【０００１】
【発明の属する技術分野】
本発明は、電子材料の、特に半導体基板の湿式洗浄工程で使用される洗浄水で、特定の気体を溶解して洗浄効果を高めた、いわゆるガス溶解機能水とその製造方法および電子材料の洗浄方法に関するものである。
【０００２】
【従来の技術】
従来、半導体基板を含む電子材料の湿式洗浄において、洗浄やリンスに使用可能な高純度の純水あるいは超純水に、特定のガスを溶解した水が数％オーダーの薬品を溶かした薬液に匹敵する洗浄効果を発揮する能力があることが分かってきた。高い酸化力を持ち、有機物や一部の金属汚染除去に有効なオゾン水に加え、水素を高濃度に溶解した水が微粒子除去用の洗浄水として注目されるようになった。
【０００３】
半導体基板を含む電子材料等の湿式洗浄において、洗浄水として水素水が用いられているが、その水素水については溶存水素濃度のみを規定して洗浄を行っており、水素以外の第二成分のガスや水素水の真空度は規定されていない（例えば、特許文献１を参照）。
【０００４】
特定のガスを溶解したガス溶解水は、純水と所望のガスをガス溶解膜に通して製造する。通常の場合、使用される純水は、真空脱気により不純なガスを除去し、純度を高めたのちに窒素パージされたタンクに貯蔵される。その後、貯蔵された純水はタンクから各々の要求に応じて装置に供給される。この場合、純水中の窒素濃度は制御されておらず水質が一定ではない。
【０００５】
従来、水素水には２通りの製造方法がある。一つは純水が溶解量不明の窒素を含んでいるため、溶解前に再度脱気処理を行い、不要な溶存ガスを取り除いてから必要量の水素ガスのみを溶解する方法である。もう一つは、工場から供給される窒素を含んだ純水に過剰固溶濃度の水素ガスを供給して窒素と置換する方法である。
【０００６】
【特許文献１】
特開平１１−２９７９４号公報（２〜４頁）
【０００７】
【発明が解決しようとする課題】
しかしながら、脱気処理してから水素を溶解する場合は、飽和濃度の水素を溶解しない限り、水素水中には真空領域が存在し、大気圧より低い不安定な水素水となる。また、純水を脱気せずに水素を溶解させたり、水素で窒素を置換したりするときは、供給される純水の状態に応じて水素濃度や水素水の真空度が変動し、安定性を欠いた水素水が製造される。それを示すかのように、水素水で洗浄した場合、同じ濃度の水素水でありながらも洗浄能力の低下やばらつきが大きく、この洗浄能力の低下やばらつきが半導体装置の不良の原因の一つになっている。
【０００８】
さらに水素水に関しては、洗浄効果に与える水素濃度以外の成分の影響を示す報文や一定濃度以上の水素水を対象とする出願などが既に多く出されているが、水素濃度以外の成分の影響については、詳細な研究成果は報告されておらず、未開拓領域となっている。
【０００９】
図５は従来の第二成分を含まず、水素のみを様々な濃度で溶解させた未飽和水素水であるガス溶解水の溶存水素濃度（ｐｐｍ）に対する洗浄水の真空度（ＭＰａ）を表す特性図である。洗浄水として使用するガス溶解水の製造については、水素水製造装置（図示せず）を用いた。
【００１０】
ガス溶解水の製造方法としては、水素のみ溶解させた第１のガス溶解水は、２本のガス透過膜内蔵モジュールを使い、１本目で減圧膜脱気を行って水素ガス以外の第２成分を除去した後に、２本目で制御された量の水素ガスを供給する方法で、第２成分を含まない様々な溶存水素濃度の未飽和水素水を調製した。第１のガス溶解水は、図５の●印で示す特性であり、水素水の真空度は、溶存水素濃度が飽和濃度である１．６ｐｐｍになるまで溶解しない限り大気圧より低い値となり、真空度は溶存水素濃度に比例して小さくなる。つまり、溶存水素濃度が飽和濃度より小さい未飽和な溶存水素水の場合は、水素水中には水素以外にガスが存在せず、水素ガス以外の領域は真空になっているため、水素水の圧力が不安定状態にあり、洗浄能力の低下やばらつきを生じ、半導体装置の歩留まりに悪影響を与えることがわかった。つまり、洗浄能力の低下やばらつきの原因が水素水の真空度にあることを見出した。
【００１１】
本発明の目的は、これまで知られていなかった水素濃度以外の成分の影響を明らかにし、従来の水素水以上の有用性を持つ洗浄水と、それを用いて洗浄する半導体基板を含む電子材料の洗浄方法および洗浄水の製造方法を提供し、半導体装置の不良を低減することにある。
【００１２】
【課題を解決するための手段】
上記目的を達成するために、本発明の電子材料用洗浄水は、電子材料を洗浄する水素水に窒素を含有し、その水素水は、溶存水素と溶存窒素の総和の飽和度が９０％以上である。
【００１３】
また、本発明の電子材料用洗浄水の製造方法は、純水に窒素を飽和濃度の９０％まで溶解させる工程と、その後に連続して水素を溶解させる工程を備えており、水素の溶解はモジュールへの通気により行なうものである。
【００１４】
また、本発明の電子材料の洗浄方法は、洗浄水に窒素を含有する水素水を使用するものである。
【００１５】
【発明の実施の形態】
水素水の未開拓領域である水素濃度以外の成分の影響や洗浄能力の低下やばらつきを明確にするために、湿式洗浄用の水素水において、純水や水素濃度以外にも着目して詳細な評価を行った。
