGRADINGSCHEDULE

16. DISTRIBUTION STATEMENT (of this Report)

The views and conclusions contained in this document are those of theauthiors.- and should not be interpreted as necessarily representing theofficial policies, either expressed or implied, of the Defense AdvancedRestrarch P'rojects Agency of the U.S. Government.

17 OIS-RIBUTI2N STATEMENT 'of 11h. ahstract entere i in Bfock 20, if different fioni Report)

18 SUPPLEMENTARY NOTES

19 KEY WORDS fCc-inue ori reverse side if neces.sar arid i hv,~a ~ blockP numrber,Di 1,.1 CAT ION. IN ) 1I'M. DOPING. GAI.I,1 UN ARSENIDE. FET. LARGE. DIAMETER.S1~ BSTRATES. DEVELOPMENT1. CRYSTALS. T'llERMAL. STRESSES.

20 ABSTRACT 'C,rniu an reverst side if necessary arid id-iily by bl-.k iin..'

nd jun doping at 5 x 1019 cm was found to he optimum for the growthi oflow-dislocation GaAs crystals, and to avoid constitutional supercoolinog effertsDislocation etch pit densities of' near- 200) cm-3 were measured in tile centralrec :1)0 o; In-doped crystals, increasing to ahove 104 cm- 2 in the peripheral

reons. Based on tile concept tilat dis locat ions are generated to rclIieveexc,.ss t;,ernoelastic stress, a preliminairyr thermal modelI Was used to designa 1i t zoro shiold to reduce ther:ial gradients durn 1W growth. An opt imum

DD I J 7r, 1473 ED' rION 0o NOV 6,5 IS OBSOLETE, I. ASS. I CATJI Ti ' PAGE )a~ir, t. Pr,i,eO

SECcJRITY CLASSIFICATION OF TIS PAGE(When Data Entered)

Item 20 continued:

combination of indium-doping, reduced thermal gradient growth, andappropriate growth parameters are expected to yi eld completelydislocation-free GaAs crvstals. A FET ictrologV mask set hasbeen fabricated and preliminary FEIf device fabrication begun, foI)revaluation of thle effects of dislocations on FET device parameters.Twenty state-of-the-art , low-dislocation, indium-doped GaAs wafersw'ere delivered to the contrac tor for 1)ARPA-rel ated prograi'. evalun ti ov

SECRIT CASSFICTIN O THS AG~~he Dte nteed

R&D STATUS REPORT NO. 2

EFFECT OF DISLOCATIONS ON GALLIUM ARSENIDE FETs

DARPA ORDER NO.: 5217 PROGRAM CODE NO.:

CONTRACTOR: Westinghouse Electric CorporationR&D Center, Pittsburgh, PA 15235

CONTRACT NO.: N00014-84-C-0632 CONTRACT AMOUNT: $498,018

EFFECTIVE DATE OF CONTRACT: 8/1/84

EXPIRATION DATE OF CONTRACT: 9/30/86

PROGRAM MANAGER: R. N. ThomasTELEPHONE NUMBER: (412) 256-1871

PRINCIPAL INVESTIGATOR: D. L. Barrett S

TELEPHONE NUMBER: (412) 256-1898

SHORT TITLE OF WORK: Dislocations in GaAs FETs

REPORTING PERIOD: 11/1/84 to 2/1/85 .5

The views and conclusions contained in this document are those

of the authors and should not be interpreted as necessarily the S

official policies, either expressed or implied, of the Defense

Advanced Research Projects Agency or the U.S. Government. .

. . . . .. . . . . . . . . . . . . "

-0

1. TECHNICAL PROGRESS

During the second quarter of this program, we have directed our

efforts toward:

i) optimization of indum doping in 50-mm diameter crystals,

ii) preparation of indium-doped polished wafers, B

iii) evaluation of dislocation reduction and electrical

characteristics in In-doped wafers,

iv) fabrication of FET metrology mask sets.

Several areas have been studied in our efforts to develop

dislocation-free 50-mm diameter In-doped GaAs with the following

results:

An indium concentration of 5 x 1019 cm- 3 is required to

obtain etch pit densities of 200 cm 2 or less in the central

regions of the 40-mm diameter grown crystals.

