Source: http://www.google.com/patents/US5391956?dq=7,603,356
Timestamp: 2014-10-01 13:12:42
Document Index: 263202972

Matched Legal Cases: ['art 108', 'art 108', 'art 1109', 'arts 1203', 'art 1109', 'art 1403']

Patent US5391956 - Electron emitting device, method for producing the same and display ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsAn electron emitting device with an insulating layer on a substrate. The insulating layer has a hollow part in which a conical electrode is formed. A conductive layer on the insulating layer has an aperture on the hollow part of the insulating layer. The hollow part is formed by etching utilizing an...http://www.google.com/patents/US5391956?utm_source=gb-gplus-sharePatent US5391956 - Electron emitting device, method for producing the same and display apparatus and electron beam drawing apparatus utilizing the sameAdvanced Patent SearchPublication numberUS5391956 APublication typeGrantApplication numberUS 07/994,459Publication dateFeb 21, 1995Filing dateDec 21, 1992Priority dateSep 7, 1989Fee statusLapsedAlso published asDE69025831D1, DE69025831T2, EP0416625A2, EP0416625A3, EP0416625B1Publication number07994459, 994459, US 5391956 A, US 5391956A, US-A-5391956, US5391956 A, US5391956AInventorsNobuo Watanabe, Takeo Tsukamoto, Masahiko OkunukiOriginal AssigneeCanon Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (14), Non-Patent Citations (5), Referenced by (9), Classifications (9), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetElectron emitting device, method for producing the same and display apparatus and electron beam drawing apparatus utilizing the sameUS 5391956 AAbstract An electron emitting device with an insulating layer on a substrate. The insulating layer has a hollow part in which a conical electrode is formed. A conductive layer on the insulating layer has an aperture on the hollow part of the insulating layer. The hollow part is formed by etching utilizing an ion beam.
As shown in FIG. 1, said field effect electron emitting device is composed of a substrate 101 composed for example of Si; a point-shaped electron emitting part 108 composed for example of molybdenum (Mo) and formed on said substrate; an insulating layer 102 composed for example of SiO2 and having an aperture around said point-shaped electron emitting part 108; and an electrode 109 the end of which is positioned close to the pointed part of the conical shape.
Such field effect electron emitting device utilizing microfabrication technology is for example reported by C. A. Spindt et al. in Journal of Applied Physics, Vol. 47, No. 12, 1976, p. 5246. Said electron emitting device is obtained by forming a hole of a diameter of about 1.5 μm in a thin film of SiO2 and a gate electrode formed in succession on a Si substrate, and further forming, by metal deposition, a conical emitter electrode with a diameter of the pointed end not exceeding 1000Å for field emission.
(1) First, as shown in FIG. 2A, an insulating layer 102 for example of a SiO2 film of a thickness of 1-1.2 μm is formed on the substrate 101 composed for example of Si.
Said insulating layer is preferably composed of a material selected from SiO2, semiconductive Si, Si3 N4 and AlS.
Said boride is preferably selected from LaB6 and SmB6.
It is well known that irradiation of a Si or GaAs single crystal with an ion beam of Be, Si or Au with an intensity of 1014 ions/cm2 or higher converts said single crystal into an amorphous state, whereby the irradiated portion shows an increased etching rate and can be selectively etched after the ion implantation. Such etching method is usable also on SiO2 crystal. Such etching method combined with focused ion beam technology forms a fine hole with a high precision.
1st embodiment FIG. 3 is a schematic cross-sectional view showing an electron emitting device constituting a preferred embodiment of the present invention. Shown are an n-GaAs (semiconductive) substrate 301; an epitaxially grown SiO2 layer 302, serving as an insulating layer, of a thickness of 0.5 μm; a tungsten gate electrode 303 of a thickness of 0.4 μm; an emitter 304; and a hole 305 formed by etching utilizing the focused ion beam technology.
(1) First, on the n-GaAs substrate 301, the SiO2 insulating layer 302 of a thickness of 0.5 μm was formed by epitaxial growth.
(2) Then, the SiO2 layer 302 was irradiated with an ion beam of 200 keV with a dose of 1016 ions/cm2, focused to a diameter of 0.1 μm, as shown in FIG. 4A.
