M. Nagao

Ion beam assisted deposition of niobium nitride thin films for vacuum microelectronics devices

Abstract We have deposited niobium nitride thin films by ion beam assisted deposition and evaluated their properties from the viewpoint of a cathode material for vacuum microelectronics devices. Substrate temperature and ion–atom arrival rate ratio were selected as deposition parameters. The film properties of nitrogen composition, crystallinity, electric resistivity, work function and sputtering yield against a low-energy argon ion bombardment were investigated. It was found that polycrystalline films could be obtained at the substrate temperature higher than 500°C, and the composition could be controlled by the ion–atom arrival rate ratio. The results also showed that the stoichiometric nitride film exhibited superior properties of a lower work function and a lower partial sputtering yield of niobium. The electron emission test also demonstrated a lower current fluctuation for the stoichiometric films. In summary, ion beam assisted deposition provided a low temperature process which could control the film properties suitable to a cathode material.

Emission characteristics of ZrN thin film field emitter array fabricated by ion beam assisted deposition technique

ZrN thin film field emitter arrays were fabricated by the ion beam assisted deposition technique. The work function of ZrN is controlled by the selection of the deposition parameters. We investigated the relationship between the work function and the emission stability, and the influence of the ambient gas on the emission stability by introducing the gases of N2 and O2 into the measurement chamber. It was found that the emission stability depended on the work function: the emitters with a lower work function were more stable than those with a higher work function. The dependence is explained qualitatively by the analysis of the Fowler–Nordheim equation. Emission noise increased with the increase of the ambient gas pressure. However, difference in the increase of noise between N2 gas and O2 gas was seen. O2 gas severely affected the emission stability of the ZrN emitter.

Influence of surface treatment and dopant concentration on field emission characteristics of boron-doped diamond thin films

Field emission characteristics of B-doped diamond thin films terminated with oxygen and hydrogen were investigated. The diamond thin films were prepared by microwave plasma chemical vapor deposition. The dependence of emission characteristics on the surface treatment and on the B concentration was investigated. The turn-on voltage required to extract a current of 0.1 nA depended on these preparation parameters. The emitters with lower B concentration emitted electrons at a lower turn-on voltage, and the H-terminated emitters had a lower turn-on voltage than O-terminated emitters. The analysis of the slope and the intercept of Fowler–Nordheim plot revealed that the dependence of turn-on voltage on the surface treatment is due to the difference of emission barrier height, and that the dependence on B concentration is due not to the emission barrier height but to the surface morphology.

Influence of the composition of a NbNx thin-film field emitter array on emission characteristics

Transition metal nitride has a potential for stable emission because of its chemical inertness, low work function and high melting point. We fabricated the NbN/sub x/ thin film field emitter arrays at relatively low temperature (500/spl deg/C) by ion beam assisted deposition technique. This technique can control the nitrogen composition of the film by selecting the deposition parameters. In this work, the relationship between the nitrogen composition of the NbN/sub x/ and emission characteristics was investigated.

Estimation of emission field and emission site of boron-doped diamond thin-film field emitters

The electric field required to emit electrons for boron-doped diamond together with the emission site was estimated using measurement systems that can precisely control the emitter–collector gap and lateral position. Three different types of field emitters were prepared by microwave plasma chemical vapor deposition. Type A was a typical diamond film on a flat silicon substrate, type B was a heteroepitaxial diamond film that was deposited on a (111) oriented platinum substrate, and type C was a pyramidal diamond film fabricated by the transfer mold method. For all the emitters, the voltage required to extract 0.2 nA was measured as a function of the emitter–collector gap, where the device of the emitter–collector configuration is approximated by a pair of parallel plates. The results showed that a strong electric field was applied in front of the emitter. For type B, the emission current distribution was measured by a device in which the collector was an etched needle. It was found that the emission curren...

