JP2010054377A - Infrared inspection device - Google Patents
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本発明は、シリコンウェハ等の半導体基板に赤外線を照射して、結晶内部に生じたマイクロクラック等を検出する赤外線検査装置に関する。 The present invention relates to an infrared inspection apparatus for irradiating a semiconductor substrate such as a silicon wafer with infrared rays to detect microcracks or the like generated inside the crystal.
マイクロクラックは、半導体ウェハ等の結晶基板の結晶内部における結晶の不整合な部分等に発生する微小な割れであり、例えば、太陽電池用結晶ウェハでは、その製造工程途中でウェハ割れを引き起こすのに加えて、完成品においては発電効率を低下させるものである。 A microcrack is a microcrack that occurs in a mismatched portion of a crystal inside a crystal of a crystal substrate such as a semiconductor wafer. For example, a crystal wafer for a solar cell may cause a wafer crack during the manufacturing process. In addition, power generation efficiency is reduced in the finished product.
製造工程途中でのウェハ割れを防止するためには、切り出された半導体ウェハについてマイクロクラックを検出することが必要であるが、外観についての目視検査ではその検出が難しい。このため、赤外線を照射して半導体ウェハ内に生じたマイクロクラックを検出する方法が用いられている（特許文献１）。 In order to prevent wafer cracking during the manufacturing process, it is necessary to detect microcracks in the cut-out semiconductor wafer, but it is difficult to detect by visual inspection of the appearance. For this reason, the method of detecting the microcrack which arose in the semiconductor wafer by irradiating infrared rays is used (patent document 1).
光源から射出された赤外線がマイクロクラックの割れの面に平行に入射すると透過率が増し、そうでない場合には割れ界面で光が部分的に反射されて透過率が低下する。 When infrared rays emitted from the light source are incident on the crack surface of the microcrack in parallel, the transmittance increases. Otherwise, the light is partially reflected at the crack interface and the transmittance decreases.
結晶基板は、結晶成分がそれぞれ異なる透過率をもつため、赤外線を照射した場合、結晶粒の構造により複雑な濃淡差を生じ、場所によって輝度が異なったランダムなパターンを有する画像が撮像されるので、そのままではクラックの検査が困難である。 Since the crystal substrate has different transmittances for each crystal component, when it is irradiated with infrared rays, a complex grayscale difference occurs due to the structure of the crystal grains, and an image having a random pattern with different brightness depending on the location is captured. As it is, inspection of cracks is difficult.
また、半導体基板における光の透過率は、その半導体の組成等によっても変化する。
本発明はかかる問題点に鑑みなされたものであって、簡易な構成でありながら、多様な半導体基板に対応して、高い精度でマイクロクラック等を検出することができる赤外線検査装置を提供することをその主たる所期課題としたものである。 The present invention has been made in view of such problems, and provides an infrared inspection apparatus capable of detecting microcracks or the like with high accuracy in correspondence with various semiconductor substrates while having a simple configuration. Is the main intended issue.
すなわち本発明に係る赤外線検査装置は、半導体基板に赤外線を照射して透過した光を検出する赤外線検査装置であって、異なる波長の光を射出する複数種類の赤外線ＬＥＤを、切り替え点灯可能に備えていることを特徴とする。なお、本発明に係る赤外線検査装置の検査対象である半導体基板としては特に限定されず、例えば、太陽電池用のシリコン膜も含まれ、このようなシリコン膜としては、単結晶シリコン型、多結晶シリコン型、微結晶シリコン型、アモルファスシリコン型のいずれであってもよい。 That is, the infrared inspection apparatus according to the present invention is an infrared inspection apparatus that detects light transmitted by irradiating a semiconductor substrate with infrared light, and includes a plurality of types of infrared LEDs that emit light of different wavelengths so that they can be switched on. It is characterized by. The semiconductor substrate to be inspected by the infrared inspection apparatus according to the present invention is not particularly limited, and includes, for example, a silicon film for a solar cell. Examples of such a silicon film include a single crystal silicon type and a polycrystalline film. Any of silicon type, microcrystalline silicon type, and amorphous silicon type may be used.
