The influence of Bi2O3 glass powder in silver paste on the fabrication of ohmic contacts and its potential effectiveness in solar cells and integrated circuits on p-type silicon substrates

TL;DR

This study explores how Bi2O3 glass powder affects the fabrication and microstructure of silver-based ohmic contacts on p-type silicon, aiming to improve their application in solar cells and integrated circuits.

Contribution

It introduces a novel composite paste with Bi2O3 glass for screen printing silver contacts and analyzes its microstructure and electrical properties after firing.

Findings

Bi2O3 glass controls silver melting and crystallization.

Higher firing temperatures lead to excessive Ag crystallite growth.

Bi2O3 glass enhances the microstructural stability of silver contacts.

Abstract

The present work critically investigates the influence of low melting glasses on the fabrication of metal contacts, with the goal of advancing applications of bismuth based oxide glass and screen printed silver contacts for use in integrated circuits (ICs), solar cells, and sensors. In this study, novel electrode contacts were fabricated by screen printing composite pastes composed of mainly silver powder, Bi2O3 glass powder, and acyclic binder, and then firing the pastes in a belt furnace. The microstructures of the composite films after firing at 830 to 890 {\deg}C were observed under different corrosion conditions, and the resulting layers were analyzed with X ray diffraction (XRD) and the transfer length method (TLM). A series of investigations to determine the influence of Bi2O3 glass in silver paste involved various tests, including differential thermal analysis (DTA), scanning electron microscopy (SEM), electron probe X ray microanalysis (EPMA), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM), to determine the effects of Bi2O3 mixed with silver and the efficacy of the resulting metal contacts in IC fabrications. It was observed that the additive, Bi2O3 glass, controlled the melting of the silver into the glass, influencing the precipitation of Ag crystallites. In addition, an increase in the firing temperature caused excessive growth of Ag crystallites and current leakage, and the size and the relationship of the Ag crystallites in the Bi2O3 glass were confirmed.