METHODS OF ARC DETECTION AND SUPPRESSION DURING RF SPUTTERING OF A THIN FILM ON A SUBSTRATE
Methods and systems of arc suppression during RF sputtering of a thin film from a semiconducting target onto a substrate are provided. During sputtering, an alternating current of RF frequency can be applied to a semiconducting target to form a plasma. Upon formation of an arc extending from the target, an arc signature can be detected, where the arc signature is simultaneously defined by decreasing plasma voltage from an initial sputtering plasma voltage to an arc plasma voltage and increasing reflective power from an initial sputtering reflective power to an arc reflective power. Upon identification of the arc signature, the alternating current can be temporarily interrupted to the semiconducting target to suppress the arc extending from the target. Thereafter, the alternating current from the electrical power supply can be reapplied to the semiconducting target.
1 . A method of arc suppression during sputtering of a thin film from a semiconducting target onto a substrate, the method comprising:
applying an alternating current from an electrical power supply to the semiconducting target to form a plasma between the substrate and the semiconducting target, wherein the alternating current has a frequency of about 500 kHz to 15 MHz;
identifying an arc signature upon formation of an arc extending from the target, wherein the are signature is defined by a decrease in plasma voltage from an initial sputtering plasma voltage to an arc plasma voltage and a simultaneous increase in reflective power from an initial sputtering reflective power to an arc reflective power; and,
upon identification of the arc signature, interrupting the alternating current from the electrical power supply to the semiconducting target to suppress the arc extending from the target.
2 . The method as in claim 1 , further comprising:
after interrupting the alternating current from the electrical power supply to the semiconducting target, reapplying the alternating current from the electrical power supply to the semiconducting target.
3 . The method as in claim 2 , wherein the alternating current is interrupted for a specified time so as to extinguish the arc and maintain the plasma between the substrate and the semiconducting target.
4 . The method as in claim 2 , wherein the alternating current is interrupted for about 1 μs to about 100 ms.
5 . The method as in claim 2 , wherein the alternating current is interrupted for about 10 μs to about 1 ms.
6 . The method as in claim 2 , wherein the alternating current is interrupted for about 100 μs to about 500 μs.
7 . The method as in claim 1 , wherein the arc plasma voltage is about 25% of the initial plasma voltage or less, and wherein the arc reflective power is about 25% of the initial sputtering reflective power or more.
8 . The method as in claim 1 , wherein the arc plasma voltage is about 33% of the initial plasma voltage or less, and wherein the arc reflective power is about 33% of the initial sputtering reflective power or more.
9 . The method as in claim 1 , wherein the plasma voltage decreases from the initial sputtering plasma voltage to the arc plasma voltage and the reflective power increases from an initial sputtering reflective power to an arc reflective power in less than about 1 second.
10 . The method as in claim 1 , wherein the plasma voltage decreases from the initial sputtering plasma voltage to the arc plasma voltage and the reflective power increases from an initial sputtering reflective power to an arc reflective power in from about 10 μs to about 100 ms.
11 . The method as in claim 1 , wherein the plasma voltage decreases from the initial sputtering plasma voltage to the arc plasma voltage and the reflective power increases from an initial sputtering reflective power to an arc reflective power in from about 50 μs to about 1 ms.
12 . The method as in claim 1 , wherein the plasma voltage decreases from the initial sputtering plasma voltage to the arc plasma voltage and the reflective power increases from an initial sputtering reflective power to an arc reflective power in from about 100 μs to about 500 μs.
13 . A method for sputtering a cadmium sulfide layer on a glass superstrate while detecting and suppressing arc formation, the method comprising:
applying an alternating current from an electrical power supply to a cadmium sulfide target to form a plasma between the glass superstrate and the target, wherein the alternating current has a frequency of about 500 kHz to 15 MHz;
identifying an arc signature upon formation of an arc extending from the target, wherein the arc signature is defined by a decrease in plasma voltage from an initial sputtering plasma voltage to an arc plasma voltage and a simultaneous increase in reflective power from an initial sputtering reflective power to an arc reflective power; and,
upon identification of the arc signature, interrupting the alternating current from the electrical power supply to the target to suppress the arc extending from the target.
14 . A method as in claim 13 , further comprising:
after interrupting the alternating current from the electrical power supply to the target, reapplying the alternating current from the electrical power supply to the target.
15 . The method as in claim 14 , wherein the alternating current is interrupted for a specified time so as to extinguish the arc and maintain the plasma between the substrate and the semiconducting target.
16 . The method as in claim 14 , wherein the alternating current is interrupted for about 1 μs to about 100 ms.
17 . The method as in claim 13 , wherein the arc plasma voltage is about 25% of the initial plasma voltage or less, and wherein the arc reflective power is about 25% of the initial sputtering reflective power or more.
18 . The method as in claim 13 , wherein the arc plasma voltage is about 50% of the initial plasma voltage or less, and wherein the arc reflective power is about 50% of the initial sputtering reflective power or more.
19 . The method as in claim 13 , wherein the plasma voltage decreases from the initial sputtering plasma voltage to the arc plasma voltage and the reflective power increases from an initial sputtering reflective power to an arc reflective power in from about 10 μs to about 100 ms.
20 . A sputtering system for arc detection and suppression during sputtering of a thin film from a semiconducting target onto a substrate, the system comprising
a sputtering chamber configured to receive a substrate and a semiconductor target;
an electrical power supply wired to the sputtering chamber to supply alternating current to the semiconducting target to form a plasma between the substrate and the semiconducting target, wherein the alternating current has a frequency of about 500 kHz to 15 MHz;
a switch between the electrical power supply and the sputtering chamber configured to supply the alternating current to the sputtering chamber when closed and interrupt the alternating current to the sputtering chamber when open;
a pair of sensors positioned within the sputtering chamber to measure the plasma voltage and the reflective power during sputtering; and,
an arc detection control configured to open the switch to interrupt the alternating current to the sputtering chamber upon detection of an arc signature simultaneously defined by decreasing plasma voltage and increasing reflective power measured by the pair of sensors.