NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 1 PFC Reduction Technologies: Destruction Recovery Optimization Phyllis Pei, Walter Worth Sematech Semicon/Korea 1997  1999 Arizona Board of Regents for The University of Arizona

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 2 Outline General Comments on PFC Abatement PFC Destruction: – Combustion – Chemical/Thermal – Plasma Recovery/Recycle Optimization

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 3 SEMATECH GLOBAL WARMING PROGRAM OBJECTIVE Decrease the use and reduce the emissions of potential global warming semiconductor processing materials; specifically the perfluorocompounds (PFCs), such as CF 4, C 2 F 6, NF 3, SF 6 and substituted PFCs such as CHF 3

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 4 Typical FAB Vacuum System Vacuum System Fab Scrubber (water) Fab Scrubber (water) N 2 Purge AtmosphereAtmosphere PFC’s CF 4 C 2 F 6 NF 3 SF 6 Etch or CVD Tool

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 5 Destruction/ * Decomposition Process * Optimization Recovery * & Recycle Combustion * Thermal/ Chemical Global Warming Gas Reduction Plasma * Alternative * Chemicals Project Strategy

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 6 cc/min Typical Etch and CVD Systems Atmosphere Scrubber Abatement Pump Pre-Pump Treatment Chamber PFC Alternatives Optimization N2N2 Recovery/Recycle Plasma Destruction Combustion Chem/Thermal Absorption L/min

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 7 Example Conversions in Chamber Clean Applications * PFC CF 4 C 2 F 6 C 3 F 8 NF 3 CHF 3 SF 6 % Consumed in Tool % Emitted * Actual values may vary significantly based on process, tool, recipe, etc.

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 8 Technology Options Commercial Availability Greener, Preferred Technology Plasma Destruction Thermal/Chemical Reaction Combustion Process Optimization Recovery/Recycle Alternative Chemicals

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 9 PFC Abatement Options / Devices Centrotherm Flawamat DAS Escape Delatech CDO* EcoSys Guardian EcoSys Phoenix* Edwards TPU* MIT Microwave* ETC DryScrub* Texas A&M rf surface wave * Los Alamos Pulsed Corona * PRC * Combustion Chemical/Thermal Destruction Plasma Destruction CS Systems Edwards GRC Kanto Denka * Evaluation supported by SEMATECH

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 10 cc/min Typical Etch and CVD Systems Atmosphere PFC Alternatives Recovery/Recycle Plasma Destruction Combustion Scrubber Abatement Pump Pre-Pump Treatment Chamber Optimization N2N2 L/min Chem/Thermal Absorption

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 11 Main Features of a Combustion Device a.A combustion chamber followed by water scrubber in POU cabinet b.Handles up to four tool chambers (200 lpm), each with separate inlet to avoid mixing reactive materials such as silane and NF 3 c.Uses either methane (CH 4 ) or hydrogen (H 2 ) as fuel d.Operates in ºC range for CF 4 destruction, the most difficult to combust

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 12 Main Features of a Combustion Device (Cont’d) e.The best can achieve > 95% destruction for all PFCs f.Combustion by-products include: COF 2, HF, NO X, CO, CO 2 g.Integral scrubber uses 6-8 gpm of water to remove HF, COF 2 and heat of combustion h.Foot print approx. 24” x 36” x (60” high)

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 13 Concerns with PFC Abatement a.Difficult for PFCs, especially CF 4, due to stability b. Often creates other environmental problems: NOx and HAPs c.Generally expensive d.Potential safety concerns: combustion, fuel gas, high temperatures and toxic byproducts e.May impact process tool uptime f.Fab floor space limitations

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 14 Combustion Technology Strengths –Industry is familiar with combustion –Industry is currently using “burn boxes” to treat pyrophorics –One device may be able to abate pyrophorics and PFCs –Most devices have an integral scrubber to remove HF –Technology is closest to being production-worthy Issues –Need open flame and high temperatures (> 850 ºC) to break down PFCs –Produces HF, CO 2 (more GW gas) & NOx (in some cases) –Costs for fuel and water (for scrubber) are significant –Fab may not be piped for fuel –Uses valuable fab floor space –Cost of ownership is high ($50-$100K)/year

