471062 經濟部中央標準局員工消費合作社印製 A7 B7 五、發明説明（1 ) 〔發明之技術領域〕 本發明係有關能有效地使鹼溶液中之金屬雜質離子形 成離子化或除去之鹼溶液的純化方法及使用該純化後之鹼 溶液蝕刻半導體晶圓且不會使品質劣化之半導體晶圓之蝕 刻方法。 〔相關技術〕 一般，半導體晶圓之製造方法具有以下的步驟；將(£) 一.、 ，，.. /ΐ晶舞置所拉晶之單晶晶錠切片)得到薄圓板狀晶圓的 步驟；爲了防止依該切片步驟製得之晶圓龜裂或缺損而將 其外圓緣部進行磁Θ之倒角步良；將倒角後之晶圓ϋ灰 晶圓平面化之g磨步驟；將倒角及研磨後之晶圓上所殘留 之加工變形予以除去之驟；研磨蝕刻後之晶圓面之 研磨步驟；及洗淨被研磨後之晶圓去除附著在晶圓上之研 磨劑或異物的洗淨争驟。 前述蝕刻步驟之蝕刻處理有使用混酸（氟酸，硝酸， 醋酸之混合液）等之酸蝕刻液的酸蝕刻，及使用氫氧化鈉 溶液等之鹼蝕刻液的鹼蝕刻。 上述之酸蝕刻之蝕刻速度快，很難將晶圓均勻蝕刻， 使晶圓不平坦。因此最近常使用鹼蝕刻（使用氫氧化鈉溶 液，氫氧化鉀溶液，烷基氫氧化銨溶液等）即使蝕刻速度 慢也能均勻蝕刻，因此不會影響晶圓的平坦度。 上述之半導體晶圓之鹼蝕刻可直接使用金屬雜質濃度 高之市售的工業用鹼溶液。一般用之工業級之鹼溶液中當 本紙張尺度適用中國國家標準（CNS ) A4規格（210 X 297公釐） n^i In— ^1^11 (請先閱讀背面之注意事項再填寫本頁) 、11 _ 4 - 471062 A7 B7 五、發明説明（2 ) 然含有許多金屬雜質，但目前即使半導體晶圓蝕刻用之電 子工業用等級之鹼溶液也含有數十p pm〜數p pm的金 屬雜質。 鹼溶液中所含之金屬雜質有鎳，鉻，鐵，銅，鹼溶液 之製造步驟所使用的不銹鋼材料特別是含有許多鎳，鉻， 以往使用含有這些金屬雜質之鹼溶液蝕刻半導體晶圓 時，這些金屬雜質僅污染晶圓表面。故蝕刻後以酸洗淨充 分除去附著於晶圓表面之金屬雜質，因此熟悉該項技藝者 之常識判斷鹼蝕刻溶液中之金屬雜質對於晶圓品質不會有 很大的影響。 本發明人等長久以來研究鹼蝕刻步驟。依據最近本發 明人等的研究結果得知與前述之熟悉該項技藝者的常識判 斷不同發現鹼蝕刻溶液中之銅，鎳等之一部分之金屬雜質 的金屬離子在鹼蝕刻中竟然會擴散至晶圓內部深處，降低 晶圓品質，明顯降低以該晶圓所形成之半導體裝置的特性 〇 經濟部中央標準局員工消費合作社印製 (請先閲讀背面之注意事項再填寫本頁) 爲了防止如上述因鹼蝕刻溶液所造成之晶圓品質劣化 而考慮使用高純度之鹼溶液。但是市售之高純度的鹼溶液 極昂貴僅作爲分析用等級的鹼溶液，成本上完全不符合工 業上使用。 〔本發明要解決的問題〕 本發明人等精心研究解決上述以往技術的問題點，結 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐） -5 一 471062 A7 __B7_ 五、發明説明（3 ) 果驚人的發現以簡單的方法使鹼溶液中之金屬雜質離子形 成非離子化，同時使用已將這些金屬離子形成非離子化或 除去金屬離子的鹼溶液蝕刻半導體晶圓時，即使物理上有 金屬雜質但不會使晶圓品質劣化，遂完成本發明。 本發明係提供一種鹼溶液之純化方法，其特徵係能夠 …一-一 一----一·一-Ό . 以低成本且極有效地使鹼溶液中之金屬雜質，特別是金屬 離子形成非離子化，及提供一種使用此純化後之鹼溶液蝕 刻半導體晶圓且不會使品質劣化之半導體晶圓之蝕刻方法 〔解決問題的手段〕 爲了解決上述問題，本發明之鹼溶液之純化方法的第 1形態，其特徵係將金屬矽/或矽化合物溶解於鹼溶液中 利用此時所產生的氫或矽酸鹽等的反應生成物使鹼溶液中 之金屬離子形成非離子化。 上述金屬矽有多晶矽及單晶矽，這些可單獨使用或混 合使用。 經濟部中央標準局員工消費合作社印製 (請先闖讀背面之注意事項再填寫本頁) 上矽化合物有二氧化矽及矽酸鹽，這些可單獨使用或 混合使用。 對於上述金屬矽的溶解量無特別限制，又要能達到本 發明的效果即可，但以0 . 2 g / ί以上較理想。溶解量 太低時無法充分達到本發明的效果，溶解量太多時也不經 濟。 對於上述矽化合物的溶解量只要能達到本發明的效果 本紙張尺度適用中國國家標準（CNS ) Α4規格（210X297公釐） -6 - 471062 A7 B7 五、發明説明（4 ) 而無特別限定，但以含S i重量爲5 g / ί以上較理想。 此溶解量太少時無法充分達到本發明的效果，溶解量太多 時也不經濟。 本發明之鹼溶液之純化方法的第2形態，其特徵係將 氫氣體溶於鹼溶液中，使鹼溶液中之金屬離子還原形成非 離子化。 本發明之半導體晶圓之蝕刻方法的第1形態，其特徵 係將鹼溶液中之金屬離子形成非離子化來進行鹼溶液之純 化處理，使用此純化處理後之鹼溶液蝕刻半導體晶圓。 上述鹼溶液之純化處理可使用前述各種形態之鹼溶液 的純化方法。 本發明之半導體晶圓之蝕刻方法的第2形態，其特徵 係除去鹼溶液中之金屬離子，再使用經除去金屬離子之鹼 溶液蝕刻半導體晶圓。 上述金屬離子之除去處理可利用離子交換樹脂，特別 是螯合樹脂。 本發明使用的鹼溶液無特別限制，可使用以往廣被使 經濟部中央標準局員工消費合作社印製 (請先閲讀背面之注意事項再填寫本頁) 用半導體晶圓之鹼蝕刻液之氫氧化鈉溶液或氫氧化鉀溶液 〇 本發明中被非離子化或被除去之鹼溶液中之雜質金屬 離子有鎳離子，銅離子，鉻離子，鐵離子等，其中特別是 對於矽結晶中擴散速度快的鎳離子及銅離子形成非離子化 或予以除去，這對半導體晶圓的品質很重要。 本發明之半導體晶圓之蝕刻用之鹼溶液中的金屬離子 本姑「張尺度適用中國國家標準（CNS ) Α4規格（210X297公釐）-7 - 471062 A7 __B7 五、發明説明（5 ) 濃度宜限定爲50ppb以下，理想爲2〇ppb以下， 更理想爲1 Ο P P b以下，這種濃度限定能更容易達成本 發明的效果。 (請先聞讀背面之注意事項再填寫本頁) 本發明所謂之鹼溶液之純化係指將鹼溶液中之雜質金 屬離子形成非離子化或予以除去的意思。雜質金屬在鹼溶 液中即使以物理方式或固態存在，只要不以金屬離子狀態 存在時即是本發明所指的純化狀態。即，鹼溶液中即使含 有固體之雜質金屬，只要不含雜質金屬離子就不會因半導 體晶圓之蝕刻而降低晶圓之品質。相反地，鹼溶液中完全 不含固體之雜質金屬而含有金屬離子時，使用此鹼溶液蝕 刻半導體晶圓時會降低晶圓品質。 換言之，本發明係由下述3發明成果所構成的，①發 現鹼溶液中含有雜質金屬離子會嚴重影響鹼蝕刻之半導體 晶圓的品質，②發現極簡便的方法作爲鹼溶液中之金屬離 子之非離子化等的純化方法，③發現使用該純化之鹼溶液 蝕刻半導體晶圓不會影響晶圓的品質。 經濟部中央標準局員工消費合作社印製 〔實施例〕 以下舉實施例具體說明本發明。 實施例1 :多晶矽之氫氧化鈉溶液的高純度化 氫氧化鈉溶液（45%，20)2，80°C)中投入 2 0 0 g之半導體等級的粒狀多晶矽，分別在投入前，投 入後10分鐘，20分鐘，30分鐘，60分鐘各採取 ( CNS ) ( 210X297^ ) - 8 ~ 471062 經濟部中央標準局員工消費合作社印製 A7 __B7_______五、發明説明（6 ) 1 Omi氫氧化鈉溶液，稀釋成4 5倍，以離子色譜法分 析鐵離子及鎳離子的濃度。結果如圖1所示。由圖1得知 鐵離子，鎳離子皆減少，特別是鎳離子減少許多或被非離 子化。圖中N . D .係檢測下限的符號。 實施例2 :單晶矽之氫氧化鈉溶液的高純度化 氫氧化鈉溶液（45%，20义，80°C)中投入 1 0片之2 0 Omm#之單晶矽晶圓，分別在投入前，投 入後10分鐘，20分鐘，30分鐘，40分鐘，60分 鐘各採取1 Omj?氫氧化鈉溶液，稀釋成4 5倍，以離子 色譜法分析鐵離子及鎳離子的濃度。結果如圖2所示。由 圖2得知鐵離子，鎳離子皆減少，特別是鎳離子減少許多 或被非離子化β 實施例3 :多晶矽之氫氧化鈉溶液的高純度化 氫氧化鈉溶液（45%，20J? ，80°C)中投入 2 0 0 g之半導體等級粒狀多晶矽，分別在投入前，投入 1分鐘後各採取1 Omj?且回收已投入之多晶矽，將氫氧 化鈉溶液稀釋成4 5倍，以離子色譜法分析。測定多晶矽 的重量算出溶解量。上述的實驗分別進行3分鐘，5分鐘 ，1 0分鐘。結果如圖3所示。由圖3得知僅以多晶矽之 少量溶解則氫氧化鈉溶液中的鎳離子量急速減少。 實施例4 :使用二氧化矽之氫氧化鈉溶液之高純度化 本^張尺度適用中國國家標準（CNS ) A4規格（210X297公釐）-9 - " (請先閱讀背面之注意事項再填寫本頁) -裝- 訂 ▼線 471062 A7 B7 — ~~ 五、發明説明（） 將1重量％之二氧化矽溶解於氫氧化鈉溶液（4 5% ，2P，25°C)中，一次採取l〇mi?之氫氧化鈉溶液 稀釋成4 5倍，使用離子色譜法分析。與二氧化矽溶解前 比較，結果如圖4所示。如圖4的結果得知添加二氧化矽 可大幅降低鎳離子濃度及鐵離子濃度。 實施例5:使用矽酸鹽之氫氧化鈉溶液之高純度化 添加各種濃度之矽酸鈉（Na2S i 〇3 )於氫氧化 鈉溶液（45%，2芡，25 °C)中，分別採取10m又 之氫氧化鈉溶液並稀釋成4 5倍，使用離子色譜法分析。 結果如圖5所示。如圖5的結果得知添加矽酸鹽使氫氧化 鈉溶液中之矽酸鹽（S i 0 32-)離子濃增加而可大幅降 低鎳離子濃度。 實施例6:使用氫氣體之氫氧化鈉溶液之高純度化 經濟部中央標準局員工消費合作社印製 (請先閱讀背面之注意事項再填寫本頁) 將氫氣體以0. 5i2/min吹入氫氧化鈉溶液（ 45%，20$，25 °C)中，將分別在實驗前及20小 時後採取1 Omj?之氫氧化鈉溶液稀釋成4 5倍，使用離 子色譜法分析鐵離子及鎳離子。結果如圖6所示。如圖6 的結果得知鐵離子，鎳離子皆降低，特別是鎳離子去效果 佳。 實施例7 :利用多晶矽所純化之氫氧化鈉溶液進行蝕刻 將2 0 〇 g之半導體等的粒狀矽晶矽投入氫氧化鈉溶 本紙張尺度適用中國國家標準（CNS)A4規格（210Χ297公釐）-10 - 47106 2 經濟部中央標準局員工消費合作社印製 A7 B7 五、發明説明（） 液（4 5 %，2 0艾，8 0 °C 0中，放置1小時後將晶圓 蝕刻，然後測定晶圓之污染量。實驗條件如下。 實驗條件 試料CZP型<1〇〇>〇. 005〜0. 