JP2011223041A - Method for separating semiconductor light-emitting device - Google Patents
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本発明は、基板上に半導体発光素子を複数個形成したウエハを分離して、個々の半導体発光素子を得る方法に関する。本発明は例えばIII族窒化物系化合物半導体発光素子の分離に特に有効である。 The present invention relates to a method for obtaining individual semiconductor light emitting elements by separating a wafer having a plurality of semiconductor light emitting elements formed on a substrate. The present invention is particularly effective for the separation of, for example, a group III nitride compound semiconductor light emitting device.
従来より、サファイア基板上にIII族窒化物系化合物半導体発光素子を形成したウエハを分離して個々の半導体発光素子を得る方法は様々提案されている。この中で特に一般的なものは、スクライバーによるスクライブライン（溝）の形成と、ダイサーブレードによるダイシングとを組み合わせるものである。この方法は、スクライバーとダイサーブレードが消耗品であるので、ランニングコストが一定以下に抑制できないと言う短所がある。 Conventionally, various methods for obtaining individual semiconductor light emitting devices by separating a wafer on which a group III nitride compound semiconductor light emitting device is formed on a sapphire substrate have been proposed. Among them, a particularly general one is a combination of formation of a scribe line (groove) by a scriber and dicing by a dicer blade. This method has the disadvantage that the running cost cannot be kept below a certain level because the scriber and dicer blade are consumables.
近年、板状物を分離又は切断する方法として、レーザ照射による溶断或いはレーザ照射による内部溶融部又は改質部が起点となった切断方法も提案されるようになった。特にパルス幅がミリ秒未満の、いわゆるナノ秒パルスレーザを用いる方法（特許文献４）、パルス幅がピコ秒未満の、いわゆるフェムト秒パルスレーザを用いる方法（特許文献１、３）も提案されている。 In recent years, as a method for separating or cutting a plate-like object, a cutting method in which melting is performed by laser irradiation or an internal melting portion or modified portion by laser irradiation is started has been proposed. In particular, a method using a so-called nanosecond pulse laser with a pulse width of less than millisecond (Patent Document 4) and a method using a so-called femtosecond pulse laser with a pulse width of less than picosecond (Patent Documents 1 and 3) have also been proposed. Yes.
レーザ照射で分離面を完全に溶断により形成してしまうと、基板の側面である分離面の溶融部の厚さが大きくなり、又は、焼け（変色し）、光取り出し効率が悪化する。これは、基板の側面である当該分離面がもはや初期の「透明状態」でなくなり、発光素子の主たる発光を吸収してしまうからである。そこで通常、例えば基板のデバイス形成面又はその反対側から一定の深さまで溝を形成する（特許文献２）、更にはパルスレーザで破断線様に溝を形成することが行われている。しかし、基板の側面である分離面の溶融部の厚さがやはり問題となる。パルスレーザの場合でも、ナノ秒パルスレーザでは当該溶融部が、分離した素子の基板側面で大きな面積を占めることで、発光した光の光吸収が問題となる。また、基板を１００μｍ厚以下に薄肉化しないと割断が困難とされていた（特許文献２）。尚、特許文献２はレーザにより形成した浅い溝を単独で用いた割断ではなく、ダイサーによる一部薄膜化との組み合わせによるものと、１００μｍもの深さのレーザ溝との組み合わせによるものである。 If the separation surface is completely melted by laser irradiation, the thickness of the melted portion of the separation surface, which is the side surface of the substrate, increases, or burns (discolors) and the light extraction efficiency deteriorates. This is because the separation surface, which is the side surface of the substrate, is no longer in the initial “transparent state” and absorbs the main light emission of the light emitting element. Therefore, for example, a groove is usually formed from a device formation surface of the substrate or the opposite side to a certain depth (Patent Document 2), and further, a groove is formed like a broken line with a pulse laser. However, the thickness of the melted portion of the separation surface, which is the side surface of the substrate, still becomes a problem. Even in the case of a pulsed laser, in the nanosecond pulsed laser, the melted portion occupies a large area on the side surface of the substrate of the separated element, so that light absorption of emitted light becomes a problem. Further, it has been considered difficult to cleave unless the substrate is thinned to a thickness of 100 μm or less (Patent Document 2). Patent Document 2 is not based on cleaving using a shallow groove formed by a laser alone, but by a combination of partial thinning with a dicer and a laser groove having a depth of 100 μm.
更には、例えば特許文献３においては、フェムト秒レーザの照射は、「分離するための応力」を発生させるためのものであり、予め分離溝をレーザ照射以外の別の方法で形成しておくことを前提としている。この場合、例えばスクライバーを用いるのであれば、上述の消耗品のランニングコストが抑制できない。
また、携帯電話の液晶画面のバックライト用途のように、矩形の発光面の短辺を２５０μｍ以下と、サファイア基板厚の２倍以下にする用途が増えている。このような発光素子においては、分割間隔が非常に狭いので、設計した分離予定面通りに分離面が基板面に垂直に形成される必要が有り、斜めにずれた割断は許容できるものではない。
Further, for example, in Patent Document 3, the irradiation with the femtosecond laser is for generating “stress for separation”, and the separation groove is previously formed by another method other than the laser irradiation. Is assumed. In this case, for example, if a scriber is used, the running cost of the above-mentioned consumables cannot be suppressed.
