JP6450637B2 - Lift-off method and ultrasonic horn - Google Patents

Lift-off method and ultrasonic horn Download PDF

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JP6450637B2
JP6450637B2 JP2015086687A JP2015086687A JP6450637B2 JP 6450637 B2 JP6450637 B2 JP 6450637B2 JP 2015086687 A JP2015086687 A JP 2015086687A JP 2015086687 A JP2015086687 A JP 2015086687A JP 6450637 B2 JP6450637 B2 JP 6450637B2
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JP2016207801A (en
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将 小柳
将 小柳
邱　暁明
暁明 邱
文照 田篠
文照 田篠
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01L2221/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof covered by H01L21/00
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Description

本発明は、エピタキシー基板の表面にバッファ層を介して積層された光デバイス層を移設基板に移し替えるリフトオフ方法及びこれに使用する超音波ホーンに関する。   The present invention relates to a lift-off method for transferring an optical device layer laminated on a surface of an epitaxy substrate via a buffer layer to a transfer substrate, and an ultrasonic horn used for the method.

光デバイス製造工程においては、略円板形状であるサファイア基板や炭化珪素基板等のエピタキシー基板の表面にバッファ層を介してGaN（窒化ガリウム）等で構成されるｎ型半導体層およびｐ型半導体層からなる光デバイス層が積層され、格子状に形成された複数のストリートによって区画された複数の領域に発光ダイオード、レーザーダイオード等の光デバイスを形成して光デバイスウエーハを構成する。そして、光デバイスウエーハをストリートに沿って分割することにより個々の光デバイスを製造している（例えば、特許文献１参照。）。   In an optical device manufacturing process, an n-type semiconductor layer and a p-type semiconductor layer formed of GaN (gallium nitride) or the like on a surface of an epitaxial substrate such as a sapphire substrate or a silicon carbide substrate having a substantially disc shape via a buffer layer An optical device wafer is formed by forming optical devices such as light-emitting diodes and laser diodes in a plurality of regions partitioned by a plurality of streets formed in a lattice shape. Each optical device is manufactured by dividing the optical device wafer along the street (for example, refer to Patent Document 1).

また、光デバイスの輝度を向上させる技術として、光デバイスウエーハを構成するエピタキシー基板の表面にバッファ層を介して積層された光デバイス層を、AuSn（金錫）等の接合層を介してMo（モリブデン）、Cu（銅）、Si（シリコン）等の移設基板に接合し、エピタキシー基板の裏面側からエピタキシー基板を透過しバッファ層で吸収される波長のレーザー光線を照射してバッファ層を破壊し光デバイス層からエピタキシー基板を剥離することにより、光デバイス層を移設基板に移し替えるリフトオフと呼ばれる光デバイス製造方法がある（例えば、特許文献２参照）。また、レーザー光線をバッファ層に照射する方法では、バッファ層を十分に破壊することができない場合があるため、エピタキシー基板を光デバイスから円滑に剥離するために、シリコン基板が浸漬される純水を介してシリコン基板に超音波を照射し、シリコン基板上の金属膜を剥離するという方法がある（例えば、特許文献３参照）。   As a technology for improving the brightness of optical devices, an optical device layer laminated on the surface of an epitaxy substrate constituting an optical device wafer via a buffer layer is bonded to Mo (through AuSn (gold tin) or other Mo ( Molybdenum), Cu (copper), Si (silicon), etc. are bonded to the transfer substrate, and the buffer layer is destroyed and irradiated by irradiating a laser beam having a wavelength that is transmitted through the epitaxy substrate and absorbed by the buffer layer from the back side of the epitaxy substrate. There is an optical device manufacturing method called lift-off in which an optical device layer is transferred to a transfer substrate by peeling the epitaxy substrate from the device layer (see, for example, Patent Document 2). In addition, in the method of irradiating the buffer layer with the laser beam, the buffer layer may not be sufficiently destroyed. Therefore, in order to smoothly peel the epitaxy substrate from the optical device, the pure silicon substrate is immersed in pure water. There is a method of irradiating a silicon substrate with ultrasonic waves and peeling a metal film on the silicon substrate (see, for example, Patent Document 3).

特開平１０−３０５４２０号公報JP-A-10-305420 特開２００４−７２０５２号公報JP 2004-72052 A 特開２０１１−１０３３６１号公報JP 2011-103361 A

ここで、特許文献３に係る発明では、光デバイス層を移設する点についての開示が全くなく、また水中で行う工程を含む方法は時間が多く掛かるという問題がある。また、光デバイスウエーハが、その直径が２インチを超える４インチや６インチものである場合には、エピタキシー基板を光デバイス層から剥離させることは困難となる。   Here, in the invention which concerns on patent document 3, there is no disclosure about the point which transfers an optical device layer, and there exists a problem that the method including the process performed in water takes time. Further, when the optical device wafer has a diameter of 4 inches or 6 inches exceeding 2 inches, it is difficult to peel the epitaxy substrate from the optical device layer.

本発明は、このような実情を鑑みてなされたものであり、直径の大きい光デバイスウエーハをリフトオフする場合でも、エピタキシー基板を光デバイス層から円滑に剥離できるようにすることを解決課題とする。   The present invention has been made in view of such circumstances, and an object of the present invention is to make it possible to smoothly peel the epitaxy substrate from the optical device layer even when lifting off an optical device wafer having a large diameter.

上記課題を解決するための本発明は、エピタキシー基板の表面にGaNからなるバッファ層を介して光デバイス層が積層された光デバイスウエーハの光デバイス層を移設基板に移し替えるリフトオフ方法であって、該光デバイスウエーハの光デバイス層の表面に接合層を介して移設基板を接合する移設基板接合工程と、該移設基板が接合された光デバイスウエーハのエピタキシー基板の裏面側からエピタキシー基板に対しては透過性を有しバッファ層に対しては吸収性を有する波長のパルスレーザー光線を照射し、エピタキシー基板とバッファ層との境界面に剥離層を形成する剥離層形成工程と、該剥離層形成工程の後、該エピタキシー基板の外周縁を囲繞する形状を有し超音波振動を発振する超音波ホーンを少なくとも該外周縁の裏面に接触させて該エピタキシー基板を振動させ、該移設基板から該エピタキシー基板を剥離し、該光デバイス層を移設基板に移設する光デバイス層移設工程と、を含むリフトオフ方法である。   The present invention for solving the above problems is a lift-off method for transferring an optical device layer of an optical device wafer in which an optical device layer is laminated on a surface of an epitaxy substrate through a buffer layer made of GaN, to a transfer substrate, A transfer substrate bonding step of bonding a transfer substrate to the surface of the optical device layer of the optical device wafer via a bonding layer, and an epitaxy substrate from the back side of the epitaxy substrate of the optical device wafer to which the transfer substrate is bonded A release layer forming step of irradiating the buffer layer having transparency with a pulsed laser beam having an absorptive wavelength to form a release layer on the boundary surface between the epitaxy substrate and the buffer layer; and Thereafter, an ultrasonic horn having a shape surrounding the outer peripheral edge of the epitaxy substrate and oscillating ultrasonic vibration is brought into contact with at least the back surface of the outer peripheral edge. Te is vibrated the epitaxy substrate, peeling the epitaxial substrate from the transfer substrate, and the optical device layer transfer step of transferring the optical device layer transfer substrate, a lift-off method comprising.

