Analysis of contamination in PV Si feedstock with the CAMECA IMS 7f-Auto
For solar photovoltaic (PV) installations, different material systems are being employed while combining two apparently contradictory challenges: increasing solar cell yield and reducing manufacturing costs. Silicon based solar cell device manufacturing is based on PV Si feedstock of upgraded metallurgical-grade silicon with at least 6N purity. The quality control of the Si purification process is mandatory to ensure high yield manufacturing.
Excellent detection limits
The CAMECA IMS 7f-Auto provides quantitative measurement of the trace element impurity concentration in PV Si feedstock with detection limits from the ppm down to the ppb range, depending on the species to be analyzed. SIMS detection limits in silicon for 15ng of analyzed material are shown on the right hand side table. The performance of the CAMECA IMS 7f-Auto is particularly attractive for the analysis of light elements (H, C, O, N), main Si dopants (B, P, As), as well as metals (Al, Cr, Fe, Ni, Cu, …). Opposite to TOF-SIMS, the detection limits of the IMS 7f-Auto are improved when increasiong the profiling speed!
The lowest detection limits are achieved for light elements, thanks to optimized Ultra High Vacuum conditions obtained by combining titanium sublimation with ion or turbomolecular pumping in the analysis chamber.
The left hand side graph demonstrates excellent light element detection limits for oxygen in silicon.
High sample throughput
PV Si can be analyzed in its original physical form with fast and easy sample preparation on the IMS 7f-Auto. In addition, the ion microprobe's storage chamber is designed to store up to 6 sample holders, thus ensuring even higher throughput.
For further details, you may request the publication: SIMS analytical technique for PV applications. P. Peres, A. Merkulov, F. Desse, and M. Schuhmacher, Surface and Interface Analysis, n/a. doi: 10.1002/sia.3525. This paper presents analytical performances provided by SIMS tools for the development and manufacture of new solar cells. Results for two main applications are presented: trace element analysis in PV (photovoltaic) Si feedstock, indepth distribution of main components and trace elements in CIGS thin films.