EP0751699A2 - Procédé et dispositif pour l'étanchement d'un dispositif électroluminescent à couche mince - Google Patents
Procédé et dispositif pour l'étanchement d'un dispositif électroluminescent à couche mince Download PDFInfo
- Publication number
- EP0751699A2 EP0751699A2 EP96304544A EP96304544A EP0751699A2 EP 0751699 A2 EP0751699 A2 EP 0751699A2 EP 96304544 A EP96304544 A EP 96304544A EP 96304544 A EP96304544 A EP 96304544A EP 0751699 A2 EP0751699 A2 EP 0751699A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- layer
- thin film
- encapsulating layer
- electroluminescent device
- thin
- 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.)
- Withdrawn
Links
- 239000010409 thin film Substances 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000007789 sealing Methods 0.000 title description 6
- 239000000463 material Substances 0.000 claims abstract description 19
- 238000000151 deposition Methods 0.000 claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 claims abstract description 8
- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 7
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000004065 semiconductor Substances 0.000 claims description 13
- 239000000758 substrate Substances 0.000 claims description 13
- 238000005229 chemical vapour deposition Methods 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 238000005240 physical vapour deposition Methods 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 239000003989 dielectric material Substances 0.000 claims 1
- 150000004767 nitrides Chemical class 0.000 claims 1
- 239000010408 film Substances 0.000 abstract description 16
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 abstract description 12
- 230000015572 biosynthetic process Effects 0.000 abstract description 6
- 239000010410 layer Substances 0.000 description 59
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 230000008021 deposition Effects 0.000 description 5
- 239000005083 Zinc sulfide Substances 0.000 description 4
- 238000005538 encapsulation Methods 0.000 description 4
- 229910052984 zinc sulfide Inorganic materials 0.000 description 4
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 4
- 230000002411 adverse Effects 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 238000004806 packaging method and process Methods 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000002019 doping agent Substances 0.000 description 2
- 238000005401 electroluminescence Methods 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 238000007736 thin film deposition technique Methods 0.000 description 2
- 239000012780 transparent material Substances 0.000 description 2
- 238000003491 array Methods 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005566 electron beam evaporation Methods 0.000 description 1
- 238000001017 electron-beam sputter deposition Methods 0.000 description 1
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000010943 off-gassing Methods 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/02—Details
- H05B33/04—Sealing arrangements, e.g. against humidity
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/10—Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
Definitions
- the invention relates generally to thin film electroluminescent devices and more particularly to a method and structure for hermetically sealing such devices.
- Thin film electroluminescent (TFEL) devices are employed in a variety of applications. For example, an array of TFEL devices may be used to form a printhead.
- a conventional TFEL device includes an active semiconductor layer sandwiched between two dielectric layers. Electrode layers are formed on the surfaces of the dielectric layers opposite to the active semiconductor layer.
- a TFEL device is typically driven by an alternating current signal. Light is generated when the potential difference between the two electrode layers reaches a threshold voltage. Electroluminescence occurs in the active semiconductor layer when electrical current is passed through the layer. The electrical current excites the dopant material, e.g. manganese. The selection of materials for forming the active semiconductor layer determines the frequency of light emitted from the TFEL device.
- TFEL devices include an hermetic seal to protect the thin film layers, particularly the active semiconductor layer.
- the hermetic seal isolates the layers from contaminants and moisture which would adversely affect a TFEL device.
- the primary concern is film degradation due to exposure of the layers to moisture. Humidity significantly shortens the useful-life of a TFEL device.
- U.S. Pat. Nos. 5,017,824 to Phillips et al. and 4,951,064 to Kun et al. describe sealing structures for forming contaminant-free environments for TFEL devices.
- a glass package is formed over the device to provide a chamber into which an oil is filled.
- an oil For example, a silicon oil may be used.
- U.S. Pat. No. 4,767,679 to Kawachi describes a seal comprised of an inner layer made of a thermoplastic resin and an outer, moisture-proof film that is heated and then press-bonded at its periphery to the substrate that supports one or more TFEL device. That is, the moisture-proof film must be aligned, heated and press-bonded to the substrate.
