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GB2378570A - Formation of a field emission backplate using laser crystallization - Google Patents

Formation of a field emission backplate using laser crystallization Download PDF

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Publication number
GB2378570A
GB2378570A GB0119659A GB0119659A GB2378570A GB 2378570 A GB2378570 A GB 2378570A GB 0119659 A GB0119659 A GB 0119659A GB 0119659 A GB0119659 A GB 0119659A GB 2378570 A GB2378570 A GB 2378570A
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United Kingdom
Prior art keywords
field emission
backplate
laser
based material
thin film
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB0119659A
Other versions
GB0119659D0 (en
GB2378570B (en
Inventor
Mervyn John Rose
Ravi Silva
John Shannon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Dundee
Original Assignee
University of Dundee
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Dundee filed Critical University of Dundee
Priority to GB0119659A priority Critical patent/GB2378570B/en
Publication of GB0119659D0 publication Critical patent/GB0119659D0/en
Priority to PCT/GB2002/003691 priority patent/WO2003015117A1/en
Priority to KR1020047002038A priority patent/KR100730808B1/en
Priority to CN028157605A priority patent/CN1639820B/en
Priority to EP02751413A priority patent/EP1417695B1/en
Priority to HK06100341.0A priority patent/HK1077919B/en
Priority to DE60224808T priority patent/DE60224808T2/en
Priority to JP2003519955A priority patent/JP4532108B2/en
Priority to AT02751413T priority patent/ATE385038T1/en
Publication of GB2378570A publication Critical patent/GB2378570A/en
Priority to US10/773,696 priority patent/US7592191B2/en
Application granted granted Critical
Publication of GB2378570B publication Critical patent/GB2378570B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02Main electrodes
    • H01J1/30Cold cathodes, e.g. field-emissive cathode
    • H01J1/304Field-emissive cathodes
    • H01J1/3042Field-emissive cathodes microengineered, e.g. Spindt-type
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02Manufacture of electrodes or electrode systems
    • H01J9/022Manufacture of electrodes or electrode systems of cold cathodes
    • H01J9/025Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104Forming layers
    • H01L21/02365Forming inorganic semiconducting materials on a substrate
    • H01L21/02367Substrates
    • H01L21/0237Materials
    • H01L21/02425Conductive materials, e.g. metallic silicides
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104Forming layers
    • H01L21/02365Forming inorganic semiconducting materials on a substrate
    • H01L21/02518Deposited layers
    • H01L21/02521Materials
    • H01L21/02524Group 14 semiconducting materials
    • H01L21/02532Silicon, silicon germanium, germanium
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104Forming layers
    • H01L21/02365Forming inorganic semiconducting materials on a substrate
    • H01L21/02518Deposited layers
    • H01L21/02587Structure
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104Forming layers
    • H01L21/02365Forming inorganic semiconducting materials on a substrate
    • H01L21/02656Special treatments
    • H01L21/02664Aftertreatments
    • H01L21/02667Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
    • H01L21/02675Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth using laser beams
    • H01L21/02686Pulsed laser beam
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104Forming layers
    • H01L21/02365Forming inorganic semiconducting materials on a substrate
    • H01L21/02656Special treatments
    • H01L21/02664Aftertreatments
    • H01L21/02667Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
    • H01L21/02691Scanning of a beam

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Cold Cathode And The Manufacture (AREA)

Abstract

Formation of a field emission backplate 20 involving laser crystallising at least an area of a planar amorphous semiconductor based material 22 such as a silicon based material. Emitter sites 24 result from the rough surface texture caused by the crystallization process. The extent of the roughening of the surface is determined by the energy absorbed by the silicon. The field emission backplate 20 may be used in a field emission device 18, such as a field emission display, and may emit into a vacuum 31 or into a wide band gap light emitting material (not shown). The semiconductor may alternatively be a germanium based material. The laser used may be a KrF (Krypton Fluorine) excimer laser, though any excimer laser could be used, or a Nd:YAG laser, preferably at a wavelength of 532nm.

