1302117 九、發明說明： 【發明所屬之技術領域】 ~ 本發明涉及一種電解蝕刻技術用以蝕刻一工作物表面 w 之一金屬材料，其中該電解蝕刻技術可應用於不良品之重 工回收或應用在半導體微影製程中之薄膜蝕刻等。 【先前技術】 • 按，習知之電解蝕刻裝置已揭露於台灣申請案第 095123018號之電解回收系統中，該電解回收系統中包括 一非接觸式之電解蝕刻設備，該電解蚀刻設備主要具有一 ' 陽極、一陰極及一電解液，該電解液係自陽極不斷地沖刷 • 一工作物及該陰極，其中該非接觸式之名稱由來係特指該 工作物並無直接或間接地電性連接至一電源供應器之一正 極，此舉有別於傳統普遍使用之電解蝕刻方式。藉由非接 觸式之電解蝕刻以及可相對該工作物活動之電極，該工作 • 物表面之金屬材料可逐步且均勻地被蝕刻去除。 又，美國專利案第5284554號係揭露一電化學蝕刻設 備及製法用於需要高精密圖案化之電子元件之製造，主要 • 係包括一平台供置放一工作物及一位於該工作物下方之陰 ζ 極设備。該工作物與該陰極設備係分別電性連接於一電源 供應裔之一正極及一負極，而該陰極設備具有一喷嘴裝置 供導引一電解液注入該工作物與該陰極設備之間以進行電 解蝕刻；再者，該平台與該陰極設備係可作相對橫向位移 使整個工作物能夠被全面蝕刻。 1302117 另外’美國專利案第6103554號更針對該第5284554 號之電化學似備作進-步之改良以加速朗該金屬材 料之速度，該» 6聰54號之發明内容主要類似該第 5284554號之發明，惟增加了該平台與該陰極設備係可作 相對橫向「轉動」之要件。1302117 IX. Description of the Invention: [Technical Field] The present invention relates to an electrolytic etching technique for etching a metal material of a workpiece surface w, wherein the electrolytic etching technique can be applied to heavy product recycling or application of defective products. Thin film etching in semiconductor lithography processes. [Prior Art] According to the conventional electrolytic etching apparatus disclosed in the electrolytic recovery system of Taiwan Application No. 095123018, the electrolytic recovery system includes a non-contact electrolytic etching apparatus, and the electrolytic etching apparatus mainly has a ' An anode, a cathode and an electrolyte, the electrolyte is continuously flushed from the anode, a workpiece and the cathode, wherein the non-contact name is specifically that the workpiece is not directly or indirectly electrically connected to the workpiece One of the power supply positive electrodes is different from the conventionally used electrolytic etching method. The metal material of the surface of the work can be removed by etching step by step and by means of non-contact electrolytic etching and electrodes movable relative to the workpiece. In addition, U.S. Patent No. 5,284,554 discloses an electrochemical etching apparatus and method for manufacturing electronic components requiring high-precision patterning, mainly comprising a platform for placing a work object and a work under the work object. Haze Extreme equipment. The working object and the cathode device are respectively electrically connected to one positive electrode and one negative electrode of a power supply source, and the cathode device has a nozzle device for guiding an electrolyte to be injected between the working object and the cathode device for performing Electrolytic etching; further, the platform and the cathode device are capable of relative lateral displacement so that the entire workpiece can be fully etched. 1302117 In addition, U.S. Patent No. 6,103,554 is directed to the electrochemical improvement of the No. 5,284,554 to improve the speed of the metal material. The invention of the article is mainly similar to the No. 5284554. The invention has only increased the requirement that the platform and the cathode device be relatively "rotating" laterally.