また、上記課題を解決するための本発明は、前記のリフトオフ方法に使用する超音波ホーンであって、エピタキシー基板の外周に沿った円弧形状に形成され、該エピタキシー基板の外周縁の裏面に接触する裏面接触面と、エピタキシー基板の外側面を囲繞して位置決めする外側面囲繞面とを備える超音波ホーンである。   In addition, the present invention for solving the above-mentioned problems is an ultrasonic horn used in the lift-off method, which is formed in an arc shape along the outer periphery of the epitaxy substrate, and contacts the back surface of the outer peripheral edge of the epitaxy substrate. An ultrasonic horn comprising a back surface contact surface and an outer surface surrounding surface that surrounds and positions the outer surface of the epitaxy substrate.

本発明に係るリフトオフ方法は、光デバイス層移設工程において、エピタキシー基板の外周縁を囲繞する形状を有し超音波振動を発振する超音波ホーンを少なくとも外周縁の裏面に接触させてエピタキシー基板を振動させることで、直径が大きい光デバイスウエーハであっても、エピタキシー基板を円滑に光デバイス層から剥離することができるので、光デバイス層の移設基板への移設を容易に行うことが可能となる。   The lift-off method according to the present invention is such that in the optical device layer transfer step, an ultrasonic horn having a shape surrounding the outer peripheral edge of the epitaxy substrate and oscillating ultrasonic vibration is brought into contact with at least the back surface of the outer peripheral edge to vibrate the epitaxy substrate. By doing so, even if the optical device wafer has a large diameter, the epitaxy substrate can be smoothly peeled from the optical device layer, so that the optical device layer can be easily transferred to the transfer substrate.

また、本発明に係る超音波ホーンは、エピタキシー基板の外周に沿った円弧形状に形成され、エピタキシー基板の外周縁の裏面に接触する裏面接触面と、エピタキシー基板の外側面を囲繞して位置決めする外側面囲繞面とを備え、本発明に係るリフトオフ方法において使用することで、エピタキシー基板の外周縁からエピタキシー基板に対してに十分に超音波を伝播でき、振動伝播の効率をより一層高め、光デバイス層の移設基板への移設を容易に行うこと可能とする。   The ultrasonic horn according to the present invention is formed in an arc shape along the outer periphery of the epitaxy substrate, and surrounds and positions the back surface contact surface that contacts the back surface of the outer periphery of the epitaxy substrate and the outer surface of the epitaxy substrate. An outer surface surrounding surface, and when used in the lift-off method according to the present invention, it is possible to sufficiently transmit ultrasonic waves from the outer peripheral edge of the epitaxy substrate to the epitaxy substrate, further improving the efficiency of vibration propagation, It is possible to easily transfer the device layer to the transfer substrate.

図１（Ａ）は、光デバイスウエーハの斜視図である。図１（Ｂ）は光デバイスウエーハの部分断面図である。FIG. 1A is a perspective view of an optical device wafer. FIG. 1B is a partial cross-sectional view of the optical device wafer. 図２（Ａ）は、移設基板接合工程において、光デバイスウエーハの光デバイス層の表面に接合層を介して移設基板を接合している状態を示す斜視図である。図２（Ｂ）は、移設基板接合工程において、光デバイスウエーハの光デバイス層の表面に接合層を介して移設基板が接合された状態を示す斜視図である。図２（Ｃ）は、光デバイス層の表面に接合層を介して移設基板が接合された光デバイスウエーハの部分断面図である。FIG. 2A is a perspective view showing a state in which the transfer substrate is bonded to the surface of the optical device layer of the optical device wafer via the bonding layer in the transfer substrate bonding step. FIG. 2B is a perspective view showing a state where the transfer substrate is bonded to the surface of the optical device layer of the optical device wafer via the bonding layer in the transfer substrate bonding step. FIG. 2C is a partial cross-sectional view of an optical device wafer in which a transfer substrate is bonded to the surface of the optical device layer via a bonding layer. 剥離層形成工程において、光デバイスウエーハにパルスレーザー光線を照射している状態を示す斜視図である。In a peeling layer formation process, it is a perspective view which shows the state which has irradiated the pulse laser beam to the optical device wafer. 剥離層形成工程において、光デバイスウエーハにパルスレーザー光線を照射している状態を示す側面図である。In a peeling layer formation process, it is a side view which shows the state which is irradiating the pulsed laser beam to the optical device wafer. 剥離層形成工程において、光デバイスウエーハのエピタキシー基板の裏面に照射されたパルスレーザー光線の照射位置の軌跡を示す平面図である。It is a top view which shows the locus | trajectory of the irradiation position of the pulse laser beam irradiated to the back surface of the epitaxy board | substrate of an optical device wafer in a peeling layer formation process. 剥離層形成工程において、パルスレーザー光線が照射された光デバイスウエーハの剥離層をエピタキシー基板の裏面側から見た透視図である。It is the perspective view which looked at the peeling layer of the optical device wafer irradiated with the pulse laser beam from the back side of the epitaxy substrate in the peeling layer forming step. 図７（Ａ）は、本発明に係るリフトオフ方法において使用される超音波ホーンの斜視図である。図７（Ｂ）は、本発明に係るリフトオフ方法において使用される超音波ホーンを仰向けにした状態の斜視図である。図７（Ｃ）は、エピタキシー基板に超音波ホーンが接触している状態を示す要部端面図である。FIG. 7A is a perspective view of an ultrasonic horn used in the lift-off method according to the present invention. FIG. 7B is a perspective view of a state in which the ultrasonic horn used in the lift-off method according to the present invention is turned upside down. FIG. 7C is an end view of the main part showing a state in which the ultrasonic horn is in contact with the epitaxy substrate. 光デバイス層移設工程において、超音波ホーンをエピタキシー基板の外周縁の裏面に接触させてエピタキシー基板を振動させている状態を示す部分端面図である。In an optical device layer transfer process, it is a partial end elevation showing the state where an ultrasonic horn is made to contact the back of the perimeter edge of an epitaxy substrate, and an epitaxy substrate is vibrated. 光デバイス層移設工程において、超音波ホーンをエピタキシー基板の外周縁の裏面に接触させてエピタキシー基板を振動させている状態を示す平面図である。It is a top view which shows the state which made the ultrasonic horn contact the back surface of the outer periphery of an epitaxy board | substrate, and vibrates the epitaxy board | substrate in the optical device layer transfer process. 図１０（Ａ）は光デバイス層移設工程において、吸引パッドでエピタキシー基板を吸引保持している状態を示す斜視図である。図１０（Ｂ）は光デバイス層移設工程において、吸引パッドで吸引保持したエピタキシー基板を光デバイス層から剥離している状態を示す斜視図である。FIG. 10A is a perspective view showing a state where the epitaxy substrate is sucked and held by the suction pad in the optical device layer transfer step. FIG. 10B is a perspective view showing a state where the epitaxy substrate sucked and held by the suction pad is peeled from the optical device layer in the optical device layer transfer step.

