經濟部智慧財產局員工消費合作社印製Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs
4 3 63 6 S 6〇〇ltwf.d〇c/006 A7 B7 -------- ------ 五、發明說明（/) 本發明是有關於一種終點偵測（end p〇int detecti⑽) 的方法，旦特別是有關於一種化擧機械硏磨（Chemical mechanical polishing, CMP)終點f貞測的方法。 目前半導體製造爲因應電子器材的工作速度，已進入 至深次微米（deeP sub-micro)的製程，而在此製程中’因 晶片尺寸的縮小，微影儀器的景深越來越小，以及金屬內 連線層數的增加，晶片在製作過程如何維持良好的平坦 度，已經是一個重要的課題。 在化學機械硏磨製程中，除了要使晶片能夠達到平坦 化的目的’如何精確地控制薄膜硏磨後的厚度，也是化學 機械硏磨製程中極需要注意的課題。目前化學機械硏磨製 程最常使用來控制薄膜硏磨程度的方法有兩種，分別爲時 間控制模式（t ime-com rolling mode)， 以及終點i貞測控 制模式。 所謂的時間控制模式，乃是利用化學機械硏磨機台對 晶片硏磨的速率，推算出硏磨晶片所需要的時間，再以此 硏磨時間作爲晶片硏磨的控制依據，只要硏磨製程開始， 晶片就必須經歷上述方法計算出的時間，也就是必須經歷 固定的硏磨時間才能停止硏磨，但薄膜硏磨程度是否巳達 製程要求’就必須從晶片硏磨後，量測其厚度加以判斷， 因此無法馬上判斷出硏磨是否真正達到終點。 一般而言’由於時間控制模式中的硏磨時間被設定爲 固定’因此對製程而言是較無彈性的，一旦晶片在此硏磨 製程前的某一個或某幾個製程控制不佳，欲被硏磨掉的材 3 本紙張尺度適用中國國家標準(CNS)A伐格⑵G X M7 — — — — — ΊΙΙΙ — F - ----- —II ^ 1111.1111 (請先閱讀背面之注意事項再填寫本頁) 經濟部智慧財產局員工消費合作社印製 436368 SOOltwf.doc/006 A7 -- B7 五、發明說明（l) 料厚度比預定的厚度增加或減少，利用時間控制模式會造 成硏磨去除的厚度不夠，必須再進行補硏磨的動作，或是 造成薄膜被硏磨掉的厚度過多，變成的嚴重的過度硏磨 (over p〇llsh)，而造成晶片報廢的結果。 因此，在目前的化學機械硏磨製程中，時間控制模式 通常不被用來控制晶片硏磨厚度的主要硏磨階段（main polish step)，而是以較能夠控制晶片硏磨程度的終點偵 測控制模式。所謂的終點偵測控制模式，就是在硏磨過程 中，工程師針對具有某種圖案（pattern)與某種薄膜的晶 片，收集其隨硏磨時間所展現的訊號等，例如薄膜所發出 的光學訊號、電性訊號強度或溫度變化的情形，對具有相 同圖形與相同薄膜的晶片而言，在相同的製程條件下，會 得到相似的硏磨時間與訊號的關係曲線。 再參照此硏磨時間與訊號強度所繪出的曲線圖，便可 設定控制硏磨停止的條件，以作爲其他同樣具有此種圖形 與薄膜的晶片硏磨的控制依據。由於終點偵測控制模式是 以訊號作爲硏磨是否繼續或停止的依據1而不被硏磨時間 所限制，因此製程彈性較大，同時也因爲利用訊號來反應 硏磨情形，所以提高了化學機械硏磨製程的再現性能力， □前一般的硏磨技術大多採用終點偵測控制模式來控制化 學機械硏磨的主要硏磨階段。 而一般在主要硏磨階段之後，會再進行一道過度硏磨 (ove r - po 1 1 sh)的步驟，S的在確保欲被磨的材料可以完 全被硏磨乾淨。因爲在主要硏磨階段’目的在於短時間內 4 本紙張尺度適用中囷國家標準（CNSM4規格（210 X 297公釐） -----------^於·-------訂----^------線 {請先閲讀背面之注意事項再填寫本頁) 436368 βOOltwf . doc / 006 五、發明說明（彡） 將大部分的欲被硏磨的材料去除掉，因此其硏磨參數用以 提供高的硏磨速率，一旦暴露出不同材料的交界，主要硏 磨階段就會停止，此時仍會有部分殘留，故需要進行過度 硏磨。習知在主要硏磨階段停止後，將再次啓動化學機械 硏磨機台，利用與主要硏磨階段相同的參數進行過度硏 磨，此時利用具有高硏磨速率的參數進行過度硏磨，常會 造成晶片表面的凹陷13 有鑑於此，本發明提供一種化學機械硏磨法終點偵測 的方法，在利用終點偵測方法進行主要硏磨階段以後，改 變硏磨的參數，例如提高晶圓承載器（earner)與硏磨台 (t a b 1 e)的轉速，降低硏磨時施加的壓力，以改變後的參 數進行過度硏磨步驟，改變後的參數可以降低化學性的硏 磨效果，而提供一個較大的切削能力，如此在進行過度硏 磨步驟時，可以改善硏漿與欲被硏磨材質反應軟化的情 況，且較大的切削能力可以迅速的將殘留的欲被硏磨材料 完全移除。 以鎢金屬插塞的硏磨爲例，在介電層中具有開口，介 電層上與開口中依序塡有一層共形的阻障層以及鎢金屬 層，進行化學機械硏磨去除開口以外的鎢金屬層，在硏磨 時，阻障層可作爲硏磨阻擋層，當硏磨至暴露出阻障層時， 即停止主要硏磨階段，之後改變硏磨參數，進行過度硏磨 以完全去除包括阻障層上方的金屬層以及阻障層，利用不 同參數進行兩階段的化學機械硏磨，以增加化學機械硏磨 製程的窗口。 (請先閲讀背面之注意事項再填寫本頁) -ίν.-------訂.---Γ-----線— 經濟部智慧財產局員工消費合作社印製 本紙張尺度適用中國國家標準（CNSM4規格（210 X 297公釐） 經濟部智慧財產局員工消費合作杜印製 43 636 8 6001twf-doc/006 A7 _B7_ 五、發明說明（t) 爲讓本發明之上述目的、特徵、和優點能更明顯易懂， 下文特舉一較佳實施例，並配合所附圖式，作詳細說明如 下： 圖式之簡單說明： 第1圖繪示依照本發明一較佳實施例的一種化學機械 硏磨終點偵測的步驟流程圖。 實施例 在化學機械硏磨的平坦化製程中，多利用兩階段的硏 磨來製作金屬內連線結構，例如雙重金屬鑲嵌結構，或是 塡充於介電層中的金屬插塞，藉以使製作的半導體元件具 有較好的物理性質與較佳的電性。 此兩階段硏磨步驟的分界是由終點偵測訊號決定，進 行兩階段硏磨的目的在於，利用終點偵測的方法對於沈積 膜的厚度改變調整硏磨進行的時間。 在製作金屬內連線結構時，金屬層與介電層之間通常 會有一層阻障層（ba r r 1 e r 1 aye r)或是阻擋層（s t op ]ayer) ’像是氮化鈦（TiN)或是氮化矽（SiN)，終點偵測控 制模式的目的就在於決定第一階段的主要硏磨階段進行的 時間，當阻障層暴露出來時，偵測器測到材料介面改變就 判定硏磨已達終點。可用於判斷材料介面改變的訊號比如 薄膜的反射係數、發出的光學訊號、電性訊號強度、摩擦 力、材料的化學特性、或溫度變化等。 當偵測到硏磨已達金屬層與阻障層之界面時，並不代 表阻障層上方之金屬層已完全被去除，因此在主要硏磨階 6 本紙張&度適用中囤國家標準（CNS)A4規格（210^ 297公餐) ----------- 叙--------訂----^„—線— (請先閱讀背面之注意事項再填寫本頁) 436368 6001twf.d〇c/006 _B7_ 五、發明說明（Γ) 段停止以後，必須再進行一道過度硏磨步驟，以確保ζ障 層上方的金屬層已完全被去除。然而不當的過度硏磨不僅 會磨去剩餘之金屬層及阻障層，且更進一步硏磨到阻障層 下方的介電層，由於介電材料與金屬材料的差異，介電層 可能會被迅速的移除，反而會造成表面的不平坦，比如凹 陷（dishing)或局部的腐鈾（erosion)。 在本發明中，利用兩組不同的參數進行主要硏磨階段 與過度硏磨階段，參數的改變就利用終點偵測訊號來進 行。 舉例來說，進行鎢的化學機械硏磨時，其終點偵測的 步驟流程如第1圖所示。在步驟100中，將欲進行硏磨的 晶片放置在化學機械硏磨機台上，開始化學機械硏磨的主 要硏磨階段，此階段所用的參數包括60 rpm的承載器轉 速、65 rpm的硏磨台轉速、而承載器向下對於硏磨墊施加 的壓力爲33〜37 kPa。 在步驟102中，當大部分的鎢金屬被硏磨掉，而暴露 出下方的阻擋層時，就判斷硏磨已達終點，停止主要硏磨 階段。