JP2020191432A - Relocation method - Google Patents

Abstract

To provide a relocation method that suppresses a decrease in the transfer rate of an optical device to a relocation member during laser lift-off.SOLUTION: A relocation method of an optical device layer includes a relocation member joining step ST11, a liquid filling step ST12, a buffer layer breaking step ST13, and an optical device layer transfer step ST14. In the relocation member joining step ST11, an optical device wafer and a relocation member are joined so as to have a gap between optical device layers divided into the chip sizes of an optical device wafer. In the liquid filling step ST12, after the relocation member joining step ST11, the gap is filled with a liquid to increase the surface tension between an epitaxy substrate and the relocation member.SELECTED DRAWING: Figure 3

Description

The present invention relates to a relocation method for relocating an optical device layer.

An optical device such as an LED (Light Emitting Diode) is formed, for example, by epitaxially growing an n-type semiconductor layer and a p-type semiconductor layer constituting a pn junction on the surface of a sapphire substrate. A peeling technique called laser lift-off, in which the optical device layer thus formed is peeled from the sapphire substrate and transferred to the transfer member, is known (see Patent Documents 1 and 2). In recent years, a technique for manufacturing an extremely small size LED called a micro LED has also been developed, and a technique for manufacturing a large number of LEDs by dividing a semiconductor layer by etching is known (see Patent Document 3).

Japanese Unexamined Patent Publication No. 2004-072052 Japanese Unexamined Patent Publication No. 2016-021464 JP-A-2018-107421

The LED may be peeled off from the sapphire substrate, transferred to the transfer member, and then further transferred to a different mounting substrate. Therefore, in consideration of the ease of transferring the LED from the relocation member to the mounting substrate, the sapphire substrate and the relocation member are joined with reduced joint strength. That is, the adhesive force between the sapphire substrate and the relocation member becomes too large, for example, the adhesive layer is controlled so as not to be completely filled in the gap between the LEDs, or the adhesive layer is joined by a metal microtube. It is joined so that there is no. However, as a result, there is a problem that the holding force of the LED on the relocation member side is lowered and the transfer rate of the LED to the relocation member is lowered.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a transfer method for suppressing a decrease in the transfer rate of an optical device to a transfer member at the time of laser lift-off.

In order to solve the above-mentioned problems and achieve the object, in the relocation method of relocating the optical device layer of the present invention, the optical device layer divided into chip sizes is laminated on the surface of the epitaxy substrate via the buffer layer. A method of relocating an optical device layer of an optical device wafer, wherein the light of the optical device wafer has a gap between the optical device layer divided into chip sizes of the optical device wafer and the optical device layer. A transfer member joining step for joining the device layer side and the transfer member, and a liquid filling step for filling the voids with a liquid to increase the surface tension between the epitaxy substrate and the transfer member after the transfer member joining step. After the liquid filling step, a pulse laser having a wavelength that is transparent to the epitaxy substrate and absorbable to the buffer layer from the back surface side of the epitaxy substrate of the optical device wafer to which the transfer member is bonded. After the buffer layer destruction step of irradiating the buffer layer with a beam to destroy the buffer layer and the buffer layer destruction step, the epitaxy substrate is separated from the optical device layer and the optical device laminated on the epitaxy substrate is separated. It comprises an optical device layer transfer step of transferring the layer to the transfer member.

The liquid to be filled in the voids in the liquid filling step may be water.

According to the present invention, it is possible to suppress a decrease in the transfer rate of the optical device to the transfer member when the laser is lifted off.

FIG. 1 is a perspective view of an optical device wafer including a relocation target of the relocation method according to the embodiment. FIG. 2 is a cross-sectional view of the optical device wafer of FIG. FIG. 3 is a flowchart showing a relocation method according to the embodiment. FIG. 4 is a cross-sectional view showing a state of the transfer member joining step of FIG. FIG. 5 is a cross-sectional view showing a state after FIG. 4 of the transfer member joining step of FIG. FIG. 6 is a cross-sectional view showing one state of the liquid filling step of FIG. FIG. 7 is a cross-sectional view showing a state of the liquid filling step of FIG. 3 after FIG. FIG. 8 is a cross-sectional view showing an example of the buffer layer destruction step of FIG. FIG. 9 is a cross-sectional view showing an example of the optical device layer transfer step of FIG. FIG. 10 is a cross-sectional view showing one state of the transfer member joining step according to the modified example.

An embodiment (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Further, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions or changes of the configuration can be made without departing from the gist of the present invention.