図１（Ａ）及び図１（Ｂ）に示す光デバイスウエーハ１０は、例えば、直径が４インチで厚みが６００μｍの円板形状であるサファイア基板からなるエピタキシー基板１１と、エピタキシー基板１１の表面１１ａ側に積層された光デバイス層１２とを有している。光デバイス層１２は、エピタキシー基板１１の表面１１ａにエピタキシャル成長法によって形成されるｎ型窒化ガリウム半導体層１２Ａ及びｐ型窒化ガリウム半導体層１２Ｂ（図１（Ａ）では不図示）からなる。エピタキシー基板１１に例えば厚みが１０μｍの光デバイス層１２を積層する際に、エピタキシー基板１１の表面１１ａとｐ型窒化ガリウム半導体層１２Ｂとの間には、GaNからなる厚みが例えば１μｍのバッファ層１３（図１（Ａ）では不図示）が形成される。光デバイス層１２には、格子状に形成された複数の分割予定ライン１５によって区画された複数の領域に光デバイス１６が形成されている（図１（Ｂ）では不図示）。   An optical device wafer 10 shown in FIGS. 1A and 1B includes, for example, an epitaxy substrate 11 made of a sapphire substrate having a disk shape of 4 inches in diameter and 600 μm in thickness, and a surface 11a of the epitaxy substrate 11. And an optical device layer 12 laminated on the side. The optical device layer 12 includes an n-type gallium nitride semiconductor layer 12A and a p-type gallium nitride semiconductor layer 12B (not shown in FIG. 1A) formed on the surface 11a of the epitaxial substrate 11 by an epitaxial growth method. When the optical device layer 12 having a thickness of, for example, 10 μm is stacked on the epitaxial substrate 11, a buffer layer 13 having a thickness of, for example, 1 μm is formed between the surface 11 a of the epitaxial substrate 11 and the p-type gallium nitride semiconductor layer 12 B. (Not shown in FIG. 1A) is formed. In the optical device layer 12, optical devices 16 are formed in a plurality of regions partitioned by a plurality of division lines 15 formed in a lattice shape (not shown in FIG. 1B).

以下に、図２〜１０を用いて本実施形態に係るリフトオフ方法の各工程及びリフトオフ方法で行われる光デバイス層移設工程において使用される超音波ホーンの動作について説明する。なお、図２〜１０に示す各工程は、あくまでも一例に過ぎず、この構成に限定されるものではない。   The operation of the ultrasonic horn used in the steps of the lift-off method according to the present embodiment and the optical device layer transfer step performed by the lift-off method will be described below with reference to FIGS. Each process shown in FIGS. 2 to 10 is merely an example, and the present invention is not limited to this configuration.

（１）移設基板接合工程
まず、図２（Ａ）〜図２（Ｃ）に示すように、光デバイスウエーハ１０の光デバイス層１２の表面に接合層２１（図２（Ａ）では不図示）を介して移設基板２０を接合する移設基板接合工程を行う。 (1) Transfer Substrate Bonding Step First, as shown in FIGS. 2A to 2C, a bonding layer 21 (not shown in FIG. 2A) is formed on the surface of the optical device layer 12 of the optical device wafer 10. The transfer board | substrate joining process which joins the transfer board | substrate 20 via is performed.

移設基板接合工程では、光デバイス層１２の表面１２ａに、例えば厚みが１ｍｍの銅基板からなる移設基板２０を、接合層２１を介して接合する。なお、移設基板２０としては、Mo、Cu、Si等を用いることができ、また、接合層２１には、例えば、Au（金）、Pt（白金）、Cr（クロム）、In（インジウム）、Pd（パラジウム）等の接合金属を用いることができる。
この移設基板接合工程では、光デバイス層１２の表面１２ａまたは移設基板２０の底面２０ａに上記接合金属を蒸着して例えば厚みが３μｍ程度の接合層２１を形成する。そして、接合層２１と、移設基板の底面２０ａまたは光デバイス層１２の表面１２ａとを対面させて圧着する。これにより、接合層２１を介して光デバイスウエーハ１０と移設基板２０とを接合した複合基板２５を形成する。なお、図４、図７（Ｃ）、図８においては、接合層２１は省略して示している。 In the transfer substrate bonding step, the transfer substrate 20 made of, for example, a copper substrate having a thickness of 1 mm is bonded to the surface 12 a of the optical device layer 12 via the bonding layer 21. As the transfer substrate 20, Mo, Cu, Si, or the like can be used. For the bonding layer 21, for example, Au (gold), Pt (platinum), Cr (chromium), In (indium), A bonding metal such as Pd (palladium) can be used.
In this transfer substrate bonding step, the bonding metal is deposited on the surface 12a of the optical device layer 12 or the bottom surface 20a of the transfer substrate 20 to form a bonding layer 21 having a thickness of about 3 μm, for example. Then, the bonding layer 21 and the bottom surface 20a of the transfer substrate or the surface 12a of the optical device layer 12 face each other and are pressure-bonded. As a result, a composite substrate 25 in which the optical device wafer 10 and the transfer substrate 20 are bonded via the bonding layer 21 is formed. Note that the bonding layer 21 is omitted in FIGS. 4, 7 </ b> C, and 8.

