Method for deposition using pulsed atmospheric pressure glow discharge
Disclosed are methods for deposition of a chemical compound or element using an atmospheric pressure glow discharge plasma in a treatment space comprising two electrodes connected to a power supply for providing electrical power during an on-time (t on ). The treatment space is filled with a gas composition of an active and an inert gas mixture, including a precursor of the chemical compound or element to be deposited. Dust formation is prevented by using Nitrogen in the gas composition, applying short pulses and using a predetermined residence time of the gas composition in the treatment space. Best results are obtained when using a stabilized plasma.
1. A method for deposition of a chemical compound or element on a substrate using an atmospheric pressure glow discharge plasma in a treatment space, the method comprising:
applying electrical power from an AC power supply to at least two electrodes in the treatment space to generate the atmospheric pressure glow discharge plasma, wherein the treatment space is filled with a gas composition comprising (i) a precursor of the chemical compound or element to be deposited; (ii) between 1 and 99.99% N 2 ; and (iii) between 0.01 and 25% O 2 , and
wherein the AC power supply generates pulse trains during an on-time (t on ) of the AC power supply, each pulse train comprising at least 10 periods of sine waves.
2. The method according to claim 1 , wherein the precursor is used in a concentration from 2 to 500 ppm.
3. The method according to claim 2 , wherein the gas composition comprises 75% to 99.99% a mixture of noble gas and N 2 and from 0.01 to 25% O 2 , wherein the amount of N 2 and noble gas in the mixture each is between 1 to 99%, and the total gas composition sums up to 100%, including the precursor amount.
4. The method according to claim 1 , wherein the gas composition further comprises an active gas, wherein the active gas partly or completely replaces the amount of O 2 in the gas composition.
5. The method of claim 4 , wherein the active gas is selected from the group consisting of hydrogen gas, carbon dioxide, ammonia, and oxides of nitrogen.
6. The method according to claim 1 , wherein the on-time (t on ) is from 0.02 ms to 500 ms.
7. The method according to claim 1 , wherein the on-time (t on ) is shorter than a time predetermined necessary for forming charged particles in the treatment space.
8. The method according to claim 7 , wherein the predetermined time period is less than 0.5 ms.
9. The method according to claim 8 , wherein the predetermined time period is less than 0.3 ms.
10. The method according to claim 7 , where the ratio between the on-time (t on ) and the sum of the on-time (t on ) and the off-time (t off ) is at least 1%.
11. The method according to claim 1 , where the atmospheric glow discharge plasma is stabilized by stabilization means counteracting local instabilities in the plasma.
12. The method according to claim 11 , wherein the local instabilities in the plasma are counteracted by applying an AC plasma energizing voltage to the electrodes causing a plasma current and a displacement current, wherein the discharge plasma is controlled by applying a displacement current change (dI/Idt) for controlling local current density variations associated with a plasma variety having a low ratio of dynamic to static resistance.
13. The method according to claim 12 , wherein the displacement current change is provided by applying a change in the applied voltage (dV/Vdt) to the two electrodes, the change in applied voltage being about equal to an operating frequency of the AC plasma energizing voltage, and the displacement current change (dI/Idt) having a value at least five times higher than the change in applied voltage (dV/Vdt).