然後在步驟104中，改變化學機械硏磨的參數，改 變後的參數包括75 rpni的承載器轉速、80 ι·ρηι的硏磨台 轉速、而承載器向下對於硏磨墊施加的壓力爲19〜23 kPa。 在步驟106中，利用改變後的參數進行過度硏磨步驟， 鎢金屬的厚度約爲4000A，過度硏磨的時間約爲45-60秒， 而在步驟108中終止化學機械硏磨製程。 習知在主要硏磨階段之後，同樣會再進行一道過度硏 7 本紙張尺度適用中國國家標準（CNSM4規格（210x297公釐） (請先閱讀背面之a意事項再填寫本頁) y 裝·-------訂----1--.---線 _ 經濟部智慧財農局員工消費合作社印制衣 436368 6001twf.doc/006 Δ7 B7 經濟部智慧財產局員工消費合作社印5λ 五、發明說明（έ) 磨步驟，目的在確保欲被磨的材料可以完全被硏磨乾淨’ 但是習知的過度硏磨步驟所用之參數仍是沿襲主要硏磨階 段之參數，僅是將過度硏磨步驟的控制改爲時間控制法， 而非終點偵測法。 由於在主要硏磨階段，目的在於短時間內將大部分的 欲被硏磨的材料去除掉，因此其硏磨參數用以提供高的硏 磨速率，一旦暴露出不同材料的交界，主要硏磨階段就會 停止，此時仍會有部分殘留，故需要進行過度硏磨。習知 在主要硏磨階段停止後，將再次啓動化學機械硏磨機台， 利用與主要硏磨階段相同的參數進行過度硏磨，此時利用 具有高硏磨速率的參數進行過度硏磨，常會造成晶片表面 的凹陷。 而本發明於實施例中說明的兩階段化學機械硏磨是採 用不同的參數進行，參數轉換的開始由終點偵測訊號決 定，在主要硏磨階段中，施加較大的壓力以產生較高的機 械硏磨力，承載器與硏磨墊之間會因此具有較大的摩擦 力’一旦硏磨至材料界面時，摩擦力的改變會較大，藉以 得到較強且較穩定的終點偵測訊號，而且較人的壓力會增 進硏漿與被硏磨物之間的化學反應，而具有較大的硏磨速 率’因此可以很快的完成主要硏磨階段。 接續的過度硏磨階段，利用較小的機械硏磨力避免因 爲化學性反應而造成介電層表面的凹陷或侵蝕現象，而利 用章父商的承載器轉速與硏磨台轉速，以對硏磨物表面產生 -個較大的切削作用，以達到平坦的表面。由於在此步驟 8 本紙張尺度適用中阄國家標準（CNS)A4規格（210 χ 297公釐） ------ Μ--------訂----. I BE I (請先閱讀背面之注意事項再填寫本頁) 436368 6001twf.doc/006 ^ _B7_ 五、發明說明（7 ) 中，向下壓力較小，硏漿與被硏磨物之間的化學反應較緩 和，因此向下硏磨的速率會較主要硏磨階段慢，故可以改 善介電層表面凹陷或腐蝕的現象，增加化學機械硏磨製程 的窗口。 此外，本發明在實施例中雖然以鎢金屬作爲被硏磨的 材料，所用之製程參數均根據厚度爲4000A之鎢金屬設 定，然而本發明提供之方法並不只限於硏磨鎢金屬，也可 以硏磨其他材質，比如銅，而當用於硏磨其他材料時，所 採用的硏漿成分，與製程參數數値均會有變化，但主要的 重點在於主要硏磨階段的向下壓力大於過度硏磨步騾，而 主要硏磨階段承載器與硏磨台的轉速要小於過度硏磨步 驟。 雖然本發明已以一較佳實施例揭露如上，然其並非用 以限定本發明，任何熟習此技藝者，在不脫離本發明之精 神和範圍內，當可作各種之更動與潤飾，因此本發明之保 護範圍當視後附之申請專利範圍所界定者爲準。 ------^---- 裝·-------訂·------.---I (請先閱讀背面之注意事項再填寫本頁) 經濟部智慧財產局員工消費合作社印製 9 本紙張尺度適用中國國家標準（CI\’S)A4規格（210 X 297公釐）4 3 63 6 S 6〇〇ltwf.d〇c / 006 A7 B7 -------- ------ V. Description of the invention (/) The present invention relates to an end point detection (end p 〇int detecti⑽) method, in particular, a method of chemical mechanical polishing (CMP) end point f. At present, semiconductor manufacturing has entered the process of deeP sub-micro in response to the working speed of electronic equipment. In this process, 'the depth of field of lithography equipment is getting smaller and smaller due to the shrinking of the chip size, and metal With the increase in the number of interconnect lines, how to maintain good flatness of the chip during the fabrication process has become an important issue. In the chemical mechanical honing process, in addition to the purpose of flattening the wafer ', how to accurately control the thickness of the thin film after honing is also a topic that requires great attention in the chemical mechanical honing process. At present, there are two methods most commonly used in the chemical mechanical honing process to control the honing degree of the thin film, which are time-com rolling mode and end-point measurement control mode. The so-called time control mode is to use the rate of honing the wafer by the chemical mechanical honing machine to calculate the time required for honing the wafer, and then use the honing time as the basis for wafer honing control, as long as the honing process From the beginning, the wafer must go through the time calculated by the above method, that is, it must go through a fixed honing time to stop honing, but if the degree of thin film honing meets the process requirements, the thickness of the wafer must be measured after honing. Judging, it is not immediately possible to determine whether the honing has actually reached the end. Generally speaking, 'the honing time in the time control mode is set to be fixed', so it is relatively inelastic to the process. Once the wafer is not well controlled