【００１６】
通常、半導体工場で供給される超純水には窒素ガスが多く溶解している。一般的に超純水使用を前提とすることから、水素とともに制御すべき第二の溶存ガス成分を窒素と定めて様々なガス溶解水を調製し、洗浄効果を比較して、有効なガス濃度領域を調べた。
【００１７】
水素および窒素各々のガス濃度の制御は、窒素を実質的に飽和付近まで超純水に溶解させた後に、水素を追加供給することで行った。
【００１８】
ここで、飽和とは、室温大気圧下で、その水が溶解させられるガスの飽和量が溶けていることであり、ガスがすべて水素ガスの場合には、１．６ｐｐｍ程度、すべて窒素ガスの場合には１９ｐｐｍ程度の溶解で飽和となる。各々が５０％ずつ溶解している場合には、０．６ｐｐｍの水素と９．５ｐｐｍの窒素が溶けて、総和として飽和となる。
【００１９】
図１はガス溶解水の溶存水素濃度（ｐｐｍ）に対する洗浄水の真空度（ＭＰａ）を表す特性図である。ガス溶解水としては、従来の技術で説明した第二成分を含まない水素のみ様々な濃度で溶解させた未飽和水素水（図１の●印で示す特性（図５と同じ））と、第二成分として窒素を含み、水素ガスと窒素ガスとの両ガスの総和でほぼ飽和している窒素含有飽和水素水（図１の▲印で示す特性）とを用いて特性を比較した。洗浄水として使用するガス溶解水の製造については、水素水製造装置（図示せず）を用いた。
【００２０】
そこで、本発明の洗浄水である窒素含有飽和水素水の製造方法としては、純水に対し、１本目のモジュールに飽和に対して過剰な量の窒素ガスを供給して、ほぼ飽和濃度の窒素溶解水を作り、２本目のモジュールに水素ガスを供給して、第２成分（窒素ガス）を含有する様々な濃度の水素水を調製した。ここでは、窒素ガスが水素ガスに置換されており、水素ガスと窒素ガスの総和では常にほぼ飽和している。この時、窒素を含有する水素水（以下、窒素含有水素水と記す）の真空度は、図１の▲印で示す特性であり、溶存水素濃度を変えても常に大気圧と同じで変動しない。溶存水素ガスと溶存窒素ガスの総和で、ほぼ飽和しているとあるが、９０％以上であれば、窒素含有水素水の溶存水素濃度に対する真空度は安定している。
【００２１】
つまり、図１に示すように窒素含有水素水の溶存水素濃度に対する真空度は、水素水のみの場合は、溶存水素濃度に応じて変わるのに対し、窒素含有水素水の場合は変動せず、水質が安定している。
【００２２】
水素ガス・窒素ガス両成分の溶解量を制御する方法としては、水素ガス以外の第２成分を十分脱気した水にこれら両ガスの供給量を各々制御する方法が考えられるが、その場合、ガス供給制御系が複数必要となり、ガス溶解水を製造する水素水製造装置が繁雑となる。従って上記記載の方法のように、まず過剰量の窒素供給によって窒素飽和水を作り、さらに水素ガスを供給することで、両方の成分を含み、両方の総和で飽和となる水が容易に作れる。
【００２３】
図２は、この方法を用いて、大気圧状態で調合した窒素含有水素水中の溶存水素濃度と溶存窒素濃度との関係を示す特性図である。水素水の溶存水素濃度が上がれば、溶存窒素濃度が下がることがわかる。
【００２４】
窒素飽和水を原水として、そこに水素を供給溶解する場合、水素の溶解は追加ではなく、窒素との置換となるようにすることが必要である。具体的には、水素の供給は加圧による水素水中への押し込みではなく、加圧を伴わないモジュールへの通気によるものとする。これによって、ガス透過膜を介して、ヘンリーの法則に従い、溶存窒素ガス（液相）の一部が気相へ、気相の水素ガスが液相へ移動し、総和として室温大気圧下で過飽和とならずに、水素・窒素両成分を含む水が得られる。水素ガスの供給条件によって、水素と窒素の比率を任意に変えることができる。
【００２５】
脱気していない水に水素ガスを溶解させるには、理論量以上の水素が必要となる。とりわけ、ガス溶解水の溶存水素濃度が１ｐｐｍ以上の高濃度領域を求める場合には、飽和濃度の４倍以上の水素ガス供給が必要となるが、溶存水素濃度が飽和の半分程度までであれば、飽和濃度〜４倍程度の水素ガス供給を行うことで、水素の溶解（窒素との置換）を進めることができる。
【００２６】
以上の要領で調製した、第二成分が無く水素のみを溶解した従来の未飽和水と、第二成分として窒素を含み、水素と窒素の両ガスの総和で飽和された窒素含有飽和水素水を用いて、超音波照射を併用した洗浄実験を行い、各々の微粒子除去効果を調べ、比較した。実験条件としては、洗浄水量を１．５Ｌ／分、超音波照射を周波数１．０ＭＨｚ、出力３８Ｗとし、微粒子測定条件は０．１２μｍ以上を対象とし、被洗浄基板としては、シリコン窒化物微粒子またはシリコン微粒子で５，０００〜７，０００個／ウエハに故意に汚染した８インチウエハを用いた。洗浄工程は６０秒間、５００ｒｐｍで、乾燥工程は窒素ガスブローを併用して、２０秒間、１５００ｒｐｍで行なった。
【００２７】