然，在該兩美國前案中均仍屬傳統之接觸式電解_ ;方式’由於該作物仍然需被電性連接於該電源供應器之 該正極，如此限制製程中電路佈局之複雜性，尤其：： 化、大量且連續性之半導體製程中徒增限制。八 又，台灣專利第1223350號亦揭露一電解式遮罩絡膜 之蝕刻製程方法，如其專利說明書中第四圖所示，:站 侧製程方法主要係將電源之正極連接待㈣之工^ ^ 陽極化’而將電源之負極連接電解液以進行電解^ 仍受限於批次式之電解方式，不利自動化。 乂 隹 处緣是，殷切期待-改善之電解姓刻技術可增進 月色，包括蝕刻速度及品質，以及切合實降 Χ 乂 生產線製程者。 錄運用在自動化之 【發明内容】 鑒於以上所述習知技術之缺點，本發明之主要 、 於提供-種電解_裝置，藉由非接觸式之電解^ = 以有效地去除一工作物之金屬材料。 式 本發明之另-目的在於提供該電解餘刻裝置 用於自動化之半導體製程設備上。 之此運 1302117 為達成上揭及其他目的，本發明之該電解钱刻裝置主 要係用來蝕刻一工作物之一表層’包括一蝕刻單元、一工 作台、一電源供應器及一電解液供應源。該蝕刻單元且右 .-陽極、-陰極及-絕緣軍，其中該陰極係位二 一側，且該絕緣罩係罩住該陽極以隔絕該陽極及陰極；該 工作台係供承放該工作物，以使該卫作物之表層面對該陽 極及該陰極；該電源供應器係具有一正極及一負極分別連 __單元之該陽極及贿極；而該電解賴應源係連 ♦ ϋ祕刻單元用以連續地注人—電解液於該陽極後，再沖 刷於該工作物之該表層，且沿該表層與該陰極間所定義之 一間隙流出。 ' 較佳地，該陽極係被一絕緣罩罩住以隔離該陰極。 • 較佳地，該絕緣罩靠近該工作物之一端設有一金屬片。 較佳地，該陰極相較於該陽極具有較大之表面積面向 該工作物。 $知此技術者可在閱讀說明書後’更了解請求項中所 界定的申請專利發明的其他好處或其他目的。 【實施方式】 在第-圖之系統示意圖中，係揭露本發明之電解餘刻 ^ :置（1Q Q)的—個較佳實施例，其中指出該電解蚀刻 衣置（1 〇 〇)係用來餘刻一工作物（8)之一表層（8 1 )’例如〆金屬層。該電解側裝置（i 〇 ◦)主要包括 蝕刻單兀（1 )工作台（2 )、_電源供應器（3 ) 1302117 及一電解液供應源（4)。 在本較佳實施中，該⑽單元（丄）係具有—陽極（工 2 )、兩陰極（1 i )及一絕緣罩（i 2 )，熟知此技術者 、虽知在一個陰極（11)的情況下亦可進行電解韻刻，但 為求車乂佳之電解效果起見，本較佳實施係採用兩個陰極（1 1 ) ’曰且該陰極（1 1 )係位於該陽極（1 〇 )之-側。其 =陽極（1〇)更被該絕緣罩（i 2)罩住用以隔絕該 =、(11)’該兩陰極（11)係分別固定在兩固定板 9、 3)的底部’兩固定板（13)分別連接該絕緣罩（i ^ ( ITIIm 2(l f f (8 ^ 工）。 θ 1)面對该陽極（10)及該陰極（1 -負=原t!器（3)係具有一正極(如正號所示)及 極（、1 0 所示）分別連接該餘刻單元（1 )之該陽 及雜極（11 )，用以提供電解時所需之電力。 (to ；la； 後i、由t 〃電解液（41)會先流經該陽極（10) 後’再相於該工作物（8) υ) 層（8 1 ) 表層（8 1 )且沿該表 =丄）與該陰極（11)所定義之一間 廷表示該電解液（4 1)係充滿該間隙（、 Γ 之間可藉由該電解液（41)^電膜層（81) 作物（8)之表声、μ、 連接。因此，該工 表層（8 1)正對該陽極（1〇)之處，會 1302117 陽極來的電解液“ 陰極(11)都;有二◦彳)4Γ 了解到’本發明係實質地首創-種非接觸式電解法。以 絕該陽極（1 罩住5陽極（1 0 )藉以隔 上端具有一開口 )=陰：（1 1 )，且該絕緣罩（1 2 ) 引該電解液（4( 5)連通該電解液供應源（4)供導 之該工作物（8) if入该陽極（1◦)並順勢流向下方 而該絕緣罩（1?;、J ’ t陽極（1 ◦)以採白金棒為佳， 愈薄愈好。）在不影響其電氣隔絕功能之情況下， 層（8 i )，'可進1^=5整個該工作物⑻之表 解液（4 1)可以掃過整個 才（10)机下來的電 例如’該_元⑴可架設 ==作(:)能相對於該工作== 合用在自動化之生產設備中。’Uj迷目的，後者特別適 虫亥j方式更可解決過去靜態 1302117 式蝕刻中因電流密度不均導致蝕刻不均之問題。 請參閱第二圖所示，該蝕刻單元（ 金屬件（1 0 1 ) ’其電接該電源供應器（3 )有― 設於該絕緣罩（12)鄰近該工作物極，並 =申’如'，該金屬件(1 〇 1 )可視為該陽極广 1 (01) 的U申，精此使該工作物（8)之表層（8工） 的地方也能被蝕刻到。又，該金屬 ' 參 連接:電源供應器⑶之該正極，以= 金屬件（icm，用以取代前述之該金屬件活動 广面(1 〇 2)的底部端係延伸到設於該絕緣 = 對該工作物(8)，頂端則且伸入向 :者t i 部’並延伸至該陽極（1〇)的上方。 動金屬件（1 〇2)係被安排成可升降位移， L 1觸或離開該陽極（1 0)及該工作物（8)的 二2父。且該兩活動金屬件（10 2)無須額外電接 =電源供應器（3)。該兩活動金屬件（102)平常係 2屬她尾端時可驅動該兩活 以同時接觸該陽極（；〇、）f ’::了:，一下方位置 1)。 及该工作物（8)的表層（8 之該第一圖所示，本較佳實施例中之該韻刻單元 該二δ二10:係呈棒狀’例如一根電極棒（10)，且 使ϋ险1)係呈板狀，例如一片金屬板（11 )，藉此 〜陰極（1 0 )相較於該陽極（i i)具有較大之表 1302117 =投影區域（未顯示），當留意的是，就尺寸而言，該複數 ，極棒（1 0 3 )所構成之該陽極（1 〇a)之大小相當於 咧例中所示由單一電極棒（1 0)所構成之該陽極（1 0 ) 史大小；就配置而言，該每一電極棒（1 〇 3)係垂直該 i作物（8 )設立，有別於前例之該陽極（1 〇)之電極 棒（1 0 )係平行於該工作物（8 );藉此，該陽極（1 〇 \However, in both of the previous US cases, it was still the traditional contact electrolysis _; the way 'because the crop still needs to be electrically connected to the positive electrode of the power supply, thus limiting the complexity of the circuit layout in the process, especially :: Increased restrictions on semiconductor processes that are large, continuous, and continuous. Eight, Taiwan Patent No. 1223350 also discloses an etching process for an electrolytic mask film, as shown in the fourth figure of the patent specification, the station side process method mainly connects the positive electrode of the power supply to the work of (4) ^ ^ Anodizing 'and connecting the negative electrode of the power supply to the electrolyte for electrolysis is still limited by the batch type of electrolysis, which is unfavorable for automation.