JP3577002B2 - Polishing liquid for copper-based metal - Google Patents

Description

【００３８】
前記表１から明らかなように研磨砥粒が添加された研磨液では、研磨砥粒が添加されない研磨液に比べてＣｕ膜の研磨速度を向上できることがわかる。また、研磨砥粒の種類を変えることによってＣｕ膜のポリシング速度を制御できることがわかる。
【００３９】
また、前記シリカ粒子およびアルミナ粒子をそれぞれ砥粒として添加された研磨液を図１に示すポリシング装置を用いて前述したのと同様な手順により基板に成膜されたＳｉＯ_２ 膜、Ｓｉ_３ Ｎ_４ 膜およびボロン添加ガラス膜（ＢＰＳＧ膜）の研磨処理をそれぞれ行った。各研磨液による各種絶縁膜のポリシング速度を下記表２に示す。なお、表２中の括弧内の値は（同種の研磨液でのＣｕ膜のポリシング速度／各絶縁膜のポリシング速度）から求めた速度比である。後述する半導体装置の製造時において絶縁膜の溝等に埋め込みＣｕ配線層を研磨処理により形成する際、前記速度比が大きい程、Ｃｕの選択ポリシング性を向上することが可能になる。つまり、下地の絶縁膜の膜減りを抑制できる。
【００４０】
【表２】

【００４１】
さらに、シリカ粒子のような研磨砥粒が添加された研磨液はＣｕ膜またはＣｕ合金膜の割れや微細な傷を生じることなく良好にポリシングすることができる。これは、図１に示すポリシング装置を用いた研磨工程においてＣｕ膜の研磨面と前記研磨パッドとの間の摩擦力を前記砥粒により緩和でき、Ｃｕ膜への衝撃力を低減して割れ等を防止することができるためである。
【００４２】
したがって、シリカ粒子のような研磨砥粒が添加された研磨液は研磨砥粒が添加されない研磨液に比べてＣｕまたはＣｕ合金のポリシング速度を向上できると共に研磨処理時におけるＣｕまたはＣｕ合金表面への損傷を抑制できる。
【００４３】
なお、有機酸がアミド硫酸で、シリカ粒子のような研磨砥粒を含む研磨液においても前記研磨砥粒が添加されない研磨液に比べてＣｕまたはＣｕ合金のポリシング速度を向上できると共に研磨処理時におけるＣｕまたはＣｕ合金表面への損傷を抑制できる。
【００４４】
本発明に係わる半導体装置の製造方法は、半導体基板上の絶縁膜に配線層の形状に相当する溝および／または開口部を形成する工程と、
前記溝および／または開口部を含む前記絶縁膜上にＣｕまたはＣｕ合金からなる配線材料膜を堆積する工程と、
アミノ酢酸およびアミド硫酸から選ばれる少なくとも１種の有機酸と酸化剤と水とを含有する研磨液を用いて前記配線材料膜を前記絶縁膜の表面が露出するまで研磨処理することにより前記絶縁膜にその表面と面一の埋め込み配線層を形成する工程と
を具備したことを特徴とするものである。
【００４５】
前記絶縁膜としては、例えばシリコン酸化膜、シリコン窒化膜、シリコン酸化膜とこの上に積層されたシリコン窒化膜の２層膜、ボロン添加ガラス膜（ＢＰＳＧ膜）、リン添加ガラス膜（ＰＳＧ膜）等を用いることができる。
【００４６】
前記Ｃｕ合金としては、例えばＣｕ−Ｓｉ合金、Ｃｕ−Ａｌ合金、Ｃｕ−Ｓｉ−Ａｌ合金、Ｃｕ−Ａｇ合金等を用いることができる。
【００４７】
前記ＣｕまたはＣｕ合金からなる配線材料膜は、スパッタ蒸着、真空蒸着等により堆積される。
【００４８】
前記研磨液中の有機酸の含有量、およびそれら有機酸および酸化剤の含有比率は、前述した銅系金属用研磨液と同様な範囲にすることが好ましい。
【００４９】
前記研磨液は、前記有機酸および酸化剤の他にｐＨを９〜１４に調節するアルカリ剤を含有することを許容する。このようなアルカリ剤としては、例えば水酸化カリウム、キノリンが好適である。
【００５０】
前記研磨液は、前記有機酸および酸化剤の他にシリカ粒子、アルミナ粒子、酸化セリウム粒子、ジルコニア粒子等の研磨砥粒を含有することを許容する。これらの研磨砥粒の平均粒径および添加量は前述した銅系金属用研磨液で説明したのと同様な範囲にすることが好ましい。
【００５１】
前記研磨液による研磨処理は、例えば前述した図１に示すポリシング装置が用いて行われる。
【００５２】
図１に示すポリシング装置を用いる研磨処理において、基板ホルダで保持された基板を前記研磨パッドに与える加重は研磨液の組成により適宜選定される。例えば、有機酸、酸化剤および水からなる組成の研磨液では前記加重を２００〜２０００ｇ／ｃｍ^２ にすることが好ましい。さらにシリカ粒子のような研磨砥粒を含む組成の研磨液では、前記加重を１５０〜１０００ｇ／ｃｍ^２ にすることが好ましい。
【００５３】
本発明に係わる半導体装置の製造において、前記半導体基板上の前記溝および／または開口部を含む前記絶縁膜には前記配線材料膜を堆積する前にバリア層を形成することを許容する。このようなバリア層を前記溝および／または開口部を含む前記絶縁膜に形成することによって、Ｃｕのような配線材料膜の堆積、エッチバックにより前記バリア層で囲まれた埋め込み配線層を形成することが可能になる。その結果、配線材料であるＣｕの拡散による半導体基板の汚染を防止できる。
【００５４】
前記バリア層は、例えばＴｉＮ、Ｔｉ、Ｎｂ、ＷまたはＣｕＴａ合金からなる。このようなバリア層は、１５〜５０ｎｍの厚さを有することが好ましい。
【００５５】
本発明に係わる半導体装置の製造において、前述した図１に示すポリシング装置の前記テーブルの回転トルクの変化、研磨パッドの温度変化、または研磨パッドに供給される前記研磨液のｐＨ変化、に基づいて前記研磨処理の終点を検出することを許容する。また、前述した図１に示すポリシング装置のホルダの回転トルクの変化に基づいて前記研磨処理の終点を検出することを許容する。このような方法によれば、研磨処理の終点を簡単に検出できる。その結果、この終点検出を利用することにより前記絶縁膜にその表面と面一の埋め込み配線層を確実に形成することができる。
【００５６】
以上説明した本発明に係わる半導体装置の製造方法は、半導体基板上の絶縁膜に配線層に相当する溝および／または開口部を形成し、前記溝および／または開口部を含む前記絶縁膜上にＣｕまたはＣｕ合金からなる配線材料膜を堆積し、さらにアミノ酢酸およびアミド硫酸から選ばれる少なくとも１種の有機酸と酸化剤と水とを含有する研磨液および例えば前述した図１に示すポリシング装置を用いて前記配線材料膜を前記絶縁膜の表面が露出するまで研磨する。前記研磨液は、既述したようにＣｕ膜またはＣｕ合金膜の浸漬時において前記Ｃｕ膜またはＣｕ合金膜を殆どエッチングせず、かつ浸漬時と研磨時との間で数倍ないし数十倍のエッチング速度差を示す。その結果、前記研磨工程において前記配線材料膜はその表面から順次ポリシングされる、いわゆるエッチバックがなされるため、前記絶縁膜の溝および／または開口部にＣｕまたはＣｕ合金からなる埋め込み配線層を前記絶縁膜表面と面一に形成できる。また、エッチバック工程後の前記配線層は前記研磨液と接触されるが、前記配線層の露出表面には酸化層が形成されるため前記酸化層により前記配線層がエッチングされるのを回避できる。したがって、高精度の埋め込み配線層を有すると共に、表面が平坦な構造を有する半導体装置を製造することができる。
【００５７】
また、水酸化カリウムのようなアルカリ剤により研磨液のｐＨを９〜１４に調節することによって、前記研磨液に含有されるアミノ酢酸のような有機酸の量を多くしてもエッチバック工程後の前記配線層のエッチングをその表面に形成されたエッチングバリア性の高い酸化膜により防止できる。しかも、研磨液中の有機酸の含有量を高めることによって、前記配線材料膜のポリシング速度を高めることができ、結果的にはエッチバック時間を短縮できる。
【００５８】
さらに、シリカ粒子のような研磨砥粒が添加された研磨液を用いることによって前記配線材料層のポリシング速度を向上できるため、エッチバック時間を短縮できる。しかも、前記エッチバック工程において配線材料膜の割れや傷の発生を抑制できるため、信頼性の高い埋め込み配線層を前記絶縁膜の溝および／または開口部に形成することができる。
【００５９】
本発明に係わる別の半導体装置の製造方法は、半導体基板上の絶縁膜に配線層の形状に相当する溝および／または開口部を形成する工程と、
前記溝および／または開口部を含む前記絶縁膜上に銅または銅合金からなる配線材料膜を堆積する工程と、
アミノ酢酸およびアミド硫酸から選ばれる少なくとも１種の有機酸と酸化剤と水とを含有する研磨液を用いて前記配線材料膜を前記絶縁膜の表面が露出するまで研磨処理することにより前記絶縁膜にその表面と面一の埋め込み配線層を形成する工程と、
前記配線層を含む前記絶縁膜表面を溶存オゾン水溶液で処理し、さらに希フッ酸水溶液で処理する工程と
を具備したことを特徴とするものである。
【００６０】
前記絶縁膜としては、例えばシリコン酸化膜、シリコン窒化膜、シリコン酸化膜とこの上に積層されたシリコン窒化膜の２層膜、ボロン添加ガラス膜（ＢＰＳＧ膜）、リン添加ガラス膜（ＰＳＧ膜）等を用いることができる。
【００６１】
前記Ｃｕ合金としては、例えばＣｕ−Ｓｉ合金、Ｃｕ−Ａｌ合金、Ｃｕ−Ｓｉ−Ａｌ合金、Ｃｕ−Ａｇ合金等を用いることができる。
【００６２】
前記ＣｕまたはＣｕ合金からなる配線材料膜は、スパッタ蒸着、真空蒸着等により堆積される。
【００６３】
前記研磨液中の有機酸の含有量およびそれら有機酸および酸化剤の含有比率は、前述した銅系金属用研磨液と同様な範囲にすることが好ましい。
【００６４】
前記研磨液は、前記有機酸および酸化剤の他にｐＨを９〜１４に調節するアルカリ剤を含有することを許容する。このようなアルカリ剤としては、例えば水酸化カリウム、キノリンが好適である。
【００６５】
前記研磨液は、前記有機酸および酸化剤の他にシリカ粒子、アルミナ粒子、酸化セリウム粒子、ジルコニア粒子等の研磨砥粒を含有することを許容する。これらの研磨砥粒の平均粒径および添加量は前述した銅系金属用研磨液で説明したのと同様な範囲にすることが好ましい。
【００６６】
前記研磨液による研磨処理は、前述した図１に示すポリシング装置を用いて行われる。
【００６７】
図１に示すポリシング装置を用いた研磨処理において、基板ホルダで保持された基板を前記研磨パッドに与える加重は研磨液の組成により適宜選定される。例えば、有機酸、酸化剤および水からなる組成の研磨液では前記加重を２００〜２０００ｇ／ｃｍ^２ にすることが好ましい。さらにシリカ粒子のような研磨砥粒を含む組成の研磨液では、前記加重を１５０〜１０００ｇ／ｃｍ^２ にすることが好ましい。
【００６８】
本発明に係わる別の半導体装置の製造において、前記半導体基板上の前記溝および／または開口部を含む前記絶縁膜には前記配線材料膜を堆積する前にバリア層を形成することを許容する。このようなバリア層を前記溝および／または開口部を含む前記絶縁膜に形成することによって、Ｃｕのような配線材料膜の堆積、エッチバックにより前記バリア層で囲まれた埋め込み配線層を形成することが可能になる。その結果、配線材料であるＣｕの拡散による半導体基板の汚染を防止できる。
【００６９】
前記バリア層は、例えばＴｉＮ、Ｔｉ、Ｎｂ、ＷまたはＣｕＴａ合金からなる。このようなバリア層は、１５〜５０ｎｍの厚さを有することが好ましい。
【００７０】
本発明に係わる別の半導体装置の製造において、前述した図１に示すポリシング装置の前記テーブルの回転トルクの変化、研磨パッドの温度変化、または研磨パッドに供給される前記研磨液のｐＨ変化、に基づいて前記研磨処理の終点を検出することを許容する。また、前述した図１に示すポリシング装置のホルダの回転トルクの変化に基づいて前記研磨処理の終点を検出することを許容する。このような方法によれば、研磨処理の終点を簡単に検出できる。その結果、前記終点検出を利用することにより前記絶縁膜にその表面と面一の埋め込み配線層を確実に形成することができる。
【００７１】
前記溶存オゾン水溶液は、オゾン濃度が０．１〜２５ｐｐｍであることが好ましい。前記溶存オゾン水溶液のオゾン濃度を０．１ｐｐｍ未満にすると前記絶縁膜上に残留した配線材料であるＣｕまたはＣｕ合金を酸化物に変換したり、有機物等の汚染物を酸化分解したりすることが困難になる。より好ましい前記溶存オゾン水溶液のオゾン濃度は、５〜２５ｐｐｍである。
【００７２】
前記希フッ酸水溶液は、フッ酸濃度が０．０５〜２０％であることが好ましい。前記希フッ酸水溶液のフッ酸濃度を０．０５％未満にすると、前記溶存オゾン水溶液での処理により変換されたＣｕまたはＣｕ合金を酸化物を効果的に溶解除去することが困難になる。一方、前記希フッ酸水溶液のフッ酸濃度が２０％を越えると絶縁膜としてシリコン酸化膜を用いた場合にはその酸化膜をも溶解除去された膜減りを生じる恐れがある。より好ましい前記希フッ酸水溶液のフッ酸濃度は０．１〜５％である。
【００７３】
以上説明した本発明に係わる別の半導体装置の製造方法は、半導体基板上の絶縁膜に配線層に相当する溝および／または開口部を形成し、前記溝および／または開口部を含む前記絶縁膜上にＣｕまたはＣｕ合金からなる配線材料膜を堆積し、さらにアミノ酢酸およびアミド硫酸から選ばれる少なくとも１種の有機酸と酸化剤と水とを含有する研磨液および例えば前述した図１に示すポリシング装置を用いて前記配線材料膜を前記絶縁膜の表面が露出するまで研磨する。前記研磨液は、既述したようにＣｕ膜またはＣｕ合金膜の浸漬時において前記Ｃｕ膜またはＣｕ合金膜を殆どエッチングせず、かつ浸漬時と研磨時との間で数倍ないし数十倍のエッチング速度差を示す。その結果、前記研磨工程において前記配線材料膜はその表面から順次ポリシングされる、いわゆるエッチバックがなされるため、前記絶縁膜の溝および／または開口部にＣｕまたはＣｕ合金からなる埋め込み配線層を前記絶縁膜表面と面一に形成できる。また、エッチバック工程後の前記配線層は前記研磨液と接触されるが、前記配線層の露出表面には酸化層が形成されるため前記酸化層により前記配線層がエッチングされるのを回避できる。
【００７４】
