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Browse Prior Art Database

Method for Controlling the Crystalline Phase of Tantalum

IP.com Disclosure Number: IPCOM000036465D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Fryer, PM: AUTHOR

Abstract

Disclosed is a process for controlling the crystalline phase of tantalum metal. Film thickness and substrate temperature are used to form the low resistivity alpha phase or the high resistivity beta phase.

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Method for Controlling the Crystalline Phase of Tantalum

Disclosed is a process for controlling the crystalline phase of tantalum metal. Film thickness and substrate temperature are used to form the low resistivity alpha phase or the high resistivity beta phase.

Tantalum metal has two crystalline phases: The alpha (bcc) phase has low resistivity (12-20 micro-ohm-cm.), and the beta (tetragonal) phase has high resistivity (160-170 micro-ohm-cm.). For electronic applications, the alpha phase is preferred, due to the lower resistivity. However, the exact deposition conditions which result in either alpha or beta phase films are unclear. It has been reported that for evaporated films, substrate temperatures up to 100oC result in beta phase films; if the films are deposited at temperatures greater than 240oC, the alpha phase is formed. On the other hand, sputtered films require a deposition temperature greater than 600oC to form the alpha phase.

The method described here is for controlling the phase by changing the deposition conditions in a magnetron sputtering system. The MRC 643 (Materials Research Corporation) magnetron sputtering system has substrate heating during deposition, and variable scan speed. Since the substrates are scanned past a stationary target, the scan speed is one of the main parameters used to control film thickness. It is disclosed that by lowering the scan speed (to deposit a thicker film), the tantalum film is deposited in the alpha phase inst...