201242700 六、發明說明： 【發明所屬之技術領域】 本發明，是有關於將具備Sic基板的板狀的加工對象 物沿著切斷預定線切斷用的雷射加工方法。 【先前技術】 s i c (矽碳化物），是作爲可製造耐熱性、對高電壓性、 省電力性優異的功率元件（p0Wer device)而受到矚目得半 導體材料。但是’ SiC，因爲是具有由次於鑽石的硬度的 難加工材料，所以欲將具備siC基板的板狀的加工對象物 藉由刀片方塊切割（blade dicing)來切斷的話，就需要低速 度中的加工和頻繁的刀片的交換。在此，已被提案：藉由 將雷射光照射在加工對象物，沿著切斷預定線在s丨C基板 的內部形成改質領域’將其改質領域作爲起點沿著切斷預 定線將加工對象物切斷的雷射加工方法（例如專利文獻i 參照）。 [先行技術文獻] [專利文獻] [專利文獻1]日本特表2007-514315號公報 【發明內容3 (本發明所欲解決的課題） 但是本發明人等發現，藉由如上述的雷射加工方法， 將具備含有與c面形成偏角的主面的六方晶系siC基板的 201242700 板狀的加工對象物切斷的情況時，存在如以下課題°即’ 在改質領域的形成時欲使龜裂從改質領域到達SiC基板的 雷射光入射面，使龜裂容易從改質領域朝siC基板的厚度 方向伸展的方式將雷射光照射在加工對象物的話’龜裂也 容易從改質領域朝C面方向伸展。 在此，本發明的目的是提供一種雷射加工方法’可以 將具備含有與C面形成偏角的主面的六方晶系SiC基板的 板狀的加工對象物，沿著切斷預定線的精度佳地切斷。 (用以解決課題的手段） 本發明的一觀點的雷射加工方法，是將具備含有與c 面形成偏角的主面的六方晶系SiC基板的板狀的加工對象 物，沿著切斷預定線切斷用的雷射加工方法’具備：將雷 射光的集光點對焦於SiC基板的內部’在與主面平行的面 內藉由位在切斷預定線的兩側且沿著與切斷預定線平行的 方向延伸的各預備線將雷射光照射在加工對象物，沿著各 預備線將預備改質領域形成於SiC基板的內部的第1過程 ;及在第1過程之後或與第1過程同時，將集光點對焦於 SiC基板的內部，藉由沿著切斷預定線將雷射光照射在加 工對象物，沿著切斷預定線’將成爲切斷起點的改質領域 形成於SiC基板的內部的第2過程；且在第1過程中，與 改質領域相比使龜裂不易從預備改質領域朝S i C基板發生 的方式，沿著各預備線將雷射光照射在加工對象物。 在此雷射加工方法中，沿著切斷預定線在SiC基板的 201242700 內部形成改質領域時，沿著預備線的各別在Sic基板的內 部形成預備改質領域。且，預備線，是在與主面平行的面 內位在切斷預定線的兩側且朝與切斷預定線平行的方向延 伸。因此’龜裂即使從改質領域朝c面方向伸展，其龜裂 的伸展可藉由預備改質領域被抑制。由此，不需考慮龜裂 是否會容易從改質領域朝c面方向伸展，就可使龜裂容易 從改質領域朝SiC基板的厚度方向伸展的方式將雷射光照 射在加工對象物。又，預備改質領域，因爲不需要作爲切 斷起點功能（即，促進龜裂從預備改質領域朝Sic基板的 厚度方向伸展），藉由不易在Sic基板發生龜裂的雷射光 的照射就可形成，所以在預備改質領域的形成時可以容易 地抑制龜裂從預備改質領域朝c面方向伸展。因此，依據 此雷射加工方法的話，可將具備含有與c面形成偏角的主 面的六方晶系SiC基板的板狀的加工對象物沿著切斷預定 線精度佳地切斷。又，偏角是包含0°的情況。此情況，主 面是與c面成爲平行。 在本發明的一觀點的雷射加工方法中，在第1過程中 ，當在第2過程中將集光點對焦於離SiC基板的雷射光入 射面預定距離的情況時，將集光點對焦於離雷射光入射面 預定的距離也可以。由此，可以更確實地抑制龜裂從改質 領域將朝c面方向的伸展。 本發明的一觀點的雷射加工方法，是進一步具備：在 第2過程之後，將改質領域作爲起點沿著切斷預定線將加 工對象物切斷的第3過程也可以。由此，可以獲得沿著切 -7- 201242700 斷預定線精度佳地被切斷加工對象物。 在本發明的一觀點的雷射加工方法中，改質領域是具 有包含熔融處理領域的情況。 [發明的效果] 依據本發明的話，可以將具備含有與C面形成偏角的 主面的六方晶系SiC基板的板狀的加工對象物，沿著切斷 預定線精度佳地進行切斷。 【實施方式】 以下，對於本發明的最佳的實施例，參照圖面詳細說 明。又，對於在各圖中相同或相當部分是附加同一符號， 並省略重複的說明。 在本發明的一實施例的雷射加工方法中，藉由沿著切 斷預定線在加工對象物照射雷射光，沿著切斷預定線在加 工對象物的內部形成改質領域。在此，首先，對於此改質 領域的形成，參照第1圖〜第6圖進行說明。 如第1圖所示，雷射加工裝置100，是具備：將雷射 光L脈衝振盪的雷射光源1 〇 1、及將雷射光L的光軸（光 路）的方向改變90°的方式被配置的分色鏡103、及將雷射 光L集光用的集光用透鏡1〇5。且，雷射加工裝置1〇〇, 是具備：將被由集光用透鏡105所集光的雷射光L照射的 加工對象物1支撐用的支撐台107、及將支撐台107移動 用的載台111、及爲了調節雷射光L的輸出和脈衝寬度等 201242700 而控制雷射光源1 ο 1的雷射光源控制部1 02、及控制載台 1 1 1的移動的載台控制部1 1 5。 在此雷射加工裝置100中，從雷射光源101被射出的 雷射光L，是藉由分色鏡103將其光軸的方向改變90°， 藉由集光用透鏡105被集光在被載置於支撐台107上的加 工對象物1的內部。與此同時，使載台1 1 1移動，使加工 對象物1對於雷射光L沿著切斷預定線5相對移動。由此 ，沿著切斷預定線5的改質領域就會形成於加工對象物1 〇 如第2圖所示，在加工對象物1中，被設定將加工對 象物1切斷用的切斷預定線5。切斷預定線5，是朝直線 狀延伸的虛線。在加工對象物1的內部形成改質領域的情 況時，如第3圖所示，在將集光點Ρ對焦於加工對象物i 的內部狀態下，將雷射光L沿著切斷預定線5(即第2圖的 箭頭A方向）相對地移動。由此，如第4圖〜第6圖所示 ，改質領域7是沿著切斷預定線5形成於加工對象物1的 內部，使沿著切斷預定線5被形成的改質領域7成爲切斷 起點領域8。 又，集光點P，是雷射光L的集光處。且，切斷預定 線5，不限定於直線狀，曲線狀也可以，不限定於虛線， 在加工對象物1的表面3實際劃線也可以。且，改質領域 7，也有連續地形成的情況，也有間斷地形成的情況。且 ，改質領域7是列狀或點狀也可以，即，改質領域7只要 是至少形成於加工對象物1的內部即可。且，將改質領域 -9- 201242700 7在起點具有形成有龜裂的情況，龜裂及改質領域7，是 露出加工對象物1的外表面（表面、背面、或外周面）也可 以。 順便，在此的雷射光L，可透過加工對象物1並且在 加工對象物1的內部的集光點附近被吸收，由此，在加工 對象物1形成改質領域7(即內部吸收型雷射加工）。因此 ’在加工對象物1的表面3，因爲雷射光L幾乎未被吸收 ’所以加工對象物1的表面3不會熔融。一般，從表面3 被熔融除去而形成孔和溝等的除去部（表面吸收型雷射加 工）情況時，加工領域是從表面3側漸漸地朝背面側進行 〇 但是由本實施例形成的改質領域，是指密度、曲折率 、機械的強度和其他的物理的特性與周圍成爲不同的狀態 的領域。改質領域，是具有例如熔融處理領域、龜裂領域 、絕緣破壞領域、曲折率變化領域等，也有這些混在的領 域。進一步，改質領域，是具有：在加工對象物的材料中 改質領域的密度與非改質領域的密度相比較有變化的領域 、和形成有格子缺陷的領域（這些也總稱爲高密轉移領域） 〇 且，熔融處理領域和曲折率變化領域、改質領域的密 度是與非改質領域的密度相比較有變化的領域，形成有格 子缺陷的領域，是進一步具有在那些領域的內部和改質領 域及非改質領域的界面內包龜裂（破裂、微龜裂）的情況。 被內包的龜裂是具有橫跨改質領域的全面的情況和只有一 -10- 201242700 部分和複數部分形成的情況。 且，在本實施例中，藉由沿著切斷預定線5將改質束 點（加工痕）複數形成，而形成改質領域7。改質束點，是 由脈衝雷射光的1脈衝的照射（即1脈衝的雷射照射）形成 的改質部分，藉由集合改質束點而成爲改質領域7。改質 束點，可舉例：龜裂束點、熔融處理束點或曲折率變化束 點，或是這些的至少1個混在者等。 對於此改質束點，考慮所要求的切斷精度、所要求的 切斷面的平坦性、加工對象物的厚度、種類、結晶方位等 ，適宜控制其大小和所發生的龜裂的長度較佳。 接著，詳細說明本發明的一實施例的雷射加工方法。 如第7圖所示，加工對象物1，是具備Sic基板12的圓形 板狀（例如直徑3英吋、厚度3 5 0 μ m)的晶圓。如第8圖所 示’ SiC基板1 2 ’是具有六方晶系的結晶構造，其結晶軸 CA ’是對於SiC基板12的厚度方向傾斜角度0 (例如4。) 。即，SiC基板12，是具有角度β的偏角的六方晶系SiC 基板。如第9圖所示’ SiC基板12，是具有與c面偏角0 的表面（主面）12a及背面（主面）12b。在SiC基板12中，a 面’是對於SiC基板1 2的厚度方向（圖中的二點鎖線）傾斜 角度Θ，m面’是對於SiC基板12的厚度,方向無傾斜。 如第7圖及第9圖所示，在加工對象物1中，朝表面 1 2a及與a面平行的方向延伸的複數條切斷預定線（第1切 斷預定線）5a、及朝表面12a及與m面平行的方向延伸的 複數條切斷預定線（第2切斷預定線）5m，是設定成格子狀 -11 - 201242700 (例如Immxlmm)。在SiC基板12的表面12a中’在藉由 切斷預定線5 a、5 m被劃界的各領域形成有功能元件’在 SiC基板12的背面12b中，在藉由切斷預定線5a、5m被 劃界的各領域形成有金屬配線。功能元件及金屬配線’是 藉由沿著切斷預定線5 a、5 m切斷加工對象物1而得的各 晶片構成功率元件。又，在SiC基板12中，在與切斷預 定線5a平行的方向形成定向平面6a，在與切斷預定線5m 平行的方向形成定向平面6m。 將以上的加工對象物1沿著切斷預定線5a、5m如下 地切斷。首先，如第10圖所示，將SiC基板12的背面 12b的金屬配線覆蓋的方式將可伸縮膠帶23貼附在加工對 象物1。接著，如第11圖（a)所示，將由20ns〜100ns的 脈衝寬度（更佳是由50ns〜60ns的脈衝寬度）被脈衝振盪的 雷射光L的集光點P對焦於SiC基板12的內部，使脈衝 間距成爲1 Ομηι〜1 8μηι的方式（更佳是使脈衝間距成爲 12μηι〜14μπι的方式）沿著切斷預定線5a將雷射光L照射 在加工對象物1。由此，沿著切斷預定線5a，將成爲切斷 起點的改質領域（第1改質領域）7a形成於SiC基板12的 內部。此改質領域7a，是成爲包含熔融處理領域者。又， 脈衝間距，是將「對於加工對象物1的雷射光L的集光點 P的移動速度」除以「脈衝雷射光L的反覆頻率」的値。 更詳細說明改質領域7a的形成的話，將SiC基板1 2 的表面12a作爲雷射光入射面使雷射光L的集光點P位在 SiC基板丨2的內部，沿著切斷預定線5a將集光點P相對 -12- 201242700 地移動。且’將沿著切斷預定線5a的集光點P的相對的 移動對於1條切斷預定線5進行複數回（例如8回）。此時 ’藉由每次改變從表面1 2 a直到集光點p的位置爲止的距 離’在SiC基板12的厚度方向並列的方式對於1條切斷 預定線5 a形成複數列（第1列數、例如8歹)的改質領域 7a。在此’第2接近SiC基板12的雷射光入射面也就是 表面1 2 a的改質領域7 a ’是使變得比最接近表面1 2 a的改 質領域7a更小的方式’從SiC基板12的背面12b側（即 遠離雷射光入射面）依序形成改質領域7a。又，改質領域 7 a的大小，是例如藉由變化雷射光L的脈衝能量就可以 進行調節。 由此，從各改質領域7a發生的龜裂，會朝siC基板 12的厚度方向伸展並彼此連接。特別是，從最接近Sic基 板12的雷射光入射面也就是表面12a的改質領域7a朝 SiC基板12的厚度方向伸展的龜裂，會到達表面i2a。這 些對於將具有由次於鑽石的硬度的難加工材料所構成的 S i C基板1 2沿著切斷預定線5 a精度佳地切斷是非常重要 〇 在沿著切斷預定線5 a形成了改質領域7 a之後，如第 11圖（b)所示，將由20ns〜100ns的脈衝寬度（更佳是由 5 0 n s〜6 0 n s的脈衝寬度）被脈衝振盪的雷射光L的集光點 Ρ對焦於Sic基板12的內部，使脈衝間距成爲10μηι〜 1 8 μ m的方式（更佳是使脈衝間距成爲1 2 μ m〜1 4 μ m的方式） 沿著切斷預定線5m將雷射光L照射在加工對象物]。由 -13- 201242700 此’沿著切斷預定線5m，將成爲切斷起點的改質領域（第 2改質領域）7m形成於SiC基板12的內部。此改質領域 7m，是成爲包含熔融處理領域者。 更詳細說明改質領域7m的形成的話，將SiC基板12 的表面12a作爲雷射光入射面使雷射光L的集光點P位在 SiC基板1 2的內部，沿著切斷預定線5m將集光點P相對 地移動。且，將沿著切斷預定線5m的集光點P的相對的 移動對於1條切斷預定線5進行複數回（例如6回）。此時 ，藉由每次改變從表面1 2a直到集光點P的位置爲止的距 離，在SiC基板12的厚度方向並列的方式對於1條切斷 預定線5m形成複數列（比第1列數更少第2列數（包含1 列的情況）、例如6列）的改質領域7m。在此，最接近SiC 基板1 2的雷射光入射面也就是表面1 2a的改質領域7m， 是壞變得比第2接近表面1 2a的改質領域7m更小的方式 ’從SiC基板12的背面12b側（即遠離雷射光入射面）依序 形成改質領域7 m。又，改質領域7 m的大小，是例如藉由 變化雷射光L的脈衝能量就可以進行調節。 由此，從各改質領域7 m發生的龜裂，會朝S i C基板 12的厚度方向伸展並彼此連接。特別是，從最接近SiC基 板12的雷射光入射面也就是表面12a的改質領域7m朝 SiC基板12的厚度方向伸展的龜裂，會到達表面i2a。這 些對於將具有由次於鑽石的硬度的難加工材料所構成的 S i C基板1 2沿著切斷預定線5 m精度佳地切斷是非常重要 -14- 201242700 沿著切斷預定線5 m形成了改質領域7 m 1 2圖（a)所示，使可伸縮膠帶2 3擴張，在其狀 可伸縮膠帶2 3沿著各切斷預定線5 m將刀緣 S i C基板.1 2的背面1 2 b。由此，將改質領域、 沿著切斷預定線5 m將加工對象物1切斷成桿 可伸縮膠帶2 3因爲是擴張的狀態，所以如第！ ’被切斷成桿狀的加工對象物1成爲彼此分離 在沿著切斷預定線5 m將加工對象物1切 著如第13圖（a)所示’在可伸縮膠帶23爲擴張 透過可伸縮膠帶23沿著各切斷預定線5a將7 在SiC基板12的背面12b。由此，將改質領相 點沿著切斷預定線5 a將加工對象物1切斷成 時’可伸縮膠帶2 3因爲是擴張的狀態，所以贫 所示，被切斷成晶片狀的加工對象物1是彼此 如以上’可獲得將加工對象物1沿著切斷預另 切斷成晶片狀而成的多數功率元件。 依據以上的雷射加工方法的話，藉由如以 將具備含有與c面形成偏角的表面12a的六方 板1 2的板狀的加工對象物1，沿著切斷預定線 度佳地切斷，其結果，就可獲得沿著切斷預定 精度佳地被切斷的加工對象物U即功率元件）。 首先，使脈衝間距成爲1 0 μ m〜1 8 μ m並沿 線5 a、5 m將雷射光L照射在加工對象物1。 將雷射光L照射在加工對象物1的話，龜裂可 之後，如第 態下，透過 41抵接在 'm作爲起點 狀。此時， 2圖（b)所示 〇 斷之後，接 的狀態下， 丨緣41抵接 ξ 7a作爲起 晶片狀。此 丨第13圖（b) 成爲分離。 [線 5 a、5 m 下的理由， 晶系SiC基 :5a、5m 精 :線 5 a、5 m 著切斷預定 由這種條件 容易從改質 -15- 201242700 領域7a、7m朝SiC基板12的厚度方向伸展，另一方面， 龜裂不易從改質領域7a、7m朝c面方向伸展。進一步， 使脈衝間距成爲12μιη〜14μηι並沿著切斷預定線5a、5m 將雷射光L照射在加工對象物1的話，龜裂可更容易從改 質領域7a、7m朝SiC基板12的厚度方向伸展，另一方面 ，龜裂更不易從改質領域7a、7m朝c面方向伸展。 且，由20ns〜l〇〇ns的脈衝寬度將雷射光L脈衝振盪 。由此，龜裂可容易且確實地從改質領域7a、7m朝SiC 基板12的厚度方向伸展，另一方面，龜裂可以確實地不 易從改質領域7a、7m朝c面方向伸展。進一步，由50ns 〜60ns的脈衝寬度將雷射光L脈衝振盪的話，龜裂更容易 確實地從改質領域7a、7m朝SiC基板12的厚度方向伸展 ，另一方面，龜裂更不易確實地從改質領域7a、7m朝c 面方向伸展。 且，沿著切斷預定線5 a的第2接近S i C基板1 2的雷 射光入射面也就是表面1 2a的改質領域7a相對地形成較 小。由此，a面即使對於SiC基板1 2的厚度方向傾斜，從 第2接近表面1 2a的改質領域7a所發生的龜裂，也會朝a 面方向伸展，可以防止從切斷預定線5 a大偏離的狀態下 到達表面1 2 a。且，沿著切斷預定線5 a的最接近S i C基板 1 2的雷射光入射面也就是表面1 2 a的改質領域7 a相對地 形成較大。由此，雖在龜裂不易從改質領域7a朝SiC基 板1 2的厚度方向伸展狀態，但是龜裂可以確實地從最接 近表面1 2a的改質領域7a到達表面1 2a。且，沿著切斷預 -16- 201242700 定線5m的第2接近SiC基板12的雷射光入射面也就是表 面12a的改質領域7m相對地形成較大。由此’與龜裂容 易從改質領域7m朝SiC基板12的厚度方向伸展進行的狀 態相輔，從第2接近表面12a的改質領域7m發生的龜裂 可以到達表面1 2a或其附近。且，沿著切斷預定線5m的 最接近S i C基板1 2的雷射光入射面也就是表面1 2 a的改 質領域7m相對地形成較小。由此，可以防止在表面12a 發生破壞，且可以使龜裂從改質領域7m確實地到達表面 1 2a。如以上，龜裂可以確實地沿著切斷預定線5a從改質 領域7a到達表面12a，且，龜裂可以沿著切斷預定線5m 從改質領域7m確實地到達表面1 2a。此效果，是可與後 述的改質領域7a、7m的形成列數和形成順序無關，依照 後述的改質領域7a、7m的形成列數和形成順序的話，更 顯著。 且，沿著1條切斷預定線5 a形成比沿著1條切斷預 定線5m形成改質領域7m的情況更多列數的改質領域7a 。由此，a面即使對於SiC基板12的厚度方向傾斜，在各 改質領域7a的形成時也可防止龜裂從改質領域7a朝a面 方向大伸展，且在全部的改質領域7a之間在SiC基板i 2 的厚度方向可以使龜裂成爲容易連繫的狀態。且，沿著i 條切斷預定線5 m形成比沿著1條切斷預定線5 a形成改質 領域7 a的情況更少列數的改質領域7 m。由此，在各改質 領域7m的形成時可以龜裂從改質領域7m朝SiC基板i 2 的厚度方向大伸展。如以上，龜裂可以沿著切斷預定線5a -17- 201242700 從改質領域7a朝SiC基板12的厚度方向伸展，且，龜裂 可以沿著切斷預定線5m從改質領域7m朝SiC基板12的 厚度方向伸展。此效果，是可與前述的改質領域7a、7m 的形成尺寸和後述的改質領域7a、7m的形成順序無關， 依照前述的改質領域7a、7m的形成尺寸和後述的改質領 域7a、7m的形成順序的話，更顯著。 且’在形成使龜裂朝SiC基板12的厚度方向伸展用 的條件較鬆的改質領域7m之前，先形成使龜裂朝SiC基 板1 2的厚度方向伸展用的條件較嚴的改質領域7a。由此 ，在改質領域7 a的形成時，在切斷預定線5 a與切斷預定 線5m交叉的部分，可以防止從改質領域7a朝SiC基板 12的厚度方向的龜裂的伸展被改質領域7m阻礙。此效果 ，是可與前述的改質領域7a、7m的形成尺寸和形成列數 之間無關。 進一步，將改質領域7m作爲起點沿著切斷預定線5 m 將加工對象物1切斷，其後，將改質領域7a作爲起點沿 著切斷預定線5 a將加工對象物1切斷。由此’藉由少列 數的改質領域7m的形成沿著設想爲切斷比較困難的切斷 預定線5 m將加工對象物1切斷，其後’藉由多列數的改 質領域7 a的形成沿著設想切斷比較容易進行的切斷預定 線5a將加工對象物1切斷。因此，沿著切斷預定線5m將 加工對象物1切斷所需要的力及沿著切斷預定線5 a將加 工對象物1切斷所需要的力被均一化，沿著切斷預定線 5 m的切斷精度及沿著切斷預定線5 a的切斷精度皆可以更 -18- 201242700 提高。此效果，是可與前述的改質領域7a、7m的形成尺 寸和形成列數之間無關。 第14圖，是顯示藉由上述的雷射加工方法沿著切斷 預定線5a被切斷的siC基板12的切斷面的照片的圖。且 ，第15圖，是顯示藉由上述的雷射加工方法沿著切斷預 定線5m被切斷的SiC基板12的切斷面的照片的圖。進一 步，第16圖，是顯示藉由上述的雷射加工方法沿著切斷 預定線5a、5m被切斷的SiC基板12的平面照片的圖。在 此，準備具有4°的偏角的厚度3 5 0μιη的六方晶系SiC基 板12 〇 首先，如第1 4圖所示，沿著切斷預定線5 a朝S i C基 板1 2的厚度方向並列的方式對於1條切斷預定線5 a形成 了 8列的改質領域7a。且，第2接近SiC基板1 2的雷射 光入射面也就是表面1 2 a的改質領域7 a，是使變得比最接 近表面12a的改質領域7a更小的方式，從SiC基板12的 背面1 2b側依序形成改質領域7a。從第1 4圖可了解，藉 由第2接近表面12a的改質領域7a的形成，從改質領域 7a發生的龜裂的伸展被停止。其結果，對於切斷預定線 5 a的切斷面的蛇行，如第1 6圖所示，被抑制在±4 μηι以下 〇 又，從表面12a直到集光點Ρ的位置爲止的距離，是 從 SiC基板12的背面12b側的改質領域 7a依序爲 3 1 4.5 μm、 2 8 0.0 μηι、 2 4 6.0 μηι、2 1 2.0 μηι、 1 7 1 . 