Source: http://www.google.com/patents/US7205213
Timestamp: 2016-07-29 13:35:29
Document Index: 209664471

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Patent US7205213 - Device transferring method - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA method of selectively transferring devices arrayed on a first substrate to a second substrate on which an adhesive resin layer is previously formed is provided. The method includes steps of selectively heating the adhesive resin layer on the second substrate by laser irradiation from the back surface...http://www.google.com/patents/US7205213?utm_source=gb-gplus-sharePatent US7205213 - Device transferring methodAdvanced Patent SearchPublication numberUS7205213 B2Publication typeGrantApplication numberUS 11/079,780Publication dateApr 17, 2007Filing dateMar 14, 2005Priority dateApr 11, 2001Fee statusPaidAlso published asUS6872635, US7195687, US7205212, US7205214, US7763139, US20030162463, US20050155699, US20050158895, US20050158896, US20050158904, US20070048891, WO2002084631A1Publication number079780, 11079780, US 7205213 B2, US 7205213B2, US-B2-7205213, US7205213 B2, US7205213B2InventorsKunihiko Hayashi, Yoshiyuki Yanagisawa, Toshiaki Iwafuchi, Hisashi OhbaOriginal AssigneeSony CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (5), Referenced by (7), Classifications (46), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetDevice transferring method
US 7205213 B2Abstract
1. A device transferring method of selectively transferring devices arrayed on a first substrate to a second substrate on which an adhesive resin layer is previously formed, the method comprising:
selectively heating the adhesive resin layer on the second substrate by laser irradiation from a back surface side of the second substrate; and
curing a selectively heated portion of the adhesive resin layer, thereby adhesively bonding devices arrayed on the first substrate to be transferred to the second substrate, wherein the adhesive resin layer includes a thermoplastic adhesive resin,
wherein after the adhesively bonding, devices on the second substrate include a red light emitting diode, a green light emitting diode, and a blue light emitting diode, and
wherein the red light emitting diode does not include a hexagonal pyramid shape.
This patent application is a continuation of U.S. application Ser. No. 10/297,872 filed on Dec. 10, 2003 which is a U.S. Pat. No. 6,872,635, the disclosure of which is herein incorporated by reference. U.S. application Ser. No. 10/297,872 is a 35 U.S.C. �371 application based on International Application PCT/JP02/03549 filed on Apr. 09, 2002. The present application claims priority to Japanese Patent Application Nos. P2001-112401 filed on Apr. 11, 2001; P2001-169857 filed on Jun. 5, 2001; P2001-194890 filed on Jun. 27, 2001; herein incorporated by reference.
Since an LED (Light Emitting Diode) representative of a light emitting device is expensive, an image display unit using such LEDs can be fabricated at a low cost by producing a large number of LEDs from one wafer. To be more specific, the cost of an image display unit can be lowered by reducing the size of an LED chip from about 300 μm square (ordinary size) to several tens μm square, and producing an image display unit by connecting such small-sized LED chips to each other.
From this viewpoint, there have been known various techniques of transferring devices densely formed on a substrate to a wide region in such a manner that the devices are enlargedly spaced from each other in the wide region, thereby obtaining a relatively large display unit such as an image display unit. For example, U.S. Pat. No. 5,438,241 has disclosed a thin film transfer method, and Japanese Patent Laid-open No. Hei 11-142878 has disclosed a method of forming a transistor array panel for display.
In the case of producing image display units by the above-described transfer techniques, it is required to selectively, certainly transfer only devices to be transferred, and to efficiently, accurately transfer only devices to be transferred. In general, there has been known a method of using a thermoplastic resin as an adhesive for mounting, micro-electronic parts, electronic devices, or electronic parts formed by burying these electronic parts or electronic devices in an insulator such as a plastic material, on a mounting substrate. For example, necessary portions of a mounting substrate are coated with a thermoplastic resin, and electronic parts are placed on the portions of the mounting substrate; and then the entire substrate is heated, to soften the adhesive and cool it, thereby fixing the electronic parts on the substrate. Alternatively, the entire surface of the substrate is coated with a thermoplastic resin, and electronic parts are placed thereon; and then the entire substrate is heated, to soften the adhesive and cool it, thereby fixing the electronic parts on the substrate. In addition, there has been known a method of obtaining the same structure by removing the exposed adhesive by etching or plasma treatment.
For example, there has been known a device transferring method shown in FIGS. 1( a) and 1(b), wherein devices 103 are arrayed on an adhesive layer 102 on a base substrate 101 as shown in FIG. 1( a), and are picked up by using an attracting head 104 as shown in FIG. 1( b), to be transferred to an adhesive layer 106 on another substrate 105.
a heating step of selectively heating the adhesive resin layer on the second substrate by laser irradiation from the back surface side of the second substrate; and
a curing step of curing the selectively heated portions of the adhesive resin layer, thereby adhesively bonding those to be transferred of the devices to the second substrate.
