201110221 六、發明說明： 【發明戶斤屬之技術領域3 發明領域 本發明與晶圓加工方法相關，前述晶圓加工方法係一 晶圓在藍寶石基板表面積層有氮化物半導體所構成之發光 層且在由複數第1切割道與複數第2切割道劃分之複數區域 形成有光學裝置，而在前述晶圓内部沿著第1切割道與第2 切割道形成變質層，前述複數第1切割道係延伸於預定方 向，前述複數第2切割道係與該複數第1切割道交叉而形成 者。 【先前技冬好;1 發明背景 光學裝置之製造步驟，係在藍寶石基板表面積層有氮 化物半導體所構成之發光層（磊晶層），且在由延伸於預定方 向之複數第1切割道、與該複數第1切割道交叉而形成之複 數第2切割道所劃分之複數區域形成光學裝置。該形成有複 數光學裝置之晶圓，係藉由沿著第1切割道及第2切割道切 斷，而分割為一個個發光二極體等光學裝置，並廣泛運用 於電子機器中。 此種沿著切割道切斷晶圓之方法，通常係藉由高速旋 轉環狀切割刀片之切削裝置來進行。然而藍寶石基板為摩 氏硬度較高的切削困難材料，加工速度必須放慢，而有生 產性不良的問題。 近年來，提案有一種沿著切割道切割晶圓之方法，係 201110221 藉由沿著切割道照射對晶圓具有吸收性之脈衝雷射光而形 成雷射加工溝，再藉由沿著該雷射加工溝施加外力而予以 割斷的方法。（例如參考專利文獻1。） 但是，若沿著形成於藍寶石基板表面之切割道照射雷 射光線，來形成雷射加工溝，則發光二極體等光學裝置之 外圍會遭到消蝕而降低亮度，有降低光學裝置之品質的問 題。 為了解決此種問題，下述專利文獻2揭示了一種藍寶石 基板之加工方法，係從沒有形成氮化物半導體所構成之發 光層（磊晶層）的藍寶石基板背面側，將對藍寶石基板具有透 過性之波長之雷射光線的聚光點定位在内部，沿著切割道 照射，在藍寶石基板内部沿著切割道形成變質層，藉此， 沿著形成有變質層之切割道來分割藍寶石基板。 先前技術文件 專利文件 【專利文件1】日本特開平10-305420號公報 【專利文件2】曰本特開2008-6492號公報 【發明内容】 發明概要 發明欲解決之課題 上述專利文獻2所揭示之藍寶石基板加工方法，雖然在 一定程度上改善了光學裝置之亮度降低，但是若雷射光線 照射至在切割道交叉點上已先形成之變質層上，則雷射光 線之聚光狀態會惡化，穿透由氮化物半導體所構成之發光 201110221 層的雷射光線量會增加，氮化物半導體所構成之發光層可 能受到損傷，而有降低光學裝置的發光功能之虞。 本發明係有鑒於上述事實而完成者，其主要之技術課 題，係提供一種可不對形成於藍寶石基板表面之光學裝置 造成傷害，就在藍寶石基板内部沿著切割道形成變質層的 晶圓加工方法。 用以欲解決課題之手段 為了解決上述主要技術課題，則依本發明提供一種晶 圓加工方法，係一晶圓在藍寶石基板表面積層有發光層且 在由複數第1切割道與複數第2切割道劃分之複數區域形成 有光學裝置，而在前述晶圓内部沿著第1切割道與第2切割 道形成變質層，前述複數第1切割道係延伸於預定方向，前 述複數第2切割道係與該複數第1切割道交叉而形成者，其 特徵在於包含： 第1變質層形成步驟，係將對藍寶石基板具有透過性之 波長之雷射光線，從藍寶石基板之背面側定位聚光點於藍 寶石基板之内部，沿著第1切割道進行照射，在藍寶石基板 内部沿著第1切割道形成連續之第]變質層；及 第2變質層形成步驟，係將對藍寶石基板具有透過性之 波長之雷射光線，從藍寶石基板之背面側定位聚光點於藍 寶石基板之内部，沿著第2切割道且排除與第1切割道之交 叉部分進行照射，在藍寶石基板内部沿著第2切割道且排除 與第1切割道之交叉部分，形成第2變質層。 發明效果 201110221 依本發明之晶圓加工方法，於藍寶石基板内部沿著第2 切割道形成第2變質層之第2變質層形成步驟，係將對藍寶 石基板具有透過性之波長之雷射光線，從藍寶石基板背面 側將聚光點定位於藍寶石基板内部，並排除與已經沿著第1 切割道連續形成之第1變質層的交叉部分而進行照射，在藍 寶石基板内部沿著第2切割道且排除與第1切割道之交叉部 分，形成第2變質層，故雷射光線不會與第1變質層干涉而 使聚光狀態惡化。因此可解決因雷射光線與第1變質層干涉 而使聚光狀態惡化，造成穿透發光層之雷射光線量增加， 對發光層帶來損傷，而降低光學裝置之發光功能的問題。 圖式簡單說明 第1(a)〜1(b)圖，係藉由本發明之晶圓加工方法加工之 晶圓的立體圖及放大表示重要部份之剖面圖。 第2圖，係表示將第1圖所示之晶圓黏貼於保護膠帶表 面且保護膠帶裝配在環狀框之狀態的立體圖。 第3圖，係用以實施本發明之晶圓加工方法之第1變質 層形成步驟及第2變質層形成步驟的雷射加工裝置的主要 部分立體圖。 第4(a)〜4(b)圖，係本發明之晶圓加工方法之第1變質層 形成步驟之說明圖。 第5圖，係本發明之晶圓加工方法之第2變質層形成步 驟之說明圖。 第6(a)〜6(b)圖，係本發明之晶圓加工方法之第2變質層 形成步驟之說明圖。 201110221 【 用以實施發明之型態 以下參考附加圖式，詳細說明本發明之晶圓加工方法 的理想實施態樣。 第1(a)及1(b)圖，係表示依據本發明之晶圓加工方法加 工之晶圓的立體圖。第1(a)及1(b)圖所表承之晶圓2，係例 如在厚度15〇pm之藍寶石基板2〇的表面2〇a ’積層有氮化物 半導體所構成之發光層（磊晶層）21。然後，在發光層（磊晶 層）21受複數第1切割道22與複數第2切割道23劃分之複數 區域形成有光學裝置24,前述複數第1切割道22係延伸於預 疋方向，前述複數第2切割道23係與該複數第1切割道22正 交而形成。 上述第1圖所示之晶圓2,係如第2圖所示，將發光層（磊 晶層）21之表面側黏貼在由聚烯烴等合成樹脂薄膜所構成 的保護膠帶4上，且前述保護膠帶4係裝配於環狀框3(保護 膠帶點貼步驟）。因此’藍寶石基板2〇之背面2〇b成為上側。 實施上述保護膠帶黏貼步驟之後，實施第〗變質層形成 步騍，將對藍寶石基板20具有透過性之波長的雷射光線， 從藍寶石基板2〇之背面側將聚光點定位於藍寶石基板2〇内 邛沿著第1切割道22進行照射，在藍寶石基板20内部沿著 第1切割道22形成連續之第！變質層。此第i變質層形成步 驟，係使用第3圖所示之雷射加工裝置5來實施。第3圖所示 之雷射加工裝置5 ’具備保持被加工物之夾具桌51、對被保 持於該夹具桌51上之被加工物照射雷射光線的雷射光線照 201110221 射機構52、及對被保持於該夹具桌51上之被加工物進行攝 像的攝像機構53。夾具桌51，係構成為可吸引保持被加工 物，藉由未圖示之加工送料機構而移動於第3圖中箭頭X所 示之加工送料方向’並藉由未圖示之切出送料機構而移動 於第3圖中箭頭Y所示之切出送料方向。另外，第3圖所示之 雷射加工裝置5具有用以檢測加工送料量的加工送料量檢 測機構(未圖示），此加工送料量檢測機構會將檢測訊號送至 未圖示之控制機構。而且，未圖示之控制機構具備記憶體， 可儲存形成於上述晶圓2之第1切割道22與第2切割道23的 交又點座標值’未圖示之控制機構比對該交叉點座標值與 加工送料量檢測機構所送出的檢測訊號，對雷射光線照射 機構52輸出控制訊號。 上述雷射光線照射機構52包含實質上被配置為水平的 圓筒形狀外殼521。外殼521内配置有未圖示之脈衝雷射光 線振盪機構，其具備由YAG雷射振盪器或γν〇4雷射振盪器 所構成的脈衝雷射光線振盪器、和重複頻率設定機構。上 述外殻521之前端部，裝設有用以將脈衝雷射光線振盪機構 所振盪之脈衝雷射光予以聚光的聚光器522。 攝像機構53裝設於構成上述雷射光線照射機構52之外 殼521的前端部，在圖示之實施態樣中，攝像機構53除具有 藉由可見光來攝像之一般攝像元件(CCD)外，還具有由對被 加工物照射紅外線之紅外線照明機構、捕捉該紅外線照明 機構所照射紅外線的光學系統、及對應該光學系統所捕捉 之紅外線而輸出電子訊號的攝像元件（紅外線CCD)等，將所 8 201110221 攝像之晝像訊號送到未圖示之控制機構。 參考第3圖及第4圖來說明第1變質層形成步驟，前述第 1變質層形成步驟係使用上述雷射加工跋置5，將對構成上 述晶圓2之藍寶石基板2()具有透過性之波長之雷射光線，從 藍寶石基板20之背面側定位聚光點於藍寶石基板2〇之内 部’沿著第1切割道22進行照射，在藍寶石基板2〇内部沿著 第1切割道22形成連續之第1變質層。 首先將黏貼有晶圓2之保護膠帶4載置於第3圖所示之 雷射加工裝置5的夹具桌51上。然後，藉由啟動未圖示之吸 引機構，透過保護膠帶4將晶圓2保持於夾具桌51上（晶圓保 持步驟）。如此一來，被保持於夾具桌5〗之晶圓2係藍寶石 基板20的背面20b在上側。另外，在第3圖中雖然省略了用 於安裝保護膠帶4之環狀框3，但環狀框3係受配設於夾具桌 51之適當的框保持機構所保持。吸引保持晶圓2之夾具桌 51，係藉由未圖示之移動機構而定位到攝像機構兄之正下 方。 當夾具桌51定位到攝像機構53之正下方，即藉由攝像 機構53及未圖不之控制機構來執行檢測晶圓2中應該進行 雷射加工之加工區域的校準作業。