（２）剥離層形成工程
移設基板接合工程を行った後、図３に示すように、移設基板２０が接合された光デバイスウエーハ１０のエピタキシー基板１１の裏面１１ｂ側からエピタキシー基板１１に対しては透過性を有しバッファ層１３に対しては吸収性を有する波長のパルスレーザー光線を照射し、エピタキシー基板１１とバッファ層１３との境界面に剥離層を形成する剥離層形成工程を行う。 (2) Release layer forming step After the transfer substrate bonding step is performed, as shown in FIG. 3, from the back surface 11b side of the epitaxy substrate 11 of the optical device wafer 10 to which the transfer substrate 20 is bonded to the epitaxy substrate 11 A release layer forming step is performed in which the buffer layer 13 having transparency is irradiated with a pulsed laser beam having an absorptive wavelength to form a release layer on the interface between the epitaxy substrate 11 and the buffer layer 13.

剥離層形成工程では、レーザー加工装置３０に備えるチャックテーブル３１の保持面となる上面に、複合基板２５の移設基板２０の表面２０ｂが接するように載置する。そして、チャックテーブル３１に接続された図示しない吸引手段で吸引し、チャックテーブル３１上で複合基板２５を吸着保持する。次いで、図示しない移動手段を作動させて、例えば、ガルバノスキャナ等を備えたレーザー光線照射手段３２を移動し、レーザー光線照射手段３２に備える集光レンズ３２ｃと複合基板２５のエピタキシー基板１１の裏面１１ｂとを対向させ、レーザー光線照射手段３２のレーザー光線照射位置をエピタキシー１１の最外周に位置付ける。その後、図４に示すように、レーザー光線照射手段３２によって、エピタキシー基板の裏面１１ｂ側からパルスレーザー光線を照射する。レーザー光線照射手段３２では、レーザー光線発振手段３２ａから、エピタキシー基板１１に対しては透過性を有しバッファ層１３に対しては吸収性を有する波長に設定されたパルスレーザー光線を発振する。そして、レーザー光線発振手段３２ａから発振したパルスレーザー光線をミラー３２ｂで反射し、集光レンズ３２ｃに入光する。集光レンズ３２ｃでは、バッファ層１３に集光点を合わせて、集光させたパルスレーザー光線を照射する。   In the release layer forming step, the composite substrate 25 is placed so that the surface 20b of the transfer substrate 20 is in contact with the upper surface serving as the holding surface of the chuck table 31 provided in the laser processing apparatus 30. Then, suction is performed by a suction means (not shown) connected to the chuck table 31, and the composite substrate 25 is sucked and held on the chuck table 31. Next, the moving means (not shown) is operated to move the laser beam irradiation means 32 including, for example, a galvano scanner, and the condensing lens 32c provided in the laser beam irradiation means 32 and the back surface 11b of the epitaxy substrate 11 of the composite substrate 25 are moved. The laser beam irradiation position of the laser beam irradiation means 32 is positioned on the outermost periphery of the epitaxy 11. Thereafter, as shown in FIG. 4, the laser beam irradiation means 32 irradiates the pulse laser beam from the back surface 11 b side of the epitaxy substrate. The laser beam irradiating means 32 oscillates from the laser beam oscillating means 32 a a pulse laser beam set to a wavelength that is transparent to the epitaxy substrate 11 and absorbable to the buffer layer 13. Then, the pulse laser beam oscillated from the laser beam oscillation means 32a is reflected by the mirror 32b and enters the condenser lens 32c. The condensing lens 32c irradiates the condensed pulsed laser beam with the condensing point aligned with the buffer layer 13.

ミラー３２ｂは、ガルバノミラー等で構成され反射角度を調整可能であり、集光レンズ３２ｃにより集光されるパルスレーザー光線がバッファ層１３の面方向に沿う任意の方向に走査可能に設けられる。ミラー３２ｂを調整して、図５に示すように、パルスレーザー光線の集光点が、エピタキシー基板１１の裏面１１ｂの最外周から中心に向けてスパイラル状の軌跡を描くようにパルスレーザー光線を走査して行う。これにより、バッファ層１３の全面に対応する領域にパルスレーザー光線が照射され、バッファ層１３を構成するGaNがN2ガスとGaとに分解される。そして、図４に示すようにエピタキシー基板１１とバッファ層１３との境界面に島状に複数形成されるN2ガス層１９ａとGa層とからなる剥離層１９が形成される。ここで、N2ガス層１９ａは、バッファ層１３の全面にわたって形成される場合もあるが、図６に示すように、エピタキシー基板１１の外周に近付く程、広範囲にわたって万遍なく形成される傾向がある。なお、剥離層形成工程において、直径が４インチと大きいエピタキシー基板１１に対してパルスレーザー光線を照射する際に、例えば、レーザー光線照射手段３２のレーザー光線照射位置をエピタキシー基板１１の最外周に位置付け、チャックテーブル３１の下部に配設された図４に示す回転手段３３によりチャックテーブル３１を回転させつつ、レーザー光線照射手段３２をエピタキシー基板１１の裏面１１ｂの中心に向けて移動することにより、バッファ層１３の全面にパルスレーザー光線を照射してもよい。 The mirror 32b is composed of a galvanometer mirror or the like and can adjust the reflection angle, and is provided so that the pulse laser beam condensed by the condenser lens 32c can be scanned in any direction along the surface direction of the buffer layer 13. By adjusting the mirror 32b, as shown in FIG. 5, the pulse laser beam is scanned so that the condensing point of the pulse laser beam draws a spiral trajectory from the outermost periphery of the back surface 11b of the epitaxy substrate 11 toward the center. Do. As a result, a region corresponding to the entire surface of the buffer layer 13 is irradiated with a pulse laser beam, and GaN constituting the buffer layer 13 is decomposed into N 2 gas and Ga. Then, as shown in FIG. 4, a release layer 19 composed of a plurality of N 2 gas layers 19 a and Ga layers formed in an island shape is formed on the boundary surface between the epitaxy substrate 11 and the buffer layer 13. Here, the N 2 gas layer 19 a may be formed over the entire surface of the buffer layer 13, but as shown in FIG. 6, the N 2 gas layer 19 a tends to be formed over a wide range as it approaches the outer periphery of the epitaxy substrate 11. is there. In the peeling layer forming step, when the pulsed laser beam is irradiated onto the epitaxy substrate 11 having a large diameter of 4 inches, for example, the laser beam irradiation position of the laser beam irradiation means 32 is positioned on the outermost periphery of the epitaxy substrate 11 and the chuck table. 4, while rotating the chuck table 31 by the rotating means 33 shown in FIG. 4, the laser beam irradiating means 32 is moved toward the center of the back surface 11 b of the epitaxy substrate 11. May be irradiated with a pulsed laser beam.

