WO2019087517A1 - Method for manufacturing soi wafer having thin-film soi layer - Google Patents

Method for manufacturing soi wafer having thin-film soi layer Download PDF

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WO2019087517A1
WO2019087517A1 PCT/JP2018/030247 JP2018030247W WO2019087517A1 WO 2019087517 A1 WO2019087517 A1 WO 2019087517A1 JP 2018030247 W JP2018030247 W JP 2018030247W WO 2019087517 A1 WO2019087517 A1 WO 2019087517A1
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soi layer
film
soi
oxide film
thickness
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French (fr)
Japanese (ja)
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阿賀　浩司
横川　功
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信越半導体株式会社
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier
    • H01L27/12—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier the substrate being other than a semiconductor body, e.g. an insulating body

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  • the present invention relates to a method of manufacturing an SOI wafer, and in particular, it is called FDSOI (Fully Depleted Silicon-On-Insulator), and requires extremely thin SOI layer film thickness and high SOI layer film thickness uniformity.
  • FDSOI Fluly Depleted Silicon-On-Insulator
  • SOI wafer As one of wafers for semiconductor devices, there is an SOI wafer in which a silicon layer (hereinafter, also referred to as an SOI layer or an SOI film) is formed on a buried oxide film which is an insulating film.
  • the SOI layer in the surface layer portion to be a device manufacturing region is electrically separated from the inside of the substrate by the buried insulating layer (buried oxide film layer (BOX layer)), so parasitic capacitance is small and radiation resistance It has features such as high ability. Therefore, effects such as high speed / low power consumption operation and soft error prevention are expected, and it is regarded as promising as a substrate for high performance semiconductor devices.
  • BOX layer buried oxide film layer
  • Patent Document 1 describes film thinning by etching using a mixed solution of HF and ozone in final film thickness adjustment of the SOI layer.
  • Patent Document 2 after adjusting the final film thickness of the SOI layer, after forming an oxide film on the surface of the SOI layer with ozone water, the oxide film is removed to thin the film thickness of the SOI layer.
  • Patent Document 3 describes thinning of the thickness of the SOI layer by ozone water + HF in adjusting the final thickness of the SOI layer.
  • JP 2007-266059 A Japanese Patent Laid-Open No. 2004-343013 Japanese Patent Application Laid-Open No. 2004-349493
  • the thickness of the natural oxide film is about 1 to 2 nm
  • the thickness at which the SOI layer becomes thinner by the growth is about 0.5 to 1 nm at the most. Therefore, even if the elapsed time after completion of the manufacture of the SOI wafer is long and the natural oxide film on the surface of the SOI layer is grown to the extent of saturation before being introduced into the device process, the SOI layer is thick to some extent In the case of a wafer, the difference from the thickness of the SOI layer at the time of product shipment is an error level, so no particular problem occurs.
  • the present invention has been made in view of the above problems, and even if it is an SOI wafer having a thin film SOI layer with a film thickness of 20 nm or less, the film thickness is almost constant regardless of the length of elapsed time after the completion of manufacturing. It is an object of the present invention to provide a method of manufacturing an SOI wafer having a thin film SOI layer having
  • the present invention is a method of manufacturing an SOI wafer having a thin film SOI layer, After an SOI layer having a film thickness of 20 nm or less is formed as the thin film SOI layer to produce an SOI wafer, As a final chemical solution cleaning step, cleaning is performed using a cleaning chemical solution capable of forming an oxide film on the surface of the thin film SOI layer to form an oxide film of 1 nm or more on the surface of the thin film SOI layer, After that, drying is performed without removing the oxide film formed by the cleaning to obtain a product.
  • a method of manufacturing an SOI wafer having a thin film SOI layer is provided.
  • the SOI wafer which has a thin film SOI layer (hereinafter referred to simply as an SOI layer) of 20 nm or less according to the present invention, even if the elapsed time after the final chemical solution cleaning step becomes extremely long, It is possible to suppress the growth of the natural oxide film. Therefore, to reduce the difference between the film thickness of the SOI layer after the final chemical solution cleaning step and the film thickness of the SOI layer after a long time (when the device process is introduced) (hereinafter, also referred to as a film thickness difference of the SOI layer due to the time). Can.
  • the film thickness of the SOI layer can be managed almost uniformly, and the occurrence of a problem (such as an adverse effect on the device process) caused by the above-mentioned difference can be prevented.
  • a problem such as an adverse effect on the device process
  • the formation of the oxide film for that purpose is performed in the final chemical solution cleaning step, it is not necessary to separately add a process such as heat treatment for forming the oxide film, and cost increase can be avoided.
  • the cleaning liquid capable of forming the oxide film can be used as ozone water.
  • the cleaning chemical solution is ozone water, a relatively dense oxide film can be formed, so that there is an advantage that the effect of suppressing the subsequent natural oxide film growth is higher.
  • the film thickness of the thin film SOI layer to be formed can be 15 nm or less.
  • the difference between the film thickness of the SOI layer after the final chemical solution cleaning step and the film thickness after a long time can be reduced.
  • An adverse effect can be prevented from occurring.
  • FIG. 4 shows the relationship between the film thickness of the surface oxide film (natural oxide film) and the elapsed time (days).
  • FIG. 5 shows the relationship between the thickness of the SOI layer and the elapsed time.
  • the oxide film thickness immediately after the final cleaning was about 0.9 nm and did not reach 1 nm.
  • FIG. 4 it can be seen that as the number of days elapsed after cleaning increases, the thickness of the natural oxide film gradually increases.
  • FIG. 5 it can be seen that the film thickness of the SOI layer gradually decreases.
  • the present inventors form an oxide film of 1 nm or more with the cleaning chemical, and pass through the drying step without removing the oxide film to obtain a product, thereby naturally oxidizing the conventional product as described above.
  • the inventors have found that it is possible to prevent an increase in the film thickness of the film (a decrease in the film thickness of the SOI layer) and complete the present invention.
  • an SOI wafer having an SOI layer formed on an insulating layer is manufactured.
  • the SOI wafer prepared here may be a wafer having an SOI structure in which an SOI layer having a thickness of 20 nm or less is formed at least on an insulating layer.
  • a wafer having a structure in which an insulating layer is formed on a supporting layer of single crystal silicon or the like (embedded insulating layer: BOX layer) and an SOI layer is formed on the embedded insulating layer can be mentioned.
  • the manufacturing method of the SOI wafer is not particularly limited. For example, a step of bonding a bond wafer having a microbubble layer formed by ion implantation and a base wafer to be a supporting substrate through an insulating film, and the microbubble layer And forming a thin film on the base wafer by separating the bond wafer at the boundary of the base wafer and forming a thin film on the base wafer.
  • the above-mentioned ion implantation peeling method (so-called Smart Cut (registered trademark) method), rT-CCP method (also called room temperature mechanical peeling method, SiGen method), or SIMOX method (Separation by Implanted Oxygen method) , Etc. regardless of the manufacturing method of the SOI wafer.
  • the SOI layer when forming the SOI layer of 20 nm or less, the SOI layer can be thinned by appropriately performing, for example, surface polishing, sacrificial oxidation treatment, or the like, as necessary, to obtain a target film thickness. Since the cleaning to form an oxide film is performed as a final chemical solution cleaning step described later, the stage of manufacturing this SOI wafer (that is, the SOI wafer is formed) in consideration of the thickness of the SOI layer to be reduced by the oxide film formed by the cleaning. It is necessary to adjust the film thickness of the SOI layer immediately before the final chemical solution cleaning step.
  • the present invention capable of suppressing a change in the thickness of the SOI layer is more effective.
  • the lower limit of the thickness of the SOI layer is not particularly limited, and may be larger than 0 nm. The thinner the film thickness, the higher the effectiveness of the invention.