In addition, there is an increasing use in which the short side of a rectangular light emitting surface is 250 μm or less and twice or less the sapphire substrate thickness, such as a backlight application for a liquid crystal screen of a mobile phone. In such a light emitting element, since the division interval is very narrow, it is necessary to form the separation surface perpendicularly to the substrate surface according to the designed planned separation surface, and the obliquely shifted cleavage is not acceptable.
本発明者らは、以上に鑑み、スクライバーやダイサーブレードと言った消耗品を全く用いずに、２００μｍ厚程度の半導体発光素子の基板の分離を行うことを目的として本発明を完成するに至った。 In view of the above, the present inventors have completed the present invention for the purpose of separating a substrate of a semiconductor light emitting element having a thickness of about 200 μm without using consumables such as a scriber or a dicer blade. .
請求項１に係る発明は、基板上に形成された半導体発光素子の分離方法において、パルス幅が１０ピコ秒未満であるパルスレーザを基板において集光させて、多光子吸収を発生させることにより、基板の内部の所定の深さに、分離予定面に対応して、パルスレーザにより形成された分離予定線方向に連続しない内部改質部であって、基板の溶融を伴わない非熱加工のフィラメンテーションによりパルスレーザの進行方向に延びた足部を有した内部改質部を形成し、連続しない内部改質部に沿って分離面を形成して、外力を加えることで各半導体発光素子を分離することを特徴とする半導体発光素子の分離方法である。 The invention according to claim 1 is a method for separating a semiconductor light emitting device formed on a substrate, by focusing a pulse laser having a pulse width of less than 10 picoseconds on the substrate to generate multiphoton absorption, A non-thermally processed filament without melting of the substrate, which is an internal reforming portion that does not continue in the direction of the planned separation line formed by a pulse laser at a predetermined depth inside the substrate, corresponding to the planned separation surface. An internal reforming part having a leg extending in the traveling direction of the pulsed laser is formed by the rotation, a separation surface is formed along the discontinuous internal reforming part, and each semiconductor light emitting element is separated by applying external force This is a method for separating a semiconductor light emitting element.
請求項２に係る発明は、基板上に形成された半導体発光素子の分離方法において、パルス幅が１０ピコ秒未満であるパルスレーザを、ピークパワー密度が１．４２Ｗ／ｃｍ2 以上となるように、前記基板において集光させて、多光子吸収を発生させることにより、基板の内部の所定の深さに、分離予定面に対応して、パルスレーザにより形成された分離予定線方向に連続しない内部改質部を形成し、連続しない内部改質部に沿って分離面を形成して、外力を加えることで各半導体発光素子を分離することを特徴とする半導体発光素子の分離方法である。請求項３に係る発明は、請求項１の発明において、パルスレーザは、ピークパワー密度が１．４２Ｗ／ｃｍ2 以上に、基板において集光されることを特徴とする。請求項４に係る発明は、改質部は、パルスレーザの集光位置に形成された基板面に平行な方向の直径が１．５μｍ以上の頭部を有し、足部は、頭部からパルスレーザの進行方向にに延び、基板面に平行な方向の直径が０．８μｍ以上であることを特徴とする。請求項５に係る発明は、連続しない内部改質部は、基板の深さ方向に２段以上形成されることを特徴とする。また、基板の表面の分離予定線に沿って、前記条件のパルスレーザにより実質的に連続した溝部を形成し、この連続した溝部と連続しない内部改質部に沿って分離面を形成しても良い。また、この連続した溝部に接続して、分離予定線方向に連続した内部改質部がパルスレーザにより更に形成されたのち、外力が加えられて、分離面で各半導体素子を分離しても良い。請求項６に係る発明は、レーザ照射は、電界成分が分離予定面に平行な直線偏光レーザ、又は電界成分の軌跡が分離予定面に平行な長軸の楕円を形成する楕円偏光レーザにより行われることを特徴とする。請求項７に係る発明は、レーザ照射は、開口数が０．５以上の対物レンズを用いて行われることを特徴とする。請求項８に係る発明は、基板はサファイア基板であることを特徴とする。 According to a second aspect of the present invention, in the method for separating a semiconductor light emitting device formed on a substrate, a pulse laser having a pulse width of less than 10 picoseconds has a peak power density of 1.42 W / cm 2 or more. In the interior of the substrate that is not continuous in the direction of the planned separation line formed by the pulse laser at a predetermined depth inside the substrate, corresponding to the planned separation surface, by collecting light on the substrate and generating multiphoton absorption A method of separating a semiconductor light emitting device, comprising forming a modified portion, forming a separation surface along a discontinuous internal modified portion, and separating each semiconductor light emitting device by applying an external force. The invention according to claim 3 is characterized in that, in the invention of claim 1, the pulse laser is focused on the substrate so that the peak power density is 1.42 W / cm 2 or more. In the invention according to claim 4, the modified portion has a head having a diameter of 1.5 μm or more in a direction parallel to the substrate surface formed at the condensing position of the pulse laser, and the foot portion extends from the head. It is characterized by extending in the traveling direction of the pulse laser and having a diameter