上記剥離層形成工程は、例えば以下のレーザー加工条件で実施する。
光源 ：ＹＡＧレーザー
波長 ：２５７ｎｍ
繰り返し周波数 ：５０ｋＨｚ
平均出力 ：０．１２Ｗ
パルス幅 ：１００ｐｓ
ピークパワー ：５μＪ−３μＪ
スポット径 ：７０μｍ
レーザー光線照射手段移動速度 ：５０−１００ｍｍ／秒 The said peeling layer formation process is implemented on the following laser processing conditions, for example.
Light source: YAG laser Wavelength: 257 nm
Repetition frequency: 50 kHz
Average output: 0.12W
Pulse width: 100ps
Peak power: 5μJ-3μJ
Spot diameter: 70 μm
Laser beam irradiation means moving speed: 50-100 mm / sec

（３）光デバイス層移設工程
剥離層形成工程を行った後、図８〜図９に示すように、エピタキシー基板１１の外周縁１１ｃを囲繞する形状を有し超音波振動を発振する超音波ホーン４０を少なくとも外周縁１１ｃの裏面１１ｄに接触させてエピタキシー基板１１を振動させ、移設基板２０からエピタキシー基板１１を剥離し、光デバイス層１２を移設基板２０に移設する光デバイス層移設工程を行う。なお、エピタキシー基板１１の外周縁１１ｃとは、例えば、エピタキシー基板１１の外側面１１ｅと、エピタキシー基板１１の裏面１１ｂのうち最外周部分を占める環状の面１１ｄとを合わせて構成される一定の面積を有する部分である。すなわち、エピタキシー基板１１の外周縁１１ｃの裏面は、エピタキシー基板１１の裏面１１ｂの最外周部分を占める環状の面１１ｄと同一となる。 (3) Optical Device Layer Transfer Step After performing the release layer forming step, as shown in FIGS. 8 to 9, an ultrasonic horn having a shape surrounding the outer peripheral edge 11c of the epitaxy substrate 11 and oscillating ultrasonic vibrations 40 is brought into contact with at least the back surface 11d of the outer peripheral edge 11c to vibrate the epitaxy substrate 11, peel off the epitaxy substrate 11 from the transfer substrate 20, and perform an optical device layer transfer step of transferring the optical device layer 12 to the transfer substrate 20. The outer peripheral edge 11c of the epitaxy substrate 11 is, for example, a certain area configured by combining the outer surface 11e of the epitaxy substrate 11 and the annular surface 11d occupying the outermost peripheral portion of the back surface 11b of the epitaxy substrate 11. It is a part which has. That is, the back surface of the outer peripheral edge 11 c of the epitaxy substrate 11 is the same as the annular surface 11 d occupying the outermost peripheral portion of the back surface 11 b of the epitaxy substrate 11.

図７（Ａ）〜図７（Ｃ）に示す超音波ホーン４０は、例えば、半環状の天板４００と、天板４００の外周から−Ｚ方向に垂直に垂れ下がる半環状の側板４０１と、側板４０１の外周側から突き出る凸部４０２とから構成され、その全形は、本実施形態ではエピタキシー基板１１の外周に沿った半円弧形状となっている。そして、超音波ホーン４０の断面は、例えば逆Ｌ字型となっている。また、超音波ホーン４０は、移動手段４０４により、鉛直方向（Ｚ軸方向）及び水平方向（Ｘ軸方向及びＹ軸方向）に移動可能となっている。なお、超音波ホーン４０の全形は、半円弧形状に限定されるものではなく、エピタキシー基板１１の外周に沿った円弧形状となっていればよい。   The ultrasonic horn 40 shown in FIGS. 7A to 7C includes, for example, a semi-annular top plate 400, a semi-annular side plate 401 that hangs vertically from the outer periphery of the top plate 400 in the −Z direction, and a side plate. The convex part 402 protrudes from the outer peripheral side of 401, The whole form is a semicircular arc shape along the outer periphery of the epitaxy substrate 11 in this embodiment. The cross section of the ultrasonic horn 40 is, for example, an inverted L shape. The ultrasonic horn 40 can be moved in the vertical direction (Z-axis direction) and the horizontal direction (X-axis direction and Y-axis direction) by the moving means 404. Note that the entire shape of the ultrasonic horn 40 is not limited to the semicircular arc shape, but may be an arc shape along the outer periphery of the epitaxy substrate 11.

天板４００の下面は、エピタキシー基板１１の外周縁１１ｃの裏面１１ｄに接触する裏面接触面４００ａとなり、凸部４０２上に配設された超音波発振器４０３（図７（Ｂ）には不図示）から発振された超音波振動は、裏面接触面４００ａからエピタキシー基板１１に対して伝播される。半環状の側板４０１の内径（半環の中空部の直径）はエピタキシー基板１１の外径と同程度またはそれ以上となっており、側板４０１の内周側の面は、エピタキシー基板１１の外側面１１ｅを囲繞して位置決めする外側面囲繞面４０１ａとなる。すなわち、例えば、エピタキシー基板１１の外側面１１ｅを外側面囲繞面４０１ａが囲繞し接触した状態となることで、超音波ホーン４０はエピタキシー基板１１に対して位置決めされる。さらに、外側面囲繞面４０１ａの鉛直方向（Ｚ軸方向）の長さすなわち裏面接触面４００ａから側板４０１の下面４０１ｂまでの長さＬ１（図７（Ａ）には不図示）は、エピタキシー基板１１の厚み以下の長さとなる。   The lower surface of the top plate 400 serves as a back surface contact surface 400a that contacts the back surface 11d of the outer peripheral edge 11c of the epitaxy substrate 11, and an ultrasonic oscillator 403 disposed on the convex portion 402 (not shown in FIG. 7B). The ultrasonic vibration oscillated from is propagated from the back contact surface 400a to the epitaxy substrate 11. The inner diameter of the semicircular side plate 401 (the diameter of the hollow portion of the semiannular ring) is approximately equal to or greater than the outer diameter of the epitaxy substrate 11, and the inner peripheral surface of the side plate 401 is the outer surface of the epitaxy substrate 11. It becomes the outer surface surrounding surface 401a which surrounds and positions 11e. That is, for example, the ultrasonic horn 40 is positioned with respect to the epitaxy substrate 11 when the outer surface 11e of the epitaxy substrate 11 is surrounded and brought into contact with the outer surface surrounding surface 401a. Further, the length in the vertical direction (Z-axis direction) of the outer surface surrounding surface 401a, that is, the length L1 from the back surface contact surface 400a to the lower surface 401b of the side plate 401 (not shown in FIG. 7A) is determined by the epitaxy substrate 11. It becomes the length below the thickness of.