(3) Subsequently the SiO2 layer 302 was treated with heated acid to selectively etch the area implanted with the ion beam in the step (2), thereby obtaining a hole 305 of waterdrop form as shown in FIG. 4B.
(4) Then, on the SiO2 layer 302, tungsten was deposited with a thickness of 0.4 μm by sputtering to form the gate electrode 303 and the emitter 304 as shown in FIG. 4C is thereby provided at the concave bottom of the waterdrop (teardrop) shaped hollow part, and, whereby the electron emitting device as shown in FIG. 3 was completed.
The substrate 301, which is composed of GaAs in the present embodiment, may also be composed of Si. Furthermore the substrate 301 may be composed for example of a glass substrate and amorphous silicon formed thereon, or an insulating substrate and a semiconductor epitaxially grown thereon, for example by SOI (silicon on insulator) technology. Also the SiO2 layer may be replaced by a layer of semiconductive Si, Si3 N4 or AlS. Also the gate electrode may be composed of Mo, Ta, Ti, Pt etc. instead of W.
Industrially, it can be utilized as the electron emitting device for an electron beam drawing apparatus for semiconductor device manufacture, utilizing the features of the present invention such as a large current and a high device density. For example, the electron emitting device of the present invention may be employed instead of the LaB6 conventionally used in such apparatus. Also utilizing the feature of high density arrangement of the present invention, the device may be provided with emitters arranged one-dimensionally or two-dimensionally and may be positioned parallel to the wafer, thereby achieving a high speed pattern drawing.
(1) At first the YIG substrate was subjected to ion implantation with a Be2+ ion beam of 160 keV focused to a spot of 0.1 μmφ or smaller as shown in FIGS. 7A and 7E. The ion dose was 4�1016 ions/cm2 in an area for forming the wiring electrode space (703), and 2�1016 ions/cm2 in an area for forming the electric field forming space (704). The ion implantation for forming the electric field forming space was conducted along a circle of 0.4 μmφ around a desired position. The implanted Be ions were scattered in the substrate 701, thus forming a waterdrop-shaped implanted area 705 as shown in FIG. 7A.
(4) For improving the electron emitting characteristics of this device, LaB6 712, as a material of low work function, was perpendicularly deposited by vacuum evaporation in a thickness of 200Å on the surface of the substrate 701, as shown in FIGS. 7D and 7H.
The field emission type electron emitting device thus completed showed electron emission of 100 μA or higher from the point-shaped electron emitting part, by a voltage application of 25 V between the electrode wiring and the electrode. Thus the surface coverage with a material of low work function reduced the required voltage or increased the emission current at a same voltage. In addition to LaB6, said material of low work function can for example be borides such as SmB6 or carbides such as TiC or ZrC.
(1) An ion beam which is field emitted from an Au--Si--Be liquid metal ion source 801 is focused by an electric condenser lens 802, and a necessary species is separated by an E�B mass separator 803.
5th embodiment FIGS. 11A to 11E are schematic cross-sectional views showing the method for producing a field emission type electron emitting device employing N--GaAs semiconductor single crystal doped with Si at 3�1018 ions/cm2 as the substrate.
(1) At first, a SiO2 film 1102 of a thickness of 0.2 μm, formed by vacuum evaporation on a substrate 1101 as shown in FIG. 11A, was irradiated with an Au2+ ion beam 1103 of 80 keV with a dose of 8�1018 ions/cm2, focused to a diameter of 0.1 μmφ, inside a circle of 0.4 μmφ around a desired position, and was thus removed by sputter-etching.
(2) Then, as shown in FIG. 11B, the substrate was irradiated with a Si2+ ion beam 1104 of 160 keV focused to a diameter of 0.1 μmφ along a circle of 0.35 μmφ around said desired position with a dose of 2�1016 ions/cm2 to form a waterdrop-shaped implanted area 1105.
(3) Then the substrate was immersed in hydrochloric acid heated to 70� C. to selectively etch off the ion implanted area, thereby forming an electric field forming space 1106 and a pointed projection 1107 as shown in FIG. 11C.
(4) Subsequently a metal, such as Au--Ge alloy, constituting an ohmic contact with N--GaAs was perpendicularly deposited onto the substrate by vacuum evaporation with a thickness of 0.2 μm, and an alloy was formed by a heat treatment for 3 minutes at 400� C. Thus an electrode 1108 and a point-shaped electron emitting part 1109 were formed as shown in FIG. 11D.
