JP7571691B2 - Silicon wafer cleaning method and manufacturing method, and method for evaluating hydrogen peroxide concentration in cleaning solution and method for managing hydrogen peroxide concentration - Google Patents
Silicon wafer cleaning method and manufacturing method, and method for evaluating hydrogen peroxide concentration in cleaning solution and method for managing hydrogen peroxide concentration Download PDFInfo
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- 238000004140 cleaning Methods 0.000 title claims description 329
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 title claims description 192
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims description 103
- 229910052710 silicon Inorganic materials 0.000 title claims description 103
- 239000010703 silicon Substances 0.000 title claims description 103
- 238000000034 method Methods 0.000 title claims description 94
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 235000012431 wafers Nutrition 0.000 claims description 175
- 239000000243 solution Substances 0.000 claims description 128
- 238000007788 roughening Methods 0.000 claims description 115
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 43
- 238000011835 investigation Methods 0.000 claims description 37
- 239000000908 ammonium hydroxide Substances 0.000 claims description 28
- 230000008569 process Effects 0.000 claims description 17
- 239000007864 aqueous solution Substances 0.000 claims description 14
- 238000011156 evaluation Methods 0.000 claims description 14
- 239000007788 liquid Substances 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 12
- 238000012545 processing Methods 0.000 claims description 12
- 230000008859 change Effects 0.000 claims description 5
- 235000011114 ammonium hydroxide Nutrition 0.000 description 36
- 238000005530 etching Methods 0.000 description 17
- 239000000126 substance Substances 0.000 description 17
- 238000007254 oxidation reaction Methods 0.000 description 12
- 230000003647 oxidation Effects 0.000 description 10
- 239000000203 mixture Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 238000012360 testing method Methods 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- QOSATHPSBFQAML-UHFFFAOYSA-N hydrogen peroxide;hydrate Chemical compound O.OO QOSATHPSBFQAML-UHFFFAOYSA-N 0.000 description 5
- 238000005498 polishing Methods 0.000 description 5
- 239000005871 repellent Substances 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 230000005660 hydrophilic surface Effects 0.000 description 4
- 230000003746 surface roughness Effects 0.000 description 4
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 238000002835 absorbance Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 238000004630 atomic force microscopy Methods 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007726 management method Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 239000003082 abrasive agent Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- -1 for example Chemical compound 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000386 microscopy Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- GSWAOPJLTADLTN-UHFFFAOYSA-N oxidanimine Chemical compound [O-][NH3+] GSWAOPJLTADLTN-UHFFFAOYSA-N 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 238000007517 polishing process Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
- H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
- H01L21/02052—Wet cleaning only
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
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- H—ELECTRICITY
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67242—Apparatus for monitoring, sorting or marking
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
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- General Physics & Mathematics (AREA)
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- Testing Or Measuring Of Semiconductors Or The Like (AREA)
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Description
本発明は、シリコンウェーハの表裏面又は裏面を粗化することができるシリコンウェーハの洗浄方法および製造方法、並びに洗浄液中の過酸化水素濃度評価方法および過酸化水素濃度管理方法に関する。 The present invention relates to a method for cleaning and manufacturing silicon wafers that can roughen the front and back surfaces or the back surface of the silicon wafer, as well as a method for evaluating and managing the hydrogen peroxide concentration in a cleaning solution.
半導体デバイス用のシリコンウェーハの製造工程は、チョクラルスキー（ＣＺ）法等を使用して単結晶インゴットを育成する単結晶製造工程と、この単結晶インゴットをスライスし、鏡面状に加工するウェーハ加工工程とから構成され、さらに付加価値をつけるために、熱処理をするアニール工程やエピタキシャル層を形成するエピタキシャル成長工程を含む場合がある。 The manufacturing process for silicon wafers for semiconductor devices consists of a single crystal manufacturing process, in which a single crystal ingot is grown using the Czochralski (CZ) method or similar, and a wafer processing process, in which this single crystal ingot is sliced and processed into a mirror-like finish. To add additional value, the process may also include an annealing process in which heat treatment is performed and an epitaxial growth process in which an epitaxial layer is formed.
この鏡面状に加工する工程には、ＤＳＰ（両面研磨）工程とその後のＣＭＰ（片面研磨）工程がある。より具体的には、パーティクル品質や搬送の観点からＤＳＰ加工されたウェーハは乾燥させず、必要に応じて洗浄した後、水中保管でＣＭＰ工程へ搬送される。したがってＣＭＰ工程では水中保管されたウェーハをロボット等でチャックしＣＭＰ装置へ搬送する必要がある。また、ＣＭＰ加工後も同様に研磨剤や純水などで濡れたウェーハをチャックし、必要に応じて洗浄工程へ搬送する必要がある。 The process of processing the wafer into a mirror-like finish includes the DSP (double-sided polishing) process followed by the CMP (single-sided polishing) process. More specifically, from the standpoint of particle quality and transportation, DSP processed wafers are not dried, but are cleaned as necessary, and then stored underwater before being transported to the CMP process. Therefore, in the CMP process, the wafers stored underwater must be chucked by a robot or similar device and transported to the CMP device. Similarly, after CMP processing, wafers wet with abrasives or pure water must be chucked and transported to the cleaning process as necessary.
このようにウェーハの加工工程では、ドライではなくウェットな環境下でウェーハを搬送することが必須であるが、特にこのようなウェット環境下では、チャックで吸着されたウェーハを脱離させる際に、チャックを解除しても脱離されず、搬送不良を引き起こすことがあった。この原因としてはチャックされるウェーハ面の粗さが影響していると考えられ、チャックされるウェーハ面粗さが良好過ぎると、チャックとの接触面積が増え、チャックを解除してもウェーハが脱離しにくくなると考えられ、対してウェーハの面粗さが悪いと接触面積が減り、ウェーハが脱離しやすくなると考えられる。一般的にチャックされた面は少なからずチャック痕が形成されやすく、品質が低下することからチャック面はシリコンウェーハの裏面であることが多い。したがって、搬送不良低減の観点からは特にシリコンウェーハ裏面のみ粗い方が良く、そのようなウェーハの製造方法が求められている。 In this way, in the wafer processing process, it is essential to transport the wafer in a wet environment, not a dry one. In particular, in such a wet environment, when trying to detach a wafer that has been adsorbed by a chuck, the wafer may not detach even when the chuck is released, causing transport problems. The cause of this is thought to be the roughness of the wafer surface being chucked. If the roughness of the chucked wafer surface is too good, the contact area with the chuck increases, making it difficult for the wafer to detach even when the chuck is released. Conversely, if the wafer surface roughness is poor, the contact area decreases, making it easier for the wafer to detach. In general, the chucked surface is prone to forming chuck marks, which reduces quality, so the chuck surface is often the back surface of the silicon wafer. Therefore, from the perspective of reducing transport problems, it is better for only the back surface of the silicon wafer to be rough, and a method for manufacturing such wafers is required.
一般的なシリコンウェーハの洗浄方法として、ＲＣＡ洗浄と呼ばれる方法がある。このＲＣＡ洗浄とはＳＣ１（Ｓｔａｎｄａｒｄ Ｃｌｅａｎｉｎｇ １）洗浄、ＳＣ２（Ｓｔａｎｄａｒｄ Ｃｌｅａｎｉｎｇ ２）洗浄、ＤＨＦ（Ｄｉｌｕｔｅｄ Ｈｙｄｒｏｆｌｕｏｒｉｃ Ａｃｉｄ）洗浄を、目的に応じて組み合わせて行う洗浄方法である。
このＳＣ１洗浄とは、アンモニア水と過酸化水素水を任意の割合で混合し、アルカリ性の洗浄液によるシリコンウェーハ表面のエッチングによって付着パーティクルをリフトオフさせ、さらにシリコンウェーハとパーティクルの静電気的な反発を利用して、シリコンウェーハへの再付着を抑えながらパーティクルを除去する洗浄方法である。また、ＳＣ２洗浄とは、塩酸と過酸化水素水を任意の割合で混合した洗浄液で、シリコンウェーハ表面の金属不純物を溶解除去する洗浄方法である。また、ＤＨＦ洗浄とは、希フッ酸によってシリコンウェーハ表面のケミカル酸化膜を除去する洗浄方法である。さらに、強い酸化力を有するオゾン水洗浄も使用される場合があり、シリコンウェーハ表面に付着している有機物の除去やＤＨＦ洗浄後のシリコンウェーハ表面のケミカル酸化膜形成を行っている。シリコンウェーハの洗浄は、目的に応じてこれらの洗浄を組み合わせて行われている。
この中でＳＣ１洗浄はエッチングを伴う洗浄であるため、ＳＣ１洗浄後はウェーハの面粗さが増加することが一般的に知られている。
A common method for cleaning silicon wafers is called RCA cleaning, which is a method that combines SC1 (Standard Cleaning 1) cleaning, SC2 (Standard Cleaning 2) cleaning, and DHF (Diluted Hydrofluoric Acid) cleaning depending on the purpose.
The SC1 cleaning is a cleaning method in which ammonia water and hydrogen peroxide water are mixed in an arbitrary ratio, and the silicon wafer surface is etched with an alkaline cleaning solution to lift off adhering particles, and further, electrostatic repulsion between the silicon wafer and the particles is utilized to remove the particles while suppressing re-adhesion to the silicon wafer. The SC2 cleaning is a cleaning method in which metal impurities on the silicon wafer surface are dissolved and removed with a cleaning solution in which hydrochloric acid and hydrogen peroxide water are mixed in an arbitrary ratio. The DHF cleaning is a cleaning method in which a chemical oxide film on the silicon wafer surface is removed with dilute hydrofluoric acid. Furthermore, ozone water cleaning, which has a strong oxidizing power, may also be used to remove organic matter adhering to the silicon wafer surface and form a chemical oxide film on the silicon wafer surface after DHF cleaning. Silicon wafer cleaning is performed by combining these cleaning methods according to the purpose.
Among these, SC1 cleaning involves etching, and it is generally known that the surface roughness of the wafer increases after SC1 cleaning.
また、ウェーハの面粗さを評価する手法としては、ＡＦＭ（原子間力顕微鏡：Ａｔｏｍｉｃ Ｆｏｒｃｅ Ｍｉｃｒｏｓｃｏｐｙ）により得られるＳａ（３次元算出平均高さ）値やパーティクルカウンターにより得られるＨａｚｅ値を指標とすることができる。Ｈａｚｅとはいわゆる曇りとして表現されるものであり、シリコン表面の粗さの指標として広く用いられており、このＨａｚｅレベルが高いとはウェーハの面が粗いことを示す。パーティクルカウンターによるＨａｚｅ検査はスループットが非常に高く、ウェーハ全面を検査することができる。 Methods for evaluating the surface roughness of a wafer include the Sa (three-dimensional calculated average height) value obtained by AFM (Atomic Force Microscopy) and the Haze value obtained by a particle counter. Haze is expressed as cloudiness and is widely used as an index of the roughness of silicon surfaces, with a high haze level indicating a rough wafer surface. Haze inspection using a particle counter has a very high throughput and can inspect the entire wafer surface.
特許文献１には水酸化アンモニウムと過酸化水素と水の組成が１：１：５～１：１：２０００の範囲の希釈水溶液でシリコンウェーハを洗浄し、異なる厚さの自然酸化膜を形成させる方法が記載されている。
特許文献２にはＳＣ１洗浄において、水酸化アンモニウムから電離されたＯＨ－の濃度が高いとＳｉの直接エッチングが優先的に起こり、ウェーハ表面粗さが増加することが記載されている。
また、特許文献３～６にも、シリコンウェーハなどの半導体基板の洗浄に関する技術が開示されている。
また、ＳＣ１洗浄液は特に高温下で用いられる場合には分解や蒸発反応により水酸化アンモニウムや過酸化水素濃度が低下する。そのため薬液濃度をモニターし、濃度が一定になるように調整することが望ましい。ＳＣ１洗浄液の濃度を評価する方法としては吸光度や屈折率による濃度測定方法があり、その精度も高いことが知られているが、その濃度範囲は限られる。特に低濃度の薬液の場合は現状評価することが困難である。 In addition, when SC1 cleaning solution is used at high temperatures, the concentrations of ammonium hydroxide and hydrogen peroxide decrease due to decomposition and evaporation reactions. For this reason, it is desirable to monitor the concentration of the chemical solution and adjust it so that the concentration remains constant. Methods for evaluating the concentration of SC1 cleaning solution include concentration measurement methods using absorbance and refractive index, which are known to be highly accurate, but the concentration range is limited. It is currently difficult to evaluate chemical solutions with low concentrations in particular.