With this device transferring method, portions, corresponding to devices to be transferred, of the adhesive resin layer are heated directly or indirectly via the devices or wiring by laser irradiation from the back surface side of the substrate. The heated portions of the adhesive resin layer are allowed to selectively exhibit adhesive forces. By curing these portions of the adhesive resin layer, only the devices to be transferred can be selectively transferred to the second substrate without peeling and positional deviation of other parts. In this case, it is not required to selectively form the adhesive resin layer by coating.
a first transferring step of transferring the devices from the first substrate to a temporarily holding member in such a manner that the devices are spaced from each other with a pitch larger than a pitch of the devices arrayed on the first substrate and holding the devices on the temporarily holding member;
a covering step of covering the devices held on the temporarily holding member with a resin;
a dicing step of dicing the resin so as to isolate the devices from each other;
a second transferring step of transferring the resin-covered devices held on the temporarily holding member to the second substrate in such a manner that the resin-covered devices are spaced from each other with a pitch larger than a pitch of the resin-covered devices held on the temporarily holding member;
wherein the second transferring step includes the steps of selectively heating an adhesive resin layer on the second substrate by laser irradiation from the back surface side of the second substrate, and curing the selectively heated portions of the adhesive resin layer, thereby adhesively bonding those to be transferred of the resin-covered devices to the second substrate.
With this device arraying method, since the devices can be efficiently and performed with certainty and accuracy, it is possible to smoothly perform enlarged transfer by means of which the devices are transferred in such a manner as to be spaced from each other with an enlarged pitch.
a first transferring step of transferring the light emitting devices from the first substrate to a temporarily holding member in such a manner that the light emitting devices are spaced from each other with a pitch larger than a pitch of the light emitting devices arrayed on the first substrate and holding the light emitting devices on the temporarily holding member;
a covering step of covering the light emitting devices held on the temporarily holding member with a resin;
a dicing step of dicing the resin so as to isolate the light emitting devices from each other;
herein the second transferring step includes the steps of selectively heating an adhesive resin layer on the second substrate by laser irradiation from the back surface side of the second substrate, and curing the selectively heated portions of the adhesive resin layer, thereby adhesively bonding those to be transferred of the resin-covered devices to the second substrate.
With this image display unit fabricating method, the light emitting devices are arrayed in a matrix by making use of the above-described device transferring method and the device arraying method, to form an image display portion. Accordingly, it is possible to efficiently re-array the light emitting devices, which have been formed on the first substrate densely, that is, with a high degree of integration, on the second substrate in such a manner as to be spaced from each other with an enlarged pitch, and hence to significantly improve the productivity.
a heating step of selectively heating the adhesive layer on the second substrate by irradiating those to be transferred of the devices with laser beams passing through the second substrate, thereby adhesively bonding the devices to be transferred to the second substrate;
wherein a light absorbing material for increasing a light absorptivity of the adhesive layer against the laser beams is contained in the adhesive layer or disposed in the vicinity of the adhesive layer.
With this device transferring method, portions, corresponding to devices to be transferred, of the adhesive layer can be selectively heated, by laser irradiation from the back surface side of the substrate, directly or indirectly via the devices or wiring without heating portions, near devices other than the devices to be transferred, of the adhesive layer. Also, since the light absorbing material for increasing the light absorptivity of the adhesive layer against laser beams is contained in the adhesive layer or disposed in the vicinity of the adhesive layer, portions, corresponding to devices to be transferred, of the adhesive layer are allowed to more desirably absorb the laser beams, and hence to be more desirably heated. As a result, it is possible to efficiently, selectively heat the portions, corresponding to the devices to be transferred, of the adhesive layer.
a device isolation step of covering the devices held on the temporarily holding member with a resin and isolating the devices covered with the resin from each other;
an adhesive layer forming step of forming an adhesive layer containing a light absorbing material for increasing a light absorptivity against laser beams on the second substrate or disposing the light absorbing material in the vicinity of the adhesive layer; and
a second transferring step of selectively heating the adhesive layer on the second substrate by irradiating those to be transferred of the devices with laser beams passing through the second substrate, thereby transferring those to be transferred of the devices covered with the resin on the temporarily holding substrate to the second substrate.
With this device arraying method, since portions, near the devices to be transferred, of the adhesive layer can be efficiently, certainly heated by using the above-described device transferring method, it is possible to efficiently and with certainty perform the transfer of the desired devices and hence to smoothly perform enlarged transfer by means of which the desired devices are transferred in such a manner as to be spaced from each other with an enlarged pitch.
a device isolation step of covering the light emitting devices held on the temporarily holding member with a resin and isolating the light emitting devices covered with the resin from each other;
a second transferring step of selectively heating the adhesive layer on the second substrate by irradiating those to be transferred of the light emitting devices with laser beams passing through the second substrate, thereby transferring those to be transferred of the light emitting devices covered with the resin on the temporarily holding substrate to the second substrate.
With this image display unit fabricating method, the light emitting devices are arrayed in a matrix by making use of the above-described device transferring method and the device arraying method, to form an image display portion. Accordingly, since portions, near the devices to be transferred, of the adhesive layer can be efficiently, certainly heated, it is possible to efficiently and with certainty perform the transfer of the devices. This makes it is possible to efficiently re-array the light emitting devices, which have been formed on the first substrate densely, that is, with a high degree of integration, on the second substrate in such a manner as to be spaced from each other with an enlarged pitch, and hence to significantly improve the productivity.
a superimposing step of superimposing a second substrate having a thermoplastic adhesive layer on a first substrate on which devices are previously fixed in array via a thermal re-peelable layer; and
a heating/cooling step of heating and cooling, in a state that the devices are in contact with the thermoplastic adhesive layer, the thermal re-peelable layer and the thermoplastic adhesive layer, to make the devices peelable from the thermal re-peelable layer and simultaneously melt and cure the thermoplastic adhesive layer, thereby transferring the devices to the second substrate.