亦即攝像機構53及未圖 示之控制機構’會執行圖案比對之畫像處理，用以進行形 成於晶圓2之預定方向的第1切割道2 2、和沿著該第！切割道 22照射雷射光線之雷射光線照射機構52之聚光器522兩者 的定位，實行雷射光線校正位置之校準（校準步驟）。另外， 對於與形成於晶圓2之上述第1切割道22正交延伸的第2切 201110221 割道23，也樣貫行雷射光線照射位置之校準。此時，晶 圓2之形成有第1切割道22及第2切割道23的發光層（磊晶 層）21之表面雖然位於下側，但是攝像機構53如上所述般具 備由紅外線照明機構、可捕捉紅外線之光學系統、及可對 應紅外線輸出電子訊號之攝像元件（紅外線CCD)等所構成 的攝像機構，故可從藍寶石基板20之背面20b穿透，對第1 切割道22及第2切割道23進行攝像。 如以上所述’若由發光層（磊晶層）21構成之晶圓2被保 持在夾具桌51上’檢測出形成於發光層21之第1切割道22及 第2切割道23，並完成雷射光線照射位置之校準，則如第4(a) 圖所示’夾具桌51會移動到雷射光線照射機構52之聚光器 522所位在的雷射光線照射區域，將預定之第1切割道22的 一端（第4(a)圖中為左端）定位在雷射光線照射機構52之聚 光器522的正下方。然後，一邊從聚光器522照射對藍寶石 基板20具有透過性之波長的脈衝雷射光線，一邊以預定之 加工送料速度將夾具桌51往第4(a)圖中箭頭χι所示的方向 移動。然後，如第4(b)圖所示，當雷射光線照射機構52之聚 光器522的照射位置抵達第！切割道22之另外一端（第4(b)圖 中為右端）位置後，則停止照射脈衝雷射光線，並停止夾具 桌51之移動。在此第1變質層形成步驟中，係將脈衝雷射光 線之聚光點P對在構成晶圓2之藍寶石基板20的厚度方向中 央。卩伤附近。結果，在構成晶圓2之藍寶石基板的内部， 沿著第1切割道22形成連續之第丨變質層21〇〇此第丨變質層 210係形成為炫融再凝固層。 10 201110221 上述第1變質層形成步驟之加工條件，係設定為例如以 下内容。 光源：Yb雷射：摻镱光纖雷射 波長：l〇45nm 重複頻率：l〇〇kHz 平均輸出：0.3W 聚光點徑：p 1〜1.5μηι 加工送料速度：400mm/秒 如上所述，在沿著延伸於晶圓2之預定方向的所有第1 切割道22執行上述第1變質層形成步驟之後，執行第2變質 層形成步驟，前述執行第2變質層形成步驟係將對藍寶石基 板20具有透過性之波長之雷射光線，從藍寶石基板20之背 面側將聚光點定位於藍寶石基板20之内部，沿著第2切割道 23並排除與第1切割道22之交叉部分而進行照射，在藍寶石 基板20内部沿著第2切割道23並排除與第1切割道22之交叉 部分來形成第2變質層。第2變質層形成步驟首先係如第5圖 所示，將保持有晶圓2(已經沿著第1切割道22形成了第1變 質層210)之夾具桌51旋轉90度之後定位於該位置。 將保持有晶圓2之夾具桌51旋轉90度之後定位於該位 置之後，如第6(a)圖所示，將夾具桌51移動到雷射光線照射 機構52之聚光器522所位在的雷射光線照射區域，將預定之 第2切割道23的一端（第6(a)圖中為左端）定位在雷射光線照 射機構52之聚光器522的正下方。其次，一邊從聚光器522 照射對藍寶石基板2 0具有透過性之波長的脈衝雷射光線， 11 201110221 邊以預疋之加工送料速度將夾具桌51往第6(a)圖中箭頭 X1所不的方向移動。然後，當由與第1切割道22之交差點朝 移動方向刚側（第6圖中為左側）例如5〜25〇叫的位置來到聚 光器522之正下方時，則停止照射脈衝雷射光線。而且，當 由與第1切割道22之交差點朝移動方向後側(第6圖中為右 側）例如5〜250μηι的位置來到聚光器522之正下方時則開始 照射脈衝雷射光線。如此-來，藉由將對藍寶石基板20具 有透過性之波長的Μ光線，沿著第2㈣道η且排除與第 1切割道22之交又部分而進行照射，可如第6⑼圖所示，在 構成晶圓2之藍寶石基板2()内部，沿著第2切割道23且排除 與第1切割道22之交3U卩分而形成第2變質層22G4述交又 部分中沒有形成第2變質層22〇之範圍，在上述實施態樣中 係10〜500μιη °另外’上述脈衝雷射光線之照射與停止係 裝設於雷射加工裝置5之未圖示控制機構，根據記憶體中所 儲存之第1切割道22與第2切割道23的交叉點座標位置、及 來自未圖示之加工送料量檢測機構的檢測訊號，來控制雷 射光線照射機構52所進行者。如此形成之第丨變質層21〇與 第2變質層220，不會在第丨切割道22與第2切割道23之交又 點重疊形成。在此第2變質層形成步驟中，亦將脈衝雷射光 線之聚光點Ρ對在構成晶圓2之藍寶石基板20的厚度方向中 央部份附近。另外，第2變質層形成步驟之加工條件，可以 與上述第1變質層形成步驟的加工條件相同。 如上所述，在第2變質層形成步驟中沿著第2切割道23 形成第2變質層220，係排除已經沿著第1切割道22形成第^ 12 201110221 變質層210的與第1切割道22之交叉部分而照射雷射光，在 藍寶石基板20内部沿著第2切割道23且排除與第1切割道22 之交又部分而形成第2變質層22 0，故雷射光線不會與第1變 質層210干涉而使聚光狀態惡化。因此，可解決因雷射光線 與第1變質層210干涉而使聚光狀態惡化，造成穿透發光層 (磊晶層）21之雷射光線量增加，損傷到發光層（磊晶層）21， 降低光學裝置24之發光功能的問題。 如上所述之業經實施第1變質層形成步驟及第2變質層 形成步驟的晶圓2，會被搬運往晶圆分割步驟，前述晶圓分 割步驟係沿著第1切割道22及第2切割道23施加外力，而沿 著形成有第1變質層21〇的第1切割道22及形成有第2變質層 220的第2切割道23斷開。 【圖式簡單說明】 第l(a)~l(b)圖，係藉由本發明之晶圓加工方法加工之 晶圓的立體圖及放大表示重要部份之剖面圖。 第2圖，係表示將第1圖所示之晶圓黏貼於保護膠帶表 面且保護膠帶裝配在環狀框之狀態的立體圖。 第3圖，係用以實施本發明之晶圓加工方法之第1變質 層形成步驟及第2變質層形成步驟的雷射加工裝置的主要 部分立體圖。 第4(a)~4(b)圖，係本發明之晶圓加工方法之第1變質戽 形成步驟之説明圖。 第5圖，係本發明之晶圓加工方法之第2變質層形戍+ 驟之說明圖。 13 201110221 第6(a)〜6(b)圖，係本發明之晶圓加工方法之第2變質層 形成步驟之說明圖。 【主要元件符號說明】 2···晶圓 3…環狀框 4…保護膠帶 5···雷射加工裝置 20…藍寶石基板 20a…表面 20b·"背面 21…發光層（蟲晶層） 22…第1分割預定線 23 :第2分割預定線 24…裝置 51…雷射加工裝置之夾具桌 52…雷射光線照射機構 53…攝像機構 210···第1變質層 220…第2變質層 521…外殼 522···聚光器 P…聚光點 14201110221 VI. Description of the Invention: [Technical Field 3 of the Invention] The present invention relates to a wafer processing method in which a wafer has a light-emitting layer composed of a nitride semiconductor on a surface area of a sapphire substrate and An optical device is formed in a plurality of regions divided by the plurality of first scribe lines and the plurality of second scribe lines, and a modified layer is formed along the first scribe line and the second scribe line inside the wafer, and the plurality of first scribe lines are formed The plurality of second scribe lines are formed to intersect with the plurality of first scribe lines and extend in a predetermined direction. [Previously, the technique of manufacturing the optical device is a light-emitting layer (epitaxial layer) composed of a nitride semiconductor on the surface area of the sapphire substrate, and