in a direction parallel to the substrate surface of 0.8 μm or more. The invention according to claim 5 is characterized in that the discontinuous internal reforming portion is formed in two or more stages in the depth direction of the substrate. Alternatively, a substantially continuous groove portion may be formed by the pulse laser of the above condition along the planned separation line on the surface of the substrate, and a separation surface may be formed along the internal modified portion that is not continuous with the continuous groove portion. good. In addition, after the internal modified portion that is connected to the continuous groove portion and is continuously formed in the direction of the separation line is further formed by the pulse laser, an external force may be applied to separate the semiconductor elements on the separation surface. . In the invention according to claim 6, the laser irradiation is performed by a linearly polarized laser whose electric field component is parallel to the plane to be separated, or an elliptically polarized laser in which the locus of the electric field component forms a long-axis ellipse parallel to the plane to be separated. It is characterized by that. The invention according to claim 7 is characterized in that laser irradiation is performed using an objective lens having a numerical aperture of 0.5 or more. The invention according to claim 8 is characterized in that the substrate is a sapphire substrate.
本発明は、フェムト秒レーザにより、内部の改質部を形成し、外力を加えた際に、これらを起点として分離面を形成することで半導体発光素子の分離を行うものである。フェムト秒レーザによる改質部の形成は、非熱加工であるため、原理的には溶融部は形成されない。また、フェムト秒レーザを基板表面に集光し、基板表面の溝部が形成されるように基板又はレーザ装置の走査速度を調整して走査方向の照射のピッチを制御することで、改質部である当該溝として極めて浅い溝を形成することが可能である。こうして、基板表面に溝部を形成した場合には、表面の浅い溝部と、基板に平行な面上での径が数μｍ程度以下の内部の改質部をつなぐ様に分離面を形成することができる。このためには、消耗品を用いず、ブレーク用の例えば刃状物を用いると良い。こうして消耗品を用いず、且つ素子分離面の改質部等の光吸収部を極めて小さい面積とした、フェムト秒レーザを用いた半導体発光素子の分離方法を実現できる。内部改質部は分離線方向に連続する必要はなく、分離予定面内に多数形成されると良い。本発明は厚さ１００μｍ以上５００μｍ未満の基板に適用できる。また、パルスレーザ照射は極めて短時間で各ウエハの処理が可能であり、その後に直ぐに割断を行うことができるので、例えばスクライバーとダイサーブレードを組み合わせた分離方法に比較して、処理時間を大幅に削減できる。また、本発明によれば、分離面を設計通りの垂直なものとすることが容易で、歩留まりを大幅に向上させることができる。 In the present invention, a semiconductor light emitting device is separated by forming an internal reforming portion by a femtosecond laser and forming a separation surface starting from these when an external force is applied. Since the formation of the modified portion by the femtosecond laser is non-thermal processing, the molten portion is not formed in principle. Further, the femtosecond laser is focused on the surface of the substrate, the scanning speed of the substrate or the laser device is adjusted so that a groove on the surface of the substrate is formed, and the irradiation pitch in the scanning direction is controlled. It is possible to form a very shallow groove as the groove. Thus, when the groove is formed on the surface of the substrate, the separation surface may be formed so as to connect the groove having a shallow surface and the internal modified portion having a diameter of about several μm or less on the surface parallel to the substrate. it can. For this purpose, it is preferable to use, for example, a blade for break without using consumables. Thus, it is possible to realize a method for separating a semiconductor light emitting device using a femtosecond laser without using consumables and having a light absorbing portion such as a modified portion of the device separation surface having a very small area. It is not necessary for the internal reforming portions to be continuous in the direction of the separation line, and it is preferable that a large number of internal reforming portions be formed in the planned separation surface. The present invention can be applied to a substrate having a thickness of 100 μm or more and less than 500 μm. In addition, pulse laser irradiation can process each wafer in a very short time, and can be cleaved immediately thereafter. For example, compared with a separation method that combines a scriber and a dicer blade, the processing time is significantly increased. Can be reduced. In addition, according to the present invention, it is easy to make the separation surface as vertical as designed, and the yield can be greatly improved.
