1260679 九、發明說明： 【發明所屬之技術領域】 本發明是有關於—種半導 一種爐管（fMace)裝置之内a ^衣置·^寸別疋有關於 滯留時g，其可降低於爐管中反應氣體 $邊¥間亚改善反應氣體之消耗情形。 【先前技術】 、，當今積體電路之製作主要藉由於半導體基底上施行多 這製程步驟以形成主動與被動元件而完成。此些製程步驟 中大夕數皆有關於高溫下於半導體晶圓之上或内沉積摻雜 有4貝（dopant doped)或未摻雜有摻質（un(j〇pe(j)之薄膜。於 實際應用上，薄膜沉積大多採用爐管（furnace)裝置施行。一 般而言，用半導體晶圓製造之薄膜沉積之爐管裝置通常包括 石英圓柱形成之一真空腔體，以設置半導體晶圓並於其内進 行反應。於薄膜沉積時，爐管内之反應腔體之溫度通常介於 400〜700°C，並視特定製程與所欲沉積薄膜而可適度改變。 此外，於上述反應腔體中亦設置有一氣體進口（gas比16〇與 一氣體排放口（exhaust) ’當設置有半導體晶圓時，可根據特 定之製程配方（recipe)，於不同化學反應條件（如壓力、氣體 流量）與適當溫度下，通入多種氣體以進行反應。爐管内之 薄膜沉積表現則依賴於反應腔體内之溫度與氣體分佈之均 勻性。 請參照第1圖，顯示了一種習知垂直式（vertical-type) 1260679 爐管I置之示意圖。在此，僅部分顯示其反應腔體單元部 分，熟悉此技藝者當能理解此類型之爐管裝置仍包括如溫度 /壓力控制單元、晶圓傳輸單元以及氣體輸送單元等其他設 備單元，並不以第丨圖所示之反應腔體單元為限。在此，反 應腔體單元1〇包括了外管（〇uter tube)i2、内管（inner 加1^)14、晶舟（1)〇以）16、基座（|^〇165131)18、以及晶舟升降平 台（boat eleVator)20等構件。其中晶舟16係設置於基座18 上，用以搭載一或多個半導體晶圓，並於薄膜沉積之施行前 後藉由升降平台20的作動而進出反應腔體1〇。外管12則 大體包覆於上述構件，於外管丨2之一側的底部設置有一排 放口（exhaust)26，用於排放反應腔體1〇内之氣體。於内管 14側之底部則設置有一進氣口（gas inlet)24，連接於氣體 供應裝置（未圖示），用於供應如反應或潔淨用等製程氣體。 一般而言，内管14為不具有上蓋之一中空圓柱，其於反應 腔體10中與晶舟16定義出了主要之反應區域。於薄膜沉積 時’來自於進氣口 24之反應氣體則於特定溫度與壓力下藉 由流經於上述反應區域内之半導體晶圓，以於半導體晶圓上 形成薄膜。 第2圖則顯示了第1圖中位於反應區域内之一區域30 之放大情形，用以解說於習知薄膜沉積爐管中當薄膜沉積時 反應氣體之流動情形。標號34顯示了對流流動之反應氣 體’其由進氣口 24流入内管14後便由下往上對流 (convection)，且部分經由擴散而橫向地流入半導 體晶圓22間之區域，如標號36所顯示之擴散流動之反應氣 6 -1260679 體’進而於半導體晶圓22上形成沉積薄膜。 於習知垂直式爐管裝置中，反應氣體主要係自内管下方 之進氣口處通入反應腔體内，經由對流方式通過内管與晶舟 間所定義出之反應區域後，最後自設置於外管底部之排放口 而導出，而於反應腔體中之薄膜沉積主要藉由半導體晶圓與 擴放至半導體晶圓處之反應氣體作用而形成。 ^然而，於上述爐管裝置中，反應氣體需要較長時間以擴 散至半導體晶圓處以進行沉積反應。另外，於爐管裝置中反 應氣體濃度容易隨著位置而改變，故需要較大之氣體流量以 達到於爐管裝置中之不同位置之氣體濃度之均一性，因而反 應氣體消耗極大。 隨著半導體元件臨界尺寸縮減以及積集度提升的趨 為’由於上述缺點的存在，f知爐管裝置之製程能力將因而 二限無法滿足製造更小線寬之次世代半導體裝置之薄膜沉 積製程之要求。 因此’便需要針對習知爐f裝置進行改良，藉以改善並 續爐管|置之薄臈沉積能力，使之適用於製造更小線寬之 半導體裝置。 【發明内容】 有1此本發明的主要目的就是藉由改良爐管裝置之 旦吕、使仔爐^内反應氣體之供輪均勾且降低反應氣體消耗 里，並進而延續薄臈沉積用之爐管裝置之製程能力。 為達上述目的，本發明提供了一種爐管裝置，包括： 7 1260679 一晶舟，用於搭載至少一半導體晶圓；一内管，用於包 覆該晶舟；一氣體注入器（gas in ject〇r)，設置於該内管 内，用於注入一反應氣體；以及一外管，用於包覆該内管， 具有一排氣口，其中該内管包括具有一底部開口之一中空圓 柱狀本體，以及設置於該中空圓柱狀本體上之複數個狹縫開 口，使彳于該内管内之該反應氣體可流經該些狹縫開口而經由 該排氣孔導出。1260679 IX. Description of the invention: [Technical field to which the invention pertains] The present invention relates to a semi-conducting device (fMace) in which a device is placed in a device, and The reaction gas in the furnace tube is used to improve the consumption of the reaction gas. [Prior Art] The fabrication of today's integrated circuits is mainly accomplished by performing multiple process steps on the semiconductor substrate to form active and passive components. In these process steps, the film has a dopant doped or undoped dopant (un(j〇pe(j)) film deposited on or in the semiconductor wafer at a high temperature. In practical applications, thin film deposition is mostly performed by a furnace device. Generally, a thin film deposition furnace tube device manufactured by using a semiconductor wafer usually includes a quartz cylinder to form a vacuum chamber to set a semiconductor wafer and The reaction is carried out therein. When the film is deposited, the temperature of the reaction chamber in the furnace tube is usually between 400 and 700 ° C, and can be appropriately changed depending on the specific process and the film to be deposited. Further, in the above reaction chamber There is also a gas inlet (gas ratio 16 〇 and a gas vent (exhaust) 'when a semiconductor wafer is provided, it can be based on a specific recipe, under different chemical reaction conditions (such as pressure, gas flow) and At a