半導体ウェハにおける光の透過率は、その半導体のエネルギーギャップによって変化し、図５に示すエネルギーギャップを上回るエネルギーを持つ光、すなわち波長の短い光を照射すると、その半導体中のキャリアを励起するためにエネルギーが消費されるので、照射光が半導体に吸収されてしまい、照射光の透過率が著しく低下する。従って、半導体ウェハにおける光の透過率は、その組成、不純物のドーピング量等によって多様に変化する。また、半導体ウェハの厚さ、処理状態等によっても、光の透過率が変化する。 The transmittance of light in a semiconductor wafer varies depending on the energy gap of the semiconductor, and when light having an energy exceeding the energy gap shown in FIG. 5, that is, light having a short wavelength is irradiated, it excites carriers in the semiconductor. Since energy is consumed, the irradiated light is absorbed by the semiconductor, and the transmittance of the irradiated light is significantly reduced. Accordingly, the light transmittance of the semiconductor wafer varies in various ways depending on its composition, the doping amount of impurities, and the like. Further, the light transmittance varies depending on the thickness of the semiconductor wafer, the processing state, and the like.
これに対して、本発明に係る赤外線検査装置は、半導体基板に赤外線を照射する光源として、異なる波長の光を射出する複数種類の赤外線ＬＥＤを切り替え点灯可能に備えており、検査対象である半導体基板の組成、処理状態や厚さに応じて最も適した波長の光を照射する赤外線ＬＥＤを容易に選択することができるので、精度の高い検査を行うことができる。そして、前記半導体基板が結晶基板である場合、選択された好適な赤外線ＬＥＤから半導体基板に光を照射して、透過光を透過画像として撮像すると、薄膜の表裏を貫通して割れが生じているため照射光が透過する透過性マイクロクラックは白く撮像され、貫通した割れは生じていないが、薄膜内部に微細な亀裂が生じているために内部の破壊面で透過光が部分的に反射される反射性マイクロクラックは黒く撮像され、その他の結晶粒は灰色に撮像される。このため、薄膜内部にマイクロクラックが生じた箇所を極めて鮮明に検出することができる。 On the other hand, the infrared inspection apparatus according to the present invention is equipped with a plurality of types of infrared LEDs that emit light of different wavelengths as a light source for irradiating the semiconductor substrate with infrared rays, and can be switched on, and is a semiconductor to be inspected. Since an infrared LED that emits light having the most suitable wavelength can be easily selected according to the composition, processing state, and thickness of the substrate, a highly accurate inspection can be performed. And when the said semiconductor substrate is a crystal substrate, when light is irradiated to a semiconductor substrate from the selected suitable infrared LED, and the transmitted light is imaged as a transmission image, the front and back of the thin film are penetrated and a crack is generated. Therefore, the transparent microcracks through which the irradiating light passes are imaged in white, and no penetrating cracks are generated. However, since the microcracks are formed inside the thin film, the transmitted light is partially reflected by the internal fracture surface. Reflective microcracks are imaged black, and other crystal grains are imaged gray. For this reason, the location where the microcrack has occurred inside the thin film can be detected very clearly.
なお、好適な波長より短い波長の光を結晶基板に照射した場合は、透過画像全体が暗くなり、好適な波長より長い波長の光を結晶基板に照射した場合は、透過画像全体が明るくなりすぎ、いずれの場合も濃淡差が低下して、マイクロクラックの検出が困難になる。 When the crystal substrate is irradiated with light having a shorter wavelength than the preferred wavelength, the entire transmission image becomes dark, and when the crystal substrate is irradiated with light having a longer wavelength than the preferred wavelength, the entire transmission image becomes too bright. In either case, the difference in lightness and darkness is reduced, making it difficult to detect microcracks.
しかしながら、従来は赤外線を発する光源として一般的にハロゲン灯等が用いられており、赤外線透過フィルタを使用して赤外線が抽出されているが、当該赤外線は波長の幅が広いため、得られる透過画像の鮮明度は充分なものではない。これに対して、ＬＥＤは射出する光の波長の幅が狭い光源であるので、当該クラックと正常な部分との透過率の比が最も大きくなる波長帯域に最適化することが可能となり、本発明によればハロゲン灯等を光源とするものと比べて極めて鮮明な透過画像が得られ、精度の高い検査を行うことができる。 However, conventionally, a halogen lamp or the like is generally used as a light source that emits infrared rays, and infrared rays are extracted using an infrared transmission filter. However, since the infrared rays have a wide wavelength range, a transmission image to be obtained is obtained. The sharpness of is not enough. On the other hand, since the LED is a light source with a narrow wavelength range of emitted light, it can be optimized for a wavelength band where the ratio of the transmittance between the crack and the normal part is the largest. According to this, a very clear transmitted image can be obtained as compared with a light source using a halogen lamp or the like, and a highly accurate inspection can be performed.