010Ω —cm 2〇〇1111110磨光晶圓 鹼蝕刻 氫氧化鈉溶液（4 5 %水溶液’溫度8 0 °C ’ 1 0分 鐘，多晶矽溶解液） 水洗（2 5 °C，3分鐘） 鹽酸過氯化氫水洗淨（8 0 °C，3分鐘） 水洗（2 5 °C，3分鐘） 乾燥（利用I P A蒸氣’ 8 1 5 °C，1分鐘） 實驗槽（共同使用） 尺寸（mm) 280X280X300H 容量 2 0文 材質石英 鹽酸過氧化氫溶液之組成：鹽酸水溶液：過氯化氫水 :水=1 : 1 : 1 0 (體積比），（鹽酸水溶液3 6重量 %，過氧化氫水3 0重量％) 如下述評價利用上述條件所蝕刻之晶圓。晶圓之單面 以噴砂處理，再以6 0 0 °C熱氧化後，利用氟酸氣將噴砂 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐）-11 - (請先閲讀背面之注意事項再填寫本頁) 裝· •項再填寫太 訂 471062 A7 B7 五、發明説明（） 處理那一面的熱氧化膜進行氣相分解，並以含氟酸之液滴 回收，利用ICP-MS(電感耦合等離子質量分析）法 分析。 結果如圖7所示，圖7也顯示利用未投入多晶矽之氫 氧化鈉溶液蝕刻時的結果。由圖7得知使用多晶矽溶解後 之氫氧化鈉溶液所蝕刻之晶圓上的鎳濃度大幅降低。 實施例8 :利用投入單晶矽所純化之氫氧化鈉溶液進行蝕 刻 將2 0 0 g之矽晶圓（單晶矽）投入氫氧化鈉溶液（ 45%，20$，80 °C)中，放置60分鐘後，以實施 例7的條件蝕刻晶圓，同實施例7的方法測量晶圓之污染 量。與矽晶圓溶解前比較，其結果如圖8所示。由圖8得 知使用砂晶圓溶解後之氫氧化鈉溶液所蝕刻之晶圓上的鎳 濃度大幅降低。 經濟部中央標準局員工消費合作社印製 (請先閲讀背面之注意事項再填寫本頁) 實施例9 :利用投入二氧化矽所純化之氫氧化鈉溶液進行 蝕刻 將2 0 0 g之二氧化矽投入氫氧化鈉溶液（4 5%， 2〇j?，80°C)中，放置60分鐘後，以實施例7的條 件蝕刻晶圓，同實施例7的方法測量晶圓之污染量。與二 氧化矽溶解前比較，其結果如圖9所示。由圖9得知使用 二氧化矽溶解後之氫氧化鈉溶液所蝕刻之晶圓上的鎳濃度 大幅降低。 本紙張尺度適用中國國家標準（CNS)A4規格（210X297公釐）_ 12 - 471062 A7 _____B7_ _ 五、發明説明（10 ) 實施例1 0 :利用矽酸鹽之溶解所純化的氫氧化鈉溶液進. 行蝕刻 添加各濃度之矽酸鈉（N a 2 S i 0 3 )於氫氧化鈉 溶液（4 5 %，2 $，2 5 °C )中，分別以實施例7的條 件蝕刻晶圓，以實施例7的方法測定晶圓的污染量。結果 如圖1 0所示。由圖1 0得知矽酸鹽的溶解量增加，隨著 矽酸鹽（S i 0 32-)離子濃度上昇所蝕刻之晶圓上的鎳 濃度大幅降低。 實施例1 1 :利用離子交換樹脂之氫氧化鈉溶液的高純度 化及蝕刻 使205之氫氧化鈉溶液（45%，25 °C)通過離 子交換樹脂（IRC — 718，Or gano (股）公司製螯合 樹脂的商品名）柱，予以循環（循環量2i?/min)， 在實驗前，循環30分鐘，60分鐘，24小時後分別採 取1 Omi?之氫氧化鈉溶液稀釋4 5倍，以離子色譜法分 析鐵離子及鎳離子的濃度。 經濟部中央標準局員工消費合作社印製 (請先閱讀背面之注意事項再填寫本頁) 結果如圖11所示。由圖11得知鐵離子、鎳離子皆 減少，特別是有效地除去鎳離子。使用此純化後之氫氧化 鈉溶液以實施例7的條件蝕刻晶圓，並以實施例7的方法 測量晶圓的污染量，得知晶圓上之鎳濃度大幅降低。 實施例12 :經鹼蝕刻之晶圓上之Ni ，Cu，Fe濃度 氫氧化鈉溶液中之濃度對應 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐13 _ ' 471062 經濟部中央標準局員工消費合作社印製 A7 B7 11 五、發明説明（） 試料CZP型<100>0. 005〜〇· 010Ω -cm 20〇mm彡磨光晶圓 實驗條件 鹼蝕刻 氫氧化鈉溶液（4 5 %水溶液，溫度8 0 °C ’ 1 0分 鐘） 水洗（2 5 °C，3分鐘） 鹽酸過氯化氫水洗淨（8 0 °C，3分鐘） 水洗（2 5 °C，3分鐘） 乾燥（利用IPA蒸氣，81. 5°C，1分鐘） 實驗槽（共同使用） 尺寸（mm)280X280X300H 容量 2 0又 材質 石英 鹽酸過氧化氫溶液之組成：鹽酸水溶液：過氯化氫水 ••水=1 ·· 1 ·· 1 0 (體積比），（鹽酸水溶液3 6重量 %，過氧化氫水3 0重量％) 晶圓上之金屬雜質之濃度之測定：晶圓之單面以噴砂 處理，再以6 0 0 °C熱氧化後，利用氟酸氣將噴砂處理那 一面的熱氧化膜進行氣相分解，並以含氟酸之液滴回收， 利用ICP-MS(電感耦合等離子質量分析）法分析。 氫氧化鈉溶液中之金屬離子濃度之測定：晶圓處理前 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐）_ 14 - l·---------------0—^------、訂----- (請先閱讀背面之注意事項再填寫本頁) 47106 經濟部中央標準局員工消費合作社印製 A7 B7 五、發明説明（12 ) 採取1 Omj?之氫氧化鈉溶液稀釋4 5倍，使用離子色譜 法分析。上述測定之各結果如圖1 2 (N i濃度），圖 13 (Cu濃度）及圖14 (Fe濃度）所示。由圖12 〜1 4得知氫氧化鈉溶液中之金屬濃度增加時晶圓上的金 屬濃度也增加，特別是N i及C u急速增加。 又氫氧化鈉溶液中之金屬濃度在1 0 p p b以下時， 得知晶圓上幾乎沒有金屬。若以5 0 p p b以下作爲氫 氧化鈉溶液中之金屬容許濃度時，晶圓上之金屬污染不會 太大，但理想爲2 0 p p b以下更理想爲1 〇 p p b以下 〇 〔發明的效果〕 如上述，依據本發明之鹼溶液的純化方法時，能以簡 單的操作及低成本來大幅降低鹼溶液中之金屬離子（鎳， 鐵，銅等）。又依據本發明之半導體晶圓的蝕刻方法時， 藉由降低金屬離子濃度的鹼溶液進行蝕刻可大幅降低因半 導體晶圓之蝕刻所造成的金屬污染量，不會影響晶圓品質 也不會降低半導體裝置的特性。 〔圖面之簡單說明〕 〔圖1〕 表示實施例1之多晶矽投入後的經過時間與氫氧化鈉 溶液中之鐵離子濃度及鎳離子濃度的關係圖。 〔圖2〕 本紙張尺度適用中國國家標準（CNS )八4規格（210X297公釐） ---i---L--.--Γ 衣-- (請先閱讀背面之注意事項再填寫本頁) -訂 -15 - 471062 A7 B7 五、發明説明（l3 ) 表示實施例2之單晶矽投人後之經過時間與氫氧化鈉 溶液中之鐵離子濃度及鎳離子濃度的關係圖。 〔圖3〕 表示實施例3之多晶矽的溶解量與氫氧化鈉溶液中的 鎳離子濃度的關係圖。 〔圖4〕 表示實施例4之二氧化矽溶解前後之氫氧化鈉溶液中 的鐵離子濃度及鎳離子濃度的關係圖。 〔圖5〕 表示實施例5之矽酸鹽添加濃度與氫氧化鈉溶液中之 鎳離子濃度的關係圖。 〔圖6〕 表示實施例6之吹入氫氣與氫氧化鈉溶液中之鐵離子 濃度及鎳離子濃度的關係。 〔圖7〕 經濟部中央標準局員工消費合作社印製 (請先閱讀背面之注意事項再填寫本頁) 表示使用實施例7之多晶矽純化之氫氧化鈉溶液進行 蝕刻及另外使用未純化之氫氧化鈉溶液進行蝕刻時之晶圓 上的鎳濃度圖。 〔圖8〕 表示使用實施例8之多晶矽純化之氫氧化鈉溶液進行 蝕刻及另外使用未純化之氫氧化鈉溶液進行蝕刻時之晶圓 上的鎳濃度圖。 〔圖9〕 表示使用實施例9之二氧化矽純化之氫氧化鈉溶液進 本紙張尺度適用中國國家標準（CNS ) A4規格（210X297公釐）10 -10 471062 經濟部中央標準局員工消費合作社印製 A7 ___B7_ ______ 五、發明説明（Η ) 行蝕刻及另外使用未純化之氫氧化鈉溶液進行蝕刻時之晶. 圓上的鎳濃度圖。 〔圖 1 0〕 表示使用實施例1 0之矽酸鹽純化之氫氧化鈉溶液進 行蝕刻及另外使用未純化之氫氧化鈉溶液蝕刻時之晶圓上 之鎳濃度圖。 〔圖 1 1〕 表示使用實施例11之離子交換樹脂之氫氧化鈉溶液 的高純度化中，氫氧化鈉溶液的循環時間與氫氧化鈉溶液 中之鐵離子，鎳離子的關係圖。 〔圖 1 2〕 表示實施例12之鹼蝕刻後之晶圓上的鎳濃度與氫氧 化鈉溶液中之鎳離子濃度的關係圖。 〔圖 1 3〕 表示實施例12之鹼蝕刻後之晶圓上的銅濃度與氫氧 氧 氫 與 度 濃 鐵. 的 上 圓 。 晶 。 圖之圖 係後係 關刻關 ^5 的 度鹼度 濃之濃 子 2 子 離 1 離 銅丨例鐵 之 4 施之 中 1 實中 液圖示液 溶ί 表溶 0 納 化 化 I.--^--.--^裝------訂------ (請先閱讀背面之注意事項再填寫本頁) 一準 標 一家 國 一國 中 用 適 度 尺 紙 I釐 公 7 9 2471062 A7 B7 printed by the Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs 5. Description of the Invention (1) [Technical Field of the Invention] The present invention relates to an alkali solution that can effectively form metal ion ions in an alkali solution to be ionized or removed. Purification method and etching method for semiconductor wafer using the purified alkali solution to etch semiconductor wafer without deteriorating quality. [Related Technology] Generally, the manufacturing method of a semiconductor wafer has the following steps; slice the single crystal ingot ((.) A ,,,, ...) to obtain a thin circular plate wafer In order to prevent cracks or defects in the wafer produced according to this slicing step, the outer edge of the wafer is chamfered with magnetic Θ. The milled surface of the chamfered wafer is polished. Steps; removal of chamfering and