1258807 ..................................................................................................... ........ 九、發明說明： 【發明所屬之技術領域】 本發明係有關於一種奈米碳管(carb〇n nanotube， CNT)的電泳沉積(electrophoretic deposition，EPD)，尤 其疋關於一種場發射裝置(emjssi〇n device)的電泳沉積方 法。 【先前技術】 夜晶顯示器(LCD)已成為最流行的顯示元件，然而許 多不同種類的顯示技術的研究仍然在進行。場發射如電 子發射用於％發射顯不器(geld emission displays，ΡΈΕ)彡 的使用在下一世代的平面顯示器被預期會大幅地增加。 不像傳統的陰極射線管(cathode ray tube，CRT)使用一熱 的陰極電子搶，場發射顯示器將冷陰極發射器尖端(tip) 用來當電子源，當一個場發射顯示器被置於電場時，冷 陰極發射法瞄準有螢光粉(phosphor)覆蓋的陽極(anode) 基板並發射一電子束。發射的電子經由加在陽極基板的 正電壓做加速後，擊中陽極基板上的螢光粉而產生冷光 (luminescence) ° 有些傳統的％發射顯不器的陰極板(ca^jj〇de piate)使 用一種網印(screen printing)法製造，此種方法的缺點是解 析度差，乃因篩孔(screen mesh)大小的限制與網布不一致 1258807 的張力造成不一致的薄膜厚度。此不一致的薄膜厚度可 能造成隨後程序的調準問題，其他傳統的場發射器是以 史賓迪特(spindt)技術產生的圓錐形的技巧來形成，上述 的方法通常造成高的起始(turn on)電壓或發射器尖端較 短的舞命。 為解決前面提及的問題，因此奈米碳管場發射器因 應而丰。相較於傳統的場發射裝置，奈米碳管場發射器 有優越的發射特性，諸如較低的起始電壓和較大的發射 電流密度，然而奈米碳管場發射器的結構受到材料處理 時遭遇的問題所妨礙。奈米碳管常用雷射熔蝕(laser ablation)或電弧放電（arc discharge)或電化學 (electrochemical)沉積來製造。一種後形成(post-formation) 方法，諸如網印或喷塗(spraying)法必需利用放置預先形 成的奈米竣管在一場發射基底上，網印或喷塗法遭受解 析度差與一致性差的問題，無法實際地大規模製造。雖 然奈米碳管可利用化學氣相沉積（chemical vapor deposition ’ CVD)技術直接在場發射基底上長成，為有 效地長成奈米碳管。惟，此類技術需相當高的溫度與易 反應(reactive)的環境，嚴酷的溫度條件嚴格地限制了可被 用於化學氣相沉積基板的材料，所以使得此技術不具實 7 1258807 用性。 因此，提出了用感光性的漿料(ph〇t〇sensitive paste) 或電泳沉積來大量製造奈米碳管場發射器，以來克服前 述的問題。美國第6,81M57號專射提出的方法是使用 一種感光性的漿料與可蝕刻的介電材質（didectric material)來製造奈米碳管場發射顯示器的陰極板。電泳沉 • 積的方法提供許多優點，諸如製作簡單、低成本、低溫 度與λ規模製造的可行性。美國第6,616,497號專利與美 國專利公開申請案2003/0102222揭露的文獻裡，提出一 種用奈米碳管微粒(particle)來形成奈米電泳沉積的方 法。此傳統的方法如第一圖所示，一電源供應器101的 偏壓配置於二個分開的電極(electrodeX陽極板102與陰 極板103)，電極沉入電泳槽(bath)104，電泳槽104包含 奈米碳管電泳液(suspension)105，電泳液105使奈米碳管 • 微粒106可選擇性地沉積在陰極107的表面，此表面經 由介電層109的閘孔(gate hole)108暴露於外，陰極板103 包含一基底110、一介電薄層109、多個陰極107、多個 閘極111與奈米碳管微粒106。當電場加至電泳槽104 時，一維的(dimensional)奈米結構材料(nanostructure materials)輕鬆地沿著長度方向(longitudinal)的轴向形成 極化的(polarized)雙極(dipole)，這些極化的雙極能沿著介 1258807 電泳動的(dielectrophorectic)力量的方向漂移。 添加物可被加人電泳财縣米結撕料(如奈米碳 管微粒)充電與促進電泳沉積，被奈米懸浮液中正離子充 電之奈米材料沿著電力的方向漂移，電力由電極之間電 位差造成。此方法的缺點是沉積的選擇性領好到可防 止間極111的頂部面積或繼被奈米碳管雜沉積。此 側壁沉積會造成陰極107與開極lu之間短路。一個解 決上淳問題的方法是在沉積程序中使用一遮蔽犧牲層 (masked sacrificial layer)(如光阻(ph〇t〇resist))來保護或覆 蓋閘極111 ’犧牲層與閘極lu頂部面積或側壁的奈米碳 管微粒在電泳沉積後被移除，此方法需要一額外的黃光 顯影(photolithographic)的程序，使製造程序複雜化和增 加製造成本。 【發明内容】 本發明之電泳沉積法使用適當安排施加電壓於具有 閘極的三極(triode)結構，以改善傳統的電泳沉積方法。 在本發明的較佳實施例中，二個分開的偏壓 voltage)施加於閘極相對於陽極以及陰極相對於陽極。根 據本發明之實施例的場發射裝置的電泳沉積方法包含以 下步驟:(a)準備一個含有奈米結構之懸浮液的電泳槽，由） 準備一個含有三極結構的場發射陰極板，此三極結構包 含閘極，其中該場發射板當作陰極板且包含一基板、多 個在基板的陰極、一形成在基底與陰極上的介電層、多 個形成在介電薄層與基板上的閘極，（C)將陽極板與場發 射陰極板沉入於電泳槽，以及(d)將二個不同的偏壓分別 施加至該閘極與該陰極一段時間，以使奈米材料選擇性 地沈積在陰極的的表面，此表面經由介電層的閘孔暴露 於外。 在本發明的第一實施例中，在電泳沉積期間，施加 一正電壓至閘極，一負電壓至陰極，而陽極板保持在一 共同電壓。 在本發明的另一實施例中，在電泳沉積時，施加一偏 壓至閘極與陰極之間，此實施例之場發射裝置的電泳沉 積方法包含相同的步驟(a)與(b)和二個不同的步驟，不用 上述的(c)與(d)步驟，此第二實施例將場發射板沉入電泳 槽，接著施加一偏壓至該閘極與該陰極一段時間，以使奈 米結構材料有選擇性地沈積在陰極的表面，此表面經由 介電層的閘孔暴露於外。 本發明之場發射裝置的電泳沉積方法不僅有傳統電 1258807 冰y儿積方法提供的優點，並且比傳統電泳沉積方法提供 較佳的沉積選擇性。其在低溫度下實施且不需要遮蔽犧 牲層’因此使製程簡單且降低成本。 茲配合下列圖示、實施例之詳細說明及申請專利範 圍，將上述及本發明之其他目的與優點詳述於後。 【實施方式】 +發明結合厚膜網印(thick-film printing)與黃光顯影 技術來建構一種具有閘極的三極結構來作電泳沉積，然 後在電泳沉積期間，安排施加電壓與適當選擇電泳槽中 的溶劑’以使奈米結構材料沈積在基板之可選擇的區域 上。基板可以是場發射基板，用來作為一場發射顯示裝 置的場發射器。 為了增進場發射器的效能，建議在做電泳沉積之 前，對奈米結構材料過濾(filtration)與純化(purification) 〇 電泳槽中的溶劑包含一溶劑基本成分(base)與添加物 (additives)。去離子水(Deionized(DI) water)或是 isopropyl alcohol(IPA)可作為溶劑基本成分。各種不同的添加物已 在文獻裡被提出。