- Email: [email protected]
SiC and group III nitride growth in MOVPE production reactors
Dian~ond and Related Materials 6 ( 1997) 1301- 1305
Sic and group
e growth in
uction reach
R. Beccard a**, D. Schmitz a, E.G. Woelk b, G. Strauch a, H. Jiirgensen a a AIXTRON Gtttbf?, Kackertstr. 15-l 7, D-52072 Aacltett, Gertttatty b AIXTRON Inc., 1569 Bar&v Blvd. Bufalo Grove, IL 60089. USA
Abstract In this study a range of MOVPE systemsfor high temperature epitaxial growth processes, such as Sic and group III nitrides, is presented. It is shown that extensive modelling of the heat transfer, gas Row and reactantdepletionhas led to bigbly etkicnt reactors that provide the capability for uniform growth of binary and terrary material systems at temperatures up to I6(J(I C in single- and multi wafer configurations. Experimental results of various layers are presented to prove the availability of statc-ofthe-art process technology in production-scale systems.ic)1997 Elsevier Science S.A. Keywords:
4.
MOCVD; Nitride: SIC: Modelling
Introduction
Silicon carbide is currently gaining much attention as it mttcrial for high tc9nperature, high speed illld high powlrr dcviccs. HOWCW, fnbricatiag spitaxial SiC lilms is still u challenge since very high growth t~mpcraturcs (191710 1600 “cI’) IWC t0 14~ llseri. ~~99dt111y &ptCd 9VXlW design t0 L’lIslIrc lil~llilli\~IlOW conditions tllKi co9itrollcJ dcl7lction 01’ the 9XilCtillltS insidc lhc reuctor. Similar cotxklcratiO9~s are valid for the group III tritrides (AIN, GIN. hN and their alloys). These mttteri~ als are also grown at high deposition te9nperati99w (up t0 1300 “C ). Furthermore, the heterostructures of these materials typically 9*equireabrupt changes in growth tctnperature. In general, both nitrides and SiC are similar in their challenges to growth equipment. This study uses a family of high temperature reactors to grow SiC and 99itridcs. Extensive nrodcllitlg was ussd in order to lind the opti9num reactor geometry. Thus a91 optimizatio9l of uniformity and efficiency, and a miuitnization of undesired parasitic reactions was obtained.
*ritcfiC IU~~I-C
Growth experi9nentsl~erfort~lcdin an AIX 200/4, saies two-flow horizontal lamitlar flow CVD reactor provided
* Corresponding author. 0925~9635/97/%19.00 0 1999Elsevier Science S.A. All rights reserved. PII SO925-9635(97)001 IO-6
Ilk2 water cooled reactor top. thus rcguialing the thermill conductivity belwccn the plate and the hcnt sink. This technique has worked for ail matcriais grown in this type of reactor so far and greatly roduccs the deposition 131. In both reactors the two-llow gas inlet introduces the metalorganic precursors keeping them separate from the ammonia in the CsaN system, or in the case of SiC growth keeping the silicon precursor away from the carbon source gas flow. Thus prc-reactions are avoideci and tuning of the two separate gas tlows can be used to and
iidjust the deposition uniformity over the rotating substrate. For the GaN matcriai growth, NI-15with semiconductor purity and convcntionai Ga- and At-precursors was used. Pd-dill’used H2 or N2 was used as a carrier gas. Most experiments were performed on basal plane AiLQJ. Typical total flow rates for the growth experiments are 6.5 and 13 slm at reactor ceil pressures of 10 and 50 mbar, respectively. In the case of SIC growth, 3C-SiC layers were deposited on Si ( 100, I 11) subst,ales and 6H-SiC substrates. For growth on Si the well known
1303
0,78
0.6
0,82
0,84
0,66
0,88
0,9
l/Td[lOOO/K]I Fig. 2. Growth
rate 01’GaN versus
carbonization techniques were used. SiH2C14 and C2H4 were used as process gases. The substrate temperature was varied between 1200 and 1390 “C; when using SiH, and CJH8 temperatures up to 1700 ‘C were employed.
