On copper diffusion in silicon measured by glow discharge mass spectrometry

• Published in: Analytical and bioanalytical chemistry Vol. 406; no. 29; pp. 7455 - 7462
• Main Authors: Modanese, Chiara, Gaspar, Guilherme, Arnberg, Lars, Di Sabatino, Marisa
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2014; Springer; Springer Nature B.V
• Subjects: Analysis; Analytical Chemistry; Annealing; Biochemistry; Characterization and Evaluation of Materials; Chemical properties; Chemistry; Chemistry and Materials Science; Contamination; Copper; Copper compounds; Diffusion; Diffusion rate; Direct current; Emerging Concepts and Strategies in Analytical Glow Discharges; Food Science; Glow discharges; Laboratory Medicine; Mass spectrometry; Mass spectroscopy; Mathematical analysis; Monitoring/Environmental Analysis; Photovoltaics; Research Paper; Room temperature; Scientific imaging; Silicon; Solid solubility; Solidification; Spectroscopy; Fast diffusers/fast diffusing species; Trace elements; Surface analysis; Mass spectrometry; Glow discharge
• DOI: 10.1007/s00216-014-8105-0
• ISSN: 1618-2642

Copper contamination occurs frequently in silicon for photovoltaic applications due to its very fast diffusion coupled with a low solid solubility, especially at room temperature. The combination of these properties exerts a challenge on the direct analysis of Cu bulk concentration in Si by sputtering techniques like glow discharge mass spectrometry (GDMS). This work aims at addressing the challenges in quantitative analysis of fast diffusing elements in Si matrix by GDMS. N-type, monocrystalline (Czochralski) silicon samples were intentionally contaminated with Cu after solidification and consequently annealed at 900 °C to ensure a homogeneous distribution of Cu in the bulk. The samples were quenched after annealing to control the extent of the diffusion to the surface prior to the GDMS analyses, which were carried out at different time intervals from within few minutes after cooling onward. The Cu profiles were measured by high-resolution GDMS operating in a continuous direct current mode, where the integration step length was set to ∼0.5 μm over a total sputtered depth of 8–30 μm. The temperature of the samples during the GDMS analyses was also measured in order to evaluate the diffusion. The Cu contamination of n-type Si samples was observed to be highly material dependent. The practical impact of Cu out-diffusion on the calculation of the relative sensitivity factor (RSF) of Cu in Si is discussed.