Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Amorphous semiconductor
Reexamination Certificate
2000-02-15
2001-05-22
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Amorphous semiconductor
C438S020000, C438S482000, C438S483000, C438S484000, C438S485000, C438S486000, C438S767000, C438S765000, C438S769000, C438S770000, C438S771000, C438S930000, C117S904000, C117S003000
Reexamination Certificate
active
06235615
ABSTRACT:
BACKGROUND OF THE INVENTION
Display and electronic devices of various types are being widely utilized. A considerable fraction of total power used to drive small electronic devices, such as laptop computers or televisions, is consumed by the video display. Flat panel displays are becoming an integral part of these devices since they are lighter and less bulky compared to conventional cathode ray tubes (CRTs). Liquid crystal displays are commercially available and are mainly used for portable computers. The disadvantages of liquid crystal displays include high energy consumption, high cost of production, low intensity, limited viewing angle, and difficulties associated with large diameter display production.
Among a few alternatives to the active matrix liquid crystal display (AMLCD) is the field emission display. These displays traditionally rely on emission of electrons from arrays of sharp tips. Each tip serves the function of a filament in a traditional CRT by providing a stream of electrons to excite a phosphor on a nearby screen. The ease of electron emissions, and therefore the reduction in energy consumption of the display, depends on the work function of material and sharpness of the tips. These arrays of tips are expensive and difficult to manufacture on small scales and, so far, have been prohibitively expensive for commercial applications. Recently, a process and apparatus has been developed which enables the deposition of low work function material on the field emission tips, and is described and claimed in copending U.S. application Ser. No. 09/080,109, filed May 18, 1998 entitled “Low Work Function Surface Layers Produced by Laser Ablation Using Short-Wavelength Photons,” assigned to the same assignee.
Several manufacturers have proposed the use of planar electron emitters in a simple diode geometry to overcome said manufacturing difficulties relative to arrays of sharp electron emission tips. One recent approach to the use of planar electron emitters is described and claimed in copending U.S. application Ser. No. 09/080,110, filed May 18, 1998, now U.S. Pat. No. 6,162,707 entitled “Low Work Function, Stable Compound Clusters and Generation Process,” assigned to the same assignee. The production of stable, low work function materials on flat substrates will enable the introduction of this technology, thus, in addition to the compound cluster approach of above-referenced application Ser. No. 09/080,110, the present invention provides for the generation of low work function, stable compound thin films produced by simultaneously laser ablating a silicon target, for example, and thermal evaporating an alkali metal, such as cesium, into an oxygen environment. The compound thin films may be deposited on a substrate, such as silicon, which is patterned to produce a pattern of compound thin films on the substrate. The work functions of the compound thin films (for example, Si/Cs/O films) can be varied by changing the ratio of the components. Tests conducted on the compound thin films have established a low work function and that the films are stable up to 500° C.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide low work function, stable compound thin films.
A further object of the invention is to produce low work function, stable compound thin films using simultaneous laser ablation and thermal evaporation of selected components in an oxygen environment.
A further object of the invention is to provide a process for producing low work function, stable compound thin films on substrates by simultaneously laser ablating a semiconductor material and thermal evaporating an alkali metal into an oxygen environment.
Another object of the invention is to synthesize compound thin films with low work functions by simultaneously laser ablating a material, such as silicon, and thermal evaporating another material, such as cesium, into an oxygen environment.
Another object of the invention is to generate a compound thin film composed of Si/Cs/O, for example, and controlling the work function of the compound thin film by changing the Si/Cs/O ratio.
Another object of the invention is to generate a compound thin film having a low work function and which is stable up to 500° C.
Another object of the invention is to provide a patterned compound thin film on a substrate which can be utilized as planar electron emitters for field emission display devices.
Another object of the invention is to provide an apparatus in which low work function compound thin films can be generated by simultaneous laser ablation and thermal evaporation of selected materials in an oxygen environment.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. Basically, the invention involves the generation of low work function, stable compound thin films on flat substrates for use as planar electron emitters. The production of stable, low work function materials on flat surfaces, which can function as electron emitters, enables the use of planar electron emitters in a simple diode geometry as an alternative to emission of electrons from arrays of sharp tips, for use in field emission displays, such as flat panel displays. The invention involves an apparatus and process whereby simultaneous laser ablation of a semiconductor material, such as silicon, and thermal evaporation of an alkali metal, such as cesium, into an oxygen environment, results in depositing a compound thin film on a substrate. The work functions of the thus formed thin films can be varied by changing the ratio of the semiconductor material, the alkali metal, and the oxygen in the compound thus produced. For example, Si/Cs/O compound thin films have been deposited on silicon substrates, and tests have verified that the thin films have low work function and are stable up to 500° C. Also, tests have verified that for certain compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. Thus the compound thin films of this invention overcome the problems associated with arrays of sharp tips for field emissions and will find use in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns, as well as photocathodes.
REFERENCES:
patent: 5726524 (1998-03-01), Debe
patent: 5886459 (1999-03-01), Auciello et al.
patent: 6019913 (2000-01-01), Dinh et al.
Balooch Mehdi
Dinh Long N.
Fehring, Jr. Edward J.
McLean, II William
Schildbach Marcus A.
Carnahan L.E.
The Regents of the University of California
Thompson Alan H.
Tsai Jey
Zarneke David A
LandOfFree
Generation of low work function, stable compound thin films... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Generation of low work function, stable compound thin films..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Generation of low work function, stable compound thin films... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2571671