Step-by-Step Guide to Silicon Wafer Fabrication (With Pictures)

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Semiconductor fabrication can be a very time-consuming and complicated procedure. This article takes you step by step on how to fabrication a silicon wafer. Beginning with a blank wafer (silicon wafer) the steps required to apply a mask and fabricate devices involve microscopes, photolithography equipment, etching stations, developer, etc. Extensive testing must also be done along the way to ensure proper electrical characteristics are obtained and to confirm that the process had been completed appropriately. Much of the work today is computer driven and done with speed and yield considerations in mind. This page is designed to serve as a simple overview over the various processes and design techniques undertaken to go from a blank wafer to a completed semiconductor device (with appropriate contacts). The devices illustrated are a P-N Diode, Schottky Diode, and NMOS.

Design Steps – Image Representation (See Below For Text)…

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Design Steps – Text Representation (See Above For Images)…

Step# Name | Description/Requirements | Image#

  1. Wafer Reception | Wafers obtained sliced from boule – 4″ Diameter <100> Si | IMG1
  2. Boron Implantation | P type implant doping of silicon (5×10^12/cm^2) | IMG2
  3. Piranha Cleaning | Wafer cleaned with 10:1 H2SO4 Piranha solution to remove organics
  4. Drive-in Annealing | 120min placement in Oxidation Furnace for annealing | IMG3
  5. Field-Oxidation Deposition | Wet Oxide Process – 5000A thickness target | IMG4
  6. Thickness Measurement | Nanospec test from each quadrant to check for uniform thickness
  7. Demos | Demos and Introduction to Lab Safety
  8. Dehydration Bake – 5min | Dry off excess moisture from wafer surface/bottom which can stick to devices
  9. HMDS Coating – 10min | Improves adhesion of photoresist
  10. Apply Photoresist/Prebake | Applies a layer of photoresist to which we will expose the mask. | IMG5
  11. Active Mask | Apply active mask to photoresist prior to development
  12. Development | Develop for 60 seconds in Developer solution | IMG6
  13. Post-Bake | For 120min @ 120C to complete the development process |
  14. Plasma Etching | Dry etching process is used to etch photoresist w/ minimal undercutting
  15. Wet Etching | 6:1 BOE solution – Wet etching process
  16. Inspection | Using the nanospec, check to ensure that oxide/silicon is properly etched
  17. Strip photoresist | Using 4:1 Piranha solution to remove organics | IMG7
  18. RCA1 + RCA2 Cleaning | Strip the organic and inorganic matrials from the wafer
  19. Dry Oxide Growth – Gate | In oxidation furnace – 30min – Target thickness 600A | IMG8
  20. LPCVD Poly Deposition | Used to deposit uniform layer of poly on the wafer – Target thickness 2000A | IMG9
  21. Oxide/Poly Thickness Nanospec | Check above steps by TA for correct measurements
  22. Dehydration Bake – 5min | Dry off excess moisture from wafer surface/bottom which can stick to devices
  23. HMDS Coating – 10min | Improves adhesion of photoresist
  24. Apply Photoresist/Prebake | Applies a layer of photoresist to which we will expose the mask.
  25. Poly Mask | Apply poly mask to photoresist prior to development
  26. Development | Develop for 60 seconds in Developer solution
  27. Post-Bake | For 120min @ 120C to complete the development process
  28. Plasma Etching | Dry etching process is used to etch photoresist w/ minimal undercutting
  29. Polysilicon Etch | DRIE Plasma etch – defines the gate of the NMOS | IMG10
  30. Nanospec Inspection | Check for Poly Thickness/Gate Oxide thickness under 20A
  31. Backside Poly Etch | The process used above deposits poly on both sides of the wafer, so the backside must also be etched – Approximately 5 minutes | IMG11
  32. Wet Oxide Etch | Etch oxide for approximately 5.5min in 6:1 BOE Solution | IMG12
  33. 4-Point Probe Inspection | Check for resistance values of monitor bars.
  34. Strip photoresist | Using 4:1 Piranha solution to remove organics
  35. Ion Implantation Procedure | Since we are using a self aligned Source/Gate/Drain, Ion implantation is necessary. Phosphorous implant done on the frontside/Boron implant done on the backside | IMG13
  36. RCA Cleaning Procedure | Strip organic and metallic elements off the wafer
  37. Activation Anneal | Activation is required to activate the implanted atoms and repair any damage caused by the annealing process | IMG14
  38. LTO Oxide Deposition | LPCVD Furnace deposition – Target Thickness 5000A | IMG15
  39. Dehydration Bake – 5min | Dry off excess moisture from wafer surface/bottom which can stick to devices
  40. HMDS Coating – 10min | Improves adhesion of photoresist
  41. Apply Photoresist/Prebake | Applies a layer of photoresist to which we will expose the mask.
  42. Contact Mask | Apply contact mask to photoresist prior to development
  43. Development | Develop for 60 seconds in Developer solution
  44. Post-Bake | For 120min @ 120C to complete the development process
  45. Plasma Etching | Dry etching process is used to etch photoresist w/ minimal undercutting – 2min
  46. Wet Etching | 6:1 BOE solution – Wet etching process – One wafer for 5min, second for 9min | IMG16
  47. Inspection | Using the nanospec, check monitor bar measurements Poly/ S/D / Con/ & Schottky
  48. 4-Point Probe measurements | Measure monitor bars and check resistance values
  49. RCA1 + RCA2 Cleaning | Strip the organic and inorganic matrials from the wafer
  50. Aluminum Sputtering | Frontside Target 5000A / Backside Target 2500A | IMG17
  51. Dehydration Bake – 5min | Dry off excess moisture from wafer surface/bottom which can stick to devices
  52. HMDS Coating – 20min | Improves adhesion of photoresist. This step was doubled for increased adhesion during this process.
  53. Apply Photoresist / Prebake | Applies a layer of photoresist to which we will expose the mask.
  54. Metal Mask | Apply metal mask to photoresist prior to development
  55. Development | Develop until proper color change is seen.
  56. Post-Bake | For 120min @ 120C to complete the development process
  57. Backside Photoresist / Prebake | Applies a layer of photoresist to the backside. Done to protect the backside Aluminum during the etching.
  58. Plasma Etching | Dry etching process is used to etch photoresist w/ minimal undercutting – 2min
  59. Metal Etching | Very fast procedure (overetching is not recommended and can kill the device). Etch until red photoresist shows – approximately 7min)
  60. Plasma Etching | Dry etching process is used to etch photoresist w/ minimal undercutting – 2min
  61. Sintering of Metal | Creates a good ohmic contact between the Aluminum and Silicon | IMG18
  62. Measurements | Characterization of all required devices using Probes | IMG19

One thought on “Step-by-Step Guide to Silicon Wafer Fabrication (With Pictures)

  1. Are you able to perform this etch in a low frequency plasma cleaner like the plasma etch pe-25? I have a pe-25 but I don’t know if it will allow me to etch. My lab-mate uses it for cleaning slides.


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