TWI849151B - Optical device relocation method - Google Patents

Abstract

[Topic] Provide a method for transferring an optical device that can reliably transfer an optical device from a substrate to a sheet. [Solution] A method for transferring an optical device is to transfer a plurality of optical devices from an optical device wafer having a plurality of optical devices, wherein the optical devices are formed on the front side of the substrate via a buffer layer, and the method for transferring the optical device comprises the following steps: a sheet attaching step, attaching the sheet to the front side of the substrate to cover the plurality of optical devices, and a buffer layer destroying step, after the sheet attaching step, irradiating a pulsed laser beam that is penetrable to the substrate and absorbent to the buffer layer from the back side of the substrate to destroy the buffer layer; and an optical device transferring step, after the buffer layer destroying step, peeling the sheet from the substrate and transferring the plurality of optical devices to the sheet.

Description

Optical device relocation method

The present invention relates to a method for transferring a plurality of optical devices from an optical device wafer.

Optical devices represented by LED (Light Emitting Diode) can be applied to various fields such as display, lighting, automobile, medical, etc. For example, LED is formed by epitaxially growing an n-type semiconductor film and a p-type semiconductor film forming a pn junction on the front side of a substrate composed of sapphire or SiC.

After the optical device formed on the substrate is separated from the substrate, it is assembled to another assembly substrate or the like. As a method of transferring the optical device in this way, there is a known technique called laser lift-off. In this laser lift-off, the optical device is first formed on the front side of the substrate with a buffer layer in between. Then, a laser beam is irradiated from the back side of the substrate to deteriorate the buffer layer, thereby weakening the bond between the substrate and the optical device. After that, the optical device is separated from the substrate and transferred to the substrate of the transfer destination (transfer substrate) (see patent documents 1 and 2).

In recent years, a manufacturing technology for a small-sized LED called a micro-LED has also been developed. For example, a micro-LED is formed by forming a layer (optical device layer) including various thin films (semiconductor films, etc.) constituting the LED on a substrate, and then dividing the optical device layer into a plurality of fine chips by etching (see Patent Document 3). Prior Art Documents Patent Documents

Patent document 1: Japanese Patent Publication No. 2004-72052 Patent document 2: Japanese Patent Publication No. 2016-21464 Patent document 3: Japanese Patent Publication No. 2018-107421

Invention Problems to be Solved

When assembling the optical device of the micro-LED described above to the transfer substrate, the optical devices that have been separated into individual pieces are separated from the substrate and transferred to the transfer substrate. Specifically, first, after the optical device layer formed on the front side of the substrate is divided into a plurality of micro-optical devices, a transfer sheet is attached to the front side of the substrate. This sheet is attached so as to contact the upper surface of all the optical devices formed on the substrate.

After a treatment is performed to weaken the bonding between the substrate and the optical device (such as deterioration of the buffer layer), the sheet is peeled off from the substrate. As a result, a plurality of optical devices can be separated from the substrate and transferred to the sheet. Then, the sheet with the transferred optical devices is attached to the transfer substrate, and the optical devices are bonded to the connection electrodes formed on the transfer substrate. In this way, the optical devices are transferred to the transfer substrate.

However, even if the above-mentioned optical device transfer steps are implemented, some optical devices may still remain on the substrate and not be transferred to the sheet. It is considered that this phenomenon occurs under the following circumstances: when the sheet is attached to the substrate, the sheet does not properly fit the plurality of optical devices, resulting in insufficient contact between the sheet and the optical devices. This is caused by, for example, unexpected tilt of the holding table that holds the substrate when the sheet is attached, or deviation in the thickness of the substrate or the sheet, and some optical devices are not properly connected to the sheet. In this case, even if the sheet is peeled off from the substrate, some optical devices will not follow the tape but remain on the substrate.

If a part of the optical device is not properly transferred to the sheet, it becomes necessary to redo the transfer step or to pick up the optical device remaining on the substrate, etc. As a result, the efficiency of the optical device transfer operation is reduced.

