CN112185877A

CN112185877A - Method for transferring optical device

Info

Publication number: CN112185877A
Application number: CN202010629777.XA
Authority: CN
Inventors: 小柳将; 李宰荣
Original assignee: Disco Corp
Current assignee: Disco Corp
Priority date: 2019-07-05
Filing date: 2020-07-03
Publication date: 2021-01-05
Also published as: KR20210004848A; TW202103533A; JP2021012936A

Abstract

Provided is a method for transferring an optical device, which can reliably transfer the optical device from a substrate to a sheet. A method for transferring a plurality of optical devices from an optical device wafer having the plurality of optical devices formed on a front surface side of a substrate with a buffer layer interposed therebetween, the method comprising the steps of: a sheet attaching step of attaching a sheet on the front surface side of the substrate so as to cover the plurality of optical devices and to simulate a gap between the optical devices; a buffer layer breaking step of, after the sheet attaching step is performed, irradiating a pulse laser beam having transparency to the substrate and absorbability to the buffer layer from a back side of the substrate to break the buffer layer; and an optical device transfer step of peeling the sheet from the substrate after the buffer layer breaking step is performed, and transferring the plurality of optical devices onto the sheet.

Description

Method for transferring optical device

Technical Field

The present invention relates to a method of transferring an optical device, in which a plurality of optical devices are transferred from an optical device wafer.

Background

Optical devices represented by LEDs (Light Emitting diodes) are used in various fields such as displays, lighting, automobiles, and medical treatment. For example, an LED is formed by epitaxially growing an n-type semiconductor film and a p-type semiconductor film constituting a pn junction on the front surface of a substrate made of sapphire or SiC.

The optical device formed on the substrate is mounted on another mounting substrate or the like after being separated from the substrate. As one of the methods for transferring the optical device, a technique called laser lift-off is known. In the laser lift-off, first, an optical device is formed on the front surface side of the substrate with a buffer layer interposed therebetween. Then, the buffer layer is modified by irradiating the substrate with a laser beam from the back surface side thereof, the bonding between the substrate and the optical device is weakened, and then the optical device is separated from the substrate and transferred onto a substrate (transfer substrate) as a transfer destination (see patent documents 1 and 2).

In recent years, a technique for manufacturing an extremely small-sized LED called a micro LED has been developed. For example, the micro LED is formed by: a layer (optical device layer) including various thin films (semiconductor films and the like) constituting an LED is formed on a substrate, and then the optical device layer is divided into a plurality of fine chips by etching (see patent document 3).

Patent document 1: japanese patent laid-open publication No. 2004-72052

Patent document 2: japanese patent laid-open publication No. 2016-

Patent document 3: japanese patent laid-open publication No. 2018-107421

When the optical device such as the micro LED is mounted on a transfer substrate, the optical device in each separated state is separated from the substrate and transferred to the transfer substrate. Specifically, first, the optical device layer formed on the front surface side of the substrate is divided into a plurality of fine optical devices, and then a transfer sheet (for transfer) is attached to the front surface side of the substrate. The sheet is attached so as to be in contact with the upper surfaces of all the optical devices formed on the substrate.

Then, after a treatment (modification of the buffer layer or the like) for weakening the bonding between the substrate and the optical device is performed, the sheet is peeled off from the substrate. As a result, the plurality of optical devices are separated from the substrate and transferred onto the sheet. Then, the sheet on which the optical device is transferred is pasted on a transfer substrate, and the optical device is bonded to a connection electrode formed on the transfer substrate. Thus, the optical device is transferred onto the transfer substrate.

However, even when the transfer step of the optical device is performed, a part of the optical device may remain on the substrate and not be transferred to the sheet. This phenomenon is considered to occur when the sheet is not properly adhered to the plurality of optical devices when the sheet is attached to the substrate, and the adhesion between the sheet and the optical devices is insufficient. For example, some of the optical devices may not be properly bonded to the sheet due to an unexpected inclination of a holding table for holding the substrate at the time of bonding the sheet, and a variation in thickness of the substrate or the sheet. In this case, even if the sheet is peeled off from the substrate, a part of the optical device does not follow the tape but remains on the substrate.

When some of the optical devices are not properly transferred onto the sheet, it is necessary to perform a transfer process again, a work of picking up the optical devices remaining on the substrate, or the like. As a result, the work efficiency of transferring the optical device is reduced.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a method for transferring an optical device, which can reliably transfer the optical device from a substrate to a sheet.