図８に示すように、光デバイス層移設工程では、まず、移設装置４に備える保持テーブル４４の保持面となる上面に、複合基板２５の移設基板２０の表面２０ｂが接するように載置する。そして、保持テーブル４４に接続された図示しない吸引手段で吸引し、チャックテーブル４４上で複合基板２５を吸着保持する。次いで、図９に示すように２つ超音波ホーン４０をそれぞれ移動手段４０４により複合基板２５上へと、各超音波ホーン４０の外側面囲繞面４０１ａが向かい合うように移動させて、エピタキシー基板１１と２つの超音波ホーン４０との位置合わせを行う。なお、図８においては、片側の超音波ホーン４０のみを図示している。この位置合わせにおいては、図８に示すように、例えば、超音波ホーン４０の外側面囲繞面４０１ａが、エピタキシー基板１１の外側面１１ｅを接した状態で囲繞するようにする。このように、本実施形態では、例えば、超音波ホーン４０をエピタキシー基板１１の円周上に２つ並べて用いることで、図９に示すようにエピタキシー基板１１の外周縁１１ｃ全てが超音波ホーン４０により囲繞された状態となる。   As shown in FIG. 8, in the optical device layer transfer step, first, the composite substrate 25 is placed so that the surface 20 b of the transfer substrate 20 is in contact with the upper surface serving as the holding surface of the holding table 44 provided in the transfer device 4. Then, suction is performed by a suction means (not shown) connected to the holding table 44, and the composite substrate 25 is sucked and held on the chuck table 44. Next, as shown in FIG. 9, the two ultrasonic horns 40 are respectively moved onto the composite substrate 25 by the moving means 404 so that the outer surface surrounding surfaces 401a of the ultrasonic horns 40 face each other. Positioning with the two ultrasonic horns 40 is performed. In FIG. 8, only the ultrasonic horn 40 on one side is shown. In this alignment, as shown in FIG. 8, for example, the outer surface surrounding surface 401 a of the ultrasonic horn 40 is surrounded with the outer surface 11 e of the epitaxy substrate 11 in contact therewith. Thus, in the present embodiment, for example, by using two ultrasonic horns 40 side by side on the circumference of the epitaxy substrate 11, the entire outer peripheral edge 11 c of the epitaxy substrate 11 is placed on the ultrasonic horn 40 as shown in FIG. 9. It will be in the state surrounded by.

次いで、図８に示す超音波ホーン４０に備える超音波発振器４０３が作動し、超音波発振器４０３から、振幅方向がエピタキシー基板１１の裏面１１ｂに対して垂直方向（Ｚ軸方向）であり例えば周波数が２０ｋＨｚで振幅が２０μｍである超音波を発振させる。この超音波は、周波数及び振幅の値を適宜変更可能であり、例えば、光デバイスウエーハ１０の厚みが薄くなると、超音波振幅を小さく変更したりする。また、２つの超音波ホーン４０を−Ｚ方向へと下降させて、エピタキシー基板１１の外周縁１１ｃの裏面１１ｄ全てに対して各超音波ホーン４０の裏面接触面４００ａを接触させる、すなわち、エピタキシー基板１１の裏面１１ｂの最外周部分を占める環状の面１１ｄ全面に対して、２つの超音波ホーン４０の裏面接触面４００ａで接触することで、超音波発振器４０３から発振された超音波がエピタキシー基板１１へと伝播する。そして、エピタキシー基板１１は、超音波が伝播することで上下方向（Ｚ軸方向）に振動する。ここで、例えば、光デバイスウエーハ１０の直径よりも移設基板２０の直径が大きい場合や、移設基板接合工程において移設基板２０と光デバイスウエーハ１０とがずれて接合されていた場合には、図８に示すように移設基板２０にはみ出し部２０ｃが形成される場合がある。このような場合においても、超音波ホーン４０の裏面接触面４００ａから側板４０１の下面４０１ｂまでの長さＬ１（図７（Ｃ）参照）は、エピタキシー基板１１の厚み以下の長さであるため、超音波ホーン４０の外側面囲繞面４０１ａは移設基板２０には接することがない。そのため、移設基板２０に対しては超音波が伝播しない。   Next, the ultrasonic oscillator 403 provided in the ultrasonic horn 40 shown in FIG. 8 is activated, and the amplitude direction from the ultrasonic oscillator 403 is the direction perpendicular to the back surface 11b of the epitaxy substrate 11 (Z-axis direction), for example, the frequency is. An ultrasonic wave having an amplitude of 20 μm at 20 kHz is oscillated. The frequency and amplitude values of this ultrasonic wave can be appropriately changed. For example, when the thickness of the optical device wafer 10 is reduced, the ultrasonic amplitude is changed to be small. Further, the two ultrasonic horns 40 are lowered in the −Z direction so that the back surface contact surface 400a of each ultrasonic horn 40 is brought into contact with all the back surfaces 11d of the outer peripheral edge 11c of the epitaxy substrate 11, that is, the epitaxy substrate. 11, the ultrasonic wave oscillated from the ultrasonic oscillator 403 is brought into contact with the entire annular surface 11d occupying the outermost peripheral portion of the back surface 11b of the 11 by the back surface contact surfaces 400a of the two ultrasonic horns 40. Propagate to. The epitaxy substrate 11 vibrates in the vertical direction (Z-axis direction) as the ultrasonic wave propagates. Here, for example, when the diameter of the transfer substrate 20 is larger than the diameter of the optical device wafer 10, or when the transfer substrate 20 and the optical device wafer 10 are bonded to each other in the transfer substrate bonding step, FIG. As shown in FIG. 5, the protruding portion 20c may be formed on the transfer substrate 20. Even in such a case, the length L1 (see FIG. 7C) from the back surface contact surface 400a of the ultrasonic horn 40 to the bottom surface 401b of the side plate 401 is equal to or shorter than the thickness of the epitaxy substrate 11. The outer surface surrounding surface 401 a of the ultrasonic horn 40 does not contact the transfer substrate 20. Therefore, ultrasonic waves do not propagate to the transfer substrate 20.