With this device transferring method, the second substrate having the thermoplastic adhesive layer is superimposed on the first substrate on which devices are previously fixed in array via the thermal re-peelable layer, and in a state that the devices are in contact with the thermoplastic adhesive layer, the thermal re-peelable layer and the thermoplastic adhesive layer are heated and cooled, to transfer the devices from the first substrate to the second substrate.
wherein the second transferring step includes:
a fixing step of fixing the resin-covered devices on a second temporarily holding member via a thermal re-peelable layer;
a superimposing step of superimposing the second substrate having a thermoplastic adhesive layer on the second temporarily holding member; and
a heating/cooling step of heating and cooling, in a state that the resin-covered devices are in contact with the thermoplastic adhesive layer, the thermal re-peelable layer and the thermoplastic adhesive layer, to make the resin-covered devices peelable from the thermal re-peelable layer and simultaneously melt and cure the thermoplastic adhesive layer, thereby transferring the resin-covered devices to the second substrate.
With this device arraying method, since the devices can be efficiently and with certainty performed by using the above-described device transferring method, it is possible to smoothly perform enlarged transfer by means of which the desired devices are transferred in such a manner as to be spaced from each other with an enlarged pitch.
With this image display unit fabricating method, the light emitting devices are arrayed in a matrix by making use of the above-described device transferring method and the device arraying method, to form an image display portion. Accordingly, since portions, near the devices to be transferred, of the adhesive layer can be efficiently, certainly heated, it is possible to efficiently, certainly perform the transfer of the devices. This makes it is possible to efficiently re-array the light emitting devices, which have been formed on the first substrate densely, that is, with a high degree of integration, on the second substrate in such a manner as to be spaced from each other with an enlarged pitch, and hence to significantly improve the productivity.
FIGS. 1( a) and 1(b) are schematic sectional views showing a related art device transferring method.
FIG. 2( a) is a schematic view showing a state that an adhesive layer is formed on a base substrate and devices 3 are formed in array on the base substrate via the adhesive layer according to an embodiment of the present invention. FIG. 2( b) is a schematic view showing a state that a temporarily holding member is disposed opposite to the base substrate and is brought into press-contact therewith, and only necessary devices are transferred to the temporarily holding member according to an embodiment of the present invention. FIG. 2( c) is a schematic view showing a state after the temporarily holding member is peeled from the base substrate according to an embodiment of the present invention. FIG. 2( d) is a schematic view showing a state that the temporarily holding member on which the devices have been transferred is disposed opposite to a transfer substrate and is brought into press-contact therewith, and the devices are transferred to the transfer substrate according to an embodiment of the present invention. FIG. 2( e) is a schematic view showing a state that excess portions of an adhesive layer are removed by etching, to accomplish the selective transfer process according to an embodiment of the present invention. FIG. 2( f) is a schematic view showing a state of the transfer substrate to which the devices have been selectively transferred in such a manner as to be located among parts according to an embodiment of the present invention.
FIGS. 6( a) to 6(d) are schematic views showing a device arraying method according to an embodiment of the present invention, wherein FIG. 6( a) shows a state that devices such as light emitting devices are densely formed on a first substrate, FIG. 6( b) shows a state that the devices are transferred from the first substrate to a temporarily holding member shown by broken lines, FIG. 6( c) shows a state that the devices held on the temporarily holding member are spaced from each other, and FIG. 6( d) shows a state that the devices in the form of resin-covered chips are transferred to a second substrate in such a manner as to be enlargedly spaced from each other.
FIGS. 9( a) and 9(b) are a sectional view and a plan view showing one example of a light emitting device according to an embodiment of the present invention.
FIGS. 18( a) to 18(c) are schematic sectional views showing one example of a transfer process according to an embodiment of the present invention, wherein FIG. 18( a) shows a state that the thermal re-peelable layer is formed on a base substrate and a plurality of devices are formed in array on the base substrate via the thermal re-peelable layer, FIG. 18( b) shows a state that a transfer substrate is disposed in a specific positional relationship with the base substrate and is brought into press-contact therewith, and FIG. 18( c) shows a state after the transfer substrate is peeled from the base substrate.
FIGS. 22( a) to 22(c) are sectional views showing one example of a process of transferring devices of one kind to a substrate, on which devices of another kind have been mounted, in accordance with an embodiment of the present invention, wherein FIG. 22( a) shows a state that the devices are mounted on a thermoplastic adhesive layer in such a manner as to be spaced from each other at a specific pitch, FIG. 22( b) shows a state that a transfer substrate is disposed in a specific positional relationship with a base substrate and is brought into press-contact therewith, and FIG. 22( c) shows a state after the transfer substrate is peeled from the base substrate.
In an embodiment, the present invention provides device transferring method, As shown in FIG. 2( a), an adhesive layer 2 is formed on a base substrate 1 as a supply source, and a plurality of devices 3 are formed in array on the adhesive layer 2.
The devices 3 formed on the adhesive layer 2 can be simply transferred to another substrate by using a sticky resin having a relatively small sticky or adhesive force as an adhesive of the adhesive layer 2.
As shown in FIG. 2( b), a temporarily holding substrate (first substrate) 4, which is taken as intermediate means of transfer, is placed opposite to the base substrate 1 and is brought into press-contact therewith, to transfer only desired devices 3 a from the base substrate 1 to the temporarily holding substrate 4.
