JP2005064276A - Cleaning method of semiconductor wafer - Google Patents
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この発明は半導体ウェーハの洗浄方法、詳しくはＳＣ１液およびＳＣ２液を使用した半導体ウェーハのウェット洗浄技術に関する。 The present invention relates to a method for cleaning a semiconductor wafer, and more particularly to a wet cleaning technique for a semiconductor wafer using SC1 liquid and SC2 liquid.
半導体プロセスにおけるウェット洗浄技術では、ＲＣＡ法による洗浄が基本となっている。このＲＣＡ法は、過酸化水素水（Ｈ2Ｏ2）をベースにした高ｐＨのアルカリ混合液と、低ｐＨの酸混合液との、２段階の洗浄工程を有している。この２種類の混合液をベースとした洗浄方法には、半導体製造プロセスにより、また、そのプロセスを実現するための設備や環境により、さまざまな改良が加えられ、今日のウェーハ洗浄方法へ至っている。
この第１段階であるアルカリ混合液での洗浄は、一般的にＳＣ１洗浄とよばれており、混合液の成分は、アンモニア水溶液と過酸化水素水と水とからなる。第２段階である酸混合液を用いた洗浄は、一般的にＳＣ２洗浄とよばれており、混合液の成分は、塩酸水溶液と過酸化水素水と水とからなる。
In the wet cleaning technology in the semiconductor process, cleaning based on the RCA method is fundamental. This RCA method has a two-step cleaning process of a high pH alkaline mixture based on hydrogen peroxide (H 2 O 2 ) and a low pH acid mixture. Various improvements have been made to the cleaning method based on these two types of mixed liquids depending on the semiconductor manufacturing process and the equipment and environment for realizing the process, leading to today's wafer cleaning method.
This first stage of cleaning with an alkali mixture is generally called SC1 cleaning, and the components of the mixture are an aqueous ammonia solution, a hydrogen peroxide solution, and water. The cleaning using the acid mixed solution which is the second stage is generally called SC2 cleaning, and the components of the mixed solution are composed of an aqueous hydrochloric acid solution, a hydrogen peroxide solution and water.
ところが、上記ＳＣ２洗浄では、ＳＣ２液を構成している塩酸水溶液中の臭素イオン（Ｂｒ−）が、半導体ウェーハ（シリコンウェーハ）の表面に付着しやすい。これを抑制するためには、ＳＣ２液中の塩酸水溶液の濃度を低下させる方法がある。しかし、塩酸水溶液の濃度を低下させて、常温で、ＳＣ２液を使用すると、シリコンウェーハの表面の洗浄能力（メタル除去力）が低下する。
逆に、加熱したＳＣ２液による洗浄を行えば、洗浄液の反応性が高まり、上記のような問題は生じない。しかし、塩酸水溶液の蒸発による液組成変化が著しく、この液組成変化によるガスの発生が盛んになり、これが洗浄設備の腐食を引き起こす。
また、半導体の量産工場などでＳＣ２洗浄を行う場合、洗浄槽内にパーティクルが蓄積し、これがシリコンウェーハを汚染している。この汚染は、ＳＣ２洗浄での処理温度に依存する。すなわち、ＳＣ２液が高温であるほど、半導体ウェーハはパーティクルによる汚染を受けやすい。逆に、常温であれば、パーティクル汚染量は高温時に比べ減少するが、上記のように半導体ウェーハの洗浄能力の低下を生じさせる。
そこで、ＳＣ２洗浄を高濃度の混合液で実施する方法が、一つの解決手段と考えられる。
However, in the SC2 cleaning described above, bromine ions (Br − ) in the hydrochloric acid aqueous solution constituting the SC2 solution tend to adhere to the surface of the semiconductor wafer (silicon wafer). In order to suppress this, there is a method of reducing the concentration of the hydrochloric acid aqueous solution in the SC2 solution. However, if the concentration of the aqueous hydrochloric acid solution is reduced and the SC2 solution is used at room temperature, the cleaning ability (metal removal ability) of the surface of the silicon wafer is reduced.
On the other hand, if cleaning with the heated SC2 liquid is performed, the reactivity of the cleaning liquid increases and the above-described problems do not occur. However, the liquid composition change due to evaporation of the hydrochloric acid aqueous solution is remarkable, and gas generation due to this liquid composition change becomes active, which causes corrosion of the cleaning equipment.
In addition, when SC2 cleaning is performed in a semiconductor mass production factory or the like, particles accumulate in the cleaning tank, which contaminates the silicon wafer. This contamination depends on the processing temperature in SC2 cleaning. That is, the higher the temperature of the SC2 solution, the more likely the semiconductor wafer is contaminated with particles. Conversely, at room temperature, the amount of particle contamination is reduced compared to that at high temperature, but as described above, the cleaning ability of the semiconductor wafer is reduced.
