Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2001-11-19
2004-04-27
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
Reexamination Certificate
active
06726517
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron emission source that is expected to be applied to flat type solid display elements, and more particularly relates to a cold cathode type electron emission element that realizes the integration and low voltage operability and a process for forming the cold cathode type electron emission element.
2. Description of Prior Art
Heretofore, the hot cathode type electron emission element has been used popularly, however, electron emission by use of a hot electrode is disadvantageous because of large energy loss due to heating and because of requirement of pre-heating.
On the other hand, a small cold cathode structure has been realized with progress of vacuum micro-electronics technology, and the cold cathode type electron emission element has attracted attentions recently. Among the cold cathode type electron emission element, field effect type electron emission element, in which a high voltage is generated locally for field emission, has been developed actively.
FIG. 1
is a schematic partial cross sectional view showing an example of a conventional field effect type electron emission element. In
FIG. 1
,
11
denotes a substrate consisting of silicon (Si),
12
denotes an insulating layer consisting of SiO
2
formed on the substrate
11
,
13
denotes a gate consisting of metal layer, and
14
denotes a circular cone electrode consisting of molybdenum (Mo).
In the case of the electron emission element having the structure as described hereinabove, when a voltage is applied between the substrate
11
and the gate
13
, electrons are emitted from the cusp of the electrode
14
where a strong electric field is applied.
Furthermore, to realize a high performance electron source that is operable with a lower driving voltage than that of the conventional electron source, the reduction of the gate aperture and fabrication of a cathode having a steeper tip have been tried by applying LSI technology.
Though the conventional electron emission element is operable with a low voltage because it has a cone-shaped cathode having a small diameter and steeper tip as described hereinabove, this type of electron emission element is disadvantageous as described herein under.
At first, material having a low electron emission threshold value (electron affinity is small) is suitably used as electron emissive material, and metal W, metal Mo, nitride and oxide of these metals have been tried to be used. However, pure material that can be formed in the shape of cone configuration is limited as long as the conventional fabrication technique is employed.
Furthermore, electron emission stability and evenness are included in the most important performance to be considered when an electron source is to be used practically. In the conventional example, the emission current of a cathode is influenced strongly by the vacuum environment in operation and surface state of a top end of the cathode, and the physical property of the surface, for example, the work function of a current emission part, is changed during current emission to results in significant change of the operation current. As the result, the above-mentioned required performance is not satisfied. The reason is likely that emitted electrons collide with residual gas drifting near the cathode to generate ions, and the ions collide against the top end of the cathode to change the surface state of the top end of the cathode.
A process in which a cathode comprises a plurality of multi electron sources arranged at the time and the individual electron emission fluctuation is leveled to stabilize the emission current has been proposed to suppress the current fluctuation, however, the fluctuation has been still problematic in practical application because the fabrication process of cone-shaping is complex and the cone shape scatters significantly.
Furthermore, use of such field emission type electron source as CRT electron source has been tried, however, the fine electron beam, which is preferable for high vision system to obtain high definition, results in poor brightness. In other words, the tradeoff relation between brightness and definition is problematic.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above-mentioned problem, and the object of the present invention is to form fine structure on a cathode surface evenly and reproducibly with simple working process and to increase and stabilize the emission current value.
To solve the above-mentioned problem, in a cold cathode forming process of the present invention, a target material and a substrate are provided in a reaction chamber, the pressure (P) of an ambient gas introduced into the reaction chamber and the distance (D) between the substrate and the target material are controlled so that the size of a high temperature high pressure area formed near the target material by irradiating a beam light onto the target material is optimal, and the material contained in the target material is excited and ejected by irradiating the beam light onto the target material with introducing the ambient gas into the reaction chamber at the pressure to deposit the material on the substrate. The above-mentioned structure is effective not only for simplification of the manufacturing process and cost reduction but also for obtaining self align type crystalline structure.
An electron emission part of an electron emission element of the present invention comprises a cold cathode having a crystalline thin film of electron emissive material formed by means of the above-mentioned cold cathode forming process. The above-mentioned structure is effective for realizing the reduced electron emission threshold value and the increased emission current value and stability, and realizing the reduced cost with the structure simpler than the conventional structure.
Furthermore, the present invention provides a cold cathode forming process characteristically comprising a step for providing a target material and a substrate in a reaction chamber, a step for controlling the pressure (P) of an ambient gas introduced into the reaction chamber and the distance (D) between the substrate and the target material so that the size of a high temperature high pressure area formed near the target material by irradiating a beam light onto the target material is optimal, and a step for exciting and ejecting the material contained in the target material by irradiating the beam light onto the target material with introducing the ambient gas into the reaction chamber at the pressure to deposit the material on the substrate.
The present invention provides a process in which the pressure (P) of the ambient gas and the distance (D) between the substrate and the target material is controlled according to the relation PD
n
=constant (n is approximately 2 to 3).
According to this process, the interaction (collision, scattering, enclosing effect) between material emitted from the target upon laser irradiation (mainly atoms, ions, and clusters) and the inert gas is optimized to bring about a thin film having the self-align type crystalline structure with maintaining the stoichiometric composition.
Furthermore, the present invention provides a process in which an inert gas is used as the ambient gas. According to this process, a cold cathode is formed without introduction of oxidative gas.
Furthermore, the present invention provides a process in which the pressure of the ambient gas is in the range from 0.1 to 10 Torr. According to this process, a thin film having the same composition as that of the target material is formed suitably.
Furthermore, the present invention provides a process in which the material that constitutes the target consists of at least two or more composition.
Herein, the material that constitutes the target material is preferably any one compound of LaB
6
, TiC, SiC, and SnC. Otherwise, the material may be any typical nitride of TiN, BN, SrN, ZrN, and HfN, or may be any one transparent conducting materi
Hori Yoshikazu
Makino Toshiharu
Suzuki Nobuyasu
Yamada Yuka
Yoshida Takehito
Browdy and Neimark , P.L.L.C.
Matsushita Electric - Industrial Co., Ltd.
Ramsey Kenneth J.
Williams Joseph
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