[Embodiment]
The relocation method according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an optical device wafer 1 including a relocation target of the relocation method according to the embodiment. FIG. 2 is a cross-sectional view of the optical device wafer 1 of FIG. Note that FIGS. 1 and 2 schematically show the optical device layer 5 and the like larger than the actual one with respect to the optical device wafer 1 for the purpose of explaining the present embodiment, and the same applies to the subsequent drawings. As shown in FIG. 2, the optical device wafer 1 includes an epitaxy substrate 2 and an optical device layer 5 laminated on the surface 3 side of the epitaxy substrate 2 via a buffer layer 4.

In the present embodiment, the epitaxy substrate 2 is a sapphire substrate having a disk shape having a diameter of about 6 inches (about 150 mm) and a thickness of about 1.2 mm to 1.5 mm. In the present embodiment, the optical device layer 5 is an n-type gallium nitride semiconductor layer 5-1 and a p-type formed on the surface 3 of the epitaxy substrate 2 by an epitaxial growth method to a total thickness of about 6 μm, as shown in FIG. It is a gallium nitride semiconductor layer 5-2, and is used as, for example, an LED (Light Emitting Diode). In the embodiment, the buffer layer 4 is formed between the surface 3 of the epitaxy substrate 2 and the p-type gallium nitride semiconductor layer 5-2 of the optical device layer 5 when the optical device layer 5 is laminated on the epitaxy substrate 2. It is a gallium nitride (GaN) layer having a thickness of about 1 μm.

In the present embodiment, as shown in FIG. 1, the optical device layer 5 is divided into chip sizes and laminated in a plurality of regions partitioned by a plurality of streets 6 intersecting in a grid pattern to form an optical device 7. doing. The distance between the optical device layers 5, that is, the distance between the optical devices 7 is the same as the width of the street 6, and is about 5 μm in the present embodiment. Further, the size of the optical device layer 5, that is, the size of the optical device 7, is the same as the distance between the streets 6, and in the present embodiment, it is about 10 μm to 20 μm. That is, in the present embodiment, the optical device layer 5 is formed with about 2 million optical devices 7 used as LEDs on the epitaxy substrate 2 having a diameter of 2 inches. The epitaxy substrate 2 may be a CMOS (Complementary Metal Oxide Semiconductor) wafer. The size of the chip of the CMOS device is, for example, about 8 mm to 11 mm, and a plurality of optical device layers 5 are formed on the CMOS device.

Next, the relocation method according to the embodiment will be described. FIG. 3 is a flowchart showing a relocation method according to the embodiment. The relocation method is a relocation method in which the optical device layer 5 of the optical device wafer 1 is relocated, and as shown in FIG. 3, the relocation member joining step ST11, the liquid filling step ST12, the buffer layer breaking step ST13, and the light The device layer transfer step ST14 is included.

FIG. 4 is a cross-sectional view showing a state of the transfer member joining step ST11 of FIG. FIG. 5 is a cross-sectional view showing a state after FIG. 4 of the transfer member joining step ST11 of FIG. As shown in FIGS. 4 and 5, the transfer member joining step ST11 has an optical device wafer so as to have a gap 15 between the optical device layer 5 and the optical device layer 5 divided into the chip sizes of the optical device wafer 1. This is a step of joining the optical device layer 5 side of 1 and the transfer member 11.

Specifically, in the transfer member joining step ST11, specifically, as shown in FIG. 4, first, a transfer substrate having the same size as the epitaxy substrate 2 is prepared as the transfer member 11, and a transfer substrate having the same size as the epitaxy substrate 2 is formed on one surface of the transfer member 11. An adhesive 12 having a volume less than the total volume of the street 6 corresponding to the gap between the optical device layer 5 and the optical device layer 5 is applied to form an adhesive layer.

In the present embodiment, the transfer member 11 is preferably a glass substrate having a thickness of about 2.0 mm, which is about the same as that of the epitaxy substrate 2, but the present invention is not limited to this, and a predetermined adhesion is performed. A substrate made of various other materials such as a metal substrate can be used as long as it can be adhered to the agent 12.

In the transfer member joining step ST11, next, the optical device layer 5 laminated on the epitaxy substrate 2 and the adhesive 12 applied to the transfer member 11 are brought into close contact with each other. In the transfer member joining step ST11, further, from the back surface 8 side, which is the surface opposite to the front surface 3 of the epitaxy substrate 2, toward the transfer member 11, or the side on which the adhesive 12 of the transfer member 11 is applied. By pressing from the opposite surface toward the epitaxy substrate 2, the adhesive 12 is deformed along the optical device layer 5 as shown in FIG. 5, and a part of the optical device layer 5 is formed by the adhesive 12. Immerse yourself in it. In this way, in the transfer member joining step ST11, the optical device wafer is provided with the adhesive 12 so as to have a gap 15 between the optical device layer 5 and the optical device layer 5 divided into the chip sizes of the optical device wafer 1. The optical device layer 5 side of No. 1 and the transfer member 11 are joined.