さらに、前記エッチバック工程後に前記配線層を含む前記絶縁膜表面を溶存オゾン水溶液で処理することにより前記絶縁膜上に残留した微細な配線材料、つまりＣｕまたはＣｕ合金を酸化物に変換したり、有機物等の汚染物質を酸化分解することができる。このような溶存オゾン水溶液での処理後に希フッ酸水溶液で処理することによって、前記絶縁膜上にＣｕまたはＣｕ合金の酸化物や前記汚染物質の酸化分解物を容易に溶解除去することができる。
【００７５】
したがって、高精度の埋め込み配線層を有すると共に、表面が平坦な構造を有し、さらに絶縁膜表面の有機物や残留配線材料が除去された清浄な表面を有する半導体装置を製造することができる。
【００７６】
また、水酸化カリウムのようなアルカリ剤により研磨液のｐＨを９〜１４に調節することによって、前記研磨液に含有されるアミノ酢酸のような有機酸の量を多くしてもエッチバック工程後の前記配線層のエッチングをその表面に形成されたエッチングバリア性の高い酸化膜により防止できる。しかも、研磨液中の有機酸の含有量を高めることによって、前記配線材料膜のポリシング速度を高めることができ、結果的にはエッチバック時間を短縮できる。
【００７７】
さらに、シリカ粒子のような研磨砥粒が添加された研磨液を用いることによって前記配線材料層のポリシング速度を向上できるため、エッチバック時間を短縮できる。しかも、前記エッチバック工程において配線材料膜の割れや傷の発生を抑制できるため、信頼性の高い埋め込み配線層を前記絶縁膜の溝および／または開口部に形成することができる。
【００７８】
【実施例】
以下、本発明の好ましい実施例を詳細に説明する。
【００７９】
実施例１
まず、図８の（Ａ）に示すように表面に図示しないソース、ドレイン等の拡散層が形成されたシリコン基板２１上にＣＶＤ法により層間絶縁膜としての例えば厚さ１０００ｎｍのＳｉＯ_２ 膜２２を堆積した後、前記ＳｉＯ_２ 膜２２にフォトエッチング技術により配線層に相当する形状を有する深さ５００ｎｍの複数の溝２３を形成した。つづいて、図８の（Ｂ）に示すように前記溝２３を含む前記ＳｉＯ_２ 膜２２上にスパッタ蒸着により厚さ１５ｎｍのＴｉＮからなるバリア層２４および厚さ６００ｎｍのＣｕ膜２５をこの順序で堆積した。
【００８０】
次いで、前述した図１に示すポリシング装置の基板ホルダ５に図８の（Ｂ）に示す基板２１を逆さにして保持し、前記ホルダ５の支持軸４により前記基板をターンテーブル１上のローデル・ニッタ社製商品名；ＳＵＢＡ８００からなる研磨パッド２に３００ｇ／ｃｍ^２ の加重を与え、前記ターンテーブル１およびホルダ５をそれぞれ１００ｐｐｍの速度で互いに反対方向に回転させながら、研磨液を供給管３から２０ｍｌ／分の速度で前記研磨パッド２に供給して前記基板２１に堆積したＣｕ膜２５およびバリア層２４を前記ＳｉＯ_２ 膜２２の表面が露出するまで研磨した。ここで、前記研磨液としてアミノ酢酸０．１重量％、過酸化水素１３．０重量％および平均粒径０．０４μｍのシリカ粉末８重量％を含む純水からなり、重量割合でアミノ酢酸１に対して過酸化水素が１３０であるものを用いた。前記研磨工程において、前記研磨液はＣｕ膜との接触時のエッチング速度が零であり、前記研磨パッドによる研磨時のポリシング速度が約７７ｎｍ／分で浸漬時に比べて十分に大きなエッチング速度差を示した。このため、研磨工程において図８の（Ｂ）に示す凸状のＣｕ膜２５は前記研磨パッドと機械的に接触する表面から優先的にポリシングされ、さらに露出したバリア層２４がポリシングされる、いわゆるエッチバックがなされた。その結果、図８の（Ｃ）に示すように前記溝２３内のみにバリア層２４が残存すると共に、前記バリア層２４で覆われた前記溝２３に前記ＳｉＯ_２ 膜２２表面と面一な埋め込みＣｕ配線層２６が形成された。また、前記ポリシング装置のホルダ５による前記研磨パッド２への加重を解除し、かつターンテーブル１およびホルダ５の回転の停止した後において、前記Ｃｕ配線層２６が前記研磨液に接触されてもエッチングが進行することがなかった。
【００８１】
また、前述した図１のポリシング装置によるポリシング工程（エッチバック工程）において研磨パッドから研磨液を逐次採取してｐＨ測定計によりｐＨの変化を測定した。研磨時間に対する研磨液のｐＨ変化を図９に示す。図９から明らかなように、ｐＨはホルダによる基板の加重後に一度下がり、再度上昇する。このｐＨが上昇する時、例えば加重開始後８分間経過した時、をエッチング終点とした。このような終点検出によりエッチバック時間を設定することによって、前記ＳｉＯ_２ 膜２２の溝２３に前記ＳｉＯ_２ 膜２２表面と面一な埋め込みＣｕ配線層２６を再現性よく形成することができた。
【００８２】
なお、前述した図１のポリシング装置によるポリシング工程（エッチバック工程）において温度センサにより前記研磨パッドの温度変化の測定、およびターンテーブルの駆動モータの電圧変化、をそれぞれ測定した。研磨時間に対する前記研磨パッドの温度変化を図１０に、研磨時間に対する前記駆動モータの電圧変化を図１１に、それぞれ示す。温度変化を示す図１０において、加重開始直後に研磨パッドの温度が上昇して一定の温度になり、再度温度が上昇する。この温度上昇が起こる時をエッチング終点とした。電圧変化を示す図１１において、加重開始直後にターンテーブルの駆動モータの電圧が上昇して一定の電圧になり、再度、電圧が上昇する。この電圧が上昇する時をエッチング終点とした。このような終点検出によりエッチバック時間を設定することによって、前述した研磨液のｐＨ測定の場合と同様に前記ＳｉＯ_２ 膜２２の溝２３に前記ＳｉＯ_２ 膜２２表面と面一な埋め込みＣｕ配線層２６を再現性よく形成することができた。
【００８３】
さらに、前記埋め込み配線層の形成後の基板をオゾン濃度０．００１％の溶存オゾン水溶液に３分間浸漬して処理した後、フッ酸濃度１０％の希フッ酸水溶液に９０秒間浸漬して処理した。図１２は、ＸＰＳで分析したスペクトル図であり、実線はＣｕ配線層形成直後の表面のスペクトル、点線は溶存オゾン水溶液で処理した後のＣｕ配線層表面のスペクトル、一点鎖線は希フッ酸処理後のＣｕ配線層表面のスペクトル、である。図１２から明らかなように配線形成後の基板を溶存オゾン水溶液に浸漬して処理すると、点線に示すスペクトルのように配線形成直後で見られた金属Ｃｕの信号はなくなり、Ｃｕ配線層表面が酸化物に変化したことがわかる。この後、希フッ酸水溶液で処理すると一点鎖線に示すスペクトルのように前記溶存オゾン水溶液の処理で見られたＣｕＯの信号がなくなり、純ＣｕがＣｕ配線層表面に露出したことがわかる。このように溶存オゾン水溶液で処理することによって、ＳｉＯ_２ 膜２２等の表面に残留したアミノ酢酸のような有機物を分解できると共に、前記ＳｉＯ_２ 膜２２に残留したＣｕを酸化物に変換できる。溶存オゾン水溶液の処理で生成された有機物の分解物およびＣｕの酸化物は、この後の希フッ酸水溶液の処理により除去できると共に、前記研磨液との接触によりＣｕ配線層２６表面に生成されたＣｕ酸化物層も除去することができる。その結果、ＳｉＯ_２ 膜２２の表面を清浄化でき、さらにＣｕ配線層２６表面に純Ｃｕを露出することができる。
【００８４】
したがって、実施例１によれば前記ＳｉＯ_２ 膜２２の溝２３内にその深さと同様な厚さを有する埋め込みＣｕ配線層２６を前記ＳｉＯ_２ 膜２２表面と面一に形成することができ、配線層２６の形成後の基板２１表面を平坦化することがてきた。また、Ｃｕ配線層２６の形成後に溶存オゾン水溶液の処理、希フッ酸水溶液の処理を行うことによって、ＳｉＯ_２ 膜２２表面の清浄化、研磨液の酸化により生成された抵抗成分となる酸化層の除去がなされるため、Ｃｕ本来の低抵抗性を持つ埋め込みＣｕ配線層を有し、かつ信頼性の高い半導体装置を製造することができる。
【００８５】
なお、前記実施例１において研磨液としてアミド硫酸０．８６重量％、過酸化水素水３０重量％、平均粒径０．０９μｍのシリカ粉末８重量％を含む純水からなるものを用いたところ、実施例１と同様、層間絶縁ＳｉＯ_２ 膜の溝内に埋め込み配線層を前記絶縁ＳｉＯ_２ 膜表面と面一に形成することができた。
【００８６】
実施例２
まず、図１３の（Ａ）に示すように表面に図示しないソース、ドレイン等の拡散層が形成されたシリコン基板２１上にＣＶＤ法により例えば厚さ８００ｎｍのＳｉＯ_２ 膜２２および厚さ２００ｎｍのＳｉ_３ Ｎ_４ 膜２７をこの順序で堆積して層間絶縁膜を形成した後、前記Ｓｉ_３ Ｎ_４ 膜２７および前記ＳｉＯ_２ 膜２２にフォトエッチング技術により配線層に相当する形状を有する深さ５００ｎｍの複数の溝２３を形成した。つづいて、図１３の（Ｂ）に示すように前記溝２３を含む前記Ｓｉ_３ Ｎ_４ 膜２７上にスパッタ蒸着により厚さ１５ｎｍのＴｉＮからなるバリア層２４および厚さ６００ｎｍのＣｕ膜２５をこの順序で堆積した。
【００８７】
次いで、前述した図１に示すポリシング装置の基板ホルダ５に図１３の（Ｂ）に示す基板２１を逆さにして保持し、前記ホルダ５の支持軸４により前記基板をローデル・ニッタ社製商品名；ＳＵＢＡ８００からなる研磨パッド２に３００ｇ／ｃｍ^２ の加重を与え、前記ターンテーブル１およびホルダ５をそれぞれ１００ｐｐｍの速度で互いに反対方向に回転させながら、研磨液を供給管３から２０ｍｌ／分の速度で前記研磨パッド２に供給して前記基板２１に堆積したＣｕ膜２５およびバリア層２４を前記Ｓｉ_３ Ｎ_４ 膜２７の表面が露出するまで研磨した。ここで、前記研磨液としてアミノ酢酸０．１重量％、過酸化水素１３．０重量％および平均粒径０．０４μｍのシリカ粉末８重量％を含む純水からなり、重量割合でアミノ酢酸１に対して過酸化水素が１３０であるものを用いた。前記研磨工程において、前記研磨液はＣｕ膜との接触時のエッチング速度が零であり、前記研磨パッドによる研磨時のポリシング速度が約７７ｎｍ／分で浸漬時に比べて十分に大きなエッチング速度差を示した。このため、図１３の（Ｂ）に示す凸状のＣｕ膜２５は前記研磨パッドと機械的に接触する表面から優先的にポリシングされ、さらに露出したバリア層２４がポリシングされる、いわゆるエッチバックがなされた。
【００８８】
その結果、図１３の（Ｃ）に示すように前記溝２３内のみにバリア層２４が残存すると共に、前記バリア層２４で覆われた前記溝２３に前記Ｓｉ_３ Ｎ_４ 膜２７表面と面一な埋め込みＣｕ配線層２６が形成された。また、前記ポリシング装置のホルダ５による前記研磨パッド２への加重を解除し、かつターンテーブル１およびホルダ５の回転の停止した後において、前記Ｃｕ配線層２６が前記研磨液に接触されてもエッチングが進行することがなかった。
【００８９】
さらに、前記シリカ粒子を研磨砥粒として含む研磨液を用いたポリシング工程において前記層間絶縁膜は表面側が優れた耐ポリシング性を有するＳｉ_３ Ｎ_４ 膜２７で形成されているため、前記エッチバック工程での膜減りを抑制することができた。このため、良好な絶縁耐圧を有する層間絶縁膜を備えた半導体装置を製造することができた。
【００９０】
実施例３
まず、図１４の（Ａ）に示すように表面に図示しないソース、ドレイン等の拡散層が形成されたシリコン基板２１上にＣＶＤ法により層間絶縁膜としての例えば厚さ１０００ｎｍのＳｉ_３ Ｎ_４ 膜２７を堆積した後、前記Ｓｉ_３ Ｎ_４ 膜２７にフォトエッチング技術により配線層に相当する形状を有する深さ５００ｎｍの複数の溝２３を形成した。つづいて、図１４の（Ｂ）に示すように前記溝２３を含む前記Ｓｉ_３ Ｎ_４ 膜２７上にスパッタ蒸着により厚さ６００ｎｍのＣｕ膜２５を堆積した。
【００９１】
次いで、前述した図１に示すポリシング装置の基板ホルダ５に図１４の（Ｂ）に示す基板２１を逆さにして保持し、前記ホルダ５の支持軸４により前記基板をローデル・ニッタ社製商品名；ＳＵＢＡ８００からなる研磨パッド２に４００ｇ／ｃｍ^２ の加重を与え、前記ターンテーブル１およびホルダ５をそれぞれ１００ｐｐｍの速度で互いに反対方向に回転させながら、研磨液を供給管３から２０ｍｌ／分の速度で前記研磨パッド２に供給して前記基板２１に堆積したＣｕ膜２５を前記Ｓｉ_３ Ｎ_４ 膜２７の表面が露出するまで研磨した。ここで、前記研磨液としてアミノ酢酸０．９重量％、過酸化水素２２．０重量％および水酸化カリウム３．７重量％を含む純水からなり、重量割合でアミノ酢酸１に対して過酸化水素が約２４であるｐＨ１０．５のものを用いた。前記研磨工程において、前記研磨液はＣｕ膜との接触時のエッチング速度が零であり、前記研磨パッドによる研磨時のポリシング速度が約２２０ｎｍ／分で浸漬時に比べて十分に大きなエッチング速度差を示した。このため、図１４の（Ｂ）に示す凸状のＣｕ膜２５は前記研磨パッドと機械的に接触する表面から優先的にポリシングされる、いわゆるエッチバックがなされた。
【００９２】
その結果、図１４の（Ｃ）に示すように前記溝２３内に前記Ｓｉ_３ Ｎ_４ 膜２７表面と面一な埋め込みＣｕ配線層２６が形成された。また、前記ポリシング装置のホルダ５による前記研磨パッド２への加重を解除し、かつターンテーブル１およびホルダ５の回転の停止した後において、前記Ｃｕ配線層２６が前記研磨液に接触されてもエッチングが進行することがなかった。
【００９３】
さらに、前記埋め込みＣｕ配線層２６が形成される溝２３を有する層間絶縁膜２７は、Ｃｕの拡散バリア性の優れたＳｉ_３ Ｎ_４ からなる。その結果、Ｃｕ配線層２６からＣｕが前記層間絶縁膜を通して前記シリコン基板２１に拡散することがないため、前記溝２３内面のＴｉＮのようなバリア層を形成しなくとも、前記シリコン基板２１の汚染を回避することができた。
【００９４】
実施例４
まず、図１５の（Ａ）に示すように表面にｎ^＋ 型拡散層３１が形成されたｐ型シリコン基板３２上にＣＶＤ法により第１層間絶縁膜としての例えば厚さ１０００ｎｍのＳｉＯ_２ 膜３３を堆積した後、前記拡散層３１に対応する前記ＳｉＯ_２ 膜３３にフォトエッチング技術によりビアホール３４を形成した。つづいて、図１５の（Ｂ）に示すように前記ビアホール３４を含む前記ＳｉＯ_２ 膜３３上にスパッタ蒸着により厚さ２０ｎｍのＴｉＮからなるバリア層３５を堆積した後、スパッタ蒸着により厚さ１１００ｎｍのＣｕ膜３６を堆積した。
【００９５】
