JP2573418C

JP2573418C -

Info

Publication number: JP2573418C
Authority: JP
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Publication date: 1998-09-10

Description

【発明の詳細な説明】〈産業上の利用分野〉本発明は半導体基板の洗浄方法に関するものであり、特にフッ酸を使用する半
導体基板の洗浄方法に関するものである。〈従来の技術〉従来の技術に於いて半導体基板の洗浄は、第３図に示すように、薬液１をため
た槽２に基板３を浸漬し、洗浄した後、薬液１をためた槽２から基板３を取出し
、純水４をオーバーフローさせている槽５に基板３を移し、基板３に残留してい
る薬品を除去した後に、純水槽５より基板３を取出すものである。この方式（Ａ
）では、薬液にフッ酸を使用する場合、基板の酸化膜が除去されて基板の活性面
（たとえば、シリコン面）が露出すると、第３図に於いて、フッ酸中より基板を
取出す際（（３））に、基板表面にフッ酸の液面に多く浮遊している異物粒子が
付着しやすく、洗浄後の基板処理に悪影響を及ぼす。このような異物の付着を減
らすために、従来技術に於いては、第４図に示すように、薬液１１中での洗浄が
終了した後に、薬液槽１２に純水１３を導入し、薬液をオーバーフローさえて純
水と置換した後に、純水１３中から基板１４を取出す方法（Ｂ）が行われている
。〈発明が解決しようとする課題〉従来技術における第４図に示す方法により、フッ酸を使用した洗浄の場合に於
いても、基板を浸漬したまま、フッ酸と純水を置換することで、槽から基板を引き上げる際に付着する異物粒子を減らすことが可能であるが、フッ酸に
浸漬する前に、基板の活性面が露出している場合には、基板をフッ酸に浸浸する
際に、フッ酸液面に浮遊する異物粒子の基板への付着がさけられない。〈課題を解決するための手段〉上記問題点を解決するための本発明の方法は、第１図に示すように、オーバー
フローさせた純水槽２１に基板２２を浸漬し、基板２２が純水２３中に浸漬して
いる状態でオーバーフローを止め、フッ酸２４を槽２１に均一に導入して調合し
、洗浄が終了後、再び純水２５を導入してフッ酸と純水を置換し、純水２５をオ
ーバーフローさせながら槽２１から基板２２を引き上げ、水切り乾燥を行うもの
である。〈作用〉本発明によれば、半導体基板の活性面が薬液の液面に触れることがなくなり、
液面での基板への異物付着をなくすことが可能である。〈実施例〉半導体基板洗浄で頻繁に使用される希フッ酸を用いる洗浄に於ける、本発明の
実施例を第１図を例に説明する。（１）純水２３をオーバーフローさせたテフ
ロン槽２１に、洗浄する基板２２を浸漬する。（２）基板２２を浸漬した後に
純水のオーバーフローを止め、槽容積の１／１０だけ純水を排水し、１０％に希
釈したフッ酸２４を槽２１に均一に槽容積の１／１０滴下し、槽内の純水を１％
の希フッ酸２４′に変えて、１分間洗浄を行う。（３）テフロン槽２１の底部
より純水２５を導入し、希フッ酸を純水で置換する。（４）槽２１内の純水２
５の比抵抗値が、１８ＭΩ・ｃｍ以上に回復したら、純水をオーバーフローさせ
ながら基板を槽から引き上げて、水切り乾燥を行う。本実施例に示した希フッ酸洗浄方法で半導体基板（６インチ・シリコンウェー
ハ）に付着する異物粒子数（粒径０．１６μｍ以上）を、従来の希フッ酸洗浄方
法Ａ，Ｂ（Ａ，Ｂとも、１％フッ酸洗浄時間１分、純水オーバーフロー、水切り
乾燥）と比較した結果を第２図に示す。基板に付着した粒子数は、従来方式Ａで
は１１０〜１７０個、従来方式Ｂでは３０〜４０個、本発明の方式Ｃでは１０〜２０個であり、本発明の希フッ酸洗浄方法により、基板に付着
する異物粒子を減らすことが可能となる。〈発明の効果〉本発明の半導体基板の洗浄方法により、洗浄液から基板に付着する異物粒子を
大幅に低減させることが可能になる。Description: TECHNICAL FIELD The present invention relates to a method for cleaning a semiconductor substrate, and more particularly to a method for cleaning a semiconductor substrate using hydrofluoric acid. <Prior Art> In the conventional technique, as shown in FIG. 3, cleaning of a semiconductor substrate is performed by immersing the substrate 3 in a tank 2 containing a chemical solution 1, cleaning the semiconductor substrate 2, and then cleaning the semiconductor substrate 1. The substrate 3 is taken out of the tank 3, the substrate 3 is transferred to the tank 5 in which the pure water 4 overflows, and after removing the chemical remaining in the substrate 3, the substrate 3 is taken out from the pure water tank 5. This method (A
In the case of using hydrofluoric acid as the chemical solution, when the oxide film of the substrate is removed and the active surface (eg, silicon surface) of the substrate is exposed, when the substrate is removed from the hydrofluoric acid in FIG. In (3)), a large amount of foreign particles floating on the surface of hydrofluoric acid easily adhere to the substrate surface, which adversely affects the substrate processing after cleaning. In order to reduce the adhesion of such foreign matter, in the prior art, as shown in FIG. 4, after the cleaning in the chemical solution 11 is completed, pure water 13 is introduced into the chemical solution tank 12, and the chemical solution is introduced. A method (B) of taking out the substrate 14 from the pure water 13 after the overflow is replaced with pure water is performed. <Problems to be Solved by the Invention> By the method shown in FIG. 4 in the prior art, even in the case of cleaning using hydrofluoric acid, by replacing hydrofluoric acid and pure water while immersing the substrate, Although it is possible to reduce foreign particles adhering when lifting the substrate from the bath, before immersion in hydrofluoric acid, if the active surface of the substrate is exposed, immerse the substrate in hydrofluoric acid. In addition, adhesion of foreign particles floating on the hydrofluoric acid liquid surface to the substrate cannot be avoided. <Means for Solving the Problems> According to the method of the present invention for solving the above problems, as shown in FIG. 1, a substrate 22 is immersed in an overflowed pure water tank 21, and the substrate 22 is supplied with pure water 23. The overflow was stopped in a state of being immersed in the bath, and hydrofluoric acid 24 was uniformly introduced into the tank 21 to prepare a mixture. After the washing was completed, pure water 25 was introduced again to replace hydrofluoric acid and pure water, The substrate 22 is pulled up from the tank 21 while the water 25 overflows , and draining and drying are performed . <Operation> According to the present invention, the active surface of the semiconductor substrate does not touch the liquid surface of the chemical solution,
It is possible to prevent foreign matter from adhering to the substrate at the liquid level. <Example> An example of the present invention in cleaning using dilute hydrofluoric acid, which is frequently used in semiconductor substrate cleaning, will be described with reference to FIG. (1) The substrate 22 to be cleaned is immersed in the Teflon tank 21 in which the pure water 23 overflows. (2) After the substrate 22 is immersed, the overflow of the pure water is stopped, the pure water is drained by 1/10 of the tank volume, and the hydrofluoric acid 24 diluted to 10% is uniformly dropped into the tank 21 by 1/10 of the tank volume. And 1% pure water in the tank
Cleaning for 1 minute in place of diluted hydrofluoric acid 24 '. (3) Pure water 25 is introduced from the bottom of the Teflon tank 21 to replace dilute hydrofluoric acid with pure water. (4) Pure water 2 in the tank 21
When the specific resistance value of No. 5 recovers to 18 MΩ · cm or more, the substrate is pulled up from the tank while overflowing pure water, and draining and drying is performed. The number of foreign particles (particle diameter of 0.16 μm or more) adhering to the semiconductor substrate (6-inch silicon wafer) by the diluted hydrofluoric acid cleaning method shown in this embodiment is determined by the conventional diluted hydrofluoric acid cleaning methods A and B (A, B). B shows the results of comparison with 1% hydrofluoric acid cleaning time of 1 minute, overflow with pure water, drying with drainage) in FIG. The number of particles adhering to the substrate is 110 to 170 in the conventional method A, 30 to 40 in the conventional method B, and 10 to 20 in the method C of the present invention. It is possible to reduce foreign particles adhering to the surface. <Effect of the Invention> According to the method for cleaning a semiconductor substrate of the present invention, foreign particles adhering to the substrate from the cleaning liquid can be significantly reduced.