An adhesive layer is previously formed on the temporarily holding substrate 4 such that adhesive layer portions 5 are selectively located at positions corresponding to those of the devices 3 a to be transferred. By making the sticky force of the adhesive layer portions 5 larger than that of the adhesive layer 2 on the base substrate 1, the devices 3 a can be simply transferred to the temporarily holding substrate 4. FIG. 2( c) shows a state that the temporarily holding substrate 4 has been peeled from the base substrate 1, wherein the devices 3 a are left as transferred on the adhesive layer portions 5 selectively formed on the temporarily holding substrate 4.
As shown in FIG. 2( d), the temporarily holding substrate 4 to which the devices 3 a have been thus transferred is placed opposite to a transfer substrate (second substrate) 6 and is brought into press-contact therewith, to transfer the devices 3 a to the transfer substrate 6 side. It is to be noted that an adhesive layer 7 is previously formed on the overall surface of the transfer substrate 6, wherein other parts 8 are already fixed to the adhesive layer 7. The adhesive layer 7 is formed by coating the surface of the transfer substrate 6 with, for example, a thermoplastic adhesive resin. At the time of transfer of the devices 3 a, it is required to partially irradiate the adhesive layer 7 with laser beams from the back surface side of the transfer substrate 6. Accordingly, the transfer substrate 6 preferably has a light transmissivity.
The heating manners shown in FIGS. 3, 4 and 5 may be performed singly or in combination. In the case of adopting the combination of the heating manners shown in FIGS. 3, 4 and 5, the portion, corresponding to the device 3 a, of the adhesive layer 7 is heated and softened by combining direct laser irradiation of the adhesive layer 7 with indirect laser irradiation of each of the device 3 a and the wiring pattern 9.
As shown in FIG. 2( e), unnecessary portions of the adhesive layer 7 are removed by etching, to accomplish the selective transfer process. Consequently, the transfer substrate 6, to which the devices 3 a have been selectively transferred so as to be located among the parts 8 as shown in FIG. 2( f), can be obtained.
As described above, very narrow portions of the adhesive layer 7 can be heated for a short time by using laser beams. To be more specific, only the portion, corresponding to the devices 3 a, of the adhesive layer 7 can be selectively heated without transfer of the heat to the adjacent portions, to which the parts 8 have been adhesively bonded, of the adhesive layer 7. As a result, the devices 3 a can be selectively transferred without exerting any thermal effect on the fixed states of the parts 8 left as adhesively bonded adjacent to the devices 3 a. If the adhesive layer 7 is overall heated as having been carried out by the related art method, there may occur an inconvenience that the portions, to which the other parts 8 have been fixed, of the adhesively layer 7 be heated and fluidized, thereby tending to displace the parts 8. Such an inconvenience can be solved by the present invention. Another advantage of the present invention is as follows: namely, in the forming the adhesive layer 7, it is not required to selectively coat only the portions, corresponding to the devices 3 a, of the transfer substrate 6 with a small amount of the adhesive, but it is sufficient to coat the overall surface of the transfer substrate 6 with the adhesive, and consequently, it is possible to simplify the selective transfer process.
FIGS. 6( a) to 6(d) show basic steps of the two-step enlarged transfer method.
As shown in FIG. 6( a), devices 12 such as light emitting devices are densely formed on a first substrate 10. By densely forming devices on a substrate, the number of devices formed per each substrate can be increased, to reduce a final product cost thereof. The first substrate 10 may be selected from substrates on each of which devices can be formed, for example, a semiconductor wafer, a glass substrate, a quartz glass substrate, a sapphire substrate, and a plastic substrate. The devices 12 may be directly formed on the first substrate 10, or may be formed once on another substrate, and then transferred to the first substrate 10.
As shown in FIG. 6( b), the devices 12 are transferred from the first substrate 10 to a temporarily holding member 11 shown by broken lines in the figure, and held on the temporarily holding member 11. On the temporarily holding member 11, the adjacent two of the devices 12 are enlargedly spaced from each other, and the devices 12 are arrayed in a matrix as a whole (see FIG. 6( b)). Specifically, the devices 12 are transferred onto the temporarily holding member 11 in such a manner as to be enlargedly spaced from each other not only in the X direction but also in the Y direction perpendicular to the X direction. The enlarged distance between the adjacent two of the devices 12 on the temporarily holding member 11 is not particularly limited, but may be determined, for example, in consideration of formation of resin portions and formation of electrode pads in the subsequent steps. The devices 12 on the first substrate 10 can be all transferred from the first substrate 10 to the temporarily holding member 11 in such a manner as to be enlargedly spaced from each other. In this case, a size of the temporarily holding member 11 in each of the X direction and the Y direction may be equal to or more than a value obtained by multiplying the enlarged distance by the number of those, arrayed in each of the X direction and the Y direction, of the devices 12 arrayed in the matrix on the temporarily holding member 11. In addition, part of the devices 12 on the first substrate 10 may be transferred to the temporarily holding member 11 in such a manner as to be enlargedly spaced from each other.
After such a first transferring step, as shown in FIG. 6( c), each of the devices 12 enlargedly spaced from each other on the temporarily holding member 11 is covered with a resin, and electrode pads are formed on the resin portion covering the device 11. The reason why each device 11 is covered with the resin is to facilitate the formation of the electrode pads and to facilitate the handling of the device 11 in the subsequent second transferring step. To prevent occurrence of a wiring failure in a final wiring step performed after the second transferring step (which will be described later), the electrode pads are formed into relatively large sizes. It is to be noted that the electrode pads are not shown in FIG. 6( c). A resin-covered chip 14 is thus formed by covering each of the devices 12 with a resin 13. The device 11 is located at an approximately central portion of the resin-covered chip 14 in a plan view in this embodiment; however, the device 11 may be located at a position offset to one side or a corner of the resin-covered chip 14.
