JP2012013447A - Method for inspecting defect in semiconductor single crystal - Google Patents

Method for inspecting defect in semiconductor single crystal Download PDF

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JP2012013447A
JP2012013447A JP2010147863A JP2010147863A JP2012013447A JP 2012013447 A JP2012013447 A JP 2012013447A JP 2010147863 A JP2010147863 A JP 2010147863A JP 2010147863 A JP2010147863 A JP 2010147863A JP 2012013447 A JP2012013447 A JP 2012013447A
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Tadayoshi Tsuchiya
忠厳 土屋
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Hitachi Cable Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting a defect in a semiconductor single crystal, which has an enhanced sensitivity in defect evaluation of an inspection object by ultrasonic scattering method.SOLUTION: In a method for inspecting a defect in a semiconductor single crystal by passing ultrasonic waves into a plate shaped semiconductor single crystal inspection object to determine presence or absence of a crystal defect in the inspection object based on the ultrasonic waves scattered or reflected in the inspection object, the incident ultrasonic waves to the inspection object have a wavelength of equal to or shorter than 60 μm or a frequency of equal to or higher than 78 MHz and form an angle between a direction perpendicular to a surface of the inspection object and an incident direction of the ultrasonic waves in the range from 10.0 degrees to 16.4 degrees.

Description

本発明は、半導体デバイスの各種特性に悪影響を及ぼす半導体単結晶中の欠陥検査方法、特に、超音波を使用した半導体単結晶中の欠陥検査方法に関するものである。   The present invention relates to a defect inspection method in a semiconductor single crystal that adversely affects various characteristics of a semiconductor device, and more particularly to a defect inspection method in a semiconductor single crystal using ultrasonic waves.

半導体単結晶中の欠陥は、半導体デバイスの特性や寿命を低下させる原因となる虞があるため、その発生を低減させる努力が続けられている。中でも多結晶欠陥、或いは結晶転位の密集したリネージと呼ばれる欠陥は、半導体デバイスの特性を著しく低下させるために、欠陥を発生させない努力は勿論、半導体単結晶製造後の検査、選別も重要となっている。   Since defects in the semiconductor single crystal may cause a decrease in the characteristics and lifetime of the semiconductor device, efforts are being made to reduce their occurrence. In particular, defects called polycrystalline defects or lineage with dense crystal dislocations are important not only for efforts to prevent defects, but also for inspection and selection after semiconductor single crystal manufacturing, in order to significantly reduce the characteristics of semiconductor devices. Yes.

従来は、成長した単結晶インゴットから切り出したウェハの表面を鏡面に研磨して、溶融KOH(水酸化カリウム)による表面エッチングにより欠陥を可視化して不良部分の検査、選別をしていた。この他、X線回折法、透過電子顕微鏡法、フォトルミネセンス法、カソードルミネセンス法なども研究目的では結晶欠陥検査に使用されている。   Conventionally, the surface of a wafer cut out from a grown single crystal ingot is mirror-polished, and defects are visualized by surface etching with molten KOH (potassium hydroxide) to inspect and select defective portions. In addition, X-ray diffraction, transmission electron microscopy, photoluminescence, and cathodoluminescence are also used for crystal defect inspection for research purposes.

一方、超音波の反射により内部の欠陥を検出する方法は、超音波探傷法と呼ばれ、主として、材料中の中空欠陥(ボイド)やクラック、異物を検出するのに用いられている。この方法は、母材と同種の材質からなる欠陥は検出できないと考えられており、従って、上述の欠陥も、超音波による検出は不可能とされていた。   On the other hand, a method of detecting internal defects by reflection of ultrasonic waves is called an ultrasonic flaw detection method and is mainly used to detect hollow defects (voids), cracks, and foreign matters in a material. In this method, it is considered that a defect made of the same kind of material as the base material cannot be detected. Therefore, the above-described defect cannot be detected by ultrasonic waves.

超音波探傷法を用いた単結晶中の欠陥検出については、例えば、特許文献1の例があるが、これは目的が肉厚測定や孔食、即ちボイドやクラックの探傷であり、上述の欠陥を検出できるものではない。   Regarding the defect detection in single crystals using the ultrasonic flaw detection method, for example, there is an example of Patent Document 1, but this is intended for thickness measurement and pitting corrosion, that is, flaw detection of voids and cracks. Cannot be detected.

しかし、78MHz以上の周波数域の超高周波の超音波を入射して、その散乱を利用する超音波散乱法を用いると測定対象が単結晶であれば、欠陥の散乱像が得られることが本発明者らの検討により分かってきた。この経緯を以下に述べる。   However, it is possible to obtain a scattered image of a defect if an object to be measured is a single crystal by using an ultrasonic scattering method using ultra-high frequency ultrasonic waves in a frequency range of 78 MHz or higher and utilizing the scattering. It became clear by the examination of the people. This process is described below.