ここで、超音波振動は、エピタキシー基板１１から剥離層１９のN2ガス層１９ａを介して伝播するものと推測されている。すなわち、N2ガス層１９ａがＺ軸方向に揺さぶられることで、バッファ層１３によるエピタキシー基板１１と光デバイス層１２との結合が徐々に破壊されていく。そして、超音波ホーン４０が接触するエピタキシー基板１１の表面１１ａの外周部には、剥離層１９にN2ガス層１９ａが広範囲にわたって万遍なく多く形成されるので、N2ガス層１９ａの真上等の極めて近い位置から十分に振動を発振でき、N2ガス層１９ａが剥離層１９の中心に向けて、バッファ層１３によるエピタキシー基板１１と光デバイス層１２との結合を破壊しながら外周側から広がっていくため、振動伝播の効率をより高めることができる。 Here, it is presumed that the ultrasonic vibration propagates from the epitaxy substrate 11 through the N 2 gas layer 19 a of the release layer 19. That is, when the N 2 gas layer 19a is shaken in the Z-axis direction, the bond between the epitaxy substrate 11 and the optical device layer 12 by the buffer layer 13 is gradually broken. Further, since the N 2 gas layer 19a is uniformly and widely formed on the release layer 19 on the outer peripheral portion of the surface 11a of the epitaxy substrate 11 with which the ultrasonic horn 40 is in contact, the N 2 gas layer 19a is directly above. The N 2 gas layer 19a is able to oscillate sufficiently from an extremely close position such as the center, and the bond between the epitaxy substrate 11 and the optical device layer 12 by the buffer layer 13 is broken toward the center of the release layer 19 from the outer peripheral side. Since it spreads, the vibration propagation efficiency can be further increased.

なお、エピタキシー基板１１への超音波振動の付与は、２つの超音波ホーン４０をエピタキシー基板１１の円周上に並べて用いずに、１つの超音波ホーン４０をエピタキシー基板１１の外周縁１１ｃに沿って円周方向に移動させることで行ってもよい。
また、例えば、超音波ホーン４０がその円弧が半円よりも短い円弧を備える形状のものである場合には、超音波ホーン４０をエピタキシー基板１１の円周上に２つ以上並べて、超音波振動の付与を行ってもよい。 Note that the application of ultrasonic vibration to the epitaxy substrate 11 does not use the two ultrasonic horns 40 arranged on the circumference of the epitaxy substrate 11, and the single ultrasonic horn 40 is aligned along the outer peripheral edge 11 c of the epitaxy substrate 11. This may be done by moving in the circumferential direction.
Further, for example, when the ultrasonic horn 40 has a shape in which the arc has an arc shorter than a semicircle, two or more ultrasonic horns 40 are arranged on the circumference of the epitaxy substrate 11 to generate ultrasonic vibrations. May be given.

超音波ホーン４０による超音波振動の付与後、図１０（Ａ）に示す移動手段４５によって鉛直方向（Ｚ軸方向）及び水平方向（Ｘ軸方向及びＹ軸方向）に移動可能な吸引パッド４６によって、エピタキシー基板１１を吸引保持して移動させる。吸引パッド４６には、吸引源４７が接続されており、吸引源４７によって生み出された吸引力がポーラス部材等で構成される吸引パッド４６の吸引面（下面）に伝達されることで、吸引パッド４６は吸引面でエピタキシー基板１１を吸引保持する。   After application of ultrasonic vibration by the ultrasonic horn 40, the suction means 46 can be moved in the vertical direction (Z-axis direction) and the horizontal direction (X-axis direction and Y-axis direction) by the moving means 45 shown in FIG. Then, the epitaxy substrate 11 is moved while being sucked and held. A suction source 47 is connected to the suction pad 46, and the suction force generated by the suction source 47 is transmitted to the suction surface (lower surface) of the suction pad 46 formed of a porous member or the like, so that the suction pad 47 A suction surface 46 sucks and holds the epitaxy substrate 11.

まず、移動手段４５により吸引パッド４６をエピタキシー基板１１へと移動させ、次いで吸引パッド４６を−Ｚ方向へ下降させて、吸引パッド４６の吸引面（下面）を複合基板２５におけるエピタキシー基板１１の裏面１１ｂに接触させる。そして、吸引源４７を作動させて吸引パッド４６の吸引面でエピタキシー基板の裏面１１ｂを吸引保持する。そして、図に示すように、移動手段４５により吸引パッド４６を保持テーブル４４から離反する＋Ｚ方向へと引き上げる。これにより、光デバイス層１２からエピタキシー基板１１が剥離され、光デバイス層１２の移設基板２０への移設が完了する。   First, the suction pad 46 is moved to the epitaxy substrate 11 by the moving means 45, and then the suction pad 46 is lowered in the −Z direction so that the suction surface (lower surface) of the suction pad 46 is the back surface of the epitaxy substrate 11 in the composite substrate 25. It is made to contact 11b. Then, the suction source 47 is operated to suck and hold the back surface 11 b of the epitaxy substrate with the suction surface of the suction pad 46. Then, as shown in the figure, the suction pad 46 is pulled up in the + Z direction away from the holding table 44 by the moving means 45. Thereby, the epitaxy substrate 11 is peeled from the optical device layer 12, and the transfer of the optical device layer 12 to the transfer substrate 20 is completed.

このように、本実施形態に係るリフトオフ方法では、光デバイス層移設工程において、超音波ホーン４０を少なくともエピタキシー基板１１の外周縁１１ｃの裏面１１ｄに接触させてエピタキシー基板１１を振動させることで、上述のように効率良く超音波振動を伝播させることができる。これにより、バッファ層１３によるエピタキシー基板１１と光デバイス層１２との結合を十分に破壊することができる。そのため、リフトオフの対象が、直径が４インチと大きい光デバイスウエーハ１０であっても、エピタキシー基板１１の剥離による光デバイス層１２の損傷を回避でき、光デバイス層１２からエピタキシー基板１１を迅速且つ円滑に剥離することができる。また、超音波ホーン４０は上記形状を備えることで、エピタキシー基板１１の外周縁１１ｃの裏面１１ｄからエピタキシー基板１１に対して十分に超音波を伝播でき、振動伝播の効率をより一層高め、光デバイス層１２の移設基板２０への移設を容易に行うこと可能とする。   Thus, in the lift-off method according to the present embodiment, in the optical device layer transfer step, the ultrasonic horn 40 is brought into contact with at least the back surface 11d of the outer peripheral edge 11c of the epitaxy substrate 11 to vibrate the epitaxy substrate 11 as described above. As described above, the ultrasonic vibration can be efficiently propagated. As a result, the bond between the epitaxy substrate 11 and the optical device layer 12 by the buffer layer 13 can be sufficiently broken. Therefore, even if the target of lift-off is the optical device wafer 10 having a large diameter of 4 inches, damage to the optical device layer 12 due to the separation of the epitaxy substrate 11 can be avoided, and the epitaxy substrate 11 can be quickly and smoothly removed from the optical device layer 12. Can be peeled off. Further, since the ultrasonic horn 40 has the above-described shape, the ultrasonic wave can be sufficiently propagated from the back surface 11d of the outer peripheral edge 11c of the epitaxy substrate 11 to the epitaxy substrate 11, and the efficiency of vibration propagation is further improved. It is possible to easily transfer the layer 12 to the transfer substrate 20.

