Passive bipolar arc control system and method
View Patent ↗An arc control system includes a sputtering chamber that houses an anode and a sputtering target formed from a target material and serving as a cathode. A DC power supply provides a DC voltage between the cathode and anode such that a cathode current flows from the anode to the cathode. A resonant network is coupled between the DC power supply and the chamber. The resonant network has sufficient Q so that in reaction to an arc, the cathode current resonates through zero, causing a positive voltage to be applied between the cathode and anode. A reverse voltage clamp is coupled across the resonant network to clamp the cathode voltage to a predetermined reverse voltage. The reverse cathode voltage inhibits subsequent arcing by positively charging insulated deposits on the sputtering target. The arc control system limits the quantity of energy that is dissipated by the arc.
1. An arc control system for responding loan arc in a DC sputtering system, comprising:
a sputtering chamber that houses an anode and a sputtering target formed from a target material and serving as a cathode;
a DC power supply configured to provide a direct current cathode voltage such that a cathode current flows through the anode and the cathode, the DC power supply having an output filter that includes an output inductor and an output capacitor;
a first circuit branch coupled across the DC power supply, the first circuit branch comprising a resonant capacitor; and
a second circuit branch coupled across the DC power supply in parallel with the first circuit branch, the second circuit branch comprising a resonant inductor in series with a parallel combination of a first circuit subbranch and a second circuit subbranch, wherein the first circuit subbranch comprises the sputtering chamber and the second circuit subbranch comprises a reverse voltage clamp;
and further wherein the resonant capacitor and the resonant inductor comprise a resonant network configured to provide a Q such that in reaction to the occurrence of an arc, the cathode current resonates to a reverse current level and wherein the reverse voltage clamp is configured to clamp the cathode voltage to a predetermined clamp voltage and further wherein the output of the DC power supply does not vary in response to the occurrence of an arc.
2. The arc control system of claim 1 wherein the reverse voltage clamp comprises at least one zener diode in series with a reverse biased diode.
3. The arc control system of claim 1 further comprising a forward voltage clamp in series with the reverse voltage clamp, wherein the reverse voltage clamp comprises at least one bi-directional zener diode and the forward voltage clamp comprises at least one unidirectional zener diode.
4. The arc control system of claim 1 wherein the DC power supply is selected from the group of: SCR power supplies, switchmode power supplies, and diode-transformer power supplies.
5. The arc control system of claim 1 wherein the predetermined clamp voltage is less than a backsputtering voltage.
6. The arc control system of claim 2 wherein the DC sputtering system is a DC reactive sputtering system.