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Browse Prior Art Database

MODULATED METAL MICROSTRUCTURE

IP.com Disclosure Number: IPCOM000012830D
Original Publication Date: 2003-May-30
Included in the Prior Art Database: 2003-May-30
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Abstract

A modulated metal microstructure for improved wet etch taper control or for the formation of an interdigitated electrode for a capacitor is disclosed. Layers of a pure refractory metal, such as Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, or alloys thereof are alternated with thin layers of the same refractory metal or alloy which contain a second element which reduces the wet etch rate.

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MODULATED METAL MICROSTRUCTURE

  A modulated metal microstructure for improved wet etch taper control or for the formation of an interdigitated electrode for a capacitor is disclosed. Layers of a pure refractory metal, such as Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, or alloys thereof are alternated with thin layers of the same refractory metal or alloy which contain a second element which reduces the wet etch rate. Such a structure is readily formed by periodic introduction of a gas, which will react with the refractory metal, such as nitrogen, oxygen, carbon containing gases, boron containing gases, silicon containing gases, or germanium containing gases, during the deposition of the metal layers. In a wet etchant such as a mixture of phosphoric, nitric and acetic acid, it was found that Mo layers doped with nitrogen, Mo(N), etched at a reduced rate compared to pure Mo layers.

With a pure Mo layer, a nearly vertical taper angle resulted at the edges of wet etched features, see (a) and (d) in the Figure below. This is believed to be due to the formation of columnar grains and continuous vertical grain boundaries as is typical in sputtered refractory metal films. For many applications, such as in the fabrication of thin film transistor (TFT) arrays for liquid crystal displays, refractory metal layers are used for the gate electrodes and it is desirable that they have a gentle and smooth taper angle to improve the step coverage of subsequent insulator layers to reduce the...