3.
odellisg
Extcnsivc modelling was pcrformcd to study the dependence of the growth rate on key process paramctcrs. such it
1Td (AIX 200/4).
originating from the TMGa decomposition is assumed to govern the growth Irate. As seen in Fig. 3(b), the MMGa gradient decreases linearly along the radius. Similar results were also found in the simulations of ;I smaller horizontal reactor which were in good agreement with the aciual growth runs [5]. 0th the modelling and the experiments show that the thermal management of heat transfer can be handled by the predicted Planclwry Rcaclor”” design. The tcmpsraturc of the reactor ceiling can be adjusted to ;~llou optimum and rcproduciblc deposition c~~~ld~~~~)~~~. Tcmpcralurc uniformitics at 1600 “C on 2 in. subslratcs th:~t ilrc bcmr than -i_S C IKIVC 19~3~ ~JL’;LSLII.~. ‘1%~ cnlculakxi strc;lmlincs ;\I 1000 mb;lr 8nd 50 mh;lr arc
free from any vortices from the centrc toward the outer radius. Further. the model clearly points out 111~’ &van~~~~ti~~y lage of this geometrical cone tb. linReaclorR which. cvcn al kigh-tc carizes thu depletion behaviour ratbcr thim cornpc~~~~~~ ing depletion effects while giving tlic bcsr ~~c~~~cv~~~~c efficiency on wafers, as often seen in the conventional III--V material system.
ylindium in ;I purilicd Trimcthylpallium an nitrogen carrier gas were used for the Ga( In)N together with purified ~~t~l~~oni~~. temperature for the 500 A bu&.r layer was 600 C. the temperalures for the GaN layer were 1050. 1900 ‘I:. using growth initiation and bulfer layer growth. cxcell layer properties of GaN were obtained. Using Of conditions. GaN with an X-ray 0002 peak FWfI
1304
R. Bcwtrrci et (II. / Ditrr~to~tdcatd Related
Matwiuls
6 ( 1997) 1301-1305
concentiation=l trimethylgallium
monomethylgallium
approximately 30 arcs was obtained. PL results show values of 50 meV FWHM. In order to grow the p-doped layers necessary for LED and laser production, Mg-doping has been used employing Cp,Mg [6]. Growth of SIC on Si also shows excellent layer properties. The X-ray analysis reveals a strong texture. Beside the main high-intensity peak, retlexes with lower intensities have been registered. X-ray dirrraction clearly shows the existence of additional 3C-SiC modifications, SEM analysis shows a smooth surface. lanetary Reactor* the following growth parameters were used: pressure 100mbar, total flow 14.1 slm, ammonia flow 4 slm and TMGa 267 pmol min-I. At these conditions a growth rate of 1.3 pm h _ ’ was observed. Higher TMGa flows yield higher growth rates. The simulated growth rate is shown
concentration
concentration
cencentration = n;ax
in Fig. 4 along with the actual growth rate. The total flow consumption of 2 I min- ’ per wafer is minimal compared to any other multiwafer MOCVB reactor described in the literature so far. The material films were characterized by Hall, X-ray and photoluminescence (PL) measurements. The mapping of the full width at half maximum (FWHM) of the X-ray peak of a GalnN film with an indium content of -5% and a thickness of 0.3 ym shows a variation of less than -1_I50 arc s. PL mappings reveal similar results; GaInN PI, uniformities across a 2 in. wafer are better than 3 nm.
In this paper it is shown that material systems like GaN and SiC which require high temperature MOVPE
R. Beecard et al / Diamond and Related Materials 6 (1997) 1301-1305
1305
The authors would like to acknowledge Prof. Razeghi’s group, Cente; of Quantum Devices. Northwestern University: Dr Makarov, Institut ftir Stremungsmechanik, Erlangen; and also E. Niemann, D. Leidich, Daimler Benz AG, Frankfurt, for providing their modelling and experimental growth results for this paper.
References
OOli_.