Therefore, a method of performing SC2 cleaning with a high-concentration mixed solution is considered as one solution.
しかし、ＳＣ２洗浄を高濃度で実施する場合、塩酸水溶液中に含まれる陰イオン、例えばＢｒ−、Ｃｌ−などがシリコンウェーハ表面に付着する現象が生じることとなる。シリコンウェーハ表面に陰イオン（Ｂｒ−）が付着すると、これが陽イオン（例えばアンモニアイオン）を引き付けることとなる。その結果、シリコンウェーハ洗浄での歩留まりに影響を与えるおそれがある。
図２は、特定の洗浄装置において所定期間にわたりシリコンウェーハに対してＳＣ１洗浄後にＳＣ２洗浄を施した場合のＳＣ２洗浄後の臭素イオンの量を示す。図２に示すように、ＳＣ２洗浄を行った後のシリコンウェーハ表面には、常に３×１０12ｉｏｎｓ／ｃｍ2程度のＢｒ−が付着している。
ところが、ＳＣ２洗浄前でＳＣ１洗浄後のシリコンウェーハの表面におけるＢｒ−のイオン量は、８×１０10ｉｏｎｓ／ｃｍ2未満であった。
したがって、ＳＣ２液に含まれる陰イオン（Ｂｒ−）がＳＣ２洗浄時にシリコンウェーハ表面に付着していることが考えられる。
つまり、通常使用する塩酸水溶液中には２００〜６００ｐｐｂのＢｒ−が含まれており、この塩酸水溶液中のＢｒ−が、ＳＣ２洗浄において、シリコンウェーハ表面に付着しているものと考えられる。このＢｒ−がシリコンウェーハの表面に付着すると、これが他の不純物（陽イオン）を引き付ける結果となる。
図３は、シリコンウェーハ表面に付着した臭素イオン（Ｂｒ−）の濃度とアンモニアイオン（ＮＨ4 ＋）の濃度との相関を示すグラフである。測定はＳＣ２洗浄後に行った。図３によれば、シリコンウェーハ表面に存在するＢｒ−の濃度が高ければ、ＮＨ4 ＋の濃度も高くなる傾向がみられる。これは、ＳＣ２洗浄後にＢｒ−がシリコンウェーハの表面に付着すると、これが陽イオンであるＮＨ4 ＋をシリコンウェーハの表面に引き付けると考えられるからである。
このようにシリコンウェーハの表面に臭素イオンが多く存在すると、これに関連してアンモニアイオン量も増加し、その結果、シリコンウェーハの再洗浄が必要になるという問題が生じていた。
However, when the SC2 cleaning is performed at a high concentration, a phenomenon occurs in which anions contained in the hydrochloric acid aqueous solution, such as Br − and Cl − , adhere to the silicon wafer surface. When an anion (Br − ) adheres to the silicon wafer surface, this attracts a cation (eg, ammonia ion). As a result, there is a possibility of affecting the yield in cleaning the silicon wafer.
FIG. 2 shows the amount of bromine ions after SC2 cleaning when the silicon wafer is subjected to SC2 cleaning after SC1 cleaning over a predetermined period in a specific cleaning apparatus. As shown in FIG. 2, about 3 × 10 12 ions / cm 2 of Br − is always adhered to the surface of the silicon wafer after SC2 cleaning.
However, the amount of Br − ions on the surface of the silicon wafer before SC2 cleaning and after SC1 cleaning was less than 8 × 10 10 ions / cm 2 .
Therefore, it is conceivable that the anions (Br − ) contained in the SC2 liquid are attached to the silicon wafer surface during the SC2 cleaning.
That is, the hydrochloric aqueous solution normally used Br of 200～600Ppb - includes a, Br in the hydrochloric acid aqueous solution - is, in SC2 cleaning, presumably adhering to the silicon wafer surface. When this Br − adheres to the surface of the silicon wafer, this results in attracting other impurities (cations).
FIG. 3 is a graph showing the correlation between the concentration of bromine ions (Br − ) attached to the silicon wafer surface and the concentration of ammonia ions (NH 4 + ). The measurement was performed after SC2 washing. According to FIG. 3, the concentration of NH 4 + tends to increase as the concentration of Br − existing on the silicon wafer surface increases. This is because if Br − adheres to the surface of the silicon wafer after SC2 cleaning, it is considered that this attracts NH 4 + which is a cation to the surface of the silicon wafer.
When a large amount of bromine ions are present on the surface of the silicon wafer in this way, the amount of ammonia ions is increased in association with this, resulting in a problem that the silicon wafer needs to be re-cleaned.