5 μηι、 12 3.5μπι、79.0μιη、32.0μιη。且，雷射光 L 的脈衝能量， -19- 201242700 是從s i C基板1 2的背面1 2 b側的改質領域7 a依序爲2 5 μ J 、2 5 μ J ' 2 5 μ J ' 2 5 μ J ' 2 0 μ J ' 1 5 μ J ' 6 μ J ' 6μ·Ι ο 且，如第15圖所示，沿著切斷預定線5m朝SiC基板 12的厚度方向並列的方式對於1條切斷預定線5m形成了 6列的改質領域7m »且，最接近SiC基板12的雷射光入 射面也就是表面1 2a的改質領域7m，是使變得比第2接 近表面12a的改質領域7m更小的方式，從SiC基板12的 背面12b側依序形成改質領域7m。從第1 5圖可了解，藉 由第2接近表面12a的改質領域7m的形成，從改質領域 7m發生的龜裂是伸展至表面12a或其附近爲止》其結果 ，對於切斷預定線5m的切斷面的蛇行，是如第16圖所示 ，在±2μπι以下抑制。 又，從表面1 2 a直到集光點Ρ的位置爲止的距離，是 從 SiC基板12的背面12b側的改質領域 7m依序爲 3 1 5 . 5 μm ' 2 6 4.5 μηι ' 2 1 3 . 5 μm ' 1 5 5.0 μm ' 9 5.5 μm ' 3 4.5 μm 。且，雷射光L的脈衝能量，是從SiC基板12的背面 12b側的改質領域7m依序爲25μ·Ι、25μ：ί、20μ〗、20μΙ、 1 5μΙ ' 7μ!。 接著說明，從改質領域7a、7m到達SiC基板12的雷 射光入射面也就是表面12a的龜裂（以下稱爲「半切」）、 及從改質領域7 a、7 m朝c面方向伸展的龜裂（以下稱爲「 c面破裂」）的關係。在此說明的對象，是如第17圖及第 1 8圖所示，龜裂是朝S i C基板1 2的厚度方向伸展的情況 時，與改質領域7m相比，半切更不易發生且c面破裂更 -20- 201242700 容易發生的改質領域7a。 第19圖’是顯示脈衝寬度及ID門檻値、HC門檻値 及加工界限的關係的表。在此，使脈衝寬度在1 ns、1 〇ns 〜1 2 0 n s的範圍變化，對於各脈衝寬度評價i d門檻値、 H C門檻値及加工界限。且，第2 0圖，是顯示脈衝間距及 ID門檻値、HC門檻値及加工界限的關係的表。在此，使 脈衝間距在6 μιη〜2 2 μιη的範圍變化，對於各脈衝間距評 價ID門檻値、HC門檻値及加工界限。 又’ID門檻値，是可使發生c面破裂的雷射光L的 脈衝能量的最小値，從ID門檻値較高者（即c面破裂發生 困難者）依序評價爲優、良、可、不可。且，HC門檻値， 是可使發生半切的雷射光L的脈衝能量的最小値，從HC 門檻値較低者（即半切發生容易者）依序評價爲優、良、可 、不可。進一步，加工界限，是ID門檻値及HC門檻値 的差，從加工界限大的者依序，評價爲優、良、可、不可 。且，總合，是由ID門檻値、HC門檻値、加工界限的優 先順位進行加權並評價爲優、良、可、不可。 其結果可了解，如第19圖所示，由20ns〜100ns的 脈衝寬度使雷射光L脈衝振盪較佳，由50ns〜60ns的脈 衝寬度使雷射光L脈衝振盪更佳。依據這些的話，可以抑 制c面破裂的發生，且可以促進半切的發生。又，脈衝寬 度是1 0ns的情況時的ID門檻値、加工界限及總合的各評 價，是比脈衝寬度是2 0ns的情況更接近不可的可。 且，如第20圖所示，使脈衝間距成爲ΙΟμιη〜18μπι -21 - 201242700 並沿著切斷預定線5a、5m朝SiC基板12照射雷射光L的 較佳’使脈衝間距成爲1 1 μηι〜1 5 μηι並沿著切斷預定線5 a 、5m朝SiC基板12照射雷射光L更佳，進一步，使脈衝 間距成爲12μπι〜14μηι並沿著切斷預定線5a、5m朝SiC 基板12照射雷射光L最佳。依據這些的話，可以抑制c 面破裂的發生，且可以促進半切的發生。又，脈衝間距是 1 Ομπι時是ID門檻値的評價因爲是可，所以若更重視c面 破裂的發生的抑制的話，脈衝間距是比1 Ομπα更大較佳。 第21圖〜第23圖，是顯示將雷射光L由開口數0.8 集光的情況時的脈衝寬度及脈衝間距的加工界限的實驗結 果的表。這些的實驗結果，是成爲第19圖及第20圖所示 的評價的根據。可獲得第21圖〜第23圖的實驗結果時的 實驗條件，是如以下。首先，將具有 4 °的偏角的厚度 ΙΟΟμιη的六方晶系SiC基板12作爲對象，將雷射光L的 集光點P沿著朝表面12a及與a面平行的方向延伸的切斷 預定線5a移動。且，將雷射光L由開口數0.8集光，將 集光點P對焦於離SiC基板12的雷射光入射面也就是表 面12a距離59μηι的位置。 將以上的實驗條件作爲前提，各別變化雷射光L的能 量（脈衝能量）及功率、及雷射光L的脈衝間距，觀察改質 領域7a以及半切及c面破裂的狀態。在第21圖〜第23 圖中，各別將雷射光L的脈衝寬度設爲27ns、40ns、57ns ，將雷射光L的脈衝寬度（重覆頻率）設爲10kHz、20kHz、 35kHz。 -22- 201242700 在第21圖〜第23圖的實驗結果中，ST’是顯示半切 未發生，HC，是顯示半切已發生。且’ ID’是顯示c面破 裂已發生，LV1〜LV3，是顯示c面破裂的發生規模。沿 著2條的切斷預定線5 a各別形成了改質領域7 a的情況時 ，對於4 0 m m的領域（2 0 m m X 2條的領域），c面破裂的發生 領域若是150μιη未滿時爲LV1 ’ c面破裂的發生領域是 450μηι未滿時爲LV2，c面破裂的發生領域是450μτη以上 時爲LV3。在LV1中，朝與切斷預定線5a垂直的方向的 c破裂的伸展是成爲ΙΟμιη〜20μιη ’對於此’在LV2、LV3 中，朝與切斷預定線5 a垂直的方向的c破裂的伸展是成 爲最大ΙΟΟμιη程度。 第24圖，是顯示脈衝間距及HC門檻値的關係的圖表 。且，第2 5圖，是顯示脈衝間距及ID門檻値的關係的圖 表。進一步，第26圖，是顯示脈衝間距及加工界限的關 係的圖表。這些的圖表，是依據第21圖〜第23圖的實驗 結果作成者。如第24圖及第25圖所示，脈衝寬度變大的 話，HC門檻値及ID門檻値的雙方雖上昇，但是與HC門 檻値的劣化（上昇）相比，ID門檻値的提高（上昇）的效果變 大。這是意味，如第26圖所示，脈衝寬度變大的話，加 工界限也會變大。例如，著眼在脈衝寬度27ns及脈衝寬 度57ns的情況時，脈衝間距是12μηι時，HC門檻値，是 從15μ·ί朝17μ】劣化（上昇）2μ】，對於此，ID門檻値，是 從17μ·Γ朝29μ·Ι提高（上昇）12μ·Ι。且，脈衝寬度40ns的情 況時，認定與脈衝寬度27ns的情況時相比，加工界限在 -23- 201242700 脈衝間距ΙΟμιη〜16μιη的範圍有大幅度的提高。且，脈衝 寬度57ns的情況時，認定與脈衝寬度27ns的情況時相比 ，加工界限在脈衝間距6μηι〜20 μηι的範圍有大幅度的提 高。 第27圖〜第29圖，是顯示將雷射光L由開口數0.6 集光的情況時的脈衝寬度及脈衝間距的加工界限的實驗結 果的表。這些的實驗結果，是成爲第19圖及第20圖所示 的評價的根據。可獲得第27圖〜第29圖的實驗結果時的 實驗條件，是如以下。首先，以設有與c面形成偏角的表 面12a的厚度350 μηι的六方晶系SiC基板12作爲對象， 將雷射光L的集光點P沿著朝表面12a及與a面平行的方 向延伸的切斷預定線5a移動。且，將雷射光L由開口數 0.6集光，將集光點P對焦於離SiC基板12的雷射光入射 面也就是表面12a距離50μιη的位置。 將以上的實驗條件作爲前提，各別變化雷射光L的能 量（脈衝能量）及功率、及雷射光L的脈衝間距，觀察改質 領域7a以及半切及c面破裂的狀態。在第27圖〜第29 圖中，各別將雷射光L的脈衝寬度設爲27ns、40ns、5 7ns ，將雷射光L的脈衝寬度（重覆頻率）設爲10kHz、20kHz 、35kHz。 在第27圖〜第29圖的實驗結果，ST，是顯示半切未 發生，HC，是顯示半切已發生。且，ID，是顯示c面破裂 已發生，LV】〜LV3，是顯示c面破裂的發生規模。LV1〜 LV3的基準，是與上述的第21圖〜第23圖的實驗結果的 -24- 201242700 情況同樣。進一步’ 〇D，是顯示：加大雷射光L的能量 時’改質領域7a也變大，由其起因而活躍的龜裂是大大 地從切斷預定線5a偏離並到達SiC基板12的表面12a。 在此情況下，對於c面破裂未評價。但是，在脈衝寬度 4〇ns及脈衝寬度57ns中，脈衝間距Ι2μηι以上未發生大 規模的c面破裂。 第3 0圖，是顯示脈衝間距及η C門檻値的關係的圖表 。此圖表’是依據第2 7圖〜第2 9圖的實驗結果作成者。 如第3 0圖所示，脈衝寬度5 7 n s的情況時，與脈衝寬度 4 0ns的情況時相比，HC門檻値是2μ·Γ〜4μ·Γ程度不易發生 。與上述的開口數0.8的情況時相比，開口數〇 . 6的情況 時，在雷射光L的集光點Ρ因爲收差的影響變小，所以在 脈衝寬度5 7ns的情況及脈衝寬度4Ons的情況時，成爲同 程度的HC門檻値。從此可知，進行收差修正的話，脈衝 寬度即使變大（至少60ns之前）HC門檻値也不會劣化。 接著，說明SiC基板1 2的雷射光入射面也就是表面 12a的附近中的HC品質的加工界限的實驗結果。第31圖 〜第3 3圖的實驗結果時的實驗條件，是如以下。首先， 將具有4°的偏角的厚度1 00 μηι的六方晶系SiC基板1 2作 爲對象，將雷射光L的集光點P沿著朝表面12a及與a面 平行的方向延伸的切斷預定線5 a移動。且，將雷射光L 由開口數0.8集光。 首先，在第31圖的實驗結果中，使用由27ns、4〇ns 、5 0ns、5 7ns的各脈衝寬度照射雷射光L，由集光點位置 -25- 201242700 40.6 μηι使半切發生，且由集光點位置40.6 μιη使半切不會 發生的能量（脈衝能量），使集光點位置在25·3μηι〜40·6μπι 的範圍變化並觀察半切的狀態。雷射光L的脈衝間距是 Ι4μηι爲固定。又，集光點位置，是從表面12a直到集光 點P的位置爲止的距離。其結果，由脈衝寬度所產生的半 切的品質的劣化是幾乎沒有’在脈衝寬度27ns〜57ns發 生高品質（對於切斷預定線的半切的蛇行是小）的半切。且 ，加工界限，是脈衝寬度愈大就愈大。脈衝寬度小的話’ 在一部分的半切容易發生分枝和破裂（〇D)。 且，在第32圖的實驗結果中，由27ns、40ns、50ns 、57ns的各脈衝寬度照射雷射光L，使脈衝能量在7μΤ〜 1 2 μ J的範圍變化並觀察半切的狀態。雷射光L的脈衝間距 是14μιη爲固定，集光點位置是34.5μηι爲固定。其結果， 由脈衝寬度所產生的HC門檻値的變化是幾乎沒有。且’ 由相同脈衝能量發生同程度品質的半切。 進一步’，在第33圖的實驗結果中’由1〇μιη、12μιη、 14μϋΐ、16μηι、18μηι的各脈衝間距將雷射光L照射，使脈 衝能量在7μ·Ι〜12μ〗的範圍變化並觀察半切的狀態。雷射 光L的脈衝寬度是57ns爲固定’集光點位置是34·5μηι爲 固定。其結果，由脈衝間距所產生的HC門檻値的變化是 幾乎沒有。且，集光點位置是3 4.5 μιη的情況時’由相同 脈衝能量發生同程度品質的半切。 接著，說明抑制c面破裂的其他的雷射加工方法。首 先，準備具備含有與c面形成偏角的表面12a的六方晶系 -26- 201242700[Technical Field] The present invention relates to a laser processing method for cutting a plate-shaped object to be processed having a Sic substrate along a line to cut. [Prior Art] s i c (矽 carbide) is a semiconductor material that has been attracting attention as a power element (p0Wer device) which is excellent in heat resistance and high in voltage and power saving. However, since SiC has a difficult-to-machine material that is inferior to the hardness of diamonds, it is necessary to cut a plate-shaped object to be processed with a siC substrate by blade dicing. Processing and frequent blade exchange. Here, it has been proposed to form a modified field in the inside of the s丨C substrate along the line to cut by irradiating the laser light to the object to be processed, and the field of reforming is used as a starting point along the line to cut. A laser processing method for cutting a workpiece (for example, refer to Patent Document i). [PRIOR ART DOCUMENT] [Patent Document 1] [Patent Document 1] Japanese Patent Application Publication No. 2007-514315 (Invention 3) The present inventors have found that laser processing as described above is employed. In the case of cutting a 201242700 plate-shaped object to be processed, which includes a hexagonal siC substrate having a principal surface having an off-angle of the c-plane, there is a problem in the field of reforming. When the crack reaches the laser light incident surface of the SiC substrate from the field of the modification, and the laser beam is irradiated to the object to be processed in such a manner that the crack is easily extended from the modified field to the thickness direction of the siC substrate, the crack is also easily changed from the field of modification. Stretch in the direction of the C plane. In view of the above, an object of the present invention is to provide a laser processing method capable of forming a plate-shaped object to be processed having a hexagonal SiC substrate having a principal surface having an off-angle with a C-plane, along the line to be cut. Good cut. (Means for Solving the Problem) The laser processing method according to one aspect of the present invention is a plate-shaped object to be processed including a hexagonal SiC substrate including a principal surface having an off-angle with the c-plane, and is cut along the cutting edge. The laser processing method for the predetermined line cutting includes: focusing the light collecting point of the laser light on the inside of the SiC substrate, by positioning on both sides of the planned cutting line in the plane parallel to the main surface Each of the preparatory lines extending in the direction parallel to the predetermined line illuminates the object to be processed, and the preliminary process is performed on the inside of the SiC substrate along each of the preparatory lines; and after the first process or At the same time, the light collecting point is focused on the inside of the SiC substrate, and the laser beam is irradiated onto the object to be processed along the line to cut, and the modified region which becomes the starting point of cutting along the line to cut is formed. In the second process of the inside of the SiC substrate; and in the first process, the laser light is irradiated along each of the preparatory lines in such a manner that cracks are less likely to occur from the preparatory modified field toward the Si C substrate than in the modified field. Processing object. In this laser processing method, when a modified region is formed inside the 201242700 of the SiC substrate along the line to be cut, a preliminary modified region is formed in the inner portion of the Sic substrate along the standby line. Further, the preparatory line is located on both sides of the planned cutting line in a plane parallel to the main surface and extends in a direction parallel to the line to cut. Therefore, even if the crack is extended from the modified field toward the c-plane, the crack extension can be suppressed by the field of preparatory modification. Therefore, it is not necessary to consider whether or not the crack easily spreads from the reforming field toward the c-plane direction, and the laser beam can be easily irradiated onto the object to be processed so as to easily extend from the modified region toward the thickness direction of