Fabrication of gated niobium nitride field emitter array

We have fabricated a gated niobium nitride field emitter by the transfer mold method. A silicon mold was fabricated by anisotropical etching, followed by oxidation of the mold and deposition of niobium nitride. Niobium nitride thin films were prepared by ion-beam-assisted deposition. After attaching the sample to a glass substrate, the silicon mold was removed by mechanical and wet etching. A molybdenum thin film was then deposited by electron-beam evaporation. Formation of a gate aperture and an insulating silicon dioxide layer were performed by wet etching of only the apex, with other regions being protected by a photoresist layer. An electron emission test of the fabricated emitter array was performed in a high vacuum. We confirmed electron emission of up to 0.1 μA at the emitter–gate voltage of 30 V.We have fabricated a gated niobium nitride field emitter by the transfer mold method. A silicon mold was fabricated by anisotropical etching, followed by oxidation of the mold and deposition of niobium nitride. Niobium nitride thin films were prepared by ion-beam-assisted deposition. After attaching the sample to a glass substrate, the silicon mold was removed by mechanical and wet etching. A molybdenum thin film was then deposited by electron-beam evaporation. Formation of a gate aperture and an insulating silicon dioxide layer were performed by wet etching of only the apex, with other regions being protected by a photoresist layer. An electron emission test of the fabricated emitter array was performed in a high vacuum. We confirmed electron emission of up to 0.1 μA at the emitter–gate voltage of 30 V.

Extension of lifetime of silicon field emitter arrays in oxygen ambient by carbon negative ion implantation

As the state of the art, ion implantation techniques require high-current ion beams with the lower energy, as the dimension of the devices becomes smaller. However, it is difficult to drive the lower-energy ion beams straightly, due to the huge ionic space charge. We proposed utilization of electron beam emitted from silicon field emitter arrays (Si-FEA) for compensation of the ionic positive space charge. One of the difficulties in utilizing Si-FEAs in ion implanter is such that the Si-FEA is easily affected by the residual gases, since the implantation generates gas molecules from photoresist materials. It is shown that the emission current decreases, especially in oxygen. One of the ways to protect the surface from oxidation is deposition of the material, which is highly resistant against oxidation, to the tip surface. We modified the surface of the Si-FEA by carbon negative ion implantation, in order to protect the surface from oxidation. In this paper we show the effectiveness of the carbon negative ion implantation to extend the lifetime of Si-FEAs.

Influence of the composition of NbN x thin film field emitter array on the emission characteristics

Transition metal nitride has a potential for stable emission because of its chemical inertness, low work function and high melting point. We fabricated the NbN/sub x/ thin film field emitter arrays at relatively low temperature (500/spl deg/C) by ion beam assisted deposition technique. This technique can control the nitrogen composition of the film by selecting the deposition parameters. In this work, the relationship between the nitrogen composition of the NbN/sub x/ and emission characteristics was investigated.

Influence of ambient nitrogen pressure on the property of zirconium nitride thin films in ion beam assisted deposition

Influence of ambient nitrogen pressure on the property of zirconium nitride thin films in ion beam assisted deposition was investigated. Deposition was performed both with and without the excess nitrogen gas near the substrate. The electrical resistivity and the crystallinity of the deposited films were investigated as a function of the substrate temperature. As a result, it was shown that the electrical resistivity of the films deposited at the substrate temperature lower than 400/spl deg/C, rapidly increased with a decrease in the substrate temperature. The results could be summarized that the high ambient pressure influences the film property even in the ion beam assisted deposition.

Emission characteristics of ZrN thin film field emitter array fabricated with ion beam assisted deposition technique

ZrN thin film field emitter arrays were fabricated with the ion beam assisted deposition technique, which can control the work function of the ZrN films b y choosing the deposition parameters. We investigated the relationship between the work function and the emission stability, and the influence of the ambient gas on the emission stability b y introducing the gases of N2 and 0 2 into the measurement chamber. It was found that the emission stability depended on the work function: the emitters with a lower work function were more stable than those with a higher work function. The dependence is explained qualitatively b y the analysis of the Fowler-Nordheim equation. Emission noise increased with the increase of the ambient gas pressure. However, digerenee in the increase of noise between N2 gas and O2 gas was seen. O2 gas severely aflected the emission stability of the ZrN emitter.