Methods for stable and repeatable ion implantation
View Patent ↗A method for plasma ion implantation of a substrate includes providing a plasma ion implantation system having a process chamber, a source for producing a plasma in the process chamber, a platen for holding a substrate in the process chamber, an anode spaced from the platen, and a pulse source for generating implant pulses for accelerating ions from the plasma into the substrate. In one aspect, a parameter of an implant process is varied to at least partially compensate for undesired effects of interaction between ions being implanted and the substrate. For example, dose rate, ion energy, or both may be varied during the implant process. In another aspect, a pretreatment step includes accelerating ions from the plasma to the anode to cause emission of secondary electrons from the anode, and accelerating the secondary electrons from the anode to a substrate for pretreatment of the substrate.
1. A method for plasma ion implantation of a substrate, comprising:
providing a plasma ion implantation system including a process chamber, a source for generating a plasma in the process chamber, a platen for holding a substrate in the process chamber, an anode spaced from the platen, and a pulse source for generating implant pulses for accelerating ions from the plasma into the substrate;
accelerating ions from the plasma to the anode to cause emission of secondary electrons from the anode;
accelerating the secondary electrons from the anode to the substrate; and
plasma ion implantation of the substrate according to an implant process.
2. A method as defined in claim 1 , wherein the secondary electrons have energies in a range of about 500 eV to 20 keV.
3. A method as defined in claim 1 , wherein the anode is coated with an electron emissive material.
4. A method as defined in claim 1 , wherein the anode is biased negatively with respect to the plasma.
5. A method as defined in claim 4 , wherein the platen is grounded.
6. A method as defined in claim 4 , wherein the platen is positively biased.
7. A method as defined in claim 4 , wherein a hollow cathode surrounds a plasma discharge region between the anode and the plasma and wherein the hollow cathode is grounded.