CVDSim Brochure


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Modeling of Epitaxy

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CVDSim Brochure

  1. 1. STR Group CVDSim: Modeling of epitaxy 2009
  2. 2. About STR About Semiconductor Technology Research Semiconductor Technology Research Group (STR) provides consulting services and offers special­ ized software for modeling of crystal growth, epitaxy, and semiconductor devices operation. STR employs highly qualified specialists capable of solving a wide range of practical problems related to semiconductor technologies. A comprehensive research underlies every consulting activity and software product which ena­ bles careful validation of physical models and approaches applied. STR’s expertise in the crystal growth science and device engineering is accumulated in variety of publications in the peer­ reviewed journals. Four product lines are developed and promoted by STR: Bulk crystal growth from the melt Bulk crystal growth from the gas phase Epitaxy and deposition CG Operation of advanced semiconductor devices Modeling of growth from the melt includes detailed 3D simulation of flow dynamics and heat transfer in the reactor. Such growth techniques as Czochralski (Cz), Liquid Encapsulated Czochralski (LEC), Vapor Pressure Controlled Czochralski (VCz), Kyropoulos, Bridgman, and Floating Zone of Si, GaAs, InP, SiGe, sapphire, etc are under study. The focus of research of growth of widebandgap semiconductors (SiC, AlN, GaN) from the gas phase is heat and mass transport in the reactor, crystal shape evolution, and stress and defects dynamics. Simulation of eptiaxy and deposition of various materials (Si, SiC, III­V and III­Nitride compounds) includes flow dynamics and heat transfer, diffusion, gas­phase and surface chemistry, particle for­ mation, parasitic deposition on reactor units. Modeling of advanced semiconductor devices concerns operation of LEDs, FETs, Schottky diodes, laser diodes, photodetectors, etc. The employed approaches allow prediction of device characteris­ tics and optimization of heterostructures and chip designs. Every STR’s product line is represented by a number of commercial software tools for industrial and research applications. 10 basic products in several editions for various semiconductor materials and growth techniques are offered today on the market. Over 50 industrial companies and academic institutions worldwide are the end­users of STR software. There are several local distribution centers of STR software: STR Group, Ltd., Saint­Petersburg, Russia (http:��www.str­ STR �S, Inc., Richmond, VA, �SA (http:�� STR Gmb�, Erlangen, Germany (http:�� SimSciD Corporation, �okohama, �apan (http:�� Next­Tech, Ltd. , Taipei, Taiwan (http:��­ INFOTEC�, Inc., South Korea (http:�� CGSim G r o u p STR
  3. 3. About CVDSim About CVDSim: Introduction of simulation and modeling into development of epitaxial technology becomes more and more intensive in the last years. Modeling may be used for both process and reactor optimization purposes. Besides the description of transport phenomena (flow, heat, species), an adequate chemistry model is necessary to predict deposition rates and uniformities and layer compositions. A surface chemistry model should be able to predict epitaxial growth on the wafer as well as parasitic deposition on the reactor inner surfaces. STR has been developing its epi simulation technology for more than 20 years and has ac­ cumulated a unique knowledge and experience resulted in a release of a specialized software package CVDSim intended for modeling of epitaxy in mass­production and research scale re­ actors. Robust and physically based process models of have been constructed and are continu­ ously improved and updated in order to meet today’s customer demand and requirements. With the tens of licenses sold throughout the world (China, Europe, �apan, South Korea, Tai­ wan, �SA), CVDSim is being used now by the leading producers of epitaxial