WO2020158210A1 - Etching method - Google Patents

Etching method Download PDF

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Publication number
WO2020158210A1
WO2020158210A1 PCT/JP2019/048847 JP2019048847W WO2020158210A1 WO 2020158210 A1 WO2020158210 A1 WO 2020158210A1 JP 2019048847 W JP2019048847 W JP 2019048847W WO 2020158210 A1 WO2020158210 A1 WO 2020158210A1
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Prior art keywords
wafer
etching
dropped
soi layer
film thickness
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PCT/JP2019/048847
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French (fr)
Japanese (ja)
Inventor
恭剛 丸山
晋 更級
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信越半導体株式会社
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Publication of WO2020158210A1 publication Critical patent/WO2020158210A1/en

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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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System 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
    • H01L21/308—Chemical or electrical treatment, e.g. electrolytic etching using masks

Definitions

  • the present invention uses spin etching on a SOI layer of a SOI wafer having a concentric circle-shaped film thickness distribution and a concentric surface/peripheral shape of a PW (polished wafer), etc.
  • the present invention relates to an etching method for improving a wafer shape.
  • Patent Document 1 describes a method of forming an oxide film on an SOI layer and removing the oxide film to form an SOI layer having a uniform film thickness. Further, paragraph 0076 of Patent Document 1 and FIG. 9 describe a spin etching apparatus for respectively providing ozone water, a hydrofluoric acid solution, and pure water used in the above method.
  • Patent Document 2 for an SOI layer having a concentric thickness distribution, a thermal oxide film having a concentric thickness distribution on the surface of the SOI layer so as to cancel the concentric thickness distribution. A technique for forming the is described.
  • the film thickness of the SOI layer is required to be uniform in-plane on the wafer surface.
  • the SOI The film thickness of the layer causes a concentric thickness distribution in the plane.
  • the polished wafer similarly to the PW leaf-to-leaf polishing, the polished wafer has a concentric surface/peripheral shape distribution. Therefore, it is an object to cancel such a concentric circle-shaped film thickness distribution and a concentric circle-shaped surface/outer peripheral shape distribution to improve the film thickness uniformity of the SOI layer and the wafer shape.
  • Local etching by laser or plasma is known as a method for improving the film thickness distribution of these SOI layers and the surface/peripheral shape distribution of the wafer such as PW.
  • the SOI layer, PW, etc. are used.
  • the application target is limited to a concentric SOI layer having a thicker film thickness distribution on the outer peripheral side than the central side, or a wafer such as a PW having a ridged outer peripheral side. Therefore, in addition to wafers having various surface shapes, for example, as described above, in addition to the SOI layer having a thicker film thickness distribution on the outer peripheral side than the central side and the wafer having the ridge shape on the outer peripheral side, the central side further has the outer peripheral side. For all thicker SOI wafers and wafers having a sagging shape on the outer peripheral side, the surface shape of the wafer cannot be improved.
  • the present invention has been made to solve the above problems, and proposes an etching method capable of improving the surface shape by spin etching, regardless of the surface shape of the wafer. To aim.
  • an etching solution is dropped onto the surface of the wafer, and by rotating the wafer, in an etching method for etching the surface of the wafer, the wafer before the etching
  • the surface shape is measured, in the etching, with the dropping of the etching liquid, a rinse liquid that suppresses the etching of the surface of the wafer by the etching liquid is dropped onto the surface of the wafer, and the position where the etching liquid is dropped and the
  • the etching method is characterized in that the position where the rinse liquid is dropped is determined based on the measured surface shape of the wafer before etching, and the surface of the wafer is etched.
  • the variation in the film thickness of the SOI layer due to polishing becomes concentric (the outer peripheral portion is thick or thin).
  • ozone water O 3 aqueous solution, hereinafter sometimes referred to simply as O 3 or O 3 water
  • HF aqueous solution hereinafter sometimes simply referred to as HF
  • the position where the rinsing liquid is dropped is usually fixed at the center of the wafer. That is, in this case, spin etching cannot sufficiently remove the concentric thickness variation of the SOI layer.
  • at least the position where the etching solution (HF) and the rinse solution are dropped can be changed in the radial direction of the wafer.
  • the treatment should be performed by shaking the position where each liquid is dropped so that the liquid is dropped outside the central portion of the wafer, that is, the rinse liquid that suppresses the etching reaction is dropped at a position different from the position where the etching liquid is dropped.
  • the rinsing liquid is supplied at the same time as the etching liquid to perform the etching, and the positions where the respective liquids are dropped are set according to the film thickness distribution of the SOI layer before the etching so that concentric circles are formed. Can be added to the local etching distribution.
  • the rinse liquid is a liquid having a function of suppressing etching of the surface of the wafer by the etching liquid (HF), and pure water or the like can be used, for example.
  • the dropping of the etching liquid and the dropping of the rinse liquid are performed at the same time.
  • the surface shape of the wafer to be subjected to the above-mentioned etching method before etching is changed from the central portion of the wafer to a concentric shape.
  • the present invention works particularly favorably, and the position where the etching solution and the rinsing solution are dropped is changed independently in the radial direction of the wafer based on the surface shape of the wafer before etching, thereby performing spin etching. , The concentric film thickness distribution or the concentric surface/peripheral shape distribution can be reliably canceled.
  • the etching liquid is dropped on the convex portion on the surface of the wafer before etching and the rinse liquid is dropped on the concave portion on the surface of the wafer before etching.
  • wafers having various surface shapes for example, an SOI wafer having an SOI layer thickness distribution thicker on the outer peripheral side than the center side, an SOI wafer having an SOI layer thickness distribution thicker on the central side than the outer peripheral side, and a peripheral edge
  • the surface shape of the wafer can be improved.
  • the position where the rinse liquid is dropped is higher than the position where the etching liquid is dropped.
  • the position where the etching solution is dropped is lower than the position where the rinse solution is dropped.
  • etching method is applied to various wafers having a concentric concavo-convex (surface shape) by polishing or the like, as well as an SOI wafer having an SOI layer having a film thickness distribution that changes concentrically from the center portion, a polished wafer, and the like. Is applicable to.
  • the type of wafer is not limited.
  • the above-described etching method includes a silicon wafer, a group IV semiconductor wafer such as Ge, SiGe, and SiC, a compound semiconductor wafer such as GaN, GaP, GaAs, and InP, an insulating wafer such as quartz and sapphire, and It can be applied to a wafer with a thin film having a thin film formed on the surface thereof, and the etching solution can also be appropriately selected according to the material of the wafer to which the present invention is applied.
  • a wafer having any surface shape such as an SOI layer having a concentric film thickness distribution or a wafer having a concentric surface/peripheral shape distribution can be used. Even if there is, it is possible to improve the film thickness uniformity of the SOI layer by canceling the distribution by spin etching and to improve the surface/peripheral shape of the wafer such as PW. Further, if necessary, local etching can be performed so as to have a target film thickness distribution.
  • FIG. 4 is a diagram showing an etching method of Example 1.
  • FIG. 5 is a diagram showing the results of Example 1.
  • FIG. 6 is a diagram showing an etching method of Example 2.
  • 5 is a diagram showing the results of Example 2.
  • FIG. 8 is a diagram showing an etching method of Example 3;
  • FIG. 5 is a diagram showing the results of Example 3. It is a figure which shows the etching method of a comparative example. It is a figure which shows the result of a comparative example.
  • the present invention particularly uses spin etching (cleaning) on an SOI layer having a concentric circular film thickness distribution or a wafer having a concentric circular surface/peripheral shape distribution to obtain a concentric circular film.
  • the invention is mainly intended to improve the surface shape of the wafer such as the uniformity of the film thickness of the SOI layer by performing etching so as to cancel the film thickness distribution or the concentric circular surface/outer peripheral shape distribution.
  • a spin etching apparatus is disclosed in Patent Document 1, but normally, the position where the etching liquid is dropped and the position where the rinse liquid is dropped are the same (for example, the central portion of the wafer). Fixed). In this case, spin etching cannot improve various surface shapes (irregularities) such as a concentric thickness distribution of the SOI layer and a concentric surface/peripheral shape distribution of the wafer.
  • the present inventors have determined that the position where the etching solution (HF) and the rinse solution (pure water) are dropped is a concentric film thickness distribution of the wafer before etching or a concentric circle.
  • etching solution HF
  • rinse solution pure water
  • the present invention by dropping the etching solution on the surface of the wafer, and by rotating the wafer, in the etching method of etching the surface of the wafer, to measure the surface shape of the wafer before etching, in the etching,
  • a rinse liquid that suppresses the etching of the surface of the wafer by the etching liquid is dropped onto the surface of the wafer, and the position where the etching liquid is dropped and the position where the rinse liquid is dropped are measured before the etching.
  • the etching method is characterized in that the surface of the wafer is etched by determining based on the shape.
  • the position where the etching liquid is dropped and the position where the rinse liquid is dropped are determined, and the surface of the wafer is etched to obtain a wafer having any surface shape. Even in this case, the surface shape can be improved by spin etching.
  • Patent Document 2 The difference between the present invention and Patent Document 2 is that the method of canceling the concentric circular film thickness distribution is spin etching in the present invention, whereas in Patent Document 2, thermal oxidation (at the time of temperature increase or temperature decrease) is performed. Oxidation).
  • spin-etching is disclosed in Patent Document 1, in spin-etching, the position where the etching liquid and the rinse liquid are dropped is determined based on the surface shape of the wafer before etching and the etching is performed. It cannot be obtained from either 1 or 2.
  • FIG. 1 shows a first example of the etching method of the present invention.
  • the wafer to be etched by the spin etching is a base substrate 1, a buried oxide layer 2 on the base substrate 1, and an SOI layer on the buried oxide layer 2. Silicon on insulator layer) 3.
  • the base substrate 1 is a silicon substrate, the buried oxide layer 2 is silicon oxide, and the SOI layer 3 is single crystal silicon.
  • the first example of the etching method of the present invention is as follows. First, the film thickness distribution is measured as the surface shape of the SOI layer 3 (step ST1).
