JP5162569B2 - Analytical method of ultra-trace impurity metals on silicon wafer surface - Google Patents
Analytical method of ultra-trace impurity metals on silicon wafer surface Download PDFInfo
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- JP5162569B2 JP5162569B2 JP2009289455A JP2009289455A JP5162569B2 JP 5162569 B2 JP5162569 B2 JP 5162569B2 JP 2009289455 A JP2009289455 A JP 2009289455A JP 2009289455 A JP2009289455 A JP 2009289455A JP 5162569 B2 JP5162569 B2 JP 5162569B2
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims description 51
- 229910052710 silicon Inorganic materials 0.000 title claims description 51
- 239000010703 silicon Substances 0.000 title claims description 51
- 238000004458 analytical method Methods 0.000 title claims description 22
- 229910052751 metal Inorganic materials 0.000 title claims description 15
- 239000002184 metal Substances 0.000 title claims description 15
- 239000012535 impurity Substances 0.000 title claims description 10
- 150000002739 metals Chemical class 0.000 title claims description 6
- 239000007789 gas Substances 0.000 claims description 60
- 238000005530 etching Methods 0.000 claims description 57
- 238000000034 method Methods 0.000 claims description 30
- 238000005507 spraying Methods 0.000 claims description 22
- 239000012808 vapor phase Substances 0.000 claims description 21
- 239000006227 byproduct Substances 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- 238000000354 decomposition reaction Methods 0.000 claims description 16
- 239000000047 product Substances 0.000 claims description 13
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 9
- 238000007664 blowing Methods 0.000 claims description 6
- 239000011261 inert gas Substances 0.000 claims description 6
- 230000000415 inactivating effect Effects 0.000 claims description 2
- 235000012431 wafers Nutrition 0.000 description 63
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 33
- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 description 27
- 239000000243 solution Substances 0.000 description 8
- 239000003595 mist Substances 0.000 description 7
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 5
- 230000002209 hydrophobic effect Effects 0.000 description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- 230000005587 bubbling Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 238000007865 diluting Methods 0.000 description 2
- 230000005661 hydrophobic surface Effects 0.000 description 2
- 239000006199 nebulizer Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 229910021642 ultra pure water Inorganic materials 0.000 description 2
- 239000012498 ultrapure water Substances 0.000 description 2
- 239000003570 air Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 238000011027 product recovery Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 229910021654 trace metal Inorganic materials 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
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- Testing Or Measuring Of Semiconductors Or The Like (AREA)
Description
本発明はシリコンウェハ表面の超微量不純物金属の分析方法に関する。 The present invention relates to a method for analyzing an ultra trace impurity metal on the surface of a silicon wafer.
シリコンウェハの表面、該表面に形成された薄膜中、あるいは表層の超微量金属不純物は、半導体素子の特性に不測の影響を与えることがあるという問題が知られている。このため、従来からシリコンウェハの表面や表層、あるいはその表面に形成された熱酸化膜等の薄膜中の金属不純物を高感度にかつ効率的に分析することが強く望まれてきた。 There is a known problem that ultra-trace metal impurities on the surface of a silicon wafer, in a thin film formed on the surface, or on the surface layer may unexpectedly affect the characteristics of the semiconductor element. For this reason, it has been strongly desired to analyze metal impurities in the surface and surface layer of a silicon wafer or in a thin film such as a thermal oxide film formed on the surface with high sensitivity and efficiency.
