Poly-Si/SiOx/c-Si passivating contact with 738 mV implied open circuit voltage fabricated by hot-wire chemical vapor deposition

Abstract

Hot-wire chemical vapor deposition (HWCVD) was utilized to develop a fast and high quality a-Si:H thin film fabrication method for poly-Si/SiOx carrier selective passivating contacts targeting at n-type passivated emitter rear totally diffused crystalline silicon solar cells. The microstructure and hydrogen content of the a-Si:H thin films were analyzed by Fourier-transform infrared spectroscopy in order to understand the influence of film properties on passivation and conductivity. Dense layers were found to be beneficial for good passivation. On the other hand, blistering appeared as a-Si:H layers became more and more dense. However, by adjusting the SiH4 flow rate and the substrate heater temperature, blistering of a-Si:H could be avoided. A suitable process window was found and firing-stable implied open circuit voltage (iVoc) of up to 738 mV was achieved. In addition to high iVoc, a low contact resistivity of 0.034 Ω cm2 was also achieved. The deposition rate of the a-Si:H layers was 7 Å/s by using HWCVD, which is one order of magnitude higher than the deposition rate reported using other deposition methods.

High‐quality amorphous silicon thin films for tunnel oxide passivating contacts deposited at over 150 nm/min

“…We have reported in an earlier work at lower deposition rates that high microstructure factor silicon layers result in low passivation quality for passivating contact, while silicon layers blister when the microstructure factor is too low 12 . Blistering also occurs in the present work when R < 0.31, which leads to deteriorated interface passivation as shown in Figure 6A.…”

“…6 To fabricate the poly-Si/SiO x passivating contact, silicon layers are deposited on top of ultrathin SiO x layers followed by a crystallization step to convert the silicon layers into poly-Si layers. For the deposition of silicon layers, various deposition techniques are proposed such as low-pressure chemical vapor deposition (LPCVD), 7,8 plasma-enhanced chemical vapor deposition (PECVD), 9,10 atmospheric pressure chemical vapor deposition (APCVD) 11 , hot-wire chemical vapor deposition (HWCVD), 12,13 and sputtering. 14 Excellent contact properties have been reported by these deposition methods.…”

Occurrence of Sharp Hydrogen Effusion Peaks of Hydrogenated Amorphous Silicon Film and Its Connection to Void Structures

“…With regard to Li et al, blistering and layer delamination were related to the FTIR determined microstructure factor R mentioned earlier . According to these authors, blistering predominantly occurs for low R values, hence dense amorphous networks are formed.…”

Morphology, microstructure, and doping behaviour: A comparison between different deposition methods for poly‐Si/SiOx passivating contacts

“…Common CVD processes used are plasma enhanced CVD (PECVD), 4,[13][14][15][16][17][18] low pressure CVD (LPCVD), 10,13,[19][20][21][22] atmospheric pressure CVD (APCVD), 23 and hot wire CVD (HWCVD) depositions. 24 Meanwhile, in the PVD approach, sputtering [25][26][27][28][29] or electron beam evaporation 30 are the techniques used so far to form poly-Si films. Each resultant poly-Si film has its unique characteristics.…”