remaining processing distortion on the polished wafer; polishing step of polishing the wafer surface after etching; and cleaning the polished wafer to remove the polishing attached to the wafer Cleaning agent or foreign matter. The etching treatment in the aforementioned etching step includes acid etching using an acid etching solution such as a mixed acid (a mixture of hydrofluoric acid, nitric acid, and acetic acid), and alkali etching using an alkali etching solution such as a sodium hydroxide solution. The above acid etching has a fast etching speed, and it is difficult to etch the wafer uniformly, making the wafer uneven. Therefore, alkali etching (using sodium hydroxide solution, potassium hydroxide solution, alkyl ammonium hydroxide solution, etc.) is often used recently. Even if the etching speed is slow, it can uniformly etch, so it will not affect the flatness of the wafer. For the above-mentioned alkali etching of the semiconductor wafer, a commercially available industrial alkali solution having a high metal impurity concentration can be directly used. For industrial grade alkaline solutions, the paper size is in accordance with China National Standard (CNS) A4 (210 X 297 mm) n ^ i In— ^ 1 ^ 11 (Please read the precautions on the back before filling this page ), 11 _ 4-471062 A7 B7 V. Description of the invention (2) Although it contains a lot of metal impurities, currently, even the alkali solution used in the electronics industry for semiconductor wafer etching contains tens of p pm to several p pm of metal. Impurities. The metal impurities contained in the alkali solution include nickel, chromium, iron, copper, and the stainless steel materials used in the manufacturing process of the alkali solution, especially containing a lot of nickel and chromium. In the past, when a semiconductor wafer was etched using an alkali solution containing these metal impurities, These metal impurities only contaminate the wafer surface. Therefore, the metal impurities attached to the wafer surface are completely removed by acid cleaning after etching, so the common sense of the skilled person judges that the metal impurities in the alkaline etching solution will not have a great impact on the quality of the wafer. The present inventors have studied the alkali etching step for a long time. According to the recent research results of the present inventors, it is known that the metal ions of metal impurities such as copper and nickel in the alkali etching solution are different from the common sense judgment of the aforementioned skilled artist. The metal ions in the alkali etching solution will diffuse to the crystal. Deep inside the circle, the quality of the wafer is reduced, and the characteristics of the semiconductor device formed by the wafer are significantly reduced. Printed by the Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs (please read the precautions on the back before filling this page). It is considered to use a high-purity alkali solution for the above-mentioned wafer quality deterioration caused by the alkali etching solution. However, the commercially available high-purity alkaline solutions are extremely expensive and are only used as analytical-grade alkaline solutions, which is totally inconsistent with industrial use in terms of cost. [Problems to be Solved by the Invention] The present inventors have carefully studied and solved the above-mentioned problems in the prior art. The paper size of the paper is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) -5 471062 A7 __B7_ V. Description of the invention (3) It is surprisingly discovered that the metal impurity ions in the alkali solution are formed non-ionized in a simple way, and the semiconductor wafer is etched using an alkali solution that has been used to form the non-ionized or removed metal ions, even when physically There are metal impurities on the wafer but the quality of the wafer will not be deteriorated, and the present invention is completed. The invention provides a method for purifying an alkaline solution, which is characterized by being able to ...