WO2014069156A1 - Method for evaluating silicon wafer and etchant for same - Google Patents

Method for evaluating silicon wafer and etchant for same Download PDF

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WO2014069156A1
WO2014069156A1 PCT/JP2013/077069 JP2013077069W WO2014069156A1 WO 2014069156 A1 WO2014069156 A1 WO 2014069156A1 JP 2013077069 W JP2013077069 W JP 2013077069W WO 2014069156 A1 WO2014069156 A1 WO 2014069156A1
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silicon wafer
lep
etching solution
etching
wafer
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PCT/JP2013/077069
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French (fr)
Japanese (ja)
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善範 矢ヶ崎
典雄 大高
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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
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/20—Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
    • H01L22/24—Optical enhancement of defects or not directly visible states, e.g. selective electrolytic deposition, bubbles in liquids, light emission, colour change
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/32—Polishing; Etching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/10—Measuring as part of the manufacturing process
    • H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions

Definitions

  • the present invention relates to a silicon wafer evaluation method and an etching solution thereof, and more specifically, an evaluation method for detecting crystal defects that degrade the electrical characteristics of a semiconductor device by selectively etching the surface of the silicon wafer, and It relates to the etching solution.
  • Patent Document 1 contains potassium dichromate at the stage where the surface of a wafer cut out from a silicon single crystal ingot is mirror-etched with a mixed solution of hydrofluoric acid and nitric acid (this stage wafer is called a mirror-etched wafer).
  • Patent Document 1 contains potassium dichromate at the stage where the surface of a wafer cut out from a silicon single crystal ingot is mirror-etched with a mixed solution of hydrofluoric acid and nitric acid (this stage wafer is called a mirror-etched wafer).
  • a method of selectively etching a crystal defect portion by dipping in a SECCO solution is disclosed. According to this method, a defective portion on the surface of the wafer appears as a ripple pattern (flow pattern), and the wafer can be easily evaluated without producing a polished wafer (at the stage of a mirror-etched wafer).
  • Patent Document 2 discloses that FPD observation shows a capability equivalent to that of secco solution, and selectively etches a mirror-etched wafer using a chromium-less etching solution that does not use potassium dichromate, which is a harmful substance. A method for detecting the above has been proposed.
  • LEP is visually observed by an operator through an optical microscope and counted. For this reason, LEP has a very low density, and it is not easy to find LEP by paying attention only to the shape of an ellipse.
  • the chromeless etching solution disclosed in Patent Document 2 is effective for FPD observation but has low sensitivity with respect to LEP. That is, since LEP is a micro-dislocation defect, even when selective etching is performed with a conventional chromeless etchant, the size of the elliptical shape is as small as several ⁇ m and observation is not easy.
  • an object of the present invention is to provide a silicon wafer evaluation method and an etching solution thereof that can easily observe LEP.
  • the silicon wafer evaluation method of the present invention is such that the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water in the etching solution is (400) :( 5-10) :( 10-50):
  • the silicon wafer is immersed in an etching solution of (80 to 120) and containing iodine or iodide to selectively etch crystal defect portions and detect LEP.
  • an etching solution having a volume ratio of hydrofluoric acid, nitric acid, acetic acid and water of (400) :( 5-10) :( 10-50) :( 80-120) and containing iodine or iodide is prepared. Therefore, the LEP of a silicon wafer made of a single crystal grown at a low speed can be evaluated without using a Secco solution containing a harmful substance (chromium) that has a strong influence on the global environment and human body.
  • LEP which is observed only as an elliptical shape in the conventional etching solution, has an elliptical pattern having a ripple pattern (flow pattern) in the same manner as FPD in the majority of all LEPs.
  • flow pattern ripple pattern
  • the size of the elliptical shape (LEP) can be made larger than when a conventional etching solution is used (diameter of about 10 ⁇ m).
  • the FPD does not form a clear flow pattern, and only the LEP is easily observed.
  • the volume ratio of nitric acid is 5-10.
  • the volume ratio of nitric acid is less than 5, the shape of the flow pattern may not be clear.
  • the sharpness improves as the volume ratio of nitric acid increases, but when the volume ratio of nitric acid exceeds 10, surface roughness of the wafer surface may occur very strongly.
  • the etching rate is faster than when the etching solution of Patent Document 2 is used, so the size of the LEP (elliptical shape) can be increased and the shape of the flow pattern is also compared. Observed clearly and vividly. Therefore, by the evaluation method of the present invention, a flow pattern having a good shape can be clearly formed in the crystal defect portion of the surface layer of the silicon wafer, and LEP can be detected with high sensitivity.
  • the content of iodine or iodide in the etching solution is 0.03 g or more per liter of the total amount of the etching solution.
  • iodine or iodide is added to the etching solution in this way is that it is effective in preventing the occurrence of stains (stain film) adhering to the wafer surface. By preventing the occurrence of a stain film, the flow pattern can be confirmed clearly and stably, leading to a reduction in reaction start time and a uniform etching allowance, thereby improving evaluation accuracy.
  • the iodide include potassium iodide, and may be added as an aqueous solution.
  • the amount of iodine or iodide added is desirably 0.03 g or more with respect to 1 liter of the total amount of the etching solution.
  • the silicon wafer is preferably a wafer after chemical mirror polishing obtained by slicing from a silicon single crystal ingot.
  • the etching solution used in the present invention can form an elliptical etching pattern having a good shape even at the stage of a wafer after chemical mirror polishing, that is, a mirror etched wafer.
  • a subsequent mechanical and chemical polishing process which saves time and money for the preparation of the sample for evaluation.
  • Good it can be evaluated by omitting the cylindrical polishing process of the grown silicon single crystal ingot and slicing it, omitting the etching to remove polishing distortion, and performing mirror etching, so an evaluation sample can be obtained in a very short process.
  • the silicon wafer can be evaluated.
  • the etch-off amount of the silicon wafer by the etching is preferably 3 to 50 ⁇ m on both sides.
  • LEP is uniformly generated in a silicon single crystal when the silicon single crystal is grown, and exists uniformly in the depth direction with respect to the wafer surface.
  • the surface portion of the wafer is removed by etching, and LEP distributed in the depth direction is detected as it is removed, and the number of LEPs accumulates on the etched wafer surface. become.
  • LEP can be accurately evaluated by setting the etch-off amount, that is, the thickness of the silicon wafer removed by etching to 3 to 50 ⁇ m. If the etch-off amount is less than 3 ⁇ m, the density of LEP is too low to perform accurate evaluation. On the other hand, if the etch-off amount exceeds 50 ⁇ m, the LEP shape at the initial stage of etching may be lost, and the LEP density may be too high to perform accurate evaluation.
  • the etching it is preferable to perform the etching at an immersion start temperature of 10 to 30 ° C.
  • the immersion start temperature 10 to 30 ° C.
  • the immersion start temperature is less than 10 ° C.
  • the progress of etching is slow and the detection sensitivity is lowered.
  • the immersion start temperature exceeds 30 ° C.
  • the etching rate is high, and the liquid temperature rises accordingly, the etching progresses remarkably fast, the shape of the etching pattern collapses and the density becomes too high to be detected. Sometimes it becomes.
  • the etching solution of the present invention is an etching solution used for detecting LEP of a silicon wafer, and the etching solution contains hydrofluoric acid, nitric acid, acetic acid and water (400): (5 to 10): (10 to 50): (80 to 120), and iodine or iodide is contained in an amount of 0.03 g or more per liter of the total amount of the etching solution. . Thereby, the same effect as the evaluation method of the silicon wafer can be obtained.
  • FIG. 7A It is the figure which illustrated the elliptical pattern observed on the silicon wafer surface. It is a histogram of the long width X of LEP in an Example and Comparative Examples 1 and 2. FIG. It is a histogram of the short width Y of LEP in an Example and Comparative Examples 1 and 2. FIG. It is a histogram of the area of LEP in an Example and the comparative examples 1 and 2. FIG. It is an image of the sample of an Example. It is an enlarged image of the A section of Drawing 5A. It is an enlarged image of the B section of Drawing 5B. It is an image of the sample of an Example with high LEP density. It is an image of the sample of the comparative example 1. It is an enlarged image of the C section of Drawing 7A.
  • a known silicon single crystal substrate manufacturing method may be used as a silicon wafer manufacturing method.
  • a silicon wafer sliced from a silicon single crystal ingot pulled up by the Czochralski method can be used.
  • the crystal growth rate (pulling rate) of the silicon single crystal ingot is low, LEP is likely to be formed, and the necessity for evaluating the LEP increases. Therefore, here, particularly from the silicon single crystal ingot having a relatively low crystal growth rate.
  • a sliced silicon wafer can be used.
  • the surface of the sliced silicon wafer and a few ⁇ m in the depth direction from the surface need to be in a state in which processing distortion due to slicing or the like does not remain, so a chemical polishing liquid such as hydrofluoric acid and nitric acid By etching with a mixed acid having a ratio of about 1: 3, it is possible to prepare a mirror-etched wafer having a chemically mirror-finished surface while removing processing distortion on the surface of the silicon wafer.
  • a polished wafer may be prepared as an evaluation sample instead of the mirror-etched wafer.
  • a general manufacturing method of a polished wafer will be described.
  • a silicon wafer is cut out from a silicon single crystal ingot grown by the Czochralski method (slicing process) and cut out (sliced).
  • Chamfering is performed to remove the corners of the periphery of the silicon wafer (beveling process).
  • mechanical polishing is applied to eliminate unevenness on the silicon wafer surface, increase flatness, and minimize surface scratches (lapping process; sometimes referred to as a wrapped wafer at this stage).
  • the strained polishing layer formed on the surface layer of the silicon wafer is removed by mixed acid etching to obtain a silicon wafer having improved chemical flatness (chemical etching process; this is called a chemically etched wafer at this stage) is there).
  • polishing is performed while overlapping the mechanical action by the free abrasive grains and the etching action by the chemical substance on the surface of the chemically etched wafer.
