200809941 九、發明說明 【發明所屬之技術領域】 本發明關於使板狀加工對象物沿著切斷預定線進行切 斷的雷射加工方法。 【先前技術】 習知技術揭示之此種雷射加工方法有，在板狀加工對 g 象物內部調整聚光點照射雷射光，沿著加工對象物之切斷 預定線，使成爲切斷起點之改質區域於加工對象物之厚度 方向被形成多數列（參照例如專利文獻1 )。於此種雷射 加工方法，通常於加工對象物檢測出雷射光射入之第1面 之位置，依據該檢測信號控制雷射光聚光點之位置，而於 加工對象物內部在字第1面起特定距離之位置形成各改質 區域。 專利文獻1 :特開2005 — 1 5053 7號公報 【發明內容】 (發明所欲解決之課題） 使改質區域於加工對象物之厚度方向形成多數列而切 斷加工對象物時，在最接近第1面的改質區域，以及最接 近和第1面呈對向之第2面的改質區域之形成位置’對於 切斷面之品質特別要求高精確度。其理由爲，彼等改質區 域於自第1面及第2面起特定距離之位置分別未形成良好 精確度時，切斷時例如於加工對象物之厚度方向中切斷面 -4- 200809941 端部會大幅偏離切斷預定線而產生所謂裙襬（skirt )現象 〇 但是，上述雷射加工方法中，僅以第1面之位置作爲 基準，而將多數列改質區域形成於加工對象物之厚度方向 ，因此，加工對象物之厚度例如因爲硏磨塊差異而於多數 加工對象物間存在變存在變動，或者於1個加工對象物存 在一部分較厚、一部分較薄情況（亦即加工對象物厚度存 _ 在變動情況）下，最接近第2面的改質區域有可能無法以 良好精確度形成於自第2面起特定距離之位置。 本發明目的在於提供一種，沿著切斷預定線使改質區 域於加工對象物之厚度方向形成多數列時，可使最接近第 1面的第1改質區域及最接近第2面的第2改質區域以良 好精確度形成的雷射加工方法。 (用以解決課題的手段） • 爲達成上述目的，本發明之雷射加工方法，係在板狀 加工對象物之內部調整聚光點照射雷射光，而沿著上述加 工對象物之切斷預定線，使成爲切斷起點之多數列改質區 _ 域形成於上述加工對象物之厚度方向者；其特徵爲包含： 於上述加工對象物以雷射光射入之第1面之位置爲基準， 形成上述改質區域之中最接近上述第1面的第1改質區域 之工程；及於上述加工對象物以和上述第1面呈對向的第 2面之位置爲基準，形成上述改質區域之中最接近上述第 2面的第2改質區域之工程。 -5- 200809941 依據該雷射加工方法’改質區域之中最接近弟 第1改質區域，係以第1面之位置爲基準被形成， 域之中最接近第2面的第2改質區域，係以第2面 爲基準被形成。如此則，以第1面及第2面雙方之 基準，即使加工對象物之厚度變化時，改質區域之 近第1面的第1改質區域之位置及最接近第2面的 質區域之位置因爲加工對象物之厚度變化引起之偏 被抑制。亦即，沿著切斷預定線使改質區域於加工 之厚度方向形成多數列時，可使最接近第1面的第 區域及最接近第2面的第2改質區域以良好精確度 結果，可保持切斷面之高品質。又，各改質區域， 工對象物之內部調整聚光點照射雷射光，於上述加 物之內部產生多光子吸收及其他之光吸收而形成。 其中可設爲，於上述第1改質區域之形成工程 檢測出上述第1面反射之反射光、取得上述第1面 關之第1位置資訊，依據該第1位置資訊在自第1 距離特定距離之內側形成上述第1改質區域；於上 改質區域之形成工程，藉由檢測出上述第2面反射 光、取得上述第2面位置相關之第2位置資訊，依 2位置資訊在自第2面起僅距離特定距離之內側形 第2改質區域。 又，可設爲，於上述第1改質區域之形成工程 檢測出上述第1面反射之反射光、取得上述弟1面 關之第1位置資訊，依據該第1位置資訊在自第1 1面的 改質區 之位置 位置爲 中最接 第2改 移可以 對象物 1改質 形成。 係在加 工對象 ，藉由 位置相 面起僅 述第2 之反射 據該第 成上述 ，藉由 位置相 面起僅 -6 - 200809941 距離特定距離之內側形成上述第1改質區域；於上述第2 改質區域之形成工程，依據上述第1位置資訊及上述加工 對象物之厚度相關的厚度資訊，在自第2面起僅距離特定 距離之內側形成上述第2改質區域。 又，可設爲，於上述第2改質區域之形成工程，藉由 檢測出上述第2面反射之反射光、取得上述第2面位置相 關之第2位置資訊，依據該第2 ί立置資訊在自第2面起僅 距離特定距離之內側形成上述第2改質區域；於上述第1 改質區域之形成工程，依據上述第2位置資訊及上述加工 對象物之厚度相關的厚度資訊，在自第1面起僅距離特定 距離之內側形成上述第1改質區域。 又，可設爲，上述加工對象物具備半導體基板，上述 改質區域包含溶融處理區域。 又，較好是包含：以上述改質區域爲切斷起點沿著上 述切斷預定線切斷上述加工對象物之工程。如此則，加工 對象物可沿著切斷預定線於良好精確度下進行切斷。 【實施方式】 以下參照圖面說明本發明較佳實施形態。於本實施形 態之雷射加工方法，利用多光子吸收之現象而於加工對象 物內部形成改質區域。首先，說明形成改質區域之雷射加 工方法。 相較於材料之吸收能隙（band gap) EG，光子之能量 (energy ) h,較小時成爲光學透明。因此，材料吸收產生 200809941 之條件爲h , > EG。但是，即使於光學透明，在雷射光強 度設爲極大時於nhw > EG之條件（n = 2、3、4、..........）下 產生材料之吸收，該現象稱爲多光子吸收。脈波時，雷射 光強度由雷射光之聚光點之峰値電力（peek power)密度 (W / cm2 )決定，例如峰値電力密度於lxlO8 ( W / cm2 )以上之條件下產生多光子吸收。峰値電力密度，可由（ 聚光點之雷射光之相當於1脈衝之能量）+(雷射光之光 點斷面積X脈寬）算出。又，連續波時，雷射光強度由雷 射光之聚光點之電場強度（W/ cm2 )決定。 參照圖1 一 6說明利用多光子吸收之本實施形態之雷 射加工方法之原理。如圖1所示，於晶圓狀（板狀）加工 對象物1之表面3存在切斷預定線5用於切斷加工對象物 1。切斷預定線5爲直線狀延伸之假想線。於本實施形態 之雷射加工方法，如圖2所示，在產生多光子吸收之條件 下使聚光點P調整於加工對象物1之內部而進行雷射光照 射形成改質區域7。又，聚光點P，係指雷射光L聚光之 處。切斷預定線5，不限定於直線狀’可爲曲線狀。不限 定於假想線，可爲描繪於加工對象物1之實際之線。 使雷射光L沿著切斷預定線5 (亦即圖1之箭頭A之 方向）相對移動，而使聚光點P沿著切斷預定線5移動。 如此則，如圖3 — 5所示，改質區域7沿著切斷預定線5 被形成於加工對象物1內部，該改質區域7成爲切斷起點 區域8。切斷起點區域8表示，加工對象物1被切斷時成 爲切斷（切割）起點之區域。該切斷起點區域8，有依改 -8 - 200809941 質區域7之連續形成而被形成’亦有依改質區域7之斷續 形成而被形成。 本實施Si之雷射加工方法’於加工對象物1之表面 3幾乎不吸收雷射光L ’加工對象物1之表面3不會被溶 融。 於加工對象物1內部形成切斷起點區域8時，以該切 斷起點區域8作爲起點容易產生切割，因此如圖6所示， 可以較小之力量切斷加工對象物1。因此，於加工對象物 1之表面3不會產生不必要之切割之情況下，可以高精確 度地切斷加工對象物1。 以該切斷起點區域8作爲起點之加工對象物1之切斷 時，可考慮以下2種方法。其一爲，切斷起點區域8形成 後，藉由人爲力量施加於加工對象物1，而以切斷起點區 域8爲起點使加工對象物1被切割，使加工對象物〗被切 斷。此爲例如加工對象物1之厚度大時之切斷。人爲力量 之施加，例如沿著加工對象物1之切斷起點區域8對加工 對象物1施加彎曲應力或切斷應力，對加工對象物1供給 溫度差而產生熱應力。其二爲，藉由形成切斷起點區域8 ，以該切斷起點區域8作爲起點朝加工對象物1之斷面方 向（厚度方向）自然切割，而使加工對象物1被切斷。此 爲，例如加工對象物1之厚度小時，藉由1列改質區域7 可形成切斷起點區域8，加工對象物1之厚度大時，於厚 度方向藉由多數列改質區域7可形成切斷起點區域8。又 ，自然切割時，於切斷處，切割不會先行到達未形成切斷 -9- 200809941 起點區域8之邰位所對應部分之表面3上，僅形成有切斷 起點區域8部位所對應之部分會被切斷，切斷之控制良好 。近年來，砂晶圓等加工對象物1之厚度有變薄之傾向， 因此此種控制性良好之切斷方法大爲有效。 又，本實施形態之雷射加工方法中，改質區域有以下 (1 )〜（3 )之情況。 (1)改質區域包含1或多數裂痕（crack)之裂痕區 域時， 於加工對象物1 (例如玻璃或LiTa03構成之壓電材料 )內部調整聚光點，於聚光點之電場強度爲lxlO8 ( W/ cm2 )以上、且脈寬爲1 // s以下之條件下照射雷射光。該 脈寬之大小爲，可產生多光子吸收，且於加工對象物1之 表面不會產生不必要之損傷，僅於加工對象物1之內部形 成裂痕區域之條件。依此則，可於加工對象物1之內部產 生多光子吸收之光學損傷現象。藉由該光學損傷現象而於 加工對象物內部誘發熱變形，如此則，可於加工對象物內 部形成裂痕區域。電場強度之上限値例如爲lxlO12 ( W/ cm2)、脈寬較好是例如Ins〜200ns。又，藉由多光子吸 收形成裂痕區域，被揭示於例如第45次雷射熱加工硏究 會論文集（1998年，12月）之第23〜28頁之「藉由固體 雷射高頻對玻璃基板內部之標記（marking)」。 本發明人藉由實驗算出電場強度與裂痕大小之關係。 實驗條件如下： (A )加工對象物·· Pyrex (派熱克斯（登記商標）） -10- 200809941 玻璃（厚度700//m) (B )雷射 光源：半導體雷射激發Nd : YAG雷射 波長：1064nm 雷射光點斷面積：3.14xl0_8cm2 振盪形態：Q開關脈衝 重複頻率：100kHz 脈寬：30ns 輸出：輸出/脈衝 雷射光品質：TEM。。 偏光特性·直線偏光 (C) 聚光透鏡 對雷射光波長之透過率：60% (D) 加工對象物被載置之載置台之移動速度： 1 0 0 m m / 秒 雷射光品質爲TEM。。意味著，聚光點高可以聚光至大 約包含雷射光波長。 圖7爲上述實驗結果之圖。橫軸表示峰値電力密度， 雷射光爲脈衝雷射光，因此電場強度以峰値電力密度表示 。縱軸表示介面1脈衝之雷射光施加形成於加工對象物內 部之裂痕部分（裂點）之大小，裂點聚集成爲裂痕區域， 裂點之大小爲，裂點形狀之中成爲最大部分之大小。分布 圖中之黑圈表示之資料，表示聚光透鏡（C)之倍率爲 100倍，開口數（NA)爲0.80。分布圖中之白圈表示之資 -11 - 200809941 料’表示聚光透鏡（c )之倍率爲5 0倍，開口數（N A ) 爲〇 _ 5 5。自峰値電力密度約1 0 11 ( w / cm2 )起於加工對 象物內部產生裂點，隨峰値電力密度變大，裂點亦變大。 以下參照圖8 - 1 1說明藉由裂痕區域之形成對加工對 象物1之切斷之機制。如圖8所示，在產生多光子吸收之 條件下於加工對象物1內部調整聚光點照射雷射光L沿著 切斷預定線於內部形成裂痕區域9。裂痕區域9爲包含1 _ 或多數裂痕之區域。如此形成之裂痕區域9成爲切斷起點 區域。如圖9所示，以裂痕區域9爲起點（亦即以切斷起 點區域爲起點）裂痕繼續成長，如圖1 〇所示，裂痕到達 加工對象物1之表面3與背面2丨，如圖1 1所示，加工對 象物1被切割，加工對象物1被切斷。到達加工對象物1 之表面3與背面21之裂痕，有自然成長者，也有對加工 對象物1施加力而成長者。 (2 )改質區域爲溶融處理區域時， # 於加工對象物（例如矽之半導體材料）內部調整聚光 點’於聚光點之電場強度爲IxlO8 ( W/ cm2)以上、且脈 寬爲1 μ s以下之條件下照射雷射光。依此則，加工對象 物內部因多光子吸收而被局部加熱。藉由該加熱於加工對 象物內部形成溶融處理區域。溶融處理區域爲暫時溶融之 後再度固化之區域，或溶融狀態之區域，或由溶融狀態再 度固化之狀態之區域，亦可爲相變化區域或結晶構造變化 區域。又，溶融處理區域亦可爲，單結晶構造、非晶質構 造、多結晶構造之中’某~*構造變化爲其他構造之區域， -12- 200809941 域，由單 造變化爲 勿1爲單 度之上限 如 1 n s〜 板）內部 外徑4英 亦即’例如由單結晶構造變化爲非晶質構造之區 結晶構造變化爲多結晶構造之區域，由單結晶構 包含非晶質構造與多結晶構造之區域。加工對象 晶矽時，溶融處理區域爲例如非晶質矽。電場強 値爲例如1 X 1 0 1 2 ( W / cm2 )，脈寬較好是例 2 0 0 n s 〇 本發明人藉由實驗確認於矽晶圓（半導體基 形成溶融處理區域。實驗條件如下： (A )加工對象物：矽晶圓（厚度3 5 0 // m， 吋） (B )雷射 光源：半導體雷射激發Nd : YAG雷] 波長：1 064nm 雷射光點斷面積：3.14xl(T8Cm2 振盪形態：Q開關脈衝 重複頻率：1 00kHz 脈寬：3 0 n s 輸出：2 0 m J /脈衝 雷射光品質：TEM^ 偏光特性：直線偏光 (C)聚光透鏡 倍率：5 0倍 N.A. ： 0.55 對雷射光波長之透過率：60% -13- 200809941 (D )加工對象物被載置之載置台之移動速度： 1 0 0 m m / 秒 圖1 2爲藉由上述條件之雷射加工切斷之矽晶圓之一 部分之斷面照片圖。於矽晶圓11之內部形成溶融處理區 域13。藉由上述條件形成之溶融處理區域13之厚度方向 尺寸（大小）約爲1 〇 〇 # m。 說明溶融處理區域1 3藉由多光子吸收被形成。圖1 3 爲雷射光波長與矽基板內部之透過率之關係圖，分別除去 矽基板表面側與背面側之反射成份，僅表示內部之透過率 ，石夕基板厚度分別爲 5 〇 μ m、1 0 0 μ m、2 0 0 // m、5 0 0 // m 、1 0 0 0 // m。 例如於Nd : YAG雷射之波長1 064nm，矽基板厚度爲 5 00 // m以下時，於矽基板內部，雷射光有80%以上透過 。圖1 2所示矽晶圓1 1之厚度爲3 5 0 /Z m，多光子吸收產 生之溶融處理區域1 3被形成於矽晶圓1 1之中心附近、亦 即表面起175//m之部分。此情況下之透過率，參考厚度 2 0 0 // m之矽晶圓時爲9 0 %以上，因此雷射光於矽晶圓1 1 內部僅些微被吸收，大部分均透過。此意味著，並非雷射 光於矽晶圓1 1內部被吸收，溶融處理區域1 3被形成於矽 晶圓1 1內部（亦即藉由雷射光之通常加熱而形成溶融處 理區域者，而是藉由多光子吸收形成溶融處理區域。藉由 多光子吸收之溶融處理區域之形成，揭示於例如溶接協會 全國大會言講槪要第66集（2000年4月）第72 — 73頁之 「1 (T 12秒脈衝雷射對矽之加工特性評估」。 -14- 200809941 又，矽晶圓係以溶融處理區域形成之切斷起點區域作 爲起點朝斷面方向產生裂痕，藉由該裂痕之到達矽晶圓表 面與背面而被切斷。到達矽晶圓表面與背面之裂痕，有自 然成長者，也有對矽晶圓施加力而成長者。由切斷起點區 域起裂痕自然成長於矽晶圓表面與背面時包含以下任一 情況，亦即包含：形成切斷起點區域之溶融處理區域 由溶融狀態成長裂痕之情況，及形成切斷起點區域之溶融 處理區域由溶融狀態再度固化時成長裂痕之情況，但是任 一情況下，溶融處理區域均僅形成於矽晶圓內部，切斷後 之切斷面如圖1 2所示僅於內部形成溶融處理區域。如上 述說明，於加工對象物內部藉由溶融處理區域形成切斷起 點區域，則切斷時不容易產生偏移切斷起點區域線之不必 要之裂痕，切斷控制變爲容易，亦即溶融處理區域之形成 不僅根據多光子吸收，亦根據其他之吸收作用。 (3 )改質區域爲折射率變化區域時 於加工對象物（例如玻璃）內部調整聚光點，於聚光 點之電場強度爲1x1 〇8 ( W/ cm2 )以上、且脈寬爲Ins以 下之條件下照射雷射光。極度縮短脈寬，於加工對象物內 部產生多光子吸收，如此則，多光子吸收引起之能不會轉 化爲熱能，於加工對象物內部誘發離子價數變化、結晶化 或分極配向等之永續構造變化而形成折射率變化區域。電 場強度之上限値爲例如1 X 1 0 12 ( W / cm2 )，脈寬較好是 例如1 n s以下，更好爲1 p s以下。藉由多光子吸收引起之 折射率變化區域之形成，被揭示於例如第42次雷射熱加 -15- 200809941 工硏究會論文集（1997年11月月）第105頁〜111頁之 「1〇_ 15秒雷射照射對玻璃內部之光誘發構造形成」。 以上以（1 )〜（3 )之情況說明改賢區域，但只要考 慮晶圓形狀加工對象物之結晶構造或其之劈開性而如下形 成切斷起點區域，以該切斷起點區域爲起點可以更小之力 、而且可以良好精確度切斷加工對象物。 亦即，矽等鑽石構造之單晶半導體構成之基板之情況 下’較好是在沿著（1 1 1 )面（第1劈開面）或（1 10 )面 (第2劈開面）之方向形成切斷起點區域。GaAs等之閃 鋅礦型構造之III-V族化合物半導體構成之基板之情況下 ’較好是在沿著（1 1 0 )面之方向形成切斷起點區域。又 ’具有監寶石（AI2O3)等六方晶系結晶構造之基板之情 況下，較好是以（0001)面爲主面，在沿著（1120)面（ A面）或（1 1 〇〇 )面（Μ面）之方向形成切斷起點區域。 又，沿著應形成上述切斷起點區域之方向（例如單晶 矽基板之沿著（1 1 1 )面之方向）、或和應形成切斷起點 區域之方向正交之方向，於基板形成定位平面，以該定位 平面爲基準，則可以容易、且正確於基板形成，沿著應形 成切斷起點區域之方向的切斷起點區域。 以下說明本發明較佳實施形態。 (第1實施形態） 如圖14、15所示，加工對象物1具備：矽晶圓1 1， 及包含多數功能性元件1 5而形成於矽晶圓1 1之表面（以 -16- 200809941 下亦有單稱爲表面之情況）1 1 a的功能性元件層1 6，其厚 度約3 00 // m。功能性元件1 5爲例如結晶成長形成之半導 體動作層、光二極體等受光元件、雷射二極體等之發光元 件、或作爲電路被形成之電路元件等’於矽晶圓1 1之定 位平面6於平行方向及垂直方向以多數矩陣狀形成。此種 加工對象物1以通過相鄰之功能性元件15間的方式沿著 以格子狀設定之切斷預定線5 (參照圖1 4之虛線）被切斷 ，成爲微小晶片之分離元件。 切斷該加工對象物1時，首先，於功能性元件層1 6 表面黏貼保護捲帶，於藉由保護捲帶保護功能性元件層1 6 之狀態下，於雷射加工裝置之載置台使保持有加工對象物 1之保護捲帶被固定。之後，自加工對象物1之背面（以 下單稱爲「背面」）2 1調整聚光點於矽晶圓1 1內部，於 產生多光子吸收之條件下照射雷射光，沿著各切斷預定線 5形成成爲切斷起點之改質區域（背面射入加工）。於此 沿著各切斷預定線5於加工對象物1之厚度方向形成6列 改質區域。之後，同時隔離被固定於載置台之保護捲帶及 加工對象物1。如此則，於矽晶圓1 1之背面21被黏貼擴 展捲帶，自功能性元件層1 6表面剝離保護捲帶之後，使 擴展捲帶擴張。如此則，以改質區域爲切斷起點使加工對 象物1沿著切斷預定線5依據每一功能性元件1 5被以良 好精確度切斷，使多數半導體晶片互相分離。又，改質區 域除溶融處理區域以外，亦有包含裂痕區域之情況。 但是，加工對象物1，其厚度例如因爲硏磨塊差異而 -17- 200809941 於多數加工對象物1間存在有變動（變化），或者於1個 加工對象物1因爲硏磨時之不均勻等而導致一部分變厚或 一部分變薄之情況（亦即加工對象物i之厚度存在變動情 況）存在。具體言之爲，於300/zm之加工對象物1，在 多數加工對象物1之間會有厚度± 1 〇 # m以上之變動，或 於於1個加工對象物1中其之一部分厚度會有厚度±5 # m 以上之變動。 B 但是’通常自動對焦功能係以加工對象物丨之厚度視 爲一定’僅藉由測定雷射光射入面之背面2 1之變位量據 以控制雷射光之聚光點位置成爲離開背面2 1特定之位置 。因此，習知技術，如圖2 0所示有如下情況，亦即形成 之改質區域Μ之中最接近表面11a的改質區域，其在加工 對象物1之較厚部分以突出該加工對象物丨的方式被形成 ，在加工對象物1之較薄部分則未到達加工對象物1之深 度位置而被形成於靠近背面21。 • 相對於此，本實施形態之雷射加工方法中，沿著加工 對象物1之切斷預定線而於加工對象物之厚度方向形成的 多數列改質區域之中，最接近背面（第1面）21的第1改 質區域係以背面21之位置作爲基準，最接近表面lla (第 2面）的第2改質區域係以表面1 1 a之位置作爲基準而形 成。以下更詳細說明該改質區域之形成。 (局度設疋） 首先’在調整加工對象物1之背面21投射之標線（ -18- 200809941 reticle )影像之焦點狀態下，照射測距用雷射光，以背面 2 1反射之測距用雷射光之反射光作爲電壓値予以檢測出， 記憶檢測出之電壓値（圖16之S1)。 (掃描） 之後，照射測距用雷射光，以背面2 1反射之測距用 雷射光之反射光作爲電壓値予以檢測出之同時，使該電壓 g 値維持於高度設定引起之電壓値而沿著切斷預定線5掃描 ，取得沿著切斷預定線5之背面2 1之變位，以該背面2 1 之變位做爲背面位置資訊（第1位置資訊）記憶之。亦即 ，背面位置資訊係以，自背面2 1起至被高度設定之背面 21位置爲止之厚度方向之相對距離被算出。 背面位置資訊=背面21之變位 =自背面21起至被高度設定之背面21 位置爲止之厚度方向之相對距離。 • 此時，掃描測距用雷射光之同時，沿著切斷預定線5 ，藉由厚度測疋益以光學測疋加工對象物1之厚度（厚g 資訊）進行運算。具體言之爲，如圖丨7 ( a )所示，沿著 切斷預定線5，使背面2 1之反射光L丨及透過加工對象物 1內部於表面1 1 a被反射之反射光L2，於線感測器5 〇受 ! 光。藉由線感測器50之中彼等反射光li、L2之受光位置 與預先算出之加工封象物1之折射率，運算自表面 背面2 1之距離，亦即運算加工對象物1之厚度。 之後’於該運算出之加工對象物1之厚度加上板狀背 -19- 200809941 面位置資訊，作爲沿著切斷預定線5之表面位置資訊（第 2位置資訊）記憶之。亦即，表面位置資訊係以，自表面 11a起至被高度設定之背面21位置爲止之厚度方向之相對 距離被算出（圖16之S2)。 表面位置資訊=背面位置資訊+加工對象物1之厚度 =自表面11a起至被高度設定之背面 2 1位置爲止之厚度方向之相對距離 〇 又，其中背面2 1之測定系及加工對象物1之厚度之 測定系以2軸構成。又，背面21之變位及加工對象物i 之厚度被和沿著切斷預定線5之方向之座標設定關連對應 而被取得。因此，背面21之測定系及加工對象物1之厚 度之測定系以2軸構成，由各測定系間之距離D 1於座標 上合成背面位置資訊及表面位置資訊，即可以良好精確度 算出背面位置資訊及表面位置資訊。 或者亦可如圖17(b)所示，藉由背面21之反射光 L 3與表面1 1 a之反射光L4之干涉，而測定加工對象物1 之厚度。此情況下，背面21之測定系及加工對象物丨之 厚度之測定系以2軸構成，背面2 1之變位及加工對象物！ 之厚度被和沿著切斷預定線5之方向之座標設定關連對應 而被取得。由各測定系間之距離D1於座標上合成背面位 置資訊及表面位置資訊，即可以良好精確度算出背面位置 資訊及表面位置資訊。 -20- 200809941 (改質區域之形成） 之後，如圖1 8 ( a)所示，於加工對象物 於自表面11a起僅距離10/zm之內側（圖示上 光點照射雷射光，沿著切斷預定線5掃描。具 於加工對象物1之內部，使聚光點移動至表面 僅距離1 0 // m之背面2 1側位置，照射輸出爲 射光，使記憶之表面位置資訊藉由位置調整元 形態中爲使用壓電元件之傳動器）再生而控制 之同時，沿著切斷預定線5掃描。如此則，以 基準而於表面1 1 a起僅距離1 0 // m之內側沿著 5形成改質區域（第2改質層）Μ1 (圖1 6之 S之爲，於表面位置資訊起僅l〇#m之背面： 成沿著切斷預定線5之改質區域（第2改質層 之後，如圖1 8 ( b )所示，於加工對象物 於自表面1 la起僅距離25 // m之內側（圖示上 光點照射雷射光，沿著切斷預定線5掃描。具 於加工對象物1之內部，使聚光點移動至表面 僅距離25 // m之背面21側位置，照射輸出爲 身寸光’使記憶之表面位置資訊藉由壓電元件再 光點位置之同時，沿著切斷預定線5掃描。如 面11a爲基準而於表面lla起僅距離25//m之 斷預定線5形成改質區域M2 (圖16之S4 ) 爲’於表面位置資訊起僅2 5 /z m之背面2 1側 著切斷預定線5之改質區域M2。 1之內部， 側）調整聚 體言之爲， 位置資訊起 0.72W之雷 件（本實施 聚光點位置 表面1 1 a爲 切斷預定線 S3)。具體 U側位置形 )Ml。 1之內部， 側）調整聚 體言之爲， 位置資訊起 1.2W之雷 生而控制聚 此則，以表 內側沿著切 。具體言之 位置形成沿 -21 - 200809941 之後’於加工對象物1之內部，於自表面lla起僅距 離3 5 // m之內側（圖示上側）調整聚光點照射雷射光，沿 著切斷預定線5掃插。具體言之爲，於加工對象物1之內 部，使聚光點移動至表面位置資訊起僅距離35//m之背面 21側位置’照射輸出爲UW之雷射光，使記憶之表面位 置資訊藉由壓電元件再生而控制聚光點位置之同時，沿著 切斷預定線5掃描。如此則，以表面丨i &爲基準而於表面 1 1 a起僅距離3 5 // m之內側沿著切斷預定線5形成改質區 域M3(圖16之S5)。具體言之爲，於表面位置資訊起 僅35// m之背面21側位置形成沿著切斷預定線5之改質 區域M3。 之後，於加工對象物1之內部，於自表面i la起僅距 離45 // m之內側（圖示上側）調整聚光點照射雷射光，沿 著切斷預定線5掃描。具體言之爲，於加工對象物1之內 部，使聚光點移動至表面位置資訊起僅距離45 # m之背面 21側位置’照射輸出爲1.2W之雷射光，使記憶之表面位 置資訊藉由壓電元件再生而控制聚光點位置之同時，沿著 切斷預定線5掃描。如此則，以表面1 1 a爲基準而於表面 1 1 a起僅距離4 5 // m之內側沿著切斷預定線5形成改質區 域M3(圖16之S6)。具體言之爲，於表面位置資訊起 僅45 // m之背面2 1側位置形成沿著切斷預定線5之改質 區域M4。 之後，如圖18 ( c )所示，於加工對象物1之內部， 於自背面21起僅距離2 5 # m之內側（圖示下側）調整聚 -22- 200809941 光點照射雷射光’沿著切斷預定線5掃描。具體言之爲’ 於加工對象物1之內部’使聚光點移動至背面位置資訊起 僅距離2 5 # m之表面1 1 a側位置.，照射輸出爲1.2 W之雷 射光，使記憶之背面位置資訊藉由壓電元件再生而控制聚 光點位置之同時’沿著切斷預定線5掃描。如此則’以背 面2 1爲基準而於背面2 1起僅距離25 // m之內側沿著切斷 預定線5形成改質區域M5 (圖16之S7)。具體言之爲 ，於背面位置資訊起僅25// m之表面11a側位置形成沿著 切斷預定線5之改質區域M5。 最後，於加工對象物1之內部，於自背面21起僅距 離1 5 # m之內側（圖示下側）調整聚光點照射雷射光，沿 著切斷預定線5掃描。具體言之爲’於加工對象物1之內 部，使聚光點移動至背面位置資訊起僅距離之表面 1 la側位置，照射輸出爲0.68W之雷射光，使記憶之背面 位置資訊藉由壓電元件再生而控制聚光點位置之同時，沿 著切斷預定線5掃描。如此則，以背面21爲基準而於背 面2 1起僅距離1 5 // m之內側沿著切斷預定線5形成改質 區域（第2改質層）M6(圖16之S8)。具體言之爲，於 背面位置資訊起僅1 5 μ m之表面1 1 a側位置形成沿著切斷 預定線5之改質區域M6。 於加工對象物1之內部，於厚度方向形成之多數列改 質區域Ml〜M6之中，改質區域M5、M6爲上面形成有半 切割（half cut )之改質區域，成爲所謂半切割SD。該半 切割可藉由擴展擴展捲帶而確實分離，因此半切割SD爲 -23- 200809941 極重要要素。又，多數列背形成之改質區域Ml〜M6之中 ’最接近表面11a之改質區域mi爲對切斷後之切斷面品 質特別有影響之改質區域，稱爲品質SD。品質SD爲，使 功能性元件層1 6以良好精確度切斷者，在維持切斷加工 對象物1之品質上爲極重要要素。 如上述說明，本實施形態中，於加工對象物1之內部 ’以背面2 1爲基準，於自背面2 1起僅特定距離之內側， 沿著切斷預定線5形成改質區域μ 5、Μ 6之同時，以表面 1 1 a爲基準，於自表面1 1 a起僅特定距離之內側，沿著切 斷預定線5形成改質區域μ丨。如此則，因爲以背面2〗極 表面11a雙方爲基準，即使加工對象物丨之厚度變動時， 改質區域M5、M6之位置及改質區域M6之位置受加工對 象物1之厚度變化引起之偏移情況可以被抑制。因此，依 據本實施形態，沿著切斷預定線使改質區域於加工對象物 1之厚度方向形成多數列時，可使最接近背面2 1的改質區 域M6、鄰接改質區域M6的改質區域M5及最接近表面 1 1 a的改質區域Μ 1以良好精確度形成。 另外，如上述說明，本實施形態中，可使改質區域 Μ5、Μ6以良好精確度形成，可達成以下效果。亦即，可 抑制改質區域Μ5、Μ6過度接近背面2 1導致半切割呈現 蛇行而使品質劣化之情況。另外，亦可防止改質區域Μ5 、Μ6過度離開背面21導致改質區域Μ5、Μ6產生之龜裂 延伸不足而無法形成良好之半切割。 另外，如上述說明，本實施形態中，可使改質區域 -24- 200809941 Μ1以良好精確度形成，可達成以下效果。亦即，可抑制 改質區域Μ 1過度接近表面1 1 a導致照射之雷射光由加工 對象物1突出而於表面11a被穿孔，減弱加工對象物1之 抗折強度。另外，亦可防止改質區域Μ1過度離開表面 11a而於切斷面使表面11a側之端部大幅偏離切斷預定線 5之所謂裙襬現象。另外，本實施形態中，背面射入加工 而於雷射光射入面與相反側之面之表面1 1 a形成有功能性 元件1 5，因此裙襬現象之產生之防止效果特別顯著。 另外，依據本實施形態，加工對象物1之厚度變化引 起之改質區域位置之偏移可被補正，另外，受表面11a起 之距離與背面2 1起之距離影響的改質區域之品質可以設 疋爲最佳’可以設定切斷後之切斷品質成爲最佳，可進行 多段加工。 又，加工對象物1之厚度可以接觸型厚度測定器測定 ，但此情況下，於加工對象物1與載置台之間有可能混入 異物，或黏貼於擴展捲帶時擴展捲帶與加工對象物1之間 有可能混入空氣，導致接觸之加工對象物1之位置未必爲 表至加工對象物1之厚度的位置。相對於此，本實施形態 中，使用利用透過型雷射之測定器，可以良好精確度測定 出加工對象物1之厚度。 亦即，上述實施形態中，如上述說明，改質區域M2 、M3、M4係以表面1 1 a爲基準形成，但本發明不限定於 上述實施形態，改質區域M2、M3、M4亦可以背面21爲 基準形成。 -25- 200809941 (第2實施形態） 說明本發明第2實施形態之雷射加工方法，該第2實 施形態之雷射加工方法和第1實施形態之雷射加工方法之 不同點爲，不測定加工對象物1之厚度，如圖〗9所示， 使用自動對焦功能之光學系分別檢測出背面21之反射光 L5及表面1 la之反射光L6。 B 具體言之爲，於本實施形態之雷射加工方法，分別檢 測出背面2 1之反射光L5及透過加工對象物1而於表面 1 1 a反射之反射光L 6，分別直接取得表面1 1 a之變位及背 面2 1之變位，直接算出背面位置資訊及表面位置資訊。 背面位置資訊=背面2 1之變位 =自背面21起至被局度設定之背面21 位置爲止之厚度方向之相對距離。 表面位置資訊=表面1 1 a之變位 Φ =自表面1 1 a起至被高度設定之背面 21位置爲止之厚度方向之相對距離 〇 依據本實施形態之雷射加工方法，可獲得和上述實施 形態之雷射加工方法同樣之效果。亦即，即使加工對象物 1之厚度有變動、變化時，改質區域M5、M6之位置及改 質區域M6之位置受加工對象物1之厚度變化引起之偏移 情況可以被抑制。因此，依據本實施形態，沿著切斷預定 線5使改質區域於加工對象物1之厚度方向形成多數列時 -26- 200809941 ，可使最接近背面21的改質區域M6、鄰接改質區域M6 的改質區域Μ 5及最接近表面1 1 a的改質區域μ 1以良好 精確度形成。 以下說明本發明之一實施形態之雷射加工裝置。 如圖2 1所示’雷射加工裝置1 00具備：雷射光源1 〇 i ’用於振盪產生脈衝狀之雷射光（加功用雷射光）L ;分 光鏡103，配置成爲使雷射光之光軸方向變化90度；及聚 光用透鏡105，用於使雷射光L聚光。另外，雷射加工裝 置1〇〇具備：載置台107，用於載置被聚光用透鏡10 5聚 光之雷射光L照射之加工對象物1 ;平台1 1 1，可使載置 台107移動於X、Y、Z軸方向；雷射光源控制器1〇2，用 於控制雷射光源1 0 1而調節雷射光L之輸出或脈寬等；及 平台控制部1 1 5，用於控制平台1 1 1之移動。 依據雷射加工裝置1 〇 〇，由雷射光源1 〇 1照射之雷射 光L，係於分光鏡1 〇 3使其光軸變化9 0度，於聚光用透 鏡105聚光於載置台107上之加工對象物1內部。與此同 時，平台1 1 1移動，加工對象物1相對於雷射光L沿著切 斷預定線5被相對移動。如此則，可沿著切斷預定線5於 加工對象物1形成改質區域。 又’雷射加工裝置1 〇 〇不限定於上述實施形態，亦可 不使用分光鏡1 0 3而將雷射光源1 〇 1照射之雷射光l導入 聚光用透鏡105。另外，雷射光L之移動，只要雷射光l 對於加工對象物1相對移動即可。特別是關於z軸方向， 可取代載置台107之移動而移動聚光用透鏡105之位置， -27 - 200809941 據此變化雷射光L之焦點位置。 以上說明本發明較佳實施形態，但本實施形態不限定 於上述實施形態。 例如上述實施形態中，測定加工對象物1之表面1 1 a 之變位後，掃描雷射光而形成改質區域，亦即所謂掃描（ trace )加工，但是測定表面1 la之變位之同時，形成改質 區域之所謂即時（r e a 1 t i m e )加工亦可。 又，透過加工對象物1之測距用雷射光及不透過而反 射之測距用雷射光之照射時，可使用多數雷射光源，或可 由1個雷射光源變化波長而照射。 又’上述實施形態中，構成爲由形成有功能性元件i 5 之表面1 1 a對向之背面21側射入雷射光的所謂背面射入 加工，但亦可爲由表面1 1 a射入雷射光。 又’加工對象物1使用具備矽晶圓1 1之加工對象物i ，但亦可以不是矽晶圓1 1，而爲鎵砷等半導體化合物材料 、壓電材料、藍寶石等具有結晶性之材料等。。 (產業上可利用性） 依據本發明，沿著切斷預定線使改質區域於加工對象 物之厚度方向形成多數列時，可使最接近第1面的第1改 質區域及最接近第2面的第2改質區域以良好精確度形成 (發明效果） -28- 200809941 依據本發明，沿著切斷預定線使多數列改質區域形成 於加工對象物之厚度方向時，亦可以良好精確度形成最接 近第1面的第1改質區域及最接近第2面的第2改質區域 【圖式簡單說明】 圖1爲本實施形態之雷射加工裝置之雷射加工中之加 工對象物之平面圖。 圖2爲圖1所示加工對象物之II 一 II線斷面圖。 圖3爲本實施形態之雷射加工裝置之雷射加工後之加 工對象物之平面圖。 圖4爲圖3所示加工對象物之IV — IV線斷面圖。 圖5爲圖3所示加工對象物之V — V線斷面圖。 圖6爲藉由本實施形態之雷射加工裝置切斷之加工對 象物之平面圖。 圖7爲本實施形態之雷射加工裝置中之電場強度與斷 裂點之大小之關係分布圖。 圖8爲本實施形態之雷射加工裝置之第1工程中之加 工對象物之斷面圖。 圖9爲本實施形態之雷射加工裝置之第2工程中之加 工對象物之斷面圖。 圖10爲本實施形態之雷射加工裝置之第3工程中之 加工對象物之斷面圖。 圖1 1爲本實施形態之雷射加工裝置之第4工程中之 -29 - 200809941 加工對象物之斷面圖。 圖1 2爲藉由本實施形態之雷射加工裝置切斷之矽晶 圓之一部分之斷面照片圖。 圖1 3爲本實施形態之雷射加工裝置中之雷射光波長 與矽基板內部之透過率之關係圖。 圖1 4爲成爲本發明第1實施形態之雷射加工方法之 對象的加工對象物之正面圖。 圖15爲圖14之乂乂一乂乂線之一部分斷面圖。 圖1 6爲本發明第1實施形態之雷射加工方法之流程 圖。 圖17爲圖16所示雷射加工方法之背面位置資訊及表 面位置資訊之計算說明圖。 圖1 8爲圖1 6所示雷射加工方法之說明用之圖1 4之 XVIII— XVIII線之一部分斷面圖。 圖1 9爲本發明第2實施形態之雷射加工方法之背面 位置資訊及表面位置資訊之計算說明圖。 圖20爲習知自動對焦功能之雷射加工方法之說明用 之圖14之XVIII — XVIII線之一部分斷面圖。 圖2 1爲本發明之一實施形態之雷射加工裝置之槪略 構成。 【主要元件符號說明】 3 1 :加工對象物 1 1 a :表面（第2面） - 30- 200809941[Technical Field] The present invention relates to a laser processing method for cutting a plate-shaped object to be processed along a line to cut. [Prior Art] The laser processing method disclosed in the prior art has a method of irradiating a laser beam with a spot light in a sheet-like processing to adjust a spotlight, and cutting a predetermined line along the object to be cut. The modified region is formed in a plurality of rows in the thickness direction of the object to be processed (see, for example, Patent Document 1). In such a laser processing method, the position of the first surface on which the laser light is incident is detected in the object to be processed, and the position of the laser light collecting spot is controlled based on the detection signal, and the inside of the object is on the first side of the object. Each modified region forms a modified region. [Problem to be Solved by the Invention] When the modified region is formed in a plurality of rows in the thickness direction of the object to be processed, the object to be processed is closest to the object to be processed. The modified region of the first surface and the formation position of the modified region closest to the second surface facing the first surface are particularly required to have high accuracy with respect to the quality of the cut surface. The reason for this is that when the modified regions are not formed with a good accuracy at a specific distance from the first surface and the second surface, for example, the cut surface is cut in the thickness direction of the object to be processed -4- 200809941 The end portion is greatly deviated from the line to cut and a so-called skirt phenomenon occurs. However, in the above-described laser processing method, a plurality of column-modified regions are formed on the object to be processed only on the basis of the position of the first surface. In the thickness direction, the thickness of the object to be processed may vary between a plurality of objects to be processed, for