suitable temperature, a variety of gases are introduced to carry out the reaction. The film deposition performance in the furnace tube depends on the temperature and gas distribution uniformity in the reaction chamber. Referring to Figure 1, a formula is shown. A schematic diagram of the vertical-type 1260679 furnace tube I. Here, only the portion of the reaction chamber unit is partially shown, and those skilled in the art will understand that this type of furnace tube apparatus still includes a temperature/pressure control unit. Other device units, such as a wafer transfer unit and a gas transfer unit, are not limited to the reaction chamber unit shown in the figure. Here, the reaction chamber unit 1 includes an outer tube (iuter tube) i2. Inner tube (inner plus 1^) 14, boat (1) 〇16, pedestal (|^〇165131) 18, and boat levator platform (boat eleVator) 20, etc. The susceptor 18 is configured to carry one or more semiconductor wafers and enter and exit the reaction chamber 1 by operation of the lifting platform 20 before and after the deposition of the film. The outer tube 12 is substantially covered by the member. The bottom of one side of the outer tube 2 is provided with an exhaust 26 for discharging the gas in the reaction chamber 1 . A gas inlet 24 is provided at the bottom of the inner tube 14 side, and the connection is provided. a gas supply device (not shown) for supplying a reaction or In general, the inner tube 14 is a hollow cylinder having no upper cover, and defines a main reaction area in the reaction chamber 10 with the crystal boat 16. When the film is deposited, 'from the intake air The reaction gas of the port 24 is formed on the semiconductor wafer by flowing through the semiconductor wafer in the reaction zone at a specific temperature and pressure. Fig. 2 shows the reaction zone in Fig. 1 An enlarged view of a region 30 for explaining the flow of the reaction gas when the film is deposited in a conventional thin film deposition furnace tube. Reference numeral 34 shows a convective flow of the reaction gas which flows into the inner tube 14 from the inlet port 24 Converging from bottom to top, and partially flowing laterally into the region between the semiconductor wafers 22 via diffusion, as shown by reference numeral 36, the diffused flowing reactant gas 6-1260679 is formed to form a deposition on the semiconductor wafer 22. film. In the conventional vertical furnace tube device, the reaction gas mainly enters the reaction chamber from the inlet port below the inner tube, and passes through the reaction region defined by the inner tube and the boat after convection, and finally The film is deposited in the bottom of the outer tube and the film deposition in the reaction chamber is mainly formed by the reaction of the semiconductor wafer with the reaction gas diffused to the semiconductor wafer. ^ However, in the above tube apparatus, the reaction gas takes a long time to diffuse to the semiconductor wafer for the deposition reaction. Further, the concentration of the reaction gas in the furnace tube apparatus tends to vary with the position, so that a large gas flow rate is required to achieve uniformity of the gas concentration at different positions in the furnace tube apparatus, and thus the reaction gas consumption is extremely large. As the critical dimension of semiconductor components shrinks and the degree