- U.S. Pat. No. 5,194,027 to Kruskopf et al. describes a seal formed by spreading a gel material over the active area of a TFEL panel and pressing a protective cover onto the gel material so as to squeeze excess gel material from underneath the protective cover.
- liquid-free seal assemblies of TFEL devices While liquid-free seal assemblies of TFEL devices are known, the oil/glass packaging remains as the conventional assembly for hermetically sealing such devices.
- the concern with the known liquid-free seals involves the tendency of defects to propagate.
- solid seals are considered to be less efficient in "self-healing," i.e. self-limiting with respect to propagation of burnouts caused by short circuits.
- Kruskopf et al. for example, identifies the concern of limiting the self-healing effects if the liquid-free packaging material covering the panel is too hard.
- Thin film deposition techniques are employed to form a thin encapsulating layer on a thin film electroluminescent (TFEL) device.
- the encapsulating layer is deposited utilizing chemical vapor deposition (CVD) techniques.
- the thin encapsulating layer is deposited by plasma enhanced CVD, since such deposition allows the TFEL device to remain at a relatively low temperature during deposition.
- plasma enhanced CVD is suitable for depositing an encapsulating layer of silicon nitride, with a low pinhole density and an adequate step coverage.
- the first step is to form the TFEL device.
- the conventional TFEL device includes an active semiconductor layer between two dielectric layers and opposed electrode layers.
- the five thin-film layers are formed on a substrate. It has been discovered that subjecting the TFEL device to a bake-out prior to depositing the encapsulating layer significantly improves the results of performance during life tests. That is, a greater percentage of devices exhibit desired performance characteristics if a pre-bake is performed in order to reduce moisture and other absorbed materials within the thin films to be encapsulated.
- the bake-out preferably takes place in an evacuated environment.
- the TFEL device is an edge emitter device and the thin film encapsulating layer extends over the emitting edge.
- the utility of this invention is in no way limited to edge emission devices, but may as readily be used on face emitting TFEL devices.
- Silicon nitride provides the desired properties, but silicon oxinitride, zinc sulfide plus silicon oxinitride, or aluminum nitride may be substituted.
- the encapsulation is typically formed of a single layer.
- the bake-out is typically performed in an evacuated environment, but may be performed in a properly selected gas environment. However, multi-layer encapsulation is also contemplated.
- An advantage of the invention is that a moisture-proof TFEL device may be formed without significantly increasing the expense or manufacturing complexity of the device.
- Fig. 1 is a side sectional view of a thin film electroluminescent device formed in accordance with the invention.
- Fig. 2 is a side sectional view of the thin film electroluminescent device of Fig. 1 having a thin film encapsulating layer in accordance with the invention.
- Fig. 3 is a side sectional view of a second embodiment of an encapsulating structure in accordance with the invention.
- Fig. 4 is an illustration of the method steps for forming the electroluminescent device of Fig. 3.
- a TFEL device 10 includes a multi-layer structure on a substrate 12.
- the substrate 12 may be formed of a transparent material, such as glass, but this is not critical.
- a thin film active semiconductor layer 14 is sandwiched between an upper dielectric layer 16 and a lower dielectric layer 18.
- An acceptable material for forming the active semiconductor layer 14 is zinc sulfide that is doped with manganese.
- the dielectric layers may be silicon oxinitride, but other materials may be selected.
- a drive signal is connected across an upper electrode layer 20 and a lower electrode layer 22.
- a TFEL device 10 is driven by an alternating current drive signal.
- Light is generated when the voltage across the TFEL device reaches a threshold voltage.
- Electroluminescence occurs in the active semiconductor layer 14 when electrical current is passed through the layer. The electrical current excites the electrons of the dopant material.
- the selection of materials for forming the active semiconductor layer determines the frequency of light emitted from the TFEL device.
- the electrode layers 20 and 22 may be formed of indium tin oxide (ITO).
- ITO is an electrically conductive, optically transparent material for use in such applications as flat panel displays.
- one or both of the electrode layers 20 and 22 may be optically opaque.
- the TFEL device 10 is an edge emitter device for radiating light from a forward edge 24. Edge emitter TFEL devices are designed to retard light radiation from the major surfaces of the devices.