係る目的で、気相分解法（又は気相エッチング法）を用いる分析方法が開発されている。この方法は、通常まずシリコンウェハの表面に分解ガス（又はエッチングガス）を接触させて所望の厚さ（量）にシリコンウェハを分解（又はエッチング）する第１工程と、該表面の分解物（エッチング物）と不純物金属を水等の溶媒を用いて分析用溶液として回収する第２工程と、分析用溶液を分析する第３工程とからなる。ここで第１工程の分解ガス（又はエッチングガス）としては、硝酸、フッ酸、又はオゾン又はそれらの混合物を用いることが知られている。通常これらの硝酸、フッ酸の水溶液を常温で又は加熱して気化させたガスをシリコンウェハの表面に接触させる。またオゾンは不活性ガスで所望の範囲の濃度に希釈してシリコンウェハの表面に接触させる（特許文献１〜４）。
For this purpose, an analytical method using a vapor phase decomposition method (or a vapor phase etching method) has been developed. In this method, usually, first, a decomposition gas (or etching gas) is brought into contact with the surface of the silicon wafer to decompose (or etch) the silicon wafer to a desired thickness (amount); Etched product) and the impurity metal are collected as a solution for analysis using a solvent such as water, and a third step of analyzing the solution for analysis. Here, it is known that nitric acid, hydrofluoric acid, ozone, or a mixture thereof is used as the decomposition gas (or etching gas) in the first step. Usually, a gas obtained by vaporizing an aqueous solution of nitric acid or hydrofluoric acid at room temperature or by heating is brought into contact with the surface of the silicon wafer. Further, ozone is diluted with an inert gas to a concentration within a desired range and is brought into contact with the surface of the silicon wafer (
本発明は、上で説明した気相分解法（又は気相エッチング法）を用いて、かつシリコンウェハ表面の超微量不純物金属の分析方法、特に第２工程の自動化を試みる際に明らかとなった問題を解決することを課題とする。 The present invention was clarified by using the above-described vapor phase decomposition method (or vapor phase etching method) and when trying to automate the ultra-trace impurity metal analysis method on the silicon wafer surface, particularly the second step. The problem is to solve the problem.
本発明者は、図４で示されるように、従来公知の第１工程で分解（又はエッチング）した際に、表面に種々の生成物が付着し、その付着物が表面を極めて親水性となる場合があること、この現象が原因で、第２工程において分解物を回収する際にシリコンウェハ表面で水滴が形成されにくくなり水滴をスキャンして表面の分解物を自動回収する方法が適用できなくなるという知見を得た。 As shown in FIG. 4, when the present inventor decomposes (or etches) in the conventionally known first step, various products adhere to the surface, and the adhered matter makes the surface extremely hydrophilic. Due to this phenomenon, when recovering decomposition products in the second step, it is difficult to form water droplets on the surface of the silicon wafer, and the method of automatically recovering surface decomposition products by scanning the water droplets cannot be applied. I got the knowledge.
そこで本発明者は、係る知見に基づき鋭意研究した結果、第１工程である分解（又はエッチング）表面に生じる種々の生成物（副生物）を除去又は不活性化処理を行い、かつその後必要であれば表面を速やかにＨＦガスで疎水性化することで、極めて再現よく効率的に、疎水性シリコンウェハ表面を水滴でスキャンして表面の分解物を回収することが可能となることを見いだし本発明を完成した。 Therefore, as a result of earnest research based on such knowledge, the present inventor removed or inactivated various products (by-products) generated on the decomposition (or etching) surface, which is the first step, and is necessary thereafter. If the surface is made hydrophobic quickly with HF gas, it is found that it is possible to scan the surface of the hydrophobic silicon wafer with water droplets and recover the decomposition products on the surface very efficiently and reproducibly. Completed the invention.
特に本発明者は、エッチングガスとしてオゾンを含むＨＦガス（以下「Ｏ３／ＨＦ」とする。）を用いた場合、表面に副生成物が生じ、シリコンウェハ表面を強い親水性としこのままでは通常のＨＦガスによる疎水性化が阻止されるという知見を得た。 In particular, when the present inventor uses HF gas containing ozone as an etching gas (hereinafter referred to as “O 3 / HF”), by-products are generated on the surface, and the silicon wafer surface is made highly hydrophilic and is usually left as it is. The knowledge that the hydrophobization by HF gas was prevented was obtained.
そこで発明者は係る知見に基づき鋭意研究した結果、係る表面の副生成物が生成した直後に不活性ガスをウェハに直接吹き付けることにより除去・不活性化できることを見いだし本発明を完成した。 As a result of intensive studies based on such knowledge, the inventors have found that the surface can be removed and deactivated by directly spraying an inert gas on the wafer immediately after the formation of the by-product on the surface, thereby completing the present invention.
また発明者は、係る表面の副生成物を、次のＨＦガスにより疎水化の前に水を噴霧することにより除去・不活性化できることを見いだし本発明を完成した。 The inventor has also found that such a surface by-product can be removed and inactivated by spraying water before hydrophobization with the next HF gas, and has completed the present invention.
