US RE40,008 E1
Method and apparatus for controlling ion implantation during vacuum fluctuation
Steven R. Walther, Andover, Mass. (US)
Assigned to Varian Semiconductor Equipment Associates, Inc., Gloucester, Mass. (US)
Filed on Jun. 24, 2003, as Appl. No. 10/602,795.
Application 10/602795 is a reissue of application No. 09/586492, filed on Jun. 02, 2000, now 6,323,497, filed on Nov. 27, 2001.
Int. Cl. G21G 5/10 (2006.01)
U.S. Cl. 250—492.21  [250/492.1] 43 Claims
OG exemplary drawing
 
2. An ion implantation system comprising:
a beam generator that generates an energetic ion beam and directs the beam [ along an ion beam path ] toward a semiconductor wafer;
a detector that detects an ion beam current;
a wafer drive that moves the semiconductor wafer in a direction transverse to the ion beam path; and
a controller that receives signals from the detector representative of a detected ion beam current, detects a vacuum fluctuation based on the [ a difference value determined from an ion beam current reference value, which corresponds to an ion beam current in the absence of vacuum fluctuations along the ion beam path, and a ] detected ion beam current [ measured in the presence of vacuum fluctuations along the ion beam path] , and controls the wafer drive to adjust a wafer scan rate to compensate for the vacuum fluctuation during implantation.