金属などの多結晶やアモルファス、或いはガラスなどは、結晶性を有していなかったり、或いは結晶であっても無数のグレインの存在する配向性のない多結晶であるため、本来、結晶に存在する音速の異方性は、上述のような材料では全ての方向に平均化されてしまって、観測されない。   A polycrystal such as a metal, an amorphous material, or a glass does not have crystallinity, or is a polycrystal without orientation with countless grains even if it is a crystal. The anisotropy of the speed of sound is averaged in all directions and is not observed in the above materials.

超音波の反射(散乱)は音速(厳密には音響インピーダンス)の異なる材質の界面で生じるから、音速の全く異なる中空のボイドやクラック、或いは異物が存在しないと超音波の反射(散乱)を明確に捉えることができないのである。   Since reflection (scattering) of ultrasonic waves occurs at the interface of materials with different sound speeds (strictly speaking, acoustic impedance), the reflection (scattering) of ultrasonic waves is clear when there are no hollow voids, cracks, or foreign objects with completely different sound speeds. I can't catch it.

これに対し、単結晶では結晶方位が明確にそろっていることから、結晶方位の異なる部分が存在したり、結晶格子に著しい乱れが存在すると、そこでは本来の結晶方向の音速とは異なる音速で伝播する。音速に違いのある媒体の界面では反射(散乱)が生じるので、結晶格子の乱れた部分では超音波が散乱され、観測できる。   On the other hand, the crystal orientation of single crystals is clearly aligned, so if there are parts with different crystal orientations, or if there is significant disturbance in the crystal lattice, there will be a sound velocity different from the sound velocity in the original crystal direction. Propagate. Since reflection (scattering) occurs at the interface of media with different sound speeds, ultrasonic waves are scattered and observed at the disordered part of the crystal lattice.

そのような有害結晶のひとつ、リネージと呼ばれる結晶欠陥は、ミリメートルサイズ以上の比較的マクロな欠陥である。このリネージは、中空のボイドやクラック、或いは異物ではないため、従来は検出されないとされていた。   One such harmful crystal, a crystal defect called lineage, is a relatively macro defect of millimeter size or more. Since this lineage is not a hollow void, a crack, or a foreign substance, it was conventionally assumed that it was not detected.

また、実際にこの欠陥に対して通常使用される10MHz程度の超音波を入射しても、全く何も検出されない。これはこの欠陥が比較的マクロな欠陥に見えていながら、個々には1〜10μm程度の非常にミクロな欠陥であって、これが高密度に密集しているために、比較的マクロな大きさに見えるためではないかと推測される。   Moreover, even if an ultrasonic wave of about 10 MHz that is normally used for this defect is actually incident, nothing is detected. Although this defect appears to be a relatively macro defect, it is a very micro defect of about 1 to 10 μm, and since this defect is densely packed, it has a relatively macro size. Presumably because it is visible.

ミクロなサイズな欠陥の観察であれば、入射する超音波の周波数を増すことにより、結晶中の音波の波長が短くなり、音波の散乱強度を増大させられると考えられることから高周波化が検討された。そして本発明者らによって78MHz以上の超音波を使用することにより、表面を鏡面加工しないウェハでも非接触で当該欠陥を検出可能であることが見出された。   When observing microscopic defects, it is considered that increasing the frequency of the incident ultrasonic wave shortens the wavelength of the sound wave in the crystal and increases the scattering intensity of the sound wave. It was. It has been found by the present inventors that the defect can be detected in a non-contact manner even on a wafer whose surface is not mirror-finished by using ultrasonic waves of 78 MHz or higher.

特許第4131598号公報Japanese Patent No. 4131598

本発明者らが検討してきた上述の超音波散乱法では、超音波の被検査物中における散乱現象を使用して、被検査物中のリネージと呼ばれる欠陥を検出している。リネージは主として螺旋転位と呼ばれる結晶欠陥の集合体であり、単結晶の育成時に形成されることが多いために、単結晶の成長方向に沿って伸びることが多い。   In the above-described ultrasonic scattering method studied by the present inventors, a defect called lineage in an inspection object is detected using a scattering phenomenon of ultrasonic waves in the inspection object. Lineage is mainly an assembly of crystal defects called screw dislocations, and is often formed during the growth of a single crystal, and therefore often extends along the growth direction of the single crystal.

昨今、ウェハのコスト削減要求のため、ウェハを切り出す単結晶インゴットは、より長尺なものが求められる傾向にあり、単結晶の成長方向に長尺化している。   In recent years, due to demands for reducing wafer costs, single crystal ingots for cutting wafers tend to be longer, and are becoming longer in the growth direction of single crystals.

ウェハは単結晶の成長方向にほぼ垂直に切断されて加工されるため、螺旋転位或いはリネージはウェハに垂直に、ウェハの表面から裏面、或いは裏面から表面へと貫通していることが多い。   Since the wafer is cut and processed almost perpendicularly to the growth direction of the single crystal, the screw dislocation or lineage often penetrates the wafer from the front surface to the back surface or from the back surface to the front surface.

