Comparison of the uniformity of thickness and crystal ...Comparison of the uniformity of thickness...
1
Comparison of the uniformity of thickness and crystal quality of III-nitride films grown by ammonia source and plasma source MBE Y. Cordier 1 , M. Portail 1 , M. Chmielowska 1 , F. Natali 1,2 , C. Chaix 2 , P. Bouchaib 2 1 CRHEA-CNRS, rue Bernard Grégory, Sophia Antipolis, 06560 Valbonne, France 2 RIBER S.A, 31 rue Casimir Périer, BP 70083, 95873 Bezons Cedex, France Complementary information Ammonia MBE : Ts~800°C (GaN) to 920°C (AlN), nitrogen rich, growth rate limited by group III fluxes Trapping of ammonia on cryo-panels recovery procedure Interest for reducing NH 3 consumption Plasma assisted MBE: Addon plasma cell (model RFN50/63) GaN (Ts~720°C), usually metal rich, more complicated : necessary to tune group III fluxes, N 2 flow rate and RF power AlN (Ts~830°C), metal or nitrogen rich GaN and AlN films grown by plasma assisted-MBE and by ammonia-MBE to study the influence of the nitrogen source and of the gas flow rate : -on the uniformity of thickness -on the surface and crystal quality AlN grown on Si(111) GaN grown on : • Si (111) with GaN/AlN buffer layers • GaN-on-sapphire templates grown by MOCVD (LUMILOG) Introduction 0,8 1,0 1,2 1,4 1,6 1,8 0,30 0,35 0,40 0,45 0,50 0,55 0,60 Ga-rich conditions (2-3MLs segregating) Power (W) = 550W Power (W) = 500W Power (W) = 400W Growth rate (μm/h) N 2 flow rate (sccm) Trade-off : growth rate – quality P ~ 400-450 W, 1-1.8 sccm, Ts ~ 720 °C ■ Mesrine et al. Appl. Phys. Lett. 72 (3) p.350 – 1998). Riber 32 reactor from 200 to 80 sccm : increase of the GaN growth rate ; reduction of the screening effect of NH 3 . Vg: 0.61 – 0.68 µm/h below 20 sccm : decrease of GaN growth rate due to insufficient supply of nitrogen. Ga : BEP ~ 5E-7 Torr NH 3 20 sccm : BEP ~ 7E-5 Torr NH 3 cracking efficiency of a few % Effect of nitrogen flow rate and RF power. Growth using a nitrogen plasma source (Ga-rich growth regime) T > 700°C Depending on growth conditions, AFM shows terraces with a mean height of step of 1 molecular monolayer (left) and 2 monolayers (right) AFM – 1x1 μm² 0,5 0,6 0,7 0,8 0,9 1 1,1 1,2 1,3 0 20 40 60 80 100 120 140 160 180 200 NH3 (sccm) Vc GaN (μm/h) this study Mesrine NH3 screening effect ‘’N’’ limited growth ‘’N’’ rich growth NH 3 min : 200 sccm NH 3 min : 80 sccm NH 3 min : 40 sccm NH 3 min : 20 sccm below 80 sccm : development of pits related to dislocations from 200 to 80 sccm : increase of the roughness. growth mode intermediate between 2D nucleation and step flow ⇒ Step height 1 ML (0.25 nm) GaN ammonia growth : effect of flow rate GaN plasma assisted growth : Thickness uniformity XRD results AFM 1x1 μm² AlN / GaN grown on 4” , 3” and 2” silicon Silicon substrate AlN Nucleation layer GaN Buffer layer Advantages: -Contactless -Fast measurements -Tunable probe size ~2-6 mm Drawbacks: -Accuracy decreases when thickness decreases in the interference regime (necessitates the simulation of TO mode broadening ) Set up bench -IR source : 50-9000cm -1 -Detector range (DGTS) : 380 – 7500cm -1 RIBER Compact 21T Vb Vb-Vg E F Conduction band Depletion region : h dh~0 Low doped Highly doped The capacitance is almost independent