前述したように、加工工程中の搬送不良低減のためにチャックされる裏面が粗いシリコンウェーハが必要とされている。本発明は、上記問題を解決するためになされたものであり、シリコンウェーハの表裏面又は裏面を粗化できる洗浄方法、片側の面のみが選択的に粗化されたシリコンウェーハを得ることができるシリコンウェーハの製造方法、及び粗化挙動に影響を与える洗浄液中の微量の過酸化水素濃度の評価方法、管理方法を提供することにある。 As mentioned above, silicon wafers with a rough back surface that are chucked are required to reduce transport failures during processing. The present invention has been made to solve the above problem, and provides a cleaning method that can roughen the front and back surfaces or the back surface of a silicon wafer, a method for manufacturing a silicon wafer that can obtain a silicon wafer in which only one side is selectively roughened, and a method for evaluating and managing the concentration of trace amounts of hydrogen peroxide in a cleaning solution that affects the roughening behavior.
上記目的を達成するために、本発明は、シリコンウェーハを粗化する洗浄方法であって、
自然酸化膜がないベア面が露出した調査用シリコンウェーハを、水酸化アンモニウムを含み、かつ、過酸化水素濃度が０～０．１５ｗｔ％の水溶液である洗浄液で洗浄することで粗化された前記調査用シリコンウェーハの表裏面又は裏面の粗化量と、
前記洗浄液の温度と、
前記洗浄液中の水酸化アンモニウム濃度と、
前記洗浄液中の過酸化水素濃度との相関関係を予め取得しておく洗浄液濃度調査工程と、
該洗浄液濃度調査工程で取得しておいた前記相関関係に基づいて、所望の粗化量から、前記洗浄液の温度、前記洗浄液中の水酸化アンモニウム濃度及び過酸化水素濃度の粗化洗浄条件を決定する粗化洗浄条件決定工程と、
該粗化洗浄条件決定工程で決定した粗化洗浄条件で、自然酸化膜がないベア面が露出した粗化対象シリコンウェーハを洗浄することで、該粗化対象シリコンウェーハの表裏面又は裏面を粗化する粗化洗浄工程とを有することを特徴とするシリコンウェーハの洗浄方法を提供する。
In order to achieve the above object, the present invention provides a cleaning method for roughening a silicon wafer, comprising the steps of:
A silicon wafer for investigation having an exposed bare surface free of a native oxide film is roughened by cleaning the silicon wafer with a cleaning solution that is an aqueous solution containing ammonium hydroxide and having a hydrogen peroxide concentration of 0 to 0.15 wt %, thereby obtaining a roughening amount of the front and back surfaces or the back surface of the silicon wafer for investigation;
The temperature of the cleaning liquid; and
a concentration of ammonium hydroxide in the cleaning solution; and
a cleaning solution concentration investigation step of acquiring a correlation with the hydrogen peroxide concentration in the cleaning solution in advance;
a roughening cleaning condition determining step of determining roughening cleaning conditions, including a temperature of the cleaning solution, an ammonium hydroxide concentration and a hydrogen peroxide concentration in the cleaning solution, from a desired roughening amount based on the correlation obtained in the cleaning solution concentration investigating step;
and a roughening cleaning step of roughening the front and back surfaces or the back surface of the silicon wafer to be roughened by cleaning the silicon wafer to be roughened, the bare surface of which is exposed and free from a native oxide film, under the roughening cleaning conditions determined in the roughening cleaning condition determination step.
このようなシリコンウェーハの洗浄方法であれば、表裏面又は裏面が所望の粗化量で粗化されたウェーハの製造が可能となる。さらに、粗化量に対する過酸化水素濃度依存性を調査することで、より好適な粗化洗浄条件を選定出来る。特には、粗化量のバラツキが小さくなるように粗化洗浄条件を選定して洗浄することができる。 This method of cleaning silicon wafers makes it possible to manufacture wafers whose front and back surfaces or the back surface are roughened to the desired degree. Furthermore, by investigating the dependency of the hydrogen peroxide concentration on the amount of roughening, more suitable roughening cleaning conditions can be selected. In particular, cleaning can be performed by selecting roughening cleaning conditions that reduce the variation in the amount of roughening.
このとき、前記洗浄液濃度調査工程において、
前記調査用シリコンウェーハの前記洗浄前後にパーティクルカウンターにてＨａｚｅ値を取得し、前記洗浄後のＨａｚｅ値の増加量を前記粗化量とすることができる。
At this time, in the cleaning solution concentration investigation step,
The haze value of the test silicon wafer is obtained by a particle counter before and after the cleaning, and the increase in the haze value after the cleaning can be regarded as the amount of roughening.
このような方法であれば、簡便かつスループット良く粗化挙動、粗化量をモニターできる。 This method allows for easy and high-throughput monitoring of the roughening behavior and amount of roughening.
また、前記粗化洗浄条件決定工程において前記粗化洗浄条件を決定するとき、
前記過酸化水素濃度が、該過酸化水素濃度の変動に対する前記粗化量の変動が所定値以下の濃度範囲内であり、かつ、前記粗化洗浄工程における前記洗浄後の粗化対象シリコンウェーハ表面に、該洗浄中に形成された自然酸化膜が残るように、
前記粗化洗浄条件を決定することができる。
In addition, when the roughening cleaning conditions are determined in the roughening cleaning condition determination step,
the hydrogen peroxide concentration is within a concentration range in which a change in the roughening amount with respect to a change in the hydrogen peroxide concentration is equal to or less than a predetermined value, and a native oxide film formed during the cleaning remains on the surface of the silicon wafer to be roughened after the cleaning in the roughening cleaning step,
The roughening cleaning conditions can be determined.
このような方法であれば、洗浄液中の過酸化水素濃度が変化したとしても所望の粗化量で粗化されたウェーハを一層安定的に供給することができる。また、粗化度合いが一層十分なウェーハを得ることができる。 With this method, even if the hydrogen peroxide concentration in the cleaning solution changes, it is possible to more stably supply wafers that have been roughened to the desired degree. It is also possible to obtain wafers that are more sufficiently roughened.
また、前記粗化洗浄条件決定工程において、前記洗浄液の温度を８０℃以上とすることができる。 In addition, in the roughening cleaning condition determination process, the temperature of the cleaning solution can be set to 80°C or higher.
このような方法であれば、過酸化水度濃度の変動に対する粗化量の変動をより小さくでき、粗化されたウェーハをより一層安定的に供給することができる。 This method can reduce the variation in the amount of roughening in response to fluctuations in the aqueous peroxide concentration, making it possible to more stably supply roughened wafers.
また、本発明は、本発明のシリコンウェーハの洗浄方法により洗浄され、表裏面が粗化されたシリコンウェーハの片方の面に対し、ＣＭＰ加工を行い、前記片方の面とは反対側の面のみが選択的に粗化されているシリコンウェーハを得ることを特徴とするシリコンウェーハの製造方法を提供する。 The present invention also provides a method for producing a silicon wafer, which comprises performing CMP processing on one side of a silicon wafer that has been cleaned by the silicon wafer cleaning method of the present invention and has roughened front and back surfaces, to obtain a silicon wafer in which only the surface opposite to the one side is selectively roughened.
このように、表裏面を粗化した後、片方の面のみ研磨することで、片方の面は良好な面状態で、該片方の面とは反対側の面のみが選択的に粗化されたウェーハを作製することができる。 In this way, by roughening the front and back surfaces and then polishing only one of the surfaces, a wafer can be produced in which one surface is in good condition and only the surface opposite the one surface is selectively roughened.
また、本発明は、本発明のシリコンウェーハの洗浄方法により、枚葉方式で裏面のみが洗浄されて粗化されているシリコンウェーハを得ることを特徴とするシリコンウェーハの製造方法を提供する。 The present invention also provides a method for producing silicon wafers, characterized in that the silicon wafers are obtained by cleaning only the backside of the wafer in a single wafer process and roughening the wafer using the silicon wafer cleaning method of the present invention.
このように、裏面のみ洗浄して粗化されたウェーハを作製することができる。 In this way, a wafer can be produced that has only the back surface cleaned and roughened.
また、本発明は、洗浄液中の過酸化水素濃度を評価する方法であって、
自然酸化膜を有する調査用シリコンウェーハを、水酸化アンモニウムを含み、かつ、過酸化水素濃度が０～０．１５ｗｔ％の水溶液である洗浄液で洗浄することで粗化された前記調査用シリコンウェーハの表裏面又は裏面の粗化量と、
前記洗浄液の温度と、
前記洗浄液中の水酸化アンモニウム濃度と、
前記洗浄液中の過酸化水素濃度との相関関係を予め取得しておく洗浄液濃度調査工程と、
該洗浄液濃度調査工程で取得しておいた前記相関関係に基づいて、
自然酸化膜を有するシリコンウェーハを、少なくとも水酸化アンモニウムを含む水溶液である評価対象洗浄液で洗浄することで粗化された前記シリコンウェーハの表裏面又は裏面の粗化量と、
前記評価対象洗浄液の温度と、
前記評価対象洗浄液中の水酸化アンモニウム濃度とから、
前記評価対象洗浄液中の過酸化水素濃度を評価する過酸化水素濃度評価工程とを有することを特徴とする洗浄液中の過酸化水素濃度評価方法を提供する。
The present invention also provides a method for evaluating a hydrogen peroxide concentration in a cleaning solution, comprising the steps of:
A roughening amount of the front and back surfaces or the back surface of the silicon wafer for investigation, which has a native oxide film and is roughened by cleaning the silicon wafer for investigation with a cleaning solution that is an aqueous solution containing ammonium hydroxide and having a hydrogen peroxide concentration of 0 to 0.15 wt %, and
The temperature of the cleaning liquid; and
a concentration of ammonium hydroxide in the cleaning solution; and
a cleaning solution concentration investigation step of acquiring a correlation with the hydrogen peroxide concentration in the cleaning solution in advance;
Based on the correlation obtained in the cleaning solution concentration investigation step,
A silicon wafer having a native oxide film is roughened by cleaning the silicon wafer with a cleaning solution to be evaluated, which is an aqueous solution containing at least ammonium hydroxide, and the roughening amount of the front and back surfaces or the back surface of the silicon wafer;
The temperature of the cleaning solution to be evaluated; and
and the concentration of ammonium hydroxide in the cleaning solution to be evaluated.
and evaluating the hydrogen peroxide concentration in the cleaning solution to be evaluated.
このような洗浄液中の過酸化水素濃度評価方法であれば、粗化挙動に影響を与える微量の過酸化水素濃度を精度良く評価することができる。 This method for evaluating the hydrogen peroxide concentration in a cleaning solution can accurately evaluate the concentration of minute amounts of hydrogen peroxide that affect roughening behavior.
また、本発明は、洗浄液中の過酸化水素濃度管理方法であって、
本発明の洗浄液中の過酸化水素濃度評価方法により、前記評価対象洗浄液中の過酸化水素濃度を評価し、
該評価結果に基づき、評価後の洗浄液中の過酸化水素濃度を調整することを特徴とする洗浄液中の過酸化水素濃度管理方法を提供する。
The present invention also provides a method for managing a hydrogen peroxide concentration in a cleaning solution, comprising the steps of:
The concentration of hydrogen peroxide in the cleaning solution to be evaluated is evaluated by the method for evaluating the concentration of hydrogen peroxide in a cleaning solution of the present invention;
The present invention provides a method for controlling the concentration of hydrogen peroxide in a cleaning solution, which comprises adjusting the concentration of hydrogen peroxide in the cleaning solution after the evaluation based on the evaluation results.
