Electrical and Structural Analysis of Crystal Defects After High-Temperature Rapid Thermal Annealing of Highly Boron Ion-Implanted Emitters

Abstract

Ion implantation of boron is a promising technique for the preparation of p-type emitters in n-type cells. We use rapid thermal annealing with temperatures up to 1250°C and annealing durations between 6 s and 20 min to anneal the implant-induced crystal defects. Experimental J 0 e is compared with simulated and measured defect densities. Perfect dislocation loops are identified to be the dominating defect species after rapid thermal annealing (RTA) above 1000°C. Even for emitters with J 0 e values around 40 fA/cm 2 , defects are present within the valleys of the textured surfaces after annealing. On textured Al 2 O 3 -passivated boron emitters, we measure J 0 e of 38 fA/cm 2 for a sheet resistance around 80 Ω/ after very short annealing processes (1 min at 1200°C).

Ion implantation of boric molecules for silicon solar cells

“…Subsequent defect annealing is performed in a conventional quartz furnace under inert ambient (dry N 2 ) at 1050°C for 80 min (textured samples with BF x and for B reference, plateau time), at 1050°C for 20 min (section 3.2) or at 800-1050°C for 30 min (Section 3.3). After ion implantation of elemental boron, annealing at 1050°C for several 10 min leads to excellent emitter saturation current densities which are not affected by implant-induced crystal defects anymore [17,18]. The lower temperatures are used to evaluate the potential of reducing the thermal budget after BF x , especially for BF 2 implantation.…”

“…For elemental boron, where due to technological reasons doses below the amorphization threshold are commonly used, the dominant defect species is determined by the annealing temperature and the used ion dose [22]. At temperatures of 1050°C as used here, commonly dislocation loops are observed [17].…”

Bifacial, fully screen-printed n-PERT solar cells with BF2 and B implanted emitters

“…Ion implantation requires a high temperature annealing step to cure implant-induced crystal defects. In the case of a nonamorphizing implantation of elemental boron, temperatures of at least 1050°C [9] are required to dissolve dislocation loops and to achieve low emitter saturation current densities. For photovoltaic applications, non-mass-analyzed ion implanters likely offer benefits regarding costs and throughput.…”

Boron Implanted Junction with In Situ Oxide Passivation and Application to p‐PERT Bifacial Silicon Solar Cell

“…Further, according to Figure , the relatively large gap of i‐V oc (10–50 mV) between the calculated τ b limited i‐V oc after B‐implant and PIA and the calculated J 0e limited i‐V oc also indicates that, such low τ b ( L D, bulk ) limits the experimental i‐V oc after B implantation and PIA . The insufficient anneal of implant‐induced defects is likely to increase the bulk SRH recombination . This can be inferred from the onset of the Kane and Swanson plot for the J 0e ‐fit in Figure , which shows a non‐linear injection‐level dependence with the inverse Auger‐corrected effective lifetime in the MCD‐range 7.5 × 10 15 –1.5 × 10 16 cm −3 .…”

“…However, with the recent development on more cost‐efficient implanter by several suppliers (Varian, Intevac, Kingston), a second fast‐developed period for ion‐implanted PV occurred in 2010s, generating a promising progress for the phosphorus (P)‐doped implantation technique and industrial full Al BSF Si solar cells . Regarding the B‐implanted junction, most of the previous research is carried out using lab‐scale implanters combined with complex lab‐scale cell processes but there are also promising studies considering the industry aspects as well …”