Here, in the transfer member joining step ST11, it is preferable that both the pressing force and the temperature at the time of bonding are controlled so that the gap 15 between the optical device layers 5 is not filled with the adhesive 12. In the transfer member joining step ST11, joining with the adhesive 12 is adopted in the present embodiment, but the present invention is not limited to this, and other joining methods may be adopted.

FIG. 6 is a cross-sectional view showing a state of the liquid filling step ST12 of FIG. FIG. 7 is a cross-sectional view showing a state of the liquid filling step ST12 of FIG. 3 after FIG. As shown in FIGS. 6 and 7, the liquid filling step ST12 is a step of filling the gap 15 with the liquid 17 to increase the surface tension between the epitaxy substrate 2 and the relocation member 11 after the relocation member joining step ST11. ..

In the liquid filling step ST12, specifically, as shown in FIG. 6, a predetermined liquid is directed from the radial outside of the optical device wafer 1 toward the void 15 formed in the transfer member joining step ST11 by the liquid injection nozzle 16. 17 is injected and supplied. Here, the predetermined liquid 17 does not cause a chemical reaction such as dissolution or polymerization with respect to any of the surface 3 of the epitaxy substrate 2 around the void 15 and the optical device layer 5 and the adhesive 12. Those that get wet with a predetermined wettability with respect to both the surface 3 of the epitaxy substrate 2 and the adhesive 12 that form the voids 15 in the thickness direction are preferably adopted. In the liquid filling step ST12, for example, water (distilled water, pure water) is preferably used as the predetermined liquid 17.

The size of the gap 15 formed in the transfer member joining step ST11 in the thickness direction is about several hundred μm to several mm. As described above, since the size of the gap 15 in the thickness direction is sufficiently small, in the liquid filling step ST12, the liquid 17 injected and supplied toward the gap 15 invades the inside of the gap 15 due to the capillary phenomenon. I will go. Therefore, in the liquid filling step ST12, as shown in FIG. 7, the gap 15 is sufficiently filled with the predetermined liquid 17 to increase the surface tension between the epitaxy substrate 2 and the transfer member 11, that is, the gap 15 is filled. Due to the surface tension of the predetermined liquid 17, the surface 3 on the epitaxy substrate 2 side and the adhesive 12 applied on the transfer member 11 side are brought into close contact with each other by attractive force (adhesive force).

In the liquid filling step ST12 of the present invention, a predetermined liquid 17 may be injected and supplied toward the gap 15 by the liquid injection nozzle 16 while removing the gas inside the gap 15 by the gas removal nozzle. Further, in the liquid filling step ST12 of the present invention, the liquid 17 stored in the liquid tank is immersed in the joint body between the optical device layer 5 side of the optical device wafer 1 in which the voids 15 are formed and the transfer member 11. The liquid 17 may be immersed in the void 15 and supplied.

FIG. 8 is a cross-sectional view showing an example of the buffer layer destruction step ST13 of FIG. As shown in FIG. 8, the buffer layer breaking step ST13 is transparent to the epitaxy substrate 2 from the back surface 8 side of the epitaxy substrate 2 of the optical device wafer 1 to which the transfer member 11 is bonded after the liquid filling step ST12. This is a step of irradiating the buffer layer 4 with a pulsed laser beam 34 having a wavelength having absorbency to the buffer layer 4 to destroy the buffer layer 4.

Specifically, in the buffer layer destruction step ST13, specifically, as shown in FIG. 8, first, in the liquid filling step ST12, the joint body of the optical device wafer 1 in which the gap 15 is filled with the predetermined liquid 17 and the transfer member 11 The surface on the transfer member 11 side is suction-held by the holding surface 21 of the chuck table 20 connected to a vacuum source (not shown).

In the buffer layer destruction step ST13, the laser beam irradiation means 30 then applies the laser beam irradiation means 30 to the epitaxy substrate 2 from the back surface 8 side of the epitaxy substrate 2 of the junction between the optical device wafer 1 held by the chuck table 20 and the transfer member 11. Destroys the buffer layer 4 by irradiating the buffer layer 4 with a pulsed laser beam 34 having a wavelength that is transparent and absorbs the buffer layer 4. In the buffer layer destruction step ST13, in the present embodiment, the entire surface of the epitaxy substrate 2 is irradiated with the pulsed laser beam 34, but the present invention is not limited to this, and the buffer layer 4 of the epitaxy substrate 2 Irradiation of the pulsed laser beam 34 may be performed only on the formed position.

