201128182 六、發明說明： 【發明所屬之技術領域】 本發明係有關於以光散射方式檢查存在於透明薄片之 類的透明平板基板之表面之異物（附著於基板表面之微細 的塵埃、或瑕疵•裂痕等之缺陷）之技術，有關一種能夠 感度良好地檢出存在於透明基板之表面背面之異物，同時 ，確實地判別異物是存在於基板之表面抑或背面之哪一面 之異物檢查裝置及檢查方法。 【先前技術】 1C製造工程中，就算在形成電路圖案之基板僅稍微有 異物（碎屑或缺陷）存在，也會有關係到不良品生成之疑 慮，因此，基板之異物檢查是不可缺少的。這樣的異物檢 查，一般採用之方法是將指向性良好的雷射光照射至基板 表面，將從異物反射之散射光用受光感應裝置加以檢出之 方法，將雷射光之照射點做二次元掃描，進行基板表面全 體之檢查。 此外’近年來’液晶顯示裝置（LCD )、電漿顯示裝 置（PDP)等之平面型面板顯示裝置（FPD)逐漸成爲影 像顯示裝置之主流’而這些都是採用玻璃基板，基板上存 在異物成爲顯示裝置畫質不良或壽命降低的原因之一，因 此，異物檢查就有其必要。特別是，在主動矩陣方式之 LCD，於透明基板之一面會被形成TFT的細微圖案，因此 ，基板之異物檢查是不可少的。 -5- 201128182 附著於透明玻璃基板或透明薄膜基板之異物之檢查， 與晶圓等不透明的基板之場合同樣地，一般上採用光散射 方式之異物檢查方法。然而，透明玻璃基板或透明薄膜基 板會讓可視域之照射光或散射光透過，因此，不僅是照射 雷射之面（以下，簡稱「表面」）存在之異物，連照射雷 射之面的相反側之面（以下，簡稱「背面」）存在的異物 也都會檢出》從而，如何判別異物是附著於基板之表面或 背面哪一面就成爲重要課題。 要解決相關問題，須作成可以只檢出附著於玻璃基板 表面之異物，而不檢出附著於背面之異物。作爲該方法， 例如，下述專利文獻1所提出之方法，係採用不透過玻璃 基板、或者透過率較低的波長域之光源進行異物檢查之方 法。作爲這光源，例示有紫外域之準分子雷射或紅外域之 二氧化碳雷射。然而，該方法，被限定於光學系之透鏡等 材料透過檢査光之方法，因而有光學系高成本之問題。 下述專利文獻2，係揭示一種將受光系之光軸傾斜調 節至玻璃基板之全反射之臨界角附近，作成來自玻璃基板 內部之散射光幾乎不會射出外部之方式，僅檢出基板表面 之異物之表面缺陷檢查裝置。 亦即，如專利文獻2之圖1所示，在玻璃基板G之表面S 上，在比雷射檢出光L所照射之檢出位置P更前方配置檢出 用光學系14，接收存在於P點之異物所形成之散射光。此 時，檢出用光學系之傾斜角（與基板表面之間之角度）爲 全反射之臨界角附近。藉此，形成使來自玻璃基板背面之 -6- 201128182 異物之散射光的大部分以基板之界面全反射，不接收來自 基板背面之散射光之構成。 再者，爲了檢出玻璃基板表面或背面之異物’同時， 判別這是在表面或背面之哪一面，也有爲數不少提案嘗試 在雷射光之投射方法或散射光之受光方法上增添一些想法 (專利文獻3、4 )。專利文獻3之圖1中，將一對雷射光束 L 1、L2以朝向玻璃基板G斜斜地交差之方式照射，形成兩 光束之交點位於基板G之表面。因此，在基板G之背面， 兩光束之照射點並不一致化。異物所形成之散射光，係利 用垂直地配置於上方之檢出用光學系14加以檢出，在該狀 態下掃描基板與光學系之相對位置。 如專利文獻3之圖2所示方式，來自存在於基板G表面 之異物（微粒子）D1之散射光，會變成Pa、Pe之類的單獨 的較高的峰値，而來自存在於背面之異物D2之散射光，則 如Pb、Pf般波形較低，於一定的時間間隔△ t下變成2個2 個一組之峰値。△ t可由掃描速度v與間隔d求出。從而， 能夠藉由解析散射光之波形，判定是表面或背面哪一面之 異物。此外，散射光之強度，會因爲異物是在表面抑或在 背面而有大幅地差異，所以能夠改變判別之閾値之水準而 進行異物有無之判定。 此外，專利文獻4係提出一種方法，於玻璃基板表面 之受光領域之空間設置散射光收集器（trap )並將受光領 域分割爲二，分別配置受光感測裝置，利用根據異物是存 在於基板表面抑或背面之哪一面而使兩受光感測裝置之受 201128182 光量之比率相異’進行異物之位置判別之方法。亦即，如 專利文獻4之圖5所示’來自雷射照射部1之雷射光，係由 於基板100表面之異物使之散射。將該散射光用橢圓鏡（ mirror) 2b集光，利用被配置於橢圓鏡2b之焦點附近之散 射光用受光器2加以檢出。此時’使收集器（trap ) 2 a直立 於橢圓鏡2b之中心附近，將受光領域分割爲二，而且，於 收集器2 a之左右配置各1個受光感測裝置（第1、2偵測器 ;detector ) 2c、2d，記錄各自之訊號。在異物存在於表 面時，如圖4 ( a )所示，收集器2a之左側（第1偵測器2c )之領域之受光量較大，使左右感測裝置之訊號波形產生 差異。另一方面，在異物存在於背面時，如圖4(b)所示 ，收集器2 a左右領域之受光量之差異較小。利用此，並利 用比較判定電路5，判定異物是存在於基板表面抑或背面 之哪一面。 [先行技術文獻] [專利文獻] [專利文獻1]日本專利特開平05 — 1 96 579號公報 [專利文獻2]日本專利特開平05 - 27 3 1 3 7號公報 [專利文獻3]日本專利特開平06 - 258232號公報 [專利文獻4]日本專利特開2003-294653號公報 【發明內容】 [發明所欲解決之課題] -8 - 201128182 例如，FPD用透明平板基板之異物，不管是在基板表 面或背面之哪一面都會影響到顯示裝置之畫質，因而，最 好是能夠在一回的異物檢查下就檢出表面背面兩者之異物 。此外，LCD用透明平板基板方面，在TFT被形成之面與 其背面，異物的影響度基本上是不同的，因而，最好是能 夠確實地檢出異物是在基板的表面或背面之哪一面。一般 而言，光散射方式之異物檢查方面，來自表面之異物之散 射光與來自背面之異物之散射光，兩者之強度差異大。因 此’問題是在表面係能夠檢出到微細的異物，而背面之微 細的異物檢出則較難。 根據本案發明人等之見解，前述專利文獻3之可以判 別表面背面之異物檢査方法方面，並未考慮到對上述問題 之對應，困難點在於檢出背面之微細的異物。此外，該等 之檢查方法，係解析受光感應裝置之訊號波形以判定異物 是在表面或背面哪一面之方法’然而，散射光之訊號波形 係隨異物種類之不同而異’因此，作成錯誤判定之情況也 不少，檢查結果之可信賴性不足，很難說具有實用性。 另一方面’專利文獻4之檢查方法方面，不僅裝置複 雜且成本高，測定前之光學系調整相當費時費事等都是問 題，期待有更爲簡便的方法。 在此，本發明之課題就在於提供一種異物檢查裝置及 檢查方法，能夠將存在於透明平板基板表面背面之微細的 異物利用光散射方式高感度地檢出，而且能夠確實地判別 異物是存在於表面抑或背面之哪一面。 -9 - 201128182 【實施方式】 用以解決上述課題之，申請專利範圍第1項記載之本 發明係一種異物檢查裝置，於透明平板基板利用投光系照 射檢出光，且利用受光系接收存在於前述透明平板基板之 異物所形成之散射光並檢出前述異物的存在之異物檢查裝 置，其特徵係具備：於前述透明平板基板一方的面（以下 ，簡稱「表、面」）對著前述透明平板基板之基板法線以特 定射入角照射前述檢出光之投光系；被設於前述表面側， 以前述檢出光之照射點爲基準，被設在與前述投光系大略 對稱之位置，接收前述檢出光照射到異物時之散射光之第 1受光系；與在前述表面側，被設於前述檢出光之照射點 的大致頭上’接收前述散射光之第2受光系。 申請專利範圍第2項記載之發明，係申請專利範圍第1 項記載之異物檢査裝置，其中前述第2受光系係具備限制 所接收之前述散射光之範圍之受光範圍限制手段。受光限 制手段’例如’能夠藉由在散射光射入第2受光系之面安 裝限制受光範圍之板或遮光濾光片而進行。 申請專利範圍第3項記載之發明，係申請專利範圍第1 或2項記載之異物檢查裝置，其中係利用前述受光範圍限 制手段’使第2受光系所接收之，透過前述透明平板基板 內之檢出光（以下’簡稱「透過光」）照射至存在於前述 透明平板基板之另一面（以下，簡稱「背面」）側之異物 時之散射光之範圍受到限制。利用該受光範圍限制手段， -10 - 201128182 例如，由存在於透明平板基板表面之異物所發生之散射光 ，係利用第1、第2受光系而被接收，而由存在於透明平板 基板背面之異物所發生之散射光，則受到第2受光系之限 制接收。結果，能夠縮小存在於背面側之異物所形成之散 射光之受光強度。 申請專利範圍第4項記載之發明，係申請專利範圔第1 、2或3任一項記載之異物檢查裝置，其中具備由前述第1 受光系與前述第2受光系所得到之散射光強度資料之對比 ，判別異物是存在於前述透明平板基板表面抑或背面之哪 一面之判別手段。例如，於透明平板基板之雷射光照射點 ，以第1受光系接收散射光，此外，同時在第2受光系也接 收到散射光。在該場合，能夠判別爲異物是存在於透明平 板基板之表面。這是因爲，第2受光系利用受光範圍限制 手段，幾乎不接收存在於背面側之異物所產生之散射光的 緣故。另一方面，在以第1受光系接收散射光，而第2受光 系不接收散射光，或其強度非常小之場合，能夠判別爲異 物是存在於透明平板基板之背面。 申請專利範圍第5項記載之發明，係申請專利範圍第1 、2、3或4任一項記載之異物檢查裝置，其中具備由前述 第1受光系與前述第2受光系所得到之散射光強度資料，檢 出前述透明平板基板之異物的位置、及大小之異物解析手 段。存在於透明平板基板之異物的位置，係能夠由檢出光 之掃描位置求出。此外，異物的大小，係能夠藉由參照將 散射光強度與異物大小建立關係之檢量線而求出。藉由該 -11 - 201128182 等，就能夠容易判別存在於透明平板基板之異物的位置、 及其大小。 申請專利範圍第6項記載之發明，係申請專利範圍第1 至5任一項記載之異物檢查裝置，其中前述檢出光係雷射 光。 申請專利範圍第7項記載之發明，係一種異物檢查方 法，掃描被照射至透明平板基板之一方的面（以下，簡稱 「表面」）之檢出光，且接收來自存在前述透明平板基板 之異物之散射光，而檢出異物之異物檢查方法，其特徵在 於：將前述檢出光對著前述透明平板基板以特定射入角照 射’有關前述檢出光之照射點，於大略對稱的位置，接收 來自被照射前述檢出光之異物之第1散射光，於前述檢出 光之照射點之大致頭上的位置，接收來自被照射前述檢出 光之異物之第2散射光，由前述第1散射光之強度、及前述 第2散射光之強度，檢出存在於前述透明平板基板之異物 〇 申請專利範圍第8項記載之發明，係申請專利範圍第7 項記載之異物檢查方法，其中將透過前述透明平板基板內 之檢出光（以下，簡稱「透過光」），在照射至存在於前 述透明平板基板之另一面（以下，簡稱「背面」）側之異 物時所產生之散射光受到第2受光系接收之範圍限制，使 存在於背面側之異物所形成之散射光的強度降低。 申請專利範圍第9項記載之發明，係申請專利範圍第7 或8項記載之異物檢查方法，其中係由前述第1散射光之強 -12- 201128182 度、前述第2散射光之強度、與事先決定之散射光強度之 閾値，判別異物是存在於前述透明平板基板之表面抑或背 面之哪一面。散射光強度之閾値，係能夠根據玻璃的厚度 、透過率、波長等加以設定。 例如，藉由決定第2受光系接收之散射光強度之閾値 ’就能夠設定第2受光系對來自透明平板基板之背面所存 在之異物之散射光之接收限制。藉此，在以第1受光系及 第2受光系接收散射光之場合，能夠判別爲異物是存在於 透明平板基板之表面。此外，在以第1受光系接收散射光 ，而第2受光系不接收散射光，就能夠判別爲異物是存在 於透明平板基板之背面。 申請專利範圍第1 〇項記載之發明，係申請專利範圍第 7至9任一項記載之異物檢查方法，其中前述檢出光係雷射 光。 [發明之效果] 利用本發明，可以提供一種異物檢查裝置及檢查方法 ，能夠將存在於透明平板基板表面背面之微細的異物高感 度地檢出，而且，可以確實地判別異物是存在於表面抑或 背面之哪一面。 [用以實施發明之最佳型態] 以下，參照圖面並針對本發明之實施型態加以說明。 圖1係圖示本發明之一實施型態之異物檢查裝置之全體槪 -13- 201128182 略構成。該異物檢查裝置，係一種檢查附著到透明的平板 基板（本實施型態爲玻璃基板20)之異物之裝置。該異物 檢查裝置，係由被設在照射雷射光之面（表面）之雷射光 源11與散射光受光器12及散射光受光器13所構成。 雷射光源11、散射光受光器〗2、13，都是被安裝於框 架（frame ) 1，對於玻璃基板20，得以X軸、Y軸之二次元 進行掃描之方式構成。當然，並非掃描雷射光源11、散射 光受光器12、13，而對於雷射光源11、散射光受光器12、 13得以二次元地掃描玻璃基板20之方式構成亦可。 雷射光源1 1，係將雷射光（標準光束徑爲例如1 . Omm )以射入角（射入光之光軸與基板法線之間的角度）對著 玻璃基板20照射之投光系。玻璃基板之場合下，例如，射 入角在70度至80度左右最佳。光源方面，例如，能使用 He-Ne雷射等之氣體雷射、半導體雷射及YAG雷射等之合 成元素雷射等等。 散射光受光器1 2，係以雷射光之照射點爲基準，被設 在與雷射光源1 1大略對稱之位置，接收雷射光照射到異物 時之散射光，檢出由此所發生之訊號。散射光受光器12, 因爲要高感度地檢出存在於表面之異物散射到前方之散射 光，所以最好是採用直徑比較大的聚光透鏡（condenser lense)。此外，散射光受光器12之散射光受光角度最好是 在60度附近。 於圖1，本發明之特徵，係在於除了散射光受光器12 ，再加上，於照射點之大致頭上設置散射光受光器13。