これまで検討してきた超音波散乱法では、このようなウェハに対し、超音波をウェハの表面に垂直に入射させ、垂直に反射されてくる超音波を観測していた。この場合、疎密波である超音波の伝搬方向と螺旋転位の転位線の向きは並行であり、得られた散乱像のコントラストが低く、問題ということがわかった。   In the ultrasonic scattering method that has been studied so far, ultrasonic waves are incident on such a wafer perpendicularly to the surface of the wafer, and the ultrasonic waves reflected vertically are observed. In this case, the propagation direction of the ultrasonic wave, which is a dense wave, and the direction of the dislocation line of the screw dislocation are in parallel, and the contrast of the obtained scattered image is low, which is a problem.

そこで、本発明の目的は、超音波散乱法における被検査物の欠陥評価の感度を向上させた半導体単結晶中の欠陥検査方法を提供することにある。   Therefore, an object of the present invention is to provide a defect inspection method in a semiconductor single crystal in which the sensitivity of defect evaluation of an inspection object in the ultrasonic scattering method is improved.

本発明は上記目的を達成するために創案されたものであり、請求項1の発明は、板状の半導体単結晶である被検査物に対して超音波を入射させ、前記被検査物内で散乱又は反射された超音波に基づいて、前記被検査物内の結晶欠陥の有無を測定する半導体単結晶中の欠陥検査方法において、前記被検査物に対して波長が60μm以下、又は周波数が78MHz以上の超音波を、前記被検査物の表面に垂直な方向と超音波の入射方向のなす角が10.0度以上16.4度以下の範囲となるように入射させる半導体単結晶中の欠陥検査方法である。   The present invention has been devised to achieve the above object, and the invention of claim 1 is directed to inject ultrasonic waves to an object to be inspected, which is a plate-like semiconductor single crystal, and within the object to be inspected. In a defect inspection method in a semiconductor single crystal for measuring the presence or absence of crystal defects in the inspection object based on scattered or reflected ultrasonic waves, the wavelength of the inspection object is 60 μm or less, or the frequency is 78 MHz. Defects in a semiconductor single crystal in which the above ultrasonic waves are incident so that the angle formed between the direction perpendicular to the surface of the object to be inspected and the incident direction of the ultrasonic waves is in the range of 10.0 degrees to 16.4 degrees Inspection method.

請求項2の発明は、板状の半導体単結晶である被検査物に対して超音波を入射させ、前記被検査物内で散乱又は反射された超音波に基づいて、前記被検査物内の結晶欠陥の有無を測定する半導体単結晶中の欠陥検査方法において、前記被検査物に対して波長が60μm以下、又は周波数が78MHz以上の超音波を、前記被検査物の表面に垂直な方向と超音波の入射方向のなす角が12.0度以上15.4度以下の範囲となるように入射させる半導体単結晶中の欠陥検査方法である。   In the invention of claim 2, an ultrasonic wave is incident on an inspection object which is a plate-like semiconductor single crystal, and based on the ultrasonic wave scattered or reflected in the inspection object, In a defect inspection method in a semiconductor single crystal for measuring the presence or absence of a crystal defect, an ultrasonic wave having a wavelength of 60 μm or less or a frequency of 78 MHz or more is applied to the inspection object in a direction perpendicular to the surface of the inspection object. This is a defect inspection method in a semiconductor single crystal that is incident so that the angle formed by the incident direction of ultrasonic waves is in the range of 12.0 degrees to 15.4 degrees.

請求項3の発明は、前記被検査物内で散乱又は反射された超音波を、前記被検査物の表面に垂直な方向と計測方向のなす角が0度以上16.4度以下の方向で計測する請求項1に記載の半導体単結晶中の欠陥検査方法である。   According to a third aspect of the present invention, ultrasonic waves scattered or reflected in the inspection object are measured in a direction in which an angle between a direction perpendicular to the surface of the inspection object and a measurement direction is 0 degree or more and 16.4 degrees or less. It is a defect inspection method in the semiconductor single crystal of Claim 1 to measure.

請求項4の発明は、前記被検査物内で散乱又は反射された超音波を、前記被検査物の表面に垂直な方向と計測方向のなす角が0度以上15.4度以下の方向で計測する請求項2に記載の半導体単結晶中の欠陥検査方法である。   According to a fourth aspect of the present invention, ultrasonic waves scattered or reflected in the inspection object are measured in a direction in which an angle between a direction perpendicular to the surface of the inspection object and a measurement direction is 0 degree or more and 15.4 degrees or less. It is a defect inspection method in the semiconductor single crystal of Claim 2 to measure.

請求項5の発明は、超音波の入射方向と計測方向のなす角の絶対値が32.8度以下の範囲となるようにする請求項1又は3に記載の半導体単結晶中の欠陥検査方法である。   The invention according to claim 5 is the method for inspecting a defect in a semiconductor single crystal according to claim 1 or 3, wherein the absolute value of the angle formed by the incident direction of the ultrasonic wave and the measuring direction is in a range of 32.8 degrees or less It is.

請求項6の発明は、超音波の入射方向と計測方向のなす角の絶対値が30.8度以下の範囲となるようにする請求項2又は4に記載の半導体単結晶中の欠陥検査方法である。   The invention according to claim 6 is the method for inspecting a defect in a semiconductor single crystal according to claim 2 or 4, wherein the absolute value of the angle formed by the incident direction of the ultrasonic wave and the measurement direction is in a range of 30.8 degrees or less. It is.

