1225658 玟、杳輕說::明 【發明所屬之技術領域】 本發明有關於離子源，使用在用以進行離子植入或離子 摻雜之裝置，在被導入有原料氣體之電漿產生容器內，具 有熱電子放出用之燈絲。實質上有關於用來抑制起因於原 料氣體所含之元素所導致的燈絲之劣化，藉以延長燈絲之 壽命之離子源。 【先前技術】 此種離子源之習知例和電源以圖3表示。上述之離子源 之構造是在被導入有原料氣體4之電漿產生容器2內，使 用二個之電流導入端子8，用來支持熱電子放出用之成爲 U字狀之燈絲1 2之端部1 2b。在各個電流導入端子8和上 述之電漿產生容器2之間，利用絕緣物1 0使其絕緣。在上 述之電漿產生容器2之開口部附近設有引出電極系1 4，利 用電場之作用，從電漿產生容器2內之電漿6中，將離子 射束1 6引出。燈絲1 2通常由高熔點金屬構成。例如由鎢 或鎢合金等之鎢系材料構成。 原料氣體4是包含作爲離子射束16之從離子源引出的 元素之氣體。例如所使用之氣體是包含有硼或硼之化合物 (亦即硼化物，例如B2H6，BF3之包含有硼者）之氣體。另 外，在本說明書中之「氣體」是包含蒸氣之廣義者。下面 說明該離子源之動作例。將原料氣體4導入到被排氣成爲 真空之電漿產生容器2內，同時利用燈絲電源1 8，使電流 在燈絲1 2流動，用來將燈絲1 2加熱成爲高溫，和在燈絲 5 312/發明說明書(補件)/92-07/92109457 1225658 1 2之一端和電漿產生容器2之間，施加來自電弧電源20 之電弧放電電壓。從燈絲1 2放出之熱電子，在朝向電漿產 生容器2加速之期間，形成與原料氣體4碰撞。被上述之 熱電子碰撞之原料氣體進行電離，用來在電漿產生容器2 內產生原料氣體4之電漿6。然後，利用上述之引出電極 系14，從上述之電漿6中，將離子射束16引出。原料氣 體4爲硼或硼之化合物時，就引出含有硼之離子射束16。 在上述之離子源中，隨著其運轉（亦即隨著電漿6之產 生），在（a)各個電流導入端子8之與電漿6接觸之接觸部 份，和（b)燈絲1 2之電流導入端子8之支持部近傍，如圖 3所示之實例之方式，堆積著構成原料氣體4之元素5(例 如硼）。該被堆積之元素5其大部份爲固相。在燈絲側之前 端部份，上述之被堆積之元素5爲液相。 下面以硼作爲上述之元素5爲例進行詳述。燈絲1 2之 熱通過電流導入端子8進行散熱。因此，在燈絲1 2之前端 附近12a之溫度成爲最高（例如3000 °C以上），從該處起朝 向兩個電流導入端子8溫度逐漸降低，存在有溫度梯度。 另外，在燈絲1 2之電流導入端子8之支持部近傍，存在有 部份13其溫度使構成原料氣體4之硼（5)以液相存在。在 該部份13成爲硼之熔點（208 0°C )附近之溫度。比起該部份 1 3的燈絲之更前端側的溫度則高於硼之熔點。特別是在燈 絲之前端附近1 2 a，因爲成爲遠高於硼之熔點溫度，所以 不能堆積硼。當在此燈絲1 2之電流導入端子8之支持部近 傍且比上述部份1 3更靠近電流導入端子8側，因爲其溫度 6 312/發明說明書(補件)/92-07/92109457 1225658 低於硼之熔點，所以以固相堆積硼。 而在上述之部份1 3，則該硼成爲液相。上述之液相的硼 浸透（換言之爲侵入）到燈絲1 2的組織內，會使燈絲1 2劣 化。因此，會使燈絲1 2之壽命變短。另外，比上述之部份 1 3更靠近電流導入端子8側之部份，以固相堆積硼。因此， 硼不會朝向燈絲1 2浸透而使燈絲劣化。液相之硼附著在燈 絲是本發明所欲解決之問題。如上述之方式，構成原料氣 體4之元素5會以液相附著在燈絲1 2，因而使元素5浸透 到燈絲1 2之組織內。因此有使燈絲1 2劣化之問題，當以 硼作爲上述之元素5，燈絲1 2之材料使用鎢系材料的組合 之情況時，其問題特別大，而且在其以外之組合的情況時， 亦會有此種問題存在。 【發明內容】 本發明之目的是經由抑制原料氣體所含之元素的浸透 到燈絲之組織內，用來延長燈絲之壽命。 本發明之離子源具備覆蓋構件，其爲上述燈絲之一部 份’其特徵是該覆蓋構件，形成與燈絲之間具有間隙，用 來至少包圍某部份之周圍，該部份之溫度使構成上述原料 氣體之元素以液相存在。 原料氣體是例如包含硼之氣體。在該情況上述之原料氣 體所含的元素爲硼。燈絲由例如鎢系材料構成。 依照上述之構造時，對於具有溫度使構成原料氣體之元 素（例如硼）以液相存在之部份的周圍，因爲至少被覆蓋構 件包圍，所以該覆蓋構件成爲障礙，在電漿產生容器內產 7 312/發明說明書(補件)/92-07/92109457 1225658 生的電漿中之上述元素’難以到達成爲上述液相溫度之部 份，難以附著在該處。其結果是可以減少以液相附著在燈 絲之上述元素，所以可以抑制該元素浸透到燈絲之組織內 而使燈絲劣化，可以延長燈絲之壽命。 【實施方式】 圖1是槪略剖面圖，用來表示本發明之離子源的一實例 和電源。 在與圖3所示之習知例相同或相當之部份附加相同的元 件符號。下面主要的說明與該習知例不同之部份。在此處 所舉例說明之情況主要的是使原料氣體4成爲包含有上述 方式之硼的氣體，燈絲1 2由上述方式之鎢系材料構成。 在該離子源其備有燈絲1 2，以電流導入端子8分別支持 上述燈絲1 2之兩個端部1 2b，在從各個電流導入端子8之 前端，到部份1 3 (圖中之以圓形包圍之部份）和比其稍前之 部份，其溫度將成爲可以使該前端近傍之構成原料氣體4 之元素（硼）5以液相存在的溫度（換言之成爲硼之熔點附近 的溫度），另外該離子源具有二個之覆蓋構件22，與該燈 絲1 2之間具有間隙，分別包圍該燈絲。在本實例中，使各 個覆蓋構件22不只包圍上述部份13之周圍，而且成爲上 述之較長的構造，其理由將於後面說明。 各個覆蓋構件22，與燈絲1 2之間具有間隙，而且包圍 該燈絲1 2之理由是假如各個覆蓋構件22緊接著燈絲1 2 時，則將通過該覆蓋構件22，燈絲12之熱進行散熱，所 以與單純地延長各個電流導入端子8之情形沒有很大之差 312/發明說明書(補件)/92-07/92109457 1225658 別’上述之部份1 3朝向各個覆蓋構件22之前端的更前方 移動’要以覆蓋構件2 2包圍該部份1 3變爲困難。 各個覆蓋構件22爲筒狀，在具體例中爲圓筒狀。各個 覆蓋構件22之材質使用可以耐燈絲1 2之加熱者。例如， 各個覆蓋構件22最好利用具有熔點高於加熱時之燈絲1 2 的最高溫度之高熔點金屬形成。其一實例是使用鉅。另外， 亦可以以陶瓷等之絕緣物形成。各個覆蓋構件2 2可以使用 導電物製，亦可以使用絕緣物製。 依照該離子源時，至少部份13之周圍被覆蓋構件22包 圍，該部份13之溫度會使構成原料氣體4之硼（5)以液相 存在。因此，該覆蓋構件22成爲障礙，在電漿產生容器2 內產生的電漿6中之硼，難以到達成爲上述之液相溫度的 部份1 3，變成難以附著在該處。其結果是以液相附著燈絲 1 2之硼可以顯著的減少。 對此進行詳述時，電漿6中之硼（5)如圖1所示，在各個 電流導入端子8與電漿6之接觸部份，和各個覆蓋構件22 外面，因爲溫度低，所以以固相進行堆積。但是，在各個 覆蓋構件22中，因爲只有通過與燈絲1 2間之間隙的路徑， 所以電漿6中之硼難以進入。另外，在覆蓋構件22深處之 上述部份1 3，硼大致完全不會到達。因此，覆蓋構件22 不只在上述部份13之周圍，而且最好如本實施例之方式， 具有比上述部份1 3某種程度之包圍到前端部份之長度。另 外，覆蓋構件22之內壁和燈絲間之間隙最好成爲例如 1〜2 m m之程度。 9 312/發明說明書(補件)/92-07/92109457 1225658 另外，各個電流導入端子8之前端和覆蓋構件22之間 亦可以分離，而且如此一來因爲通過兩者8、22間之空間， 硼成爲易於到達上述部份1 3，所以如本實施例之方式，連 接兩者8、22，最好在兩者8、22間不產生空間。而且成 爲此種方式時，因爲可以利用各個電流導入端子8用來支 持各個覆蓋構件22，所以各個覆蓋構件22之支持變爲容 •易。 在該離子源中，利用上述方式之作用，可以減少以液相 附著在燈絲1 2之硼。因此，可以抑制該硼浸透到燈絲1 2 之組織內造成之燈絲1 2的劣化，可以用來延長燈絲1 2之 壽命。其結果是離子源之保養循環週期可以延長，和可以 提高離子源之性能的穩定性。另外，可以減低使用有該離 子源之離子植入和離子摻雜用裝置等之運轉成本，和可以 提高性能的穩定性。 圖2擴大的表示圖1中之覆蓋構件22附近之具體例。 