JPWO2010074288A1 - High voltage drive light emitting diode module - Google Patents

Abstract

The object of the present invention is to improve the overall brightness and light collection efficiency even if the size of each light emitting diode element is reduced, and at a high voltage by connecting a plurality of the light emitting diode elements. It is to provide a light emitting diode module that can be driven. For this reason, a plurality of light emitting diode elements each having a built-in side reflecting portion that reflects light emitted in the lateral direction of the light emitting layer in a light collecting direction perpendicular to the light emitting layer are arranged, and the light emitting diodes are connected in series. It was possible to form the module on one substrate. Of the light emitted from the active layer in the light emitting layer, the light emitted in the light collecting direction is directly emitted through the transparent substrate in the light collecting direction, and the light emitted in the direction opposite to the light collecting direction is the back surface. The light reflected in the condensing direction by the reflecting film and emitted in the direction along the active layer is reflected by the side reflecting portion and gathers in the substantially condensing direction. Each light emitting diode element is electrically isolated and connected by a power supply wiring layer.

Description

  The present invention relates to a high-voltage-driven light-emitting diode module composed of a plurality of light-emitting diode elements. The present invention relates to a light emitting diode module that can improve brightness and light collection efficiency and can be driven at a high voltage by connecting built-in light emitting diode elements in series.

  Conventionally, many light emitting diodes (LEDs) are composed of one light emitting element (chip). In general, an LED is driven by a low voltage (DC 2 V to 4 V or so) and operates with a large current (several tens of mA to hundreds of mA). For this reason, when driving with a commercial power supply or a high-voltage battery, there are problems such as a complicated power supply circuit and difficulty in miniaturization. In order to solve this problem, there is a series structure of light emitting diodes that can be used at a high voltage by arranging a plurality of light emitting diodes on the same substrate in a two-dimensional array and connecting the light emitting diodes in series. It is disclosed (see Patent Document 4).

  A conventional LED composed of one light emitting element has a structure as shown in FIG. 39, for example (see Patent Document 2). A light emitting element 791 made of GaAlN or the like is mounted on a metal stem, and electrodes are taken out through wire bonding to metal posts 792 and 793. The phosphor 795 is excited by the ultraviolet light emitted from the light emitting element 791, and light having a long wavelength is emitted.

  In another example of the conventional LED element, as shown in FIG. 40, the light emitting element 891, the substrate 892 of the package on which the light emitting element is mounted, the lead 893 that takes out the electrode from the package to the outside, the bond wire 894, the phosphor 895, cover glass 896, and the like. Light is emitted to the outside through the cover glass 896. The light-emitting element 891 is a semiconductor made of GaAlN or the like formed on a sapphire substrate 991, and this semiconductor is composed of an N-type semiconductor layer 992 and a P-type semiconductor layer 994 with an active layer 993 interposed therebetween. Bonding pad portions (electrodes) 996 and 997 are provided on the N-type semiconductor layer 992 and the P-type semiconductor layer 994, respectively. A reflective film 995 is provided on the lower surface of the sapphire substrate 991.

  Originally, from the active layer of the light emitting element that emits light, not only the direction in which the cover glass or the like is disposed (condensing direction), but also the opposite direction or a direction perpendicular to the condensing direction, that is, the side surface of the light emitting element Also released in the direction. Conventionally, light emitted from the active layer in the condensing direction is extracted as it is in the condensing direction, and light emitted from the active layer in the direction opposite to the condensing direction is reflected by the reflective film and extracted in the condensing direction. ing. Light emitted in a direction perpendicular to the light collecting direction is mostly attenuated by scattering, but the remaining light is reflected by tilting the inner wall surface of the light emitting diode package, etc. (See Patent Documents 1 and 3). However, the use of the light emitted in the direction perpendicular to the light collecting direction is limited.

JP 2006-303547 A JP-A-10-93146 W02006-126330 Japanese Patent Application Laid-Open No. 2004-14899

  First, a light emitting diode composed of a single light emitting element of the conventional example has a problem that a driving voltage for operating the light emitting diode is low. The operating voltage of these light emitting elements is about 2 volts for red light emitting diodes and about 5 volts for white light emitting diodes. In recent years, white light-emitting diodes have spread in place of light bulbs and fluorescent lamps for home use, and for headlights for vehicles, and there is an increasing need for use at higher voltages. When using a commercial power supply, it is about AC100V or AC200V, and for vehicles, it is expected that the battery voltage will increase from DC100V to about DC300V with the spread of hybrid vehicles and electric vehicles. In such an application, an example in which the voltage is lowered to a voltage at which the light emitting diode is used is generally used. For this reason, there are problems such as loss due to voltage conversion, complicated power supply circuits, and difficulty in miniaturization.