なお、本発明に係るリフトオフ方法は上記実施形態に限定されるものではなく、また、添付図面に図示されている超音波ホーン４０の大きさや形状等についても、これに限定されず、本発明の効果を発揮できる範囲内で適宜変更可能である。   The lift-off method according to the present invention is not limited to the above embodiment, and the size and shape of the ultrasonic horn 40 shown in the attached drawings are not limited to this, and the present invention is not limited thereto. It can be appropriately changed within a range where the effect can be exhibited.

１０：光デバイスウエーハ １１：エピタキシー基板 １１ａ：エピタキシー基板の表面 １１ｂ：エピタキシー基板の裏面 １１ｃ：エピタキシー基板の外周縁
１１ｄ：外周縁の裏面 １１ｅ：エピタキシー基板の外側面
１２：光デバイス層
１２Ａ：ｎ型窒化ガリウム半導体層 １２Ｂ：ｐ型窒化ガリウム半導体層
１２ａ：光デバイス層の表面
１３：バッファ層 １５：分割予定ライン １６：光デバイス
１９：剥離層 １９ａ：Ｎ２ガス層
２０：移設基板
２０ａ：移設基板の底面 ２０ｂ：移設基板の表面 ２０ｃ：移設基板のはみ出し部
２１：接合層 ２５：複合基板
３０：レーザー加工装置 ３１：チャックテーブル ３２：レーザー光線照射手段
３２ａ：レーザー光線発振手段 ３２ｂ：ミラー ３２ｃ：集光レンズ ３３：回転手段
４０：超音波ホーン ４００：天板 ４００ａ：裏面接触面
４０１：側板 ４０１ａ：外側面囲繞面 ４０１ｂ：側板の下面 ４０２：凸部
４０３：超音波発振器 ４０４：移動手段
Ｌ１：長さ
４４：保持テーブル ４５：移動手段 ４６：吸引パッド ４７：吸引源 DESCRIPTION OF SYMBOLS 10: Optical device wafer 11: Epitaxy board | substrate 11a: The surface of an epitaxy board | substrate 11b: The back surface of an epitaxy board | substrate 11c: The outer periphery of an epitaxy board | substrate
11d: Back surface of outer peripheral edge 11e: Outer surface of epitaxy substrate 12: Optical device layer
12A: n-type gallium nitride semiconductor layer 12B: p-type gallium nitride semiconductor layer
12a: Surface of optical device layer 13: Buffer layer 15: Planned division line 16: Optical device
19: Release layer 19a: N 2 gas layer 20: Transfer substrate
20a: bottom surface of the transfer substrate 20b: surface of the transfer substrate 20c: protruding portion of the transfer substrate
21: Bonding layer 25: Composite substrate 30: Laser processing device 31: Chuck table 32: Laser beam irradiation means
32a: Laser beam oscillation means 32b: Mirror 32c: Condensing lens 33: Rotating means 40: Ultrasonic horn 400: Top plate 400a: Back contact surface
401: side plate 401a: outer surface surrounding surface 401b: lower surface of side plate 402: convex portion
403: Ultrasonic oscillator 404: Moving means
L1: Length 44: Holding table 45: Moving means 46: Suction pad 47: Suction source

Claims (2)

エピタキシー基板の表面にGaNからなるバッファ層を介して光デバイス層が積層された光デバイスウエーハの光デバイス層を移設基板に移し替えるリフトオフ方法であって、
該光デバイスウエーハの光デバイス層の表面に接合層を介して移設基板を接合する移設基板接合工程と、
該移設基板が接合された光デバイスウエーハのエピタキシー基板の裏面側からエピタキシー基板に対しては透過性を有しバッファ層に対しては吸収性を有する波長のパルスレーザー光線を照射し、エピタキシー基板とバッファ層との境界面に剥離層を形成する剥離層形成工程と、
該剥離層形成工程の後、該エピタキシー基板の外周縁を囲繞する形状を有し超音波振動を発振する超音波ホーンを少なくとも該外周縁の裏面に接触させて該エピタキシー基板を振動させ、該移設基板から該エピタキシー基板を剥離し、該光デバイス層を該移設基板に移設する光デバイス層移設工程と、を含むリフトオフ方法。 A lift-off method for transferring an optical device layer of an optical device wafer in which an optical device layer is laminated on a surface of an epitaxy substrate via a buffer layer made of GaN to a transfer substrate,
A transfer substrate bonding step of bonding a transfer substrate to the surface of the optical device layer of the optical device wafer via a bonding layer;
From the back side of the epitaxy substrate of the optical device wafer to which the transfer substrate is bonded, the epitaxy substrate is irradiated with a pulsed laser beam having a wavelength that is transparent and the buffer layer is absorptive. A release layer forming step of forming a release layer on the interface with the layer;
After the release layer forming step, an ultrasonic horn having a shape surrounding the outer periphery of the epitaxy substrate and oscillating ultrasonic vibration is brought into contact with at least the back surface of the outer periphery to vibrate the epitaxy substrate, and the transfer An optical device layer transfer step of peeling the epitaxy substrate from the substrate and transferring the optical device layer to the transfer substrate. 請求項１記載のリフトオフ方法に使用する超音波ホーンであって、
エピタキシー基板の外周に沿った円弧形状に形成され、該エピタキシー基板の外周縁の裏面に接触する裏面接触面と、エピタキシー基板の外側面を囲繞して位置決めする外側面囲繞面とを備える超音波ホーン。 An ultrasonic horn for use in the lift-off method according to claim 1,
An ultrasonic horn that is formed in an arc shape along the outer periphery of the epitaxy substrate and includes a back surface contact surface that contacts the back surface of the outer peripheral edge of the epitaxy substrate and an outer surface surrounding surface that surrounds and positions the outer surface of the epitaxy substrate .
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