JP3572366B2 - Method for manufacturing device having microstructure - Google Patents

Description

【００１９】
で示される。従って、濡れ性の良い系では、液体の凝集力よりも固体の液体に対する付着力が上回って、液体は固体表面に速やかに拡張し、濡れ性の悪い系では、固体の液体に対する付着力よりも液体の凝集力が上回って、液体は固体表面に拡張せず、ボールアップする。
【００２０】
上述したように、微小装置の表面は、一般に、酸化膜系の材料が主たる地位を占めているため、ナフタレンの融液（加熱によって融解し、液体となったナフタレン）は、微小装置の形成された領域と濡れ性が悪く、従って、薄膜状に拡張することなくボールアップしてしまうために、このままでは、微小装置の形成された領域をナフタレンでコーティングすることはできない。しかし、アルミニウムの表面であればナフタレンの融液は薄膜状に拡張するので、アルミニウムの領域をナフタレンでコーティングすることはできる。
着目すべきことは、固体（微小装置の形成された領域、アルミニウム領域、酸化膜領域）、液体（ナフタレン融液）、気体（大気）の３相の接触点がどうなっているかによって、一つの凝集体としての液体（ナフタレン融液）の振る舞いが定まることにある。下記する実施例の図１の（Ｄ）において、微小装置の形成された領域にナフタレン融液が拡張している理由は、固体、液体、気体の３相の接触点（実際は閉曲線）の位置による。ナフタレン融液の接触点が微小装置の形成された領域あるいはウエハ周辺の酸化膜領域にあれば、ナフタレン融液の凝集力が付着力を上回り、従って、ナフタレン融液は凝集して表面積を減らそうとするし、一方、ナフタレン融液の接触点が微小装置の形成された領域を取り囲むアルミニウム領域にあれば、ナフタレン融液の付着力が凝集力を上回り、従って、ナフタレン融液は拡張して固体表面を濡らそうとする。これらの攻めぎあいの結果、ナフタレン融液の接触点は、微小装置の形成された領域を取り囲むアルミニウム領域の最外周部であって、アルミニウム領域を取り囲む酸化膜領域の最内周部、すなわち、微小装置の形成された領域を取り囲むアルミニウム領域と該アルミニウム領域を取り囲む酸化膜領域との境界にピニングされることになる。この状態は熱力学的には準安定な状態であって、もし固体、液体、気体の３相の接触点が微小装置の形成された領域に発生したならば、例えば微小装置の内部のキャビティから気泡が上がってきた場合、ナフタレン融液は速やかにちぎれちぎれのボールアップした状態に転移する。
【００２１】
実際には、例えば下記の実施例に出てくるシリコンウエハサイズの液量は、重力を無視できる微小液滴ではないし、また、微小装置の形成された主面には微小装置の複雑な構造があり、いわゆる濡れと毛管現象とが同一の凝集液体に対して起り、しかも液体内部の圧力分布と微小装置を構成する部材の応力等と複雑に関与しているため、濡れの議論を行うことはかなり難しい。従って、ここでは定性的に下記表１にまとめるに留める。
【００２２】
【表１】

【００２３】
表１において、例えばＩＰＡ系の濡れ性を「良い」、接触角を「小さい」と定性的に表現してあるが、より正しくは、接触角（θ）を０とし、固気界面張力σ_ｓと固液界面張力（σ_ｉ）との差（σ_ｓ−σ_ｉ）すなわち付着張力を濡れ性の尺度とすべきものである。また、微小装置の構造のうち、毛管とみなし得る構造に対しての濡れは、固気界面張力（σ_ｓ）が、固液界面張力（σ_ｉ）を上回っていれば、濡れ性が良いと言うことが出来、多孔質体に液体が染み込むように、自発的に濡れていき、場合にもよるが、液体の表面張力そのものはあまり問題にならない。
【００２４】
【実施例】
以下、本発明の微小装置の製造方法について、実施例によって具体的に説明する。
【００２５】
【実施例１】
本発明の、一時的な保護膜としての昇華性物質の固体被膜の形成方法について、図１によって説明する。
（Ａ）まず、半導体素子あるいは微小装置を形成した半導体基板１００を加熱する。加熱温度は低くとも、用いる昇華性物質の融点以上であれば充分であり、該物質の沸点までは可能である。ここで、１０３は半導体素子あるいは微小装置の形成された領域、１０２は半導体素子あるいは微小装置を形成した領域１０３を取り囲むアルミニウム領域、１０１はアルミニウム領域１０２を取り囲む酸化膜領域である。
【００２６】
（Ｂ）次に、上記構造体の主面に、アルミニウム領域１０２を覆う程度の量のナフタレン融液を滴下し、ナフタレン融液陵１０４を形成する。なお、ナフタレン融液と半導体素子あるいは微小装置の形成された領域１０３とは濡れ性が悪く、滴下するナフタレン融液の量が少ないうちは、フライパンに水を滴下したときのように、半導体素子あるいは微小装置の形成された領域１０３をナフタレン融液が覆うことはないが、滴下するナフタレン融液の量がある程度になると、半導体基板１００のサイズの液膜を表面張力で保持した状態となる。もちろん多すぎれば、半導体基板１００からナフタレン融液が溢れだしてしまう。滴下するナフタレン融液の最適量は、半導体基板１００のサイズと、ナフタレン融液と酸化膜領域１０１との濡れ性によって定まる。
【００２７】
（Ｃ）次に、上記構造体のナフタレン融液陵１０４を蒸発により目減りさせる。なお、ナフタレン融液は酸化膜とは濡れ性が悪く、酸化膜領域１０１とアルミ領域１０２との境界までは、ナフタレン融液陵１０４は大きな接触角を保ったまま底面積を減少させていく。
【００２８】
（Ｄ）次に、上記構造体のナフタレン融液陵１０４を蒸発によってさらに目減りさせる。なお、ナフタレン融液はアルミとは濡れ性が良く、酸化膜領域１０１とアルミニウム領域１０２との境界までは、ナフタレン融液陵１０４は大きな接触角を保ったまま底面積を減少させていき、その後は底面をアルミニウム領域１０２の最外周にそろえたまま接触角を小さくしていく。
【００２９】
（Ｅ）最後に、上記構造体のナフタレン融液陵１０４の液体被膜の厚さが適当な厚さ、例えば１００μｍ、まで目減りしたところで、上記構造体を冷却し、ナフタレン融液陵１０４を一時的な保護膜としての、半透明のナフタレン固体被膜１０５にする。
【００３０】
上記例においては、半導体素子あるいは微小装置の形成された領域１０３を取り囲むアルミニウム領域１０２を基板１００の外周部に設けた場合について説明したが、これに限定されるわけではなく、各チップごと、あるいは数チップごとにそれらを取り囲むように設けても良いし、基板１００上に設けず、治具に設けても良い。また、材質もアルミニウムに限らず、濡れ性が良ければなんでも良く、種々の金属を利用することができる。治具は、基板一枚に限らず、基板複数枚を同時に取り囲むものでもよい。治具と基板との隙間に昇華性物質を含む液体が毛管現象で侵入することを防止するために、他の液体を予め注入しておいてもよい。また、酸化膜領域１０１は、ナフタレン融液陵１０４と濡れ性の悪い部材であればなんでも良く、テフロン樹脂も利用することができ、また基板１００上に設けず、治具に設けても良い。
【００３１】
また、上記例においては、ナフタレン融液を滴下させる場合について説明したが、これに限らず、ナフタレンの溶液を用いてもよい。ナフタレンの溶液は、室温で溶液である必要もなく、飽和（室温）濃度以上の、加熱された濃厚溶液であっても良い。また、滴下後に溶剤を選択的に蒸発させ、濃縮を行ってもよい。
また、上記例においては、ナフタレン融液陵１０４を形成するに際して、半導体基板１００を加熱してからナフタレン融液を滴下する場合について説明したが、逆でも良いし、半導体基板１００にナフタレンの粉末を散布してから加熱し、融解させてもかまわない。もちろん、粉末の散布に限らず、半導体基板１００に静電付着させてから加熱し、融解させてもかまわない。
【００３２】
また、半導体基板１００の加熱方法は、ヒータ加熱の他種々の方を用いることができる。また、上記例ではナフタレンを例に説明したが、これに限られるわけではなく常温・常圧で固体の昇華性物質であればよく、例えばｐ−ジクロロベンゼン、テトラクロロジフロロエタン、場合によっては水に溶解性のあるショウノウでも良い。また、昇華性物質を単独で使用する他、他の成分が混じっていてもよく、有機溶剤を混入し、凝固点降下を起こしている昇華性物質を用いてもよい。また、一時的な保護膜も完全な固体被膜でなくてもよく、ミクロにみたときに、多孔質の固相に液相が共存しても良い。
【００３３】
