Browse Prior Art Database

20:1, H202:HF DELINEATION ETCH

IP.com Disclosure Number: IPCOM000006192D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-12
Document File: 2 page(s) / 79K

Publishing Venue

Motorola

Related People

Larry Rice: AUTHOR

Abstract

Cross sectioned device junctions with TiW metal etch out of proportion when traditional etches are used or yield a graded junction making accurate depth mea- surements impossible.

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MOTOROLA INC. Technical Developments Volume 13 July 1991

20:1, H202:HF DELINEATION ETCH

by Larry Rice

PROBLEM

  Cross sectioned device junctions with TiW metal etch out of proportion when traditional etches are used or yield a graded junction making accurate depth mea- surements impossible.

  Present day techniques for accurately measuring junction depths are SRP (spreading resistance probe) and SIMS (secondary ion mass spectrometry) but require relatively large areas for their analysis (125 and 250~2). These techniques can't be used on small geometry devices such as real product or transistor structures used for electrical testing. As devices become smaller we tend to rely on the cross section and SEM (scanning electron microscope) as essential tools to verify junction depths. This type of analysis can be performed on very small areas but the problem associated with this technique are the delineation etches necessary to see the junctions yield a graded delineation. This makes accurate measurements impossible and this problem is enhanced by the pres- ence of tungsten. This is due to the strong galvanic cell action of the TiW, Al metallization structure and enlarges the apparent junctions.

SOLUTION

Finding an oxidizing agent for selective etching.

  Typically we mix an oxidizing agent such as peri- odic acid, nitric acid, or chromium trioxide with hydrogen fluoride. The etch rate of silicon in these etches is dependent on dopant species and concentra- tion so a boro...