with Vb, Nd-Na Vb Vb-Vg E F Conduction band Depletion region : h dh~0 Low doped Conduction band discontinuity high polarization field at the interface Fermi level pinning by defects Mercury probe CV (Hg-CV) Fourier Transform InfraRed spectroscopy (FTIR) centre RMS = 1.66 nm centre + 25 mm RMS = 1.54 nm centre + 40 mm RMS = 1.66 nm centre RMS = 0.31 nm centre + 30 mm RMS =0.47 nm centre + 20 mm RMS = 1.40 nm centre RMS = 0.96 nm 150 nm AlN plasma N-rich on 3’’ Si centre RMS = 0.51 nm centre + 20 mm RMS = 0.58 nm centre + 30 mm RMS = 0.55 nm 200 nm AlN NH3 130 sccm on 4’’ Si centre RMS = 0.12 nm centre + 30 mm RMS = 0.12 nm centre + 40 mm RMS=0.13 nm Uniformity Influence of nitrogen source and flow rate Thickness uniformity from Hg-CV Comparison Hg-CV vs FTIR Thickness uniformity from FTIR AFM : surface morphology centre + 30 mm RMS = 2.90 nm 150 nm AlN plasma Al-rich on 3’’ Si 600 nm GaN NH3 200 sccm on 4’’ Si 600 nm GaN plasma Ga-rich on 3’’ Si 0 1000 2000 3000 4000 5000 6000 0 50 100 150 200 250 NH3 flow rate (sccm) FWHM (arcsec) 0,13 µm AlN NH3: XRD (002), (101) AlN FWHM (101) AlN FWHM (002) 0 500 1000 1500 2000 2500 3000 3500 4000 4500 centre c+10mm c+20mm c+30mm c+40mm 0,6µm GaN NH3 (200 sccm) 0,6µm GaN NH3 (200 sccm) 0,5µm GaN plasma (Ga-rich) 1µm GaN NH3 (200 sccm) 2,6µm GaN NH3 (200 sccm) GaN (302) XRD FWHM (arcsec) Position (mm) 0 200 400 600 800 1000 1200 1400 1600 centre c+10mm c+20mm c+30mm c+40mm 0,6µm GaN NH3 (200 sccm) 0,6µm GaN NH3 (200 sccm) 0,5µm GaN plasma (Ga-rich) 1µm GaN NH3 (200 sccm) 2,6µm GaN NH3 (200 sccm) GaN (002) XRD FWHM (arcsec) Position (mm) 0,00 0,05 0,10 0,15 0,20 0,25 -50 -40 -30 -20 -10 0 10 20 30 40 50 h AlN (μm) NH3 MBE position (mm) NH3 10 sccm NH3 130 sccm NH3 200 sccm σ = 1,9-2 % over 50 mm σ = 2,6-3,1 % over 60 mm σ = 1,9 % over 60 mm σ = 5 % over 80 mm 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 -50 -40 -30 -20 -10 0 10 20 30 40 50 h GaN & AlN (μm) NH3 MBE position (mm) AlN GaN σ = 1 % over 60 mm σ = 3 % over 80 mm σ = 0,9 % over 50 mm σ = 1,2 % over 60 mm NH3 200 sccm NH3 130 sccm Continuous lines are data from Hg-CV 0,00 0,05 0,10 0,15 0,20 0,25 0 10 20 30 40 50 h AlN (μm) RF vs NH3 position (mm) AlN NH3 AlN Al-rich RF N2 = 0,4 sccm AlN N-rich RF N2 = 2 sccm σ = 2,8 % over 25 mm σ = 3,7 % over 30 mm σ = 2,7 % over 25 mm σ = 4,0 % over 30 mm σ = 1,5 % over 25 mm σ = 3,2 % over 30 mm 0,30 0,40 0,50 0,60 0,70 0,80 0,90 1,00 1,10 1,20 0 10 20 30 40 50 h GaN (μm) RF vs NH3 position (mm) GaN NH3 GaN RF N2=1,8 sccm σ = 1,5 % over 30 mm σ = 2,7 % over 40 mm σ = 1,4 % over 25 mm σ = 1,9 % over 30 mm σ = 2,2 % over 25 mm σ = 3,4 % over 30 mm -Influence of nitrogen precursor and its flow rate on the quality and the residual doping in GaN grown by molecular beam epitaxy, Y.Cordier, F.Natali, M.Chmielowska, M.Leroux, C.Chaix, P.Bouchaib, Physica Status Solidi C 9, 523–526 (2012). -Advances in quality and uniformity of (Al,Ga)N/GaN quantum wells grown by molecular beam epitaxy with plasma source, F.Natali, Y.Cordier, C. Chaix, P.Bouchaib, Journal of Crystal Growth (311) 2029–2032 (2009). -Signature of monolayer and bilayer fluctuations in the width of (Al,Ga)N/GaN quantum wells, F.Natali, Y.Cordier, J.Massies, S.Vezian, B.Damilano, M.Leroux, Physical