また、従来のハロゲン灯等を光源とする検査装置では、赤外線透過フィルタを備える必要があるので、その分検査装置の構成が複雑になる。これに対して、本発明に係る赤外線検査装置ではこのようなフィルタが不要であるので、フィルタ交換等の煩わしい作業が不要であるとともに、装置構成を簡易なものとすることができる。 In addition, in a conventional inspection apparatus using a halogen lamp or the like as a light source, it is necessary to include an infrared transmission filter, so that the configuration of the inspection apparatus is complicated accordingly. In contrast, since the infrared inspection apparatus according to the present invention does not require such a filter, troublesome work such as filter replacement is unnecessary, and the apparatus configuration can be simplified.
本発明に係る赤外線検査装置の具体的な構成としては、複数種類の赤外線ＬＥＤに加えて、検査対象である前記半導体基板に応じて、前記複数種類の赤外線ＬＥＤから点灯する赤外線ＬＥＤを選択するＬＥＤ選択部と、前記赤外線ＬＥＤから照射された光が前記半導体基板を透過した光を透過画像として撮像する撮像装置と、前記撮像装置で撮像された透過光の輝度値を算出する輝度算出部と、前記透過光を前記輝度算出部で算出された輝度値により３群に分類し、３群のうち輝度値が最も高い群と最も低い群とに属する透過光が検出された前記半導体基板のポイントを抽出するクラック抽出部と、を備えていることが好ましい。 As a specific configuration of the infrared inspection apparatus according to the present invention, in addition to a plurality of types of infrared LEDs, an LED that selects an infrared LED to be lit from the plurality of types of infrared LEDs according to the semiconductor substrate to be inspected. A selection unit; an imaging device that captures, as a transmission image, light transmitted from the infrared LED through the semiconductor substrate; a luminance calculation unit that calculates a luminance value of the transmitted light captured by the imaging device; The transmitted light is classified into three groups according to the luminance value calculated by the luminance calculation unit, and points of the semiconductor substrate where the transmitted light belonging to the group having the highest luminance value and the group having the lowest luminance among the three groups are detected. It is preferable to include a crack extraction unit for extraction.
また、本発明に係る赤外線検査装置の検査対象がアモルファスからなる半導体基板である場合は、膜厚、ムラ、異物の有無等を良好に検査することができる。 Moreover, when the inspection object of the infrared inspection apparatus according to the present invention is an amorphous semiconductor substrate, it is possible to inspect the film thickness, unevenness, presence / absence of foreign matter, and the like.
このような構成の本発明によれば、半導体基板中のマイクロクラックが生じた箇所等を極めて鮮明に検出することができる。 According to the present invention having such a configuration, a location where a microcrack is generated in a semiconductor substrate can be detected very clearly.
以下に本発明の一実施形態について図面を参照して説明する。 An embodiment of the present invention will be described below with reference to the drawings.
本実施形態に係る赤外線検査装置１は、図１に示すように、試料Ｗを載置するための保持台２と、保持台２上に載置された試料Ｗを下方から照明する複数種類の赤外線ＬＥＤ３１、３２、３３を備えた光源３と、試料Ｗの上方に配設され、光源３から発せられた光が試料Ｗを透過した光を透過画像として撮像する撮像装置４と、情報処理装置５と、を備えている。このような赤外線検査装置１の検査対象である試料Ｗとしては、シリコンウェハや、当該ウェハに回路パターンが形成された基板等の結晶基板が挙げられる。 As shown in FIG. 1, the infrared inspection apparatus 1 according to the present embodiment has a holding table 2 on which a sample W is placed, and a plurality of types that illuminate the sample W placed on the holding table 2 from below. A light source 3 including infrared LEDs 31, 32, and 33; an imaging device 4 that is disposed above the sample W and that captures light transmitted from the light source 3 through the sample W as a transmission image; and an information processing device 5 is provided. Examples of the sample W to be inspected by the infrared inspection apparatus 1 include a silicon wafer and a crystal substrate such as a substrate on which a circuit pattern is formed on the wafer.
各部を詳述する。光源３は、ピーク波長の異なる複数種類の赤外線ＬＥＤ３１、３２、３３が切り替え点灯可能に設けられたものである。赤外線ＬＥＤ３１、３２、３３としては、例えば、９００〜１５００ｎｍの波長の光を照射するものが挙げられる。なお、ＬＥＤは射出する光の波長の幅が狭いという特徴を有する。 Each part will be described in detail. The light source 3 is provided with a plurality of types of infrared LEDs 31, 32, and 33 having different peak wavelengths so that they can be switched on. As infrared LED31,32,33, what irradiates light with a wavelength of 900-1500 nm is mentioned, for example. The LED has a feature that the wavelength range of the emitted light is narrow.