散 -14 - 201128182 射光受光器I3，係由散射光檢出部131、鏡筒132、與觀察 用攝影機133所構成。 圖2，係圖示將雷射光110照射至玻璃基板20時之反射 光、異物所形成之散射光之狀態 '及散射光受光器12接受 之散射光的範圍。雷射光110，係從雷射光源11之雷射輸 出部111以一定之射入角被照射至玻璃基板20。在異物並 不存在於玻璃基板20之場合’雷射光1 10係在照射點正反 射形成反射光1 5 1到達散射光受光器1 2。因爲散射光受光 器1 2係以接收存在於玻璃基板20之異物所發生之散射光作 爲目的，所以反射光151是不要的。於是，本實施型態， 係作成以例示受光範圍限制手段之一之遮光膠帶1 2 7進行 遮罩，使反射光151之光線無法進入散射光檢出部124。 在有異物30a存在於玻璃基板20之場合，由被照射到 異物3 0 a之雷射光1 1 0會產生散射光1 5 2。散射光1 5 2，係利 用聚光透鏡121 ( 121a、121b)被聚光，利用散射光檢出 部124而被檢出。 另一方面’在有異物30b存在於玻璃基板20背面之場 合，透過玻璃基板之雷射光（以下，簡稱「透過光」）會 被照射到異物30b、產生散射光153。本實施型態中，散射 光152、153都是利用聚光透鏡121 ( 121a、121b)被聚光 ’利用散射光檢出部124而被檢出。因此，散射光受光器 12成爲接收來自玻璃基板20表面之異物30a之散射光152、 與來自背面之異物3 Ob之散射光153雙方之散射光。 圖3，係圖示將雷射光11〇照射至玻璃基板20時之反射 -15- 201128182 光、異物所形成之散射光之狀態、及散射光受光器 之散射光的狀態。本發明之特徵係在於除了散射光 12，加上，散射光受光器13被設成對水平設置之玻 2 0直交之方式。藉著如此設置，使散射光受光器13 面與玻璃基板20大致平行。 此外，本發明之特徵係在散射光受光器13之受 裝受光範圍限制板1 30。利用該受光範圍限制板1 30 限制散射光受光器1 3接收之散射光的範圍。 針對散射光受光器13接收之散射光加以說明， 並不存在於玻璃基板20之場合，雷射光1 10係在照 反射變成反射光151。散射光受光器13，因爲是設 璃基板20之照射點的大致頭上，所以反射光151射 光受光器1 3的情形是幾乎不可能發生。 在有異物30a存在於玻璃基板20表面之場合， 照射到異物30a之雷射光1 10產生散射光152。藉著| ，於上方發生之散射光152，則藉由被設在雷射照 大致頭上之散射光受光器13而被接收。散射光152 過鏡筒132，利用反射鏡134被曲折成大致直角、射 用攝影機133、而被檢出。 在玻璃基板20的背面有異物30b之場合，透過 照射到異物30b。藉此使散射光153發生，但是散射 器13並不在異物30b的大致頭上。正因爲根據玻璃 的折射率與玻璃基板的厚度所決定之距離，所以 3 〇b偏離散射光受光器13之中心點。因此，散射至 1 3接受 受光器 璃基板 之受光 光面安 ，能夠 在異物 射點正 置於玻 入散射 藉由被 !物 3 0 a 射點之 ，係通 入觀察 光會被 光檢出 基板20 使異物 背面側 -16- 201128182 之異物30b之上方之散射光153，由散射光受光器13所接收 之比例變少。再者，於散射光受光器13之受光面設置受光 範圍限制板130。藉此，由異物30b所產生之散射光153之 受光範圍便受到限制。根據此等，散射光受光器1 3，雖接 收來自玻璃基板20表面之異物30a之散射光152，接收來自 背面之異物3 Ob之散射光1 5 3之比例卻變得極少。 圖4 (a)係圖示利用散射光受光器12、13而被接收之 散射光之受光領域。散射光受光器1 2之受光領域係受光領 域140。此外，散射光受光器13之受光領域係受光領域141 〇 更確切地說，當玻璃基板20表面之異物30a被雷射光 1 1 〇照射時，因爲散射光受光器1 2之受光領域爲受光領域 140，所以受光器12會接收散射光。此外，因爲散射光受 光器13之受光領域爲受光領域141，所以30a產生之散射光 也會被散射光受光器13所接收。亦即，由玻璃基板20表面 之異物30a所發生之散射光會被散射光受光器12、13雙方 所接收。 一方面，由存在於玻璃基板2〇背面之異物30b所發生 之散射光，因爲利用受光範圍限制板1 3 0讓其受光領域受 限制於受光領域的緣故，而不會射入散射光受光器13 。另一方面，因爲散射光受光器12之受光領域爲受光領域 140內，所以散射光受光器12會接收散射光。 又，於圖4(b)，以剖面圖顯示存在於玻璃基板20表 面之異物3 0a以及存在於背面之異物3 Ob之位置關係、與依 -17- 201128182 照散射光受光器1 2、1 3之散射光之檢出領域。 圖5係圖示將以散射光受光器12、13接收到之散射光 所發生之訊號加以處理之散射光檢出電路40。來自散射光 受光器12、散射光受光器13之輸出訊號，在利用增幅器41 (41a、41b)增幅後，被輸入資料解析電路42 (42a、4 2b )，判別異物之位置' 大小。 於資料解析電路42，準備著附以散射光強度與異物尺 寸關聯性之表（table )。能夠藉由用散射光受光器12、13 所得到之散射光強度之資料、與作成關聯表而被蓄積之資 料將兩者加以比較，解析異物之尺寸。此外，由雷射光源 1 1、散射光受光器1 2、1 3與雷射光1 1 〇之照射位置，解析 附著於玻璃基板20之異物之位置。 於資料解析電路42設置記憶體，讓解析結果可蓄積、 記憶於該記憶體。該等之資料係於比較判別電路43，將事 先決定之散射光強度之閾値與資料解析電路42之輸出進行 對比，判別異物是存在於玻璃基板20之表面或背面之哪一 面。 圖6以及圖7係圖示針對在玻璃基板20之移動伴隨雷射 光之照射位置之移動時來自異物之散射光輸出之強弱 。圖6 (a)係圖示針對存在於玻璃基板20表面之異物30a 被照射到雷射光1 1 0時之散射光之輸出。 當異物30a被雷射光1 1〇照射時，其散射光係如圖7 ( b )所示’由散射光受光器12作成散射光輸出訊號160而被 輸出。此外，從散射光受光器1 3則是作成散射光輸出訊號 -18- 201128182 170而被輸出（圖7(c))。該等之散射光輸出訊號（160 、170)，係利用圖5所示之散射光檢出電路40，作成表背 分離輸出訊號180而被輸出（圖7(a))。結果，判別異 物30a係在玻璃基板20之表側。 又，藉由玻璃基板20往右移動，如圖6 ( c)所示，本 來在雷射光1 10之照射點應該沒有的異物30a’，會由散射 光受光器I2作成散射光輸出訊號161而被輸出（圖7(b) )。這樣的散射光輸出訊號161係弱的輸出訊號。此外， 作成用散射光受光器13幾乎不會被檢出之程度之非常弱的 散射光輸出訊號171而被檢出（圖7(c))。 該種疑似異物的檢出係能夠用以下作法除去。首先， 異物3 0a’之位置，係如圖6 ( c )所示方式能夠從玻璃基板 20之移動距離、與取決於玻璃厚度之折射率加以決定。因 此，在異物3 0 a被檢出之後，於一定時間後進行由散射光 受光器12被輸出之散射光輸出訊號161與由散射光受光器 13被輸出之散射光輸出訊號171之輸出訊號強度、以及輸 出訊號之比較。在散射光輸出訊號171比散射光輸出訊號 161還要極爲微弱，而且散射光輸出訊號161比散射光輸出 訊號160還要小之場合，此時判斷被檢出之異物30a’之輸 出訊號爲疑似異物訊號，可以當作實際上並不存在之異物 而除去。 圖8係圖示如圖6 ( b )所示之類的，於玻璃基板20背 面有異物之場合下散射光受光器12之輸出（圖8(b))、 散射光受光器13之輸出（圖8(c))、以及表背分離輸出 -19- 201128182 (圖8(a))。如圖8(b)所示，在玻璃基板2〇之背面有 異物時，會由散射光受光器12輸出散射光輸出訊號190。 另一方面，如圖8(c)所示，並無來自散射光受光器13之 輸出訊號。因爲這些，所以表背分離輸出訊號就成爲圖8 (a)所示之類的輸出訊號，判別出在玻璃基板20之表面 並不存在異物。 【圖式簡單說明】 圖1係顯示本發明之一實施例之異物檢查裝置之全體 構成之槪念圖。 圖2係圖示針對用散射光受光器12所接收之散射光之 範圍。 圖3係圖示針對用散射光受光器1 3所接收之散射光之 範圍。 圖4係圖示依照散射光受光器12，13之散射光之受光 範圍。 圖5係圖示將以散射光受光器1 2、1 3接收到之散射光 所發生之訊號加以處理之散射光檢出電路。 圖6係圖示針對雷射光照射位置之移動所伴隨之來自 異物之散射光輸出之強弱。 圖7係圖示針對雷射光照射位置之移動所伴隨之來自 異物之散射光輸出之強弱。 圖8係圖不針對雷射光照射位置之移動所伴隨之來自 異物之散射光輸出之強弱 -20- 201128182 【主要元件符號說明】 1 :框架（frame) 1 1 :雷射光源 12、13:散射光受光器 20 :玻璃基板 30a:玻璃基板20表面之異物 30b :玻璃基板20背面之異物 40 :散射光檢出電路 41 ( 41a,41b):增幅器（amplifier) 42 ( 42a，42b ):資料解析電路 43 :比較判別電路 1 1 〇 :雷射光 1 1 1 :雷射輸出部 121 ( 121a,121b):聚光透鏡(condenser lense 124 :散射光檢出部 127 :遮光膠帶 1 3 0 :受光範圍限制板 1 3 1 :散射光檢出部 1 3 2 :鏡筒 1 3 3 =觀察用攝影機 1 3 4 :反射鏡 140 :散射光受光器12之受光領域 1 4 1 :散射光受光器1 3之受光領域 -21 - 201128182 142 :觀察用攝影機133之視野 143 :玻璃基板20表面之雷射光照射領域 1 5 1 :反射光 152、153 :散射光 160，161，170，171,190:散射光輸出訊號 180:背表分離輸出訊號 -22-BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter (a fine dust adhering to a surface of a substrate, or a ruthenium attached to a surface of a transparent flat substrate such as a transparent sheet by light scattering. A technique for detecting a foreign matter existing on the back surface of a transparent substrate with a good sensitivity, and at the same time, reliably determining whether the foreign matter is on the surface of the substrate or the back surface, and the inspection method and inspection method . [Prior Art] In the 1C manufacturing process, even if there is only a slight foreign matter (debris or defect) in the substrate on which the circuit pattern is formed, there is a concern that the defective product is generated. Therefore, the foreign matter inspection of the substrate is indispensable. Such a foreign matter inspection generally adopts a method in which laser light having good directivity is irradiated onto the surface of the substrate, and the scattered light reflected from the foreign matter is detected by the light receiving induction device, and the irradiation point of the laser light is subjected to a secondary scanning. The entire surface of the substrate is inspected. In addition, 'in recent years' flat panel display devices (FPDs) such as liquid crystal display devices (LCDs) and plasma display devices (PDPs) have gradually become the mainstream of image display devices, and these are glass substrates, and foreign matter is present on the