of integration increases, the process capability of the furnace tube device will not be able to meet the thin film deposition process of the next generation semiconductor device for manufacturing smaller line widths. Requirements. Therefore, it is necessary to improve the conventional furnace f device in order to improve the continuous deposition of the furnace tube and make it suitable for manufacturing semiconductor devices with smaller line widths. SUMMARY OF THE INVENTION The main object of the present invention is to reduce the reaction gas consumption by improving the supply of the reaction gas in the furnace tube by reducing the heat of the furnace tube device, and further reducing the deposition of the thin gas. Process capability of the furnace tube device. To achieve the above object, the present invention provides a furnace tube apparatus comprising: 7 1260679 a boat for carrying at least one semiconductor wafer; an inner tube for coating the wafer boat; and a gas injector (gas in a 〇r) disposed in the inner tube for injecting a reactive gas, and an outer tube for covering the inner tube, having an exhaust port, wherein the inner tube includes a hollow cylinder having a bottom opening And a plurality of slit openings disposed on the hollow cylindrical body, so that the reaction gas in the inner tube can flow through the slit openings and be led out through the vent holes.
此外，本發明亦提供了 一種爐管裝置，包括： 一晶舟，搭載至少一半導體晶圓；一内管，包覆該晶舟； 以及=氣體注入器（gasinject〇r)，設置於該内管内，依大 脰平:於該半導體晶圓表面之—方向注人—反應氣體，其中 違内官包括具有—底部開口之_中空圓柱狀本體，以及設置 二、:中：圓柱狀本體上之複數個狹縫開口，使得該反應氣體 :級15亥半導體晶圓後經由該些狹縫開口而導出該内管。 再者，本發明提供了一種爐管用内管，包括： 開口，I:圓柱狀本體’具有-底部開口；以及複數個狹縫 開口，设置於該中空圓柱狀本體上。 噯 顯易之二，目的、一 說明如下：特舉一車父佳貫施例，並配合所附圖示，作詳細 【實施方式】 圖至爐::：管與爐管裝置之實施例將配合第3 ⑽利田敘述如下。首先請參照第3圖，顯示了 8 • 1260679 依據本發明之一實施例之爐管裝置之反應腔體1 〇〇，其包括 外盲（outer tube)l〇2、内管（inner tube)104、晶舟 (boat)106、基座（pedestal)1〇8、與晶舟升降平台（b〇at elevator)110，其中晶舟ι〇6係設置於基座1〇8上，用於搭 載一或多個半導體晶圓，並於薄膜沉積之施行前後藉由晶舟 升降平台110的作動而進出反應腔體1 〇〇。外管丨〇2則大體 包覆於上述構件，其一側之底部設置有一排放口 118，用於 反應腔體10 0内氣體之排放。 於本實施例中，針對習知爐管裝置進行改良，並提供了 一種新穎之内管104。如第3圖所示，於内管1〇4 一側之底 部设置有一進氣口 114，進氣口 114包括一連接於氣體供應 衣置（未圖示）之氣體注入管（gas inject〇r)116，以供應反 應氣體之用，而其他潔淨用氣體則經由進氣口 114導入。於 本實施例中，於反應腔體1〇〇内，氣體注入管116係設置於 内笞104之側壁與晶舟丨〇6之間，且大體平行於内管1⑽與 晶舟106。 值得注意的，相較於習知爐管裝置，本實施例中之内管 104之上部為封閉而不具備開口，僅於底部形成有開口。此 夕―卜’於内官1〇4中未設置有進氣口 114之其他側邊上形成有 複數個個狹縫開口（sHt： Qpening)s，此些狹縫開口 $較佳 為設置於對應於進氣口 114之内管104侧邊上。因此，内管 104内工間即為主要薄膜沉積反應之反應區域，而由氣體注 入态U6所注入之反應氣體等則可經由形成於内管1〇4 —侧 邊上之狹縫開D s導出，進而由排氣口 118排出反應腔體 9 1260679 110 〇 請參照第4圖，用以說明第3圖中之反應區域内之一區 域130之放大情形，用以解說本發明之爐管裝置中，於薄膜 沉積時，反應區域内反應氣體之流動情形。在此，藉由於設 置於氣體注入器116上之數個氣孔116a，將反應氣體直接 地供應至鄰近半導體晶圓112，並依大體對流之傳輸方式， 例如標號為150之氣體流動，流經半導體晶圓丨丨2表面，並In addition, the present invention also provides a furnace tube apparatus comprising: a wafer boat carrying at least one semiconductor wafer; an inner tube covering the wafer boat; and a gas injector (gas injector) disposed therein In the tube, according to the Daping: on the surface of the semiconductor wafer - the direction of the injection - the reaction gas, wherein the violation of the official includes a hollow cylindrical body with a bottom opening, and the setting of two,: medium: cylindrical body The plurality of slit openings are such that the reaction gas is discharged from the semiconductor wafer through the slit openings. Furthermore, the present invention provides an inner tube for a furnace tube comprising: an opening, I: a cylindrical body 'having a bottom opening; and a plurality of slit openings disposed on the hollow cylindrical body.