The onset of constitutional supercooling in 50-mm diameter

crystals grown from 1 atomic % In-doped melts was observed to

occur at approximately g = 0.7 (where g = fraction of melt

solidified), with crystal growth rates of 9 mm per hour.

Calculations indica~c that reducing the growth rate from 9 mm

to 3 mm per hour will delay the onset of constitutional

supercooling until 90% of the melt has been solidified. This

effect will be explored during this next quarter by gradually

decreasing the growth rate as the crystal is pulled to avoid

growth instabilities.

* Etch pit densities of near 104 cm-2 are observed in the

peripheral region of grown crystals. Increasing the indium

_._ ,'.' _._ -2'_._._'.' ' .. m '- '*'~ n " """. ' ...... . . . . . .... . . . . . . . " - ''': ' '

i

content to >1020 cm- 3 to eliminate these peripheral

dislocations results in the onset of constitutional

supercooling effects. Consequently, we will explore reduced

thermal gradient growth to reduce excess peripheral stresses

with the resulting generation of dislocations; however, a

trade-off is anticipated since reduced gradients will cause S

the onse. of constitutional supercooling at lower indium

concentrations.

Thermal heat-transfer modeling shows that an increase in S

boron oxide thickness from 2 cm to 10 cm reduces the

temperature gradient in the encapsulant from 12C 0 G/cm to

30°C/cm, and will reduce the excess shear stress by a factor

of four. In a growth experiment, a temperature gradient of

60°C/cm was measured in a 6-cm B203 layer, in qualitative

agreement with the calculation. However, attempts to ow

crystals from both a 6-cm encapsulated melt and a 4-cm

encapsulated melt were not successful because of twin .

formation. A modification of our crystal growth parameters

will be necessary to achieve twin-free crystals from melts

with thick encapsulant layers.

Preliminary modeling of conduction, convection, and radiative

heat transfer in the LEC puller shows upper radiation

shielding as well as thick B20 3 layers to be the most

influential factor in reducing thermal gradients in the S

encapsulant. As a result of these calculations, design

criteria for a double-shell radiation shield were

established, and this shield is currently being fabricated.

Annealing indium-doped crystals at 9800 C for 18 hours has

been found to relieve grown-in stress, with the result that

crystal cracking is virtually eliminated and yields of

2

polished wafers were improved significantly. Improved

uniformity was also observed in radial resistivity and

mobility profiles as a result of this whole crystal-annealing

process.

Electrical evaluation of In-doped GaAs grown from

stoichiometric to slightly As-rich melts show high, thermally

stable resistivities and electron mobilities typically

5000 cm2 /Vsec or better, with exceptional radial uniformity

(±7% across wafer diameters).

The FET metrology DSW mask set has been fabricated, and

preliminary device fabrication on 50-mm indium-doped and

75-mm undoped wafers is in progress. This mask design

consists of seven levels: alignment marks, n+ implant,

n-channel implant, ohmic contact, gate contact, isolation

implant, and passivation access.

* One quarter of the mask field is devoted to conventional FETs

(1.2 inm gate on 7 iim source-drain spacings) laid out on three

spacing centers to evaluate uniformity and correlation with

dislocation position. A second quarter is devoted to process

verification structures. Both gradients are rotated by 900

to complete the mask field and to permit correlation of FET

characteristics with growth striations and residual slip

planes.

Implant qualification and characterization of In-doped wafers

is in process using standard contact photolithographic

techniques. The relative merits of transient and capped

annealing techniques are also under evaluation using low-

dislocation indium-doped GaAs substrate wafers to optimize

implant technology. The flatness of presently polished wafer

3 ..

.. ..

substrates is more than sufficient to meet projection

printing autofocus requirements.

Two crystals grown from I atomic % indium-doped melts have been

characterized and processed into polished wafers for FET characterization

and material evaluations. Indium-doped GaAs wafers have been supplied

to several DARPA contractors for evaluation, and 20 wafers have been

supplied to the scientific officer as part of contract-required

delivery. Table I lists pertinent crystal and wafer evaluations. The

etch pit density profiles are different in the two crystals even Lhoug!h

the indium content in both is nearly identical. Crystal BN109 has

center etch-pit densities near 200 cm- 2 , while the center region in

crystal BNI08 has a density near 104 cm-2 . This result cannot be

accounted for by seed-generated dislocations. Additional studies aro?

required to describe a m chanism for this difference in dislocation

density.