As shown in FIG. 6( d), a second transferring step is carried out. In this second transferring step, the devices 12 arrayed in the matrix on the temporarily holding member 11 in the form of the resin-covered chips 14 are transferred to a second substrate 15 in such a manner as to be more enlargedly spaced from each other.
It is to be noted that as will be described in detail, the transfer method shown in FIGS. 2( a) to 2(f) is applied to the second transferring step.
In the two-step enlarged transfer shown in FIGS. 6( a) to 6(d), each device 11 is covered with the resin and electrode pads are formed on the resin portion covering the device 11 by making use of the enlarged distance between adjacent two of the devices 12 after the first transfer, and wiring can be performed after the second transfer without occurrence of any connection failure by making use of the previously formed electrode pads and the like. As a result, it is possible to improve a fabrication yield of the image display unit.
In the two-step enlarged transfer method shown in FIGS. 6( a) to 6(d), the device 12 is exemplified by a light emitting device; however, the device 12 is not limited thereto but may be selected from a liquid crystal control device, a photoelectric transfer device, a piezoelectric device, a thin film transistor device, a thin film diode device, a resistance device, a switching device, a micro-magnetic device, a micro-optical device, and a combination thereof.
FIGS. 9( a) and 9(b) are a sectional view and a plan view, showing a light emitting device as one example of the device used for the two-step enlarged transfer method according to an embodiment of the present invention.
The light emitting diode has a p-electrode 35 and an n-electrode 36. A metal material such as Ni/Pt/Au or Ni(Pd)/Pt/Au is vapor-deposited on the GaN layer 34 doped with magnesium, to form the p-electrode 35. A metal material such as Ti/Al/Pt/Au is vapor-deposited in an opening formed in the above-described insulating film (not shown), to form the n-electrode 36. If an n-electrode is extracted from the back surface side of the under growth layer 31 as shown in FIG. 11, the n-electrode 36 is not required to be formed on the front surface side of the under growth layer 31.
A concrete method of arraying the light emitting devices shown in FIGS. 6( a) to 6(d) will be described below with reference to FIGS. 10 to 16.
The GaN based light emitting diode shown in FIGS. 9( a) and 9(b) is used as the light emitting device. First, as shown in FIG. 10, a plurality of light emitting diodes 42 are formed in a matrix on a principal plane of a first substrate 41. A size of the light emitting diode 42 is set to about 20 μm. The first substrate 41 is made from a material having a high transmittance for a wavelength of a laser beam used for irradiation of the light emitting diode 42, for example, made from sapphire. The light emitting diode 42 is already provided with a p-electrode and the like but is not subjected to final wiring. Device isolation grooves 42 g are already formed, to make the light emitting diodes 42 isolatable from each other. The formation of the grooves 42 g may be made, for example, by reactive ion etching. As shown in FIG. 11, such a first substrate 41 is placed opposite to a temporarily holding member 43 for selective transfer of the light emitting diodes 42 therebetween.
The light emitting diode 42, which has been selectively irradiated with a laser beam, is peeled from the first substrate 41 at the interface between the GaN layer and the first substrate 41 by laser abrasion, and is transferred to the opposed temporarily holding member 43 in such a manner that the p-electrode portion of the light emitting diode 42 is pieced in the corresponding non-cured region 45 y of the adhesive layer 45. The other light emitting diodes 42, which are left as not irradiated with laser beams and also located at positions corresponding to those of the cured region 45 s of the adhesive layer 45, are not transferred to the temporarily holding member 43. It is to be noted that only one light emitting diode 42 is depicted as selectively irradiated with a laser beam in FIG. 10; however, in actual, the light emitting diodes 42 spaced from each other with an n-pitch are similarly irradiated with laser beams. With such selective transfer, the light emitting diodes 42 are arrayed on the temporarily holding member 43 in such a manner as to be enlargedly spaced from each other with a pitch larger than an original pitch of the light emitting diodes 42 arrayed on the first substrate 41.
As one example of cleaning the back surface of the light emitting device 42 to remove the adhesive resin of the adhesive layer 45 therefrom, the adhesive resin is etched with oxygen plasma, followed by cleaning by irradiation of UV ozone. In addition, when the GaN based light emitting diode 42 is peeled from the first substrate 41 made from sapphire by laser irradiation, gallium is deposited on the peeling plane. Such an element must be etched, for example, by using an NaOH containing water solution or dilute nitric acid. The electrode pad 46 is then patterned. At this time, the electrode pad 46 on the cathode side can be formed into a size of about 60 μm square. As the electrode pad 46, there can be used a transparent electrode (ITO or ZnO based electrode) or a Ti/Al/Pt/Au electrode. In the case of using a transparent electrode, even if the electrode largely covers the back surface of the light emitting diode 42, it does not shield light emission from the light emitting diode 42. Accordingly, a patterning accuracy of the transparent electrode may be rough and further the size of the electrode can be made large, to thereby facilitate the patterning process.