在該實例中，在電流導入端子8之前端部形成有突起部9 用來夾緊和保持燈絲1 2之端部1 2b，在其外周部形成有陽 螺紋。符號9 a是縫隙（割縫）。使用來以螺紋結合在該突起 部9藉以固定燈絲1 2的螺帽部24 ;和圓筒狀之上述覆蓋 構件22 —體成形。 電流導入端子8(包含突起部9)之材質使用鉬，覆蓋構件 22和螺帽24之材質使用鉅，燈絲1 2之材質使用鎢。突起 部9和螺帽24使用不同種之金屬可以防止熔執（seizure)。 所使用之原料氣體4例如成爲包含有B2H6、BF3等之硼化 10 312/發明說明書(補件)/92-07/92109457 1225658 物之氣體。 在此實例之情況，部份13(其溫度使硼以液相存在）之中 心和突起部9之前端之間之距離L1，大約爲2mm。但是， 該距離L 1由於燈絲1 2之加熱溫度和支持構造等之不同， 可以成爲2 mm左右。覆蓋構件22之長度大約爲15 mm。更 嚴密的說，從突起部9之前端到覆蓋構件22之前端間之距 離L2大約爲15mm。但是該距離L2亦可以成爲 10mm〜2Omm之程度。燈絲12之直徑D1爲1mm。覆蓋構 件2之內徑D2爲4mm，但是亦可以成爲3mm之程度。 習知之離子源未具有此種方式之覆蓋構件22，該種情況 之至燈絲12夭折（或截止）之壽命大約爲30〜50小時。與此 相對的，在設有圖2所示之覆蓋構件22的本發明之離子源 中，燈絲12之壽命大約爲3 00小時，成爲習知者之5〜10 倍，燈絲1 2之壽命顯著的延長。 另外，原料氣體4之種類和燈絲1 2之材質性亦可以使 用上述實例以外者。另外，燈絲1 2之形狀亦可以使用上述 實例以外者。例如，亦可以使用以電流導入端子8分別支 持直線狀之燈絲1 2之兩個端部之構造等。依照上述方式之 本發明時，因爲具備有上述方式之覆蓋構件，所以可以抑 制構成原料氣體之元素浸透到燈絲之組織內因而使燈絲劣 化，可以延長燈絲之壽命。 【圖式簡單說明】 圖1爲槪略剖面圖，用來表示本發明之離子源的一實例 和電源。 11 312/發明說明書(補件)/92-07/92109457 1225658 圖2爲擴大的表示圖1中之覆蓋構件22附近之具體例。 圖3爲表示離子源之習知例和電源。 (元件 符號說明） 2 電 漿 產 生 容 器 4 原 料 氣 體 5 元 素 6 電 漿 8 電 流 導 入 端 子 9 突 起 部 9a 縫 隙 10 絕 緣 物 12 燈 絲 12a 燈 絲 Λ.人 刖 端 附 近 12b 燈 絲 端 部 13 部 份 14 引 出 電 極 系 16 離 子 射 束 18 燈 絲 電 弧 20 電 弧 電 源 22 覆 蓋 構 件 24 螺 帽 LI 突 起 部 至 部 份1 3的距離 L2 突 起 部 至 覆 蓋構件之前端的距離 D 1 燈 絲 之 直 徑 312/發明說明書(補件)/92-07/921094571225658 玟, 杳 Qing said: Ming [Technical Field of the Invention] The present invention relates to an ion source, which is used in a device for ion implantation or ion doping, in a plasma generation container into which a source gas is introduced With a filament for thermionic emission. Essentially, the ion source is used to suppress the deterioration of the filament caused by the elements contained in the raw material gas, thereby extending the life of the filament. [Prior Art] A conventional example and power source of such an ion source are shown in FIG. 3. The structure of the above-mentioned ion source is that in the plasma generating container 2 into which the raw material gas 4 is introduced, two current introduction terminals 8 are used to support the ends of the U-shaped filament 12 for thermionic emission. 1 2b. Between each of the current introduction terminals 8 and the above-mentioned plasma generating container 2, they are insulated by an insulator 10. An extraction electrode system 14 is provided near the opening of the plasma generating container 2 described above, and an ion beam 16 is extracted from the plasma 6 in the plasma generating container 2 by using an electric field. The filament 12 is usually composed of a high melting point metal. For example, it is made of a tungsten-based material such as tungsten or a tungsten alloy. The source gas 4 is a gas containing an element extracted from an ion source as the ion beam 16. For example, the gas used is a gas containing boron or a compound of boron (that is, a boride, such as B2H6, BF3 containing boron). In addition, "gas" in this specification is a broad term including vapor. An operation example of the ion source will be described below. The raw material gas 4 is introduced into the plasma generating container 2 which is exhausted into a vacuum. At the same time, a filament power source 18 is used to cause a current to flow in the filament 12 to heat the filament 12 to a high temperature, and the filament 5 312 / Invention Specification (Supplement) / 92-07 / 92109457 1225658 1 Between the one end and the plasma generating container 2, an arc discharge voltage from an arc power source 20 is applied. The thermoelectrons emitted from the filaments 12 collide with the source gas 4 while accelerating toward the plasma generating container 