ENGR-45_Lec-06_Diffusion_Fick-1.ppt 1 Bruce Mayer, PE Engineering-45: Materials of Engineering Bruce Mayer, PE Registered Electrical & Mechanical Engineer Engineering 45 PhotoLithography MOSFET Fab

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 2 Bruce Mayer, PE Engineering-45: Materials of Engineering PhotoLithoGraphic Patterning - 1  Begin with a precise flat surface such as silicon wafer silicon substrate

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 3 Bruce Mayer, PE Engineering-45: Materials of Engineering PhotoLithoGraphic Patterning - 2  A THIN layer of a different material is deposited or grown on the substrate silicon substrate oxide field oxide

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 4 Bruce Mayer, PE Engineering-45: Materials of Engineering PhotoLithoGraphic Patterning - 3  A Thin layer of PHOTOsensitive, and acid/etch chemical RESISTING material (a.k.a. PhotoResist) is applied to the wafer silicon substrate oxide photoresist

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 5 Bruce Mayer, PE Engineering-45: Materials of Engineering Shadow on photoresist photoresist Exposed area of photoresist Chrome plated glass mask Ultraviolet Light silicon substrate oxide Litho-4: Ultraviolet light Exposes photoresist through windows in a photomask

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 6 Bruce Mayer, PE Engineering-45: Materials of Engineering PhotoLithoGraphic Patterning – 5  Exposed photoresist becomes soluble and can be easily removed by a “developer” chemical. Unexposed area of photoresist silicon substrate Exposed area of photoresistoxide photoresist

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 7 Bruce Mayer, PE Engineering-45: Materials of Engineering PhotoLithoGraphic Patterning – 6  Unexposed photoresist remains on surface of oxide to serve as a temporary protective mask for areas of the oxide that are not to be etched/disolved silicon substrate oxide photoresist photoresist

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 8 Bruce Mayer, PE Engineering-45: Materials of Engineering PhotoLithoGraphic Patterning – 7  Areas of oxide protected by photoresist remain on the silicon substrate while exposed oxide is removed by the etching process. silicon substrate oxide oxide photoresist

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 9 Bruce Mayer, PE Engineering-45: Materials of Engineering PhotoLithoGraphic Patterning – 8  The photoresist is removed using a “stripping process” -- revealing the patterned “window” on the thin oxide layer. silicon substrate oxide oxide Oxide Layer

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 10 Bruce Mayer, PE Engineering-45: Materials of Engineering Intel squeezes 2 BILLION transistors onto new Itanium chip – Feb08  The new 65-nanometer Tukwila Itanium processor, which is expected to be released at the end of 2009, will run at up to 2 GHz, have dual-integrated memory controllers and use Intel's QuickPath interconnect instead of a front-side bus. The processor also will have 2 billion transistors on one chip  BUT...What is a TRANSISTOR? What KIND of Transistors are used? HOW are the Transistors MADE?

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 11 Bruce Mayer, PE Engineering-45: Materials of Engineering Acknowledgement  These Following Images Were Graciously Provided by Michael W. Davidson National High Magnetic Field Laboratory 1800 E. Paul Dirac Dr. The Florida State University Tallahassee, Florida Tel: Fax: web:

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 12 Bruce Mayer, PE Engineering-45: Materials of Engineering n-MOSFET Electronic Device  negative channel, Metal-Oxide-Silicon, Field-Effect Transfer-resistor (Transistor) Source Drain Gate Drain Electrical Current VgVg VdVd VsVs d s g

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 13 Bruce Mayer, PE Engineering-45: Materials of Engineering 1. Form Gate & Isolation Dielectric  Oxidize P-Type Silicon in Tube Furnace °C in O 2 or Wafer-Vapor Forms Insulating Layer of Silicon Dioxide (SiO 2 ) –Yellow Layer Below

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 14 Bruce Mayer, PE Engineering-45: Materials of Engineering 2. Apply Photo Resist  Spin on “Thick” Liquid Photo Resist (blue) and “Soft- Bake” to make resist plastic-like

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 15 Bruce Mayer, PE Engineering-45: Materials of Engineering 3. Expose the Negative PhotoResist  First Mask Placed Over PhotoResist  UltraViolet Light Projected onto the Mask  Exposed PhotoResist Hardens (negative resist)

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 16 Bruce Mayer, PE Engineering-45: Materials of Engineering 4. Develop Exposed PhotoResist  Unexposed (and soft) PhotoResist (PR) is Washed away by the “Developer” Solution Leaves the exposed PR and SiO 2 in tact

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 17 Bruce Mayer, PE Engineering-45: Materials of Engineering 5. Etch SiO 2 to form Gate Dielectric  Etch the Thin the SiO 2 Using “Plasma Etching”  Leave only a Very Thin Insulating Layer