  • the film thickness of the SOI layer 3 is required to be in-plane uniform on the wafer surface. For example, in the polishing process performed to improve the surface roughness of the SOI layer 3, the film thickness of the SOI layer 3 is This is because it usually has a concentric thickness distribution in the plane.
  • the SOI layer 3 has a thick film thickness distribution in the central portion and a thin film thickness distribution in the outer peripheral portion.
  • the position where the O 3 water and the etching liquid (HF) are dropped and the position where the rinse liquid is dropped are determined based on the film thickness distribution of the SOI layer 3 before etching measured in the above process (step ST2). ).
  • the position where the O 3 water and the etching solution (HF) are dropped is the center.
  • the position where the rinse liquid is dropped is O 3 water and the etching liquid (HF).
  • the outer peripheral side of the position where the liquid crystal is dropped for example, on the outer peripheral side of the center of the radius of the wafer.
  • the positions of dropping the O 3 water and the etching solution (HF) may be the same or different. However, it is preferable that these positions are as close as possible.
  • step ST3 the wafer is rotated around its center
  • O 3 water is dropped on the central portion of the wafer and a rinse liquid is dropped on the outer peripheral side of the central portion of the wafer to oxidize the surface of the SOI layer 3 (step ST4).
  • the O 3 water is dropped for a fixed amount or for a predetermined fixed period.
  • the rinse liquid is dropped on the central portion of the wafer (step ST5).
  • the rinse liquid flows from the central portion of the wafer to the outer peripheral portion to clean the surface of the wafer.
  • the etching liquid (HF) is dropped on the central portion of the wafer, and the rinse liquid is dropped on the outer peripheral side of the central portion of the wafer to etch the surface of the SOI layer 3 (step ST6). Note that the etching liquid (HF) is dropped for a fixed amount or for a predetermined fixed period.
  • the rinse solution is dropped on the central portion of the wafer (step ST7).
  • the rinse liquid flows from the central portion of the wafer to the outer peripheral portion to clean the surface of the wafer.
  • step ST8 spin drying is performed and the film thickness distribution of the SOI layer 3 is measured (step ST8).
  • the etching method is finished.
  • steps ST3 to ST8 are repeated.
  • the etching method of the present invention by performing spin etching for canceling the film thickness distribution on an SOI layer having a film thickness distribution that is thick in the central portion and thin in the outer peripheral portion, The surface shape of the SOI wafer can be improved.
  • FIG. 2 shows a second example of the etching method of the present invention.
  • a wafer as an etching target of spin etching includes a base substrate 1, a buried oxide layer 2 on the base substrate 1, and an SOI layer 3 on the buried oxide layer 2.
  • the base substrate 1 is a silicon substrate
  • the buried oxide layer 2 is silicon oxide
  • the SOI layer 3 is single crystal silicon.
  • a second example of the etching method of the present invention is as follows. First, similarly to the first example, the film thickness distribution is measured as the surface shape of the SOI layer 3 (step ST1), and the position where O 3 water, the etching solution (HF), and the rinse solution are dropped is measured. It is determined based on the film thickness distribution of the SOI layer 3 before etching (step ST2).
  • the SOI layer 3 has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion. Therefore, the position where the O 3 water and the etching solution (HF) are dropped is the outer peripheral portion of the wafer. The position where the rinsing liquid is dropped is set to the central portion so that the etching liquid (HF) does not enter the central portion of the wafer and etch the SOI layer 3.
  • the SOI layer 3 has a sagging shape at the edge portion of the wafer. Therefore, the rinse liquid is dropped not only on the center of the wafer but also on the edge of the wafer. That is, the position where the rinsing liquid is dropped is both on the center side and the outer peripheral side of the position where the O 3 water and the etching liquid (HF) are dropped.
  • step ST3 the wafer is rotated around its center
  • O 3 water is dropped onto the outer peripheral portion of the wafer (at the position where the SOI layer 3 is thickest or at the center side thereof), and the rinse liquid is applied to the center portion of the wafer and The surface of the SOI layer 3 is oxidized by being dropped onto the edge portion (step ST4).
  • the rinse liquid is dropped onto the central portion of the wafer (step ST5).
  • the etching liquid (HF) is dropped on the same outer peripheral portion of the wafer as in step ST4, and the rinse liquid is dropped on the central portion and the edge portion of the wafer to etch the surface of the SOI layer 3 (step ST6).
  • the rinse liquid is dropped onto the central portion of the wafer (step ST7).
  • step ST8 spin drying is performed and the film thickness distribution of the SOI layer 3 is measured (step ST8).
  • the etching method is finished.
  • the steps ST3 to ST8 or the steps ST1 to ST8 are repeated.
  • the second example of the etching method of the present invention by performing the spin etching for canceling the film thickness distribution on the SOI layer having the thin film thickness distribution in the central portion and the thick film thickness in the outer peripheral portion, The surface shape of the SOI wafer can be improved.
  • FIG. 3 shows the etching method of the first embodiment.
  • the wafer was an SOI wafer with a diameter of 200 mm.
  • the etching method of Example 1 corresponds to the second example (FIG. 2) of the etching method of the present invention. That is, the SOI layer has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion, and the thickest position is 20 mm from the edge of the wafer toward the central portion of the wafer. Further, the SOI layer has a sagging shape at the edge portion of the wafer. Therefore, the position where the O 3 water and the etching solution (HF) are dropped is a position slightly inside the outer peripheral portion of the wafer, that is, the thickest position of the SOI layer, for example, from the edge of the wafer toward the central portion of the wafer. The position is 25 mm. The positions where the rinsing liquid is dropped are the central portion and the edge portion of the wafer.
  • the SOI layer has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion, and the thickest position is 20 mm from the edge of the wafer toward the central
  • Fig. 4 shows the results that local etching was realized by such an etching method and the surface shape of the wafer was improved.
  • the maximum value (Max) of the film thickness of the SOI layer before spin local etching is 80.3 nm
  • the minimum value (Min) is 73.9 nm
  • the average value (AVE) is 77.18 nm. is there. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.4 nm.
  • the maximum value of the film thickness of the SOI layer after the spin local etching is 75.1 nm
  • the minimum value is 69.4 nm
  • the average value is 72.45 nm. Therefore, the difference (range) between the maximum value and the minimum value of the thickness of the SOI layer is 5.7 nm.
  • FIG. 5 shows the etching method of the second embodiment.
  • the wafer was an SOI wafer with a diameter of 200 mm.
  • the etching method of Example 2 also corresponds to the second example (FIG. 2) of the etching method of the present invention. That is, the SOI layer has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion, and the thickest position is 20 mm from the edge of the wafer toward the central portion of the wafer. Therefore, the position where the O 3 water and the etching solution (HF) are dropped is a position slightly inside the outer peripheral portion of the wafer, that is, the thickest position of the SOI layer, for example, from the edge of the wafer toward the central portion of the wafer. The position is 25 mm. The position where the rinsing liquid is dropped is the central portion of the wafer.
  • the SOI layer has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion, and the thickest position is 20 mm from the edge of the wafer toward the central portion of the wafer. Therefore, the position where the O 3 water and the etching solution (HF) are
  • Fig. 6 shows the result that local etching was realized by such an etching method and the surface shape of the wafer was improved.
  • the maximum value of the film thickness of the SOI layer before spin local etching is 78 nm
  • the minimum value is 71.7 nm
  • the average value is 75.18 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.3 nm.
  • the maximum value of the film thickness of the SOI layer after spin local etching is 73.6 nm
  • the minimum value is 67.5 nm
  • the average value is 71.1 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.1 nm.
  • the local etching of the outer peripheral portion (projection) of the wafer is realized by the spin etching of the present invention, and the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6. It can be seen that the thickness is improved from 3 nm to 6.1 nm. Specifically, as shown by the difference in FIG. 6, the difference between the maximum value and the minimum value of the film thickness of the SOI layer was improved by 0.2 nm.
  • FIG. 7 shows the etching method of the third embodiment.
  • the wafer was an SOI wafer with a diameter of 200 mm.
  • the etching method of Example 3 corresponds to the first example (FIG. 1) of the etching method of the present invention.
  • the wafer used in this example has an SOI layer having a thin central portion and a thick outer peripheral portion, and the thickest position is 10 mm from the edge of the wafer toward the central portion of the wafer.
  • the position where the O 3 water and the etching solution (HF) are dropped is the central part of the wafer, and the position where the rinse solution is dropped is the outer peripheral part of the wafer, that is, a position slightly inside the thickest position of the SOI layer. , 15 mm from the edge of the wafer toward the center of the wafer.
  • Example 3 the effect of locally etching the central portion of the wafer is shown. Therefore, if the difference between the maximum value and the minimum value of the film thickness of the SOI layer becomes large before and after the spin local etching. To some extent, it means that the effect of local etching occurs in the central portion.
  • FIG. 8 shows the results showing that the local etching was realized by Example 3 and the surface shape of the wafer was formed into a desired shape.
  • the maximum value of the film thickness of the SOI layer before spin local etching is 81.3 nm
  • the minimum value is 74.6 nm
  • the average value is 77.76 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.7 nm.
  • the maximum value of the film thickness of the SOI layer after spin local etching is 74.1 nm
  • the minimum value is 66.9 nm
  • the average value is 70.36 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 7.2 nm.
  • the wafer used in this example is an SOI layer having a thick central portion and a thin outer peripheral portion
  • the SOI layer It means that the difference (range) between the maximum value and the minimum value of the film thickness of is reduced. Further, if necessary, it is possible to intentionally perform local etching so as to have a desired film thickness distribution.
  • FIG. 9 shows an etching method of a comparative example.
  • the wafer was an SOI wafer with a diameter of 200 mm.
  • the wafer used in the etching method of the comparative example has an SOI layer having a thin central portion and a thick outer peripheral portion, as in Examples 1 to 3, and the thickest position is from the edge of the wafer toward the central portion of the wafer. It is assumed that the position is 20 mm. However, in the comparative example, the position where the O 3 water and the etching liquid (HF) are dropped is fixed to the center of the wafer, and the rinse liquid is not dropped onto the wafer.
  • HF etching liquid
  • the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer before spin etching is 3.9 nm.