in one or several processes before the honing process, Honed material 3 This paper is in accordance with the Chinese National Standard (CNS) A Valg ⑵G X M7 — — — — — ΊΙΙΙ — F------ —II ^ 1111.1111 (Please read the precautions on the back before (Fill in this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 436368 SOOltwf.doc / 006 A7-B7 V. Description of the invention (l) The thickness of the material is increased or decreased compared to the predetermined thickness, and the use of time control mode will cause honing removal The thickness is not enough, and it is necessary to perform the honing operation again, or the thickness of the film is honed too much, and it becomes a serious over honing, which results in the wafer being scrapped. Therefore, in the current chemical mechanical honing process, the time control mode is usually not used to control the main polish step of the wafer honing thickness. Instead, it is detected by an endpoint that can control the degree of wafer honing. Control mode. The so-called endpoint detection control mode is that during the honing process, the engineer collects the signals displayed by the honing time for wafers with a certain pattern and a certain film, such as the optical signals sent by the film. In case of changes in electrical signal strength or temperature, for wafers with the same pattern and the same film, under the same process conditions, a similar relationship between the honing time and the signal will be obtained. Referring to the graph of honing time and signal intensity, the conditions for controlling honing stop can be set as the basis for other wafer honing with the same pattern and film. The end point detection control mode is based on the signal as the basis for honing whether to continue or stop1 and is not limited by the honing time, so the process is more flexible, and because the signal is used to reflect the honing situation, the chemical machinery is improved. The reproducibility of the honing process. □ Most of the previous honing techniques used the endpoint detection control mode to control the main honing stages of the chemical mechanical honing. Generally, after the main honing stage, an over honing (ove r-po 1 1 sh) step is performed, and S is to ensure that the material to be ground can be completely honed. Because in the main honing stage, the purpose is to apply 4 national paper standards (CNSM4 specification (210 X 297 mm) in a short period of time) ----------- ^ in · ----- --Order ---- ^ ------ Line {Please read the notes on the back before filling this page) 436368 βOOltwf .doc / 006 V. Description of the invention (彡) Most of the desire to be tortured The material is removed, so its honing parameters are used to provide a high honing rate. Once the interface between different materials is exposed, the main honing phase will stop, and there will still be some residues at this time, so excessive honing is required. It is known that after the main honing phase is stopped, the chemical mechanical honing machine will be started again to use the same parameters as the main honing phase for excessive honing. At this time, the parameters with high honing rate will be used for excessive honing. In view of this, the present invention provides a method for detecting the end point of a chemical mechanical honing method by using the end point detection method to change the honing parameters, such as increasing the wafer carrier. (Earner) and honing