1. ESS480000Lecture 4: (Wafer clean and clean room facilities) (Wafer clean and clean room facilities) (Da-Jeng Jeffrey Yao) 1

2. Outline Introduction Clean room () Wafer Clean () Gettering () Clean Room Facilities () 2 3. Why Clean and be Cleaned? Contamination can Ruin devices A single ruined device in a complex circuit can cause thewhole chip to fail Leads to a lower yield of good chips per wafer Leads to higher costs and lower profits per chip Poison equipment Equipment must be removed from the manufacturing line Reduces production throughput and revenue Pose a health risk Endanger employees, customers, and environment Greatly increasing costs, possible litigation, etc3 4. Type of Contamination Particulates Inorganic Dust metallic, silicon, glass, quartz... Organic Dust dried skin, hair, clothing fibers, makeup, bacteria, Films Residues oil, grease, finger prints, incomplete etch, solvent residues (acetone, IPA, ), photoresist developer residue,inadequate rinsing, water stains, Oxides grown by thermal, chemical, or electrochemical processes Atomic Contamination Absorbed / Adsorbed Atoms or Ions in / on the films or substrate (Na, K, Ca, Au, Cu, Fe, Ni, Cr, )4 5. Source of Contamination Humans cause most of the contamination dirt, oils, etc. tracked into labs on shoe soles bodies continuously exfoliate skin, replace hair, widespread use of make-up, perfume, hair gels, spread throughout lab by central air system use of mechanical tweezers scratch and chip wafer edge and surface Machines abrasion during automated wafer handling mechanical mechanism wear and lubrication aging plastic and rubber parts 5 6. Contamination Induced Problems Mobile ions in oxides can change electric fields and voltages at Si surface mostly an issue for MOSFETs ( threshold voltage) but also exploited for anodic wafer bonding (covered in EE M250A) Impurities in silicon act as recombination centers for electron-hole pairs andimpact carrier concentration / distribution Particles on surface or in release etchant create numerous problems during photolithography can jam micromechanical structures Unintentional films between layers create open circuits or short circuits between layers impede adhesion between films (release etch)6 7. Device Yield () 7 8. Impact of Device Yield8 9. How to Keep Cleanness? : : (gettering): 9 10. Cleanroom () () 10 11. Cleanroom () 11 12. 0.5 1 0.5 Class 10.5 Class 100.5 1000 Class 1000 Class 1 No . of particles ft 3 12 13. Types of Cleanroom Conventionally ventilated Unidirectional flow typetype of cleanroom of cleanroom13 14. Clean Room Design 14 15. Clean Room Air Filter 15 16. Clean Room Classification 16 17. 17 18. Clean Room Dos andDonts18 19. 1000019 20. 1020 21. Material Safety DataSheet (MSDS) MSDS provides safety information: Chemical breakdown (what it is) Methods of exposure (how it gets in you) Effects/risks of exposure (what it does) Permissible air concentration (how much) Any unusual chronic toxicity Flash point, autoignition temperature MSDS is compiled by manufacturer Required for shipping and storage No standard format21 22. Operating a Cleanroom Identification of sources and routes of contamination Assessment of the importance of hazards Identification of methods to control hazards Sampling methods to monitor hazards and control methods Establishing a monitoring schedule with alert and action levels Verification and reappraisal of the system Documentation Staff training22 23. Wafer Cleaning23 24. Wafer Cleaning24 25. 25 26. RCA RCARCA 1965RCA 1970 RCA (SC-1)(SC-2) RCA 26 27. RCA SC-1 Standard clean 1 SC-1 5130129 70-80 rinse 27 28. -1 (double layer) megasonic cleaning 28 29. RCA SC-2 Standard clean 2 SC-2 6130137 70-80 rinse SC-2 29 30. (Native Oxide) SC-1SC-2 hydrophobic30 31. RCA hydrophobic 120-130 31 32. Step 1 H2SO4+H2O2(4:1) 120C 2 D.I. H2O 3 HF+H2O (1:50) 4 D.I. H2O NH4OH+H2O2+H2O5 70 - 80C P(1:1:5) (SC1)6 D.I. H2OHCl+H2O2+H2O7 70 - 80C (1:1:6) (SC2) 328 D.I. H2O 33. Video ()33 34. Gettering() () 34 35. Gettering () Gettering: a process that removes harmfulimpurities or defects from the region in awafer where devices are fabricated. 