このような洗浄液中の過酸化水素濃度管理方法であれば、過酸化水素濃度を精度良く管理することができ、粗化を安定して行うことができる。 This method of controlling the hydrogen peroxide concentration in the cleaning solution allows the hydrogen peroxide concentration to be controlled with high precision, enabling stable roughening.
本発明のシリコンウェーハの洗浄方法であれば、シリコンウェーハの表裏面又は裏面を粗化することができる。
また、本発明のシリコンウェーハの製造方法であれば、片方の面は良好な面状態で、該片方の面とは反対側の面のみが選択的に粗化されたウェーハを作製することができる。
また、本発明の洗浄液中の過酸化水素濃度評価方法及び管理方法であれば、粗化洗浄に用いる洗浄液中の微量の過酸化水素濃度を精度良く評価及び管理をすることができる。
The method for cleaning a silicon wafer of the present invention can roughen the front and back surfaces or the back surface of a silicon wafer.
Furthermore, the method for producing a silicon wafer of the present invention can produce a wafer in which one surface is in a good surface condition and only the surface opposite to the one surface is selectively roughened.
Furthermore, the method for evaluating and controlling the concentration of hydrogen peroxide in a cleaning solution of the present invention makes it possible to accurately evaluate and control the concentration of a trace amount of hydrogen peroxide in a cleaning solution used in roughening cleaning.
以下、本発明について、実施態様の一例として、図を参照しながら詳細に説明するが、本発明はこれに限定されるものではない。
初めに本発明における粗化現象についてその方法とメカニズムを述べる。図２には、ベア面が露出したＤＳＰ後ウェーハをＳＣ１組成（液組成ＮＨ４ＯＨ：Ｈ２Ｏ２：Ｈ２Ｏ）、洗浄温度及び洗浄時間を変えて洗浄し（水準１から水準１２と表記）、パーティクルカウンターにて粗さ指標であるＨａｚｅ値を取得し、予め洗浄前に取得しておいたＨａｚｅ値との差分を示した。この洗浄後のＨａｚｅ値の増加量（以下、Ｈａｚｅ増加量とも言う）は粗化量の一例である。この値が高いほど面があれていることを示す。併せて、粗化処理なしのＲｅｆと水準５，９のＳＥＭ（走査型電子顕微鏡：Ｓｃａｎｎｉｎｇ Ｅｌｅｃｔｒｏｎｉｃ Ｍｉｃｒｏｓｃｏｐｙ）の表面観察結果も示した。
Hereinafter, the present invention will be described in detail with reference to the drawings as an example of an embodiment, but the present invention is not limited thereto.
First, the method and mechanism of the roughening phenomenon in the present invention will be described. In FIG. 2, a post-DSP wafer with an exposed bare surface was cleaned with SC1 composition (liquid composition NH 4 OH:H 2 O 2 :H 2 O) at different cleaning temperatures and cleaning times (denoted as
用いた薬液は２８質量％のアンモニア水（ＮＨ４ＯＨ）、３０質量％の過酸化水素水（Ｈ２Ｏ２）で、それぞれ質量（ｗｔ）％でも表記した。尚、質量％とは洗浄溶液とそれに含まれる溶質（水酸化アンモニウム、過酸化水素）の質量比を百分率で表した濃度で、ｗｔ％とも表記する。 The chemical solutions used were 28% by mass ammonia water ( NH4OH ) and 30% by mass hydrogen peroxide water ( H2O2 ), each of which is expressed as a percentage by mass (wt%). Note that mass% is the concentration expressed as a percentage of the mass ratio of the cleaning solution to the solutes (ammonium hydroxide, hydrogen peroxide) contained therein, and is also expressed as wt%.
水準５，６，８，９，１２において顕著にＨａｚｅ値が増加していることがわかる。さらにＳＥＭ画像を見ると、水準５と水準９は凹凸形状が観察され、Ｒｅｆではこのような凹凸形状は観察されていない。以上より、これらの水準では面が大きくあれており、粗化されていることがわかる。
一方、水準３，４，１１では０．８～０．９ｐｐｍ程度増加しているが、その増加量、即ち粗化度合いが小さく、粗化されているとは言えない。さらにＬＬＳ（局所光散乱欠陥：Ｌｏｃａｌｉｚｅｄ Ｌｉｇｈｔ Ｓｃａｔｔｅｒ）数も非常に多く、欠陥品質が大きく悪化していた。洗浄後の面状態が撥水面であることから、洗浄中にベア面が露出し、Ｓｉのエッチングが顕著に進行し、エッチピットが形成されたためと考えられる。残りの水準では面状態は親水面であったが、Ｈａｚｅ増加量も僅かであった。
It can be seen that the haze value increases significantly in
On the other hand, in the
この粗化メカニズムについて詳しく述べる。ＳＣ１洗浄では過酸化水素は酸化剤として機能しＳｉは酸化されＳｉＯ２（自然酸化膜。以下、単に酸化膜とも言う。）が形成される。水酸化アンモニウムは電離反応によりＯＨ－を放出し、このＯＨ－によりウェーハ表面のＳｉＯ２がエッチングされる。一般的な薬液（洗浄液）組成（例えばＮＨ４ＯＨ：Ｈ２Ｏ２：Ｈ２Ｏ＝１：１：１０）では洗浄中は常にウェーハには酸化膜が存在しており、ベア面（Ｓｉ）が露出することなく、形成される酸化膜厚さは洗浄時間に依存せず常に約１ｎｍ程度である。これは酸化速度とエッチング速度のバランスに起因することが知られている。つまり、Ｈ２Ｏ２が所定濃度以上である薬液ではＨ２Ｏ２によるＳｉの酸化速度の方がＯＨ－によるＳｉＯ２のエッチング速度よりも速いために、Ｓｉが露出することなく常にウェーハには酸化膜が存在していると解釈できる。言い換えれば、Ｈ２Ｏ２が所定濃度以下になるとＯＨ－によるエッチング速度の方がＨ２Ｏ２によるＳｉの酸化速度よりも速くなるため、酸化が追い付かず、ＯＨ－によるＳｉのエッチング反応が進行する。このような場合は洗浄後にＳｉが露出しているため、撥水面となる。 This roughening mechanism will be described in detail. In SC1 cleaning, hydrogen peroxide functions as an oxidizing agent, and Si is oxidized to form SiO 2 (a natural oxide film, hereinafter also referred to as an oxide film). Ammonium hydroxide releases OH - by ionization reaction, and this OH - etches SiO 2 on the wafer surface. In a general chemical (cleaning) composition (for example, NH 4 OH:H 2 O 2 :H 2 O=1:1:10), an oxide film always exists on the wafer during cleaning, and the bare surface (Si) is not exposed, and the thickness of the oxide film formed is always about 1 nm regardless of the cleaning time. It is known that this is due to the balance between the oxidation rate and the etching rate. In other words, in a chemical with H 2 O 2 at a certain concentration or higher, the oxidation rate of Si by H 2 O 2 is faster than the etching rate of SiO 2 by OH - , so it can be interpreted that an oxide film always exists on the wafer without exposing Si. In other words, when the concentration of H2O2 falls below a certain level, the etching rate by OH- becomes faster than the oxidation rate of Si by H2O2 , so the oxidation cannot keep up and the etching reaction of Si by OH- proceeds. In such a case, the Si is exposed after cleaning, resulting in a water-repellent surface.
ここで粗化された水準の薬液組成は、例えば水準５のＮＨ４ＯＨ：Ｈ２Ｏ２：Ｈ２Ｏ＝１：０．４：１０００のようにＨ２Ｏ２比率がＮＨ４ＯＨよりも低いことが分かる。したがって、このような薬液でベア面のシリコンウェーハを洗浄すると、洗浄後の面状態が親水面であることから、初めに酸化反応が進行し酸化膜が形成されるが、酸化速度が遅いため、ＳｉＯ２のエッチングが相対的に優勢となり、ＳｉＯ２がエッチングされ局所的にＳｉが露出された箇所でＳｉのエッチングが進行し、粗化が進行すると考えられる。 It can be seen that the chemical composition of the roughened level has a lower H2O2 ratio than NH4OH , for example, NH4OH : H2O2 : H2O =1: 0.4 :1000 in level 5. Therefore, when a bare silicon wafer is cleaned with such a chemical, since the surface state after cleaning is hydrophilic, an oxidation reaction proceeds first to form an oxide film, but since the oxidation rate is slow, etching of SiO2 becomes relatively dominant, and etching of Si proceeds in the places where SiO2 is etched and Si is locally exposed, leading to roughening.
このように本発明における粗化現象は酸化反応とエッチング反応のバランスがある範囲内であると進行する現象である。また安定して粗化を進行させるには、これらの反応が安定した液組成、薬液濃度で洗浄を行う必要がある。 As described above, the roughening phenomenon in the present invention progresses when the balance between the oxidation reaction and the etching reaction is within a certain range. Furthermore, in order to allow the roughening to proceed stably, cleaning must be performed with a liquid composition and chemical concentration that ensures stable reactions.
これらを踏まえ、本発明の洗浄方法について述べる。
図１は本発明のシリコンウェーハの洗浄方法の一例を示すフローチャートである。
（工程Ｓ１：洗浄液濃度調査工程）
図１のＳ１では、安定して粗化現象が進行する粗化洗浄条件を選定するための予備試験として洗浄液濃度調査工程を行う。すなわち、粗化量と、洗浄液の温度と、洗浄液中の水酸化アンモニウム濃度と、洗浄液中の過酸化水素濃度との相関関係を予め取得しておく工程である。ここで、上記の粗化量とは、調査用シリコンウェーハ（自然酸化膜がなくベア面が露出している）を洗浄液（水酸化アンモニウムを含み、かつ、過酸化水素濃度が０～０．１５ｗｔ％の水溶液）で洗浄することで粗化された表裏面（又は裏面）の粗化量を言い、例えば、前述したＨａｚｅ増加量とすることができる。Ｈａｚｅ増加量であれば、簡便かつスループット良く粗化挙動、粗化量をモニターできるので好ましい。
なお、上記洗浄液の例としては、過酸化水素濃度が０ｗｔ％のときは、水酸化アンモニウムを含む水溶液とすることができ、また、過酸化水素濃度が０ｗｔ％ではないときは、水酸化アンモニウムと過酸化水素水を含む水溶液とすることができる。
Taking these factors into consideration, the cleaning method of the present invention will be described.
FIG. 1 is a flow chart showing an example of a method for cleaning a silicon wafer according to the present invention.
(Step S1: Cleaning solution concentration investigation step)
In S1 of FIG. 1, a cleaning solution concentration investigation step is performed as a preliminary test to select the roughening cleaning conditions under which the roughening phenomenon proceeds stably. That is, this is a step of acquiring in advance the correlation between the roughening amount, the temperature of the cleaning solution, the ammonium hydroxide concentration in the cleaning solution, and the hydrogen peroxide concentration in the cleaning solution. Here, the above-mentioned roughening amount refers to the roughening amount of the front and back surfaces (or the back surface) roughened by cleaning a silicon wafer for investigation (without a native oxide film and with an exposed bare surface) with a cleaning solution (an aqueous solution containing ammonium hydroxide and with a hydrogen peroxide concentration of 0 to 0.15 wt %), and can be, for example, the above-mentioned haze increase amount. The haze increase amount is preferable because it allows the roughening behavior and the roughening amount to be monitored easily and with good throughput.
As an example of the cleaning liquid, when the hydrogen peroxide concentration is 0 wt%, it can be an aqueous solution containing ammonium hydroxide, and when the hydrogen peroxide concentration is not 0 wt%, it can be an aqueous solution containing ammonium hydroxide and hydrogen peroxide.