図３はそれぞれのガス溶解水での溶存水素濃度（ｐｐｍ）に対するシリコン窒化膜微粒子の除去率（％）を示す特性図である。その結果、溶存水素濃度が１．０ｐｐｍ以下の領域で、微粒子除去効果は、窒素含有飽和水素水の方が、水素のみ溶解の未飽和水よりも高いことが分かる。特に際だった特徴として、０．２〜１．０ｐｐｍ領域で、窒素含有水素水の微粒子除去効果はほぼ安定していることが分かる。特に低濃度領域では、水素のみ溶解させた未飽和水との微粒子除去効果の差は大きく、窒素含有飽和水素水の方が優れていることがわかる。
【００２８】
図４はそれぞれのガス溶解水での溶存水素濃度（ｐｐｍ）に対するシリコン微粒子の除去率（％）を示す特性図である。その結果、溶存水素濃度が１．０ｐｐｍ以下の領域で、微粒子除去効果は、窒素含有飽和水素水の方が、水素のみ溶解の未飽和水よりも高いことが分かる。溶存水素濃度が０．２ｐｐｍ以上で効果があり、０．４〜１．０ｐｐｍ領域で、窒素含有水素水の微粒子除去効果はほぼ安定していることが分かる。特に低濃度領域では、水素のみ溶解させた未飽和水との微粒子除去効果の差は大きく、窒素含有飽和水素水の方が優れていることがわかる。
【００２９】
図３および図４において、ガス溶解水での溶存水素濃度に対するシリコン窒化膜微粒子およびシリコン微粒子の両方の除去率が、溶存水素濃度０．２〜１．０ｐｐｍ領域で、従来の水素のみ溶解の未飽和水よりも優れていることがわかる。
【００３０】
なお、窒素含有飽和水素水を用いた洗浄方法において、超音波照射を併用した方法について説明したが、ブラシ洗浄でも同様の効果が得られることはいうまでもない。
【００３１】
【発明の効果】
電子材料用洗浄水として、水素水に窒素を含有したものを用いることにより、半導体基板を含む電子材料を洗浄したときに、単なる水素水より効果の高い微粒子除去効果を示す。また、電子材料用洗浄水の製造方法は、純水に窒素を飽和濃度の９０％まで溶解させる工程と、その後に連続して水素を溶解させる工程とからなり、非常に簡単な方法で製造でき、溶存水素濃度が０．２〜１．０ｐｐｍに制御することにより、高い微粒子除去効果が得られる洗浄水を製造できる。
【図面の簡単な説明】
【図１】本発明の洗浄水の溶存水素濃度に対する真空度を表す特性図
【図２】本発明の洗浄水の溶存水素濃度と溶存窒素濃度の関係を示す特性図
【図３】本発明の洗浄水の溶存水素濃度に対するシリコン窒化膜微粒子の除去率を示す特性図
【図４】本発明の洗浄水の溶存水素濃度に対するシリコン微粒子の除去率を示す特性図
【図５】従来の洗浄水の溶存水素濃度に対する真空度を表す特性図[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a so-called gas-dissolving functional water in which a specific gas is dissolved in a cleaning water used in a wet cleaning step of an electronic material, in particular, a semiconductor substrate to enhance a cleaning effect, a method for producing the same, and cleaning of the electronic material. It is about the method.
[0002]
[Prior art]
Conventionally, in wet cleaning of electronic materials including semiconductor substrates, a chemical solution in which water in which a specific gas is dissolved in high-purity pure water or ultrapure water that can be used for cleaning and rinsing dissolves a few percent order of chemicals. It has been found that it has the ability to exert a cleaning effect. In addition to ozone water, which has a high oxidizing power and is effective in removing organic substances and some metal contamination, water in which hydrogen is dissolved at a high concentration has been attracting attention as cleaning water for removing fine particles.
[0003]