2. The raw material gas collided by the above-mentioned thermionic electrons is ionized to generate the plasma 6 of the raw material gas 4 in the plasma generating container 2. Then, the ion beam 16 is extracted from the plasma 6 using the extraction electrode system 14 described above. When the source gas 4 is boron or a compound of boron, an ion beam 16 containing boron is extracted. In the above-mentioned ion source, with its operation (that is, with the generation of the plasma 6), in (a) the contact portions of each current introduction terminal 8 in contact with the plasma 6, and (b) the filament 1 2 The element 5 (for example, boron) constituting the source gas 4 is deposited near the support portion of the current introduction terminal 8 as shown in the example shown in FIG. 3. Most of the stacked elements 5 are in a solid phase. At the front end portion of the filament side, the above-mentioned stacked element 5 is in a liquid phase. In the following, boron is used as the above-mentioned element 5 as an example for detailed description. The heat of the filament 12 is radiated through the current introduction terminal 8. Therefore, the temperature of 12a near the front end of the filament 12 becomes the highest (for example, 3000 ° C or more), and the temperature gradually decreases toward the two current introduction terminals 8 from there, and there is a temperature gradient. In addition, near the support portion of the current introduction terminal 8 of the filament 12, there is a portion 13 whose temperature causes the boron (5) constituting the source gas 4 to exist in a liquid phase. The temperature at this portion 13 is near the melting point (2080 ° C) of boron. The temperature on the front end side of the filament compared to this part 13 is higher than the melting point of boron. Especially, 1 2 a near the front end of the filament, because it is much higher than the melting point of boron, boron cannot be deposited. When the support part of the current introduction terminal 8 of the filament 12 is near and closer to the current introduction terminal 8 side than the part 13 above, because its temperature is 6 312 / Instruction Manual (Supplement) / 92-07 / 92109457 1225658 is low At the melting point of boron, boron is deposited in a solid phase. In the above-mentioned part 1 3, the boron becomes a liquid phase. The above-mentioned liquid phase of boron penetrates (in other words, penetrates) into the tissue of the filament 12 and deteriorates the filament 12. Therefore, the life of the filament 12 is shortened. In addition, a portion closer to the current introduction terminal 8 side than the above-mentioned portion 1 3 is used to deposit boron in a solid phase. Therefore, boron does not penetrate the filament 12 and the filament is not deteriorated. The adhesion of boron in the liquid phase to the filament is a problem to be solved by the present invention. As described above, the element 5 constituting the raw material gas 4 is adhered to the filament 12 in a liquid phase, so that the element 5 penetrates into the structure of the filament 12. Therefore, there is a problem that the filament 12 is deteriorated. When boron is used as the above-mentioned element 5 and the material of the filament 12 is a combination of tungsten-based materials, the problem is particularly large, and when it is combined with other materials, There will be such problems. [Summary of the Invention] The purpose of the present invention is to extend the life of a filament by suppressing the