以下、洗浄液濃度調査工程について、より具体的な例を挙げて説明する。
図３には、ＮＨ４ＯＨ濃度を０．０３，０．１３，０．２５ｗｔ％の３水準でＨ２Ｏ２濃度を変化させ、自然酸化膜がないベア面の調査用シリコンウェーハを８０℃で３ｍｉｎ洗浄したときの、洗浄前後のＨａｚｅ増加量を示した。ＮＨ４ＯＨ濃度が０．０３ｗｔ％の場合については、洗浄後の面状態についても示した（〇は撥水面、●は親水面）。
The cleaning solution concentration checking step will be described below with a more specific example.
3 shows the increase in haze before and after cleaning when the H2O2 concentration was changed to three levels, 0.03, 0.13, and 0.25 wt%, and a bare silicon wafer without a native oxide film was cleaned at 80° C. for 3 minutes. When the NH4OH concentration was 0.03 wt%, the surface condition after cleaning is also shown (◯ is a water-repellent surface, ● is a hydrophilic surface).
例えばＮＨ４ＯＨ濃度が０．０３ｗｔ％の場合に着目すると、Ｈ２Ｏ２濃度に依存してＨａｚｅ増加量が変動していることが分かる。Ｈ２Ｏ２濃度が０ｗｔ％や０．００７ｗｔ％ではＨａｚｅ増加量が小さかった。Ｈ２Ｏ２が低濃度過ぎるため、酸化速度が遅すぎてしまい、Ｓｉへのエッチング作用のみが働いたためである。このことはＨ２Ｏ２が低濃度の水準のみ洗浄後の面状態が撥水面（ベアＳｉ面が露出）であることと一致する。
前述のように撥水面の場合はＳｉのエッチングが顕著となりＬＬＳ品質（ＬＬＳ数）が悪化することから、親水面となる範囲で粗化を進行させることが望ましい。Ｈ２Ｏ２濃度が０．０１９ｗｔ％から０．０７８ｗｔ％では面状態は親水面でＨａｚｅ増加量が大きく粗化が進行していた。次いで０．０９ｗｔ％以降は親水面であったが、Ｈａｚｅ増加量が小さくなった。これはＨ２Ｏ２が高濃度過ぎるため、Ｓｉの酸化速度がエッチング速度よりも著しく速くなり、相対的にエッチング作用が弱くなったためである。
For example, when the NH4OH concentration is 0.03 wt%, it can be seen that the haze increase varies depending on the H2O2 concentration. When the H2O2 concentration is 0 wt% or 0.007 wt%, the haze increase is small. This is because the H2O2 concentration is too low, so the oxidation rate is too slow and only the etching effect on the Si occurs. This coincides with the fact that the surface state after cleaning is water-repellent (bare Si surface exposed) only at the low H2O2 concentration level.
As mentioned above, in the case of a water-repellent surface, etching of Si becomes prominent and the LLS quality (LLS number ) deteriorates, so it is desirable to proceed with roughening within the range that results in a hydrophilic surface. When the H2O2 concentration was 0.019 wt% to 0.078 wt%, the surface state was hydrophilic, the increase in haze was large, and roughening progressed. Next, from 0.09 wt%, the surface was hydrophilic, but the increase in haze became smaller. This is because the H2O2 concentration was too high, so the oxidation rate of Si became significantly faster than the etching rate, and the etching effect became relatively weak.
尚、この洗浄液濃度調査工程は複数水準のＮＨ４ＯＨ濃度、洗浄温度で実施することが好ましい。図示したようにＨａｚｅ増加量はＮＨ４ＯＨ濃度が高いほど大きくなることから、後述する工程Ｓ２で所望のＨａｚｅ増加量（悪化量）を設定する際に、複数水準の調査結果がある方が粗化洗浄条件の選定が容易となる。 In addition, it is preferable to carry out this cleaning solution concentration investigation step at multiple levels of NH 4 OH concentration and cleaning temperature. As shown in the figure, the haze increase amount increases as the NH 4 OH concentration increases, so when a desired haze increase amount (deterioration amount) is set in step S2 described later, it is easier to select the roughening cleaning conditions if there are investigation results at multiple levels.
また、本発明者らが調査した結果、Ｈ２Ｏ２濃度が０．１５ｗｔ％より大では、ＮＨ４ＯＨを現実的な範囲で高濃度化しても酸化速度の方が速くなってしまい、粗化が進行しなかったことから、工程Ｓ１では前述したようにＨ２Ｏ２濃度が０～０．１５ｗｔ％以下で行う。 Furthermore, as a result of the inventors' investigation, it was found that when the H2O2 concentration was greater than 0.15 wt%, even if the NH4OH concentration was increased within a practical range, the oxidation rate became faster and roughening did not progress, so in step S1, as described above, the H2O2 concentration is set to 0 to 0.15 wt% or less.
（工程Ｓ２：粗化洗浄条件決定工程）
続いて、Ｓ１の結果に基づき、Ｓ２の粗化洗浄条件決定工程を行う。すなわち、Ｓ１の相関関係に基づいて、所望の粗化量（Ｈａｚｅ増加量）から、洗浄液の温度、洗浄液中の水酸化アンモニウム濃度及び過酸化水素濃度の粗化洗浄条件を決定する工程である。
なお、所望のＨａｚｅ増加量の値については、その都度決定することができる。
(Step S2: Roughening cleaning conditions determination step)
Next, a roughening cleaning condition determination step S2 is performed based on the result of S1. That is, based on the correlation of S1, the temperature of the cleaning solution, the water content of the cleaning solution, and the like are determined from the desired roughening amount (amount of haze increase). This is the step of determining the roughening cleaning conditions, ie, the concentrations of ammonium oxide and hydrogen peroxide.
The desired haze increase amount can be determined on a case-by-case basis.
この工程では、特には、Ｓ１で得られた相関関係からＨ２Ｏ２濃度の変動に対するＨａｚｅ増加量の変動が安定した粗化洗浄条件を選定することが目的である。
図３において、ＮＨ４ＯＨ濃度が０．０３ｗｔ％の場合では、０．０３２～０．０７８ｗｔ％の範囲でＨａｚｅ増加量の変動が小さく、安定していることが分かる。この場合、例えば０．０５ｗｔ％のＨ２Ｏ２濃度にすることで、意図せず洗浄液中のＨ２Ｏ２濃度が変動したとしても、その変動に対してＨａｚｅ増加量の変動は比較的小さく安定しているので、所望のＨａｚｅ増加量から大きく外れることもなく、より安定して所望のＨａｚｅ増加量で粗化を進行させることができる。このように、粗化洗浄条件の一つとして選定するＨ２Ｏ２濃度は、Ｈ２Ｏ２濃度の変動に対するＨａｚｅ増加量の変動が比較的小さな値（所定値）以下に収まるようなＨ２Ｏ２濃度の範囲から決定すると好ましい。この所定値は、要求される精度等に応じて、０以上の数値から適宜設定することができる。
In this step, the object is to select roughening cleaning conditions under which the variation in the amount of increase in haze relative to the variation in the H 2 O 2 concentration is stable, based on the correlation obtained in S1.
In Fig. 3, when the NH 4 OH concentration is 0.03 wt%, it can be seen that the variation in the haze increase is small and stable in the range of 0.032 to 0.078 wt%. In this case, for example, by setting the H 2 O 2 concentration to 0.05 wt%, even if the H 2 O 2 concentration in the cleaning solution fluctuates unintentionally, the variation in the haze increase is relatively small and stable with respect to the fluctuation, so that the desired haze increase does not deviate significantly, and roughening can be progressed more stably with the desired haze increase. In this way, the H 2 O 2 concentration selected as one of the roughening cleaning conditions is preferably determined from a range of H 2 O 2 concentrations in which the variation in the haze increase with respect to the fluctuation in the H 2 O 2 concentration falls within a relatively small value (predetermined value). This predetermined value can be appropriately set from a value equal to or greater than 0 according to the required accuracy, etc.
次にＮＨ４ＯＨ濃度が０．１３ｗｔ％、０．２５ｗｔ％の場合に着目すると、Ｈ２Ｏ２濃度が小さい場合は酸化速度が遅く、エッチング優勢となりＨａｚｅ増加量が大きく変動しており、不安定であると判断できる。したがって、この範囲で粗化を行うことは好ましくない。ＮＨ４ＯＨ濃度が高いほど、エッチング速度が速くなったため、０．０３ｗｔ％よりもその変動が大きくなっていると考えられる。
ただ、Ｈ２Ｏ２濃度が高くなると、０．０３ｗｔ％の場合と同様に、Ｈａｚｅ増加量が安定となるＨ２Ｏ２濃度範囲が存在していることが分かる。ＮＨ４ＯＨ濃度が異なるとＨａｚｅ増加量が安定するために必要なＨ２Ｏ２濃度範囲が変化するため、予めＨ２Ｏ２の適正濃度範囲を求めておくことでより安定して粗化を進行させることができる。
Next, when the NH 4 OH concentration is 0.13 wt % and 0.25 wt %, the oxidation rate is slow when the H 2 O 2 concentration is low, etching is dominant, and the increase in haze fluctuates greatly, which can be judged to be unstable. Therefore, it is not preferable to roughen the surface in this range. It is considered that the higher the NH 4 OH concentration, the faster the etching rate becomes, and therefore the fluctuation is larger than that of 0.03 wt %.
However, as the H2O2 concentration increases, there is a H2O2 concentration range in which the haze increase is stable, as in the case of 0.03 wt%. Since the H2O2 concentration range required for the haze increase to be stable changes depending on the NH4OH concentration, the roughening can be progressed more stably by determining the appropriate H2O2 concentration range in advance.
また、ＮＨ４ＯＨ濃度が高いほど、Ｈａｚｅ増加量が大きくなることから、ＮＨ４ＯＨ濃度を調整することで、所望の粗さ（Ｈａｚｅ増加量）を形成させることもできる。例えばＨａｚｅ増加量が５ｐｐｍのウェーハを得たい場合は、ＮＨ４ＯＨ濃度が０．０３ｗｔ％でＨ２Ｏ２濃度を０．０５ｗｔ％とし、８０℃かつ３ｍｉｎで粗化洗浄条件を選定することができる。一方、例えばＨａｚｅ増加量を３０ｐｐｍのウェーハを得たい場合は、ＮＨ４ＯＨ濃度を０．２５ｗｔ％で、Ｈ２Ｏ２濃度を０．０７ｗｔ％とし、８０℃かつ３ｍｉｎで粗化洗浄条件を選定することができる。このようにＨ２Ｏ２濃度に対するＨａｚｅ増加量の変動を把握しておくことで、より安定して粗化を進行させる粗化洗浄条件を選定することができる。 In addition, the higher the NH 4 OH concentration, the larger the haze increase amount, so the desired roughness (haze increase amount) can be formed by adjusting the NH 4 OH concentration. For example, if a wafer with a haze increase amount of 5 ppm is to be obtained, the roughening cleaning conditions can be selected as follows: NH 4 OH concentration is 0.03 wt%, H 2 O 2 concentration is 0.05 wt%, 80° C., and 3 min. On the other hand, if a wafer with a haze increase amount of 30 ppm is to be obtained, the roughening cleaning conditions can be selected as follows: NH 4 OH concentration is 0.25 wt%, H 2 O 2 concentration is 0.07 wt%, 80° C., and 3 min. In this way, by understanding the fluctuation of the haze increase amount relative to the H 2 O 2 concentration, it is possible to select the roughening cleaning conditions that allow the roughening to proceed more stably.
また、この工程Ｓ２では、後述する工程Ｓ３における洗浄後の粗化対象シリコンウェーハ表面に、Ｓ３での洗浄中に形成された自然酸化膜が残るような粗化洗浄条件を決定すれば、粗化度合いもより一層十分なものとすることができるため好ましい。親水面の表面を得ることもでき、ＬＬＳ数が悪化するのを防ぐこともできる。 In addition, in this step S2, if the roughening cleaning conditions are determined such that the natural oxide film formed during cleaning in step S3 remains on the surface of the silicon wafer to be roughened after cleaning in step S3 described below, the degree of roughening can be made even more sufficient, which is preferable. It is also possible to obtain a hydrophilic surface and prevent the LLS number from deteriorating.