分離線方向に連続しない内部改質部は、基板の深さ方向に複数段形成すると良い。これにより、表面の溝部から、複数段の内部改質部を経るクラックを容易に形成させることで、精度の良い分離が実現できる。連続した溝部の底から接続するように、分離予定線方向に連続した内部改質部をパルスレーザにより更に形成したのち、外力を加える構成にすると、更に精度良い割断が可能となる。レーザ照射は、電界成分が分離予定面に平行な直線偏光レーザ、又は電界成分の軌跡が分離予定面に平行な長軸の楕円を形成する楕円偏光レーザにより行われると良い。当該楕円偏光は、電界成分が分離予定面に平行な直線偏光と、円偏光とに分解できるものである。要するに、分離予定面に平行な電界成分により、分離面方向により広がった改質部が形成されることとなる。 The internal reforming portion that is not continuous in the separation line direction is preferably formed in a plurality of stages in the depth direction of the substrate. Thereby, a precise separation can be realized by easily forming a crack through a plurality of internal reforming portions from the groove portion on the surface. By further forming an internal reforming portion continuous in the direction of the planned separation line so as to be connected from the bottom of the continuous groove portion by a pulse laser and then applying an external force, further accurate cleaving is possible. The laser irradiation is preferably performed by a linearly polarized laser whose electric field component is parallel to the planned separation surface or an elliptically polarized laser whose electric field component locus forms a long-axis ellipse parallel to the planned separation surface. The elliptically polarized light can be decomposed into linearly polarized light whose electric field component is parallel to the plane to be separated and circularly polarized light. In short, a modified portion that spreads in the direction of the separation surface is formed by the electric field component parallel to the separation surface.
レーザ照射を、開口数の大きいものとすることで、いわゆる焦点深度が浅くなり、集光部（スポット）が基板の深さ方向に広がることを避けることができる。これにより、基板内で多光子吸収による改質部の形成を深さ方向に短くことができる。本発明は特にサファイア基板のような、他の方法による精度の良い割断が困難な基板に適用することが可能である。集光部に形成される改質部が、フィラメンテーションにより、より深い位置まで延びたより細い足部を有することにより、光吸収が小さいまま確実な割断を可能とすることができる。 By making the laser irradiation have a large numerical aperture, the so-called depth of focus becomes shallow and it is possible to avoid the converging part (spot) from spreading in the depth direction of the substrate. Thereby, the formation of the modified portion by multiphoton absorption in the substrate can be shortened in the depth direction. The present invention can be applied particularly to a substrate such as a sapphire substrate, which is difficult to cleave with high accuracy by other methods. The reforming part formed in the light collecting part has a narrower leg part extending to a deeper position by filamentation, so that it is possible to perform reliable cleaving with small light absorption.
本発明によるいわゆるフェムト秒レーザは、例えば特許文献１記載の装置により発生させることが可能である。その他任意の公知の装置を用いることができる。 The so-called femtosecond laser according to the present invention can be generated by, for example, an apparatus described in Patent Document 1. Any other known device can be used.
改質部の大きさに特に限定は無いが、基板面に平行な面上でのスポット径が１〜１０μｍとすると良い。更に望ましくは１〜４μｍ、更に望ましくは１．５〜３μｍである。パルス当たりのエネルギー、レーザビーム径、対物レンズの開口数の調整により当該スポット径が調整される。また、併せて、基板の深さ方向のスポット長も決定される。また、「足」状の改質部がスポットの先に形成されうる。この「足」は、フィラメンテーションと呼ばれる自己集光作用により形成される。当該改質部の「足部」が形成されることは、外力を加えた際に「足部」がクラックの起点となる点で好ましい。また、この「足部」は、拡大しないので、分割面における面精度が高くなる。以下の実施例では、基板面に平行な改質部のスポット径が約２．５μｍ、深さ方向のスポット長は約５μｍ、そこから延びた「足部」は約１５μｍとなった。パルス当たりのエネルギーは０．１〜１０μＪが好ましく、０．５〜５μＪがより好ましく、１〜３μＪがより好ましい。パルス幅が１０ｐｓ、パルス当たりのエネルギーが１μＪ、スポット径が３μｍのとき、ピークパワー密度は１．４２Ｗ／ｃｍ2 となる。したがって、パルス幅が１０ｐｓ未満、パルス当たりのエネルギーが１μＪ以上、スポット径が３μｍ以下の場合には、ピークパワー密度は１．４２Ｗ／ｃｍ2 以上となる。対物レンズの開口数を大きくとることで、ビーム径を容易に細くでき、基板に平行な面上のスポット径を小さくできる。また、対物レンズの開口数を大きくとることで、焦点深度を浅くできるのでスポット長を短くすることが可能である。対物レンズの開口数は０．４以上、好ましくは０．５以上、更に好ましくは０．６以上である。尚、開口数は１を越える必要はなく、０．８以下がより好ましい。深さ方向の改質部の間隔（１の足部を含めた改質部の最下部の深さと、その下段の改質部の最上部の深さ）は、１μｍ以上５０μｍ以下とすると良い。本発明は個々の改質部を小さくするものであるので、深さ方向の改質部の間隔が５０μｍを越えると基板の割断が困難となる。一方、深さ方向の改質部の間隔が１μｍを下回ると、１枚の基板の割断に必要な改質部の段数を増やさなければならなくなり、問題である。深さ方向の改質部の間隔はより好ましくは２μｍ以上３０μｍ以下であり、更に望ましくは５μｍ以上１０μｍ以下である。 