equipment, wafer� epiwafer suppliers and optoelectronic�electronic device manufacturers in everyday work on development of new generation technologies. Scientific leadership and expertise of STR in modeling of epitaxy is evidenced by the numer­ ous invited talks and seminars at the international conferences and discussion forums on epi­ taxial technologies and modeling�simulation techniques. There are 5 different Editions of the CVDSim tool: Nitride Edtion for modeling of Metal­Organic Vapor Phase Epitaxy of GaN­, InN­ and AlN­based materials III­V Edition for modeling of Metal­Organic Vapor Phase Epitaxy of arsenides and phosphides �VPE Edition for modeling of GaN growth by �ydride Vapor Phase Epitaxy SiC Edition for modeling of silicon carbide epitaxy Si Edition for modeling of silicon epitaxy We offer two versions of CVDSim tool: version for simulation teams at customer companies�universities(add­ons for CFD­ACE+ and Fluent codes) stand­alone version for epi­engineers with limited�no modeling experience (Nitride and III­V Editions) www.str­
  4. 4. Modeling Global model of Epi process Detailed modeling of Epi process Phenomena being Model output simulated Flow pattern Flow dynamics Temperature Heat transfer including distribution conduction, convection, and radiation Species Mass transport distributions of precursors and reaction products Growth rate Gas-phase chemical Layer composition reactions affecting for ternary deposition behavior and quaternary layers Layer composition Surface chemistry for ternary and quaternary layers Parasitic deposition on reactor walls and constructive elements How modeling can be applied? Modeling solutions Problems ► understanding of the ► loss of the process stability underlying mechanisms ► poor uniformity of the ► optimization of the growth thickness and composition recipe ► parasitic reactions and deposit ► optimization of the reactor design formation Benefits ► increase of the wafers size ► increase of the throughput ► improvement of the process controllability ► cutting down the cost CGSim G r o u p STR
  5. 5. CVDSim G�I CVDSim GUI The CVDSim program is developed for industries and research teams. Graphical User Interface allows one to set up the problem in terms similar to those used in real reactor. All setup and computational steps are highly automated to minimize user efforts. The CVDSim GUI includes everything required for the problem specification, solution control, and visualization of the results. The user can define the substrate temper- ature, system pressure, precursor flow rates and a few other reactor-dependent settings. Quick problem set up CVDSim GUI ► The New Simulation dialog is activated automatically when CVDSim™ G�I starts. The user can select one of the reactor geometries to be modeled from the drop­down list Reactor Type. ► Chemical model name is chosen from drop­down list of the Material section ► Gas flow rates of carrier gas, hydride and MO precursors at reactor inlet(s) are set on the Flow Rates tab. Each MO species flow rate can be computed using bubbler instead of providing exact value. ► Operation conditions as well as optional processes to be accounted for are set on the Model Options tab. There are three Options which control the account of material losses due to Residuals tab Particles formation in the gas, the Wafer Deposition (material growth on the substrate), and parasitic Wall Deposition on reactor walls. ► The specific residuals provide general view of the convergence process, illustrating change of the essential simulation results in course of computations. Other residuals give more insight into the solution convergence, as these residuals reflect the internals of the solution process. www.str­