- the substrate 12 supports an array of TFEL devices, allowing the device to be used in such applications as printing.
- Each of the layers 14, 16, 18, 20 and 22 is a thin film layer.
- Thin film is defined herein as a film having a maximum thickness of 15 microns.
- the layers may be formed using thin film deposition techniques known in the art. For example, electron beam evaporation or sputtering may be utilized.
- an encapsulating layer 26 is deposited upon the upper surface of the TFEL device 10.
- the encapsulating layer is a silicon nitride layer deposited by plasma enhanced chemical vapor deposition (PECVD).
- PECVD plasma enhanced chemical vapor deposition
- An acceptable thickness is 4000 A.
- PECVD utilizes radio frequency-induced glow discharge to transfer energy into a reactant gas, thereby allowing the substrate 12 to remain at a relatively low temperature. Room-temperature deposition is possible, so that the substrate and the layers 14-20 remain thermally stable during the formation of the encapsulating layer 26.
- PECVD is a technique in which deposited films have a low pinhole density and a good step coverage. Thus, the downward step from the upper electrode layer 20 to the surface of the substrate 12 is achieved without creating gaps.
- Silicon nitride is the preferred material, but other materials may be substituted for forming the encapsulating layer 26.
- silicon oxinitride, zinc sulfide plus silicon oxinitride, and aluminum nitride have been found to exhibit the desired characteristics for an encapsulating layer.
- integrated circuit fabrication techniques other than PECVD may be used to form the encapsulating layer. Physical vapor deposition offers many of the same advantages afforded by PECVD.
- the encapsulating layer must be optically transparent. Moreover, the index of refraction of the encapsulating material must be considered. Preferably, the index of refraction of the encapsulating layer is matched to the index of refraction of the active semiconductor layer 14. Also, the thickness may be constrained by the desired spectra of the device. However, there may be some applications in which a mismatch achieves desired results.
- the encapsulating layer is a multi-film structure.
- a lower film 28 may be selected for its desired characteristics with respect to hardness.
- An upper, capping film 30 can then be formed to fill and/or cover any pinholes that may be created during the deposition of the lower film 28. In this manner, the moisture impermeability of the structure is improved.
- a polycrystalline material such as zinc sulfide, which has been shown to have excellent resistance to pinhole formation, or polymeric materials may be used to form the lower film 28.
- the capping film 30 may then be silicon nitride. Capping of polymeric films under controlled-stress conditions is possible, because of the use of a room-temperature deposition system.
- the steps of fabricating the structure of Fig. 3 begin with the formation 32 of a TFEL array.
- This step may be performed using any of the known techniques for forming thin films on a substrate.
- the TFEL array is then subjected to a bake-out 34.
- a 30-minute bake-out at 250°C in an evacuated environment has been used to fabricate TFEL arrays in which a high percentage of light-emitting devices have survived a life test of more than 1000 hours at 45°C and 85% relative humidity.
- the bake-out at an elevated temperature in an evacuated environment provides outgassing that acts against sealing in moisture or other volatile substances when the encapsulating layer is introduced.
- the bake-out may also be performed in a controlled gas environment.
- PECVD encapsulation 36 seals the TFEL array.
- the bake-out step 34 and the physics of PECVD substantially overcome the problem of propagating defects typical of prior art solid sealing structures.
- the final step is one of depositing 38 the capping layer.
- the PECVD encapsulation may be a step that takes place after formation of a lower layer in a multi-film encapsulating structure.