Description

<Desc/Clms Page number 1>
IMPROVED FIELD EMISSION BACKPLATE FIELD OF INVENTION The present invention relates to a field emission backplate and related arrangement, and in particular though not exclusively, to a field emission backplate comprising a plurality of emission sites or"silicon tips"formed by laser crystallisation e. g. for use in a display.
BACKGROUND TO INVENTION Flat panel displays are of immense importance in electronics. In current developments, Active Matrix Liquid Crystal Displays (AMLCD) are beginning to challenge the dominance of Cathode Ray Tube (CRT) technology. AMLCD devices are non-emissive and require complex lithography.
Filters and matching spectral backlights are required to produce colour. However, there are many light losses and inherent complexity in AMLCD devices because of the nonlinear nature of liquid crystal materials. This results in a display that is less bright than CRT with a smaller colour gamut and poorer viewing angle and contrast. Also, due to the non-emissive nature of the display, inefficient use of input electrical power is made often with well over 70% of the energy being lost as non-useful energy.
Field emission displays, based on conventional'Spindt
<Desc/Clms Page number 2>
tip'technology, promised a solution to flat panel display problems. Field emission displays (FEDs) are essentially flat cathode ray tube (CRT) devices. However, rather than one electron gun firing electrons at a phosphor on a screen through a shadow mask, the FED has tens or hundreds of individual tips in each display pixel. The tips are known as Spindt tips, after the inventor Cap Spindt. The process of fabrication relies on defining a pattern of holes in a gate metal by leaving a well beneath the metal. A sacrificial layer (usually nickel) is then evaporated on the surface at an oblique angle to ensure the well is not filled. The emitter material (usually tungsten or molybdenum is then evaporated through the holes in to the well. As the evaporate metal builds up on the surface, on the sacrificial layer, it closes the hole as the thickness increases, and has the effect of providing an emitter tip in the well. The top metal is then removed by etching the sacrificial layer, leaving the tip, the well, and the original gate metal. This forms the back plate of Spindt tips. A top plate containing a patterned phosphor is then placed using spacers. The final device is evacuated to allow the emitted electrons a long mean free path. The principle of field emission from micro-tips is well understood and is governed by Fowler-Nordheim tunnelling. The emission current, and therefore brightness of the display depends then only on the current density, the
<Desc/Clms Page number 3>
number of tips and their sharpness, i. e.
I JFN I = JFN Where n = number of tips, a the tip sharpness and JFN the Fowler-Nordheim tunnel current density.
The tips will provide a sharp electron source that will provide hot electron injection into, for example, a phosphor.
Unfortunately, the extreme complication in fabrication has limited the use of this technology. Additionally, crystal silicon emitters are limited by the wafer size.
Other thin-film materials may also be used for field emission. Carbon is the main contender with diamond, diamond like carbon and carbon nano-tubes also suitable.
The diamond seemed a good choice, although it is difficult to fabricate and also the mechanism of a supposed negative electron affinity which diamond was claimed to have has now been questioned.
An object of the present invention is to obviate or mitigate at least one of the aforementioned problems.
SUMMARY OF INVENTION According to a first aspect of the present invention there is provided: a method of forming a field emission backplate comprising: providing a planar body of amorphous semiconductor based material upon a substrate ; and laser crystallising at least a portion of the
<Desc/Clms Page number 4>
amorphous semiconductor based material; wherein upon crystallising the amorphous semiconductor based material a plurality of emitter sites are formed.
Preferably the planar body of amorphous semiconductor based material is provided by depositing a thin film of the material upon a substrate.
Conveniently, the semiconductor based material is silicon or an alloy thereof.
Preferably the laser crystallising is performed using an excimer laser or Nd : YAG laser.
Conveniently, the excimer laser is a KrF laser.
According to a second aspect of the invention there is provided a field emission backplate comprising a plurality of emitter sites formed by laser crystallisation of a thin film of amorphous semiconductor based material.
Conveniently, the semiconductor based material is silicon or an alloy thereof.
According to a third aspect of the invention there is provided a field emitting device comprising a field emission backplate having a plurality of emitter sites formed by laser crystallising of a thin film of amorphous semiconductor based material.
Preferably the field emission device is a vacuum device wherein the emitter sites of the backplate acts as an emission source in the device.
Conveniently, the field emission device comprises a substrate, a field emitting backplate, and an evacuated
<Desc/Clms Page number 5>
space and a transparent window, e. g. thin film transparent metal or metallised phosphor, wherein the field emission backplate is formed upon the substrate and the evacuated space is located between the field emitting backplate and the thin film transparent metal or metallised phosphor.
Alternatively, the field emission device further comprises a wide band-gap light emitting material, e. g. light emitting polymer into which electrons from the emitter sites of the backplate are emitted.