  • the mechanochemical polishing method is employed, and this polishing method is usually composed of two or three steps. That is, it is called primary polishing, secondary polishing (in some cases, there is also tertiary polishing), and finish polishing in the order of the steps.
  • polishing cloth Polishing is performed while relaxing the polishing conditions such as decreasing the hardness and setting the conditions so that the flatness and surface roughness of the mirror surface polished at each stage become low values.
  • a polished wafer is manufactured through the above processes. In the following description, it is assumed that a mirror-etched wafer is prepared as an evaluation sample.
  • an etchant used to detect crystal defects (LEP) of the prepared mirror-etched wafer As the etchant, hydrofluoric acid, nitric acid, acetic acid and water in the etchant have a volume ratio of (400) :( 5-10) :( 10-50) :( 80-120), and iodine or An etching solution containing 0.03 to 0.15 g of iodide with respect to 1 liter of the total amount of the etching solution is prepared.
  • the etching solution a commercially available semiconductor grade chemical solution can be used.
  • hydrofluoric acid (50% by weight) is for semiconductors of Daikin Industries, Ltd.
  • nitric acid (61% by weight) is Kanto Chemical.
  • the EL grade of Co., Ltd. and acetic acid (99.7% by weight) can be prepared by mixing the special grade of Kanto Chemical Co., Ltd. as it is at the above volume ratio.
  • water it is preferable to use ultrapure water used in the semiconductor industry in consideration of adhesion of dust and dirt to the wafer during the etching process.
  • the mirror etched wafer obtained as described above is added to the etching solution of the present invention having a liquid temperature of 10 to 30 ° C., and the etching off time is 3 to 50 ⁇ m on both sides of the mirror etched wafer. Then, it is left to stand without stirring, and the crystal defect portion is selectively etched. As a result, an elliptical etching pattern can appear on the surface of the mirror-etched wafer. This elliptical etching pattern is a pattern resulting from LEP. Further, most of all elliptical shapes (LEPs) appearing on the mirror-etched wafer surface (about 80% as shown in the examples below) have a flow pattern similar to FPD.
  • LEPs elliptical shapes
  • the remaining 20% appears as a conventional elliptical single pattern.
  • the flow pattern can be easily confirmed by visual observation by placing the etched wafer under light collection.
  • the existence of an elliptical pattern (LEP) in the flow pattern can be easily confirmed by confirming the confirmed flow pattern in an enlarged form with an optical microscope or the like.
  • the LEP cannot be confirmed unless the entire surface of the wafer is scanned with an optical microscope or the like.
  • the number of elliptical patterns is measured as an LEP density by visual detection through an optical microscope or by an automatic detection device that automatically detects LEP (see Japanese Patent Application Laid-Open No. 2004-117147). Based on the above, the quality of the crystal quality of the silicon wafer is evaluated.
  • a silicon wafer for evaluation after being sliced from a silicon single crystal ingot having a diameter of 300 mm, a conductivity type of P type, and a resistivity of about 10 ⁇ ⁇ cm grown under various manufacturing conditions, a chemical mirror polishing (mirror etching) solution A wafer (mirror etched wafer) in a mirror state was prepared. These sample wafers were divided into four fan shapes. LEP was evaluated according to each condition of the following Example and comparative example with respect to the wafer.
  • a conventional chromeless etchant specifically, an etchant having a volume ratio of 400: 3: 33: 80 (hereinafter referred to as a conventional etchant) of 50 wt% hydrofluoric acid, 61 wt% nitric acid, 99.7 wt% acetic acid and water. 12 liters of chromeless solution) was prepared. This conventional chromeless solution was mixed with 132 ml of 61 wt% nitric acid and 480 ml of water. Further, 63.6 ml of 0.1 mol / liter potassium iodide aqueous solution was added to prepare the etching solution of the present invention.
  • the volume ratio of the prepared etching solution is hydrofluoric acid 400, nitric acid 5.3, acetic acid 33, and water 90.
  • the content of potassium iodide is about 0.08 g per liter of the total amount of the etching solution.
  • the etching solution was allowed to stand for 1 day, and then immersed in the etching solution with the above-described 30 samples standing vertically at an immersion start temperature of 24 ° C., without stirring. Left for a minute.
  • the etch-off amount at this time was about 28 ⁇ m on both sides.
  • the size of each elliptical pattern that appeared on the surface of each sample wafer was measured.
  • the size of the elliptical pattern is a longer width X of the elliptical pattern (corresponding to the length of the major axis of the ellipse) (hereinafter referred to as a long width), and shorter.
  • the width Y (corresponding to the length of the minor axis of the ellipse) (hereinafter referred to as the short width) and the area were measured.
  • the long width X and the short width Y were measured from an enlarged image of an elliptical pattern using image analysis software (software that can calculate the distance between pixels).
  • a value obtained by multiplying the long width X and the short width Y was defined as an area (X ⁇ Y) of the pattern (LEP).
  • FIG. 2 to 4 show LEP size histograms (frequency distribution) as measurement results of the LEP (elliptical pattern) size (long width X, short width Y, area).
  • FIG. 2 shows a histogram of the LEP long width X in Examples and Comparative Examples 1 and 2, in detail, the horizontal axis indicates the long width X, and the vertical axis indicates a plurality of samples ( Example 1 and Comparative Example 1 indicate 30% of the long width X obtained from 30 samples and Comparative Example 2 37 samples), that is, the frequency.
  • FIG. 3 shows a histogram of the short width Y of the LEP in Examples and Comparative Examples 1 and 2. Specifically, the horizontal axis indicates the short width Y, and the vertical axis indicates the short width Y obtained from each sample.
  • FIG. 4 shows a histogram of LEP areas in Examples and Comparative Examples 1 and 2. Specifically, the horizontal axis indicates the area, and the vertical axis indicates which area section is what percentage of the area obtained from each sample. The frequency of whether it belongs to is shown.
  • the average value of the sizes (long width X, short width Y, area) of the plurality of LEPs is calculated, and one long width X, short per sample is calculated. Width Y and area were obtained. Further, the long width X, the short width Y, and the area can be obtained by the number of samples (30 sheets in the case of Example and Comparative Example 1 and 37 sheets in the case of Comparative Example 2). Shows a histogram of the long width X, the short width Y, and the area of those 30 sheets and 37 sheets.
  • Table 1 below is a table of LEP size measurement results in Examples and Comparative Examples 1 and 2.
  • the first column in Table 1 indicates the number of samples N.
  • the second column shows the average value of the long width X obtained from each sample.
  • the third column shows the average value of the short width Y obtained from each sample.
  • the fourth column shows the average area obtained from each sample.
  • the etching solution of the present invention in the etching solution of the present invention, a LEP having a larger size (area) is more easily observed than the conventional etching solution (particularly, the conventional chromeless solution).
  • the average value of the long width X of the example is 14.9 ⁇ m
  • the average value of the short width Y is 10.4 ⁇ m
  • LEP which is a micro dislocation defect is observed in a large size having a diameter of 10 ⁇ m or more.
  • 5A to 5C show images obtained by appropriately selecting one of the 30 samples of the embodiment and imaging a part of the surface of the selected sample.
  • FIG. 5A shows an image with the same magnification
  • FIG. 5B shows an enlarged image of part A in FIG. 5A
  • FIG. 5C shows an enlarged image of part B in FIG. 5B. Note that the enlarged image in FIG. 5C is an image having a unit length of 10 ⁇ m.
  • FIG. 6 is an equal-magnification image of the sample of Example 1 different from the samples of FIGS. 5A to 5C, and shows an image of a sample having a higher LEP density than the samples of FIGS. 5A to 5C. .
  • the LEP flow pattern (white portion) can be easily observed visually. As described above, when the etching solution of the present invention is used, the LEP flow pattern is observed, so that the LEP can be easily found and observed.
  • FIG. 7A and FIG. 7B are images obtained by picking one of the 30 samples of Comparative Example 1 (conventional chromeless liquid) appropriately and capturing a part of the surface of the selected sample.
  • FIG. 7A shows the same-size image
  • FIG. 7B is an enlarged image (enlarged image of the elliptical pattern 4 (LEP)) in part C of FIG. 7A.
  • the enlarged image in FIG. 7B is an image having the same enlargement ratio as that in FIG.
  • FIGS. 7A and 7B when the etching solution of Comparative Example 1 was used, no LEP flow pattern was observed. It can also be seen that pattern 3 in FIG. 5C is larger than pattern 4 in FIG. 7B.
  • the incidence of LEP having a flow pattern was measured for the samples of Example and Comparative Example 1. Specifically, three samples A, B, and C are appropriately selected from the 30 samples in the embodiment, and the number of all LEPs N1, the flow pattern for each of the samples A, B, and C is selected. The number of LEPs having N2 and the occurrence rate of LEPs having a flow pattern (N2 / N1 ⁇ 100) were measured. Further, one sample D is appropriately selected from the 30 samples of Comparative Example 1, and the total number of LEPs N1, the number of LEPs having a flow pattern N2, and the flow pattern are associated with the sample D. The incidence of LEP (N2 / N1 ⁇ 100) was measured. Table 2 below shows the measurement results.
  • the electrical characteristics of the silicon wafer are deteriorated without using potassium dichromate which is a harmful substance to the global environment and the human body. LEP can be easily observed.

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Abstract

A silicon wafer is immersed in an etchant and the crystal defect portion are selectively etched, the volumetric ratio of hydrofluoric acid, nitric acid, acetic acid, and water in the etchant being (400):(5-10):(10-50):(80-120), and the iodine or iodide content of the etchant being at least 0.03 g per liter of the total volume thereof. An ellipsoidal pattern (LEP) having a diameter of approximately 10 µm thereby appears on the surface of the silicon wafer, and a large portion of the total LEP can be observed as a flow pattern. The rest of the LEP appears as a single pattern in an ellipsoidal shape as in the past. Provided are a method for evaluating a silicon wafer and an etchant for same, said method having performance equivalent to or greater than a secco solution in LEP observation and being capable of observing the LEP easily, without using a fluid containing potassium dichromate, which is a toxic substance.