the SiC substrate. Further, in the field of preparatory modification, since it is not necessary to function as a cutting start point (that is, to promote cracking from the field of preparatory modification to the thickness direction of the Sic substrate), it is possible to irradiate laser light which is less likely to be cracked on the Sic substrate. Since it can be formed, it is possible to easily suppress the crack from extending from the field of preparatory upgrading to the direction of c-plane in the formation of the preparatory reforming field. Therefore, according to the laser processing method, the plate-shaped object to be processed including the hexagonal SiC substrate including the principal surface having the off-angle of the c-plane can be accurately cut along the line to cut. Also, the off angle is a case where 0° is included. In this case, the main surface is parallel to the c-plane. In the laser processing method of one aspect of the present invention, in the first process, when the light collecting point is focused on a predetermined distance from the incident surface of the laser light of the SiC substrate in the second process, the spot is focused. A predetermined distance from the incident surface of the laser light is also possible. Thereby, it is possible to more reliably suppress the extension of the crack from the reforming field toward the c-plane direction. The laser processing method according to the first aspect of the present invention may further include a third process of cutting the object to be processed along the line to cut along the line to be cut after the second process. As a result, it is possible to obtain an object to be cut with a high accuracy along the cut line of -7-201242700. In the laser processing method of one aspect of the present invention, the field of upgrading has a case including a field of melt processing. [Effects of the Invention] According to the present invention, a plate-shaped object to be processed including a hexagonal SiC substrate having a principal surface having an off-angle with the C-plane can be cut with high precision along a line to cut. [Embodiment] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and the repeated description is omitted. In the laser processing method according to the embodiment of the present invention, the object to be processed is irradiated with laser light along the line to cut, and a modified region is formed inside the object to be processed along the line to cut. Here, first, the formation of this modified field will be described with reference to Figs. 1 to 6 . As shown in Fig. 1, the laser processing apparatus 100 is provided such that the laser light source 1 〇1 that pulsates the laser light L and the direction of the optical axis (optical path) of the laser light L are changed by 90°. The dichroic mirror 103 and the light collecting lens 1〇5 for collecting the laser light L are provided. In addition, the laser processing apparatus 1 includes a support table 107 for supporting the object 1 to be irradiated with the laser light L collected by the light collecting lens 105, and a support for moving the support table 107. The stage 111 and the laser light source control unit 102 for controlling the laser light source 1 ο 1 to adjust the output of the laser light L and the pulse width, etc., and the stage control unit 1 1 5 for controlling the movement of the stage 1 1 1 . In the laser processing apparatus 100, the laser light L emitted from the laser light source 101 is changed by the direction of the optical axis by the dichroic mirror 103 by 90°, and is collected by the light collecting lens 105. The inside of the object 1 placed on the support table 107. At the same time, the stage 1 1 1 is moved to relatively move the object 1 with respect to the laser beam L along the line to cut 5 . Thus, the modified area along the line to cut 5 is formed in the object 1 to be processed. As shown in FIG. 2, the object to be cut 1 is cut in the object 1 to be cut. Schedule line 5. The cut line 5 is a broken line extending in a straight line. When a modified region is formed inside the object 1 as shown in FIG. 3, the laser beam L is focused on the inside of the object to be processed i, and the laser beam L is along the line to cut 5 (ie, the direction of the arrow A in Fig. 2) relatively moves. As a result, as shown in FIG. 4 to FIG. 6, the modified region 7 is formed inside the object 1 along the line to cut 5, and the modified region 7 formed along the line to cut 5 is formed. Become the cut-off starting point area 8. Further, the light collecting point P is a light collecting portion of the laser light L. Further, the cutting planned line 5 is not limited to a straight line, and may be curved, and is not limited to a broken line, and may be actually scribed on the surface 3 of the object 1 to be processed. Moreover, the field of upgrading 7 is also formed continuously, and there are cases where it is formed intermittently. Further, the modified field 7 may be in the form of a column or a dot, that is, the modified region 7 may be formed at least inside the object 1 to be processed. Further, the modified field -9-201242700 7 may have cracks formed at the starting point, and the cracking and modifying field 7 may expose the outer surface (surface, back surface, or outer peripheral surface) of the object 1 to be processed. By the way, the laser light L here is permeable to the object 1 and is absorbed in the vicinity of the light collecting point inside the object 1, thereby forming the modified field 7 in the object 1 (that is, the internal absorption type mine) Shot processing). Therefore, on the surface 3 of the object 1 to be processed, since the laser light L is hardly absorbed, the surface 3 of the object 1 is not melted. In general, when the surface 3 is melted and removed to form a removal portion (surface absorption type laser processing) such as a hole or a groove, the processing area is gradually changed from the surface 3 side toward the back surface side, but the modification is performed by the present embodiment. The field refers to the field of density, tortuosity, mechanical strength, and other physical properties that are different from the surrounding. In the field of upgrading, there are fields such as a field of melting treatment, a field of cracking, a field of dielectric breakdown, a field of tortuosity change, and the like. Further, the field of reforming has fields in which the density of the field of modification in the material of the object to be processed is changed in comparison with the density of the field of non-modification, and a field in which lattice defects are formed (these are also collectively referred to as a high-density transfer field). Moreover, the field of melting treatment and the field of tortuosity change, the density of the field of modification is a field that changes compared with the density of the non-metamorphic field, and the field in which lattice defects are formed is further internal and modified in those fields. The crack in the interface between the qualitative and non-modified areas (cracking, microcracking). The cracked in the package is a comprehensive situation with a cross-over reform field and only a part of the -10- 201242700 part and the plural part. Further, in the present embodiment, the modified region 7 is formed by forming a plurality of modified beam spots (machining marks) along the line to cut 5 . The modified beam spot is a modified portion formed by one pulse of pulsed laser light (i.e., one-pulse laser irradiation), and becomes a modified field 7 by collecting the modified beam spot. For the modified beam spot, for example, a crack beam spot, a melt processing beam spot or a tortuosity change beam spot, or at least one of these may be mixed. For the modified beam spot, the required cutting accuracy, the required flatness of the cut surface, the thickness, type, and crystal orientation of the object to be processed are appropriately controlled, and the size and the length of the crack generated are appropriately controlled. good. Next, a laser processing method according to an embodiment of the present invention will be described in detail. As shown in Fig. 7, the object 1 is a wafer having a circular plate shape (for example, a diameter of 3 inches and a thickness of 350 μm) including the Sic substrate 12. The SiC substrate 1 2 ' is a crystal structure having a hexagonal crystal system, and the crystal axis CA ' is an angle of inclination 0 (for example, 4) with respect to the thickness direction of the SiC substrate 12 as shown in Fig. 8. That is, the SiC substrate 12 is a hexagonal SiC substrate having an off angle of an angle β. As shown in Fig. 9, the SiC substrate 12 has a surface (main surface) 12a and a back surface (main surface) 12b having an off-angle of 0 to the c-plane. In the SiC substrate 12, the a-plane ' is an inclination angle Θ with respect to the thickness direction (two-point lock line in the drawing) of the SiC substrate 12, and the m-plane' is the thickness of the SiC substrate 12, and the direction is not inclined. As shown in Fig. 7 and Fig. 9, in the object 1 to be