As one example of the above process of forming the anode side electrode pad 49, the surface of the second temporarily holding member 47 is etched by oxygen plasma until the surface of the light emitting diode 42 is exposed. The formation of the via-hole 50 having a diameter of about 3 to 7 μm can be made by an excimer laser beam, a harmonic YAG laser beam, or a carbon dioxide laser beam. The anode side electrode pad 49 is formed by, for example, Ni/Pt/Au. The dicing process is performed by using a usual blade, and if a narrow cut-in width of 20 μm or less is needed, the dicing process may be performed by using the above-described laser beam. The cut-in width is dependent on the size of a resin-covered chip, formed by covering the light emitting diode 42 with the adhesive layer 45 made from the resin, within a pixel of the final image display unit. As one example, the device isolation grooves having the cut-in width of about 40 μm are formed by an excimer laser beam, to form each resin-covered chip.
FIG. 14 is a view showing a state that the light emitting diode 42 is transferred to a second substrate 60 by using the above-described transfer method shown in FIG. 2( a) to FIG. 5. An adhesive layer 56 is previously formed on the second substrate 60 before the light emitting diode 42 is transferred to the second substrate 60. By curing a portion, located on the back surface of the light emitting diode 42, of the adhesive layer 56, the light emitting diode 42 is fixed on the second substrate 60. Upon this mounting, the pressure of the attracting chamber 54 of the attracting system 53 becomes high, to release the coupling state between the light emitting diode 42 and the attracting system 53 by attraction.
FIG. 16 is a view showing a wiring formation step. Opening portions 65, 66, 67, 68, 69, and 70 are formed in the insulating layer 59, and wiring portions 63, 64 and 71 for connecting the electrode pads for the anode and cathode of each of the light emitting diodes 42, 61 and 62 to the electrode layer 57 for wiring on the second substrate 60 are formed in the opening portions 65, 66, 67, 68, 69 and 70. Since the areas of the electrode pads 46 and 49 of each of the light emitting diodes 42, 61, and 62 are large, the shapes of the opening portions, that is, via-holes can be made large. As a result, each via-hole can be formed with a rough positioning accuracy as compared with a via-hole directly formed in each light emitting diode. For each of the electrode pads 46 and 49 having a size of about 60 μm square, the via-hole having a diameter of about 20 μm can be formed. The via-holes are of three kinds having different depths: the first kind is connected to the wiring substrate, the second kind is connected to the anode electrode, and the third kind is connected to the cathode electrode. The depth of each via-hole is optimized by controlling the pulse number of a laser beam depending on the kind of the via-hole. A protective layer is then formed on the wiring, to accomplish a panel of an image display unit. The protective layer may be made from the same transparent epoxy adhesive as that used for the insulating layer 59 shown in FIG. 17. The protective layer is heated to be cured, to perfectly cover the wiring. A driver IC is then connected to the wiring at the end portion of the panel, to produce a drive panel.
The presence of the light absorbing material 7 a has another advantage that since the laser beams L are absorbed by the light absorbing material 7 a for increasing a light absorptivity of the adhesive layer 7 against the laser beams L, and therefore, the laser beams L do not reach the device 3 a, it is possible to prevent the device 3 a from being damaged by the laser beams L.
The adhesive layer 7 containing the light absorbing material 7 a for increasing a light absorptivity of the adhesive layer 7 against the laser beams L can be performed in another manner. In the device transferring method according to the first embodiment, as shown in FIG. 3, the device 3 a to be transferred is irradiated with the laser beams L having passed through the adhesive layer 7, to indirectly heat the portion, corresponding to the device 3 a, of the adhesive layer 7. In this laser irradiation manner, according to the second embodiment, since the light absorbing material 7 a for increasing a light absorptivity of the adhesive layer 7 against the laser beams is contained in the adhesive layer 7 (or disposed in the vicinity of the adhesive layer 7), the laser beams L are absorbed by the light absorbing material 7 a having a light absorptivity against the laser beams L, with a result that the laser beams L do not reach the device 3 a, thereby preventing the device 3 a from being damaged by the laser beams L.
Since the light absorbing material having a light absorptivity against the laser beams L prevents the laser beams L from reaching the device 3 a, the laser beams L do not reach the device 3 a. As a result, it is possible to freely select the kind and wavelength of the laser irrelevant to the material of the device 3 a without taking into account the fact that the device 3 a is damaged by the laser beams L.
A further advantage of the device transferring method according to an embodiment is that since the time required for irradiating each light emitting diode 42 to be transferred with the laser beams 73 is short because of efficient heating the portion, corresponding to the light emitting diode 42, of the adhesive layer 56 and the portions, corresponding to the light emitting diodes not to be transferred, of the adhesive layer 56 are not heated, the light emitting diodes 42 to be transferred can be certainly, accurately arrayed without exerting adverse effect on the fixed states of the other light emitting diodes, that is, without peeling and positional deviation of the light emitting diodes other than the light emitting diodes 42 to be transferred.
A device transferring method according to an embodiment of the present invention will be described below. To transfer devices 3 in accordance with the device transferring method of the present invention, as shown in FIG. 18( a), a thermal re-peelable layer 81 is formed on a base substrate 1 as a supply source, and a plurality of devices are formed in array on the base substrate 1.