請求項7の発明は、前記被検査物が、III−V族化合物半導体単結晶である請求項1〜6のいずれかに記載の半導体単結晶中の欠陥検査方法である。   The invention of claim 7 is the method for inspecting a defect in a semiconductor single crystal according to any one of claims 1 to 6, wherein the object to be inspected is a group III-V compound semiconductor single crystal.

請求項8の発明は、前記被検査物が、砒化ガリウム単結晶である請求項1〜6のいずれかに記載の半導体単結晶中の欠陥検査方法である。   The invention of claim 8 is the method for inspecting defects in a semiconductor single crystal according to any one of claims 1 to 6, wherein the object to be inspected is a gallium arsenide single crystal.

本発明によれば、超音波散乱法における被検査物の欠陥評価の感度を向上させることができる。   ADVANTAGE OF THE INVENTION According to this invention, the sensitivity of the defect evaluation of the to-be-inspected object in an ultrasonic scattering method can be improved.

本発明を実施するための超音波測定装置の一例を示す図である。It is a figure which shows an example of the ultrasonic measuring apparatus for implementing this invention. 図1の要部拡大図である。It is a principal part enlarged view of FIG. 入射角と反射率の関係を示す図である。It is a figure which shows the relationship between an incident angle and a reflectance. 入射角と散乱係数の関係を示す図である。It is a figure which shows the relationship between an incident angle and a scattering coefficient. 実施例により得られた超音波散乱像である。It is an ultrasonic scattering image obtained by the Example.

以下、本発明の好適な実施の形態を添付図面にしたがって説明する。   Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

先ず、本発明を実施するための超音波測定装置の構成を説明する。   First, the configuration of an ultrasonic measurement apparatus for carrying out the present invention will be described.

図1に示すように、本発明を実施するための超音波測定装置1は、液体槽2と、液体槽2内に設けられた被検査物3と、被検査物3に対して波長が60μm以下、又は周波数が78MHz以上の超音波を入射させる超音波発振器4と、被検査物3内で散乱又は反射された超音波を検出する検出器(探針子)5とを備える。   As shown in FIG. 1, an ultrasonic measuring apparatus 1 for carrying out the present invention includes a liquid tank 2, an inspection object 3 provided in the liquid tank 2, and a wavelength of 60 μm with respect to the inspection object 3. Hereinafter, an ultrasonic oscillator 4 that makes an ultrasonic wave having a frequency of 78 MHz or more incident, and a detector (probe) 5 that detects ultrasonic waves scattered or reflected in the inspection object 3 are provided.

液体槽2内は液体6で満たされており、この液体6中に被検査物3、超音波発振器4、及び検出器5が浸漬される。   The liquid tank 2 is filled with the liquid 6, and the inspection object 3, the ultrasonic oscillator 4, and the detector 5 are immersed in the liquid 6.

被検査物3としては、例えば、厚さ2mm以下の板状の半導体単結晶(ウェハ)を対象としている。半導体単結晶としては、砒化ガリウムなどのIII−V族化合物半導体単結晶や、シリコン、サファイア、炭化珪素など、単結晶からなるウェハ全般を用いることができる。   As the inspected object 3, for example, a plate-shaped semiconductor single crystal (wafer) having a thickness of 2 mm or less is targeted. As a semiconductor single crystal, a group III-V compound semiconductor single crystal such as gallium arsenide, or a general wafer made of a single crystal such as silicon, sapphire, or silicon carbide can be used.

液体6としては、ヘキサン、ベンゼン、トルエンのような炭化水素系液体、又はメタノール、エタノール、プロパノール、ブタノールのようなアルコール系液体が好適である。これらの液体を用いることで、78MHz以上の超高周波の超音波によっても被検査物3の表面に変色や変質などを生じさせないようにすることができる。なお、液体6として水(純水)を用いても、欠陥の検査は可能であるが、被検査物3の表面に変色や変質などが生じる場合がある。   The liquid 6 is preferably a hydrocarbon liquid such as hexane, benzene or toluene or an alcohol liquid such as methanol, ethanol, propanol or butanol. By using these liquids, it is possible to prevent the surface of the inspection object 3 from being discolored or deteriorated even by an ultrasonic wave having an ultrahigh frequency of 78 MHz or higher. Note that even if water (pure water) is used as the liquid 6, the defect can be inspected, but discoloration or alteration may occur on the surface of the inspection object 3.

この超音波測定装置1を用いた半導体単結晶中の欠陥検査方法を説明する。   A defect inspection method in a semiconductor single crystal using the ultrasonic measurement apparatus 1 will be described.

先ず、超音波発振器4で波長が60μm以下、又は周波数が78MHz以上の超音波を発振させると共に被検査物3に対して入射させる。   First, an ultrasonic wave having a wavelength of 60 μm or less or a frequency of 78 MHz or more is oscillated by the ultrasonic oscillator 4 and incident on the inspection object 3.