Description

シリコンウェーハの評価方法及びそのエッチング液Silicon wafer evaluation method and etching solution thereof
　本発明は、シリコンウェーハの評価方法及びそのエッチング液に関し、さらに詳しくはシリコンウェーハの表面を選択的にエッチングすることにより半導体デバイスの電気特性を劣化させるような結晶欠陥を検出するための評価方法及びそのエッチング液に関する。 The present invention relates to a silicon wafer evaluation method and an etching solution thereof, and more specifically, an evaluation method for detecting crystal defects that degrade the electrical characteristics of a semiconductor device by selectively etching the surface of the silicon wafer, and It relates to the etching solution.
　近年、半導体集積回路はその集積度を著しく増し、性能・信頼性・歩留まりの高い集積回路を得る為には、機械的な精度だけではなく、電気的な特性についても高いことが要請されるようになってきた。それに伴い半導体集積回路に使用されるシリコンウェーハの結晶品質に対し、より厳しい条件が課せられるようになった。シリコンウェーハの結晶品質の一例については、シリコン単結晶育成時に導入される空孔が原因となる、いわゆるフローパターン欠陥（Ｆｌｏｗ　Ｐａｔｔｅｒｎ　Ｄｅｆｅｃｔ；以下、ＦＰＤと呼ぶことがある）やＣＯＰ（Ｃｒｙｓｔａｌ　Ｏｒｉｇｉｎａｔｅｄ　Ｐａｒｔｉｃｌｅ）と呼ばれるＧｒｏｗｎ－ｉｎ欠陥がシリコンウェーハの酸化膜耐圧特性などを劣化させることがあり、このようなＧｒｏｗｎ－ｉｎ欠陥を低減したシリコンウェーハやＧｒｏｗｎ－ｉｎ欠陥が実質的に存在しないシリコンウェーハが重要視されてきている。このＦＰＤやＣＯＰは、近年の研究では、同じＧｒｏｗｎ－ｉｎ欠陥であり、シリコン単結晶育成時の熱履歴に起因して発生する空孔が原因であることが明らかにされてきた。 In recent years, the degree of integration of semiconductor integrated circuits has increased significantly, and in order to obtain integrated circuits with high performance, reliability, and yield, it is required that not only mechanical precision but also electrical characteristics be high. It has become. As a result, more severe conditions have been imposed on the crystal quality of silicon wafers used in semiconductor integrated circuits. Examples of crystal quality of silicon wafers include so-called flow pattern defects (hereinafter sometimes referred to as FPD) and COPs (Crystal Originated Particles) caused by vacancies introduced during silicon single crystal growth. Grown-in defects called silicon wafers may degrade the oxide film breakdown voltage characteristics of silicon wafers. Silicon wafers with reduced growth-in defects and silicon wafers that are substantially free of grown-in defects are regarded as important. Has been. In recent studies, it has been clarified that FPD and COP are the same Grown-in defect and are caused by vacancies generated due to thermal history during the growth of a silicon single crystal.
　さて、このようなシリコンウェーハの電気特性を劣化させるＧｒｏｗｎ－ｉｎ欠陥を検出する方法として、従来、シリコンウェーハの表面をエッチング液でエッチングし、結晶欠陥のあるところないところの被エッチング速度の差を利用した選択エッチング法が知られている（例えば特許文献１、２参照）。例えば特許文献１には、シリコン単結晶インゴットから切り出したウェーハの表面をフッ酸と硝酸の混合液でミラーエッチングした段階（この段階のウェーハをミラーエッチドウェーハという）で、重クロム酸カリウムを含有するセコ（ＳＥＣＣＯ）液に浸漬して結晶欠陥部分を選択的にエッチングする方法が開示されている。この方法によれば、ウェーハの表面の欠陥部分がさざ波模様（フローパターン）として現れ、ポリッシュドウェーハを作製しなくても（ミラーエッチドウェーハの段階で）簡便にウェーハを評価できるとしている。 Now, as a method for detecting a grown-in defect that deteriorates the electrical characteristics of such a silicon wafer, conventionally, the surface of the silicon wafer is etched with an etching solution, and the difference in etching rate where there is no crystal defect is calculated. A selective etching method is known (see, for example, Patent Documents 1 and 2). For example, Patent Document 1 contains potassium dichromate at the stage where the surface of a wafer cut out from a silicon single crystal ingot is mirror-etched with a mixed solution of hydrofluoric acid and nitric acid (this stage wafer is called a mirror-etched wafer). A method of selectively etching a crystal defect portion by dipping in a SECCO solution is disclosed. According to this method, a defective portion on the surface of the wafer appears as a ripple pattern (flow pattern), and the wafer can be easily evaluated without producing a polished wafer (at the stage of a mirror-etched wafer).
　また、特許文献２には、ＦＰＤ観察においてセコ液と同等の能力を示し、かつ有害な物質である重クロム酸カリウムを使わないクロムレスエッチング液を用いてミラーエッチドウェーハを選択エッチングし、ＦＰＤを検出する方法が提案されている。 Patent Document 2 discloses that FPD observation shows a capability equivalent to that of secco solution, and selectively etches a mirror-etched wafer using a chromium-less etching solution that does not use potassium dichromate, which is a harmful substance. A method for detecting the above has been proposed.
特公平６－１０３７１４号公報Japanese Patent Publication No. 6-103714 特開２００３－２０９１５０号公報JP 2003-209150 A
　ところで、最近、より低欠陥のウェーハが求められ、このため単結晶インゴットを育成する際に結晶成長速度を遅くするなどの対策がとられている。単結晶インゴットの結晶成長速度が比較的遅い場合、作製したウェーハに、セコ液による選択エッチングを行うと、ウェーハ表面には上記ＦＰＤとは大きさ及び形状が全く異なる楕円形状の欠陥が観察される。この楕円形状の欠陥は、ＬＥＰ（Ｌａｒｇｅ　Ｅｔｃｈｉｎｇ　Ｐｉｔ）と呼ばれ（ディスロケーションループと呼ばれることもある）、結晶成長過程の熱履歴の違いによってＦＰＤと区別されるものである。このＬＥＰは、Ｇｒｏｗｎ－ｉｎ欠陥の一つで、格子間シリコンタイプの点欠陥が集合した転位ループ、転位クラスタに起因して形成されるものであると考えられている。したがって、このＬＥＰを正確に評価することによって、半導体結晶内の結晶欠陥を評価することができる。 By the way, recently, a wafer having a lower defect has been demanded. For this reason, when a single crystal ingot is grown, measures such as slowing the crystal growth rate are taken. When the crystal growth rate of the single crystal ingot is relatively slow, when the produced wafer is selectively etched with a seco solution, an elliptical defect having a size and shape completely different from that of the FPD is observed on the wafer surface. . This elliptical defect is called LEP (Large Etching Pit) (sometimes called a dislocation loop) and is distinguished from FPD by the difference in thermal history of the crystal growth process. This LEP is one of the grown-in defects and is considered to be formed due to dislocation loops and dislocation clusters in which interstitial silicon type point defects are gathered. Therefore, the crystal defects in the semiconductor crystal can be evaluated by accurately evaluating the LEP.
　通常、このような選択エッチングによってウェーハ表面に現れた楕円形状のＬＥＰを評価する場合、ＬＥＰは作業者によって光学顕微鏡を介した目視にて観察され、カウントされている。そのため、ＬＥＰは非常に低密度であることも相俟って、単なる楕円形状だけに着目してＬＥＰを発見するのは容易ではなく、多大な労力を必要としていた。 Usually, when evaluating an elliptical LEP that appears on the wafer surface by such selective etching, the LEP is visually observed by an operator through an optical microscope and counted. For this reason, LEP has a very low density, and it is not easy to find LEP by paying attention only to the shape of an ellipse.
　また、特許文献２に開示のクロムレスエッチング液は、ＦＰＤ観察には効果的であるが、ＬＥＰに関しては感度が低いことがわかってきた。つまり、ＬＥＰは微小転位欠陥であることから、従来のクロムレスエッチング液で選択エッチングしたとしても、楕円形状のサイズは数μｍと小さく、観察が容易ではなかった。 Further, it has been found that the chromeless etching solution disclosed in Patent Document 2 is effective for FPD observation but has low sensitivity with respect to LEP. That is, since LEP is a micro-dislocation defect, even when selective etching is performed with a conventional chromeless etchant, the size of the elliptical shape is as small as several μm and observation is not easy.
　本発明は、上記事情に鑑みてなされたものであり、セコ液のような有害な物質である重クロム酸カリウムを含有する液を使用せず、ＬＥＰ観察においてセコ液と同等以上の能力を有し、かつ容易にＬＥＰを観察できるシリコンウェーハの評価方法及びそのエッチング液を提供することを課題とする。 The present invention has been made in view of the above circumstances, and does not use a liquid containing potassium dichromate, which is a harmful substance such as Secco liquid, and has an ability equal to or higher than that of Secco liquid in LEP observation. In addition, an object of the present invention is to provide a silicon wafer evaluation method and an etching solution thereof that can easily observe LEP.
　上記課題を解決するために、本発明のシリコンウェーハの評価方法は、エッチング液中のフッ酸、硝酸、酢酸及び水の容量比が（４００）：（５～１０）：（１０～５０）：（８０～１２０）であり且つヨウ素又はヨウ化物を含有するエッチング液に、シリコンウェーハを浸漬して結晶欠陥部分を選択的にエッチングし、ＬＥＰを検出することを特徴とする。 In order to solve the above-mentioned problems, the silicon wafer evaluation method of the present invention is such that the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water in the etching solution is (400) :( 5-10) :( 10-50): The silicon wafer is immersed in an etching solution of (80 to 120) and containing iodine or iodide to selectively etch crystal defect portions and detect LEP.