  • the difference (range) between the maximum value and the minimum value of the thickness of the SOI layer after spin etching is also 3.9 nm. That is, as shown by the difference in FIG. 10, it can be seen that there is no change in the difference between the maximum value and the minimum value of the film thickness of the SOI layer, and local etching is not realized.
  • the maximum value and the minimum value of the film thickness of the SOI layer are matched by matching the variation of the concentric film thickness of the SOI layer due to polishing with the local etching. It is possible to improve the surface shape of the wafer by reducing the difference between the thickness of the SOI layer and the in-plane uniformity of the film thickness of the SOI layer. Moreover, since the film thickness distribution or the wafer shape can be controlled by local etching if necessary, it becomes easy to obtain a desired desired film thickness distribution or wafer shape.
  • the present invention is not limited to the above embodiment.
  • the above-described embodiment is an exemplification, and the invention having substantially the same configuration as the technical idea described in the scope of the claims of the present invention and exhibiting the same action and effect is the present invention It is included in the technical scope of.

Abstract

This etching method, in which an etching solution is dripped onto a wafer surface and the wafer surface is etched by rotating the wafer, is characterized in that the surface shape of the wafer prior to etching is measured, and during etching, in addition to dripping the etching solution, a rinse solution that suppresses etching of the wafer surface by the etching solution is dripped onto the wafer surface, and a position for dripping the etching solution and a position for dripping the rinse solution are determined on the basis of the measured surface shape of the wafer prior to etching, and the wafer surface is etched. Thus, an etching method is provided which, for wafers of any surface shape, can improve the surface shape by spin etching.

Description

エッチング方法Etching method
　本発明は、同心円状の膜厚分布を有するＳＯＩウェーハのＳＯＩ層やＰＷ（ポリッシュド・ウェーハ）などの同心円状の表面／外周形状に対し、スピンエッチングを用い、ＳＯＩ層の膜厚均一性及びウェーハ形状の改善を図るためのエッチング方法に関する。 The present invention uses spin etching on a SOI layer of a SOI wafer having a concentric circle-shaped film thickness distribution and a concentric surface/peripheral shape of a PW (polished wafer), etc. The present invention relates to an etching method for improving a wafer shape.
　回転させたウェーハ上の中心部にオゾン水（Ｏ３水溶液）を滴下することによってウェーハ上に酸化膜を形成し、その後、ＨＦ水溶液で当該酸化膜を除去する方法によってウェーハ表層を均一に、かつ微量ずつエッチングして洗浄する技術がある。例えば、特許文献１には、ＳＯＩ層上に酸化膜を形成し、当該酸化膜を除去することで、均一な膜厚のＳＯＩ層を形成する方法が記載されている。また、特許文献１の００７６段落、及び図９には、上記方法に用いられるオゾン水、フッ化水素酸溶液、純水をそれぞれ提供するスピンエッチング装置が記載されている。 Ozone water (O 3 aqueous solution) is dropped onto the center of the rotated wafer to form an oxide film on the wafer, and then the oxide film is removed with an HF aqueous solution so that the wafer surface layer is uniform and There is a technique of etching and cleaning a small amount. For example, Patent Document 1 describes a method of forming an oxide film on an SOI layer and removing the oxide film to form an SOI layer having a uniform film thickness. Further, paragraph 0076 of Patent Document 1 and FIG. 9 describe a spin etching apparatus for respectively providing ozone water, a hydrofluoric acid solution, and pure water used in the above method.
　また、特許文献２には、同心円状の膜厚分布を有するＳＯＩ層に対し、当該同心円状の膜厚分布を相殺するように、ＳＯＩ層の表面に同心円状の膜厚分布を有する熱酸化膜を形成する技術が記載されている。 Further, in Patent Document 2, for an SOI layer having a concentric thickness distribution, a thermal oxide film having a concentric thickness distribution on the surface of the SOI layer so as to cancel the concentric thickness distribution. A technique for forming the is described.
特開２００５－５６７４号公報JP-A-2005-5674 特許第５９２７８９４号公報Japanese Patent No. 5927894
　ＳＯＩ層の膜厚は、ウェーハ表面において面内均一であることが要求されるが、スマートカット法（登録商標）による貼り合わせウェーハ剥離後の表面粗さ改質のために行う研磨工程で、ＳＯＩ層の膜厚は、面内で同心円状の厚さ分布を生じさせてしまう。また、ＰＷの毎葉研磨も同様に、研磨後のウェーハは、同心円状の表面／外周形状分布を有する。従って、このような同心円状の膜厚分布、及び同心円状の表面／外周形状分布を相殺し、ＳＯＩ層の膜厚均一性及びウェーハ形状の改善を図ることが課題である。 The film thickness of the SOI layer is required to be uniform in-plane on the wafer surface. However, in the polishing step performed to improve the surface roughness after the bonded wafer is peeled by the smart cut method (registered trademark), the SOI The film thickness of the layer causes a concentric thickness distribution in the plane. Further, similarly to the PW leaf-to-leaf polishing, the polished wafer has a concentric surface/peripheral shape distribution. Therefore, it is an object to cancel such a concentric circle-shaped film thickness distribution and a concentric circle-shaped surface/outer peripheral shape distribution to improve the film thickness uniformity of the SOI layer and the wafer shape.
　これらＳＯＩ層の膜厚分布や、ＰＷなどのウェーハの表面／外周形状分布を改善する方法としては、レーザ又はプラズマによる局所エッチングが知られているが、この方法には、ＳＯＩ層や、ＰＷなどのウェーハの表面にダメージ、金属汚染などの問題を発生させるという課題がある。 Local etching by laser or plasma is known as a method for improving the film thickness distribution of these SOI layers and the surface/peripheral shape distribution of the wafer such as PW. In this method, the SOI layer, PW, etc. are used. There is a problem of causing problems such as damage and metal contamination on the surface of the wafer.
　また、従来の技術では、例えば、外周側のみ選択的にエッチングすることしかできない。即ち、適用対象は、同心円状に外周側が中心側よりも厚い膜厚分布を有するＳＯＩ層や、外周側がハネ形状を有するＰＷなどのウェーハに限られる。従って、様々な表面形状を有するウェーハ、例えば、上記のように、外周側が中心側よりも厚い膜厚分布を有するＳＯＩ層や、外周側がハネ形状を有するウェーハに加えて、さらに、中心側が外周側よりも厚いＳＯＩウェーハや、外周側がダレ形状を有するウェーハのすべてに対して、ウェーハの表面形状の改善を図ることができない。 Also, with the conventional technology, for example, only the outer peripheral side can be selectively etched. That is, the application target is limited to a concentric SOI layer having a thicker film thickness distribution on the outer peripheral side than the central side, or a wafer such as a PW having a ridged outer peripheral side. Therefore, in addition to wafers having various surface shapes, for example, as described above, in addition to the SOI layer having a thicker film thickness distribution on the outer peripheral side than the central side and the wafer having the ridge shape on the outer peripheral side, the central side further has the outer peripheral side. For all thicker SOI wafers and wafers having a sagging shape on the outer peripheral side, the surface shape of the wafer cannot be improved.
　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、どのような表面形状を持つウェーハであっても、スピンエッチングにより表面形状の改善を図ることが可能なエッチング方法を提案することを目的とする。 The present invention has been made to solve the above problems, and proposes an etching method capable of improving the surface shape by spin etching, regardless of the surface shape of the wafer. To aim.
　上記課題を達成するために、本発明では、エッチング液をウェーハの表面に滴下し、かつ前記ウェーハを回転させることで、前記ウェーハの表面のエッチングを行うエッチング方法において、前記エッチング前の前記ウェーハの表面形状を測定し、前記エッチングにおいて、前記エッチング液の滴下とともに、前記エッチング液による前記ウェーハの表面のエッチングを抑制するリンス液を前記ウェーハの表面に滴下し、前記エッチング液を滴下する位置と前記リンス液を滴下する位置を、前記測定されたエッチング前の前記ウェーハの表面形状に基づき決定して、前記ウェーハの表面のエッチングを行うことを特徴とするエッチング方法を提供する。 To achieve the above object, in the present invention, an etching solution is dropped onto the surface of the wafer, and by rotating the wafer, in an etching method for etching the surface of the wafer, the wafer before the etching The surface shape is measured, in the etching, with the dropping of the etching liquid, a rinse liquid that suppresses the etching of the surface of the wafer by the etching liquid is dropped onto the surface of the wafer, and the position where the etching liquid is dropped and the The etching method is characterized in that the position where the rinse liquid is dropped is determined based on the measured surface shape of the wafer before etching, and the surface of the wafer is etched.
　このようなエッチング方法によれば、どのような表面形状を持つウェーハであっても、スピンエッチングにより表面形状の改善を図ることが可能となる。 According to such an etching method, it is possible to improve the surface shape of a wafer having any surface shape by spin etching.
　例えば、研磨によるＳＯＩ層の膜厚のばらつきは同心円状となる（外周部が厚い、薄いなど）。一方で、スピンエッチング（洗浄）に用いるオゾン水（Ｏ３水溶液、以下、単にＯ３、又はＯ３水と記載することがある。）、ＨＦ水溶液（以下、単にＨＦと記載することがある。）、リンス液を滴下する位置（ウェーハ上の位置）は、通常、ウェーハの中心部に固定である。即ち、この場合、スピンエッチングでは、ＳＯＩ層の同心円状の膜厚のばらつきを十分に除去することができない。これに対し、上記エッチング方法では、少なくともエッチング液（ＨＦ）及びリンス液を滴下する位置をウェーハの径方向に変化させることができる。 For example, the variation in the film thickness of the SOI layer due to polishing becomes concentric (the outer peripheral portion is thick or thin). On the other hand, ozone water (O 3 aqueous solution, hereinafter sometimes referred to simply as O 3 or O 3 water) used for spin etching (cleaning), and HF aqueous solution (hereinafter sometimes simply referred to as HF). ), the position where the rinsing liquid is dropped (the position on the wafer) is usually fixed at the center of the wafer. That is, in this case, spin etching cannot sufficiently remove the concentric thickness variation of the SOI layer. On the other hand, in the above etching method, at least the position where the etching solution (HF) and the rinse solution are dropped can be changed in the radial direction of the wafer.