這些添加物包到氣化苯二甲羥錢 (Benzalkonium Chloride)、硝酸鎂(Mg(N03)26H20)、八〇了 11 1258807 (bis (l-ethylhexyl) sodium sulfosuccinate)、碳酸納 (Na2C〇3)與含硝酸鹽(nitrate)的氫氧化鎂(Mg(〇H)2)或是 氫氧化銘(A1(〇H)3)或是氫氧化。直流或交流 電源都可使用。根據本發明，在做電泳沉積之前把陰極 板沉入含硝酸鹽的電泳槽，以增進奈米結構材料(如奈米 碳官微粒)在陰極表面的黏著力。此外，1 ??111的碳酸納 被當作添加物加入含50 ppm奈米碳管的去離子水溶 劑，以增進電泳的效能。溶劑導電率從a444ms/m增加 至0.702ms/m，電泳沉積溫度維持在攝氏5〇度。 第二A至第二D圖說明根據本發明之第一實施例的 一種場發射裝置之電泳沉積方法的步驟。在本實施例 中，首先，準備一含有奈米結構懸浮液204的電泳槽203, 如第二A圖所示。其次，準備一具有閘極2〇6之三極結 構的場發射陰極板202,其中場發射陰極板2〇2當作陰極 板且包含一基板212、多個在基板212上的陰極2〇8、一 形成在基板212與陰極208上的介電層211、多個形成在 在介電層211與基板212上的閘極206，如第二b圖所 示。然後’將陽極板201與場發射陰極板2〇2沉入電泳 槽203，如第二C圖所示。最後，如第二d圖所示，根 據此電泳沉積法，施加一電源供應器205的偏壓V1至閘 極206，及施加一電源供應器207的偏壓V2至陰極208 12 1258807 段時間’以使奈米結構材料2〇9可選擇沈積在陰極2〇8 的表面，此表面藉由介電層211的閘孔210暴露於外。 參考第一D圖’陽極板剔電路連接至電源供應器 205與電源供應器207的其他二端且保持在一共同電壓 V0〇 根據本發明奈米材料可包括奈米管(nanotubes)、奈 米線(nanGwire)、奈轉管、奈轉_奈綠粒。此實 施例中的閘孔210尺寸約為8〇呵，介電層211的厚度約 為25μιη。為了使電場的分佈均句，陽極板肌以多孔狀 的結構製成。 第三圖為第二Α至第二D圖電泳槽中電場的分佈概 要圖。帶電荷或極化的奈米結構材料沿著電力線漂移， 然後沈積在陰極板。靠近閘極的電場排斥在電泳槽中帶 電荷或極化的奈米結構材料，如此可避免帶電荷或極化 的奈米結構材料沈積在閘極。 相對於共同電壓VG之偏壓％通常是正電壓但並不限 於是正電壓，相對於共同電壓v〇之偏壓％通常是負電壓 但並不限於是負電壓。在選擇性電泳沉積的期間，帶電 13 1258807 荷或極化的奈米結構懸浮液204被負陰極電壓％電力線 經由閘孔210而被吸引，並朝向陰極識漂移。正問極 電壓(positive gate v〇ltage)Vl排斥在電泳槽中帶電触極 化的奈米結構懸浮液204，可避免奈米結構材料沈積在問 極206上。所以，奈米結構材料可選擇地沈積在陰極2〇8。 因此，可避免陰極208與閘極206之間的電路短路。 藝㈣A ffi與第四B圖分別說明場發射器交叉型 (cross-type)陰極板在根據本發明電泳沉積法之前與之後 的放大俯視圖。垂直的線是陰極線4Q1，水平的線是問極 線402。在陰極線與閘線之間的基底為一介電層。於第四 B圖可觀察到一沉積在陰極閘孔奈米碳管微粒之示意圖。 大量奈米碳管覆蓋在陰極線，因奈米碳管粉末在事 • 先處理時未被純化，仍存在有碳微粒蓋在陰極線，建議 移除這些碳微粒，可增進場發射性能與改善在封裝過程 期間真空狀態。 第四C圖與第四D圖分別說明場發射器平行型 (parallel-type)陰極板在根據本發明電泳沉積法之前與之 後的放大俯視圖。 14 1258807 第五圖為根據本發明CNT場發射器電場發射電流對 施加電壓之制絲圖。參料五圖，起始電場強度低 至4.5volt/micron，而電流密度達到3·5ιηΑ/αη2在％ volt/micron時。第四a圖與第四Β圖與第五圖確認根據 本發明場發射裝置的電泳沉積法可達成好的電泳沉積選 擇性和場發射性能。 在本發明的另一實施例中，在電泳沉積期間，施加 一偏壓至閘極與陰極之間，此實施例中的場發射裝置的 電冰/儿積方法包含與第二Α圖及第二β圖相同的步驟和 兩個以下不同的步驟。第六A圖與第六B圖分別說明此 兩個不同的步驟。在經過第二A圖及第圖的步驟後， 將場發射陰極板202沉入電泳槽203中，如第六A圖所 示。接著施加一電源供應器604的偏壓y2至閘極206與 陰極208 —段時間，以使奈米結構材料2〇9選擇性地沈 積在陰極208的表面，此表面藉由介電層211的閘孔6〇8 暴露於外。電源供應器604的另一端維持在電壓％，並 電氣連接至閘極206,如第六B圖所示。 相對於共同電壓VG，偏壓％通常是正電壓但並不限 於是正電壓。在選擇性電泳沉積期間，帶電荷或極化的 奈米結構懸浮液204被由閘極2〇6與陰極208之間的電 15 1258807 位差所形成的電場經由閘孔608而被吸引，並朝向陰極 208漂移，沈積在陰極208的表面。在閘極206周圍的電 場排斥在電泳槽中帶電荷或極化的奈米結構懸浮液 204 ’可避免奈米結構材料沈積在閘極206上。所以，奈 米結構材料209可選擇地沈積在陰極2〇8,而可避免陰極 208與閘極206之間的電路短路。 综上所述，本發明利用選擇性沉積在一種具有閘極 \ 之三極結構的陰極，提供一種場發射裝置的電泳沉積方 法。其經由改善電泳沉積方法的選擇性，來解決陰極與 閘極之間的電馳關題。此外，本發嘱電泳沉積法 在低溫度下實施，並且;Ρ需要雜犧牲層，所以使製程 簡單且降低成本。 准，以上所述者，僅為本發明之較佳實施例而已，當 不此以此限定本發明實施之範圍。即大凡依本發明申請 專利範騎作之解賊與修飾，皆應仍屬本發明專利 涵蓋之範圍内。 16 1258807 【圖式簡單說明】 第一圖為說明一種傳統的奈米碳管場發射器電泳沉積示 意圖。 第二A至第二D圖說明根據本發明之第一實施例的場發 射裝置之電泳沉積方法的步驟流程。 第二圖為第二A至第二d圖之電泳槽中電場的分佈概要 圖。 藝第四A圖係一種場發射器交叉型陰極板在根據本發明選 擇性電泳沉積之前的放大俯視圖。 第四B圖係一種場發射器交叉型陰極板在根據本發明選 擇性電泳沉積之後的放大俯視圖。 第四C圖係一種場發射器平行型陰極板在根據本發明選 擇性電泳沉積之前的放大俯視圖。 第四D圖係一種場發射器平行型陰極板在根據本發明選 φ 擇性電泳沉積之後的放大俯視圖。 第五圖為根據本發明奈米碳管場發射器電場發射電流對 施加電壓之量測結果圖。 第六A圖與第六B圖說明根據本發明另一實施例之場發 射裝置的電泳沉積法的步驟流程。 【主要元件符號說明】 101電源供應聋_ 102陽極板 17 1258807 103陰極板 104電泳槽 105電泳液 206 CNT微粒 107陰極 108閘 109介電層 110基板 111閘極 201陽極板 202場發射陰極板 203電泳槽 204奈米結構懸浮液 205電源供應器 206閘極 207電源供應器 208陰極 209奈米結構材料 210閘孔 211介電層 212基板 401陰極線 402閘極線 181258807 ................................................. .................................