processed, a plurality of planned cutting lines (first cutting planned lines) 5a extending toward the surface 12a and the direction parallel to the a-plane, and the surface 12a and a plurality of predetermined cutting lines (second cutting planned lines) extending in a direction parallel to the m-plane are set to a lattice shape of -11 - 201242700 (for example, Immxlmm). In the surface 12a of the SiC substrate 12, 'a functional element is formed in each of the fields demarcated by the cutting planned lines 5a, 5m' in the back surface 12b of the SiC substrate 12, by cutting the predetermined line 5a, Metal wiring is formed in each area where 5 m is demarcated. The functional element and the metal wiring ′ constitute a power element by each of the wafers obtained by cutting the object 1 along the line to cut 5 a and 5 m. Further, in the SiC substrate 12, the orientation flat surface 6a is formed in a direction parallel to the cutting predetermined line 5a, and the orientation flat surface 6m is formed in a direction parallel to the cutting planned line 5m. The above-described object 1 is cut along the line to cut 5a, 5m as follows. First, as shown in Fig. 10, the stretchable tape 23 is attached to the processed object 1 so that the metal wiring of the back surface 12b of the SiC substrate 12 is covered. Next, as shown in FIG. 11(a), the light-collecting point P of the laser light L pulse-pulsed by a pulse width of 20 ns to 100 ns (more preferably, a pulse width of 50 ns to 60 ns) is focused on the inside of the SiC substrate 12. In a method in which the pulse pitch is 1 Ομηι to 1 8 μη (more preferably, the pulse pitch is 12 μη to 14 μm), the laser light L is irradiated onto the object 1 along the line to cut 5a. Thereby, along the line to cut 5a, the modified region (first modified region) 7a which is the starting point of the cutting is formed inside the SiC substrate 12. This modified field 7a is intended to be in the field of melt processing. In addition, the pulse pitch is obtained by dividing "the moving speed of the light collecting point P of the laser light L of the object 1 to be processed" by the "repetition frequency of the pulsed laser light L". When the formation of the modified field 7a is described in detail, the surface 12a of the SiC substrate 1 is used as the laser light incident surface, and the light collecting spot P of the laser light L is placed inside the SiC substrate 2, along the line to cut 5a. The spot P is moved relative to -12-201242700. And the relative movement of the light collecting point P along the line to cut 5a is plural (for example, eight times) for one line to cut. At this time, a plurality of columns (column 1) are formed for one planned cutting line 5 a in such a manner that the distance 'from the surface 1 2 a to the position of the light collecting point p is changed in the thickness direction of the SiC substrate 12 every time. The modified field 7a of the number, for example, 8歹). Here, the 'light-light incident plane of the second SiC substrate 12, that is, the modified region 7 a ' of the surface 1 2 a is a mode that becomes smaller than the modified region 7a closest to the surface 1 2 a' from SiC The modified region 7a is sequentially formed on the side of the back surface 12b of the substrate 12 (i.e., away from the incident surface of the laser light). Further, the size of the modified field 7 a can be adjusted, for example, by varying the pulse energy of the laser light L. Thereby, the cracks generated from the respective modified areas 7a are extended toward the thickness direction of the siC substrate 12 and connected to each other. In particular, the surface of the laser light incident surface closest to the Sic substrate 12, i.e., the modified region 7a of the surface 12a extending in the thickness direction of the SiC substrate 12, reaches the surface i2a. It is very important that the S i C substrate 1 2 having a hard-to-machine material having a hardness lower than the hardness of the diamond is cut along the line to cut 5 a with high precision, and is formed along the line 5 a along the line to cut. After the modification field 7a, as shown in Fig. 11(b), a set of laser light L that is pulse-oscillated by a pulse width of 20 ns to 100 ns (more preferably, a pulse width of 50 ns to 60 ns) is used. The spot Ρ focuses on the inside of the Sic substrate 12 so that the pulse pitch is 10 μm to 1 8 μm (more preferably, the pulse pitch is 1 2 μm to 14 μm) along the line to cut 5 m. The laser light L is irradiated onto the object to be processed]. From -13 to 201242700, the field of modification (second modification field) 7m which is the starting point of the cutting is formed in the inside of the SiC substrate 12 along the cutting line 5m. This field of modification is 7m, and it is intended to be included in the field of melt processing. When the formation of the modified field 7m is described in detail, the surface 12a of the SiC substrate 12 is used as the laser light incident surface, and the light collecting point P of the laser light L is placed inside the SiC substrate 12, and is set along the cutting line 5m. The spot P moves relatively. Further, the relative movement of the light collecting point P along the cutting planned line 5m is plural (for example, six times) for one cutting planned line 5. In this case, a plurality of columns (more than the first column) are formed for one planned cutting line 5m in such a manner that the distance from the surface 12 2a to the position of the light collecting point P is changed in the thickness direction of the SiC substrate 12 Less modified field 7m in the second column number (including one column), for example, six columns. Here, the laser light incident surface closest to the SiC substrate 12 is the modified region 7m of the surface 12a, which is a mode that is smaller than the modified region 7m of the second proximity surface 1 2a' from the SiC substrate 12 The back side 12b side (ie, away from the incident surface of the laser light) sequentially forms a modified field of 7 m. Further, the size of the modified field of 7 m can be adjusted, for example, by varying the pulse energy of the laser light L. Thereby, cracks occurring from 7 m in each modified region extend in the thickness direction of the Si C substrate 12 and are connected to each other. In particular, the surface of the laser light incident surface closest to the SiC substrate 12, i.e., the modified region 7m of the surface 12a extending in the thickness direction of the SiC substrate 12, reaches the surface i2a. It is very important that the S i C substrate 1 2 having a hard-to-machine material having a hardness lower than the hardness of the diamond is cut along the line to cut 5 m with high precision - 14 - 201242700 along the line to cut 5 m formed the modified field 7 m 1 2 shown in Figure (a), the expansion tape 2 3 is expanded, in its shape of the retractable tape 2 3 along the respective cutting line 5 m will be the edge of the S i C substrate. 1 2 back 1 2 b. As a result, the object to be processed 1 is cut into a rod along the line to cut 5 m along the line to cut. The stretchable tape 2 3 is in an expanded state, so as the first! The workpiece 1 that has been cut into a rod shape is separated from each other, and the object 1 is cut along the line to cut 5 m as shown in Fig. 13 (a). The stretchable tape 23 is 7 on the back surface 12b of the SiC substrate 12 along each of the line to cut 5a. As a result, when the object to be processed 1 is cut along the line to cut 5 a along the line to cut 5, the stretchable tape 2 3 is in a state of being expanded, so that it is poor and is cut into a wafer shape. The object 1 to be processed is a plurality of power elements obtained by cutting the object 1 into a wafer shape along the cutting. According to the above-described laser processing method, the object 1 having a plate shape including the hexagonal plate 12 including the surface 12a having an off-angle with the c-plane is cut off along the predetermined cutting degree. As a result, it is possible to obtain a processing object U that is cut along the predetermined cutting accuracy, that is, a power element. First, the laser light is irradiated onto the object 1 at a pulse pitch of 10 μm to 18 μm along the lines 5 a and 5 m. When the laser light L is irradiated onto the object 1 to be processed, the crack can be made, and in the first state, the transmission 41 abuts on 'm as a starting point. At this time, after the breakage shown in Fig. 2(b), the rim 41 abuts the ξ 7a as a wafer shape in the connected state. Figure 13 (b) of this 成为 becomes a separation. [Line 5 a, 5 m reasons, crystal SiC base: 5a, 5m fine: line 5 a, 5 m cut scheduled by this condition easily from the modified -15- 201242700 field 7a, 7m toward the SiC substrate The thickness of 12 is extended in the thickness direction, and on the other hand, the crack does not easily extend from the modified areas 7a and 7m toward the c-plane. Further, when the pulse pitch is 12 μm to 14 μm and the laser beam L is irradiated onto the object 1 along the line to cut 5a, 5m, the crack can be more easily changed from the modified