Contactless mapping of lifetime and diffusion length scan map of minority carriers in silicon wafers

Laboratoire de Photoélectricité LPDSO (EA 2192), Université de Marseille, 13397 Marseille Cedex 20, France

Corresponding author: santo.martinuzzi@DSO.U-3mrs.fr

Received: 17 September 1999
Revised: 3 February 2000
Accepted: 17 March 2000
Published online: 15 May 2000

Abstract

The lifetime of minority carriers in crystalline silicon wafers is determined by means of the contactless microwave phase-shift technique, when the surfaces of the samples are passivated using an iodine aqueous solution of polyvidone. The stability of the passivation is sufficient in order to obtain a lifetime scan map with spatial resolution of 50 µm, using a thin coaxial cable which directs 9.4 GHz microwaves onto the investigated samples and a fiber coupled laser diode which generates carriers in excess. In gold contaminated single crystals an acceptable correlation is found between the lifetime scan maps and the local concentrations of gold determined by deep level transient spectroscopy applied to an array of aluminium silicon diodes. For multicrystalline silicon wafers containing large densities of different extended crystallographic defects, a good correlation is obtained between the lifetime maps and the diffusion length maps obtained by the light beam induced current technique. Both the maps display the same features of extended crystallographic defects and are in agreement with optical micrographs of the scanned samples after they have been chemically etched.