Conveniently, the field emission device comprises a substrate, a field emitting backplate, one side of which is formed a plurality of emitter sites, a light emitting polymer and a thin film transparent metal or metallised phosphor wherein a field emitting backplate is formed upon the substrate, one surface of the light emitting polymer is disposed on the plurality of emitter sites of the light emitting backplate, the thin film transparent metal being disposed on the other surface of the light emitting polymer.
Conveniently, the field emission device is a display device.
BRIEF DESCRIPTION OF DRAWINGS These and other aspects of the invention will become apparent from the following description when taken in combination with the accompanying drawings which show: Figure 1A-IF a thin film semiconductor crystallised at various energies according to the present invention.
<Desc/Clms Page number 6>
Figure 2 a field emission device according to an embodiment of the present invention; and Figure 3 a graph of field emission current vs electric field for a field emission backplate according to the present invention.
DETAILED DESCRIPTION OF DRAWINGS With reference to Figures 1A-1F there is shown a field emitter backplate formed of a amorphous semiconductor based material, in this case n-type hydrogenated amorphous silicon, on the surface of which a plurality of emitter sites are formed. The field emitter backplate is formed by the deposition of a thin film of approximately 100 nm of ntype hydrogenated amorphous silicon onto a substrate of, for example, aluminium by plasma enhanced chemical vapour deposition (PECVD). The deposited thin film then undergoes laser crystallisation by an excimer laser or Nd : YAG laser, in this case a KrF laser operating at a wavelength of 248 nm scanning at 2 mm\s in an atmosphere of oxygen and then quenched, or a Nd : YAG laser operating at a wavelength of 532 nm pulsed at 3 to 7 nseconds, stepped and repeated to form a pattern. This process results in the surface of the silicon having a rough texture. The energy absorbed by the silicon, influences the extent of roughening of the surface, as can be seen in Figures 1A-IF, with Figure 1A showing the effect of a small amount of absorbed energy to
<Desc/Clms Page number 7>
Figure 1F i. e. approximately 100 mJ\cm2 which shows the rounded tips achieved by the most absorbed energy, in the region of 300 mJ\cm-. In each case, each of the tips acts as an emitter site. In a field emission device an emitter site emits electrons at low fields in a field emission configuration. The backplate results in emission currents in excess of 10-5A and low field threshold of around 10Vm.
An example field emission device, having a field emission backplate formed as described with reference to Figures 1A-IF, is shown in Figure 2. The device shown is a triode device having a field emission backplate with a substrate of aluminium and a thin film of n-type hydrogenated amorphous silicon which has been treated by an excimer laser and thus has a plurality of emitter sites upon the surface an insulating layer, for example, a layer of an insulating material such as silicon nitride, has been disposed on the crystallised silicon, and subsequently etched thus providing spacer elements. Upon each of these elements is disposed a thin film of phosphor, e. g. metallised phosphor and the device is completed with a layer of glass thus giving a three terminal gate control arrangement. The area between the glass and the emitter sites is evacuated which allows the emission to be controlled using low voltages and this is important for effective spacial control when used in displays.
Emission currents measured in such a device having a
<Desc/Clms Page number 8>
vacuum below 5 x 10-'bars are shown in Figure 3 which is a graphical representation of the emission current vs the electric field. It is also estimated that the beta factor for the described device is in excess of 450 with this figure including both geometric enhancement and internal enhancement.
The device hereinbefore described is suitable for many display applications having low power consumption and being relatively simple to fabricate. Such devices may also be used as the cathodes for high power transistors for microwave amplifiers in the satellite and mobile communication markets.
Various modifications can be made to the invention as hereinbefore described without parting from the scope of the invention. For example TFT control circuitry can be fabricated in the same manner as the described field emission backplate either at pixel level or via integrated peripheral drivers. It is possible that the field emission device having field emission backplate of the present invention is of the type that embitter sites inject directly into a wide band gap light emitting material to produce light emission. Such arrangements would be particularly useful in the case of the thin film semiconductor not being of N-type and there being no low barrier metal that enables electrons to be injected. The thin film semiconductor of an example given is an N-type
<Desc/Clms Page number 9>
hydrogenated amorphous silicon however the semiconductor may alternatively may be germainiun or germainiun alloy or similar. The substrate on which the thin film semiconductor as disposed has been described as being aluminium however may be formed of various other types of metal such as mobidium, chromium or similar. The use of a KrF (Krypton Fluorine) excimer laser is described however any excimer laser may be used. Further, the use of a Nd : YAG laser at 532 nm is described, however any other wavelength of Nd : YAG laser can be used.