field 7a, 7m toward the thickness direction of the SiC substrate 12. Stretching, on the other hand, cracks are less likely to extend from the modified areas 7a, 7m toward the c-plane. Further, the laser light L is pulse-oscillated by a pulse width of 20 ns to 1 〇〇 ns. Thereby, the crack can be easily and surely extended from the reforming fields 7a and 7m toward the thickness direction of the SiC substrate 12. On the other hand, the crack can be reliably prevented from extending from the modified fields 7a and 7m toward the c-plane direction. Further, when the laser beam L is pulse-oscillated by a pulse width of 50 ns to 60 ns, the crack is more easily and reliably extended from the modified fields 7a and 7m toward the thickness direction of the SiC substrate 12. On the other hand, the crack is more difficult to reliably The modified areas 7a and 7m extend in the direction of the c-plane. Further, the laser light incident surface of the second proximity S i C substrate 1 2 along the line to cut 5 a, that is, the modified region 7a of the surface 12a is relatively formed relatively. Therefore, even if the a-plane is inclined in the thickness direction of the SiC substrate 12, the crack generated from the modified region 7a of the second proximity surface 12a extends in the a-plane direction, and can prevent the cut line 5 from being cut. A large deviation state reaches the surface 1 2 a. Further, the laser light incident surface closest to the Si C substrate 12 along the line to cut 5 a, that is, the modified region 7 a of the surface 12 a is relatively large. Thereby, although the crack does not easily extend from the reforming field 7a toward the thickness direction of the SiC substrate 12, the crack can surely reach the surface 12a from the modified region 7a closest to the surface 12a. Further, the laser light incident surface of the second proximity SiC substrate 12, which is 5 m apart from the pre-cut 16-201242700, that is, the modified region 7m of the surface 12a is relatively large. Thus, the state in which the crack is easily extended from the modified region 7m toward the thickness direction of the SiC substrate 12, and the crack generated from the modified region 7m of the second proximity surface 12a can reach the surface 12a or its vicinity. Further, the laser light incident surface closest to the Si C substrate 1 2 along the line to cut 5m, that is, the modified region 7m of the surface 12 a is relatively formed relatively small. Thereby, it is possible to prevent the surface 12a from being broken, and it is possible to surely reach the surface 1 2a from the modified field 7m. As described above, the crack can surely reach the surface 12a from the reforming field 7a along the line to cut 5a, and the crack can surely reach the surface 12a from the reformed field 7m along the line 5m to be cut. This effect is remarkable irrespective of the number of formation columns and the formation order of the modified regions 7a and 7m to be described later, and is more remarkable in accordance with the number of formation columns and the formation order of the modified regions 7a and 7m to be described later. Further, a plurality of rows of modified areas 7a are formed along the one line to be cut 5 a along the case where the modified field 7m is formed along one cutting line 5m. Therefore, even if the a-plane is inclined in the thickness direction of the SiC substrate 12, it is possible to prevent the crack from extending greatly from the modified region 7a toward the a-plane direction at the time of formation of each modified region 7a, and in all the modified regions 7a. In the thickness direction of the SiC substrate i 2 , the crack can be easily connected. Further, along the i-cut predetermined line 5 m, a modified field 7 m having a smaller number of rows than the case where the modified field 7 a is formed along one of the planned cut lines 5 a is formed. Thereby, cracks can be greatly extended from the modified region 7m toward the thickness direction of the SiC substrate i 2 at the time of formation of 7 m in each modified region. As described above, the crack may extend from the modified field 7a toward the thickness direction of the SiC substrate 12 along the line to cut 5a -17-201242700, and the crack may be from the modified field 7m toward the SiC along the line to cut 5m. The substrate 12 is stretched in the thickness direction. This effect is independent of the formation dimensions of the above-described modified fields 7a and 7m and the order of formation of the modified regions 7a and 7m to be described later, in accordance with the formation dimensions of the above-described modified fields 7a and 7m and the modified region 7a to be described later. The order of formation of 7m is more remarkable. In addition, before the formation of the modified region 7m in which the crack is formed in the thickness direction of the SiC substrate 12, the modified region in which the crack is extended in the thickness direction of the SiC substrate 1 2 is formed. 7a. Thus, in the formation of the reforming field 7a, the portion of the cutting line 5a that intersects the line to cut 5m is prevented from being stretched in the thickness direction of the SiC substrate 12 from the modified field 7a. 7m obstacles in the field of upgrading. This effect is independent of the formation size and the number of formation columns of the aforementioned modified fields 7a, 7m. Further, the object to be processed 1 is cut along the line to cut 5 m as the starting point of the modified field 7m, and thereafter, the object 1 is cut along the line to cut 5a using the modified field 7a as a starting point. . Thus, the formation of the modified region 7m with a small number of rows cuts the object 1 along the line 5 m which is supposed to be difficult to cut, and then the field of modification by the number of columns The formation of 7 a cuts the object 1 along the line to cut 5 a which is relatively easy to cut. Therefore, the force required to cut the object 1 along the line to cut 5m and the force required to cut the object 1 along the line to cut 5a are uniform, along the line to cut. The cutting accuracy of 5 m and the cutting accuracy of 5 a along the cutting line can be increased by -18-201242700. This effect is independent of the formation size and the number of formation columns of the aforementioned modified fields 7a, 7m. Fig. 14 is a view showing a photograph of a cut surface of the siC substrate 12 cut along the line to cut 5a by the above-described laser processing method. Further, Fig. 15 is a view showing a photograph of a cut surface of the SiC substrate 12 cut along the cutting predetermined line 5m by the above-described laser processing method. Further, Fig. 16 is a view showing a plan view of the SiC substrate 12 cut along the line to cut 5a, 5m by the above-described laser processing method. Here, a hexagonal SiC substrate 12 having a thickness of 3°°° with an off angle of 4° is prepared. First, as shown in FIG. 4, the thickness along the line to cut 5 a toward the surface of the Si C substrate 1 2 The manner in which the directions are juxtaposed forms eight modified fields 7a for one cut planned line 5a. Further, the laser light incident surface of the second adjacent SiC substrate 1 2 is the modified region 7 a of the surface 1 2 a, and is a mode smaller than the modified region 7a closest to the surface 12a, from the SiC substrate 12 The back side 1 2b side sequentially forms the modified field 7a. As is apparent from Fig. 14, the extension of the crack generated from the modified field 7a is stopped by the formation of the modified region 7a of the second proximity surface 12a. As a result, the meandering of the cut surface of the cut line 5a is suppressed to ±4 μηι or less, as shown in Fig. 6, and the distance from the surface 12a to the position of the light collecting point , is The modified region 7a from the side of the back surface 12b of the SiC substrate 12 is sequentially 3 1 4. 5 μm, 2 8 0. 0 μηι, 2 4 6. 0 μηι, 2 1 2. 0 μηι, 1 7 1 . 5 μηι, 12 3. 5μπι, 79. 0μιη, 32. 0μιη. Moreover, the pulse energy of the laser light L, -19-201242700 is the modified field 7a from the back side 1 2 b side of the si C substrate 1 2 in order of 2 5 μ J , 2 5 μ J ' 2 5 μ J ' 2 5 μ J ' 2 0 μ J ' 1 5 μ J ' 6 μ J ' 6μ·Ι ο , 第 , ' ' ' ' ' 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着 沿着One line of cut line 5m forms 6 rows of modified areas 7m » and the laser light incident surface closest to the SiC substrate 12 is the modified field 7m of the surface 12a, so that it becomes closer to the second close surface 12a. In the modified region of 7 m, the modified region 7m is sequentially formed from the back surface 12b side of the SiC substrate 12. As can be seen from Fig. 15, it is understood that the crack generated from the modified field 7m is extended to the surface 12a or its vicinity by the formation of the modified region 7m of the second proximity surface 12a. The meandering of the cut surface of 5 m is suppressed as ±16 μm as shown in Fig. 16. Further, the distance from the surface 1 2 a to the position of the collecting spot 是 is from the modified region 7m on the side of the back surface 12b of the SiC substrate 12 in the order of 3 1 5 . 