嗳显易二, the purpose, a description is as follows: special one car father best example, and with the attached diagram, for details [embodiment] Figure to the furnace::: tube and furnace tube device embodiment will The third paragraph (10) Litian is described below. Referring first to Figure 3, there is shown a reaction chamber 1 炉 of a furnace tube apparatus according to an embodiment of the present invention, which includes an outer tube l2 and an inner tube 104. a boat 106, a pedestal 1〇8, and a b〇at elevator 110, wherein the boat 〇6 is disposed on the base 1〇8 for carrying one Or a plurality of semiconductor wafers are moved in and out of the reaction chamber 1 by the operation of the boat lifting platform 110 before and after the deposition of the film. The outer tube 丨〇 2 is substantially covered by the above member, and a discharge port 118 is provided at the bottom of one side for discharging the gas in the reaction chamber 10 . In the present embodiment, a conventional furnace tube assembly is modified and a novel inner tube 104 is provided. As shown in Fig. 3, an air inlet 114 is provided at the bottom of the inner tube 1〇4 side, and the air inlet 114 includes a gas injection pipe (gas inject〇r) connected to a gas supply device (not shown). 116 is for supplying a reaction gas, and other clean gas is introduced through the air inlet 114. In the present embodiment, the gas injection pipe 116 is disposed between the side wall of the inner crucible 104 and the boat raft 6 in the reaction chamber 1 ,, and is substantially parallel to the inner tube 1 (10) and the wafer boat 106. It is to be noted that the upper portion of the inner tube 104 in the present embodiment is closed without an opening, and an opening is formed only at the bottom, as compared with the conventional tube device. In the present day, a plurality of slit openings (sHt: Qpening) s are formed on the other side of the inner nozzle 1 which is not provided with the air inlet 114, and the slit openings $ are preferably provided in the Corresponding to the inner side of the inner tube 104 of the air inlet 114. Therefore, the inside of the inner tube 104 is the reaction area of the main thin film deposition reaction, and the reaction gas injected by the gas injection state U6 can be opened through the slit formed on the side of the inner tube 1〇4. Derived, and then discharged from the exhaust port 118 to the reaction chamber 9 1260679 110. Please refer to FIG. 4 for explaining the enlargement of a region 130 in the reaction region in FIG. 3 for illustrating the furnace tube device of the present invention. In the case of film deposition, the flow of the reaction gas in the reaction zone. Here, the reactant gas is directly supplied to the adjacent semiconductor wafer 112 by the plurality of pores 116a disposed on the gas injector 116, and flows through the semiconductor in a general convection manner, for example, a gas flow of 150, flowing through the semiconductor Wafer 丨丨 2 surface, and
於反應腔體1〇〇所處之壓力與溫度下與半導體晶圓112進行 反應，因而完成薄膜的沉積。上述氣體注入器116之材質例 如為石英。The semiconductor wafer 112 is reacted at a pressure and temperature at which the reaction chamber 1 is placed, thereby completing deposition of the film. The material of the gas injector 116 is, for example, quartz.