次いで、前述した図１に示すポリシング装置のホルダ５に図１５の（Ｂ）に示す基板３２を逆さにして保持し、前記ホルダ５の支持軸４により前記基板をローデル・ニッタ社製商品名；ＳＵＢＡ８００からなる研磨パッド２に３００ｇ／ｃｍ^２ の加重を与え、前記ターンテーブル１およびホルダ５をそれぞれ１００ｐｐｍの速度で互いに反対方向に回転させながら、研磨液を供給管３から２０ｍｌ／分の速度で前記研磨パッド２に供給して前記基板３２に堆積したＣｕ膜３６およびバリア層３５を前記ＳｉＯ_２ 膜３３の表面が露出するまで研磨した。ここで、前記研磨液としてアミノ酢酸０．２重量％、過酸化水素２０．０重量％および平均粒径０．０４μｍのシリカ粉末１０重量％を含む純水からなり、重量割合でアミノ酢酸１に対して過酸化水素が１００であるものを用いた。前記研磨工程において、前記研磨液はＣｕ膜との接触時のエッチング速度が零であり、前記研磨パッドによる研磨時のポリシング速度が約７０ｎｍ／分で浸漬時に比べて十分に大きなエッチング速度差を示した。このため、図１５の（Ｂ）に示す凸状のＣｕ膜３６は前記研磨パッドと機械的に接触する表面から優先的にポリシングされ、さらに露出したバリア層３５がポリシングされる、いわゆるエッチバックがなされた。その結果、図１５の（Ｃ）に示すように前記ビアホール３４内のみにバリア層３５が残存すると共に、前記バリア層３５で覆われた前記ビアホール３４に前記ＳｉＯ_２ 膜３３表面と面一なＣｕからなるビアフィル３７が形成された。また、前記ポリシング装置のホルダ５による前記研磨パッド２への加重を解除し、かつターンテーブル１およびホルダ５の回転の停止した後において、前記ビアフィル３７が前記研磨液に接触されてもエッチングが進行することがなかった。つづいて、前記ビアフィル３７の形成後の基板をオゾン濃度０．００２％の溶存オゾン水溶液に３分間浸漬して処理した後、フッ酸濃度５％の希フッ酸水溶液に９秒間浸漬して処理することによりＳｉＯ_２ 膜３３表面を清浄化した。
【００９６】
次いで、図１６の（Ｄ）に示すように前記ビアフィル３７を含む前記ＳｉＯ_２ 膜３３上にＣＶＤ法により第２層間絶縁膜としての例えば厚さ８００ｎｍのＳｉ_３ Ｎ_４ 膜３８を堆積した後、前記Ｓｉ_３ Ｎ_４ 膜３８にフォトエッチング技術により配線層に相当する形状を有する深さ４００ｎｍの複数の溝３９を形成した。さらに、前記ビアフィル３７上にに位置する前記溝３９にフォトエッチング技術によりスルーホール４０を形成した。つづいて、図１６の（Ｅ）に示すように前記溝３９およびスルーホール４０を含む前記Ｓｉ_３ Ｎ_４ 膜３８上にスパッタ蒸着により厚さ９００ｎｍのＣｕ膜４１を堆積した。
【００９７】
次いで、前述した図１に示すポリシング装置の基板ホルダ５に図１６の（Ｅ）に示す基板３２を逆さにして保持し、前記ホルダ５の支持軸４により前記基板をローデル・ニッタ社製商品名；ＳＵＢＡ８００からなる研磨パッド２に３００ｇ／ｃｍ^２ の加重を与え、前記ターンテーブル１およびホルダ５をそれぞれ１００ｐｐｍの速度で互いに反対方向に回転させながら、前述したエッチバック工程で用いたのと同様な組成を有する研磨液を供給管３から２０ｍｌ／分の速度で前記研磨パッド２に供給して前記基板３２に堆積したＣｕ膜４１を前記Ｓｉ_３ Ｎ_４ 膜３８の表面が露出するまで研磨した。その結果、図１６の（Ｅ）に示す凸状のＣｕ膜４１は前記研磨パッドと機械的に接触する表面から優先的にポリシングされる、いわゆるエッチバックがなされた。このようなエッチバックにより図１６の（Ｆ）に示すように前記溝３９内に前記Ｓｉ_３ Ｎ_４ 膜３８表面と面一な埋め込みＣｕ配線層４２が形成された。同時に、前記スルーホール４０を通して前記ビアフィル３７と接続される埋め込みＣｕ配線層４２が形成された。また、前記ポリシング装置のホルダ５による前記研磨パッド２への加重を解除し、かつターンテーブル１およびホルダ５の回転の停止した後において、前記Ｃｕ配線層４２が前記研磨液に接触されてもエッチングが進行することがなかった。
【００９８】
したがって、実施例４によれば第１、第２の層間絶縁膜３３、３９を有し、前記第１層間絶縁膜３３にその表面と面一なビアフィル３７が形成され、第２層間絶縁膜３９にその表面と面一なＣｕ配線層４２が形成された多層配線構造を有し、かつ表面が平坦化された半導体装置を製造することができた。
【００９９】
【発明の効果】
以上説明したように、本発明によればＣｕまたはＣｕ合金の浸漬時においてＣｕ、Ｃｕ合金を殆どエッチングせず、かつ浸漬時と研磨時との間で数倍ないし数十倍のエッチング速度差を示す銅系金属用研磨液を提供できる。
【０１００】
また、本発明によれば半導体基板上の絶縁膜に溝および／または開口部を形成し、前記絶縁膜上に堆積されたＣｕまたはＣｕ合金からなる配線材料膜を短時間でエッチバックでき、ひいては前記絶縁膜にＣｕまたはＣｕ合金からなる埋め込み配線層を前記絶縁膜表面と面一となるように形成した表面が平坦な半導体装置の製造方法を提供できる。
【０１０１】
さらに、本発明によれば半導体基板上の絶縁膜に溝および／または開口部を形成し、前記絶縁膜上に堆積されたＣｕまたはＣｕ合金からなる配線材料膜を短時間でエッチバックして絶縁膜表面と面一の埋め込み配線層を形成することができ、さらにエッチバック後の絶縁膜表面の有機物や残留配線材料が除去された清浄で平坦な表面を有する半導体装置の製造方法を提供できる。
【図面の簡単な説明】
【図１】本発明の研磨工程に使用されるポリシング装置を示す概略図。
【図２】０．１重量％のアミノ酢酸、過酸化水素および水からなる組成の研磨液における過酸化水素の量とその研磨液に浸漬した時のＣｕ膜のエッチング速度、研磨処理時のＣｕ膜のポリシング速度との関係を示す特性図。
【図３】凹凸を有するＣｕ膜をアミノ酢酸、過酸化水素および水からなる組成の研磨液に浸漬した時、ポリシング装置を用いて研磨処理した時の状態を示す断面図。
【図４】加工前、本発明の研磨液の浸漬後および研磨処理後のＣｕ膜表面のＸＰＳによるスペクトル図。
【図５】０．９重量％のアミノ酢酸、過酸化水素および水からなる組成の研磨液における過酸化水素の量とその研磨液に浸漬した時のＣｕ膜のエッチング速度、研磨処理時のＣｕ膜のポリシング速度との関係を示す特性図。
【図６】アミド硫酸、過酸化水素および水からなる組成の研磨液における過酸化水素の量とその研磨液に浸漬した時のＣｕ膜のエッチング速度、研磨処理時のＣｕ膜のポリシング速度との関係を示す特性図。
【図７】本発明の研磨液のｐＨとＣｕ膜表面に生成される酸化層の厚さ変化を示す特性図。
【図８】本発明の実施例１における半導体装置の製造工程を示す断面図。
【図９】実施例１の研磨処理（エッチバック工程）での研磨液のｐＨ変化を示す特性図。
【図１０】実施例１の研磨処理（エッチバック工程）での研磨布の温度変化を示す特性図。
【図１１】実施例１の研磨処理（エッチバック工程）でのターンテーブルの駆動モータの電圧変化を示す特性図。
【図１２】本発明の実施例１におけるＣｕ配線層形成直後の表面、オゾン処理後のＣｕ配線層表面、および希フッ酸処理後のＣｕ配線層表面のＸＰＳ分析により得られたスペクトル図。
【図１３】本発明の実施例２おける半導体装置の製造工程を示す断面図。
【図１４】本発明の実施例３おける半導体装置の製造工程を示す断面図。
【図１５】本発明の実施例４おける半導体装置の製造工程を示す断面図。
【図１６】本発明の実施例４おける半導体装置の製造工程を示す断面図。
【符号の説明】
１…ターンテーブル、２…研磨パッド、３…供給管、５…ホルダ、１１、２１、３２…シリコン基板、１２、２５、３６、４１…Ｃｕ膜、１３…酸化層、２２、３３…ＳｉＯ_２ 膜、２３、３９…溝、２４、３５…バリア層、２６、４２…Ｃｕ配線層、３７…ビアフィル。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing liquid for a copper-based metal.
[0002]
[Prior art]
J. Electrochem. Soc. , VoL. 138. No. 11, 3460 (1991), VMIC Conference, ISMIC-101 / 92/0156 (1992) or VMIC Conference, ISMIC-102 / 93/0205 (1993) include amine-based colloidal silica slurry or K ₃ Fe (CN). No. ₆ , K ₄ (CN) ₆ , and a polishing solution for a Cu film or a Cu alloy film made of a slurry to which Co (NO ₃ ) ₂ is added are disclosed.
[0003]
However, the polishing liquid has the following problem because there is no difference in the dissolution rate of the Cu film between immersion and polishing.
[0004]
2. Description of the Related Art In forming a wiring layer, which is one of the manufacturing processes of a semiconductor device, an etch-back technique is employed for the purpose of eliminating a step on a surface. In this etch-back technique, a groove is formed in an insulating film on a semiconductor substrate, a Cu film is deposited on the insulating film including the groove, and the Cu film is polished using a polishing solution, and only the inside of the groove is polished. This is a method of forming a buried wiring layer by leaving a Cu film on the substrate. After such an etch-back step, the Cu wiring layer in the groove is brought into contact with the polishing liquid, so that the polishing liquid having the above-described composition having no difference in the etching rate of the Cu film between immersion and polishing is used. When used, the Cu wiring layer is further etched by the polishing liquid. As a result, since the surface position of the Cu wiring layer in the groove is lower than the surface of the insulating film, it is difficult to form a wiring layer flush with the surface of the insulating film, and the flatness is impaired. Further, the formed buried Cu wiring layer has a higher resistance value than the Cu wiring layer buried flush with the surface of the insulating film.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to hardly etch Cu or the like during immersion of copper (Cu) or a copper alloy (Cu alloy), and to dissolve the Cu or Cu alloy during a polishing process, so It is an object of the present invention to provide a polishing liquid for a copper-based metal which shows a difference in etching rate of several to several tens times between the above.
[0006]
[Means for Solving the Problems]