substrate. The display device has one of the reasons for poor image quality or reduced life. Therefore, foreign matter inspection is necessary. In particular, in an active matrix type LCD, a fine pattern of a TFT is formed on one surface of a transparent substrate, and therefore, foreign matter inspection of the substrate is indispensable. -5- 201128182 Inspection of foreign matter attached to a transparent glass substrate or a transparent film substrate is similar to the case of an opaque substrate such as a wafer, and a foreign matter inspection method using a light scattering method is generally employed. However, since the transparent glass substrate or the transparent film substrate transmits the irradiation light or the scattered light in the visible region, it is not only the foreign matter existing on the surface irradiated with the laser (hereinafter referred to as "surface"), but the opposite of the surface irradiated with the laser. The foreign matter existing on the side surface (hereinafter referred to as "back surface") is also detected. Therefore, it is an important issue to determine which side of the substrate is attached to the surface or the back surface of the substrate. To solve the problem, it is necessary to detect only the foreign matter adhering to the surface of the glass substrate, and not to detect the foreign matter attached to the back surface. As such a method, for example, the method proposed in Patent Document 1 below is a method of performing foreign matter inspection without passing through a glass substrate or a light source having a low transmittance. As this light source, a carbon dioxide laser having a pseudo-molecular laser in the ultraviolet region or an infrared region is exemplified. However, this method is limited to a method of inspecting light by a material such as a lens of an optical system, and thus has a problem of high cost of the optical system. Patent Document 2 listed below discloses a method in which the optical axis of the light receiving system is tilted to the vicinity of the critical angle of total reflection of the glass substrate, and the scattered light from the inside of the glass substrate is hardly emitted from the outside, and only the surface of the substrate is detected. Surface defect inspection device for foreign objects. In other words, as shown in FIG. 1 of Patent Document 2, on the surface S of the glass substrate G, the detection optical system 14 is disposed in front of the detection position P irradiated by the laser detection light L, and the reception is present on the surface. Scattered light formed by foreign matter at point P. At this time, the tilt angle of the optical system for detection (the angle from the surface of the substrate) is near the critical angle of total reflection. Thereby, most of the scattered light from the -6-201128182 foreign matter on the back surface of the glass substrate is totally reflected at the interface of the substrate, and the scattered light from the back surface of the substrate is not received. Furthermore, in order to detect the foreign matter on the surface or the back surface of the glass substrate, and to determine which side is on the surface or the back side, there are also many proposals to add some ideas to the projection method of the laser light or the light receiving method of the scattered light. (Patent Documents 3 and 4). In Fig. 1 of Patent Document 3, a pair of laser beams L1, L2 are irradiated obliquely to the glass substrate G so that the intersection of the two beams is located on the surface of the substrate G. Therefore, on the back surface of the substrate G, the irradiation points of the two beams do not coincide. The scattered light formed by the foreign matter is detected by the detection optical system 14 disposed vertically above, and the relative position of the substrate and the optical system is scanned in this state. As shown in FIG. 2 of Patent Document 3, the scattered light from the foreign matter (fine particles) D1 existing on the surface of the substrate G becomes a single higher peak of Pa or Pe, and the foreign matter existing on the back side. The scattered light of D2 has a low waveform like Pb and Pf, and becomes a peak of two groups of two at a certain time interval Δt. Δt can be obtained from the scanning speed v and the interval d. Therefore, it is possible to determine which side of the surface or the back surface is foreign matter by analyzing the waveform of the scattered light. Further, since the intensity of the scattered light is greatly different depending on whether the foreign matter is on the surface or on the back surface, the level of the threshold 判别 can be changed to determine the presence or absence of the foreign matter. Further, Patent Document 4 proposes a method of disposing a scattered light collector (trap) in a space in a light receiving area of a surface of a glass substrate and dividing the light receiving area into two, respectively arranging a light receiving sensing device, which is present on the surface of the substrate according to the foreign matter. Or which side of the back side is used to make the position of the two light-receiving devices different by the ratio of the amount of light of 201128182'. That is, as shown in Fig. 5 of Patent Document 4, the laser light from the laser irradiation unit 1 is scattered by foreign matter on the surface of the substrate 100. This scattered light is collected by an elliptical mirror 2b, and is detected by the light-receiver 2 disposed near the focal point of the elliptical mirror 2b. At this time, 'the trap 2 a is erected near the center of the elliptical mirror 2b, and the light-receiving area is divided