is formed by a plurality of first dicing lines extending in a predetermined direction, The plurality of regions defined by the plurality of second scribe lines formed by crossing the plurality of first scribe lines form an optical device. The wafer in which the plurality of optical devices are formed is cut into individual optical devices such as light-emitting diodes by cutting along the first scribe line and the second scribe line, and is widely used in electronic equipment. Such a method of cutting a wafer along a scribe line is usually performed by a cutting device that rotates the annular cutting blade at a high speed. However, the sapphire substrate is a difficult-to-cut material with a high Mohs hardness, and the processing speed must be slowed down, which has a problem of poor productivity. In recent years, there has been proposed a method of cutting a wafer along a scribe line by forming a laser processing groove by irradiating a pulsed laser light having absorption on a wafer along a dicing street, and by following the laser. A method of cutting a groove by applying an external force. (For example, refer to Patent Document 1.) However, if a laser beam is irradiated along a dicing street formed on the surface of the sapphire substrate to form a laser processing groove, the periphery of the optical device such as the light-emitting diode is ablated and lowered. Brightness has the problem of reducing the quality of the optical device. In order to solve such a problem, Patent Document 2 listed below discloses a method for processing a sapphire substrate which is permeable to a sapphire substrate from the back side of a sapphire substrate on which a light-emitting layer (epitaxial layer) composed of a nitride semiconductor is not formed. The condensed spot of the laser light of the wavelength is positioned inside, and is irradiated along the scribe line to form a metamorphic layer along the scribe line inside the sapphire substrate, whereby the sapphire substrate is divided along the scribe line in which the altered layer is formed. [Patent Document 1] Japanese Patent Laid-Open Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. The sapphire substrate processing method improves the brightness reduction of the optical device to a certain extent, but if the laser light is irradiated onto the metamorphic layer which has been formed at the intersection of the scribe line, the condensed state of the laser light is deteriorated. The amount of laser light that penetrates the layer of the light-emitting layer 201110221 composed of a nitride semiconductor increases, and the light-emitting layer composed of the nitride semiconductor may be damaged, which may reduce the light-emitting function of the optical device. The present invention has been made in view of the above-described facts, and its main technical object is to provide a wafer processing method capable of forming a deteriorated layer along a scribe line inside a sapphire substrate without causing damage to an optical device formed on a surface of a sapphire substrate. . Means for Solving the Problems In order to solve the above-mentioned main technical problems, the present invention provides a wafer processing method in which a wafer has a light-emitting layer on a surface area of a sapphire substrate and is cut by a plurality of first scribe lines and a plurality of second cuts. An optical device is formed in the plurality of regions of the track, and a modified layer is formed along the first scribe line and the second scribe line in the wafer, and the plurality of first scribe lines extend in a predetermined direction, and the plurality of second scribe lines are Formed to intersect with the plurality of first scribe lines, comprising: a first modified layer forming