This invention is made in view of the above-mentioned problem, and its purpose is to provide a method for transferring optical devices from a substrate to a sheet material. Means for solving the problem

According to one aspect of the present invention, a method for transferring an optical device can be provided, which is to transfer a plurality of optical devices from an optical device wafer having a plurality of optical devices, wherein the aforementioned optical devices are formed on the front side of a substrate via a buffer layer, and the aforementioned method for transferring the optical device comprises the following steps: A sheet attaching step, attaching a sheet to the front side of the substrate to cover the plurality of optical devices, and conforming to The gap between the optical devices; a buffer layer destroying step, after the sheet attaching step is performed, a pulsed laser beam having penetrability to the substrate and having absorption to the buffer layer is irradiated from the back side of the substrate to destroy the buffer layer; and an optical device transferring step, after the buffer layer destroying step is performed, the sheet is peeled off from the substrate and a plurality of the optical devices are transferred to the sheet.

Furthermore, it is preferred that, in the sheet attaching step, the sheet is attached to the substrate by heat pressing. Also, it is preferred that the sheet has a resin layer and an annular adhesive layer corresponding to the area of the substrate where the optical device is not formed, and in the sheet attaching step, the sheet is attached to the substrate in a manner that the adhesive layer does not contact the optical device and the resin layer conforms to the gap between the optical devices. Effect of the invention

In one aspect of the optical device transfer method of the present invention, the tape is attached to conform to the gap between the optical devices formed on the substrate. In this way, a plurality of optical devices can be firmly fixed to the sheet, and when the sheet is peeled off from the substrate, the plurality of optical devices can be surely separated from the substrate. In this way, the optical device can be surely transferred from the substrate to the sheet.

The form used to implement the invention

The present embodiment will be described below with reference to the attached drawings. First, a configuration example of an optical device wafer having a plurality of optical devices that can be transferred by the optical device transfer method of the present embodiment will be described. FIG1 is a perspective view showing an optical device wafer 11.

The optical device wafer 11 has a disc-shaped substrate 13, and the substrate 13 has a front surface 13a and a back surface 13b. The substrate 13 is divided into a plurality of regions by arranging a plurality of scribe lines 15 arranged in a grid shape, and an optical device 17 is formed on the front surface 13a side of each of the plurality of regions. In the following, as an example, the optical device 17 is described as an LED (Light Emitting Diode). However, there is no limitation on the type, quantity, shape, structure, size, arrangement, etc. of the optical device 17.

2(A) is a cross-sectional view showing the manufacturing steps of the optical device wafer 11. In the manufacturing steps of the optical device wafer 11, first, the optical device layer 23 is formed on the front surface 13a side of the substrate 13 with the buffer layer 21 interposed therebetween.

The optical device layer 23 is a layer including various films (semiconductor film, conductive film, insulating film, etc.) constituting the optical device 17 (see FIG. 1 ). For example, the optical device layer 23 includes a p-type semiconductor film 25 composed of a p-type semiconductor with holes as the majority carriers, and an n-type semiconductor film 27 composed of an n-type semiconductor with electrons as the majority carriers. However, the structure of the optical device layer 23 can be appropriately selected according to the structure or function of the optical device 17 finally formed on the substrate 13.

The buffer layer 21 is a layer that suppresses the generation of defects caused by lattice mismatch between the substrate 13 and the optical device layer 23. The material of the buffer layer 21 can be appropriately selected according to the lattice constants of the front surface 13a side of the substrate 13 and the lower surface side of the optical device layer 23 (the lower surface side of the p-type semiconductor film 25). In addition, the buffer layer 21 can be composed of a single layer of film or a plurality of layers of films that have been stacked.

The buffer layer 21, the p-type semiconductor film 25, and the n-type semiconductor film 27 are formed on the substrate 13 by, for example, epitaxial growth. In this case, an epitaxial substrate on which a desired thin film can be epitaxially grown is used as the substrate 13.

For example, a single crystal substrate made of sapphire, SiC, etc. can be used as the substrate 13, and a buffer layer 21 made of GaN, a p-type semiconductor film 25 made of p-type GaN, and an n-type semiconductor film 27 made of n-type GaN are sequentially formed by epitaxial growth on the substrate 13. Furthermore, in the formation of each film, a MOCVD (Metal Organic Chemical Vapor Deposition) method or an MBE (Molecular Beam Epitaxy) method can be used.

Next, the buffer layer 21 and the optical device layer 23 are divided along the dicing street 15. The buffer layer 21 and the optical device layer 23 are divided by, for example, etching. Specifically, first, an etching mask is formed on the optical device layer 23. The mask is patterned so that the optical device layer 23 is exposed along the dicing street 15.