また、上記の（Ｂ）から（Ｄ）に至る、ナフタレン融液陵１０４の目減りは、蒸発による目減りの他、スポイトで吸い出しても良い。場合によっては、（Ｄ）の被膜形成に必要なだけのナフタレン融液を滴下し、加速度等によってアルミニウム領域１０２まで拡張してもよい。この加速度による液体の拡張は、１０３の微小装置の形成された領域とナフタレン融液との濡れ性が極めて悪く、ナフタレン融液を滴下していった時、（Ｂ）の基板１００の主面全面を覆うナフタレン融液陵１０４を形成する前に基板からナフタレン融液が溢れだしてしまうような場合にも有効である。
また、半導体素子あるいは微小装置の形成された領域１０３を取り囲むアルミニウム領域１０２が完全に連なって形成されている必要はなく、例えば、ある間隔をおいて島状に形成されていても良い。また、アルミニウム領域１０２を取り囲む酸化膜領域１０１も、完全に連なって形成されている必要はなく、例えばある間隔をおいて島状に形成されていても良い。
【００３４】
次に、本発明の方法を用いた場合のダイシングの手順の一例を、図２によって説明する。
（Ａ）まず、フォト・ファブリケーションで代表される半導体要素プロセスや、マイクロマシーニング技術を駆使して、半導体基板１の主面に、半導体素子あるいは微小装置を形成する。
（Ｂ）次に、上記構造体の半導体素子あるいは微小装置を形成した主面に、図で説明した手法によって、一時的な保護膜としてのナフタレン固体被膜１０５を形成する。
（Ｃ）次に、上記構造体の裏面にマウントテープ３を貼付する。
（Ｄ）次いで、上記構造体をダイアモンド砥石でダイシング４し、チップ５に分割する。
（Ｅ）最後に、ピックアップ６によってチップ５をマウントテープ３から取り外す。
【００３５】
チップ上の昇華性物質の固体被膜は、放置するだけで容易にしかも完全に除去でき、残渣が残ることは無い。必要があれば加熱あるいは減圧条件下で速やかに除去することができる。
【００３６】
次に、図１で説明した手法を、表面型マイクロマシンに適用した場合について、例えば熱分離構造の赤外線センサを例として、図３によって説明する。なお、図３（Ａ）〜（Ｅ）は、それぞれ図１（Ａ）〜（Ｅ）に対応する。
（Ａ） 図３において、５００は主面に赤外線センサの形成されたシリコン基板、５０１はシリコン窒化膜、５０２はアルカリ異方性エッチングによりキャビティ５０４を形成するためのエッチング開口部、５０３は熱分離されたシリコン窒化膜のダイアフラムである。ここで、一般的なダイアフラム５０３のサイズはおよそ数十〜数百μｍ、エッチング開口部５０２のサイズはおよそ数〜数十μｍである。なお、実際には、ダイアフラム５０３上には熱電対や赤外線吸収部等が形成されているが、ここでの説明には不要なので省略した。
【００３７】
（Ｂ）および（Ｃ） ナフタレン融液陵１０４を形成したとき、ナフタレン融液と赤外線センサを構成する部材であるシリコンやシリコン窒化膜とは濡れ性が悪いため、高々数十μｍのエッチング開口部５０２からキャビティ５０４内にナフタレン融液は侵入しない。
（Ｄ） ナフタレン融液陵１０４が目減りして液膜厚さが薄くなったときでも、赤外線センサの形成された領域に拡がった被膜は保持される。これはナフタレン融液と濡れ性の良いアルミニウム領域１０２が設けられ、これによってナフタレン融液が拡げられているためであり、ナフタレン融液と濡れ性の良いアルミニウム領域１０２が設けられていない場合、フライパンの中で水を加熱蒸発させるときのように、ちぎれちぎれのボールアップした状態で縮小していくことになる。
（Ｅ） 上記（Ｄ）のようにナフタレン融液の液体被膜が素子の形成された領域を覆っている状態から冷却すると、一時的な保護膜としてのナフタレンの固体被膜１０５が形成される。
【００３８】
【実施例２】
次に、図１の１０３の微小装置の形成された領域とナフタレン融液との濡れ性が極めて悪く、ナフタレン融液を滴下していったときに、図１（Ｂ）の基板１００の主面全面を覆うナフタレン融液陵１０４を形成する前に、基板からナフタレン融液が溢れだしてしまう場合の実施例を図４によって説明する。なお、このような例は、例えば、微小装置を構成する表面の主たる部位がシリコン酸化膜で形成されている場合である。
【００３９】
（Ａ） 半導体素子あるいは微小装置の形成された半導体基板１００を加熱する。
（Ｂ） 上記構造体の主面に、適当量のナフタレン融液を滴下し、ナフタレン融液島群６００を形成する。
（Ｃ） 上記構造体のナフタレン融液島群６００を、ナフタレン融液と濡れ性の良い部材、例えば金属ワイヤ６０１、で基板１００上をスキャンする。
（Ｄ） これによって、上記構造体のナフタレン融液島群６００がつながり、ナフタレン融液陵１０４が形成される。
（Ｅ） 上記構造体のナフタレン融液陵１０４を蒸発によって目減りさせる。
（Ｆ） 上記構造体のナフタレン融液陵１０４の液体被膜の厚さが適当な厚さ、例えば１００μｍ、まで目減りしたところで、上記構造体を冷却し、ナフタレン融液陵１０４を半透明のナフタレン固体被膜１０５にする。
上記方法は、図１に記載した方法でナフタレン固体被膜１０５が形成できる場合であっても適用でき、ナフタレン固体被膜１０５程度の体積のナフタレン融液を滴下すれば良いので、蒸発・目減りさせる工程に要する時間を極端に短くすることができる。
【００４０】
以上、図１及び図４に示した実施例では、図３で説明したように、キャビティ内部まで昇華性物質を充填する手法ではない。本発明方法を適用する微小装置、あるいは製造工程において、場合によっては、表面を被覆保護するのみならず、キャビティ内部まで昇華性物質を充填したいというニーズがある。このような例は、例えば、ダイシングソーがキャビティを横切って切断する場合に発生する。
【００４１】
【実施例３】
上記のようなニーズに応える実施例について、図５及び図６によって説明する。なお、図５と図６において（Ａ）〜（Ｆ）はそれぞれ同じ工程に対応する。
（Ａ） まず、半導体素子あるいは微小装置を形成した半導体基板１００を加熱する。この場合、加熱温度は、ナフタレンの融点以上で、ＩＰＡの沸点以下が良い。なお、１０１は酸化膜領域、１０２はアルミニウム領域である。
（Ｂ） 上記構造体の主面に、適当量のＩＰＡ（イソプロピルアルコール）を滴下し、ＩＰＡ液体被膜７００を形成する。ＩＰＡは素子を構成する材料と濡れ性が良いために、エッチングのための開口部５０２からキャビティ５０４内に侵入し、従ってキャビティ５０４内の空気が、ＩＰＡで置換される。この時、アルミニウム領域１０２を取り囲む酸化膜領域１０１がないと、ＩＰＡはアルミニウムに対して極めて濡れ性が良いために、基板１００の上面から流れ出し、ＩＰＡ液体被膜７００を形成することができない。
（Ｃ） 上記構造体にナフタレン融液を滴下し、ナフタレン融液陵１０４を形成する。この時、滴下したナフタレン融液とＩＰＡ液体被膜７００とは相互に溶解する。キャビティ５０４内のＩＰＡとナフタレン融液とは相互に拡散し、キャビティ５０４内のＩＰＡはナフタレン融液で置換されていく。
（Ｄ）および（Ｅ） 上記構造体のナフタレン融液陵１０４を蒸発により目減りさせる。このとき、ＩＰＡの蒸発の方がナフタレンの蒸発より優先して起り、ナフタレン融液陵１０４内のＩＰＡ濃度もキャビティ５０４内のＩＰＡ濃度も下がっていく。
（Ｆ） 上記構造体のナフタレン融液陵１０４の液体被膜の厚さが適当な厚さ、例えば１００μｍ、まで目減りしたところで、上記構造体を冷却し、ナフタレン融液陵１０４を半透明のナフタレン固体被膜１０５とする。この時、キャビティ５０４内のナフタレン融液も固化する。
【００４２】
上記説明は、ＩＰＡを用いた場合を例として説明したが、これに限られるわけではなく、用いる昇華性物質を溶解し、微小装置を構成する材料と濡れ性の良い溶剤であれば何でもよく、ＩＰＡのほか、メタノール、エタノール、アセトン、ベンゼン等が利用可能である。また、溶剤も単独で用いるほか、混合溶剤であっても良いし、昇華性物質を溶解した溶剤であっても良い。
【００４３】
次に、以上の実施例における、微小装置の形成された領域を取り囲むアルミニウム領域のパターン形状について図７によって説明する。図７において、（Ａ）は図１における微小装置の形成された基板１００の主面を上方から見た図で、チップ９０１と、これらチップ９０１の集まった領域が図１における微小装置の形成された領域１０３であって、それを取り囲むアルミニウム領域１０２は、チップ９０１の四分の一サイズのアルミニウムのベタパターン９０２を配して形成してある。図７（Ａ）の構造体に図１〜図６で説明した手法によってナフタレン固体被膜１０５を形成すると、図７（Ｂ）に示したように、ナフタレン固体被膜１０５がアルミニウム領域１０２の最外周形状で形成される。