Here, as shown in FIG. 8, the laser beam irradiating means 30 oscillates the pulse laser beam 34 having the above-mentioned predetermined wavelength by the laser beam oscillating means 31, and the pulse laser beam 34 from the laser beam oscillating means 31 by the optical mirror 32. The direction is changed in the direction orthogonal to the back surface 8 of the epitaxy substrate 2 of the joined body held by the chuck table 20, and the pulsed laser beam 34 from the optical mirror 32 is focused by the condenser lens 33 to spot the pulsed laser beam 34. By adjusting the diameter and defocus, the irradiation conditions of the pulsed laser beam 34 in the buffer layer destruction step ST13 are adjusted.

In the buffer layer destruction step ST13, for example, an ultraviolet laser beam having a repetition frequency of 50 kHz or more and 200 kHz or less and an average output of 0.1 W or more and 2.0 W or less is used as the pulse laser beam 34, and the spot diameter is 10 μm or more and 50 μm or less. Then, the defocus is adjusted to about 1.0 mm, the overlap rate is adjusted to 50%, and the destructive treatment of the buffer layer 4 is executed.

FIG. 9 is a cross-sectional view showing an example of the optical device layer transfer step ST14 of FIG. The optical device layer transfer step ST14 is a step of peeling the epitaxy substrate 2 from the optical device layer 5 and transferring the optical device layer 5 laminated on the epitaxy substrate 2 to the transfer member 11 after the buffer layer destruction step ST13. is there.

Specifically, in the optical device layer transfer step ST14, an ultrasonic vibration means (not shown) was arranged from the back surface 8 side of the epitaxy substrate 2 of the bonded body in which the buffer layer 4 was destroyed in the buffer layer destruction step ST13. By applying ultrasonic vibration with a horn, the epitaxy substrate 2 is peeled from the optical device layer 5 and the optical device layer 5 is transferred to the transfer member 11 starting from the destroyed buffer layer 4.

In the optical device layer transfer step ST14, as shown in FIG. 9, when the epitaxy substrate 2 peeled from the optical device layer 5 is separated from the optical device layer 5, the transfer member 11, and the adhesive 12, the gap 15 is filled. Liquid 17 flows down and is removed. As a result, in the optical device layer transfer step ST14, the optical device layer transfer substrate 10 in which the optical device layer 5 (optical device 7) transferred to the transfer member 11 protrudes from the adhesive 12 is formed.

The transfer method according to the embodiment further includes a drying step of drying the optical device layer 5 (optical device 7) wet with a predetermined liquid 17 after peeling the epitaxy substrate 2 after the optical device layer transfer step ST14. Is preferable. In the drying step, drying with warm air toward the optical device layer 5 (optical device 7) and drying with infrared rays are performed.

The relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment is the transfer member joining step ST11 between the optical device layer 5 and the optical device layer 5 divided into the chip sizes of the optical device wafer 1. The optical device wafer 1 and the transfer member 11 are joined so as to have a gap 15, and in the liquid filling step ST12, the gap 15 is filled with the liquid 17 to increase the surface tension between the epitaxy substrate 2 and the transfer member 11. Therefore, the relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment preferably uses the liquid 17 for laser lift-off even when the bonding between the optical device wafer 1 and the relocation member 11 is relatively weak. It is possible to increase the adhesion between the epitaxy substrate 2 and the transfer member 11 at the time of the operation. As a result, the relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment suppresses a decrease in the transfer rate of the optical device 7 (optical device layer 5) to the relocation member 11 when the laser is lifted off. This has the effect of improving the productivity of the optical device 7 (optical device layer 5).

Further, in the relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment, in the optical device layer transfer step ST14, the close contact state between the epitaxy substrate 2 and the relocation member 11 is released, and the liquid 17 is released. When removed, the bond between the optical device layer 5 and the transfer member 11 is relatively weak, so that the optical device 7 (optical device layer 5) protruding from the adhesive 12 is preferably mounted on a mounting substrate or the like. It has the effect of being able to relocate to.