Thereafter, an etching liquid is supplied to the buffer layer 21 and the optical device layer 23 through a mask, and the buffer layer 21 and the optical device layer 23 are etched. Thus, the optical device layer 23 can be divided into a plurality of optical devices 17 along the dicing streets 15.

FIG2(B) is a cross-sectional view of the optical device wafer 11 showing a state where the optical device layer 23 has been divided into a plurality of optical devices 17. If the optical device layer 23 is divided along the dicing line 15, a plurality of optical devices 17 can be formed, each of which has a p-type semiconductor film 25a formed by individualizing the p-type semiconductor film 25 and an n-type semiconductor film 27a formed by individualizing the n-type semiconductor film 27. The p-type semiconductor film 25a and the n-type semiconductor film 27a can form a pn junction, and the optical device 17 emits light due to the recombination of holes and electrons.

Furthermore, a buffer layer 21a formed by individualizing the buffer layer 21 by etching is disposed between the substrate 13 and the optical device 17. That is, the optical device 17 is disposed on the substrate 13 with the buffer layer 21a interposed therebetween. The buffer layer 21a is equivalent to a layer destroyed by irradiation with a laser beam in a buffer layer destruction step described later, and functions as a separation layer for separating the substrate 13 and the optical device 17.

As described above, if etching is used for segmenting the optical device layer 23, the optical device layer 23 can be finely processed, and an extremely small-sized optical device 17 such as a micro-luminescent diode can be formed. Furthermore, when the etching of the buffer layer 21 and the optical device layer 23 is completed, the mask formed on the optical device layer 23 can be removed.

Furthermore, although FIG. 2(B) shows an optical device 17 including a p-type semiconductor film 25a and an n-type semiconductor film 27a, the structure of the optical device 17 is not limited thereto. For example, the optical device 17 may also be provided with a light-emitting layer between the p-type semiconductor film 25a and the n-type semiconductor film 27a. In this case, recombination of holes and electrons occurs in the light-emitting layer, and light is emitted from the light-emitting layer. In addition, an electrode (connecting electrode) for connecting the optical device 17 to other electrodes or terminals may be formed on the upper surface or lower surface of the optical device 17.

After being separated from the substrate 13, the plurality of optical devices 17 formed on the substrate 13 are assembled to other assembly substrates, etc. In the relocation of the optical devices 17, for example, a sheet for relocation (transfer) can be used. The following describes a specific example of a method for relocating the optical devices 17 using a sheet.

In the optical device relocation method of this embodiment, first, a sheet is attached to the front surface 13a side of the substrate 13 on which the plurality of optical devices 17 are formed so as to cover the plurality of optical devices 17 (sheet attaching step). FIG. 3(A) is a cross-sectional view showing a state where a sheet (tape, film) 31 for transfer (transfer) is attached to the substrate 13. The following describes, as an example, a state where the sheet 31 is attached to the substrate 13 by heat pressing.

In the sheet attachment step, the optical device wafer 11 is first held by the holding table 10. For example, the holding table 10 is formed to be circular in a planar view corresponding to the shape of the optical device wafer 11, and the upper surface of the holding table 10 constitutes a holding surface 10a for holding the optical device wafer 11.

Specifically, the holding table 10 includes a cylindrical frame 12 formed of a metal such as stainless steel (SUS), and a disc-shaped porous member 14 mounted on the upper surface side of the frame 12. The porous member 14 is made of porous ceramics, etc., and is embedded in a circular recess formed on the upper surface side of the frame 12. The porous member 14 is connected to a suction source 18 such as an ejector through a flow path 10b and a valve 16 formed inside the holding table 10. Furthermore, the upper surface of the porous member 14 is equivalent to a part of the holding surface 10a of the holding table 10, and constitutes a suction surface for attracting the optical device wafer 11.

When the optical device wafer 11 is held by the holding table 10, the optical device wafer 11 is first placed on the holding table 10. At this time, the optical device wafer 11 is placed so that the back surface 13b of the substrate 13 covers the entire upper surface (attraction surface) of the porous member 14. When the negative pressure of the attraction source 18 is applied to the holding surface 10a through the valve 16, the flow path 10b and the porous member 14 in this state, the optical device wafer 11 can be held by the holding table 10 by attraction.