In any light emitting diode, the driving voltage is determined by the band gap voltage of the light emitting element and cannot be driven at a higher voltage. Therefore, if there is a light-emitting diode that operates at a high voltage, for example, it becomes possible to drive directly from a commercial AC power supply through a simple power supply circuit such as a smoothing circuit, and the drive current can be reduced accordingly. The circuit can be simplified. In addition, the cost of the power supply circuit and the drive circuit of the light emitting diode can be reduced, and the use range of the light emitting diode with high energy efficiency is expanded.
However, depending on the series structure of the light emitting diodes as in the conventional example, the problem of light collection efficiency described later cannot be solved, and there are the following contradictory problems.

Based on the same idea as the conventional example, it is conceivable that the light emitting diodes having a series structure are arranged with a plurality of light emitting elements as shown in FIG. 41, for example. In this example, the light emitting diode 670 having a series structure is composed of 24 cells of 4 × 6, two of which are assigned to the P electrode 671 and the N electrode 671, and the cells “1” to “1” to “22” is a cell having a light emitting function. The 22 cells “1” to “22” are connected in series. For example, the cell “11” includes a p-electrode portion 674 and an n-electrode portion 675, and the other cells are the same. When the size of each cell is about 0.15 mm in width and about 0.1 mm in length, the overall size of the light emitting diode 670 can be about 0.6 mm in width and about 0.6 mm in length. Fig.42 (a) is a top view of said one cell. A semiconductor layer is formed in a boundary 677 on the substrate, and the boundary 680 indicates a boundary between the p-type semiconductor region and the n-type semiconductor region. In addition, a transparent conductive film of the n electrode portion is formed in the boundary 678, and a transparent conductive film of the p electrode portion is formed in the boundary 679. FIG. 42B shows a YY ′ cross section of FIG. In this cell, an insulating film 683 such as a silicon oxide film, a light reflection layer 684 made of a highly conductive metal, an n-type semiconductor (for example, n-type GaAlN) layer 685, an active layer 686, a p-type semiconductor ( For example, a p-type GaAlN) layer 687 and a silicon oxide film 688 which is a transparent insulating film are stacked. Further, a p-electrode portion 689 and an n-electrode portion 690 made of a transparent electrode such as indium oxide are formed. In this structure, light is emitted from the active layer by injecting current from the p-type semiconductor to the n-type semiconductor. This cell and other cells are electrically insulated by silicon oxide films 683 and 688.
43 is a cross-sectional view of the light emitting diode shown in FIG. 41 taken along the line XX ′. That is, the cells “18”, “17”, “6”, and “5” are represented. The p electrode portion 693 of the cell “6” and the n electrode portion 694 of the cell “5” are connected by a transparent conductive film 692 such as indium oxide. Similarly, the n-electrode portion of the cell “17” and the p-electrode portion of the cell “18” are connected by the transparent conductive film 695.

With the configuration as described above, the object of connecting cells (elements) in series to form one light emitting diode can be achieved. However, by dividing one light-emitting diode into elements having a small area, two disadvantages occur. One is that a space for separating the elements is necessary, and this space has no function other than the separation, and disadvantageous in terms of area efficiency occurs. Another disadvantage is that the ratio of the portion closer to the end face than the center of the element is higher in a small area element, and the light emission efficiency due to the crystal discontinuity is lower in the vicinity of the end face. The light emission efficiency is disadvantageous in the assembly. This is based on the mathematical principle that the ratio of the end faces is proportional to the length of one side of the element, and the area of the element is proportional to the square of the length of one side.
As described above, there is a problem that the disadvantage is increased only by dividing the light emitting elements and connecting them in series to form a light emitting diode capable of high voltage driving.