Review B 79, 035328 (2009). -Developments for the production of high quality and high uniformity AlGaN/GaN heterostructures by Ammonia MBE, Y.Cordier, F.Semond, J.Massies, M.Leroux, P.Lorenzini, C.Chaix, Journal of Crystal Growth (301/302) 434-436 (2007). -Quality and uniformity assessment of AlGaN/GaN Quantum Wells and HEMT heterostructures grown by molecular beam epitaxy with ammonia source, Y.Cordier, F.Pruvost, F.Semond, J.Massies, M.Leroux, P.Lorenzini, C.Chaix, Physica Status Solidi C 3, 2325-2328 (2006). 0 2000 4000 6000 8000 10000 FWHM 002 FWHM 101 FWHM 103 FWHM (arcsec) AlN RF-MBE : XRD (002), (101), (103) 0,16µm plasma (N-rich) 0,15µm plasma (N-rich)* 0,15µm plasma (Al-rich)* * : with 40 nm AlN NH3 nucleation layer 0,00 0,10 0,20 0,30 0,40 0,50 0,60 0,70 0 10 20 30 40 50 position (mm) h (μm) AlN GaN centre + 15 mm RMS = 0.33 nm 0 1000 2000 3000 4000 5000 6000 7000 8000 centre c+10mm c+20mm c+30mm c+40mm 0,16µm plasma (N-rich) 0,15µm plasma (Al-rich) 0,15µm plasma (N-rich) 0,13µm NH3 (10 sccm) 0,16µm NH3 (130 sccm) 0,2µm NH3 (130 sccm) 0,2µm NH3 (130 sccm) AlN (002) XRD FWHM (arcsec) Position (mm) 0 2000 4000 6000 8000 10000 12000 14000 centre c+10mm c+20mm c+30mm c+40mm 0,16µm plasma (N-rich) 0,15µm plasma (Al-rich) 0,15µm plasma (N-rich) 0,13µm NH3 (10 sccm) 0,16µm NH3 (130 sccm) 0,2µm NH3 (130 sccm) 0,2µm NH3 (130 sccm) AlN (101) XRD FWHM (arcsec) Position (mm)
Transcript of Comparison of the uniformity of thickness and crystal ...Comparison of the uniformity of thickness...
-
Comparison of the uniformity of thickness and cryst al quality of III-nitride films grown by ammonia source and plasma source MBE
Y. Cordier 1, M. Portail 1, M. Chmielowska 1, F. Natali 1,2, C. Chaix 2, P. Bouchaib 2
1 CRHEA-CNRS, rue Bernard Grégory, Sophia Antipolis, 06560 Valbonne, France2 RIBER S.A, 31 rue Casimir Périer, BP 70083, 95873 Bezons Cedex, France
Complementary information
Ammonia MBE :
Ts~800°C (GaN) to 920°C (AlN), nitrogen rich, growth rate limited by
group III fluxes
Trapping of ammonia on cryo-panels ���� recovery procedure
Interest for reducing NH3 consumption
Plasma assisted MBE: Addon plasma cell (model RFN50/63)
GaN (Ts~720°C), usually metal rich, more complicated : necessary to
tune group III fluxes, N2 flow rate and RF power
AlN (Ts~830°C), metal or nitrogen rich
GaN and AlN films grown by plasma assisted-MBE and by ammonia-MBE
to study the influence of the nitrogen source and of the gas flow rate :
-on the uniformity of thickness
-on the surface and crystal quality
AlN grown on Si(111)
GaN grown on :
• Si (111) with GaN/AlN buffer layers
• GaN-on-sapphire templates grown by MOCVD (LUMILOG)
Introduction
0,8 1,0 1,2 1,4 1,6 1,8
0,30
0,35
0,40
0,45
0,50
0,55
0,60
Ga-rich conditions (2-3MLs segregating)
Power (W ) = 550W Power (W ) = 500W Power (W ) = 400W
Gro
wth
rat
e (µ
m/h
)
N2 flow rate (sccm)
Trade-off : growth rate – quality ���� P ~ 400-450 W, 1-1.8 sccm, Ts ~ 720 °C
■ Mesrine et al . Appl. Phys. Lett. 72 (3) p.350 – 1998).Riber 32 reactor
� from 200 to 80 sccm : increase of
the GaN growth rate ; reduction of
the screening effect of NH3.
Vg: 0.61 – 0.68 µm/h
� below 20 sccm : decrease of
GaN growth rate due to insufficient
supply of nitrogen.