In addition, the holding table 10 has a heating unit (heating assembly) 20 for heating the optical device wafer 11. For example, the heating unit 20 is composed of a heater, etc., and has a disc-shaped heating element 22 that generates heat by supplying electric power. The heating element 22 is sandwiched between a disc-shaped metal plate 24 and a disc-shaped heat insulating member 26. The metal plate 24 is arranged on the upper side of the heating element 22 and is composed of a metal such as aluminum. The heat insulating member 26 is arranged on the lower side of the heating element 22.

When power is supplied to the heating element 22 while the optical device wafer 11 is held by the holding table 10, the heating element 22 generates heat. The heat generated by the heating element 22 is then transmitted to the optical device wafer 11 through the metal plate 24, the frame 12, and the porous member 14, thereby heating the optical device wafer 11. Furthermore, the conduction of heat from the heating element 22 to the lower side of the holding table 10 is blocked by the heat insulating member 26.

A sheet 31 for transferring a plurality of optical devices 17 can be attached to the optical device wafer 11 held by the holding table 10. For example, the sheet 31 is made of a resin such as polyolefin or polyester, and is attached to the front surface 13a side of the substrate 13 on which the plurality of optical devices 17 are formed by thermal compression.

Specifically, the sheet 31 is first arranged above the front surface 13a of the substrate 13 so that the plurality of optical devices 17 overlap with the sheet 31, and the sheet 31 is pressed toward the front surface 13a of the substrate 13. In this way, the plurality of optical devices 17 come into contact with the sheet 31. When the holding table 10 is heated by the heating unit 20 in this state, the heat of the holding table 10 is conducted to the sheet 31 through the substrate 13, so that the sheet 31 softens. As a result, the plurality of optical devices 17 are buried in the sheet 31, and the plurality of optical devices 17 and the sheet 31 are joined in a state of being closely attached to each other.

In this way, the sheet 31 can be attached to the substrate 13 by heat pressing. Furthermore, the temperature and time of heating performed by the heating unit 20 are appropriately set according to the melting point of the sheet 31. For example, when using a sheet 31 made of polyolefin, the heating temperature can be set to about 100°C and the heating time can be set to about 1 minute.

FIG3(B) is a cross-sectional view showing the substrate 13 with the sheet 31 attached. When the sheet 31 is attached to the substrate 13 by heat pressing, the plurality of optical devices 17 are covered by the sheet 31, and the sheet 31 is deformed to conform to (along) the gaps between the optical devices 17. More specifically, the plurality of optical devices 17 are each buried in the sheet 31, and the sheet 31 contacts not only the upper surface of the optical device 17 but also the side surface of the optical device 17 and the front surface 13a of the substrate 13 exposed between the optical devices 17.

When the sheet 31 is attached to conform to the gap between the optical devices 17, the contact area between the sheet 31 and the optical device 17 becomes larger than when the sheet 31 is in contact only with the upper surface of the optical device 17. As a result, a plurality of optical devices 17 can be firmly fixed to the sheet 31.

Furthermore, the attachment of the sheet 31 can also be implemented in a depressurized chamber. That is, the optical device wafer 11 can also be held by the holding table 10 disposed in the depressurized chamber. In this case, the sheet 31 can be moved into the depressurized chamber and attached to the substrate 13 under depressurization.

Specifically, first, in a state where the pressure in the decompression chamber has been reduced, the sheet 31 is pressed toward the substrate 13. By reducing the pressure in the chamber, it is possible to prevent gas (air) from entering between the substrate 13 and the sheet 31.

After that, the decompression chamber is opened to the atmosphere, and the atmosphere (air) is introduced into the decompression chamber. Thereby, the atmospheric pressure acts on the sheet 31, and the sheet 31 is deformed along the shape of the gap between the optical devices 17, and is closely attached to the front surface 13a of the substrate 13. Thereby, the sheet 31 can be attached to the substrate 13 so that no gap is formed between the sheet 31 and the side surface of the optical device 17, and between the sheet 31 and the front surface 13a of the substrate 13.

Furthermore, although the above description describes the case where the heating treatment during the heat pressing is performed by the heating unit 20 disposed inside the holding table 10, there is no limitation on the heating method. For example, the heating treatment may also be performed by an infrared heater, a warm air heater, a lamp, etc. disposed separately above the holding table 10.