--one-one-one-Ό. The metal impurities, especially metal ions, in the alkaline solution can be formed at a low cost and extremely effectively. Non-ionization, and an etching method for etching a semiconductor wafer using the purified alkali solution without deteriorating the quality [Means for Solving Problems] In order to solve the above-mentioned problems, the method for purifying the alkali solution of the present invention The first aspect of the invention is characterized in that metal silicon and / or a silicon compound are dissolved in an alkali solution, and reaction products such as hydrogen or silicate generated at this time are used to deionize metal ions in the alkali solution. The above-mentioned metallic silicon includes polycrystalline silicon and single crystal silicon, and these can be used alone or in combination. Printed by the Consumer Cooperatives of the Central Bureau of Standards of the Ministry of Economic Affairs (please read the precautions on the back before filling out this page). The silicon compounds on this page include silicon dioxide and silicates. These can be used alone or in combination. There is no particular limitation on the amount of dissolution of the above-mentioned metal silicon, and the effects of the present invention may be achieved, but it is preferably 0.2 g / L or more. When the amount of dissolution is too low, the effects of the present invention cannot be fully achieved, and when the amount of dissolution is too large, it is not economical. As long as the dissolved amount of the above-mentioned silicon compound can achieve the effect of the present invention, the paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) -6-471062 A7 B7 5. The invention description (4) is not particularly limited, but It is more preferable to contain S i with a weight of 5 g / ί or more. When the amount of dissolution is too small, the effect of the present invention cannot be sufficiently achieved, and when the amount of dissolution is too large, it is not economical. A second aspect of the method for purifying an alkali solution of the present invention is characterized in that hydrogen gas is dissolved in an alkali solution, and metal ions in the alkali solution are reduced to form non-ionization. The first aspect of the etching method of a semiconductor wafer according to the present invention is characterized in that metal ions in an alkali solution are formed into non-ionized form to perform a purification treatment of the alkali solution, and the alkali solution after the purification treatment is used to etch the semiconductor wafer. For the purification treatment of the alkaline solution, a method for purifying the alkaline solution of the aforementioned various forms can be used. A second aspect of the etching method of a semiconductor wafer according to the present invention is characterized in that metal ions are removed from an alkali solution, and the semiconductor wafer is etched using the alkali solution from which the metal ions have been removed. The removal of the metal ions can be performed using an ion exchange resin, particularly a chelating resin. The alkali solution used in the present invention is not particularly limited, and can be printed by the consumer cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs (please read the precautions on the back before filling this page). Hydroxide for alkaline etching solution of semiconductor wafers Sodium solution or potassium hydroxide solution. The impurity metal ions in the non-ionized or removed alkali solution in the present invention are nickel ions, copper ions, chromium ions, iron ions, etc., among which the diffusion rate is fast especially for silicon crystals. The formation of non-ionized or removed nickel ions and copper ions is important to the quality of semiconductor wafers. The metal ions in the alkaline solution used for etching the semiconductor wafer of the present invention are "the scale is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) -7-471062 A7 __B7 V. Description of the invention (5) The concentration should be appropriate" It is limited to 50 ppb or less, preferably 20 ppb or less, and more preferably 10 pp b or less. This concentration limitation can more easily achieve the effect of the invention. (Please read the precautions on the back before filling out this page) The present invention The so-called purification of an alkali solution means that the impurity metal ions in the alkali solution are formed non-ionized or removed. Even if the impurity metal exists physically or solidly in the alkali solution, as long as it does not exist in the state of metal ions The purification state referred to in the present invention means that even if a solid impurity metal is contained in the alkali solution, as long as the impurity metal ion is not contained, the quality