penetration of elements contained in the raw material gas into the tissue of the filament. The ion source of the present invention is provided with a covering member, which is a part of the filament described above. The feature is that the covering member is formed with a gap between the covering member and the filament to surround at least a portion of the filament. Elements of the above-mentioned source gas exist in a liquid phase. The source gas is, for example, a gas containing boron. In this case, the element contained in the above-mentioned raw material gas is boron. The filament is made of, for example, a tungsten-based material. According to the above-mentioned structure, the surroundings of a part having a temperature such that elements (such as boron) constituting the raw material gas exist in a liquid phase are surrounded by at least a covering member, so that the covering member becomes an obstacle and is produced in a plasma generating container. 7 312 / Invention Specification (Supplement) / 92-07 / 92109457 1225658 The above-mentioned element 'in the plasma produced by it is difficult to reach the part that becomes the liquid phase temperature mentioned above, and it is difficult to adhere to it. As a result, it is possible to reduce the above-mentioned elements adhering to the filament in a liquid phase, so that it is possible to suppress the element from penetrating into the filament structure to degrade the filament, and to prolong the filament life. [Embodiment] Fig. 1 is a schematic sectional view showing an example of an ion source and a power source of the present invention. The same components as those of the conventional example shown in FIG. 3 are assigned the same reference numerals. The main explanation below differs from this conventional example. The case exemplified here is mainly that the source gas 4 is a gas containing boron of the above-mentioned method, and the filament 12 is made of the tungsten-based material of the above-mentioned method. The ion source is provided with a filament 12 and the current introduction terminals 8 respectively support the two ends 1 2b of the filament 12 above. From the front end of each current introduction terminal 8 to the portion 13 (shown in the figure) The part surrounded by the circle) and the part before it, its temperature will become the temperature at which the element (boron) 5 constituting the raw material gas 4 near the front end exists in the liquid phase (in other words, it is near the melting point of boron). Temperature), in addition, the ion source has two covering members 22, and a gap is formed between the ion source and the filament 12 to surround the filament, respectively. In this example, each of the covering members 22 not only surrounds the periphery of the above-mentioned portion 13, but also has a relatively long structure as described above. The reason will be described later. Each covering member 22 has a gap with the filament 12 and the reason for surrounding the filament 12 is that if each covering member 22 is next to the filament 12, the heat from the covering member 22 and the filament 12 will be radiated, Therefore, it is not much different from the case of simply extending each current introduction terminal 8 312 / Invention Specification (Supplement) / 92-07 / 92109457 1225658 Don't move the above part 1 3 toward the front end of each covering member 22 'It becomes difficult to surround the portion 1 3 with the cover member 2 2. Each covering member 22 has a cylindrical shape, and is a