そして、検出器5で被検査物3内で散乱又は反射された超音波を検出し、この検出結果に基づいて、被検査物3内の結晶欠陥の有無を測定する。   And the ultrasonic wave scattered or reflected in the to-be-inspected object 3 is detected with the detector 5, and the presence or absence of the crystal defect in the to-be-inspected object 3 is measured based on this detection result.

この半導体単結晶中の欠陥検査方法について本発明者が鋭意検討を重ねた結果、被検査物3の転位線の方向と超音波の入射方向とが平行であるときに散乱強度は最も低くなり、また、被検査物3の転位線の方向と超音波の入射方向とが垂直に近いほど散乱強度が高くなる傾向にあることが分かった。   As a result of intensive studies by the inventor on the defect inspection method in this semiconductor single crystal, the scattering intensity is lowest when the direction of the dislocation line of the inspection object 3 and the incident direction of the ultrasonic wave are parallel, Further, it was found that the scattering intensity tends to increase as the direction of the dislocation line of the inspection object 3 and the incident direction of the ultrasonic wave are closer to vertical.

図2に示すように、被検査物3であるウェハは単結晶の成長方向にほぼ垂直に切断されて加工されるので、被検査物3に転位(貫通転位)7が生じているとき、転位7は表面にほぼ垂直に存在している。そのため、超音波の入射方向が被検査物3の表面に垂直であると散乱強度が低くなってしまうことから、板状の被検査物3の表面に対し超音波を垂直入射する方法では欠陥評価の感度を向上させることができないと考えた。   As shown in FIG. 2, the wafer that is the object to be inspected 3 is processed by being cut almost perpendicularly to the growth direction of the single crystal. Therefore, when dislocations (threading dislocations) 7 are generated in the inspected object 3, dislocations are generated. 7 exists almost perpendicular to the surface. For this reason, if the incident direction of the ultrasonic wave is perpendicular to the surface of the inspection object 3, the scattering intensity becomes low. I thought it was impossible to improve the sensitivity.

そこで本発明者は、図2に示すように、超音波の入射方向を被検査物3の表面に対して傾けることで、欠陥評価の感度を向上させることができるのではないかと考えた。   Therefore, the present inventor thought that the sensitivity of defect evaluation could be improved by tilting the incident direction of the ultrasonic wave with respect to the surface of the inspection object 3 as shown in FIG.

本発明で対象とする被検査物3は、音響インピーダンスが比較的大きい(液体6と比べて)。超音波が液体6から音響インピーダンスの大きく異なる被検査物3に入射する際には、被検査物3の表面で強く反射される。   The object 3 to be inspected in the present invention has a relatively large acoustic impedance (compared to the liquid 6). When the ultrasonic wave enters the inspection object 3 having a greatly different acoustic impedance from the liquid 6, it is strongly reflected on the surface of the inspection object 3.

平滑な被検査物3の表面での反射は、表面に浅い角度で入射させるほど強くなり、被検査物3に侵入する超音波は弱くなる。従って、被検査物3の内部で散乱される超音波強度も大きく低下してしまう。   Reflection on the surface of the smooth inspected object 3 becomes stronger as it enters the surface at a shallow angle, and ultrasonic waves that enter the inspected object 3 become weaker. Therefore, the intensity of ultrasonic waves scattered inside the inspection object 3 is also greatly reduced.

本発明者による検討の結果、被検査物3が砒化ガリウムである場合、被検査物3に侵入する超音波を強めるためには、被検査物3に対して超音波発振器4を、被検査物3の表面に垂直な方向(図1,2の一点鎖線で示した方向)と超音波の入射方向のなす角(入射角)θ1が0度、若しくはその方向から16度程度までとなるように配置するのが望ましいことが分かった。それ以上の角度では、超音波が被検査物3の表面で反射され、被検査物3の内部に超音波が入らない。 As a result of examination by the present inventor, when the inspection object 3 is gallium arsenide, in order to strengthen the ultrasonic wave entering the inspection object 3, the ultrasonic oscillator 4 is connected to the inspection object 3. The angle (incident angle) θ 1 formed between the direction perpendicular to the surface 3 (the direction indicated by the alternate long and short dash line in FIGS. 1 and 2) and the incident direction of the ultrasonic waves is 0 degree or about 16 degrees from that direction. It was found to be desirable to place it in At an angle larger than that, the ultrasonic waves are reflected by the surface of the inspection object 3, and the ultrasonic waves do not enter the inspection object 3.

これらの関係から被検査物3に入射させる超音波の角度は、浅くても深くても欠陥評価の感度が悪くなってしまうことが分かる。検討の結果、良好な超音波散乱像を得るためには、被検査物3の表面と垂直な方向に対して10.0度以上16.4度以下の範囲、より好ましくは12.0度以上15.4度以下の範囲で超音波を入射させることが有効である。   From these relationships, it can be seen that the sensitivity of defect evaluation deteriorates even if the angle of the ultrasonic wave incident on the inspection object 3 is shallow or deep. As a result of the examination, in order to obtain a good ultrasonic scattering image, a range of 10.0 degrees or more and 16.4 degrees or less with respect to a direction perpendicular to the surface of the inspection object 3, more preferably 12.0 degrees or more. It is effective to make the ultrasonic wave incident within a range of 15.4 degrees or less.

