Method of Removing Metallic, Inorganic and Organic Contaminants From Chip Passivation Layer Surfaces

Abstract

A method of removing and/or reducing undesirable contaminants removes residues including graphitic layers, fluorinate layers, calcium sulfate (CaSO 4 ) particles, tin oxides and organotin, from a chip passivation layer surface. The method uses a plasma process with an argon and oxygen mixture with optimized plasma parameters to remove both the graphitic and fluorinated layers and to reduce the level of the inorganic/tin oxides/organotin residue from an integrated circuit wafer while keeping the re-deposition of metallic compounds is negligible. This invention discloses the plasma processes that organics are not re-deposited from polymers to solder ball surfaces and tin oxide thickness does not increase on solder balls. The ratio of argon/oxygen is from about 50% to about 99% Ar and about 1% to about 50% O 2 by volume. Incoming wafers, after treatment, are then diced to form individual chips that are employed to produce flip chip plastic ball grid array packages.

1 .- 12 . (canceled) 
   
   
       13 . An apparatus for removing contaminants from a wafer arrangement, comprising:
 a dispenser configured to dispense Ar and O 2  to form a gas mixture in a ratio of about 80% Ar and about 20% O 2  to about 99% Ar and about 1% O 2  by volume;   a plasma generator configured to ionize the gas mixture to form a plasma state to clean residue from a wafer arrangement; and   a process chamber configured to contain the wafer arrangement within, to expose the wafer arrangement for a period of time in a range of about 1 minute to about 30 minutes sufficient to remove substantially all of a graphitic/fluorinated polymer layer and at least some of a tin residue, at a gas pressure in a range of about 10 mTorr to about 500 mTorr, at a plasma power in a range of about 100 W to about 1000 W, and to repeatedly expose the wafer arrangement to the plasma state that is generated with the mixture of Ar and O 2  until a sufficient amount of the tin residue is removed.   
   
   
       14 . The apparatus of  claim 13 , wherein the ratio is about 90% to about 95% Ar and about 5% to about 10% O 2 . 
   
   
       15 . The apparatus of  claim 13 , where the plasma generator operates with a power level in a range of about 500 W to about 700 W, a pressure of the gas mixture is in a range of about 200 mTorr to about 300 mTorr, and the plasma is maintained for a duration in a range of about 5 minutes to about 10 minutes. 
   
   
       16 .- 20 . (canceled) 
   
   
       21 . The apparatus of  claim 13 , where the wafer arrangement comprises a semiconductor wafer upon which are mounted solder balls. 
   
   
       22 . The apparatus of  claim 21 , where the solder balls comprise lead. 
   
   
       23 . The apparatus of  claim 21 , where the solder balls comprise mostly tin but no lead. 
   
   
       24 . An apparatus for removing contaminants from a passivation layer, comprising:
 a dispenser configured to dispense Ar and O 2  to form a gas mixture in a ratio of about 80% Ar and about 20% O 2  to about 99% Ar and about 1% O 2  by volume;   a plasma generator configured to ionize the gas mixture to form a plasma state to clean residue from a passivation layer; and   a process chamber configured to contain the passivation layer within, to expose the passivation layer for a period of time in a range of about 1 minute to about 30 minutes sufficient to remove substantially all of a graphitic/fluorinated polymer layer and at least some of a tin residue, at a gas pressure in a range of about 10 mTorr to about 500 mTorr, at a plasma power in a range of about 100 W to about 1000 W, and to repeatedly expose the passivation layer to the plasma state that is generated with the mixture of Ar and O 2  until a sufficient amount of the tin residue is removed.   
   
   
       25 . The apparatus of  claim 24 , wherein the ratio is about 90% to about 95% Ar and about 5% to about 10% O 2 . 
   
   
       26 . The apparatus of  claim 24 , where the plasma generator operates with a power level in a range of about 500 W to about 700 W, a pressure of the gas mixture is in a range of about 200 mTorr to about 300 mTorr, and the plasma is maintained for a duration in a range of about 5 minutes to about 10 minutes. 
   
   
       27 . The apparatus of  claim 24 , where solder balls are mounted upon the passivation layer. 
   
   
       28 . The apparatus of  claim 27 , where the solder balls comprise lead. 
   
   
       29 . The apparatus of  claim 27 , where the solder balls comprise mostly tin but no lead.