into two, and one light-sensing device is disposed on the left and right sides of the collector 2a (the first and second detectors) Detector; 2c, 2d, record their respective signals. When foreign matter is present on the surface, as shown in Fig. 4 (a), the amount of light received by the left side of the collector 2a (the first detector 2c) is large, and the signal waveforms of the left and right sensing devices are different. On the other hand, when foreign matter is present on the back surface, as shown in Fig. 4(b), the difference in the amount of light received by the left and right fields of the collector 2a is small. With this, the comparison judging circuit 5 is used to determine which side of the substrate is present or which is on the back side. [PRIOR ART DOCUMENT] [Patent Document 1] Japanese Patent Laid-Open Publication No. Hei 05-196-579 [Patent Document 4] Japanese Laid-Open Patent Publication No. 2003-294653 [Draft of the Invention] [Problems to be Solved by the Invention] -8 - 201128182 For example, a foreign matter of a transparent flat substrate for FPD, regardless of Which side of the substrate surface or the back surface affects the image quality of the display device, and therefore it is preferable to detect foreign matter on both the front and back surfaces under one-time foreign matter inspection. Further, in the case of a transparent flat substrate for LCD, the degree of influence of foreign matter on the surface on which the TFT is formed and the back surface thereof are substantially different. Therefore, it is preferable to reliably detect which side of the substrate is the surface or the back surface of the substrate. In general, in the inspection of a foreign matter by a light scattering method, the intensity of the difference between the scattered light from the foreign matter on the surface and the scattered light from the foreign matter on the back surface is large. Therefore, the problem is that it is possible to detect fine foreign matter on the surface, and it is difficult to detect fine foreign matter on the back surface. According to the inventors of the present invention, in the above-mentioned Patent Document 3, it is possible to determine the foreign matter inspection method on the back surface of the surface, and the above problem is not considered. The difficulty lies in detecting fine foreign matter on the back surface. In addition, the inspection method is a method of analyzing the signal waveform of the light-sensing device to determine which side of the surface is on the surface or the back surface. However, the signal waveform of the scattered light varies depending on the type of foreign matter. Therefore, an error is determined. There are also many cases, and the reliability of the inspection results is insufficient, so it is difficult to say that it is practical. On the other hand, in the inspection method of Patent Document 4, not only is the apparatus complicated and the cost is high, but the adjustment of the optical system before the measurement is time consuming and troublesome, and the like, and a simpler method is expected. In view of the above, an object of the present invention is to provide a foreign matter inspection device and an inspection method capable of detecting a fine foreign matter existing on the back surface of a transparent flat substrate by light scattering, and reliably detecting that foreign matter is present in the foreign matter. Which side of the surface or the back side. -9 - 201128182 EMBODIMENT OF THE INVENTION The present invention described in claim 1 is a foreign matter inspection device that emits light on a transparent flat substrate by a light projecting system and receives it by a light receiving system. The foreign matter inspection device that detects the scattered light of the foreign matter on the transparent flat substrate and detects the presence of the foreign matter is characterized in that the surface of the transparent flat substrate (hereinafter, simply referred to as "table, surface") faces the aforementioned a substrate normal line of the transparent flat substrate is irradiated with the light-emitting system for detecting the light at a specific incident angle; and is provided on the surface side, and is provided symmetrically with the light-emitting system based on the irradiation point of the detected light. a first light receiving system that receives the scattered light when the detected light is irradiated onto the foreign matter; and a second light receiving system that receives the scattered light on a substantially head of the irradiation point of the detected light on the surface side . The invention according to claim 2, wherein the second light receiving system includes a light receiving range restricting means for limiting a range of the received scattered light. The light-receiving means "for example" can be performed by mounting a plate or a light-shielding filter that limits the light-receiving range on the surface on which the scattered light is incident on the second light-receiving system. The invention according to claim 1 is the foreign matter inspection device according to the first or second aspect of the invention, wherein the second light receiving system is received by the light receiving range limiting means, and is transmitted through the transparent flat substrate. The range of the scattered light when the detected light (hereinafter referred to as "transmitted light") is irradiated onto the other side of the transparent plate substrate (hereinafter referred to as "back surface") is limited. By the light-receiving range restriction means, for example, the scattered light generated by the foreign matter existing