© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 1 Rochester Institute of Technology Microelectronic Engineering ROCHESTER INSTITUTE OF TECHNOLOGY MICROELECTRONIC ENGINEERING Gig Ohm Resistor Process Details  Dr. Lynn Fuller/Paul John  Webpage:  Microelectronic Engineering  Rochester Institute of Technology  82 Lomb Memorial Drive  Rochester, NY  Tel (585)  Fax (585)   MicroE Webpage: GigOhmResistors.ppt

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 2 Rochester Institute of Technology Microelectronic Engineering INTRODUCTION This project is to design and make Gig Ohm Resistors. The process will use ion implanted (Boron) poly silicon resistors. The design is for discrete devices of size suitable for automated pick and place surface mounting for printed circuit board assembly. The individual resistors are 2mm x 3mm and eight different designs are arranged in an array which will be cut into individual chips at the end of the process. The first run will use aluminum metal. Future runs will use a metal stack of aluminum, chrome, nickel, and solder. Applications for resistors of this high value are MOSFET biasing of high input impedance amplifiers, charge sensors for piezoelectric (quartz) pressure sensors, and more. In these applications the exact value is not usually important.

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 3 Rochester Institute of Technology Microelectronic Engineering LAYOUT

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 4 Rochester Institute of Technology Microelectronic Engineering ALIGNMENT KEY LOCATIONS, CHIP SIZE, ETC. Lower Left Corner =(0,0) Upper Right Corner = (9400,6400) Step Size in X = 9.6 mm Step Size in Y = 6.6 mm Center of Die = (4700, 3200) Location of PA alignment Mark = Center of Die = (4700,3200) B scope (Y-Direction) Fine Alignment 20P4F Island Center = 4955,3680 B scope (Y-Direction) Fine Alignment 20P4F Window Center = 4955,3500 C scope (X-Direction) Fine Alignment 20P4F Island Center = 4550,3700 C scope (X-Direction) Fine Alignment 20P4F Window Center = 4350,3699

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 5 Rochester Institute of Technology Microelectronic Engineering PROCESS STEPS Gig Ohm Resistor process 1. ID01 scribe 2. CL01RCA clean 3. OX ,000 wet oxide 4. CV01 deposit poly 5. IM01 – Ion Implant poly Si 6. PH03 – 1 – poly 7. ET08 poly etch 8. ET07 strip resist 9. CL01 RCA clean 10. OX08 – poly reox 11. CV03 – LTO 12. OX08 DS anneal 13. PH03 – 2 CC 14. ET10 etch CC 15. ET07 strip resist 16. CL01 RCA Clean, modified 17. ME01 Deposit Metal 18. PH metal 19. ET05 etch metal 20. ET07 strip resist 21. SI01 SINTER 22. TE01 Test SA01 Saw Wafer

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 6 Rochester Institute of Technology Microelectronic Engineering STARTING WAFER P-TYPE, 35 OHM-CM For this project the starting silicon wafer type and resistivity is not that important because the resistors will be made of poly silicon on an insulating oxide layer. The starting wafer is only a substrate for the thin films on its surface.

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 7 Rochester Institute of Technology Microelectronic Engineering ID01 - IDENTIFY WAFER (SCRIBE WAFER) Paul John D1

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 8 Rochester Institute of Technology Microelectronic Engineering RCA CLEAN DI water rinse, 5 min. H HF sec. HPM H 2 O–4500ml HCL-300ml H 2 O 2 – 900ml 75 °C, 10 min. SPIN/RINSE DRY APM H 2 O – 4500ml NH 4 OH–300ml H 2 O 2 – 900ml 75 °C, 10 min. DI water rinse, 5 min. DI water rinse, 5 min. PLAY ANSWER What does RCA stand for?

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 9 Rochester Institute of Technology Microelectronic Engineering RCA CLEAN RCA Bench Spin/Rinse/Dry Tool

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 10 Rochester Institute of Technology Microelectronic Engineering GROW 30,000 Å OXIDE 30,000 Å SiO2 Push at 800 C in N2 Ramp to 1100 C in dry O2 Time = ~900 min. in wet O2 Ramp down to 800 C in N2 Pull at 800 C in N2 Use Recipe 430 – Tube 1

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 11 Rochester Institute of Technology Microelectronic Engineering WET OXIDE GROWTH CHART Steam 900C 1300C Time in minutes Oxide Thickness in microns

