Bulk and surface passivation of silicon solar cells accomplished by silicon nitride deposited on industrial scale by microwave PECVD

Abstract

Bulk and surface passivation by silicon nitride has become an indispensable element in industrial production of multicrystalline silicon (mc-Si) solar cells. Microwave PECVD is a very effective method for high-throughput deposition of silicon nitride layers with the required properties for bulk and surface passivation. In this paper an analysis is presented of the relation between deposition parameters of microwave PECVD and material properties of silicon nitride. By tuning the process conditions (substrate temperature, gas flows, working pressure) we have been able to fabricate silicon nitride layers which fulfill almost ideally the four major requirements for mcSi solar cells: (1) good anti-reflection coating (refractive index tunable between 2Á0 and 2Á3); (2) good surface passivation on p-type FZ wafers (S eff < 30 cm/s); (3) good bulk passivation (improvement of IQE at 1000 nm by 30% after short thermal anneal); (4) long-term stability (no observable degradation after several years of exposure to sunlight). By implementing this silicon nitride deposition in an inline production process of mc-Si solar cells we have been able to produce cells with an efficiency of 16Á5%.Finally, we established that the continuous deposition process could be maintained for at least 20 h without interruption for maintenance. On this timescale we did not observe any significant changes in layer properties or cell properties. This shows the robustness of microwave PECVD for industrial production.

Relation between light trapping and surface topography of plasma textured crystalline silicon wafers

“…Note that the ETP technique has been used for etching of silicon wafers by Beulens et al, who achieved etch rates larger than 15 μm/min in a setup for single wafer treatment [21]. The deposition rate of the LMP system developed by Roth&Rau for deposition of a-SiN x :H anti-reflection coating is 1-2 nm s À1 [22]. For the study described in this paper, the ETP technique and the LMP technique have both been used for texturing of silicon wafers.…”

Hydrogénation effect on low temperature internal gettering in multicrystalline silicon

“…Silicon nitride dielectric layers deposited by plasma-enhanced chemical vapour deposition (PECVD) are commonly used to passivate wafer surfaces in silicon solar cell production [25,26]. These films have a high hydrogen concentration [27,28].…”

X-ray photoelectron spectroscopic study of silicon surface passivation in alcoholic iodine and bromine solutions

“…Chemical passivation and field effect passivation [3][4][5][6][7] are commonly used processes for surface passivation. In the former, the interface defect density is reduced by passivation of dangling bonds by attachment of atomic hydrogen present in thin dielectric layers of a-Si:H, Si x N y :H, etc., or by chemisorption of Br or I atoms with silicon surface.…”