Etch process employing asymmetric bipolar pulsed DC

Claim 2

Asymmetric bipolar plasma etching process for etching a workpiece to be later coated, and which is positioned within a plasma chamber, comprising the steps of: applying a negative dc forward etching current at an applied forward voltage level between said workpiece and an anode in said chamber such that said applied forward voltage level causes noble gas ions in said chamber to impinge upon said workpiece with sufficient energy to flee impurities from the surface of said workpiece; and applying onto said forward etching current pulses of a positive reverse voltage at a suitable pulse width and a suitable reverse bias level relative to said anode, so that the voltage applied between said workpiece and said anode is a train of asymmetric bipolar pulses with the reverse bias voltage having a pulse duty cycle that is significantly below 50%; wherein said applied forward voltage is between negative 300 and negative 4,000 volts and said reverse bias voltage is selected at a smaller level between positive 50 volts and positive 300 volts.

Claim 3

Process according to claim 1 wherein said negative voltage is on the order of 1,500 to 1,800 volts.

Claim 4

A combined etching and sputtering process in which a workpiece is first subjected to plasma etching in a plasma chamber that contains a sputtering target to remove impurities from the surface of the article, and then is subjected to reactive sputtering to produce a coating on the article; comprising the steps of a) etching said article in a plasma chamber by i) applying a negative dc forward etching current at an applied forward voltage level between said workpiece and an anode in said chamber such that said forward voltage level causes noble gas ions in said chamber to impinge upon said workpiece with sufficient energy to free impurities from the surface of said workpiece; while ii) applying onto said forward etching current pulses of a positive reverse bias voltage at a suitable pulse width and pulse rate and a suitable reverse bias level relative to said anode, so that the voltage applied between said workpiece and said anode is a train of asymmetric bipolar pulses wherein the positive reverse bias voltage has a pulse duty cycle significantly below fifty percent; wherein said forward applied voltage is between negative 300 and negative 4,000 volts and said reverse bias voltage is provided at a substantially smaller level between positive 50 volts and positive 300 volts; and with said pulse width being between 0.25 μsec and 3 μsec; and directly after said workpiece has been etched sufficiently to carry out a sputter coating operation thereon, b) carrying out a reactive sputtering process in the very same plasma chamber, by i) introducing into said chamber a reactive gas; and ii) applying a dc sputtering current between said target and an anode in said chamber at an applied voltage level that causes noble gas ions in the chamber to impinge upon said target with sufficient energy to free atoms of said target material from said target; iii) wherein the free atoms of said target material react with said reactive gas to form a compound that is then deposited on the etched surface of said workpiece.

Claim 5

A combined etching and sputtering process in which a workpiece is first subjected to plasma etching in a plasma chamber that contains a sputtering target to remove impurities from the surface of the article, and then is subjected to reactive sputtering to produce a coating on the article; comprising the steps of a) etching said article in a plasma chamber by i) applying a negative dc forward etching current at an applied forward voltage level between said workpiece and an anode in said chamber such that said forward voltage level causes noble gas ions in said chamber to impinge upon said workpiece with sufficient energy to free impurities from the surface of said workpiece; while ii) applying onto said forward etching current pulses of a positive reverse bias voltage at a suitable pulse width and pulse rate and a suitable reverse bias level relative to said anode, so that the voltage applied between said workpiece and said anode is a train of asymmetric bipolar pulses wherein the positive reverse bias voltage has a pulse duty cycle significantly below fifty percent; wherein said forward applied voltage is between negative 300 and negative 4,000 volts and said reverse bias voltage is provided at a substantially smaller level between positive 50 volts and positive 300 volts; and with said pulse width being between 0.25 μsec and 3 μsec; and directly after said workpiece has been etched sufficiently to carry out a sputter coating operation thereon, b) carrying out a reactive sputtering process in the very same plasma chamber, by i) introducing into said chamber a reactive gas; and ii) applying a dc sputtering current between said target and an anode in said chamber at an applied voltage level that causes noble gas ions in the chamber to impinge upon said target with sufficient energy to free atoms of said target material from said target; iii) wherein the free atoms of said target material react with said reactive gas to form a compound that is then deposited on the etched surface of said workpiece.

Claim 6

Combined etching and sputtering process according to claim 3, wherein said step ii) of applying a dc sputtering current includes supplying said sputtering current to said target at a forward negative voltage level relative to said anode, and applying onto said sputtering current pulses of a positive reverse bias voltage relative to said anode at a predetermined pulse rate having a pulse duty cycle that is significantly below fifty percent and a predetermined pulse width so that accumulations of said compound which have deposited on said target are bombarded by said noble gas ions with sufficient energy to free molecules of said compound from said target.

Claim 7

Combined etching and sputtering process according to claim 4 wherein said pulses of positive voltage have a pulse width between about 0.25 and 3 μsec.

Claim 8

Combined etching and sputtering process according to claim 4, wherein said negative applied voltage is between 300 and 700 volts and said positive voltage is between 50 and 300 volts.

Claim 9

Process according to claim 1 wherein said pulses have a pulse rate of between 40 KHz and 200 Khz.

Claim 10

Process according to claim 1 wherein said reverse bias voltage is about +75 volts.

Claim 11

Process according to claim 1 wherein said applied forward voltage is at least minus 1,200 volts.

Claim 12

Process according to claim 9, wherein said applied forward voltage is between about minus 1,200 volts and minus 1,800 volts.