DIY RF Coupling Plasma

An RF-coupled plasma can be created using standard laboratory equipment.

Atoms consist of a positively charged nucleus surrounded by a cloud of negatively charged electrons. Sometimes atoms can gain or lose electrons, which leads to them acquiring a net positive or negative charge. An atom with a net charge is known as an ion. Plasma is a cloud of ions, and these can have a number of uses in the semiconducting processing industry. A plasma can be produced inside an Argon-filled vacuum chamber by using a power supply that generates radio frequency (RF) radiation.

Things You'll Need

• RF vacuum chamber with Argon mass flow controller
• Rotary pump
• Turbo pump
• RF power supply
• RF matching network
• 2 RF cables

Instructions

1. Switch on the rotary pump and wait for the pressure to get to 10^-3 millibar. Switch on the turbo pump, and wait for it to ramp up. Wait until a pressure of approximately 10^-6 millibar is reached.

2. Connect an RF cable between the RF matching unit and RF power supply. Connect another cable between the RF matching unit, and the RF vacuum chamber electrode socket.

3. Partially close the valve to the turbo pump. Switch on the Argon mass flow controller, and set a pressure of 15 millibar. Switch on the RF power supply and matching unit. Set a forward power of 50 Watts. The matching unit is heard as it tries to minimize the reflected RF power. When the reflected power is less than 1 percent of the forward power, increase the forward power to approximately 150 Watts. The plasma within the chamber should light, and be visible though the chamber view-port. Slowly decrease the forward power back to 50 Watts. The RF couple plasma is created.

References

• Kurt J Lesker: RF Power Supply Generators
• Quorum Technologies: RF Plasma Techniques and Advantages