The size of the modified portion is not particularly limited, but the spot diameter on the plane parallel to the substrate surface is preferably 1 to 10 μm. More desirably, the thickness is 1 to 4 μm, and more desirably 1.5 to 3 μm. The spot diameter is adjusted by adjusting the energy per pulse, the laser beam diameter, and the numerical aperture of the objective lens. In addition, the spot length in the depth direction of the substrate is also determined. In addition, a “foot” -shaped modified portion may be formed at the tip of the spot. This “foot” is formed by a self-collecting action called filamentation. The formation of the “foot” of the reformed portion is preferable in that the “foot” becomes the starting point of the crack when an external force is applied. Further, since the “foot” is not enlarged, the surface accuracy on the divided surface is increased. In the following examples, the spot diameter of the modified portion parallel to the substrate surface was about 2.5 μm, the spot length in the depth direction was about 5 μm, and the “foot” extending therefrom was about 15 μm. The energy per pulse is preferably 0.1 to 10 μJ, more preferably 0.5 to 5 μJ, and more preferably 1 to 3 μJ. When the pulse width is 10 ps, the energy per pulse is 1 μJ, and the spot diameter is 3 μm, the peak power density is 1.42 W / cm 2 . Therefore, when the pulse width is less than 10 ps, the energy per pulse is 1 μJ or more, and the spot diameter is 3 μm or less, the peak power density is 1.42 W / cm 2 or more. By increasing the numerical aperture of the objective lens, the beam diameter can be easily reduced, and the spot diameter on the surface parallel to the substrate can be reduced. Also, by increasing the numerical aperture of the objective lens, the depth of focus can be reduced, so that the spot length can be shortened. The numerical aperture of the objective lens is 0.4 or more, preferably 0.5 or more, more preferably 0.6 or more. The numerical aperture does not need to exceed 1, and is preferably 0.8 or less. The interval between the reforming portions in the depth direction (the depth of the lowermost portion of the reforming portion including one leg and the depth of the uppermost portion of the lower reforming portion) is preferably 1 μm or more and 50 μm or less. Since the present invention reduces the size of each modified portion, it becomes difficult to cleave the substrate when the distance between the modified portions in the depth direction exceeds 50 μm. On the other hand, if the distance between the modified portions in the depth direction is less than 1 μm, the number of modified portions necessary for cleaving one substrate must be increased, which is a problem. The distance between the modified portions in the depth direction is more preferably 2 μm or more and 30 μm or less, and further preferably 5 μm or more and 10 μm or less.
分離線方向に連続しない改質部の分離線方向のピッチは、分離線方向に隣り合う改質部と接続されてしまわないようにすると良く、一方、クラックの発生により分離線方向に隣り合う改質部との間に分離面が十分に形成されるようにすると良い。この点で、改質部のピッチは、改質部の基板面に平行な面上の最大径を１として、１．２乃至８とすると良い。更には１．５乃至６が好ましく。２乃至４がより好ましい。以下の実施例では、改質部は、基板面方向のスポット径が約２．５μｍであったので、ピッチが５μｍ（改質部の間隔が約２．５μｍ）とすると良いことが分かった。 The pitch in the separation line direction of the reforming parts that are not continuous in the separation line direction should not be connected to the reforming part adjacent in the separation line direction. It is preferable that a separation surface is sufficiently formed between the mass part. In this respect, the pitch of the modified portion is preferably 1.2 to 8 with the maximum diameter on the surface parallel to the substrate surface of the modified portion being 1. Furthermore, 1.5 to 6 is preferable. 2 to 4 are more preferable. In the following examples, since the modified portion had a spot diameter in the substrate surface direction of about 2.5 μm, it was found that the pitch should be 5 μm (the interval between the modified portions is about 2.5 μm).
分離線方向に連続した溝部の深さは、０．５〜１０μｍ程度が良い。浅すぎると割断が不可能となり、深すぎると溝の側面の面積が大きくなる。溝部の深さは１〜５μｍがより好ましい。レーザは、分割線方向に偏光した直線偏光が望ましい。 The depth of the groove continuous in the separation line direction is preferably about 0.5 to 10 μm. If it is too shallow, it is impossible to cleave, and if it is too deep, the area of the side surface of the groove increases. As for the depth of a groove part, 1-5 micrometers is more preferable. The laser is preferably linearly polarized light polarized in the direction of the dividing line.