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . In particular, an electrophoretic deposition method for a field emission device (emjssi〇n device). [Prior Art] The night crystal display (LCD) has become the most popular display element, but research on many different types of display technologies is still in progress. The use of field emission, such as electron emission for geld emission displays (被), is expected to increase substantially in the next generation of flat panel displays. Unlike conventional cathode ray tubes (CRTs) that use a hot cathode electron capture, field emission displays use a cold cathode emitter tip as an electron source when a field emission display is placed in an electric field. The cold cathode emission method is aimed at an anode substrate having a phosphor coating and emitting an electron beam. The emitted electrons are accelerated by the positive voltage applied to the anode substrate, and the fluorescent powder on the anode substrate is hit to generate luminescence. Some conventional % emission cathode plates (ca^jj〇de piate) The use of a screen printing method has the disadvantage of poor resolution due to the inconsistency of the film thickness due to the limitation of the screen mesh size and the tension of the mesh 1258807. This inconsistent film thickness may cause alignment problems in subsequent procedures. Other conventional field emitters are formed by the conical technique produced by the spindt technique, which usually results in a high start (turn) On) A short dance of the voltage or the tip of the transmitter. In order to solve the aforementioned problems, the carbon nanotube emitters are so rich. Compared to conventional field emission devices, nanocarbon tube emitters have superior emission characteristics, such as lower initial voltage and larger emission current density, whereas the structure of the nanocarbon tube field emitter is materialized. The problems encountered at the time are hindered. Nanocarbon tubes are commonly fabricated by laser ablation or arc discharge or electrochemical deposition. A post-formation method, such as screen printing or spraying, must rely on the placement of pre-formed nanotubes on a single launch substrate. Screen printing or spray coating suffers from poor resolution and poor consistency. The problem cannot be actually produced on a large scale. Although the carbon nanotubes can be grown directly on the field emission substrate by chemical vapor deposition (CVD) technology, they are effectively grown into carbon nanotubes. However, such techniques require relatively high temperatures and reactive environments. Severe temperature conditions severely limit the materials that can be used for chemical vapor deposition of substrates, making this technology impractical. Therefore, it has been proposed to overcome the above-mentioned problems by mass-producing a carbon nanotube field emitter with a photosensitive paste or electrophoretic deposition. The method proposed by the US No. 6,81M57 is to use a photosensitive paste and an etchable dielectric material to fabricate a cathode plate of a carbon nanotube field emission display. The electrophoretic sinking method offers many advantages, such as ease of fabrication, low cost, low temperature and lambda scale manufacturing. In the documents disclosed in U.S. Patent No. 6,616,497 and U.S. Patent Application