Magnetic barrier for plasma in chamber exhaust

A plasma reactor comprising:

• a chamber having a process gas inlet and enclosing a plasma process region;
• a workpiece support pedestal within said chamber capable of supporting a workpiece at a processing location interfacing with said plasma process region, said support pedestal and said chamber defining an annulus therebetween to permit gas to be evacuated therethrough from said plasma process region;
• a ring horseshoe magnet adjacent and about one side of the annulus, said magnet being spaced from said plasma processing location by a spacing substantially greater than the smallest distance across said annulus, said magnet defining opposite poles which are substantially closer together than said spacing of said magnet from said processing location, said magnet being oriented to provide its maximum magnetic flux across said annulus and a minimum of said flux at said plasma processing location;
• said opposite poles being spaced similarly to or closer together than said smallest distance across said annulus.

A plasma reactor comprising:

• a chamber having a process gas inlet and enclosing a process region;
• a workpiece support pedestal capable of supporting a workpiece at a processing location interfacing with said process region, said support pedestal and said chamber defining an annulus therebetween to permit gas to be evacuated therethrough from said process region;
• a ring horseshoe magnet adjacent and about one side of the annulus and oriented to provide its maximum magnetic flux across said annulus and a minimum of said flux at said processing location, said horseshoe magnet being displaced from said processing location by a distance substantially greater than the smallest distance across said annulus;
• wherein the spacing between opposing poles of said horseshoe magnet is substantially less than the distance of said horseshoe magnet from the processing location.

A plasma reactor comprising:

• a chamber having a process gas inlet and enclosing a process region;
• a workpiece support pedestal capable of supporting a workpiece at a processing location interfacing with said process region, said support pedestal and said chamber defining an annulus therebetween to permit gas to be evacuated therethrough from said process region;
• a ring horseshoe magnet adjacent and about one side of the annulus and oriented to provide its maximum magnetic flux across said annulus and a minimum of said flux at said processing location, said horseshoe magnet being displaced from said processing location by a distance substantially greater than the smallest distance across said annulus;
• wherein the spacing between opposing poles of said horseshoe magnet is substantially less than the distance of said horseshoe magnet from the processing location and is similar to or less than said smallest distance across said annulus.