NMOS Fabrication Process DescriptionPart 2: Process Flow (Process Overview)Week 1: Starting Materials. (No lab this week.)Week 2: Initial Oxidation - 5200 Å. (Performed by TA in microlab.)Week 3: Active Area PhotolithographyWeek 4: Gate Oxidation - 800 ÅWeek 5 Poly-Si Deposition. (Performed by TA in Microlab.)Week 6: Gate PhotolithographyWeek 7a: Source-Drain Deposition (N+)Week 7b: Source-Drain (N+) Drive and Intermediate OxidationWeek 8: Contact CutWeek 9: MetallizationWeek 10: Metal DefinitionThe fabrication process is now completed and the devices are ready for characterization!1NMOS Fabrication Process Description Modified by Alex Chediak on March 2000.Modified by TAs team (Eric Hobbs, Paul Hung, Paul Friedberg, Min She) in Fall semester, 2002.Part 1) A checklist: what do you need in EE143 lab andmicrolab?At the beginning of the semester, the TAs team in the current semester should check the followingstuff to make sure they are in EE143 lab or microlab.1) General stuff: stuff Usage purpose quantity commentsLong Teflon wafer handlerHold 3” wafer during chemical etching6Need RCA cleaningMetal tweezer Hold and Transfer wafer6Teflon tweezer Hold wafer 3Need RCA cleaning. If wafer must be kept clean, (for example, before gate oxidation) you should use Teflon tweezer. No metal tweezer!HF burn paste 2Use it if you contact HF2 ) Oxidation (sintering) process modulestuff Usage quantity CommentsClean 3” quartz boat Field oxidation growth in microlab1 Kept in microlab. Need RCA cleaning.Clean 3” quartz boat Gate oxidation growth 1 In EE43 lab, need RCA cleaning.3” quartz boat Intermediate oxide growth and sintering1 in EE143 lab, need RCA cleaning.Cylindrical carrier Carry boat 1 Need HF cleaning in microlabThermal couple Measure temperature 1Long glass thermometerMeasure temperature 3 Each furnace has oneThick cotton gloves Hold hot stuff Several pairsBrick Hold the hot end cap 1End cap Seal the furnace 3 Each furnace have oneGlass bubbler Supply vapor during wet oxidation1 Connected to center furnace tubeHeater for glass bubblerHeating water into vapor1Spin-on-glass liquid Dope S/D 1 bottles Kept in the refrigerator. Expire in 6 monthsBlue wafer transfer Transfer wafer 1 Need RCA cleaning Week 12box between microlab and EE143 laband always put into a plastic bag.3” white Teflon cassettesHold wafer in the bluewafer transfer box1 Kept in the blue box and need RCA cleaningOxygen gas Oxidation 1 bottleNitrogen gas Annealing 1 bottleForming gas sintering 1 bottle3) Chemical Cleaning and Etching module stuff usage quantity CommentsYellow acid-resistanceglovesPut it on when dealingwith chemicals6 pairs Kept in plastic bag after being used.Beaker Piranha cleaning 1 Each beaker should belabeled and should notmixed.Piranha rinsing 25:1BHF 110:1BHF 1HF rinsing 2At etching 1Si etching 1General rinsing 2Glass heating bath Al etching process 1 Keep water temp at 50oCHeating oven Heat the glass bath During Al etchingTall Teflon Bath RCA cleaning 3White Teflon CassettesWafer cleaning and spindrying1 Kept in sink6 drawer, microlab, need RCA cleaning2 In EE143 labCassettes handler Handle the cassettes 1 In sink6 drawer, microlabThermometer Measure temperature 14) Photoresist Developing and Acetone Stripping Module stuff usage quantity CommentsBeakers Develop photoresist 1PR rinsing 2Acetone 1 Strip PRAcetone rinsing 2Blue wafer transfer boxTransfer wafer 2Small bottles and dropletsContainer for photoresist3 PR should be obtainedfrom microlabWeek 135) Aluminum Evaporations ModuleCherry bomb ContainerLiquid N2 inside 1cart For cherry bomb 1cup Pour liquid N2 1Al targets Al source One bag (>50 piece)Tungsten coil Heating the Al targets One bag (>20 piece)6) Chemical Material in EE143 labChemicals Purpose quantity CommentsSulfuric acid Wafer cleaning 2Hydrogen peroxide Wafer cleaning 25:1 BHF Etch oxide210:1 BHF Etch oxide 2Si etchant Etching polysilicon2 Ask microlab at least 48 hours before you need it.Al etchant Etching Al 2Ammonium HydroxideRCA cleaning purpose 22-Propanol Cleaning dirty stuff 2OCG825 Photoresist2 Use small bottles to get PR from microlabOCG934 developer Developing PR 2Acetone Strip PR 2 Note: 1) The 3” boat and cassettes, handler kept in microlab is for microlab usage only. Pleasedon’t take them back to EE143 lab or take any stuff from EE143 into microlab, to preventcontamination.2) RCA cleaning procedure: All of the clean stuff needs to be RCA cleaned. First, put thestuff into one of the white tall Teflon bath, then pour 5 part of DI water, 1 part ofAmmonium Hydroxide, then 1 part of H2O2 . RCA liquid should be aspirated after RCAcleaning is done.3) In Fall semester, 2002, the small beakers used in the previous years have been replacedwith larger beakers. At the beginning of the semester, the TAs should check the beaker inthe following way: put a wafer handler with 3” wafer into the beaker, fill the beaker with DIwater till the water immerse the 3” wafer completely, mark the water level. Then in future,you can always fill the BHF, HF, poly etchant and so on to this level.Part 2: Process Flow (Process Overview)Week 1: Starting MaterialsWeek 2: Initial Oxidation - 5200 Å Week 3: Active Area PhotolithographyWeek 14Week 4: Gate Oxidation - 800 Å Week 5: Poly-Si Deposition - In MicrolabWeek 6: Gate PhotolithographyWeek 7: Source-Drain Deposition (N+)Week 7: Source-Drain (N+) Drive and Intermediate OxidationWeek 8: Contact CutWeek 9: MetallizationWeek 10: Metal DefinitionWeek 1: Starting Materials. (No lab this week.) - Wafers 1. 3" p-type silicon wafers with a resistivity of 14-16 ohm-cm and <100> crystalorientation. In addition to work wafers to each student group, each section will receiveone wafer to be used as a control during week #4. And each session should have one totwo TA wafers.2. Blanket Implant: 3.0x1012 /cm2, B11, 60 KeV. 3. Uniquely identify each of the wafers Label wafers with diamond scribe. Label usingsmall letters near the flat. Do not scrib off the edge of the wafer as this will cause thewafer to break. DO NOT LABEL YOUR WAFER ACROSS THE CENTER AS IT WILLDESTROY YOUR DEVICES. 4. Divide Wafers into lab sections.5. Measure resistivity on one control wafer. Resistivity to be reported to students in week 3 - Check Masks and Clean the Mask (4" x 4" Chrome Plates) 1. ACTV = Defines the Active Area (Dark Field) 2. POLY = Defines the Gate (Light Field) 3. CONT = Defines the Contacts
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