According to one aspect of the present invention, there is provided a method for transferring an optical device, the method for transferring an optical device being a method for transferring a plurality of optical devices from an optical device wafer having the plurality of optical devices formed on a front surface side of a substrate with a buffer layer interposed therebetween, the method comprising the steps of: a sheet attaching step of attaching a sheet on the front surface side of the substrate so as to cover the plurality of optical devices and to simulate a gap between the optical devices; a buffer layer breaking step of, after the sheet attaching step is performed, irradiating a pulse laser beam having transparency to the substrate and absorbability to the buffer layer from a back side of the substrate to break the buffer layer; and an optical device transfer step of peeling the sheet from the substrate after the buffer layer breaking step is performed, and transferring the plurality of optical devices onto the sheet.

In the sheet attaching step, the sheet is preferably attached to the substrate by thermocompression bonding. Alternatively, it is preferable that the sheet has a resin layer and an annular adhesive layer corresponding to a region of the substrate where the optical devices are not formed, and in the sheet attaching step, the sheet is attached to the substrate so that the adhesive layer does not contact the optical devices and the resin layer conforms to the gaps between the optical devices.

In the method for transferring an optical device according to one aspect of the present invention, the tape is attached so as to follow a gap between the optical devices formed on the substrate. Thus, the plurality of optical devices are firmly fixed to the sheet, and when the sheet is peeled off from the substrate, the plurality of optical devices are reliably separated from the substrate. This enables the optical device to be reliably transferred from the substrate to the sheet.

Drawings

Fig. 1 is a perspective view showing a photo device wafer.

Fig. 2 (a) is a cross-sectional view showing a manufacturing process of the optical device wafer, and fig. 2 (B) is a cross-sectional view of the optical device wafer showing a state where the optical device layer is divided into a plurality of optical devices.

Fig. 3 (a) is a cross-sectional view showing a state where a sheet is attached to a substrate, and fig. 3 (B) is a cross-sectional view showing the substrate to which the sheet is attached.

Fig. 4 (a) is a cross-sectional view showing a case where another sheet is attached to the substrate, and fig. 4 (B) is a cross-sectional view showing the substrate to which another sheet is attached.

Fig. 5 is a cross-sectional view showing the optical device wafer in the buffer layer destruction step.

Fig. 6 is a perspective view showing the optical device wafer in the optical device transfer step.

Description of the reference symbols

11: an optical device wafer; 13: a substrate; 13 a: a front side; 13 b: a back side; 15: a spacing channel; 17: an optical device; 21: a buffer layer; 21 a: a buffer layer; 23: a light device layer; 25: a p-type semiconductor film; 25 a: a p-type semiconductor film; 27: an n-type semiconductor film; 27 a: an n-type semiconductor film; 31: sheets (tapes, films); 33: sheets (tapes, films); 35: a substrate; 37: a resin layer; 39: an adhesive layer (paste layer); 10: a holding table; 10 a: a holding surface; 10 b: a flow path; 12: a frame body; 14: a porous member; 16: a valve; 18: an attraction source; 20: a heating unit (heating member); 22: a heating element; 24: a metal plate; 26: a heat insulating member; 30: a holding table; 30 a: a holding surface; 40: a laser processing device; 42: a holding table; 42 a: a holding surface; 44: a laser irradiation unit; 46: a laser oscillator; 48: a mirror; 50: a condenser lens; 52: a laser beam.

Detailed Description

The present embodiment will be described below with reference to the drawings. First, a configuration example of an optical device wafer having a plurality of optical devices that can be transferred by the method of transferring an optical device according to the present embodiment will be described. Fig. 1 is a perspective view showing an optical device wafer 11.

The optical device wafer 11 has a disk-shaped substrate 13, and the substrate 13 has a front surface 13a and a back surface 13 b. The substrate 13 is divided into a plurality of regions by a plurality of streets 15 arranged in a lattice shape, and optical devices 17 are formed on the front surfaces 13a of the plurality of regions, respectively. Hereinafter, a case where the optical device 17 is an led (light Emitting diode) will be described as an example. The kind, number, shape, structure, size, arrangement, and the like of the optical device 17 are not limited.