続いて、洗浄液の温度（洗浄温度）の影響について述べる。
図４にはＮＨ４ＯＨ濃度が０．０３ｗｔ％、０．２５ｗｔ％で洗浄時間３ｍｉｎとして、洗浄温度を４５℃、６０℃で洗浄した場合のＨａｚｅ増加量の変動を示した。全３水準ともＨａｚｅ増加量が大きくなる条件はあるが、８０℃の場合の図３に比べて、前述のようなＨａｚｅ増加量が安定したＨ２Ｏ２濃度範囲が狭いことが分かる。したがって、洗浄温度を８０℃以上で、Ｓ１の洗浄液濃度調査工程を実施したり、Ｓ２の粗化洗浄条件決定工程での選定を行った方がより安定した粗化洗浄条件を選定しやすいと解釈できる。この理由としては温度が高い方が過酸化水素の酸化作用が安定するためと考えられる。洗浄温度の上限値は特には決められないが、例えば９０℃もあれば十分である。
Next, the effect of the temperature of the cleaning solution (cleaning temperature) will be described.
FIG. 4 shows the variation of the haze increase when cleaning is performed at 45° C. and 60° C. with NH 4 OH concentrations of 0.03 wt. % and 0.25 wt. % for a cleaning time of 3 min. Although there are conditions for a large haze increase in all three levels, it can be seen that the H 2 O 2 concentration range in which the haze increase is stable as described above is narrower than that in FIG. 3 for 80° C. Therefore, it can be interpreted that it is easier to select more stable roughening cleaning conditions by performing the cleaning solution concentration investigation step S1 or selecting in the roughening cleaning condition determination step S2 at a cleaning temperature of 80° C. or higher. The reason for this is thought to be that the oxidation action of hydrogen peroxide is more stable at higher temperatures. The upper limit of the cleaning temperature is not particularly determined, but for example, 90° C. is sufficient.
ただし、必ずしも８０℃やそれ以上である必要はなく、６０℃以下でもＨａｚｅ増加量が大きくなる領域が存在することから、粗化を進行させることは可能で、例えば薬液ライフを短くすることなどで洗浄液中のＨ２Ｏ２濃度の変動に起因したＨａｚｅ増加量のバラツキを抑制することもできる。 However, the temperature does not necessarily have to be 80° C. or higher, and since there are regions where the amount of haze increase is large even at temperatures below 60° C., it is possible to advance roughening, and it is also possible to suppress variations in the amount of haze increase caused by fluctuations in the H 2 O 2 concentration in the cleaning solution, for example, by shortening the chemical solution life.
続いて、洗浄時間の影響について述べる。
図５には、ＮＨ４ＯＨ濃度が０．０３ｗｔ％、Ｈ２Ｏ２濃度が０．０５ｗｔ％の洗浄液で、洗浄温度が８０℃で、洗浄時間を３０，６０，１８０，３６０ｓｅｃで洗浄した際のＨａｚｅ増加量を示した。洗浄時間が長いほど、Ｈａｚｅ増加量が増加していることが分かる。したがって、ＮＨ４ＯＨ濃度、Ｈ２Ｏ２濃度、洗浄温度の他、さらには洗浄時間を調整することで粗化度合いを調整することもできる。上述のようにＮＨ４ＯＨ濃度を調整しても良いし、洗浄時間を調整して粗化度合いを制御しても良く、適宜必要に応じて使い分ければよい。このように、Ｓ１での相関関係取得やＳ２での粗化洗浄条件の決定を、洗浄時間をさらに考慮して行うことも可能である。
Next, the effect of cleaning time will be described.
FIG. 5 shows the increase in haze when cleaning is performed with a cleaning solution having an NH 4 OH concentration of 0.03 wt % and an H 2 O 2 concentration of 0.05 wt %, at a cleaning temperature of 80° C., and for cleaning times of 30, 60, 180, and 360 seconds. It can be seen that the longer the cleaning time, the greater the increase in haze. Therefore, the degree of roughening can be adjusted by adjusting the NH 4 OH concentration, the H 2 O 2 concentration, the cleaning temperature, and even the cleaning time. As described above, the NH 4 OH concentration may be adjusted, or the cleaning time may be adjusted to control the degree of roughening, and these may be used appropriately as needed. In this way, it is also possible to obtain the correlation in S1 and determine the roughening cleaning conditions in S2 by further considering the cleaning time.
（工程Ｓ３：粗化洗浄工程）
続いてＳ３の粗化洗浄工程では、Ｓ２で決定した粗化洗浄条件で、自然酸化膜がないベア面の粗化対象シリコンウェーハを洗浄する。該洗浄により、粗化対象シリコンウェーハの表裏面（又は裏面）を粗化する工程である。このように、前述したＳ１、Ｓ２を経てこのＳ３の工程を行うことで、前述した所望のＨａｚｅ増加量の粗化ウェーハを確実に得ることができる。しかも、特には、所望のＨａｚｅ増加量から大きく外れることがなく（すなわち、Ｈａｚｅ増加量のバラツキが小さく）、安定した粗化度合いで作製することができる。
(Step S3: Roughening and Cleaning Step)
Next, in the roughening cleaning step S3, the bare surface of the silicon wafer to be roughened, which does not have a natural oxide film, is cleaned under the roughening cleaning conditions determined in S2. This cleaning is a step for roughening the front and back surfaces (or the back surface) of the silicon wafer to be roughened. In this way, by performing the steps S1 and S2 described above and then the step S3, it is possible to reliably obtain a roughened wafer having the desired haze increase amount described above. Moreover, in particular, the desired haze increase amount is not significantly deviated from (i.e., the variation in the haze increase amount is small), and the wafer can be produced with a stable degree of roughening.
続いて、本発明の洗浄を実施する際の洗浄方式について述べる。現在、ウェーハの洗浄方式は大半が薬液や純水などの液体を使用するものでウェット洗浄と呼ばれる。その中で主な方式としては一度に多くのウェーハをまとめて洗浄するバッチ方式とウェーハを１枚ずつ処理する枚葉方式に分かれる。バッチ方式は装置構成上ウェーハの表面及び裏面の両方が薬液に浸漬するため、本発明の洗浄を行うと表裏面が粗化される。対して、枚葉方式はウェーハを回転させながら、薬液をスプレーするため、ウェーハの片面のみを洗浄することができる。本発明者らが調査したところ、本発明ではバッチ方式及び枚葉方式どちらの方式でも粗化することができる。ウェーハの製造工程を考慮し、適宜方式を選定することができる。 Next, the cleaning method used in carrying out the cleaning of the present invention will be described. Currently, most wafer cleaning methods use liquids such as chemicals or pure water, and are called wet cleaning. The main methods are the batch method, in which many wafers are cleaned at once, and the single-wafer method, in which wafers are processed one by one. In the batch method, both the front and back sides of the wafer are immersed in the chemical solution due to the configuration of the equipment, so when the cleaning of the present invention is carried out, both the front and back sides are roughened. In contrast, in the single-wafer method, the wafer is rotated while the chemical solution is sprayed, so only one side of the wafer can be cleaned. According to the inventors' investigation, the present invention can be roughened using either the batch method or the single-wafer method. The appropriate method can be selected taking into consideration the wafer manufacturing process.
上述のように裏面のみが粗いウェーハを作製するには、枚葉方式の場合は裏面のみを洗浄すればよく、バッチ方式の場合は表裏面両方ともが粗化されてしまう。そこで本発明のシリコンウェーハの製造方法のように、本発明の洗浄方法により洗浄した後、研磨工程により、特には表面側の品質を良好にすることが望ましい。
例えば、本発明のシリコンウェーハの洗浄方法をバッチ式の洗浄機で行ってシリコンウェーハの表裏面共に粗化し、その後ＣＭＰ加工のような片面研磨を片方の面（すなわち表面）に対して行うことで、該片方の面とは反対側の面（すなわち裏面）のみが選択的に粗化されたウェーハを製造することができる。
このようなウェーハであれば、ウェット環境下でもチャック不良を引き起こさず、安定した製造が可能となる。
As described above, to produce a wafer with only a rough back surface, in the case of a single wafer method, only the back surface needs to be cleaned, whereas in the case of a batch method, both the front and back surfaces are roughened. Therefore, as in the silicon wafer manufacturing method of the present invention, it is desirable to improve the quality of the front surface side in particular by a polishing process after cleaning by the cleaning method of the present invention.
For example, by carrying out the silicon wafer cleaning method of the present invention in a batch-type cleaning machine to roughen both the front and back surfaces of a silicon wafer, and then carrying out single-sided polishing such as CMP processing on one surface (i.e., the front surface), it is possible to produce a wafer in which only the surface opposite to the one surface (i.e., the back surface) is selectively roughened.
Such a wafer will not cause chucking failure even in a wet environment, enabling stable manufacturing.
続いて、前述した本発明の洗浄方法において粗化に用いる洗浄液に関し、該洗浄液中の過酸化水素濃度を評価する方法及び管理する方法について述べる。
上述のように本発明の粗化挙動は過酸化水素濃度に強く依存することから、過酸化水素濃度を管理することでより安定的に粗化を進行させることができる。一般的なＳＣ１洗浄液の薬液濃度を評価する方法としては吸光度や屈折率による濃度測定方法があり、その精度も高いことが知られている。しかし、本発明者らが、粗化洗浄を行うため、例えばＮＨ４ＯＨが０．２５ｗｔ％、Ｈ２Ｏ２濃度が０．０７ｗｔ％で配合した洗浄液を吸光度方式の濃度計にて濃度を計測したところ、ＮＨ４ＯＨ濃度は０．２４ｗｔ％と計測されたが、Ｈ２Ｏ２濃度は検出下限値以下となり、計測できなかった。
Next, a method for evaluating and controlling the concentration of hydrogen peroxide in the cleaning solution used for roughening in the above-mentioned cleaning method of the present invention will be described.
As described above, the roughening behavior of the present invention strongly depends on the hydrogen peroxide concentration, so that roughening can be progressed more stably by controlling the hydrogen peroxide concentration. A method for evaluating the chemical concentration of a general SC1 cleaning solution includes a concentration measurement method using absorbance or refractive index, and it is known that the accuracy is high. However, when the present inventors measured the concentration of a cleaning solution containing, for example, 0.25 wt% NH 4 OH and 0.07 wt% H 2 O 2 in order to perform roughening cleaning, the NH 4 OH concentration was measured to be 0.24 wt%, but the H 2 O 2 concentration was below the detection limit and could not be measured.
そこで本発明者らは上述した粗化挙動を利用してＨ２Ｏ２濃度を評価及び管理できないか鋭意検討を行った。図６は本発明の洗浄液中の過酸化水素濃度の評価方法および管理方法のフローである。
（工程Ｓ１１：洗浄液濃度調査工程）
初めにＳ１１の洗浄液濃度調査工程のように、調査用シリコンウェーハ（自然酸化膜を有する）について、粗化量（例えばＨａｚｅ増加量）と、洗浄液（水酸化アンモニウムを含み、かつ、過酸化水素濃度が０～０．１５ｗｔ％の水溶液）の温度と、洗浄液中の水酸化アンモニウム濃度と、洗浄液中の過酸化水素濃度との相関関係を取得しておく工程である。
なお、上記洗浄液の例としては、過酸化水素濃度が０ｗｔ％のときは、水酸化アンモニウムを含む水溶液とすることができ、また、過酸化水素濃度が０ｗｔ％ではないときは、水酸化アンモニウムと過酸化水素水を含む水溶液（ＳＣ１洗浄液）とすることができる。
Therefore, the present inventors have conducted extensive research into whether the H 2 O 2 concentration can be evaluated and controlled by utilizing the above-mentioned roughening behavior. Fig. 6 shows a flow chart of the method for evaluating and controlling the hydrogen peroxide concentration in a cleaning solution according to the present invention.
(Step S11: Cleaning solution concentration investigation step)
First, as in the cleaning solution concentration investigation step of S11, this is a step of obtaining correlations between the amount of roughening (e.g., the amount of haze increase) for a test silicon wafer (having a native oxide film), the temperature of the cleaning solution (an aqueous solution containing ammonium hydroxide and having a hydrogen peroxide concentration of 0 to 0.15 wt %), the ammonium hydroxide concentration in the cleaning solution, and the hydrogen peroxide concentration in the cleaning solution for the silicon wafer under investigation (having a native oxide film).
