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Browse Prior Art Database

THIN FILM MICROFABRICATED HYDROGEN ION SOURCES

IP.com Disclosure Number: IPCOM000004722D
Original Publication Date: 2001-Apr-20
Included in the Prior Art Database: 2001-Apr-20
Document File: 2 page(s) / 9K

Publishing Venue

Motorola

Related People

Babu R. Chalamala: AUTHOR [+2]

Related Documents

US5789318: PATENT [+3]

Abstract

The concept of a thin film hydrogen ion source integrating field emission cathode arrays with metal hydride thin film technology is proposed. A prototype hydrogen ion source was fabricated using Mo field emitter arrays with titanium hydride thin films, and the emission characteristics of the device were demonstrated.

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THIN FILM MICROFABRICATED HYDROGEN ION SOURCES

by Babu R. Chalamalaa and Robert H. Reussb

ABSTRACT

The concept of a thin film hydrogen ion source integrating field emission cathode arrays with metal hydride thin film technology is proposed. A prototype hydrogen ion source was fabricated using Mo field emitter arrays with titanium hydride thin films, and the emission characteristics of the device were demonstrated.

INTRODUCTION

Broad beam hydrogen ion sources are of interest for diverse applications in research and industry. Ultrahigh vacuum compatible solid state hydrogen ion sources are useful in surface science, thin film studies and for passivation of silicon in thin film transistors. The development of solid state hydrogen ion sources with regenerative capabilities could provide substantial benefits for applications in the semiconductor process industry.

In this paper, we demonstrate a solid state microfabricated thin film hydrogen ion sources based on the successful integration of field emission vacuum microelectronics with thin film metal hydride technology. Such an integration is possible due to the advances in field emission vacuum microelectronics.

DEVICE STRUCTURE CONCEPT

The concept involves the integration of stable metal hydride thin films with field emission cathode arrays (FEAs). Bombardment of the metal hydrides with the field emitted electrons causes desorption of hydrogen and some of these molecules undergo electron impact ionization. A schematic outline of the concept is illustrated in Figure 1.

The simplest approach is to deposit the metal hydride film on top of the gate electrode of the FEA.

In another embodiment, a separate metal hydride electrode can be fabricated and biased more positive than the gate electrode. In such a configuration, the electrode potential can also be adjusted to increase both the hydrogen desorption rate and ionization probabilities. This geometry is also better suited for the generation of intense hydrogen beams.

FABRICATION

Several metal hydrides materials can be used for the generation of hydrogen by electron bombardment.l Based on material stability and ease of thin film fabrication, TiH2 is our material of choice for fabrication of thin film hydrogen ion sources. TiHx=2 thin films were deposited by the electron beam evaporation of Ti in a 8x10-5 Torr H2 atmosphere.

Ti to H ratio in these films depends on process parameters, and therefore the titanium hydride film is referred to as TiHx. For characterization purposes, TiHx films were grown on Si substrates and were studied using several analytical techniques. X-ray diffraction spectra show that in the absence of H2 during film growth, a highly textured (l00) Ti layer is deposited.

With a H2 partial pressures of 5x10-5 Torr or higher, diffraction peaks characteristic of TiHx are observed. Presence of Ti-H bonds is also indicated by X-ray photoelectron spectra, where we observe characteristic shifts in the binding energies of core Ti electrons, indicative of a +2...