Commercial Hot Wire Chemical Vapor Deposition (HWCVD) Diamond History to Photovoltaic Future? www.sp3inc.com
Outline sp 3 Background Diamond and HWCVD Reactors and Applications PV Applications sp 3 Equipment Capabilities for PV 2
sp 3 History Founded June 1993 Founders are all ex semiconductor process and equipment people Initial Focus on CVD Diamond for Cutting Tools Developed in house HWCVD production tools by necessity Current sp 3 hot wire reactors are used for a wide variety of diamond coated products Cutting Tools Seals and other wear surfaces Semiconductor devices for thermal management MEMS devices for membranes and inert coatings Electrodes CMP Conditioners Fusion Reactor Coatings Atomic Hydrogen Anneals 3
Reactor Development History The original sp 3 DT Model 500 Diamond deposition reactor was designed to be used internally only. Outside interest prompted redesigns. The present sp 3 DT Model 650 Diamond deposition reactor was designed to be used internally as well as be available for sale The system was designed to meet semiconductor industry standards 4th generation product A fully integrated process control computer allows for unattended operation while preserving the reproducibility and safety of the process. The sp 3 Model 650 is the most economical system available for hot wire CVD diamond deposition. sp 3 DT has an installed base of 15 HWCVD systems worldwide 4
Wafer Scale Diamond - Thin Film Reactor Deposition 1999 Reactor Evolution 5 1994 2006
6 Model 650 Reactor Configurations Available in a standard production configuration and a more flexible configuration for R & D applications. Round or irregular shaped substrates are supported in the reactor by proprietary fixturing A three-dimensional filament array produces process uniformity without the complexity and reliability sacrifices of moving mechanisms inside the process chamber Flat substrates are coated with planar filament array fixturing package. The Model 650 can be configured to produce diamond coatings from submicron to 50 micron thickness and in nano-crystalline or micro-crystalline structures.
Model 650 CVD Reactor Features Model 650 Reactor Fixturing for 100, 150, 200 or 300mm wafers Wafers above or below filaments Key Features All Aluminum, cold wall chamber 30 kw filament power supply 125 micron filaments for optimum activation efficiency Large (15 x 15 ) deposition area Computer controlled for process development and replication Doped or undoped films Option for temperature controlled substrates Standard Processes for Polycrystalline and Nanocrystalline diamond films 7
Proven Performance Over 200,000 reactor hours of operational experience with the basic platform Reliable operation in any environment >95% uptime >500 hr MTBF at 25kW filament power <5 hr/month scheduled downtime Well understood system variables with regard to process development 8
Unattended Operation Capabilities Windows XP or Vista Network/User Interface Real time controller for process execution Hardware Interlocks for Machine and Personnel Protection Software control of recipe abort vectors Remote viewing of reactor data using stand alone data viewer Remote recipe editing with stand alone recipe editor software 9
Model 650 Network Connections FUNCTION LIST Desktop System Edit Recipes Vie w Data Files View Eve nt Logs Analyze Data File s Print Recipes Print Data Files Print Eve nt Logs Netw ork printer Print Recipes Print Data Files Print Event Logs Desktop System Ethernet FUNCTION LIST 10 Touch Screen Monitor Rack mount PC Mypro Process Controller sp3 Diamond Reactor Local printer Touch Screen Monitor Rack mount PC Mypro Process Controller sp3 Diamond Reactor Start Proce ss Recipe Stop Proce ss Recipe Colle ct Data File s Edit M achine Configuration Edit Recipes View Data File s Vie w Eve nt Logs Analyze Data File s Print Recipes Print Data File s Print Eve nt Logs
Graphical User Interface 11
Recipe Editor 12
What Can Be Grown Besides Diamond? Photovoltaic Applications Polysilicon Amorphous silicon Silicon Nitride Atomic hydrogen anneals Epitaxial silicon Compound Semiconductor Applications GaN AlN SiC 13
Ag Grid Examples of Solar Cell Architecture that can Benefit from Hot Wire CVD Processes SiN x AR Coating n + emitter Emitter Contacts TCO/AR a-si(i-p) p-si c-si (n-type) Homojunction device 14 Al-BSF Ag Contact BSF Contacts Hetrojunction device (shown without texture) a-si(i-n) TCO Hydrogen passivation of defects in the silicon ( multicrystalline solar cells) Deposition of - Si as a surface passivation layer ( front and back surfaces) Deposition of Silicon Nitride as an Antireflection Coating Deposition of high quality, thin, doped and undoped amorphous silicon layers, - Low damage process critical for hetrojunction devices
Operating Conditions for PV applications Atomic Hydrogen Anneals 5-50 Torr pressure 100-700 deg. C Substrate Temp 2000 2500 deg C Filament Temp Model 650 α-silicon, silicon nitride, polysilicon, epitaxial silicon 10-500 mtorr pressure 100-500 deg. C Substrate Temp 1200-2500 deg. C Filament Temp Gases Used Silane Dopants Ammonia Hydrogen Model 700 Reactor 15
Model 700 PV Model 650 feature set plus the following: High Conductance Pumping System for Deposition Pressures as low as 5 mtorr Gas Distribution showerhead for Optimized Uniformity Active substrate cooling for deposition temperatures as low as 50C at filament temperatures >2000C Multiple filament wire options Inverted filament operation capability Fast Ramp low mass filaments 16
Model 700 Deposit Down Configuration Gas Showerhead Substrate Cooling 380 mm square filament array 2x2 156 mm Si 17
Model 700 Deposit Up Configuration Substrate Cooling 2x2 156 mm Si 380 mm square filament array Gas Showerhead 18
Model 700 Double Side Configuration Gas Showerhead 2x2 156 mm Si Gas Showerhead 380 mm square filament array 19
Why Use an sp 3 Reactor for PV Applications? Large Area Deposition (>350mm square) Large enough to eliminate edge effects and to study multiple substrate uniformity issues Small Reactor footprint Adapts easily to R&D environment Minimal mechanical automation allows quick configuration changes Most Processes can be run on one reactor Reactor chamber is easily adaptable for different configurations and could also be adapted to form an automated inline mini production system 15 years of hot wire experience with processes and operational conditions substantially more challenging than most PV processes 20
Summary HWCVD for diamond deposition has been a production reality since 1994 Many different applications exist for HWCVD diamond Many new PV films can be grown using existing HWCVD technology used for diamond growth sp 3 DT is well placed to service the preproduction market with both the equipment and knowledge learned from an installed base of 15 HWCVD systems worldwide sp 3 DT is currently planning larger scale HWCVD Reactors 21