Tool Cleanliness Tool Cleanliness Characterization for Improving Characterization for Improving Productivity and Yields Productivity and Yields Victor K.F. Chia, Ph.D. Victor K.F. Chia, Ph.D. victor.chia@balazs.com victor.chia@balazs.com
Agenda � Introduction � Tool components � Starting material selection and bulk characterization � Surface cleanliness • Chemical characterization • Physical characterization � Completed tools New and used components � Tool cleanliness specification • Particles • Metals • Organics � Tool escalation case study PECVD chamber � Conclusion Reducing Contamination
Introduction � Tool parts cleanliness is an invisible parameter that must be controlled to enable clean processing � The target contaminants affecting process yields are particles, metals and organics � In the sub-100 nm technology node even irreducible differences in the components of identical tool chambers can influence yield and mean time between failure (MTBF) � The first line of defense for a fab is to have clean tools for processing, from acceptance trials of the new tool to after each PM. Only with clean tools can a fab maximize its yield by increasing overall equipment productivity and wafer throughput for increased profit margin � This may be accomplished with strict quality control of the supplier chain for starting materials, machine shops, cleaning vendors and contract manufacturing. In addition, cleanliness specifications must be in place for the BOM. � This presentation reviews cleanliness specifications for components and completed tools and characterization methods for verifying their cleanliness Reducing Contamination
Starting Materials Requirements � The materials used in the BOM, including lubricants and grease, must be compatible to its function and cleanliness requirements � Multi-alloy parts must be cleanable � Bulk material characterization is important as the root source of wafer contamination may be from the bulk of the material; no amount of cleaning will remove this contamination source Com plex Wafer Arm Assem bly Common materials used in build of materials (BOM) Metals Al Ni SST Mo Ti Ta Cu / Cu Alloys Ni Plating Au Plating Powder Coatings Paint Alodine Anodized Zn Coating Plastics PEEK PTFE Polyimide Polyethylene Kapton Viton Calrez Ceramics Alumina Glass Saphire DLC Quartz Welded Welded Assemblies Steel Brazed Bonded Flex Circuit Aluminum Alloys Reducing Contamination
Starting Materials Characterization Laser ablation I CP- MS Quartz 80E Layer 1 80E Layer 2 80E Layer 3 Layer 4 Mass Spectrum 80E Substrate 100000 Si Defect I nclusion Si 80000 that is only visible Signal Intensity (c/s) under UV light 60000 O-Ring O X 40000 O O-rings with inorganic fillers like SiO 2 , BaSO 4 , ZnO, X � Y 20000 C or TiO 2 lasts about 6,000 wafer counts before Y particulation issues occurs 0 0 10 20 30 40 50 60 70 80 O-rings using organic filled material can reach � m/z (amu) upwards of 20,000 wafer counts with reduced number of metallic particles escalations Ceram ic 100000 “dirty” Mass Spectrum Fe 500000 C w afer O-ring defect O-Ring Defect 400000 Signal Intensity (c/s) Metals on wafer w afer ICP-MS Signal Intensity (c/s) 10000 using VPD ICP-MC 300000 Metal or metal I alloy whose I “clean” 200000 melting Fe Fe temperature is 100000 considerably lower Mo Iron (Fe) Fe S Mn S than the sintering 1000 Ni Mo Zn Zinc (Zn) temperature of the 0 ceramic body are 0 20 40 60 80 100 120 140 160 180 200 used to fill voids in m/z (amu) the ceramic to achieve a Cu Copper (Cu) particular physical 100 property – -1 0 1 2 3 4 conduction, Sampling Depth in µm brazing, etc. Reducing Contamination
Metal Escalation Escalation: Metal contamination � BULK CONCENTRATION Contamination identification: � (atoms/cm 3 ) VPD ICP-MS Element Ceramic A Ceramic B Ceramic C Partitioning test: metal wipe test Ba 3.0E16 9.1E15 2.2E13 � B 1.2E18 1.7E16 6.3E15 Hypothesis: micro-arcing � Ca 1.1E19 9.1E17 6.6E15 Co 8.6E14 1.2E13 2.4E13 Verify root cause: fix short and � Cu 6.1E15 2.1E16 1.7E13 replace ceramic rods Element 300mm Wafer Fe 1.6E17 2.9E16 3.8E15 E10 at/cm 2 Li 3.3E16 1.2E15 ND Escalation resolved DL � Mg 7.7E16 1.8E17 3.4E15 0.3 250 Al Mn 3.1E15 2.8E15 7.5E13 0.3 110 Ca Ni 1.7E16 1.0E15 3.4E13 0.2 24 Cr K 1.8E18 1.0E17 4.4E14 0.05 0.82 Na 5.3E18 1.1E18 3.5E15 Cu Partitioning Sr 8.8E15 2.8E15 