on the surface of the transparent flat substrate is received by the first and second light receiving systems, and is present on the back surface of the transparent flat substrate. The scattered light generated by the foreign matter is received by the second light receiving system. As a result, the received light intensity of the scattered light formed by the foreign matter existing on the back side can be reduced. The invention according to claim 4, wherein the foreign matter inspection device according to any one of the first, second or third aspect, wherein the first light receiving system and the second light receiving system are provided with scattered light intensity According to the comparison of the data, it is discriminated that the foreign matter is a side of the surface of the transparent flat substrate or the back surface. For example, at the laser light irradiation point of the transparent flat substrate, the scattered light is received by the first light receiving system, and the scattered light is also received by the second light receiving system. In this case, it can be determined that the foreign matter is present on the surface of the transparent flat substrate. This is because the second light receiving system uses the light receiving range restricting means to hardly receive the scattered light generated by the foreign matter existing on the back side. On the other hand, when the first light receiving system receives the scattered light and the second light receiving system does not receive the scattered light, or the intensity thereof is extremely small, it can be determined that the foreign matter is present on the back surface of the transparent flat substrate. The foreign matter inspection device according to any one of the first, second, third or fourth aspect of the invention, wherein the first light receiving system and the second light receiving system are provided with scattered light. The strength data is a foreign matter analysis means for detecting the position and size of the foreign matter on the transparent flat substrate. The position of the foreign matter present on the transparent flat substrate can be obtained from the scanning position of the detected light. Further, the size of the foreign matter can be obtained by referring to a calibration curve that establishes a relationship between the intensity of the scattered light and the size of the foreign matter. With this -11 - 201128182 or the like, the position and size of the foreign matter existing on the transparent flat substrate can be easily discriminated. The foreign matter inspection device according to any one of claims 1 to 5, wherein the light-detecting laser light is detected. The invention described in the seventh aspect of the invention is a foreign matter inspection method for scanning the detected light that is irradiated onto one of the surfaces of the transparent flat substrate (hereinafter referred to as "surface"), and receives foreign matter from the existence of the transparent flat substrate. The foreign matter inspection method for detecting foreign matter is characterized in that the detection light is irradiated to the transparent plate substrate at a specific incident angle with respect to an irradiation point of the detected light at a substantially symmetrical position. Receiving the first scattered light from the foreign matter irradiated with the detection light, and receiving the second scattered light from the foreign matter irradiated with the detection light at a position on the approximate head of the irradiation point of the detection light, by the first The invention according to the eighth aspect of the patent application scope of claim 4, wherein the strength of the scattered light and the intensity of the second scattered light are detected in the foreign matter of the transparent plate substrate, and the method for inspecting the foreign matter described in claim 7 The light that has passed through the transparent flat substrate (hereinafter referred to as "transmitted light") is irradiated to the other of the transparent flat substrates. When scattering of the generated surface (hereinafter, referred to as "back surface") side of the foreign substance by the second optical system receiving light of the limited range, so that the intensity of scattered light in the presence of the foreign body is formed of the rear surface side is reduced. The invention according to claim 9 is the foreign matter inspection method according to the seventh or eighth aspect of the invention, wherein the intensity of the first scattered light is -12 to 201128182 degrees, and the intensity of the second scattered light is The predetermined threshold of the scattered light intensity determines whether the foreign matter is present on the surface or the back surface of the transparent flat substrate. The threshold 散射 of the scattered light intensity can be set according to the thickness, transmittance, wavelength, and the like of the glass. For example, by determining the threshold 値 ' of the intensity of the scattered light received by the second light receiving system, it is possible to set the reception restriction of the scattered light of the foreign matter existing on the back surface of the transparent flat substrate by the second light receiving system. Thereby, when the scattered light is received by the first light receiving system and the second light receiving system, it can be determined that the foreign matter is present on the surface of the transparent flat substrate. Further, when the scattered light is received by the first light receiving system and the scattered light is not received by the second light receiving