The thermal peelable material is a material capable of reducing its sticky force by a foaming or expansion treatment due to heating, thereby making a member adhesively bonded to the material simply peelable therefrom. Specifically, when the thermal peelable material is heated, a foaming agent or an expanding agent contained in the material is foamed or expanded, to reduce the sticky area of the material, thereby losing the sticky force of the material. For example, a heating re-peelable type sticky sheet composed of a base material and a sticky layer containing a foaming agent provided thereon is disposed, for example, in Japanese Patent Laid-open Nos. Sho 50-13878 and Sho 51-24534, and Japanese Patent Publication Nos. Sho 56-61468, Sho 56-61469, and Sho 60-252681. A heating peelable type sticky sheet composed of a thermal expandable layer containing thermal expandable micro-balls and thereby being expandable by heating and a non-expandable sticky layer provided at least one surface of the thermal expandable layer is disclosed, for example, in Japanese Patent Laid-open No. 2000-248240. A heating peelable type sticky sheet configured such that a thermal expandable layer containing thermal expandable micro-balls and a sticky layer containing a sticky material are provided at least on one surface of a base material having a heat resistance and a flexibility is disclosed, for example, in Japanese Patent Laid-open No. 2000-169808.
The thermal expandable layer can be formed by mixing thermal expandable micro-balls with a binder. The binder is exemplified by a polymer or a wax allowing foaming and/or expansion of the thermal expandable micro-balls due to heating. In particular, from the viewpoint of controlling the heating expansion characteristic of thermal expandable micro-balls and the sticking characteristic such as a sticky force against a member bonded to a sticky layer via the sticky layer, a sticker is preferably used as the binder. The sticker is not particularly limited but may be selected from polymers such as a rubber based polymer, an acrylic based polymer, a vinyl alkyl ether based polymer, a silicone based polymer, a polyester based polymer, a polyamide based polymer, an urethane based polymer, a fluorine based polymer, and a styrene-diene copolymer. Such a polymer may be added with a thermally molten resin having a melting point of about 200� C. or less for improving the creep characteristic of the polymer. The sticker may be an ultraviolet-curing type polymer. The above polymer used for the sticker may be further added with one or more additives such as a crosslinking agent, a tackifier, a plasticizer, a softener, a filler, a pigment, a coloring agent, an antioxidant, and a surface active agent.
The sticky layer may contain, in addition to the sticky material, one or more additives, for example, a crosslinking agent such as an isocyanate based crosslinking agent or an epoxy based crosslinking agent, a tackifier such as a rosin derivative resin, a polyterpene resin, a petroleum resin, or an oil soluble resin, a plasticizer, a filler, and an antioxidant.
The thermal re-peelable layer 81 may be formed on the overall surface of a principal plane, on the side on which the devices 3 are to be arrayed, of the base substrate 1, or selectively formed on the principal plane of the base substrate 1 at positions corresponding to those f the devices 3. In the case of forming the thermal re-peelable layer 81 by coating, however, it is desirable to uniformly form the thermal re-peelable layer 81 on the overall surface from the viewpoint of simplifying the process.
As shown in FIG. 18( a), the thermoplastic adhesive layer 82 is formed on a principal plane, taken as a transfer plane of the devices 3, on the transfer substrate 83. The transfer substrate 83 is disposed in a specific positional relationship with the base substrate 1 such that the devices 3 are opposed to the thermoplastic adhesive layer 82.
To transfer the devices 3, as shown in FIG. 18( b), the transfer substrate 83 is disposed in a specific positional relationship with the base substrate 1 and is then brought into press-contact therewith, and in such a state, the thermal re-peelable layer 81 is heated by giving heat H to the overall surface by a heat source such as an oven, to reduce the sticky force of the thermal re-peelable layer 81 against the devices 3, whereby the devices 3 become peelable from the thermal re-peelable layer 81. The thermoplastic adhesive layer 82 is softened by heating the layer 82, and is then cooled to be cured, to fix the devices 3 to the thermoplastic adhesive layer 82. That is to say, the softened thermoplastic adhesive layer 82 exhibits an adhesive force against the devices 3. When the thermoplastic adhesive layer 82 is softened, the heating is stopped, to cool and cure the thermoplastic adhesive layer 82, so that the devices 3 are transferred to the transfer substrate 83 via the thermoplastic adhesive layer 82. The transfer substrate 83 is then peeled from the base substrate 1, and the thermoplastic adhesive layer 82 is cooled to room temperature, whereby the devices 3 are certainly fixed to the transfer substrate 83. The transfer step is thus accomplished.
FIG. 18( c) shows a state after the transfer substrate 83 is peeled from the base substrate 21, wherein the devices 3 are left as transferred on the thermoplastic adhesive layer 82.
As shown in FIG. 22( a), a thermoplastic adhesive layer 82 made from a thermoplastic resin is formed on a transfer substrate 83 and devices 3 of one kind are mounted on the thermoplastic adhesive layer 82 in such a manner as to be spaced at specific intervals. Meanwhile, a thermal re-peelable layer 81 is formed on a base substrate 81 and devices 7 of another kind are arrayed on the thermal re-peelable layer 81 in such a manner as to be spaced from each other at specific intervals. Here, the height of the device 7 is set to be larger than that of the device 3.
