Browse Prior Art Database

Measurement of Substrate Impurity Concentration by the Use of Alphaparticle Radiation

IP.com Disclosure Number: IPCOM000046403D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hsieh, CM: AUTHOR [+2]

Abstract

The impurity concentration of a substrate is determined accurately and conveniently in a nondestructive manner by the use of alpha particle radiation.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 89% of the total text.

Page 1 of 2

Measurement of Substrate Impurity Concentration by the Use of Alphaparticle Radiation

The impurity concentration of a substrate is determined accurately and conveniently in a nondestructive manner by the use of alpha particle radiation.

At present the most common method of measuring the impurity concentration of a substrate is to determine its resistivity by the four- point probe method. However, due to rectifying effects at the contacts, the four-point probe technique is very inaccurate in determining the resistivity of substrates of low impurity concentration.

Computer calculations and experimental results show that the collection of charge generated by an alpha particle which strikes a depletion region is a strong function of the substrate impurity concentration. The lower the substrate impurity concentration, the deeper the alpha particle will force the depletion field into the substrate and the greater the magnitude of the charge collected at the surface. The collection node can be an N diffusion, an FET gate, or a Schottky barrier diode.

Fig. 1 shows a typical setup. Wafer 1 is placed on holder 2 and irradiated by alpha particle source 3. The alpha-generated charge is collected and fed into a charge-sensitive preamplifer 4, amplified by a spectroscopic amplifer 5, and the magnitude of the charge collected on each hit is displayed on a multichannel analyzer 6.

Fig. 2 shows the magnitude of the charge collected per alpha particle hit as a function of substrat...