Fig. 2 (a) is a cross-sectional view showing a manufacturing process of the optical device wafer 11. In the process of manufacturing 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 (a semiconductor film, a conductive film, an insulating film, and the like) constituting the optical device 17 (see fig. 1). For example, the optical device layer 23 includes: a p-type semiconductor film 25 made of a p-type semiconductor in which holes are a plurality of carriers; and an n-type semiconductor film 27 made of an n-type semiconductor in which electrons are a plurality of carriers. However, the structure of the optical device layer 23 is ultimately selected as appropriate depending on the configuration or function of the optical device 17 formed on the substrate 13.

The buffer layer 21 is a layer that suppresses generation of defects caused by lattice mismatch of the substrate 13 and the optical device layer 23. The material of the buffer layer 21 is appropriately selected in accordance with 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). The buffer layer 21 may be formed of a single film or a plurality of films 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 capable of epitaxially growing a desired thin film on the substrate 13 is used as the substrate 13.

For example, as the substrate 13, a single crystal substrate made of sapphire, SiC, or the like is used, and the buffer layer 21 made of GaN, the p-type semiconductor film 25 made of p-type GaN, and the n-type semiconductor film 27 made of n-type GaN are sequentially formed on the substrate 13 by epitaxial growth. For forming each film, mocvd (metal Organic Chemical Vapor deposition) method, mbe (molecular Beam epitaxy) method, or the like can be used.

Next, the buffer layer 21 and the optical device layer 23 are divided along the streets 15. The buffer layer 21 and the optical device layer 23 are divided by, for example, etching. Specifically, first, a mask for etching is formed on the optical device layer 23. The mask is patterned to expose the photo device layer 23 along the streets 15.

Then, an etching solution 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. Thereby, the optical device layer 23 is divided into a plurality of optical devices 17 along the streets 15.

Fig. 2 (B) is a cross-sectional view of the optical device wafer 11 showing a state in which the optical device layer 23 is divided into a plurality of optical devices 17. When the photo device layer 23 is divided along the streets 15, a plurality of photo devices 17 each having a p-type semiconductor film 25a obtained by singulating the p-type semiconductor film 25 and an n-type semiconductor film 27a obtained by singulating the n-type semiconductor film 27 are formed. The p-type semiconductor film 25a and the n-type semiconductor film 27a form a pn junction, and the optical device 17 emits light by recombination of holes and electrons.

A buffer layer 21a obtained by singulating the buffer layer 21 by etching is disposed between the substrate 13 and the optical device 17. That is, the optical devices 17 are disposed on the substrate 13 with the buffer layers 21a interposed therebetween. The buffer layer 21a corresponds to a layer which is 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, when etching is used for dividing the optical device layer 23, the optical device layer 23 can be finely processed, and the optical device 17 having an extremely small size such as a micro LED can be formed. Also, when the etching of the buffer layer 21 and the photo device layer 23 is completed, the mask formed on the photo device layer 23 is removed.

In addition, the optical device 17 including the p-type semiconductor film 25a and the n-type semiconductor film 27a is shown in fig. 2 (B), but the structure of the optical device 17 is not limited thereto. For example, the optical device 17 may further have a light emitting layer between the p-type semiconductor film 25a and the n-type semiconductor film 27 a. In this case, recombination of holes and electrons occurs in the light-emitting layer, and light is emitted from the light-emitting layer. Further, an electrode (connection electrode) for connecting the optical device 17 to another electrode or a terminal may be formed on the upper surface side or the lower surface side of the optical device 17.

The plurality of optical devices 17 formed on the substrate 13 are separated from the substrate 13 and then mounted on another mounting substrate or the like. For transferring the optical device 17, for example, a sheet for transfer (transfer) is used. A specific example of a method of transferring the optical device 17 using the sheet will be described below.

In the method of transferring an optical device according to the present embodiment, first, a sheet is attached so as to cover the plurality of optical devices 17 on the front surface 13a side of the substrate 13 on which the plurality of optical devices 17 are formed (sheet attaching step). Fig. 3a is a cross-sectional view showing a state in which a sheet (tape, film) 31 for transfer (transfer) is stuck to the substrate 13. Hereinafter, a case where the sheet 31 is attached to the substrate 13 by thermocompression bonding will be described as an example.

