Real-Time Advanced Real-Time Advanced Process Control for Process Control for

GaN MOCVDGaN MOCVD

Rubloff Research Group Accomplishments

Rubloff: Real-time advanced process control for GaN MOCVD

Real-Time APC for GaN MOCVD ProcessingReal-Time APC for GaN MOCVD Processing

Accomplishment Mass spectrometric sampling of reaction

products provides real-time measurement of layer growth rates and thickness

Real-time end point control demonstrated at 1-2% precision for critical 20nm AlGaN cap layer

Sensing also enables prediction of crystal quality

SignificanceGaN HEMT technology requires precise control

of AlGaN thickness for device speed and manufacturability

Advanced process control (APC) now essential in semiconductor manufacturing

Mass spectrometry sensing platform supports real-time APC for metrology, material quality, and fault detection

Researchers involvedSoon Cho, Gary W. Rubloff

Rinku Parikh, Ray A. Adomaitis

Collaborations with Northrop Grumman group: Deborah Partlow, Michael Aumer, Darren Thomson

SupportNorthrop Grumman

fT 1 /dd

Rubloff: Real-time advanced process control for GaN MOCVD

Real-Time APC for GaN MOCVD ProcessingReal-Time APC for GaN MOCVD Processing

Publications“In-situ chemical sensing in AlGaN/GaN high electron mobility transistor metalorganic chemical

vapor deposition process for real-time prediction of product crystal quality and advanced process control”, Soon Cho, Gary W. Rubloff, Michael E. Aumer, Darren B. Thomson, Deborah P. Partlow, Rinku Parikh, and Raymond A. Adomaitis, J. Vac. Sci. Technol. B 23 (4), 1386-1397 (Jul/Aug 2005).

“In-situ chemical sensing in AlGaN/GaN metal organic chemical vapor deposition process for precision film thickness metrology and real-time advanced process control”, S. Cho, D. S. Janiak, G. W. Rubloff, M. E. Aumer, D. B. Thomson, and D. P. Partlow, J. Vac. Sci. Technol. B 23 (5), 2007-2013 (Sep/Oct 2005).

“Real-time material quality prediction, fault detection and contamination control in AlGaN/GaN high electron mobility transistor metalorganic chemical vapor deposition process using in-situ chemical sensing”, Soon Cho, Gary W. Rubloff, Michael E. Aumer, Darren B. Thomson, and Deborah P. Partlow, J. Vac. Sci. Technol. B 23 (5), 1849-1855 (Sept/Oct 2005).

Presentations“Real-time In-situ Chemical Sensing in GaN MOCVD for Advanced Process Control”, S. Cho, G. W.

Rubloff, M. E. Aumer, D. B. Thomson, and D. P. Partlow, AVS 50th Natl. Symp., Baltimore, MD, Nov. 2-7, 2003

Rubloff: Real-time advanced process control for GaN MOCVD

GaN Heterostructure DesignGaN Heterostructure Design

Crystal QualityThickness (~100 nm desired)

Thin: GaN crystal quality suffersThick: GaN cracks

Desire pitted surface for stress relief in GaN layer

Crystal QualityMaterial Quality (nbkg < 1014 cm-3, even lower desired)Thickness (~1 um thick)

4H-SiC(0001) substrate

AlN nucleation layer

GaN layer

AlxGa1-xN capComposition (~30 to 35% AlN)

High: breakdown suffersLow: 2DEG diminished

Thickness (~20 to 25 nm)Thick: pinch-off voltage increasesThin: 2DEG diminished

Abrupt, high quality interfaces required for all layers

Cap layer thickness is directly related to transconductance and the frequency of unit current gain

1T mf g

d

Rubloff: Real-time advanced process control for GaN MOCVD

GaN MOCVD ChemistryGaN MOCVD Chemistry

Chemistry is complex – adducts, gas phase and surface reactions

Overall pathways distinguishable by reaction product distributions

Real-time mass spectrometry provides quantitative measures of adduct vs. surface pathways

Benefits obtained from new methods for real-time APC without complete understanding of reaction chemistry

NH3 Ga(CH3)3

Ga(CH3)2 + CH3 GaCH3 + CH3

R1R2

S1

(CH3)3Ga:NH3

R3

(CH3)2Ga:NH2 + CH4

R4 S2

[(CH3)2Ga:NH2]3

6CH4 + GaN-compounds

R5

Ad

du

cts

Dep

osi

tio

n

Wafer R. Adomaitis

Gas Phase = Me Path

CH4

Surface = Et Path

C2H6

Rubloff: Real-time advanced process control for GaN MOCVD

APC ImplementationAPC Implementation

MetricPost-process

characterization

Film Thickness

XRR (AlGaN),

PL (GaN),

SEM (AlN)

Crystal Quality

XRD,

PL

Impurities

(C & O)

PL,

Sheet Resistance,

SIMS

Composition

PL

4H-SiC(0001) substrate

AlN nucleation layer

GaN layer

AlxGa1-xN cap

APC:Early identification of process excursions

and equipment faults

MetricReal-time in-situ

measurementPost-process

characterization

Film Thickness

Time-integration of selected byproduct

generation signals (e.g. methane, ethane)

XRR (AlGaN),

PL (GaN),

SEM (AlN)

Crystal Quality

Ratio of selected byproduct signals

(e.g. methane/ethane)

XRD,

PL

Impurities

(C & O)Impurities in gas phase

PL,

Sheet Resistance,

SIMS

CompositionUpstream acoustic

sensing for TMA & TMGPL

Rubloff: Real-time advanced process control for GaN MOCVD

Real-Time AlGaN Thickness MetrologyReal-Time AlGaN Thickness Metrology

0.01.0x10-2 1.5x10-2 2.0x10-2 2.5x10-2 3.0x10-2 3.5x10-2

0140

160

180

200

220

240

260

G287

G288G289

G290

G406

G409

G413

Precision 3.1A or 1.45%

Total drift 109A or 51.2%

AlG

aN t

hic

knes

s (A

)

Integrated Methane+Ethane signals (Amp-sec)

0.01.0x10-2

2.0x10-2

3.0x10-2

4.0x10-2

5.0x10-2

6.0x10-2

7.0x10-2

0100

150

200

250

300

350

400

G287

G288G289G290

G379

G380

G382

G383

G386

G387G406G409G413

AlG

aN t

hic

knes

s (A

)

Integrated Methane+Ethane signal (Amp-sec)

In-situ mass spectrometry provides real-time thickness metrology

Integrated methane (CH4) and ethane (C2H6) product signals quantitatively reflect deposited AlGaN

Actual (post-process) thickness measurements determined by mass spec to 1-2% precision

Implemented and applied routinely in Northrop Grumman’s GaN technology development

Real-time mass spectrometry used for process end point control of AlGaN cap layer thickness

Prototype for advanced process control application in GaN HEMT manufacturing

Rubloff: Real-time advanced process control for GaN MOCVD

Real-Time GaN Quality ControlReal-Time GaN Quality Control

In-situ mass spectrometry indicates GaN material quality in real time

Electronic quality Determined post-process by photoluminescence

spectroscopyCorrelated with impurity levels in gas phase

measured by mass spec

Crystal quality Determined post-process by x-ray diffractionIndicated by mass spec methane/ethane ratio

Photoluminescence

X-ray diffraction