The polishing liquid for a copper-based metal according to the present invention contains aminoacetic acid, an oxidizing agent, abrasive grains and water. Such a polishing liquid forms an oxide layer functioning as an etching barrier on the surface of the Cu or Cu alloy by the oxidizing action of the oxidizing agent during immersion of Cu or Cu alloy, and during polishing of Cu or Cu alloy. The Cu or Cu alloy exposed by mechanically removing the oxide layer is etched with the aminoacetic acid. Therefore, when the Cu or Cu alloy is immersed in the polishing liquid, the etching is suppressed or prevented by the oxide layer, and the Cu or Cu alloy exposed at the time of polishing is physically polished by polishing abrasive grains or the like and in the polishing liquid. Etching with an organic acid proceeds. As a result, it is possible to make a sufficiently large difference in the etching rate of Cu or Cu alloy between immersion and polishing.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the polishing liquid for a copper-based metal according to the present invention will be described in detail.
[0012]
The polishing liquid for a copper-based metal contains an organic acid that reacts with copper to form a complex, for example, aminoacetic acid, an oxidizing agent, and water.
[0013]
As the oxidizing agent, for example, hydrogen peroxide (H ₂ O ₂ ), sodium hypochlorite (NaClO) or the like can be used.
[0014]
It is preferable that the polishing liquid contains the organic acid in an amount of 0.01 to 10% by weight, and the oxidizing agent is 20 or more with respect to 1 of the organic acid in a weight ratio. The content of the organic acid in the polishing liquid and the content ratio of the organic acid and the oxidizing agent are specified for the following reasons.
[0015]
When the content of the organic acid is less than 0.01% by weight, a polishing rate (mainly a chemical dissolution rate) of Cu or a Cu alloy during polishing may be reduced. On the other hand, if the content of the organic acid exceeds 10% by weight, etching of Cu or Cu alloy proceeds excessively when immersed in a polishing liquid, and the difference in etching rate between immersion and polishing may be approximated. There is. A more preferred content of the organic acid is 0.01 to 1% by weight.
[0016]
If the oxidizing agent is less than 20 with respect to 1 organic acid by weight, there is a possibility that a sufficient etching rate difference cannot be obtained between immersion of Cu or Cu alloy and polishing. The content ratio of the organic acid to the oxidizing agent in the polishing liquid is preferably 40 or more, more preferably 100 or more, with respect to 1 organic acid by weight.
[0017]
The upper limit ratio of the oxidizing agent to the organic acid is desirably defined based on the content of the oxidizing agent. For example, the content of the oxidizing agent is preferably set to 30% by weight. If the content of the oxidizing agent exceeds 30% by weight, an oxidized layer is immediately formed on an exposed surface during polishing of Cu or a Cu alloy, which may cause a reduction in polishing rate.
[0018]
When the content of the organic acid is set to the lower limit (0.01% by weight) in the above range, the content ratio of the organic acid to the oxidizing agent is 1 weight ratio of the oxidizing agent to 1 organic acid. Is preferably 40 or more.
[0019]
The polishing liquid according to the present invention is allowed to contain an alkali agent for adjusting the pH to 9 to 14 in addition to the organic acid and the oxidizing agent. As such an alkali agent, for example, potassium hydroxide and quinoline are preferable.
[0020]
The polishing liquid according to the present invention allows addition of polishing abrasive grains such as silica particles, alumina particles, cerium oxide particles, and zirconia particles in addition to the organic acid and the oxidizing agent. These abrasive grains may be used in the form of a mixture of two or more.
[0021]
It is preferable that the abrasive grains have an average particle diameter of 0.02 to 0.1 μm.
[0022]
The abrasive grains are preferably added in an amount of 1 to 14% by weight. If the amount of the abrasive grains is less than 1% by weight, it is difficult to sufficiently achieve the effect. On the other hand, if the addition amount of the polishing abrasive grains exceeds 14% by weight, the viscosity of the polishing liquid and the like become high, making it difficult to handle. A more preferable addition amount of the abrasive grains is in the range of 3 to 10% by weight.
[0023]
In order to polish a Cu film or a Cu alloy film formed on a substrate, for example, with the polishing liquid for a copper-based metal according to the present invention, a polishing apparatus shown in FIG. 1 is used. That is, the turntable 1 is covered with a polishing pad 2 made of, for example, cloth. A supply pipe 3 for supplying a polishing liquid is disposed above the polishing pad 2. A substrate holder 5 having a support shaft 4 on the upper surface is arranged above the polishing pad 2 so as to be vertically movable and rotatable. In such a polishing apparatus, the substrate 6 is held by the holder 5 such that the polished surface (eg, Cu film) of the substrate 2 faces the pad 2, and the polishing liquid 7 having the above-described composition is supplied from the supply pipe 3. The Cu film on the substrate is polished by applying a desired load to the substrate 6 by the support shaft 4 toward the polishing pad 2 and further rotating the holder 5 and the turntable 1 in opposite directions. You.
[0024]
The polishing liquid for a copper-based metal according to the present invention described above contains at least one organic acid selected from aminoacetic acid and amidosulfuric acid, an oxidizing agent, and water. Etc. are hardly etched (preferably at an etching rate of 100 nm / min or less), and the etching rate difference is several times to several tens times between immersion and polishing.
[0025]
That is, an organic acid (for example, aminoacetic acid), which is a component of the polishing liquid, has a property of reacting with a hydrate of Cu to form a complex as shown in the following reaction formula.
[0026]
Cu (H ₂ O) ₄ ²⁺ + 2H ₂ NCH ₂ COOH
→ Cu (H ₂ NCH ₂ COOH) ₂ + 4H ₂ O + 2H ⁺
Cu does not react with the mixed liquid of aminoacetic acid and water. In such a reaction system, by adding an oxidizing agent (for example, hydrogen peroxide), the reaction proceeds in the direction indicated by the arrow in the above reaction formula, and Cu is etched.