Publication No. 2003/0102222, a method of forming nanoelectrophoretic deposition using carbon nanotube particles is proposed. The conventional method is as shown in the first figure. A bias voltage of a power supply 101 is disposed on two separate electrodes (electrode X anode plate 102 and cathode plate 103), and the electrode sinks into an electrophoresis bath 104, and the electrophoresis tank 104 A carbon nanotube electrophoresis solution 105 is included, and the electrophoresis liquid 105 allows the carbon nanotubes/particles 106 to be selectively deposited on the surface of the cathode 107 exposed through a gate hole 108 of the dielectric layer 109. Further, the cathode plate 103 includes a substrate 110, a dielectric thin layer 109, a plurality of cathodes 107, a plurality of gate electrodes 111, and carbon nanotube particles 106. When an electric field is applied to the electrophoresis tank 104, the dimensional nanostructure materials easily form polarized dipoles along the longitudinal axis, these poles The bipolar can drift in the direction of the dielectrophorectic force of 1258807. The additive can be charged by electrophoresis Caixian rice knot tearing material (such as carbon nanotube particles) and promote electrophoretic deposition. The nano-material charged by the positive ion in the nano-suspension drifts along the direction of electric power, and the electric power is driven by the electrode. Caused by the difference in potential. A disadvantage of this method is that the selectivity of the deposition is such that the top area of the interpole 111 can be prevented or subsequently deposited by the carbon nanotubes. This sidewall deposition causes a short circuit between the cathode 107 and the open electrode lu. One way to solve the problem of the upper jaw is to use a masked sacrificial layer (such as a photoresist) to protect or cover the gate 111 'sacrificial layer and the top surface of the gate lu in the deposition process. Or the sidewall carbon nanotube particles are removed after electrophoretic deposition. This method requires an additional photolithographic procedure that complicates the manufacturing process and increases manufacturing costs. SUMMARY OF THE INVENTION The electrophoretic deposition method of the present invention uses a proper arrangement of applying a voltage to a triode structure having a gate to improve a conventional electrophoretic deposition method. In a preferred embodiment of the invention, two separate bias voltages are applied to the gate relative to the anode and the cathode relative to the anode. An electrophoretic deposition method of a field emission device according to an embodiment of the present invention includes the steps of: (a) preparing an electrophoresis tank containing a suspension of a nanostructure, preparing) a field emission cathode plate containing a three-pole structure, the third The pole structure comprises a gate, wherein the field emitter plate serves as a cathode plate and comprises a substrate, a plurality of cathodes on the substrate, a dielectric layer formed on the substrate and the cathode, and a plurality of dielectric thin layers and the substrate are formed on the substrate a gate, (C) sinking the anode plate and the field