　従って、各液を滴下する位置を振ってウェーハの中心部以外に滴下する様にして処理を行うこと、即ち、エッチング液を滴下する位置とは別の位置にエッチング反応を抑制するリンス液を滴下する位置を配置し、エッチング液と同時にリンス液を供給してエッチングを行い、その際の各液を滴下する位置は、エッチング前のＳＯＩ層の膜厚分布に応じて設定することで、同心円状の分布に局所的なエッチング分布を加えることができる。 Therefore, the treatment should be performed by shaking the position where each liquid is dropped so that the liquid is dropped outside the central portion of the wafer, that is, the rinse liquid that suppresses the etching reaction is dropped at a position different from the position where the etching liquid is dropped. The rinsing liquid is supplied at the same time as the etching liquid to perform the etching, and the positions where the respective liquids are dropped are set according to the film thickness distribution of the SOI layer before the etching so that concentric circles are formed. Can be added to the local etching distribution.
　これにより、研磨によって生じる同心円状の分布を、スピンエッチング（洗浄）による局所エッチングによってマッチングすることで、ＳＯＩ層の膜厚公差を低減することができる。また、上記エッチング方法であれば、ＳＯＩ層や、ＰＷなどのウェーハの表面にダメージ、金属汚染などの問題を発生させることもない。 By doing this, by matching the concentric distribution generated by polishing by local etching by spin etching (cleaning), it is possible to reduce the film thickness tolerance of the SOI layer. Further, the above etching method does not cause problems such as damage to the SOI layer and the surface of the wafer such as PW and metal contamination.
　なお、リンス液とは、エッチング液（ＨＦ）によるウェーハの表面のエッチングを抑制する機能を有する液体のことであり、例えば、純水などを用いることができる。 Note that the rinse liquid is a liquid having a function of suppressing etching of the surface of the wafer by the etching liquid (HF), and pure water or the like can be used, for example.
　上記エッチング方法において、エッチング液の滴下とリンス液の滴下とは同時に行われることが好ましい。 In the above etching method, it is preferable that the dropping of the etching liquid and the dropping of the rinse liquid are performed at the same time.
　この場合、リンス液によるエッチングの抑制効果を高めることが可能となる。 In this case, the effect of suppressing the etching by the rinse liquid can be enhanced.
　また、上記エッチング方法の対象となるエッチング前のウェーハの表面形状は、ウェーハの中心部から同心円状に変化していることが好ましい。 Moreover, it is preferable that the surface shape of the wafer to be subjected to the above-mentioned etching method before etching is changed from the central portion of the wafer to a concentric shape.
　この場合に本発明は特に好適に作用し、エッチング液及びリンス液を滴下する位置を、エッチング前のウェーハの表面形状に基づき、ウェーハの径方向にそれぞれ独立に変化させてスピンエッチングを行うことで、同心円状の膜厚分布、又は同心円状の表面／外周形状分布を確実に相殺することができる。 In this case, the present invention works particularly favorably, and the position where the etching solution and the rinsing solution are dropped is changed independently in the radial direction of the wafer based on the surface shape of the wafer before etching, thereby performing spin etching. , The concentric film thickness distribution or the concentric surface/peripheral shape distribution can be reliably canceled.
　また、エッチング液は、エッチング前のウェーハの表面の凸部に滴下し、リンス液は、エッチング前のウェーハの表面の凹部に滴下することが好ましい。 Further, it is preferable that the etching liquid is dropped on the convex portion on the surface of the wafer before etching and the rinse liquid is dropped on the concave portion on the surface of the wafer before etching.
　この場合、様々な表面形状を有するウェーハ、例えば、外周側が中心側よりも厚いＳＯＩ層膜厚分布を有するＳＯＩウェーハ、中心側が外周側よりも厚いＳＯＩ層膜厚分布を有するＳＯＩウェーハ、外周側がハネ形状を有するウェーハ、外周側がダレ形状を有するウェーハなどに対して、ウェーハの表面形状の改善を図ることができる。 In this case, wafers having various surface shapes, for example, an SOI wafer having an SOI layer thickness distribution thicker on the outer peripheral side than the center side, an SOI wafer having an SOI layer thickness distribution thicker on the central side than the outer peripheral side, and a peripheral edge With respect to a wafer having a shape, a wafer having a sagging shape on the outer peripheral side, and the like, the surface shape of the wafer can be improved.
　また、中心側が外周側よりも厚いＳＯＩ層膜厚分布を有するＳＯＩウェーハ、外周側がダレ形状を有するウェーハなどに対しては、リンス液を滴下する位置は、エッチング液を滴下する位置よりも、ウェーハの外周側とする。 Further, for an SOI wafer having an SOI layer thickness distribution that is thicker on the center side than on the outer peripheral side, or a wafer having a sagging shape on the outer peripheral side, the position where the rinse liquid is dropped is higher than the position where the etching liquid is dropped. The outer peripheral side of.
　この場合、ウェーハの中心側をエッチングするために、薬液としてのＯ３水及びエッチング液（ＨＦ）がウェーハの中心側に滴下されることになるが、当該薬液は、ウェーハの回転により外周側にも拡がる。しかし、ウェーハの外周側には、エッチングを抑制するリンス液が滴下されるため、外周側に拡がるエッチング液はリンス液によって薄まり、外周側でのエッチング反応が抑制される。 In this case, in order to etch the center side of the wafer, O 3 water as a chemical solution and the etching solution (HF) are dropped on the center side of the wafer, but the chemical solution is rotated to the outer peripheral side by the rotation of the wafer. Also spreads. However, since the rinse liquid that suppresses etching is dropped on the outer peripheral side of the wafer, the etching liquid that spreads to the outer peripheral side is thinned by the rinse liquid, and the etching reaction on the outer peripheral side is suppressed.
　また、外周側が中心側よりも厚いＳＯＩ層膜厚分布を有するＳＯＩウェーハ、外周側がハネ形状を有するウェーハなどに対しては、エッチング液を滴下する位置は、リンス液を滴下する位置よりも、ウェーハの外周側とする。 Further, for an SOI wafer having an SOI layer thickness distribution that is thicker on the outer peripheral side than on the center side, a wafer having an edge-shaped outer peripheral side, etc., the position where the etching solution is dropped is lower than the position where the rinse solution is dropped. The outer peripheral side of.
　この場合、ウェーハの外周側をエッチングするために、薬液としてのＯ３水及びエッチング液（ＨＦ）がウェーハの外周側に滴下されることになるが、当該薬液の一部は、凹部であるウェーハの中心側に流れる可能性がある。しかし、ウェーハの中心側には、エッチングを抑制するリンス液が滴下されるため、中心側に流れるエッチング液はリンス液によって薄まり、中心側でのエッチング反応が抑制される。 In this case, in order to etch the outer peripheral side of the wafer, O 3 water as a chemical solution and an etching solution (HF) are dripped on the outer peripheral side of the wafer, but a part of the chemical solution is a recessed wafer. May flow to the center side of. However, since the rinse liquid that suppresses etching is dropped on the center side of the wafer, the etching liquid that flows toward the center side is diluted by the rinse liquid, and the etching reaction on the center side is suppressed.
　なお、上記エッチング方法は、中心部から同心円状に変化する膜厚分布を持つＳＯＩ層を有するＳＯＩウェーハ、ポリッシュドウェーハなどの他、研磨などにより同心円状の凹凸（表面形状）を有する様々なウェーハに対して適用可能である。 The above-mentioned etching method is applied to various wafers having a concentric concavo-convex (surface shape) by polishing or the like, as well as an SOI wafer having an SOI layer having a film thickness distribution that changes concentrically from the center portion, a polished wafer, and the like. Is applicable to.
　また、ウェーハの種類も限定されることはない。例えば、上記エッチング方法は、シリコンウェーハ、Ｇｅ、ＳｉＧｅ、ＳｉＣなどのＩＶ族半導体ウェーハ、ＧａＮ、ＧａＰ、ＧａＡｓ、ＩｎＰなどの化合物半導体ウェーハ、石英、サファイアなどの絶縁性ウェーハ、さらに、これらのウェーハの表面上に薄膜を形成した薄膜付きウェーハなど、に適用可能であり、エッチング液についても、本発明を適用するウェーハの材質に合わせて適宜選択可能である。 Also, the type of wafer is not limited. For example, the above-described etching method includes a silicon wafer, a group IV semiconductor wafer such as Ge, SiGe, and SiC, a compound semiconductor wafer such as GaN, GaP, GaAs, and InP, an insulating wafer such as quartz and sapphire, and It can be applied to a wafer with a thin film having a thin film formed on the surface thereof, and the etching solution can also be appropriately selected according to the material of the wafer to which the present invention is applied.
　以上のように、本発明のエッチング方法であれば、例えば、同心円状の膜厚分布を有するＳＯＩ層や、同心円状の表面／外周形状分布を有するウェーハなど、どのような表面形状を持つウェーハであっても、スピンエッチングによる当該分布の相殺によるＳＯＩ層の膜厚均一性の向上、ＰＷなどのウェーハの表面／外周形状の改善を図ることができる。また、必要に応じて、目的とする膜厚分布を有するように局所エッチングを行うことも可能である。 As described above, according to the etching method of the present invention, for example, a wafer having any surface shape such as an SOI layer having a concentric film thickness distribution or a wafer having a concentric surface/peripheral shape distribution can be used. Even if there is, it is possible to improve the film thickness uniformity of the SOI layer by canceling the distribution by spin etching and to improve the surface/peripheral shape of the wafer such as PW. Further, if necessary, local etching can be performed so as to have a target film thickness distribution.