即ち本発明は、気相エッチング法を用いるシリコンウェハ表面の超微量不純物金属の分析方法であって、シリコンウェハの表面を気相エッチングする工程（Ｉ）と、表面疎水性化処理工程（ＩＩ）と、液滴スキャン回収分解物回収処理工程（ＩＩＩ）と、金属分析工程（ＩＶ）からなる。 That is, the present invention is a method for analyzing an ultra-trace impurity metal on the surface of a silicon wafer using a vapor phase etching method, which comprises a step (I) of performing a vapor phase etching on the surface of the silicon wafer and a surface hydrophobizing step (II). And a droplet scan recovery decomposition product recovery processing step (III) and a metal analysis step (IV).
また本発明に係る分析方法は、前記気相エッチングする工程（Ｉ）が、エッチングガスをシリコンウェハ表面に接触させてエッチングする工程（Ｉ−１）と、続いて前記エッチングされた表面を不活性ガスを吹き付けて副生成物を除去する工程（Ｉ−２）とを繰り返して行うことを特徴とする。 Further, in the analysis method according to the present invention, the vapor phase etching step (I) is performed by bringing the etching gas into contact with the surface of the silicon wafer (I-1) and subsequently the etched surface is inactivated. The step (I-2) of removing a by-product by blowing gas is repeated.
また本発明に係る分析方法は、前記気相エッチングする工程（Ｉ）が、エッチングガスをシリコンウェハ表面に接触させてエッチングした後（工程（Ｉ−２））、続く工程（ＩＩ）の前に前記エッチングされた表面に水を噴霧して（工程（Ｉ−３））、表面疎水性化処理で副生成物を除去もしくは不活性化する工程（Ｉ−４）を行うことを特徴とする。 Moreover, the analysis method according to the present invention is such that the step (I) of vapor phase etching is performed by bringing an etching gas into contact with the surface of the silicon wafer and etching (step (I-2)) and before the subsequent step (II). Water is sprayed on the etched surface (step (I-3)), and a step (I-4) of removing or inactivating by-products by surface hydrophobization treatment is performed.
さらに本発明には、上で説明した本発明にかかる分析方法を実施するための装置、特に自動化された分析装置も含まれる。 Furthermore, the present invention includes an apparatus for carrying out the analysis method according to the present invention described above, particularly an automated analysis apparatus.
本発明に係る分析方法は、第１工程である分解（又はエッチング）表面に生じる種々の生成物（副生物）を除去又は不活性化処理を行い、かつその後必要であれば表面を速やかにＨＦガスで疎水性化することで、極めて再現よく効率的に、疎水性シリコンウェハ表面を水滴でスキャンして表面の分解物を回収することが可能となる。 The analysis method according to the present invention removes or inactivates various products (by-products) generated on the decomposition (or etching) surface, which is the first step, and then promptly removes the surface from HF if necessary. By hydrophobizing with gas, it becomes possible to scan the surface of the hydrophobic silicon wafer with water droplets very efficiently with high reproducibility and to collect the decomposition products on the surface.
以下本発明を図に即して実施の形態に即してさらに詳しく説明する。 Hereinafter, the present invention will be described in more detail with reference to the drawings and the embodiments.
（シリコンウェハ）
本発明の分析方法はシリコンウェハであってその表面、該表面に形成された薄膜中、あるいは表層に存在する微量の金属を分析するものである。ここでシリコンウェハのサイズ・形状には特に限定はされないが、円形、略円形、正方形、長方形、多角形が含まれる。サイズも特に制限はなく、通常公知の種々のサイズのものに適用可能である。
(Silicon wafer)
The analysis method of the present invention analyzes a trace amount of metal present on the surface of a silicon wafer, in a thin film formed on the surface, or on the surface layer. Here, the size and shape of the silicon wafer are not particularly limited, but include a circle, a substantially circle, a square, a rectangle, and a polygon. The size is not particularly limited, and can be applied to various known sizes.
図１に示されるとおり、本発明は、気相エッチングにて表面を分解する工程（Ｉ）と、さらに表面を疎水性化する処理工程（ＩＩ）と、さらに液滴で表面から分解物を回収する工程（ＩＩＩ）と、回収された液滴に基づき金属を分析する工程（Ｖ）とからなる。以下各工程について説明する。 As shown in FIG. 1, the present invention includes a step (I) for decomposing a surface by vapor-phase etching, a treatment step (II) for further hydrophobizing the surface, and further collecting a decomposition product from the surface with droplets. The process (III) which performs this, and the process (V) which analyzes a metal based on the collect | recovered droplet. Each step will be described below.