In wet cleaning of electronic materials including semiconductor substrates, hydrogen water is used as cleaning water, and the hydrogen water is cleaned only by defining the dissolved hydrogen concentration, and the second component other than hydrogen is cleaned. The degree of vacuum of gas or hydrogen water is not specified (for example, see Patent Document 1).
[0004]
Gas-dissolved water in which a specific gas is dissolved is produced by passing pure water and a desired gas through a gas-dissolving membrane. In the usual case, the pure water used is stored in a nitrogen-purged tank after removing impurities by vacuum degassing and increasing the purity. Thereafter, the stored pure water is supplied from the tank to the apparatus according to each request. In this case, the nitrogen concentration in the pure water is not controlled, and the water quality is not constant.
[0005]
Conventionally, there are two methods for producing hydrogen water. One is a method in which pure water contains nitrogen whose dissolved amount is unknown, so that degassing is performed again before dissolving, unnecessary dissolved gas is removed, and only a necessary amount of hydrogen gas is dissolved. The other is a method in which a hydrogen gas having an excessive solid solution concentration is supplied to pure water containing nitrogen supplied from a factory to replace it with nitrogen.
[0006]
[Patent Document 1]
JP-A-11-29794 (pages 2 to 4)
[0007]
[Problems to be solved by the invention]
However, in the case of dissolving hydrogen after the degassing process, unless the saturated concentration of hydrogen is dissolved, a vacuum region exists in the hydrogen water, and the hydrogen water becomes an unstable hydrogen water lower than the atmospheric pressure. Also, when dissolving hydrogen without degassing pure water or replacing nitrogen with hydrogen, the hydrogen concentration and the degree of vacuum of the hydrogen water change depending on the state of the supplied pure water, and the Hydrogen water lacking properties is produced. As can be seen, when cleaning with hydrogen water, even if the hydrogen water has the same concentration, the cleaning performance is greatly reduced and widely varied, and this reduced cleaning performance is one of the causes of semiconductor device failure. It has become.