乂 隹 At the edge, it is eagerly expected that the improved electrolytic surname technology will enhance the moonlight, including the etching speed and quality, as well as the production process of the 降 乂 production line. [Invented by Automation] In view of the above-mentioned shortcomings of the prior art, the present invention mainly provides an electrolysis apparatus by means of non-contact electrolysis ^= to effectively remove a metal of a work object. material. Another object of the present invention is to provide such an electrolytic remanufacturing device for use in an automated semiconductor process equipment. In order to achieve the above and other objects, the electrolysis device of the present invention is mainly used for etching a surface layer of a work object, including an etching unit, a work table, a power supply, and an electrolyte supply. source. The etching unit and the right anode, the cathode, and the cathode, wherein the cathode is on one side, and the insulating cover covers the anode to isolate the anode and the cathode; the table is for receiving the work a substance such that the surface of the medicinal crop is opposite to the anode and the cathode; the power supply has a positive electrode and a negative electrode respectively connected to the anode and the bribe of the __ unit; and the electrolysis source is connected to the ♦ ϋ ϋ The unit is used for continuously injecting the electrolyte. After the electrolyte is applied to the anode, it is flushed to the surface layer of the workpiece and flows out along a gap defined between the surface layer and the cathode. Preferably, the anode is covered by an insulating cover to isolate the cathode. • Preferably, the insulating cover is provided with a metal piece near one end of the workpiece. Preferably, the cathode has a larger surface area facing the workpiece than the anode. Those skilled in the art will be able to understand more about the other benefits or other purposes of the patented invention as defined in the claims after reading the specification. [Embodiment] In the system diagram of the first embodiment, a preferred embodiment of the electrolytic residue of the present invention is disclosed, wherein the electrolytic etching device (1 〇〇) is used. For example, one of the surface layers (8 1 ) of a work object (8) is, for example, a base metal layer. The electrolysis side device (i 〇 ◦) mainly comprises an etching unit (1) table (2), a power supply (3) 1302117 and an electrolyte supply source (4). In the preferred embodiment, the (10) unit has a cathode (work 2), two cathodes (1 i ), and an insulating cover (i 2 ). Those skilled in the art, although known in a cathode (11) In the case of electrolysis, electrolysis can also be performed, but for the purpose of electrolysis, the preferred embodiment uses two cathodes (1 1 ) '曰 and the cathode (1 1 ) is located at the anode (1 〇 ) - side. The anode (1〇) is further covered by the insulating cover (i 2) for isolating the =, (11)' the two cathodes (11) are respectively fixed at the bottom of the two fixing plates 9, 3) The plate (13) is respectively connected to the insulating cover (i ^ (ITIIm 2 (lff (8 ^). θ 1) faces the anode (10) and the cathode (1 - negative = original t! (3) has A positive electrode (shown as a positive sign) and a pole (shown at 10) are respectively coupled to the