一 >如此，相較於第丨圖所示之傳統薄膜沉積爐管裝置，本 貝鈀例所提供之反應腔體1〇〇，藉由氣體注入器116之設 置’可提升爐管|置中之薄膜沉積效果並可因而降低反應氣 體之消耗量，有利於改善反應腔體中半導體晶圓之整體：積 效果如不同位置之半導體晶圓之薄膜㈣度等）。於本發明 :’熟習此技藝者當能知悉，4體注人器116上之氣孔⑴ =置位置以及數量’以及設置於内管1G4上狹缝開口 s之數 置與位置二可依照實際薄膜沉積之應用而作適當的調整，並 不以上述實施例之描述與圖式而限定本發明之範脅。 於下文中則詳細介紹本發明之爐 1。如第5圖所示，顯示了内管-之上視示意圖ΤΙ =二為封閉的，其為具有一特定壁厂旱τ之中空圓柱 則形成有二為石英或碳化石夕（SlC)。於内管104之一側 ' 固狹縫開口 S(未圖示），其大體互為對準且沿圓 10 1260679 周方向設置於内管1G4、約3Q〜5⑽之圓周面上，較佳地設置 於約40〜50%之圓周面上，以利反應氣體之導出。 ，主/青繼續參照第6圖，顯示了沿第5圖巾6一6切線之剖面 情形。内管104之上部可為一大體平坦之上蓋c，，或為一 圓弧狀之上蓋c，以形成一如圓柱狀或鐘狀之内管104。於 本圖中：顯示了狹缝開口 S分布之一實施例，縫開口 s間 的間距係由上往下遞減，換言之，形成於靠近内管_相對 上部之狹缝開π S之間距較為縝密，而形成於内管_相對 下部之狹縫開口 3之間距較為鬆散。此外，位於内管ι〇4相 對I部之狹縫開口 3之垂直寬度不大於俊於上方之狹缝開 二且較佳地由上往下遞減。一般而言，狹缝開口 S之垂 直覓度約介於4〜40.厘米（mm)。 於本發明中，藉由於爐管裝置中氣體注入哭以 内管側邊上之複數個狹_口之制，使得反錢财= 採用氣體對流方式流過半導體晶圓表面。相較於習知先對；^ 氣體供應方式，本發明之方法可有效且迅速地 使反應氣體與半導濟曰π^w /、千¥奴日日圓反應，且較容易控制爐 體半導體晶圓沉積效果的均勾性，.有利於爐u 錢續往下延伸至如Q.u微米（_)或以下之_=: 私。本發明之爐管用内f與爐f裝置實適用、、衣 多晶石夕PDl y S1】}咖）以及淺溝_ p、:如4雜 ⑴1哑）等相對複雜之薄膜製程之爐管裝^的應用回填咖 雖然本發明已以較佳實施例揭露如上，然其並 定本發明，任何熟習此技藝者，在不脫離切明之 11 .1260679 圍内，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為準。Thus, compared to the conventional thin film deposition furnace tube apparatus shown in the second figure, the reaction chamber provided by the Ben Palladium example is ', by the setting of the gas injector 116, the furnace tube can be lifted. The thin film deposition effect and thus the consumption of the reaction gas are beneficial to improve the overall semiconductor wafer in the reaction chamber: the product effect is the film (four degrees) of the semiconductor wafer at different positions, etc.). In the present invention: 'When the skilled person knows, the air hole (1) on the body of the body 116 and the number and the number of the slot opening s on the inner tube 1G4 can be set according to the actual film. The application of the deposition is appropriately adjusted, and the scope of the invention is not limited by the description and the drawings of the above embodiments. The furnace 1 of the present invention will be described in detail below. As shown in Fig. 5, it is shown that the inner tube - top view ΤΙ = two is closed, which is a hollow cylinder having a specific wall plant dry τ, and two are formed of quartz or carbon carbide (SlC). One of the inner tube 104's solid slit openings S (not shown) are substantially aligned with each other and are disposed on the circumferential surface of the inner tube 1G4 and about 3Q to 5 (10) in the circumferential direction of the circle 10 1260679, preferably It is disposed on a circumferential surface of about 40 to 50% to facilitate the derivation of the reaction gas. The main/green continues to refer to Fig. 6, which shows the section along the tangential line of the sixth figure 6-6. The upper portion of the inner tube 104 may be a substantially flat upper cover c, or an arc-shaped upper cover c to form a cylindrical or bell-shaped inner tube 104. In the figure: an embodiment of the slit opening S distribution is shown, the spacing between the slit openings s is