step of concentrating a laser beam having a wavelength of transparency to a sapphire substrate from a back side of the sapphire substrate The inside of the sapphire substrate is irradiated along the first scribe line, and a continuous gradation layer is formed along the first scribe line inside the sapphire substrate; and the second altered layer forming step is a wavelength having transparency to the sapphire substrate Laser light, positioning the condensed spot from the back side of the sapphire substrate inside the sapphire substrate, along the second scribe line and excluding the first scribe line The intersection portion is irradiated, and a second altered layer is formed along the second scribe line inside the sapphire substrate and excluding the intersection with the first scribe line. According to the wafer processing method of the present invention, the second altered layer forming step of forming the second altered layer along the second scribe line in the sapphire substrate is a laser beam having a wavelength of transparency to the sapphire substrate. Positioning the condensed spot inside the sapphire substrate from the back side of the sapphire substrate, excluding the intersection with the first altered layer that has been continuously formed along the first scribe line, and irradiating the inside of the sapphire substrate along the second scribe line Since the second altered layer is formed by the intersection with the first scribe line, the laser beam does not interfere with the first altered layer and the condensed state is deteriorated. Therefore, it is possible to solve the problem that the condensed state is deteriorated due to the interference of the laser light with the first metamorphic layer, and the amount of laser light that penetrates the luminescent layer is increased, which damages the luminescent layer and reduces the illuminating function of the optical device. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1(a) to 1(b) are perspective views of a wafer processed by the wafer processing method of the present invention and a cross-sectional view showing an important portion in an enlarged manner. Fig. 2 is a perspective view showing a state in which the wafer shown in Fig. 1 is adhered to the surface of the protective tape and the protective tape is attached to the ring frame. Fig. 3 is a perspective view showing a main part of a laser processing apparatus for carrying out the first modified layer forming step and the second modified layer forming step of the wafer processing method of the present invention. 4(a) to 4(b) are explanatory views showing the steps of forming the first altered layer in the wafer processing method of the present invention. Fig. 5 is an explanatory view showing a second modification layer forming step of the wafer processing method of the present invention. Figs. 6(a) to 6(b) are explanatory views showing a second modification layer forming step of the wafer processing method of the present invention. 201110221 [Formation for Carrying Out the Invention] The preferred embodiment of the wafer processing method of the present invention will be described in detail below with reference to additional drawings. Figs. 1(a) and 1(b) are perspective views showing wafers processed by the wafer processing method of the present invention. The wafer 2 shown in the first (a) and (b) drawings is a light-emitting layer composed of a nitride semiconductor (for example, a surface of a sapphire substrate 2〇 having a thickness of 15 μm). Layer) 21. Then, an optical device 24 is formed in a plurality of regions in which the light-emitting layer (the epitaxial layer) 21 is divided by the plurality of first dicing streets 22 and the plurality of second dicing streets 23, and the plurality of first