In addition, although the above description is directed to an example of attaching the sheet 31 by heat pressing, there is no limitation on the material or attaching method of the sheet 31 as long as the sheet 31 can be attached to conform to the gap between the optical devices 17. FIG4(A) is a cross-sectional view showing a state where a sheet (tape, film) 33 different from the sheet 31 is attached to the substrate 13.

The sheet 33 includes a base material 35 formed into a circle having substantially the same diameter as the substrate 13, a circular resin layer 37 formed on the lower surface of the base material 35, and a ring-shaped adhesive layer (paste layer) 39 formed of an adhesive for bonding to the substrate 13 and formed on the lower surface of the outer periphery of the resin layer 37. The base material 35 is more rigid than the resin layer 37, and the resin layer 37 is made of a softer resin than the base material 35. For example, the base material 35 is made of a resin such as polyethylene terephthalate (PET), and the resin layer 37 is made of a softer resin such as polyolefin (PO) and polyvinyl chloride (PVC).

The adhesive layer 39 is formed to correspond to the peripheral region (peripheral remaining region) of the substrate 13 where the plurality of optical devices 17 are not formed. Specifically, when the sheet 33 is arranged to overlap with the substrate 13, the adhesive layer 39 is arranged to overlap only with the peripheral remaining region of the substrate 13.

When the sheet 33 is attached to the optical device wafer 11, the optical device wafer 11 is first held by the holding table 30. The upper surface of the holding table 30 constitutes a holding surface 30a for holding the optical device wafer 11. In addition, the optical device wafer 11 is configured so that the back surface 13b side of the substrate 13 faces the holding surface 30a of the holding table 30. Furthermore, the structure of the holding table 30 is not limited as long as it can hold the optical device wafer 11. For example, the holding table 30 can be constructed in the same manner as the holding table 10 shown in Figures 3(A) and 3(B).

Next, the sheet 33 is attached to the optical device wafer 11 held by the holding table 30. Specifically, the sheet 33 is first arranged above the substrate 13 in such a manner that the adhesive layer 39 side faces the front surface 13a side (optical device 17 side) of the substrate 13. Then, the sheet 33 is pressed toward the front surface 13a side of the substrate 13 and attached to the substrate 13.

At this time, the adhesive layer 39 of the sheet 33 is in contact with only the peripheral area (peripheral remaining area) of the substrate 13 where the plurality of optical devices 17 are not formed, and is bonded to the substrate 13. In addition, the resin layer 37 made of a soft resin is in contact with the upper surface of the plurality of optical devices 17 and enters the gaps between the optical devices 17.

As with the aforementioned attachment of the sheet 31 (see FIG. 3(A) and FIG. 3(B)), the attachment of the sheet 33 is preferably carried out in a depressurized chamber. Specifically, the optical device wafer 11 is held by a holding table 30 that has been set in the depressurized chamber. Then, in a state where the depressurized chamber has been depressurized, the sheet 33 is pressed against the substrate 13 while being heated. Thereby, the sheet 33 is closely attached to the substrate 13 in a manner that no gap is formed between the resin layer 37 and the side surface of the optical device 17 and between the resin layer 37 and the front surface 13a of the substrate 13.

FIG4(B) is a cross-sectional view showing the substrate 13 with the sheet 33 attached thereto. When the sheet 33 is attached to the front surface 13a of the substrate 13, the plurality of optical devices 17 are covered by the sheet 33, and the sheet 33 is deformed to conform to (along) the gaps between the optical devices 17. Specifically, the resin layer 37 of the sheet 33 is deformed to fit closely to the optical devices 17 in a manner conforming to the gaps between the optical devices 17.

Thereby, the plurality of optical devices 17 are buried in the resin layer 37, and the sheet 33 contacts not only the upper surface of the optical device 17 but also the side surface of the optical device 17 and the front surface 13a of the substrate 13 exposed between the optical devices 17. Then, the resin layer 37 is in close contact with the upper surface and the side surface of the optical device 17 and is bonded by the van der Waals force.

Furthermore, the sheet 33 has the adhesive layer 39 only in the area corresponding to the peripheral remaining area of the substrate 13. Therefore, even if the sheet 33 is attached to the substrate 13, the adhesive layer 39 and the optical device 17 will not contact each other. Thereby, when the optical device 17 and the sheet 33 are finally separated in the subsequent step, a part of the adhesive layer 39 can be prevented from remaining on the optical device 17.