. 0.04
0.06
0.08
0.10
0.12
distance from center (m) Fig. 4. Simulated and observed growth rates in the reactor.
reactors can be grown successfully. A two-flow reactor concept is required to separate the precursors until shortly before the growth area on the susceptor. Simulation has shown how to optimize the reactor geometry to guarantee high quality deposition. Using the Planetary Reactor@ concept, multiwafer mass production of Sic and GaN is possible and available on the market. Modelling has shown that high quality and high efficiency layers can be deposited across large areas. Temperature uniformities at 1600 “C on 2 in. substrates of better than -t_5 “C have been obtained. Currently a number of these 7 x 2 in. reactors arc used to scale-up production quantities for both material systems.
[I] P.M. Frijlink, A new versatile, large size MOVPE reactor, J. Cryst. Growth 93 (1988) 207-215. [2J BurkA.A., Jr., L.B. Rowland, Reduction of unintentional aluminum spikes at SE vapor phase epitaxial layer/substrate interfaces, Appl. Phys. Lett. 68 (1996) 382-384. [3] P.M. Frijlink, Epitaxial Reactor having a wall which is protected from deposits, United Slates Patent No 5.027.746 July 2, L991. [4] T. Bergunde. M. Dauelsberg, Yu. Egorov, L. Kadinski, Yu.N. Makarov, M. SchBfer, G. Strauch, M. Weyers, Algorithms and models for simulation of MQCVD of III-V layers in the planetary reactor, in: H. Ryssel, P. Pichler (Eds.). Simulation ofSemiconductor Devices and Processes, vol. 6, Springer Wien. New York. 1995. [5] M. Dauelsberg, L. Kadinski, Yu. N. Makarov, E. Woelk, 6. Strauch, D. Schmitz, H. Juergensen. GaN-MOVPE: Correlation between computer modeling and experimental data, Proceedings of the 6th International Conference on Silicon Carbide and Related Materials, Kyoto, September 18-21, 199.5(in press). [h] P. Kung, X. Zhang. E. Bigan. M. Razeghi. A. Saxlcr, Low pressure mctalorganic chemical vapor deposition of high quality AIN and GaN thin films on sapphire and silicon substrates, Procccdinps of SPIE Photonics West. San Jo&, February 4 IO, 1995 (in prcrs).
Sic and group
e growth in
uction reach
R. Beccard a**, D. Schmitz a, E.G. Woelk b, G. Strauch a, H. Jiirgensen a a AIXTRON Gtttbf?, Kackertstr. 15-l 7, D-52072 Aacltett, Gertttatty b AIXTRON Inc., 1569 Bar&v Blvd. Bufalo Grove, IL 60089. USA
Abstract In this study a range of MOVPE systemsfor high temperature epitaxial growth processes, such as Sic and group III nitrides, is presented. It is shown that extensive modelling of the heat transfer, gas Row and reactantdepletionhas led to bigbly etkicnt reactors that provide the capability for uniform growth of binary and terrary material systems at temperatures up to I6(J(I C in single- and multi wafer configurations. Experimental results of various layers are presented to prove the availability of statc-ofthe-art process technology in production-scale systems.ic)1997 Elsevier Science S.A. Keywords:
4.
MOCVD; Nitride: SIC: Modelling
Introduction
Silicon carbide is currently gaining much attention as it mttcrial for high tc9nperature, high speed illld high powlrr dcviccs. HOWCW, fnbricatiag spitaxial SiC lilms is still u challenge since very high growth t~mpcraturcs (191710 1600 “cI’) IWC t0 14~ llseri. ~~99dt111y &ptCd 9VXlW design t0 L’lIslIrc lil~llilli\~IlOW conditions tllKi co9itrollcJ dcl7lction 01’ the 9XilCtillltS insidc lhc reuctor. Similar cotxklcratiO9~s are valid for the group III tritrides (AIN, GIN. hN and their alloys). These mttteri~ als are also grown at high deposition te9nperati99w (up t0 1300 “C ). Furthermore, the heterostructures of these materials typically 9*equireabrupt changes in growth tctnperature. In general, both nitrides and SiC are similar in their challenges to growth equipment. This study uses a family of high temperature reactors to grow SiC and 99itridcs. Extensive nrodcllitlg was ussd in order to lind the opti9num reactor geometry. Thus a91 optimizatio9l of uniformity and efficiency, and a miuitnization of undesired parasitic reactions was obtained.