To transfer the devices 7 of another kind, as shown in FIG. 22( b), the transfer substrate 83 is disposed in a specific positional relationship with the base substrate 1 and is then brought into press-contact therewith, and in such a state, only the devices 7 are selectively irradiated with laser beams L from the back surface side of the transfer substrate 83, to be thus heated. The heat of the devices 7 is transmitted to the thermal re-peelable layer 81, to heat portions, corresponding to the devices 7, of the peelable layer 2, to reduce the sticky force of the thermal re-peelable layer 81 against the devices 7, thereby making the devices 7 peelable from the thermal re-peelable layer 81. The heat of the devices 7 is also transmitted to the thermoplastic adhesive layer 82, to soften portions, corresponding to the devices 7, of the thermoplastic adhesive layer 82. As a result, the portions, corresponding to the devices 7, of the thermoplastic adhesive layer 82 exhibit the adhesive forces against the devices 7. In this case, since the heated areas of the thermal re-peelable layer 81 are small, they are not affected by the thermal contraction characteristic of the base substrate 1, whereby the devices can be accurately positioned. When the thermoplastic adhesive layer 82 is softened, the heating is stopped, to cool and cure the thermoplastic adhesive layer 82, so that the devices 7 are fixed to the transfer substrate 83 via the thermoplastic adhesive layer 82. In this way, the devices 7 can be transferred from the base substrate 1 to the transfer substrate 83. The transfer substrate 83 is then peeled from the base substrate 1, and the thermoplastic adhesive layer 82 is cooled to room temperature, whereby the devices 3 are certainly fixed to the transfer substrate 83. The transfer step is thus accomplished.
FIG. 22( c) shows a state after the transfer substrate 83 is peeled from the base substrate 1, wherein the devices 8 of another kind are left as transferred to the thermoplastic adhesive layer 82 in such a manner as to be located among the devices 3.
With a device transferring method according to an embodiment of the present invention, since the peeling of the devices from the first substrate and the adhesive bonding of the devices on the second substrate can be performed only by the heating process, the devices can be very simply transferred without the need of provision of members such as an attracting head and an ultraviolet irradiation apparatus required in the case of using an ultraviolet-curing type material. Since the transfer process is simple, it is possible to easily, certainly perform the positioning of the devices, and hence to accurately transfer the devices without occurrence of any positional deviation of the transferred devices.
With a device arraying method according to an embodiment of the present invention, since the devices can be efficiently, certainly performed by using the above-described device transferring method, it is possible to smoothly perform enlarged transfer by means of which the desired devices are transferred in such a manner as to be spaced from each other with an enlarged pitch.
With an image display unit fabricating method according to an embodiment of the present invention, it is possible to efficiently re-array the light emitting devices, which have been formed on the first substrate densely, that is, with a high degree of integration, on the second substrate in such a manner as to be spaced from each other with an enlarged pitch by using the above-described device transferring method and device arraying method, and hence to fabricate a precise image display unit with a high productivity.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS5438241 *Nov 1, 1993Aug 1, 1995Kopin CorporationSingle crystal silicon arrayed devices for display panelsUS6872635 *Apr 9, 2002Mar 29, 2005Sony CorporationDevice transferring method, and device arraying method and image display unit fabricating method using the sameUS20020171089 *Mar 6, 2002Nov 21, 2002Hiroyuki OkuyamaDisplay unit and semiconductor light emitting deviceUS20050158094 *Jan 21, 2004Jul 21, 2005Xerox CorporationHigh print rate merging and finishing system for parallel printingUS20050158896 *Mar 14, 2005Jul 21, 2005Kunihiko HayashiDevice transferring method* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS7701424Mar 11, 2004Apr 20, 2010Seiko Epson CorporationDisplay panel having a substratum and a plurality of scan lines formed on the substratum, a display device, and electronic device thereofUS8228454Mar 10, 2010Jul 24, 2012Semiconductor Energy Laboratory Co., Ltd.Peeling method and method for manufacturing display device using the peeling methodUS8508682Jul 12, 2012Aug 13, 2013Semiconductor Energy Laboratory Co., Ltd.Peeling method and method for manufacturing display device using the peeling methodUS8830413Jul 25, 2013Sep 9, 2014Semiconductor Energy Laboratory Co., Ltd.Peeling method and method for manufacturing display device using the peeling methodUS9013650Aug 4, 2014Apr 21, 2015Semiconductor Energy Laboratory Co., Ltd.Peeling method and method for manufacturing display device using the peeling methodUS9299879Mar 19, 2015Mar 29, 2016Semiconductor Energy Laboratory Co., Ltd.Peeling method and method for manufacturing display device using the peeling methodUS20100167437 *Mar 10, 2010Jul 1, 2010Semiconductor Energy Laboratory Co., Ltd.Peeling method and method for manufacturing display device using the peeling method* Cited by examinerClassifications U.S. Classification438/463, 438/66, 438/464International ClassificationH01L21/68, H01L25/075, H01L21/60, H01L21/336, H01L21/00, B44C1/165, B44C1/00, H01L21/50Cooperative ClassificationH01L2924/12042, H01L2924/12041, H01L2924/0102, H01L2924/01013, H01L2224/18, H01L2924/01075, H01L2924/3025, H01L2221/68368, H01L2924/01033, H01L2924/01058, H01L2924/01029, H01L2924/01052, H01L2924/01024, H01L24/18, H01L25/0753, H01L33/0079, H01L24/82, H01L2924/01006, H01L2924/01039, H01L21/6835, H01L2924/01005, H01L2924/01012, H01L2221/68354, H01L2221/68318, H01L2221/68359, H01L2224/82039, H01L2924/01079, H01L2924/01015, H01L33/20, H01L2924/01078, H01L2924/014, H01L2924/01046European ClassificationH01L24/82, H01L24/18, H01L21/683TLegal EventsDateCodeEventDescriptionOct 8, 2010FPAYFee paymentYear of fee payment: 4Oct 9, 2014FPAYFee paymentYear of fee payment: 8RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services