  Secondly, the conventional light emitting diode has a problem that light emitted in a direction perpendicular to the light condensing direction, that is, in a direction parallel to the light emitting layer composed of a thin film, is not effectively used. In general, light emitted from an active layer of a semiconductor layer (light emitting layer) constituting a light emitting diode is perpendicular to the surface side of the light emitting layer (condensing direction) and the back side of the light emitting layer, that is, the light collecting direction. A substantially equivalent amount of light is emitted in the opposite direction to the direction and the direction substantially along the light emitting layer, that is, the direction (side surface direction) perpendicular to the light collecting direction. Although the light emitting layer is a thin film, in many cases, the amount of light emitted in the lateral direction is as large as about 40% of the whole. For this reason, in order to improve the luminance of the light emitting diode comprehensively, a structure for efficiently extracting light emitted from the light emitting layer in the side surface direction in the light collecting direction is required.

Of the light emitted from the light-emitting layer, if the light emitted in the direction substantially along the light-emitting layer is reflected and directed in the light collecting direction, the light emitted from the light-emitting layer can be used without waste. It is considered that the luminance of the light emitting diode can be increased. For example, as shown in FIG. 44, by tilting the wall surface inside the light emitting diode package 97, the light emitted from the light emitting element 100 in the side surface direction can be reflected in the light collecting direction z. Further, in order not to place a light shielding object such as an electrode in the optical path, it is conceivable to employ a structure in which the electrode is taken out from the side opposite to the light condensing direction by using a flip chip technique.
The light emitting element 100 is a chip cut to about 1 mm square, and includes a semiconductor layer (light emitting layer) using, for example, GaAlN on the lower surface of the sapphire substrate 30. The light emitting layer includes a P-type semiconductor layer 40a and an N-type semiconductor layer 40b, and a reflective film 50 is provided on the lower surface of the light emitting layer. Light is emitted from the active layer formed at the interface between the P-type semiconductor layer 40a and the N-type semiconductor layer 40b. Among them, the light emitted to the sapphire substrate 30 side is extracted upward (condensing direction z) through the sapphire substrate. The light emitted from the active layer in the direction opposite to the sapphire substrate 30 is reflected by the reflective film 50 and extracted in the light collecting direction z. Further, by inclining the inner side surface of the package 97 in a tapered shape, light emitted from the active layer in the side surface direction (direction perpendicular to the light collecting direction z) can be reflected in the light collecting direction. . A phosphor 90 that emits light having a longer wavelength when excited by light from the light emitting element and a transparent cover cap (cover glass) 98 are disposed on the light collection element z side of the light emitting element 100. Yes. Thereby, the light of the light emitting element excites the fluorescent material of the phosphor to emit light, and the light is emitted to the outside through the cover glass.
In addition, the electrodes of the light emitting element 100 are preferably arranged so as not to interfere with the optical path. Therefore, the flip chip electrode 81a electrically connected to the P-type semiconductor layer of the light-emitting layer through the wiring inside the light-emitting element, and the flip chip electrode 81b electrically connected to the N-type semiconductor layer are defined as a light collecting direction z. Is provided on the opposite side. Each flip chip electrode is electrically connected to a conductor on the substrate of the package substrate 94. The electrodes of the light emitting element 100 are further electrically connected to the outside through conductor wiring and leads 85 in the package substrate.

  However, in order to reflect the light emitted from the light emitting layer in the lateral direction in the condensing direction, much light is attenuated inside the light emitting element before reaching the end face of the light emitting element and further to the outside of the element. Since the light is scattered at the element interface, light cannot be efficiently captured unless a mirror is formed at a position close to the light emitting layer. That is, in order to suppress the attenuation of light in the direction substantially along the light emitting layer, it is necessary to make the optical path in the light emitting element in that direction as short as possible. For this reason, it is necessary to make the size of the light emitting layer as small as possible and to install a mirror that reflects light in the vicinity of the light emitting layer. However, such a configuration has been put to practical use because it is difficult to form a mirror inclined with respect to the light emitting layer because the light emitting element is as small as 1 mm square and the thickness of the light emitting layer is as thin as several microns. There is no reality. For this reason, the light that can be effectively used out of the light emitted from the light emitting layer is only the light emitted in the condensing direction and the light emitted in the opposite direction and reflected by the reflective film on the back surface. It is no exaggeration to say. Light emitted in a direction perpendicular to the light collecting direction, that is, light emitted in a direction substantially along the light emitting layer is almost absorbed or scattered, and is not used effectively.