【００４４】
この例は、アルミ領域１０２が角部を有する形状である。図１（Ｄ）、図４（Ｅ）、図５（Ｅ）において、ナフタレン融液陵１０４は、接触角が小さく、表面張力によってちじこまろうとしているところを、若干濡れ性の良いアルミニウムによって保持されている状態にある。アルミニウム領域１０２が角部を有していると、角部のナフタレン融液陵１０４は、アルミ領域１０２と酸化膜領域１０１との境界よりも内側、すなわち微小装置の形成された領域１０３側、に若干引き込まれる。チップ９０１が極めて小さい場合、この引き込まれる量が、ベタパターン９０２の対角線よりも大きくなってしまう場合がある。このような場合には、ナフタレン融液陵１０４と基板１００表面と大気との境界線が微小装置の形成された領域の角部まで引き込まれた途端に、ナフタレン融液陵１０４は被膜として存在できなくなり、フライパンの上の水のような島状の形態に変化し、従ってナフタレン固体被膜を形成することができない。
【００４５】
図８は、このような不具合の発生しないアルミニウム領域パターンである。ここでは、アルミニウム領域の最外周形状を丸パターン９０３とし、角部を有しない形状とした。もちろん、丸パターンの他、楕円でも良く、緩やかな曲線で構成されていれば良い。
【００４６】
【実施例４】
本実施例においては、本発明方法のダイシング工程への適用ではなく、犠牲層エッチング後の乾燥工程への適用について、図１２によって説明する。
（Ａ） 図１０（Ｆ）と同様にして、構造体を純水２０９に浸漬する。
（Ｂ） 次いで、上記構造体をＩＰＡ槽に浸漬し、純水２０９をＩＰＡ２１１で置換する。
（Ｃ） 上記構造体をナフタレン融液槽に浸漬し、ＩＰＡ２１１をナフタレン融液で置換した後、ナフタレン融液槽から引き上げ、ナフタレン融液を固化し、ナフタレン固体被膜２１２を形成する。
【００４７】
（Ｄ） 上記構造体を放置するだけで、固体であるナフタレンが昇華し、スティッキングすることなく微小装置２００を得ることができる。これは、ギャップ２０４内に置換されているものが液体の水ではなく固体のナフタレンであるため、蒸発に際して表面張力による引き込み現象が起らないことによるものである。
【００４８】
上記実施例、すなわち、犠牲層エッチング工程をダイシングによるチップ分割工程の直前に行なえば、図１２（Ｃ）の状態でダイシングすればよく、スティッキング防止策と、ダイシング時の保護策を同時に行なうことが可能であり、トータルプロセスを極めて簡素化することができる。
【００４９】
また、上記実施例では、溶剤としてＩＰＡを、昇華性物質としてナフタレンを用いた場合の例について説明したが、これに限定されるものではなく、溶剤としては、水とナフタレンとを溶解させるものであれば何でもよく、ＩＰＡのほか、メタノール、エタノール、アセトン等が利用可能であり、また、溶剤も単独で用いるほか、混合溶剤であっても良く、例えば昇華性物質の溶けた溶剤であっても良い。また、昇華性物質としては常温・常圧で固体の昇華性物質であればよく、例えば犠牲層エッチング工程の乾燥方法として用いるのであれば、水に対して溶解性のあるショウノウを用いることもできる。
【００５０】
なお、本発明の実施例の説明は、主として半導体基板に形成したセンサを例として行なったが、これに限られるわけではなく、例えば、ガラス基板や金属基板であっても良く、さらには、基板ではなく、構造体の一主面であっても適用可能である。もちろん微小装置が形成されている必要もなく、微小構造を有する装置あるいは部品の、一時的な保護膜を必要とする種々の工程に適用することができる。
【００５１】
【発明の効果】
以上述べてきたように、微小装置の製造方法を本発明構成の方法とすることにより、従来技術の有していた課題を解決し、微小装置を破損することなく、均一で半透明で保持時間の長い一時的な保護膜を形成することが出来る。そして本発明の方法によれば、工数が少なく、設備投資及びコストが安く、汚染の心配が少なく、保護膜の除去が容易かつ完全で検査が不要で、かつ歩留まりが高く生産性に優れているという特徴がある。そのため、例えば微小装置のダイシング工程に用いれば、高歩留りでチップ分割をすることができる。また、例えば犠牲槽エッチング後の乾燥工程に用いれば、特殊な装置を必要とすることなく、容易に、スティッキングなしに微小装置を得ることが出来る、という効果が得られる。
【図面の簡単な説明】
【図１】本発明の、昇華性物質の固体被膜による一時的な保護膜の形成方法（その一）を示す工程図。
【図２】本発明の、昇華性物質の固体被膜を一時的な保護膜として用いるダイシング方法を示す工程図。
【図３】本発明の、昇華性物質の固体被膜の形成方法（その一）の赤外線センサへの適用例を示す工程図。
【図４】本発明の、昇華性物質の固体被膜による一時的な保護膜の形成方法（その二）を示す工程図。
【図５】本発明の、昇華性物質の固体被膜による一時的な保護膜の形成方法（その三）を示す工程図。
【図６】本発明の、昇華性物質の固体被膜による一時的な保護膜の形成方法（その三）の赤外線センサへの適用例を示す工程図。
【図７】本発明の、昇華性物質の固体被膜による一時的な保護膜の形成方法による保護膜のパターン（その一）を示す図。
【図８】本発明の、昇華性物質の固体被膜による一時的な保護膜の形成方法による保護膜のパターン（その二）を示す図。
【図９】微小装置の基本構造を示す図。
【図１０】微小装置の製造方法を示す図。
【図１１】フリーズドライ法を説明するための図。
【図１２】本発明の乾燥方法を説明するための図。
【図１３】従来の製造方法の第１の例を示す工程図であり、樹脂やワックスを一時的な保護膜として用いたダイシング方法を示す図。
【図１４】従来の製造方法の第２の例を示す工程図であり、紫外線硬化型の糊剤を用いた粘着テープを一時的な保護膜として用いたダイシング方法を示す図。
【図１５】従来の製造方法の第３の例を示す工程図であり、樹脂やワックスを一時的な保護膜として用いたダイシング方法の微小機械への適用を示す図。
【符号の説明】
１…半導体基板 ２…樹脂またはワックスからなる保護膜
３…マウントテープ ４…ダイシング溝
５…チップ ６…ピックアップ
７…洗浄トレー １０…紫外線硬化型の糊剤を用いた粘着テープ１１…チップ表面の紫外線硬化型の糊剤を用いた粘着テープ
１２…粘着テープ
１００…微小装置の形成された半導体基板
１０１…微小装置の形成された領域を取り囲むアルミニウム領域を取り囲む酸化膜領域
１０２…素子領域を取り囲むアルミニウム領域
１０３…微小装置の形成された領域 １０４…ナフタレン融液陵
１０５…ナフタレン固体被膜 ２００…微小装置
２０１…シリコン基板 ２０２…固定部
２０３…可動部 ２０４…ギャップ
２０５…酸化膜 ２０６…開口部
２０７…ポリシリコン膜 ２０８…酸化膜エッチング液
２０９…純水 ２１０…氷
２１１…ＩＰＡ ２１１…ナフタレン固体被膜
３０１…センサチップのシリコン基板 ３０２…ボンディングパッド
３０３…重り部 ３０４…ダイアフラム
３０５…ガラス基板 ３０６…固定電極
３０７…樹脂またはワックス ３０８…ギャップ
３０９…ギャップ３０８内の樹脂またはワックス
５００…主面に赤外線センサの形成されたシリコン基板
５０１…シリコン窒化膜
５０２…アルカリ異方性エッチングによりキャビティ５０４を形成するためのエッチング開口部
５０３…熱分離されたシリコン窒化膜のダイアフラム
５０４…キャビティ ６００…ナフタレン融液島群
６０１…ワイヤ ７００…ＩＰＡ液体被膜
９０１…チップ ９０２…ベタパターン
９０３…丸パターン。[0001]
[Industrial applications]
The present invention relates to a method for manufacturing a device having a microstructure typified by a micromachine, and more particularly to a method for manufacturing a device having a low-cost and highly reliable microstructure for preventing contamination or damage of a microstructure portion.