system, it can be determined that the foreign matter is present on the back surface of the transparent flat substrate. The invention of claim 1 is the foreign matter inspection method according to any one of claims 7 to 9, wherein the light-based laser light is detected. [Effect of the Invention] According to the present invention, it is possible to provide a foreign matter inspection device and an inspection method capable of detecting a fine foreign matter existing on the back surface of the surface of a transparent flat substrate with high sensitivity, and reliably determining whether the foreign matter is present on the surface or Which side of the back. [Best Mode for Carrying Out the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the entire configuration of a foreign matter inspection device according to an embodiment of the present invention. This foreign matter inspection device is a device for inspecting foreign matter attached to a transparent flat substrate (the present embodiment is a glass substrate 20). The foreign matter inspection device is composed of a laser light source 11 and a scattered light receiver 12 and a scattered light receiver 13 which are provided on a surface (surface) on which laser light is irradiated. The laser light source 11 and the scattered light receivers 2 and 13 are mounted on a frame 1. The glass substrate 20 is formed by scanning a binary element of the X-axis and the Y-axis. Of course, the laser light source 11 and the scattered light receivers 12 and 13 are not scanned, and the laser light source 11 and the scattered light receivers 12 and 13 may be configured to scan the glass substrate 20 twice. The laser light source 1 1 is a projection light system that irradiates the glass substrate 20 with laser light (the standard beam diameter is, for example, 1.0 mm) at an incident angle (an angle between the optical axis of the incident light and the substrate normal). . In the case of a glass substrate, for example, the incident angle is preferably about 70 to 80 degrees. For the light source, for example, a gas laser such as a He-Ne laser, a semiconductor laser, a synthetic element laser such as a YAG laser, or the like can be used. The scattered light receiver 12 is set at a position slightly symmetrical with the laser light source 1 1 based on the irradiation point of the laser light, and receives the scattered light when the laser beam is irradiated to the foreign object, and detects the signal generated thereby. . In the scattered light receiver 12, it is preferable to use a condenser lens having a relatively large diameter because it is highly sensitive to detect scattered light that is scattered to the front by foreign matter existing on the surface. Further, the light receiving angle of the scattered light by the scattered light receiver 12 is preferably around 60 degrees. In Fig. 1, the present invention is characterized in that, in addition to the scattered light receiver 12, a scattered light receiver 13 is provided on the approximate head of the irradiation spot.散 -14 - 201128182 The illuminating light receiver I3 is composed of a scattered light detecting unit 131, a lens barrel 132, and an observation camera 133. Fig. 2 is a view showing a range of the reflected light when the laser light 110 is irradiated onto the glass substrate 20, the state of the scattered light formed by the foreign matter, and the scattered light received by the scattered light receiver 12. The laser light 110 is irradiated onto the glass substrate 20 from the laser output portion 111 of the laser light source 11 at a predetermined incident angle. In the case where the foreign matter does not exist on the glass substrate 20, the laser light 10 is reflected at the irradiation spot to form the reflected light 157 to reach the scattered light photoreceiver 12. Since the scattered light is received by the photoreceptor 12 to receive the scattered light generated by the foreign matter existing on the glass substrate 20, the reflected light 151 is unnecessary. Then, in the present embodiment, the light-shielding tape 1 2 7 which is one of the light-receiving range restricting means is masked so that the light of the reflected light 151 cannot enter the scattered light detecting portion 124. When the foreign matter 30a is present on the glass substrate 20, the scattered light 1 5 2 is generated by the laser light 110 that is irradiated to the foreign matter 30 a. The scattered light 152 is collected by the condensing lens 121 (121a, 121b), and detected by the scattered light detecting portion 124. On the other hand, in the case where the foreign matter 30b is present on the back surface of the glass substrate 20, the laser beam transmitted through the glass substrate (hereinafter simply referred to as "transmitted light") is irradiated onto the foreign matter 30b to generate the scattered light 153. In the present embodiment, the scattered light 152 and 153 are both collected by the condensing lens 121 (121a, 121b) by the scattered light detecting portion 124. Therefore, the scattered light receiver 12 is the scattered light that receives both the scattered light 152 from the foreign matter 30a on the surface of the glass substrate 20 and the scattered light 153 from the back surface foreign object 3 Ob. Fig. 3 is a view showing the state of the reflection -15-201128182 when the laser beam 11 is irradiated onto the glass substrate 20, the state of the scattered light formed by the foreign matter, and the state of the scattered light of the scattered light receiver. The present invention is characterized in that, in addition to the scattered light 12, the scattered light receiver 13 is set to be orthogonal to