この発明は、上記問題点を改善するためになされたもので、ＳＣ１洗浄後の半導体ウェーハにＳＣ２洗浄を施した場合、その半導体ウェーハの表面に陰イオンが付着することを防止し、この後、この半導体ウェーハ表面に陽イオンが付着することを未然に防止した半導体ウェーハの洗浄方法を提供することを目的とする。
また、この発明の目的は、半導体ウェーハの洗浄での歩留まりを高めることである。
The present invention was made to improve the above problems. When the semiconductor wafer after SC1 cleaning is subjected to SC2 cleaning, anion is prevented from adhering to the surface of the semiconductor wafer. An object of the present invention is to provide a method for cleaning a semiconductor wafer in which cations are prevented from adhering to the surface of the semiconductor wafer.
Another object of the present invention is to increase the yield in cleaning semiconductor wafers.
請求項１に記載の発明は、陽イオン化した金属を、半導体ウェーハの表面に所定濃度で残留又は付着させるように、アンモニア水溶液と過酸化水素水と水との混合液で、半導体ウェーハの表面を洗浄する第１の洗浄工程と、この後、表面に陽イオン化した金属を残留又は付着させた半導体ウェーハを、塩酸水溶液と過酸化水素水と水との混合液で洗浄する第２の洗浄工程とを含む半導体ウェーハの洗浄方法である。
まず、第１の洗浄工程であるＳＣ１液の洗浄には、アンモニア水溶液（ＮＨ4ＯＨ）と過酸化水素水（Ｈ2Ｏ2）と水（Ｈ2Ｏ）との混合液が使用される。この場合の洗浄は、半導体ウェーハをＳＣ１液中に浸漬する方法などで実施される。
アンモニア水溶液と過酸化水素水と水との混合比（容量比）は限定されない。例えば、アンモニア水溶液：過酸化水素水：水＝１：５：５０で使用される。
また、アンモニア水溶液中のアンモニアおよび過酸化水素水中の過酸化水素の濃度は限定されない。例えば、アンモニア水溶液中のアンモニアの濃度は２９％、過酸化水素水中の過酸化水素の濃度は３０％で使用される。
このＳＣ１液は、過酸化水素水の強い酸化作用とアンモニア水溶液の溶解作用により有機汚染物を除去する。また、ＳＣ１液は、Ａｕ、Ａｇ、Ｃｕ、などのＩｂ族、ＩＩｂ族やその他の金属不純物を、ＮＨ4ＯＨとの化合物生成反応により除去する。
半導体ウェーハは、シリコンウェーハ、ガリウム砒素ウェーハなどを含む。
陽イオン化した金属としては、例えばＦｅ、Ｚｎなどがある。また、その濃度は任意とされる。
第２の洗浄工程であるＳＣ２液の洗浄には、塩酸水溶液（ＨＣｌ）と過酸化水素水（Ｈ2Ｏ2）と水（Ｈ2Ｏ）との混合液が使用される。また、この場合の洗浄は、例えば半導体ウェーハをＳＣ２液中に浸漬する。
ＳＣ２液の塩酸水溶液と過酸化水素水と水との混合比（容量比）は限定されない。塩酸水溶液：過酸化水素水：水＝１：１：１００〜１：１：５であることが好ましい。
また、塩酸水溶液中の塩酸および過酸化水素水中の過酸化水素の濃度は限定されない。例えば、塩酸水溶液中の塩酸の濃度は３７％、過酸化水素水中の過酸化水素の濃度は３０％で使用される。
このＳＣ２液は、ＳＣ１液に不溶のアルカリイオンやＡｌ、Ｆｅ、Ｍｇなどの陽イオンを除去する。また、ＳＣ２液は、ＳＣ１液で除去しきれなかったＡｕなどの金属不純物も除去する。
また、上記ＳＣ１液での洗浄後ＳＣ２液での洗浄までの間には、例えば純水リンス、乾燥の工程を配置することができる。リンス処理、乾燥処理は、この発明に係るＳＣ１液での洗浄工程で残留・付着させた金属に影響を与えないことが確認されている。
According to the first aspect of the present invention, the surface of the semiconductor wafer is made of a mixed solution of an aqueous ammonia solution, a hydrogen peroxide solution, and water so that the cationized metal remains or adheres to the surface of the semiconductor wafer at a predetermined concentration. A first cleaning step for cleaning, and a second cleaning step for cleaning a semiconductor wafer having a cationized metal remaining or attached to the surface with a mixed solution of hydrochloric acid aqueous solution, hydrogen peroxide water and water. A method for cleaning a semiconductor wafer including
First, a mixed solution of an aqueous ammonia solution (NH 4 OH), a hydrogen peroxide solution (H 2 O 2 ), and water (H 2 O) is used for cleaning the SC1 solution, which is the first cleaning step. The cleaning in this case is performed by a method of immersing the semiconductor wafer in the SC1 solution.