【図面の簡単な説明】第１図は、本発明の洗浄方法の説明図、第２図は、従来の洗浄方法（Ａ，Ｂ）
と本発明の洗浄方法（Ｃ）で実際に洗浄を行った６インチ径シリコンウェーハに
付着した異物粒子数を示す図、第３図及び第４図は、それぞれ従来の洗浄方法Ａ
及びＢの説明図である。符号の説明２１：洗浄槽、２２：半導体基板、２３：純水、２４：フッ酸、２４′：希フ
ッ酸、２５：純水。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of the cleaning method of the present invention, and FIG. 2 is a conventional cleaning method (A, B).
And FIG. 3 and FIG. 4 show the number of foreign particles adhering to a 6-inch diameter silicon wafer actually cleaned by the cleaning method (C) of the present invention, respectively.
And FIG. DESCRIPTION OF SYMBOLS 21: cleaning tank, 22: semiconductor substrate, 23: pure water, 24: hydrofluoric acid, 24 ′: dilute hydrofluoric acid, 25: pure water.

Claims

[Claims] 1. In the method for cleaning a semiconductor substrate using hydrofluoric acid as a cleaning liquid, the semiconductor substrate is immersed in a cleaning tank in which pure water overflows, and hydrofluoric acid is introduced into the pure water while the substrate is immersed in the pure water. perform cleaning of the substrate Te, then the substrate is taken out from the pure water in the overflow was replaced with pure water hydrofluoric acid by introducing pure water into the hydrofluoric acid, characterized thereby draining dried, the semiconductor substrate Cleaning method.