Next, a pulsed laser beam that is penetrable to the substrate 13 and absorbs the buffer layer 21a is irradiated from the back surface 13b of the substrate 13 to destroy the buffer layer 21a (buffer layer destroying step). FIG5 is a cross-sectional view of the optical device wafer 11 in the buffer layer destroying step.

The buffer layer destroying step is performed by using, for example, a laser processing apparatus 40. The laser processing apparatus 40 includes a holding table 42 for holding the optical device wafer 11, and a laser irradiation unit 44 for irradiating a laser beam toward the optical device wafer 11 held by the holding table 42.

The holding table 42 is formed, for example, in a circular shape in a planar view corresponding to the shape of the optical device wafer 11, and the upper surface of the holding table 42 constitutes a holding surface 42a for holding the optical device wafer 11. The holding surface 42a is connected to a suction source (not shown) such as an ejector through a flow path (not shown) formed inside the holding table 42.

The optical device wafer 11 is arranged on the holding table 42 in such a manner that the front surface 13a side of the substrate 13 (optical device 17 side, sheet 31 side) faces the holding surface 42a, and the back surface 13b side of the substrate 13 is exposed upward. When the negative pressure of the suction source is applied to the holding surface 42a in this state, the optical device wafer 11 can be held by suction by the holding table 42.

Furthermore, a moving mechanism (not shown) is connected to the holding table 42 to move the holding table 42 in the horizontal direction. The position of the holding table 42 in the horizontal direction can be controlled by this moving mechanism. In addition, a rotating mechanism (not shown) is connected to the holding table 42 to rotate the holding table 42 around a rotating axis that is substantially parallel to the vertical direction of the lead.

A laser irradiation unit 44 is provided above the holding table 42. The laser irradiation unit 44 has a laser oscillator 46 that generates a laser beam of a predetermined wavelength by pulse oscillation. For example, a YAG laser, a _YVO4 laser, a YLF laser, etc. can be used as the laser oscillator 46. The laser beam generated by the pulse oscillation of the laser oscillator 46 is reflected by the mirror 48 and then incident on the focusing lens 50, and is focused at a predetermined position by the focusing lens 50.

The laser irradiation unit 44 can irradiate the optical device wafer 11 held by the holding table 42 with a laser beam 52. The wavelength of the laser beam 52 is set such that the laser beam 52 is penetrable to the substrate 13 and absorbs the buffer layer 21a. Therefore, the laser beam 52 that penetrates the substrate 13 and can be absorbed by the buffer layer 21a is irradiated to the optical device wafer 11 from the laser irradiation unit 44.

In the buffer layer destroying step, first, the holding table 42 holding the optical device wafer 11 is positioned below the condensing lens 50. Then, the laser irradiation unit 44 irradiates the back surface 13b of the substrate 13 with a laser beam 52.

The laser beam 52 penetrates the substrate 13 and irradiates a buffer layer 21a, and is absorbed by the buffer layer 21a. As a result, the buffer layer 21a is destroyed, and the bonding between the optical device 17 and the substrate 13 that is in contact with the destroyed buffer layer 21a is weakened. The irradiation conditions (power, spot diameter, repetition frequency, focusing position, etc.) of the laser beam 52 are appropriately set within a range that can destroy the buffer layer 21a.

Furthermore, the focal point of the laser beam 52 is positioned, for example, inside or near the buffer layer 21a. However, the focal position of the laser beam 52 is not limited as long as it can destroy the buffer layer 21a.

Furthermore, in the buffer layer destroying step, it is not necessary to completely remove the buffer layer 21a and completely separate the substrate 13 and the optical device 17. Specifically, it is sufficient as long as the bonding between the optical device 17 and the substrate 13 is weakened to the extent that when the sheet 31 is peeled off from the substrate 13 in the optical device transferring step described later, the optical device 17 can be separated from the substrate 13 along with the sheet 31.

For example, in the buffer layer destruction step, the buffer layer 21a is irradiated with the laser beam 52 to form a degraded layer (degraded layer) in the buffer layer 21a, thereby weakening the bonding between the optical device 17 and the substrate 13. This degraded layer is equivalent to a layer (separation layer) that becomes a trigger for separation when the optical device 17 is separated from the substrate 13. However, the mode of destruction of the buffer layer 21a is not limited to this, and the substrate 13 and the optical device 17 can also be completely separated by adjusting the irradiation conditions of the laser beam 52.