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 15 cc/min Typical Etch and CVD Systems Atmosphere Scrubber Abatement Pump Pre-Pump Treatment Chamber PFC Alternatives Optimization N2N2 Recovery/Recycle Plasma Destruction Combustion L/min Chem/Thermal Absorption

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 16 Main Features of Chemical/Thermal Device a.Gases are chemisorbed on reactive granular solids b.Chemistry is generally trade secret c.Solids are held in disposable or reusable stainless steel cartridge d.Solids are electrically heated to °C e.PFCs are converted to stable, non-hazardous salts f.Solids are replaced when the bed is exhausted g.Footprint of dual cartridge cabinet is 30” x 57” (72” high) h.Limited ability to destroy CF 4 in some cases

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 17 Example: CS System a.A packed-bed reactor filled with iron-based granules b.Irreversible chemisorption on catalytically active absorbents c.Laboratory tests show it can treat all PFCs (99% DRE) d.Conversion of PFCs to stable, non-hazardous salts e.Capacity for CF 4 and C 2 F 6 not yet known f.Operating temperatures are °C g.Foot print for dual bed cabinet: 57” x 30” x 71” (H)

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 18 Chemical/Thermal Destruction Technologies Strengths –Reaction product is a non- hazardous solid that can be landfilled –Industry is familiar with concept (technology is used in fabs today to treat toxic hydrides) –Low energy cost –It is a passive system; no moving parts –Scalable, and can accommodate intermittent operations Issues –Cartridge has limited capacity, may only be suitable for etch tools (low PFC flow rates) –Packed bed reactor issues (e.g., plugging, break- through, pressure drop) –Disposal of solids is a concern (e.g., long term liability of landfilled waste) –Cost of ownership is high –Uses valuable fab floor space

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 19 cc/min Typical Etch and CVD Systems Scrubber Atmosphere Abatement Pump Pre-Pump Treatment Chamber PFC Alternatives Optimization N2N2 Recovery/Recycle Combustion Chem/Thermal Absorption L/min Plasma Destruction

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 20 Example: ETC DryScrub a.RF plasma device normally installed downstream of the tool and ahead of the vacuum pump b.Electrode consists of multi-turn, high-conductance spirals that form the path for the gas flow (45 sq. ft. of surface area) c.The residual process gases leaving the tool are reacted to depletion as they pass through device d.The electrode is both the reaction and collection chamber for the solid products formed from the reaction e.The solids-laden electrode is replaced and discarded

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 21 Plasma Destruction Technology Strengths –Industry is familiar with plasma technology –Treats tool exhaust upstream of pump (no N 2 dilution form vacuum pump) –Promises to have low cost of ownership –Products of destruction may all be water-scrubbed Issues –Commercially available RF plasma devices have shown limited effectiveness for PFCs –May require microwave plasma based on successful laboratory tests –Technology still in experimental phase –May not be transparent to process tool –May require additional water scrubber

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 22 Status of PFC Abatement Technology a.Suppliers are working feverishly to develop new devices and improve existing ones. b.Chip manufacturers have committed significant resources to evaluate the systems under development. c.Progress is slow, but significant progress has already been made and further advances are on the horizon. d.Combustion technology is the most advanced and has the most players. e.Packed bed, thermal/chemical destruction is becoming viable. f.Plasma decomposition is still in the experimental phase.

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 23 cc/min Typical Etch and CVD Systems Scrubber Atmosphere Abatement Pump Pre-Pump Treatment Chamber PFC Alternatives Optimization N2N2 Recovery/Recycle Combustion Chem/Thermal Absorption L/min Plasma Destruction

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 24 PFC Recovery Technologies Membrane Separation (Air Liquide) Pressure Swing Absorption (Air Products/Radian, BOC) Cryogenic Extraction (Praxair/Ecosys)

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 25 Example: MEGASORB TM Approach a.Process developed by Air Products & Dow Environmental (now Radian International LLC) b.Uses SORBATHENE TM resins proven for VOCs c.Captures all PFCs for central abatement, recovery and/or purification d.Flexible for varying recipes, fab sizes, purity levels, flow rates e.Synergistic with MEGASYS TM onsite services and analytical expertise f.Demonstrated recovery >99% possible