[0027]
FIG. 2 shows a film formed on a substrate when the content of hydrogen peroxide was changed while the content of aminoacetic acid was kept constant at 0.1% by weight in a polishing liquid composed of aminoacetic acid, hydrogen peroxide and water. 3 is a plot of an etching rate during immersion of a Cu film and a polishing rate during polishing. The polishing process is performed by using the polishing apparatus shown in FIG. That is, the substrate on which the Cu film is formed on the substrate holder 5 is held upside down such that the Cu film faces the polishing pad 2 side made of, for example, SUBA800 (trade name, manufactured by Rodel-Nitta), and is supported by the support shaft 4. The polishing liquid is supplied from the supply pipe 3 to the polishing pad 2 at a rate of 12.5 ml / min while applying a load of 400 g / cm ² to the polishing pad 2 and rotating the turntable 1 and the holder 5 in opposite directions at a speed of 100 rpm. The polishing process was performed by supplying the polishing pad 2 at the above speed.
[0028]
As is apparent from FIG. 2, when the polishing liquid to which hydrogen peroxide is not added is used during the immersion of the Cu film, the Cu film is not etched at all. It can be seen that it is etched. This is because hydrogen peroxide in the polishing liquid generates a hydrate of Cu, and aminoacetic acid reacts with the hydrate to form a complex and Cu is etched. Further, it can be seen that when the content of the hydrogen peroxide is further increased, the etching rate of the Cu film is reduced, and when the content of the hydrogen peroxide is 5% by weight, the etching rate becomes zero. This is considered to be because if the content of hydrogen peroxide is increased, an oxide layer is formed on the surface of the Cu film, which prevents etching by the polishing liquid.
[0029]
In fact, as shown in FIG. 3A, a Cu film 12 having irregularities is formed on a substrate 11, and this substrate 11 is polished with a polishing liquid (aminoacetic acid 0.1 3% by weight (containing 13% by weight of hydrogen peroxide), an oxide layer 13 is formed on the surface of the Cu film 12 as shown in FIG. In addition, when the substrate is immersed in the polishing liquid and the surface of the Cu film is analyzed by XPS (X-ray photoelectron spectroscopy), an oxide layer is formed because the spectrum shown by the solid line in FIG. 4 appears. Was confirmed. The dotted line in FIG. 4 shows a spectrum immediately before the Cu film is formed on the substrate and before processing.
[0030]
When the above-mentioned polishing treatment is performed using the polishing apparatus shown in FIG. 1 and the polishing liquid containing 0.1% by weight of aminoacetic acid and 13% by weight of hydrogen peroxide, the polishing rate of the Cu film is immersed as shown in FIG. It was confirmed that a difference of about 10 nm / min was generated as compared with the case. The increase in the polishing rate of the Cu film due to such a polishing treatment is caused by polishing the Cu film 12 having the oxide layer 13 formed on the surface thereof as shown in FIG. (C), the oxide layer 13 corresponding to the convex portion of the Cu film 12 is mechanically polished by the pad to expose pure Cu on the surface, and the action of aminoacetic acid and hydrogen peroxide in the polishing solution is performed. This is because chemical polishing is rapidly performed. That is, in the polishing process, pure Cu is always exposed on the polished surface of the Cu film, and chemical etching is performed by aminoacetic acid and hydrogen peroxide in the polishing liquid. In fact, when the surface of the Cu film immediately after the polishing treatment was analyzed by XPS, a spectrum indicated by a dashed line in FIG. 4 appeared, and it was confirmed that Cu was exposed.
[0031]
FIG. 5 shows a film formed on a substrate when the content of hydrogen peroxide was changed while the content of aminoacetic acid was kept constant at 0.9% by weight in a polishing solution comprising aminoacetic acid, hydrogen peroxide and water. 3 is a plot of an etching rate during immersion of a Cu film and a polishing rate during polishing. The polishing was performed using the polishing apparatus shown in FIG. 1 in the same procedure as described above. As is clear from FIG. 5, when the polishing liquid to which hydrogen peroxide is not added is used at the time of immersion of the Cu film, the etching of the Cu film does not occur at all. It can be seen that it is etched. It can also be seen that when the hydrogen peroxide content is further increased, the etching rate of the Cu film is reduced, and when the hydrogen peroxide content is about 18% by weight, the etching rate becomes zero. This is considered to be because if the content of hydrogen peroxide is increased, an oxide layer is formed on the surface of the Cu film, which prevents etching by the polishing liquid. In such a polishing liquid, when a Cu film is polished at a rate of about 85 nm / min by using a polishing liquid containing 15% by weight of hydrogen peroxide by the same method as described above, the Cu film is polished. And a sufficient etching rate difference occurs between the polishing process and the polishing process. However, a polishing liquid containing 20% by weight of hydrogen peroxide, which is a condition under which the Cu film is not reliably etched at the time of immersion, that is, the content ratio of aminoacetic acid to hydrogen peroxide is 1% by weight of hydrogen peroxide to aminoacetic acid. Even with a polishing liquid of about 20, the polishing rate at the time of polishing the Cu film is about 60 nm / min. Therefore, even when a polishing liquid having a large content of hydrogen peroxide is used, a sufficient etching rate difference can be obtained between immersion and polishing.
[0032]
Further, FIG. 6 shows a substrate obtained when the content of amidosulfuric acid was kept constant at 0.86% by weight and the content of hydrogen peroxide was changed in a polishing solution composed of organic acids such as amidosulfuric acid, hydrogen peroxide and water. It is a plot of an etching rate during immersion of a Cu film formed thereon and a polishing rate during polishing. The polishing was performed using the polishing apparatus shown in FIG. 1 in the same procedure as described above. As is clear from FIG. 6, when the polishing liquid to which hydrogen peroxide is not added is used, the Cu film is not etched at all, but when a small amount of hydrogen peroxide is contained, the Cu film is rapidly etched. . Further, it can be seen that when the content of the hydrogen peroxide is further increased, the etching rate of the Cu film is decreased, and when the content of the hydrogen peroxide is about 22% by weight or more, the etching rate becomes 50 nm / min. This is considered to be because if the content of hydrogen peroxide is increased, an oxide layer is formed on the surface of the Cu film, which prevents etching by the polishing liquid. In such a polishing liquid, a polishing liquid containing 30% by weight of hydrogen peroxide, that is, a polishing liquid in which the content ratio of amidosulfuric acid and hydrogen peroxide is about 35 by weight of hydrogen peroxide relative to 1 aminoacetic acid is used. When the Cu film is polished by the same method as described above, the Cu film is polished at a rate of about 950 nm / min, and the difference between the immersion rate and the polishing rate is about 19 times, which is sufficiently large.
[0033]
Therefore, the polishing liquid according to the present invention hardly etches Cu or Cu alloy when immersing Cu or Cu alloy, and shows a difference of several times to several tens of times between immersion and polishing. Therefore, it is possible to avoid a problem that the etching amount of Cu fluctuates due to the supply timing of the polishing liquid or the like in the polishing process, and the operation can be performed easily. Further, after the polishing of the Cu film on the substrate by the polishing apparatus is completed, when the Cu film is brought into contact with a polishing liquid, an oxide layer is formed on the Cu film by hydrogen peroxide as described above. Even after the treatment, so-called over-etching, in which the Cu film is further etched, can be prevented. Further, as shown in FIG. 3C, the Cu film 12 having the unevenness is not etched from the side in the polishing step, and can be sequentially etched from the surface of the convex portion in contact with the polishing pad. Very suitable for etchback technology.
[0034]
In the polishing liquid according to the present invention, when immersing Cu or Cu alloy in the polishing liquid by adding an alkaline agent such as potassium hydroxide to adjust the pH to 9 to 14, the surface of Cu or Cu alloy An oxide layer having excellent etching barrier properties with respect to a polishing liquid can be generated. Further, the thickness of the oxide layer generated on the surface of Cu or Cu alloy can be controlled. FIG. 7 shows a Cu film formed on a substrate in a polishing liquid containing, for example, 0.9% by weight of aminoacetic acid and 12% by weight of hydrogen peroxide and adjusted to pH 8.5 to 11 by adding potassium hydroxide. FIG. 4 is a characteristic diagram showing a change in thickness of an oxide layer generated on the surface of the Cu film when the film is immersed. As shown in FIG. 7, as the pH increases, the thickness of the oxide layer formed on the Cu film surface increases.
[0035]
Such a polishing liquid whose pH is adjusted to 9 to 14 can form an oxide layer having a high etching barrier property on the surface of the Cu or Cu alloy when the Cu or Cu alloy is immersed. For this reason, even if the content of an organic acid such as aminoacetic acid in the polishing liquid is increased, Cu or the like is hardly etched during immersion of Cu or a Cu alloy, while the content of the organic acid is reduced during polishing. The polishing rate of Cu or Cu alloy can be increased by increasing the amount. Therefore, the difference in etching rate between immersion and polishing can be increased as compared with the case where no alkali agent is added, and as a result, the polishing time for Cu or Cu alloy can be reduced.
[0036]
In the polishing liquid according to the present invention, by adding polishing grains such as silica particles, the polishing rate at the time of polishing Cu or Cu alloy can be improved as compared with a polishing liquid in which the polishing grains are not added. For example, an aqueous solution containing 0.1% by weight of aminoacetic acid and 13% by weight of hydrogen peroxide contains silica particles having an average particle size of 30 nm, alumina particles having an average particle size of 740 nm, cerium oxide particles having an average particle size of 1300 nm, and an average particle size of 1100 nm. Of zirconia particles was added in an amount of about 9% by weight to prepare a polishing liquid. These polishing liquids were used to polish a Cu film having irregularities formed on a substrate in the same procedure as described above using the polishing apparatus shown in FIG. Table 1 below shows the polishing rate of the Cu film by each polishing liquid. Table 1 below also shows the polishing rate of the Cu film when using a polishing liquid containing 0.1% by weight of aminoacetic acid and 13% by weight of hydrogen peroxide to which no abrasive grains were added.
[0037]
[Table 1]

[0038]
As is clear from Table 1, the polishing rate of the Cu film can be improved in the polishing liquid to which the polishing abrasive grains are added, as compared with the polishing liquid to which the polishing abrasive grains are not added. Further, it can be seen that the polishing rate of the Cu film can be controlled by changing the type of the abrasive grains.
[0039]
A polishing liquid to which the silica particles and the alumina particles were added as abrasive grains was used to form a SiO ₂ film and a Si ₃ N ₄ film on a substrate in the same procedure as described above using the polishing apparatus shown in FIG. The film and the boron-added glass film (BPSG film) were polished. Table 2 below shows the polishing rates of the various insulating films by the respective polishing liquids. The values in parentheses in Table 2 are speed ratios determined from (polishing speed of Cu film with the same type of polishing liquid / polishing speed of each insulating film). When forming a Cu wiring layer buried in a groove or the like of an insulating film by a polishing process at the time of manufacturing a semiconductor device to be described later, it becomes possible to improve the selective polishing property of Cu as the speed ratio increases. That is, the thickness of the underlying insulating film can be prevented from being reduced.
[0040]
[Table 2]

[0041]
Further, the polishing liquid to which polishing abrasive grains such as silica particles are added can be polished well without causing cracks or fine scratches in the Cu film or Cu alloy film. This is because the frictional force between the polishing surface of the Cu film and the polishing pad can be reduced by the abrasive grains in the polishing step using the polishing apparatus shown in FIG. This is because it can prevent.
[0042]
Therefore, the polishing liquid to which polishing abrasive grains such as silica particles are added can improve the polishing rate of Cu or Cu alloy as compared with the polishing liquid to which polishing abrasive grains are not added, and can reduce the polishing rate on the Cu or Cu alloy surface during the polishing process. Damage can be suppressed.
[0043]
Incidentally, the organic acid is amidosulfuric acid, and the polishing rate of Cu or Cu alloy can be improved even in a polishing liquid containing polishing abrasive grains such as silica particles and the polishing rate can be improved as compared with a polishing liquid in which the polishing abrasive grains are not added. Damage to the Cu or Cu alloy surface can be suppressed.