As an example of the above cleaning liquid, when the hydrogen peroxide concentration is 0 wt%, it can be an aqueous solution containing ammonium hydroxide, and when the hydrogen peroxide concentration is not 0 wt%, it can be an aqueous solution containing ammonium hydroxide and hydrogen peroxide (SC1 cleaning liquid).
ここで、前述した本発明のシリコンウェーハの洗浄方法における工程Ｓ１の洗浄液濃度調査工程（調査用シリコンウェーハとして自然酸化膜がないものを使用）とは異なり、本発明の洗浄液中の過酸化水素濃度評価方法のこの工程Ｓ１１の洗浄液濃度調査工程で自然酸化膜を有するものを使用する理由は以下の通りである。
洗浄方法では、特には過酸化水素量の変動に対する粗化量のバラツキが小さく、安定した領域を求めるため図３のような傾向が得られるように自然酸化膜がないものを用いたが、この場合は逆に言えば粗化量に対応する過酸化水素濃度を一義的に求められなくなる。一方で自然酸化膜を有する場合は、後述するように過酸化水素濃度が高いほど粗化量が減少する傾向があり、粗化量から過酸化水素濃度を一義的に求めることができるからである。
Unlike the cleaning solution concentration investigation step S1 in the above-described silicon wafer cleaning method of the present invention (wherein a silicon wafer having no native oxide film is used as the investigation silicon wafer), the reason why a wafer having a native oxide film is used in the cleaning solution concentration investigation step S11 in the method for evaluating the hydrogen peroxide concentration in a cleaning solution of the present invention is as follows.
In the cleaning method, the variation in the amount of roughening relative to the change in the amount of hydrogen peroxide is particularly small, and in order to obtain a stable region, a sample without a native oxide film was used so that the trend shown in Figure 3 could be obtained, but in this case, conversely speaking, it is not possible to uniquely determine the hydrogen peroxide concentration corresponding to the amount of roughening. On the other hand, when a native oxide film is present, as described later, the amount of roughening tends to decrease as the hydrogen peroxide concentration increases, and the hydrogen peroxide concentration can be uniquely determined from the amount of roughening.
以下、洗浄液濃度調査工程について、より具体的な例を挙げて説明する。
まず、自然酸化膜を有する調査用シリコンウェーハを用意し、Ｈａｚｅ増加量を算出するため、洗浄前にパーティクルカウンターにてＨａｚｅ値を取得する。
なお、自然酸化膜の形成方法としては、一般的なＳＣ１洗浄やオゾン水洗浄が挙げられる。これらの洗浄は洗浄後に自然酸化膜が形成されれば特に制限されない。ＳＣ１洗浄液の混合比（体積比）は例えばＮＨ４ＯＨ：Ｈ２Ｏ２：Ｈ２Ｏ＝１：１：１０、温度は３０～８０℃、洗浄時間は９０～３６０秒が好ましい。オゾン水の濃度は３～２５ｐｐｍの範囲で、温度は１０～３０℃、洗浄時間は６０～３６０秒が好ましい。
The cleaning solution concentration checking step will be described below with a more specific example.
First, a silicon wafer for investigation having a native oxide film is prepared, and the haze value is obtained using a particle counter before cleaning in order to calculate the amount of haze increase.
Methods for forming a natural oxide film include general SC1 cleaning and ozone water cleaning. There are no particular limitations on these cleaning methods as long as a natural oxide film is formed after cleaning. The mixture ratio (volume ratio) of the SC1 cleaning solution is, for example, NH 4 OH:H 2 O 2 :H 2 O=1:1:10, the temperature is preferably 30 to 80°C, and the cleaning time is preferably 90 to 360 seconds. The concentration of the ozone water is preferably in the range of 3 to 25 ppm, the temperature is preferably 10 to 30°C, and the cleaning time is preferably 60 to 360 seconds.
次に、前述した洗浄液を種々の温度で用意し、ＮＨ４ＯＨ濃度やＨ２Ｏ２濃度を振って（さらには必要に応じて洗浄時間も振って）、自然酸化膜が存在する調査用シリコンウェーハを洗浄して表裏面（又は裏面）を粗化した後、パーティクルカウンターにてＨａｚｅ値を取得する。
図７は、洗浄温度が８０℃で、洗浄時間３ｍｉｎ、洗浄液中のＮＨ４ＯＨ濃度が０．０３ｗｔ％の場合のＨ２Ｏ２濃度に対するＨａｚｅ増加量を示した結果である。ベア面の場合（例えば図３）とは傾向が異なり、Ｈ２Ｏ２濃度が高いほど、Ｈａｚｅ増加量が減少する傾向が分かる。このように、予め、洗浄温度と、ＮＨ４ＯＨ濃度と、Ｈ２Ｏ２濃度と、Ｈａｚｅ増加量との相関関係を取得しておく。
尚、本発明者らが調査した結果、Ｈ２Ｏ２濃度が０．１５ｗｔ％より大きい場合では、Ｈａｚｅ増加量はほぼ０に近い値となり、指標とすることが難しい。一方、本発明はＨ２Ｏ２濃度が０．１５ｗｔ％以下の洗浄液に対する評価方法であり、このような微量の場合でも精度よくＨ２Ｏ２濃度を評価することでできる。
Next, the above-mentioned cleaning solution is prepared at various temperatures, and the NH 4 OH concentration and H 2 O 2 concentration are varied (and the cleaning time is also varied as necessary) to clean the silicon wafer to be investigated that has a native oxide film thereon, roughening the front and back surfaces (or the back surface), and then the haze value is obtained using a particle counter.
7 shows the results of haze increase versus H2O2 concentration when the cleaning temperature is 80°C, the cleaning time is 3 minutes, and the NH4OH concentration in the cleaning solution is 0.03 wt%. The tendency is different from that of the bare surface (e.g., FIG. 3), and it can be seen that the higher the H2O2 concentration, the smaller the haze increase. In this way, the correlation between the cleaning temperature, the NH4OH concentration, the H2O2 concentration , and the haze increase is obtained in advance.
As a result of investigation by the present inventors, when the H2O2 concentration is more than 0.15 wt%, the haze increase amount is close to 0, making it difficult to use it as an index. On the other hand, the present invention is an evaluation method for cleaning solutions with H2O2 concentrations of 0.15 wt% or less, and can accurately evaluate the H2O2 concentration even in such a small amount .
（工程Ｓ１２：過酸化水素濃度評価工程）
次にＳ１２の過酸化水素濃度評価工程のように、Ｈ２Ｏ２濃度を計測したい評価対象洗浄液（少なくとも水酸化アンモニウムを含む水溶液）で、Ｓ１１のときと同様の自然酸化膜を有するシリコンウェーハを、Ｓ１１で取得した相関関係のうちの所定の洗浄温度（さらには所定の洗浄時間）で洗浄し、Ｈａｚｅ増加量を取得する。なお、ＮＨ４ＯＨ濃度は例えば従来法により測定して求めておいても良い。
特には、洗浄温度（および洗浄時間）を予め設定しておき、Ｓ１１とＳ１２の工程を同じ洗浄温度（および洗浄時間）で行うと簡便である。
次いで、Ｓ１１で求めた相関関係に基づいて、上記で得られたＨａｚｅ増加量、洗浄温度（および洗浄時間）、ＮＨ４ＯＨ濃度から、Ｈ２Ｏ２濃度を評価することができる。
(Step S12: Hydrogen peroxide concentration evaluation step)
Next, as in the hydrogen peroxide concentration evaluation step of S12, a silicon wafer having a native oxide film similar to that in S11 is washed with a cleaning solution to be evaluated (aqueous solution containing at least ammonium hydroxide) for which the H2O2 concentration is to be measured, at a predetermined cleaning temperature (and further, a predetermined cleaning time) in the correlation obtained in S11, and the haze increase amount is obtained. Note that the NH4OH concentration may be measured by a conventional method, for example.
In particular, it is convenient to preset the cleaning temperature (and cleaning time) and perform steps S11 and S12 at the same cleaning temperature (and cleaning time).
Next, based on the correlation obtained in S11, the H 2 O 2 concentration can be evaluated from the haze increase amount, cleaning temperature (and cleaning time), and NH 4 OH concentration obtained above.
（工程Ｓ１３：過酸化水素濃度管理工程）
また、さらにはＳ１３の過酸化水素濃度管理工程のように、Ｓ１２で得られた評価結果に応じて、洗浄液中の過酸化水素濃度を調整することもできる。
例えば、初めにＮＨ４ＯＨ濃度が０．０３ｗｔ％、Ｈ２Ｏ２濃度が０．０５ｗｔ％となるように配合した洗浄液を用いて、所定時間洗浄した後、本発明の評価方法でＨ２Ｏ２濃度を評価したところ、０．０４ｗｔ％と判定された場合は、Ｈ２Ｏ２濃度が０．０５ｗｔ％となるように過酸化水素水を注加することができる。逆に０．０６ｗｔ％と判定された場合はＨ２Ｏ２濃度が０．０５ｗｔ％となるように純水を注加することができる。このような管理方法を行うことで、薬液ライフを長くすることもでき、Ｈａｚｅ増加量が安定した粗化ウェーハを製造することができる。
このようにして、洗浄液中の０～０．１５ｗｔ％という微量のＨ２Ｏ２濃度を精度良く評価し、また管理することができ、ひいては所望の粗化ウェーハを安定して製造可能である。
(Step S13: Hydrogen peroxide concentration management step)
Furthermore, as in the hydrogen peroxide concentration control step S13, the hydrogen peroxide concentration in the cleaning liquid can be adjusted according to the evaluation results obtained in S12.
For example, after first cleaning for a predetermined time using a cleaning solution formulated so that the NH4OH concentration is 0.03 wt % and the H2O2 concentration is 0.05 wt%, if the H2O2 concentration is evaluated using the evaluation method of the present invention and judged to be 0.04 wt%, hydrogen peroxide solution can be injected so that the H2O2 concentration becomes 0.05 wt%. Conversely, if the H2O2 concentration is judged to be 0.06 wt%, pure water can be injected so that the H2O2 concentration becomes 0.05 wt%. By carrying out such a management method, the chemical life can be extended and a roughened wafer with a stable increase in haze can be manufactured.
In this manner, the minute H 2 O 2 concentration of 0 to 0.15 wt % in the cleaning solution can be accurately evaluated and controlled, and thus desired roughened wafers can be stably manufactured.
以下、本発明を実施例に基づきさらに説明するが、これらの実施例は例示的に示されるもので限定的に解釈されるべきではない。
（実施例１）
図１の本発明の洗浄方法に示すように、初めに予備試験のＳ１の洗浄液濃度調査工程を実施した。
ＫＬＡ社製パーティクルカウンター ＳＰ３にて、ＤＳＰ加工後の自然酸化膜のないベア面のシリコンウェーハ（調査用シリコンウェーハ）のＨａｚｅ値を取得した。続いて、２８質量％のアンモニア水（ＮＨ４ＯＨ）と、さらには必要に応じて３０質量％の過酸化水素水（Ｈ２Ｏ２）を用いて、洗浄液の温度が８０℃で、ＮＨ４ＯＨ濃度が０．０３ｗｔ％と０．２５ｗｔ％の２水準の洗浄液を準備し、Ｈ２Ｏ２濃度を０～０．１５ｗｔ％の範囲内で変えて上記のベア面のシリコンウェーハを洗浄時間３ｍｉｎで洗浄した後、ＳＰ３にてＨａｚｅ値を取得し、洗浄前後の差分から粗化量の指標であるＨａｚｅ増加量を算出した。
洗浄温度が８０℃の場合における、Ｈａｚｅ増加量、ＮＨ４ＯＨ濃度、およびＨ２Ｏ２濃度の相関関係を図８に示す。
The present invention will be further described below with reference to examples. However, these examples are presented for illustrative purposes and should not be construed as limiting.