  • the natural oxide film already formed on the surface of the SOI layer may be removed after forming the SOI layer having a predetermined film thickness by immersing in an aqueous solution containing HF. By this, the contaminant adhering to the surface of the natural oxide film can be removed together with the natural oxide film.
  • an oxide film can be formed on the surface of the SOI layer for the SOI wafer manufactured as described above. Perform cleaning using a cleaning solution. Then, an oxide film of 1 nm or more is formed by this cleaning.
  • a cleaning chemical solution used in this final chemical solution cleaning process for example, ozone water, SC1 (mixed aqueous solution of NH 4 OH and H 2 O 2 ), SC 2 (mixed aqueous solution of HCl and H 2 O 2 ), etc.
  • FIG. 2 shows the relationship between the cleaning time with ozone water and the oxide film thickness (the surface oxide film thickness on the SOI layer) formed by the cleaning. Cleaning was performed in advance with dilute hydrofluoric acid, and then cleaning was performed using ozone water while changing the cleaning time. Three minute patterns of 1 minute, 2 minutes and 3 minutes were set as the cleaning time. It can be seen from FIG. 2 that the results described above are obtained.
  • FIG. 3 shows the relationship between the amount of change in film thickness of the surface oxide film and the SOI layer ( ⁇ film thickness) and elapsed time when the cleaning time is 3 minutes.
  • ⁇ film thickness the film thickness of the surface oxide film increases only by about 0.03 nm after about 70 days
  • the change in the thickness of the SOI layer is remarkably suppressed.
  • An oxide film of 1 nm or more is formed in this final chemical solution cleaning step, and the product is left as it is without removing this oxide film as will be described later, thereby making the product more natural than the SOI wafer manufactured by the conventional manufacturing method.
  • An increase in the thickness of the oxide film can be suppressed, and a difference in the thickness of the SOI layer due to the passage of time can be remarkably suppressed.
  • the value of the film thickness difference of the SOI layer over time can be reduced to half or less than that of the conventional one.
  • the thickness of the oxide film to be formed may be 1 nm or more, preferably 1.1 nm or more, and more preferably 1.2 nm or more. By forming a film having such a film thickness, it is possible to more reliably suppress the decrease in the film thickness of the SOI layer.
  • the upper limit of the thickness of the oxide film to be formed is not particularly limited as long as it can be formed in the final chemical solution cleaning step, but in general, about 2.0 nm is sufficient.
  • the drying step for example, rinsing with pure water can be performed as required without removing the formed oxide film.
  • the drying method itself is not particularly limited, and any method such as air drying or spin drying may be used as long as the formed oxide film can be dried without being removed.
  • the product SOI wafer is packaged in a shipping box and shipped to the client.
  • the difference in film thickness of the SOI layer due to the elapsed time can be remarkably reduced.
  • the decrease in the thickness of the SOI layer due to the increase in the thickness of the native oxide film can be suppressed, and the device process caused by the change in film thickness It is possible to prevent the occurrence of the adverse effect of
  • the oxide film can be formed by the cleaning chemical during the final chemical cleaning process, it is not necessary to separately provide a process for forming the oxide film such as a heat treatment process. It is possible to save labor, time, and costs as compared to the case of providing those processes. Therefore, it is possible to provide the client with the SOI wafer in which the SOI film thickness is managed more accurately and accurately, without cost.
  • ozone water ozone concentration: 12 ppm, 3 minutes
  • the oxide film on the surface of the SOI layer was left without being removed with the above film thickness.
  • ozone water ozone concentration 12 ppm, 1 minute
  • Table 1 summarizes the various conditions and measurement results of the above-described Examples 1 and 2 and Comparative Examples 1 and 2.
  • Example 1 As shown in Table 1, comparing Example 1 and Comparative Example 1 in which the thickness of the SOI layer immediately after the final chemical solution cleaning step is 12.04 nm, the thickness reduction of the SOI layer in Example 1 is 0. In contrast to 03 nm, in Comparative Example 1, it was 0.08 nm. Also, comparing Example 2 and Comparative Example 2 in which both the SOI layer film thickness immediately after the final chemical solution cleaning step is 19.98 nm, the thickness reduction amount of the SOI layer film thickness in Example 2 is 0.04 nm. In contrast, in Comparative Example 2, it was 0.09 nm.
  • the present invention since the growth of the natural oxide film on the surface of the SOI layer formed after a long period of time immediately after the final chemical solution cleaning step can be suppressed, Compared to the conventional case (when the film thickness of the natural oxide film immediately after the final step is thinner than 1 nm), it can be reduced to half or less.
  • ozone water was used in the final chemical solution cleaning step, but in the case where an oxide film of 1 nm or more is separately formed using SC1 and SC2 separately, similarly to the first and second embodiments, The thickness reduction of the SOI layer after a long period of time could be significantly suppressed.
  • the present invention is not limited to the above embodiment.
  • the above embodiment is an exemplification, and it has substantially the same configuration as the technical idea described in the claims of the present invention, and any one having the same function and effect can be used. It is included in the technical scope of the invention.

Abstract

The present invention relates to a method for manufacturing an SOI wafer which has a thin-film SOI layer, the method including: forming, as a thin-film SOI layer, an SOI layer having a film thickness of 20 nm or less to prepare an SOI wafer; then, as a final chemical solution cleaning step, performing cleaning using a cleaning chemical solution capable of forming an oxide film on the surface of the thin-film SOI layer; forming an oxide film having a thickness of 1 nm or more on the surface of the thin-film SOI layer; and thereafter drying without removing the oxide film formed by the cleaning, thereby obtaining a product of an SOI wafer having the thin-film SOI layer. In this way, the present invention provides a method for manufacturing an SOI wafer which has a thin-film SOI layer having a substantially constant film thickness irrespective of the length of time elapsed from the completion of manufacturing even if the SOI wafer has a thin-film SOI layer having a film thickness of 20 nm or less.

Description

薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法Method of manufacturing SOI wafer having thin film SOI layer
　本発明は、ＳＯＩウェーハの製造方法に関し、特に、ＦＤＳＯＩ（Ｆｕｌｌｙ　Ｄｅｐｌｅｔｅｄ　Ｓｉｌｉｃｏｎ－Ｏｎ－Ｉｎｓｕｌａｔｏｒ：完全空乏型ＳＯＩ）と呼ばれ、極めて薄いＳＯＩ層膜厚と、高いＳＯＩ層膜厚均一性が要求されるＳＯＩウェーハの製造方法に関する。 The present invention relates to a method of manufacturing an SOI wafer, and in particular, it is called FDSOI (Fully Depleted Silicon-On-Insulator), and requires extremely thin SOI layer film thickness and high SOI layer film thickness uniformity. A method of manufacturing an SOI wafer.
　半導体素子用のウェーハの一つとして、絶縁膜である埋め込み酸化膜の上にシリコン層（以下、ＳＯＩ層、またはＳＯＩ膜ともいう）を形成したＳＯＩウェーハがある。このＳＯＩウェーハは、デバイス作製領域となる基板表層部のＳＯＩ層が埋め込み絶縁層（埋め込み酸化膜層（ＢＯＸ層））により基板内部と電気的に分離されているため、寄生容量が小さく、耐放射性能力が高いなどの特徴を有する。そのため、高速・低消費電力動作、ソフトエラー防止などの効果が期待され、高性能半導体素子用の基板として有望視されている。 As one of wafers for semiconductor devices, there is an SOI wafer in which a silicon layer (hereinafter, also referred to as an SOI layer or an SOI film) is formed on a buried oxide film which is an insulating film. In this SOI wafer, the SOI layer in the surface layer portion to be a device manufacturing region is electrically separated from the inside of the substrate by the buried insulating layer (buried oxide film layer (BOX layer)), so parasitic capacitance is small and radiation resistance It has features such as high ability. Therefore, effects such as high speed / low power consumption operation and soft error prevention are expected, and it is regarded as promising as a substrate for high performance semiconductor devices.