  6. 6. Results Visualization of results The solution residuals are visualized by the GUI, allowing easy convergence control. 2D distribution of the main variables: temperature, velocity, density, species mass and molar fractions, and particle concentration and density. Flow, temperature, species distributions in a reactor Run­time and post­processing visualization is available within the G�I, presenting 1D distribution of the growth rate and layer composition for ternary and quaternary layers over the substrate. 1D results can saved to a text file for additional post­processing. Both 1D and 2D results can be exported to a picture file. Additional results of the computations are presented graphically in Deposits tab as profile of the parasitic deposit growth rate at the reactor wall. Growth rate and layer composition Parasitic deposit growth rate over the wafer along the reactor wall CGSim G r o u p STR
  7. 7. Examples of CVDSim application Nitride edition: Materials: GaN AlN AlGaN InGaN p-GaN �nder development: ► AlInN ► InGaN on various GaN planes ► Correlation between growth condition and surface quality • Prediction of the growth rate and composition, dopant concentration • Parasitic reactions and particle formation • Parasitic deposition on injectors and walls (low temperature kinetics, condensation of the adducts and non-volatile products) • Effect of the lattice mismatch on alloy composition www.str­
  8. 8. Examples of CVDSim application Effect of inlet design on AlGaN deposition in a horizontal reactor Ref: E.V. Yakovlev et al, J. Crystal Growth 298, 413 (2007) Analysis of the efficiency of aluminum incorporation for two different configurations of the precursor supply has been made. Inversion of the inlet configuration has shown reduction of parasitic deposition and higher growth reproducibility in case of GaN MOVPE. 90 90 exp., RBS exp., RBS 80 80 exp., XRD exp., XRD Al content in the solid phase, % Al content in the solid phase, % calc. calc. 70 70 ideal ideal calc. (const. flow) calc. (const. flow) 60 60 50 50 40 40 30 30 20 20 inverted inlet conventional inlet 10 10 0 0 0 10 20 30 40 50 60 70 80 90 0 10 20 30 40 50 60 70 80 90 Al content in the gas phase, % Al content in the gas phase, % The Al incorporation efficiency is high up to the Al content of about 60 %. �owever, to get the Al ► composition of about 70 %, the total flow in the reactor was increased up to 10 slm to suppress the formation of particles. Inverted supply provides generally lower Al contents, which is especially pronounced at high ► TMAl flows. At the constant total flow of 7.5 slm (blue dashed line), increase of the Al gas­phase composition ► from 55 % to 79.5 % does not provide a significant enhancement of the aluminum incorporation efficiency. This behavior is related to intensification of particle formation and strong depletion of the gaseous mixture with aluminum in flow direction. CGSim G r o u p STR
  9. 9. Examples of CVDSim application Parametric dependencies of AlGaN growth in a Planetary reactor Ref: A.V.Kondratyev et al., J. Crystal Growth, 272, 420 (2004) 0,14 0,14 0,12 0,12 experiment experiment 0,10 computation 0,10 AlN mole fraction AlN mole fraction computation mass-transport limit mass-transport limit 0,08 0,08 0,06 0,06 0,04 0,04 0,02 0,02 0,00 0,00 100 200 300 400 16 18 20 22 24 26 28 Reactor pressure, mbar Total Flow, slm 0,40 Exp, 100 mbar, 16 slm experiment 0,35 Exp, 400 mbar, 27 slm computation 0,35 Comp, 100 mbar, 16 slm mass-transport limit 0,30 0,30 Comp, 400 mbar, 27 slm AlN mole fraction Mass-transport limit AlN mole fraction 0,25 0,25 0,20 0,20 0,15 0,15 0,10 0,10 0,05 0,05 0,00 0,00 0,04 0,06 0,08 0,10 0,12 0,14 10 15 20 25 30 1/(H2 flow through TMGa bubbler), 1/sccm H2 flow through TMAl bubbler, sccm Model predicts general trends of AlGaN growth behavior. ► Pressure reduction and total flow increase make residence time shorter and alkyl partial ► pressure higher that result in smaller losses. At high pressure, additional TMA contributes to losses exhibiting saturation of Al content. ► At a given pressure and total flow high Al content can be reached by simply decreasing TMGa ► flow rate. www.str­