cylindrical shape in a specific example. The material of each covering member 22 is a material that can withstand the heating of the filament 12. For example, each covering member 22 is preferably formed of a high-melting-point metal having a melting point higher than the highest temperature of the filament 12 during heating. One example is the use of giants. Alternatively, it may be formed of an insulator such as ceramic. Each of the covering members 22 may be made of a conductive material or may be made of an insulating material. According to the ion source, at least the portion 13 is surrounded by the covering member 22, and the temperature of the portion 13 causes the boron (5) constituting the raw material gas 4 to exist in the liquid phase. Therefore, the covering member 22 becomes an obstacle, and it is difficult for boron in the plasma 6 generated in the plasma generating container 2 to reach the portion 13 which becomes the above-mentioned liquidus temperature, and it becomes difficult to adhere there. As a result, the boron attached to the filament 12 in the liquid phase can be significantly reduced. In detail, the boron (5) in the plasma 6 is shown in FIG. 1. At the contact portions between the current introduction terminals 8 and the plasma 6 and outside the covering members 22, the temperature is low, so The solid phase was deposited. However, in each covering member 22, since there is only a path through the gap with the filament 12, it is difficult for boron in the plasma 6 to enter. In addition, in the above-mentioned portion 13 deep in the covering member 22, boron hardly reaches at all. Therefore, the covering member 22 is not only around the above-mentioned portion 13, but preferably has a length that surrounds the front end portion to a certain extent than the above-mentioned portion 13 as in the embodiment. The gap between the inner wall of the covering member 22 and the filament is preferably about 1 to 2 mm, for example. 9 312 / Invention Specification (Supplement) / 92-07 / 92109457 1225658 In addition, the front end of each current introduction terminal 8 and the cover member 22 can also be separated, and because of this, because of the space between the two 8, 8 Boron becomes easy to reach the above-mentioned part 1 3, so as in the embodiment, it is preferable to connect the two 8, 22, and it is better not to create a space between the two 8, 22. Moreover, in this method, since each current introduction terminal 8 can be used to support each covering member 22, the support of each covering member 22 becomes easy. In this ion source, the effect of the above-mentioned method can reduce boron that is attached to the filament 12 in the liquid phase. Therefore, the deterioration of the filament 12 caused by the penetration of the boron into the structure of the filament 12 can be suppressed, and the life of the filament 12 can be extended. As a result, the maintenance cycle of the ion source can be extended, and the performance stability of the ion source can be improved. In addition, it is possible to reduce the running cost of using the ion implantation and ion doping device and the like, and to improve performance stability. FIG. 2 shows an enlarged specific example of the vicinity of the covering member 22 in FIG. 1. In this example, a protruding portion 9 is formed at an end portion before the current introduction terminal 8 for clamping and holding the end portion 12b of the filament 12, and a male screw is formed at an outer peripheral portion thereof. The symbol 9a is