複数種類の赤外線ＬＥＤ３１、３２、３３から、検査対象である試料Ｗに応じた好適な赤外線ＬＥＤが選択されて、当該赤外線ＬＥＤから試料Ｗに対して所定の波長の赤外線が照射されると、試料Ｗの表裏を貫通して割れが生じているため照射光が透過する透過性マイクロクラックは白く観察され、試料Ｗ内部に微細な亀裂が生じているために内部の破壊面で透過光が部分的に反射される反射性マイクロクラックは黒く観察され、その他の結晶粒は灰色に観察される。 When a suitable infrared LED corresponding to the sample W to be inspected is selected from the plurality of types of infrared LEDs 31, 32, 33 and the sample W is irradiated with infrared rays of a predetermined wavelength, the sample Since the cracks are generated through the front and back of W, the transparent microcracks through which the irradiation light passes are observed in white, and because the microcracks are generated inside the sample W, the transmitted light is partially transmitted on the internal fracture surface. Reflective microcracks reflected on the surface are observed in black, and other crystal grains are observed in gray.
照射光の波長と透過率との関係は、波長が長いほど、透過率が高くなるので、結晶粒間の濃淡差が低くなり、試料Ｗ内部に生じた反射性マイクロクラックが黒く撮像される。そして、波長が短いほど、透過率が低くなるので、結晶粒間の濃淡差が高くなり、試料Ｗ内部に生じた反射性マイクロクラックの検出が困難になる。この境界となる波長は、ほぼ、その試料Ｗの組成から求められるエネルギーギャップと等しいエネルギーを有する波長であり、例えば、シリコン結晶の場合は約１１０８ｎｍである。 Regarding the relationship between the wavelength of the irradiation light and the transmittance, the longer the wavelength, the higher the transmittance. Therefore, the difference in density between crystal grains is reduced, and the reflective microcracks generated inside the sample W are imaged black. And the shorter the wavelength, the lower the transmittance, so the difference in density between crystal grains increases, making it difficult to detect reflective microcracks generated inside the sample W. The wavelength serving as the boundary is a wavelength having an energy substantially equal to the energy gap obtained from the composition of the sample W. For example, in the case of a silicon crystal, the wavelength is about 1108 nm.
しかし、好適な赤外線ＬＥＤ３１、３２、３３は単に試料Ｗの組成で定まるものではなく、不純物のドーピング量やその厚さや処理状態にも依存する。例えば、試料Ｗが多結晶シリコンからなる太陽電池用ウェハであって、ＡＲＣ（Ａｎｔｉ Ｒｅｆｌｅｃｔｉｖｅ Ｃｏａｔｉｎｇ（反射防止コーティング））処理が施されている場合は、結晶粒間の濃淡差が未処理のものに比べて低くなり傾向があるので、組成から求められる好適な波長より短い波長の光を射出する赤外線ＬＥＤが適している。 However, suitable infrared LEDs 31, 32, and 33 are not simply determined by the composition of the sample W, but also depend on the doping amount of impurities, the thickness thereof, and the processing state. For example, when the sample W is a solar cell wafer made of polycrystalline silicon and has been subjected to ARC (Anti Reflective Coating) treatment, the difference in density between crystal grains is untreated. Infrared LEDs that emit light having a shorter wavelength than the preferred wavelength required from the composition are suitable because they tend to be lower.
撮像装置４は、光源３から発せられた光が試料Ｗを透過した光を透過画像として撮像するものであるが、例えば、ＣＣＤカメラ、ラインセンサカメラ、ＣＭＯＳカメラ、ビジコンカメラ等が用いられる。なお、従来は赤外線を発する光源としてハロゲン灯等が用いられており、この場合は、赤外線だけを撮像するためには、赤外線透過フィルタを併用して他の可視光成分を取り除くことが必要であった。これに対して、赤外線検査装置１では光源３として赤外線ＬＥＤ３１、３２、３３を用いているので、このような赤外線透過フィルタは不要である。 The imaging device 4 captures, as a transmission image, light transmitted from the light source 3 through the sample W. For example, a CCD camera, a line sensor camera, a CMOS camera, a vidicon camera, or the like is used. Conventionally, a halogen lamp or the like is used as a light source that emits infrared light. In this case, in order to image only infrared light, it is necessary to remove other visible light components in combination with an infrared transmission filter. It was. In contrast, since the infrared inspection apparatus 1 uses the infrared LEDs 31, 32, and 33 as the light source 3, such an infrared transmission filter is unnecessary.