[0002]
[Prior art]
As a conventional method for manufacturing a microdevice, a dicing method of a semiconductor substrate on which a microdevice or a semiconductor element is formed will be described as an example.
FIG. 13 shows an example in which wax is used as a temporary protective film as a method for dicing without fixing chips to the surface of the semiconductor substrate.
That is, first, a semiconductor element or a microdevice is formed on the main surface of the semiconductor substrate 1 by making full use of a semiconductor element process represented by photofabrication or micromachining technology (A). Next, a resin or wax is applied to the main surface of the structure on which the semiconductor element or the micro device is formed, a protective film 2 made of the resin or wax is formed, and a mount tape 3 is attached to the back surface of the structure. (B). The above structure is diced 4 with a diamond grindstone and divided into chips 5 (C). Next, the chip 6 is removed from the mount tape 3 by the pickup 6 (D). The removed chip 5 is placed in a washing tray 7 and washed with an organic solvent to remove the protective film 2 made of resin or wax (E).
[0003]
However, in the above example in which resin or wax is used as a temporary protective film, the protective film made of resin or wax is washed and removed with an organic solvent, so that cleaning after dividing the chip requires a lot of man-hours. There was a problem that it took. Particularly, in the case of a micro device having a cavity or a movable portion, it is difficult to sufficiently wash and remove the resin and wax in the cavity, which requires a large amount of an organic solvent and has been sufficiently removed. There are not many methods for nondestructively inspecting. Further, it is difficult to improve the yield because the microdevice is damaged in the cleaning process or the periphery of the chip is damaged by hitting the periphery thereof, so that this method may increase the cost.
[0004]
Next, as a micro device having a cavity portion or a movable portion, a semiconductor capacitive acceleration sensor described in “Transducers 1987 (The 4th International Conference on Solid-State Sensors and Actuators) pp. 336-339” as an example, Alternatively, a dicing method using wax as a temporary protective film will be described in some detail with reference to FIG.
In FIG. 15, reference numeral 301 denotes a silicon substrate of a sensor chip, on which an overlapping portion 303 and a diaphragm 304 are formed by anisotropic etching. The diaphragm 304 is opened to improve sensor sensitivity, and a so-called beam may be formed. A fixed electrode 306 and a bonding pad 302 are formed on a glass substrate 305 using PYREX7740. The silicon substrate 301 and the glass substrate 305 processed as described above are joined by anodic bonding. The bottom surface of the weight portion 303 and the fixed electrode 306 face each other with a gap of at most 1 to several μm to form a capacitor, and the movement of the weight portion 303 due to acceleration is detected by a change in the capacitor (A). Although only one chip structure is shown in the drawing, many of them are actually formed on a substrate.
[0005]
A resin or wax 307 is applied to the above-mentioned structure by brush coating or the like, and divided into chips by dicing. At this time, the gap 308 is also filled with a resin or wax to fix and hold the movable weight 303 to prevent breakage due to dicing and also prevent dicing chips from entering the gap 308. ing. The gap 308 is no more than 1 to several μm at most. Therefore, the movement of the weight portion 303 due to acceleration cannot obtain the designed stroke due to the penetration of only one chip of the dicing chips of the gap, and the weight portion 303 Strikes the fixed electrode 306. In some cases, the chip does not function as a sensor because the weight portion 303 and the fixed electrode 306 are electrically short-circuited (B).
[0006]
Next, the dicing-divided chip is washed with an organic solvent such as acetone (C). At this time, the resin or wax 309 in the gap 308 is difficult to clean and remains very persistently. Some means such as boiling with an organic solvent may be used to increase the detergency, but boiling with an organic solvent with flammable and explosive properties is extremely dangerous and requires special equipment to take measures against it. And Further, there is no appropriate means for non-destructively knowing that the resin or wax 309 in the gap 308 has been removed. For example, when an attempt is made to confirm from a transmission image of some energy rays, a filter of a glass substrate 305 made of glass, a weight portion 303 made of silicon, and a fixed electrode 306 made of metal is applied. There is no energy beam that can be used up to infrared rays and X-rays as well as light.
[0007]
As a method for improving the conventional example shown in FIG. 13 using a resin or wax as a temporary protective film, there is a method disclosed in Japanese Patent Publication No. 23324/1990. This uses an adhesive tape using an ultraviolet-curable glue as a temporary protective film instead of wax, and is shown in FIG. 14 (created according to FIG. 13 and different from the original). This will be described below.
First, a semiconductor element or a micro device is formed on a main surface of a semiconductor substrate 1 by making full use of a semiconductor element process represented by photo fabrication or a micromachining technique (A). Next, an adhesive tape 10 using an ultraviolet-curable glue is attached to the main surface of the structure on which the semiconductor element or the microdevice is formed, and a mount tape 3 is attached to the back surface of the structure (B). Next, the above structure is diced 4 with a diamond grindstone and divided into chips 5 (C). Next, ultraviolet rays are irradiated on the adhesive tape 11 using an ultraviolet-curable glue on the surface of the chip 5 of the above structure, and the glue is cured (D). Next, the adhesive tape 11 on the surface of the chip 5 of the above structure using the ultraviolet curing adhesive is removed by another adhesive tape 12 (E). Finally, the chip 5 is removed from the mount tape 3 by the pickup 6 (F).
[0008]
However, in the method of the above-mentioned conventional example in which an adhesive tape using an ultraviolet-curable glue is used as a temporary protective film, it only protects the outermost surface and cannot protect the cavity and the movable part. There are inherent defects and it is difficult to apply to micro devices having cavities and movable parts. In addition, since the paste is applied to the surface on which the semiconductor element or the micro device is formed, there is a problem that the paste remains on the surface. This is because the adhesive of the UV-curing type adhesive loses its adhesive strength due to the irradiation of ultraviolet rays, and does not lose its adhesive strength. There was a problem that it was peeled off. Further, in order to attach the adhesive tape, a certain amount of pressure must be applied to the tape, and there is a problem that the microdevice is damaged when the tape is attached. As described above, it is difficult to apply the protection method of mechanically applying a force to a micro device both during protection and removal to a micro device that is easily damaged.
[0009]
In fact, not only the above two dicing methods but also a method of dicing and dividing a micro device with a high yield has not yet been developed. The protection methods other than the method for temporary protection at the time of dicing, and whether these methods can be applied to the dicing division of a micro device will be described below.