dicing streets 22 extend in the forward direction, and the aforementioned The plurality of second scribe lines 23 are formed to be orthogonal to the plurality of first scribe lines 22. As shown in FIG. 2, the wafer 2 shown in FIG. 1 is adhered to the surface of the light-emitting layer (the epitaxial layer) 21 on a protective tape 4 made of a synthetic resin film such as polyolefin, and the aforementioned The protective tape 4 is attached to the ring frame 3 (protective tape dot sticking step). Therefore, the back surface 2〇b of the sapphire substrate 2 is the upper side. After the protective tape pasting step is performed, the tempering layer forming step is performed, and the laser beam having a wavelength of transparency to the sapphire substrate 20 is positioned from the back side of the sapphire substrate 2 to the sapphire substrate. The inner cymbal is irradiated along the first scribe line 22, and the inside of the sapphire substrate 20 forms a continuous first along the first scribe line 22! Metamorphic layer. This i-th metamorphic layer forming step is carried out using the laser processing apparatus 5 shown in Fig. 3. The laser processing apparatus 5' shown in Fig. 3 is provided with a jig table 51 for holding a workpiece, a laser beam for irradiating a laser beam to a workpiece held on the jig table 51, and a laser beam 201110221; An imaging mechanism 53 that images an object to be processed held on the jig table 51. The jig table 51 is configured to be capable of sucking and holding a workpiece, and is moved in a processing feed direction indicated by an arrow X in FIG. 3 by a processing feed mechanism (not shown), and is cut out by a feeding mechanism (not shown). The movement direction indicated by the arrow Y in Fig. 3 is cut out. Further, the laser processing apparatus 5 shown in Fig. 3 has a processing feed amount detecting means (not shown) for detecting a machining feed amount, and the machining feed amount detecting means sends a detection signal to a control mechanism not shown. . Further, the control unit (not shown) is provided with a memory, and can store the coordinate value of the intersection of the first scribe line 22 and the second scribe line 23 formed on the wafer 2, which is not shown, as compared with the intersection. The coordinate value and the detection signal sent by the processing feed amount detecting means output a control signal to the laser light irradiation means 52. The above-described laser beam irradiation mechanism 52 includes a cylindrical casing 521 which is substantially horizontal. A pulsed laser beam oscillating mechanism (not shown) is disposed in the casing 521, and includes a pulsed laser ray oscillator composed of a YAG laser oscillator or a γν〇4 laser oscillator, and a repetition frequency setting mechanism. The front end portion of the outer casing 521 is provided with a concentrator 522 for collecting the pulsed laser light oscillated by the pulsed laser beam oscillating mechanism. The imaging unit 53 is attached to the distal end portion of the outer casing 521 constituting the laser beam irradiation unit 52. In the illustrated embodiment, the imaging unit 53 has a general imaging element (CCD) that is imaged by visible light. An infrared ray illumination mechanism that irradiates infrared rays to a workpiece, an optical system that captures infrared rays that are irradiated by the infrared illumination mechanism, and an imaging element (infrared CCD) that outputs an electronic signal in response to infrared rays captured by the optical system, etc. 201110221 Camera image signal is sent to the control unit (not shown). The first modified layer forming step is described with reference to FIGS. 3 and 4, and the first modified layer forming step uses the laser processing unit 