example, due to the difference in the honing block, or a part of the object to be processed may be thicker or a part thinner (that is, the object to be processed) In the case where the thickness of the material is _ in the case of a change, the modified region closest to the second surface may not be formed at a certain distance from the second surface with good precision. An object of the present invention is to provide a first modified region closest to the first surface and a second closest to the second surface when the modified region is formed in a plurality of rows in the thickness direction of the object to be processed along the line to cut. 2 Laser processing method in which the modified region is formed with good precision. (Means for Solving the Problem) In order to achieve the above object, the laser processing method of the present invention adjusts the spotlight to illuminate the laser beam inside the plate-shaped object to be processed, and the cutting target along the object to be processed is scheduled. a line in which a plurality of column reforming regions _ regions which are the starting points of the cutting are formed in the thickness direction of the object to be processed, and the method includes: a position on the first surface of the object to be processed by the laser light, Forming a project of the first modified region closest to the first surface among the modified regions; and forming the modified region based on a position of the second surface facing the first surface of the object to be processed The project of the second modified region closest to the second surface in the region. -5- 200809941 According to the laser processing method, the closest to the first modified region in the modified region is formed based on the position of the first surface, and the second modification closest to the second surface among the regions The area is formed based on the second surface. In this way, even if the thickness of the object to be processed changes according to the criteria of both the first surface and the second surface, the position of the first modified region near the first surface of the modified region and the region closest to the second surface are The position is suppressed due to the change in the thickness of the object to be processed. In other words, when the modified region is formed in a plurality of rows in the thickness direction of the processing along the line to cut, the first region closest to the first surface and the second modified region closest to the second surface can be obtained with good precision results. It can maintain the high quality of the cut surface. Further, in each of the modified regions, the internal adjustment spot of the object is irradiated with the laser light, and multiphoton absorption and other light absorption are formed inside the additive. In the formation of the first modified region, the reflected light reflected by the first surface is detected, and the first position information obtained by the first surface is obtained, and the first position information is specified from the first distance. The first modified region is formed on the inner side of the distance; and the second surface information related to the second surface position is detected by detecting the second surface reflected light in the forming process of the upper modified region, The second surface is only the inner modified second modified region from a certain distance. In addition, the first position information of the first surface is detected in the formation of the first modified region, and the first position information of the first face is obtained, and the first position information is based on the first position. The position of the modified region of the surface is the most in the middle of the second change, and the object 1 can be modified. In the object to be processed, only the second reflection is reflected by the positional surface, and the first modified region is formed on the inner side of the specific distance by only -6 - 200809941 from the positional surface; (2) The formation of the modified region is based on the first position information and the thickness information relating to the thickness of the object to be processed, and the second modified region is formed inside only a certain distance from the second surface. Further, in the forming process of the second modified region, the second position information related to the position of the second surface may be detected by detecting the reflected light reflected by the second surface, and the second position may be set according to the second position The second modified region is formed on the inner side of the first distance from the second surface, and the thickness information related to the thickness of the object to be processed is based on the second position information and the formation of the first modified region. The first modified region is formed only on the inner side of the specific distance from the first surface. Further, the object to be processed may include a semiconductor substrate, and the modified region may include a molten processed region. Moreover, it is preferable to include a process of cutting the object to be processed along the line to cut with the modified region as a cutting starting point. In this way, the object to be processed can be cut with good precision along the line to cut. [Embodiment] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the laser processing method of the present embodiment, a modified region is formed inside the object by the phenomenon of multiphoton absorption. First, a laser processing method for forming a modified region will be described. Compared to the material's band gap EG, the photon energy h is optically transparent when it is small. Therefore, the material absorption yields the condition of 200809941 as h , > EG. However, even in the case of optical transparency, the condition of nhw > EG when the laser light intensity is set to be extremely large (n = 2, 3, 4, . . . . . . . . . . Under the absorption of the material, this phenomenon is called multiphoton absorption. In the case of pulse waves, the intensity of the laser light is determined by the peak power of the laser light (peek power) (W / cm2), for example, the multi-photon absorption is generated under the condition that the peak power density is above lxlO8 (W / cm2). . The peak power density can be calculated from (the energy equivalent to one pulse of the laser light at the spotlight) + (the spot diameter of the laser light, the X pulse width). Further, in the case of a continuous wave, the intensity of the laser light is determined by the electric field intensity (W/cm2) of the light collecting point of the laser light. The principle of the laser processing method of the present embodiment using multiphoton absorption will be described with reference to Figs. As shown in Fig. 1, a predetermined line 5 for cutting is formed on the surface 3 of the wafer-like (plate-shaped) object 1 for cutting the object 1 to be processed. The cutting planned line 5 is an imaginary line extending linearly. In the laser processing method of the present embodiment, as shown in Fig. 2, the light-converging point P is adjusted inside the object 1 under the condition of multiphoton absorption, and the laser beam is irradiated to form the modified region 7. Further, the condensed spot P refers to where the laser light L is concentrated. The line to cut 5 is not limited to a straight line, and may be curved. It is not limited to the imaginary line, and may be the actual line drawn on the object 1 to be processed. The laser light L is relatively moved along the line to cut 5 (i.e., the direction of the arrow A in Fig. 1), and the spot P is moved along the line to cut 5. As described above, as shown in Figs. 3 to 5, the modified region 7 is formed inside the object 1 along the line to cut 5, and the modified region 7 serves as the cutting start region 8. The cutting start point area 8 indicates an area where the object to be cut 1 is cut (cut) when it is cut. The cutting start point region 8 is formed by continuous formation of the modified region -8 - 200809941, and is formed by intermittent formation of the modified region 7. In the laser processing method of the present embodiment, the surface 3 of the object 1 is hardly absorbed by the laser light L. The surface 3 of the object 1 is not melted. When the cutting start point region 8 is formed inside the object 1 to be processed, the cutting is easily generated by using the cutting starting point region 8 as a starting point. Therefore, as shown in Fig. 6, the object 1 can be cut with a small force. Therefore, when the surface 3 of the object 1 is not subjected to unnecessary cutting, the