of the wafer will not be lowered by the etching of the semiconductor wafer. On the contrary, the alkali solution is completely free from impurities. When solid impurity-containing metals and metal ions are contained, the use of this alkali solution to etch semiconductor wafers will degrade wafer quality. In other words, the present invention is based on the following 3 According to the results of the research, ① found that impurity metal ions contained in the alkali solution would seriously affect the quality of semiconductor wafers etched by alkali, ② found a very simple method as a purification method such as non-ionization of metal ions in the alkali solution, ③ It was found that etching the semiconductor wafer using the purified alkali solution will not affect the quality of the wafer. Printed by the Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs [Example] The following examples are used to illustrate the present invention in detail. Example 1: Hydrogenation of polycrystalline silicon 200 g of semiconductor-grade granular polycrystalline silicon was charged into a high-purity sodium hydroxide solution of sodium solution (45%, 20) (2, 80 ° C), before the investment, 10 minutes, 20 minutes, 30 minutes Minutes, 60 minutes each (CNS) (210X297 ^)-8 ~ 471062 A7 __B7_______ printed by the Consumer Cooperatives of the Central Standards Bureau of the Ministry of Economic Affairs 5. Description of the invention (6) 1 Omi sodium hydroxide solution, diluted 4 to 5 times, Ion chromatography was used to analyze the concentration of iron ions and nickel ions. The results are shown in Figure 1. According to Figure 1, it is known that iron ions and nickel ions are reduced, especially nickel ions are greatly reduced or non-ionized. In the figure, N.D. is the symbol of the lower limit of detection. Example 2: 10 tablets of high-purity sodium hydroxide solution (45%, 20%, 80 ° C) of single crystal silicon sodium hydroxide solution For single crystal silicon wafers of 20 Omm #, before the input, 10 minutes, 20 minutes, 30 minutes, 40 minutes, and 60 minutes, respectively, take 1 Omj? Sodium hydroxide solution, dilute it 4 to 5 times, and Ion chromatography analysis of the concentration of iron ions and nickel ions. The results are shown in Figure 2. From Figure 2, it is known that iron ions and nickel ions are reduced, especially nickel ions are reduced a lot or are non-ionized β Example 3: Polycrystalline silicon 200 g of semiconductor-grade granular polycrystalline silicon was added to a high-purity sodium hydroxide solution (45%, 20J ?, 80 ° C) of sodium hydroxide solution, and 1 Omj? And the recovered polycrystalline silicon was recovered, and the sodium hydroxide solution was diluted to 4 to 5 times, and analyzed by ion chromatography. The weight of the polycrystalline silicon was measured to calculate the dissolved amount. The above experiments were performed for 3 minutes, 5 minutes, and 10 minutes, respectively. The results are shown in Figure 3. From Fig. 3, it is understood that the amount of nickel ions in the sodium hydroxide solution decreases rapidly only with a small amount of polycrystalline silicon being dissolved. Example 4: High purity using sodium hydroxide solution of silicon dioxide This standard is applicable to China National Standard (CNS) A4 specification (210X297 mm) -9-" (Please read the precautions on the back before filling (This page)-Installation-Binding ▼ Line 471062 A7 B7 — ~~ V. Description of the invention () Dissolve 1% by weight of silicon dioxide in sodium hydroxide solution (4 5%, 2P, 25 ° C), and take it once 10 mi? of sodium hydroxide solution was diluted 4 to 5 times, and analyzed by ion chromatography. The results are shown in Fig. 4 when compared with before the dissolution of silicon dioxide. The results shown in Figure 4 show that the addition of silicon dioxide can significantly reduce the nickel ion concentration and iron ion concentration. Example 5: Use of high purity of sodium silicate solution of sodium silicate, add various concentrations of sodium silicate (Na2Sio3) to sodium hydroxide solution (45%, 2 芡, 25 ° C), respectively 10m sodium hydroxide solution was diluted 4 to 5 times and analyzed by ion chromatography. The results are shown in Figure 5. The results shown in Figure 5 show that the addition of silicate increases the concentration of silicate (S i 0 32-) ions in the sodium hydroxide solution and can significantly reduce the nickel ion concentration. Example 6: Printed