For example, as disclosed in JP-A-63-41855, in order to prevent dust from directly adhering to a mask substrate, a solution of a sublimable substance is spin-coated on the mask substrate and temporarily There is a method of forming a protective film. However, since this method uses a spin coating method, a dedicated device is required, and a structure having a cavity portion or a movable portion has a problem that it is difficult to apply due to a breakage problem. That is, a so-called bulk micromachine using the bulk of a silicon substrate also has a mechanical structure on the back side, and the element is damaged even by a vacuum chuck at the time of spin coating. In addition, since the thickness of the protective film that can be formed is thin, being several thousand m to several μm at most, it is not enough to protect the microdevice, and moreover, the film of the sublimable substance is sublimated and disappears. The method has a short holding time and cannot be used as a protective film at the time of dicing.
[0010]
Further, for example, a freeze-dry method is available as a method for holding the movable portion formed on the surface (IEEE 1991 pp. 63-66). The freeze-dry method is a method in which water or an organic solvent is applied to a movable portion, the applied droplet is cooled and frozen, and the frozen droplet is sublimated under reduced pressure. This method is used, for example, in a drying process of a surface-type micromachine, in order to prevent a movable portion formed on the surface from being deformed or destroyed by surface tension with a substrate.
[0011]
Hereinafter, the manufacture of the microdevice will be described in some detail. FIG. 9 illustrates one of the basic structures of the microdevice. Here, 200 is a micro device made of polysilicon, 201 is a silicon substrate that holds the micro device 200, 202 is a fixed portion that connects the micro device 200 to the silicon substrate 201, 203 is a movable portion of the micro device 200, 204 Is a gap for making the movable portion of the micro device 200 movable. Various surface-type micromachines are configured mainly by combining this basic structure.
Next, a basic manufacturing procedure of the microdevice shown in FIG. 9 will be described with reference to FIG. That is, first, an oxide film 205 as a sacrificial layer is formed on the main surface of the silicon substrate 201 by a method such as CVD (A). Next, an opening 206 is formed in the oxide film 205 at a position corresponding to the fixed portion where the microdevice 200 is connected to the silicon substrate 201 by photo-oxide film etching (B). Next, polysilicon 207, which is a member constituting the microdevice, is formed on the structure by a technique such as CVD (C). Next, the polysilicon 207 is formed into the shape of the micro device 200 by photo-dry etching (D). Next, the structure is immersed in an oxide etching solution 208 mainly containing hydrofluoric acid to etch the oxide film 205 serving as a sacrificial layer. By this step, a gap 204 for moving the movable portion of the micro device is formed, and the movable portion 203 of the micro device can be moved (E). Next, the structure is immersed in pure water 209 and sufficiently washed. By this step, the oxide film etching solution 208 in the gap 204 is replaced with pure water (F). Conventionally, the structure was dried as it was to obtain a micro device. At this time, as the pure water 209 as a liquid evaporates and its volume decreases, the movable part 203 of the micro device 200 is drawn to the silicon substrate 201 due to the surface tension of the pure water 209 and finally sticks (sticking). It becomes. In this state, the function as a microdevice can no longer be developed (G).
[0012]
The freeze drying method is a drying method for preventing the sticking, and will be described with reference to FIG. FIG. 11A corresponds to FIG. 10F, and in some cases, the pure water 209 is replaced with an organic solvent. Next, the structure is taken out of the tank, and the pure water is frozen without drying to form ice 210 (B). Next, when the above structure is vacuum-dried, the solid ice 210 sublimes, and the micro device 200 can be obtained without causing sticking (C). This is because the liquid in the gap 204 is not liquid water but solid ice, so that no evaporation phenomenon due to surface tension occurs during evaporation.
In the freeze-drying method, when a substance having a melting point near room temperature, for example, t-butyl alcohol (melting point 25.6 ° C.) is used, a melt can be obtained by simple heating. The movable part can be held. However, this freeze-drying method requires special equipment to control temperature and pressure, and must be kept well below room temperature to prevent melting and high rate sublimation during the holding period. Further, since water and a solid of t-butyl alcohol are soluble in water, they cannot be applied to a step in contact with water or an aqueous solution represented by a dicing step, a wet etching step, a washing step, and the like.
[0013]
In view of such a problem, the present inventors have previously applied a solution of a sublimable substance to a cavity or a movable part, and filled the cavity or the movable part with the sublimable substance by heat treatment. A method for easily and surely providing a temporarily sealed and protected microdevice which can be stably held for a period of time and thereafter easily removed completely has already been filed (Japanese Patent Application No. Hei. -145845: undisclosed). However, since this method was an excellent method for selectively filling the sublimable substance only in the cavity or the movable part inside the outermost surface of the microdevice, the coating of the outermost surface of the microdevice was removed. No formation was possible.
[0014]
[Problems to be solved by the invention]
As described above, in the method of manufacturing a device having a microstructure, the related art has various problems and problems.
SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to form a uniform, translucent and long-retention protective film without damaging a microdevice, and to reduce the number of steps and capital investment. Providing a means for forming a temporary protective film with low cost, low risk of contamination, easy and complete removal of the protective film, no inspection required, and high yield and excellent productivity. When applied to a dicing process, chips can be divided with a high yield.For example, when applied to a drying process after etching a sacrificial layer, a micro device that does not stick and does not require a special device is used. Easy to get.
[0015]
[Means for Solving the Problems]
The object is to form a solid sublimable material melt film at normal temperature and pressure on one principal surface on which the micro structure is formed in the manufacture of a device having a microstructure, and then cool the melt film. Forming a protective film having a structure having at least a solid phase, and then vaporizing and removing the protective film.Providing a member having a good wettability with the melt of the sublimable substance in the vicinity of the microstructure, and dropping the melt of the sublimable substance by dropping the melt with the good wettability, and This can be achieved by providing a step of forming a melted film of the sublimable substance on the upper surface of the provided portion.
[0016]
[Action]
In the present invention, a difference in wettability between a melt of a sublimable substance and an organic solvent such as naphthalene melt and isopropyl alcohol (hereinafter abbreviated as IPA) as a liquid and a wettability between aluminum and an oxide film as a solid surface are used. are doing. The surface constituting the microdevice is composed of various members, but when roughly classified, an oxide film material represented by a PSG (phosphosilicate glass) film occupies a main position, and the other is represented by an aluminum film. Wiring materials. Here, for the sake of simplicity, the wettability of an aluminum film and an oxide film as solid surfaces and IPA and molten naphthalene as liquids will be described.
[0017]
In general, the term “wetability” refers to a degree of a phenomenon in which a liquid pushes a gas (atmosphere) from a solid surface, and is synonymous with wettability. (A brief explanation of terms relating to wettability is described, for example, in the Dictionary of Chemistry (Kyoritsu Shuppan). The phenomenon of wetting is described, for example, in Basic Course on Metal Properties Vol. 10, Interface Properties (Maruzen). Has been). The “wettability” of the liquid with respect to the solid surface is defined as “contact angle”, that is, at the “contact point (P) of the three phases of solid, liquid, and gas”, the angle between the tangent drawn to the liquid and the solid surface. The system having a small contact angle is said to have good wettability, and the system having a large contact angle is said to have poor wettability. The driving force for the wetting phenomenon is the solid-gas interfacial tension (σ_s) And the solid-liquid interfacial tension (σ_i) And the difference (σ_s−σ_i) Is the decrease in wetting free energy. From the balance of the tension in the solid surface direction at the three-phase contact point (P), the surface tension of the liquid (σ₁Between)
σ₁  cosθ = σ_s−σ_i            ... (Equation 1)
There is a relationship.
[0018]
Also, the contact angle (θ) is determined by the work of adhesion (W_a) And the work per unit area of liquid aggregation (W_c)

[0019]
Indicated by Therefore, in a system with good wettability, the adhesion of the solid to the liquid exceeds the cohesion of the liquid, and the liquid spreads quickly to the surface of the solid. When the cohesive force of the liquid exceeds, the liquid does not spread to the solid surface but ball-ups.
[0020]
As described above, since the surface of a microdevice is generally dominated by an oxide film-based material, a melt of naphthalene (a naphthalene melted by heating and turned into a liquid) forms a microdevice. Since the wetted area and the wettability are poor, and the ball-up occurs without expansion into a thin film, the area where the microdevice is formed cannot be coated with naphthalene as it is. However, since the melt of naphthalene expands into a thin film on the surface of aluminum, the aluminum region can be coated with naphthalene.