　このＳＯＩ層という薄い層に関して、目的の値の膜厚を有するものが得られるよう、様々な膜厚調整方法がとられている（例えば、特許文献１－３）。
　特許文献１では、ＳＯＩ層の最終の膜厚調整において、ＨＦとオゾンの混合液を用いたエッチングによる薄膜化が記載されている。また、特許文献２では、ＳＯＩ層の最終の膜厚調整において、オゾン水によりＳＯＩ層表面に酸化膜を形成後、該酸化膜を除去してＳＯＩ層膜厚の薄膜化を行っている。また、特許文献３では、ＳＯＩ層の最終の膜厚調整において、オゾン水＋ＨＦによるＳＯＩ層膜厚の薄膜化が記載されている。 Various film thickness adjustment methods have been taken to obtain a thin film of the SOI layer having a target value (for example, Patent Documents 1 to 3).
Patent Document 1 describes film thinning by etching using a mixed solution of HF and ozone in final film thickness adjustment of the SOI layer. Further, in Patent Document 2, after adjusting the final film thickness of the SOI layer, after forming an oxide film on the surface of the SOI layer with ozone water, the oxide film is removed to thin the film thickness of the SOI layer. Further, Patent Document 3 describes thinning of the thickness of the SOI layer by ozone water + HF in adjusting the final thickness of the SOI layer.
特開２００７－２６６０５９号公報JP 2007-266059 A 特開２００４－３４３０１３号公報Japanese Patent Laid-Open No. 2004-343013 特開２００４－３４９４９３号公報Japanese Patent Application Laid-Open No. 2004-349493
　ところで、ＦＤＳＯＩと呼ばれる完全空乏形デバイス用のＳＯＩウェーハではＳＯＩ層膜厚の高い制御性が求められるが、通常のＲＣＡ洗浄をしたウェーハは洗浄後の経過時間に応じて表面に自然酸化膜が成長する。本発明者らが、鋭意研究を行ったところ、この自然酸化膜は空気中の酸素とＳＯＩ層表面のＳｉとが反応したもので、反応が進むに従って、表面酸化膜は厚くなり、ＳＯＩ層膜厚は薄くなる傾向が見られ、ＳＯＩ層膜厚が経過時間に依存して変化する事がわかった。 By the way, although a high controllability of the SOI layer film thickness is required in an SOI wafer for a fully depleted device called FDSOI, a natural oxide film grows on the surface according to the elapsed time after cleaning in a wafer subjected to ordinary RCA cleaning. Do. The inventors of the present invention conducted intensive studies, and this natural oxide film is a reaction of oxygen in air with Si on the surface of the SOI layer, and as the reaction proceeds, the surface oxide film becomes thicker, and the SOI layer film The thickness tended to decrease, and it was found that the thickness of the SOI layer changed depending on the elapsed time.
　この際、自然酸化膜の膜厚は１～２ｎｍ程度の厚さであるため、その成長によってＳＯＩ層が薄くなる厚さは高々０．５～１ｎｍ程度である。従って、たとえＳＯＩウェーハの製造完了後の経過時間が長く、デバイスプロセスに投入されるまでの間にＳＯＩ層表面の自然酸化膜厚が飽和する程度にまで成長したとしても、ＳＯＩ層がある程度厚いＳＯＩウェーハの場合には、製品出荷時のＳＯＩ層膜厚との差異は誤差レベルになるため、特に問題は発生しない。 At this time, since the thickness of the natural oxide film is about 1 to 2 nm, the thickness at which the SOI layer becomes thinner by the growth is about 0.5 to 1 nm at the most. Therefore, even if the elapsed time after completion of the manufacture of the SOI wafer is long and the natural oxide film on the surface of the SOI layer is grown to the extent of saturation before being introduced into the device process, the SOI layer is thick to some extent In the case of a wafer, the difference from the thickness of the SOI layer at the time of product shipment is an error level, so no particular problem occurs.
　しかしながら、２０ｎｍ以下のＳＯＩ層膜厚が要求されるＦＤＳＯＩ用などのＳＯＩウェーハでは、ＳＯＩ層が薄くなる厚さが０．５～１ｎｍ程度であっても無視できる膜厚の変化（減厚）ではなく、製品出荷時のＳＯＩ層膜厚と、実際にデバイスプロセスに投入する際のＳＯＩ層膜厚との差異の比率が大きくなるため、デバイスプロセスに悪影響を及ぼすという問題があった。 However, in the case of an SOI wafer for FDSOI or the like, which requires a film thickness of SOI layer of 20 nm or less, the change in thickness (reduction of thickness) which can be ignored even if the thickness of the SOI layer becomes thin is about 0.5 to 1 nm. Instead, the ratio of the difference between the thickness of the SOI layer at the time of product shipment and the thickness of the SOI layer at the time of actual introduction to the device process becomes large, which adversely affects the device process.
　本発明は上記問題点に鑑みなされたものであり、膜厚が２０ｎｍ以下の薄膜ＳＯＩ層を有するＳＯＩウェーハであっても、製造完了後の経過時間の長さに関係なく、ほぼ一定の膜厚を有する薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法を提供することを目的とする。 The present invention has been made in view of the above problems, and even if it is an SOI wafer having a thin film SOI layer with a film thickness of 20 nm or less, the film thickness is almost constant regardless of the length of elapsed time after the completion of manufacturing. It is an object of the present invention to provide a method of manufacturing an SOI wafer having a thin film SOI layer having
　上記目的を達成するために、本発明は、薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法であって、
　前記薄膜ＳＯＩ層として膜厚が２０ｎｍ以下のＳＯＩ層を形成してＳＯＩウェーハを作製した後、
　最終薬液洗浄工程として、前記薄膜ＳＯＩ層の表面に酸化膜を形成可能な洗浄薬液を用いた洗浄を行って前記薄膜ＳＯＩ層の表面に１ｎｍ以上の酸化膜を形成し、
　その後、該洗浄で形成した酸化膜を除去することなく、乾燥を行って製品とすることを特徴とする薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法を提供する。 In order to achieve the above object, the present invention is a method of manufacturing an SOI wafer having a thin film SOI layer,
After an SOI layer having a film thickness of 20 nm or less is formed as the thin film SOI layer to produce an SOI wafer,
As a final chemical solution cleaning step, cleaning is performed using a cleaning chemical solution capable of forming an oxide film on the surface of the thin film SOI layer to form an oxide film of 1 nm or more on the surface of the thin film SOI layer,
After that, drying is performed without removing the oxide film formed by the cleaning to obtain a product. A method of manufacturing an SOI wafer having a thin film SOI layer is provided.
　このような本発明の２０ｎｍ以下という薄膜ＳＯＩ層（以下、単にＳＯＩ層ともいう）を有するＳＯＩウェーハの製造方法であれば、最終薬液洗浄工程後の経過時間が極めて長時間になったとしても、自然酸化膜の成長を抑制できる。従って、最終薬液洗浄工程後のＳＯＩ層膜厚と長時間経過後（デバイスプロセス投入時）のＳＯＩ層膜厚との差異（以下、時間経過によるＳＯＩ層の膜厚差異ともいう）を低減することができる。そのため、ＳＯＩ層膜厚をほぼ一定に管理でき、上記差異を起因とする問題（デバイスプロセスへの悪影響等）の発生を防ぐことが可能である。
　また、そのための酸化膜の形成を最終薬液洗浄工程で行うので、酸化膜を形成するための熱処理等のプロセスを別途付加する必要がなく、コストアップを回避できる。 If it is a manufacturing method of the SOI wafer which has a thin film SOI layer (hereinafter referred to simply as an SOI layer) of 20 nm or less according to the present invention, even if the elapsed time after the final chemical solution cleaning step becomes extremely long, It is possible to suppress the growth of the natural oxide film. Therefore, to reduce the difference between the film thickness of the SOI layer after the final chemical solution cleaning step and the film thickness of the SOI layer after a long time (when the device process is introduced) (hereinafter, also referred to as a film thickness difference of the SOI layer due to the time). Can. Therefore, the film thickness of the SOI layer can be managed almost uniformly, and the occurrence of a problem (such as an adverse effect on the device process) caused by the above-mentioned difference can be prevented.
