1. Hello from Mike Deal at Stanford University - Senior Research Scientist at the Stanford Nanofabrication Facility
V5.15

2. Nanotechnology
“Nano” – From the Greek word for “dwarf” and means 10-9, or one-billionth.
Here it refers to one-billionth of a meter, or 1 nanometer (nm).
1 nanometer is about 3 atoms long.
“Nanotechnology” – Building and using materials, devices and machines at the nanometer (atomic/molecular) scale.

3. Nanostructures Carbon nanotube
Gold/Silver nanoparticle (U. Notre Dame)
Intel’s transistors used in their integrated circuits (computer chips)

4. How do you build something so small?
“Top-down” – building something by starting with a larger piece and carving away material (like a sculpture).
“Bottom-up” – building something by putting together smaller pieces (like building a car engine).
Chemistry is important in both top-down and bottom-up processes

5. Bottom-up fabrication
Adding atoms to atoms, molecules to molecules
“Self-assembly” of atoms and molecules
Use of chemical and biological processes
Current day examples:
Self-assemble of organic monolayers for molecular transistors, etc. (Yale)
Carbon Nanotubes
Vertical growth of nanowires for electronic devices (Stanford)
More extreme example: Self-replicating robots.

6. Top-down fabrication
Method used by integrated circuit industry to fabricate computer chips down to ~ 15 nm size
Makes use of depositing thin films, then “photolithography” and plasma etching to make films into desired patterns on a silicon wafer.

7. “Top-Down” nanofabrication
Silicon wafer

8. Deposition equipment
Silicon wafer

9. Deposition equipment
Gas phase reactants
Silicon wafer

10. Deposition equipment
Gas phase reactants
SiN film
Silicon wafer

11. SiN film
Silicon wafer

12. Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

13. Photolithography equipment Photo-sensitive layer (“photoresist”)
Light source
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

14. Photolithography equipment Photo-sensitive layer (“photoresist”)
Light source
Ultraviolet light
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

15. Photolithography equipment Photo-sensitive layer (“photoresist”)
Light source
Ultraviolet light
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

16. Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

17. Photo-sensitive layer (“photoresist”)
Chemical developer
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

18. Photo-sensitive layer (“photoresist”)
Chemical developer
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

19. Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

20. Plasma gas (etches film) Photo-sensitive layer (“photoresist”)
Etching equipment
Plasma gas (etches film)
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

21. Plasma gas (etches film) Photo-sensitive layer (“photoresist”)
Etching equipment
Plasma gas (etches film)
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

22. SiN thin film patterned correctly!
SiN film
Silicon wafer
SiN thin film patterned correctly!

23. Starting at photoresist step: Photo-sensitive layer (“photoresist”)
With contamination present
Starting at photoresist step:
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

24. Photo-sensitive layer (“photoresist”)
With contamination present
Dust particle
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

25. Photo-sensitive layer (“photoresist”)
With contamination present
Light source
Ultraviolet light
“mask”
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

26. Photo-sensitive layer (“photoresist”)
With contamination present
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

27. Photo-sensitive layer (“photoresist”)
With contamination present
Another dust particle
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

28. Plasma gas (etches film) Photo-sensitive layer (“photoresist”)
With contamination present
Plasma gas (etches film)
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer

29. Photo-sensitive layer (“photoresist”)
With contamination present
Photo-sensitive layer (“photoresist”)
SiN film
Silicon wafer
SiN thin film patterned incorrectly!

30. Relative size of clean room contaminants
How do you build something so small?
Requires very clean environment: “clean room”
Magnified image of contaminant on wafer surface, which can cause defects and failures in nanostructures
Relative size of clean room contaminants

31. A lab user “gowning-up” in SNF
How do you build something so small?
Requires very clean environment: “clean room”
People wear clean room suits (also called “gowns” or “bunny-suits)
Huge fans circulate filtered air throughout the facility
Wafers are cleaned in liquid solutions between every processing step
A lab user “gowning-up” in SNF

32. Greg Haugstad at University of Minnesota
Gregory Book and Swaminathan Rajaraman (Swami) at Georgia Tech University
Greg Haugstad at University of Minnesota