  10. 10. Examples of CVDSim application Effect of V/III ratio on AlN growth in a close coupled showerhead reactor Ref: A.V.Lobanova et al., J. Crystal Growth, 287 (2006) 601 Effect of TMAl flow rate Effect of V/III ratio 2,0 2,5 QTMAl=30µmol/min QTMAl=15µmol/min (QNH3=0.36slm) experiment experiment Growth rate, micron/hr 2,0 experiment 1,5 computation computation computation Growth rate, µµ/h TL 1,5 1,0 1,0 (QNH3=6slm) 0,5 experiment 0,5 computation TL 0,0 0,0 0 2000 4000 6000 8000 0 15 30 45 60 QTMAl, µmol/min V/III ratio AlN particle concentration in the reactor At low ammonia flows small amount At high ammonia flows there is of TMAl passes into particles, growth a noticeable layer of particles efficiency is high. over the susceptor. AlN model reproduces well the following tendencies: ► Linear AlN growth rate variation with the TMAl supply at low ammonia flow rate. ► Sublinear behavior indicating the parasitic processes leading to precursor losses at high ammonia flow rate. ► More pronounced effect of V�III ratio at increased TMAl supply. CGSim G r o u p STR
  11. 11. Examples of CVDSim application Indium incorporation in InGaN MOVPE reactor: horizontal, single­wafer AIX 200 RF data: M. Schwambera et al, J. Crystal Growth, 203, 340 (1999) 30 25 In Content in InGaN, % In Content in InGaN, % Experiment Experiment 20 25 Computations Computations 15 20 10 15 5 10 In/(In+Ga)=80% In/(In+Ga)=20% 0 5 750 800 850 900 800 820 840 860 880 900 o o Temperature, C Temperature, C reactor: horizontal, single­wafer AIX 200�4 RF­S data: E.V. Yakovlev et al., Phys. Stat. Sol. (c) 3 (6) (2006) 1620 0.4 0.35 InN mole fraction in InGaN Strong fall­off of indium 0.3 incorporation with tem­ 0.25 perature due to desorp­ tion is reproduced well by 0.2 the computations. Strain 0.15 enhances desorption from EPMA the layer 0.1 RBS, single layer fit RBS, multilayer average fit 0.05 computations 0 650 700 750 800 850 900 Temperature, oC www.str­
  12. 12. III­V Edition III-V Edition Materials Substrates GaAs GaAs InP InP AlGaAs InGaAs InGaP InGaAlP • Prediction of the growth rate and composition uniformity over the large wafers • Parasitic deposition on the walls and injectors (low temperature growth kinetics) • Effect of the lattice mismatch on alloy composition 1700 1600 1500 Growth rate, nm/h 1400 12 SLM 1300 16 SLM 20 SLM 1200 1100 1000 0 20 40 60 80 100 Distance along the substrate, mm Flow pattern (left) and AlGaAs growth rate distribution (right) in a Planetary reactor CGSim G r o u p STR
  13. 13. �VPE Edition HVPE Edition Materials GaN �nder development: AlN, AlGaN • Prediction of the chemical reactions in Ga source • Prediction of the GaN growth rate over the wafer • Parasitic deposition on the walls and injectors 100 T = 1050°C Carrier gas: 1.55 slm N2 + 1.5 slm H2 Growth rate ( µm / h ) 80 0.25 slm NH3 , 1 slm NH3 , 60 40 20 0 0 5 10 15 20 25 30 HCl flow rate (sccm) GaCl concentration distribution (left) and GaN growth rate versus HCl source flow (right) in a horizontal HVPE reactor www.str­
  14. 14. SiC Edition SiC Edition Materials SiC �nder development: SiC CVD with addition of �Cl • Gas­phase chemistry and particle formation • Prediction of the SiC growth rate over the wafer • Parasitic deposition�etching on the walls and injectors 6 3 D m ode l 5 E xpe rim e nt Growth rate, µm/h 4 3 2 1 0 0 0.02 0.04 0.06 0.08 0.1 P osition a long susce ptor, m Temperature distribution (up) and SiC growth rate distribution (down) in horizontal hot-wall reactors CGSim G r o u p STR
  15. 15. Si Edition Si Edition Materials Si • Deposition and epitaxy of silicon from trichlorosilane (TCS) and dichlorosilane (DCS) • Prediction of the Si growth rate over the wafer • Parasitic deposition on the walls and injectors Flow pattern and temperature distribution (up) and Si growth rate versus growth temperature (down) in Centura reactor for Si and SiGe epitaxy www.str­
  16. 16. STR Group, Ltd. Engels av. 27, P.O. Box 89, 194156 CGSim Saint­Petersburg, Russia Tel: +7 (812) 603 2658 Fax: +7 (812) 326 6194 www.str­ e­mail: cvdsim­support@str­