　本発明では、フッ酸、硝酸、酢酸及び水の容量比が（４００）：（５～１０）：（１０～５０）：（８０～１２０）であり且つヨウ素又はヨウ化物を含有したエッチング液を用いるので、地球環境や人体に影響の強い有害物質（クロム）を含むセコ液を用いなくても、特に低速成長させた単結晶からなるシリコンウェーハのＬＥＰを評価することができる。上記組成のエッチング液を用いることで、従来のエッチング液では単なる楕円形状としてしか観察されないＬＥＰが、全ＬＥＰ中の大部分において、ＦＰＤと同じようにさざ波模様（フローパターン）を持つ楕円形状のパターンとして観察されるようになる。また、楕円形状（ＬＥＰ）のサイズを従来のエッチング液を用いたときよりも大きくできる（直径約１０μｍ）。さらに、逆にＦＰＤは明瞭なフローパターンは形成されず、ＬＥＰのみが容易に観察されるようになる。 In the present invention, an etching solution having a volume ratio of hydrofluoric acid, nitric acid, acetic acid and water of (400) :( 5-10) :( 10-50) :( 80-120) and containing iodine or iodide is prepared. Therefore, the LEP of a silicon wafer made of a single crystal grown at a low speed can be evaluated without using a Secco solution containing a harmful substance (chromium) that has a strong influence on the global environment and human body. By using an etching solution having the above composition, LEP, which is observed only as an elliptical shape in the conventional etching solution, has an elliptical pattern having a ripple pattern (flow pattern) in the same manner as FPD in the majority of all LEPs. As will be observed. In addition, the size of the elliptical shape (LEP) can be made larger than when a conventional etching solution is used (diameter of about 10 μm). In contrast, the FPD does not form a clear flow pattern, and only the LEP is easily observed.
　特に硝酸の容量比は５～１０とする。硝酸の容量比が５未満の場合、フローパターンの形状がはっきりしないことがある。また、硝酸の容量比が増加するに従い鮮明度は向上するが、硝酸の容量比が１０を超えると、ウェーハ表面の面荒れが非常に強く発生してしまう場合がある。硝酸の容量比を５～１０にすることにより、特許文献２のエッチング液を用いたときよりもエッチングレートが速くなる為、ＬＥＰ（楕円形状）のサイズを大きくできるとともに、フローパターンの形状も比較的はっきりと鮮明に観察される。したがって、本発明の評価方法によりシリコンウェーハ表層の結晶欠陥部分に形のよいフローパターンを鮮明に形成させることができ、高感度にＬＥＰを検出できるようになる。 Especially, the volume ratio of nitric acid is 5-10. When the volume ratio of nitric acid is less than 5, the shape of the flow pattern may not be clear. In addition, the sharpness improves as the volume ratio of nitric acid increases, but when the volume ratio of nitric acid exceeds 10, surface roughness of the wafer surface may occur very strongly. By setting the volume ratio of nitric acid to 5-10, the etching rate is faster than when the etching solution of Patent Document 2 is used, so the size of the LEP (elliptical shape) can be increased and the shape of the flow pattern is also compared. Observed clearly and vividly. Therefore, by the evaluation method of the present invention, a flow pattern having a good shape can be clearly formed in the crystal defect portion of the surface layer of the silicon wafer, and LEP can be detected with high sensitivity.
　この場合、前記エッチング液中のヨウ素又はヨウ化物の含有量は、前記エッチング液の総液量１リットル当たり０．０３ｇ以上であることが好ましい。 In this case, it is preferable that the content of iodine or iodide in the etching solution is 0.03 g or more per liter of the total amount of the etching solution.
　このようにエッチング液にヨウ素又はヨウ化物を添加するのは、ウェーハ表面に付着するしみ（ステイン膜）の発生を防止するのに効果があるためである。ステイン膜の発生を防止することで、フローパターンを明瞭かつ安定して確認できるとともに、反応開始時間の短縮、エッチング代の均一化につながり、評価精度が向上する。ヨウ化物としては例えばヨウ化カリウムなどが挙げられ、水溶液として添加しても良い。ヨウ素又はヨウ化物の添加量は、エッチング液の総液量１リットルに対して０．０３ｇ以上の比率で添加するのが望ましい。なお、ヨウ素又はヨウ化物を添加しない場合は欠陥の検出が安定しない。一方、添加量が多いと泡切れが悪くなり、フローパターンをカウントし辛くなるので、０．１５ｇを超えないようにするのが好ましい。 The reason why iodine or iodide is added to the etching solution in this way is that it is effective in preventing the occurrence of stains (stain film) adhering to the wafer surface. By preventing the occurrence of a stain film, the flow pattern can be confirmed clearly and stably, leading to a reduction in reaction start time and a uniform etching allowance, thereby improving evaluation accuracy. Examples of the iodide include potassium iodide, and may be added as an aqueous solution. The amount of iodine or iodide added is desirably 0.03 g or more with respect to 1 liter of the total amount of the etching solution. In addition, when no iodine or iodide is added, the detection of defects is not stable. On the other hand, if the amount added is too large, the bubble breakage deteriorates and it is difficult to count the flow pattern, so it is preferable not to exceed 0.15 g.
　そしてこの場合、前記シリコンウェーハはシリコン単結晶インゴットからスライスして得られた化学鏡面研磨後のウェーハであることが好ましい。 In this case, the silicon wafer is preferably a wafer after chemical mirror polishing obtained by slicing from a silicon single crystal ingot.
　本発明で用いるエッチング液は、化学鏡面研磨後のウェーハ、すなわちミラーエッチドウェーハの段階でも形のよい楕円形状のエッチングパターンを形成させることができる。被検体がミラーエッチドウェーハの段階ということは、その後の機械的化学的研磨工程が不要となり、評価用サンプルの作製に費やす時間や費用を節約することができるので、効率的であり検出感度もよい。また、育成されたシリコン単結晶インゴットの円筒研磨工程をも省略してスライスし、研磨歪みを取るエッチングをも省略してミラーエッチングを施して評価可能なので、非常に短い工程で評価用サンプルを得てシリコンウェーハを評価することができる。 The etching solution used in the present invention can form an elliptical etching pattern having a good shape even at the stage of a wafer after chemical mirror polishing, that is, a mirror etched wafer. When the specimen is in the mirror-etched wafer stage, there is no need for a subsequent mechanical and chemical polishing process, which saves time and money for the preparation of the sample for evaluation. Good. In addition, it can be evaluated by omitting the cylindrical polishing process of the grown silicon single crystal ingot and slicing it, omitting the etching to remove polishing distortion, and performing mirror etching, so an evaluation sample can be obtained in a very short process. The silicon wafer can be evaluated.
　また、この場合、前記エッチングによるシリコンウェーハのエッチオフ量は両面で３～５０μｍであることが好ましい。 In this case, the etch-off amount of the silicon wafer by the etching is preferably 3 to 50 μm on both sides.
　通常ＬＥＰは、シリコン単結晶を育成する際にシリコン単結晶中に均一に生じ、ウェーハ表面に対する深さ方向に均一に存在することになる。シリコンウェーハを前記エッチング液に浸漬すると、ウェーハ表層部分がエッチング除去され、除去されるに従い深さ方向に分布しているＬＥＰが検出され、エッチングされたウェーハ表面にＬＥＰの個数が累積していくことになる。エッチオフ量、すなわちエッチングによって除去されるシリコンウェーハの厚さを３～５０μｍとすることで、ＬＥＰを正確に評価することができる。エッチオフ量が３μｍ未満だとＬＥＰの密度が低すぎて正確な評価が行えない。一方、エッチオフ量が５０μｍを超えると、エッチング初期のＬＥＰの形が崩れることもあり、またＬＥＰの密度も高すぎて正確な評価が行えない場合もある。 Usually, LEP is uniformly generated in a silicon single crystal when the silicon single crystal is grown, and exists uniformly in the depth direction with respect to the wafer surface. When a silicon wafer is immersed in the etching solution, the surface portion of the wafer is removed by etching, and LEP distributed in the depth direction is detected as it is removed, and the number of LEPs accumulates on the etched wafer surface. become. LEP can be accurately evaluated by setting the etch-off amount, that is, the thickness of the silicon wafer removed by etching to 3 to 50 μm. If the etch-off amount is less than 3 μm, the density of LEP is too low to perform accurate evaluation. On the other hand, if the etch-off amount exceeds 50 μm, the LEP shape at the initial stage of etching may be lost, and the LEP density may be too high to perform accurate evaluation.
　この場合、前記エッチング液の浸漬開始温度を１０～３０℃でエッチングを行うことが好ましい。 In this case, it is preferable to perform the etching at an immersion start temperature of 10 to 30 ° C.
　前記エッチング液にシリコンウェーハを浸漬してエッチングがはじまると、前記エッチング液の温度が上昇し、エッチング速度が速くなってしまう。安定した反応を得て均一なエッチング量とするためには浸漬開始温度を１０～３０℃とすることが好ましい。浸漬開始温度が１０℃未満ではエッチングの進行が遅く検出感度が低下する。一方、浸漬開始温度が３０℃を超えるとエッチング速度が速く、それに伴い液温上昇も早くなり、エッチングの進行が著しく速くなってエッチングパターンの形状が崩れたり密度が高すぎたりして検出不能になってしまうこともある。 When the silicon wafer is immersed in the etching solution and etching starts, the temperature of the etching solution rises and the etching rate increases. In order to obtain a stable reaction and a uniform etching amount, it is preferable to set the immersion start temperature to 10 to 30 ° C. When the immersion start temperature is less than 10 ° C., the progress of etching is slow and the detection sensitivity is lowered. On the other hand, when the immersion start temperature exceeds 30 ° C., the etching rate is high, and the liquid temperature rises accordingly, the etching progresses remarkably fast, the shape of the etching pattern collapses and the density becomes too high to be detected. Sometimes it becomes.
　そしてまた、この場合、前記エッチング液中でシリコンウェーハを撹拌しないで放置してエッチングすることが好ましい。 In this case, it is preferable to etch the silicon wafer in the etching solution without stirring.