The mixing ratio (volume ratio) of the aqueous ammonia solution, the hydrogen peroxide solution, and water is not limited. For example, ammonia aqueous solution: hydrogen peroxide solution: water = 1: 5: 50.
In addition, the concentration of ammonia in the aqueous ammonia solution and the concentration of hydrogen peroxide in the hydrogen peroxide solution is not limited. For example, the concentration of ammonia in the aqueous ammonia solution is 29%, and the concentration of hydrogen peroxide in the hydrogen peroxide solution is 30%.
This SC1 solution removes organic contaminants by the strong oxidizing action of hydrogen peroxide solution and the dissolving action of aqueous ammonia solution. In addition, the SC1 solution removes Ib group, IIb group and other metal impurities such as Au, Ag, and Cu by a compound formation reaction with NH 4 OH.
The semiconductor wafer includes a silicon wafer, a gallium arsenide wafer, and the like.
Examples of the cationized metal include Fe and Zn. Moreover, the density | concentration is made arbitrary.
The cleaning of the SC2 solution is the second cleaning step, a mixture of aqueous hydrochloric acid (HCl) and hydrogen peroxide and the (H 2 O 2) and water (H 2 O) is used. In this case, for example, the semiconductor wafer is immersed in the SC2 liquid.
The mixing ratio (volume ratio) of the SC2 solution of hydrochloric acid, hydrogen peroxide, and water is not limited. Hydrochloric acid aqueous solution: hydrogen peroxide solution: water = 1: 1: 100 to 1: 1: 5 is preferable.
Further, the concentration of hydrochloric acid in the aqueous hydrochloric acid solution and the concentration of hydrogen peroxide in the hydrogen peroxide water are not limited. For example, the concentration of hydrochloric acid in the aqueous hydrochloric acid solution is 37%, and the concentration of hydrogen peroxide in the hydrogen peroxide water is 30%.
This SC2 solution removes alkali ions insoluble in the SC1 solution and cations such as Al, Fe, and Mg. The SC2 solution also removes metal impurities such as Au that could not be removed by the SC1 solution.
Further, for example, pure water rinsing and drying processes can be arranged between the cleaning with the SC1 liquid and the cleaning with the SC2 liquid. It has been confirmed that the rinsing process and the drying process do not affect the metal remaining and adhered in the cleaning process with the SC1 solution according to the present invention.
請求項２に記載の発明は、上記第１の洗浄工程では、上記アンモニア水溶液と過酸化水素水と水との混合液中に所定濃度の上記金属を含有させた請求項１に記載の半導体ウェーハの洗浄方法である。 According to a second aspect of the present invention, in the first cleaning step, the semiconductor wafer according to the first aspect in which the metal at a predetermined concentration is contained in a mixed solution of the aqueous ammonia solution, the hydrogen peroxide solution, and water. This is a cleaning method.
請求項３に記載の発明は、上記陽イオン化した金属は、Ｆｅ、Ｚｎ、Ｃａのうちの少なくともいずれか１つである請求項１または請求項２に記載の半導体ウェーハの洗浄方法である。
すなわち、上記第１の洗浄工程における洗浄では、半導体ウェーハの表面に陽イオン化したＦｅなどの金属が付着して残留する。そして、この後のＳＣ２液を用いた洗浄において、付着したＦｅイオンは、その半導体ウェーハの表面から完全に除去される。ＳＣ２液による洗浄で容易に除去することができ、かつ、イオン吸着抑制効果を発揮する金属としては、上記Ｆｅ、Ｚｎ、Ｃａが好ましい。
The invention according to claim 3 is the semiconductor wafer cleaning method according to
That is, in the cleaning in the first cleaning step, a metal such as Fe ionized on the surface of the semiconductor wafer adheres and remains. In the subsequent cleaning using the SC2 solution, the adhered Fe ions are completely removed from the surface of the semiconductor wafer. Fe, Zn, and Ca are preferred as metals that can be easily removed by washing with the SC2 solution and exhibit an ion adsorption suppressing effect.
