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Compound Semiconductor Wafer Processing Facility

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  • 1.WAFER PROCESSING EQUIPMENTAND CLEAN ROOM INVENTORYFOR A RESEARCH BASED IC FABRICATION FACILITYSAMI UR REHMAN (sami-rehman.blogspot.com)1 SAMI UR REHMAN

2. Difference between Si wafer processingand compound (III/V) wafer processingOxidationSilicon has a natural oxide while compound semiconductorsSAMI UR REHMAN (sami-rehman.blogspot.com)do not (deposition required). Compound semiconductorrequires epitaxial deposition techniques which are quietexpensive!StabilityMost of these compound semiconductors are not stable athigh temperatures unlike Si. For Si, one would therefore makeMOSFET kind of structures.2 3. Difference between Si wafer processingand compound (III/V) wafer processing Lattice Constants The first and principal difference between a Siand a GaAs substrate is the respective latticeSAMI UR REHMAN (sami-rehman.blogspot.com)constants. Crystalline materials (thin films) whichwill be deposited on top of such substrates willhave to take this into account.Etching Compound semiconductors like GaAs alsorequires a complex Chlorine based etch processunlike Si (F based etch). 3 4. WHAT IS A CLEAN ROOM? A clean-room or clean room is an environment, typicallyused in manufacturing and scientific research, that has a lowlevel of environmental pollutants such as dust,airborne microbes, aerosol particles and chemical vapors(Wikipedia)SAMI UR REHMAN (sami-rehman.blogspot.com) What matters is Particle size and particle number The standard is called: FED-STD-209 E This standard was cancelled on Nov 2011 Standardizing Agency: U.S. General ServicesAdministration (GSA) Replaced by ISO 14644-1 4 5. CLEAN ROOMCLEAN ROOM STANDARDS SAMI UR REHMAN (sami- rehman.blogspot.com)Particle Counters are used to determine the air quality by counting and sizing thenumber of particles in the air.This information is useful in determining the amount of particles inside a building or 5in the ambient air It also is useful in understanding the cleanliness level in a controlled environment. 6. Cost Analysis Quotations have been sent SANCO Rough estimates of the equipment have been obtained from:SAMI UR REHMAN (sami-rehman.blogspot.com)6 7. CLEAN ROOMPARTICLE COUNTERS ManufacturerCapovani Brothers Inc ModelPARTICLE MEASURMENT SYSTEMS LPS A-310 Price$ 7,350.00 (each) Year of2001 Manufacture DimensionsWidth8.750 in (22.2 cm) Depth18.000 in (45.7 cm) HSAMI UR REHMAN (sami-rehman.blogspot.com)eight7.000 in (17.8 cm) Weight30 lb (14 kg) Accessories/OtheMaximum Number of Channels =4 r InformationChannel Sizes= 0.3, 0.5, 1.0, 5.0 m Light Source=HeNe Multimode, Passive Cavity7 $7,350 8. CLEAN ROOM PARTICLE COUNTERSManufacturerPacific ScientificModel MET ONEPrice $ 4,250.00Year of2001ManufactureDimensionsWidth13.000 in (33.0 cm) Depth12.000 in (30.5 cm) Heig SAMI UR REHMAN (sami- rehman.blogspot.com) ht7.000 in (17.8 cm)Weight 30 lb (14 kg)Accessories/Other Part no.: 331-3-1-ALInformationParticle size: 0.3 to 10 Micron 8 $4,250 9. CLEAN ROOMAIR CONDITIONER/AIR FLOW CONTROLLERManufacturerAir Control Inc.Model VLF CARTPrice $ 3,250.00Year of Manufacture 1998DimensionsWidth 74.000 in (188.0 cm)SAMI UR REHMAN (sami-rehman.blogspot.com)Depth 21.000 in (53.3 cm)Height 74.000 in (188.0 cm)Weight5,459 lb (2,476 kg)Accessories/Other Unit contains a 9W X 10H array ofInformation stainless steel cubicles (6.25"W x 4"Hx 11"D)Blower: (2) EBMs STD 9Prefilter #: (2) 16 x 20 x 1 $3,250Hepa Filter #: (1) 18 x 48 x 3 10. CLEAN ROOMAIR CONDITIONER/AIR FLOW CONTROLLERManufacturerAir Control Inc.Model AirPodPriceYear of ManufactureDimensionsWidth: AirPod I: 62.50, AirPod II:80.50, AirPod III: 104.50 SAMI UR REHMAN (sami- rehman.blogspot.com)Height: 31.00Depth: 31.00WeightWeight (lbs): AirPod I: 312, AirPod II:394, AirPod III: 455Nominal Air flow: 2500 CFM (3/4 HP), 5000 CFM (3HP),Accessories/Other 4000 CFM (3HP with AD after-filter).Information Blower Pkg (HP): AirPod I: 2-speed forward curve,direct drive; AirPod II & III: Dynamically balanced, non-sparking, motor/blowers. (Optional 2-speedmotor/blower available for AirPod II.) 10Electrical: AirPod I, standard: 115/1/60, 11.4 amps, 3/4HP; AirPod II & III, standard: 208-230/460/3/60, 7.8-7.2/4 amps, 3 HP; optional: 230/1/60 11.7 amps, 3 HP.