また、被検査物3内で散乱又は反射された超音波は、被検査物3の内外における音速の差によって、被検査物3の表面で再び屈折する(図2参照)。そのため、被検査物3に対して検出器5を、被検査物3の表面に垂直な方向と計測方向のなす角(検出角)θ2が0度、若しくはその方向から16度程度まで、具体的には0度以上16.4度以下となるように配置するのが望ましい。それを超える角度では、超音波が被検査物3の内部から外部に出られないため、検出できない。なお、被検査物3の表面にうねりのような凹凸が存在する場合は、検出器5を被検査物3の表面に垂直な方向から15.4度までの範囲に配置することが、表面のうねりの影響を受けにくく、より好ましい。 In addition, the ultrasonic waves scattered or reflected in the inspection object 3 are refracted again on the surface of the inspection object 3 due to the difference in sound velocity inside and outside the inspection object 3 (see FIG. 2). Therefore, the detector 5 with respect to the inspected object 3 has an angle (detection angle) θ 2 formed by the direction perpendicular to the surface of the inspected object 3 and the measurement direction is 0 degree or about 16 degrees from that direction. Specifically, it is desirable to arrange it so that it is 0 degree or more and 16.4 degree or less. At an angle exceeding that, ultrasonic waves cannot be detected from the inside of the inspection object 3 and cannot be detected. If the surface of the inspection object 3 has irregularities such as undulations, the detector 5 may be arranged in a range from the direction perpendicular to the surface of the inspection object 3 to 15.4 degrees. It is less affected by swell and is more preferable.

以下、入射角θ1を10.0度以上16.4度以下、より好ましくは12.0度以上15.4度以下の範囲とする数値的根拠と、検出角θ2を0度以上16.4度以下、より好ましくは0度以上15.4度以下とする数値的根拠を説明する。 Hereinafter, a numerical basis for setting the incident angle θ 1 in the range of 10.0 ° to 16.4 °, more preferably 12.0 ° to 15.4 °, and the detection angle θ 2 to 0 ° to 16. A numerical basis for setting the angle to 4 degrees or less, more preferably 0 to 15.4 degrees will be described.

図3に示すように、入射角θ1を大きくしていくと、被検査物3の表面での反射率が大きくなる。また、16.1度以上では反射率が高すぎるために超音波は被検査物3内にほとんど侵入せず、A部として示した臨界角である16.4度を超えると被検査物3の表面で反射してしまう。同様に、検出角θ2も16.4度を超えると超音波が被検査物3内に閉じ込められて出てこないために、16.4度以下にしなければ計測できない。 As shown in FIG. 3, as the incident angle θ 1 is increased, the reflectance on the surface of the inspection object 3 increases. Further, since the reflectivity is too high at 16.1 degrees or more, the ultrasonic wave hardly penetrates into the inspection object 3 and exceeds 16.4 degrees which is the critical angle shown as the A part. Reflected on the surface. Similarly, if the detection angle θ 2 also exceeds 16.4 degrees, the ultrasonic wave is confined in the inspection object 3 and does not come out, so measurement cannot be performed unless the angle is 16.4 degrees or less.

次いで、種々の入射角θ1に対して、超音波観察での欠陥の散乱強度を検討した結果を図4に示す。 Next, FIG. 4 shows the results of examining the scattering intensity of defects in ultrasonic observation with respect to various incident angles θ 1 .

この結果から、入射角θ1が16.4度以下であれば計測は可能であることが分かる。しかし、15.4度を超えると、表面での反射と散乱で計測が不安定になった。そのため、15.4度以下とした方がより安定に計測が可能である。また、10.0度以上では計測は十分可能であるが、12.0度以上とした方がより計測しやすく、安定的に計測が可能となる。以上より、図4中に矢印で示している、入射角θ1として12.0度以上15.4度以下が適正であることが分かった。 From this result, it can be seen that measurement is possible if the incident angle θ 1 is 16.4 degrees or less. However, when it exceeded 15.4 degrees, the measurement became unstable due to reflection and scattering on the surface. Therefore, it is possible to measure more stably when the angle is 15.4 degrees or less. In addition, the measurement is sufficiently possible at 10.0 degrees or more, but the measurement is easier and more stable at 12.0 degrees or more. From the above, it was found that the incident angle θ 1 indicated by the arrow in FIG.

検出角θ2も同様で、16.4度以下であれば計測可能であるが、計測の安定性などを考慮すれば、12.0度以上15.4度以下がより好ましい。 Similarly, the detection angle θ 2 can be measured if it is 16.4 degrees or less, but it is more preferably 12.0 degrees or more and 15.4 degrees or less in consideration of measurement stability or the like.

