Welcome to the site! My name is Vishantak Srikrishna and I’m a high school student from the US. My ultimate goal of this site is to document my research and help others improve on it.
Demonstrated in the video is how you can use the fact that bare silicon is hydrophobic to check if the etch is completed.
Basically, the water should bead up on the wafer. On SiO2 (a hydrophilic surface), the water spreads out as it would a normal surface.
Recently, I was able to get a clean etch for the first time. I had the leave the wafer in 2.3% HF for 50 minutes in order for it to fully etch.
As for masking, I used duct tape. Originally, I used “car vinyl” because I though it would give me the best adhesive. But, I was getting lifting off the vinyl and I was etching in areas I did not want etched. Duct tape seemed to work well.
I put yesterday’s wafer back in for another 12 – 13 mins to grow more oxide.
I’m now getting a purplish tint, but I can’t actually use this wafer as I scratched it up when pushing it of the tube with a steel rod.
Today (Oct. 8, 2018), I was able to grow my first field oxide. I had the tube furnace hovering between 1000C and 1050C while I pumped steam into it by a boiling vacuum flask right next to it.
After around 50 mins of heating, I pulled the wafer back out and I saw a yellowish to purple tint; it looks very yellow on camera.
Looking at a chart, it indicates 400 – 490 nm. However, it was my first time and it very well could have been much lower than that.