*ritcfiC IU~~I-C
Growth experi9nentsl~erfort~lcdin an AIX 200/4, saies two-flow horizontal lamitlar flow CVD reactor provided
* Corresponding author. 0925~9635/97/%19.00 0 1999Elsevier Science S.A. All rights reserved. PII SO925-9635(97)001 IO-6
Ilk2 water cooled reactor top. thus rcguialing the thermill conductivity belwccn the plate and the hcnt sink. This technique has worked for ail matcriais grown in this type of reactor so far and greatly roduccs the deposition 131. In both reactors the two-llow gas inlet introduces the metalorganic precursors keeping them separate from the ammonia in the CsaN system, or in the case of SiC growth keeping the silicon precursor away from the carbon source gas flow. Thus prc-reactions are avoideci and tuning of the two separate gas tlows can be used to and
iidjust the deposition uniformity over the rotating substrate. For the GaN matcriai growth, NI-15with semiconductor purity and convcntionai Ga- and At-precursors was used. Pd-dill’used H2 or N2 was used as a carrier gas. Most experiments were performed on basal plane AiLQJ. Typical total flow rates for the growth experiments are 6.5 and 13 slm at reactor ceil pressures of 10 and 50 mbar, respectively. In the case of SIC growth, 3C-SiC layers were deposited on Si ( 100, I 11) subst,ales and 6H-SiC substrates. For growth on Si the well known
1303
0,78
0.6
0,82
0,84
0,66
0,88
0,9
l/Td[lOOO/K]I Fig. 2. Growth
rate 01’GaN versus
carbonization techniques were used. SiH2C14 and C2H4 were used as process gases. The substrate temperature was varied between 1200 and 1390 “C; when using SiH, and CJH8 temperatures up to 1700 ‘C were employed.
3.
odellisg
Extcnsivc modelling was pcrformcd to study the dependence of the growth rate on key process paramctcrs. such it
1Td (AIX 200/4).
originating from the TMGa decomposition is assumed to govern the growth Irate. As seen in Fig. 3(b), the MMGa gradient decreases linearly along the radius. Similar results were also found in the simulations of ;I smaller horizontal reactor which were in good agreement with the aciual growth runs [5]. 0th the modelling and the experiments show that the thermal management of heat transfer can be handled by the predicted Planclwry Rcaclor”” design. The tcmpsraturc of the reactor ceiling can be adjusted to ;~llou optimum and rcproduciblc deposition c~~~ld~~~~)~~~. Tcmpcralurc uniformitics at 1600 “C on 2 in. subslratcs th:~t ilrc bcmr than -i_S C IKIVC 19~3~ ~JL’;LSLII.~. ‘1%~ cnlculakxi strc;lmlincs ;\I 1000 mb;lr 8nd 50 mh;lr arc
free from any vortices from the centrc toward the outer radius. Further. the model clearly points out 111~’ &van~~~~ti~~y lage of this geometrical cone tb. linReaclorR which. cvcn al kigh-tc carizes thu depletion behaviour ratbcr thim cornpc~~~~~~ ing depletion effects while giving tlic bcsr ~~c~~~cv~~~~c efficiency on wafers, as often seen in the conventional III--V material system.