これらの関係より必然的に、被検査物3に入射させる超音波の伝搬方向とこの被検査物3から散乱されてくる超音波を検出する検出器5に入射する超音波の伝搬方向のなす角は、−6.4度以上32.8度以下の範囲となる。そして、好ましくは−3.4度以上30.8度以下の範囲である。従って、角度の絶対値では32.8度以下、より好ましくは30.8度以下となる。   From these relationships, the angle formed by the propagation direction of the ultrasonic wave incident on the inspection object 3 and the propagation direction of the ultrasonic wave incident on the detector 5 that detects the ultrasonic wave scattered from the inspection object 3 is inevitably formed. Is in the range of −6.4 degrees to 32.8 degrees. And preferably it is the range of -3.4 degree or more and 30.8 degree or less. Therefore, the absolute value of the angle is 32.8 degrees or less, more preferably 30.8 degrees or less.

以上要するに、本発明の半導体単結晶中の欠陥検査方法によれば、被検査物3に対して波長が60μm以下、又は周波数が78MHz以上の超音波を、入射角θ1が10.0度以上16.4度以下、より好ましくは12.0度以上15.4度以下の範囲となるように入射させると共に、被検査物3内で散乱又は反射された超音波を、検出角θ2が0度以上16.4度以下、より好ましくは0度以上15.4度以下の方向で計測するので、被検査物3の表面に垂直な方向に貫通する螺旋転位或いはリネージなどの欠陥を精度良く測定できる。つまり、超音波散乱法における被検査物の欠陥評価の感度を向上させることができる。 In short, according to the defect inspection method in a semiconductor single crystal of the present invention, an ultrasonic wave having a wavelength of 60 μm or less or a frequency of 78 MHz or more with respect to the inspection object 3 and an incident angle θ 1 of 10.0 degrees or more. While making it enter so that it may become 16.4 degrees or less, More preferably, it is the range of 12.0 degrees or more and 15.4 degrees or less, the detection angle (theta) 2 is 0 in the ultrasonic wave scattered or reflected in the to-be-inspected object 3. Measurement is performed in the direction of not less than 16.4 degrees and more preferably in the range of not less than 0 degrees and not more than 15.4 degrees, so that defects such as screw dislocations or lineage penetrating in a direction perpendicular to the surface of the inspection object 3 can be accurately measured. it can. That is, it is possible to improve the sensitivity of the defect evaluation of the inspection object in the ultrasonic scattering method.

本発明の効果を確認すべく実施例を行った。   Examples were conducted to confirm the effects of the present invention.

本実施例では、125MHz以上の周波数の超音波で、被検査物中の欠陥検査を実施した。超音波測定装置としては、図1で説明したものを用いた。被検査物を浸漬する液体にはエチレングリコールを用いた。   In this example, the defect inspection in the inspection object was performed with ultrasonic waves having a frequency of 125 MHz or higher. As the ultrasonic measurement apparatus, the apparatus described with reference to FIG. 1 was used. Ethylene glycol was used as the liquid in which the test object was immersed.

試料は、LEC(液体封止チョクラルスキー)法で成長した砒化ガリウム単結晶である。直径100mmの単結晶インゴットから約1mm厚でウェハを切り出し、その表面を鏡面加工後、超音波にて欠陥検査を行った。   The sample is a gallium arsenide single crystal grown by the LEC (liquid sealed Czochralski) method. A wafer was cut out from a single crystal ingot with a diameter of 100 mm to a thickness of about 1 mm, and the surface was mirror-finished, followed by ultrasonic inspection for defects.

このとき、入射角を15度、検出角を12度として欠陥検査を行った。その結果を図5に示す。   At this time, the defect inspection was performed with an incident angle of 15 degrees and a detection angle of 12 degrees. The result is shown in FIG.

図5から分かるように、本発明により得られた超音波散乱像は、コントラストが高く、欠陥部分50をはっきりと測定することができた。   As can be seen from FIG. 5, the ultrasonic scattering image obtained by the present invention has high contrast, and the defect portion 50 can be measured clearly.

以上より、本発明を用いることで、超音波散乱法における被検査物の欠陥評価の感度を向上させることができた。   From the above, by using the present invention, it was possible to improve the sensitivity of the defect evaluation of the inspection object in the ultrasonic scattering method.

また、他の実施例として、被検査物を浸漬する液体としてエタノールを用いて同様の測定を行った。   Further, as another example, the same measurement was performed using ethanol as a liquid in which the object to be inspected was immersed.

測定の結果、上記実施例と同じ観察像が得られた。エタノールを用いる場合には、大気中の水分を吸収する影響を避けるためエタノールを液体槽に満たした直後に測定を行う。   As a result of the measurement, the same observation image as in the above example was obtained. When ethanol is used, measurement is performed immediately after filling the liquid tank with ethanol to avoid the effect of absorbing moisture in the atmosphere.

さらに、被検査物を浸漬する液体として純水を用いて同様の測定を行ったところ、上記実施例と同様の観察像が得られたものの、測定後の試料の表面は黒ずんだ色に変色していた。   Furthermore, when the same measurement was performed using pure water as a liquid for immersing the object to be inspected, an observation image similar to the above example was obtained, but the surface of the sample after the measurement changed to a dark color. It was.