（気相エッチング工程）
本発明においてはまずシリコンウェハの分析すべき表面を所望の範囲、所望の深さで気相エッチングする（（Ｉ）工程）。気相エッチングガスの種類及び発生方法には特に制限はなく通常公知のエッチングガス又はそれらの混合ガスがそのまま、又は適当な濃度に希釈されて使用可能である。具体的には、硝酸、フッ酸（ＨＦ）、オゾン（Ｏ３）、窒素酸化物（ＮＯｘ）が挙げられる。またそれらの混合ガスも好ましく使用可能である。本発明においては特にＨＦ又はオゾン含有ＨＦ（Ｏ３／ＨＦ）の使用が好ましい。
(Gas phase etching process)
In the present invention, first, the surface of the silicon wafer to be analyzed is vapor-phase etched at a desired range and a desired depth (step (I)). There are no particular limitations on the type and generation method of the vapor-phase etching gas, and generally known etching gases or their mixed gases can be used as they are or after being diluted to an appropriate concentration. Specific examples include nitric acid, hydrofluoric acid (HF), ozone (O 3 ), and nitrogen oxide (NOx). Moreover, those mixed gases can also be used preferably. In the present invention, it is particularly preferable to use HF or ozone-containing HF (O 3 / HF).
エッチングは、これらのガスをシリコンウェハの表面に接触させることにより可能であるが、当該ガスの移送方法、ガスとシリコンウェハ表面との接触方法には特に限定はない。具体的にはガスの発生装置と、必要ならば希釈用ガスと希釈装置、シリコンウェハ表面に移送するための移送手段とを組み合わせて当該ガスを移送してシリコンウェハ表面と接触させることが可能となる。接触させるための手段としては、特に限定はないが、エッチングガスの流量と流出口の位置とを調節可能な公知の移動可能なノズルを用いてシリコンウェハの表面の望ましい位置に所望の時間、所望の量のエッチングガスと接触させることが可能である。接触はシリコンウェハ表面全体、一部分を一回又は数回に亘り接触させることが可能である。別の手段としては、シリコンウェハをチャンバー内に設置し、エッチングガスをチャンバー内に供給し、シリコンウェハの表面全体に所望の時間、所望の量のエッチングガスと接触させることも可能である。エッチング反応によりシリコンウェハは表面が加熱される場合、シリコンウェハを所定の温度に維持することが好ましい。 Etching can be performed by bringing these gases into contact with the surface of the silicon wafer, but there are no particular limitations on the method of transferring the gas and the method of contacting the gas with the surface of the silicon wafer. Specifically, the gas generator can be combined with a diluting gas, a diluting device, and a transfer means for transferring to the silicon wafer surface, if necessary, so that the gas can be transferred and brought into contact with the silicon wafer surface. Become. There are no particular limitations on the means for contacting, but a known movable nozzle that can adjust the flow rate of the etching gas and the position of the outlet is used for a desired time and a desired position on the surface of the silicon wafer. It is possible to contact with an amount of etching gas. The contact can bring the entire surface of the silicon wafer, a part, into contact once or several times. As another means, it is possible to place a silicon wafer in the chamber, supply an etching gas into the chamber, and bring the entire surface of the silicon wafer into contact with a desired amount of etching gas for a desired time. When the surface of the silicon wafer is heated by the etching reaction, it is preferable to maintain the silicon wafer at a predetermined temperature.
気相エッチング工程により、シリコンウェハの所定の量のシリコンが分解されるが、そのエッチング厚さについては特に限定はなく、分析したい深さ、位置に応じて適宜選択することが可能である。本発明においてはエッチング厚さとして通常は２μｍ程度で十分であるが、エピタキシャル層の評価までを目的とする場合１５μｍまでの深さが選択可能である。 Although a predetermined amount of silicon in the silicon wafer is decomposed by the vapor phase etching process, the etching thickness is not particularly limited, and can be appropriately selected according to the depth and position to be analyzed. In the present invention, an etching thickness of about 2 μm is usually sufficient, but a depth of up to 15 μm can be selected for the purpose of evaluating the epitaxial layer.