anode and the heteropole (11) of the residual unit (1) for providing the power required for electrolysis. After i, the electrolyte (41) will flow through the anode (10) and then re-phase to the work (8) υ layer (8 1 ) surface layer (8 1 ) and along the table =丄) and one of the cathodes defined by the cathode (11) indicates that the electrolyte (4 1) is filled with the gap (the Γ can be separated by the electrolyte (41) and the electric film layer (81) crops (8) The sound, μ, and connection of the surface. Therefore, the surface layer (8 1) is opposite to the anode (1 〇), and the electrolyte from the anode of 1302117 is “cathode (11); there are two turns) 4Γ To the 'the invention is essentially the first non-contact electrolysis method. To the anode (1 Covering the anode 5 (10) so as to have an opening at the upper end) = negative: (1 1 ), and the insulating cover (1 2 ) leads the electrolyte (4 ( 5 ) to communicate with the electrolyte supply source ( 4 ) The working object (8) is inserted into the anode (1◦) and flows down to the lower side, and the insulating cover (1?;, J't anode (1 ◦) is preferably a white gold rod, the thinner the better.) Without affecting its electrical isolation function, the layer (8 i ), 'can enter 1 ^=5 the entire solution (8) of the surface solution (4 1) can sweep through the entire (10) machine down, for example 'The _ yuan (1) can be erected == for (:) can be used in combination with the work == in the automated production equipment. 'Uj fans, the latter especially suitable for the worm method can solve the past static 1302117 etch Uneven current density leads to uneven etching. Please refer to the second figure, the etching unit (metal piece (1 0 1 ) ' is electrically connected to the power supply (3) - is provided in the insulating cover (12 ) adjacent to the working object pole, and = 申 '如', the metal piece (1 〇 1 ) can be regarded as the anode of the anode 1 (01), which makes the surface of the work (8) (8 workers) of The place can also be etched. Also, the metal 'parameter connection: the positive electrode of the power supply (3), with the metal part (icm), which replaces the bottom end of the movable surface of the metal piece (1 〇 2). Extending to the insulation = for the workpiece (8), the top end extends into the ti portion and extends above the anode (1 〇). The moving metal parts (1 〇 2) are arranged The displacement can be raised and lowered, L 1 touches or leaves the anode (10) and the two 2 fathers of the workpiece (8). And the two movable metal parts (10 2) do not need additional electrical connection = power supply (3). The two movable metal members (102) can drive the two activities when they are at their tail ends to simultaneously contact the anode (; 〇,) f ′:::, a lower position 1). And the surface layer of the work object (8) (the first figure in the preferred embodiment shows the second δ20: a rod shape), such as an electrode rod (10), And making the risk 1) a plate, such as a piece of metal plate (11), whereby the ~ cathode (10) has a larger table 1302117 than the anode (ii) = projection area (not shown), when It is to be noted that, in terms of size, the anode (1 3 a) formed by the complex number (1 0 3 ) is equivalent in size to the single electrode rod (10) shown in the example. The anode (1 0 ) is sized; in terms of configuration, each electrode rod (1 〇 3) is set up perpendicular to the i crop (8), which is different from the electrode rod of the anode (1 〇) of the previous example (1 0 ) is parallel to the work (8); thereby, the anode (1 〇 \