情報処理装置５は、ＣＰＵやメモリ、Ａ／Ｄ変換器、Ｄ／Ａ変換器等を有したデジタル乃至アナログ電気回路で構成されたもので、専用のものであってもよいし、一部又は全部にパソコン等の汎用コンピュータを利用するようにしたものであってもよい。また、ＣＰＵを用いず、アナログ回路のみで前記各部としての機能を果たすように構成してもよいし、物理的に一体である必要はなく、有線乃至無線によって互いに接続された複数の機器からなるものであってもよい。更に、キーボード等の入力手段、ディスプレイ等の出力手段等を有していてもよい。 The information processing apparatus 5 is configured by a digital or analog electric circuit having a CPU, a memory, an A / D converter, a D / A converter, and the like, and may be a dedicated one or a part or A general-purpose computer such as a personal computer may be used for all. Further, it may be configured such that the functions of the respective units are achieved by using only an analog circuit without using a CPU, and need not be physically integrated, but includes a plurality of devices connected to each other by wire or wirelessly. It may be a thing. Furthermore, an input unit such as a keyboard and an output unit such as a display may be included.
そして前記メモリに所定のプログラムを格納し、そのプログラムにしたがってＣＰＵやその周辺機器を協働動作させることによって、この情報処理装置５が、ＬＥＤ選択部５１、輝度算出部５２、クラック抽出部５３としての機能を少なくとも発揮するように構成している。 Then, by storing a predetermined program in the memory and operating the CPU and its peripheral devices in cooperation with each other according to the program, the information processing apparatus 5 serves as an LED selection unit 51, a luminance calculation unit 52, and a crack extraction unit 53. It is comprised so that the function of at least may be exhibited.
ＬＥＤ選択部５１は、例えばオペレータにより入力された試料Ｗの組成、処理状態（ＡＲＣ処理等の有無）や厚さ等の情報に従い、複数種類の赤外線ＬＥＤ３１、３２、３３から試料Ｗに応じて好適な波長の光を照射するものを選択するものである。 The LED selection unit 51 is suitable according to the sample W from a plurality of types of infrared LEDs 31, 32, 33 in accordance with, for example, information such as the composition, processing state (presence / absence of ARC processing) and thickness of the sample W input by the operator The one that irradiates light of various wavelengths is selected.
輝度算出部５２は、撮像装置４から画像データを取得して、所定の演算処理を行うことにより、試料Ｗのそれぞれのポイントにおいて撮像された透過光の輝度値を算出するものである。 The luminance calculation unit 52 acquires the image data from the imaging device 4 and performs a predetermined calculation process, thereby calculating the luminance value of the transmitted light imaged at each point of the sample W.
クラック抽出部５３は、輝度算出部５２から輝度値データを取得して、輝度値により透過光を３群に分類し、３群のうち輝度値が最も高い群と最も低い群とに属する透過光が検出された試料Ｗのポイントを、マイクロクラックが生じている箇所として抽出するものである。 The crack extraction unit 53 acquires the luminance value data from the luminance calculation unit 52, classifies the transmitted light into three groups according to the luminance value, and transmits the transmitted light belonging to the group having the highest luminance value and the group having the lowest luminance among the three groups. The point of the sample W in which the detection is detected is extracted as a location where a microcrack is generated.
すなわち、図２（ａ）は、試料Ｗとして、太陽電池用多結晶シリコンウェハを用い、これに１５５０ｎｍの赤外線を照射し、試料Ｗからの透過光を撮像した画像であり、図２（ｂ）は、図２（ａ）で撮像された透過光の輝度分布を示すグラフであるが、試料Ｗに好適な波長の光を射出する赤外線ＬＥＤ３１、３２、３３を選択して光を照射すれば、マイクロクラックと正常な部分との透過率の差が明確になり、図２の場合、正常な多結晶部分の透過率は７０〜８０％であった。そして、図２（ｂ）に示すように、１３００ｃｄ／ｍ２付近及び２３００ｃｄ／ｍ２付近を境にして、輝度値により透過光が３つの群に明確に分かれた。 That is, FIG. 2 (a) is an image obtained by using a polycrystalline silicon wafer for solar cells as the sample W, irradiating this with infrared rays of 1550 nm, and imaging the transmitted light from the sample W. FIG. Is a graph showing the luminance distribution of the transmitted light imaged in FIG. 2 (a). If infrared LEDs 31, 32, and 33 that emit light having a wavelength suitable for the sample W are selected and irradiated with light, The difference in transmittance between the microcrack and the normal part became clear, and in the case of FIG. 2, the transmittance of the normal polycrystalline part was 70 to 80%. Then, as shown in FIG. 2 (b), in the border around 1300 cd / m 2 and 2300cd / m 2 nearby, the transmitted light is clearly divided into three groups by the brightness value.