請求項４に記載の発明は、上記半導体ウェーハの表面に残留または付着させた陽イオン化した金属の濃度は、１×１０10ａｔｏｍｓ／ｃｍ2以上である請求項１〜請求項３のいずれか１項に記載の半導体ウェーハ洗浄方法である。
例えば半導体ウェーハをＳＣ１液中に浸漬する方法では、ＳＣ１液中に高純度Ｆｅ試薬を約１００ｐｐｔ混合しておくか、または、Ｆｅが１ｐｐｂ入った過酸化水素水を上記配合比（アンモニア水溶液：過酸化水素水：水＝１：５：５０）にて使用する。
この結果、半導体ウェーハの表面へのＦｅイオンの残留量が１×１０1０ａｔｏｍｓ／ｃｍ2未満であると、ＳＣ２洗浄後の半導体ウェーハ表面へのＢｒ−の付着量を１×１０11ｉｏｎｓ／ｃｍ2未満に抑えることができない。
According to a fourth aspect of the present invention, the concentration of the cationized metal remaining or adhered to the surface of the semiconductor wafer is 1 × 10 10 atoms / cm 2 or more. The method for cleaning a semiconductor wafer according to the item.
For example, in the method of immersing a semiconductor wafer in the SC1 solution, about 100 ppt of high-purity Fe reagent is mixed in the SC1 solution, or hydrogen peroxide containing 1 ppb of Fe is mixed with the above-mentioned mixing ratio (ammonia aqueous solution: excess Hydrogen oxide water: water = 1: 5: 50).
As a result, if the residual amount of Fe ions on the surface of the semiconductor wafer is less than 1 × 10 10 atoms / cm 2 , the amount of Br − deposited on the semiconductor wafer surface after SC2 cleaning is 1 × 10 11 ions / cm 2. It cannot be kept below 2 .
請求項１〜４に記載の発明にあっては、まず、半導体ウェーハをＳＣ１液（アンモニア水溶液／過酸化水素水／水）で洗浄し、次に、この半導体ウェーハをＳＣ２液（塩酸水溶液／過酸化水素水／水）で洗浄する。例えばいずれの工程でも半導体ウェーハを液中に所定時間だけ浸漬する。
ＳＣ１洗浄では、過酸化水素水の強い酸化作用とＮＨ4ＯＨの溶解作用により、半導体ウェーハ表面の有機汚染物を除去する。また、Ｉｂ、ＩＩｂ族の金属不純物もＮＨ4ＯＨとの化合物生成反応により除去される。さらに、このＳＣ１洗浄では、半導体ウェーハ表面に、陽イオン化した金属（Ｆｅ＋）を所定の濃度（例えば１×１０10ａｔｏｍｓ／ｃｍ2以上、好ましくは１０×１０10ａｔｏｍｓ／ｃｍ2以上）で残留（付着）させておく。
次いで行われるＳＣ２洗浄では、ＳＣ１液で除去しきれなかったＡｕなどの金属不純物も除去する。
この結果、ＳＣ２液に含まれる陰イオン（Ｂｒ−）が半導体ウェーハの表面に付着することを防止することができる。具体的には、Ｂｒ−は、半導体ウェーハ表面に残留させた所定濃度のＦｅ＋から電子を奪われＢｒになる。このＢｒは、半導体ウェーハ表面に付着することはなくＳＣ２液で洗浄除去される。また、Ｆｅ＋もＢｒ−から電子を受け取り、ＦｅになりＳＣ２液で洗浄される。
In the first to fourth aspects of the invention, first, the semiconductor wafer is washed with the SC1 solution (ammonia aqueous solution / hydrogen peroxide solution / water), and then the semiconductor wafer is washed with the SC2 solution (hydrochloric acid aqueous solution / peroxide solution). Wash with hydrogen oxide water / water. For example, in any process, the semiconductor wafer is immersed in the liquid for a predetermined time.
In SC1 cleaning, organic contaminants on the surface of the semiconductor wafer are removed by the strong oxidizing action of hydrogen peroxide and the dissolving action of NH 4 OH. In addition, Ib and IIb group metal impurities are also removed by a compound formation reaction with NH 4 OH. Further, in this SC1 cleaning, cationized metal (Fe + ) remains on the surface of the semiconductor wafer at a predetermined concentration (for example, 1 × 10 10 atoms / cm 2 or more, preferably 10 × 10 10 atoms / cm 2 or more). Leave it attached.
In the subsequent SC2 cleaning, metal impurities such as Au that could not be removed by the SC1 solution are also removed.
As a result, it is possible to prevent anions (Br − ) contained in the SC2 liquid from adhering to the surface of the semiconductor wafer. Specifically, Br − is deprived of electrons from a predetermined concentration of Fe + remaining on the surface of the semiconductor wafer and becomes Br. This Br does not adhere to the surface of the semiconductor wafer and is removed by cleaning with the SC2 solution. Fe + also receives electrons from Br − , becomes Fe, and is washed with the SC2 solution.
