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Browse Prior Art Database

Method for Measuring Doping Profiles

IP.com Disclosure Number: IPCOM000045831D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Kerr, DR: AUTHOR

Abstract

A critical parameter in the process control and development of bipolar transistors is the base doping profile. Disclosed here are two simple methods of fabricating diodes which can give the profile from C-V data.

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Method for Measuring Doping Profiles

A critical parameter in the process control and development of bipolar transistors is the base doping profile. Disclosed here are two simple methods of fabricating diodes which can give the profile from C-V data.

First method: Form a blanket N+ P+ junction simulating an emitter-base junction on a P-type substrate. Evaporate aluminum dots 10. Etch silicon using the aluminum dots as a mask to form mesa diodes, as seen in Fig. 1. A polysilicon diffusion source 12 was used to form the N region.

Second method: Form a silicon dioxide mask 20 with openings therein slightly smaller than the aluminum dot mask in the first method. Form an N+ P+ junction. Evaporate aluminum dots 24, over lapping the hole edges. Aluminum dots 24 can be used as an etch mask for polysilicon 22 if a polysilicon diffusion source is used.

Neither method requires any photolithographic or reactive ion etching processing after the diffusion step. The second method will have a more accurately defined junction area and lower perimeter leakage.

The P+ doping profile can be calculated from C-V data. Since N(see original)N(emitter)>>, the abrupt junction equations: (see original) are good approximations for the base doping and depletion layer thick ness, respectively, where q is electron charge, Epsilon is dielectric constant of silicon, A is junction area, C is capacitance, and v is bias voltage.

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