5 to permeable the sapphire substrate 2 () constituting the wafer 2. The laser beam of the wavelength is irradiated from the back side of the sapphire substrate 20 to the inside of the sapphire substrate 2' to illuminate along the first scribe line 22, and is formed along the first scribe line 22 inside the sapphire substrate 2 The first metamorphic layer in succession. First, the protective tape 4 to which the wafer 2 is pasted is placed on the jig table 51 of the laser processing apparatus 5 shown in Fig. 3. Then, the wafer 2 is held on the jig table 51 through the protective tape 4 by activating an suction mechanism (not shown) (wafer holding step). As a result, the back surface 20b of the wafer 2 sapphire substrate 20 held by the jig table 5 is on the upper side. Further, in Fig. 3, the annular frame 3 for attaching the protective tape 4 is omitted, but the annular frame 3 is held by an appropriate frame holding mechanism disposed on the jig table 51. The jig table 51 that sucks and holds the wafer 2 is positioned directly below the image pickup mechanism by a moving mechanism (not shown). When the jig table 51 is positioned directly below the image pickup mechanism 53, the calibration operation of the processing area in the wafer 2 where laser processing should be performed is performed by the image pickup mechanism 53 and the control mechanism not shown. That is, the image pickup mechanism 53 and the control means (not shown) perform image pattern processing for patterning to form the first scribe line 2 2 formed in the predetermined direction of the wafer 2, and along the first! The scribe line 22 illuminates both of the concentrators 522 of the laser beam illumination mechanism 52 that illuminate the laser beam, and performs calibration of the laser beam correction position (calibration step). Further, the second cut 201110221 cut path 23 extending orthogonally to the first scribe line 22 formed on the wafer 2 is also aligned with the laser light irradiation position. At this time, although the surface of the light-emitting layer (the epitaxial layer) 21 in which the first scribe line 22 and the second scribe line 23 are formed on the wafer 2 is located on the lower side, the imaging unit 53 includes the infrared ray illumination mechanism as described above. The imaging system including an optical system capable of capturing infrared rays and an imaging element (infrared CCD) capable of responding to an infrared output electronic signal can be penetrated from the back surface 20b of the sapphire substrate 20, and the first cutting path 22 and the second cutting are performed. Lane 23 performs imaging. As described above, when the wafer 2 composed of the light-emitting layer (the epitaxial layer) 21 is held on the jig table 51, the first dicing street 22 and the second dicing street 23 formed on the light-emitting layer 21 are detected and completed. The calibration of the position of the laser beam irradiation is as shown in Fig. 4(a), and the fixture table 51 is moved to the laser beam irradiation area where the concentrator 522 of the laser beam illumination mechanism 52 is located. One end of the scribe line 22 (the left end in the fourth drawing (a)) is positioned directly below the concentrator 522 of the laser beam irradiation mechanism 52. Then, while irradiating the concentrator 522 with the pulsed laser beam having a wavelength that is transparent to the sapphire substrate 20, the jig table 51 is moved in the direction indicated by the arrow χι in the fourth (a) drawing at a predetermined processing feed rate. . Then, as shown in Fig. 4(b), when the illuminating position of the concentrator 522 of the laser beam irradiation mechanism 52 reaches the first position! After the other end of the cutting path 22 (the