In the sheet sticking step, first, the optical device wafer 11 is held by the holding table 10. For example, the holding table 10 is formed in a circular shape in a plan 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 frame 12 formed in a cylindrical shape using a metal such as stainless steel (SUS); and a disk-shaped porous member 14 attached to the upper surface side of the frame 12. The porous member 14 is made of porous ceramic or the like, and is fitted into 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 via a valve 16 and a flow path 10b formed inside the holding table 10. The upper surface of the porous member 14 corresponds to a part of the holding surface 10a of the holding table 10, and constitutes a suction surface for sucking the optical device wafer 11.

When the optical device wafer 11 is held by the holding table 10, first, the optical device wafer 11 is placed on the holding table 10. At this time, the optical device wafer 11 is disposed so that the rear surface 13b side of the substrate 13 covers the entire upper surface (suction surface) of the porous member 14. In this state, when the negative pressure of the suction source 18 is applied to the holding surface 10a via the valve 16, the flow path 10b, and the porous member 14, the optical device wafer 11 is sucked and held by the holding table 10.

The holding table 10 has a heating unit (heating member) 20 for heating the optical device wafer 11 therein. The heating unit 20 is constituted by a heater or the like, for example, and has a disc-shaped heating element 22 that generates heat by supplying electric power. The heating element 22 is sandwiched by a disk-shaped metal plate 24 and a disk-shaped heat insulating member 26, the metal plate 24 being provided on the upper side of the heating element 22 and made of metal such as aluminum, and the heat insulating member 26 being provided on the lower side of the heating element 22.

When power is supplied to the heating element 22 in a state where the optical device wafer 11 is held by the holding table 10, the heating element 22 generates heat. Then, the heat generated by the heating element 22 is transmitted to the optical device wafer 11 via the metal plate 24, the frame 12, and the porous member 14, and the optical device wafer 11 is heated. Further, heat transfer 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 the plurality of optical devices 17 is attached to the optical device wafer 11 held by the holding table 10. The sheet 31 is made of resin such as polyolefin or polyester, and is bonded to the front surface 13a side of the substrate 13 on which the plurality of optical devices 17 are formed by thermocompression bonding.

Specifically, first, the sheet 31 is disposed above the front surface 13a of the substrate 13 so that the plurality of optical devices 17 overlap the sheet 31, and the sheet 31 is pressed toward the front surface 13a of the substrate 13. Thereby, the plurality of optical devices 17 are in contact with the sheet 31. In this state, when the holding table 10 is heated by the heating unit 20, the heat of the holding table 10 is transmitted to the sheet 31 via the substrate 13, and the sheet 31 is softened. 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 bonded in close contact with each other.

In this way, the sheet 31 is attached to the substrate 13 by thermal compression. The heating temperature and time of the heating unit 20 are appropriately set according to the melting point of the sheet 31 and the like. For example, in the case of using the sheet 31 made of polyolefin, the heating temperature may be set to about 100 ℃ and the heating time may be set to about 1 minute.

Fig. 3 (B) is a cross-sectional view showing the substrate 13 to which the sheet 31 is attached. When the sheet 31 is attached to the substrate 13 by thermocompression bonding, the plurality of optical devices 17 are covered by the sheet 31, and the sheet 31 is deformed in such a manner as to mimic (follow) the gaps between the optical devices 17. More specifically, the plurality of optical devices 17 are buried in the sheet 31, respectively, and the sheet 31 is in contact with not only the upper surfaces of the optical devices 17 but also the side surfaces of the optical devices 17 and the front surface 13a of the substrate 13 exposed between the optical devices 17.

In this way, when the sheet 31 is attached so as to mimic the gap between the optical devices 17, the contact area of the sheet 31 with the optical devices 17 increases as compared with the case where the sheet 31 is in contact with only the upper surface of the optical devices 17. As a result, the plurality of optical devices 17 are firmly fixed to the sheet 31.

The sheet 31 may be bonded in a decompression chamber. That is, the optical device wafer 11 may be held by the holding table 10 provided in the decompression chamber. In this case, the sheet 31 is carried into the pressure reducing chamber, and the sheet 31 is bonded to the substrate 13 under reduced pressure.

Specifically, first, the sheet 31 is pressed against the substrate 13 in a state where the pressure in the pressure reduction chamber is reduced. By reducing the pressure in the chamber, gas (air) can be prevented from entering between the substrate 13 and the sheet 31.

