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EPI Concentration Measurement in Bipolar Technology

IP.com Disclosure Number: IPCOM000087343D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Bhatia, HS: AUTHOR [+4]

Abstract

Epi (epitaxial) concentration measurements are only important in a technology where very light tolerances for Schottky barrier diodes (e.g., series resistant effect) are desired, as for example:. Minimum Concentration Target Maximum 1.5 x 10/16/ 2.21 x 10/16/ 3.5 x 10/16/.

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EPI Concentration Measurement in Bipolar Technology

Epi (epitaxial) concentration measurements are only important in a technology where very light tolerances for Schottky barrier diodes (e.g., series resistant effect) are desired, as for example:. Minimum Concentration Target Maximum

1.5 x 10/16/ 2.21 x 10/16/ 3.5 x 10/16/.

As can be seen from the close tolerance indicated, an accurate method is required for measuring epi doping.

Heretofore, a P- wafer was employed (Fig. 1), and on which a thin layer of oxide was grown, followed by opening of subcollector areas, and diffusion of an N+ subcollector with drive-in. After drive-in, the oxide was stripped, followed by growth of an epi layer and oxidation. Aluminum dots were then deposited (with gallium on back-side of wafer for ohmic contact) and C-V (capacitance-voltage) traces made. From the Cmax, Cmin and oxide thickness, the epitaxial doping level was calculated.

This procedure has the disadvantage in that reliance has to be placed on the dot size and oxide thickness, wherein the true oxide capacitance is the parallel combination of PN junction capacitance and oxide capacitance, and also in the safety requirements in the use of gallium for back-side contact.

The present method eliminates the need of gallium for ohmic contact, as well as provides measurements of dot size. The present method involves the growth of an N- wafer of an epi layer (as well as formation of a subcollector, if required), followed by growth o...