5 μm ' 2 6 4. 5 μηι ' 2 1 3 . 5 μm ' 1 5 5. 0 μm ' 9 5. 5 μm ' 3 4. 5 μm. Further, the pulse energy of the laser light L is 25 μ·Ι, 25 μ: ί, 20 μ, 20 μΙ, and 15 μΙ '7 μ! from the modified region 7m on the back surface 12b side of the SiC substrate 12. Next, the laser light incident surface that reaches the SiC substrate 12 from the modified regions 7a and 7m is the crack of the surface 12a (hereinafter referred to as "half cut"), and extends from the modified region 7a, 7m toward the c-plane. The relationship between cracks (hereinafter referred to as "c-plane cracks"). The object described here is that when the crack is extended in the thickness direction of the Si C substrate 12 as shown in FIGS. 17 and 18, the half cut is less likely to occur than the modified field 7 m. C-face rupture more -20- 201242700 Easy to change field 7a. Fig. 19 is a table showing the relationship between the pulse width, the ID threshold, the HC threshold, and the processing limit. Here, the pulse width is changed in the range of 1 ns, 1 〇 ns to 1 2 0 n s, and the i d threshold, the H C threshold, and the processing limit are evaluated for each pulse width. Further, Fig. 20 is a table showing the relationship between the pulse pitch, the ID threshold, the HC threshold, and the processing limit. Here, the pulse pitch is varied in the range of 6 μm to 2 2 μm, and the ID threshold, the HC threshold, and the processing limit are evaluated for each pulse pitch. The 'ID threshold is the minimum 脉冲 of the pulse energy of the laser light L that can cause the c-plane rupture. The higher the ID threshold (ie, the c-plane rupture is difficult), the evaluation is excellent, good, and No. Further, the HC threshold is the minimum 脉冲 of the pulse energy of the half-cut laser light L, and it is excellent, good, and not possible from the lower HC threshold (i.e., the half-cut is easy). Further, the processing limit is the difference between the ID threshold and the HC threshold, and those who have a large processing limit are evaluated as excellent, good, acceptable, and impossible. Moreover, the total weight is weighted by the priority threshold of the ID threshold, the HC threshold, and the processing limit, and is evaluated as excellent, good, and acceptable. As a result, it can be understood that, as shown in Fig. 19, it is preferable that the laser light L pulse is oscillated by a pulse width of 20 ns to 100 ns, and the laser light pulse oscillation is better by a pulse width of 50 ns to 60 ns. According to these, the occurrence of c-plane rupture can be suppressed, and the occurrence of half-cut can be promoted. Further, in the case where the pulse width is 10 ns, the evaluation of the ID threshold, the processing limit, and the total is closer to the case where the pulse width is 20 ns. Further, as shown in Fig. 20, the pulse pitch is set to ΙΟμιη to 18μπι -21 - 201242700, and the laser light L is preferably irradiated toward the SiC substrate 12 along the line to cut 5a, 5m so that the pulse pitch becomes 1 1 μηι. It is preferable that the laser light L is irradiated toward the SiC substrate 12 along the line 5 a and 5 m, and the pulse pitch is 12 μm to 14 μm, and the SiC substrate 12 is irradiated with lightning along the line to cut 5a, 5m. The light L is optimal. According to these, the occurrence of c-plane rupture can be suppressed, and the occurrence of half-cut can be promoted. Further, when the pulse pitch is 1 Ομπι, the evaluation of the ID threshold is possible. Therefore, if the suppression of the occurrence of the c-plane rupture is more important, the pulse pitch is preferably larger than 1 Ομπα. Figure 21 to Figure 23 show the laser light L from the opening number of 0. 8 A table showing the experimental results of the pulse width and the processing limit of the pulse pitch in the case of light collection. The results of these experiments are the basis for the evaluations shown in Figs. 19 and 20. The experimental conditions at which the experimental results of Figs. 21 to 23 can be obtained are as follows. First, the hexagonal SiC substrate 12 having a thickness of 4° is used as a target, and the light-collecting point P of the laser light L is along a line to cut 5a extending toward the surface 12a and a direction parallel to the a-plane. mobile. Moreover, the laser light L is made up of 0. At 8 episodes, the collection point P is focused on a position away from the incident surface of the laser light of the SiC substrate 12, that is, the surface 12a is 59 μm. On the premise of the above experimental conditions, the energy (pulse energy) and power of the laser light L and the pulse pitch of the laser light L were individually changed, and the state of the modified field 7a and the half-cut and c-plane rupture were observed. In the 21st to 23rd drawings, the pulse width of the laser light L is set to 27 ns, 40 ns, and 57 ns, respectively, and the pulse width (repetition frequency) of the laser light L is set to 10 kHz, 20 kHz, and 35 kHz. -22- 201242700 In the experimental results of Fig. 21 to Fig. 23, ST' is a half cut that does not occur, and HC is a half cut. And ' ID' indicates that the c-plane rupture has occurred, and LV1 to LV3 are the scales at which the c-plane rupture occurs. When the modified field 7a is formed separately along the two planned cutting lines 5a, for the field of 40 mm (the field of 20 mm X 2), the occurrence area of the c-plane crack is 150 μm. The LV1 'c-plane rupture occurs at full time when the 450μηι is less than LV2, and the c-plane rupture occurs when the field is 450μτη or more. In LV1, the stretch of c which is ruptured in the direction perpendicular to the line to cut 5a is 伸展μηη~20μηη 'for this', in LV2, LV3, the crack of c is broken in the direction perpendicular to the line to cut 5a. It is the maximum ΙΟΟμιη degree. Fig. 24 is a graph showing the relationship between the pulse pitch and the HC threshold. Further, Fig. 25 is a graph showing the relationship between the pulse pitch and the ID threshold. Further, Fig. 26 is a graph showing the relationship between the pulse pitch and the processing limit. These charts are based on the experimental results of Figures 21 to 23. As shown in Fig. 24 and Fig. 25, when the pulse width is increased, both the HC threshold and the ID threshold increase, but the ID threshold is increased (rised) compared to the deterioration (rise) of the HC threshold. The effect becomes bigger. This means that, as shown in Fig. 26, if the pulse width becomes large, the processing limit will also become large. For example, when the pulse width is 27 ns and the pulse width is 57 ns, the pulse threshold is 12 μηι, and the HC threshold is degraded (rising) from 15 μ·ί to 17 μ]. For this, the ID threshold is from 17 μ.・Γ29μ·Ι increases (rises) by 12μ·Ι. Further, in the case where the pulse width is 40 ns, it is considered that the processing limit is greatly improved in the range of -23 - 201242700 pulse pitch ΙΟ μιη to 16 μιη compared with the case where the pulse width is 27 ns. Further, in the case where the pulse width is 57 ns, it is considered that the processing limit is greatly improved in the range of the pulse pitch of 6 μm to 20 μm compared to the case where the pulse width is 27 ns. Figure 27 ~ Figure 29, is to show the laser light L from the opening number of 0. 6 Table of experimental results of the pulse width and the processing limit of the pulse pitch in the case of light collection. The results of these experiments are the basis for the evaluations shown in Figs. 19 and 20. The experimental conditions at which the experimental results of Figs. 27 to 29 are obtained are as follows. First, the hexagonal SiC substrate 12 having a thickness of 350 μm which is provided on the surface 12a which is deviated from the c-plane is used as a target, and the light-collecting point P of the laser light L is extended in the direction parallel to the surface 12a and the a-plane. The cut line 5a moves. And, the laser light L is made up of the number of openings. At 6 sets of light, the collecting spot P is focused on the incident surface of the laser light from the SiC substrate 12, that is, the surface 12a is at a distance of 50 μm. On the premise of the above experimental conditions, the energy (pulse energy) and power of the laser light L and the pulse pitch of the laser light L were individually changed, and the state of the modified field 7a and the half-cut and c-plane rupture were observed. In the 27th to 29th drawings, the pulse width of the laser light L is set to 27 ns, 40 ns, and 5 7 ns, respectively, and the pulse width (repetition frequency) of the laser light L is set to 10 kHz, 20 kHz, and 35 kHz. In the experimental results of Fig. 27 to Fig. 29, ST, which shows that half cut did not occur, HC, is showing that half cut has occurred. Moreover, the ID indicates that the c-plane rupture has occurred, and LV]~LV3 is the scale at which the c-plane rupture occurs. The reference of LV1 to LV3 is the same as the case of -24-201242700 of the experimental results of the above 21st to 23rd. Further, 〇D is a display: when the energy of the laser light L is increased, the modified field 7a also becomes large, and the crack which is active therefrom is greatly deviated from the cut line 5a and reaches the surface of the SiC substrate 12. 