Investigation of the implanted phosphorus in a boron doped SiGe epitaxial layer

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Abstract

Phosphorus diffusion into strained SiGe layers was studied by different methods. Doping profiles and carrier concentration profiles N(x), depth of pn junction, Ge content in SiGe and thickness of epitaxial layer were measured and simulated. Several experimental methods such as secondary ion mass spectroscopy, spreading resistance method, Raman spectroscopy—and process simulator ISE TCAD have been used. The results obtained by different methods and at different places of work have been compared and analysed.

Introduction

The electrical properties of SiGe materials grown on a Si substrate depend on the germanium mole fraction. The resulting layer and the quality of interfaces can be characterized by the strain and lattice mismatch. The band gap of SiGe alloy varies from 1.1 to 0.7 eV, corresponding to the wavelength range of about 1.1–1.5 μm in dependence on the Ge mole fraction. This is a very useful range for discrete optoelectronic devices and for integrated optoelectronics on silicon. The research and development of semiconductor devices with SiGe layers requires reliable determination of their properties and of the doping profiles in device layer structures. For these purposes, thus for optimization of the technological process, different simulation programs and experimental methods are used [1], [2], [3], [4], [5], [6].

Section snippets

Experiment

The measurements and simulations were conducted on phosphorus implanted epitaxial layers (2–4 μm) with a SiGe layer doped with boron (concentration 1×1016 cm–3). Two epitaxial Si0.6Ge0.4 layers were grown on p-type Si (100), with substrate resistivity 0.001 Ωcm. The samples were phosphorus implanted with 30 keV energy and a dose of 5×1015 cm–2. The first sample (A) was activated in vapour ambient at a temperature of 1000 °C for 20 min. The second sample (B) was activated in the forming gas (FG) at 700 

Results and discussion

The obtained simulated and measured results—by SIMS, SR and Raman spectroscopy in different laboratories are shown in Table 1.

At ILC we analysed samples A and B by TOF SIMS. For both samples we measured secondary ion spectra and, subsequently, depth profiles. The negative secondary ion mass spectra were typical for the Si and Ge. A high intensity O peak and related OH peak (17.02 amu) dominate in the negative secondary ion mass spectra. The surface is covered by a SiOx layer, which can be

Conclusion

In this paper, we presented methods that can be used to determine the doping profile, depth of pn junction, and Ge content in SiGe structures. The basic aims were to compare the results from various laboratories with data simulated by DIOS software.

SIMS analysis and depth profiling can be used for determining the doping profile, the pn junction depth and the Ge content in SiGe. The results show some differences caused by different apparatuses and methods used. The depth profile of sample A

Acknowledgements

This work was supported by grants of the Slovak Grant Agency Vega No. 1/0154/03, 1/0152/03, APVT 20-013902 and grants No. GAER 102/03/0316. The authors would like to thank Prof. H. Frank for discussions and careful reading of the article.

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