この発明によれば、陽イオン化した金属を半導体ウェーハの表面に残留させるようにＳＣ１液で洗浄し、この金属が残留した半導体ウェーハをＳＣ２液で洗浄する。これにより、ＳＣ２液による洗浄時に半導体ウェーハの表面に陰イオンが付着することを防止することができる。ＳＣ１洗浄時に半導体ウェーハ表面に残留している陽イオン化した金属は、陰イオンとともにＳＣ２洗浄により除去される。この結果、洗浄歩留まりを高めることができ、その後のパーティクルなどの付着も未然に防止することができる。 According to the present invention, the cationized metal is washed with the SC1 liquid so as to remain on the surface of the semiconductor wafer, and the semiconductor wafer with the metal remaining is washed with the SC2 liquid. Thereby, it is possible to prevent anions from adhering to the surface of the semiconductor wafer during cleaning with the SC2 liquid. The cationized metal remaining on the surface of the semiconductor wafer during the SC1 cleaning is removed together with the anions by SC2 cleaning. As a result, the cleaning yield can be increased, and subsequent adhesion of particles and the like can be prevented in advance.
以下、この発明に係る半導体ウェーハの洗浄方法の一実施例を説明する。 Hereinafter, an embodiment of a semiconductor wafer cleaning method according to the present invention will be described.
図１は、ＳＣ１洗浄を施した後のシリコンウェーハ表面のＦｅ濃度と、その後ＳＣ２洗浄を実行した後のその表面のＢｒ-濃度との関係を示している。
この実施例にあっては、８インチのシリコンウェーハ（片面が鏡面研磨されたウェーハ）の洗浄を例にとって説明する。すなわち、研磨後のシリコンウェーハに対してＳＣ１洗浄、ＳＣ２洗浄を連続して施すものとする。
まず、第１の洗浄工程であるＳＣ１洗浄において、ＳＣ１液であるアンモニア水溶液（ＮＨ4ＯＨ）と過酸化水素水（Ｈ2Ｏ2）と水（Ｈ2Ｏ）との混合液を準備する。すなわち、ＳＣ１液は、アンモニア水溶液：過酸化水素水：水＝１：５：５０の比（容量比）で生成し、これを洗浄槽に注入する。そして、この洗浄槽内のＦｅは、１〜１００ｐｐｔの間で変化させて設定する。例えば高純度Ｆｅ試薬を用いてＳＣ１洗浄液中のＦｅ濃度を設定する。
そして、上記研磨後の複数枚のシリコンウェーハをウェーハカセットに入れ、このウェーハカセットを洗浄槽中のＳＣ１液に浸す（Ｆｅ濃度が上述のように１ｐｐｔ〜１００ｐｐｔにまで変化させた洗浄液毎に行う）。このときのＳＣ１液は７５〜８０℃に保持されている。ウェーハカセットは、ＳＣ１液中に１０分間保持するものとする。ウェーハカセットを、このＳＣ１液から引き上げた後、ウェーハカセットはリンス工程に移行する。このリンス工程では、シリコンウェーハは超純水で洗浄される。例えばウェーハカセットは複数の流水タンク（超純水）に連続して浸漬される。
この結果、シリコンウェーハの表面にはＦｅイオンが例えば２×１０11ａｔｏｍｓ／ｃｍ2の濃度で残留している。その測定は、以下の方法で行った。
Ｂｒについては、（１）純水をこのシリコンウェーハ表面に滴下し、イオンクロマトグラフィで純水試料を測定した。または、（２）市販の全反射Ｘ線評価機ＴＸＲＦにてこのシリコンウェーハ表面を直接測定した。
Ｆｅについては、混合酸液でウェーハ表面不純物を回収した後、ＩＣＰ−ＭＳ（誘導結合プラズマ質量分析装置）で測定した。
このＳＣ１液による洗浄では、上述したように、シリコンウェーハの表面からＨ2Ｏ2の強い酸化作用とＮＨ4ＯＨの溶解作用により有機汚染物が除去される。また、Ａｕ、Ａｇ、Ｃｕなどの金属不純物も併せて除去される。例えば、Ｃｕは、ＮＨ4ＯＨとの化合物生成反応により、Ｃｕ（ＮＨ3）4 2＋を形成して除去される。
FIG. 1 shows the relationship between the Fe concentration on the silicon wafer surface after the SC1 cleaning and the Br − concentration on the surface after the SC2 cleaning.
In this embodiment, an explanation will be given taking as an example the cleaning of an 8-inch silicon wafer (a wafer whose one side is mirror-polished). That is, it is assumed that SC1 cleaning and SC2 cleaning are successively performed on the polished silicon wafer.