　ＬＥＰは、前記エッチング液にシリコンウェーハを浸漬すると、シリコンウェーハ表面の欠陥部分に気泡が付き、その気泡がある程度の時間を経て離脱して液中を上昇し、その気泡の流れによって生じるエッチング液の上昇流により、欠陥部分に付いた気泡周辺部分にフローパターンを形成させることによって検出されるものである。したがって、意図的にあるいは故意にシリコンウェーハを揺動あるいは攪拌させて強制的に気泡を離脱させると、フローパターンが形成し辛くなるので、前記エッチング液中にシリコンウェーハを静止放置させることが好ましい。 In LEP, when a silicon wafer is immersed in the etching solution, bubbles are attached to defective portions on the surface of the silicon wafer, and the bubbles are released after a certain period of time and rise in the solution. It is detected by forming a flow pattern in the peripheral part of the bubble attached to the defective part by the upward flow. Accordingly, if the silicon wafer is intentionally or intentionally rocked or stirred to forcibly release the bubbles, it becomes difficult to form a flow pattern. Therefore, it is preferable to leave the silicon wafer stationary in the etching solution.
　また、本発明のエッチング液は、シリコンウェーハのＬＥＰを検出するために用いられるエッチング液であって、前記エッチング液はその液中のフッ酸、硝酸、酢酸及び水が（４００）：（５～１０）：（１０～５０）：（８０～１２０）の容量比を有し、且つヨウ素又はヨウ化物が前記エッチング液の総液量１リットル当たり０．０３ｇ以上含有していることを特徴とする。これにより、上記シリコンウェーハの評価方法と同じ効果を得ることができる。 The etching solution of the present invention is an etching solution used for detecting LEP of a silicon wafer, and the etching solution contains hydrofluoric acid, nitric acid, acetic acid and water (400): (5 to 10): (10 to 50): (80 to 120), and iodine or iodide is contained in an amount of 0.03 g or more per liter of the total amount of the etching solution. . Thereby, the same effect as the evaluation method of the silicon wafer can be obtained.
シリコンウェーハ表面に観察される楕円形状のパターンを例示した図である。It is the figure which illustrated the elliptical pattern observed on the silicon wafer surface. 実施例、比較例１、２におけるＬＥＰの長幅Ｘのヒストグラムである。It is a histogram of the long width X of LEP in an Example and Comparative Examples 1 and 2. FIG. 実施例、比較例１、２におけるＬＥＰの短幅Ｙのヒストグラムである。It is a histogram of the short width Y of LEP in an Example and Comparative Examples 1 and 2. FIG. 実施例、比較例１、２におけるＬＥＰの面積のヒストグラムである。It is a histogram of the area of LEP in an Example and the comparative examples 1 and 2. FIG. 実施例のサンプルの画像である。It is an image of the sample of an Example. 図５ＡのＡ部の拡大画像である。It is an enlarged image of the A section of Drawing 5A. 図５ＢのＢ部の拡大画像である。It is an enlarged image of the B section of Drawing 5B. ＬＥＰ密度が高い実施例のサンプルの画像である。It is an image of the sample of an Example with high LEP density. 比較例１のサンプルの画像である。It is an image of the sample of the comparative example 1. 図７ＡのＣ部の拡大画像である。It is an enlarged image of the C section of Drawing 7A.
　以下、本発明の実施形態について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。本発明のシリコンウェーハを評価するにあたり、先ず、用いるシリコンウェーハの作製方法は、公知のシリコン単結晶基板作製方法で良い。例えば、チョクラルスキー法により引き上げたシリコン単結晶インゴットからスライスしたシリコンウェーハを用いることができる。なお、シリコン単結晶インゴットの結晶成長速度（引き上げ速度）が遅いとＬＥＰが形成されやすくなり、ＬＥＰの評価の必要性が高まるので、ここでは特に、結晶成長速度が比較的遅いシリコン単結晶インゴットからスライスしたシリコンウェーハを用いることができる。 Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these. In evaluating the silicon wafer of the present invention, first, a known silicon single crystal substrate manufacturing method may be used as a silicon wafer manufacturing method. For example, a silicon wafer sliced from a silicon single crystal ingot pulled up by the Czochralski method can be used. In addition, when the crystal growth rate (pulling rate) of the silicon single crystal ingot is low, LEP is likely to be formed, and the necessity for evaluating the LEP increases. Therefore, here, particularly from the silicon single crystal ingot having a relatively low crystal growth rate. A sliced silicon wafer can be used.
　ここで、評価用サンプルとして、スライスしたシリコンウェーハの表面及び表面から深さ方向の数μｍはスライス等による加工歪みが残留していない状態が必要であるため、化学研磨液、例えばフッ酸と硝酸の比率が１：３程度の混酸でエッチングすることにより、シリコンウェーハ表面の加工歪みを除去するとともに化学的に鏡面状にしたミラーエッチドウェーハを準備することができる。 Here, as a sample for evaluation, the surface of the sliced silicon wafer and a few μm in the depth direction from the surface need to be in a state in which processing distortion due to slicing or the like does not remain, so a chemical polishing liquid such as hydrofluoric acid and nitric acid By etching with a mixed acid having a ratio of about 1: 3, it is possible to prepare a mirror-etched wafer having a chemically mirror-finished surface while removing processing distortion on the surface of the silicon wafer.
　なお、ミラーエッチドウェーハに代えて、ポリッシュドウェーハを評価用サンプルとして準備しても良い。参考までに、ポリッシュドウェーハの一般的な製造方法を説明すると、チョクラルスキー法等により育成されたシリコン単結晶インゴットからウェーハ状のシリコンウェーハが切り出され（スライス加工工程）、切り出された（スライスした）シリコンウェーハの周辺部の角を落とすために面取りが施される（ベベリング加工工程）。さらに、このシリコンウェーハ表面の凹凸を無くし、平坦度を高め、表面の傷を最小にする為に機械研磨が施され（ラッピング加工工程；この段階でラップドウェーハと呼ぶことがある）、機械研磨時にシリコンウェーハの表面層に形成された研磨歪み層が混酸エッチングにより除去され、化学的に平坦度を向上させたシリコンウェーハが得られる（ケミカルエッチング工程；この段階でケミカルエッチドウェーハと呼ぶことがある）。次いで、シリコンウェーハ表面の平坦度をさらに上げ面粗さを小さくするために、前記ケミカルエッチドウェーハの表面に対して遊離砥粒による機械的作用と、化学物質によるエッチング作用とを重複させながら研磨するメカノケミカル研磨法が採用されており、この研磨法は通常、２～３段階に分けた工程で構成されている。すなわち、その工程順に１次研磨、２次研磨（場合によっては３次研磨もある）、仕上げ研磨と称し、この研磨の回を重ねる毎に、研磨砥粒の粒度を細かくしたり、研磨布の硬度を下げる等、研磨条件を緩和させたりしながら、その段階毎に研磨される鏡面部の平坦度や面粗さ等を低い値となるように条件を設定して研磨している。以上のような工程を経てポリッシュドウェーハが製造される。なお、以下では、評価用サンプルとしてミラーエッチドウェーハを準備したとして説明する。 Note that a polished wafer may be prepared as an evaluation sample instead of the mirror-etched wafer. For reference, a general manufacturing method of a polished wafer will be described. A silicon wafer is cut out from a silicon single crystal ingot grown by the Czochralski method (slicing process) and cut out (sliced). Chamfering is performed to remove the corners of the periphery of the silicon wafer (beveling process). Furthermore, mechanical polishing is applied to eliminate unevenness on the silicon wafer surface, increase flatness, and minimize surface scratches (lapping process; sometimes referred to as a wrapped wafer at this stage). Sometimes the strained polishing layer formed on the surface layer of the silicon wafer is removed by mixed acid etching to obtain a silicon wafer having improved chemical flatness (chemical etching process; this is called a chemically etched wafer at this stage) is there). Next, in order to further increase the flatness of the silicon wafer surface and reduce the surface roughness, polishing is performed while overlapping the mechanical action by the free abrasive grains and the etching action by the chemical substance on the surface of the chemically etched wafer. The mechanochemical polishing method is employed, and this polishing method is usually composed of two or three steps. That is, it is called primary polishing, secondary polishing (in some cases, there is also tertiary polishing), and finish polishing in the order of the steps. Each time this polishing is repeated, the abrasive grain size is reduced or the polishing cloth Polishing is performed while relaxing the polishing conditions such as decreasing the hardness and setting the conditions so that the flatness and surface roughness of the mirror surface polished at each stage become low values. A polished wafer is manufactured through the above processes. In the following description, it is assumed that a mirror-etched wafer is prepared as an evaluation sample.
　準備したミラーエッチドウェーハの結晶欠陥（ＬＥＰ）を検出するために用いられるエッチング液を準備する。そのエッチング液として、前記エッチング液中のフッ酸、硝酸、酢酸及び水が（４００）：（５～１０）：（１０～５０）：（８０～１２０）の容量比を有し、且つヨウ素又はヨウ化物が前記エッチング液の総液量１リットルに対し０．０３～０．１５ｇ含有したエッチング液を準備する。ここで、エッチング液については、市販されている半導体グレードの薬液を用いることができ、例えば、フッ酸（５０重量％）はダイキン工業株式会社の半導体用を、硝酸（６１重量％）は関東化学株式会社のＥＬ級を、酢酸（９９．７重量％）は関東化学株式会社の特級をそのまま前記容量比で混合して作製できる。また、水については、エッチング処理時にゴミや汚れなどのウェーハへの付着を考慮すると半導体工業で使われている超純水を用いることが好ましい。 Prepare an etchant used to detect crystal defects (LEP) of the prepared mirror-etched wafer. As the etchant, hydrofluoric acid, nitric acid, acetic acid and water in the etchant have a volume ratio of (400) :( 5-10) :( 10-50) :( 80-120), and iodine or An etching solution containing 0.03 to 0.15 g of iodide with respect to 1 liter of the total amount of the etching solution is prepared. Here, as the etching solution, a commercially available semiconductor grade chemical solution can be used. For example, hydrofluoric acid (50% by weight) is for semiconductors of Daikin Industries, Ltd., and nitric acid (61% by weight) is Kanto Chemical. The EL grade of Co., Ltd. and acetic acid (99.7% by weight) can be prepared by mixing the special grade of Kanto Chemical Co., Ltd. as it is at the above volume ratio. As for water, it is preferable to use ultrapure water used in the semiconductor industry in consideration of adhesion of dust and dirt to the wafer during the etching process.