decreased from top to bottom, in other words, the slits formed near the inner tube _ the upper portion are relatively close to each other. And the distance between the slit openings 3 formed in the inner tube_the lower portion is relatively loose. Further, the slit width of the slit opening 3 located at the opposite end of the inner tube ι 4 is not larger than the slit opening of the upper portion and preferably decreases from the top to the bottom. In general, the slit opening S has a vertical twist of about 4 to 40 centimeters (mm). In the present invention, by the gas injection in the furnace tube device, a plurality of slits are formed on the side of the inner tube, so that the anti-money money flows through the surface of the semiconductor wafer by gas convection. Compared with the conventional gas supply method, the method of the invention can effectively and quickly react the reaction gas with the semi-conducting 曰π^w /, and the Japanese yen, and it is easier to control the deposition of the semiconductor wafer of the furnace body. The effect of the hook, which is conducive to the furnace u money continued down to _=: private such as Qu micro (_) or below. The furnace tube of the present invention is suitable for the inner f and furnace f devices, and the relatively complicated thin film process of the furnace tube, such as the polycrystalline stone, the PD1 y S1]} coffee, and the shallow groove _ p, such as 4 (1) 1 dummy. </ RTI> </ RTI> </ RTI> </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> The scope of the invention is defined by the scope of the appended claims.
12 *1260679 【圖式簡單說明】 第1圖為一示意圖，用以說明習知爐管裝置之反應腔 體； 第2圖為一示意圖，用以解說第1圖内區域3〇之放大 情形； 第3圖為一示意圖，用以說明依據本發明一實施例之爐 管裝置之反應腔體； 第4圖為一示意圖，用以解說第3圖内區域ι3〇之放大 情形； 第5圖為一上視圖，用以說明依據本發明一實施例之内 管；以及 第6圖為一剖面圖，用以說明沿第5圖中6 —6切線之剖 面情形。 【主要元件符號說明】 10、100〜反應腔體； 12、102〜外管； 14、104〜内管； 16、106〜晶舟； 18、108〜基座； 20、110〜晶舟升降平台； 22、112〜半導體晶圓； 24、114〜進氣口； 13 .126067912 * 1260679 [Simple description of the drawings] Fig. 1 is a schematic view for explaining the reaction chamber of the conventional furnace tube device; Fig. 2 is a schematic view for explaining the enlargement of the region 3 in Fig. 1; 3 is a schematic view for explaining a reaction chamber of a furnace tube device according to an embodiment of the present invention; FIG. 4 is a schematic view for explaining an enlargement of a region ι3 第 in FIG. 3; An upper view for explaining an inner tube according to an embodiment of the present invention; and a sixth sectional view for explaining a cross-sectional view taken along line 6-6 of Fig. 5. [Main component symbol description] 10, 100~ reaction chamber; 12, 102~ outer tube; 14, 104~ inner tube; 16, 106~ boat; 18, 108~ pedestal; 20, 110~ boat lift platform 22, 112 ~ semiconductor wafer; 24, 114 ~ air inlet; 13 .1260679
26、116〜排氣口； 11 6〜氣體注入器； 116a〜氣孔； S〜狹缝開口； C、C’〜内管之上蓋； T〜内管管壁厚度。 1426, 116~ exhaust port; 11 6~ gas injector; 116a~ air hole; S~ slit opening; C, C'~ inner tube upper cover; T~ inner tube wall thickness. 14