Influence of Polysilicon Thickness on Properties of Screen-Printed Silver Paste Metallized Silicon Oxide/Polysilicon Passivated Contacts

This work investigates how the thickness of the polysilicon layer and temperatures during contact sintering influence the properties of SiO_x/polysilicon passivated contacts. The n⁺ polysilicon layers deposited by low-pressure chemical vapor deposition (LPCVD) on top of a thin wet chemically grown interface oxide layer providing chemical and field-effect passivation on n-type monocrystalline silicon wafers are investigated. Three different polysilicon layer thicknesses of 50, 100, and 150 nm are considered in this work. A high level of passivation with implied V_oc values above 735 mV and J₀₁ below 5 fA cm⁻² is obtained for symmetric lifetime test samples. These samples are used to investigate the interaction of the silver paste with the polysilicon layer at different fast firing peak temperatures. Reduction in polysilicon layer thickness leads to an increase in contact resistivity as well as in J_0met. Excellent J_0met values of the order of J₀₁ with contact resistivity values below 2 mΩ cm² are obtained for samples with polysilicon layers of 100 and 150 nm thickness.