本発明のエッチング方法の第１の例を示す図である。It is a figure which shows the 1st example of the etching method of this invention. 本発明のエッチング方法の第２の例を示す図である。It is a figure which shows the 2nd example of the etching method of this invention. 実施例１のエッチング方法を示す図である。FIG. 4 is a diagram showing an etching method of Example 1. 実施例１の結果を示す図である。FIG. 5 is a diagram showing the results of Example 1. 実施例２のエッチング方法を示す図である。FIG. 6 is a diagram showing an etching method of Example 2. 実施例２の結果を示す図である。5 is a diagram showing the results of Example 2. FIG. 実施例３のエッチング方法を示す図である。FIG. 8 is a diagram showing an etching method of Example 3; 実施例３の結果を示す図である。FIG. 5 is a diagram showing the results of Example 3. 比較例のエッチング方法を示す図である。It is a figure which shows the etching method of a comparative example. 比較例の結果を示す図である。It is a figure which shows the result of a comparative example.
　上述のように、本発明は、特には、同心円状の膜厚分布を有するＳＯＩ層、又は同心円状の表面／外周形状分布を有するウェーハに対して、スピンエッチング（洗浄）を用い、同心円状の膜厚分布、又は同心円状の表面／外周形状分布を相殺するようにエッチングを行い、ＳＯＩ層の膜厚均一性などのウェーハの表面形状の改善を図ることを主体とした発明である。 As described above, the present invention particularly uses spin etching (cleaning) on an SOI layer having a concentric circular film thickness distribution or a wafer having a concentric circular surface/peripheral shape distribution to obtain a concentric circular film. The invention is mainly intended to improve the surface shape of the wafer such as the uniformity of the film thickness of the SOI layer by performing etching so as to cancel the film thickness distribution or the concentric circular surface/outer peripheral shape distribution.
　従来の技術では、例えば、スピンエッチング装置については、特許文献１に開示されているが、通常、エッチング液を滴下する位置と、リンス液を滴下する位置とは、同じ（例えば、ウェーハの中心部に固定）である。この場合、スピンエッチングでは、ＳＯＩ層の同心円状の膜厚分布や、ウェーハの同心円状の表面／外周形状分布などの様々な表面形状（凹凸）の改善を図ることができない。 In the prior art, for example, a spin etching apparatus is disclosed in Patent Document 1, but normally, the position where the etching liquid is dropped and the position where the rinse liquid is dropped are the same (for example, the central portion of the wafer). Fixed). In this case, spin etching cannot improve various surface shapes (irregularities) such as a concentric thickness distribution of the SOI layer and a concentric surface/peripheral shape distribution of the wafer.
　本発明者らは、上記課題について鋭意検討を重ねた結果、エッチング液（ＨＦ）及びリンス液（純水）を滴下する位置を、エッチング前のウェーハの同心円状の膜厚分布、又は同心円状の表面／外周形状分布に基づきウェーハの径方向に独立に変化させることで、これら膜厚分布、又は表面／外周形状分布の形状によらず、スピンエッチングによりこれら膜厚分布、又は表面／外周形状分布を相殺できることを見出し、本発明を完成させた。 As a result of intensive studies on the above problems, the present inventors have determined that the position where the etching solution (HF) and the rinse solution (pure water) are dropped is a concentric film thickness distribution of the wafer before etching or a concentric circle. By independently changing the wafer radial direction based on the surface/peripheral shape distribution, these film thickness distributions or surface/peripheral shape distributions can be spin-etched regardless of the shape of the film thickness distribution or the surface/peripheral shape distribution. The inventors have found that the above can be offset, and have completed the present invention.
　即ち、本発明は、エッチング液をウェーハの表面に滴下し、かつウェーハを回転させることで、ウェーハの表面のエッチングを行うエッチング方法において、エッチング前のウェーハの表面形状を測定し、エッチングにおいて、エッチング液の滴下とともに、エッチング液によるウェーハの表面のエッチングを抑制するリンス液をウェーハの表面に滴下し、エッチング液を滴下する位置とリンス液を滴下する位置を、測定されたエッチング前のウェーハの表面形状に基づき決定して、ウェーハの表面のエッチングを行うことを特徴とするエッチング方法である。 That is, the present invention, by dropping the etching solution on the surface of the wafer, and by rotating the wafer, in the etching method of etching the surface of the wafer, to measure the surface shape of the wafer before etching, in the etching, Along with the dropping of the liquid, a rinse liquid that suppresses the etching of the surface of the wafer by the etching liquid is dropped onto the surface of the wafer, and the position where the etching liquid is dropped and the position where the rinse liquid is dropped are measured before the etching. The etching method is characterized in that the surface of the wafer is etched by determining based on the shape.
　このように、エッチング前のウェーハの表面形状に基づき、エッチング液を滴下する位置とリンス液を滴下する位置とを決定し、ウェーハの表面のエッチングを行うことで、どのような表面形状を持つウェーハであっても、スピンエッチングにより表面形状の改善を図ることが可能となる。 Thus, based on the surface shape of the wafer before etching, the position where the etching liquid is dropped and the position where the rinse liquid is dropped are determined, and the surface of the wafer is etched to obtain a wafer having any surface shape. Even in this case, the surface shape can be improved by spin etching.
　なお、本発明と特許文献２との相違点は、同心円状の膜厚分布を相殺する方法が、本発明ではスピンエッチングであるのに対し、特許文献２では熱酸化（昇温時又は降温時における酸化）である点にある。一方、スピンエッチングについては、特許文献１に開示されるが、スピンエッチングにおいて、エッチング液とリンス液を滴下する位置をエッチング前のウェーハの表面形状に基づき決定してエッチングを行う点は、特許文献１及び２のいずれからも得ることができない。 The difference between the present invention and Patent Document 2 is that the method of canceling the concentric circular film thickness distribution is spin etching in the present invention, whereas in Patent Document 2, thermal oxidation (at the time of temperature increase or temperature decrease) is performed. Oxidation). On the other hand, although spin-etching is disclosed in Patent Document 1, in spin-etching, the position where the etching liquid and the rinse liquid are dropped is determined based on the surface shape of the wafer before etching and the etching is performed. It cannot be obtained from either 1 or 2.
　以下、本発明の実施形態について、図面を参照しながら詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
　図１は、本発明のエッチング方法の第１の例を示す。
　スピンエッチングのエッチング対象としてのウェーハは、ベース基板（Base substrate）１と、ベース基板１上の埋め込み酸化層（BOX Layer: Buried oxide layer）２と、埋め込み酸化層２上のＳＯＩ層（SOI Layer: Silicon on insulator layer）３と、を備える。ベース基板１は、シリコン基板であり、埋め込み酸化層２は、酸化シリコンであり、ＳＯＩ層３は、単結晶シリコンである。 FIG. 1 shows a first example of the etching method of the present invention.
The wafer to be etched by the spin etching is a base substrate 1, a buried oxide layer 2 on the base substrate 1, and an SOI layer on the buried oxide layer 2. Silicon on insulator layer) 3. The base substrate 1 is a silicon substrate, the buried oxide layer 2 is silicon oxide, and the SOI layer 3 is single crystal silicon.
　本発明のエッチング方法の第１の例は、以下の通りである。
　まず、ＳＯＩ層３の表面形状として膜厚分布を測定する（ステップＳＴ１）。
　ＳＯＩ層３の膜厚は、ウェーハ表面において面内均一であることが要求されるが、例えば、ＳＯＩ層３の表面粗さ改質のために行う研磨工程で、ＳＯＩ層３の膜厚は、面内で同心円状の厚さ分布を有するのが通常だからである。
　本例では、同図に示すように、ＳＯＩ層３は、中心部で厚く、外周部で薄い膜厚分布を有する。 The first example of the etching method of the present invention is as follows.
First, the film thickness distribution is measured as the surface shape of the SOI layer 3 (step ST1).
The film thickness of the SOI layer 3 is required to be in-plane uniform on the wafer surface. For example, in the polishing process performed to improve the surface roughness of the SOI layer 3, the film thickness of the SOI layer 3 is This is because it usually has a concentric thickness distribution in the plane.
In this example, as shown in the figure, the SOI layer 3 has a thick film thickness distribution in the central portion and a thin film thickness distribution in the outer peripheral portion.
　次に、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置と、リンス液を滴下する位置とを、上記工程で測定されたエッチング前のＳＯＩ層３の膜厚分布に基づき決定する（ステップＳＴ２）。
　本例では、ＳＯＩ層３は、ウェーハの中心部で厚いため、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置は、当該中心部とする。また、ＳＯＩ層３は、ウェーハの外周部で薄いため、当該外周部でのＳＯＩ層３のエッチングを抑制することを目的に、リンス液を滴下する位置は、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置よりも外周側、例えば、当該ウェーハの半径の中心部よりも外周側とする。 Next, the position where the O 3 water and the etching liquid (HF) are dropped and the position where the rinse liquid is dropped are determined based on the film thickness distribution of the SOI layer 3 before etching measured in the above process (step ST2). ).
In this example, since the SOI layer 3 is thick at the center of the wafer, the position where the O 3 water and the etching solution (HF) are dropped is the center. Further, since the SOI layer 3 is thin on the outer peripheral portion of the wafer, in order to suppress the etching of the SOI layer 3 on the outer peripheral portion, the position where the rinse liquid is dropped is O 3 water and the etching liquid (HF). On the outer peripheral side of the position where the liquid crystal is dropped, for example, on the outer peripheral side of the center of the radius of the wafer.
　なお、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置は、同じでもよいし、又は異なってもよい。但し、これらの位置は、できるだけ近接していることが好ましい。 The positions of dropping the O 3 water and the etching solution (HF) may be the same or different. However, it is preferable that these positions are as close as possible.
　次に、ウェーハをその中心部を軸に回転させる（ステップＳＴ３）。 Next, the wafer is rotated around its center (step ST3).
　次に、Ｏ３水をウェーハの中心部に滴下するとともに、リンス液をウェーハの中心部よりも外周側に滴下して、ＳＯＩ層３の表面の酸化を行う（ステップＳＴ４）。
　なお、Ｏ３水の滴下は、一定量、又は予め決められた一定期間だけ行う。 Next, O 3 water is dropped on the central portion of the wafer and a rinse liquid is dropped on the outer peripheral side of the central portion of the wafer to oxidize the surface of the SOI layer 3 (step ST4).
The O 3 water is dropped for a fixed amount or for a predetermined fixed period.
