Ni CATALYST CVD GROWTH OF PATTERNED CARBON NANOTUBES

By Sofia Sotiropoulou - 2006

Note: I tried to attach the image files but couldn't get them to export from the Word document. If you'd like to see the attached images, please go hunting for them on Caliban (\\caliban\home-caliban\admin\My Documents\Fabrication and Growth Recipes)

As for the quality of the tubes, I have attached some pictures along with the recipe. One is a TEM and you will see that the tubes are mostly double-walled with average diam. 20nm.

I am not sure about the length but it is around 5um.

1. Lithographic patterning of catalyst and lift-off procedure. The substrate used is a Si wafer with a thermally grown oxide layer (500nm). The oxide is crucial for CNT growth.

Spin P20, 2000 rpm, 60 sec. Let it rest for 1min Spin LOR5A at 1000rpm for 60sec (1um thickness). Soft Bake 90 0C 5min Spin 955CM 2.1 at 5000rpm, 60sec (1.5um thickness). Soft Bake 90 0C, 5min

Expose (i-line) PEB 90 0 C, 5min Develop 300MIF 1min.

Clean the wafer using UV/O3 for 10min.

Evaporate Ti (acts as an underlayer to avoid catalyst migration and diffusion in the silicon) and Ni using e-beam evaporation. The evaporation chamber has to be very clean. Make sure that no Au is present on the chamber wall, because Au can mask CNT growth. If needed do a run to cover up any gold residues (deposition of Ti 1kǺ and Al 1-5kǺ is sufficient)

Change crystal sensor Evaporate Ti 20nm and Ni 5nm (same run, without breaking the vacuum)

Lift off using PG Remover (N-methyl-pyrrolidone) overnight. Clean the wafer in Acetone, IPA and H2O and finally in UV/O3 for 10min.

2. Chemical Vapor Deposition

Place the chip at the end of the furnace (middle and forth)

Purge the tube Ar 0.80slm 5min Heat up to 900 0C Ar 0.15slm Anneal: Ar 0.15 slm and H2 0.15 slm 20min Grow: Ar 0.15 slm + H2 0.15 slm + C2H4 6.3sccm 20min Growth is probably taking place only the first 5-10min Cool down until ~ 150 0C. Ar 0.80slm