Method of calculating a pressure compensation recipe for a semiconductor wafer implanter

1. A process comprising:

while implanting a first wafer, determining a rate at which ions are implanted;

while implanting the first wafer, determining a pressure;

using pressure changes and a pressure compensation factor to estimate a rate at which neutral atoms are implanted;

selecting a modified pressure compensation factor that would have achieved a uniform rate of implanted ions plus implanted neutral atoms across a surface of the first wafer; and

using the modified pressure compensation factor to implant a second wafer.

2. A process according to claim 1 , wherein ions are implanted in the first wafer using a pressure compensation factor different from the modified pressure compensation factor.

3. A process according to claim 2 , further comprising moving the first wafer radially with respect to an ion beam while implanting ions into the first wafer so as to achieve a uniform total dose based on the rate at which ions are implanted and the estimated rate at which neutral atoms are implanted.

4. A process according to claim 1 , wherein the first and second wafers are implanted with ions in an Axcelis GSD™ platform implanter.

5. A process according to claim 1 , further comprising testing the second wafer by forming a sheet resistance contour map.

6. A process according to claim 5 , further comprising using the modified pressure compensation factor to implant wafers subsequent to the second wafer if the sheet resistant contour map shows uniform resistance across the wafer.

7. A process according to claim 1 , wherein the following equation is used to estimate the rate at which neutral ions are implanted:

I MEASURED =I DOSE ·e −kp

where I MEASURED is the rate at which ions are implanted, I DOSE is the sum of the rate at which ions are implanted and the estimated rate at which neutral atoms are implanted, K is a pressure compensation factor and P is the pressure.

8. A process according to claim 7 , further comprising:

selecting a parameter P-COMP, which relates to the pressure compensation factor K according to the following equation:

K

=

ln

⁡

(

1

+

P

-

COMP

100

)

⁢

(

10000

)

.

9. A process comprising:

using pressure changes and a pressure compensation factor to estimate a rate at which neutral atoms are implanted;

while implanting a first wafer using a first pressure compensation factor, determining the rate at which ions are implanted;

moving the first wafer radially with respect to an ion beam while implanting ions into the first wafer so as to achieve a uniform total dose based on the rate at which ions are implanted and the estimated rate at which neutral atoms are implanted;

while implanting the first wafer, determining a pressure;

selecting a second pressure compensation factor, that would have achieved a uniform rate of implanted ions plus implanted neutral atoms across a surface of the first wafer, the second pressure compensation factor being different from the first pressure compensation factor;

using the second pressure compensation factor to implant a second wafer;

testing the second wafer by forming a sheet resistance contour map; and

using the second pressure compensation factor to implant wafers subsequent to the second wafer if the sheet resistant contour map shows uniform resistance across the wafer.