I

. 2. - ., ." . - . , -, .. .. i ." . . . . • . . . .,. ..~~~~~~~. . ...... . .. ". - - .. ° ° - .° " " . - . . . ' - o " . • .

TABLE 1 0

In-DOPED GaAs CRYSTAL ANL WAFER EVALUATIONS

Boule BN108 BN109

Dia. (mm) 53 ± 2 54 ± 2

Ground and Flat 50.8 No

Wafer

Orientation 20 off approx.

Diameter (mm) 50.5 (edge rounded) 49.3 - 0.6 (edge ground)

Thickness (mm) 0.55 ± .02 0.55 ± .02

Polish (NaOCI) Double-side Double-side

Wafer Delivery 64-65-66-67-68 60-66-67-68-69

69-70-71-72-74 70-71-72-73-74 1

Calc. In Content (cm- 3 ) 6 . 101

9 8 x 1019

(Keff = 0.1)

EPD (cm- 2) Wafer No. 110 Wafer No. 61

Center 13,000 220

r/2 7,300 1,200

Edge 72,000 28,000

Sheet Resistance 4 x 109 1 109•

(ohm/square) (As grown)

Mobility (cm 2/Vs) 3400 seed 7000 seed

(as grown) 5900 tang 5600 tang

Sheet Resistance > I 108 > 1 108

(ohm/square) Annealed

5

I

I

5

I

*

2. KEY PERSONNEL

No change in key personnel associated wi~th the conitraict has

occurred during the reporting period.

3. SPECIAL EVENTS

None.

4. PROBLEM ENCOUNTERED AND/OR ANTICIPATED

No deviat ion f rom the or iginal1 pl anned e ff o rc oc ~cive h -

objectives of the contract is anticipated at present.

5. ACTION REQUIRED BY THE GOVERNMENT

No action is required by the Governiment at this time.

6. FISCAL STATUS (as 1f1/31:!65)

I.Amount currewt .v p.r'v ~dtd kon -i!! rlc $130,018

2. Expenditures and commitments to date: $135,370

3. Fund s requ ired to c nrnp ~e wo r K: $498,01F

ENCLOSURE NUV-ER 3 CONTIACT ITER: 10014-84-C-0632 0

DSO TECHNICAL REPOPTSDistribution ListGaAs TECHNOLOGY

Dr. Richard W. Griffith Mr. Sven A. Roosild

US Ar'. Research Office DARPA/DSOP. 0. Box 12211 1400 Wilson Boulevard Research

Triangle Park, NC 27709 Arlington, VA 22209

Dr. Williaz Lindley Dr. James Degenford

MIT Lincoln Laboratory Westinghouse Electric

Lexington. MA 02173 MS 3173P. 0. Box 1521

Dr. John M. Hurrell Baltimore, M 21203

MS M2/24U

Electronic Research Lab Dr. Martin Buehler

The Aerospace Corporation Jet Propulsion Lab

P.O. Box 92957 MS 198-226

Los Angeles, CA 90009 4800 Oak Grove DrivePasadena, CA 91109

Mr. Ricardo Zucca

Rockwell International/MRDC Mr. Gordon Rabanus

P. 0. Box 1085 AFWAL/AADE

Thousand Oaks. CA 91360 Wright-Patterson AFB, OH 45433

Mr. Edward A. Palo Dr. Rainer Zuleeg

The MITRE Corporation McDonnell Douglas Astronautics Co.