Thereafter, the decompression chamber is opened to the atmosphere, and the atmosphere (air) is introduced into the decompression chamber. Thus, atmospheric pressure acts on the sheet 31, and the sheet 31 deforms along the shape of the gap between the optical devices 17 and comes into close contact with the front surface 13a side of the substrate 13. This makes it possible to attach the sheet 31 to the substrate 13 without forming a gap 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.

In the above description, the heating process in the thermocompression bonding is performed by the heating unit 20 provided inside the holding table 10, but the heating method is not limited. For example, the heating process may be performed by an infrared heater, a hot air heater, a lamp, or the like separately provided above the holding table 10.

In the above description, an example in which the sheet 31 is attached by heat pressing has been described, but the material and the attaching method of the sheet 31 are not limited as long as the sheet 31 can be attached so as to simulate the gap between the optical devices 17. Fig. 4 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 has: a circular base material 35 formed to have substantially the same diameter as the substrate 13; a circular resin layer 37 formed on the lower surface side of the base material 35; and an annular adhesive layer (paste layer) 39 which is adhered to the substrate 13, made of an adhesive, and formed on the lower surface side of the outer peripheral portion of the resin layer 37. The rigidity of the substrate 35 is higher than that of the resin layer 37, and the resin layer 37 is made of a resin softer than the substrate 35. For example, the base 35 is made of a resin such as polyethylene terephthalate (PET), and the resin layer 37 is made of a soft resin such as Polyolefin (PO) and polyvinyl chloride (PVC).

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

When the sheet 33 is attached to the optical device wafer 11, first, the optical device wafer 11 is 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. Then, the optical device wafer 11 is disposed so that the back surface 13b side of the substrate 13 faces the holding surface 30a of the holding table 30. In addition, the structure of the holding table 30 is not limited as long as the optical device wafer 11 can be held. For example, the holding table 30 is configured in the same manner as the holding table 10 shown in fig. 3 (a) and 3 (B).

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

At this time, the adhesive layer 39 of the sheet 33 is in contact with and adhered to only the outer peripheral region (outer peripheral surplus region) of the substrate 13 where the plurality of optical devices 17 are not formed on the substrate 13. Also, the resin layer 37 made of a soft resin is in contact with the upper surfaces of the plurality of optical devices 17, and enters the gaps between the optical devices 17.

The sheet 33 is preferably attached in a reduced pressure chamber, as in the case of the above-described sheet 31 (see fig. 3a and 3B). Specifically, the optical device wafer 11 is held by the holding stage 30 provided in the decompression chamber. Then, the sheet 33 is pressed against the substrate 13 while being heated in a state where the pressure in the pressure reducing chamber is reduced. Thereby, the sheet 33 is brought into close contact with the substrate 13 so 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.

Fig. 4 (B) is a cross-sectional view showing the substrate 13 to which the sheet 33 is attached. When the sheet 33 is pasted on the front surface 13a side of the substrate 13, the plurality of optical devices 17 are covered with the sheet 33, and the sheet 33 is deformed in such a manner as to mimic (follow) the gap between the optical devices 17. Specifically, the resin layer 37 of the sheet 33 deforms and comes into close contact with the optical devices 17 in a manner to simulate the gaps between the optical devices 17.

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

Further, the sheet 33 has the adhesive layer 39 only in a region corresponding to the outer peripheral remaining region of the substrate 13. Therefore, even if the sheet 33 is attached to the substrate 13, the adhesive layer 39 does not contact the optical device 17. This prevents a part of the adhesive layer 39 from remaining on the optical device 17 when the optical device 17 is finally separated from the sheet 33 in the subsequent process.

Next, a pulse laser beam having transparency to the substrate 13 and having absorptivity to the buffer layer 21a is irradiated from the back surface 13b side of the substrate 13, thereby damaging the buffer layer 21a (buffer layer damaging step). Fig. 5 is a sectional view showing the optical device wafer 11 in the buffer layer destruction step.

The buffer layer breaking step is performed 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 that irradiates a laser beam toward the optical device wafer 11 held by the holding table 42.

The holding table 42 is formed in a circular shape in plan view corresponding to the shape of the optical device wafer 11, for example, 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 injector via a flow path (not shown) formed inside the holding table 42.

The optical device wafer 11 is disposed on the holding table 42 so that the front surface 13a side (the optical device 17 side, the sheet 31 side) of the substrate 13 faces the holding surface 42a and the back surface 13b side of the substrate 13 is exposed upward. In this state, when the negative pressure of the suction source is applied to the holding surface 42a, the optical device wafer 11 is sucked and held by the holding table 42.

