How to clean a sample prior to lithography

Cleaning of substrates / samples should always be done in the fume cupboard. Lab coat, goggles and gloves should be worn at all times.

Start with a clean beaker add ethyl lactate (yellow bottle) to the bottom to cover the samples, then put the beaker in the ultrasonic bath for ~ 8 minutes. The bath should be ~half full of water, top up with ultra pure water or distiled if required.

When the time is up, carefully remove the samples and dry using the nitrogen gun and place in a clean beaker. The nitrogen should be turned on at the gas bottle with the pressure set to ~1 bar, then turn on the gas feed for the nitrogen on the fume cupboard itself. when all samples are dry cover with acetone and put back in the bath for 8 minutes.

As acetone is not very good to breath in, when the time is up, do not dry with the nitrogen gun, just rinse with methanol and place in a clean beaker, top up with methanol and return to the bath for ~8 minutes again.

Dry the samples with nitrogen and add to a beaker of isopropanol (blue bottle) and put back in the bath for 8 minutes.

Finally dry the samples and put into a clean beaker. The samples are now clean and ready to use.

Between the stages the beakers should be cleaned. to do this, wash out the beaker with the same chemicals in order as above and place upside down at the back of the fume cupboard on a tissue to dry. Once dry they can be used again or put into the glassware cupboard.

If the wash bottles get low/empty, they can be refilled by topping up from the main store bottles in the chemical cupboard. bottles should be topped up in the fume cupboard and any spillage wiped off the main bottle before being put back into the cupboard.

When finished turn off the nitrogen both at the main bottle and at the fume cupboard.