It should be noted that depending on what the three-phase contact points of the solid (region where microdevices are formed, aluminum region, oxide film region), liquid (naphthalene melt), and gas (atmosphere) are different. This is to determine the behavior of the liquid (naphthalene melt) as an aggregate. In FIG. 1 (D) of the embodiment described below, the reason why the naphthalene melt is extended in the region where the microdevice is formed depends on the position of the contact point (actually a closed curve) of the three phases of solid, liquid and gas. . If the contact point of the naphthalene melt is in the area where the microdevice is formed or in the oxide film area around the wafer, the cohesive force of the naphthalene melt exceeds the adhesive force, and therefore the naphthalene melt will aggregate and reduce the surface area On the other hand, if the contact point of the naphthalene melt is in the aluminum region surrounding the region where the microdevice is formed, the adhesive force of the naphthalene melt exceeds the cohesive force, and therefore, the naphthalene melt expands and becomes solid Try to wet the surface. As a result of these struggles, the contact point of the naphthalene melt is the outermost periphery of the aluminum region surrounding the region where the microdevice is formed, and the innermost periphery of the oxide film region surrounding the aluminum region, Pinning will occur at the boundary between the aluminum region surrounding the region where the device is formed and the oxide region surrounding the aluminum region. This state is thermodynamically metastable, and if a solid, liquid, and gas three-phase contact point occurs in the area where the microdevice is formed, for example, from the cavity inside the microdevice. When bubbles rise, the naphthalene melt quickly transitions to a torn ball-up state.
[0021]
Actually, for example, the liquid amount of the size of the silicon wafer appearing in the following examples is not a microdroplet that can ignore the gravity, and the complicated structure of the microdevice is formed on the main surface on which the microdevice is formed. Yes, so-called wetting and capillarity occur for the same coagulated liquid, and are complicatedly involved in the pressure distribution inside the liquid and the stress of the members that make up the microdevice. Quite difficult. Therefore, only qualitatively summarized in Table 1 below.
[0022]
[Table 1]

[0023]
In Table 1, for example, the wettability of the IPA system is qualitatively expressed as “good”, and the contact angle is qualitatively expressed as “small”. More precisely, the contact angle (θ) is set to 0 and the solid-gas interface tension σ_sAnd the solid-liquid interfacial tension (σ_i) And the difference (σ_s−σ_i) That is, the adhesion tension should be used as a measure of wettability. Further, among the structures of the microdevice, the wetting of the structure that can be regarded as a capillary is caused by the solid-gas interfacial tension (σ_s) Is the solid-liquid interfacial tension (σ_iIf it exceeds, it can be said that the wettability is good, and the liquid will soak spontaneously so that the liquid penetrates into the porous body, and depending on the case, the surface tension itself of the liquid does not matter much. .
[0024]
【Example】
Hereinafter, the method for manufacturing a microdevice of the present invention will be specifically described with reference to examples.
[0025]
Embodiment 1
A method for forming a solid film of a sublimable substance as a temporary protective film according to the present invention will be described with reference to FIG.
(A) First, the semiconductor substrate 100 on which a semiconductor element or a micro device is formed is heated. Even if the heating temperature is low, it is sufficient if the heating temperature is equal to or higher than the melting point of the sublimable substance used, and it is possible to reach the boiling point of the substance. Here, 103 is a region where a semiconductor element or a microdevice is formed, 102 is an aluminum region surrounding the region 103 where a semiconductor element or a microdevice is formed, and 101 is an oxide film region surrounding the aluminum region 102.
[0026]
(B) Next, a naphthalene melt is dropped on the main surface of the structure so as to cover the aluminum region 102 to form a naphthalene melt ridge 104. In addition, the wettability between the naphthalene melt and the region 103 where the semiconductor element or the microdevice is formed is poor, and as long as the amount of the naphthalene melt to be dropped is small, as in the case where water is dropped into a frying pan, Although the naphthalene melt does not cover the region 103 where the microdevice is formed, when the amount of the dropped naphthalene melt reaches a certain level, the liquid film having the size of the semiconductor substrate 100 is held at the surface tension. Of course, if the amount is too large, the naphthalene melt overflows from the semiconductor substrate 100. The optimal amount of the dropped naphthalene melt depends on the size of the semiconductor substrate 100 and the wettability between the naphthalene melt and the oxide film region 101.
[0027]
(C) Next, the naphthalene melt edge 104 of the above structure is reduced by evaporation. Note that the naphthalene melt has poor wettability with the oxide film, and the naphthalene melt 104 has a reduced bottom area while maintaining a large contact angle up to the boundary between the oxide film region 101 and the aluminum region 102.
[0028]
(D) Next, the naphthalene melt layer 104 of the above structure is further reduced by evaporation. The naphthalene melt has good wettability with aluminum, and until the boundary between the oxide film region 101 and the aluminum region 102, the naphthalene melt 104 keeps a large contact angle and decreases the bottom area. Reduces the contact angle while keeping the bottom surface at the outermost periphery of the aluminum region 102.
[0029]
(E) Finally, when the thickness of the liquid film of the naphthalene melt ridge 104 of the structure is reduced to an appropriate thickness, for example, 100 μm, the structure is cooled and the naphthalene melt ridge 104 is temporarily cooled. The translucent naphthalene solid film 105 is used as a protective film.
[0030]
In the above example, the case where the aluminum region 102 surrounding the region 103 where the semiconductor element or the microdevice is formed is provided in the outer peripheral portion of the substrate 100 is not limited to this. They may be provided so as to surround them every few chips, or may be provided not on the substrate 100 but on a jig. Further, the material is not limited to aluminum, and any material having good wettability may be used, and various metals can be used. The jig is not limited to a single substrate, and may be one that simultaneously surrounds a plurality of substrates. In order to prevent the liquid containing the sublimable substance from entering the gap between the jig and the substrate by capillary action, another liquid may be injected in advance. The oxide film region 101 may be made of any material as long as it has poor wettability with the naphthalene melt ridge 104, a Teflon resin may be used, and the oxide film region 101 may be provided on a jig without being provided on the substrate 100.
[0031]
Further, in the above example, the case where the naphthalene melt is dropped has been described, but the invention is not limited thereto, and a naphthalene solution may be used. The naphthalene solution need not be a solution at room temperature, but may be a heated, concentrated solution having a saturation (room temperature) concentration or higher. Further, after the dropping, the solvent may be selectively evaporated to perform concentration.
Further, in the above example, when forming the naphthalene melt edge 104, the case where the semiconductor substrate 100 is heated and then the naphthalene melt is dropped has been described. Spray and then heat to melt. Of course, the present invention is not limited to the spraying of the powder, and may be applied by electrostatically adhering to the semiconductor substrate 100, followed by heating and melting.
[0032]
As a method for heating the semiconductor substrate 100, various methods other than heater heating can be used. Further, in the above example, naphthalene was described as an example.However, the present invention is not limited to this, and any sublimable substance that is solid at normal temperature and normal pressure may be used.For example, p-dichlorobenzene, tetrachlorodifluoroethane, and in some cases, Camphor, which is soluble in water, may be used. Further, in addition to using the sublimable substance alone, other components may be mixed, or an organic solvent may be mixed and a sublimable substance having a freezing point drop may be used. Also, the temporary protective film need not be a complete solid film, and when viewed microscopically, a liquid phase may coexist with a porous solid phase.
[0033]
The reduction of the naphthalene melt ridge 104 from (B) to (D) described above may be performed by a dropper instead of the reduction by evaporation. In some cases, as much naphthalene melt as necessary for forming the film (D) may be dropped and expanded to the aluminum region 102 by acceleration or the like. The expansion of the liquid due to this acceleration is very poor in wettability between the region where the microdevices 103 are formed and the naphthalene melt, and when the naphthalene melt is dropped, the entire main surface of the substrate 100 in FIG. This is also effective in a case where the naphthalene melt overflows from the substrate before the naphthalene melt ridge 104 covering the substrate is formed.
Further, the aluminum region 102 surrounding the region 103 where the semiconductor element or the microdevice is formed does not need to be completely connected, and may be formed in an island shape at a certain interval, for example. Further, the oxide film region 101 surrounding the aluminum region 102 does not need to be formed completely continuously, and may be formed in an island shape at a certain interval, for example.
[0034]
Next, an example of a dicing procedure using the method of the present invention will be described with reference to FIG.