emission cathode plate into the electrophoresis tank, and (d) applying two different bias voltages to the gate and the cathode for a period of time to select the nanomaterial It is deposited on the surface of the cathode, which is exposed to the outside via the gate of the dielectric layer. In a first embodiment of the invention, during electrophoretic deposition, a positive voltage is applied to the gate, a negative voltage is applied to the cathode, and the anode plate is maintained at a common voltage. In another embodiment of the present invention, a bias is applied between the gate and the cathode during electrophoretic deposition, and the electrophoretic deposition method of the field emission device of this embodiment comprises the same steps (a) and (b) and Two different steps, instead of the above steps (c) and (d), the second embodiment sinks the field emission plate into the electrophoresis tank, and then applies a bias voltage to the gate and the cathode for a period of time to The meter structure material is selectively deposited on the surface of the cathode, the surface being exposed to the outside via the gate opening of the dielectric layer. The electrophoretic deposition method of the field emission device of the present invention not only has the advantages provided by the conventional electrothermal deposition method, but also provides better deposition selectivity than the conventional electrophoretic deposition method. It is implemented at low temperatures and does not require masking of the sacrificial layer' thus making the process simple and reducing cost. The above and other objects and advantages of the present invention will be described in detail with reference to the accompanying drawings. [Embodiment] + The invention combines thick-film printing and yellow light developing technology to construct a three-pole structure with a gate for electrophoretic deposition, and then arranges voltage application and appropriate selective electrophoresis during electrophoretic deposition. The solvent in the bath 'so that the nanostructure material is deposited on selectable regions of the substrate. The substrate can be a field emission substrate that acts as a field emitter for a field emission display device. In order to improve the performance of the field emitter, it is recommended to filter and purify the nanostructure material before the electrophoretic deposition. The solvent in the electrophoresis tank contains a solvent base and additives. Deionized (DI) water or isopropyl alcohol (IPA) can be used as a solvent base. A variety of different additives have been proposed in the literature. These additives are packaged in Benzalkonium Chloride, Magnesium Nitrate (Mg(N03)26H20), Gossip 11 1258807 (bis (l-ethylhexyl) sodium sulfosuccinate), Naphthalate (Na2C〇3) With magnesium nitrate (Mg (〇H) 2) or hydroxide (A1 (〇H) 3) or hydrogen hydroxide. Both DC or AC power can be used. According to the present invention, the cathode plate is submerged in a nitrate-containing electrophoresis tank prior to electrophoretic deposition to enhance the adhesion of the nanostructure material (e.g., nano-carbon particles) to the surface of the cathode. In addition, 1 ? 