In addition, since the formation of the oxide film for that purpose is performed in the final chemical solution cleaning step, it is not necessary to separately add a process such as heat treatment for forming the oxide film, and cost increase can be avoided.
　このとき、前記酸化膜形成可能な洗浄薬液をオゾン水とすることができる。 At this time, the cleaning liquid capable of forming the oxide film can be used as ozone water.
　このように上記洗浄薬液がオゾン水であれば、比較的緻密な酸化膜を形成することができるので、その後の自然酸化膜成長を抑制する効果がより高いという利点がある。 As described above, if the cleaning chemical solution is ozone water, a relatively dense oxide film can be formed, so that there is an advantage that the effect of suppressing the subsequent natural oxide film growth is higher.
　また、前記形成する薄膜ＳＯＩ層の膜厚を１５ｎｍ以下とすることができる。 Further, the film thickness of the thin film SOI layer to be formed can be 15 nm or less.
　１５ｎｍ以下という極めて薄いＳＯＩ層膜厚が必要とされる場合には、最終薬液洗浄工程後（あるいは製品出荷時）のＳＯＩ層膜厚と、実際にデバイスプロセスに投入する際のＳＯＩ層膜厚との差異の比率がかなり大きくなる。そのため、１５ｎｍ以下のＳＯＩ層を有するＳＯＩウェーハを製造するにあたって本発明の製造方法を適用することは、デバイスプロセスに悪影響が生じるのを防ぐ上で、特に有効である。 When an extremely thin SOI layer film thickness of 15 nm or less is required, the SOI layer film thickness after the final chemical solution cleaning step (or at the time of product shipment), and the SOI layer film thickness when actually introduced into the device process The ratio of the difference between Therefore, application of the manufacturing method of the present invention in manufacturing an SOI wafer having an SOI layer of 15 nm or less is particularly effective in preventing adverse effects on device processes.
　本発明のＳＯＩウェーハの製造方法であれば、最終薬液洗浄工程後と長時間経過後のＳＯＩ層膜厚との差異を低減でき、ＳＯＩ層の膜厚変化により長時間経過後のデバイスプロセス等で悪影響が生じるのを防ぐことができる。また、そのための酸化膜の形成を最終薬液洗浄工程で行うので、酸化膜を形成するための熱処理等のプロセスを別途付加する必要がなく、コスト面での向上を図ることができる。 According to the method for manufacturing an SOI wafer of the present invention, the difference between the film thickness of the SOI layer after the final chemical solution cleaning step and the film thickness after a long time can be reduced. An adverse effect can be prevented from occurring. In addition, since the formation of the oxide film for that purpose is performed in the final chemical solution cleaning step, it is not necessary to separately add a process such as heat treatment for forming the oxide film, and the cost can be improved.
本発明のＳＯＩウェーハの製造方法における工程フローの一例を示す説明図である。It is explanatory drawing which shows an example of the process flow in the manufacturing method of the SOI wafer of this invention. オゾン水による洗浄時間と該洗浄により形成された酸化膜厚との関係を示すグラフである。It is a graph which shows the relationship between the washing | cleaning time by ozone water, and the oxide film thickness formed by this washing | cleaning. 表面酸化膜およびＳＯＩ層の膜厚の変化量と経過時間との関係を示すグラフである。It is a graph which shows the relationship between the variation of the film thickness of a surface oxide film and an SOI layer, and elapsed time. 自然酸化膜の膜厚と経過時間との関係を示すグラフである。It is a graph which shows the relationship between the film thickness of a natural oxide film, and elapsed time. ＳＯＩ層膜厚と経過時間との関係を示すグラフである。It is a graph which shows the relationship between SOI layer film thickness and elapsed time. 自然酸化膜およびＳＯＩ層の膜厚の変化量と経過時間との関係を示すグラフである。It is a graph which shows the relationship between the variation | change_quantity of the film thickness of a natural oxide film and an SOI layer, and elapsed time.
　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。
　前述したように、本発明者らが洗浄後のＳＯＩ層膜厚について鋭意研究を行ったところ、ＳＯＩ層の表面に形成された自然酸化膜は経過時間に依存して変化する事がわかった。
　具体的には、以下のような調査を行って上記変化を見出した。
　従来の製造方法で作製され、洗浄されたＳＯＩウェーハを用意し、最終洗浄した直後と、所定時間経過後における自然酸化膜（表面酸化膜）、ＳＯＩ層の膜厚を測定して調べた。ＳＯＩウェーハのＳＯＩ層、ＢＯＸ層の膜厚、最終洗浄条件、膜厚測定条件は以下の通りである。
（ＳＯＩウェーハ）ＳＯＩ層膜厚／ＢＯＸ層膜厚＝１２ｎｍ／２５ｎｍ
（最終洗浄条件）ＳＣ１　、８０℃、５分
（測定条件）　エリプソメータ、面内４１点測定の平均値 Hereinafter, the present invention will be described in detail by way of an embodiment with reference to the drawings, but the present invention is not limited thereto.
As described above, the inventors of the present invention conducted intensive studies on the thickness of the SOI layer after cleaning, and it was found that the natural oxide film formed on the surface of the SOI layer changes depending on the elapsed time.
Specifically, the following investigation was conducted to find out the above change.
Immediately after the final cleaning and after a predetermined time, the thickness of the natural oxide film (surface oxide film) and the thickness of the SOI layer were measured and examined. The film thicknesses of the SOI layer and the BOX layer of the SOI wafer, the final cleaning conditions, and the film thickness measurement conditions are as follows.
(SOI wafer) SOI layer thickness / BOX layer thickness = 12 nm / 25 nm
(Final cleaning conditions) SC1, 80 ° C, 5 minutes (measurement conditions) Ellipsometer, average value of 41 points in plane measurement
図４に表面酸化膜（自然酸化膜）の膜厚と経過時間（日数）との関係を示す。また、図５にＳＯＩ層膜厚と経過時間との関係を示す。最終洗浄直後（すなわち、図４の経過日数が０日のとき）の酸化膜厚は約０．９ｎｍであり、１ｎｍに届いていなかった。
　図４に示すように、洗浄後の経過日数が増えるに従い、自然酸化膜の膜厚が徐々に厚くなっていくのが分かる。一方で、図５に示すように、ＳＯＩ層の膜厚が徐々に薄くなっていくのが分かる。 FIG. 4 shows the relationship between the film thickness of the surface oxide film (natural oxide film) and the elapsed time (days). Further, FIG. 5 shows the relationship between the thickness of the SOI layer and the elapsed time. The oxide film thickness immediately after the final cleaning (that is, when the elapsed day in FIG. 4 is 0 day) was about 0.9 nm and did not reach 1 nm.
As shown in FIG. 4, it can be seen that as the number of days elapsed after cleaning increases, the thickness of the natural oxide film gradually increases. On the other hand, as shown in FIG. 5, it can be seen that the film thickness of the SOI layer gradually decreases.