by the Consumer Cooperatives of the Central Standards Bureau of the Ministry of Economic Affairs with high purity using sodium hydroxide solution of hydrogen gas (please read the precautions on the back before filling this page) The hydrogen gas is blown in at 0.5i2 / min In sodium hydroxide solution (45%, 20 $, 25 ° C), the sodium hydroxide solution of 1 Omj? Was diluted 4 to 5 times before and 20 hours after the experiment, respectively, and iron ions and nickel were analyzed by ion chromatography. ion. The results are shown in Figure 6. As can be seen from the results in Fig. 6, both iron ions and nickel ions are reduced, and nickel ion removal effect is particularly good. Example 7: Etching using a sodium hydroxide solution purified by polycrystalline silicon, 200 g of granular silicon crystals such as semiconductors were put into sodium hydroxide, and the paper size was in accordance with Chinese National Standard (CNS) A4 (210 × 297 mm) ) -10-47106 2 A7 B7 printed by the Consumer Cooperatives of the Central Bureau of Standards of the Ministry of Economic Affairs 5. Description of the invention () liquid (45%, 20 Ai, 80 ° C 0), the wafer is etched after being left for 1 hour, Then the amount of contamination of the wafer was measured. The experimental conditions were as follows. Experimental conditions Sample CZP < 1〇〇 > 005 ~ 0. 010Ω-cm 2 001111110 Polished wafer alkaline etching sodium hydroxide solution (4 5 % Aqueous solution 'temperature 8 0 ° C' 10 minutes, polycrystalline silicon solution) Wash with water (25 ° C, 3 minutes) Wash with hydrochloric acid hydrogen chloride (80 ° C, 3 minutes) Wash with water (2 5 ° C, 3 Minutes) Drying (using IPA vapor '8 1 5 ° C, 1 minute) Experiment tank (common use) Size (mm) 280X280X300H Capacity 20 Quartz Hydrochloric acid hydrogen peroxide solution Composition: hydrochloric acid aqueous solution: hydrogen chloride water: water = 1: 1: 1 0 (volume ratio), (aqueous hydrochloric acid solution 3 6 % By weight, 30% by weight of hydrogen peroxide water) The wafers etched using the above conditions were evaluated as described below. One side of the wafer was blasted, and then thermally oxidized at 600 ° C, then blasted with fluoric acid gas. This paper size applies Chinese National Standard (CNS) A4 specification (210X297 mm) -11-(Please read the precautions on the back before filling this page) Installation · • Item and then fill out too much 471062 A7 B7 V. Description of the invention () The thermally oxidized film on the other side was processed for gas phase decomposition, and was recovered as droplets containing fluoric acid, and analyzed by ICP-MS (Inductively Coupled Plasma Mass Analysis) method. The results are shown in FIG. 7 and FIG. Results of etching of polycrystalline silicon with a sodium hydroxide solution. From FIG. 7, it can be seen that the concentration of nickel on the wafer etched by using the sodium hydroxide solution after the polycrystalline silicon is dissolved is greatly reduced. Example 8: Hydrogen purified by using single crystal silicon Etching with a sodium oxide solution Put a 200 g silicon wafer (single-crystal silicon) into a sodium hydroxide solution (45%, 20 $, 80 ° C), and leave it for 60 minutes, and then etch the crystal under the conditions of Example 7. Round, same as in Example 7 The amount of contamination. The results are compared with those before the silicon wafer was dissolved, and the results are shown in Fig. 8. From Fig. 8, it is known that the concentration of nickel on the wafer etched using the sodium hydroxide solution after the sand wafer is dissolved has been greatly reduced. Printed by the Consumer Bureau of Standards Bureau (please read the precautions on the back before filling this page). Example 9: Use sodium hydroxide solution purified by adding silicon dioxide for etching. Put 200 g of silicon dioxide into the hydroxide. After being left in a sodium solution (45%, 20 ° C, 80 ° C) for 60 minutes, the wafer was etched under the conditions of Example 7 and the amount of contamination of the wafer was measured in the same manner as in Example 7. The results are shown in Fig. 9 compared with those before the silica was dissolved. It can be seen from FIG. 9 that the nickel concentration on the wafer etched by using the sodium hydroxide solution after the silicon dioxide is dissolved is greatly reduced. This paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) _ 12-471062 A7 _____B7_ _ V. Description of the invention (10) Example 10 0: Purified sodium hydroxide solution by dissolution of silicate . Adding each concentration of sodium silicate (N a 2 S i 0 3) to a sodium hydroxide solution (45%, 2 $, 25 ° C) for etching, and etching the wafer under the conditions of Example 7, respectively. The amount of wafer contamination was measured by the method of Example 7. The results are shown in Figure 10. It can be seen from FIG. 10 that the dissolution amount of the silicate increases, and the nickel concentration on the etched wafer decreases with the increase of the silicate (S i 0 32-) ion concentration. Example 11 1: Purification and etching of sodium hydroxide solution of ion exchange resin was used to pass 205 sodium hydroxide solution (45%, 25 ° C) through an ion exchange resin (IRC — 718, Organo Co., Ltd.) Chelating resin (trade name) column was circulated (circulation volume 2i? / Min). Before the experiment, it was circulated for 30 minutes, 60 minutes, and after 24 hours, it was diluted 4 to 5 times with 1 Omi sodium hydroxide solution. The concentration of iron ions and nickel ions was analyzed by ion chromatography. Printed by the Consumers' Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs (please read the precautions on the back before filling this page) The results are shown in Figure 11. It can be seen from FIG. 11 that both iron ions and nickel ions are reduced, and nickel ions are effectively removed particularly. The purified sodium hydroxide solution was used to etch the wafer under the conditions of Example 7, and the amount of contamination of the wafer was measured by the method of Example 7. It was found that the nickel concentration on the wafer was greatly reduced. Example 12: The concentration of Ni, Cu, and Fe in the sodium hydroxide solution on the alkali-etched wafer corresponds to the size of this paper. The Chinese National Standard (CNS) A4 specification (210X297 mm 13 _ '471062 Central Standard of the Ministry of Economic Affairs Printed by the Consumer Cooperative of the Bureau A7 B7 11 V. Description of the invention () Sample CZP < 100 > 0.005 ~ 〇. 010Ω -cm 20〇mm Honed polished wafer Experimental conditions Alkaline etching sodium hydroxide solution (4 5 % Aqueous solution, temperature 80 ° C '10 minutes) Wash with water (2 5 ° C, 3 minutes) Wash with hydrochloric acid hydrogen chloride (80 ° C, 3 minutes) Wash with water (2 5 ° C, 3 minutes) Dry ( Using IPA vapor, 81.5 ° C, 1 minute) Experimental tank (commonly used) Size (mm) 280X280X300H Capacity 20 Composition of quartz hydrochloric acid hydrogen peroxide solution: hydrochloric acid aqueous solution: hydrogen chloride water •• water = 1 · · 1 · · 10 (volume ratio), (36% by weight of hydrochloric acid in water, 30% by weight of hydrogen peroxide in water) Determination of the concentration of metal impurities on the wafer: One side of the wafer is sandblasted, and then After thermal oxidation at 6 0 ° C, the side is sandblasted with fluoric acid gas Thermally oxidized film is decomposed in the gas phase, recovered as droplets containing fluoric acid, and analyzed by ICP-MS (Inductively Coupled Plasma Mass Analysis). Measurement of metal ion concentration in sodium hydroxide solution: this paper before wafer processing The scale is applicable to China National Standard (CNS) A4 specification (210X297 mm) _ 14-l · --------------- 0 — ^ ------, order ---- -(Please read the precautions on the back before filling out this page) 47106 Printed by the Consumer Standards Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the invention (12) Dilute 4 5 times with 1 Omj? Sodium hydroxide solution, use ion Chromatographic analysis. The results of the above measurements are shown in Fig. 12 (Ni concentration), Fig. 13 (Cu concentration), and Fig. 14 (Fe concentration). The metals in the sodium hydroxide solution are known from Figs. 12 to 14. When the concentration increases, the metal concentration on the wafer also increases, especially Ni and Cu increase rapidly. When the metal concentration in the sodium hydroxide solution is below 10 ppb, it is found that there is almost no metal on the wafer. If 5 When the allowable concentration of metal in sodium hydroxide solution is less than 0 ppb, the metal contamination on the wafer will not be too large, but It is desirable to be 20 ppb or less, and more preferably 10 ppb or less. [Effects of the Invention] As described above, according to the method for purifying an alkaline solution according to the present