　次に、前述したようにして得られたミラーエッチドウェーハを、液温が１０～３０℃の本発明の前記エッチング液に、エッチオフ量がミラーエッチドウェーハの両面で３～５０μｍになる時間、攪拌せずに放置して浸漬し、結晶欠陥部分を選択的にエッチングする。これにより、ミラーエッチドウェーハの表面に楕円形状のエッチングパターンを現すことができる。この楕円形状のエッチングパターンはＬＥＰに起因したパターンである。さらに、ミラーエッチドウェーハ表面に現れた全ての楕円形状（ＬＥＰ）のうちの大部分（下記実施例で示すが約８０％程度）が、ＦＰＤと同じようにフローパターンを持つ。残りの約２０％は従来どおりの楕円形状の単独パターンとして現れる。これにより、例えばエッチング後のウェーハを集光下に置くことで、目視でもフローパターンを容易に確認できる。そして、確認したフローパターンを光学顕微鏡等で拡大した形で確認することで、フローパターン中の楕円形状のパターン（ＬＥＰ）の存在を容易に確認できる。ＬＥＰのフローパターンが現れない従来のエッチング液では、ウェーハの全面を光学顕微鏡等でくまなく走査しなければＬＥＰを確認できない。 Next, the mirror etched wafer obtained as described above is added to the etching solution of the present invention having a liquid temperature of 10 to 30 ° C., and the etching off time is 3 to 50 μm on both sides of the mirror etched wafer. Then, it is left to stand without stirring, and the crystal defect portion is selectively etched. As a result, an elliptical etching pattern can appear on the surface of the mirror-etched wafer. This elliptical etching pattern is a pattern resulting from LEP. Further, most of all elliptical shapes (LEPs) appearing on the mirror-etched wafer surface (about 80% as shown in the examples below) have a flow pattern similar to FPD. The remaining 20% appears as a conventional elliptical single pattern. Thereby, for example, the flow pattern can be easily confirmed by visual observation by placing the etched wafer under light collection. And the existence of an elliptical pattern (LEP) in the flow pattern can be easily confirmed by confirming the confirmed flow pattern in an enlarged form with an optical microscope or the like. In the case of the conventional etching solution in which the LEP flow pattern does not appear, the LEP cannot be confirmed unless the entire surface of the wafer is scanned with an optical microscope or the like.
　その後、例えば、楕円形状のパターンの数を、光学顕微鏡を介して目視により又はＬＥＰを自動検出する自動検出装置（特開２００４－１１７１４７号公報参照）により、ＬＥＰの密度として測定し、測定した密度に基づいてシリコンウェーハの結晶品質の良否等を評価する。 Thereafter, for example, the number of elliptical patterns is measured as an LEP density by visual detection through an optical microscope or by an automatic detection device that automatically detects LEP (see Japanese Patent Application Laid-Open No. 2004-117147). Based on the above, the quality of the crystal quality of the silicon wafer is evaluated.
　以下、本発明の実施例及び比較例を挙げて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。評価用のシリコンウェーハとして、種々の製造条件により育成された直径が３００ｍｍ、導電型がＰ型、抵抗率が約１０Ω・ｃｍのシリコン単結晶インゴットからスライスした後、化学鏡面研磨（ミラーエッチング）液により鏡面状態となったウェーハ（ミラーエッチドウェーハ）を準備した。これらのサンプルウェーハを扇形状に４分割した。そのウェーハに対して下記実施例及び比較例の各々の条件に従ってＬＥＰを評価した。 Hereinafter, although an example and a comparative example of the present invention are given and explained concretely, the present invention is not limited to these. As a silicon wafer for evaluation, after being sliced from a silicon single crystal ingot having a diameter of 300 mm, a conductivity type of P type, and a resistivity of about 10 Ω · cm grown under various manufacturing conditions, a chemical mirror polishing (mirror etching) solution A wafer (mirror etched wafer) in a mirror state was prepared. These sample wafers were divided into four fan shapes. LEP was evaluated according to each condition of the following Example and comparative example with respect to the wafer.
　（実施例）
　先ず、従来のクロムレスエッチング液、具体的には５０重量％フッ酸、６１重量％硝酸、９９．７重量％酢酸及び水の容量比が４００：３：３３：８０のエッチング液（以下、従来クロムレス液という）を１２リットル準備した。この従来クロムレス液に、６１重量％硝酸１３２ｍｌ及び水４８０ｍｌを調合した。さらに、０．１モル／リットルのヨウ化カリウム水溶液６３．６ｍｌを追加して、本発明のエッチング液を作成した。作成したエッチング液の容量比は、フッ酸４００、硝酸５．３、酢酸３３、水９０となる。またヨウ化カリウムの含有量はエッチング液の総液量１リットル当たり約０．０８ｇである。 (Example)
First, a conventional chromeless etchant, specifically, an etchant having a volume ratio of 400: 3: 33: 80 (hereinafter referred to as a conventional etchant) of 50 wt% hydrofluoric acid, 61 wt% nitric acid, 99.7 wt% acetic acid and water. 12 liters of chromeless solution) was prepared. This conventional chromeless solution was mixed with 132 ml of 61 wt% nitric acid and 480 ml of water. Further, 63.6 ml of 0.1 mol / liter potassium iodide aqueous solution was added to prepare the etching solution of the present invention. The volume ratio of the prepared etching solution is hydrofluoric acid 400, nitric acid 5.3, acetic acid 33, and water 90. The content of potassium iodide is about 0.08 g per liter of the total amount of the etching solution.
　このエッチング液の組成及び温度を安定させる為、エッチング液を１日放置した後、浸漬開始温度２４℃にて、上記サンプル３０枚を垂直に立てた状態でエッチング液に浸漬し、攪拌しないで６分間放置した。この時のエッチオフ量は両面で約２８μｍであった。 In order to stabilize the composition and temperature of the etching solution, the etching solution was allowed to stand for 1 day, and then immersed in the etching solution with the above-described 30 samples standing vertically at an immersion start temperature of 24 ° C., without stirring. Left for a minute. The etch-off amount at this time was about 28 μm on both sides.
　その後、各サンプルウェーハ表面に現れた各楕円形状のパターンのサイズを測定した。具体的には、楕円形状のパターンのサイズとして、図１に示すように、楕円形状のパターンの長い方の幅Ｘ（楕円の長軸の長さに相当）（以下、長幅という）、短い方の幅Ｙ（楕円の短軸の長さに相当）（以下、短幅という）及び面積を測定した。なお、長幅Ｘ、短幅Ｙは、画像解析ソフト（画素間の距離を計算できるソフト）を用いて、楕円形状のパターンの拡大画像から測定した。それら長幅Ｘ、短幅Ｙを乗算して得られる値をパターン（ＬＥＰ）の面積（Ｘ×Ｙ）とした。 Then, the size of each elliptical pattern that appeared on the surface of each sample wafer was measured. Specifically, as shown in FIG. 1, the size of the elliptical pattern is a longer width X of the elliptical pattern (corresponding to the length of the major axis of the ellipse) (hereinafter referred to as a long width), and shorter. The width Y (corresponding to the length of the minor axis of the ellipse) (hereinafter referred to as the short width) and the area were measured. The long width X and the short width Y were measured from an enlarged image of an elliptical pattern using image analysis software (software that can calculate the distance between pixels). A value obtained by multiplying the long width X and the short width Y was defined as an area (X × Y) of the pattern (LEP).
　（比較例１）
　上記従来クロムレス液を１２リットル準備し、その従来クロムレス液を用いてサンプルのエッチングを行った。このときのエッチング条件は実施例と同じ条件、つまり、従来クロムレス液を１日放置した後、浸漬開始温度２４℃にて、上記サンプル３０枚を垂直に立てた状態で従来クロムレス液に浸漬し、攪拌しないで６分間放置した。その後、各サンプルウェーハ表面に現れた各楕円形状のパターンのサイズとして、各パターンの長幅Ｘ、短幅Ｙ及び面積（Ｘ×Ｙ）を測定した。 (Comparative Example 1)
12 liters of the conventional chromeless solution was prepared, and the sample was etched using the conventional chromeless solution. Etching conditions at this time are the same as in the example, that is, after leaving the conventional chromeless liquid for one day, at the immersing start temperature of 24 ° C., the above 30 samples are vertically immersed in the conventional chromeless liquid, The mixture was left for 6 minutes without stirring. Thereafter, as the size of each elliptical pattern that appeared on the surface of each sample wafer, the long width X, the short width Y, and the area (X × Y) of each pattern were measured.
　（比較例２）
　セコ液（ＨＦ１００ｃｍ３＋Ｋ２Ｃｒ２Ｏ７（０．１５Ｍ）５０ｃｍ３の混合比で調製）を１２リットル準備し、そのセコ液を用いてサンプルのエッチングを行った。このときのエッチング条件は実施例と同じ条件（ただしサンプル数は異なる）、つまり、セコ液を１日放置した後、浸漬開始温度２４℃にて、上記サンプル３７枚を垂直に立てた状態でセコ液に浸漬し、攪拌しないで６分間放置した。その後、各サンプルウェーハ表面に現れた各楕円形状のパターンのサイズとして、各パターンの長幅Ｘ、短幅Ｙ及び面積（Ｘ×Ｙ）を測定した。 (Comparative Example 2)
12 liters of Secco liquid (HF100 cm 3 + K 2 Cr 2 O 7 (0.15M) prepared at a mixing ratio of 50 cm 3 ) was prepared, and the sample was etched using the Seco liquid. Etching conditions at this time are the same as in the example (however, the number of samples is different), that is, after leaving the Secco solution for one day, the Secco with the 37 samples upright at an immersion start temperature of 24 ° C. It was immersed in the liquid and left for 6 minutes without stirring. Thereafter, as the size of each elliptical pattern that appeared on the surface of each sample wafer, the long width X, the short width Y, and the area (X × Y) of each pattern were measured.