　次に、Ｏ３水の滴下を終えた後、リンス液をウェーハの中心部に滴下する（ステップＳＴ５）。
　リンス液をウェーハの中心部に滴下することで、リンス液がウェーハの中心部から外周部に流れ、ウェーハの表面が洗浄される。 Next, after the dropping of the O 3 water is completed, the rinse liquid is dropped on the central portion of the wafer (step ST5).
By dropping the rinse liquid on the central portion of the wafer, the rinse liquid flows from the central portion of the wafer to the outer peripheral portion to clean the surface of the wafer.
　次に、エッチング液（ＨＦ）をウェーハの中心部に滴下するとともに、リンス液をウェーハの中心部よりも外周側に滴下して、ＳＯＩ層３の表面のエッチングを行う（ステップＳＴ６）。
　なお、エッチング液（ＨＦ）の滴下は、一定量、又は予め決められた一定期間だけ行う。 Next, the etching liquid (HF) is dropped on the central portion of the wafer, and the rinse liquid is dropped on the outer peripheral side of the central portion of the wafer to etch the surface of the SOI layer 3 (step ST6).
Note that the etching liquid (HF) is dropped for a fixed amount or for a predetermined fixed period.
　次に、エッチング液（ＨＦ）の滴下を終えた後、リンス液をウェーハの中心部に滴下する（ステップＳＴ７）。
　リンス液をウェーハの中心部に滴下することで、リンス液がウェーハの中心部から外周部に流れ、ウェーハの表面が洗浄される。 Next, after finishing the dropping of the etching solution (HF), the rinse solution is dropped on the central portion of the wafer (step ST7).
By dropping the rinse liquid on the central portion of the wafer, the rinse liquid flows from the central portion of the wafer to the outer peripheral portion to clean the surface of the wafer.
　この後、必要に応じて、上記ステップＳＴ４～ＳＴ７を所定回数だけ繰り返す。 After that, the above steps ST4 to ST7 are repeated a predetermined number of times as required.
　上記工程を終えた後、スピン乾燥を行い、ＳＯＩ層３の膜厚分布を測定する（ステップＳＴ８）。
　測定の結果、ＳＯＩ層３の膜厚の最大値と最小値との差が所定のレンジ内に収まっていれば、上記エッチング方法を終了する。一方、測定の結果、ＳＯＩ層３の膜厚の最大値と最小値との差が所定のレンジ内に収まっていなければ、上記ステップＳＴ３～ＳＴ８を繰り返す。 After the above process is completed, spin drying is performed and the film thickness distribution of the SOI layer 3 is measured (step ST8).
As a result of the measurement, if the difference between the maximum value and the minimum value of the film thickness of the SOI layer 3 is within the predetermined range, the etching method is finished. On the other hand, as a result of the measurement, if the difference between the maximum value and the minimum value of the film thickness of the SOI layer 3 is not within the predetermined range, steps ST3 to ST8 are repeated.
　なお、測定の結果、ＳＯＩ層３の膜厚の最大値と最小値との差が所定のレンジ内に収まっていない場合、再び、ＳＯＩ層３の膜厚分布に応じて、Ｏ３水、エッチング液（ＨＦ）、及びリンス液を滴下する位置を修正して決定した後（ステップＳＴ２）、上記ステップＳＴ３～ＳＴ８を繰り返してもよい。 Note that as a result of the measurement, when the difference between the maximum value and the minimum value of the film thickness of the SOI layer 3 is not within the predetermined range, O 3 water, etching is performed again depending on the film thickness distribution of the SOI layer 3. After the position where the liquid (HF) and the rinse liquid are dropped is corrected and determined (step ST2), the above steps ST3 to ST8 may be repeated.
　以上、本発明のエッチング方法の第１の例によれば、中心部で厚く、外周部で薄い膜厚分布を有するＳＯＩ層に対して、その膜厚分布を相殺するスピンエッチングを行うことにより、ＳＯＩウェーハの表面形状の改善を図ることができる。 As described above, according to the first example of the etching method of the present invention, by performing spin etching for canceling the film thickness distribution on an SOI layer having a film thickness distribution that is thick in the central portion and thin in the outer peripheral portion, The surface shape of the SOI wafer can be improved.
　図２は、本発明のエッチング方法の第２の例を示す。
　スピンエッチングのエッチング対象としてのウェーハは、ベース基板１と、ベース基板１上の埋め込み酸化層２と、埋め込み酸化層２上のＳＯＩ層３と、を備える。ベース基板１は、シリコン基板であり、埋め込み酸化層２は、酸化シリコンであり、ＳＯＩ層３は、単結晶シリコンである。 FIG. 2 shows a second example of the etching method of the present invention.
A wafer as an etching target of spin etching includes a base substrate 1, a buried oxide layer 2 on the base substrate 1, and an SOI layer 3 on the buried oxide layer 2. The base substrate 1 is a silicon substrate, the buried oxide layer 2 is silicon oxide, and the SOI layer 3 is single crystal silicon.
　本発明のエッチング方法の第２の例は、以下の通りである。
　まず、上記第１の例と同様に、ＳＯＩ層３の表面形状として膜厚分布を測定し（ステップＳＴ１）、Ｏ３水、エッチング液（ＨＦ）、及びリンス液を滴下する位置を、測定されたエッチング前のＳＯＩ層３の膜厚分布に基づき決定する（ステップＳＴ２）。 A second example of the etching method of the present invention is as follows.
First, similarly to the first example, the film thickness distribution is measured as the surface shape of the SOI layer 3 (step ST1), and the position where O 3 water, the etching solution (HF), and the rinse solution are dropped is measured. It is determined based on the film thickness distribution of the SOI layer 3 before etching (step ST2).
　本例では、同図に示すように、ＳＯＩ層３は、中心部で薄く、外周部で厚い膜厚分布を有する。従って、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置は、ウェーハの外周部とする。また、リンス液を滴下する位置は、エッチング液（ＨＦ）がウェーハの中心部に入り込んでＳＯＩ層３をエッチングしてしまわないように、当該中心部とする。 In this example, as shown in the figure, the SOI layer 3 has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion. Therefore, the position where the O 3 water and the etching solution (HF) are dropped is the outer peripheral portion of the wafer. The position where the rinsing liquid is dropped is set to the central portion so that the etching liquid (HF) does not enter the central portion of the wafer and etch the SOI layer 3.
　また、本例では、ウェーハのエッジ部において、ＳＯＩ層３がダレ形状を有する。そこで、リンス液を滴下する位置は、ウェーハの中心部に加えて、ウェーハのエッジ部にも滴下する。即ち、リンス液を滴下する位置は、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置よりも中心側、及び外周側の双方とする。 Further, in this example, the SOI layer 3 has a sagging shape at the edge portion of the wafer. Therefore, the rinse liquid is dropped not only on the center of the wafer but also on the edge of the wafer. That is, the position where the rinsing liquid is dropped is both on the center side and the outer peripheral side of the position where the O 3 water and the etching liquid (HF) are dropped.
　次に、ウェーハをその中心部を軸に回転させる（ステップＳＴ３）。 Next, the wafer is rotated around its center (step ST3).
　次に、上記第１の例と同様に、Ｏ３水をウェーハの外周部（ＳＯＩ層３が最も厚い位置か、又はそれよりも中心側）に滴下するとともに、リンス液をウェーハの中心部及びエッジ部に滴下して、ＳＯＩ層３の表面の酸化を行う（ステップＳＴ４）。Ｏ３水の滴下を終えた後、リンス液をウェーハの中心部に滴下する（ステップＳＴ５）。 Next, as in the first example, O 3 water is dropped onto the outer peripheral portion of the wafer (at the position where the SOI layer 3 is thickest or at the center side thereof), and the rinse liquid is applied to the center portion of the wafer and The surface of the SOI layer 3 is oxidized by being dropped onto the edge portion (step ST4). After the dropping of the O 3 water is completed, the rinse liquid is dropped onto the central portion of the wafer (step ST5).
　また、エッチング液（ＨＦ）をウェーハのステップＳＴ４と同じ外周部に滴下するとともに、リンス液をウェーハの中心部及びエッジ部に滴下して、ＳＯＩ層３の表面のエッチングを行う（ステップＳＴ６）。エッチング液（ＨＦ）の滴下を終えた後、リンス液をウェーハの中心部に滴下する（ステップＳＴ７）。 Further, the etching liquid (HF) is dropped on the same outer peripheral portion of the wafer as in step ST4, and the rinse liquid is dropped on the central portion and the edge portion of the wafer to etch the surface of the SOI layer 3 (step ST6). After the dropping of the etching liquid (HF) is completed, the rinse liquid is dropped onto the central portion of the wafer (step ST7).
　この後、上記ステップＳＴ４～ＳＴ７を必要に応じて所定回数だけ繰り返す。 After that, the above steps ST4 to ST7 are repeated a predetermined number of times as necessary.
　上記工程を終えた後、スピン乾燥を行い、ＳＯＩ層３の膜厚分布を測定する（ステップＳＴ８）。
　測定の結果、ＳＯＩ層３の膜厚の最大値と最小値との差が所定のレンジ内に収まっていれば、上記エッチング方法を終了する。一方、測定の結果、ＳＯＩ層３の膜厚の最大値と最小値との差が所定のレンジ内に収まっていなければ、上記ステップＳＴ３～ＳＴ８、又は上記ステップＳＴ１～ＳＴ８を繰り返す。 After the above process is completed, spin drying is performed and the film thickness distribution of the SOI layer 3 is measured (step ST8).
As a result of the measurement, if the difference between the maximum value and the minimum value of the film thickness of the SOI layer 3 is within the predetermined range, the etching method is finished. On the other hand, as a result of the measurement, if the difference between the maximum value and the minimum value of the film thickness of the SOI layer 3 is not within the predetermined range, the steps ST3 to ST8 or the steps ST1 to ST8 are repeated.