111 of sodium carbonate was added as an additive to a deionized water solvent containing 50 ppm of carbon nanotubes to enhance the efficiency of electrophoresis. The solvent conductivity increased from a444 ms/m to 0.702 ms/m, and the electrophoretic deposition temperature was maintained at 5 degrees Celsius. The second to second D diagrams illustrate the steps of an electrophoretic deposition method of a field emission device according to the first embodiment of the present invention. In the present embodiment, first, an electrophoresis tank 203 containing a nanostructure suspension 204 is prepared as shown in Fig. 2A. Next, a field emission cathode plate 202 having a gate structure of a gate 2〇6 is prepared, wherein the field emission cathode plate 2〇2 serves as a cathode plate and includes a substrate 212 and a plurality of cathodes 2〇8 on the substrate 212. A dielectric layer 211 formed on the substrate 212 and the cathode 208, and a plurality of gate electrodes 206 formed on the dielectric layer 211 and the substrate 212 are as shown in FIG. Then, the anode plate 201 and the field emission cathode plate 2〇2 are sunk into the electrophoresis tank 203 as shown in Fig. 2C. Finally, as shown in the second d diagram, according to this electrophoretic deposition method, a bias voltage V1 of the power supply 205 is applied to the gate 206, and a bias voltage V2 of the power supply 207 is applied to the cathode 208 12 1258807 for a period of time ' The nanostructure material 2〇9 may be selectively deposited on the surface of the cathode 2〇8 which is exposed to the outside by the gate hole 210 of the dielectric layer 211. Referring to the first D diagram, the anode plate splicing circuit is connected to the power supply 205 and the other two ends of the power supply 207 and maintained at a common voltage V0. According to the present invention, the nano material may include nanotubes, nanometers, and nanometers. Line (nanGwire), nai tube, nai turn _ nai green. The size of the gate hole 210 in this embodiment is about 8 Å, and the thickness of the dielectric layer 211 is about 25 μm. In order to make the distribution of the electric field uniform, the anode plate muscle is made of a porous structure. The third figure is a schematic diagram of the distribution of the electric field in the electrophoresis tank from the second to the second D. The charged or polarized nanostructured material drifts along the power line and is then deposited on the cathode plate. The electric field near the gate repels the charged or polarized nanostructured material in the electrophoresis tank, thus avoiding the deposition of charged or polarized nanostructured material at the gate. The bias voltage % with respect to the common voltage VG is usually a positive voltage but is not limited to a positive voltage, and the bias voltage % with respect to the common voltage v 通常 is usually a negative voltage but is not limited to a negative voltage. During selective electrophoretic deposition, charged 13 1258807 charged or polarized nanostructure suspension 204 is attracted by the negative cathode voltage % power line via gate 210 and drifts toward the cathode. The positive gate v〇ltage Vl repels the charged structure of the nanostructure suspension 204 in the electrophoresis