[0008]
Regarding hydrogen water, many reports have already been issued indicating the effect of components other than hydrogen concentration on the cleaning effect, and many applications have been filed for hydrogen water with a certain concentration or higher. As for, no detailed research results have been reported, and it is an unexplored area.
[0009]
FIG. 5 is a characteristic showing the degree of vacuum (MPa) of washing water with respect to the dissolved hydrogen concentration (ppm) of gas-dissolved water, which is an unsaturated hydrogen water in which only hydrogen is dissolved at various concentrations, without the conventional second component. FIG. Hydrogen water production equipment (not shown) was used for production of gas-dissolved water used as cleaning water.
[0010]
As a method for producing gas-dissolved water, the first gas-dissolved water in which only hydrogen is dissolved is subjected to decompression membrane degassing with the first module using two modules with a built-in gas-permeable membrane, and the second component other than hydrogen gas is used. After removing the hydrogen gas, unsaturated hydrogen water having various dissolved hydrogen concentrations not containing the second component was prepared by a method of supplying a controlled amount of hydrogen gas by the second gas. The first gas-dissolved water has the characteristics indicated by ● in FIG. 5, and the degree of vacuum of the hydrogen water becomes a value lower than the atmospheric pressure unless the dissolved hydrogen concentration is dissolved until it reaches 1.6 ppm which is the saturation concentration. The degree of vacuum decreases in proportion to the dissolved hydrogen concentration. In other words, in the case of unsaturated dissolved hydrogen water having a dissolved hydrogen concentration smaller than the saturated concentration, there is no gas other than hydrogen in the hydrogen water, and the area other than the hydrogen gas is evacuated. Has been found to be in an unstable state, resulting in a reduction or variation in cleaning ability, which adversely affects the yield of semiconductor devices. That is, it has been found that the cause of the deterioration and the variation of the cleaning ability is the degree of vacuum of the hydrogen water.
[0011]
An object of the present invention is to clarify the influence of components other than the hydrogen concentration, which has not been known, and to provide a cleaning water having more usefulness than conventional hydrogen water, and an electronic material including a semiconductor substrate to be cleaned using the same. Another object of the present invention is to provide a cleaning method and a method for producing cleaning water to reduce defects of a semiconductor device.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the electronic material cleaning water of the present invention contains hydrogen in hydrogen water for cleaning the electronic material, and the hydrogen water has a saturation degree of 90% or more of the total of dissolved hydrogen and dissolved nitrogen. It is.
[0013]
Also, the method for producing electronic material cleaning water of the present invention includes a step of dissolving nitrogen in pure water to 90% of a saturation concentration and a step of subsequently dissolving hydrogen continuously. This is performed by ventilating the module.
[0014]
Further, the method for cleaning an electronic material of the present invention uses hydrogen water containing nitrogen in the cleaning water.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to clarify the effects of components other than the hydrogen concentration, which is an unexplored region of hydrogen water, and the reduction and dispersion of the cleaning performance, the hydrogen water for wet cleaning focuses on pure water and hydrogen concentration other than pure water. An evaluation was performed.
[0016]
Usually, a large amount of nitrogen gas is dissolved in ultrapure water supplied at a semiconductor factory. Since it is generally assumed that ultrapure water is used, nitrogen is used as the second dissolved gas component to be controlled together with hydrogen, and various gas-dissolved waters are prepared. The area was examined.
[0017]
The gas concentrations of hydrogen and nitrogen were controlled by dissolving nitrogen in ultrapure water substantially to near saturation and then additionally supplying hydrogen.
[0018]
Here, the term “saturation” means that a saturated amount of a gas in which water is dissolved is dissolved at room temperature and atmospheric pressure. When all gases are hydrogen gas, about 1.6 ppm, and all of nitrogen gas are dissolved. In this case, the solution is saturated by dissolution of about 19 ppm. When each of them is dissolved by 50%, 0.6 ppm of hydrogen and 9.5 ppm of nitrogen are dissolved, and the total is saturated.