図１は本発明の半導体発光素子の分離方法の概略を示す断面図である。サファイア基板１０の一方の面１２に、III族窒化物系化合物半導体発光素子部３０をエピタキシャル成長及び電極形成その他により形成する。サファイア基板１０の他方の面１１から、対物レンズ４０を介してフェムト秒パルスレーザ光４１をサファイア基板１０の所望の深さに集光させる。これにより、多光子吸収が起こる集光部において、改質部５１、５２、５３及び５４並びに溝部５０が形成される。図１は、分離予定面（紙面に垂直）とサファイア基板１０の面１１及び１２とに垂直な断面図である。分離線は分離予定面とサファイア基板１０の面１１の交線であって、紙面手前から奥側に連続した線である。溝部５０はこの分離線上に形成される。改質部５１は、溝部５０と接続されており、且つ分離線方向に、連続して形成される。一方、改質部５２は、改質部５１及び５３とはサファイア基板１０の深さ方向に接続されておらず、且つ分離線方向にも、連続されずに個々に形成される。改質部５３及び５４も、改質部５２と５４、５３とはサファイア基板１０の深さ方向には接続されておらず、且つ分離線方向にも、連続されずに個々に形成される。分離面に表れる改質部５２乃至５４の形状は後に示す。 FIG. 1 is a cross-sectional view schematically showing a method for separating a semiconductor light emitting device of the present invention. A group III nitride compound semiconductor light emitting element portion 30 is formed on one surface 12 of the sapphire substrate 10 by epitaxial growth, electrode formation, or the like. From the other surface 11 of the sapphire substrate 10, femtosecond pulsed laser light 41 is condensed to a desired depth of the sapphire substrate 10 through the objective lens 40. Thereby, the reforming parts 51, 52, 53 and 54 and the groove part 50 are formed in the light collecting part where multiphoton absorption occurs. FIG. 1 is a cross-sectional view perpendicular to the plane to be separated (perpendicular to the paper surface) and the surfaces 11 and 12 of the sapphire substrate 10. The separation line is a line of intersection between the planned separation surface and the surface 11 of the sapphire substrate 10 and is a line continuous from the front side to the back side of the drawing. The groove part 50 is formed on this separation line. The reforming part 51 is connected to the groove part 50 and is continuously formed in the separation line direction. On the other hand, the modified portions 52 are not connected to the modified portions 51 and 53 in the depth direction of the sapphire substrate 10 and are individually formed in the separation line direction without being continuous. The modified portions 53 and 54 are also not individually connected to the modified portions 52, 54, and 53 in the depth direction of the sapphire substrate 10 and are not continuously formed in the separation line direction. The shapes of the reforming portions 52 to 54 appearing on the separation surface will be described later.
図２は本発明によるフェムト秒パルスレーザによる溝部５０と改質部５１乃至５４の様子を示すＳＥＭ画像である。改質部が極めて薄い（細い）ことが分かる。 FIG. 2 is an SEM image showing the state of the groove 50 and the modified portions 51 to 54 by the femtosecond pulse laser according to the present invention. It can be seen that the reforming part is extremely thin (thin).
図３は本発明の具体的な一実施例に係る半導体発光素子の分離方法を示す工程図である。図３．Ａのように、厚さ１４０μｍのサファイア基板１０の一方の面１２に、III族窒化物系化合物半導体発光素子部３０をエピタキシャル成長及び電極形成その他により形成した。次に、III族窒化物系化合物半導体発光素子部３０の分離線付近に形成された不要部をエッチングより除去した（図３．Ｂ）。 FIG. 3 is a process diagram illustrating a method of separating a semiconductor light emitting device according to a specific embodiment of the present invention. FIG. Like A, the group III nitride compound semiconductor light emitting element part 30 was formed in the one surface 12 of the 140-micrometer-thick sapphire substrate 10 by epitaxial growth, electrode formation, etc. FIG. Next, unnecessary portions formed in the vicinity of the separation line of the group III nitride compound semiconductor light emitting element portion 30 were removed by etching (FIG. 3.B).
次に、粘着テープ６０をサファイア基板１０のIII族窒化物系化合物半導体発光素子部３０を形成した側から接着させ、裏面であるサファイア基板１０の面１１側から、フェムト秒パルスレーザを走査して、溝部５０と改質部５１乃至５４を形成した。 Next, the adhesive tape 60 is adhered from the side of the sapphire substrate 10 where the group III nitride compound semiconductor light emitting element portion 30 is formed, and a femtosecond pulse laser is scanned from the surface 11 side of the sapphire substrate 10 which is the back surface. The groove part 50 and the reforming parts 51 to 54 were formed.