Example 1
As shown in the cleaning method of the present invention in FIG. 1, first, a preliminary test S1 was carried out to investigate the concentration of the cleaning solution.
The haze value of the bare silicon wafer (investigation silicon wafer) without a natural oxide film after DSP processing was obtained using a particle counter SP3 manufactured by KLA Corporation. Next, 28 mass% ammonia water (NH 4 OH) and, if necessary, 30 mass% hydrogen peroxide water (H 2 O 2 ) were used to prepare two levels of cleaning solution with a cleaning solution temperature of 80° C. and NH 4 OH concentration of 0.03 wt% and 0.25 wt%, and the H 2 O 2 concentration was changed within the range of 0 to 0.15 wt% to clean the bare silicon wafer for a cleaning time of 3 minutes, and then the haze value was obtained using the SP3, and the haze increase amount, which is an index of the roughening amount, was calculated from the difference before and after cleaning.
FIG. 8 shows the correlation between the haze increase amount, the NH 4 OH concentration, and the H 2 O 2 concentration when the cleaning temperature was 80° C.
次にＳ２の粗化洗浄条件決定工程を実施した。
Ｈａｚｅ増加量が１０ｐｐｍと３０ｐｐｍの２水準のウェーハを作製することを目的とした。Ｓ１で求めた図８の相関関係からこれらのＨａｚｅ増加量を得られるような粗化洗浄条件を決定した。
１０ｐｐｍについては、ＮＨ４ＯＨ濃度が０．０３ｗｔ％の場合に着目すると、Ｈ２Ｏ２濃度が約０．０３～０．０８ｗｔ％範囲でＨａｚｅ増加量が約５～６ｐｐｍ程度と安定した範囲が存在していること分かる。したがって、次のＳ３の工程で、粗化対象シリコンウェーハに対して用いる洗浄液は、ＮＨ４ＯＨ濃度を０．０３ｗｔ％とし、Ｈ２Ｏ２濃度を０．０３～０．０８ｗｔ％の範囲内のうちの０．０５ｗｔ％とし、洗浄温度は８０℃とした。洗浄時間については、Ｈａｚｅ増加量と洗浄時間には正の相関があり、３ｍｉｎで５～６ｐｐｍのＨａｚｅ増加量であることを踏まえ、洗浄時間を３ｍｉｎの２倍の６ｍｉｎと設定した。この設定により、約１０ｐｐｍのＨａｚｅ増加量が見込まれる。
Next, the roughening cleaning condition determination step S2 was carried out.
The objective was to produce wafers with two levels of haze increase, 10 ppm and 30 ppm. Roughening cleaning conditions that would obtain these haze increases were determined from the correlation in FIG. 8 obtained in S1.
For 10 ppm, when the NH 4 OH concentration is 0.03 wt%, it is found that there is a stable range where the haze increase is about 5 to 6 ppm when the H 2 O 2 concentration is in the range of about 0.03 to 0.08 wt%. Therefore, in the next step S3, the cleaning solution used for the silicon wafer to be roughened has an NH 4 OH concentration of 0.03 wt%, an H 2 O 2 concentration of 0.05 wt% within the range of 0.03 to 0.08 wt%, and a cleaning temperature of 80°C. Regarding the cleaning time, there is a positive correlation between the haze increase and the cleaning time, and considering that the haze increase is 5 to 6 ppm in 3 minutes, the cleaning time was set to 6 minutes, which is twice 3 minutes. With this setting, a haze increase of about 10 ppm is expected.
３０ｐｐｍについては、ＮＨ４ＯＨ濃度が０．２５ｗｔ％の場合に着目すると、Ｈ２Ｏ２濃度が０．０５～０．０９ｗｔ％の範囲でＨａｚｅ増加量が約３０ｐｐｍと安定している。このことから、洗浄液は、ＮＨ４ＯＨ濃度を０．２５ｗｔ％とし、Ｈ２Ｏ２濃度を０．０５～０．０９ｗｔ％の範囲内の０．０７ｗｔ％とし、洗浄温度は８０℃とした。洗浄時間は、３ｍｉｎで３０ｐｐｍのＨａｚｅ増加量であることから、Ｓ１のときと同様に３ｍｉｎとした。 Regarding 30 ppm, when the NH 4 OH concentration is 0.25 wt%, the haze increase is stable at about 30 ppm when the H 2 O 2 concentration is in the range of 0.05 to 0.09 wt%. For this reason, the cleaning solution has an NH 4 OH concentration of 0.25 wt%, an H 2 O 2 concentration of 0.07 wt% within the range of 0.05 to 0.09 wt%, and a cleaning temperature of 80° C. The cleaning time was set to 3 min, as with S1, since the haze increase is 30 ppm in 3 min.
次いで、Ｓ３の粗化洗浄工程を実施した。
Ｓ２で決定したＨａｚｅ増加量が１０ｐｐｍと３０ｐｐｍ狙いの２水準の粗化洗浄条件にて、ＤＳＰ加工後の自然酸化膜がないベア面のシリコンウェーハ（粗化対象シリコンウェーハ）を各水準５枚をバッチ式洗浄機で洗浄して両面を粗化し、ＳＰ３にてＨａｚｅ値を取得し、Ｈａｚｅ増加量を算出した。１０ｐｐｍ狙いのウェーハのＨａｚｅ増加量の平均値は１０．７ｐｐｍ、３０ｐｐｍ狙いのウェーハのＨａｚｅ増加量の平均値は３１．２ｐｐｍとなり、狙いＨａｚｅ増加量と同等の粗さを形成したウェーハを作製することができた。またＬＬＳ品質は１０ｐｐｍ狙いのウェーハでは１ｐｃｓ、３０ｐｐｍ狙いのウェーハでは０ｐｃｓとなり良好であった。
Next, the roughening cleaning step S3 was carried out.
Under the two levels of roughening cleaning conditions, with the haze increase amount determined in S2 being 10 ppm and 30 ppm, five bare silicon wafers (silicon wafers to be roughened) without natural oxide film after DSP processing were cleaned with a batch type cleaner to roughen both sides, and the haze value was obtained in SP3 to calculate the haze increase amount. The average haze increase amount of the wafers with a target of 10 ppm was 10.7 ppm, and the average haze increase amount of the wafers with a target of 30 ppm was 31.2 ppm, and it was possible to produce wafers with roughness equivalent to the target haze increase amount. In addition, the LLS quality was good, being 1 pcs for the wafers with a target of 10 ppm and 0 pcs for the wafers with a target of 30 ppm.
このように両面が粗化された狙いＨａｚｅ増加量が１０ｐｐｍと３０ｐｐｍの各１枚について、その表面側に対して取り代５００ｎｍのＣＭＰ加工を行った。ＣＭＰ加工後の各ウェーハのＫＬＡ社製ＳＰ５／１９ｎｍＵｐにてＬＬＳ数を評価したところ、１０ｐｐｍ狙いでは１２ｐｃｓ、３０ｐｐｍ狙いでは９ｐｃｓとなり、後述する比較例の水準１と同等で良好な品質であった。
その後、水中保管した各ウェーハの裏面側をチャックし研磨機のステージにウェーハをアンチャックさせる搬送テストを繰り返し２００回行ったところ、２水準とも２００回ともすべて不良なく搬送することができた。
For each wafer with a roughened surface and a haze increase of 10 ppm and 30 ppm, CMP was performed on the front surface with a removal allowance of 500 nm. The number of LLS was evaluated using a KLA SP5/19nmUp after CMP, and the number was 12 pcs for the 10 ppm target and 9 pcs for the 30 ppm target, which was equivalent to
Thereafter, a transport test was performed 200 times in which the back side of each wafer stored underwater was chucked and the wafer was unchucked on the stage of the polishing machine. All 200 transport tests were performed without any defects for both levels.
（実施例２）
次に、図６の本発明の評価方法に基づき、粗化洗浄を安定的に行うための洗浄液中の過酸化水素濃度の評価を行った。
Ｈａｚｅ増加量が１０ｐｐｍとなるように、実施例１のＳ２，Ｓ３の結果を元に、ＮＨ４ＯＨ濃度が０．０３ｗｔ％でＨ２Ｏ２濃度が０．０５ｗｔ％、温度が８０℃の洗浄液の過酸化水素濃度を評価した。
初めにＳ１１の洗浄液濃度調査工程のように、洗浄温度（８０℃）、ＮＨ４ＯＨ濃度（０．０３ｗｔ％）、Ｈ２Ｏ２濃度および粗化量の相関関係を取得した。
具体的には、まず、シリコンウェーハをＮＨ４ＯＨ：Ｈ２Ｏ２：Ｈ２Ｏ＝１：１：１０の洗浄液にて８０℃で３ｍｉｎ洗浄し自然酸化膜が存在するウェーハを作製し（調査用シリコンウェーハ）、ＳＰ３にてＨａｚｅ値を取得した。次に、ＮＨ４ＯＨ濃度が０．０３ｗｔ％、洗浄温度が８０℃の洗浄液でＨ２Ｏ２濃度を変えて自然酸化膜が存在するシリコンウェーハを３ｍｉｎ洗浄した。洗浄後のウェーハのＨａｚｅ値をＳＰ３にて取得し、Ｈａｚｅ増加量を算出した。その結果は図７と同様であった。すなわち、例えばＨ２Ｏ２濃度が０．０５ｗｔ％の場合は４１ｐｐｍ、０．０２ｗｔ％の場合は１８１ｐｐｍとなり、Ｈ２Ｏ２濃度の増加に伴い粗化量（即ちＨａｚｅ増加量）が小さくなる相関関係が得られた。
Example 2
Next, based on the evaluation method of the present invention shown in FIG. 6, an evaluation was made of the hydrogen peroxide concentration in the cleaning solution for stably carrying out roughening cleaning.
Based on the results of S2 and S3 in Example 1, the hydrogen peroxide concentration of a cleaning solution having an NH 4 OH concentration of 0.03 wt %, an H 2 O 2 concentration of 0.05 wt %, and a temperature of 80° C. was evaluated so that the haze increase amount was 10 ppm.
First, as in the cleaning solution concentration investigation step S11, the correlations among the cleaning temperature (80° C.), the NH 4 OH concentration (0.03 wt %), the H 2 O 2 concentration, and the roughening amount were obtained.
Specifically, first, a silicon wafer was cleaned at 80° C. for 3 min with a cleaning solution of NH 4 OH:H 2 O 2 :H 2 O=1:1:10 to prepare a wafer with a natural oxide film (silicon wafer for investigation), and the haze value was obtained by SP3. Next, the silicon wafer with a natural oxide film was cleaned for 3 min with a cleaning solution of NH 4 OH concentration of 0.03 wt% and cleaning temperature of 80° C., with the H 2 O 2 concentration changed. The haze value of the wafer after cleaning was obtained by SP3, and the haze increase was calculated. The results were the same as those in FIG. 7. That is, for example, when the H 2 O 2 concentration was 0.05 wt%, it was 41 ppm, and when it was 0.02 wt%, it was 181 ppm, and a correlation was obtained in which the roughening amount (i.e., the haze increase amount) decreased with the increase in H 2 O 2 concentration.
次に、Ｓ１２の過酸化水素濃度評価工程を行った。
まず、この洗浄液にてシリコンウェーハを２００枚洗浄し、両面粗化されたシリコンウェーハを製造した。２００枚洗浄後の洗浄液（評価対象洗浄液）中の過酸化水素濃度を評価するため、Ｈａｚｅ値を取得してある自然酸化膜が存在するウェーハを洗浄した後、ＳＰ３にてＨａｚｅ値を取得し、Ｈａｚｅ増加量を算出した。その結果、Ｈａｚｅ増加量は６０ｐｐｍとなった。
図７の相関関係を参照すると、評価対象洗浄液中のＨ２Ｏ２濃度が約０．０４ｗｔ％と求まった。２００枚洗浄前の狙いＨ２Ｏ２濃度が０．０５ｗｔ％であることから、約０．０１ｗｔ％濃度が低下したと判断した。恐らく、２００枚洗浄したことで、ウェーハに薬液が付着したことや、純水（リンス）槽からの持ち込みが原因と考えられる。
Next, the hydrogen peroxide concentration evaluation step S12 was carried out.
