Ion implanter vacuum integrity check process and apparatus

Abstract

An ion implanter vacuum integrity check process and apparatus that enables a vacuum integrity check at a pressure substantially below the ion implantation process pressure, while storing an ion implantation process pressure set point for a subsequent ion implantation process. An ion implanter includes an end station chamber, a high vacuum system, a disk, a gas supply system and a controller for storing at least a vacuum integrity check pressure set point and an ion implantation process pressure set point. A disk inserted into the end station is accelerated to a predetermined rotational speed, while the high vacuum system is used to pump down the end station chamber. The end station chamber is, then, purged with an inert gas for a first predetermined time period, while maintaining the disk rotational speed and continuing to pump down the end station chamber. The pressure of the end station chamber is monitored, while the disk rotational speed and pumping of the chamber are maintained. If the vacuum integrity check pressure set point was reached in the end station chamber within a second predetermined time period, then the ion implanter is considered to have acceptable vacuum integrity. If not, then the process is ended and appropriate equipment maintenance action is taken for a possible leak. The apparatus includes a controller for storing at least a vacuum integrity check pressure set point, an ion implantation process pressure set point and an over-pressure set point.

What is claimed is:  
     
         1 . A method for checking the vacuum integrity of an ion implanter and purging the ion implanter of contaminants, the method comprising: 
 inserting a disk into, and sealing, an end station chamber of the ion implanter;    accelerating the disk to a predetermined rotational speed and pumping down the end station chamber;    purging the end station chamber with an inert gas at a first predetermined flow rate for a first predetermined time period, while maintaining the predetermined rotational speed of the disk and continuing to pump down the end station chamber;    monitoring the pressure of the end station chamber, while maintaining the predetermined rotational speed of the disk and continuing to pump down the end station chamber; and    determining whether the pressure in the end station chamber reached the vacuum integrity check pressure set point within a second predetermined time period.    
     
     
         2 . The method of  claim 1  further comprising, during the monitoring step, disabling the ion implantation process pressure set point and enabling the vacuum integrity check pressure set point.  
     
     
         3 . The method of  claim 1 , wherein the purging step purges the end station chamber with nitrogen gas with a purity of at least 99.99%.  
     
     
         4 . The method of  claim 1 , wherein the purging step purges the end station chamber with argon gas with a purity of at least 99.99%.  
     
     
         5 . The method of  claim 1 , wherein the first predetermined time period is in the range of 10 seconds to 15 seconds.  
     
     
         6 . The method of  claim 1 , wherein the second predetermined time period is less than 1 minute.  
     
     
         7 . The method of  claim 1 , wherein the predetermined rotational speed is in the range of 951 rpm to 955 rpm.  
     
     
         8 . The method of  claim 1 , further comprising storing at least a vacuum integrity check pressure set point and an implantation process pressure set point, wherein the vacuum integrity check pressure set point is less then the implantation process pressure set point.  
     
     
         9 . The method of  claim 8 , wherein the vacuum integrity check pressure set point is 1.0 E-5 Torr and the ion implantation process pressure set point is 8.5 E-5 Torr.  
     
     
         10 . The method of  claim 1 , wherein the inserting step includes inserting a disk with semiconductor wafers mounted thereon into the end station chamber, 
 and wherein the method further includes the steps of:    introducing, when it has been determined in the determining step that the pressure in the end station chamber has reached the vacuum integrity check pressure set point within the second predetermined time period, an inert gas into the end station chamber at a second predetermined flow rate, while maintaining the predetermined rotational speed of the disk and continuing to use the high vacuum system to pump down the end station chamber;    stabilizing the pressure in the end station chamber at the implantation process pressure set point; and    implanting dopant ions into the semiconductor wafers.    
     
     
         11 . The method of  claim 10 , further comprising, during the stabilizing step, disabling the vacuum integrity check pressure set point and enabling the ion implantation process pressure set point.  
     
     
         12 . The method of  claim 1 , further comprising storing an over-pressure set point.  
     
     
         13 . An apparatus for controlling an ion implanter, the apparatus comprising: 
 a controller for storing at least a vacuum integrity check pressure set point, an ion implantation process pressure set point and an over-pressure set point, wherein the vacuum integrity check pressure set point is lower than the ion implantation process pressure set point.    
     
     
         14 . The apparatus of  claim 13 , wherein the controller is capable of disabling the ion implantation process pressure set point when the ion implanter is being pumped down to the vacuum integrity check pressure set point.  
     
     
         15 . The apparatus of  claim 14 , wherein the controller is capable of re-enabling the ion implantation process pressures set point after the ion implanter has been pumped down to the vacuum integrity check pressure set point.  
     
     
         16 . The apparatus of  claim 13 , wherein the controller activates a gas purge of the ion implanter for a predetermined time period when a disk rotational speed is within a predetermined disk rotational speed range.  
     
     
         17 . The apparatus of  claim 16 , wherein the predetermined time period is in the range of 10 seconds to 15 seconds and the predetermined disk rotational speed range is from 951 rpm to 955 rpm.  
     
     
         18 . The apparatus of  claim 16 , wherein the controller includes a circuit board with terminal connectors for receiving a signal from a first low vacuum sensor, a signal from a second low vacuum sensor and a signal from a disk rotation sensor and outputting a signal to a gas flow controller.