また、本実施例では、砒化ガリウム単結晶を用いたが、本発明はシリコン、インジウム燐などのウェハ状の単結晶について、同様に適用することができる。特にこれらは可視光線に対して不透明であり、また、透過赤外線での観察は表面粗さに強く影響を受けるため、超音波にて測定することが好ましい。   In this embodiment, a gallium arsenide single crystal is used. However, the present invention can be similarly applied to a wafer-like single crystal such as silicon or indium phosphide. In particular, they are opaque to visible light, and observation with transmitted infrared light is strongly influenced by surface roughness, so measurement with ultrasonic waves is preferable.

Claims (8)

板状の半導体単結晶である被検査物に対して超音波を入射させ、前記被検査物内で散乱又は反射された超音波に基づいて、前記被検査物内の結晶欠陥の有無を測定する半導体単結晶中の欠陥検査方法において、
前記被検査物に対して波長が60μm以下、又は周波数が78MHz以上の超音波を、前記被検査物の表面に垂直な方向と超音波の入射方向のなす角が10.0度以上16.4度以下の範囲となるように入射させることを特徴とする半導体単結晶中の欠陥検査方法。
An ultrasonic wave is incident on an inspection object which is a plate-like semiconductor single crystal, and the presence or absence of crystal defects in the inspection object is measured based on the ultrasonic wave scattered or reflected in the inspection object. In a defect inspection method in a semiconductor single crystal,
The angle between the direction perpendicular to the surface of the inspection object and the incident direction of the ultrasonic wave is 10.0 degrees or more and 16.4 with respect to the inspection object with a wavelength of 60 μm or less or a frequency of 78 MHz or more. A method for inspecting a defect in a semiconductor single crystal, wherein the incidence is made to be in a range of less than or equal to a degree.
板状の半導体単結晶である被検査物に対して超音波を入射させ、前記被検査物内で散乱又は反射された超音波に基づいて、前記被検査物内の結晶欠陥の有無を測定する半導体単結晶中の欠陥検査方法において、
前記被検査物に対して波長が60μm以下、又は周波数が78MHz以上の超音波を、前記被検査物の表面に垂直な方向と超音波の入射方向のなす角が12.0度以上15.4度以下の範囲となるように入射させることを特徴とする半導体単結晶中の欠陥検査方法。
An ultrasonic wave is incident on an inspection object which is a plate-like semiconductor single crystal, and the presence or absence of crystal defects in the inspection object is measured based on the ultrasonic wave scattered or reflected in the inspection object. In a defect inspection method in a semiconductor single crystal,
The angle formed between the direction perpendicular to the surface of the inspection object and the incident direction of the ultrasonic wave is 12.0 degrees or more and 15.4 degrees with respect to the inspection object with a wavelength of 60 μm or less or a frequency of 78 MHz or more. A method for inspecting a defect in a semiconductor single crystal, wherein the incidence is made to be in a range of less than or equal to a degree.
前記被検査物内で散乱又は反射された超音波を、前記被検査物の表面に垂直な方向と計測方向のなす角が0度以上16.4度以下の方向で計測する請求項1に記載の半導体単結晶中の欠陥検査方法。   The ultrasonic wave scattered or reflected in the inspection object is measured in a direction in which an angle between a direction perpendicular to the surface of the inspection object and a measurement direction is 0 degree or more and 16.4 degrees or less. Inspection method for defects in semiconductor single crystals. 前記被検査物内で散乱又は反射された超音波を、前記被検査物の表面に垂直な方向と計測方向のなす角が0度以上15.4度以下の方向で計測する請求項2に記載の半導体単結晶中の欠陥検査方法。   The ultrasonic wave scattered or reflected in the inspection object is measured in a direction in which an angle between a direction perpendicular to the surface of the inspection object and a measurement direction is 0 degree or more and 15.4 degrees or less. Inspection method for defects in semiconductor single crystals. 超音波の入射方向と計測方向のなす角の絶対値が32.8度以下の範囲となるようにする請求項1又は3に記載の半導体単結晶中の欠陥検査方法。   The method for inspecting defects in a semiconductor single crystal according to claim 1 or 3, wherein an absolute value of an angle formed by an incident direction of ultrasonic waves and a measurement direction is in a range of 32.8 degrees or less. 超音波の入射方向と計測方向のなす角の絶対値が30.8度以下の範囲となるようにする請求項2又は4に記載の半導体単結晶中の欠陥検査方法。   The defect inspection method in a semiconductor single crystal according to claim 2 or 4, wherein an absolute value of an angle formed by an incident direction of ultrasonic waves and a measurement direction is in a range of 30.8 degrees or less. 前記被検査物が、III−V族化合物半導体単結晶である請求項1〜6のいずれかに記載の半導体単結晶中の欠陥検査方法。   The defect inspection method in a semiconductor single crystal according to claim 1, wherein the inspection object is a group III-V compound semiconductor single crystal. 前記被検査物が、砒化ガリウム単結晶である請求項1〜6のいずれかに記載の半導体単結晶中の欠陥検査方法。   The method for inspecting defects in a semiconductor single crystal according to claim 1, wherein the object to be inspected is a gallium arsenide single crystal.
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