the horizontally disposed glass. With this arrangement, the surface of the scattered light receiver 13 is substantially parallel to the glass substrate 20. Further, the present invention is characterized in that the light receiving range limiting plate 1 30 is attached to the scattered light receiver 13. The range of the scattered light received by the scattered light receiver 13 is limited by the light receiving range limiting plate 1 30. The scattered light received by the scattered light receiver 13 will be described. When it is not present on the glass substrate 20, the laser light 10 is converted into reflected light 151 by the reflection. Since the scattered light receiver 13 is on the substantially head of the irradiation point of the glass substrate 20, it is almost impossible for the reflected light 151 to be emitted to the light receiver 13. When the foreign matter 30a exists on the surface of the glass substrate 20, the laser beam 10 irradiated to the foreign object 30a generates the scattered light 152. The scattered light 152 generated at the top by || is received by the scattered light receiver 13 provided on the head of the laser. The scattered light 152 passes through the lens barrel 132, is bent at a substantially right angle by the mirror 134, and is detected by the camera 133. When the foreign material 30b is present on the back surface of the glass substrate 20, the foreign matter 30b is irradiated. Thereby, the scattered light 153 is generated, but the diffuser 13 is not on the substantially head of the foreign matter 30b. Because of the distance determined by the refractive index of the glass and the thickness of the glass substrate, 3 〇b deviates from the center point of the scattered light receiver 13. Therefore, the light is scattered to the light receiving surface of the receiver glass substrate, and the foreign matter can be placed in the glass scattering by the object 30h, and the observation light is detected by the light. The substrate 20 reduces the proportion of the scattered light 153 above the foreign matter 30b of the foreign matter back side-16-201128182 by the scattered light receiver 13. Further, a light receiving range restricting plate 130 is provided on the light receiving surface of the scattered light receiver 13. Thereby, the light receiving range of the scattered light 153 generated by the foreign matter 30b is restricted. According to these, the scattered light receiver 13 receives the scattered light 152 from the foreign matter 30a on the surface of the glass substrate 20, and the ratio of the scattered light 1 5 3 from the back surface foreign object 3 Ob becomes extremely small. Fig. 4 (a) shows the light receiving field of the scattered light received by the scattered light receivers 12, 13. The light receiving area of the scattered light receiver 1 is the light receiving area 140. Further, the light-receiving field of the scattered light receiver 13 is the light-receiving field 141. More specifically, when the foreign matter 30a on the surface of the glass substrate 20 is irradiated with the laser light 1 1 ,, since the light-receiving field of the scattered light-receiver 12 is the light-receiving field 140, so the light receiver 12 will receive the scattered light. Further, since the light receiving area of the scattered light receiver 13 is the light receiving area 141, the scattered light generated by 30a is also received by the scattered light receiving unit 13. That is, the scattered light generated by the foreign matter 30a on the surface of the glass substrate 20 is received by both of the scattered light receivers 12, 13. On the other hand, the scattered light generated by the foreign matter 30b existing on the back surface of the glass substrate 2 is restricted from the light receiving field by the light receiving range limiting plate 1300, and does not enter the scattered light receiver. 13 . On the other hand, since the light receiving region of the scattered light receiver 12 is within the light receiving region 140, the scattered light receiver 12 receives the scattered light. 4(b), the positional relationship between the foreign matter 30a existing on the surface of the glass substrate 20 and the foreign matter 3 Ob existing on the back surface is shown in a cross-sectional view, and the scattered light receivers 1 and 2 are used according to -17-201128182. 3 detection field of scattered light. Fig. 5 is a view showing a scattered light detecting circuit 40 which processes signals generated by scattered light received by the scattered light receivers 12, 13. The output signals from the scattered light receiver 12 and the scattered light receiver 13 are amplified by the amplifier 41 (41a, 41b), and then input to the data analysis circuit 42 (42a, 4 2b) to determine the position of the foreign object. The data analysis circuit 42 is prepared with a table in which the intensity of the scattered light and the size of the foreign object are correlated. The size of the foreign matter can be analyzed by comparing the data of the scattered light intensity obtained by the scattered light receivers 12 and 13 with the data accumulated in the correlation table. Further, the position of the foreign matter adhering to the glass substrate 20 is analyzed by the irradiation position of the laser light source 1 1 , the scattered light receivers 1, 2, and 3 and the laser light 1 1 。. The data analysis circuit 42 is provided with a memory so that the analysis result can be accumulated and memorized in the memory. The data is based on the comparison discriminating circuit 43 and compares the threshold 値 of the previously determined scattered light intensity with the output of the data analysis