Pre-Clean for Contacts

Abstract

The present disclosure describes a method that includes forming a dielectric layer over a contact region on a substrate; etching the dielectric layer to form a contact opening to expose the contact region; and pre-cleaning the exposed contact region to remove a residual material formed by the etching. During the pre-cleaning, the contact region is exposed to an inductively coupled radio frequency (RF) plasma. Also, during the pre-cleaning, a direct current power supply unit (DC PSU) provides a bias voltage to the substrate and a magnetic field is applied to the inductively coupled RF plasma to collimate ions.

What is claimed is: 
     
         1 . A system, comprising:
 a pedestal configured to support a substrate;   a direct current power supply unit electrically coupled to the substrate through the pedestal and configured to apply a bias voltage to the substrate;   an inductively coupled radio frequency (RF) power supply configured to generate a plasma; and   a magnet configured to generate a magnetic field that collimates ions in the plasma.   
     
     
         2 . The system of  claim 1 , wherein a diameter of the pedestal ranges from about 300 mm to about 330 mm. 
     
     
         3 . The system of  claim 1 , wherein the bias voltage ranges from about −100 Volts to about +100 Volts. 
     
     
         4 . The system of  claim 1 , wherein the magnet is configured to generate the magnetic field to be perpendicular to a top surface of the pedestal. 
     
     
         5 . The system of  claim 1 , wherein the magnet comprises cylindrical electron magnets or electron magnet coils electrically connected to an RF power supply different from the RF power supply used to generate the plasma. 
     
     
         6 . The system of  claim 1 , wherein the magnet comprises two magnet units positioned on opposite sidewall surfaces of a reactor housing the pedestal. 
     
     
         7 . The system of  claim 6 , wherein the two magnet units are configured to have reversed polarities. 
     
     
         8 . The system of  claim 6 , wherein the two magnet units are electron magnets comprising two sets of coils. 
     
     
         9 . The system of  claim 6 , wherein the two magnet units are cylindrical magnets. 
     
     
         10 . A system, comprising:
 a reactor configured to pre-clean contact openings formed on a wafer, wherein the reactor comprises:
 a reactor housing; 
 a pedestal in the reactor housing configured to support the wafer; and 
 a pair of magnets on opposite sidewall surfaces of the reactor housing and positioned above the pedestal; 
   an inductively coupled radio frequency (RF) power supply configured to generate a plasma in the reactor housing above the wafer and the pair of magnets; and   a direct current power supply unit (DC PSU) configured to apply a bias voltage to the wafer in the reactor housing through the pedestal.   
     
     
         11 . The system of  claim 10 , wherein the pair of magnets are configured to have opposite polarities. 
     
     
         12 . The system of  claim 10 , wherein the pair of magnets are configured to collimate ions from the plasma across a top surface of the wafer. 
     
     
         13 . The system of  claim 10 , wherein each magnet of the pair of magnets comprises an electromagnet electrically coupled to an RF power supply different from the RF power supply used to generate the plasma. 
     
     
         14 . The system of  claim 10 , wherein the pedestal has a larger diameter than the wafer. 
     
     
         15 . The system of  claim 10 , wherein the pedestal has a height between about 12 mm and about 12.5 mm. 
     
     
         16 . The system of  claim 10 , wherein the DC PSU is coupled to the pedestal through an RF generator. 
     
     
         17 . A system, comprising:
 a reactor, comprising:
 a pedestal configured to support a wafer; 
 a first electromagnet on a first sidewall surface of the reactor; and 
 a second electromagnet on a second sidewall surface of the reactor, wherein the first and second electromagnets have opposite polarities; 
   an inductively coupled radio frequency (RF) power supply configured to generate a plasma in the reactor; and   a direct current power supply unit (DC PSU) configured to apply a bias voltage to the wafer through the pedestal.   
     
     
         18 . The system of  claim 17 , wherein the first sidewall surface is opposite to the second sidewall surface. 
     
     
         19 . The system of  claim 17 , wherein the first and second electromagnets are positioned above the pedestal. 
     
     
         20 . The system of  claim 17 , further comprising an RF generator electrically coupled to the pedestal and the DC PSU.