[0044]
A method of manufacturing a semiconductor device according to the present invention includes a step of forming a groove and / or an opening corresponding to the shape of a wiring layer in an insulating film on a semiconductor substrate;
Depositing a wiring material film made of Cu or Cu alloy on the insulating film including the groove and / or the opening;
Polishing the wiring material film using a polishing liquid containing at least one organic acid selected from aminoacetic acid and amidosulfuric acid, an oxidizing agent, and water until the surface of the insulating film is exposed; Forming a buried wiring layer flush with the surface thereof.
[0045]
Examples of the insulating film include a silicon oxide film, a silicon nitride film, a two-layer film of a silicon oxide film and a silicon nitride film laminated thereon, a boron-added glass film (BPSG film), and a phosphorus-added glass film (PSG film). Etc. can be used.
[0046]
As the Cu alloy, for example, a Cu-Si alloy, a Cu-Al alloy, a Cu-Si-Al alloy, a Cu-Ag alloy, or the like can be used.
[0047]
The wiring material film made of Cu or Cu alloy is deposited by sputter deposition, vacuum deposition, or the like.
[0048]
It is preferable that the content of the organic acid in the polishing liquid and the content ratio of the organic acid and the oxidizing agent are in the same range as the above-mentioned polishing liquid for copper-based metal.
[0049]
The polishing liquid is allowed to contain an alkali agent for adjusting pH to 9 to 14 in addition to the organic acid and the oxidizing agent. As such an alkali agent, for example, potassium hydroxide and quinoline are preferable.
[0050]
The polishing liquid is allowed to contain abrasive grains such as silica particles, alumina particles, cerium oxide particles, and zirconia particles in addition to the organic acid and the oxidizing agent. It is preferable that the average particle size and the amount of these abrasive grains be in the same ranges as those described for the polishing liquid for copper-based metal.
[0051]
The polishing process using the polishing liquid is performed using, for example, the above-described polishing apparatus shown in FIG.
[0052]
In the polishing process using the polishing apparatus shown in FIG. 1, the weight applied to the polishing pad by the substrate held by the substrate holder is appropriately selected according to the composition of the polishing liquid. For example, in the case of a polishing liquid having a composition comprising an organic acid, an oxidizing agent and water, the weight is preferably set to 200 to 2000 g / cm ² . Further, in a polishing liquid having a composition containing polishing abrasive grains such as silica particles, the weight is preferably set to 150 to 1000 g / cm ² .
[0053]
In the manufacture of the semiconductor device according to the present invention, a barrier layer may be formed on the insulating film including the groove and / or the opening on the semiconductor substrate before depositing the wiring material film. By forming such a barrier layer in the insulating film including the groove and / or the opening, a wiring material film such as Cu is deposited, and an embedded wiring layer surrounded by the barrier layer is formed by etch-back. It becomes possible. As a result, contamination of the semiconductor substrate due to diffusion of Cu as a wiring material can be prevented.
[0054]
The barrier layer is made of, for example, TiN, Ti, Nb, W, or CuTa alloy. Such a barrier layer preferably has a thickness of 15 to 50 nm.
[0055]
In the manufacture of the semiconductor device according to the present invention, based on the change in the rotation torque of the table, the change in the temperature of the polishing pad, or the change in the pH of the polishing liquid supplied to the polishing pad in the polishing apparatus shown in FIG. It is allowed to detect the end point of the polishing process. Further, it is allowed to detect the end point of the polishing process based on the change in the rotational torque of the holder of the polishing apparatus shown in FIG. According to such a method, the end point of the polishing process can be easily detected. As a result, a buried wiring layer flush with the surface of the insulating film can be reliably formed on the insulating film by utilizing the end point detection.
[0056]
In the method of manufacturing a semiconductor device according to the present invention described above, a groove and / or an opening corresponding to a wiring layer is formed in an insulating film on a semiconductor substrate, and the groove and / or the opening is formed on the insulating film including the groove and / or the opening. A polishing liquid containing a wiring material film made of Cu or a Cu alloy, and further containing at least one organic acid selected from aminoacetic acid and amidosulfuric acid, an oxidizing agent, and water, and a polishing apparatus shown in FIG. Then, the wiring material film is polished until the surface of the insulating film is exposed. As described above, the polishing liquid hardly etches the Cu film or the Cu alloy film when the Cu film or the Cu alloy film is immersed, and several times to several tens times between the time of the immersion and the time of the polishing. 3 shows an etching rate difference. As a result, in the polishing step, the wiring material film is sequentially polished from its surface, that is, so-called etch back is performed. Therefore, the embedded wiring layer made of Cu or a Cu alloy is formed in the groove and / or the opening of the insulating film. It can be formed flush with the surface of the insulating film. Further, the wiring layer after the etch-back step is brought into contact with the polishing liquid, but since an oxide layer is formed on the exposed surface of the wiring layer, the wiring layer can be prevented from being etched by the oxide layer. . Therefore, a semiconductor device having a buried wiring layer with high precision and a structure having a flat surface can be manufactured.
[0057]
In addition, by adjusting the pH of the polishing solution to 9 to 14 with an alkali agent such as potassium hydroxide, even if the amount of the organic acid such as aminoacetic acid contained in the polishing solution is increased, Of the wiring layer can be prevented by an oxide film having a high etching barrier property formed on the surface thereof. Moreover, by increasing the content of the organic acid in the polishing liquid, the polishing rate of the wiring material film can be increased, and as a result, the etch-back time can be reduced.
[0058]
Further, by using a polishing liquid to which polishing abrasive grains such as silica particles are added, the polishing rate of the wiring material layer can be improved, so that the etch back time can be reduced. In addition, since the occurrence of cracks and scratches in the wiring material film in the etch-back step can be suppressed, a highly reliable embedded wiring layer can be formed in the groove and / or opening of the insulating film.
[0059]
Another method for manufacturing a semiconductor device according to the present invention includes a step of forming a groove and / or an opening corresponding to the shape of a wiring layer in an insulating film on a semiconductor substrate;
Depositing a wiring material film made of copper or a copper alloy on the insulating film including the groove and / or the opening;
Polishing the wiring material film using a polishing liquid containing at least one organic acid selected from aminoacetic acid and amidosulfuric acid, an oxidizing agent, and water until the surface of the insulating film is exposed; Forming a buried wiring layer flush with the surface thereof,
Treating the surface of the insulating film including the wiring layer with a dissolved ozone aqueous solution, and further treating with a diluted hydrofluoric acid aqueous solution.
[0060]
Examples of the insulating film include a silicon oxide film, a silicon nitride film, a two-layer film of a silicon oxide film and a silicon nitride film laminated thereon, a boron-added glass film (BPSG film), and a phosphorus-added glass film (PSG film). Etc. can be used.
[0061]
As the Cu alloy, for example, a Cu-Si alloy, a Cu-Al alloy, a Cu-Si-Al alloy, a Cu-Ag alloy, or the like can be used.
[0062]
The wiring material film made of Cu or Cu alloy is deposited by sputter deposition, vacuum deposition, or the like.
[0063]
It is preferable that the content of the organic acid and the content ratio of the organic acid and the oxidizing agent in the polishing liquid are in the same range as the above-described polishing liquid for a copper-based metal.
[0064]
The polishing liquid is allowed to contain an alkali agent for adjusting pH to 9 to 14 in addition to the organic acid and the oxidizing agent. As such an alkali agent, for example, potassium hydroxide and quinoline are preferable.
[0065]
The polishing liquid is allowed to contain abrasive grains such as silica particles, alumina particles, cerium oxide particles, and zirconia particles in addition to the organic acid and the oxidizing agent. It is preferable that the average particle size and the amount of these abrasive grains be in the same ranges as those described for the polishing liquid for copper-based metal.
[0066]
The polishing process using the polishing liquid is performed using the polishing apparatus shown in FIG.
[0067]
In the polishing process using the polishing apparatus shown in FIG. 1, the weight applied to the polishing pad by the substrate held by the substrate holder is appropriately selected according to the composition of the polishing liquid. For example, in the case of a polishing liquid having a composition comprising an organic acid, an oxidizing agent and water, the weight is preferably set to 200 to 2000 g / cm ² . Further, in a polishing liquid having a composition containing polishing abrasive grains such as silica particles, the weight is preferably set to 150 to 1000 g / cm ² .
[0068]
In the manufacture of another semiconductor device according to the present invention, a barrier layer may be formed on the insulating film including the groove and / or the opening on the semiconductor substrate before depositing the wiring material film. By forming such a barrier layer in the insulating film including the groove and / or the opening, a wiring material film such as Cu is deposited, and an embedded wiring layer surrounded by the barrier layer is formed by etch-back. It becomes possible. As a result, contamination of the semiconductor substrate due to diffusion of Cu as a wiring material can be prevented.
[0069]
The barrier layer is made of, for example, TiN, Ti, Nb, W, or CuTa alloy. Such a barrier layer preferably has a thickness of 15 to 50 nm.
[0070]
In the manufacture of another semiconductor device according to the present invention, the change in the rotational torque of the table, the change in the temperature of the polishing pad, or the change in the pH of the polishing liquid supplied to the polishing pad in the polishing apparatus shown in FIG. Based on this, it is allowed to detect the end point of the polishing process. Further, it is allowed to detect the end point of the polishing process based on the change in the rotational torque of the holder of the polishing apparatus shown in FIG. According to such a method, the end point of the polishing process can be easily detected. As a result, a buried wiring layer flush with the surface of the insulating film can be reliably formed on the insulating film by utilizing the end point detection.
[0071]
The dissolved ozone aqueous solution preferably has an ozone concentration of 0.1 to 25 ppm. When the ozone concentration of the dissolved ozone aqueous solution is less than 0.1 ppm, Cu or a Cu alloy, which is a wiring material remaining on the insulating film, may be converted to an oxide, or contaminants such as organic substances may be oxidized and decomposed. It becomes difficult. The more preferable ozone concentration of the dissolved ozone aqueous solution is 5 to 25 ppm.
[0072]
The diluted hydrofluoric acid aqueous solution preferably has a hydrofluoric acid concentration of 0.05 to 20%. If the concentration of hydrofluoric acid in the diluted hydrofluoric acid solution is less than 0.05%, it becomes difficult to effectively dissolve and remove oxides of Cu or Cu alloy converted by the treatment with the dissolved ozone aqueous solution. On the other hand, if the concentration of hydrofluoric acid in the diluted hydrofluoric acid solution exceeds 20%, when a silicon oxide film is used as the insulating film, the oxide film may be dissolved and removed, and the film may be reduced. More preferably, the concentration of hydrofluoric acid in the dilute aqueous hydrofluoric acid solution is 0.1 to 5%.
[0073]
According to another method of manufacturing a semiconductor device according to the present invention described above, a groove and / or an opening corresponding to a wiring layer is formed in an insulating film on a semiconductor substrate, and the insulating film including the groove and / or the opening is formed. A wiring material film made of Cu or a Cu alloy is deposited thereon, and a polishing solution containing at least one organic acid selected from aminoacetic acid and amidosulfuric acid, an oxidizing agent, and water, and the polishing solution shown in FIG. The wiring material film is polished using an apparatus until the surface of the insulating film is exposed. As described above, the polishing liquid hardly etches the Cu film or the Cu alloy film when the Cu film or the Cu alloy film is immersed, and several times to several tens times between the time of the immersion and the time of the polishing. 3 shows an etching rate difference. As a result, in the polishing step, the wiring material film is sequentially polished from its surface, that is, so-called etch back is performed. Therefore, the embedded wiring layer made of Cu or a Cu alloy is formed in the groove and / or the opening of the insulating film. It can be formed flush with the surface of the insulating film. Further, the wiring layer after the etch-back step is brought into contact with the polishing liquid, but since an oxide layer is formed on the exposed surface of the wiring layer, the wiring layer can be prevented from being etched by the oxide layer. .
[0074]
Further, the fine wiring material remaining on the insulating film, that is, Cu or Cu alloy is converted into an oxide by treating the surface of the insulating film including the wiring layer with an aqueous solution of dissolved ozone after the etch back process, Pollutants such as organic substances can be oxidatively decomposed. By treating with a diluted hydrofluoric acid aqueous solution after the treatment with the dissolved ozone aqueous solution, it is possible to easily dissolve and remove the oxide of Cu or Cu alloy and the oxidatively decomposed product of the contaminant on the insulating film.