object 1 can be cut with high precision. When cutting the object 1 to be processed with the cutting starting point region 8 as a starting point, the following two methods can be considered. When the cutting start point region 8 is formed, the workpiece 1 is applied by the artificial force, and the object 1 is cut with the cutting start region 8 as a starting point, so that the object to be processed is cut. This is, for example, cutting when the thickness of the object 1 is large. In the application of the artificial force, for example, a bending stress or a cutting stress is applied to the object 1 along the cutting starting point region 8 of the object 1 to be applied, and a temperature difference is applied to the object 1 to generate thermal stress. In the second aspect, the cutting starting point region 8 is formed, and the cutting starting point region 8 is used as a starting point to cut naturally in the cross-sectional direction (thickness direction) of the object 1 to be cut, whereby the object 1 is cut. In this case, for example, when the thickness of the object 1 is small, the cutting start region 8 can be formed by one column of the modified region 7, and when the thickness of the object 1 is large, the plurality of column modified regions 7 can be formed in the thickness direction. The starting point area 8 is cut. Moreover, at the time of natural cutting, at the cutting position, the cutting does not advance to the surface 3 of the portion corresponding to the position of the starting point region 9 where the cut-off -9-200809941 is not formed, and only the portion corresponding to the cutting starting point region 8 is formed. Some will be cut off and the cutoff is well controlled. In recent years, the thickness of the object 1 to be processed, such as a sand wafer, tends to be thin, so that such a cutting method with good controllability is greatly effective. Further, in the laser processing method of the present embodiment, the modified region has the following cases (1) to (3). (1) When the modified region contains a crack region of 1 or a lot of cracks, the spotlight is adjusted inside the object 1 (for example, a piezoelectric material composed of glass or LiTa03), and the electric field intensity at the spotlight is lxlO8. Laser light is irradiated under conditions of (W/cm2) or more and a pulse width of 1 // s or less. The pulse width is such a condition that multi-photon absorption is generated, and unnecessary damage is not caused on the surface of the object 1 to be processed, and only the crack region is formed inside the object 1. According to this, an optical damage phenomenon of multiphoton absorption can be generated inside the object 1 to be processed. Thermal deformation is induced inside the object by the optical damage phenomenon, and thus, a crack region can be formed inside the object to be processed. The upper limit of the electric field strength is, for example, lxlO12 (W/cm2), and the pulse width is preferably, for example, Ins to 200 ns. Further, the formation of a crack region by multiphoton absorption is disclosed, for example, in the Proceedings of the 45th Laser Thermal Processing Research Conference (1998, December) on pages 23 to 28 "by solid-state laser HF pairing Marking inside the glass substrate. The inventors calculated the relationship between the electric field strength and the size of the crack by experiments. The experimental conditions are as follows: (A) Objects to be processed · Pyrex (Pexex (registered trademark)) -10- 200809941 Glass (thickness 700//m) (B) Laser source: Semiconductor laser excitation Nd: YAG Ray Shooting wavelength: 1064nm Laser spot break area: 3. 14xl0_8cm2 Oscillation mode: Q switching pulse Repetition frequency: 100kHz Pulse width: 30ns Output: Output / pulse Laser light quality: TEM. . Polarization characteristics and linear polarization (C) Condenser lens Transmittance of laser light wavelength: 60% (D) Movement speed of the stage on which the object to be placed is placed: 1 0 0 m m / sec The laser light quality is TEM. . This means that the concentrating point can be concentrated to approximately the wavelength of the laser light. Figure 7 is a graph of the above experimental results. The horizontal axis represents the peak-to-peak power density, and the laser light is pulsed laser light, so the electric field intensity is expressed by the peak power density. The vertical axis indicates the size of the crack portion (crack) formed in the inner portion of the object by the application of the laser light of the interface 1 pulse, and the crack gathers to form the crack region, and the size of the crack is the largest portion among the crack shapes. The black circle in the distribution diagram indicates that the condenser lens (C) has a magnification of 100 times and the number of openings (NA) is 0. 80. The white circle in the distribution diagram indicates the capital -11 - 200809941. The material indicates that the condenser lens (c) has a magnification of 50 times and the number of openings (N A ) is _ _ 5 5 . From the peak power density of about 10 11 (w / cm2), cracks occur inside the processing object, and as the peak power density increases, the crack point also increases. The mechanism for cutting the processed object 1 by the formation of the crack region will be described below with reference to Figs. As shown in Fig. 8, the condensed spot irradiation laser light L is adjusted inside the object 1 under the condition that multiphoton absorption is generated, and the crack region 9 is formed inside along the line to cut. The crack region 9 is an area containing 1 _ or a majority of cracks. The cracked region 9 thus formed serves as a cutting starting point region. As shown in Fig. 9, the crack continues to grow with the crack region 9 as a starting point (i.e., starting from the cutting starting region). As shown in Fig. 1, the crack reaches the surface 3 and the back surface of the object 1 as shown in Fig. 1 . As shown in FIG. 1, the object 1 is cut, and the object 1 is cut. When the cracks on the surface 3 and the back surface 21 of the object 1 are naturally grown, the force is applied to the object 1 to grow. (2) When the modified region is a molten processing region, the electric field intensity at the condensed spot is adjusted to be greater than or equal to IxlO8 (W/cm2), and the pulse width is equal to the inside of the object to be processed (for example, the semiconductor material of germanium). Laser light is irradiated under conditions of 1 μs or less. According to this, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a molten processing region is formed inside the processed object. The region to be melted after being temporarily melted, or the region in the molten state, or the region in which the molten state is re-solidified may be a phase change region or a crystal structure change region. Further, the molten processed region may be a region in which a certain crystal structure, an amorphous structure, or a polycrystalline structure changes to a structure of another structure, and the domain of -12-200809941 is changed from a single creation to a single one. The upper limit of the degree is, for example, 1 ns to plate. The inner diameter of the inner diameter is 4 inches, that is, for example, a region in which the crystal structure changes from a single crystal structure to an amorphous structure to a polycrystalline structure, and the amorphous structure is composed of a single crystal structure. The area of the polycrystalline structure. When the object is processed, the molten processed region is, for example, amorphous germanium. The electric field strength is, for example, 1 X 1 0 1 2 (W / cm2), and the pulse width is preferably 2 00 ns. The inventors confirmed by experiment that the semiconductor wafer forms a molten processing region. The experimental conditions are as follows: : (A) Object to be processed: 矽 wafer (thickness 3 5 0 // m, 吋) (B) Laser source: semiconductor laser excitation Nd : YAG Ray] Wavelength: 1 064 nm Laser spot area: 3. 14xl (T8Cm2 oscillation mode: Q switch pulse repetition frequency: 1 00kHz Pulse width: 3 0 ns Output: 2 0 m J / pulse laser light quality: TEM^ Polarization characteristics: linear polarization (C) Concentrating lens magnification: 50 times N. A. : 0. 55 Transmittance of laser light wavelength: 60% -13- 200809941 (D) Moving speed of the mounting table on which the object is placed: 1 0 0 mm / sec Figure 1 2 is laser cutting by the above conditions A cross-sectional photo of one of the wafers. A molten processing region 13 is formed inside the wafer 11 . The thickness direction dimension (size) of the molten processed region 13 formed by the above conditions is about 1 〇 〇 # m. It is explained that the molten processed region 13 is formed by multiphoton absorption. Fig. 13 is a diagram showing the relationship between the wavelength of the laser light and the transmittance of the inside of the ruthenium substrate, respectively removing the reflection components on the surface side and the back side of the ruthenium substrate, respectively, showing only the internal transmittance, and the thickness of the shixi substrate is 5 〇μm, 1 respectively. 