Claims (16)

1. A method of forming a field emission backplate comprising : providing a planar body of amorphous semiconductor based material upon a substrate; and laser crystallising at least a portion of the amorphous semiconductor based material; wherein upon crystallising the amorphous semiconductor based material a plurality of emitter sites are formed.
2. A method, as claimed in claim 1, wherein the planar body of amorphous semiconductor based material is provided by depositing a thin film of material upon a substrate.
3. A method, as claimed in claim 1 or 2, wherein the semiconductor based material is silicon or an alloy thereof.
4. A method, as claimed in claim 2, further comprising the step of performing laser crystallising using an excimer laser or Nd : YAG laser.
5. A method, as claimed in claim 4, wherien the excimer laser is a KrF laser.
<Desc/Clms Page number 11>
6. A field emission backplate comprising a plurality of emitter cites formed by laser crystallisation of a thin film of amorphous semiconductor based material.
7. A field emission backplate, as claimed in claim 6, wherein the semiconductor based material is silicon or an alloy thereof.
8. A field emission device comprising a field emission backplate having a plurality of emitter sites formed by laser crystallising of a thin film of amorphous semiconductor based material.
9. A field emission device, as claimed in claim 8, wherein the field emission device is a vacuum device wherein the emitter sites of the backplate act as an emission source in the device.
10. A field emission device as claimed in claim 9, further comprising a substrate, a field emission backplate, and an evacuated space and a transparent window, wherein the field emission backplate is formed upon the substrate and the evacuated space is located between the field emission backplate and the thin film transparent metal or metalised phosphor.
<Desc/Clms Page number 12>
11. A field emission device as claimed in claim 8, further comprising a wide band-gap light emitting material, into which the electrons from the emitter sites of the backplate are emitted.
12. A field emission device as claimed in claim 11, further comprising a substrate, a field emission backplate on one side of which is formed a plurality of emitter sites, a light emitting polymer and a thin film transparent metal or metalised phosphor, wherein a field emission backplate is formed upon the substrate, one surface of the light emitting polymer is disposed on a plurality of emitter sites of the light emitting backplate, the thin film transparent metal being disposed on the other surface of the light emitting polymer.
13. A field emission device as claimed in claim 11, wherein the device is a display device.
14. A method of forming a field emission backplate, as hereinbefore described, with reference to figures 1A to F, 2 and 3.
15. A field emission backplate, as hereinbefore described, with reference to figures 1A to F, 2 and 3.
<Desc/Clms Page number 13>
16. A field emission device, as hereinbefore described, with reference to figures 1A to F, 2 and 3.
GB0119659A 2001-08-11 2001-08-11 Improved field emission backplate Expired - Lifetime GB2378570B (en)

Priority Applications (10)

Application Number Priority Date Filing Date Title
GB0119659A GB2378570B (en) 2001-08-11 2001-08-11 Improved field emission backplate
AT02751413T ATE385038T1 (en) 2001-08-11 2002-08-09 REAR FIELD EMISSION PLATE
PCT/GB2002/003691 WO2003015117A1 (en) 2001-08-11 2002-08-09 Field emission backplate
CN028157605A CN1639820B (en) 2001-08-11 2002-08-09 field emission backplane
EP02751413A EP1417695B1 (en) 2001-08-11 2002-08-09 Field emission backplate
HK06100341.0A HK1077919B (en) 2001-08-11 2002-08-09 Field emission backplate
DE60224808T DE60224808T2 (en) 2001-08-11 2002-08-09 REAR FIELD EMISSION PLATE
JP2003519955A JP4532108B2 (en) 2001-08-11 2002-08-09 Field emission back plate, field emission device using the field emission back plate, and method for manufacturing the field emission back plate
KR1020047002038A KR100730808B1 (en) 2001-08-11 2002-08-09 Field emission backplates and methods of manufacturing the same and field emission devices
US10/773,696 US7592191B2 (en) 2001-08-11 2004-02-06 Field emission backplate

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0119659A GB2378570B (en) 2001-08-11 2001-08-11 Improved field emission backplate

Publications (3)

Publication Number Publication Date
GB0119659D0 GB0119659D0 (en) 2001-10-03
GB2378570A true GB2378570A (en) 2003-02-12
GB2378570B GB2378570B (en) 2005-11-16

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GB0119659A Expired - Lifetime GB2378570B (en) 2001-08-11 2001-08-11 Improved field emission backplate

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2440783A (en) * 2006-08-07 2008-02-13 Quantum Filament Technologies Improved field emission backplate
US7592191B2 (en) 2001-08-11 2009-09-22 The University Court Of The University Of Dundee Field emission backplate

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0578428A1 (en) * 1992-07-02 1994-01-12 Xerox Corporation Method for making a field emission structure
JPH07141984A (en) * 1993-11-22 1995-06-02 Futaba Corp Manufacture of field emission cathode

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0578428A1 (en) * 1992-07-02 1994-01-12 Xerox Corporation Method for making a field emission structure
JPH07141984A (en) * 1993-11-22 1995-06-02 Futaba Corp Manufacture of field emission cathode

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7592191B2 (en) 2001-08-11 2009-09-22 The University Court Of The University Of Dundee Field emission backplate
GB2440783A (en) * 2006-08-07 2008-02-13 Quantum Filament Technologies Improved field emission backplate
WO2008017809A1 (en) * 2006-08-07 2008-02-14 Quantum Filament Technologies Limited Field emission backplate

Also Published As

Publication number Publication date
GB0119659D0 (en) 2001-10-03
GB2378570B (en) 2005-11-16

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Free format text: PATENT REVOKED; PATENT REVOKED UNDER SECTION 73(2) ON 8 JANUARY 2010