12a. In this case, the c-plane fracture was not evaluated. However, in the pulse width of 4 ns and the pulse width of 57 ns, large-scale c-plane cracking did not occur at a pulse pitch of μ 2 μm or more. Fig. 30 is a graph showing the relationship between the pulse pitch and the η C threshold. This chart ' is based on the experimental results of Figures 27 to 29. As shown in Fig. 30, when the pulse width is 5 7 n s, the HC threshold is 2μ·Γ~4μ·Γ, which is less likely to occur than when the pulse width is 40 ns. The number of openings with the above is 0. In the case of 8 cases, the number of openings is 〇. In the case of 6, the light collecting point of the laser light L is reduced by the influence of the difference. Therefore, when the pulse width is 5 ns and the pulse width is 4 Ons, the HC threshold is the same. From this, it can be seen that if the correction is performed, the HC threshold will not deteriorate even if the pulse width becomes large (before at least 60 ns). Next, an experimental result of the processing limit of the HC quality in the vicinity of the surface 12a of the laser light incident surface of the SiC substrate 12 will be described. The experimental conditions at the experimental results of Fig. 31 to Fig. 3 are as follows. First, a hexagonal SiC substrate 1 2 having a thickness of 4° and a thickness of 100°N is used as a target, and the light collecting point P of the laser light L is cut along the surface 12a and a direction parallel to the a surface. The predetermined line 5 a moves. And, the laser light L is 0. 8 episodes of light. First, in the experimental results of Fig. 31, the laser light L is irradiated with pulse widths of 27 ns, 4 ns, 50 ns, and 5 7 ns, from the spot position -25 - 201242700 40. 6 μηι causes the half cut to occur, and the position of the light collection point is 40. 6 μιη makes the energy (pulse energy) that does not occur in the half cut, and changes the position of the light collecting point in the range of 25·3μηι~40·6μπι and observes the half cut state. The pulse pitch of the laser light L is Ι4μηι is fixed. Further, the position of the light collecting point is the distance from the surface 12a to the position of the light collecting point P. As a result, the deterioration of the half-cut quality due to the pulse width is almost no half-cutting in which the high-quality (small-cut serpentine for the cut line) is high in the pulse width of 27 ns to 57 ns. Moreover, the processing limit is that the larger the pulse width, the larger. If the pulse width is small, branching and cracking (〇D) are likely to occur in a part of the half cut. Further, in the experimental results of Fig. 32, the laser light L was irradiated with pulse widths of 27 ns, 40 ns, 50 ns, and 57 ns, and the pulse energy was changed in the range of 7 μΤ to 1 2 μJ, and the half-cut state was observed. The pulse pitch of the laser light L is fixed at 14 μm, and the position of the light collection point is 34. 5μηι is fixed. As a result, there is almost no change in the HC threshold due to the pulse width. And a half-cut of the same quality is produced by the same pulse energy. Further, in the experimental results of Fig. 33, 'the laser light L is irradiated by pulse intervals of 1 〇 μιη, 12 μιη, 14 μϋΐ, 16 μηι, 18 μηι, and the pulse energy is varied in the range of 7 μ·Ι~12 μ and the half cut is observed. status. The pulse width of the laser light L is 57 ns for the fixed 'collection spot position is 34·5 μηι is fixed. As a result, there is almost no change in the HC threshold generated by the pulse pitch. And, the position of the light collection point is 3 4. In the case of 5 μιη, a half-cut of the same quality is produced by the same pulse energy. Next, another laser processing method for suppressing c-plane cracking will be described. First, a hexagonal system having a surface 12a having an off-angle with the c-plane is prepared -26-201242700
SiC基板12的板狀的加工對象物1，設定切斷預定線5a、 5m。接著，如第34圖（a)所示，將雷射光L的集光點p對 焦於SiC基板1 2的內部，各別沿著被設定於切斷預定線 5a(5m)兩側的2條的預備線5p將雷射光L照射在加工對 象物1。由此，沿著各預備線5p將預備改質領域7p形成 於SiC基板12的內部。此預備改質領域7p，是成爲包含 熔融處理領域者。 預備線5p，是在與表面12a平行的面內位在切斷預定 線5a(5m)兩側且朝與切斷預定線5a(5m)平行的方向延伸 的線。又，在藉由切斷預定線5a、5m被劃界各領域在 SiC基板12的表面12a形成功能元件的情況時，預備線 5p，是從SiC基板12的厚度方向所見，設定於相鄰接的 功能元件之間的領域內較佳。 沿著各預備線5p將雷射光L照射在加工對象物！時 ，與成爲切斷起點的改質領域7a(7m)相比，龜裂不易從預 備改質領域7p朝SiC基板12發生。預備改質領域7p，藉 由減小雷射光L的脈衝能量 '脈衝間距、脈衝寬度等，與 成爲切斷起點的改質領域7a(7m)相比，可以使龜裂不易在 SiC基板12發生。 沿著預備線5p形成了預備改質領域7p之後，將雷射 光L的集光點P對焦於SiC基板12的內部，沿著切斷預 定線5a(5m)將雷射光L照射在加工對象物1。由此，沿著 切斷預定線5a(5m) ’將成爲切斷起點的改質領域7a(7m) 形成於SiC基板12的內部。此改質領域7a(7m)，是成爲 -27- 201242700 包含熔融處理領域者。沿著切斷預定線5a(5m)形成了改質 領域7a(7m)之後，將改質領域7a(7m)作爲起點沿著切斷 預定線5a(5m)將加工對象物1切斷。 依據以上的雷射加工方法的話，藉由如以下的理由， 將具備含有與c面形成偏角的表面12a的六方晶系SiC基 板1 2的板狀的加工對象物1，沿著切斷預定線5a、5m精 度佳地切斷，其結果，就可獲得沿著切斷預定線5a、5m 精度佳地被切斷的加工對象物1 (即功率元件）。 即，沿著切斷預定線5a(5m)在SiC基板12的內部形 成改質領域7a(7m)時，是沿著各預備線5p在SiC基板12 的內部形成預備改質領域7p。且，預備線5p，是在與表 面12a平行的面內位在切斷預定線5a(5m)的兩側且朝與切 斷預定線5a(5m)平行的方向延伸。因此，龜裂即使從改質 領域7a(7m)朝c面方向伸展，如第34圖（b)所示與未形成 預備改質領域7p情況時相比，如第34圖（a)所示，其龜裂 (c面破裂）的伸展是成爲藉由預備改質領域7p被抑制。由 此，不需考慮龜裂是否容易從改質領域7a(7m)朝c面方向 伸展，就可使龜裂容易從改質領域7a(7m)朝SiC基板12 的厚度方向伸展的方式將雷射光照射在加工對象物1。又 ，預備改質領域7p，因爲不需要作爲切斷起點功能（即促 進從預備改質領域7p朝SiC基板12的厚度方向的龜裂的 伸展），且藉由在SiC基板12龜裂發生困難的雷射光L照 射而形成，所以在預備改質領域7p的形成時可以容易地 抑制龜裂從預備改質領域7p朝c面方向伸展。因此，可 -28- 201242700 將具備含有與c面形成偏角的主面的六方晶系Sic基板12 的板狀的加工對象物沿著切斷預定線5a(5m)精度佳地切斷 0 且’在改質領域7a(7m)的形成時，將雷射光L的集光 點P對焦於離SiC基板12的雷射光入射面也就是表面12a 預定的距離的情況時，在預備改質領域7p的形成時，也 將雷射光L的集光點p對焦於離表面i2a相同距離較佳。 由此’可以更確實地抑制龜裂從改質領域7a(7m)朝c面方 向伸展。 又’沿著各預備線5p在SiC基板1 2的內部形成預備 改質領域7p的同時，沿著被設定於那些預備線5p之間的 切斷預定線5a(5m)在SiC基板12的內部形成改質領域 7a(7m)時，c面破裂的伸展皆可藉由預備改質領域7p被抑 制。在此情況下，對於沿著切斷預定線5a(5m)的改質領域 7a(7m)的形成，使沿著預備線5p的預備改質領域7p的形 成先行較佳。 [產業上的利用可能性] 依據本發明的話，可以將具備含有與c面形成偏角的 主面的六方晶系S i C基板的板狀的加工對象物，沿著切斷 預定線精度佳地進行切斷。 【圖式簡單說明】 [第1圖]在改質領域的形成所使用的雷射加工裝置的 -29- 201242700 構成圖。 [第2圖]雷射加工前的加工對象物的平面圖。 [第3圖]第2圖的加工對象物的III-III線的剖面圖。 [第4圖]雷射加工後的加工對象物的平面圖。 [第5圖]第4圖的加工對象物的V-V線的剖面圖。 [第6圖]第4圖的加工對象物的VI-VI線的剖面圖。 [第7圖]成爲本發明的一實施例的雷射加工方法的對 象的加工對象物的平面圖。 [第8圖]顯示第7圖的加工對象物的結晶構造的圖。 [第9圖]第7圖的加工對象物的一部分剖面圖。 [第10圖]由本發明的一實施例的雷射加工方法實施的 加工對象物的一部分剖面圖。 [第11圖]由本發明的一實施例的雷射加工方法實施的 加工對象物的一部分剖面圖。 [第1 2圖]由本發明的一實施例的雷射加工方法實施的 加工對象物的一部分剖面圖。 [第1 3圖]由本發明的一實施例的雷射加工方法實施的 加工對象物的一部分剖面圖。 [第1 4圖]顯示藉由本發明的一實施例的雷射加工方& 被切斷的SiC基板的切斷面的照片的圖。 [第15圖]顯示藉由本發明的一實施例的雷射加工方$ 被切斷的SiC基板的切斷面的照片的圖。 [第1 6圖]顯示藉由本發明的一實施例的雷射加工方、法 被切斷的SiC基板的平面照片的圖。 -30- 201242700 [第17圖]說明在SiC基板的內部所發生的c面破裂用 的立體圖。 [第18圖]顯示c面破裂發生的SiC基板的切斷面的照 片的圖。 [第19圖]顯示脈衝寬度及ID門檻値、HC門檻値及 加工界限的關係的表。 [第20圖]顯示脈衝間距及ID門檻値、HC門檻値及 加工界限的關係的表。 [第2 1圖]顯示脈衝寬度及脈衝間距的加工界限的實驗 結果的表》 [第22圖]顯示脈衝寬度及脈衝間距的加工界限的實驗 結果的表。 [第23圖]顯示脈衝寬度及脈衝間距的加工界限的實驗 結果的表。 [第24圖]顯示脈衝間距及HC門檻値的關係的圖表。 [第25圖]顯示脈衝間距及id門檻値的關係的圖表。 [第26圖]顯示脈衝間距及加工界限的關係的圖表。 [第27圖]顯示脈衝寬度及脈衝間距的加工界限的實驗 結果的表。 [第2 8圖]顯示脈衝寬度及脈衝間距的加工界限的實驗 結果的表。 [第29圖]顯示脈衝寬度及脈衝間距的加工界限的實驗 結果的表。 [第30圖]顯示脈衝間距及hc門檻値的關係的圖表。 -31 - 201242700 [第3 1圖]顯示雷射光入射面附近中的HC品質的加工 界限的實驗結果的表。 [第32圖]顯示雷射光入射面附近中的HC品質的加工 界限的實驗結果的表。 [第33圖]顯示雷射光入射面附近中的HC品質的加工 界限的實驗結果的表。 [第3 4圖]說明本發明的其他的實施例的雷射加工方法 用的平面圖。 【主要元件符號說明】 1 :加工對象物 3 :表面 5 :切斷預定線 5a ’ 5m :切斷預定線 5p :預備線 6 :脈衝間距 6a :定向平面 6m :定向平面 7 :改質領域 7a，7m :改質領域 7p :預備改質領域 8 :切斷起點領域 1 〇 :脈衝間距 12 : SiC基板 32- 201242700 1 2a :表面（主面） 1 2b :背面（主面） 2 3 :可伸縮膠帶 4 0 :集光點位置 4 1 :刀緣 1 0 0 :雷射加工裝置 1 0 1 :雷射光源 102 :雷射光源控制部 1 〇 3 :分色鏡 105 :集光用透鏡 107 :支撐台 1 1 1 :載台 1 1 5 :載台控制部 L :雷射光 P :集光點 -33-In the plate-shaped object 1 of the SiC substrate 12, the planned cutting lines 5a and 5m are set. Next, as shown in Fig. 34(a), the light collecting point p of the laser light L is focused on the inside of the SiC substrate 12, and each of them is along two sides set on both sides of the planned cutting line 5a (5m). The preparatory line 5p irradiates the object 1 with the laser light L. Thereby, the preliminary modified region 7p is formed inside the SiC substrate 12 along each of the preliminary lines 5p. This preparatory upgrade field 7p is intended to be included in the field of melt processing. The preparatory line 5p is a line extending in a direction parallel to the line to cut 5a (5m) in a plane parallel to the surface 12a on both sides of the cutting planned line 5a (5m). When the functional elements are formed on the surface 12a of the SiC substrate 12 by the cutting lines 5a and 5m, the standby line 5p is seen from the thickness direction of the SiC substrate 12, and is set adjacent to each other. The field between the functional elements is preferred. The laser light L is irradiated onto the object to be processed along each of the preparatory lines 5p! In the case of the modified field 7a (7 m) which is the starting point of the cutting, the crack is less likely to occur from the prepared reforming field 7p toward the SiC substrate 12. In the preparatory modification field 7p, by reducing the pulse energy of the laser light L, the pulse pitch, the pulse width, and the like, it is possible to make the crack hard to occur on the SiC substrate 12 as compared with the modified field 7a (7 m) which is the starting point of the cutting. . After the preliminary modified region 7p is formed along the preliminary line 5p, the light collecting point P of the laser light L is focused on the inside of the SiC substrate 12, and the laser beam L is irradiated onto the object to be processed along the line to cut 5a (5 m). 