[0019]
FIG. 1 is a characteristic diagram showing the degree of vacuum (MPa) of the cleaning water with respect to the dissolved hydrogen concentration (ppm) of the gas dissolved water. As the gas-dissolved water, the unsaturated hydrogen water (only the characteristics indicated by the black circles in FIG. 1 (the same as FIG. 5)) in which only hydrogen not containing the second component described in the related art is dissolved at various concentrations, and The characteristics were compared using nitrogen-containing saturated hydrogen water containing nitrogen as a two component and being substantially saturated by the sum of both hydrogen gas and nitrogen gas (characteristic indicated by the symbol ▲ in FIG. 1). Hydrogen water production equipment (not shown) was used for production of gas-dissolved water used as cleaning water.
[0020]
Therefore, as a method for producing the nitrogen-containing saturated hydrogen water that is the washing water of the present invention, an excessive amount of nitrogen gas is supplied to pure water to the first module with respect to the saturation, and the nitrogen concentration is substantially saturated. Dissolved water was prepared, and hydrogen gas was supplied to the second module to prepare various concentrations of hydrogen water containing the second component (nitrogen gas). Here, the nitrogen gas is replaced by the hydrogen gas, and the total of the hydrogen gas and the nitrogen gas is almost saturated at all times. At this time, the degree of vacuum of the nitrogen-containing hydrogen water (hereinafter, referred to as nitrogen-containing hydrogen water) is a characteristic indicated by the symbol ▲ in FIG. 1, and does not fluctuate at the same level as the atmospheric pressure even when the dissolved hydrogen concentration is changed. . Although the total of the dissolved hydrogen gas and the dissolved nitrogen gas is said to be almost saturated, if it is 90% or more, the degree of vacuum with respect to the dissolved hydrogen concentration of the nitrogen-containing hydrogen water is stable.
[0021]
That is, as shown in FIG. 1, the degree of vacuum with respect to the dissolved hydrogen concentration of the nitrogen-containing hydrogen water changes according to the dissolved hydrogen concentration in the case of only the hydrogen water, but does not change in the case of the nitrogen-containing hydrogen water, Water quality is stable.
[0022]
As a method of controlling the dissolution amount of both components of hydrogen gas and nitrogen gas, a method of controlling the supply amounts of these two gases to water in which the second component other than hydrogen gas has been sufficiently degassed can be considered. A plurality of gas supply control systems are required, and the hydrogen water producing apparatus for producing gas dissolved water becomes complicated. Therefore, as in the method described above, first, nitrogen-saturated water is produced by supplying an excessive amount of nitrogen, and then hydrogen gas is supplied, whereby water containing both components and being saturated in the sum of both can be easily produced.
[0023]
FIG. 2 is a characteristic diagram showing the relationship between the concentration of dissolved hydrogen and the concentration of dissolved nitrogen in a nitrogen-containing hydrogen water prepared under atmospheric pressure using this method. It can be seen that when the dissolved hydrogen concentration of the hydrogen water increases, the dissolved nitrogen concentration decreases.
[0024]
In the case where nitrogen-saturated water is used as raw water and hydrogen is supplied and dissolved therein, it is necessary to dissolve hydrogen instead of adding it and replace it with nitrogen. Specifically, the supply of hydrogen is not by pushing into the hydrogen water by pressurization, but by ventilation to the module without pressurization. As a result, a part of the dissolved nitrogen gas (liquid phase) moves to the gas phase and the hydrogen gas in the gas phase moves to the liquid phase through the gas permeable membrane according to Henry's law, and the total is supersaturated at room temperature and atmospheric pressure. Instead, water containing both hydrogen and nitrogen components is obtained. The ratio between hydrogen and nitrogen can be arbitrarily changed depending on the supply conditions of the hydrogen gas.
[0025]
In order to dissolve hydrogen gas in water that has not been degassed, more than the theoretical amount of hydrogen is required. In particular, when a high-concentration region where the dissolved hydrogen concentration of the gas-dissolved water is 1 ppm or more is required, a hydrogen gas supply at least four times the saturation concentration is required. By supplying a hydrogen gas having a saturation concentration of about 4 times, dissolution of hydrogen (replacement with nitrogen) can be promoted.