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 18 Bruce Mayer, PE Engineering-45: Materials of Engineering 6. Remove Used PhotoResist  Hardened PhotoResist is removed by one of: Liquid Solvent Gaseous Ozone “Ashing”

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 19 Bruce Mayer, PE Engineering-45: Materials of Engineering 7. Deposit Gate Electrode Film  Deposit a Layer of Polycrystalline Silicon (red) by Low Pressure Chemical Vapor Deposition (LPCVD)

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 20 Bruce Mayer, PE Engineering-45: Materials of Engineering 8. Apply 2 nd Layer of PhotoResist  Cover PolySi with PhotoResist in Preparation for the Next Mask Step

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 21 Bruce Mayer, PE Engineering-45: Materials of Engineering 9. Expose PhotoResist Using Mask-2  The 2 nd Mask is placed Over the PR  PR exposed to UV Light

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 22 Bruce Mayer, PE Engineering-45: Materials of Engineering 10. Develop Gate Electrode PR  Use the Developer to Wash Away UnWanted PR Leave Behind a “T” shaped PR pattern

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 23 Bruce Mayer, PE Engineering-45: Materials of Engineering 11. Pattern Gate PolySilicon  Use “Dry” Plasma Etching Techniques to Remove BOTH PolySi and SiO 2 in areas Not Protected by PR

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 24 Bruce Mayer, PE Engineering-45: Materials of Engineering 12. Remove PR to Complete Gate Electrode  Remove PR by Ozone Ashing  Leaves a Strip of PolySi which Rises Above the Exposed Silicon

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 25 Bruce Mayer, PE Engineering-45: Materials of Engineering 13. Change Exposed Si from P-type to N-type  Ion-Implant Phosphorus or Arsenic to Convert the Exposed Silicon to N-Type

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 26 Bruce Mayer, PE Engineering-45: Materials of Engineering 14. Deposit Electrical Contact Insulation  Deposit SiO 2 by TEOS+O 3 APCVD The SiO 2 may P or P+B doped

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 27 Bruce Mayer, PE Engineering-45: Materials of Engineering 15. Apply Contact Via PR  Apply a 3 rd Layer of PhotoResist that Will be used to Form the Vertical Shafts used for Electrical Contacts

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 28 Bruce Mayer, PE Engineering-45: Materials of Engineering 16. Expose PR using 3 rd Mask  Again Exposed Masked PR to UV Light  The Black Rectangles Will Define the Contact Holes

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 29 Bruce Mayer, PE Engineering-45: Materials of Engineering 17. Develop Contact-Via PR  Develop the PR to Expose the SiO 2 in the desired Contract areas

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 30 Bruce Mayer, PE Engineering-45: Materials of Engineering 18. Expose Silicon Thru Etching  Etch the SiO 2 Not Protected by the PR to Expose the underlying Silicon PolySi at rear N-Type Si at Front-Left & Front-Right

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 31 Bruce Mayer, PE Engineering-45: Materials of Engineering 19. Remove Contact-Via PR  Remove the PR to Reveal Contact holes, or vias, in the insulating APCVD-SiO 2

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 32 Bruce Mayer, PE Engineering-45: Materials of Engineering 20. Deposit Aluminum Contact Wiring  Blanket Deposit Al-Cu Alloy by Sputtering  Al Contacts the Si and PolySi thru the holes in the APCVD-SiO 2

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 33 Bruce Mayer, PE Engineering-45: Materials of Engineering 21. Apply “Wiring” PhotoResist  Apply a 4 th Layer of PhotoResist that Will be used to Form the Al-Cu “wires” that Carry Electrical Current and Potential (Voltage) to the Transistor

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 34 Bruce Mayer, PE Engineering-45: Materials of Engineering 22. Metallization Exposure  Expose the PR using the Metallization Mask

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 35 Bruce Mayer, PE Engineering-45: Materials of Engineering 23. Develop Metallization PR  Develop PR Exposing Regions of the Al-Cu Metal for Subsequent Removal

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 36 Bruce Mayer, PE Engineering-45: Materials of Engineering 24. Etch UnProtected Al-Cu to Form “Wires”  The Final Etching Step Removes the Unwanted Metal; Leaving only Metal used for Contacting thru the Vertical-Shaft Vias the Silicon Source/Drain and Poly-Si Gate Forming Strips of Al-Cu that act as Wires

ENGR-45_Lec-06_Diffusion_Fick-1.ppt 37 Bruce Mayer, PE Engineering-45: Materials of Engineering 25. Remove Remaining Resist  Xsistor Done  Remove the Remaining Metallization Resist, Completing the n-MOSFET Transistor Millions of transistors can be formed Simultaneously