table (tab 1 e), reduce the pressure applied during honing, and perform an over honing step with the changed parameters. The changed parameters can reduce the chemical honing effect and provide a Large cutting ability, so that when the honing step is performed, the reaction between the mortar and the material to be honed can be improved, and the large cutting ability can quickly remove the remaining honing material to be completely removed. . Taking the honing of a tungsten metal plug as an example, there is an opening in the dielectric layer, and a conformal barrier layer and a tungsten metal layer are sequentially formed on the dielectric layer and the opening, and the mechanical mechanical honing is used to remove the opening. When honing, the barrier layer can be used as a honing barrier layer. When the honing layer is exposed, the main honing phase is stopped, and then the honing parameters are changed, and the honing is performed to completely complete the honing. The metal layer above the barrier layer and the barrier layer are removed, and two stages of chemical mechanical honing are performed using different parameters to increase the window of the chemical mechanical honing process. (Please read the precautions on the back before filling out this page) -ίν .------- Order .--- Γ ----- line — printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs Chinese National Standard (CNSM4 Specification (210 X 297 mm) Duty Printing of Employees' Intellectual Property Bureau, Ministry of Economic Affairs, Du Printed 43 636 8 6001twf-doc / 006 A7 _B7_ V. Description of the Invention (t) In order to allow the above-mentioned objects and features of the present invention , And advantages can be more obvious and easy to understand. The following is a detailed description of a preferred embodiment, in conjunction with the accompanying drawings, as follows: Brief description of the drawings: FIG. 1 illustrates a preferred embodiment according to the present invention. A flow chart of steps for detecting end points of chemical mechanical honing. Embodiments In the planarization process of chemical mechanical honing, two-stage honing is used to make metal interconnect structures, such as double metal mosaic structures, or honing. The metal plugs filled in the dielectric layer are used to make the manufactured semiconductor device with better physical properties and better electrical properties. The boundary of this two-stage honing step is determined by the end point detection signal, which is performed in two stages. The purpose of the mill is to use The method of endpoint detection adjusts the honing time for the thickness change of the deposited film. When making metal interconnect structures, there is usually a barrier layer (ba rr 1 er 1 aye r) between the metal layer and the dielectric layer. ) Or a barrier layer (st op) ayer) 'Like titanium nitride (TiN) or silicon nitride (SiN), the purpose of the endpoint detection control mode is to determine the time of the main honing phase of the first phase When the barrier layer is exposed, the detector detects the material interface change and judges that the honing has reached the end. It can be used to determine the signal of the material interface change such as the reflection coefficient of the film, the optical signal emitted, the strength of the electrical signal, friction Force, chemical characteristics of the material, or temperature change, etc. When it is detected