　また、多数のサンプルについて、同様の条件で洗浄して膜厚測定を行った。そのときの自然酸化膜（表面酸化膜）およびＳＯＩ層の膜厚の変化量（Δ膜厚）と経過時間（日数）との関係を図６に示す。
　図６においても、同様に、自然酸化膜の膜厚は徐々に厚くなっていき、ＳＯＩ層の膜厚は徐々に薄くなっていった。また、例えば７０日経過付近を見ると、自然酸化膜の膜厚は約０．２ｎｍ増え、ＳＯＩ層膜厚は０．０８ｎｍ程度減少していることが分かる。 Moreover, about many samples, it wash | cleaned on the same conditions and film thickness measurement was performed. The relationship between the amount of change in film thickness (Δ film thickness) of the native oxide film (surface oxide film) and the SOI layer at that time and the elapsed time (days) is shown in FIG.
Also in FIG. 6, similarly, the film thickness of the natural oxide film gradually increases, and the film thickness of the SOI layer gradually decreases. Also, for example, looking at the vicinity of 70 days, it can be seen that the film thickness of the natural oxide film increases by about 0.2 nm and the film thickness of the SOI layer decreases by about 0.08 nm.
　さらに本発明者らは、最終薬液洗浄工程において洗浄薬液で１ｎｍ以上の酸化膜を形成し、これを除去せずに乾燥工程を経て製品とすることで、上記のような従来品での自然酸化膜の膜厚増加（ＳＯＩ層の膜厚減少）を防ぐことができることを見出し、本発明を完成させた。 Furthermore, in the final chemical cleaning step, the present inventors form an oxide film of 1 nm or more with the cleaning chemical, and pass through the drying step without removing the oxide film to obtain a product, thereby naturally oxidizing the conventional product as described above. The inventors have found that it is possible to prevent an increase in the film thickness of the film (a decrease in the film thickness of the SOI layer) and complete the present invention.
　以下、本発明のＳＯＩウェーハの製造方法について詳細に述べる。図１に本発明の製造方法の工程フローの一例を示す。
　まず、図１（工程Ａ）に示すように、絶縁層上にＳＯＩ層が形成されたＳＯＩウェーハを作製する。
　ここで準備するＳＯＩウェーハは、少なくとも絶縁層上に、膜厚が２０ｎｍ以下のＳＯＩ層が形成されたＳＯＩ構造を有するウェーハであればよい。例えば、単結晶シリコン等の支持層上に絶縁層が形成され（埋め込み絶縁層：ＢＯＸ層）、この埋め込み絶縁層上にＳＯＩ層が形成された構造を有するウェーハ等が挙げられる。 Hereinafter, the method for producing an SOI wafer of the present invention will be described in detail. An example of the process flow of the manufacturing method of this invention is shown in FIG.
First, as shown in FIG. 1 (process A), an SOI wafer having an SOI layer formed on an insulating layer is manufactured.
The SOI wafer prepared here may be a wafer having an SOI structure in which an SOI layer having a thickness of 20 nm or less is formed at least on an insulating layer. For example, a wafer having a structure in which an insulating layer is formed on a supporting layer of single crystal silicon or the like (embedded insulating layer: BOX layer) and an SOI layer is formed on the embedded insulating layer can be mentioned.
　ＳＯＩウェーハの作製方法等は特に限定されないが、例えば、イオン注入により形成された微小気泡層を有するボンドウェーハと支持基板となるベースウェーハとを絶縁膜を介して接合する工程と、この微小気泡層を境界としてボンドウェーハを剥離してベースウェーハ上に薄膜を形成する工程とを有するイオン注入剥離法によって作製されたＳＯＩウェーハとすることができる。 The manufacturing method of the SOI wafer is not particularly limited. For example, a step of bonding a bond wafer having a microbubble layer formed by ion implantation and a base wafer to be a supporting substrate through an insulating film, and the microbubble layer And forming a thin film on the base wafer by separating the bond wafer at the boundary of the base wafer and forming a thin film on the base wafer.
　なお、本発明は、上記のイオン注入剥離法（いわゆるスマートカット（登録商標）法）やｒＴ－ＣＣＰ法（室温機械剥離法、ＳｉＧｅｎ法とも呼ばれる。）、或いはＳＩＭＯＸ法（Ｓｅｐａｒａｔｉｏｎ　ｂｙ　Ｉｍｐｌａｎｔｅｄ　Ｏｘｙｇｅｎ法）、といったＳＯＩウェーハの製法にかかわらず適用できる。 In the present invention, the above-mentioned ion implantation peeling method (so-called Smart Cut (registered trademark) method), rT-CCP method (also called room temperature mechanical peeling method, SiGen method), or SIMOX method (Separation by Implanted Oxygen method) , Etc. regardless of the manufacturing method of the SOI wafer.
　また、２０ｎｍ以下のＳＯＩ層を形成するにあたって、必要に応じて、例えば表面研磨や犠牲酸化処理などを適宜行うことによってＳＯＩ層の薄膜化を行い、目標の膜厚とすることもできる。
　なお、後述の最終薬液洗浄工程として酸化膜を形成する洗浄を行うので、その洗浄で形成される酸化膜により減厚されるＳＯＩ層膜厚を考慮した上で、このＳＯＩウェーハの作製段階（すなわち、最終薬液洗浄工程直前）でのＳＯＩ層膜厚調整を行う必要がある。 In addition, when forming the SOI layer of 20 nm or less, the SOI layer can be thinned by appropriately performing, for example, surface polishing, sacrificial oxidation treatment, or the like, as necessary, to obtain a target film thickness.
Since the cleaning to form an oxide film is performed as a final chemical solution cleaning step described later, the stage of manufacturing this SOI wafer (that is, the SOI wafer is formed) in consideration of the thickness of the SOI layer to be reduced by the oxide film formed by the cleaning. It is necessary to adjust the film thickness of the SOI layer immediately before the final chemical solution cleaning step.
　ＦＤＳＯＩに要求される、２０ｎｍ以下という薄膜ＳＯＩ層の場合、ＳＯＩ層の膜厚の変化（減厚）が例えば１ｎｍ程度と微々たるものであっても、ＳＯＩ層全体の膜厚とその変化の比率の関係上では無視できるものではなく、デバイスプロセス等への悪影響は大きい。しかし本発明はこの膜厚変化を抑制できるため、上記のような膜厚が薄く、その膜厚変化の影響が次のデバイスプロセスに影響を大きく与えやすいものに対して実に有効的である。 In the case of a thin film SOI layer having a thickness of 20 nm or less, which is required for FDSOI, even if the change (reduction in thickness) of the thickness of the SOI layer is small, for example, about It is not negligible in relation to the above, and the adverse effect on device processes etc. is large. However, since the present invention can suppress this change in film thickness, it is extremely effective for those whose film thickness is small as described above and the influence of the change in film thickness is likely to greatly affect the next device process.
　また、特には上記比率がより大きくなる、５～１５ｎｍという極めて薄い膜厚のＳＯＩ層の場合に、ＳＯＩ層膜厚の変化を抑制できる本発明は一層効果的である。
　なお、ＳＯＩ層膜厚の下限は特に限定されず、０ｎｍより大きければ良い。膜厚が薄ければ薄いほど本発明の有効性は高い。 Further, in the case of an SOI layer having an extremely small thickness of 5 to 15 nm, in which the above ratio becomes larger, in particular, the present invention capable of suppressing a change in the thickness of the SOI layer is more effective.
The lower limit of the thickness of the SOI layer is not particularly limited, and may be larger than 0 nm. The thinner the film thickness, the higher the effectiveness of the invention.