right end in Fig. 4(b)) is positioned, the irradiation of the pulsed laser light is stopped, and the movement of the jig table 51 is stopped. In the first modified layer forming step, the light collecting point P of the pulsed laser light is directed to the center of the thickness direction of the sapphire substrate 20 constituting the wafer 2. Bruises nearby. As a result, a continuous third metamorphic layer 21 is formed along the first scribe line 22 inside the sapphire substrate constituting the wafer 2, and the ninth metamorphic layer 210 is formed as a smelting and resolidifying layer. 10 201110221 The processing conditions of the first altered layer forming step are set as follows, for example. Light source: Yb laser: Erbium-doped fiber laser wavelength: l〇45nm Repeat frequency: l〇〇kHz Average output: 0.3W Spot diameter: p 1~1.5μηι Processing feed speed: 400mm/sec As mentioned above, in After the first modified layer forming step is performed along all of the first dicing streets 22 extending in the predetermined direction of the wafer 2, the second altered layer forming step is performed, and the performing the second altered layer forming step is performed on the sapphire substrate 20 The laser beam having a transparent wavelength is positioned from the back side of the sapphire substrate 20 to the inside of the sapphire substrate 20, and is irradiated along the second scribe line 23 so as to exclude the intersection with the first scribe line 22. The second altered layer is formed inside the sapphire substrate 20 along the second scribe line 23 and excluding the intersection with the first scribe line 22. The second altered layer forming step is first positioned at the position after the jig table 51 holding the wafer 2 (the first altered layer 210 has been formed along the first scribe line 22) is rotated by 90 degrees as shown in FIG. . After the jig table 51 holding the wafer 2 is rotated by 90 degrees and positioned at the position, as shown in Fig. 6(a), the jig table 51 is moved to the concentrator 522 of the laser beam irradiation mechanism 52. The laser light irradiation region is positioned at one end of the predetermined second cutting lane 23 (the left end in the sixth (a) diagram) directly below the concentrator 522 of the laser beam irradiation mechanism 52. Next, the pulsed laser beam having a wavelength that is transparent to the sapphire substrate 20 is irradiated from the concentrator 522, and the jig table 51 is turned to the arrow X1 in the sixth (a) drawing at the pre-processed feed speed of 11 201110221. Move in the wrong direction. Then, when the intersection with the first scribe line 22 comes to the front side of the moving direction (the left side in FIG. 6), for example, 5 to 25 squeaking, directly below the concentrator 522, the irradiation pulse ray is stopped. Shoot the light. Further, when the intersection with the first scribe line 22 comes to the rear side (the right side in Fig. 6) of the moving direction, for example, 5 to 250 μm, the laser beam is irradiated. In this way, by irradiating the ray light having a wavelength of transparency to the sapphire substrate 20 along the second (fourth) η and excluding the intersection with the first scribe line 22, as shown in the sixth (9) diagram, In the sapphire substrate 2 () constituting the wafer 2, the second modified layer 22G4 is formed along the second scribe line 23 and excluding the intersection with the first scribe line 22, and the second modified layer 22G4 is formed. The range of the layer 22 is 10 to 500 μm in the above embodiment, and the irradiation and stop of the pulsed laser light is mounted on a control mechanism (not shown) of the laser processing apparatus 5, and is stored in the memory. The position of the intersection of the