1.7E13 0.05 86 Tests Fe Sn 2.8E15 1.4E13 1.1E13 0.1 61 Mg Ti 1.2E19 7.4E15 1.1E15 0.05 0.7 Ni W 6.1E15 5.0E14 5.0E13 0.3 40 K Zn 2.0E16 1.1E18 1.4E15 0.3 77 Na Zr 7.7E15 6.0E16 4.0E13 0.1 13 Zn SARIS (10 µ m) of ceramic insulator rods VPD ICP-MS Results Element DL Area 1 Area 2 Area 3 Area 4 ng/cm 2 1 2 3 4 5 6 7 8 9 10 11 12 50 130 590 58000 5260 420 590 1500 12500 15000 2300 350 730 Al 50 Cr * * * * * * * * * * * * 50 1200 1000 3600 300 Fe * * * * * * * * 50 270 310 460 1200 12000 550 4500 1350 1000 Mg * * * 50 150 760 1500 560 590 Ni * * * * * * * 50 300 200 600 200 400 1800 300 1500 8100 300 200 250 K 50 1400 1200 6000 6200 750 6800 1200 1900 50000 1200 400 1200 Na Metal wipe test results Reducing Contamination
Starting Materials Characterization Organic outgassing sources Part Description Material/Composition Conductor Material: Silver Plated Copper Covered Steel (SPCCS); Insulation Material: Tetrafluoroethylene Cable Coaxial (TFE); Outer Shield Material: Silver Plated Copper; Outer Jacket Material: Fluorinated Ethylene Propoylene Shell: Brass; Plug Body: Brass; Cable Clamp, Inner Sleeve, Washer or Nuts: Brass; Male Crimp Contacts: Connector for Coaxial Plug Bronze; Female Crimp Contacts: Bronze Outer Shell: Brass, Stainless Steel, Aluminum Alloy, PEEK; Sealing Resin: Epoxy; Grounding Crown: Bronze, Beryllium Copper, Stainless Steel; Latch Sleeve: Special Brass, Stainless Steel; Locking Connector for Coaxial Plug - 50 Ohm Washer: Bronze; Hexagonal or Round Nut: Brass, Stainless Steel, Aluminium alloy; Other Metallic Components: Brass, Stainless Steel; O-Ring and Gaskets: Silicone Conductor Material: Silver Plated Copper Covered Steel; Insulation Material: Tetrafluoroethylene (TFE); Cable Coaxial Outer Shield Material: Silver Plated Copper Covered Steel; Outer Jacket Material: Fluorinated Ethylene Propylene Contact Material: Copper Alloy; Contact Underplating: Nickel; Insulation Material: Glass Filled Polyester Connector Socket, Open End (PBT) Sensor, Light/Dark Materials: Polybutylene Phthalate (PBT); Cover: Polycarbonate; Emitter: Polycarbonate Wire, 28 AWG, Black * Conductor Material: Silver Plated Copper; Insulation Material: Tetrafluoroethylene (TFE) Contact Material: Copper Alloy; Contact Underplating: Nickel; Insulation Material: Glass Filled Polyester Connector, Socket 26 Position, Open End (PBT) Shrink Tubing, 3/32 ID, Kyanr, Clear Polyvinylidene Fluoride Wire, 28 AWG, Black * Conductor Material - Silver Plated Copper, Insulation Material: Fluorinated Ethylene Propylene (FEP) Silver Plated Conductor, Overlapping tapes of Gore TM Corona Resistant (PTFE) Cable, High Voltage, 22 AWG, Stranded Terminal Ring, 12-10 AWG Electrolytically Refined Copper RED: material that may outgas Reducing Contamination
Bulk Organic Characterization Thermal Desorption Gas Chromatography Mass Spectrometry (TD-GCMS) Primary (Tube) Desorption Desorb Flow Carrier Gas To Mass Inlet _ _ _ Detector Cold Trap GC Analytical Hot Sample Tube Carrier Column (400 O C) Gas Inlet � In-instrument outgassing � Tenax tube � For medium to high outgassing material � Off-line outgassing � Quartz tube � Larger sample to increase detection limit � For low outgassing material Reducing Contamination
Surface Cleanliness of Tool Components Target contaminants depend on the history of the part � Starting material � Gross contamination � Not a concern as the material will be machined and later cleaned � Bulk contamination is more critical � Machined part � Major contamination is from machine oil, metal cross-contamination, Trend is for water and solvent residue, oven, etc. machine shops � Machine shops are not semiconductor clean environments to pre-clean in-house , � Contaminants of concern: Organic > Particle > Metal > Anion outsource Precision � After Precision cleaning Cleaning and send parts � Minor contamination directly to the custom er � Typically from handling, environment, packaging, etc. � Contaminants of concern: Metal > Particle > Organic > Anion a) Precision cleaning is defined as “The removal of undesirable contaminants to a pre-determined measurable standard without introducing new contaminants or changing the surface integrity” b) Precision cleaning dictates the tool BOM must have a cleanliness specification Reducing Contamination
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