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 12 Rochester Institute of Technology Microelectronic Engineering BRUCE FURNACE RECIPE 430 – WET OXIDE 30,000Å 1100°C 800 °C Boat Out Boat InBoat Out Load Push StabilizeRamp-UpSoak AnnealRamp-Down Pull Recipe # °C 25 °C Any 0 lpm none 800 °C At the end of a run the furnace returns to Interval 0 which is set for boat out, 25 °C and no gas flow. The furnace waits in that state until someone aborts the current recipe or loads a new recipe. Wet Oxide Growth, Target 30,000 Å Interval 0 Interval 1 Interval 2 Interval 3 Interval 4 Interval 5Interval 6 Interval 7Interval 8 12 min15 min 30 min5 min 15 hrs5 min 60 min12 min 10 lpm10 lpm 5 lpm5 lpm 10 lpm15 lpm 10 lpm15 lpm N2N2 N2O2O2/H2N2 N2N2

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 13 Rochester Institute of Technology Microelectronic Engineering 30,000 Å OXIDE GROWTH Polysilicon, 3500A 30,000 Å SiO2

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 14 Rochester Institute of Technology Microelectronic Engineering OXIDE COLOR VERSUS THICKNESS TABLE SiO 2 Yes! No! Silicon To observe a valid color, the wafer must be observed perpendicular to the surface under white (all wavelengths) light or the optical path length will be different, hence the color will change with the angle.

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 15 Rochester Institute of Technology Microelectronic Engineering TENCORE SPECTRAMAP Measure Oxide Thickness

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 16 Rochester Institute of Technology Microelectronic Engineering REFLECTANCE SPECTROMETER NANOSPEC FILM THICKNESS MEASUREMENT INCIDENT WHITE LIGHT, THE INTENSITY OF THE REFLECTED LIGHT IS MEASURED VS WAVELENGTH WHITE LIGHT SOURCE OPTICS WAFER MONOCHROMATOR & DETECTOR 3000 Å OXIDE 7000 Å OXIDE Oxide on Silicon400-30,000 Å Nitride400-30,000 Neg Resist500-40,000 Poly on Ox400-10,000 Neg Resist on Ox Nitride on Oxide Thin Oxide Thin Nitride Polyimide500-10,000 Positive Resist500-40,000 Pos Resist on Ox ,0004,000-30,000

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 17 Rochester Institute of Technology Microelectronic Engineering STEP ETCH APPARATUS BUFFERED HF Lower 1/4 inch every 45 seconds

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 18 Rochester Institute of Technology Microelectronic Engineering ETCH STEPS IN OXIDE ON C Å BARE SILICON

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 19 Rochester Institute of Technology Microelectronic Engineering DEPOSIT LPCVD POLY SILICON Polysilicon, 3500A LPCVD, 610C, ~45min 30,000 Å SiO2

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 20 Rochester Institute of Technology Microelectronic Engineering DOPE POLY SILICON BY ION IMPLANT Polysilicon, 3500A 30,000 Å SiO2 50kEV, Boron, B11 from BF3 gas Dose ~1e12 Wafer 1 Dose = Wafer 2 Dose = Wafer 3 Dose = Wafer 4 Dose =

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 21 Rochester Institute of Technology Microelectronic Engineering VARIAN 350 D ION IMPLANTER (4” AND 6” WAFERS)

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 22 Rochester Institute of Technology Microelectronic Engineering B 11 IMPLANT FOR BORON THRESHOLD ADJUSTS, STOP, P-WELL I µA ION MASS (AMU) B10 B11 BF2 BF+ USE THIS PEAK PLAY

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 23 Rochester Institute of Technology Microelectronic Engineering PHOTO 1 RESISTOR Polysilicon, 3500A 30,000 Å SiO2 Coat with ~1.0µm Photoresist

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 24 Rochester Institute of Technology Microelectronic Engineering COAT PHOTORESIST ON SSI TRACK COAT.RCP

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 25 Rochester Institute of Technology Microelectronic Engineering EXPOSE RESIST ON CANON STEPPER i-Line Stepper = 365 nm NA = 0.52,  = 0.6 Resolution = 0.7 / NA = ~0.5 µm 20 x 20 mm Field Size Depth of Focus = k 2 /(NA) 2 = 0.8 µm

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 26 Rochester Institute of Technology Microelectronic Engineering DEVELOP RESIST ON SSI TRACK Polysilicon, 3500A 30,000 Å SiO2

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 27 Rochester Institute of Technology Microelectronic Engineering ETCH POLY SILICON ON LAM 490 Polysilicon, 3500A 30,000 Å SiO2 Use Lam 490 Recipe FACPOLY SF6 140 sccm O2 40 sccm Gap 1.5 cm Power 140 watts 325 mTorr 150 Sec/wafer

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 28 Rochester Institute of Technology Microelectronic Engineering STRIP PHOTORESIST ON BRANSON ASHER Polysilicon, 3500A 30,000 Å SiO2

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 29 Rochester Institute of Technology Microelectronic Engineering RCA CLEAN DI water rinse, 5 min. H HF sec. HPM H 2 O–4500ml HCL-300ml H 2 O 2 – 900ml 75 °C, 10 min. SPIN/RINSE DRY APM H 2 O – 4500ml NH 4 OH–300ml H 2 O 2 – 900ml 75 °C, 10 min. DI water rinse, 5 min. DI water rinse, 5 min. PLAY ANSWER What does RCA stand for?

