Protective offset sputtering
Sputtering in a physical vapor deposition (PVD) chamber may, in one embodiment, utilize a target laterally offset from and tilted with respect to the substrate. In another aspect, target power may be reduced to enhance film protection. In yet another aspect, magnetron magnets may be relatively strong and well balanced to enhance film protection. In another aspect, a shutter may be provided to protect the substrate in start up conditions. Other embodiments are described and claimed.
1. A method for physical vapor deposition, comprising:
forming a gate of a transistor on a semiconductor wafer substrate, said forming including:
rotating a magnetron adjacent a target;
rotating said semiconductor wafer substrate in a chamber body;
sputtering a surface of the target to deposit target material on said substrate in a layer of said gate wherein said gate layer has a thickness less than 100 angstroms; and
inhibiting plasma damage to underlying material of said gate while depositing said layer, said inhibiting including laterally offsetting the center of the target sputtering surface with respect to the center of the substrate within a range of 300 to 400 mm, and controlling the pressure within said chamber within a range of 1 to 7 milliTorr.
2. The method of claim 1 , wherein said inhibiting includes controlling the power of a signal biasing said target within a power range of 50 to 6000 watts.
3. The method of claim 1 , wherein said inhibiting includes disposing the target at an angle between about 15 to about 50 degrees.
4. The method of claim 1 , wherein said inhibiting includes vertically offsetting said target sputtering surface center with respect to said substrate center within a range of 300 to 400 mm.
5. The method of claim 1 wherein said inhibiting includes matching the magnetic strength of a center pole substantially to that of outer poles of the magnetron.
6. The method of claim 5 wherein the maximum unbalance of the poles is within 0.9.
7. The method of claim 1 wherein said inhibiting includes each pole of the magnetron producing a magnetic field having a field strength of at least 150 gauss measured in a direction parallel to the surface of the associated pole at a distance of about one inch from the surface of the associated pole.
8. The method of claim 1 wherein said inhibiting includes each pole of the magnetron producing a magnetic field having a field strength of at least 80 gauss measured in a direction normal to the surface of the associated pole at a distance of about one inch from the surface of the associated pole.
9. The method of claim 1 wherein said sputtering includes sputtering a surface of the target to deposit a conductive target material in a conductive gate electrode layer having a thickness in a range of 5-30 angstroms and wherein said inhibiting includes inhibiting plasma damage to an underlying gate insulative layer of insulative material of said gate while depositing said conductive gate electrode layer of said gate wherein said gate insulative layer has a thickness less than 100 angstroms.