Afterwards, the other buffer layers 21a are irradiated with the laser beam 52 in the same manner. Thus, all buffer layers 21a are destroyed, and the connection between the substrate 13 and the plurality of optical devices 17 is weakened.

Next, the sheet 31 is peeled off from the substrate 13, and the plurality of optical devices 17 are transferred to the sheet 31 (optical device transfer step). FIG. 6 is a perspective view of the optical device wafer 11 in the optical device transfer step. In the optical device transfer step, the sheet 31 is moved away from the substrate 13 while the substrate 13 is fixed. In this way, the sheet 31 can be peeled off from the front surface 13a of the substrate 13.

Before the sheet 31 is peeled off, the sheet 31 has been attached to conform to the gap between the optical devices 17 and is closely attached to the upper surface and side surface of the optical device 17 (see FIG. 3 (B) and FIG. 4 (B)). In addition, by the aforementioned buffer layer destruction step, the buffer layer 21a (see FIG. 5, etc.) has been destroyed and embrittled, or has been removed. Therefore, when the sheet 31 is peeled off from the substrate 13, the plurality of optical devices 17 will follow the separation of the sheet 31 from the substrate 13 as shown in FIG. 6 and transfer to the sheet 31.

Furthermore, there is no limitation on the method for peeling the sheet 31. For example, the sheet 31 may be peeled off by gripping the end of the sheet 31 with a gripper. Alternatively, a peeling tape may be attached to the sheet 31 to integrate the sheet 31 with the peeling tape, and then the peeling tape and the sheet 31 may be peeled off from the substrate 13 together.

Furthermore, a treatment to promote peeling may be performed when peeling the sheet 31. For example, ultrasonic vibration may be applied to the substrate 13 to promote the peeling of the substrate 13 and the sheet 31. Furthermore, a sharp tool such as a cutter or tweezers may be inserted into the interface between the substrate 13 and the sheet 31 to partially peel the substrate 13 and the sheet 31. Furthermore, a gas such as air may be sprayed from the side of the substrate 13 toward the interface between the substrate 13 and the sheet 31 to promote the separation of the substrate 13 and the sheet 31.

As described above, in the optical device transfer method of the present embodiment, the sheet 31 (or sheet 33) is attached to conform to the gaps between the optical devices 17 formed on the substrate 13. In this way, the plurality of optical devices 17 can be firmly fixed to the sheet 31, and when the sheet 31 is peeled off from the substrate 13, the plurality of optical devices 17 can be reliably separated from the substrate 13. In this way, the optical device 17 can be reliably transferred from the substrate 13 to the sheet 31.

The plurality of optical devices 17 transferred to the sheet 31 can be transferred and bonded to, for example, another substrate (transfer substrate) on which the optical devices 17 are to be assembled. In this embodiment, the sheet 31 to which the plurality of optical devices 17 have been transferred is attached to the transfer substrate, and the plurality of optical devices 17 are bonded to the transfer substrate (bonding step). In this way, the plurality of optical devices 17 can be bonded in batches.

Specifically, first, a substrate (assembly substrate) is prepared for assembling a plurality of optical devices 17. A plurality of electrodes connected to the optical devices 17 are formed on the front surface of the assembly substrate. Here, the arrangement of the plurality of electrodes provided on the assembly substrate is described to correspond to the arrangement of the plurality of optical devices 17 buried in the sheet 31 (see FIG. 6 ).

In the bonding step, first, a bonding agent for bonding the optical device 17 and the electrodes of the assembly substrate is applied to the exposed surfaces of the plurality of optical devices 17 buried in the sheet 31 and the exposed surfaces of the plurality of electrodes formed on the assembly substrate. There is no limitation on the material of the bonding agent, and for example, a Sn-Cu solder for electrically connecting the optical device 17 and the electrodes of the assembly substrate can be used.

Next, the sheet 31 is attached to the assembly substrate so that the surface of the assembly substrate on which the electrodes are formed faces the surface of the sheet 31 on which the optical devices 17 are exposed. In this way, the plurality of optical devices 17 are bonded to the electrodes of the assembly substrate through the bonding agent, and the plurality of optical devices 17 are bonded in batches. Afterwards, when the sheet 31 is peeled off from the assembly substrate, the plurality of optical devices 17 are separated from the sheet 31 in a state of being bonded to the assembly substrate.