[0075]
Therefore, it is possible to manufacture a semiconductor device having a high-precision buried wiring layer, a flat surface structure, and a clean surface from which organic substances and residual wiring materials on the insulating film surface have been removed.
[0076]
In addition, by adjusting the pH of the polishing solution to 9 to 14 with an alkali agent such as potassium hydroxide, even if the amount of the organic acid such as aminoacetic acid contained in the polishing solution is increased, Of the wiring layer can be prevented by an oxide film having a high etching barrier property formed on the surface thereof. Moreover, by increasing the content of the organic acid in the polishing liquid, the polishing rate of the wiring material film can be increased, and as a result, the etch-back time can be reduced.
[0077]
Further, by using a polishing liquid to which polishing abrasive grains such as silica particles are added, the polishing rate of the wiring material layer can be improved, so that the etch back time can be reduced. In addition, since the occurrence of cracks and scratches in the wiring material film in the etch-back step can be suppressed, a highly reliable embedded wiring layer can be formed in the groove and / or opening of the insulating film.
[0078]
【Example】
Hereinafter, preferred embodiments of the present invention will be described in detail.
[0079]
Example 1
First, as shown in FIG. 8A, an SiO ₂ film 22 having a thickness of, for example, 1000 nm as an interlayer insulating film is formed on a silicon substrate 21 having a diffusion layer such as a source and a drain (not shown) formed on the surface thereof by a CVD method. After the deposition, a plurality of trenches 23 having a shape corresponding to the wiring layer and having a depth of 500 nm were formed in the SiO ₂ film 22 by a photoetching technique. Subsequently, as shown in FIG. 8B, a barrier layer 24 made of TiN having a thickness of 15 nm and a Cu film 25 having a thickness of 600 nm are formed in this order on the SiO ₂ film 22 including the groove 23 by sputtering deposition. Deposited.
[0080]
Then, the substrate 21 shown in FIG. 8B is held upside down on the substrate holder 5 of the polishing apparatus shown in FIG. 1 described above, and the substrate is loaded on the turntable 1 by the support shaft 4 of the holder 5. A polishing pad 2 made of Nitta Corporation; a polishing pad 2 made of SUBA800 was given a load of 300 g / cm ² , and the polishing liquid was supplied from the supply pipe 3 while rotating the turntable 1 and the holder 5 in directions opposite to each other at a speed of 100 ppm. The Cu film 25 and the barrier layer 24 supplied to the polishing pad 2 at a rate of 20 ml / min and polished on the substrate 21 were polished until the surface of the SiO ₂ film 22 was exposed. Here, the polishing liquid comprises pure water containing 0.1% by weight of aminoacetic acid, 13.0% by weight of hydrogen peroxide, and 8% by weight of silica powder having an average particle size of 0.04 μm. On the other hand, the one having hydrogen peroxide of 130 was used. In the polishing step, the polishing liquid has an etching rate of zero at the time of contact with the Cu film, and a polishing rate at the time of polishing with the polishing pad of about 77 nm / min. Was. For this reason, in the polishing step, the convex Cu film 25 shown in FIG. 8B is preferentially polished from the surface that is in mechanical contact with the polishing pad, and the exposed barrier layer 24 is polished. An etchback has been made. As a result, as shown in FIG. 8C, the barrier layer 24 remains only in the groove 23 and the groove 23 covered with the barrier layer 24 is buried flush with the surface of the SiO ₂ film 22. The Cu wiring layer 26 was formed. Further, after the weight of the polishing pad 2 by the holder 5 of the polishing apparatus is released, and the rotation of the turntable 1 and the holder 5 is stopped, even if the Cu wiring layer 26 comes into contact with the polishing liquid, etching is performed. Did not progress.
[0081]
In the above-described polishing step (etch-back step) using the polishing apparatus of FIG. 1, polishing liquid was sequentially collected from the polishing pad, and the change in pH was measured by a pH meter. FIG. 9 shows a change in pH of the polishing liquid with respect to the polishing time. As is clear from FIG. 9, the pH drops once after the weight of the substrate by the holder and rises again. When this pH rises, for example, when 8 minutes have elapsed after the start of the load, the etching end point was determined. By setting the etch-back time by such endpoint detection, said SiO ₂ layer 22 flush with the surface of buried Cu wiring layer 26 can be reproducibly formed in the groove 23 of the SiO ₂ film 22.
[0082]
In the above-described polishing step (etch-back step) using the polishing apparatus shown in FIG. 1, the temperature change of the polishing pad and the voltage change of the drive motor of the turntable were measured by a temperature sensor. FIG. 10 shows a change in the temperature of the polishing pad with respect to the polishing time, and FIG. 11 shows a change in the voltage of the drive motor with respect to the polishing time. In FIG. 10 showing the temperature change, the temperature of the polishing pad rises immediately after the start of the load, becomes a constant temperature, and rises again. The time when this temperature rise occurred was defined as the etching end point. In FIG. 11 showing the voltage change, the voltage of the drive motor of the turntable rises to a constant voltage immediately after the start of the weighting, and the voltage rises again. The time when this voltage rises was taken as the etching end point. By setting the etch-back time by such endpoint detection, the SiO ₂ film 22 flush with the surface of buried Cu wiring layer in the groove 23 in the case of pH measurement in the same manner as the SiO ₂ film 22 of the polishing liquid as described above 26 could be formed with good reproducibility.
[0083]
Further, the substrate after the formation of the buried wiring layer was immersed in a dissolved ozone aqueous solution having an ozone concentration of 0.001% for 3 minutes, and then immersed in a dilute hydrofluoric acid aqueous solution having a hydrofluoric acid concentration of 90% for 90 seconds. . FIG. 12 is a spectrum diagram analyzed by XPS. The solid line is the spectrum of the surface immediately after the formation of the Cu wiring layer, the dotted line is the spectrum of the surface of the Cu wiring layer after the treatment with the dissolved ozone aqueous solution, and the one-dot chain line is the dilute hydrofluoric acid treatment. Is the spectrum of the surface of the Cu wiring layer. As is clear from FIG. 12, when the substrate after the formation of the wiring is immersed in a dissolved ozone aqueous solution and processed, the signal of metal Cu observed immediately after the formation of the wiring disappears as shown by the dotted line spectrum, and the surface of the Cu wiring layer is oxidized. You can see that it has changed to something. Thereafter, when treated with a diluted hydrofluoric acid aqueous solution, the signal of CuO observed in the treatment with the dissolved ozone aqueous solution disappears as shown by the dashed line, indicating that pure Cu was exposed on the surface of the Cu wiring layer. By treating with the dissolved ozone aqueous solution in this manner, organic substances such as aminoacetic acid remaining on the surface of the SiO ₂ film 22 and the like can be decomposed, and Cu remaining on the SiO ₂ film 22 can be converted into an oxide. Decomposed products of organic substances and oxides of Cu generated by the treatment of the dissolved ozone aqueous solution can be removed by the subsequent treatment of the diluted hydrofluoric acid aqueous solution, and formed on the surface of the Cu wiring layer 26 by contact with the polishing solution. The Cu oxide layer can also be removed. As a result, the surface of the SiO ₂ film 22 can be cleaned and pure Cu can be exposed on the surface of the Cu wiring layer 26.
[0084]
Therefore, it is possible to form the Cu wiring layer 26 buried with the depth in the groove 23 and the same thickness of the SiO ₂ film 22 according to the first embodiment in the SiO ₂ film 22 flush with the surface of the wiring The surface of the substrate 21 after the formation of the layer 26 has been planarized. Further, by performing a treatment with a dissolved ozone aqueous solution and a treatment with a dilute hydrofluoric acid aqueous solution after the formation of the Cu wiring layer 26, the surface of the SiO ₂ film 22 is cleaned, and an oxide layer serving as a resistance component generated by oxidation of the polishing liquid is formed. Since the removal is performed, a highly reliable semiconductor device having a buried Cu wiring layer having the original low resistance of Cu can be manufactured.
[0085]
In Example 1, pure water containing 0.86% by weight of amidosulfuric acid, 30% by weight of hydrogen peroxide, and 8% by weight of silica powder having an average particle size of 0.09 μm was used as the polishing liquid in Example 1. as in example 1, it was possible to form a wiring layer embedded in the groove of the interlayer insulating SiO ₂ film on the insulating SiO ₂ film surface flush.
[0086]
Example 2
First, as shown in FIG. 13A, an SiO ₂ film 22 having a thickness of, for example, 800 nm and a Si film having a thickness of 200 nm are formed on a silicon substrate 21 having a diffusion layer such as a source and a drain (not shown) formed on the surface thereof. ₃ after forming an interlayer insulating film by a N ₄ layer 27 is deposited in this order, a depth of 500nm having a shape corresponding to the _{the Si} 3 _{N 4} film 27 and the wiring layer by a photo-etching technique to the SiO ₂ film 22 A plurality of grooves 23 were formed. Subsequently, as shown in FIG. 13B, a barrier layer 24 made of TiN having a thickness of 15 nm and a Cu film 25 having a thickness of 600 nm are formed on the Si ₃ N ₄ film 27 including the groove 23 by sputter deposition. Deposited in order.
[0087]
Then, the substrate 21 shown in FIG. 13B is held upside down on the substrate holder 5 of the polishing apparatus shown in FIG. 1 described above, and the substrate is supported on the support shaft 4 of the holder 5 by a trade name of Rodel-Nitta. ; the polishing pad 2 consisting of SUBA800 give a load of 300 g / cm ^2, the rate of the while rotating in opposite directions the turntable 1 and the holder 5 at a rate of 100ppm respectively, 20 ml / min polishing liquid from the supply pipe 3 Then, the Cu film 25 and the barrier layer 24 supplied to the polishing pad 2 and deposited on the substrate 21 were polished until the surface of the Si ₃ N ₄ film 27 was exposed. Here, the polishing liquid comprises pure water containing 0.1% by weight of aminoacetic acid, 13.0% by weight of hydrogen peroxide, and 8% by weight of silica powder having an average particle size of 0.04 μm. On the other hand, the one having hydrogen peroxide of 130 was used. In the polishing step, the polishing liquid has an etching rate of zero at the time of contact with the Cu film, and a polishing rate at the time of polishing with the polishing pad of about 77 nm / min. Was. Therefore, the convex Cu film 25 shown in FIG. 13B is preferentially polished from the surface that is in mechanical contact with the polishing pad, and the exposed barrier layer 24 is polished. It was done.
[0088]
As a result, as shown in FIG. 13C, the barrier layer 24 remains only in the groove 23 and the groove 23 covered with the barrier layer 24 is flush with the surface of the Si ₃ N ₄ film 27. A buried Cu wiring layer 26 was formed. Further, after the weight of the polishing pad 2 by the holder 5 of the polishing apparatus is released, and the rotation of the turntable 1 and the holder 5 is stopped, even if the Cu wiring layer 26 comes into contact with the polishing liquid, etching is performed. Did not progress.
[0089]
Further, in the polishing step using a polishing solution containing the silica particles as polishing abrasive grains, the interlayer insulating film is formed of the Si ₃ N ₄ film 27 having excellent polishing resistance on the surface side. In the film was suppressed. Therefore, a semiconductor device provided with an interlayer insulating film having a good withstand voltage can be manufactured.
[0090]
Example 3
First, as shown in FIG. 14A, for example, a 1000 nm-thick Si ₃ N ₄ film as an interlayer insulating film is formed on a silicon substrate 21 having a diffusion layer such as a source and a drain (not shown) formed on the surface thereof by a CVD method. After depositing 27, a plurality of trenches 23 having a shape corresponding to the wiring layer and having a depth of 500 nm were formed in the Si ₃ N ₄ film 27 by a photoetching technique. Subsequently, as shown in FIG. 14B, a Cu film 25 having a thickness of 600 nm was deposited on the Si ₃ N ₄ film 27 including the groove 23 by sputter deposition.