invention, metal ions in the alkaline solution can be greatly reduced with simple operation and low cost. (Nickel, iron, copper, etc.). In the etching method of the semiconductor wafer according to the present invention, the etching by reducing the concentration of metal ions to the alkali solution can greatly reduce the amount of metal contamination caused by the etching of the semiconductor wafer. Will affect the quality of the wafer without degrading the characteristics of the semiconductor device. [Brief description of the drawing] [Figure 1] A graph showing the relationship between the elapsed time after the polycrystalline silicon was introduced in Example 1 and the iron ion concentration and nickel ion concentration in the sodium hydroxide solution. [Figure 2] This paper size is applicable to China National Standard (CNS) 8-4 specifications (210X297 mm) --- i --- L --.-- Γ clothing-(Please read the precautions on the back before filling in this Page)--15-471062 A7 B7 V. Description of the Invention (l3) A graph showing the relationship between the elapsed time after the single crystal silicon was introduced in Example 2 and the iron ion concentration and nickel ion concentration in the sodium hydroxide solution. [Fig. 3] A graph showing the relationship between the amount of polycrystalline silicon dissolved in Example 3 and the nickel ion concentration in a sodium hydroxide solution. [Fig. 4] A graph showing the relationship between the iron ion concentration and the nickel ion concentration in the sodium hydroxide solution before and after the dissolution of the silicon dioxide in Example 4. [Fig. 5] A graph showing the relationship between the concentration of silicate added in Example 5 and the concentration of nickel ions in a sodium hydroxide solution. [Fig. 6] The relationship between the injected hydrogen gas and the iron ion concentration and the nickel ion concentration in the sodium hydroxide solution in Example 6 are shown. [Figure 7] Printed by the Consumer Cooperatives of the Central Bureau of Standards of the Ministry of Economic Affairs (please read the precautions on the back before filling out this page), indicating that the sodium hydroxide solution purified using polycrystalline silicon in Example 7 was used for etching and another unpurified hydroxide Graph of nickel concentration on the wafer when sodium solution is being etched. [Fig. 8] A graph showing the nickel concentration on the wafer when the polycrystalline silicon-purified sodium hydroxide solution of Example 8 was used for etching and the unpurified sodium hydroxide solution was used for etching. [Fig. 9] It is shown that the sodium hydroxide solution purified by silica in Example 9 was used as the standard for this paper to apply the Chinese National Standard (CNS) A4 specification (210X297 mm) 10 -10 471062 Printed by the Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs Preparing A7 ___B7_ ______ V. Description of the Invention (Η) Crystals when etching is performed and an unpurified sodium hydroxide solution is used for etching. The nickel concentration chart on the circle. [Fig. 10] A graph showing the nickel concentration on the wafer when the silicate-purified sodium hydroxide solution of Example 10 was used for etching and when the non-purified sodium hydroxide solution was used for etching. [Figure 11] A graph showing the relationship between the cycle time of the sodium hydroxide solution and the iron ions and nickel ions in the sodium hydroxide solution during the purification of the sodium hydroxide solution using the ion exchange resin of Example 11. [Fig. 12] A graph showing the relationship between the nickel concentration on the wafer after the alkali etching in Example 12 and the nickel ion concentration in the sodium hydroxide solution. [Fig. 1 3] The upper circle of the copper concentration, hydrogen, oxygen, hydrogen, and ferric iron on the wafer after the alkali etching in Example 12 is shown. Crystal. The picture shows the strong alkalinity of the strong strontium 2 with the degree of alkalinity 2 and the ionization 1 with the ionization 1 and the separation with copper 丨 Example 4 with iron 1 The solution in the solid solution shows the solution of the solution 表 The solution of the solution 0 The chemical solution I. -^ --.-- ^ pack ------ order ------ (Please read the precautions on the back before filling in this page) One standard one country and one country use moderate rule paper I centimeters 7 9 2