　以上、本発明のエッチング方法の第２の例によれば、中心部で薄く、外周部で厚い膜厚分布を有するＳＯＩ層に対して、その膜厚分布を相殺するスピンエッチングを行うことにより、ＳＯＩウェーハの表面形状の改善を図ることができる。 As described above, according to the second example of the etching method of the present invention, by performing the spin etching for canceling the film thickness distribution on the SOI layer having the thin film thickness distribution in the central portion and the thick film thickness in the outer peripheral portion, The surface shape of the SOI wafer can be improved.
　以下、実施例１～３、並びに比較例を用いて、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。 Hereinafter, the present invention will be specifically described with reference to Examples 1 to 3 and Comparative Examples, but the present invention is not limited thereto.
（実施例１）
　図３は、実施例１のエッチング方法を示す。ウェーハは、直径２００ｍｍのＳＯＩウェーハとした。 (Example 1)
FIG. 3 shows the etching method of the first embodiment. The wafer was an SOI wafer with a diameter of 200 mm.
　実施例１のエッチング方法は、本発明のエッチング方法の第２の例（図２）に対応する。即ち、ＳＯＩ層は、中心部で薄く、外周部で厚い膜厚分布を有し、最も厚い位置は、ウェーハのエッジからウェーハの中心部に向かって２０ｍｍの位置である。また、ＳＯＩ層は、ウェーハのエッジ部においてダレ形状を有する。そこで、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置は、ウェーハの外周部、即ち、ＳＯＩ層の最も厚い位置よりも少し内側の位置、例えば、ウェーハのエッジからウェーハの中心部に向かって２５ｍｍの位置とする。また、リンス液を滴下する位置は、ウェーハの中心部及びエッジ部とする。 The etching method of Example 1 corresponds to the second example (FIG. 2) of the etching method of the present invention. That is, the SOI layer has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion, and the thickest position is 20 mm from the edge of the wafer toward the central portion of the wafer. Further, the SOI layer has a sagging shape at the edge portion of the wafer. Therefore, the position where the O 3 water and the etching solution (HF) are dropped is a position slightly inside the outer peripheral portion of the wafer, that is, the thickest position of the SOI layer, for example, from the edge of the wafer toward the central portion of the wafer. The position is 25 mm. The positions where the rinsing liquid is dropped are the central portion and the edge portion of the wafer.
　このようなエッチング方法により局所エッチングが実現され、ウェーハの表面形状の改善が図られたことを示す結果が図４である。 Fig. 4 shows the results that local etching was realized by such an etching method and the surface shape of the wafer was improved.
　図４の結果によれば、ウェーハの中心部及びエッジ部におけるＳＯＩ層のエッチングを抑制しつつ、ウェーハの外周部におけるＳＯＩ層の局所エッチングが実現されていることが分かる。 According to the result of FIG. 4, it is understood that the local etching of the SOI layer in the outer peripheral portion of the wafer is realized while suppressing the etching of the SOI layer in the central portion and the edge portion of the wafer.
　例えば、スピン局所エッチング前のＳＯＩ層の膜厚の最大値（Ｍａｘ）は、８０．３ｎｍであり、最小値（Ｍｉｎ）は、７３．９ｎｍであり、平均値（ＡＶＥ）は、７７．１８ｎｍである。従って、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）は、６．４ｎｍである。これに対し、スピン局所エッチング後のＳＯＩ層の膜厚の最大値は、７５．１ｎｍであり、最小値は、６９．４ｎｍであり、平均値は、７２．４５ｎｍである。従って、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）は、５．７ｎｍである。 For example, the maximum value (Max) of the film thickness of the SOI layer before spin local etching is 80.3 nm, the minimum value (Min) is 73.9 nm, and the average value (AVE) is 77.18 nm. is there. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.4 nm. On the other hand, the maximum value of the film thickness of the SOI layer after the spin local etching is 75.1 nm, the minimum value is 69.4 nm, and the average value is 72.45 nm. Therefore, the difference (range) between the maximum value and the minimum value of the thickness of the SOI layer is 5.7 nm.
　即ち、図４からは、本発明のスピンエッチングにより、ウェーハの外周部（凸部）の局所エッチングが実現され、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）が、６．４ｎｍから５．７ｎｍに改善されたことが分かる。具体的には、図４中の差分に示すように、ＳＯＩ層の膜厚の最大値と最小値との差は、０．７ｎｍだけ改善された。 That is, from FIG. 4, local etching of the outer peripheral portion (projection portion) of the wafer is realized by the spin etching of the present invention, and the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6. It can be seen that it has been improved from 4 nm to 5.7 nm. Specifically, as shown by the difference in FIG. 4, the difference between the maximum value and the minimum value of the film thickness of the SOI layer was improved by 0.7 nm.
（実施例２）
　図５は、実施例２のエッチング方法を示す。ウェーハは、直径２００ｍｍのＳＯＩウェーハとした。 (Example 2)
FIG. 5 shows the etching method of the second embodiment. The wafer was an SOI wafer with a diameter of 200 mm.
　実施例２のエッチング方法も、本発明のエッチング方法の第２の例（図２）に対応する。即ち、ＳＯＩ層は、中心部で薄く、外周部で厚い膜厚分布を有し、最も厚い位置は、ウェーハのエッジからウェーハの中心部に向かって２０ｍｍの位置である。そこで、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置は、ウェーハの外周部、即ち、ＳＯＩ層の最も厚い位置よりも少し内側の位置、例えば、ウェーハのエッジからウェーハの中心部に向かって２５ｍｍの位置とする。また、リンス液を滴下する位置は、ウェーハの中心部とする。 The etching method of Example 2 also corresponds to the second example (FIG. 2) of the etching method of the present invention. That is, the SOI layer has a thin film thickness distribution in the central portion and a thick film thickness in the outer peripheral portion, and the thickest position is 20 mm from the edge of the wafer toward the central portion of the wafer. Therefore, the position where the O 3 water and the etching solution (HF) are dropped is a position slightly inside the outer peripheral portion of the wafer, that is, the thickest position of the SOI layer, for example, from the edge of the wafer toward the central portion of the wafer. The position is 25 mm. The position where the rinsing liquid is dropped is the central portion of the wafer.
　このようなエッチング方法により局所エッチングが実現され、ウェーハの表面形状の改善が図られたことを示す結果が図６である。 Fig. 6 shows the result that local etching was realized by such an etching method and the surface shape of the wafer was improved.
　図６の結果によれば、ウェーハの中心部におけるＳＯＩ層のエッチングを抑制しつつ、ウェーハの外周部におけるＳＯＩ層の局所エッチングが実現されていることが分かる。 According to the results of FIG. 6, it is understood that the local etching of the SOI layer on the outer peripheral portion of the wafer is realized while suppressing the etching of the SOI layer on the central portion of the wafer.
　例えば、スピン局所エッチング前のＳＯＩ層の膜厚の最大値は、７８ｎｍであり、最小値は、７１．７ｎｍであり、平均値は、７５．１８ｎｍである。従って、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）は、６．３ｎｍである。これに対し、スピン局所エッチング後のＳＯＩ層の膜厚の最大値は、７３．６ｎｍであり、最小値は、６７．５ｎｍであり、平均値は、７１．１ｎｍである。従って、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）は、６．１ｎｍである。 For example, the maximum value of the film thickness of the SOI layer before spin local etching is 78 nm, the minimum value is 71.7 nm, and the average value is 75.18 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.3 nm. On the other hand, the maximum value of the film thickness of the SOI layer after spin local etching is 73.6 nm, the minimum value is 67.5 nm, and the average value is 71.1 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.1 nm.
　即ち、図６からは、本発明のスピンエッチングにより、ウェーハの外周部（凸部）の局所エッチングが実現され、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）が、６．３ｎｍから６．１ｎｍに改善されたことが分かる。具体的には、図６中の差分に示すように、ＳＯＩ層の膜厚の最大値と最小値との差は、０．２ｎｍだけ改善された。 That is, from FIG. 6, the local etching of the outer peripheral portion (projection) of the wafer is realized by the spin etching of the present invention, and the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6. It can be seen that the thickness is improved from 3 nm to 6.1 nm. Specifically, as shown by the difference in FIG. 6, the difference between the maximum value and the minimum value of the film thickness of the SOI layer was improved by 0.2 nm.
（実施例３）
　図７は、実施例３のエッチング方法を示す。ウェーハは、直径２００ｍｍのＳＯＩウェーハとした。 (Example 3)
FIG. 7 shows the etching method of the third embodiment. The wafer was an SOI wafer with a diameter of 200 mm.
　実施例３のエッチング方法は、本発明のエッチング方法の第１の例（図１）に対応する。但し、本実施例に用いるウェーハは、中心部が薄く、外周部が厚いＳＯＩ層を有し、最も厚い位置は、ウェーハのエッジからウェーハの中心部に向かって１０ｍｍの位置であるものとする。また、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置は、ウェーハの中心部とし、リンス液を滴下する位置は、ウェーハの外周部、即ち、ＳＯＩ層の最も厚い位置よりも少し内側の位置、例えば、ウェーハのエッジからウェーハの中心部に向かって１５ｍｍの位置とする。 The etching method of Example 3 corresponds to the first example (FIG. 1) of the etching method of the present invention. However, the wafer used in this example has an SOI layer having a thin central portion and a thick outer peripheral portion, and the thickest position is 10 mm from the edge of the wafer toward the central portion of the wafer. The position where the O 3 water and the etching solution (HF) are dropped is the central part of the wafer, and the position where the rinse solution is dropped is the outer peripheral part of the wafer, that is, a position slightly inside the thickest position of the SOI layer. , 15 mm from the edge of the wafer toward the center of the wafer.
　ここで注意しておく点は、実施例３では、ウェーハの中心部を局所エッチングする効果を示すため、スピン局所エッチング前後でＳＯＩ層の膜厚の最大値と最小値との差が大きくなればなるほど、当該中心部における局所エッチングの効果が発生していることを示すことになる。 The point to be noted here is that in Example 3, the effect of locally etching the central portion of the wafer is shown. Therefore, if the difference between the maximum value and the minimum value of the film thickness of the SOI layer becomes large before and after the spin local etching. To some extent, it means that the effect of local etching occurs in the central portion.