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 26 MEGASORB ™ Process Flow Scheme Process Chamber Pretreatment Wet Scrubber Dryer Packaging Cryo Distillation Condenser Sorbathene PSA

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 27 Recycling/Recovery Technology Strengths –Closed loop system with no PFC emissions –Recovers costly PFC gases –High recovery using currently available technologies –Purification uses proven cryogenic techniques Issues –Requires pre-treatment of gases prior to recovery –Repurifying PFCs to “like new” may not be cost effective –Need to replumb PFC exhaust to a common manifold –NF 3 and CF 4 have almost identical boiling points - separation may be difficult –Low concentration of recovered PFC using pressure swing absorption

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 28 cc/min Typical Etch and CVD Systems Scrubber Atmosphere Abatement Pump Pre-Pump Treatment Chamber PFC Alternatives Optimization N2N2 Recovery/Recycle Plasma Destruction Combustion Chem/Thermal Absorption L/min

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 29 Process Optimization Example IBM Burlington optimized the TEOS & PSG CVD processes –Used endpoint detection (Fourth State RF metrology) to optimize two- step clean; PFC reduction was not the major objective Achieved the following : –50% reduction in C 2 F 6 usage –100% reduction in NF 3 usage –25% reduction in chamber consumable parts –increased throughput Implementation in one fab produced annual savings of: –$1.2 M in added throughput –$300 K in chemicals

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 30 Validation of C 3 F 8 as Drop-in Replacement for C 2 F 6 Project Tasks: –Perform Design of Experiments (DOE) to compare C 3 F 8 vs C 2 F 6 –Marathon wafer run to monitor TEOS film properties (particle count, stress, thickness uniformity) –Compare PFC emission and etch gas utilization

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 31 C 3 F 8 Tests at AMD C 3 F 8 DOE optimization conditions: –1000 sccm C 3 F 8, 1400 sccm O 2 and 3.6 torr With C 3 F 8 : –C 3 F 8 flow is 60% less (45% fewer pounds) –O 2 flow is 30% less –etch gas utilization = 60-70% (vs 30-40% for C 2 F 6 ) –net greenhouse gas reduction = 70% No TEOS film or chamber hardware degradation

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 32 Optimization Strengths –Most desirable, chemical and cost saving option –Good for CVD chamber clean applications –Equipment suppliers are active in this area Issues –Requires experimentation on process, which may be too costly, risky, and time consuming –Needs beta test demonstration to transfer technology –May require equipment retrofit

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 33 Status of Technology Alternative Chemistries –Most desirable, but probably most difficult –A long-term solution –Most likely flourine-based, less stable and more hazardous –MIT study underway to find suitable replacements –Schumacher, 3M, DuPont also doing R&D Process Optimization –Very desirable –Reduces chemical cost & emissions, may increase throughput and prolong life of reactor internals –End-point detection and reactor modifications –Progress already made, room for more (reductions of 50% have been demonstrated on some processes)

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 34 Status of Technology (cont’d) Recovery/ Recycle of Unused PFCs –Preferred over abatement –“Greener” technology with potential pay-back –Significant appeal for larger fabs –Five gas companies are developing systems currently Combustion –Abatment option closest to commercialization –Need flame and high temperatures to break down PFCs –Produces HF, NO x, COF 2 and CO 2 (more GW gas) –Fuel and water (for scrubber) costs are significant –Cost of Ownership ranges from $47 - $106K/year for device handling four chambers –Opportunities for suppliers to optimize

NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Pei, et al. 35 Technology Status (cont’d) Chemical/Thermal Destruction –Involves reacting the PFCs with granular solids –Technology is well developed for hydrides, but treating PFCs requires new chemistries and elevated temperatures –Cartridge has limited capacity, may only be suitable for etch tools –Disposal of spent solids a concern Plasma Destruction –Advantage: treats tool exhaust upstream of pump (no N 2 purge dilution) –MIT study showed excellent abatement of CF 4, C 2 F 6 & SF 6 in a microwave plasma reactor –Commercially available RF plasma devices such as DryScrub and PRC are not effective –Requires water scrubber