tank to prevent deposition of the nanostructure material on the interrogation pole 206. Therefore, the nanostructure material is optionally deposited on the cathode 2〇8. Therefore, a short circuit between the cathode 208 and the gate 206 can be avoided. Art (4) Affi and Figure 4B illustrate enlarged top views of field emitter cross-type cathode plates before and after electrophoretic deposition according to the present invention, respectively. The vertical line is the cathode line 4Q1 and the horizontal line is the question line line 402. The substrate between the cathode line and the gate line is a dielectric layer. A schematic diagram of a carbon nanotube particle deposited in the cathode gate can be observed in Figure 4B. A large number of carbon nanotubes are covered on the cathode line. Since the carbon nanotube powder is not purified during the first treatment, there are still carbon particles covering the cathode line. It is recommended to remove these carbon particles to improve the field emission performance and improve the package. Vacuum state during the process. The fourth C and fourth D diagrams respectively illustrate enlarged top views of the field emitter parallel-type cathode plates before and after the electrophoretic deposition process according to the present invention. 14 1258807 The fifth figure is a wire drawing of the applied electric field of the CNT field emitter according to the present invention. In the fifth chart, the initial electric field strength is as low as 4.5 volt/micron, and the current density is 3·5 ιηΑ/αη2 at % volt/micron. The fourth a diagram and the fourth diagram and the fifth diagram confirm that good electrophoretic deposition selectivity and field emission performance can be achieved by the electrophoretic deposition method of the field emission device according to the present invention. In another embodiment of the present invention, during electrophoretic deposition, a bias voltage is applied between the gate and the cathode, and the electric ice/child method of the field emission device in this embodiment includes the second map and the second The second beta diagram has the same steps and two different steps below. The sixth and sixth panels illustrate these two different steps, respectively. After passing through the steps of the second A and the drawings, the field emission cathode plate 202 is sunk into the electrophoresis tank 203 as shown in Fig. 6A. A bias voltage y2 of the power supply 604 is then applied to the gate 206 and the cathode 208 for a period of time to selectively deposit the nanostructure material 2〇9 on the surface of the cathode 208, the surface of which is through the dielectric layer 211. The gate hole 6〇8 is exposed to the outside. The other end of the power supply 604 is maintained at voltage % and is electrically connected to the gate 206 as shown in Figure 6B. The bias voltage % is usually a positive voltage with respect to the common voltage VG but is not limited to a positive voltage. During selective electrophoretic deposition, the charged or polarized nanostructure suspension 204 is attracted by the electric field formed by the electrical 15 1258807 difference between the gate 2〇6 and the cathode 208 via the gate