0 0 μ m, 2 0 0 // m, 5 0 0 // m , 1 0 0 0 // m. For example, when the wavelength of the Nd:YAG laser is 1 064 nm and the thickness of the ruthenium substrate is 5 00 // m or less, more than 80% of the laser light is transmitted through the inside of the ruthenium substrate. The thickness of the germanium wafer 11 shown in FIG. 1 is 3 5 0 /Z m, and the molten photo processing region 13 generated by multiphoton absorption is formed near the center of the germanium wafer 1 1 , that is, the surface is 175 / / m Part of it. In this case, the transmittance is more than 90% of the thickness of the wafer after the thickness of 2 0 0 // m. Therefore, the laser light is only slightly absorbed inside the wafer 1 1 and most of it is transmitted. This means that not the laser light is absorbed inside the germanium wafer 1 1 , and the molten processed region 13 is formed inside the germanium wafer 11 (that is, the molten region is formed by the usual heating of the laser light, but The molten processed region is formed by multiphoton absorption. The formation of the molten processed region by multiphoton absorption is disclosed, for example, in the National Assembly of the Fusion Association, Episode 66 (April 2000), pages 72-73. (Evaluation of the processing characteristics of a T 12-second pulsed laser pair.) -14- 200809941 In addition, the tantalum wafer is cracked in the cross-section direction by using the cutting starting point region formed by the molten processing region as a starting point, and the crack is reached. The surface of the wafer is cut off from the surface and the back surface. The cracks on the surface and the back surface of the wafer are naturally grown, and the growth of the wafer is also applied. The crack originates from the starting point region and grows naturally on the wafer. The surface and the back surface include any of the following cases, that is, the case where the molten processing region forming the cutting starting point region is cracked by the molten state, and the molten processing region forming the cutting starting region is In the case where the molten state is solidified, the crack is formed. However, in either case, the molten processed region is formed only inside the tantalum wafer, and the cut surface after cutting is formed into a molten processed region only as shown in FIG. In the case where the cutting starting point region is formed in the molten processed region in the object to be processed, it is not easy to cause unnecessary cracks in the cutting starting point region line at the time of cutting, and the cutting control becomes easy, that is, the molten processing region The formation is based not only on multiphoton absorption but also on other absorption effects. (3) When the modified region is a refractive index change region, the spotlight is adjusted inside the object to be processed (for example, glass), and the electric field intensity at the spot is 1x1. Laser light is irradiated under conditions of 〇8 (W/cm2) or more and the pulse width is less than Ins. The pulse width is extremely shortened, and multiphoton absorption occurs inside the object to be processed. Thus, the multiphoton absorption does not translate into The thermal energy causes a change in the valence of ions, crystallization, or polarization alignment in the object to be processed to form a refractive index change region. The upper limit 値 is, for example, 1 X 1 0 12 (W / cm 2 ), and the pulse width is preferably, for example, 1 ns or less, more preferably 1 ps or less. The formation of the refractive index change region by multiphoton absorption is disclosed, for example. The 42nd Laser Heat Plus -15- 200809941 The Proceedings of the Working Conference (November 1997), pages 105 to 111, "1 〇 _ 15 seconds of laser irradiation to the formation of light-induced structures inside the glass". In the case of (1) to (3), the area of the cultivating area is described above. However, the cutting starting point area may be formed as follows, taking into consideration the crystal structure of the wafer-shaped object to be processed or the cleavage property thereof. Smaller force, and the object to be processed can be cut with good precision. That is, in the case of a substrate made of a single crystal semiconductor such as a diamond structure, it is preferably along the (1 1 1 ) plane (the first opening) The direction of the surface or the (1 10) plane (the second opening surface) forms a cutting starting point region. In the case of a substrate composed of a III-V compound semiconductor of a zinc blende structure of GaAs or the like, it is preferable to form a cutting start region in the direction along the (1 1 0 ) plane. In the case of a substrate having a hexagonal crystal structure such as jewel (AI2O3), it is preferred that the (0001) plane is the main surface and the (1120) plane (A surface) or (1 1 〇〇) The direction of the face (facet) forms a cut-off starting point area. Further, the substrate is formed along a direction in which the cutting start region is to be formed (for example, a direction along the (1 1 1 ) plane of the single crystal germanium substrate) or a direction orthogonal to a direction in which the cutting start region is to be formed. The positioning plane, based on the positioning plane, can be easily and correctly formed on the substrate, along a cutting starting point region in which the cutting starting point region should be formed. Preferred embodiments of the present invention are described below. (First Embodiment) As shown in Figs. 14 and 15, the object 1 includes a ruthenium wafer 1 1 and a plurality of functional elements 15 formed on the surface of the ruthenium wafer 1 (by -16-200809941). There is also a single functional layer 1 1 of 1 1 a, which has a thickness of about 300 pm. The functional element 15 is, for example, a semiconductor operation layer formed by crystal growth, a light-receiving element such as a photodiode, a light-emitting element such as a laser diode, or a circuit element formed as a circuit, etc. The plane 6 is formed in a plurality of matrix shapes in the parallel direction and the vertical direction. The object 1 to be processed is cut along the line to cut 5 (see broken line in Fig. 14) which is set in a lattice shape so as to pass between the adjacent functional elements 15, and becomes a separation element of the minute wafer. When the object 1 is cut, first, a protective tape is adhered to the surface of the functional device layer 16, and the functional device layer 16 is protected by a protective tape to be placed on a mounting table of the laser processing apparatus. The protective tape that holds the object 1 is fixed. Thereafter, the back surface of the object 1 (hereinafter simply referred to as "back surface") 2 1 adjusts the condensed spot inside the 矽 wafer 1 1 and irradiates the laser light under conditions of multiphoton absorption, and is scheduled to be cut along each The line 5 forms a modified region (back surface injection processing) which serves as a cutting start point. Here, six rows of modified regions are formed in the thickness direction of the object 1 along the respective cutting planned lines 5. Thereafter, the protective tape and the object 1 to be fixed to the mounting table are simultaneously separated. In this manner, the expanded tape is adhered to the back surface 21 of the wafer 1 1 and the protective tape is peeled off from the surface of the functional device layer 16 to expand the expanded tape. In this manner, the modified object region is used as the cutting start point, and the processed object 1 is cut along the line to cut 5 in accordance with each functional element 15 with good precision, so that the plurality of semiconductor wafers are separated from each other. Further, in addition to the molten processing region, the modified region may also include a cracked region. However, the thickness of the object to be processed 1 varies depending on the difference in the honing block, -17-200809941, and there is a variation (change) between the plurality of objects to be processed, or the unevenness of one object to be processed 1 due to honing. There is a case where a part of the object is thickened or a part of it is thinned (that is, the thickness of the object i is changed). Specifically, in the object 1 of 300/zm, a variation