The holding table 42 is connected to a moving mechanism (not shown) for moving the holding table 42 in the horizontal direction. The position of the holding table 42 in the horizontal direction is controlled by the moving mechanism. The holding table 42 is connected to a rotation mechanism (not shown) that rotates the holding table 42 about a rotation axis substantially parallel to the vertical direction.

On the holding table 4A laser irradiation unit 44 is provided above the substrate 2. The laser irradiation unit 44 includes a laser oscillator 46 that pulses a laser beam having a predetermined wavelength. Examples of the laser oscillator 46 include a YAG laser and YVO₄Lasers, YLF lasers, etc. The laser beam pulsed by the laser oscillator 46 is reflected by the mirror 48, enters the condenser lens 50, and is condensed by the condenser lens 50 to a predetermined position.

The laser beam 52 is irradiated from the laser irradiation unit 44 toward the optical device wafer 11 held by the holding table 42. The wavelength of the laser beam 52 is set so that the laser beam 52 is transparent to the substrate 13 and absorptive to the buffer layer 21 a. Therefore, the laser beam 52 that is transmitted through the substrate 13 and absorbed by the buffer layer 21a is irradiated from the laser irradiation unit 44 to the optical device wafer 11.

In the buffer layer breaking step, first, the holding table 42 holding the optical device wafer 11 is positioned below the condenser lens 50. Then, the laser beam 52 is irradiated from the laser irradiation unit 44 toward the back surface 13b side of the substrate 13.

The laser beam 52 is irradiated onto one buffer layer 21a through the substrate 13, and is absorbed by the buffer layer 21 a. This causes the buffer layer 21a to be broken, and the junction between the optical device 17 and the substrate 13 in contact with the broken buffer layer 21a is weakened. The irradiation conditions (power, spot diameter, repetition frequency, condensing position, etc.) of the laser beam 52 are appropriately set within a range capable of breaking the buffer layer 21 a.

In addition, the focal point of the laser beam 52 is positioned, for example, inside or near the buffer layer 21 a. The position of the laser beam 52 is not limited as long as the buffer layer 21a can be broken.

In the buffer layer destruction step, it is not always necessary to completely remove the buffer layer 21a and completely separate the substrate 13 and the optical device 17. Specifically, when the sheet 31 is peeled off from the substrate 13 in the optical device transfer step described later, the bonding between the optical device 17 and the substrate 13 may be weakened to such an extent that the optical device 17 follows the separation of the sheet 31 from the substrate 13.

For example, in the buffer layer destruction step, the buffer layer 21a is irradiated with the laser beam 52 to form a modified layer (modified layer) in the buffer layer 21a, whereby the junction between the optical device 17 and the substrate 13 is weakened. This altered layer corresponds to a layer (separation layer) which is the start of separation when the optical device 17 is separated from the substrate 13. However, the mode of breaking the buffer layer 21a is not limited to this, and the substrate 13 and the optical device 17 may be completely separated by adjusting the irradiation conditions of the laser beam 52.

Thereafter, the other buffer layer 21a is also irradiated with the laser beam 52 in the same manner. Thereby, all the buffer layers 21a are broken, and the bonding 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 onto the sheet 31 (optical device transfer step). Fig. 6 is a perspective view showing the optical device wafer 11 in the optical device transfer step. In the optical device transfer step, the sheet 31 is moved in a direction away from the substrate 13 in a state where the substrate 13 is fixed. Thereby, the sheet 31 is peeled from the front surface 13a side of the substrate 13.

Immediately before the sheet 31 is peeled off, the sheet 31 is stuck so as to follow the gap between the optical devices 17, and is brought into close contact with the upper surface and the side surface of the optical device 17 (see fig. 3B and 4B). In the buffer layer breaking step, the buffer layer 21a (see fig. 5 and the like) is broken to be embrittled or removed. Therefore, when the sheet 31 is peeled off from the substrate 13, as shown in fig. 6, the plurality of optical devices 17 are separated from the substrate 13 following the sheet 31 and transferred onto the sheet 31.

In addition, the method of peeling the sheet 31 is not limited. For example, the end of the sheet 31 may be gripped by a gripping tool to peel the sheet 31. Further, a peeling tape may be attached to the sheet 31 to integrate the sheet 31 and the peeling tape, and then the peeling tape may be peeled from the substrate 13 together with the sheet 31.