35 36. Extrinsic Gettering 36 37. 37 38. Clean Room Facilities 38 39. (Photolithgraphy Systems) Laser Pattern Generator (Mask Repeater) (Mask Aligner)(A5mB:5m) (IR Aligner) Negative Resist Developer and Rinse Photo Resist Spinner Vacuum Oven Optical Microscope (Furnace System) (Oxidation & Diffusion furnaces ) (Chemical Vapor Deposition System) (Low Pressure Chemical Vapor Deposition, LPCVD) (Plasma-Enhanced Chemical Vapor Deposition, PECVD) (Rapid Thermal Process Chemical Vapor Deposition,RTP-CVD) (Vacuum Deposition Systems) (Thermal Evaporation Coater) (Dual E-Gun Evaporation System) (Sputtering System)39 40. () (Wet Bench) (Dry Etching Systems) (Poly-Si Reactive Ion Etching System, Poly-Si RIE) ()( Dielectric Reactive Ion Etching System, Dielectric RIE ) (High Density Plasma Reactive Ion Etching System, HDP-RIE) (Chemical Mechanical Polishing System, CMP) (Analysis Systems) (S-4700I)(High-Resolution Cold Field Emission Scanning Electron Microscope & Energy Dispersive Spectrometer, SEM, EDS) (S-570)(Scanning Electron Microscope) (Spreading Resistance Probe System) (4-point Probe) (Ellipsometer) (Surface Profile) 40 41. (LASER Pattern Generator) 4"5" 442nm(g-line) Helium _Cadmium LASER Power 70mW Smallest feature size is .20um at effective NA 0.5 4 8cm x 8cm, 5 10cm x 10 cm Maximum die's number 256 GDSII DATA _INPUT Auto CAD *. dwg *. dxf Dual CCD camera alignment system41 42. (MASK Exposure IR Aligner ) 4" Wave Length 320nm Exposure Source 350WHg Lamp Wafer size 3"~4" Mask Holder size 4"~5" 42 43. (Photoresist Spinner) 7500rpm 43 44. (Vacuum Oven) HMDS Heaters : 8 ~ 200 W High Capacity HMDS Flask Power Requirements : 115V 60HZ15A Chamber Dimensions : 16"W X 16"D X 16"H Microprocessor Control Over-Temperature Shut-Off Setpoint 250 Optional : Vacuum Pump44 45. (Negative Resist Developer and Rinse) 0-10000 rpm Vacuum Pump 45 46. (Oxidation &Diffusion furnaces ) TCA (dry & wet oxidation (silicidation) N-P-drive-in Al sintering reflow POCl3 predeposition 1200oC 36"(chamber)6" 30cm 0~1200C30 46 47. (LPCVD) (poly-Si & amorphous-Si)620oC550oCSiH4Si2H6100mtorr (Si3N4)800oC750oC680oCSiH2Cl2NH3120mtorr chamber)6"36" 5*10-3 Torr POLY-Si-620 oCSi3N4-800 oC 47 48. (PECVD) SiO2Si3N4 HeArN2ONH3CF4SiH4N2SiO2Si3N448 49. (Thermal Evaporation Coater) () 1500L/SN21.0E-6 Torr 4"6" +-5%449 50. (Dual E-Gun Evaporation System) EB gun Model EGK-3M*2.5kw EB power Cryo pump U-10pu(2300 L/S N2)3.0E-7 Torr 4"6" 50 51. (Sputtering System) 4" * 3 power RF 1.25kw *1DC 1.5kw * 2 4" * 36"* 3 MFC for O2N251 52. (Wet Bench) III-VRCA 1 1 1 3"4"1 DI 52 53. (Poly-Si RIE) RF30013.56MHz CF4PO2SF6CHF353 54. (Dielectric RIE) RF100W13.56MHzCF4O2 54 55. (HDP-RIE) Al BCl3Cl2CF4CHF3ArO2SF6ICP RF900WBias RF300W He gas 4" wafer55 56. (CMP) SiO2,TEOS-Oxide,PECVD-Oxide,BPSG 656 57. (SEM&EDS) SEM EDS 0.5kV~30kV 20mm diameter x 10mm(t) 15A (at 15kV) or 25A (at 1kV) 50 10 1.5nm(15kV) EDS B5~U92 57 58. (SEM S-570) Normal SEM : detect secondary emission electron image. Backscattering image (BEI) : observe the reflected electron image. Absorbed electron image (AEI) : observing absorbed electron image. TEI : observe transmitted electron image. 0.55~20KV Maximum diameter < 2 inches Maximum height < 10mm 4 0.5u 58 59. (Spreading Resistance Probe System) 1 - 1010 1011 cm-3 1021 cm-3 1.24 nm59 60. (Surface Profile) 65um 5A 50u-->30mm 12.5um 50mg 60 61. (Ellipsometer) 6328A 70 6061 62. (4-point Probe) < 400/square62 63. References W.D. Callister, Jr., Materials Science and Engineering: An Introduction, (Sixth Edition) John Wiley (New York, 2003). 2000 Semiconductor Devices, Physics and Technology, S.M. Sze, 2nd Edition, 2001 Physics of Semiconductor Devices, S.M. Sze, 2nd Edition, 1981 VLSI Fabrication Principles, Silicon and GaAs, S.K. Ghandhi, 1994, 2nd Edition, 1981 Semiconductor Material and Device Characterization, D. K. Schroder, John Wiley (New York, 1990). Fundamentals of Semiconductor Fabrication, G. S. May, and S. M. Sze,John Wiley (New York, 2004).63 64. Thank You! ()510(03)5715131~42850djyao@mx.nthu.edu.tw 64