of thickness ± 1 〇 # m or more is generated between a plurality of objects 1 or a part of the thickness of one object 1 There are variations of thickness ±5 # m or more. B However, 'normal autofocus function is regarded as a certain thickness of the object to be processed' only by measuring the displacement amount of the back surface 2 of the laser light incident surface to control the position of the spotlight of the laser light to leave the back surface 2 1 specific location. Therefore, the conventional technique, as shown in Fig. 20, is a case where the modified region closest to the surface 11a among the formed modified regions , is formed in the thick portion of the object 1 to protrude the processed object. The material is formed in such a manner that the thin portion of the object 1 does not reach the depth position of the object 1 and is formed close to the back surface 21. In contrast, in the laser processing method of the present embodiment, among the plurality of column-modified regions formed in the thickness direction of the object to be processed along the line to be cut of the object 1 is the closest to the back surface (first The first modified region of the surface 21 is based on the position of the back surface 21, and the second modified region closest to the surface 11a (second surface) is formed based on the position of the surface 11a. The formation of the modified region will be described in more detail below. (Setting degree) First, in the focus state of the image of the reticle ( -18- 200809941 reticle ) projected on the back surface 21 of the object 1 to be processed, the laser beam for the distance measurement is irradiated, and the distance is measured by the back surface 21 The reflected light of the laser light is detected as a voltage ,, and the detected voltage 记忆 is detected (S1 of Fig. 16). After (scanning), the laser light for the distance measurement is irradiated, and the reflected light of the laser light reflected by the back surface 21 is detected as a voltage 値, and the voltage g 値 is maintained at a voltage caused by the height setting. The cutting line 5 is scanned, and the displacement along the back surface 2 1 of the line to cut 5 is obtained, and the displacement of the back surface 2 1 is stored as the back position information (first position information). That is, the back position information is calculated from the relative distance in the thickness direction from the back surface 21 to the height-receiving back surface 21. Back position information = displacement of the back side 21 = relative distance in the thickness direction from the back surface 21 to the position of the back surface 21 of the height setting. • At this time, while scanning the laser light for ranging, along the line to cut 5, the thickness of the object 1 (thickness g information) is optically measured by the thickness measurement. Specifically, as shown in FIG. 7(a), along the line to cut 5, the reflected light L丨 of the back surface 2 1 and the reflected light L2 reflected by the inside of the object 1 are reflected on the surface 1 1 a. , in the line sensor 5 〇 received! Light. The distance from the front surface back surface 2 1 is calculated by the light receiving position of the reflected light li, L2 in the line sensor 50 and the refractive index of the processed image forming object 1 calculated in advance, that is, the thickness of the object 1 is calculated. . Then, the thickness of the object 1 to be calculated and the plate-shaped back -19-200809941 surface position information are stored as surface position information (second position information) along the line to cut 5 . That is, the surface position information is calculated by the relative distance in the thickness direction from the surface 11a to the height-receiving back surface 21 (S2 in Fig. 16). Surface position information = back position information + thickness of the object 1 = relative distance in the thickness direction from the surface 11a to the height of the back surface 2 1 position, and the measurement system of the back surface 21 and the object to be processed 1 The thickness is measured in two axes. Further, the displacement of the back surface 21 and the thickness of the object to be processed i are obtained in association with the coordinate setting in the direction along the line to cut 5 . Therefore, the measurement system of the back surface 21 and the thickness of the object 1 are measured by two axes, and the back surface position information and the surface position information are synthesized on the coordinates by the distance D 1 between the measurement systems, that is, the back surface can be calculated with good precision. Location information and surface location information. Alternatively, as shown in Fig. 17 (b), the thickness of the object 1 to be processed may be measured by the interference of the reflected light L 3 of the back surface 21 and the reflected light L4 of the surface 11a. In this case, the measurement of the thickness of the measurement system of the back surface 21 and the object to be processed is performed by two axes, and the displacement of the back surface 21 and the object to be processed are obtained! The thickness is obtained in association with the coordinate setting in the direction of the line to cut 5 . The back position information and the surface position information are synthesized on the coordinates by the distance D1 between the measurement systems, so that the back position information and the surface position information can be calculated with good accuracy. -20- 200809941 (Formation of the modified region), as shown in Fig. 18 (a), the object to be processed is only inside the distance of 10/zm from the surface 11a (the light spot on the icon is irradiated with laser light, along the The cutting line 5 is scanned. The inside of the object 1 is moved so that the spot is moved to a position on the back side of the surface of the surface only 1 0 // m, and the illumination output is light, so that the surface position information of the memory is borrowed. It is scanned along the line to cut 5 while being controlled by the actuator of the piezoelectric element in the position adjustment element form. In this case, the modified region (second modified layer) Μ1 is formed along the inner side of the surface 1 1 a from the surface 1 1 a along the distance of 1 0 // m (the S of Fig. 16 is the surface position information). Only the back surface of l〇#m: the modified region along the line to cut 5 (after the second modified layer, as shown in Fig. 18 (b), the object to be processed is only from the surface 1 la 25 / / m on the inside (the light point on the screen is irradiated with laser light, and scanned along the line 5 to be cut. It is inside the object 1 and moves the spot to the surface only 25 mm away from the back surface 21 The side position, the illumination output is the body light', so that the surface position information of the memory is scanned along the line to cut 5 while the position of the spot is re-spotted by the piezoelectric element. As the surface 11a is the reference, only the distance 25 is from the surface 11a. The predetermined line 5 of /m is formed into the modified region M2 (S4 of Fig. 16) as the modified region M2 of the cut line 5 on the back surface 2 1 of only 2 5 /zm from the surface position information. Internal, side) adjustment of the aggregate, as the position information from 0. The 72W mine (the position of the condensed spot in this embodiment is 1 1 a is the cut line S3). Specific U side position shape) Ml. 1 internal, side) adjustment of the aggregate, as the position information begins. The 2W thunder is born and controlled to gather. Then, cut along the inside of the table. Specifically, the position is formed along the inside of the object 1 after the period from -21 to 200809941, and the spotlight is irradiated to the inside of the object (the upper side of the figure) from the surface 11a only at a distance of 3 5 // m. Break the line 5 to sweep. Specifically, in the inside of the object to be processed 1, the spotlight is moved to the surface position information, and only the distance of the back side 21 side of the distance of 35//m is irradiated to the UW laser light, so that the surface position information of the memory is borrowed. The piezoelectric element is regenerated to control the position of the light collecting point, and is scanned along the line to cut 5 . In this manner, the modified region M3 is formed along the line to cut 5 on the inner side of the surface 1 1 a with a distance of only 3 5 // m on the basis of the surface 丨i & (S5 of Fig. 16). Specifically, the modified region M3 along the line to cut 5 is formed at the side of the back surface 21 