Dry Oxidation

Purpose

To grow thin high quality gate oxide film to insulate transistor gate.

Equipment

Oxidation furnace module, quartz oxidation boat, quartz push rod, stainless steel boat forks and endcap remover.

Safety

Always wear safety glasses when near hot furnace.

Special Cleanroom Protocol Considerations

Do not touch any quartzware with gloved hands except end of push rod.

Instructions

The TA will remove the boat from the mouth of the quartz furnace.

Wafer Loading

• Transfer cleaned wafer into quartz boat
• The wafers should face the back of the furnace
• Place a dummy wafer in the first and last slot
• Make sure all wafers are evenly spaced and centered in the boat including dummys

Furnace Preparation

The TA must perform or supervise the remaining instructions.

• Open valves on appropriate nitrogen and oxygen wall valves.
• Turn oxidation valve to 'close'
• Set furnace temperature to 600°C
• Once the center zone reaches 600°C, open the nitrogen ball valve. Use needle valve to adjust flow to 6 lpm
• Purge furnace for 5 minutes

Quartz Boat Loading

• Carefully remove endcap and load boat using appropriate tools
• Slowly (this should take 60 seconds), push the boat into the furnace until it is near the center zone thermocouple (quartz rod 1 foot out of furnace)
• Replace the endcap

Start Oxidation

• Ramp furnace to 1000°C
• Once furnace reaches 1000°C turn oxidation valves to dry
• Open oxygen vavle. Adjust needle valve to read 6 lpm on flowmeter
• Turn off nitrogen ball valve
• After specified dry oxidation time (40 min for gate oxide), close oxygen ball valve and needle valve
• Open nitrogen ball valve and set needle valve to flow 6 lpm
• Set temperature to 20°C
• When temperature reaches 600°C, wafers may be unloaded and nitrogen turned off.

Unloading and Cooling Wafers

• Unload wafer by reversing loading procedure
• Close gas valves
• Set boat on the quartz cooling rack and allow to cool for 10 minutes before handling
• Leave dummys in the quartz boat

Special Notes

Quartzware and wafers should be clean and dry when loaded into the furnace. Contaminated quartz can be cleaned with HF. Never place wafers with photoresist or aluminum in the furnaces. This will cause severe contamination.

TA Preparation

Check pressures of oxygen and nitrogen gas cylinders in the bottle room. Make sure they are at least 300 psi. If less that 300 psi, replace the bottles.