さらにＯ３／ＨＦエッチング工程の後、シリコンウェハの表面には種々の副生成物が付着し表面が一見曇っていることが多く係る副生成物は一般に続くＨＦによる表面疎水化処理を受けにくい性質を有する。 Furthermore, after the O 3 / HF etching process, various by-products adhere to the surface of the silicon wafer, and the surface is often cloudy at first glance. Such by-products are generally less susceptible to subsequent surface hydrophobization treatment with HF. Have
（不活性ガス吹き付け）
本発明において気相エッチングにより表面に形成される副生成物は目視で認識可能なものも含めて種々の物がエッチング直後に形成される。またそれら副生成物が、続く表面疎水性化の工程（ＩＩ）を妨げる場合が多い。図２に示される本発明において使用される不活性ガス吹き付けは、かかる生成した副生成物を除去することを可能とするものである。具体的には、不活性ガスとしては、シリコンウェハの表面に対して不活性であればよく、かつさらなる汚染とならないように清浄化処理されたガスであればよい。具体的には空気、窒素、アルゴンが挙げられる。シリコンウェハの吹き付け位置は気相エッチングの後の表面又はその周辺であればよい。吹き付け量についても特に制限はなく、副生成物が除去できる程度であればよい。吹き付けにはエッチングが進行した直後が好ましいが、特に限定されるものではない。具体的には、通常公知の吹き付け用ガスノズルを使用して、エッチングの直後の領域をトレースしながら吹き付ける方法が好ましい。
(Inert gas blowing)
In the present invention, various by-products formed on the surface by vapor-phase etching, including those that can be visually recognized, are formed immediately after etching. In addition, these by-products often prevent the subsequent surface hydrophobization step (II). The inert gas spray used in the present invention shown in FIG. 2 makes it possible to remove such produced by-products. Specifically, the inert gas only needs to be inert with respect to the surface of the silicon wafer, and may be any gas that has been cleaned to prevent further contamination. Specific examples include air, nitrogen, and argon. The silicon wafer spraying position may be the surface after the vapor phase etching or the vicinity thereof. There is no restriction | limiting in particular also about the amount of spraying, and it should just be a grade which can remove a by-product. The spraying is preferably performed immediately after the etching has progressed, but is not particularly limited. Specifically, a method of spraying while tracing a region immediately after etching using a generally known gas nozzle for spraying is preferable.
（水の噴霧）
上で説明した通り、本発明において気相エッチングにより表面に形成される副生成物は続く表面疎水性化の工程（ＩＩ）を妨げる場合が多いが、図３において示される本発明において使用される水の噴霧は、かかる生成した副生成物を次の疎水化処理で除去もしくは不活性化することを可能とするものである。具体的には、気相エッチングが行われた後、シリコンウェハのエッチングされた表面に水をミスト状にして吹き付けることで可能である。水は汚染を避けるべく超純水が好ましい。シリコンウェハの吹き付け位置は気相エッチングの後の表面又はその周辺、又はシリコンウェハの全面で、表面疎水化処理後の噴霧させた水の乾燥もしくは液滴回収処理での噴霧させた水の回収を考慮すると、吹き付け量は数十μＬ以下が好ましい。具体的には、通常公知の吹き付け用ガスノズル（ネブライザー等）を使用して、ミスト状態の水を吹き付ける方法が好ましい。
(Water spray)
As explained above, by-products formed on the surface by vapor phase etching in the present invention often prevent the subsequent surface hydrophobization step (II), but are used in the present invention shown in FIG. The spraying of water makes it possible to remove or inactivate such produced by-products by the subsequent hydrophobization treatment. Specifically, after vapor phase etching is performed, water can be sprayed on the etched surface of the silicon wafer in the form of a mist. The water is preferably ultrapure water to avoid contamination. The spraying position of the silicon wafer is the surface after vapor phase etching or the periphery thereof, or the entire surface of the silicon wafer, and the sprayed water is recovered by the drying of the sprayed water after the surface hydrophobization process or the droplet recovery process. Considering this, the spraying amount is preferably several tens of μL or less. Specifically, a method of spraying water in a mist state using a generally known gas nozzle for spraying (nebulizer or the like) is preferable.