　図２～図４は、ＬＥＰ（楕円形状のパターン）のサイズ（長幅Ｘ、短幅Ｙ、面積）の測定結果として、ＬＥＰサイズのヒストグラム（度数分布）を示している。図２は、実施例、比較例１、２におけるＬＥＰの長幅Ｘのヒストグラムを示しており、詳細には、横軸は長幅Ｘを示し、縦軸は、実験を行った複数のサンプル（実施例１、比較例１では３０枚のサンプル、比較例２では３７枚のサンプル）から得られた長幅Ｘのうちの何％がどの長幅区間に属するか、つまり度数を示している。図３は、実施例、比較例１、２におけるＬＥＰの短幅Ｙのヒストグラムを示しており、詳細には、横軸は短幅Ｙを示し、縦軸は各サンプルから得られた短幅Ｙの何％がどの短幅区間に属するかの度数を示している。図４は、実施例、比較例１、２におけるＬＥＰの面積のヒストグラムを示しており、詳細には、横軸は面積を示し、縦軸は各サンプルから得られる面積の何％がどの面積区間に属するかの度数を示している。 2 to 4 show LEP size histograms (frequency distribution) as measurement results of the LEP (elliptical pattern) size (long width X, short width Y, area). FIG. 2 shows a histogram of the LEP long width X in Examples and Comparative Examples 1 and 2, in detail, the horizontal axis indicates the long width X, and the vertical axis indicates a plurality of samples ( Example 1 and Comparative Example 1 indicate 30% of the long width X obtained from 30 samples and Comparative Example 2 37 samples), that is, the frequency. FIG. 3 shows a histogram of the short width Y of the LEP in Examples and Comparative Examples 1 and 2. Specifically, the horizontal axis indicates the short width Y, and the vertical axis indicates the short width Y obtained from each sample. It shows the frequency of what percentage of the part belongs to which short interval. FIG. 4 shows a histogram of LEP areas in Examples and Comparative Examples 1 and 2. Specifically, the horizontal axis indicates the area, and the vertical axis indicates which area section is what percentage of the area obtained from each sample. The frequency of whether it belongs to is shown.
　なお、１つのサンプルで複数のＬＥＰが観察されるので、それら複数のＬＥＰのサイズ（長幅Ｘ、短幅Ｙ、面積）の平均値を算出し、１つのサンプル当たり１つの長幅Ｘ、短幅Ｙ、面積を得た。そして、サンプル数の分（実施例、比較例１の場合は３０枚分、比較例２の場合は３７枚分）だけ長幅Ｘ、短幅Ｙ、面積が得られるので、図２～図４は、それら３０枚分、３７枚分の長幅Ｘ、短幅Ｙ、面積のヒストグラムを示している。 Since a plurality of LEPs are observed in one sample, the average value of the sizes (long width X, short width Y, area) of the plurality of LEPs is calculated, and one long width X, short per sample is calculated. Width Y and area were obtained. Further, the long width X, the short width Y, and the area can be obtained by the number of samples (30 sheets in the case of Example and Comparative Example 1 and 37 sheets in the case of Comparative Example 2). Shows a histogram of the long width X, the short width Y, and the area of those 30 sheets and 37 sheets.
　また、下記表１は、実施例、比較例１、２におけるＬＥＰサイズの測定結果の表である。なお、表１における１番目の縦欄はサンプル数Ｎを示している。２番目の縦欄は、各サンプルから得られた長幅Ｘの平均値を示している。３番目の縦欄は、各サンプルから得られた短幅Ｙの平均値を示している。４番目の縦欄は、各サンプルから得られた面積の平均値を示している。 Table 1 below is a table of LEP size measurement results in Examples and Comparative Examples 1 and 2. The first column in Table 1 indicates the number of samples N. The second column shows the average value of the long width X obtained from each sample. The third column shows the average value of the short width Y obtained from each sample. The fourth column shows the average area obtained from each sample.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　図２に示すように、比較例１の従来クロムレス液を用いた場合（■のプロット点）には、長幅Ｘが１０μｍ付近の区間で度数が高くなっており、長幅Ｘが１４μｍ以上の区間では度数が極端に低くなっている。これに対し、実施例のエッチング液を用いた場合（●のプロット点）には、比較例２のセコ液を用いた場合（◆のプロット点）と類似の傾向を示しており、長幅Ｘ＝１４μｍ以上の区間でも度数が高くなっている。よって、図２、表１の２番目の縦欄に示すように、本発明のエッチング液では、従来のエッチング液（特に従来クロムレス液）に比べて、大きな長幅ＸのＬＥＰが観察されやすくなる。 As shown in FIG. 2, when the conventional chromeless liquid of Comparative Example 1 is used (the plot point of ■), the frequency is high in the section where the long width X is around 10 μm, and the long width X is 14 μm or more. The frequency is extremely low in the section. On the other hand, when the etching solution of the example is used (● plotted points), a tendency similar to that when the secco solution of Comparative Example 2 is used (♦ plotted points) is shown. = The frequency is high even in the section of 14 μm or more. Therefore, as shown in the second column of FIG. 2 and Table 1, in the etching solution of the present invention, LEP having a large long width X is easily observed as compared with the conventional etching solution (particularly, the conventional chromeless solution). .
　図３に示すように、比較例１の従来クロムレス液を用いた場合（■のプロット点）には、短幅Ｙ＝６μｍ付近の区間で度数が最も高くなっており、短幅Ｙ＝１０μｍ以上の区間では度数が極端に低くなっている。これに対して、実施例のエッチング液を用いた場合（●のプロット点）には、短幅Ｙ＝１２μｍ付近の区間で度数が最も高くなっている。また、比較例２のセコ液を用いた場合（◆のプロット点）には、実施例、比較例１に比べて広い区間に渡って度数が分布しているが、短幅Ｙ＝１２μｍ付近の区間では実施例より度数が低くなっている。よって、図３、表１の３番目の縦欄に示すように、本発明のエッチング液では、従来クロムレス液（比較例１）に比べて大きな短幅ＹのＬＥＰが観察されやすくなり、セコ液（比較例２）と同等又はそれ以上の短幅ＹのＬＥＰが観察されやすくなる。 As shown in FIG. 3, when the conventional chromeless liquid of Comparative Example 1 is used (the plot point of ■), the frequency is highest in the section near the short width Y = 6 μm, and the short width Y = 10 μm or more. The frequency is extremely low in this section. On the other hand, when the etching solution of the example is used (● plotted points), the frequency is highest in the section near the short width Y = 12 μm. In addition, when the secco solution of Comparative Example 2 was used (plotted points in ◆), the frequencies were distributed over a wider section than in the Example and Comparative Example 1, but the short width was about Y = 12 μm. In the section, the frequency is lower than in the example. Therefore, as shown in the third column of FIG. 3 and Table 1, in the etching solution of the present invention, LEP having a large short width Y is more easily observed compared to the conventional chromeless solution (Comparative Example 1). LEP with a short width Y equivalent to or greater than (Comparative Example 2) is easily observed.
　図４に示すように、比較例１の従来クロムレス液を用いた場合（■のプロット点）には、面積＝８０μｍ２付近の区間で度数が最も高くなっており、面積＝１２０μｍ２以上の区間では度数が極端に低くなっている。また、比較例２のセコ液を用いた場合（◆のプロット点）には、面積＝８０～１６０μｍ２付近の区間である程度高い度数を示しているものの、面積＝２００μｍ２以上の区間では度数が低くなっている。これに対し、実施例のエッチング液を用いた場合（●のプロット点）には、面積＝１６０μｍ２以上の区間では、比較例１、２に比べて高い度数を示す。よって、図４、表１の４番目の縦欄に示すように、本発明のエッチング液では、従来のエッチング液（特に従来クロムレス液）に比べて大きなサイズ（面積）のＬＥＰが観察されやすくなる。表１に示すように、実施例の長幅Ｘの平均値が１４．９μｍ、短幅Ｙの平均値が１０．４μｍであり、微小転位欠陥であるＬＥＰが直径１０μｍ以上の大きなサイズで観察される。 As shown in FIG. 4, when the conventional chromeless solution of Comparative Example 1 is used (the plot point of ■), the frequency is highest in the section near area = 80 μm 2 , and the section where area = 120 μm 2 or more. Then the frequency is extremely low. In addition, when the secco solution of Comparative Example 2 was used (the plotted point in ◆), the frequency was somewhat high in the area near area = 80 to 160 μm 2, but the frequency was higher in the area where area = 200 μm 2 or more. It is low. On the other hand, when the etching solution of the example is used (the plot point of ●), in the section where the area = 160 μm 2 or more, the frequency is higher than those of the comparative examples 1 and 2. Therefore, as shown in the fourth column of FIG. 4 and Table 1, in the etching solution of the present invention, a LEP having a larger size (area) is more easily observed than the conventional etching solution (particularly, the conventional chromeless solution). . As shown in Table 1, the average value of the long width X of the example is 14.9 μm, the average value of the short width Y is 10.4 μm, and LEP which is a micro dislocation defect is observed in a large size having a diameter of 10 μm or more. The
　また、実施例、比較例１、２の各サンプルに対して、フローパターンのＬＥＰが観察されるか否かを確認した。図５Ａ～図５Ｃは、実施例の３０枚のサンプルの中から適当に１つを選択し、その選択したサンプルの表面の一部を撮像した画像を示している。図５Ａは撮像倍率が等倍の画像を示し、図５Ｂは図５ＡのＡ部の拡大画像を示し、図５Ｃは図５ＢのＢ部の拡大画像を示している。なお、図５Ｃの拡大画像は、単位長１０μｍの画像である。 In addition, it was confirmed whether or not the LEP of the flow pattern was observed for each sample of Example and Comparative Examples 1 and 2. 5A to 5C show images obtained by appropriately selecting one of the 30 samples of the embodiment and imaging a part of the surface of the selected sample. FIG. 5A shows an image with the same magnification, FIG. 5B shows an enlarged image of part A in FIG. 5A, and FIG. 5C shows an enlarged image of part B in FIG. 5B. Note that the enlarged image in FIG. 5C is an image having a unit length of 10 μm.