circuit 42, and determines which side of the surface or the back surface of the glass substrate 20 the foreign matter is present. Fig. 6 and Fig. 7 are diagrams showing the intensity of the scattered light output from foreign matter when the movement of the glass substrate 20 is accompanied by the irradiation position of the laser light. Fig. 6(a) is a diagram showing the output of the scattered light when the foreign matter 30a existing on the surface of the glass substrate 20 is irradiated to the laser light 110. When the foreign matter 30a is irradiated with the laser light 1 1 ,, the scattered light is outputted by the scattered light receiver 12 as the scattered light output signal 160 as shown in Fig. 7 (b). Further, the scattered light receiver 13 is output as a scattered light output signal -18-201128182 170 (Fig. 7(c)). The scattered light output signals (160, 170) are output by using the scattered light detecting circuit 40 shown in Fig. 5 to form the front and back separated output signals 180 (Fig. 7(a)). As a result, the foreign matter 30a is discriminated on the front side of the glass substrate 20. Further, as the glass substrate 20 is moved to the right, as shown in FIG. 6(c), the foreign matter 30a' which should be absent at the irradiation spot of the laser light 110 is generated by the scattered light receiver I2 as the scattered light output signal 161. It is output (Fig. 7(b)). Such scattered light output signal 161 is a weak output signal. Further, a very small scattered light output signal 171 which is hardly detected by the scattered light receiver 13 is detected (Fig. 7(c)). The detection of such a suspected foreign matter can be removed by the following method. First, the position of the foreign matter 30a' can be determined from the moving distance of the glass substrate 20 and the refractive index depending on the thickness of the glass as shown in Fig. 6(c). Therefore, after the foreign matter 30 a is detected, the output signal intensity of the scattered light output signal 161 outputted by the scattered light receiver 12 and the scattered light output signal 171 outputted by the scattered light receiver 13 is performed after a certain period of time. And the comparison of the output signals. When the scattered light output signal 171 is extremely weaker than the scattered light output signal 161, and the scattered light output signal 161 is smaller than the scattered light output signal 160, the output signal of the detected foreign object 30a' is judged to be suspected. The foreign matter signal can be removed as a foreign object that does not actually exist. Fig. 8 is a view showing the output of the scattered light receiver 12 (Fig. 8(b)) and the output of the scattered light receiver 13 in the case where there is a foreign matter on the back surface of the glass substrate 20, as shown in Fig. 6(b). Figure 8(c)), and the front and back separation output -19- 201128182 (Fig. 8(a)). As shown in Fig. 8(b), when there is a foreign matter on the back surface of the glass substrate 2, the scattered light output signal 190 is output from the scattered light receiver 12. On the other hand, as shown in Fig. 8(c), there is no output signal from the scattered light receiver 13. Because of this, the front-back separation output signal becomes an output signal as shown in Fig. 8(a), and it is discriminated that no foreign matter exists on the surface of the glass substrate 20. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing the overall configuration of a foreign matter inspection apparatus according to an embodiment of the present invention. Fig. 2 is a diagram showing the range of scattered light received by the scattered light receiver 12. Fig. 3 is a diagram showing the range of scattered light received by the scattered light receiver 13. Fig. 4 is a view showing the light receiving range of the scattered light in accordance with the scattered light receivers 12, 13. Fig. 5 is a view showing a scattered light detecting circuit which processes signals generated by scattered light received by the scattered light receivers 1, 2, and 13. Fig. 6 is a view showing the intensity of the scattered light output from the foreign matter accompanying the movement of the laser light irradiation position. Fig. 7 is a graph showing the intensity of the scattered light output from the foreign matter accompanying the movement of the laser light irradiation position. Fig. 8 is a diagram showing the intensity of scattered light output from foreign matter accompanying the movement of the laser light irradiation position-20-201128182 [Description of main component symbols] 1: Frame 1 1 : Laser light source 12, 13: scattering Optical light receiver 20: glass substrate 30a: foreign matter 30b on the surface of glass substrate 20: foreign matter 40 on the back surface of glass substrate 20: scattered light detecting circuit 41 (41a, 41b): amplifier 42 (42a, 42b): data Analysis circuit 43: comparison determination circuit 1 1 〇: laser light 1 1 1 : laser output unit 121 (121a, 121b): condensing lens (condenser lense 124: scattered light detecting portion 127: light-shielding tape 1 3 0 : light receiving Range limiting plate 1 3 1 : scattered light detecting portion 1 3 2 : lens barrel 1 3 3 = observation camera 1 3 4 : mirror 140 : light receiving area of the scattered light receiver 12 1 1 : scattered light receiver 1 3 Light-receiving field-21 - 201128182 142 : Field of view of the observation camera 133 143 : Laser light irradiation field on the surface of the glass substrate 20 1 5 1 : Reflected light 152, 153 : Scattered light 160, 161, 170, 171, 190: Scattered light output Signal 180: Back table separation output signal-22-