$3,000 11. IC FABRICATION PHILOSOPHY! Adding impurities inAdding layer onto wafer! wafer!SAMI UR REHMAN (sami-rehman.blogspot.com) Deposition ImplantationRemoving an added layer!Photolithography11 Etching 12. III/V Group ingot productionSimilar to the silicon ingot growth process, elementalforms of III and V group elements, plus small quantities Quartz Tubeof dopant material-silicon,Rotating Chucktellurium or zinc-are reacted atSAMI UR REHMAN (sami-rehman.blogspot.com) Seed Crystalelevated temperatures to Growing Crystal(boule)form ingots of doped single-crystal III/V material like GaAs. RF or Resistance Heating Coils Molten Silicon (Melt) 12 Crucible 13. Photomask Creation The photomask is a copy of the circuit pattern, drawn on a glass plate coated with a metallic film. The glass plate lets light pass, but the metallic film does not. Due to increasingly high integration andSAMI UR REHMAN (sami-rehman.blogspot.com) miniaturization of the pattern, the size of the photomask is usually magnified four to ten times the actual size.13 14. PHOTOLITHOGRAPHYWafer processing consists of a sequence of additive and subtractive steps with patterning!!!!! oxidationdepositionetching lithography ion implantationSAMI UR REHMAN (sami-rehman.blogspot.com)Lithography refers to the process of transferring a circuit pattern, embedded on a mask, to the surface of the waferEquipment, materials, and processes needed: A mask (for each layer to be patterned) with the desired pattern A light-sensitive material (called photoresist) covering the wafer so as to receivethe pattern A light source and method of projecting the image of the mask onto thephotoresist (printer or projection stepper or projection scanner) A method of developing the photoresist, that is selectively removing it from the14regions where it was exposed Photolithography is a process analogous to developing film in a darkroom 15. PHOTOLITHOGRAPHY STEPS 1 # PRE BAKE THE WAFER Wafer is preheated to about 200 - 250 degrees C in a bakeoven. The purpose of this step is to ensure that the wafer iscompletely dry. Any moisture on the wafer surface wouldinterfere with the photolithography process, causing it to yield SAMI UR REHMAN (sami- rehman.blogspot.com)poor results. 15 16. PHOTOLITHOGRAPHY STEPS 2 # PHOTORESIST APPLICATION AND SPINNING The wafer is placed on the wafer chuck in the center of thePhotoresist Spinner. After properly adjusting the wafer on thespinner, photo resist material is applied onto the surface ofthe wafer and is spun so that photo resist evenly distributes SAMI UR REHMAN (sami- rehman.blogspot.com)on the wafer Using the Nitrogen Gun, now the wafer surface isBlown to remove any dustparticles. 16 17. PHOTOLITHOGRAPHY STEPSPhotoresist Raw Materialshttp://www.mitsuichemicals.com/photoresist.htmSAMI UR REHMAN (sami-rehman.blogspot.com)17 18. PHOTOLITHOGRAPHY STEPSPhoto resist properties http://www.cleanroom.byu.edu/photoresists.phtml SAMI UR REHMAN (sami- rehman.blogspot.com) 18 19. Photoresist Spin Coater PR Wafer SAMI UR REHMAN (sami- rehman.blogspot.com) EBRWaterSleeveChuck DrainExhaust Vacuum 19 20. Photoresist Applying PR dispenser nozzleSAMI UR REHMAN (sami-rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump20 21. Photoresist Suck Back PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 21 22. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 22 23. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 23 24. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 24 25. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 25 26. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 26 27. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 27 28. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 28 29. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 29 30. Photoresist Spin Coating PR dispenser nozzle PR suck back SAMI UR REHMAN (sami- rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump 30 31. Edge Bead RemovalSolventSAMI UR REHMAN (sami-rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump31 32. Edge Bead RemovalSolventSAMI UR REHMAN (sami-rehman.blogspot.com)Wafer Chuck SpindleTo vacuum pump32 33. Optical Edge Bead RemovalExposureLight sourceLight beam Photoresist SAMI UR REHMAN (sami- rehman.blogspot.com) WaferExposed ChuckPhotoresistSpindle 33 34. PHOTOLITHOGRAPHY STEPS 3 # SOFT BAKE The wafer is placed into the Soft-Bake Oven for 30 minutes. The purpose of the soft bake is to semi-hardenSAMI UR REHMAN (sami-rehman.blogspot.com)the photoresist34 35. Methods of Soft Bake Hot plates Convection oven Infrared ovenSAMI UR REHMAN (sami-rehman.blogspot.com) Microwave oven35 36. Baking SystemsWaferMW Source Photoresist SAMI UR REHMAN (sami- rehman.blogspot.com)HeaterHeated N 2ChuckWafersVacuumWaferHeaterVacuum Hot plate Convection ovenMicrowave oven 36 37. Hot Plates Widely used in the industry Back side heating, no surface WaferSAMI UR REHMAN (sami-rehman.blogspot.com) crust Heater In-line track system37 38. PHOTOLITHOGRAPHY STEPS 4 # EXPOSE TO UV LIGHT carefully place the wafer on the wafer chuck of the