一方、図３（ａ）は、図２におけると同じ試料Ｗに対して９７０ｎｍの赤外線を照射し、試料Ｗからの透過光を撮像した画像であり、図３（ｂ）は、図３（ａ）で撮像された透過光の輝度分布を示すグラフであるが、試料Ｗに照射する光の波長が適切でない場合は、マイクロクラックと正常な部分との透過率の差は僅かであり、図３の場合、正常な多結晶部分の透過率は２０％程度であった。そして、図３（ｂ）に示すように、輝度値により透過光を分類することは困難であった。 On the other hand, FIG. 3A is an image obtained by irradiating the same sample W as in FIG. 2 with infrared rays of 970 nm and picking up the transmitted light from the sample W, and FIG. 3) is a graph showing the luminance distribution of the transmitted light imaged in FIG. 3. When the wavelength of the light applied to the sample W is not appropriate, the difference in transmittance between the microcrack and the normal part is slight, and FIG. In this case, the transmittance of the normal polycrystalline portion was about 20%. And as shown in FIG.3 (b), it was difficult to classify | transmitted light according to a luminance value.
図２（ａ）及び図３（ｂ）のいずれにおいても、反射性マイクロクラックに由来する透過光は輝度値は７５０ｃｄ／ｍ２前後に観察され、透過性マイクロクラックに由来する透過光は輝度値は３０００ｃｄ／ｍ２前後に観察された。このため、正常な多結晶部分に由来する輝度値がこの間に観察される波長帯の赤外線を射出するＬＥＤが最適なものであると言える。 In both FIG. 2 (a) and FIG. 3 (b), the transmitted light derived from the reflective microcracks is observed to have a luminance value of around 750 cd / m 2, and the transmitted light derived from the transparent microcracks is the luminance value. Was observed around 3000 cd / m 2 . For this reason, it can be said that an LED that emits infrared light in a wavelength band in which a luminance value derived from a normal polycrystalline portion is observed during this period is optimal.
なお、試料Ｗ上の検査ポイントによっては、輝度値が最も高い群に試料Ｗの端部の試料Ｗが存在しない箇所が含まれ、輝度値が最も低い群に半導体ウェハ上に形成された金属配線等が含まれる場合もあるので、その場合、これらのマイクロクラック以外のものは除外される。 Depending on the inspection point on the sample W, the group having the highest luminance value includes a portion where the sample W at the end of the sample W does not exist, and the metal wiring formed on the semiconductor wafer in the group having the lowest luminance value Etc. may be included, and in this case, those other than these micro cracks are excluded.
次に赤外線検査装置１を用いて試料Ｗを検査する方法を図４のフローチャートを参照して説明する。 Next, a method for inspecting the sample W using the infrared inspection apparatus 1 will be described with reference to the flowchart of FIG.
まず、オペレータが検査対象である試料Ｗの状態（組成、不純物のドーピング量、処理状態（ＡＲＣ処理等の有無）、厚さ等）を示す識別子を入力する（ステップＳ１）。 First, an operator inputs an identifier indicating the state (composition, impurity doping amount, processing state (whether or not ARC processing is performed), thickness, etc.) of the sample W to be inspected (step S1).
するとＬＥＤ選択部５１が、その入力に基づいて、複数種類の赤外線ＬＥＤ３１、３２、３３から試料Ｗに適した波長の光を照射するものを選択する（ステップＳ２）。 Then, the LED selection part 51 selects what irradiates the light of the wavelength suitable for the sample W from multiple types of infrared LED31,32,33 based on the input (step S2).
そして、選択された赤外線ＬＥＤ３１、３２、３３が点灯し試料Ｗに光を照射する（ステップＳ３）。 Then, the selected infrared LEDs 31, 32, and 33 are turned on to irradiate the sample W with light (step S3).
次いで、撮像装置４が試料Ｗを透過した光を透過画像として撮像する（ステップＳ４）。 Next, the imaging device 4 captures the light transmitted through the sample W as a transmission image (step S4).
