Etching aluminum over refractory metal with successive plasmas

A method of etching an exposed region of a multi-layer metal on a semiconductor workpiece, wherein the metal includes at least a first layer of refractory metal underlying a second layer of aluminum or aluminum alloy, comprising the steps of:

• providing a semiconductor workpiece that includes
• an exposed region of a multi-layer metal, wherein the multi-layer metal includes at least a first layer composed of a first refractory metal, a second layer composed of aluminum or aluminum alloy overlying the first layer, and a third layer overlying the second layer, the third layer being composed of a second refractory metal;
• and
• other material underlying the multi-layer metal on the workpiece;
• exposing the workpiece to a first atmosphere having a chemistry that etches both aluminum and the second refractory metal, wherein the first atmosphere is produced by plasma decomposition of a first gas mixture;
• and
• subsequently exposing the workpiece to a second atmosphere having a chemistry that etches the first refractory metal faster than it etches aluminum, wherein the second atmosphere is produced by plasma decomposition of a second gas mixture;
• wherein the step of exposing the workpiece to the first atmosphere is performed until the third layer of the exposed region is removed and all of the aluminum in the second layer of the exposed region is removed.

A method of etching an exposed region of a multi-layer metal on a semiconductor workpiece, wherein the metal includes at least a first layer of refractory metal underlying a second layer of aluminum or aluminum alloy, comprising the steps of:

• providing a semiconductor workpiece that includes
• an exposed region of a multi-layer metal that includes at least a first layer composed of aluminum or aluminum alloy overlying the first layer composed of a refractory metal, and
• other material underlying the multi-layer metal on the workpiece;
• exposing the workpiece to a first atmosphere that etches aluminum, wherein the first atmosphere is produced by plasma decomposition of a first gas mixture;
• and
• subsequently exposing the workpiece to a second atmosphere that etches the refractory metal faster than it etches aluminum, wherein the second atmosphere is produced by plasma decomposition of a second gas mixture;
• wherein the first gas mixture includes a compound of boron;
• and
• wherein the second gas mixture does not include any compound of boron or any compound of any element having an atomic mass greater than the atomic mass of argon.

A method of etching an exposed region of a multi-layer metal on a semiconductor workpiece, wherein the metal includes at least a first layer of refractory metal underlying a second layer of aluminum or aluminum alloy, comprising the steps of:

• providing a semiconductor workpiece that includes
• an exposed region of a multi-layer metal that includes at least a first layer composed of a first refractory metal underlying a second layer composed of aluminum or aluminum alloy, and
• other material underlying the multi-layer metal on the workpiece;
• exposing the workpiece to a first atmosphere that etches aluminum, wherein the first atmosphere is produced by plasma decomposition of a first gas mixture;
• and
• subsequently exposing the workpiece to a second atmosphere that etches the refractory metal faster than it etches aluminum, wherein the second atmosphere is produced by plasma decomposition of a second gas mixture;
• wherein the first gas mixture includes a compound of carbon;
• and
• wherein the second gas mixture includes an oxygen-containing species.