フェムト秒パルスレーザは、次の通り。波長１μｍ、パルス幅５００ｆｓ、パルス周波数１００ｋＨｚ、パルス当たりエネルギー１．５μＪ。直線偏光成分が分離予定面と平行となるように設定した。また、対物レンズは開口数０．６５のものを用いた。サファイア基板１０の面１１側を走査し、送り速度は、溝部５０と改質部５１を形成する際は２５０ｍｍ／ｓ、改質部５２乃至５４を形成する際は５００ｍｍ／ｓとした。また、集光位置は、溝部５０の形成の際は面１１からの深さ０μｍ、改質部５１の形成の際は深さ５μｍ、改質部５２の形成の際は深さ２５μｍ、改質部５３の形成の際は５５μｍ、改質部５４の形成の際は８５μｍとした。尚、改質部５４、改質部５３、改質部５２、溝部５０、改質部５１の順に形成した（図３．Ｃ及び図３．Ｄ）。 The femtosecond pulse laser is as follows. Wavelength 1 μm, pulse width 500 fs, pulse frequency 100 kHz, energy per pulse 1.5 μJ. The linearly polarized light component was set to be parallel to the planned separation surface. An objective lens having a numerical aperture of 0.65 was used. The surface 11 side of the sapphire substrate 10 was scanned, and the feed rate was 250 mm / s when forming the groove 50 and the modified part 51, and 500 mm / s when forming the modified parts 52 to 54. The condensing position is 0 μm deep from the surface 11 when the groove 50 is formed, 5 μm deep when the modified portion 51 is formed, and 25 μm deep when the modified portion 52 is formed. When the portion 53 was formed, the thickness was 55 μm, and when the modified portion 54 was formed, the thickness was 85 μm. The reforming part 54, the reforming part 53, the reforming part 52, the groove part 50, and the reforming part 51 were formed in this order (FIGS. 3.C and 3.D).
次に、ウエハを反転させ、ブレーキング刃を用いて、粘着テープ６０を貼ったサファイア基板１０のIII族窒化物系化合物半導体発光素子部３０を形成した側から外力を加えて個々の素子に分離した（図３．Ｅ）。分離面は分離予定面と一致するものであり、サファイア基板１０の面１１及び１２に垂直であった。また、ダイサー及びスクライバーによる分離と比較して、分離面の平面度が高くなった。また、厚い基板の分離が可能となった。 Next, the wafer is inverted and using a breaking blade, an external force is applied from the side of the sapphire substrate 10 on which the adhesive tape 60 is pasted to the group III nitride compound semiconductor light emitting element portion 30 to separate the individual elements. (Fig. 3.E). The separation surface coincided with the planned separation surface and was perpendicular to the surfaces 11 and 12 of the sapphire substrate 10. Further, the flatness of the separation surface was higher than that of the separation by the dicer and the scriber. In addition, a thick substrate can be separated.
図４に断面図のＳＥＭ画像を示す。改質部５２乃至５４は深さ方向に幅２０μｍ、間隔１０μｍで整然と形成されている。また、１パルス毎に形成される個々の改質部は、径約２．５μｍ、長さ約５μｍの頭部Ｈと、径約０．６μｍ、長さ約１５μｍの足部Ｌとで構成され、それらの何れからも分離の際にクラックがまず左右方向の隣の改質部に向かって成長することが分かる。分離線方向の隣の改質部とのピッチは５μｍである。長さ約１５μｍの足部は、径約２．５μｍ、長さ約５μｍの頭部が形成されることで、レーザが集光されて「フィラメンテーション」を生じたものである。上下方向のクラックは、上記左右方向のクラックの後に極めて面精度高く生じていることも理解できる。 FIG. 4 shows a cross-sectional SEM image. The reforming parts 52 to 54 are regularly formed with a width of 20 μm and an interval of 10 μm in the depth direction. Each reformed portion formed for each pulse is composed of a head H having a diameter of about 2.5 μm and a length of about 5 μm, and a foot L having a diameter of about 0.6 μm and a length of about 15 μm. From any of these, it can be seen that cracks first grow toward the adjacent modified portion in the left-right direction during separation. The pitch with the modified part adjacent to the separation line direction is 5 μm. The foot portion having a length of about 15 μm is formed with a head having a diameter of about 2.5 μm and a length of about 5 μm, so that the laser is focused and “filamentation” occurs. It can also be understood that the vertical crack is generated with extremely high surface accuracy after the horizontal crack.
〔比較例１〕
偏光の方向を、分離面に垂直方向に直線偏光成分を有する様にして上記と同様に分離を行った。その断面図のＳＥＭ画像を図５．Ｂに示す。図５．Ａは、図４の拡大写真である。分離面に垂直な方向の直線偏光成分を有する場合は、改質部の頭部が分離線方向に対して薄く、また、クラックが各改質部の分離線方向の両側には発生しなかった。このことから、分離面に平行な直線偏光成分を有する場合のほうが、より小さい外力で分離が容易であることが理解できる。
[Comparative Example 1]
Separation was performed in the same manner as described above, with the polarization direction having a linearly polarized light component perpendicular to the separation plane. The SEM image of the cross-sectional view is shown in FIG. Shown in B. FIG. A is an enlarged photograph of FIG. In the case of having a linearly polarized light component in a direction perpendicular to the separation surface, the head of the reforming part was thin relative to the separation line direction, and cracks did not occur on both sides of each reforming part in the separation line direction. . From this, it can be understood that the separation is easier with a smaller external force when the linearly polarized light component is parallel to the separation surface.