(5) For improving the electron emitting characteristics of this device, LaB6 1110, as a material of low work function, was perpendicularly deposited by vacuum evaporation with a thickness of 200Å, as shown in FIG. 11E.
In the present embodiment, the electron emitting parts were arranged with a pitch of 1.2 μm, and 4 lines by 15 columns in a unit, and 64 units were formed in a square of 250�250 μm.
An emission current density of 300 A/cm2 could be obtained by a voltage application of 45 V between the electrodes 1202 and all the electron emitting parts 1203.
(1) First the YIG substrate was subjected to ion implantation with a Be2+ ion beam of 160 keV focused to a spot of 0.1 μmφ or smaller as shown in FIGS. 13A and 13E. The ion dose was 4�1016 ions/cm2 in an area for forming the electrode wiring space (1303), and 2�1016 ions/cm2 in an area for forming the electric field forming space (1304). The ion implantation for forming the electric field forming space was conducted along a race track shape having linear portions of 1 μm between semi-circles of a radius of 0.2 μm at a predetermined position. The implanted Be ions were scattered in the substrate 1301, thus forming a waterdrop-shaped implanted area 1305 as shown in FIG. 13A.
(4) For improving the electron emitting characteristics of this device, LaB6 1312, as a material of low work function, was perpendicularly deposited by vacuum evaporation in a thickness of 200Å on the surface of the substrate 1301, as shown in FIGS. 13D and 13H.
The field emission type electron emitting device thus completed showed electron emission of 10 mA or higher from the line-shaped electron emitting part, by a voltage application of 25 V between the electrode wiring and the electrode. Thus the surface covering with a material of low work function reduced the required voltage or increased the emission current at a same voltage. In addition to LaB6, said material of low work function can for example be borides such as SmB6 or carbides such as TiC or ZrC. The present embodiment is basically the same as the 4th embodiment, except for the difference in the shape of the electric field forming space 1306. However, because of said difference in shape, the present embodiment provides a considerably stronger electron emission in comparison with the 4th embodiment. The electron emitting device of the present embodiment can also be prepared by the ion beam scanning apparatus explained above.
FIGS. 11A to 11E are schematic cross-sectional views showing the method for producing a field emission type electron emitting device employing N--GaAs semiconductor single crystal doped with Si at 3�1018 ions/cm2 as the substrate.
(1) First, a SiO2 film 1102 of a thickness of 0.2 μm, formed by vacuum evaporation on a substrate 1101 as shown in FIG. 11A, was irradiated with an Au2+ ion beam 1103 of 80 keV with a dose of 8�1018 ions/cm2, focused to a diameter of 0.1 μmφ, inside a race track shape having linear portions of 1 μm between semi-circles of a radius of 0.2 μm and placed in a predetermined position, and said film was thus removed by sputter-etching.
(2) Then, as shown in FIG. 11B, the substrate was irradiated with a Si2+ ion beam 1104 of 160 keV focused to a diameter of 0.1 μmφ along a trajectory which is 0.05 μm inside said race track shape with a dose of 2�1016 ions/cm2 to form a water drop-shaped implanted area 1105.
(4) Subsequently, a metal such as Au--Ge alloy, constituting an ohmic contact with N--GaAs was deposited onto the substrate by perpendicular vacuum evaporation with a thickness of 0.2 μm, and an alloy was formed by a heat treatment for 3 minutes at 400� C. Thus an electrode 1108 and a line-shaped electron emitting part 1109 were formed as shown in FIG. 11D.
(5) For improving the electron emitting characteristics of this device, LaB6 1110, as a material of low work function, was deposited by perpendicular vacuum evaporation with a thickness of 200Å, as shown in FIG. 11E.
In the present embodiment, the electron emitting parts were arranged with a line pitch of 2.0 μm and a column pitch of 1.2 μm, and 2 lines by 8 columns in a unit, and 64 units were formed in a square of 250�250 μm.
An emission current density as high as 8000 A/cm2 could be obtained by a voltage application of 45 V between the electrode 1402 and all the electron emitting part 1403.