In Situ Reflectometry and Diffraction Investigation of the Multiscale Structure of p-Type Polysilicon Passivating Contacts for c-Si Solar Cells

Abstract

The integration of passivating contacts based on a highly doped polycrystalline silicon (poly-Si) layer on top of a thin silicon oxide (SiO x ) layer has been identified as the next step to further increase the conversion efficiency of current mainstream crystalline silicon (c-Si) solar cells. However, the interrelation between the final properties of poly-Si/SiO x contacts and their fabrication process has not yet been fully unraveled, which is mostly due to the challenge of characterizing thin-film stacks with features in the nanometric range. Here, we apply in situ X-ray reflectometry and diffraction to investigate the multiscale (1 Å–100 nm) structural evolution of poly-Si contacts during annealing up to 900 °C. This allows us to quantify the densification and thinning of the poly-Si layer during annealing as well as to monitor the disruption of the thin SiO x layer at high temperature >800 °C. Moreover, results obtained on a broader range of thermal profiles, including firing with dwell times of a few seconds, emphasize the impact of high thermal budgets on poly-Si contacts’ final properties and thus the importance of ensuring a good control of such high-temperature processes when fabricating c-Si solar cells integrating such passivating contacts. Overall, this study demonstrates the robustness of combining different X-ray elastic scattering techniques (here XRR and GIXRD), which present the unique advantage of being rapid, nondestructive, and applicable on a large sample area, to unravel the multiscale structural evolution of poly-Si contacts in situ during high-temperature processes.

QCM-D Investigations of Anisotropic Particle Deposition Kinetics: Evidences of the Hydrodynamic Slip Mechanisms

“…Because of its significance, nanoparticle and microparticle adsorption kinetics was extensively studied by a variety of experimental techniques such as optical microscopy, 22 atomic force microscopy (AFM), 23 − 25 scanning electron microscopy (SEM), 25 − 28 ellipsometry, 29 − 31 reflectometry, 32 , 33 surface plasmon resonance, 34 and electrokinetic methods. 35 , 36 However, these techniques cannot provide valid information about the adhesive contact strength between the particles and the substrate surfaces.…”

“…Because of its significance, nanoparticle and microparticle adsorption kinetics was extensively studied by a variety of experimental techniques such as optical microscopy, atomic force microscopy (AFM), − scanning electron microscopy (SEM), − ellipsometry, − reflectometry, , surface plasmon resonance, and electrokinetic methods. , However, these techniques cannot provide valid information about the adhesive contact strength between the particles and the substrate surfaces. In this respect, the quartz crystal microbalance (QCM) method exhibits pronounced advantages, enabling precise, in situ deposition/desorption kinetic measurements for the nano- and microparticles under flow conditions. − However, these investigations were almost exclusively focused on spherical particles.…”

Anisotropic Particle Deposition Kinetics from Quartz Crystal Microbalance Measurements: Beyond the Sphere Paradigm

“…Because of its significance, nano- and microparticle adsorption kinetics was extensively studied by numerous experimental techniques, such as atomic force microscopy (AFM), − scanning electron microscopy (SEM), − ellipsometry, − reflectometry, − surface plasmon resonance (SPR), , and electrokinetic methods. , …”

Revealing Surface and Interface Evolution of Molybdenum Nitride as Carrier-Selective Contacts for Crystalline Silicon Solar Cells

“…Here, the detailed structural and chemical information of MoN x films are investigated by the combination of different relevant characterization techniques, including X-ray reflectivity (XRR), grazing incidence wide- and small-angle X-ray scattering (GIWAXS and GISAXS), depth-profile X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), and high-resolution transmission electron microscopy (HRTEM). XRR, GIWAXS and GISAXS are powerful techniques that do not require ultra-high vacuum environments, to probe the thickness and density of each layer in thin-film stacks, crystallinity, and domain structures on both atomic and nanometer scales, in a rapid, averaged statistical and nondestructive way. − At first, surface layers with a density lower than that of the bulk phase are found on MoN x films through XRR analysis, and the compositions and work functions of both the surface and bulk phase are confirmed by XPS and UPS with argon ions (Ar + ) etching. Second, the interfacial evolution of Si/MoN x with aging time is verified by HRTEM characterizations.…”