（表面疎水性化処理）
吹き付け量についても特に制限はなく、副生成物が除去できる程度であればよい。本発明の工程（Ｉ−４）および（ＩＩ）は、上で得られた気相エッチングされたシリコンウェハの表面を通常公知の方法で疎水性化することである。本発明においては具体的には、ＨＦガスの吹き付け装置を使用して、シリコンウェハ全面に吹き付ける方法が好ましい。ウェハ表面を均一な疎水面に仕上げるため、ＨＦガスの吹き付けタイミングは、ミストの乾燥むらが生じる前（前記の水の噴霧の直後）に行うことが好ましい。
(Surface hydrophobization treatment)
There is no restriction | limiting in particular also about the amount of spraying, and it should just be a grade which can remove a by-product. Steps (I-4) and (II) of the present invention are to make the surface of the vapor-etched silicon wafer obtained above hydrophobic by a generally known method. In the present invention, specifically, a method of spraying the entire surface of the silicon wafer using a HF gas spraying device is preferable. In order to finish the wafer surface into a uniform hydrophobic surface, it is preferable to perform the HF gas spraying timing before the mist drying unevenness occurs (immediately after the water spraying).
（液滴回収処理）
本発明の工程（ＩＩＩ）は、上で得られた疎水性化処理された表面を、液滴でスキャンすることで、表面の汚染物を溶解して液滴内に回収し、回収された液滴を適当な水等の溶媒で希釈し、分析工程（ＩＶ）への準備とする工程である。本発明において、疎水性のシリコンウェハの表面を液滴でスキャンして、表面の汚染物を溶解して回収する方法、装置については特に制限なく通常公知の方法・装置が好ましく使用できる。
(Droplet recovery process)
In the step (III) of the present invention, the surface obtained by the above hydrophobization treatment is scanned with droplets, so that surface contaminants are dissolved and collected in the droplets. In this step, the droplet is diluted with a suitable solvent such as water to prepare for the analysis step (IV). In the present invention, the method and apparatus for scanning the surface of the hydrophobic silicon wafer with droplets and dissolving and recovering contaminants on the surface are not particularly limited, and generally known methods and apparatuses can be preferably used.
（金属分析）
本発明の工程（ＶＩ）は、上の工程（ＩＩＩ）で得られた汚染物の溶解した液滴から調製された分析用溶液を種々の分析装置を用いて分析する工程である。分析方法・装置は分析対象に依存して選択することが可能である。具体的には金属イオンの分析には通常公知のＡＡ、ＩＣＰＭＳ等が好ましく使用可能である。
(Metal analysis)
The step (VI) of the present invention is a step of analyzing the analytical solution prepared from the contaminated droplets obtained in the above step (III) using various analyzers. The analysis method / apparatus can be selected depending on the analysis target. Specifically, generally known AA, ICPMS, etc. can be preferably used for the analysis of metal ions.
以下実施例を用いて本発明をさらに詳しく説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
（実施例１） 空気吹きつけの具体的な方法と結果を示した。
８インチシリコンウェハ｛（Ｐ型、１０〜１５Ωｃｍ、主面方位（１００）｝を準備した。シリコンウェハ表面の自然酸化膜を除去するため、５０ｗｔ％ＨＦ溶液が２００ｍＬ入ったガス洗浄瓶に２Ｌ／分の流量でＮ２ガスを流しバブリングさせ、生じたＨＦガスをノズルからウェハに向けて６分間程度照射した。
(Example 1) The specific method and result of air blowing were shown.
An 8-inch silicon wafer {(P type, 10 to 15 Ωcm, main surface orientation (100)}) was prepared.To remove the natural oxide film on the silicon wafer surface, 2 L / in a gas cleaning bottle containing 200 mL of 50 wt% HF solution. Bubbling was performed by flowing N 2 gas at a flow rate of minutes, and the generated HF gas was irradiated from the nozzle toward the wafer for about 6 minutes.