　図５Ａの○で囲った部分に白い点を観察でき、その拡大図である図５Ｂを見ると、図５Ａの白い点はフローパターン２であることが分かる。さらに、図５Ｃに示すように、フローパターン２の先端には楕円形状のパターン３、つまりＬＥＰが現れている。なお、図６には、図５Ａ～図５Ｃのサンプルとは別の実施例１のサンプルの等倍画像であり、図５Ａ～図５ＣのサンプルよりもＬＥＰ密度が高いサンプルの画像を示している。図６の例では、目視でも容易にＬＥＰのフローパターン（白い部分）を観察することができる。このように、本発明のエッチング液を用いると、ＬＥＰのフローパターンが観察されるようになるので、容易にＬＥＰを発見し、観察することができる。 A white dot can be observed in the portion surrounded by a circle in FIG. 5A, and it can be seen that the white dot in FIG. Further, as shown in FIG. 5C, an elliptical pattern 3, that is, LEP appears at the tip of the flow pattern 2. FIG. 6 is an equal-magnification image of the sample of Example 1 different from the samples of FIGS. 5A to 5C, and shows an image of a sample having a higher LEP density than the samples of FIGS. 5A to 5C. . In the example of FIG. 6, the LEP flow pattern (white portion) can be easily observed visually. As described above, when the etching solution of the present invention is used, the LEP flow pattern is observed, so that the LEP can be easily found and observed.
　これに対して、図７Ａ、図７Ｂは、比較例１（従来クロムレス液）の３０枚のサンプルの中から適当に１つを選択し、その選択したサンプルの表面の一部を撮像した画像であり、図７Ａは等倍画像を示し、図７Ｂは図７ＡのＣ部の拡大画像（楕円形状のパターン４（ＬＥＰ）の拡大画像）である。なお、図７Ｂの拡大画像は、図５Ｃと同じ拡大率、つまり単位長１０μｍの画像である。図７Ａ、図７Ｂに示すように、比較例１のエッチング液を用いた場合には、ＬＥＰのフローパターンは観察されなかった。また、図５Ｃのパターン３のほうが図７Ｂのパターン４よりも大きいことが分かる。 On the other hand, FIG. 7A and FIG. 7B are images obtained by picking one of the 30 samples of Comparative Example 1 (conventional chromeless liquid) appropriately and capturing a part of the surface of the selected sample. FIG. 7A shows the same-size image, and FIG. 7B is an enlarged image (enlarged image of the elliptical pattern 4 (LEP)) in part C of FIG. 7A. Note that the enlarged image in FIG. 7B is an image having the same enlargement ratio as that in FIG. As shown in FIGS. 7A and 7B, when the etching solution of Comparative Example 1 was used, no LEP flow pattern was observed. It can also be seen that pattern 3 in FIG. 5C is larger than pattern 4 in FIG. 7B.
　さらに、実施例と比較例１のサンプルに対してフローパターンを持つＬＥＰの発生率を測定した。具体的には、実施例の３０枚のサンプルの中から適当に３枚のサンプルＡ、Ｂ、Ｃを選択し、それらサンプルＡ、Ｂ、Ｃそれぞれに対して、全ＬＥＰの個数Ｎ１、フローパターンを持つＬＥＰの個数Ｎ２及びフローパターンを持つＬＥＰの発生率（Ｎ２／Ｎ１×１００）を測定した。また、比較例１の３０枚のサンプルの中から適当に１枚のサンプルＤを選択し、そのサンプルＤに対して、全ＬＥＰの個数Ｎ１、フローパターンを持つＬＥＰの個数Ｎ２及びフローパターンを持つＬＥＰの発生率（Ｎ２／Ｎ１×１００）を測定した。下記表２はその測定結果である。表２に示すように、実施例のサンプルＡ、Ｂ、Ｃのいずれも高い割合でフローパターンを持つＬＥＰが発生しており、特にサンプルＢでは全ＬＥＰ中の８０％のＬＥＰがフローパターンを持っている。なお、サンプルＡ、Ｂ、Ｃのフローパターンの発生率を平均すると、６５．４％になる。これに対して、比較例１のサンプルＤではフローパターンを持つＬＥＰは１つも無く、フローパターンの発生率は０％となった。このことから、従来クロムレス液は、ＬＥＰの観察には不向きであるといえる。 Furthermore, the incidence of LEP having a flow pattern was measured for the samples of Example and Comparative Example 1. Specifically, three samples A, B, and C are appropriately selected from the 30 samples in the embodiment, and the number of all LEPs N1, the flow pattern for each of the samples A, B, and C is selected. The number of LEPs having N2 and the occurrence rate of LEPs having a flow pattern (N2 / N1 × 100) were measured. Further, one sample D is appropriately selected from the 30 samples of Comparative Example 1, and the total number of LEPs N1, the number of LEPs having a flow pattern N2, and the flow pattern are associated with the sample D. The incidence of LEP (N2 / N1 × 100) was measured. Table 2 below shows the measurement results. As shown in Table 2, all of the samples A, B, and C of the examples have LEPs having a flow pattern at a high rate. In particular, in sample B, 80% of all LEPs have a flow pattern. ing. Note that the average of the occurrence rates of the flow patterns of Samples A, B, and C is 65.4%. In contrast, Sample D of Comparative Example 1 had no LEP with a flow pattern, and the flow pattern occurrence rate was 0%. From this, it can be said that the conventional chromeless liquid is not suitable for LEP observation.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　以上説明したように、本発明のシリコンウェーハの評価方法、エッチング液によれば、地球環境や人体に有害な物質である重クロム酸カリウムを使用せずに、シリコンウェーハの電気的特性を劣化させるＬＥＰを容易に観察できる。 As described above, according to the silicon wafer evaluation method and the etching solution of the present invention, the electrical characteristics of the silicon wafer are deteriorated without using potassium dichromate which is a harmful substance to the global environment and the human body. LEP can be easily observed.
　２　フローパターン
　３、４　楕円形状のパターン（ＬＥＰ） 2 Flow pattern 3, 4 Elliptical pattern (LEP)

Claims (7)

  1. 　シリコンウェーハの評価方法であって、エッチング液中のフッ酸、硝酸、酢酸及び水の容量比が（４００）：（５～１０）：（１０～５０）：（８０～１２０）であり且つヨウ素又はヨウ化物を含有するエッチング液に、シリコンウェーハを浸漬して結晶欠陥部分を選択的にエッチングし、ＬＥＰを検出することを特徴とするシリコンウェーハの評価方法。 A method for evaluating a silicon wafer, wherein the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water in the etching solution is (400) :( 5-10) :( 10-50) :( 80-120) and iodine Alternatively, the silicon wafer is immersed in an etching solution containing iodide, a crystal defect portion is selectively etched, and LEP is detected.
  2. 　前記エッチング液中のヨウ素又はヨウ化物の含有量は。前記エッチング液の総液量１リットル当たり０．０３ｇ以上であることを特徴とする請求項１に記載のシリコンウェーハの評価方法。 What is the content of iodine or iodide in the etching solution? 2. The method for evaluating a silicon wafer according to claim 1, wherein the total amount of the etching solution is 0.03 g or more per liter.
  3. 　前記シリコンウェーハはシリコン単結晶インゴットからスライスして得られた化学鏡面研磨後のウェーハであることを特徴とする請求項１又は請求項２に記載のシリコンウェーハの評価方法。 3. The silicon wafer evaluation method according to claim 1, wherein the silicon wafer is a wafer after chemical mirror polishing obtained by slicing from a silicon single crystal ingot.
  4. 　前記エッチングによるシリコンウェーハのエッチオフ量が両面で３～５０μｍであることを特徴とする請求項１ないし請求項３のいずれか１項に記載のシリコンウェーハの評価方法。 4. The method for evaluating a silicon wafer according to claim 1, wherein an etch-off amount of the silicon wafer by the etching is 3 to 50 μm on both sides.
  5. 　前記エッチング液の浸漬開始温度を１０～３０℃でエッチングを行うことを特徴とする請求項１ないし請求項４のいずれか１項に記載のシリコンウェーハの評価方法。 The method for evaluating a silicon wafer according to any one of claims 1 to 4, wherein the etching is performed at an immersion start temperature of 10 to 30 ° C.
  6. 　前記エッチング液中でシリコンウェーハを攪拌しないで放置してエッチングすることを特徴とする請求項１ないし請求項５のいずれか１項に記載のシリコンウェーハの評価方法。 6. The method for evaluating a silicon wafer according to claim 1, wherein the etching is performed by leaving the silicon wafer in the etching solution without stirring.
  7. 　シリコンウェーハのＬＥＰを検出するために用いられるエッチング液であって、前記エッチング液はその液中のフッ酸、硝酸、酢酸及び水が（４００）：（５～１０）：（１０～５０）：（８０～１２０）の容量比を有し、且つヨウ素又はヨウ化物が前記エッチング液の総液量１リットル当たり０．０３ｇ以上含有していることを特徴とするエッチング液。 An etchant used for detecting LEP of a silicon wafer, wherein the etchant contains hydrofluoric acid, nitric acid, acetic acid and water (400): (5-10): (10-50): An etching solution having a volume ratio of (80 to 120) and containing 0.03 g or more of iodine or iodide per liter of the total amount of the etching solution.
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CN111662717A (en) * 2020-07-14 2020-09-15 北京航空航天大学宁波创新研究院 Metallographic corrosive liquid of bismuth selenide material and metallographic display method

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3629694B2 (en) * 1998-02-19 2005-03-16 信越半導体株式会社 Silicon wafer evaluation method
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3629694B2 (en) * 1998-02-19 2005-03-16 信越半導体株式会社 Silicon wafer evaluation method
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* Cited by examiner, † Cited by third party
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CN111662717A (en) * 2020-07-14 2020-09-15 北京航空航天大学宁波创新研究院 Metallographic corrosive liquid of bismuth selenide material and metallographic display method
CN111662717B (en) * 2020-07-14 2021-08-31 北京航空航天大学宁波创新研究院 Metallographic corrosive liquid of bismuth selenide material and metallographic display method

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