Excellent Silicon Surface Passivation Achieved by Industrial Inductively Coupled Plasma Deposited Hydrogenated Intrinsic Amorphous Silicon Suboxide

Abstract

We present an alternative method of depositing a high-quality passivation film for heterojunction silicon wafer solar cells, in this paper. The deposition of hydrogenated intrinsic amorphous silicon suboxide is accomplished by decomposing hydrogen, silane, and carbon dioxide in an industrial remote inductively coupled plasma platform. Through the investigation on CO 2 partial pressure and process temperature, excellent surface passivation quality and optical properties are achieved. It is found that the hydrogen content in the film is much higher than what is commonly reported in intrinsic amorphous silicon due to oxygen incorporation. The observed slow depletion of hydrogen with increasing temperature greatly enhances its process window as well. The effective lifetime of symmetrically passivated samples under the optimal condition exceeds 4.7 ms on planar -type Czochralski silicon wafers with a resistivity of 1 Ωcm, which is equivalent to an effective surface recombination velocity of less than 1.7 cms −1 and an implied open-circuit voltage ( oc ) of 741 mV. A comparison with several high quality passivation schemes for solar cells reveals that the developed inductively coupled plasma deposited films show excellent passivation quality. The excellent optical property and resistance to degradation make it an excellent substitute for industrial heterojunction silicon solar cell production.

Atomic Layer Deposition TiO2 Films and TiO2/SiNx Stacks Applied for Silicon Solar Cells

“…For the process, we employed TiCl 4 and H 2 O as the reactants and Ar (99.999%) as the purging gas. One cycle (one monolayer) of TiO 2 growth was 0.066 nm in thick and included eight steps, i.e., TiCl 4 reactant, pump-down, Ar purge, pump-down, H 2 O reactant, pump-down, Ar purge, and pump-down.…”

“…One cycle (one monolayer) of TiO 2 growth was 0.066 nm in thick and included eight steps, i.e., TiCl 4 reactant, pump-down, Ar purge, pump-down, H 2 O reactant, pump-down, Ar purge, and pump-down. Due to the self-limiting growth of ALD, we grew four different thicknesses of TiO 2 thin films by controlling the cycle numbers (125, 250, 530, and 1000 cycles).…”

“…As the thickness of c-Si solar cells decreases due to lowering the manufacturing cost of solar cells, Si surface passivation becomes a more and more important issue for high efficiency solar cells [1]. Therefore, a variety of dielectric materials have been proposed for the surface passivation of solar cells, such as silicon dioxide (SiO 2 ), amorphous silicon nitride (a-SiN x ), amorphous silicon (a-Si), and aluminum oxide (Al 2 O 3 ) [2][3][4]. Beside the use of dielectric thin films, Si surface passivation also depends on the deposition techniques, treatments of surface cleaning, and types of Si substrates.…”

Investigation of Wide Process Temperature Window for Amorphous Silicon Suboxide Thin-Film Passivation Deposited by Inductively Coupled PECVD

“…The detailed description on the ICP platform is shown elsewhere [15]. Films of interest [a-Si:H(i) and a-SiO x :H(i)] were formed on both sides of (1 0 0) Czochralski Si wafers with a resistivity of 1-Ω · cm, while varying the process temperature.…”

“…In our previous work [15], and the contributions from Mueller et al [16]- [19], excellent surface passivation quality was shown by hydrogenated amorphous silicon suboxide [a-SiO x :H(i)] using different PECVD setups. It was demonstrated by Rattanapan et al [20] and others [21], [22] that a-SiO x :H(i) is able to suppress the epitaxial growth.…”