撮像装置４が撮像した画像データを取得した輝度算出部５２は、所定の演算処理を行い、試料Ｗのそれぞれのポイントにおける透過光の輝度値を算出する（ステップＳ５）。 The luminance calculation unit 52 that has acquired the image data captured by the imaging device 4 performs a predetermined calculation process, and calculates the luminance value of the transmitted light at each point of the sample W (step S5).
クラック抽出部５３は、輝度算出部５２から輝度値データを取得して、輝度値により透過光を３群に分類し、３群のうち輝度値が最も高い群と最も低い群とに属する透過光が検出された試料Ｗのポイントを、クラックが生じている箇所として抽出する（ステップＳ６）。 The crack extraction unit 53 acquires the luminance value data from the luminance calculation unit 52, classifies the transmitted light into three groups according to the luminance value, and transmits the transmitted light belonging to the group having the highest luminance value and the group having the lowest luminance among the three groups. The point of the sample W from which is detected is extracted as a location where a crack has occurred (step S6).
クラック抽出部５３がクラックの抽出結果データを示す信号を出力し、試料Ｗのマイクロクラックが生じている箇所をディスプレイ等に色分け等して表示する（ステップＳ７）。 The crack extraction unit 53 outputs a signal indicating the extraction result data of the crack, and displays the portion of the sample W where the micro crack is generated by color-coding or the like on the display or the like (step S7).
したがって、このように構成された赤外線検査装置１によれば、試料Ｗに赤外線を照射する光源として、異なる波長の光を射出する複数種類の赤外線ＬＥＤを切り替え点灯可能に備えており、検査対象である試料Ｗの組成、処理状態や厚さに応じて最も適した波長の光を照射する赤外線ＬＥＤを容易に選択することができるので、精度の高い検査を行うことができる。そして、試料Ｗに応じた好適な波長の光を照射することにより、透過性マイクロクラックは白く撮像され、反射性マイクロクラックは黒く撮像され、その他の結晶粒は灰色に撮像されるので、薄膜内部のマイクロクラックが生じた箇所を極めて鮮明に検出することができる。 Therefore, according to the infrared inspection apparatus 1 configured in this way, as a light source for irradiating the sample W with infrared light, a plurality of types of infrared LEDs that emit light of different wavelengths can be switched and lit. Since an infrared LED that emits light having the most suitable wavelength can be easily selected according to the composition, processing state, and thickness of a sample W, high-accuracy inspection can be performed. Then, by irradiating light of a suitable wavelength according to the sample W, the transparent microcracks are imaged white, the reflective microcracks are imaged black, and the other crystal grains are imaged gray, so the inside of the thin film It is possible to detect the portion where the microcracks are generated very clearly.
また、赤外線検査装置１では赤外線透過フィルタが不要であるので、フィルタ交換等の煩わしい作業が不要であるとともに、装置構成を簡易なものとすることができる。 Further, since the infrared ray inspection filter is unnecessary in the infrared inspection apparatus 1, troublesome work such as filter replacement is unnecessary, and the apparatus configuration can be simplified.
更に、ＬＥＤは射出する光の波長の幅が狭い光源であるので、赤外線ＬＥＤ３１、３２、３３を光源とする赤外線検査装置１では、マイクロクラックと正常な部分との透過率の比が最も大きくなる波長帯域に最適化することが可能となり、ハロゲン灯等を光源とするものと比べて極めて鮮明な透過画像が得られ、精度の高い検査を行うことができる。 Furthermore, since the LED is a light source with a narrow wavelength range of emitted light, in the infrared inspection apparatus 1 using the infrared LEDs 31, 32, and 33 as the light source, the transmittance ratio between the microcrack and the normal portion is the largest. It is possible to optimize the wavelength band, and a very clear transmission image can be obtained as compared with a light source using a halogen lamp or the like, and a highly accurate inspection can be performed.
なかでも、多結晶基板は、基板面に対してそれぞれの結晶面が異なっているため、結晶表面の反射率がそれぞれ異なっており、赤外線を照射した場合も光の照射面において反射率が異なることによって、その透過光の強度も異なり、結晶粒の構造により複雑な濃淡差を生じるので、そのままではクラックの検査が困難である。これに対して、赤外線検査装置１によれば、複数の赤外線ＬＥＤ３１、３２、３３から最適な波長帯域の赤外線を射出するものを選択可能であるので、試料Ｗが多結晶基板であっても、マイクロクラックと正常な部分との透過率の差を最適化することが可能となる。 In particular, the polycrystalline substrate has different crystal planes with respect to the substrate surface, so that the reflectivity of the crystal surface is different, and even when irradiated with infrared light, the reflectivity is different on the light irradiation surface. Therefore, the intensity of the transmitted light is different, and a complicated density difference is caused by the structure of the crystal grains, so that it is difficult to inspect the crack as it is. On the other hand, according to the infrared inspection apparatus 1, it is possible to select one that emits infrared light in the optimum wavelength band from the plurality of infrared LEDs 31, 32, 33, so that even if the sample W is a polycrystalline substrate, It becomes possible to optimize the difference in transmittance between the microcrack and the normal part.
