Process and apparatus for forming stoichiometric layer of metal compound by closed loop voltage controlled reactive sputtering

Claim 1

A process for forming a layer of a stoichiometric metal compound on a semiconductor wafer by reactive sputtering a metal target in the presence of a reactive gas, comprising the step of changing the negative potential on a metal target to increase or decrease the supply of sputtered metal atoms available to react with the atoms of said reactive gas at a fixed flow of said gas by resetting the power level of a constant power source electrically connected to said target; to thereby provide a stoichiometric ratio of said sputtered metal atoms and said reactive gas atoms adjacent said wafer to form said stoichiometric metal compound on said wafer.

Claim 7

An apparatus for forming a layer of a stoichiometric metal compound on a semiconductor wafer (70) by reactive sputtering a metal target (30) in a chamber (10) in the presence of a reactive gas, comprising: means (44) for changing the negative potential on said metal target (30) to increase or decrease the supply of sputtered metal atoms available to react with the atoms of said reactive gas at a fixed flow of said gas comprising means for resetting the power level of a constant power source (40) electrically connected to said target (30); to thereby provide a stoichiometric ratio of said sputtered metal atoms and said reactive gas atoms adjacent said wafer (70) to form said stoichiometric metal compound on said wafer (70).

Claim 9

The apparatus of any of the claims 7 and 8, further comprising means (110, 120, 130, 136) for providing a path for the flow of said reactive gas to a zone (100) between said target (30) and said wafer (70), while restricting the travel of said stoichiometric metal compound from said zone (100) to other portions of said chamber (10).

Claim 10

The apparatus of any of the claims 7 to 9, wherein said means for providing said path for said reactive gas further comprises a series of coaxially nested members (110, 120, 130, 136) surrounding said zone (100) between said target (30) and said wafer (70) defining one or more gas passages (126, 132, 138) between said members.

Claim 11

The apparatus of any of the claims 7 to 10, wherein said means for providing said path for said reactive gas further comprises a series of at least three coaxially nested members surrounding the zone (100) between the target (30) and the wafer (70), comprising: (a) outermost and innermost members (120, 130) spaced downwardly from the top wall (14) of said chamber (10) to respectively define an inlet passageway (126) between the top wall (14) of said chamber (10) and said outermost member (120) and an outlet passageway (138) between said innermost member (130) and said top wall (14); (b) a bottom wall (136) joining the bottom edges of said innermost and outermost members (130, 120) together; and (c) a middle member (110) depending downwardly from said top wall (14) of said chamber (10) to a point spaced above said bottom wall (136); to thereby define a gas passage between said members from the portion of said chamber outside said members to said zone (100) within said members.

Claim 12

The apparatus of any of the claims 7 to 10, wherein said means for providing said path for said reactive gas further comprises a series of at least three coaxially nested cylinders surrounding the zone (100) between the target (30) and the wafer (70), comprising: (a) a first cylinder (110) having an upper end mounted to said top wall (14) of said chamber (10) and depending downwardly below said target (70) and generally symmetrically surrounding said target (70); (b) a second cylinder (120) generally coaxially surrounding said first cylinder (110) and having an upper end spaced from said top wall (14) to define a first passageway (126) therebetween and a lower end depending downwardly beyond a lower end of said first cylinder (110); (c) support means (122) in said chamber (10) to support said second cylinder (120) in said chamber (10) in said position coaxially surrounding said first cylinder (110); (d) a third cylinder (130) coaxially positioned within said first cylinder (110) having an inner diameter slightly larger than said semiconductor wafer (70) and having an upper end spaced from said top wall (14) of said chamber (10) to define a second passageway (138) therebetween and a lower end depending down approximately the same distance as said lower end of said second cylinder (120); and (e) a circular bottom wall (136) joined to said lower ends of said second and third cylinders (120, 130) to seal off the space therebetween; whereby a gas passage will be leading from the space in said chamber (10) outside of said second cylinder (120) through said first passageway (126) into the space between said first and second cylinders (110, 120), then down around said lower end of said first cylinder (110) and to the space between said first and third cylinders (110, 130) and then through said second passageway (138) to permit said reactive gas to emerge adjacent said wafer (70) to react with said sputtered metal to form said coating on said wafer (70).

Claim 16

The apparatus of any of the claims 12 to 15, wherein said third cylinder (130) has a clamping ring (140) carried at the upper end of said cylinder to engage the outer edge of said wafer (70).