# US 5,708,365 A · Method for analysis of silicon wafers

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- Number: US 5,708,365 A
- Document ID: US5708365A
- Status: Granted
- Kind: A
- Application number: 08/703,887
- Filed: 1996-08-27
- Granted: 1998-01-13
- Earliest claimed: 1996-08-27
- Assignees: Komatsu Electronic Metals Co., Ltd.
- Inventors: Shiro Yoshino; Seiichi Shimura; Mitsuo Kono
- Web page: https://patentgrep.com/patent/US5708365A

## CPC

- H10P 74/207: {Electrical properties, e.g. testing or measuring of resistance, deep levels or capacitance-voltage characteristics}
- G01R 31/2656: {using non-ionising electromagnetic radiation, e.g. optical radiation}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A simple method for evaluating the dielectric breakdown of an oxide layer on a silicon wafer is disclosed. The SPV method is utilized to measure a diffusion length L.sub.on of minority carriers when the silicon wafer is illuminated by white light from another source and a diffusion length L.sub.off of the minority carriers when the silicon wafer is not illuminated by white light from another source. A diffusion length L.sub.safe, which is determined by trap sites in the silicon wafer, is calculated from an equation L.sub.safe =(L.sub.off.sup.-2 -L.sub.on.sup.-2).sup.-1/2. Since L.sub.safe has a strong correlation with the dielectric breakdown of the oxide layer, the dielectric breakdown of the oxide layer can be easily evaluated by L.sub.safe during the fabrication of the silicon wafer.

## Claims

### Claim 1

A method for evaluating a dielectric breakdown of an oxide layer on a silicon wafer fabricated by the Czochralski process, based on results of measurement of diffusion lengths of minority carriers in the silicon wafer by the surface photovoltage process; wherein the method comprises the steps of:
measuring a diffusion length L.sup.on of the minority carriers of the silicon wafer while illuminating by another light source;
measuring a diffusion length L.sub.off of the minority carriers of the silicon wafer without illuminating by another light source; and
calculating a diffusion length L.sub.safe of the minority carriers from an equation L.sub.safe =(L.sub.off.sup.-2 -L.sub.on.sup.-2).sup.-1/2 ; where L.sub.safe is determined by trap sites in the as-grown silicon wafer and represents the dielectric breakdown of the oxide layer.