of only 35/m from the surface position information. Then, inside the object 1 to be processed, the spotlight is irradiated with laser light from the inside of the surface i la at a distance of only 45 // m (upper side in the drawing), and is scanned along the line to cut 5 . Specifically, in the inner portion of the object 1, the spotlight is moved to the surface position information, and only the distance of 45 #m is the back side 21 side position. The 2W laser light causes the surface position information of the memory to be scanned along the line to cut 5 while controlling the position of the light collecting point by the reproduction of the piezoelectric element. In this manner, the modified region M3 is formed along the line to cut 5 on the inner side of the surface 1 1 a with a distance of only 4 5 // m on the surface 1 1 a (S6 of Fig. 16). Specifically, the modified region M4 along the line to cut 5 is formed at the side of the back surface 2 1 of only 45 // m from the surface position information. Then, as shown in Fig. 18 (c), inside the object 1 is adjusted, from the back surface 21, only the inner side (the lower side of the figure) of the distance of 2 5 # m is adjusted. Scanning along the line to cut 5 is performed. Specifically, it is 'inside the object 1', and the spotlight is moved to the back position information. The distance is only 1 5 a. The illumination output is 1. The lightning of 2 W emits light so that the position information of the back side of the memory is scanned along the line to cut 5 while controlling the position of the focused spot by the reproduction of the piezoelectric element. In this manner, the modified region M5 is formed along the cut line 5 on the inner side of the back surface 2 1 with a distance of only 25 // m on the back surface 2 1 (S7 of Fig. 16). Specifically, the modified region M5 along the line to cut 5 is formed at the position on the surface 11a side of only 25//m from the back position information. Finally, inside the object 1 to be processed, the spotlight is irradiated to the inside of the object 1 (the lower side of the figure) from the back surface 21, and the laser beam is irradiated along the line 5 to be cut. Specifically, it is 'inside the object 1 to be processed, and the spotlight position is moved to the position of the back side position only from the surface 1 la side position, and the illumination output is 0. The laser light of 68 W causes the position information on the back side of the memory to be scanned along the line to cut 5 while controlling the position of the light collecting point by the reproduction of the piezoelectric element. In this manner, the modified region (second modified layer) M6 is formed along the line to cut 5 on the inner side of the back surface 21 with a distance of only 1 5 // m on the back surface 21 (S8 in Fig. 16). Specifically, the modified region M6 along the line to cut 5 is formed at a position on the surface 1 1 a side of only 1 5 μm from the back position information. Among the plurality of column modified regions M1 to M6 formed in the thickness direction inside the object 1 , the modified regions M5 and M6 are modified regions in which a half cut is formed on the object 1 to be a half-cut SD. . This half-cut can be separated by expanding the extended tape, so the half-cut SD is an extremely important element of -23-200809941. Further, among the modified regions M1 to M6 formed by the plurality of rows, the modified region mi closest to the surface 11a is a modified region which particularly affects the quality of the cut surface after cutting, and is referred to as a quality SD. The quality SD is such that the functional element layer 16 is cut with good precision, and is extremely important in maintaining the quality of the object 1 to be cut. As described above, in the present embodiment, the modified region μ 5 is formed along the line to cut 5 from the inside of the object 1 on the basis of the back surface 2 1 and only a certain distance from the back surface 2 1 . At the same time, the modified region μ丨 is formed along the line to cut 5 on the inner side of the specific distance from the surface 1 1 a with respect to the surface 1 1 a as a reference. In this case, the position of the modified regions M5 and M6 and the position of the modified region M6 are changed by the thickness of the object 1 when the thickness of the object to be processed fluctuates based on both the back surface 2 and the surface 11a. The offset condition can be suppressed. Therefore, according to the present embodiment, when the modified region is formed in a plurality of rows in the thickness direction of the object 1 along the line to cut, the modified region M6 closest to the back surface 21 and the modified region M6 can be changed. The qualitative region M5 and the modified region Μ 1 closest to the surface 1 1 a are formed with good precision. Further, as described above, in the present embodiment, the modified regions Μ5 and Μ6 can be formed with good precision, and the following effects can be achieved. That is, it is possible to suppress the deterioration of the modified regions Μ5 and Μ6 to the back surface 2 1 to cause the half cut to appear serpentine and deteriorate the quality. Further, it is also possible to prevent the modified regions Μ5 and Μ6 from excessively leaving the back surface 21, so that the cracks in the modified regions Μ5 and Μ6 are insufficiently extended to form a good half cut. Further, as described above, in the present embodiment, the modified region -24 - 200809941 Μ1 can be formed with good precision, and the following effects can be achieved. In other words, it is possible to suppress the excessively close contact of the modified region Μ 1 to the surface 1 1 a, and the laser light to be irradiated protrudes from the object 1 and is perforated on the surface 11a, thereby weakening the bending strength of the object 1 . Further, it is possible to prevent the modified region Μ1 from excessively leaving the surface 11a and causing the end portion on the surface 11a side to largely deviate from the cut line 5 by the so-called skirting phenomenon. Further, in the present embodiment, since the functional element 15 is formed on the surface 1 1 a of the surface on the opposite side of the laser light incident surface and the surface on the opposite side, the effect of preventing the occurrence of the skirting phenomenon is particularly remarkable. Further, according to the present embodiment, the offset of the position of the modified region caused by the change in the thickness of the object 1 can be corrected, and the quality of the modified region affected by the distance between the surface 11a and the back surface 21 can be It is best to set the cutting quality after cutting, and it is possible to perform multi-stage processing. Further, the thickness of the object 1 to be processed can be measured by a contact type thickness measuring device. However, in this case, a foreign matter may be mixed between the object 1 and the mounting table, or the tape may be stretched and the object to be processed may be attached to the extended tape. There is a possibility that air is mixed between 1 and the position of the object 1 to be contacted is not necessarily the position of the thickness of the object 1 to be processed. On the other hand, in the present embodiment, the thickness of the object 1 can be measured with good accuracy using a measuring device using a transmission type laser. That is, in the above embodiment, as described above, the modified regions M2, M3, and M4 are formed on the basis of the surface 1 1 a. However, the present invention is not limited to the above embodiment, and the modified regions M2, M3, and M4 may be used. The back surface 21 is formed as a reference. -25-200809941 (Second Embodiment) A laser processing method according to a second embodiment of the present invention is described. The laser processing method according to the second embodiment differs from the laser processing method according to the first embodiment in that the laser processing method is not measured. As shown in Fig. 9, the thickness of the object 1 is detected by the optical system using the autofocus function, and the reflected light L5 of the back surface 21 and the reflected light L6 of the surface 1 la are respectively detected. Specifically, in the laser processing method of the present embodiment, the reflected light L5 on the back surface 21 and the reflected light L6 reflected on the surface 11 a are transmitted, respectively, and the surface 1 is directly obtained. The displacement of 1 a and the displacement of the back 2 1 directly calculate the back position information and surface position information. Back position information = displacement