　実施例３により局所エッチングが実現され、ウェーハの表面形状が目的通りの形状にされたことを示す結果が図８である。 FIG. 8 shows the results showing that the local etching was realized by Example 3 and the surface shape of the wafer was formed into a desired shape.
　図８の結果によれば、ウェーハの外周部におけるＳＯＩ層のエッチングを抑制しつつ、ウェーハの中心部におけるＳＯＩ層の局所エッチングが実現されていることが分かる。 According to the result of FIG. 8, it is understood that the local etching of the SOI layer in the central portion of the wafer is realized while suppressing the etching of the SOI layer in the outer peripheral portion of the wafer.
　例えば、スピン局所エッチング前のＳＯＩ層の膜厚の最大値は、８１．３ｎｍであり、最小値は、７４．６ｎｍであり、平均値は、７７．７６ｎｍである。従って、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）は、６．７ｎｍである。これに対し、スピン局所エッチング後のＳＯＩ層の膜厚の最大値は、７４．１ｎｍであり、最小値は、６６．９ｎｍであり、平均値は、７０．３６ｎｍである。従って、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）は、７．２ｎｍである。 For example, the maximum value of the film thickness of the SOI layer before spin local etching is 81.3 nm, the minimum value is 74.6 nm, and the average value is 77.76 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.7 nm. On the other hand, the maximum value of the film thickness of the SOI layer after spin local etching is 74.1 nm, the minimum value is 66.9 nm, and the average value is 70.36 nm. Therefore, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 7.2 nm.
　即ち、図８からは、本発明のスピンエッチングにより、ウェーハの中心部（凹部）の局所エッチングが実現され、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）が、６．７ｎｍから７．２ｎｍに増大したことが分かる。具体的には、図８中の差分に示すように、ＳＯＩ層の膜厚の最大値と最小値との差は、－０．５ｎｍとなった。 That is, from FIG. 8, local etching of the central portion (recess) of the wafer is realized by the spin etching of the present invention, and the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer is 6.7 nm. It can be seen that the value increased from 7.2 nm to 7.2 nm. Specifically, as shown by the difference in FIG. 8, the difference between the maximum value and the minimum value of the film thickness of the SOI layer was −0.5 nm.
　この結果は、ウェーハの中心部の局所エッチングが実現されたことを示すもので、仮に、本実施例に用いるウェーハを、中心部が厚く、外周部が薄いＳＯＩ層とした場合には、ＳＯＩ層の膜厚の最大値と最小値との差（レンジ）が縮小されることを意味する。また、必要に応じて、目的とする膜厚分布を有するように、意図的に局所エッチングを行うことも可能となる。 This result shows that local etching of the central portion of the wafer was realized. If the wafer used in this example is an SOI layer having a thick central portion and a thin outer peripheral portion, the SOI layer It means that the difference (range) between the maximum value and the minimum value of the film thickness of is reduced. Further, if necessary, it is possible to intentionally perform local etching so as to have a desired film thickness distribution.
（比較例）
　図９は、比較例のエッチング方法を示す。ウェーハは、直径２００ｍｍのＳＯＩウェーハとした。 (Comparative example)
FIG. 9 shows an etching method of a comparative example. The wafer was an SOI wafer with a diameter of 200 mm.
　比較例のエッチング方法に用いるウェーハは、実施例１～３と同様に、中心部が薄く、外周部が厚いＳＯＩ層を有し、最も厚い位置は、ウェーハのエッジからウェーハの中心部に向かって２０ｍｍの位置であるものとする。但し、比較例では、Ｏ３水及びエッチング液（ＨＦ）を滴下する位置は、ウェーハの中心部に固定し、リンス液は、ウェーハ上に滴下しないものとする。 The wafer used in the etching method of the comparative example has an SOI layer having a thin central portion and a thick outer peripheral portion, as in Examples 1 to 3, and the thickest position is from the edge of the wafer toward the central portion of the wafer. It is assumed that the position is 20 mm. However, in the comparative example, the position where the O 3 water and the etching liquid (HF) are dropped is fixed to the center of the wafer, and the rinse liquid is not dropped onto the wafer.
　比較例では、Ｏ３水及びエッチング液（ＨＦ）が、ウェーハの中心部から外周部に向かって一様に拡がるため、局所エッチングを実現することができない。その結果が図１０である。 In the comparative example, since the O 3 water and the etching solution (HF) spread uniformly from the central portion of the wafer toward the outer peripheral portion, local etching cannot be realized. The result is shown in FIG.
　図１０の結果によれば、スピンエッチング前におけるＳＯＩ層の膜厚の最大値と最小値との差（レンジ）は、３．９ｎｍである。また、スピンエッチング後におけるＳＯＩ層の膜厚の最大値と最小値との差（レンジ）も、３．９ｎｍである。即ち、図１０中の差分に示すように、ＳＯＩ層の膜厚の最大値と最小値との差に変化はなく、局所エッチングが実現されていないことが分かる。 According to the result of FIG. 10, the difference (range) between the maximum value and the minimum value of the film thickness of the SOI layer before spin etching is 3.9 nm. The difference (range) between the maximum value and the minimum value of the thickness of the SOI layer after spin etching is also 3.9 nm. That is, as shown by the difference in FIG. 10, it can be seen that there is no change in the difference between the maximum value and the minimum value of the film thickness of the SOI layer, and local etching is not realized.
　以上、説明したように、本発明のエッチング方法によれば、例えば、研磨によるＳＯＩ層の同心円状の膜厚のばらつきを局所エッチングにマッチングさせることで、ＳＯＩ層の膜厚の最大値と最小値との差を低減し、ＳＯＩ層の膜厚の面内均一性の向上によるウェーハの表面形状の改善を図ることができる。また、必要に応じて、局所エッチングにより膜厚分布又はウェーハ形状をコントロールすることができるため、目的とする所望の膜厚分布又はウェーハ形状を得ることが容易となる。 As described above, according to the etching method of the present invention, for example, the maximum value and the minimum value of the film thickness of the SOI layer are matched by matching the variation of the concentric film thickness of the SOI layer due to polishing with the local etching. It is possible to improve the surface shape of the wafer by reducing the difference between the thickness of the SOI layer and the in-plane uniformity of the film thickness of the SOI layer. Moreover, since the film thickness distribution or the wafer shape can be controlled by local etching if necessary, it becomes easy to obtain a desired desired film thickness distribution or wafer shape.
　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-described embodiment is an exemplification, and the invention having substantially the same configuration as the technical idea described in the scope of the claims of the present invention and exhibiting the same action and effect is the present invention It is included in the technical scope of.

Claims (8)

  1. 　エッチング液をウェーハの表面に滴下し、かつ前記ウェーハを回転させることで、前記ウェーハの表面のエッチングを行うエッチング方法において、
    　前記エッチング前の前記ウェーハの表面形状を測定し、
    　前記エッチングにおいて、前記エッチング液の滴下とともに、前記エッチング液による前記ウェーハの表面のエッチングを抑制するリンス液を前記ウェーハの表面に滴下し、
    　前記エッチング液を滴下する位置と前記リンス液を滴下する位置を、前記測定されたエッチング前の前記ウェーハの表面形状に基づき決定して、前記ウェーハの表面のエッチングを行うことを特徴とするエッチング方法。     In an etching method of etching the surface of the wafer, by dropping an etching solution on the surface of the wafer, and rotating the wafer,
    Measuring the surface shape of the wafer before the etching,
    In the etching, with the dropping of the etching solution, a rinse solution that suppresses the etching of the surface of the wafer by the etching solution is dropped on the surface of the wafer,
    An etching method characterized in that the position where the etching liquid is dropped and the position where the rinse liquid is dropped are determined based on the measured surface shape of the wafer before etching, and the surface of the wafer is etched. ..
  2. 　前記エッチング液の滴下と前記リンス液の滴下とは同時に行われることを特徴とする請求項１に記載のエッチング方法。 The etching method according to claim 1, wherein the dropping of the etching liquid and the dropping of the rinse liquid are performed at the same time.
  3. 　前記エッチング前の前記ウェーハの表面形状は、前記ウェーハの中心部から同心円状に変化することを特徴とする請求項１又は２に記載のエッチング方法。 The etching method according to claim 1 or 2, wherein the surface shape of the wafer before the etching changes from the central portion of the wafer to a concentric shape.
  4. 　前記エッチング液は、前記エッチング前の前記ウェーハの表面の凸部に滴下し、前記リンス液は、前記エッチング前の前記ウェーハの表面の凹部に滴下することを特徴とする請求項１から３のいずれか１項に記載のエッチング方法。 4. The etching liquid is dropped onto a convex portion on the surface of the wafer before the etching, and the rinse liquid is dropped onto a concave portion on the surface of the wafer before the etching. The etching method according to item 1.
  5. 　前記リンス液を滴下する位置は、前記エッチング液を滴下する位置よりも、前記ウェーハの外周側であることを特徴とする請求項１から４のいずれか１項に記載のエッチング方法。 The etching method according to any one of claims 1 to 4, wherein a position where the rinsing liquid is dropped is closer to the outer peripheral side of the wafer than a position where the etching liquid is dropped.
  6. 　前記エッチング液を滴下する位置は、前記リンス液を滴下する位置よりも、前記ウェーハの外周側であることを特徴とする請求項１から４のいずれか１項に記載のエッチング方法。 The etching method according to any one of claims 1 to 4, wherein the position where the etching liquid is dropped is closer to the outer peripheral side of the wafer than the position where the rinse liquid is dropped.
  7. 　前記ウェーハは、前記ウェーハの中心部から同心円状に変化する膜厚分布を持つＳＯＩ層を有するＳＯＩウェーハであり、前記エッチングは、前記ＳＯＩ層に対して行われることを特徴とする請求項１から６のいずれか１項に記載のエッチング方法。 2. The wafer is an SOI wafer having an SOI layer having a film thickness distribution that changes concentrically from the center of the wafer, and the etching is performed on the SOI layer. 6. The etching method according to any one of 6 above.
  8. 　前記ウェーハは、ポリッシュドウェーハであることを特徴とする請求項１から６のいずれか１項に記載のエッチング方法。
          7. The etching method according to claim 1, wherein the wafer is a polished wafer.
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