New Method for Determination of Electrically Inactive Phosphorus in n-type Emitters

The precise knowledge of the amount and the location in depth of inactive phosphorus in an n-type emitter is still a challenge. As a new approach, we determine the total amount of phosphorus (P dose) in the emitter stepwise in dependence of etching depth with the characterization tool ICP-OES. A comparison of the data with the electrically active P concentration profile measured by ECV allows to determine in which depths electrically inactive phosphorus is present. For a highly doped emitter, we show that most of the inactive P dose is located next to the sample surface. Furthermore, we compare the determined P dose in dependence of depth with the P dose extracted from a SIMS profile. In a second experiment, we investigate the amount of inactive phosphorus in the whole emitter for various n-type emitters, depending on the POCl3-N2 gas flow as a significant diffusion parameter. It is shown that an increase of the POCl3-N2 gas flow results in a saturation effect of the active phosphorus, while the amount of inactive phosphorus is strongly increasing.