of the back side 2 1 = relative distance in the thickness direction from the back surface 21 to the position of the back surface 21 which is set to the degree. Surface position information = displacement of the surface 1 1 a Φ = relative distance in the thickness direction from the surface 1 1 a to the height of the back surface 21 position 〇 According to the laser processing method of the present embodiment, the above implementation is possible The same effect of the laser processing method of the form. In other words, even if the thickness of the object 1 is changed or changed, the position of the modified regions M5 and M6 and the position of the modified region M6 can be suppressed by the change in the thickness of the object 1 . Therefore, according to the present embodiment, when the modified region is formed in a plurality of rows in the thickness direction of the object 1 along the line to cut 5 to -26-200809941, the modified region M6 closest to the back surface 21 and the adjacent modified region can be modified. The modified region Μ 5 of the region M6 and the modified region μ 1 closest to the surface 1 1 a are formed with good precision. Hereinafter, a laser processing apparatus according to an embodiment of the present invention will be described. As shown in Fig. 21, 'the laser processing apparatus 100 has: a laser light source 1 〇i ' is used to oscillate to generate pulsed laser light (additive laser light) L; the beam splitter 103 is configured to make the light of the laser light The axial direction is changed by 90 degrees; and the collecting lens 105 is used to condense the laser light L. Further, the laser processing apparatus 1A includes a mounting table 107 for placing the object 1 to be irradiated with the laser light L collected by the collecting lens 105, and a stage 1 1 1 for moving the mounting table 107. In the X, Y, and Z axis directions; the laser light source controller 1〇2 is used to control the laser light source 1 0 1 to adjust the output or pulse width of the laser light L; and the platform control unit 1 1 5 is used for control The movement of the platform 1 1 1 . According to the laser processing apparatus 1 〇〇, the laser light L irradiated by the laser light source 1 〇1 is changed to 90 degrees by the beam splitter 1 〇3, and is concentrated on the mounting table 107 by the collecting lens 105. The inside of the object 1 is processed. At the same time, the stage 1 1 1 moves, and the object 1 is relatively moved with respect to the laser light L along the line to cut 5 . In this way, the modified region can be formed on the object 1 along the line to cut 5 . Further, the laser processing apparatus 1 is not limited to the above embodiment, and the laser beam 1 irradiated with the laser light source 1 〇 1 may be introduced into the condensing lens 105 without using the beam splitter 1300. Further, the movement of the laser light L is as long as the laser light 1 relatively moves to the object 1 to be processed. In particular, regarding the z-axis direction, the position of the condensing lens 105 can be moved instead of the movement of the mounting table 107, and -27 - 200809941 changes the focus position of the laser light L accordingly. The preferred embodiments of the present invention have been described above, but the embodiment is not limited to the above embodiment. For example, in the above embodiment, after the displacement of the surface 1 1 a of the object 1 is measured, the laser beam is scanned to form a modified region, that is, a so-called scanning process, but the displacement of the surface 1 la is measured. The so-called rea 1 time processing for forming the modified region is also possible. Further, when the laser light for the distance measurement by the object 1 and the laser light for the distance measurement which is reflected without reflection are used, a plurality of laser light sources may be used, or one laser light source may be used to change the wavelength. Further, in the above-described embodiment, the so-called back surface incident processing in which the laser beam is incident on the back surface 21 side of the surface 1 1 a on which the functional element i 5 is formed may be formed, but the surface 11 1 a may be incident. laser. In addition, the object to be processed 1 is the object to be processed i having the tantalum wafer 1 1 , but may be a semiconductor compound material such as gallium arsenide, a material having crystallinity such as piezoelectric material or sapphire, or the like. . . (Industrial Applicability) According to the present invention, when the modified region is formed in a plurality of rows in the thickness direction of the object to be processed along the line to cut, the first modified region closest to the first surface and the closest to the first surface can be obtained. The second modified region on the two sides is formed with good precision (effect of the invention) -28- 200809941 According to the present invention, it is also possible to form a plurality of column-modified regions along the line to cut in the thickness direction of the object to be processed. Accuracy forms the first modified region closest to the first surface and the second modified region closest to the second surface. [Simplified illustration] FIG. 1 is a processing in laser processing of the laser processing apparatus of the present embodiment. A plan view of the object. Fig. 2 is a sectional view taken along line II-II of the object to be processed shown in Fig. 1. Fig. 3 is a plan view showing the object to be processed after the laser processing of the laser processing apparatus of the embodiment. Fig. 4 is a sectional view taken along the line IV-IV of the object to be processed shown in Fig. 3. Fig. 5 is a cross-sectional view taken along line V - V of the object to be processed shown in Fig. 3; Fig. 6 is a plan view showing the processed object cut by the laser processing apparatus of the embodiment. Fig. 7 is a distribution diagram showing the relationship between the electric field strength and the magnitude of the breaking point in the laser processing apparatus of the embodiment. Fig. 8 is a cross-sectional view showing the object to be processed in the first project of the laser processing apparatus of the embodiment. Fig. 9 is a cross-sectional view showing the object to be processed in the second project of the laser processing apparatus of the embodiment. Fig. 10 is a cross-sectional view showing the object to be processed in the third project of the laser processing apparatus of the embodiment. Fig. 1 is a cross-sectional view of the object to be processed in the fourth project of the laser processing apparatus of the embodiment -29 - 200809941. Fig. 12 is a cross-sectional photograph showing a portion of a twin circle cut by the laser processing apparatus of the embodiment. Fig. 13 is a graph showing the relationship between the wavelength of the laser light and the transmittance of the inside of the ruthenium substrate in the laser processing apparatus of the embodiment. Fig. 14 is a front view of the object to be processed which is the object of the laser processing method according to the first embodiment of the present invention. Figure 15 is a partial cross-sectional view of the first line of Figure 14. Fig. 16 is a flow chart showing a laser processing method according to a first embodiment of the present invention. Fig. 17 is a diagram for explaining the calculation of the back position information and the surface position information of the laser processing method shown in Fig. 16. Figure 18 is a partial cross-sectional view of the XVIII-XVIII line of Figure 14 for the description of the laser processing method shown in Figure 16. Fig. 19 is a diagram for explaining the calculation of the back surface position information and the surface position information of the laser processing method according to the second embodiment of the present invention. Fig. 20 is a partial cross-sectional view showing the XVIII-XVIII line of Fig. 14 for explaining the laser processing method of the conventional autofocus function. Fig. 2 is a schematic view showing the configuration of a laser processing apparatus according to an embodiment of the present invention. [Description of main component symbols] 3 1 : Object to be processed 1 1 a : Surface (2nd surface) - 30- 200809941
5 :切斷ί 1 5 :功能 21 :背面 L :雷射i LI : L3 : L2 ： L4 ： Ml 〜M6 P :聚光1 頁定線 性元件 (第12面） L5 :反射光（第1面反射之反射光） L6 :反射光（第2面反射之反射光） :改質區域5 : Cut off ί 1 5 : Function 21 : Back L : Laser i LI : L3 : L2 : L4 : Ml ~ M6 P : Spotlight 1 page linear component (12th face) L5 : Reflected light (1st face Reflected light) L6: reflected light (reflected light from the second side): modified area
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