[0091]
Next, the substrate 21 shown in FIG. 14B is held upside down on the substrate holder 5 of the polishing apparatus shown in FIG. 1 described above, and the support shaft 4 of the holder 5 holds the substrate 21 by the trade name of Rodel-Nitta. 400 g / cm ² is applied to the polishing pad 2 made of SUBA800, and the polishing liquid is supplied from the supply pipe 3 at a rate of 20 ml / min while rotating the turntable 1 and the holder 5 in opposite directions at a speed of 100 ppm. Then, the Cu film 25 supplied to the polishing pad 2 and deposited on the substrate 21 was polished until the surface of the Si ₃ N ₄ film 27 was exposed. Here, the polishing liquid is composed of pure water containing 0.9% by weight of aminoacetic acid, 22.0% by weight of hydrogen peroxide and 3.7% by weight of potassium hydroxide. A solution having a pH of 10.5 with about 24 hydrogen was used. In the polishing step, the polishing liquid has an etching rate of zero at the time of contact with the Cu film, and a polishing rate at the time of polishing with the polishing pad of about 220 nm / min. Was. For this reason, the convex Cu film 25 shown in FIG. 14B is polished preferentially from the surface that is in mechanical contact with the polishing pad, that is, so-called etch back is performed.
[0092]
As a result, a buried Cu wiring layer 26 flush with the surface of the Si ₃ N ₄ film 27 was formed in the groove 23 as shown in FIG. Further, after the weight of the polishing pad 2 by the holder 5 of the polishing apparatus is released, and the rotation of the turntable 1 and the holder 5 is stopped, even if the Cu wiring layer 26 comes into contact with the polishing liquid, etching is performed. Did not progress.
[0093]
Further, the interlayer insulating film 27 having the groove 23 in which the buried Cu wiring layer 26 is formed is made of Si ₃ N _{4 having} an excellent Cu diffusion barrier property. As a result, since Cu does not diffuse from the Cu wiring layer 26 to the silicon substrate 21 through the interlayer insulating film, contamination of the silicon substrate 21 can be performed without forming a barrier layer such as TiN on the inner surface of the groove 23. Was able to avoid.
[0094]
Example 4
First, as shown in FIG. 15A, an SiO ₂ film 33 having a thickness of, for example, 1000 nm as a first interlayer insulating film is formed on a p-type silicon substrate 32 having an n ⁺ -type diffusion layer 31 formed on the surface by a CVD method. Then, via holes 34 were formed in the SiO ₂ film 33 corresponding to the diffusion layers 31 by photo-etching technology. Subsequently, as shown in FIG. 15B, a barrier layer 35 made of TiN having a thickness of 20 nm is deposited on the SiO ₂ film 33 including the via hole 34 by sputtering deposition, and then a barrier layer 35 having a thickness of 1100 nm is deposited by sputtering deposition. A Cu film 36 was deposited.
[0095]
Then, the substrate 32 shown in FIG. 15B is held upside down on the holder 5 of the polishing apparatus shown in FIG. 1 described above, and the support shaft 4 of the holder 5 holds the substrate 32 by a trade name of Rodel-Nitta; giving a load of 300 g / cm ² to the polishing pad 2 consisting of SUBA800, the turntable 1 and the holder 5 is rotated in the opposite directions at a rate of 100ppm respectively, the polishing liquid from the supply pipe 3 20 ml / min of rate The Cu film 36 and the barrier layer 35 supplied to the polishing pad 2 and deposited on the substrate 32 were polished until the surface of the SiO ₂ film 33 was exposed. Here, the polishing liquid is composed of pure water containing 0.2% by weight of aminoacetic acid, 20.0% by weight of hydrogen peroxide and 10% by weight of silica powder having an average particle size of 0.04 μm. On the other hand, one having 100 hydrogen peroxide was used. In the polishing step, the polishing liquid has an etching rate of zero at the time of contact with the Cu film, and a polishing rate at the time of polishing with the polishing pad is about 70 nm / min, which shows a sufficiently large etching rate difference as compared with the immersion. Was. For this reason, the convex Cu film 36 shown in FIG. 15B is preferentially polished from the surface that is in mechanical contact with the polishing pad, and the exposed barrier layer 35 is polished. It was done. As a result, as shown in FIG. 15C, the barrier layer 35 remains only in the via hole 34, and the Cu that is flush with the surface of the SiO ₂ film 33 is formed in the via hole 34 covered with the barrier layer 35. Was formed. Further, after the weight of the polishing pad 2 by the holder 5 of the polishing apparatus is released, and the rotation of the turntable 1 and the holder 5 is stopped, the etching proceeds even if the via fill 37 comes into contact with the polishing liquid. I never did. Subsequently, the substrate after forming the via-fill 37 is immersed in a dissolved ozone aqueous solution having an ozone concentration of 0.002% for 3 minutes, and then immersed in a dilute hydrofluoric acid aqueous solution having a hydrofluoric acid concentration of 5% for 9 seconds. Thus, the surface of the SiO ₂ film 33 was cleaned.
[0096]
Next, as shown in FIG. 16D, an Si ₃ N ₄ film 38 having a thickness of, for example, 800 nm as a second interlayer insulating film is deposited on the SiO ₂ film 33 including the via fill 37 by a CVD method. A plurality of trenches 39 having a shape corresponding to the wiring layer and having a depth of 400 nm were formed in the Si ₃ N ₄ film 38 by a photoetching technique. Further, a through hole 40 was formed in the groove 39 located on the via fill 37 by a photo-etching technique. Subsequently, as shown in FIG. 16E, a 900 nm-thick Cu film 41 was deposited on the Si ₃ N ₄ film 38 including the grooves 39 and the through holes 40 by sputter deposition.
[0097]
Next, the substrate 32 shown in FIG. 16E is held upside down on the substrate holder 5 of the polishing apparatus shown in FIG. 1 described above, and the substrate is manufactured by Rodel-Nitta by the support shaft 4 of the holder 5. A polishing pad 2 made of SUBA800 is applied with a load of 300 g / cm ² , and the turntable 1 and the holder 5 are rotated in opposite directions at a speed of 100 ppm, respectively, while rotating the turntable 1 and the holder 5 in a direction similar to that used in the above-described etch-back process. A polishing liquid having a composition was supplied from the supply pipe 3 to the polishing pad 2 at a rate of 20 ml / min, and the Cu film 41 deposited on the substrate 32 was polished until the surface of the Si ₃ N ₄ film 38 was exposed. As a result, the convex Cu film 41 shown in FIG. 16E was polished preferentially from the surface that mechanically contacts the polishing pad, that is, so-called etch back was performed. As a result of such etchback, a buried Cu wiring layer 42 flush with the surface of the Si ₃ N ₄ film 38 was formed in the groove 39 as shown in FIG. At the same time, a buried Cu wiring layer 42 connected to the via fill 37 through the through hole 40 was formed. Further, even after the weight of the polishing pad 2 by the holder 5 of the polishing apparatus is released and the rotation of the turntable 1 and the holder 5 is stopped, even if the Cu wiring layer 42 comes into contact with the polishing liquid, etching is performed. Did not progress.
[0098]
Therefore, according to the fourth embodiment, the first and second interlayer insulating films 33 and 39 are provided, and the first interlayer insulating film 33 is formed with the via fill 37 flush with the surface thereof. In addition, a semiconductor device having a multilayer wiring structure in which a Cu wiring layer 42 flush with the surface was formed and having a flattened surface could be manufactured.
[0099]
【The invention's effect】
As described above, according to the present invention, when immersing Cu or Cu alloy, Cu or Cu alloy is hardly etched, and the etching rate difference between immersion and polishing is several times to several tens times. The following polishing liquid for copper-based metal can be provided.
[0100]
Further, according to the present invention, a groove and / or an opening is formed in an insulating film on a semiconductor substrate, and a wiring material film made of Cu or Cu alloy deposited on the insulating film can be etched back in a short time. A method for manufacturing a semiconductor device having a flat surface in which a buried wiring layer made of Cu or a Cu alloy is formed in the insulating film so as to be flush with the surface of the insulating film can be provided.
[0101]
Further, according to the present invention, a groove and / or an opening is formed in an insulating film on a semiconductor substrate, and a wiring material film made of Cu or a Cu alloy deposited on the insulating film is etched back in a short time to achieve insulation. It is possible to form a buried wiring layer flush with the film surface, and to provide a method of manufacturing a semiconductor device having a clean and flat surface from which organic substances and residual wiring material on the insulating film surface after etch-back are removed.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a polishing apparatus used in a polishing step of the present invention.
FIG. 2 shows the amount of hydrogen peroxide in a polishing liquid having a composition of 0.1% by weight of aminoacetic acid, hydrogen peroxide and water, the etching rate of a Cu film when immersed in the polishing liquid, and the Cu during polishing. FIG. 3 is a characteristic diagram showing a relationship with a polishing speed of a film.
FIG. 3 is a cross-sectional view showing a state in which a Cu film having irregularities is immersed in a polishing solution having a composition composed of aminoacetic acid, hydrogen peroxide, and water, and is polished using a polishing apparatus.
FIG. 4 is a spectrum diagram by XPS of a Cu film surface before processing, after immersion of the polishing liquid of the present invention, and after polishing treatment.
FIG. 5 shows the amount of hydrogen peroxide in a polishing solution having a composition of 0.9% by weight of aminoacetic acid, hydrogen peroxide and water, the etching rate of a Cu film when immersed in the polishing solution, and the Cu during polishing. FIG. 3 is a characteristic diagram showing a relationship with a polishing speed of a film.
FIG. 6 shows the relationship between the amount of hydrogen peroxide in a polishing liquid having a composition consisting of amidosulfuric acid, hydrogen peroxide and water, the etching rate of a Cu film when immersed in the polishing liquid, and the polishing rate of the Cu film during polishing processing. FIG. 4 is a characteristic diagram showing a relationship.
FIG. 7 is a characteristic diagram showing a pH of a polishing liquid of the present invention and a thickness change of an oxide layer formed on a Cu film surface.
FIG. 8 is a sectional view showing a manufacturing step of the semiconductor device according to the first embodiment of the present invention.
FIG. 9 is a characteristic diagram showing a change in pH of a polishing liquid in a polishing process (etch-back step) of Example 1.
FIG. 10 is a characteristic diagram showing a temperature change of a polishing cloth in a polishing process (etchback process) of Example 1.
FIG. 11 is a characteristic diagram illustrating a voltage change of a drive motor of a turntable in a polishing process (etchback process) according to the first embodiment.
FIG. 12 is a spectrum diagram obtained by XPS analysis of the surface immediately after the formation of the Cu wiring layer, the surface of the Cu wiring layer after ozone treatment, and the surface of the Cu wiring layer after dilute hydrofluoric acid treatment in Example 1 of the present invention.
FIG. 13 is a sectional view showing a manufacturing step of the semiconductor device in the second embodiment of the present invention.
FIG. 14 is a cross-sectional view showing a manufacturing step of the semiconductor device according to the third embodiment of the present invention.
FIG. 15 is a sectional view showing a manufacturing step of the semiconductor device in the fourth embodiment of the present invention.
FIG. 16 is a sectional view illustrating a manufacturing step of the semiconductor device in the fourth embodiment of the present invention.
[Explanation of symbols]
1 ... turntable 2 ... polishing pad, 3 ... supply pipe, 5 ... holder, 11,21,32 ... silicon substrate, 12,25,36,41 ... Cu film, 13 ... oxide layer, 22 and 33 ... SiO ₂ Films, 23, 39 ... grooves, 24, 35 ... barrier layers, 26, 42 ... Cu wiring layers, 37 ... via fills.

Claims (5)

A polishing liquid for a copper-based metal, comprising an aminoacetic acid, an oxidizing agent, abrasive grains and water. The polishing liquid according to claim 1, wherein the oxidizing agent is hydrogen peroxide. 3. The polishing liquid according to claim 1, wherein the aminoacetic acid is contained in the polishing liquid in an amount of 0.01 to 10% by weight. 4. 2. The polishing liquid according to claim 1, wherein the content ratio of the amino acetic acid and the oxidizing agent is 20 or more with respect to 1 of the organic acid by weight. The polishing liquid for copper-based metals according to any one of claims 1 to 4, further comprising an alkali agent for adjusting the pH to 9 to 14.

Images