First, 200 silicon wafers were cleaned with this cleaning solution to produce silicon wafers with roughened surfaces on both sides. In order to evaluate the hydrogen peroxide concentration in the cleaning solution (evaluation target cleaning solution) after cleaning 200 wafers, the haze value was acquired, and then the wafers with native oxide films were cleaned, and the haze value was acquired in SP3, and the haze increase was calculated. As a result, the haze increase was 60 ppm.
7, the H2O2 concentration in the cleaning solution to be evaluated was found to be about 0.04 wt%. Since the target H2O2 concentration before cleaning 200 wafers was 0.05 wt%, it was determined that the concentration had decreased by about 0.01 wt%. This was probably due to the chemical solution adhering to the wafers after cleaning 200 wafers, or carryover from the pure water (rinse) tank.
次にＳ１３の過酸化水素濃度管理工程にて、狙いＨ２Ｏ２濃度である０．０５ｗｔ％になるように、Ｈ２Ｏ２を洗浄液に注加した。
その後、確認のため、Ｈａｚｅ値を取得してある自然酸化膜が存在するウェーハを洗浄した後、ＳＰ３にてＨａｚｅ値を取得し、Ｈａｚｅ増加量を算出した。その結果、４０ｐｐｍと求まり、相関関係からＨ２Ｏ２が約０．０５ｗｔ％と求まり、Ｈ２Ｏ２濃度が狙い通りであることを確認できた。
Next, in the hydrogen peroxide concentration control step S13, H2O2 was added to the cleaning solution so that the target H2O2 concentration became 0.05 wt %.
After that, for confirmation, the wafer with the native oxide film having the haze value was cleaned, and the haze value was acquired by SP3, and the haze increase was calculated. As a result, it was found to be 40 ppm , and from the correlation, H2O2 was found to be about 0.05 wt%, and it was confirmed that the H2O2 concentration was as targeted.
以上の結果から、本発明の洗浄方法を用いることで、シリコンウェーハの表裏面（特に裏面）を、チャックによる吸着に適した粗さを示すのに十分に粗化することができたことが分かる。さらに本発明の洗浄液中の過酸化水素濃度の評価方法や管理方法を用いることで、従来困難であった微量の過酸化水素濃度を評価でき、また管理できることが分かる。 These results show that by using the cleaning method of the present invention, it is possible to sufficiently roughen the front and back surfaces (particularly the back surface) of a silicon wafer to provide a roughness suitable for adhesion by a chuck. Furthermore, by using the method of evaluating and controlling the hydrogen peroxide concentration in a cleaning solution of the present invention, it is possible to evaluate and control minute amounts of hydrogen peroxide concentration, which was previously difficult to do.
（比較例）
ＤＳＰ加工後の自然酸化膜がないベア面のシリコンウェーハを用意し、ＳＰ３にてＨａｚｅ評価を行った。次にバッチ式洗浄機にて、表１に示した６つの水準の条件（液組成、洗浄温度、洗浄時間）にて洗浄を行った。洗浄液の調製には２８質量％のアンモニア水（ＮＨ４ＯＨ）、３０質量％の過酸化水素水（Ｈ２Ｏ２）を用いた。洗浄後のウェーハをＳＰ３で評価し、Ｈａｚｅ値を取得し、Ｈａｚｅ増加量を算出した。
(Comparative Example)
A bare silicon wafer without a native oxide film after DSP processing was prepared, and a haze evaluation was performed using SP3. Next, cleaning was performed using a batch cleaning machine under six levels of conditions (liquid composition, cleaning temperature, cleaning time) shown in Table 1. 28% by mass of ammonia water (NH 4 OH) and 30% by mass of hydrogen peroxide water (H 2 O 2 ) were used to prepare the cleaning liquid. The wafer after cleaning was evaluated using SP3, the haze value was obtained, and the haze increase was calculated.
表１の全水準ともＨａｚｅ増加量は１ｐｐｍ以下となり、実施例１の１０ｐｐｍや３０ｐｐｍと比較すると小さいことから粗化されていないと判断した。
水準１及び水準５のウェーハに対し、取り代５００ｎｍのＣＭＰ加工を行った後、ＳＰ５／１９ｎｍＵＰにてＬＬＳ数を評価したところ、水準１では１０ｐｃｓ、水準５では３４２ｐｃｓとなった。水準１のＬＬＳレベルは実施例１と同等であったが、水準５は粗化洗浄工程時にエッチング優勢となり形成されたエッチピットがＣＭＰ工程で残留したためＬＬＳ品質が悪化したと考えられる。次に水準１と水準５のウェーハに対し、実施例１と同様のチャックテストを２００回行った。ウェーハがチャックから脱離しない不良が水準１は４回、水準５では３回発生した。
また水準５の洗浄液のＨ２Ｏ２濃度を吸光度方式の濃度計で計測したが、検出下限値以下となり評価することができなかった。
For all levels in Table 1, the increase in haze was 1 ppm or less, which was smaller than the 10 ppm and 30 ppm in Example 1, and therefore it was determined that no roughening was occurred.
After CMP processing with a removal allowance of 500 nm was performed on the wafers of
The H 2 O 2 concentration of the cleaning solution of
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.
Claims (8)
自然酸化膜がないベア面が露出した調査用シリコンウェーハを、水酸化アンモニウムを含み、かつ、過酸化水素濃度が０～０．１５ｗｔ％の水溶液である洗浄液で洗浄することで粗化された前記調査用シリコンウェーハの表裏面又は裏面の粗化量と、
前記洗浄液の温度と、
前記洗浄液中の水酸化アンモニウム濃度と、
前記洗浄液中の過酸化水素濃度との相関関係を予め取得しておく洗浄液濃度調査工程と、
該洗浄液濃度調査工程で取得しておいた前記相関関係に基づいて、所望の粗化量から、前記洗浄液の温度、前記洗浄液中の水酸化アンモニウム濃度及び過酸化水素濃度の粗化洗浄条件を決定する粗化洗浄条件決定工程と、
該粗化洗浄条件決定工程で決定した粗化洗浄条件で、自然酸化膜がないベア面が露出した粗化対象シリコンウェーハを洗浄することで、該粗化対象シリコンウェーハの表裏面又は裏面を粗化する粗化洗浄工程とを有することを特徴とするシリコンウェーハの洗浄方法。 A cleaning method for roughening a silicon wafer, comprising the steps of:
A silicon wafer for investigation having an exposed bare surface free of a native oxide film is roughened by cleaning the silicon wafer with a cleaning solution that is an aqueous solution containing ammonium hydroxide and having a hydrogen peroxide concentration of 0 to 0.15 wt %, thereby obtaining a roughening amount of the front and back surfaces or the back surface of the silicon wafer for investigation;
The temperature of the cleaning liquid; and
a concentration of ammonium hydroxide in the cleaning solution; and
a cleaning solution concentration investigation step of acquiring a correlation with the hydrogen peroxide concentration in the cleaning solution in advance;
a roughening cleaning condition determining step of determining roughening cleaning conditions, including a temperature of the cleaning solution, an ammonium hydroxide concentration and a hydrogen peroxide concentration in the cleaning solution, from a desired roughening amount based on the correlation obtained in the cleaning solution concentration investigating step;
and a roughening cleaning step of roughening a silicon wafer to be roughened, the bare surface of which is exposed and free from a native oxide film, by cleaning the silicon wafer to be roughened under the roughening cleaning conditions determined in the roughening cleaning condition determination step, thereby roughening the front and back surfaces or the back surface of the silicon wafer to be roughened.
前記調査用シリコンウェーハの前記洗浄前後にパーティクルカウンターにてＨａｚｅ値を取得し、前記洗浄後のＨａｚｅ値の増加量を前記粗化量とすることを特徴とする請求項１に記載のシリコンウェーハの洗浄方法。 In the cleaning solution concentration investigation step,
2. The method for cleaning a silicon wafer according to claim 1, wherein a haze value of the investigated silicon wafer is obtained by a particle counter before and after the cleaning, and an increase in the haze value after the cleaning is defined as the amount of roughening.
前記過酸化水素濃度が、該過酸化水素濃度の変動に対する前記粗化量の変動が所定値以下の濃度範囲内であり、かつ、前記粗化洗浄工程における前記洗浄後の粗化対象シリコンウェーハ表面に、該洗浄中に形成された自然酸化膜が残るように、
前記粗化洗浄条件を決定することを特徴とする請求項１または請求項２に記載のシリコンウェーハの洗浄方法。 When the roughening cleaning conditions are determined in the roughening cleaning condition determination step,
the hydrogen peroxide concentration is within a concentration range in which a change in the roughening amount with respect to a change in the hydrogen peroxide concentration is equal to or less than a predetermined value, and a native oxide film formed during the cleaning remains on the surface of the silicon wafer to be roughened after the cleaning in the roughening cleaning step,
3. The method for cleaning a silicon wafer according to claim 1, further comprising determining the roughening cleaning conditions.
自然酸化膜を有する調査用シリコンウェーハを、水酸化アンモニウムを含み、かつ、過酸化水素濃度が０～０．１５ｗｔ％の水溶液である洗浄液で洗浄することで粗化された前記調査用シリコンウェーハの表裏面又は裏面の粗化量と、
前記洗浄液の温度と、
前記洗浄液中の水酸化アンモニウム濃度と、
前記洗浄液中の過酸化水素濃度との相関関係を予め取得しておく洗浄液濃度調査工程と、
該洗浄液濃度調査工程で取得しておいた前記相関関係に基づいて、
自然酸化膜を有するシリコンウェーハを、少なくとも水酸化アンモニウムを含む水溶液である評価対象洗浄液で洗浄することで粗化された前記シリコンウェーハの表裏面又は裏面の粗化量と、
前記評価対象洗浄液の温度と、
前記評価対象洗浄液中の水酸化アンモニウム濃度とから、
前記評価対象洗浄液中の過酸化水素濃度を評価する過酸化水素濃度評価工程とを有することを特徴とする洗浄液中の過酸化水素濃度評価方法。 1. A method for assessing a hydrogen peroxide concentration in a cleaning solution, comprising:
A roughening amount of the front and back surfaces or the back surface of the silicon wafer for investigation, which has a native oxide film and is roughened by cleaning the silicon wafer for investigation with a cleaning solution that is an aqueous solution containing ammonium hydroxide and having a hydrogen peroxide concentration of 0 to 0.15 wt %, and
The temperature of the cleaning liquid; and
a concentration of ammonium hydroxide in the cleaning solution; and
a cleaning solution concentration investigation step of acquiring a correlation with the hydrogen peroxide concentration in the cleaning solution in advance;
Based on the correlation obtained in the cleaning solution concentration investigation step,
A silicon wafer having a native oxide film is roughened by cleaning the silicon wafer with a cleaning solution to be evaluated, which is an aqueous solution containing at least ammonium hydroxide, and the roughening amount of the front and back surfaces or the back surface of the silicon wafer;
The temperature of the cleaning solution to be evaluated; and
and the concentration of ammonium hydroxide in the cleaning solution to be evaluated.
and evaluating the hydrogen peroxide concentration in the cleaning solution to be evaluated.
請求項７に記載の洗浄液中の過酸化水素濃度評価方法により、前記評価対象洗浄液中の過酸化水素濃度を評価し、
該評価結果に基づき、評価後の洗浄液中の過酸化水素濃度を調整することを特徴とする洗浄液中の過酸化水素濃度管理方法。 A method for managing a hydrogen peroxide concentration in a cleaning solution, comprising:
The method for evaluating a hydrogen peroxide concentration in a cleaning solution according to claim 7 is used to evaluate the hydrogen peroxide concentration in the cleaning solution to be evaluated;
A method for controlling the concentration of hydrogen peroxide in a cleaning solution, comprising adjusting the concentration of hydrogen peroxide in the cleaning solution after the evaluation based on the evaluation results.
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