hole 608, and Drifting toward the cathode 208 is deposited on the surface of the cathode 208. The electric field around the gate 206 repels the charged or polarized nanostructure suspension 204' in the electrophoresis bath to prevent nanostructure material from depositing on the gate 206. Therefore, the nanostructure material 209 is selectively deposited on the cathode 2〇8, and the short circuit between the cathode 208 and the gate 206 can be avoided. In summary, the present invention provides a method of electrophoretic deposition of a field emission device by selectively depositing a cathode having a gate structure of a gate electrode. It solves the electrical switching between the cathode and the gate by improving the selectivity of the electrophoretic deposition method. In addition, the present invention electrophoretic deposition method is carried out at a low temperature, and Ρ requires a sacrificial layer, so that the process is simple and the cost is reduced. The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto. That is to say, it is still within the scope of the patent of the present invention to apply to the thief and the modification of the patent application. 16 1258807 [Simple description of the diagram] The first figure is a schematic diagram illustrating the electrophoretic deposition of a conventional carbon nanotube field emitter. The second to second D diagrams illustrate the flow of steps of the electrophoretic deposition method of the field emission device according to the first embodiment of the present invention. The second figure is a schematic diagram of the distribution of the electric field in the electrophoresis tanks of the second A to the second d. Art Figure 4A is an enlarged plan view of a field emitter cross-type cathode plate prior to selective electrophoretic deposition in accordance with the present invention. Figure 4B is an enlarged plan view of a field emitter cross-type cathode plate after selective electrophoretic deposition in accordance with the present invention. The fourth C is an enlarged plan view of a field emitter parallel type cathode plate prior to selective electrophoretic deposition in accordance with the present invention. The fourth D is an enlarged plan view of a field emitter parallel type cathode plate after selective electrophoretic deposition according to the present invention. Fig. 5 is a graph showing the measurement results of the electric field emission current versus the applied voltage of the carbon nanotube field emitter according to the present invention. The sixth and sixth B diagrams illustrate the flow of steps of the electrophoretic deposition method of the field emission device according to another embodiment of the present invention. [Main component symbol description] 101 power supply 聋 _ 102 anode plate 17 1258807 103 cathode plate 104 electrophoresis tank 105 electrophoresis liquid 206 CNT particles 107 cathode 108 gate 109 dielectric layer 110 substrate 111 gate 201 anode plate 202 field emission cathode plate 203 Electrophoresis tank 204 nanostructure suspension 205 power supply 206 gate 207 power supply 208 cathode 209 nanostructure material 210 gate hole 211 dielectric layer 212 substrate 401 cathode line 402 gate line 18