Aluminum Etch

Aluminum etch process should be verified on a test wafer before committing an entire lot.
It is recommended that the photoresist be hard-baked at 140°C for 1 minute to achieve maximum stability during etch.
When etching very small features in aluminum, it may be beneficial to put the wafers through an oxygen plasma descum before etching.
Make sure that there is enough etchant to cover the thermocouple. If not, ask a staff member for assistance. Do not add water to the etch bath.
Allow the tank temperature to stabilize.
Place the wafers in the tank until the aluminum clears and then give an additional 10 seconds of over-etch. Make sure to agitate the wafers every 15 seconds. It is important to use a visual endpoint for this process because many factors can affect the etch rate. Make sure there is space between wafers in the cassette so that the endpoint will be easy to see.
After completing an aluminum etch, rinse the wafers for 5 minutes in the rinse tank before transferring to the rinser/dryer.
Examine wafers under a microscope. If there are any remaining large spots of aluminum, the wafers can be etched for an additional 10-20 seconds.
If you are etching aluminum with 1% silicon, there may be a silicon residue left over after the etch. This residue may be removed by immersing the wafers in Freckle Etch for 1 minute.