Furthermore, when the arrangement of the plurality of optical devices 17 buried in the sheet 31 is different from the arrangement of the plurality of electrodes on the assembly substrate, the interval between the optical devices 17 can be adjusted by stretching and expanding the sheet 31. Specifically, an adhesive tape that can be expanded (stretched) by the application of external force is used as the sheet 31. And, the sheet attaching step, the buffer layer destroying step, and the optical device transferring step described above are implemented using this sheet 31.

After that, the intervals of the optical devices 17 are enlarged by expanding the sheet 31. The expansion amount of the sheet 31 at this time is adjusted so that the arrangement of the plurality of optical devices 17 corresponds to the arrangement of the plurality of electrodes formed on the transfer substrate. Then, by attaching the expanded sheet 31 to the assembly substrate, the plurality of optical devices 17 are assembled to the assembly substrate in batches.

In addition, the structures, methods, etc. of the above-mentioned embodiments may be implemented with appropriate modifications as long as they do not deviate from the scope of the purpose of the present invention.

10,30,42: holding table 10a,30a,42a: holding surface 10b: flow path 11: optical device wafer 12: frame 13: substrate 13a: front 13b: back 14: porous component 15: cutting path 16: valve 17: optical device 18: suction source 20: heating unit (heating component) 21,21a: buffer layer 22: heating element 2 4: Metal plate 26: Heat insulation component 23: Optical device layer 25,25a: p-type semiconductor film 27,27a: n-type semiconductor film 31,33: Sheet (tape, film) 35: Base material 37: Resin layer 39: Adhesive layer (paste layer) 40: Laser processing device 44: Laser irradiation unit 46: Laser oscillator 48: Mirror 50: Focusing lens 52: Laser beam

FIG. 1 is a perspective view showing an optical device wafer. FIG. 2(A) is a cross-sectional view showing a manufacturing step of an optical device wafer, and FIG. 2(B) is a cross-sectional view showing an optical device wafer in a state where an optical device layer has been divided into a plurality of optical devices. FIG. 3(A) is a cross-sectional view showing a sheet being attached to a substrate, and FIG. 3(B) is a cross-sectional view showing a substrate to which a sheet is attached. FIG. 4(A) is a cross-sectional view showing a state where another sheet is attached to a substrate, and FIG. 4(B) is a cross-sectional view showing a substrate to which another sheet is attached. FIG. 5 is a cross-sectional view showing an optical device wafer in a buffer layer destruction step. FIG. 6 is a perspective view showing an optical device wafer in an optical device transfer step.

10: Keep the workbench

10a: Keep the face

10b: Flow path

11: Optical device wafer

12: Frame

13: Substrate

13a: Front

13b: Back

14: Porous components

16: Valve

17: Optical devices

18: Attraction source

20: Heating unit (heating component)

21a: Buffer layer

22: Heat generating body

24:Metal plates

26: Thermal insulation components

31: Sheet (tape, film)

Claims (2)

A method for transferring an optical device is to transfer a plurality of the optical devices from an optical device wafer having the plurality of optical devices, wherein the optical devices are formed on the front side of a substrate via a buffer layer. The method for transferring the optical device is characterized in that it comprises the following steps: a sheet attaching step, attaching a sheet on the front side of the substrate to cover the plurality of the optical devices and conform to the gaps between the optical devices; a buffer layer destroying step, after the sheet attaching step is performed, removing the buffer layer from the back side of the substrate; The buffer layer is destroyed by irradiating the surface with a pulsed laser beam that is penetrable to the substrate and absorbent to the buffer layer; and an optical device transfer step is performed. After the buffer layer destruction step is performed, the sheet is peeled off from the substrate and a plurality of optical devices are transferred to the sheet. The sheet attaching step is performed in a depressurized chamber. In the sheet attaching step, the sheet is pressed toward the substrate while being heated while the depressurized chamber is depressurized. As in claim 1, the optical device relocation method, wherein the sheet has a resin layer and a ring-shaped adhesive layer corresponding to the area of the substrate where the optical device is not formed, and in the sheet attaching step, the sheet is attached to the substrate in a manner such that the adhesive layer does not contact the optical device and the resin layer conforms to the gap between the optical devices.