a gap (slit). A nut portion 24 for screwing the protruding portion 9 to fix the filament 12; and the cylindrical covering member 22 are integrally formed. The material of the current introduction terminal 8 (including the protruding portion 9) is molybdenum, the material of the covering member 22 and the nut 24 is giant, and the material of the filament 12 is tungsten. The protrusion 9 and the nut 24 use different metals to prevent seizure. The raw material gas 4 used is, for example, a gas containing boronated compounds such as B2H6, BF3, etc. 10 312 / Invention Specification (Supplement) / 92-07 / 92109457 1225658. In the case of this example, the distance L1 between the center of the portion 13 whose temperature causes boron to exist in the liquid phase and the front end of the protrusion 9 is approximately 2 mm. However, the distance L 1 may be about 2 mm due to the heating temperature of the filament 12 and the supporting structure. The length of the covering member 22 is approximately 15 mm. More strictly, the distance L2 from the front end of the protruding portion 9 to the front end of the covering member 22 is about 15 mm. However, the distance L2 may be about 10 mm to 20 mm. The diameter D1 of the filament 12 is 1 mm. The inner diameter D2 of the covering member 2 is 4 mm, but may be about 3 mm. The conventional ion source does not have the covering member 22 in this way. In this case, the life span of the filament 12 to the breakage (or cutoff) is about 30 to 50 hours. In contrast, in the ion source of the present invention provided with the covering member 22 shown in FIG. 2, the life of the filament 12 is about 300 hours, which is 5 to 10 times that of a conventional person, and the life of the filament 12 is remarkable. Extension. In addition, the type of the raw material gas 4 and the material properties of the filament 12 may be other than the above examples. In addition, the shape of the filament 12 can be other than the above examples. For example, a structure in which both ends of the linear filament 12 are supported by the current introduction terminal 8 may be used, for example. When the present invention according to the above-mentioned aspect is provided with the covering member of the above-mentioned aspect, it is possible to suppress the element constituting the raw material gas from penetrating into the filament structure, thereby deteriorating the filament, and extending the filament life. [Brief description of the drawings] Fig. 1 is a schematic sectional view showing an example of an ion source and a power source of the present invention. 11 312 / Invention Specification (Supplement) / 92-07 / 92109457 1225658 Fig. 2 is an enlarged specific example showing the vicinity of the covering member 22 in Fig. 1. Fig. 3 shows a conventional example of an ion source and a power source. (Explanation of component symbols) 2 Plasma generation container 4 Raw material gas 5 Element 6 Plasma 8 Current introduction terminal 9 Protrusion 9a Gap 10 Insulator 12 Filament 12a Filament Λ. Near the end of the mandible 12b Filament end 13 Part 14 Lead-out electrode Department 16 Ion beam 18 Filament arc 20 Arc power source 22 Cover member 24 Distance from nut LI projection to part 13 L2 Distance from projection to front end of cover member D 1 Diameter of filament 312 / Invention specification (Supplement) / 92-07 / 92109457
12 1225658 D2 覆蓋構件之內徑12 1225658 D2 Inner diameter of cover member
312/發明說明書(補件)/92-07/92109457 13312 / Invention Specification (Supplement) / 92-07 / 92109457 13