その後、このウェハにオゾンガス（１５０ｇ／ｍ３、０．２５Ｌ／分）とＨＦガス（５０ｗｔ％ＨＦ溶液が２００ｍＬ入ったガス洗浄瓶に２Ｌ／分の流量でＮ２ガスをバブリング）の混合ガスを照射した。混合ガスがウェハ上に照射されるとその部分が瞬時に白っぽく曇りながらエッチングが進行した。この状態でエッチング１０分間行った毎にウェハ表面に直接エアーを１０秒程度ブローして乾燥させた場合と、エッチング１分間行った毎にウェハ表面に直接エアーを１０秒間程度ブローして乾燥させた場合とで、ウェハ表面（鏡面）への残渣生成状態を目視にて比較した。 After that, a mixed gas of ozone gas (150 g / m 3 , 0.25 L / min) and HF gas (bubbling N 2 gas at a flow rate of 2 L / min into a gas cleaning bottle containing 200 mL of 50 wt% HF solution) was applied to this wafer. Irradiated. When the mixed gas was irradiated onto the wafer, the etching proceeded while the portion was immediately whitish and cloudy. In this state, every time etching is performed for 10 minutes, air is blown directly on the wafer surface for about 10 seconds and dried, and every time etching is performed for 1 minute, air is blown directly on the wafer surface for about 10 seconds and dried. In some cases, the residue generation state on the wafer surface (mirror surface) was visually compared.
０．１〜２．０μｍ程度の平均エッチング量になるように、複数のウェハに対してエッチング時間を変更してサンプルを作成した。エッチング量は静電容量式センサーでエッチング前後の平均厚みを計測することにより算出した。その結果を表１に示した。残渣の生成はエッチング量に依存する傾向は見られず、エッチング中に表面をエアーブローして乾燥させる頻度に依存する傾向があることが分かる。 Samples were prepared by changing the etching time for a plurality of wafers so that the average etching amount was about 0.1 to 2.0 μm. The etching amount was calculated by measuring the average thickness before and after etching with a capacitance sensor. The results are shown in Table 1. It can be seen that the generation of the residue does not tend to depend on the etching amount, but tends to depend on the frequency of drying the surface by air blowing during etching.
（実施例２）ミスト吹きつけの具体的な方法と結果を示した。
８インチシリコンウェハ｛（Ｐ型、１０〜１５Ωｃｍ、主面方位（１００））｝を準備した。シリコンウェハ表面の自然酸化膜を除去するため、５０ｗｔ％ＨＦ溶液が２００ｍＬ入ったガス洗浄瓶に２Ｌ／分の流量でＮ２ガスを流しバブリングし、生じたＨＦガスをノズルからウェハに向けて６分間程度照射した。
(Example 2) A specific method and result of mist spraying are shown.
An 8-inch silicon wafer {(P type, 10 to 15 Ωcm, principal plane orientation (100))} was prepared. In order to remove the natural oxide film on the silicon wafer surface, N 2 gas was bubbled at a flow rate of 2 L / min into a gas cleaning bottle containing 200 mL of 50 wt% HF solution, and the generated HF gas was directed from the nozzle toward the wafer. Irradiated for about minutes.
このウェハにオゾンガス（１５０ｇ／ｍ３、０．２５Ｌ／分）とＨＦガス（５０ｗｔ％ＨＦ溶液が２００ｍＬ入ったガス洗浄瓶に２Ｌ／分の流量でＮ２ガスをバブリング）の混合ガスを、０．１〜２．０μｍ程度の平均エッチング量になるように、複数のウェハに対してエッチング時間を変更してサンプルを作成した。 A mixed gas of ozone gas (150 g / m 3 , 0.25 L / min) and HF gas (a gas cleaning bottle containing 200 mL of a 50 wt% HF solution was bubbled with N 2 gas at a flow rate of 2 L / min) was added to this wafer. Samples were prepared by changing the etching time for a plurality of wafers so that the average etching amount was about 1 to 2.0 μm.
