Realization of ultra shallow junctions by PIII: application to solar cells Frank Torregrosa a, * , Cyrille Laviron b , Hasnaa Faik a , Damien Barakel c , Fre ´de ´ric Milesi a , Se ´bastien Beccaccia c a Ion Beam Services, ZI Peynier-Rousset, rue G. Imbert prolonge ´e, F 13790 Peynier, France b LETI, 17 rue des martyrs, F-38054 Grenoble cedex 9, France c TESCEN, Faculte ´ des Sciences et Techniques de St-Je ´ro ˆme F-13997 Marseille cedex 20, France Available online 17 June 2004 Abstract The efficiency of plasma immersion ion implantation (PIII) is no more to prove for the realization of ultra shallow junctions (USJ) in semiconductor applications. Interest for the fabrication of submicrometer CMOS devices is well known, but the ability of PIII to implant quickly high doses at very low energy and low price makes it a good candidate for the fabrication of solar cells. In this paper, we present results obtained by a semi-industrial prototype of PIII (PULSIONR) designed by the French company IBS. First, metallic contamination, homogeneity, reproducibility, and SIMS profiles of ultra shallow junctions made by PULSIONR BF 3 implantation on 200-mm silicon wafers are presented. Results are compared with BF 2 + implantations made on an AXCELIS NV-8200P beam line implanter and demonstrate the compatibility with semiconductor requirements. Then, results on solar cells with BF 3 shallow junctions made by PIII are presented. The simulated and measured internal quality factor (IQE) with an improved behavior in blue wavelengths demonstrates the interest of PIII for this applications field. D 2004 Elsevier B.V. All rights reserved. Keywords: Plasma immersion ion implantation; Ultra shallow junction 1. Introduction Due to the continuous shrink of lateral sizes of compo- nents and the increase of wafers sizes, the semiconductor world has a need for doping junctions as low as 10 nm on 300-mm substrates within the next 5 years. As these junction depths request implantation energies lower than 1 keV, plasma-based technologies (PIII or PLAD) are forecasted to replace widely used beam line implanters for ultra shallow junction fabrications [1–10]. Indeed, even if the risk of metallic contamination is higher (due to the absence of mass selection) and even if the dose is difficult to measure (due to secondary electron emission), engineers have succeed to reach the same level of metallic contamination as that on beam line implanters [11,12] and have developed sophisti- cated systems to measure the implanted dose [13,14]. Sev- eral articles have been published demonstrating the feasibility of 0.17- to 0.13-Am CMOS devices using PIII (or PLAD) to implant source and drain [12,15 – 18]. However, advanced microelectronic application is not the only one needing shallow junctions with a very low level of metallic contamination. The fabrication of solar cells also requires shallow emitter with high dose to allow low energetic photons to go through. The level of metallic contamination must be as low as possible (may be more than in advanced semiconductor) in all the bulk to insure a maximized carrier diffusion length and avoid electron-hole recombination between emitter (front side) and collector (back side). Several publications refer to the use of beam line implantation to make ‘‘optimized’’ solar cells [19]. However, due to prohibitive price, classical PoCl 3 diffusion is still widely used in production (added to its benefit gettering effect). Thanks to its simple and robust structure and its ability to implant high dose on large substrate in a short time, PIII implantation technique could be economi- cally acceptable and find its place in this increasing market [20]. Only a few articles are related to the use of this doping technique to solar cells. They show that obtained cells behave the same way as classically implanted solar cells [20,21]. Here we prove that using PIII allows to make 0257-8972/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2004.04.046 * Corresponding author. Tel.: +33-4-42-53-89-53; fax: +33-4-42-53- 89-59. E-mail address: frank.torregrosa@ion-beam-services.fr (F. Torregrosa). www.elsevier.com/locate/surfcoat Surface & Coatings Technology 186 (2004) 93– 98