(A) First, a semiconductor element or a micro device is formed on the main surface of the semiconductor substrate 1 by making full use of a semiconductor element process represented by photo fabrication or a micromachining technique.
(B) Next, a naphthalene solid film 105 as a temporary protective film is formed on the main surface of the above structure on which the semiconductor element or the micro device is formed by the method described in the drawings.
(C) Next, the mount tape 3 is attached to the back surface of the structure.
(D) Next, the above structure is diced 4 with a diamond grindstone and divided into chips 5.
(E) Finally, the chip 5 is removed from the mount tape 3 by the pickup 6.
[0035]
The solid film of the sublimable substance on the chip can be easily and completely removed only by standing, and no residue remains. If necessary, it can be quickly removed under heating or reduced pressure conditions.
[0036]
Next, a case where the method described with reference to FIG. 1 is applied to a surface-type micromachine will be described with reference to FIG. 3 using, for example, an infrared sensor having a thermal isolation structure as an example. FIGS. 3A to 3E correspond to FIGS. 1A to 1E, respectively.
(A) In FIG. 3, reference numeral 500 denotes a silicon substrate having a main surface on which an infrared sensor is formed; 501, a silicon nitride film; 502, an etching opening for forming a cavity 504 by alkali anisotropic etching; This is a diaphragm of a silicon nitride film formed. Here, the size of the general diaphragm 503 is about several tens to several hundreds μm, and the size of the etching opening 502 is about several to several tens μm. It should be noted that a thermocouple, an infrared absorbing part, and the like are actually formed on the diaphragm 503, but are omitted here because they are unnecessary for the description here.
[0037]
(B) and (C) When the naphthalene melt layer 104 is formed, since the wettability between the naphthalene melt and the silicon or silicon nitride film constituting the infrared sensor is poor, the etching opening having a thickness of at most several tens μm is formed. The naphthalene melt does not enter the cavity 504 from 502.
(D) Even when the naphthalene melt ridge 104 is reduced and the liquid film thickness is reduced, the film spread in the region where the infrared sensor is formed is retained. This is because the aluminum region 102 having good wettability with the naphthalene melt is provided, and thereby the naphthalene melt is expanded. If the aluminum region 102 having good wettability with the naphthalene melt is not provided, As in the case of heating and evaporating water in a room, it shrinks in a state where the ball is broken up.
(E) When the liquid film of the naphthalene melt is cooled from the state where the liquid film of the naphthalene melt covers the region where the element is formed as in the above (D), a solid film 105 of naphthalene is formed as a temporary protective film.
[0038]
Embodiment 2
Next, the wettability between the region where the microdevice 103 of FIG. 1 is formed and the naphthalene melt is extremely poor, and when the naphthalene melt is dropped, the main surface of the substrate 100 of FIG. An embodiment in which the naphthalene melt overflows from the substrate before forming the naphthalene melt ridge 104 covering the entire surface will be described with reference to FIG. Note that such an example is a case where a main part of a surface constituting a microdevice is formed of a silicon oxide film, for example.
[0039]
(A) The semiconductor substrate 100 on which a semiconductor element or a micro device is formed is heated.
(B) An appropriate amount of naphthalene melt is dropped on the main surface of the structure to form a naphthalene melt island group 600.
(C) The naphthalene melt island group 600 of the above structure is scanned on the substrate 100 with a member having good wettability with the naphthalene melt, for example, a metal wire 601.
(D) Thereby, the naphthalene melt island group 600 of the above-mentioned structure is connected, and the naphthalene melt ridge 104 is formed.
(E) The naphthalene melt 104 of the above structure is reduced by evaporation.
(F) When the thickness of the liquid film of the naphthalene melt 104 of the above structure is reduced to an appropriate thickness, for example, 100 μm, the structure is cooled, and the naphthalene melt 104 is turned into a translucent naphthalene solid. The coating 105 is formed.
The above method can be applied even when the naphthalene solid film 105 can be formed by the method described in FIG. The required time can be extremely shortened.
[0040]
As described above, the embodiment shown in FIGS. 1 and 4 is not a method of filling the inside of the cavity with the sublimable substance as described with reference to FIG. In a micro device to which the method of the present invention is applied or in a manufacturing process, there is a need not only to cover and protect the surface, but also to fill the inside of the cavity with a sublimable substance in some cases. Such an example occurs, for example, when a dicing saw cuts across a cavity.
[0041]
Embodiment 3
An embodiment that meets the above needs will be described with reference to FIGS. In FIGS. 5 and 6, (A) to (F) correspond to the same steps.
(A) First, the semiconductor substrate 100 on which a semiconductor element or a micro device is formed is heated. In this case, the heating temperature is preferably higher than the melting point of naphthalene and lower than the boiling point of IPA. Note that 101 is an oxide film region, and 102 is an aluminum region.
(B) An appropriate amount of IPA (isopropyl alcohol) is dropped on the main surface of the structure to form an IPA liquid coating 700. Since the IPA has good wettability with the material constituting the device, the IPA enters the cavity 504 from the opening 502 for etching, and the air in the cavity 504 is replaced with the IPA. At this time, if there is no oxide film region 101 surrounding the aluminum region 102, IPA flows out from the upper surface of the substrate 100 and the IPA liquid film 700 cannot be formed because IPA has extremely good wettability to aluminum.
(C) A naphthalene melt is dropped on the above structure to form a naphthalene melt edge 104. At this time, the dropped naphthalene melt and the IPA liquid film 700 are mutually dissolved. The IPA and the naphthalene melt in the cavity 504 are mutually diffused, and the IPA in the cavity 504 is replaced by the naphthalene melt.
(D) and (E) The naphthalene melt edge 104 of the above structure is reduced by evaporation. At this time, the evaporation of IPA takes precedence over the evaporation of naphthalene, and the IPA concentration in the naphthalene melt 104 and the IPA concentration in the cavity 504 decrease.
(F) When the thickness of the liquid film of the naphthalene melt 104 of the above structure is reduced to an appropriate thickness, for example, 100 μm, the structure is cooled, and the naphthalene melt 104 is turned into a translucent naphthalene solid. The coating 105 is formed. At this time, the naphthalene melt in the cavity 504 also solidifies.
[0042]
In the above description, the case of using IPA has been described as an example. However, the present invention is not limited to this. Any solvent may be used as long as it dissolves the sublimable substance to be used and has a good wettability with the material constituting the micro device. In addition to IPA, methanol, ethanol, acetone, benzene and the like can be used. The solvent may be used alone, may be a mixed solvent, or may be a solvent in which a sublimable substance is dissolved.
[0043]
Next, the pattern shape of the aluminum region surrounding the region where the microdevice is formed in the above embodiment will be described with reference to FIG. 7A is a top view of the main surface of the substrate 100 on which the microdevice in FIG. 1 is formed. FIG. 7A shows a chip 901 and a region where these chips 901 are gathered in which the microdevice in FIG. 1 is formed. An aluminum region 102 surrounding the region 103 is formed by arranging a solid pattern 902 of a quarter size aluminum of the chip 901. When the naphthalene solid film 105 is formed on the structure shown in FIG. 7A by the method described with reference to FIGS. 1 to 6, the naphthalene solid film 105 becomes the outermost peripheral shape of the aluminum region 102 as shown in FIG. Is formed.
[0044]
In this example, the aluminum region 102 has a shape having a corner. 1 (D), 4 (E) and 5 (E), the naphthalene melt 104 has a small contact angle and is about to be stuck due to surface tension. It is being held. When the aluminum region 102 has a corner, the naphthalene melt ridge 104 at the corner is located inside the boundary between the aluminum region 102 and the oxide film region 101, that is, on the side of the region 103 where the microdevice is formed. Slightly retracted. When the chip 901 is extremely small, the amount of pull-in may be larger than the diagonal line of the solid pattern 902. In such a case, the naphthalene melt ridge 104 exists as a film as soon as the boundary between the naphthalene melt ridge 104 and the surface of the substrate 100 and the atmosphere is drawn to the corner of the region where the microdevice is formed. No longer, it changes to an island-like form like water on a frying pan, so that a naphthalene solid film cannot be formed.
[0045]
FIG. 8 shows an aluminum region pattern in which such a problem does not occur. Here, the outermost peripheral shape of the aluminum region was a circular pattern 903, and had a shape without corners. Of course, other than the round pattern, an ellipse may be used, as long as it is constituted by a gentle curve.
