Ion-implantation machine, control method thereof, and process for manufacturing integrated devices

Abstract

An ion-implantation machine has an implantation chamber with a vent inlet; a vacuum pump is connected to the implantation chamber through a vacuum valve. A pipe connects the vent inlet of the implantation chamber to a source of a fluid containing oxygen. The fluid containing oxygen is preferably environmental air. A flow-rate control valve is arranged on the pipe and is activated only after closing the vacuum valve.

1 . A method for controlling an ion-implantation machine, comprising: 
 implanting heavy ionic species in an implantation chamber kept in vacuum conditions; and    decontaminating said implantation chamber by supplying air into the implantation chamber through a pipe having an inlet exposed to environmental air, an outlet connected to the implantation chamber, and a controlled vent valve that is opened to expose the implantation chamber to the environmental air.    
   
   
       2 . The control method according to  claim 1  wherein during said step of implanting the implantation chamber is connected to a cryogenic pump, and wherein before said step of decontaminating, said cryogenic pump is disconnected from said implantation chamber.  
   
   
       3 . The control method according to  claim 1  wherein said step of decontaminating comprises supplying the environmental air to said implantation chamber only after the implanting step has been completed.  
   
   
       4 . The control method according to  claim 1  wherein said supplying air into the implantation chamber includes supplying the environmental air into implantation chamber through a flow-rate metering valve coupled to the vent valve.  
   
   
       5 . The control method according to  claim 1  wherein said heavy ionic species are first ionic species and said step of decontaminating is performed during crossover between implanting said heavy ionic species and implanting second ionic species lighter than said heavy ionic species.  
   
   
       6 . The control method according to  claim 5  wherein said first ionic species are chosen from among arsenic, antimony and indium.  
   
   
       7 . The control method according to  claim 1 , wherein the implanting step includes controlling a switching module having a first output coupled to a first valve that controls the vacuum conditions of the implantation chamber, wherein the decontaminating step includes controlling a second output of the switching module, the second output controlling a second valve that controls the supplying of the fluid containing oxygen into the implantation chamber.  
   
   
       8 . The control method according to  claim 1 , wherein supplying air into the implantation chamber includes supplying the environmental air into implantation chamber through a particulate filter coupled to the vent valve.  
   
   
       9 . A process for manufacturing electronic devices, comprising: 
 positioning a semiconductor wafer in an implantation chamber kept in vacuum conditions;    implanting heavy ionic species in the wafer while the wafer is in the implantation chamber kept in vacuum conditions, wherein the implanting step includes controlling a switching module having a first output coupled to a first valve that controls the vacuum conditions of the implantation chamber; and    decontaminating said implantation chamber by supplying a fluid containing oxygen into the implantation chamber, wherein the decontaminating step includes controlling a second output of the switching module, the second output controlling a second valve that controls the supplying of the fluid containing oxygen into the implantation chamber.    
   
   
       10 . The process for manufacturing according to  claim 9  wherein said decontaminating comprises supplying environmental air to said implantation chamber.  
   
   
       11 . The process for manufacturing according to  claim 9  wherein said decontaminating is performed during crossover between said heavy ionic species and ionic species lighter than said heavy ionic species.  
   
   
       12 . The process for manufacturing according to  claim 9  wherein said electronic devices are flash memories, and said decontaminating is followed by implanting threshold modification ions and growing a tunnel oxide layer.  
   
   
       13 . The process for manufacturing according to  claim 9  wherein said heavy ionic species comprise arsenic, and said implanting threshold modification ions comprises implanting boron ions.  
   
   
       14 . The process for manufacturing according to  claim 9 , wherein the decontaminating step includes supplying the fluid containing oxygen into the implantation chamber through a particulate filter.  
   
   
       15 . A process for manufacturing electronic devices, comprising: 
 implanting heavy ionic species in a wafer positioned in an implantation chamber kept in vacuum conditions; and    decontaminating the implantation chamber by supplying a fluid containing oxygen into the implantation chamber through a flow-rate metering valve and a particulate filter.    
   
   
       16 . The process of  claim 15 , further comprising: 
 controlling a vacuum pump connected to the implantation chamber to vacuum the implantation chamber while the heavy ionic species are implanted in the wafer and disconnect the vacuum pump from the implantation chamber when the implantation chamber is decontaminated.    
   
   
       17 . The process of  claim 15 , wherein the decontaminating step includes supplying environmental air to the implantation chamber.  
   
   
       18 . The process of  claim 17 , wherein supplying the environmental air includes supplying the environmental air through a vent valve coupled to the flow-rate metering valve and the particulate filter.  
   
   
       19 . The process of  claim 15 , wherein the heavy ionic species are first ionic species and the decontaminating step is performed during crossover between implanting the heavy ionic species and implanting second ionic species lighter than the heavy ionic species.