1. Thereby, the modified region 7a (7m) which is the starting point of the cutting is formed inside the SiC substrate 12 along the line to cut 5a (5m)'. This upgrading field 7a (7m) is to become the -27- 201242700 including the field of melt processing. After the modified region 7a (7 m) is formed along the line to cut 5a (5 m), the object 1 is cut along the line to cut 5a (5 m) with the modified field 7a (7 m) as a starting point. According to the above-described laser processing method, the plate-shaped object 1 having the hexagonal SiC substrate 1 2 including the surface 12a having an off-angle from the c-plane is prepared along the cutting schedule for the following reasons. The lines 5a and 5m are cut off with high precision, and as a result, the object 1 (i.e., power element) that is accurately cut along the line to cut 5a, 5m can be obtained. In other words, when the modified region 7a (7 m) is formed inside the SiC substrate 12 along the line to cut 5a (5 m), the preliminary modified region 7p is formed inside the SiC substrate 12 along each of the preliminary lines 5p. Further, the preliminary line 5p is located on both sides of the line to cut 5a (5m) in a plane parallel to the surface 12a and extends in a direction parallel to the line 5a (5m) to be cut. Therefore, even if the crack extends from the modified field 7a (7m) toward the c-plane direction, as shown in Fig. 34(b), as shown in Fig. 34(a), when the preliminary reforming field 7p is not formed. The extension of the crack (c-plane rupture) is suppressed by the preparatory modification field 7p. Therefore, it is not necessary to consider whether or not the crack is easily extended from the modified field 7a (7m) toward the c-plane direction, so that the crack can be easily extended from the modified field 7a (7m) toward the thickness direction of the SiC substrate 12. The incident light is irradiated onto the object 1 to be processed. Further, in the preliminary reforming field 7p, it is not necessary to function as a cutting start point (i.e., to promote the stretching of the crack from the preliminary reforming field 7p toward the thickness direction of the SiC substrate 12), and it is difficult to crack the SiC substrate 12 Since the laser light L is formed by irradiation, it is possible to easily suppress the crack from extending from the preliminary reforming field 7p toward the c-plane direction in the formation of the preliminary reforming field 7p. Therefore, the plate-shaped object to be processed including the hexagonal Sic substrate 12 having the principal surface having the off-angle of the c-plane is accurately cut by 0 along the line to cut 5a (5 m) and In the case where the reforming field 7a (7 m) is formed, when the light collecting point P of the laser light L is focused on a laser light incident surface of the SiC substrate 12, that is, a predetermined distance from the surface 12a, in the field of preliminary reforming, 7p At the time of formation, it is preferable to focus the light collecting point p of the laser light L at the same distance from the surface i2a. Thus, it is possible to more reliably suppress the crack from extending from the modified field 7a (7m) toward the c-plane. Further, while the preliminary modified region 7p is formed inside the SiC substrate 12 along each of the preliminary lines 5p, the cut line 5a (5m) set between the preliminary lines 5p is inside the SiC substrate 12. When the modified field 7a (7 m) is formed, the stretching of the c-plane rupture can be suppressed by the preparatory modification field 7p. In this case, for the formation of the modified region 7a (7m) along the line to cut 5a (5m), the formation of the preliminary modified region 7p along the preliminary line 5p is preferably advanced. [Industrial Applicability] According to the present invention, it is possible to provide a plate-shaped object to be processed having a hexagonal Si c substrate including a principal surface having an off-angle with the c-plane, and to have an accuracy along the line to be cut. Cut off the ground. [Simplified description of the drawings] [Fig. 1] A configuration diagram of the laser processing apparatus used in the field of reforming -29-201242700. [Fig. 2] A plan view of an object to be processed before laser processing. [Fig. 3] A cross-sectional view taken along line III-III of the object to be processed in Fig. 2 . [Fig. 4] A plan view of an object to be processed after laser processing. [Fig. 5] A cross-sectional view taken along the line V-V of the object to be processed in Fig. 4. [Fig. 6] A cross-sectional view taken along line VI-VI of the object to be processed in Fig. 4. [Fig. 7] Fig. 7 is a plan view of an object to be processed which is an object of the laser processing method according to the embodiment of the present invention. [Fig. 8] A view showing the crystal structure of the object to be processed in Fig. 7. [Fig. 9] A partial cross-sectional view of the object to be processed in Fig. 7. [Fig. 10] A partial cross-sectional view of an object to be processed which is carried out by a laser processing method according to an embodiment of the present invention. [Fig. 11] A partial cross-sectional view of an object to be processed which is carried out by a laser processing method according to an embodiment of the present invention. [Fig. 1] A partial cross-sectional view of the object to be processed carried out by the laser processing method according to the embodiment of the present invention. [Fig. 1 3] A partial cross-sectional view of an object to be processed which is carried out by a laser processing method according to an embodiment of the present invention. [Fig. 14] Fig. 14 is a view showing a photograph of a cut surface of a SiC substrate to be cut by a laser processing method according to an embodiment of the present invention. [Fig. 15] Fig. 15 is a view showing a photograph of a cut surface of a SiC substrate cut by a laser processing unit according to an embodiment of the present invention. [Fig. 16] Fig. 16 is a plan view showing a plan view of a SiC substrate cut by a laser processing method according to an embodiment of the present invention. -30- 201242700 [Fig. 17] A perspective view for explaining c-plane cracking occurring inside the SiC substrate. [Fig. 18] A view showing a photograph of a cut surface of a SiC substrate in which c-plane cracking occurs. [Fig. 19] A table showing the relationship between the pulse width, the ID threshold, the HC threshold, and the processing limit. [Fig. 20] A table showing the relationship between the pulse pitch, the ID threshold, the HC threshold, and the processing limit. [Fig. 2] A table showing the experimental results of the processing limits of the pulse width and the pulse pitch. [Fig. 22] A table showing the experimental results of the processing limits of the pulse width and the pulse pitch. [Fig. 23] A table showing the experimental results of the processing limits of the pulse width and the pulse pitch. [Fig. 24] A graph showing the relationship between the pulse pitch and the HC threshold. [Fig. 25] A graph showing the relationship between the pulse pitch and the id threshold. [Fig. 26] A graph showing the relationship between the pulse pitch and the machining limit. [Fig. 27] A table showing the experimental results of the processing limits of the pulse width and the pulse pitch. [Fig. 28] A table showing the experimental results of the processing limits of the pulse width and the pulse pitch. [Fig. 29] A table showing the experimental results of the processing limits of the pulse width and the pulse pitch. [Fig. 30] A graph showing the relationship between the pulse pitch and the hc threshold. -31 - 201242700 [Fig. 3 1] A table showing the experimental results of the processing limits of HC quality in the vicinity of the incident surface of the laser light. [Fig. 32] A table showing experimental results of processing limits of HC quality in the vicinity of the incident surface of the laser light. [Fig. 33] A table showing experimental results of processing limits of HC quality in the vicinity of the incident surface of the laser light. [Fig. 4] A plan view for explaining a laser processing method according to another embodiment of the present invention. [Description of main component symbols] 1 : Object to be processed 3 : Surface 5 : Cut line 5a ' 5m : Cut line 5p : Preliminary line 6 : Pulse pitch 6a : Orientation plane 6 m : Orientation plane 7 : Modification area 7a , 7m : modification field 7p : preparatory modification field 8 : cutting starting point field 1 〇: pulse spacing 12 : SiC substrate 32 - 201242700 1 2a : surface (main surface) 1 2b : back surface (main surface) 2 3 : Telescopic tape 40: Spot light spot position 4 1 : Blade edge 1 0 0 : Laser processing device 1 0 1 : Laser light source 102 : Laser light source control unit 1 〇 3 : Dichroic mirror 105 : Light collecting lens 107 : Support table 1 1 1 : Stage 1 1 5 : Stage control unit L: Laser light P: Light collecting point -33-