面積面向該工作物（8 )。藉由這樣的配比，可分散電流分 佈，避免局部電流密度過高，而得到較均勻之蝕二文 第四圖係為該蝕刻單元（1 )相對於該工作物（8) 之俯視圖，顯示該蝕刻單元（丄）之該陽極（i 的另 一例子，其中該陽極（1 0a)係具有複數電極棒（1 〇 3 )， 該複數電極棒（1 〇 3 )係形成一陣列（1 0a)，用以加 強姓刻该複數電極棒（1 〇 3)投影於該工作物（8)之 之整個下表面係形成一均勻之工作區，用以均勻地力口強 餞刻该工作物（8)之該投影區域。因此，此種具有陣列 武複數電極棒（10 3)之該電解蝕刻裝置（1〇 〇 )特 $適合應用在半導體微影製程中以取代薄膜蝕刻之步驟， 、、§其疋濕餘刻（Wetetching)，這種電解蝕刻之方式兼具 ^餘刻之高選擇性（Selectivity)及乾蝕刻（ ching)之尚精確性之優點，更重要的是本發明所述之電 餘刻裝置所耗用的電功率相較於一般傳統電解蝕刻装裏 成更高功率之餘刻裝置為低。 棒另方面，第五圖係為該陽極（1 0β)之該複數電極 ^ 1 〇 3 )之該陣列（i 〇a)之另一例子，其中該陣列 、 視龙圖案，用以使該工作物（8)之該投影區威奚 12 1302117 為 現該視覺圖案，如此可在該工作物（8)上蝕刻製作出一 序號或一公司標記等視覺圖案，例如當該陣列（1 〇a)如 第五圖所示呈現「I LU」之字樣之該視覺圖案時，則在 電解蝕刻後所得之該工作物（8 )之投影區域恰形成該「工 L U」之字樣。The area faces the work (8). With such a ratio, the current distribution can be dispersed to avoid the local current density being too high, and the uniformity is obtained. The fourth figure is the top view of the etching unit (1) relative to the workpiece (8), showing Another example of the anode of the etching unit (丄), wherein the anode (10 a) has a plurality of electrode rods (1 〇 3 ), and the plurality of electrode rods (1 〇 3 ) form an array (10 a ), to strengthen the surname, the plurality of electrode rods (1 〇 3) are projected onto the entire lower surface of the workpiece (8) to form a uniform working area for uniformly engraving the workpiece (8 The projection area of the array. Therefore, the electrolytic etching apparatus (1〇〇) having the array of the plurality of electrode rods (10 3) is suitable for use in the semiconductor lithography process to replace the thin film etching step, § Its Wetetching, the method of electrolytic etching combines the advantages of high selectivity and dry etching, and more importantly, the electricity according to the present invention. The power consumed by the engraved device is compared to the conventional electric power. The device for lowering the power of the etched device is low. In another aspect, the fifth figure is the other of the array (i 〇a) of the plurality of electrodes (1 〇3) of the anode (10β) For example, the array and the visual dragon pattern are used to make the projection area of the work object (8) deterrence 12 1302117 as the current visual pattern, so that a serial number or a etch can be made on the work object (8). A visual pattern such as a company mark, for example, when the array (1 〇a) exhibits the visual pattern of the word "I LU" as shown in the fifth figure, the projection area of the workpiece (8) obtained after electrolytic etching Just form the word "work LU".