First, in the SC1 cleaning, which is the first cleaning step, a mixed solution of an ammonia aqueous solution (NH 4 OH), a hydrogen peroxide solution (H 2 O 2 ), and water (H 2 O) as an SC1 solution is prepared. That is, SC1 liquid is produced | generated by the ratio (volume ratio) of aqueous ammonia solution: hydrogen peroxide water: water = 1: 5: 50, and this is inject | poured into a washing tank. And Fe in this washing tank is changed and set between 1-100ppt. For example, the Fe concentration in the SC1 cleaning solution is set using a high purity Fe reagent.
Then, a plurality of the polished silicon wafers are put in a wafer cassette, and the wafer cassette is immersed in the SC1 liquid in the cleaning tank (performed for each cleaning liquid in which the Fe concentration is changed from 1 ppt to 100 ppt as described above). . The SC1 solution at this time is maintained at 75 to 80 ° C. The wafer cassette is held in the SC1 solution for 10 minutes. After the wafer cassette is pulled up from the SC1 solution, the wafer cassette moves to a rinsing process. In this rinsing process, the silicon wafer is cleaned with ultrapure water. For example, the wafer cassette is continuously immersed in a plurality of flowing water tanks (ultra pure water).
As a result, Fe ions remain on the surface of the silicon wafer at a concentration of 2 × 10 11 atoms / cm 2 , for example. The measurement was performed by the following method.
For Br, (1) pure water was dropped on the surface of the silicon wafer, and a pure water sample was measured by ion chromatography. Alternatively, (2) the surface of the silicon wafer was directly measured with a commercially available total reflection X-ray evaluation machine TXRF.
Fe was measured by ICP-MS (Inductively Coupled Plasma Mass Spectrometer) after recovering wafer surface impurities with a mixed acid solution.
In the cleaning with the SC1 liquid, as described above, organic contaminants are removed from the surface of the silicon wafer by the strong oxidizing action of H 2 O 2 and the dissolving action of NH 4 OH. Further, metal impurities such as Au, Ag, and Cu are also removed. For example, Cu is removed by forming a Cu (NH 3 ) 4 2+ by a compound formation reaction with NH 4 OH.
次に、このシリコンウェーハは第２の洗浄工程でＳＣ２液によって洗浄される。この洗浄工程では、塩酸水溶液（ＨＣｌ）と過酸化水素水（Ｈ2Ｏ2）と水（Ｈ2Ｏ）との混合液が洗浄槽に満たされる。このとき、ＳＣ２液は、塩酸水溶液：過酸化水素水：水＝１：１：１００〜１：１：５の比で生成する。
シリコンウェーハは上記ウェーハカセットに保持された状態でＳＣ２液（７５〜８０℃）に浸される。ＳＣ２液中には１０〜１５分間保持される。
この後、シリコンウェーハは超純水で冷却、リンスされる。
このＳＣ２液洗浄では、アルカリイオン、Ａｌ、Ｆｅ、Ｍｇなどの陽イオンを除去する。また、Ａｕなどの金属不純物も除去される。したがって、ＳＣ１洗浄時にシリコンウェーハの表面に残留させたＦｅ＋はこのＳＣ２液で除去される。このＳＣ２洗浄の結果、たとえＳＣ２液中にＢｒ−イオンが存在しても、これがシリコンウェーハ表面に付着するおそれがなくなり、清浄な表面を有するシリコンウェーハを得ることができる。
Next, this silicon wafer is cleaned with the SC2 liquid in the second cleaning step. In this cleaning step, the cleaning tank is filled with a mixed solution of hydrochloric acid aqueous solution (HCl), hydrogen peroxide solution (H 2 O 2 ), and water (H 2 O). At this time, the SC2 solution is generated at a ratio of aqueous hydrochloric acid solution: hydrogen peroxide solution: water = 1: 1: 100 to 1: 1: 5.
A silicon wafer is immersed in SC2 liquid (75-80 degreeC) in the state hold | maintained at the said wafer cassette. It is held in the SC2 solution for 10-15 minutes.
Thereafter, the silicon wafer is cooled and rinsed with ultrapure water.
In this SC2 liquid cleaning, cations such as alkali ions, Al, Fe, and Mg are removed. Also, metal impurities such as Au are removed. Therefore, Fe + remaining on the surface of the silicon wafer during the SC1 cleaning is removed by this SC2 solution. As a result of this SC2 cleaning, even if Br − ions are present in the SC2 solution, there is no risk that they will adhere to the silicon wafer surface, and a silicon wafer having a clean surface can be obtained.