P. 0. Box 208 5301 Bolsa Avenue

Bedford, .A 01730 Huntington Beach, CA 92,47

Dr. JTaes D. Murphy Dr. Harvey Nathanson

Attn: ORD Westinghcuse R&D Center

P. 0. Box 1925 1310 Beulah Road

Washington, DC 20013 Pittsburg, PA 15235 S

Mr. W4illia= Yanzanares Professor Greg Stillman

At:n: OF D University of Illinois

P. 0. Box 1925 155 Electrical Engineering Bldg.

Washington. DC 20013 1406 West Green StreetUrbana, IL 61801

Mr. Kenneth SlegerNaval Research Laboratory Dr. Ken Galloway

Code 6811 National Bureau of Standards

Washington, DC 20375 Building 225, Room B352Washington, DC 20234 S

Mr. Robert Bierig

Raytheon Ccmpany Dr. Paul Greiling

Research Division Hughes Research Laboratory

131 Spring Street 3011 Malibu Canyon Road

Lexington. YA 02173 Malibu, CA 90265 S

' .. .. . ,

ENCLOSURE NUP BTR 3 t 'A 1 ", " )4 -S4 C -632

-. Barry K. Gilbert Prcfessor 2L:,es Harris- Mavo Clinic Stanford Eeczrcr.;s Laborator!es

2(, First Street, SW De; tment cf HX:ctrica-

R::,ester. N 55905 Erg -ring 0Stanford Univ rs.ty

Dr. Gerald Witt Stanford, CA 94 3C5

AFOSR/NEBuilding 410 Professor Augsr F. Watt

Boiling AFB MiT, Room 13-4134

Washington, DC 20332 Dertrert cf Materl: Sciencean~ Engineezing

Dr. Michael Shapiro Car-ridge, - 02139DoD Advisory Group onElectron Devices Dr. Brian G. Ku shner

201 Varick Street The BDM Corporation

lth Floor 79:5 Jones Bra7nc Drive

New York, NY 10014 McLean, VA 22102

Dr. Joseph A. Saloom Professor Jan Mcill

MACOX, Inc. Hail Station :26095

Corporate Cozponents Califcrria rnstiru.e cf Tec'ig"

Technology Center Pasadera. CA 91"5

South Avenue, Building 7

Burlington, Y_; 01803 Mr. Charaev DareBalliszi ,ile Defense

Dr. Jeff Woolhouse Advan:Ld Technoloey CntE.

Advanced Research and Appli- P.O. Box ]500

cations Corporation Huntsville, Al 35EO71223 E. Arques AvenueS2:nnyvale, CA 94086 Dr " ' anPA.D 17-

Mr. J. P. Letellier Fansccz AFB, MA 01731

Naval Electronics SystemsCommand Dr. Freeman Sheperd

Ccde 6142 FC--FSE

Washington, DC 20363 Han!com AFB, MA 01731

Mr. James Buss Mr. Jim Kesperis S

Naval Ocean Systems Center ETDL-FRADCOM

MS 7321 Mail Stop DELET-IB-S

271 Catalina Boulevard Fort Mt.mouth, NJ 07703

San Diego, CA 92152*Mr. D. 3. Connolly

Dr. Steve Swierkowski YS-54-5

Electrical Engineering Laboratory NASA Lewis

S M Ll-56 2100 Brook Park Road

P. 0. Box 808 Clevcland, OH 44135

Livermore, CA 94550Mr. Jack Garrett *0

Dr. J. Richard Burke Mpterials Laboratory

Office of Naval 7echnolc~gy AF "A

800 North Quincy StreEt Writer-Patterson AFB, OH 45433

Arlington, VA 22)7"

... ...~ :. .. *: , .. .. : ., -:.. .. : . , .. . i ,.. -. .: .k .

L1 CLUSUEE NUBER B CO:.TRACT rUhIBER: IOOO '--b4-C-0632 0

Dr. Kenneth Davis Mr. JLck S. Kilby

Office of Naval Research 5924 Royal Lane 6

800 North Quincy Street Suite 150

Arlington, VA 22217 Dallas, TX 75230

Dr. Richard Eden Dr. William HowardCigaBit Logic, Inc. Vice President

2640 Tovnsgate Motorola SemiconductorsSuite 600 Director of Technology and PlanningP. 0. Box 5083 Motorola Semiconductor ProductsWest Lake Village, CA 91361 Sector

5005 East McDowell RoadPhoenix. AZ 85008

Dr. Richard A. ReynoldsDeputy Director, Defense W. R. WissemanSciences Office MS 134, Box 225936

Defense Advanced Research Texas Instruments. Inc.Projects Agency Dallas, TX 752651400 Wilson BoulevardArlington, VA 22209 Professor Eugene Haller

Department of Material ScienceLawrence Berkeley LaboratoryUniversity of California. BerkeleyBerkeley, CA 94720

...

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