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 30 Rochester Institute of Technology Microelectronic Engineering OXIDE REGROWTH Polysilicon, 3500A 30,000 Å SiO2 500A recipe 250

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 31 Rochester Institute of Technology Microelectronic Engineering LPCVD LTO Polysilicon, 3500A 30,000 Å SiO2 4000A LTO Or 4000A TEOS + Densify

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 32 Rochester Institute of Technology Microelectronic Engineering PHOTO – 2 CONTACT CUTS Polysilicon, 3500A 30,000 Å SiO2

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 33 Rochester Institute of Technology Microelectronic Engineering EXPOSE i-Line Stepper = 365 nm NA = 0.52,  = 0.6 Resolution = 0.7 / NA = ~0.5 µm 20 x 20 mm Field Size Depth of Focus = k 2 /(NA) 2 = 0.8 µm

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 34 Rochester Institute of Technology Microelectronic Engineering ETCH CONTACT CUTS Polysilicon, 3500A 30,000 Å SiO2

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 35 Rochester Institute of Technology Microelectronic Engineering STRIP RESIST Branson Asher

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 36 Rochester Institute of Technology Microelectronic Engineering MODIFIED RCA CLEAN DI water rinse, 5 min. H HF sec. HPM H 2 O–4500ml HCL-300ml H 2 O 2 – 900ml 75 °C, 10 min. H HF sec APM H 2 O – 4500ml NH 4 OH–300ml H 2 O 2 – 900ml 75 °C, 10 min. DI water rinse, 5 min. DI water rinse, 5 min. DI water rinse, 5 min. SPIN/RINSE DRY

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 37 Rochester Institute of Technology Microelectronic Engineering DEPOSIT METAL CVC 601 Sputter Tool

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 38 Rochester Institute of Technology Microelectronic Engineering PHOTO METAL

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 39 Rochester Institute of Technology Microelectronic Engineering SSI COAT AND DEVELOP TRACK FOR 6” WAFERS SSI coat and develop track

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 40 Rochester Institute of Technology Microelectronic Engineering ASML 5500/200 NA = 0.48 to 0.60 variable  = 0.35 to 0.85 variable With Variable Kohler, or Variable Annular illumination Resolution = K1 /NA = ~ 0.35µm for NA=0.6,  =0.85 Depth of Focus = k 2 /(NA) 2 = > 1.0 µm for NA = 0.6 i-Line Stepper = 365 nm 22 x 27 mm Field Size

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 41 Rochester Institute of Technology Microelectronic Engineering ETCH METAL Wet Etch

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 42 Rochester Institute of Technology Microelectronic Engineering STRIP RESIST Branson Asher

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 43 Rochester Institute of Technology Microelectronic Engineering SINTER Native Oxide Before Sinter After Sinter Reduce Surface States Reduce Contact Resistance Oxygen Hydrogen, neutral region Silicon Crystal + charge region Silicon DiOxide Interface silicon atom that lost an electron

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 44 Rochester Institute of Technology Microelectronic Engineering PICTURES

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 45 Rochester Institute of Technology Microelectronic Engineering TEST R = 1/slope = 106 Gigohms Rhos = /1800 = 2.94 Gigohms/square

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 46 Rochester Institute of Technology Microelectronic Engineering TEST R=1/slope; Rhos=R / #sqs; Rho=Rhos x thickness (3500Å); Dose=implanter setting R wafer 4 = 106 G ; Rhos = 2.94 Gohm/sq; Rho = 103K ohm-cm; Dose=1E12 cm-2 R wafer 3 = 339 G ; Rhos = 9.42 Gohm/sq; Rho = 330K ohm-cm; Dose = ? R wafer 2 = 943 G ; Rhos = 26.2 Gohm/sq; Rho = 917K ohm-cm; Dose = ? R wafer 1 = 1104 G; Rhos = 30.7 Gohm/sq; Rho = 1075K ohm-cm; Dose = ?

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 47 Rochester Institute of Technology Microelectronic Engineering SAW WAFER

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 48 Rochester Institute of Technology Microelectronic Engineering SUMMARY A process has been created.

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 49 Rochester Institute of Technology Microelectronic Engineering REFERENCES 1.Silicon Processing for the VLSI Era, Volume 1 – Process Technology, 2 nd, S. Wolf and R.N. Tauber, Lattice Press. 2.The Science and Engineering of Microelectronic Fabrication, Stephen A. Campbell, Oxford University Press, 1996.

© March 24, 2008, Dr. Lynn Fuller Gig Ohm Resistors Fabrication Process Page 50 Rochester Institute of Technology Microelectronic Engineering HOMEWORK – GIG OHM RESISTORS