　また、ＳＯＩウェーハの作製後、必要に応じて、純水によるリンスや各種薬液を使用した洗浄を適宜行うことができる。
　特には、次に行う最終薬液洗浄工程の前に、ＨＦ含有水溶液に浸漬することによって、所定膜厚のＳＯＩ層形成後に既にＳＯＩ層表面に形成されている自然酸化膜を除去してもよい。これによって、自然酸化膜の表面に付着している汚染物を自然酸化膜ごと除去することができる。 In addition, after production of the SOI wafer, rinse with pure water and cleaning using various chemical solutions can be appropriately performed as needed.
In particular, before the final chemical solution cleaning step to be performed next, the natural oxide film already formed on the surface of the SOI layer may be removed after forming the SOI layer having a predetermined film thickness by immersing in an aqueous solution containing HF. By this, the contaminant adhering to the surface of the natural oxide film can be removed together with the natural oxide film.
　次に、洗浄薬液を使用する場合の最終洗浄工程（最終薬液洗浄工程：図１（工程Ｂ））として、上記のようにして作製したＳＯＩウェーハに対し、ＳＯＩ層表面に酸化膜を形成可能な洗浄薬液を用いた洗浄を行う。そして、この洗浄によって１ｎｍ以上の酸化膜を形成する。
　この最終薬液洗浄工程で用いる洗浄薬液としては、例えば、オゾン水、ＳＣ１（ＮＨ４ＯＨとＨ２Ｏ２の混合水溶液）、ＳＣ２（ＨＣｌとＨ２Ｏ２の混合水溶液）など、ＳＯＩ層表面に酸化膜を形成可能な薬液であれば特に限定されないが、特にオゾン水であれば比較的緻密な酸化膜が形成されるので、その後の自然酸化膜成長を抑制する効果が高いという利点がある。 Next, as a final cleaning step (final chemical cleaning step: FIG. 1 (step B)) in the case of using a cleaning chemical solution, an oxide film can be formed on the surface of the SOI layer for the SOI wafer manufactured as described above. Perform cleaning using a cleaning solution. Then, an oxide film of 1 nm or more is formed by this cleaning.
As a cleaning chemical solution used in this final chemical solution cleaning process, for example, ozone water, SC1 (mixed aqueous solution of NH 4 OH and H 2 O 2 ), SC 2 (mixed aqueous solution of HCl and H 2 O 2 ), etc. It is not particularly limited as long as it is a chemical solution capable of forming an oxide film, but in particular if ozone water is used, a relatively dense oxide film is formed, so that there is an advantage that the effect of suppressing the subsequent natural oxide film growth is high.
　オゾン水を用いた場合、オゾン濃度が１２ｐｐｍであれば、洗浄時間が１分で約１．１ｎｍ、２分で約１．２ｎｍ、３分で約１．３ｎｍの酸化膜を簡単に形成できる。
　図２に、オゾン水による洗浄時間と該洗浄により形成された酸化膜厚（ＳＯＩ層上の表面酸化膜厚）との関係を示す。予め、希フッ酸による洗浄を行い、その後にオゾン水を用いて洗浄時間を変えて洗浄した。洗浄時間として１分、２分、３分の３パターンを設定した。図２から、前述した結果が得られていることが分かる。
　なお、この実験におけるＳＯＩウェーハのＳＯＩ層、ＢＯＸ層の膜厚、洗浄条件、膜厚測定条件は以下の通りである。
（ＳＯＩウェーハ）ＳＯＩ層膜厚／ＢＯＸ層膜厚＝　１２ｎｍ／２５ｎｍ
（洗浄条件）
ＨＦ溶液（５ｗｔ％、３分）→オゾン水（オゾン濃度　１２ｐｐｍ）、２５℃、１－３分
（測定条件）　エリプソメータ、面内４１点測定の平均値 When ozone water is used, if the ozone concentration is 12 ppm, it is possible to easily form an oxide film having a cleaning time of about 1.1 nm in 1 minute, about 1.2 nm in 2 minutes, and about 1.3 nm in 3 minutes.
FIG. 2 shows the relationship between the cleaning time with ozone water and the oxide film thickness (the surface oxide film thickness on the SOI layer) formed by the cleaning. Cleaning was performed in advance with dilute hydrofluoric acid, and then cleaning was performed using ozone water while changing the cleaning time. Three minute patterns of 1 minute, 2 minutes and 3 minutes were set as the cleaning time. It can be seen from FIG. 2 that the results described above are obtained.
The film thicknesses, cleaning conditions and film thickness measurement conditions of the SOI layer and the BOX layer of the SOI wafer in this experiment are as follows.
(SOI wafer) SOI layer thickness / BOX layer thickness = 12 nm / 25 nm
(Washing conditions)
HF solution (5 wt%, 3 minutes) → ozone water (ozone concentration 12 ppm), 25 ° C, 1-3 minutes (measurement conditions) Ellipsometer, average value of in-plane 41 points measurement
　また、洗浄時間が３分のときの、その後の表面酸化膜およびＳＯＩ層の膜厚の変化量（Δ膜厚）と経過時間との関係を図３に示す。
　図３に示すように、表面酸化膜の膜厚は７０日程度経過しても０．０３ｎｍ程度しか増えておらず、また、ＳＯＩ層膜厚は０．０３ｎｍ程度しか減少していないことが分かる。図６の場合（前述したように０．０８ｎｍ程度）と比較して格段にＳＯＩ層膜厚の変化が抑えられている。 Further, FIG. 3 shows the relationship between the amount of change in film thickness of the surface oxide film and the SOI layer (Δ film thickness) and elapsed time when the cleaning time is 3 minutes.
As shown in FIG. 3, it can be seen that the film thickness of the surface oxide film increases only by about 0.03 nm after about 70 days, and the film thickness of the SOI layer decreases by only about 0.03 nm. . Compared to the case of FIG. 6 (about 0.08 nm as described above), the change in the thickness of the SOI layer is remarkably suppressed.
　この最終薬液洗浄工程で１ｎｍ以上の酸化膜を形成し、後述するようにこの酸化膜を除去することなく残した状態で製品とすることによって、従来の製造方法で製造したＳＯＩウェーハよりも、自然酸化膜の膜厚増加を抑えることができ、時間経過によるＳＯＩ層の膜厚差異を格段に抑制することができる。例えば、時間経過によるＳＯＩ層の膜厚差異の値を従来の半分以下に留めることができる。 An oxide film of 1 nm or more is formed in this final chemical solution cleaning step, and the product is left as it is without removing this oxide film as will be described later, thereby making the product more natural than the SOI wafer manufactured by the conventional manufacturing method. An increase in the thickness of the oxide film can be suppressed, and a difference in the thickness of the SOI layer due to the passage of time can be remarkably suppressed. For example, the value of the film thickness difference of the SOI layer over time can be reduced to half or less than that of the conventional one.
　なお、特許文献３のオゾン水＋ＨＦによるＳＯＩ層膜厚の最終調整について前に述べたが、そのＨＦ処理後に表面を親水性にするため、オゾン水による洗浄が記載されている。しかしながら、このオゾン水による表面酸化膜の厚さや、ＳＯＩ層の薄膜化の防止については記載がない。時間経過によるＳＯＩ層の膜厚差異の値を半分以下に抑えることができるという、１ｎｍという酸化膜の膜厚の臨界性は本発明者らが初めて見出したものである。 Although the final adjustment of the thickness of the SOI layer with ozone water + HF in Patent Document 3 has been described above, cleaning with ozone water is described in order to make the surface hydrophilic after the HF treatment. However, the thickness of the surface oxide film and the prevention of thinning of the SOI layer by the ozone water are not described. The inventors of the present invention have found for the first time the criticality of the oxide film thickness of 1 nm that the value of the film thickness difference of the SOI layer due to the passage of time can be reduced to half or less.