first scribe line 22 and the second scribe line 23 and the detection signal from the processing feed amount detecting means (not shown) control the laser light irradiation means 52. The second metamorphic layer 21A and the second altered layer 220 thus formed are not formed to overlap each other at the intersection of the second scribe line 22 and the second scribe line 23. In the second modified layer forming step, the condensed spot of the pulsed laser light is also placed in the vicinity of the central portion in the thickness direction of the sapphire substrate 20 constituting the wafer 2. Further, the processing conditions of the second altered layer forming step may be the same as the processing conditions of the first modified layer forming step. As described above, in the second altered layer forming step, the second altered layer 220 is formed along the second scribe line 23, and the first scribe line which has formed the modified layer 210 along the first scribe line 22 is excluded. The laser beam is irradiated with the intersection of 22, and the second altered layer 22 is formed along the second scribe line 23 inside the sapphire substrate 20 and excluding the intersection with the first scribe line 22, so that the laser light does not The metamorphic layer 210 interferes to deteriorate the condensed state. Therefore, it is possible to solve the problem that the condensed state is deteriorated due to the interference of the laser beam with the first altered layer 210, and the amount of the laser light that penetrates the luminescent layer (the epitaxial layer) 21 is increased, and the luminescent layer (the epitaxial layer) 21 is damaged. The problem of reducing the illumination function of the optical device 24 is reduced. The wafer 2 subjected to the first altered layer forming step and the second altered layer forming step as described above is transported to the wafer dividing step, and the wafer dividing step is along the first cutting lane 22 and the second cutting The external force is applied to the channel 23, and is broken along the first scribe line 22 in which the first altered layer 21 is formed and the second scribe line 23 in which the second altered layer 220 is formed. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1(a) to 1(b) are perspective views of a wafer processed by the wafer processing method of the present invention and enlarged views showing important portions. Fig. 2 is a perspective view showing a state in which the wafer shown in Fig. 1 is adhered to the surface of the protective tape and the protective tape is attached to the ring frame. Fig. 3 is a perspective view showing a main part of a laser processing apparatus for carrying out the first modified layer forming step and the second modified layer forming step of the wafer processing method of the present invention. Figs. 4(a) to 4(b) are explanatory views showing the first modification 戽 formation step of the wafer processing method of the present invention. Fig. 5 is an explanatory view showing a second modified layer shape 骤 + step of the wafer processing method of the present invention. 13 201110221 Figures 6(a) to 6(b) are explanatory views of the second altered layer forming step of the wafer processing method of the present invention. [Description of main component symbols] 2··· wafer 3...ring frame 4...protective tape 5·· laser processing apparatus 20...sapphire substrate 20a...surface 20b·"back surface 21...light-emitting layer (worm layer) 22...first division planned line 23: second division planned line 24...device 51...laser table 52 of laser processing apparatus...laser light irradiation unit 53...image pickup unit 210···1st metamorphic layer 220...second deterioration Layer 521...shell 522···concentrator P...light spot 14