that the honing has reached the interface between the metal layer and the barrier layer, it does not mean that the metal layer above the barrier layer has been completely removed, so the main honing is Tier 6 This paper & degree is applicable to China National Standard (CNS) A4 specifications (210 ^ 297 meals) ----------- Syria -------- Order ---- ^ „—Line— (Please read the notes on the back before filling this page) 436368 6001twf.d〇c / 006 _B7_ V. Description of the invention After the (Γ) segment stops, an over honing step must be performed to ensure that the metal layer above the ζ barrier layer has been completely removed. However, improper over honing will not only remove the remaining metal layer and resistance. Barrier layer, and further honing the dielectric layer below the barrier layer, due to the difference between the dielectric material and the metal material, the dielectric layer may be quickly removed, but it will cause surface unevenness, such as depression ( dishing) or local erosion. In the present invention, two sets of different parameters are used for the main honing phase and the excessive honing phase, and the parameter change is performed by using an endpoint detection signal. For example, when performing chemical mechanical honing of tungsten, the process of the end point detection is shown in Figure 1. In step 100, the wafer to be honed is placed on a chemical mechanical honing machine table, and the main honing phase of the chemical mechanical honing is started. The parameters used at this stage include a carrier speed of 60 rpm and a honing speed of 65 rpm. The rotation speed of the grinding table and the downward pressure applied by the carrier to the honing pad are 33 ~ 37 kPa. In step 102, when most of the tungsten metal is honed away and the lower barrier layer is exposed, it is judged that the honing has reached the end, and the main honing phase is stopped. Then, in step 104, the parameters of the chemical mechanical honing are changed. The changed parameters include a carrier rotation speed of 75 rpni, a honing table rotation speed of 80 ι · ρηι, and a downward pressure applied by the carrier to the honing pad is 19 ~ 23 kPa. In step 106, the over-honing step is performed by using the changed parameters. The thickness of the tungsten metal is about 4000 A, and the time for over-honing is about 45-60 seconds. In step 108, the chemical mechanical honing process is terminated. After the main honing phase, there will be another overhaul. 7 This paper size applies to the Chinese national standard (CNSM4 specification (210x297 mm) (please read the notice on the back before filling out this page). Y Loading ·- ------ Order ---- 1 --.--- line_ Printed by the Consumers ’Cooperative of the Ministry of Economy, Smart Finance and Agriculture Bureau 436368 6001twf.doc / 006 Δ7 B7 Printed by the Consumer ’s Cooperative of the Intellectual Property Bureau of the Ministry of Economy 5λ V. Description of the invention (Handling) The grinding step is to ensure that the material to be ground can be completely honed. However, the parameters used in the conventional over-honing step are still the parameters of the main honing stage, only the excessive The control of the honing step is changed to the time control method instead of the endpoint detection method. Since the purpose of the main honing phase is to remove most of the material to be honed in a short time, its honing parameters are used to