Ga : BEP ~ 5E-7 Torr
NH3 20 sccm : BEP ~ 7E-5 Torr
����NH3 cracking efficiency of a few %
Effect of nitrogen flow rate and RF power.
Growth using a nitrogen plasma source (Ga-rich growth regime) T > 700°C
Depending on growth conditions, AFM shows terraces with a mean height of step of 1 molecular monolayer (left)
and 2 monolayers (right)
AFM – 1x1 µm²
0,5
0,6
0,7
0,8
0,9
1
1,1
1,2
1,3
0 20 40 60 80 100 120 140 160 180 200
NH3 (sccm)
Vc
GaN
(µm
/h)
this study
Mesrine
NH3 screening effect
‘’N’’ limited growth
‘’N’’ rich growth
NH3 min :
200 sccm
NH3 min :
80 sccm
NH3 min :
40 sccm
NH3 min :
20 sccm
below 80 sccm : development of pits related to dislocations
from 200 to 80 sccm : increase of the roughness.
growth mode intermediate between
2D nucleation and step flow
⇒ Step height 1 ML (0.25 nm)
GaN ammonia growth : effect of flow rate GaN plasma assisted growth :
Thickness uniformity
XRD results
AFM 1x1 µm²
AlN / GaN grown on 4” , 3” and 2” silicon
Silicon substrate
AlN Nucleation layer
GaNBuffer layer
Advantages:-Contactless -Fast measurements-Tunable probe size ~2-6 mmDrawbacks:-Accuracy decreases when thickness decreasesin the interference regime (necessitates thesimulation of TO mode broadening )Set up bench-IR source : 50-9000cm-1
-Detector range (DGTS) : 380 – 7500cm-1
RIBER Compact 21T
VbVb-Vg
EF
Conduction band
Depletion region : h dh~0
Low doped
Highly doped
The capacitance is almost independent with Vb, Nd-Na
VbVb-Vg
EF
Conduction band
Depletion region : h dh~0
Low doped
Conduction band discontinuityhigh polarization field at the interfaceFermi level pinning by defects
Mercury probe CV (Hg-CV) Fourier Transform InfraRed spectroscopy (FTIR)
centre RMS = 1.66 nm
centre + 25 mmRMS = 1.54 nm
centre + 40 mm RMS = 1.66 nm
centreRMS = 0.31 nm
centre + 30 mm RMS =0.47 nm
centre + 20 mm RMS = 1.40 nm
centreRMS = 0.96 nm
150 nm AlN plasma N-rich on 3’’ Si
centreRMS = 0.51 nm
centre + 20 mmRMS = 0.58 nm
centre + 30 mmRMS = 0.55 nm
200 nm AlN NH3 130 sccm on 4’’ Si
centreRMS = 0.12 nm
centre + 30 mmRMS = 0.12 nm
centre + 40 mm RMS=0.13 nm
UniformityInfluence of nitrogen source and flow rate
Thickness uniformity from Hg-CV Comparison Hg-CV vs FTIR Thickness uniformity from F TIR
AFM : surface morphology
centre + 30 mm RMS = 2.90 nm
150 nm AlN plasma Al-rich on 3’’ Si
600 nm GaN NH3 200 sccm on 4’’ Si
600 nm GaN plasma Ga-rich on 3’’ Si
0
1000
2000
3000
4000
5000
6000
0 50 100 150 200 250
NH3 flow rate (sccm)
FW
HM
(a
rcse
c)
0,13 µm AlN NH3: XRD (002), (101)
AlN FWHM (101)
AlN FWHM (002)
0
500
1000
1500
2000
2500
3000
3500
4000
4500
centre c+10mm c+20mm c+30mm c+40mm
0,6µm GaN NH3 (200 sccm)
0,6µm GaN NH3 (200 sccm)
0,5µm GaN plasma (Ga-rich)
1µm GaN NH3 (200 sccm)
2,6µm GaN NH3 (200 sccm)
GaN (302) XRD
FW
HM
(a
rcse
c)
Position (mm)
0
200
400
600
800
1000
1200
1400
1600
centre c+10mm c+20mm c+30mm c+40mm
0,6µm GaN NH3 (200 sccm)
0,6µm GaN NH3 (200 sccm)
0,5µm GaN plasma (Ga-rich)
1µm GaN NH3 (200 sccm)
2,6µm GaN NH3 (200 sccm)
GaN (002) XRD
FW
HM
(a
rcse
c)
Position (mm)
0,00
0,05
0,10
0,15
0,20
0,25
