Search International and National Patent Collections

1. (WO2018046855) METHOD FOR SORTING SILICON WAFERS ACCORDING TO THEIR BULK LIFETIME

Pub. No.:    WO/2018/046855    International Application No.:    PCT/FR2017/052375
Publication Date: Fri Mar 16 00:59:59 CET 2018 International Filing Date: Fri Sep 08 01:59:59 CEST 2017
IPC: H01L 31/18
C30B 29/06
Applicants: COMMISSARIAT A L'ENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
Inventors: LETTY, Elénore
FAVRE, Wilfried
VEIRMAN, Jordi
Title: METHOD FOR SORTING SILICON WAFERS ACCORDING TO THEIR BULK LIFETIME
Abstract:
The invention relates to a Czochralski-type method for sorting wafers obtained by cutting a single-crystal silicon ingot, the method being implemented when the wafers are in an as-cut state or in a shaped-surface state. The method comprises the following steps: a) measuring the majority free charge carrier concentration in at least one area of each wafer; b) calculating the thermal donor concentration in said area of each wafer, on the basis of the majority free charge carrier concentration; c) calculating the charge carrier lifetime limited by the thermal donors in said area of each wafer, on the basis of the thermal donor concentration; d) determining a bulk lifetime value for the charge carriers in each wafer on the basis of the lifetime limited by the thermal donors; e) comparing the bulk lifetime value or a normalised bulk lifetime value with a threshold value; and f) discarding the wafer when the bulk lifetime value or the normalised bulk lifetime value is lower than the threshold value.