エッチング量は静電容量式センサーでエッチング前後の平均厚みを計測することにより算出した。ミストの吹き付けありの水準はネブライザー（吹き出し流量１００μＬ／分）を用い、１０秒間程度ウェハ全面に均一に分布するように行った。その後、上記エッチングで用いたのと同じノズルを使用し、ＨＦガス（５０ｗｔ％ＨＦ溶液が２００ｍＬ入ったガス洗浄瓶に２Ｌ／分の流量でＮ２ガスをバブリング）を６〜１０分間ほどウェハに照射した。ミスト吹き付けなしの水準は、エッチング後のウェハ表面に上記ＨＦガスを６〜１５０分間ほど照射した。その後、各々のウェハに対して液滴回収装置を用いて（液滴量２００μＬ、スキャンスピード２５ｍｍ／秒、トラックピッチ３ｍｍ）液滴がウェハ表面全体を最後までスキャンできるかを確認した。その結果を表２に示した。 The etching amount was calculated by measuring the average thickness before and after etching with a capacitance sensor. A level with mist spraying was performed using a nebulizer (blowing flow rate 100 μL / min) so that it was uniformly distributed over the entire surface of the wafer for about 10 seconds. Then, using the same nozzle as used in the above etching, HF gas (bubbling N 2 gas at a flow rate of 2 L / min into a gas cleaning bottle containing 200 mL of 50 wt% HF solution) is applied to the wafer for about 6 to 10 minutes. Irradiated. As for the level without mist spraying, the wafer surface after etching was irradiated with the HF gas for 6 to 150 minutes. Then, using a droplet collection device for each wafer (droplet amount 200 μL, scan speed 25 mm / second, track pitch 3 mm), it was confirmed whether the droplet could scan the entire wafer surface to the end. The results are shown in Table 2.
オゾンガスでエッチングした後の表面は、ＨＦガスに暴露させただけではどんなに時間をかけても、液滴をスキャンできるほどの疎水面を得ることはできず、ＨＦガスを暴露させる前に、僅か約１０〜２０μＬ程度の超純水をミスト状にして表面に吹き付けるだけで、１０分間以内のＨＦガス暴露で、液滴がウェハ表面を十分にスキャンできるほどの疎水面を得ていることが分かる。 The surface after etching with ozone gas cannot obtain a hydrophobic surface that can scan the droplets, no matter how long it takes to be exposed to HF gas. It can be seen that by simply spraying the surface with about 10 to 20 μL of ultrapure water as a mist, the surface of the wafer can be sufficiently scanned by HF gas exposure within 10 minutes.
本発明に係る方法は、広くシリコンウェハ表面の超微量不純物金属の分析、特に自動分析の分野に利用可能である。 The method according to the present invention can be widely used in the field of analysis of ultra-trace impurity metals on the surface of a silicon wafer, in particular, automatic analysis.
Claims (3)
シリコンウェハ表面を気相エッチングして分解する工程（Ｉ）と、
表面を疎水性化処理する工程（ＩＩ）と、
表面を液滴でスキャンして分解物を回収する工程（ＩＩＩ）と、
回収した分解物の金属を分析する工程（ＩＶ）からなり、
前記工程（Ｉ）が、気相エッチングする工程（Ｉ−１）と、該エッチングによる副生成物を不活性ガスを吹き付けることにより除去・不活性化する工程（Ｉ−２）とを含むことを特徴とする分析方法。 A method for analyzing ultra-trace impurity metals on the surface of a silicon wafer,
A step (I) of decomposing the silicon wafer surface by vapor phase etching;
A step (II) of hydrophobizing the surface;
A step (III) of recovering decomposition products by scanning the surface with droplets;
Analyzing the metals recovered decomposition product (IV) Tona is,
The step (I) includes a step (I-1) of performing vapor phase etching, and a step (I-2) of removing and inactivating the by-product obtained by the etching by blowing an inert gas. Characteristic analysis method.
シリコンウェハ表面を気相エッチングして分解する工程（Ｉ）と、
表面を疎水性化処理する工程（ＩＩ）と、
表面を液滴でスキャンして分解物を回収する工程（ＩＩＩ）と、
回収した分解物の金属を分析する工程（ＩＶ）からなり、
前記工程（Ｉ）が、次のＨＦガスによる疎水化工程（ＩＩ）の前に、表面に水を噴霧する工程（Ｉ−３）により副生成物を続く疎水化処理で除去もしくは不活性化する工程（Ｉ−４）を含むことを特徴とする分析方法。 A method for analyzing ultra-trace impurity metals on the surface of a silicon wafer,
A step (I) of decomposing the silicon wafer surface by vapor phase etching;
A step (II) of hydrophobizing the surface;
A step (III) of recovering decomposition products by scanning the surface with droplets;
Analyzing the metals recovered decomposition product (IV) Tona is,
In the step (I), the by-product is removed or inactivated by the subsequent hydrophobization treatment by the step (I-3) of spraying water on the surface before the hydrophobization step (II) with the next HF gas. The analysis method characterized by including a process (I-4) .
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