　また、形成する酸化膜の厚さは１ｎｍ以上であれば良く、１．１ｎｍ以上が好ましく、１．２ｎｍ以上がより好ましい。このような膜厚のものを形成することで、より確実に、ＳＯＩ層膜厚の減少を抑えることができる。また、形成する酸化膜の厚さは、最終薬液洗浄工程で形成可能な厚さであればその上限は特に限定されないが、一般的には２．０ｎｍ程度もあれば十分である。 The thickness of the oxide film to be formed may be 1 nm or more, preferably 1.1 nm or more, and more preferably 1.2 nm or more. By forming a film having such a film thickness, it is possible to more reliably suppress the decrease in the film thickness of the SOI layer. The upper limit of the thickness of the oxide film to be formed is not particularly limited as long as it can be formed in the final chemical solution cleaning step, but in general, about 2.0 nm is sufficient.
　この最終薬液洗浄工程の後、形成された酸化膜を除去することなく、例えば純水によるリンス等を必要に応じて行うこともできる。
　そして、乾燥工程（図１（工程Ｃ））を経て、製品として出荷する（図１（工程Ｄ））。乾燥方法自体は特に限定されるものではなく、風乾、スピン乾燥等、形成された酸化膜が除去されずに残存させたまま乾燥できる方法であれば良い。乾燥後には、その製品ＳＯＩウェーハを出荷ボックスに梱包してクライアントへ出荷する。 After the final chemical solution cleaning step, for example, rinsing with pure water can be performed as required without removing the formed oxide film.
Then, through the drying step (FIG. 1 (step C)), it is shipped as a product (FIG. 1 (step D)). The drying method itself is not particularly limited, and any method such as air drying or spin drying may be used as long as the formed oxide film can be dried without being removed. After drying, the product SOI wafer is packaged in a shipping box and shipped to the client.
　以上のような本発明のＳＯＩウェーハの製造方法であれば、経過時間によるＳＯＩ層の膜厚差異を著しく低減することができる。最終薬液洗浄工程後、デバイスプロセスに投入するまでに長時間経過していたとしても、自然酸化膜の膜厚増加によるＳＯＩ層の膜厚減少が抑えられ、膜厚変化を起因とするデバイスプロセスでの悪影響の発生を従来よりも格段に防ぐことができる。
　しかも、最終薬液洗浄工程中に洗浄薬液で酸化膜を形成することができるので、熱処理工程などの酸化膜を形成するための工程をわざわざ別途に設ける必要もない。それらのプロセスを設ける場合に比べて手間や時間、費用を削減することができる。
　したがって、ＳＯＩ膜厚がより確実に精度高く管理されたＳＯＩウェーハを、コストをかけずにクライアントに提供することができる。 According to the method for manufacturing an SOI wafer of the present invention as described above, the difference in film thickness of the SOI layer due to the elapsed time can be remarkably reduced. After the final chemical cleaning process, even if a long time has passed before being introduced into the device process, the decrease in the thickness of the SOI layer due to the increase in the thickness of the native oxide film can be suppressed, and the device process caused by the change in film thickness It is possible to prevent the occurrence of the adverse effect of
Moreover, since the oxide film can be formed by the cleaning chemical during the final chemical cleaning process, it is not necessary to separately provide a process for forming the oxide film such as a heat treatment process. It is possible to save labor, time, and costs as compared to the case of providing those processes.
Therefore, it is possible to provide the client with the SOI wafer in which the SOI film thickness is managed more accurately and accurately, without cost.
　以下、実施例及び比較例を示して、本発明を具体的に説明するが、本発明はこれらに限定されるものではない。
（実施例１）
　直径３００ｍｍ、結晶方位＜１００＞のシリコン単結晶ウェーハを用い、イオン注入剥離法により、ＳＯＩ層膜厚／ＢＯＸ層膜厚＝１２ｎｍ／２５ｎｍのＳＯＩウェーハを作製した。そして、最終薬液洗浄工程としてオゾン水による洗浄（オゾン濃度１２ｐｐｍ、３分）を行い、ＳＯＩ層表面に約１．３ｎｍの酸化膜を形成した。
　その後、純水によるリンスを施し、乾燥させた。このとき、ＳＯＩ層表面の酸化膜は上記膜厚のまま、除去されずに残っていた。これを製品ＳＯＩウェーハとし、ウェーハ収納ボックスにＳＯＩウェーハを収納し、クリーンルーム内に７０日間放置した。その後にＳＯＩ層膜厚を測定し、最終薬液洗浄工程直後の上記膜厚と比較した。 EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.
Example 1
An SOI wafer having a film thickness of SOI layer / a film thickness of BOX layer = 12 nm / 25 nm was produced by an ion implantation separation method using a silicon single crystal wafer having a diameter of 300 mm and a crystal orientation of <100>. Then, cleaning with ozone water (ozone concentration: 12 ppm, 3 minutes) was performed as a final chemical solution cleaning step, and an oxide film of about 1.3 nm was formed on the surface of the SOI layer.
Thereafter, it was rinsed with pure water and dried. At this time, the oxide film on the surface of the SOI layer was left without being removed with the above film thickness. This was used as a product SOI wafer, and the SOI wafer was stored in a wafer storage box and left in a clean room for 70 days. Thereafter, the film thickness of the SOI layer was measured and compared with the film thickness immediately after the final chemical solution cleaning step.
（比較例１）
　直径３００ｍｍ、結晶方位＜１００＞のシリコン単結晶ウェーハを用い、イオン注入剥離法により、ＳＯＩ層膜厚／ＢＯＸ層膜厚＝１２ｎｍ／２５ｎｍのＳＯＩウェーハを作製した。そして、最終薬液洗浄工程としてＳＣ１による洗浄（８０℃、５分）を行った。ＳＯＩ層表面には、約０．９ｎｍの酸化膜が形成されていた。
　その後、純水によるリンスを施し、乾燥させた。このとき、ＳＯＩ層表面の酸化膜は上記膜厚のまま、除去されずに残っていた。これを製品ＳＯＩウェーハとし、ウェーハ収納ボックスにＳＯＩウェーハを収納し、クリーンルーム内に７０日間放置した。その後にＳＯＩ層膜厚を測定し、最終薬液洗浄工程直後の上記膜厚と比較した。 (Comparative example 1)
An SOI wafer having a film thickness of SOI layer / a film thickness of BOX layer = 12 nm / 25 nm was produced by an ion implantation separation method using a silicon single crystal wafer having a diameter of 300 mm and a crystal orientation of <100>. Then, as a final chemical solution cleaning step, cleaning with SC1 (80 ° C., 5 minutes) was performed. An oxide film of about 0.9 nm was formed on the surface of the SOI layer.
Thereafter, it was rinsed with pure water and dried. At this time, the oxide film on the surface of the SOI layer was left without being removed with the above film thickness. This was used as a product SOI wafer, and the SOI wafer was stored in a wafer storage box and left in a clean room for 70 days. Thereafter, the film thickness of the SOI layer was measured and compared with the film thickness immediately after the final chemical solution cleaning step.