[0026]
Conventional unsaturated water prepared in the above manner, having no second component and only hydrogen dissolved, and nitrogen-containing saturated hydrogen water containing nitrogen as the second component and saturated with the sum of both hydrogen and nitrogen gases A cleaning experiment using ultrasonic irradiation was also performed using the samples, and the effect of removing fine particles was examined and compared. The experimental conditions were as follows: the amount of cleaning water was 1.5 L / min, the frequency of ultrasonic irradiation was 1.0 MHz, the output was 38 W, and the fine particle measurement condition was 0.12 μm or more. An 8-inch wafer intentionally contaminated with 5,000 to 7,000 silicon particles / wafer with silicon fine particles was used. The cleaning step was performed at 500 rpm for 60 seconds, and the drying step was performed at 1500 rpm for 20 seconds using nitrogen gas blowing.
[0027]
FIG. 3 is a characteristic diagram showing the removal rate (%) of silicon nitride film fine particles with respect to the dissolved hydrogen concentration (ppm) in each gas-dissolved water. As a result, in the region where the concentration of dissolved hydrogen is 1.0 ppm or less, the effect of removing fine particles is higher in the nitrogen-containing saturated hydrogen water than in the unsaturated water in which only hydrogen is dissolved. As a particularly remarkable feature, it can be seen that the effect of removing fine particles of nitrogen-containing hydrogen water is almost stable in the range of 0.2 to 1.0 ppm. In particular, in the low concentration region, the difference in the particulate removal effect from the unsaturated water in which only hydrogen was dissolved was large, and it can be seen that the nitrogen-containing saturated hydrogen water was superior.
[0028]
FIG. 4 is a characteristic diagram showing the removal rate (%) of silicon fine particles with respect to the dissolved hydrogen concentration (ppm) in each gas-dissolved water. As a result, in the region where the concentration of dissolved hydrogen is 1.0 ppm or less, the effect of removing fine particles is higher in the nitrogen-containing saturated hydrogen water than in the unsaturated water in which only hydrogen is dissolved. It can be seen that the effect is obtained when the concentration of dissolved hydrogen is 0.2 ppm or more, and the effect of removing fine particles of nitrogen-containing hydrogen water is almost stable in the range of 0.4 to 1.0 ppm. In particular, in the low concentration region, the difference in the particulate removal effect from the unsaturated water in which only hydrogen was dissolved was large, and it can be seen that the nitrogen-containing saturated hydrogen water was superior.
[0029]
3 and 4, the removal rate of both the silicon nitride film fine particles and the silicon fine particles with respect to the dissolved hydrogen concentration in the gas-dissolved water is within the range of the dissolved hydrogen concentration of 0.2 to 1.0 ppm. It turns out that it is superior to saturated water.
[0030]
In the cleaning method using the nitrogen-containing saturated hydrogen water, the method using ultrasonic irradiation has been described. However, it goes without saying that the same effect can be obtained by brush cleaning.
[0031]
【The invention's effect】
By using hydrogen water containing nitrogen as the cleaning water for electronic materials, a fine particle removing effect that is more effective than mere hydrogen water is exhibited when the electronic materials including the semiconductor substrate are cleaned. Further, the method for producing the cleaning water for electronic materials comprises a step of dissolving nitrogen in pure water to 90% of the saturation concentration and a step of successively dissolving hydrogen thereafter, and can be produced by a very simple method. By controlling the concentration of dissolved hydrogen to 0.2 to 1.0 ppm, it is possible to produce washing water having a high particulate removal effect.
[Brief description of the drawings]
FIG. 1 is a characteristic diagram showing the degree of vacuum with respect to the concentration of dissolved hydrogen in the cleaning water of the present invention. FIG. 2 is a characteristic diagram showing the relationship between the concentration of dissolved hydrogen and the concentration of dissolved nitrogen in the cleaning water of the present invention. FIG. 4 is a characteristic diagram showing the removal rate of silicon nitride film fine particles with respect to the concentration of dissolved hydrogen in the cleaning water. FIG. 4 is a characteristic diagram showing the removal ratio of silicon fine particles with respect to the concentration of dissolved hydrogen in the cleaning water of the present invention. Characteristic diagram showing degree of vacuum with respect to dissolved hydrogen concentration