〔比較例２〕
対物レンズの開口数を０．２、０．４として、レーザによりサファイア基板を切断した場合の断面図を図６．Ａ及び図６．Ｂに示す。但し、改質部を１段のみ形成した実験である。対物レンズの開口数を０．２とした場合、改質部が基板の１／２以上の厚さに形成された（図６．Ａ）。対物レンズの開口数を０．４とした場合、改質部が基板の１／３程度の厚さに形成された（図６．Ｂ）。対物レンズの開口数を０．２、０．４とした場合は、精度が悪いために断面の平滑度が悪く、切断の際の切り代が大きくなるので、小さなチップには適用できない。また、不本意なクラックも発生していた。図４の「縮小図」である図６．Ｃと比較すると、集光を十分に行うためには対物レンズの開口数が０．５以上であることが必要と言える。
[Comparative Example 2]
FIG. 6 is a cross-sectional view when the sapphire substrate is cut by a laser with the objective lens having a numerical aperture of 0.2 and 0.4. A and FIG. Shown in B. However, it is an experiment in which only one reforming part is formed. When the numerical aperture of the objective lens was 0.2, the modified portion was formed with a thickness of 1/2 or more of the substrate (FIG. 6.A). When the numerical aperture of the objective lens was 0.4, the modified portion was formed to a thickness of about 1/3 of the substrate (FIG. 6.B). When the numerical aperture of the objective lens is set to 0.2 and 0.4, the accuracy is poor, and the smoothness of the cross section is poor, and the cutting allowance for cutting becomes large. Unintentional cracks were also generated. FIG. 6 is a “reduced view” of FIG. Compared with C, it can be said that the numerical aperture of the objective lens is required to be 0.5 or more in order to sufficiently collect light.
１０：サファイア基板
３０：III族窒化物系化合物半導体発光素子部
４０：対物レンズ
４１：フェムト秒パルスレーザ光
５０：分離線方向に連続した溝部
５１：分離線方向に連続した改質部
５２、５３、５４：分離線方向に連続しない改質部
10: Sapphire substrate 30: Group III nitride compound semiconductor light emitting element portion 40: Objective lens 41: Femtosecond pulse laser beam 50: Groove portion continuous in the separation line direction 51: Modified portion 52, 53 continuous in the separation line direction , 54: reforming part not continuous in the direction of the separation line
Claims (8)
パルス幅が１０ピコ秒未満であるパルスレーザを前記基板において集光させて、多光子吸収を発生させることにより、
前記基板の内部の所定の深さに、分離予定面に対応して、前記パルスレーザにより形成された分離予定線方向に連続しない内部改質部であって、前記基板の溶融を伴わない非熱加工のフィラメンテーションにより前記パルスレーザの進行方向に延びた足部を有した内部改質部を形成し、
前記連続しない内部改質部に沿って分離面を形成して、外力を加えることで各半導体発光素子を分離することを特徴とする半導体発光素子の分離方法。 In a method for separating a semiconductor light emitting device formed on a substrate,
By focusing a pulsed laser with a pulse width of less than 10 picoseconds on the substrate to generate multiphoton absorption,
An internal reforming portion that does not continue in the direction of the planned separation line formed by the pulse laser in a predetermined depth inside the substrate, corresponding to the planned separation surface, and is non-thermal without melting of the substrate Forming an internal reforming portion having a leg portion extending in the traveling direction of the pulse laser by processing filamentation;
A method for separating a semiconductor light emitting element, comprising forming a separation surface along the discontinuous internal reforming portion and applying an external force to separate each semiconductor light emitting element.
パルス幅が１０ピコ秒未満であるパルスレーザを、ピークパワー密度が１．４２Ｗ／ｃｍ2 以上となるように、前記基板において集光させて、多光子吸収を発生させることにより、
前記基板の内部の所定の深さに、分離予定面に対応して、前記パルスレーザにより形成された分離予定線方向に連続しない内部改質部を形成し、
前記連続しない内部改質部に沿って分離面を形成して、外力を加えることで各半導体発光素子を分離することを特徴とする半導体発光素子の分離方法。 In a method for separating a semiconductor light emitting device formed on a substrate,
By condensing a pulse laser having a pulse width of less than 10 picoseconds on the substrate so that the peak power density is 1.42 W / cm 2 or more, and generating multiphoton absorption,
Forming an internal reforming portion that is not continuous in the direction of the planned separation line formed by the pulse laser, corresponding to the planned separation surface, at a predetermined depth inside the substrate,
A method for separating a semiconductor light emitting element, comprising forming a separation surface along the discontinuous internal reforming portion and applying an external force to separate each semiconductor light emitting element.
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