また、結晶基板における光の透過率は、結晶の種類や、不純物のドーピング量等によって多様に変化するが、複数の赤外線ＬＥＤ３１、３２、３３から赤外線の射出源を選択可能である赤外線検査装置１によれば、最適な波長帯域の赤外線を射出することができるので、結晶の種類や不純物のドーピング量の変化に応じた透過率の変化にも対応することができ、マイクロクラックと正常な部分との透過率の差を最適化することが可能となる。 The light transmittance of the crystal substrate varies in various ways depending on the type of crystal, the amount of impurities doped, etc., but the infrared inspection apparatus 1 can select an infrared emission source from a plurality of infrared LEDs 31, 32, 33. Can emit infrared rays in the optimum wavelength band, and can respond to changes in transmittance according to changes in crystal type and impurity doping amount. It is possible to optimize the difference in transmittance.
このような赤外線検査装置１の用途としては特に限定されないが、例えば、太陽電池用の半導体基板の検査装置として好適に用いられる。 Although it does not specifically limit as an application of such an infrared test | inspection apparatus 1, For example, it uses suitably as a test | inspection apparatus of the semiconductor substrate for solar cells.
なお、本発明は前記実施形態に限られるものではない。 The present invention is not limited to the above embodiment.
例えば、赤外線検査装置１の検査対象である試料Ｗは結晶基板に限られず、例えば、アモルファスシリコンからなる太陽電池用基板を試料Ｗとして、膜厚、ムラ、異物の有無等の検査を行ってもよい。 For example, the sample W to be inspected by the infrared inspection apparatus 1 is not limited to a crystal substrate. For example, even if a solar cell substrate made of amorphous silicon is used as the sample W, a film thickness, unevenness, presence / absence of foreign matter, and the like are inspected Good.
その他、本発明の趣旨を逸脱しない限り、前述した種々の構成の一部又は全部を適宜組み合わせて構成してもよい。 In addition, a part or all of the various configurations described above may be appropriately combined without departing from the spirit of the present invention.
１・・・赤外線検査装置
３・・・光源
３１、３２、３３・・・赤外線ＬＥＤ
４・・・撮像装置
５・・・情報試料装置
５１・・・ＬＥＤ選択部
５２・・・輝度算出部
５３・・・クラック抽出部
Ｗ・・・試料
DESCRIPTION OF SYMBOLS 1 ... Infrared inspection apparatus 3 ... Light source 31, 32, 33 ... Infrared LED
4 ... Imaging device 5 ... Information sample device 51 ... LED selection unit 52 ... Luminance calculation unit 53 ... Crack extraction unit W ... Sample
Claims (2)
異なる波長の光を射出する複数種類の赤外線ＬＥＤを、切り替え点灯可能に備えている赤外線検査装置。 An infrared inspection apparatus for detecting light transmitted by irradiating infrared rays onto a semiconductor substrate,
An infrared inspection apparatus provided with a plurality of types of infrared LEDs that emit light of different wavelengths so that they can be switched on.
前記赤外線ＬＥＤから照射された光が前記半導体基板を透過した光を透過画像として撮像する撮像装置と、
前記撮像装置で撮像された透過光の輝度値を算出する輝度算出部と、
前記透過光を前記輝度算出部で算出された輝度値により３群に分類し、３群のうち輝度値が最も高い群と最も低い群とに属する透過光が検出された前記半導体基板のポイントを抽出するクラック抽出部と、を備えている請求項１記載の赤外線検査装置。 According to the semiconductor substrate to be inspected, an LED selection unit that selects an infrared LED to be lit from the plurality of types of infrared LEDs;
An imaging device that captures, as a transmission image, light transmitted from the infrared LED through the semiconductor substrate;
A luminance calculation unit for calculating a luminance value of transmitted light imaged by the imaging device;
The transmitted light is classified into three groups according to the luminance value calculated by the luminance calculation unit, and points of the semiconductor substrate where the transmitted light belonging to the group having the highest luminance value and the group having the lowest luminance value among the three groups are detected. The infrared inspection apparatus according to claim 1, further comprising: a crack extracting unit that extracts.
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