（実施例２）
　直径３００ｍｍ、結晶方位＜１００＞のシリコン単結晶ウェーハを用い、イオン注入剥離法により、ＳＯＩ層膜厚／ＢＯＸ層膜厚＝２０ｎｍ／２５ｎｍのＳＯＩウェーハを作製した。そして、最終薬液洗浄工程としてオゾン水による洗浄（オゾン濃度１２ｐｐｍ、１分）を行い、ＳＯＩ層表面に約１．１ｎｍの酸化膜を形成した。
　その後、純水によるリンスを施し、乾燥させた。このとき、ＳＯＩ層表面の酸化膜は上記膜厚のまま、除去されずに残っていた。これを製品ＳＯＩウェーハとし、ウェーハ収納ボックスにＳＯＩウェーハを収納し、クリーンルーム内に７０日間放置した。その後にＳＯＩ層膜厚を測定し、最終薬液洗浄工程直後の上記膜厚と比較した。 (Example 2)
Using a silicon single crystal wafer having a diameter of 300 mm and a crystal orientation of <100>, an SOI wafer having a film thickness of SOI layer / a film thickness of BOX layer = 20 nm / 25 nm was manufactured by an ion implantation peeling method. Then, cleaning with ozone water (ozone concentration 12 ppm, 1 minute) was performed as a final chemical solution cleaning step to form an oxide film of about 1.1 nm on the surface of the SOI layer.
Thereafter, it was rinsed with pure water and dried. At this time, the oxide film on the surface of the SOI layer was left without being removed with the above film thickness. This was used as a product SOI wafer, and the SOI wafer was stored in a wafer storage box and left in a clean room for 70 days. Thereafter, the film thickness of the SOI layer was measured and compared with the film thickness immediately after the final chemical solution cleaning step.
（比較例２）
　直径３００ｍｍ、結晶方位＜１００＞のシリコン単結晶ウェーハを用い、イオン注入剥離法により、ＳＯＩ層膜厚／ＢＯＸ層膜厚＝２０ｎｍ／２５ｎｍのＳＯＩウェーハを作製した。そして、最終薬液洗浄工程としてＳＣ１による洗浄（８０℃、５分）を行った。ＳＯＩ層表面には、約０．９ｎｍの酸化膜が形成されていた。
　その後、純水によるリンスを施し、乾燥させた。このとき、ＳＯＩ層表面の酸化膜は上記膜厚のまま、除去されずに残っていた。これを製品ＳＯＩウェーハとし、ウェーハ収納ボックスにＳＯＩウェーハを収納し、クリーンルーム内に７０日間放置した。その後にＳＯＩ層膜厚を測定し、最終薬液洗浄工程直後の上記膜厚と比較した。 (Comparative example 2)
Using a silicon single crystal wafer having a diameter of 300 mm and a crystal orientation of <100>, an SOI wafer having a film thickness of SOI layer / a film thickness of BOX layer = 20 nm / 25 nm was manufactured by an ion implantation peeling method. Then, as a final chemical solution cleaning step, cleaning with SC1 (80 ° C., 5 minutes) was performed. An oxide film of about 0.9 nm was formed on the surface of the SOI layer.
Thereafter, it was rinsed with pure water and dried. At this time, the oxide film on the surface of the SOI layer was left without being removed with the above film thickness. This was used as a product SOI wafer, and the SOI wafer was stored in a wafer storage box and left in a clean room for 70 days. Thereafter, the film thickness of the SOI layer was measured and compared with the film thickness immediately after the final chemical solution cleaning step.
　なお、膜厚測定は、エリプソメータを用い、ウェーハ面内の４１点において測定し、それらの平均値をとった。
　以上の実施例１、２、比較例１、２の各種条件、測定結果を表１にまとめた。 The film thickness was measured at 41 points in the wafer surface using an ellipsometer, and their average value was taken.
Table 1 summarizes the various conditions and measurement results of the above-described Examples 1 and 2 and Comparative Examples 1 and 2.
　表１に示すように、最終薬液洗浄工程直後のＳＯＩ層膜厚が共に１２．０４ｎｍの実施例１、比較例１を比べると、実施例１でのＳＯＩ層膜厚の減厚量は０．０３ｎｍであるのに対し、比較例１では０．０８ｎｍであった。また、最終薬液洗浄工程直後のＳＯＩ層膜厚が共に１９．９８ｎｍの実施例２、比較例２を比べると、実施例２でのＳＯＩ層膜厚の減厚量は０．０４ｎｍであるのに対し、比較例２では０．０９ｎｍであった。
　このように本発明によれば、最終薬液洗浄工程直後から長時間経過した後に形成されるＳＯＩ層表面の自然酸化膜の成長を抑制できるため、長期間経過後のＳＯＩ層膜厚の減厚を、従来（最終工程直後の自然酸化膜の膜厚が１ｎｍよりも薄い場合）に比べて半分以下に低減することができた。 As shown in Table 1, comparing Example 1 and Comparative Example 1 in which the thickness of the SOI layer immediately after the final chemical solution cleaning step is 12.04 nm, the thickness reduction of the SOI layer in Example 1 is 0. In contrast to 03 nm, in Comparative Example 1, it was 0.08 nm. Also, comparing Example 2 and Comparative Example 2 in which both the SOI layer film thickness immediately after the final chemical solution cleaning step is 19.98 nm, the thickness reduction amount of the SOI layer film thickness in Example 2 is 0.04 nm. In contrast, in Comparative Example 2, it was 0.09 nm.
As described above, according to the present invention, since the growth of the natural oxide film on the surface of the SOI layer formed after a long period of time immediately after the final chemical solution cleaning step can be suppressed, Compared to the conventional case (when the film thickness of the natural oxide film immediately after the final step is thinner than 1 nm), it can be reduced to half or less.
　上記実施例１、２では最終薬液洗浄工程でオゾン水を用いたが、これとは別にＳＣ１やＳＣ２を用いて１ｎｍ以上の酸化膜を形成した場合においても、実施例１、２と同様に、長期間経過後のＳＯＩ層膜厚の減厚を格段に抑制することができた。 In the above first and second embodiments, ozone water was used in the final chemical solution cleaning step, but in the case where an oxide film of 1 nm or more is separately formed using SC1 and SC2 separately, similarly to the first and second embodiments, The thickness reduction of the SOI layer after a long period of time could be significantly suppressed.
　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 embodiment. The above embodiment is an exemplification, and it has substantially the same configuration as the technical idea described in the claims of the present invention, and any one having the same function and effect can be used. It is included in the technical scope of the invention.

Claims (3)

  1. 　薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法であって、
    　前記薄膜ＳＯＩ層として膜厚が２０ｎｍ以下のＳＯＩ層を形成してＳＯＩウェーハを作製した後、
    　最終薬液洗浄工程として、前記薄膜ＳＯＩ層の表面に酸化膜を形成可能な洗浄薬液を用いた洗浄を行って前記薄膜ＳＯＩ層の表面に１ｎｍ以上の酸化膜を形成し、
    　その後、該洗浄で形成した酸化膜を除去することなく、乾燥を行って製品とすることを特徴とする薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法。     A method of manufacturing an SOI wafer having a thin film SOI layer, comprising:
    After an SOI layer having a film thickness of 20 nm or less is formed as the thin film SOI layer to produce an SOI wafer,
    As a final chemical solution cleaning step, cleaning is performed using a cleaning chemical solution capable of forming an oxide film on the surface of the thin film SOI layer to form an oxide film of 1 nm or more on the surface of the thin film SOI layer,
    Thereafter, drying is performed without removing the oxide film formed by the cleaning to obtain a product, which is a method for producing an SOI wafer having a thin film SOI layer.
  2. 　前記酸化膜形成可能な洗浄薬液をオゾン水とすることを特徴とする請求項１に記載の薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法。 The method for manufacturing an SOI wafer having a thin film SOI layer according to claim 1, wherein the cleaning chemical solution capable of forming the oxide film is ozone water.
  3. 　前記形成する薄膜ＳＯＩ層の膜厚を１５ｎｍ以下とすることを特徴とする請求項１又は請求項２に記載の薄膜ＳＯＩ層を有するＳＯＩウェーハの製造方法。 The method for manufacturing an SOI wafer having a thin film SOI layer according to claim 1 or 2, wherein the film thickness of the thin film SOI layer to be formed is 15 nm or less.
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