-50 -40 -30 -20 -10 0 10 20 30 40 50
h A
lN (
µm)
NH
3 M
BE
position (mm)
NH3 10 sccm
NH3 130 sccm
NH3 200 sccm
σ = 1,9-2 % over 50 mm σ = 2,6-3,1 % over 60 mm
σ = 1,9 % over 60 mm σ = 5 % over 80 mm
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
-50 -40 -30 -20 -10 0 10 20 30 40 50
h G
aN &
AlN
(µm
) N
H3
MB
E
position (mm)
AlN
GaN
σ = 1 % over 60 mm σ = 3 % over 80 mm
σ = 0,9 % over 50 mm σ = 1,2 % over 60 mm NH3 200 sccm
NH3 130 sccm
Continuous lines are data from Hg-CV
0,00
0,05
0,10
0,15
0,20
0,25
0 10 20 30 40 50
h A
lN (
µm)
RF
vs
NH
3
position (mm)
AlN NH3
AlN Al-rich RF N2 = 0,4 sccmAlN N-rich RF
N2 = 2 sccm
σ = 2,8 % over 25 mm σ = 3,7 % over 30 mm
σ = 2,7 % over 25 mm σ = 4,0 % over 30 mm
σ = 1,5 % over 25 mm σ = 3,2 % over 30 mm
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
1,10
1,20
0 10 20 30 40 50
h G
aN (
µm)
RF
vs
NH
3
position (mm)
GaN NH3
GaN RF N2=1,8 sccm
σ = 1,5 % over 30 mm σ = 2,7 % over 40 mm
σ = 1,4 % over 25 mm σ = 1,9 % over 30 mm
σ = 2,2 % over 25 mm σ = 3,4 % over 30 mm
-Influence of nitrogen precursor and its flow rate on the quality and the residual doping in GaN grown by molecular beam epitaxy, Y.Cordier, F.Natali, M.Chmielowska, M.Leroux, C.Chaix, P.Bouchaib, Physica Status Solidi C 9, 523–526 (2012).
-Advances in quality and uniformity of (Al,Ga)N/GaN quantum wells grown by molecular beam epitaxy with plasma source, F.Natali, Y.Cordier, C. Chaix, P.Bouchaib, Journal of Crystal Growth (311) 2029–2032 (2009).
-Signature of monolayer and bilayer fluctuations in the width of (Al,Ga)N/GaN quantum wells, F.Natali, Y.Cordier, J.Massies, S.Vezian, B.Damilano, M.Leroux, Physical Review B 79, 035328 (2009).
-Developments for the production of high quality and high uniformity AlGaN/GaN heterostructures by Ammonia MBE, Y.Cordier, F.Semond, J.Massies, M.Leroux, P.Lorenzini, C.Chaix, Journal of Crystal Growth (301/302) 434-436 (2007).
-Quality and uniformity assessment of AlGaN/GaN Quantum Wells and HEMT heterostructures grown by molecular beam epitaxy with ammonia source, Y.Cordier, F.Pruvost, F.Semond, J.Massies, M.Leroux, P.Lorenzini, C.Chaix, Physica Status Solidi C 3, 2325-2328 (2006).
0
2000
4000
6000
8000
10000
FWHM 002
FWHM 101
FWHM 103
FW
HM
(a
rcse
c)
AlN RF-MBE : XRD (002), (101), (103)
0,16µm plasma
(N-rich)
0,15µm plasma
(N-rich)*
0,15µm plasma
(Al-rich)*
* : with 40 nm AlN NH3 nucleation layer
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0 10 20 30 40 50
position (mm)
h (
µm)
AlN
GaN
centre + 15 mm RMS = 0.33 nm
0
1000
2000
3000
4000
5000
6000
7000
8000
centre c+10mm c+20mm c+30mm c+40mm
0,16µm plasma (N-rich)
0,15µm plasma (Al-rich)
0,15µm plasma (N-rich)
0,13µm NH3 (10 sccm)
0,16µm NH3 (130 sccm)
0,2µm NH3 (130 sccm)
0,2µm NH3 (130 sccm)
AlN (002) XRD
FW
HM
(a
rcse
c)
Position (mm)
0
2000
4000
6000
8000
10000
12000
14000
centre c+10mm c+20mm c+30mm c+40mm
0,16µm plasma (N-rich)
0,15µm plasma (Al-rich)
0,15µm plasma (N-rich)
0,13µm NH3 (10 sccm)
0,16µm NH3 (130 sccm)
0,2µm NH3 (130 sccm)
0,2µm NH3 (130 sccm)
AlN (101) XRD
FW
HM
(a
rcse
c)
Position (mm)