[0046]
Embodiment 4
In this embodiment, application of the method of the present invention to a drying process after etching of a sacrificial layer, instead of application to a dicing process, will be described with reference to FIG.
(A) The structure is immersed in pure water 209 in the same manner as in FIG.
(B) Next, the structure is immersed in an IPA tank, and the pure water 209 is replaced with IPA 211.
(C) The above structure is immersed in a naphthalene melt bath, and the IPA 211 is replaced by a naphthalene melt.
[0047]
(D) Just by leaving the above-mentioned structure, solid naphthalene sublimates and the microdevice 200 can be obtained without sticking. This is due to the fact that what is replaced in the gap 204 is not liquid water but solid naphthalene, so that no entrainment phenomenon due to surface tension occurs during evaporation.
[0048]
In the above embodiment, that is, if the sacrificial layer etching step is performed immediately before the chip dividing step by dicing, dicing may be performed in the state of FIG. 12C, and the sticking prevention measure and the protection measure at the time of dicing can be performed simultaneously. It is possible and can greatly simplify the total process.
[0049]
Further, in the above embodiment, an example was described in which IPA was used as the solvent and naphthalene was used as the sublimable substance. However, the present invention is not limited to this, and the solvent is one that dissolves water and naphthalene. Anything may be used, in addition to IPA, methanol, ethanol, acetone and the like can be used.In addition, a solvent may be used alone, or a mixed solvent may be used, for example, a solvent in which a sublimable substance is dissolved. good. Further, the sublimable substance may be any sublimable substance that is solid at normal temperature and normal pressure. For example, if it is used as a drying method in a sacrificial layer etching step, water-soluble camphor can be used. .
[0050]
In the description of the embodiments of the present invention, a sensor formed on a semiconductor substrate is mainly described as an example, but the present invention is not limited to this. For example, a glass substrate or a metal substrate may be used. However, the present invention is applicable even to one main surface of the structure. Needless to say, it is not necessary to form a micro device, and the present invention can be applied to various processes that require a temporary protective film of a device or a component having a micro structure.
[0051]
【The invention's effect】
As described above, by using the method of the present invention for the manufacturing method of the micro device, the problems of the prior art can be solved, and the micro device can be uniformly and translucently maintained without damaging the micro device. A temporary protective film having a long length can be formed. According to the method of the present invention, the number of man-hours is small, the capital investment and cost are low, there is little fear of contamination, the removal of the protective film is easy and complete, no inspection is required, and the yield is high and the productivity is excellent. There is a feature. Therefore, for example, when used in a dicing process of a micro device, a chip can be divided with a high yield. Further, for example, when used in a drying process after the etching of the sacrificial tank, there is an effect that a micro device can be easily obtained without sticking without requiring a special device.
[Brief description of the drawings]
FIG. 1 is a process chart showing a method (part 1) of forming a temporary protective film using a solid film of a sublimable substance according to the present invention.
FIG. 2 is a process chart showing a dicing method using a solid film of a sublimable substance as a temporary protective film according to the present invention.
FIG. 3 is a process diagram showing an example in which the method (part 1) for forming a solid film of a sublimable substance of the present invention is applied to an infrared sensor.
FIG. 4 is a process diagram illustrating a method (part 2) of forming a temporary protective film using a solid film of a sublimable substance according to the present invention.
FIG. 5 is a process chart showing a method (part 3) of forming a temporary protective film using a solid film of a sublimable substance according to the present invention.
FIG. 6 is a process diagram showing an example of applying the method (part 3) of forming a temporary protective film using a solid film of a sublimable substance to an infrared sensor according to the present invention.
FIG. 7 is a view showing a pattern (No. 1) of a protective film by a method for forming a temporary protective film using a solid film of a sublimable substance according to the present invention.
FIG. 8 is a view showing a pattern (No. 2) of a protective film by a method for forming a temporary protective film using a solid film of a sublimable substance according to the present invention.
FIG. 9 illustrates a basic structure of a microdevice.
FIG. 10 is a diagram showing a method for manufacturing a microdevice.
FIG. 11 is a diagram illustrating a freeze-drying method.
FIG. 12 is a diagram for explaining the drying method of the present invention.
FIG. 13 is a process diagram showing a first example of a conventional manufacturing method, and is a diagram showing a dicing method using a resin or wax as a temporary protective film.
FIG. 14 is a process diagram showing a second example of the conventional manufacturing method, and is a diagram showing a dicing method using an adhesive tape using a UV-curable adhesive as a temporary protective film.
FIG. 15 is a process diagram showing a third example of the conventional manufacturing method, and is a diagram showing application of a dicing method using a resin or wax as a temporary protective film to a micromachine.
[Explanation of symbols]
1. Semiconductor substrate 2. Protective film made of resin or wax
3… Mount tape 4… Dicing groove
5 ... chip 6 ... pickup
7: Cleaning tray 10: Adhesive tape using ultraviolet curing adhesive 11: Adhesive tape using ultraviolet curing adhesive on chip surface
12 ... Adhesive tape
100: semiconductor substrate on which microdevices are formed
101: oxide film region surrounding the aluminum region surrounding the region where the microdevice is formed
102 ... Aluminum region surrounding element region
103: a region where a microdevice is formed 104: a naphthalene melt
105: Naphthalene solid film 200: Micro device
201: silicon substrate 202: fixed part
203: movable part 204: gap
205: oxide film 206: opening
207: polysilicon film 208: oxide film etching solution
209: pure water 210: ice
211 ... IPA 211 ... Naphthalene solid film
301: silicon substrate of sensor chip 302: bonding pad
303: Weight part 304: Diaphragm
305: glass substrate 306: fixed electrode
307: resin or wax 308: gap
309: resin or wax in gap 308
500: Silicon substrate with infrared sensor formed on main surface
501: silicon nitride film
502: Etching opening for forming cavity 504 by alkali anisotropic etching
503: diaphragm of thermally separated silicon nitride film
504: Cavity 600: Naphthalene melt island group
601 wire 700 IPA liquid coating
901: chip 902: solid pattern
903: Round pattern.

Claims (9)

In the manufacture of a device having a microstructure, a melt film of a solid sublimable substance is formed on one main surface on which the microstructure is formed at normal temperature and normal pressure, and then the melt film is cooled to at least solid state. Forming a protective film having a structure having a phase, and then vaporizing the protective film, comprising a step of removing,
Providing a member having a good wettability with the melt of the sublimable substance in the vicinity of the microstructure, providing a place where the member having a good wettability is provided by dropping the melt of the sublimable substance, and providing the microstructure. Forming a melt film of the sublimable substance on the upper surface of the device at a location where the device is formed . The method for manufacturing a device having a microstructure according to claim 1, wherein a member having good wettability with the melt of the sublimable substance is provided on one main surface on which the microstructure is formed. The step of forming a melt coating of the sublimable substance, the method further comprising a step of heating at least one main surface on which the microdevice is formed to a temperature equal to or higher than the melting point of the sublimable substance. A method for manufacturing a device having a microstructure according to claim 1 . The method for manufacturing a device having a microstructure according to any one of claims 1 to 3, wherein the member having good wettability with the melt of the sublimable substance is an aluminum region. The closed film of the three-phase boundary between the melt film of the sublimable substance, the member (solid) having good wettability with the melt film of the sublimable substance, and the gas has a shape having no corner. A method for manufacturing a device having a microstructure according to claim 1 or 2 . The step of forming a melt film of the sublimable substance is performed by using a jig composed of the melt film and a member having good wettability to convert the liquid containing the sublimable substance into at least one of the micro devices. 3. The method for manufacturing a device having a microstructure according to claim 1, further comprising a step of developing the device on a surface. The region surrounding the upper Symbol sublimable substance and wettable member, microstructure according to claim 1 or claim 2, characterized in that a melt coating and poor wettability member of the sublimable substance A method for manufacturing a device having: The method for manufacturing a device having a microstructure according to claim 7, wherein a member having poor wettability with the melted film of the sublimable substance is provided on one main surface on which the microstructure is formed. 9. The method for manufacturing a device having a microstructure according to claim 7, wherein the member having poor wettability with the melted film of the sublimable substance is an oxide film region or a Teflon resin.

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