睛再參閱苐一圖’有鑑於資源回收之考量，該電解名虫 刻裝置（1 0 0 )更包括一儲槽（5 )，該儲槽（5 )係設 於該工作台（2)下方用以接收電解蝕刻使用之該電解液 (4 1 )。该使用過的電解液（4 1 )中也許含有可資再利 用之金屬，例如貴重金屬，因此可採用傳統之方法將之電 鍵回收。 另外，該電解蝕刻裝置（i 〇 0)更可包括一純化設 備（6 )，該純化設備（6 )係用以過濾該使用過的電解液 (4 1 )。在實際應用時可將該使用過的電解液（4 1 )藉 由一幫浦（7)將之打入該純化設備（6)過濾後排入該 電解液供應源（4)以重新再利用，不僅減低污染，而且 資源不浪費。 综上所述，本發明所述之電解蝕刻裝置能夠有效地蝕 f一工作物之金屬材料，經由整合陰、陽兩電極之該電解 f 之没計展現高度動作之彈性，藉由適當的輔助元件使 得钱刻效果更加完全，不僅適合應用在自動化之不良品基 板的回收製程，更可應用在自動輯膜_之生產製程， 如此再經由環保回收之設計，無疑之高度環境友善之表態。 無論如何， 夠教導，並據而 任何人都可以從上述例子的說明中獲得足 了解到本發明確實具有產業上之利用性及 13 1302117 進步性，且本發明在同一領域中均未見有相同或類似技術 揭露在先而具足有新穎性，是本發明確已符合發明專利要 件，爰依法提出申請。The eye is further referred to the first picture. In view of the resource recovery considerations, the electrolysis insect engraving device (100) further includes a storage tank (5), which is located below the workbench (2). It is used to receive the electrolyte (4 1 ) used for electrolytic etching. The used electrolyte (4 1 ) may contain a reusable metal such as a precious metal, so it can be recovered by a conventional method. Further, the electrolytic etching apparatus (i 〇 0) may further comprise a purification device (6) for filtering the used electrolyte (4 1 ). In practical application, the used electrolyte (4 1 ) can be driven into the purification device (6) by a pump (7) and discharged into the electrolyte supply source (4) for reuse. Not only reduces pollution, but resources are not wasted. In summary, the electrolytic etching device of the present invention can effectively etch a metal material of a working object, and exhibits high flexibility of elasticity through the integration of the electrodes of the anode and the cathode, with appropriate assistance. The components make the money engraving effect more complete, not only suitable for the recycling process of the defective substrate for automation, but also for the production process of automatic film-making, so that the design of environmental recycling is undoubtedly a highly environmentally friendly statement. In any case, it is sufficient to teach, and anyone can obtain from the description of the above examples that the invention is indeed industrially usable and 13 1302117 progressive, and the present invention is not identical in the same field. Or similar technology reveals the prior and has novelty, and the invention has indeed met the requirements of the invention patent, and the application is filed according to law.
14 ^02117 【圖式簡單說明】 第—圖，係顯示本發明之電解韻刻裝置的一個較佳實 施例。 、 第二圖’係顯示該較佳實施例之刻單元之-例子。 第一圖，係顯示該钱刻單元之另一例子。 第四圖’係為該較佳實施例之俯視圖，顯示該餘刻單 元之一陽極結構。 第五圖，係顯示該蝕刻單元之另一陽極結構。 【主要元件符號說明】 (1 )蝕刻單元 (1 0 ) ( 1 0a)陽極 (1 0 0)電解钮刻裝置 (1 0 1)金屬件 (1 0 2)活動金屬件 (1 0 3)電極棒 (1 1)陰極 (12)絕緣罩 (121)末端 (1 3)固定板 (1 4)間隙 (1 5)開口 (2)工作台 (3)電源供應器 (4)電解液供應源 (4 1 )電解液 (5 )儲槽 (6)純化設備 (7 )幫浦 (8)工作物 (81)表層 1514 ^ 02117 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a preferred embodiment of the electrolytic engraving apparatus of the present invention. The second figure shows an example of the unit of the preferred embodiment. The first figure shows another example of the money engraving unit. The fourth figure is a top view of the preferred embodiment showing one of the anode structures of the remainder unit. The fifth figure shows another anode structure of the etching unit. [Main component symbol description] (1) Etching unit (1 0 ) (1 0a) Anode (1 0 0) Electrolytic button engraving device (1 0 1) Metal member (1 0 2) movable metal member (1 0 3) electrode Rod (1 1) Cathode (12) Insulation cover (121) End (1 3) Fixing plate (14) Clearance (1 5) Opening (2) Table (3) Power supply (4) Electrolyte supply source ( 4 1) Electrolyte (5) Storage tank (6) Purification equipment (7) Pump (8) Work material (81) Surface layer 15