Further, when the sheet 31 is peeled, a treatment for promoting the peeling may be performed. For example, the peeling between the substrate 13 and the sheet 31 may be promoted by applying ultrasonic vibration to the substrate 13. Further, 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. Further, a gas such as air may be ejected from the side of the substrate 13 toward the interface between the substrate 13 and the sheet 31 to promote separation of the substrate 13 and the sheet 31.

As described above, in the method of transferring an optical device according to the present embodiment, the sheet 31 (or the sheet 33) is attached so as to follow the gap between the optical devices 17 formed on the substrate 13. Thereby, the plurality of optical devices 17 are firmly fixed to the sheet 31, and when the sheet 31 is peeled off from the substrate 13, the plurality of optical devices 17 are reliably separated from the substrate 13. This enables the optical device 17 to be reliably transferred from the substrate 13 to the sheet 31.

The plurality of optical devices 17 transferred onto the sheet 31 are, for example, transferred and bonded onto another substrate (transfer substrate) on which the optical devices 17 are intended to be mounted. In the present embodiment, the sheet 31 to which the plurality of optical devices 17 are transferred is attached to a transfer substrate, and the plurality of optical devices 17 are bonded to the transfer substrate (bonding step). This enables the plurality of optical devices 17 to be collectively bonded.

Specifically, first, a substrate (mounting substrate) on which a plurality of optical devices 17 are mounted is prepared. A plurality of electrodes connected to the optical devices 17 are formed on the front surface of the mounting substrate. Here, a case will be described where the arrangement of the plurality of electrodes provided on the mounting substrate corresponds to the arrangement of the plurality of optical devices 17 (see fig. 6) buried in the sheet 31.

In the bonding step, first, an adhesive for bonding the optical device 17 and the electrode of the mounting 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 mounting substrate. The material of the bonding agent is not limited, and for example, Sn — Cu solder or the like that electrically connects the optical device 17 and the electrode of the mounting substrate can be used.

Next, the surface of the mounting substrate on which the electrodes are formed is opposed to the surface of the sheet 31 on which the optical devices 17 are exposed, and the sheet 31 is bonded to the mounting substrate. Thereby, the plurality of optical devices 17 are bonded to the electrodes of the mounting substrate via the bonding agent, and the plurality of optical devices 17 are collectively bonded. Thereafter, when the sheet 31 is peeled off from the mounting substrate, the plurality of optical devices 17 are separated from the sheet 31 in a state of being bonded to the mounting substrate.

In addition, 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 provided in the mounting substrate, the intervals between the optical devices 17 may be adjusted by stretching and expanding the sheet 31. Specifically, as the sheet 31, a tape that can be expanded (stretched) by application of an external force is used. Then, the sheet 31 is used to perform the sheet attaching step, the buffer layer breaking step, and the optical device transfer step.

Thereafter, the interval of the optical devices 17 is expanded by expanding the sheet 31. The amount of expansion 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, the expanded sheet 31 is attached to the mounting substrate, whereby the plurality of optical devices 17 are collectively mounted on the mounting substrate.

The structure, method, and the like of the above embodiments can be modified and implemented as appropriate within a range not departing from the object of the present invention.

Claims

1. A method of transferring an optical device, in which a plurality of optical devices are transferred from an optical device wafer having the plurality of optical devices formed on a front surface side of a substrate with a buffer layer interposed therebetween,

the method for transferring the optical device comprises the following steps:

a sheet attaching step of attaching a sheet on the front surface side of the substrate so as to cover the plurality of optical devices and to simulate a gap between the optical devices;

a buffer layer breaking step of, after the sheet attaching step is performed, irradiating a pulse laser beam having transparency to the substrate and absorbability to the buffer layer from a back side of the substrate to break the buffer layer; and

and an optical device transfer step of peeling the sheet from the substrate after the buffer layer breaking step is performed, and transferring the plurality of optical devices to the sheet.

2. The method for transferring an optical device according to claim 1,

in the sheet attaching step, the sheet is attached to the substrate by thermocompression bonding.

3. The method for transferring an optical device according to claim 1,

the sheet has a resin layer and an annular adhesive layer corresponding to a region of the substrate where the optical device is not formed,

in the sheet attaching step, the sheet is attached to the substrate in such a manner that the adhesive layer does not contact the optical devices and the resin layer mimics a gap between the optical devices.