ylindium in ;I purilicd Trimcthylpallium an nitrogen carrier gas were used for the Ga( In)N together with purified ~~t~l~~oni~~. temperature for the 500 A bu&.r layer was 600 C. the temperalures for the GaN layer were 1050. 1900 ‘I:. using growth initiation and bulfer layer growth. cxcell layer properties of GaN were obtained. Using Of conditions. GaN with an X-ray 0002 peak FWfI
1304
R. Bcwtrrci et (II. / Ditrr~to~tdcatd Related
Matwiuls
6 ( 1997) 1301-1305
concentiation=l trimethylgallium
monomethylgallium
approximately 30 arcs was obtained. PL results show values of 50 meV FWHM. In order to grow the p-doped layers necessary for LED and laser production, Mg-doping has been used employing Cp,Mg [6]. Growth of SIC on Si also shows excellent layer properties. The X-ray analysis reveals a strong texture. Beside the main high-intensity peak, retlexes with lower intensities have been registered. X-ray dirrraction clearly shows the existence of additional 3C-SiC modifications, SEM analysis shows a smooth surface. lanetary Reactor* the following growth parameters were used: pressure 100mbar, total flow 14.1 slm, ammonia flow 4 slm and TMGa 267 pmol min-I. At these conditions a growth rate of 1.3 pm h _ ’ was observed. Higher TMGa flows yield higher growth rates. The simulated growth rate is shown
concentration
concentration
cencentration = n;ax
in Fig. 4 along with the actual growth rate. The total flow consumption of 2 I min- ’ per wafer is minimal compared to any other multiwafer MOCVB reactor described in the literature so far. The material films were characterized by Hall, X-ray and photoluminescence (PL) measurements. The mapping of the full width at half maximum (FWHM) of the X-ray peak of a GalnN film with an indium content of -5% and a thickness of 0.3 ym shows a variation of less than -1_I50 arc s. PL mappings reveal similar results; GaInN PI, uniformities across a 2 in. wafer are better than 3 nm.
In this paper it is shown that material systems like GaN and SiC which require high temperature MOVPE
R. Beecard et al / Diamond and Related Materials 6 (1997) 1301-1305
1305
The authors would like to acknowledge Prof. Razeghi’s group, Cente; of Quantum Devices. Northwestern University: Dr Makarov, Institut ftir Stremungsmechanik, Erlangen; and also E. Niemann, D. Leidich, Daimler Benz AG, Frankfurt, for providing their modelling and experimental growth results for this paper.
References
OOli_.
. 0.04
0.06
0.08
0.10
0.12
distance from center (m) Fig. 4. Simulated and observed growth rates in the reactor.
reactors can be grown successfully. A two-flow reactor concept is required to separate the precursors until shortly before the growth area on the susceptor. Simulation has shown how to optimize the reactor geometry to guarantee high quality deposition. Using the Planetary Reactor@ concept, multiwafer mass production of Sic and GaN is possible and available on the market. Modelling has shown that high quality and high efficiency layers can be deposited across large areas. Temperature uniformities at 1600 “C on 2 in. substrates of better than -t_5 “C have been obtained. Currently a number of these 7 x 2 in. reactors arc used to scale-up production quantities for both material systems.
[I] P.M. Frijlink, A new versatile, large size MOVPE reactor, J. Cryst. Growth 93 (1988) 207-215. [2J BurkA.A., Jr., L.B. Rowland, Reduction of unintentional aluminum spikes at SE vapor phase epitaxial layer/substrate interfaces, Appl. Phys. Lett. 68 (1996) 382-384. [3] P.M. Frijlink, Epitaxial Reactor having a wall which is protected from deposits, United Slates Patent No 5.027.746 July 2, L991. [4] T. Bergunde. M. Dauelsberg, Yu. Egorov, L. Kadinski, Yu.N. Makarov, M. SchBfer, G. Strauch, M. Weyers, Algorithms and models for simulation of MQCVD of III-V layers in the planetary reactor, in: H. Ryssel, P. Pichler (Eds.). Simulation ofSemiconductor Devices and Processes, vol. 6, Springer Wien. New York. 1995. [5] M. Dauelsberg, L. Kadinski, Yu. N. Makarov, E. Woelk, 6. Strauch, D. Schmitz, H. Juergensen. GaN-MOVPE: Correlation between computer modeling and experimental data, Proceedings of the 6th International Conference on Silicon Carbide and Related Materials, Kyoto, September 18-21, 199.5(in press). [h] P. Kung, X. Zhang. E. Bigan. M. Razeghi. A. Saxlcr, Low pressure mctalorganic chemical vapor deposition of high quality AIN and GaN thin films on sapphire and silicon substrates, Procccdinps of SPIE Photonics West. San Jo&, February 4 IO, 1995 (in prcrs).