Further, in the relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment, the liquid 17 to be filled in the void 15 in the liquid filling step ST12 is water. Therefore, the method of relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment is the liquid filling step ST12, in which the surface 3 of the epitaxy substrate 2, the optical device layer 5, and the adhesive 12 are all relocated. Therefore, it is possible to form a state of close contact with both the surface 3 of the epitaxy substrate 2 and the adhesive 12 without causing a chemical reaction such as dissolution or polymerization. That is, the method of relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment is when the water of the liquid 17 does not affect the quality of the optical device 7 (optical device layer 5) and the laser lifts off. It is possible to suitably suppress the decrease in the transfer rate with respect to the relocation of the light device 7 and to contribute to the improvement of the productivity of the optical device 7 (optical device layer 5).

[Modification example]
The relocation method according to the modified example of the embodiment of the present invention will be described. FIG. 10 is a cross-sectional view showing one state of the transfer member joining step ST11 according to the modified example. In FIG. 10, the same parts as those in the embodiment are designated by the same reference numerals, and the description thereof will be omitted. The relocation method according to the modified example is the same as that of the embodiment except that the relocation member joining step ST11 is different.

In the transfer member joining step ST11 according to the modified example, instead of joining the optical device layer 5 side of the optical device wafer 1 and the transfer member 11 with the adhesive 12, in the transfer member joining step ST11 according to the embodiment, FIG. As shown in FIG. 10, the bonding layer 52 joins the optical device layer 5 side of the optical device wafer 1 and the transfer member 11.

Specifically, in the transfer member joining step ST11 according to the modified example, first, as shown in FIG. 10, a joining metal layer 53 forming a joining layer 52 is formed on a part of the optical device wafer 1 on the optical device layer 5 side. To form. Indium (In) is used as a suitable metal material for the bonded metal layer 53 in the modified example, but the present invention is not limited to this, and AuSn (gold tin), gold (Au), platinum (Pt). , Chromium (Cr), Palladium (Pd), etc. can be used. Further, in the bonded metal layer 122, one type or two or more types of the above-mentioned metal materials can be used in combination.

Next, in the transfer member joining step ST11 according to the modified example, as shown in FIG. 10, a metal tube 54 constituting the joining layer 52 is arranged between the joining metal layer 53 and the moving member 11 along the thickness direction. By doing so, the bonded metal layer 53 and the metal tube 54 form a weak-strength bond between the optical device layer 5 side of the optical device wafer 1 and the transfer member 11, and are divided into chip sizes of the optical device wafer 1. A gap 51 is formed between the optical device layer 5 and the optical device layer 5.

In the modified example, a copper (Cu) substrate having a thickness of 1 mm is used as a suitable substrate for the transfer member 11, but the present invention is not limited to this, and the molybdenum (Mo) substrate, A silicon (Si) substrate, etc. can be used. Further, as the transfer member 11, in the modified example, a substrate obtained by combining one type or two or more types of the above-mentioned materials can be used. Further, in the present modification, the metal tube 54 having a diameter on the order of several μm to several nm, that is, a metal microtube or a metal nanotube can be preferably used.

The relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the modification is the relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment, in which the gap 51 and the bonding are performed in the transfer member joining step ST11. Since it is modified so as to form the layer 52, it has the same effect as the relocation method for relocating the optical device layer 5 of the optical device wafer 1 according to the embodiment.

The present invention is not limited to the above embodiment. That is, it can be modified in various ways without departing from the gist of the present invention.

1 Optical device wafer 2 Epitaxy substrate 3 Front surface 4 Buffer layer 5 Optical device layer 7 Optical device 8 Back surface 11 Relocation member 12 Adhesive 15, 51 Void 16 Liquid injection nozzle 17 Liquid 52 Joint layer 53 Joint metal layer 54 Metal tube

Claims (2)

This is a relocation method in which an optical device layer divided into chip sizes is laminated on the surface of an epitaxy substrate via a buffer layer, and the optical device layer of the optical device wafer is relocated.
A transfer member joining step of joining the optical device layer side of the optical device wafer and the transfer member so as to have a gap between the optical device layer and the optical device layer divided into chip sizes of the optical device wafer.
After the transfer member joining step, a liquid filling step of filling the gap with a liquid to increase the surface tension between the epitaxy substrate and the transfer member,
After the liquid filling step, a pulsed laser beam having a wavelength that is transparent to the epitaxy substrate and absorbable to the buffer layer from the back surface side of the epitaxy substrate of the optical device wafer to which the transfer member is bonded. To the buffer layer and destroy the buffer layer.
After the buffer layer destruction step, an optical device layer transfer step of peeling the epitaxy substrate from the optical device layer and transferring the optical device layer laminated on the epitaxy substrate to the transfer member.
A relocation method for relocating an optical device layer, which comprises. The transfer method for relocating the optical device layer according to claim 1, wherein the liquid to be filled in the voids in the liquid filling step is water.

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