Provides a high honing rate. Once the interface between different materials is exposed, the main honing phase will stop, and there will still be some residues at this time, so excessive honing is required. Once the main honing phase is stopped, it will be again Start chemical machine The honing machine table uses the same parameters as the main honing stage for excessive honing. At this time, using the parameter with a high honing rate for excessive honing will often cause the surface of the wafer to be depressed. The invention is described in the embodiment. The two-stage chemical mechanical honing is performed with different parameters. The start of parameter conversion is determined by the end point detection signal. In the main honing phase, a larger pressure is applied to generate a higher mechanical honing force. The carrier and honing There will be greater friction between the pads. Once the material is honed to the material interface, the change in friction will be greater, so that a stronger and more stable end point detection signal will be obtained, and more pressure will increase. The chemical reaction between the pulp and the material being honing has a large honing rate, so the main honing phase can be completed quickly. The subsequent over honing phase uses a smaller mechanical honing force to avoid chemistry The surface of the dielectric layer is caused by the electrical reaction, and the speed of the carrier and the speed of the honing table are used to generate a larger cut on the surface of the honing object. Role to achieve a flat surface. As this paper is 8 in this step, the Chinese National Standard (CNS) A4 specification (210 x 297 mm) is applied ------ Μ -------- order- ---. I BE I (Please read the precautions on the back before filling out this page) 436368 6001twf.doc / 006 ^ _B7_ 5. In the description of the invention (7), the downward pressure is small, and the mortar and the object to be honed The chemical reaction between them is relatively gentle, so the rate of downward honing will be slower than the main honing stage, so the phenomenon of surface depression or corrosion of the dielectric layer can be improved, and the window of the chemical mechanical honing process can be increased. Although tungsten metal is used as the material to be honed in the embodiment, the process parameters used are set according to the tungsten metal with a thickness of 4000A. However, the method provided by the present invention is not limited to honing tungsten metal, and can be honing other materials, such as Copper, and when used for honing other materials, the components of the honing paste and the process parameters will vary, but the main point is that the downward pressure in the main honing stage is greater than the excessive honing step, and The main honing stage of the carrier and the honing table The speed should be less than the excessive honing step. Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and decorations without departing from the spirit and scope of the present invention. The scope of protection of the invention shall be determined by the scope of the attached patent application. ------ ^ ---- Install · ------- Order · ------.--- I (Please read the precautions on the back before filling this page) Ministry of Economic Affairs Intellectual Property Printed by the Bureau ’s Consumer Cooperatives 9 This paper size applies to the Chinese National Standard (CI \ 'S) A4 (210 X 297 mm)