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Electroluminescent Light Sources (AREA)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US49506495A | 1995-06-26 | 1995-06-26 | |
| US495064 | 1995-06-26 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0751699A2 true EP0751699A2 (fr) | 1997-01-02 |
| EP0751699A3 EP0751699A3 (fr) | 1997-05-07 |
Family
ID=23967114
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP96304544A Withdrawn EP0751699A3 (fr) | 1995-06-26 | 1996-06-19 | Procédé et dispositif pour l'étanchement d'un dispositif électroluminescent à couche mince |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0751699A3 (fr) |
| JP (1) | JPH0917572A (fr) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0977469A2 (fr) * | 1998-07-30 | 2000-02-02 | Hewlett-Packard Company | Barrière perméable flexible transparente améliorée pour dispositifs organiques électroluminescents |
| WO2002104077A1 (fr) * | 2001-06-16 | 2002-12-27 | Cld, Inc. | Realisation d'un affichage organique electroluminescent |
| WO2004061993A2 (fr) * | 2002-12-27 | 2004-07-22 | Add-Vision, Inc. | Procede d'encapsulation de dispositifs a polymeres lumineux et appareil fabrique au moyen de ce procede |
| US7880167B2 (en) | 1999-06-04 | 2011-02-01 | Semiconductor Energy Laboratory Co., Ltd. | Method for manufacturing an electro-optical device or electroluminescence display device |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4515469B2 (ja) * | 1999-06-04 | 2010-07-28 | 株式会社半導体エネルギー研究所 | 電気光学装置の作製方法 |
| JP4532453B2 (ja) * | 1999-06-04 | 2010-08-25 | 株式会社半導体エネルギー研究所 | 電気光学装置の作製方法 |
| JP4532452B2 (ja) * | 1999-06-04 | 2010-08-25 | 株式会社半導体エネルギー研究所 | 電気光学装置 |
| JP4722746B2 (ja) * | 2006-03-29 | 2011-07-13 | 京セラ株式会社 | Ｅｌ装置 |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0109589A1 (fr) * | 1982-11-15 | 1984-05-30 | GTE Products Corporation | Dispositif indicateur électroluminescent à couche mince |
| US4721631A (en) * | 1985-02-14 | 1988-01-26 | Sharp Kabushiki Kaisha | Method of manufacturing thin-film electroluminescent display panel |
| US4880661A (en) * | 1984-09-17 | 1989-11-14 | Sharp Kabushiki Kaisha | Method of manufacturing a thin-film electroluminescent display element |
-
1996
- 1996-06-12 JP JP8149655A patent/JPH0917572A/ja active Pending
- 1996-06-19 EP EP96304544A patent/EP0751699A3/fr not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0109589A1 (fr) * | 1982-11-15 | 1984-05-30 | GTE Products Corporation | Dispositif indicateur électroluminescent à couche mince |
| US4880661A (en) * | 1984-09-17 | 1989-11-14 | Sharp Kabushiki Kaisha | Method of manufacturing a thin-film electroluminescent display element |
| US4721631A (en) * | 1985-02-14 | 1988-01-26 | Sharp Kabushiki Kaisha | Method of manufacturing thin-film electroluminescent display panel |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0977469A2 (fr) * | 1998-07-30 | 2000-02-02 | Hewlett-Packard Company | Barrière perméable flexible transparente améliorée pour dispositifs organiques électroluminescents |
| EP0977469A3 (fr) * | 1998-07-30 | 2000-09-20 | Hewlett-Packard Company | Barrière perméable flexible transparente améliorée pour dispositifs organiques électroluminescents |
| US7880167B2 (en) | 1999-06-04 | 2011-02-01 | Semiconductor Energy Laboratory Co., Ltd. | Method for manufacturing an electro-optical device or electroluminescence display device |
| US8890172B2 (en) | 1999-06-04 | 2014-11-18 | Semiconductor Energy Laboratory Co., Ltd. | Method for manufacturing an electro-optical device |
| WO2002104077A1 (fr) * | 2001-06-16 | 2002-12-27 | Cld, Inc. | Realisation d'un affichage organique electroluminescent |
| WO2004061993A2 (fr) * | 2002-12-27 | 2004-07-22 | Add-Vision, Inc. | Procede d'encapsulation de dispositifs a polymeres lumineux et appareil fabrique au moyen de ce procede |
| WO2004061993A3 (fr) * | 2002-12-27 | 2004-12-23 | Add Vision Inc | Procede d'encapsulation de dispositifs a polymeres lumineux et appareil fabrique au moyen de ce procede |
| US7261795B2 (en) | 2002-12-27 | 2007-08-28 | Add-Vision, Inc. | Method for encapsulation of light emitting polymer devices |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0751699A3 (fr) | 1997-05-07 |
| JPH0917572A (ja) | 1997-01-17 |
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| 18D | Application deemed to be withdrawn |
Effective date: 19971108 |