図１は、ＳＣ１洗浄直後のＦｅ＋の濃度と、ＳＣ２洗浄後のシリコンウェーハ表面に付着したＢｒ−のイオン量との相関を示す。この図に示すように、ＳＣ１洗浄後におけるシリコンウェーハ表面のＦｅ＋の濃度が高くなると、ＳＣ２洗浄後のＢｒ−のイオン量は減少する。
これは、ＳＣ１洗浄で残留したＦｅ＋により、これと異極性であるＢｒ−は、Ｆｅ＋から電子を奪われＢｒになる。Ｂｒは、シリコンウェーハ表面に付着することなく、ＳＣ２液で洗浄除去される。Ｆｅ＋も同時にＢｒ−から電子を受けてＦｅになり、ＳＣ２液で洗浄除去される。
この結果、シリコンウェーハ表面に付着するＢｒ−の量を１×１０11ｉｏｎｓ／ｃｍ2未満に抑えるには、１×１０10ａｔｏｍｓ／ｃｍ2以上の濃度を有するＦｅ＋をシリコンウェーハ表面に残留させればよいことが判る。
なお、ＳＣ１洗浄では上記Ｆｅ＋を残留させても、ＳＣ１液によりパーティクルなどが除去されること、また、ＳＣ２液により金属不純物が除去される通常の洗浄が行えることはいうまでもない。
このような半導体ウェーハ表面に付着する陰イオンの除去は、半導体ウェーハ洗浄の歩留まりの向上に効果的である。例えば陰イオンによる塩の形成を防止するからである。
FIG. 1 shows the correlation between the Fe + concentration immediately after SC1 cleaning and the amount of Br − ions attached to the silicon wafer surface after SC2 cleaning. As shown in this figure, as the Fe + concentration on the silicon wafer surface after SC1 cleaning increases, the amount of Br − ions after SC2 cleaning decreases.
This is because, due to Fe + remaining after SC1 cleaning, Br − , which has a different polarity from this, loses electrons from Fe + and becomes Br. Br is removed by washing with the SC2 liquid without adhering to the silicon wafer surface. At the same time, Fe + receives electrons from Br − to become Fe and is removed by washing with the SC2 solution.
As a result, to suppress the amount of Br − adhering to the silicon wafer surface to less than 1 × 10 11 ions / cm 2 , Fe + having a concentration of 1 × 10 10 atoms / cm 2 or more is left on the silicon wafer surface. You can see that
In the SC1 cleaning, it is needless to say that even if the Fe + is left, particles and the like are removed by the SC1 solution, and normal cleaning in which metal impurities are removed by the SC2 solution can be performed.
Such removal of anions adhering to the surface of the semiconductor wafer is effective in improving the yield of cleaning the semiconductor wafer. For example, salt formation due to anions is prevented.
Claims (4)
この後、表面に陽イオン化した金属を残留又は付着させた半導体ウェーハを、塩酸水溶液と過酸化水素水と水との混合液で洗浄する第２の洗浄工程とを含む半導体ウェーハの洗浄方法。 A first cleaning step of cleaning the surface of the semiconductor wafer with a mixed solution of an aqueous ammonia solution, a hydrogen peroxide solution, and water so that the cationized metal remains or adheres to the surface of the semiconductor wafer at a predetermined concentration;
Thereafter, a semiconductor wafer cleaning method including a second cleaning step of cleaning the semiconductor wafer having the cationized metal remaining or adhered on the surface thereof with a mixed solution of an aqueous hydrochloric acid solution, a hydrogen peroxide solution, and water.
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| KR20180125473A (en) | 2016-03-18 | 2018-11-23 | 신에쯔 한도타이 가부시키가이샤 | Method for cleaning semiconductor wafers |
| CN117276299A (en) * | 2023-11-21 | 2023-12-22 | 粤芯半导体技术股份有限公司 | CIS device structure and manufacturing method thereof |
| CN117542728A (en) * | 2024-01-09 | 2024-02-09 | 河北同光半导体股份有限公司 | Dynamic cleaning method for removing metal ions on surface of silicon carbide substrate |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20180125473A (en) | 2016-03-18 | 2018-11-23 | 신에쯔 한도타이 가부시키가이샤 | Method for cleaning semiconductor wafers |
| DE112017000938T5 (en) | 2016-03-18 | 2019-01-03 | Shin-Etsu Handotai Co., Ltd. | Method for cleaning a semiconductor wafer |
| US10692714B2 (en) | 2016-03-18 | 2020-06-23 | Shin-Etsu Handotai Co., Ltd. | Method for cleaning semiconductor wafer |
| CN117276299A (en) * | 2023-11-21 | 2023-12-22 | 粤芯半导体技术股份有限公司 | CIS device structure and manufacturing method thereof |
| CN117542728A (en) * | 2024-01-09 | 2024-02-09 | 河北同光半导体股份有限公司 | Dynamic cleaning method for removing metal ions on surface of silicon carbide substrate |
| CN117542728B (en) * | 2024-01-09 | 2024-03-19 | 河北同光半导体股份有限公司 | Dynamic cleaning method for removing metal ions on surface of silicon carbide substrate |
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