The present invention has been made in view of the circumstances as described above, and actively reflects the light in the lateral direction by reflecting the light emitted from the light emitting layer in the lateral direction in the light collecting direction perpendicular to the light emitting layer. If it is possible to use the light-emitting diode, the light-emitting elements described above can be divided and connected in series to offset the disadvantages of a light-emitting diode that can be driven at high voltage. . In other words, the positive effect of suppressing the attenuation in the lateral direction by reducing the size of each light emitting element, the negative effect of increasing the end face ratio by reducing the light emitting part, and between the light emitting parts. By offsetting the negative effect of requiring a separation space, it is possible to create a large positive effect that exceeds the disadvantages.
The present invention incorporates a structure for reflecting light emitted from the light emitting layer of the light emitting element in the lateral direction in a light collecting direction perpendicular to the light emitting layer, and realizing a structure in which a plurality of the light emitting elements are connected in series. An object of the present invention is to provide a light emitting diode module that can improve luminance and light collection efficiency comprehensively even if the size of each light emitting element is reduced, and that can be driven at a high voltage.

The present invention is as follows.
1. A light-emitting diode module in which a plurality of light-emitting diode elements each having a light-emitting layer formed of a semiconductor thin film are connected in series, and light emitted from the light-emitting layer is extracted in a light collecting direction perpendicular to the light-emitting layer, The diode element reflects the light emitted from the light emitting layer in a direction substantially parallel to the light emitting layer in a direction substantially parallel to the light emitting layer in the vicinity of the side surface of the light emitting layer formed in a certain region on the substrate. And a plurality of side reflectors that are inclined with respect to the light emitting layer at an angle within a predetermined range, and are arranged on the substrate and electrically separated from each other. A light emitting diode module comprising: the light emitting diode element; and a power supply wiring layer electrically connecting at least a part of the plurality of light emitting diode elements in series.
2. The side reflecting portion is formed so as to surround all or part of the side surface of the light emitting layer, and the angle in the predetermined range is 0 degree or more and 90 degrees or less. The light emitting diode module of description.
3. A back reflection film is further provided on the side opposite to the light collection direction across the light emitting layer, and light emitted from the light emitting layer to the side opposite to the light collection direction is reflected in the light collection direction by the back reflection film. Reflecting 1. Or 2. The light emitting diode module according to 1.
4). The light emitting diode element and the power supply wiring layer are formed on the surface of the substrate on the light collecting direction side. To 3. The light emitting diode module according to any one of the above.
5. A wall surface formed on the substrate surrounding the side surface of the light emitting layer and facing the side surface of the light emitting layer is inclined at an angle of the predetermined range, and at least on the wall surface facing the side surface of the light emitting layer. 4. The formed reflective film constitutes the side reflecting portion. The light emitting diode module of description.
6). The substrate is a transparent substrate that transmits light emitted from the light emitting layer, and the light emitting diode element and the power supply wiring layer are formed on a surface of the transparent substrate opposite to the light collecting direction. Said 1. To 3. The light emitting diode module according to any one of the above.
7). A transmissive membrane layer formed so as to transmit light emitted from the light emitting layer so as to cover at least a side surface of the light emitting layer and to have a thickness that is thick on the substrate side and thin toward the opposite side; 5. The reflection film formed on the outer surface of the transmission film layer constitutes the side reflection part. The light emitting diode module of description.
8). The light emitting layer is formed in a substantially trapezoidal shape that is wide on the substrate side and narrows toward the opposite side, and transmits light emitted from the light emitting layer so as to cover at least the side surface of the light emitting layer. The reflective film formed on the outer surface of the transmission film layer constitutes the side reflection part. The light emitting diode module of description.
9. The substrate includes a transparent substrate that transmits light emitted from the light emitting layer and a second substrate, and the light emitting layer formed on a surface of the transparent substrate opposite to the light collecting direction. And the side reflection part formed on the second substrate so as to correspond to the light emitting layer, and the transparent substrate on which the light emitting layer is formed and the side reflection part are formed. The above-described 1. The second substrate is bonded to face to face, and further provided with the power wiring layer. To 3. The light emitting diode module according to any one of the above.
10. Each of the light emitting diode elements includes a first electrode layer and a second electrode layer electrically connected to the light emitting layer, and further includes a power supply wiring layer formed on the plurality of light emitting diode elements. And at least two flip-chip electrodes or flip-chip electrodes provided on the power supply wiring layer, wherein in the power supply wiring layer, the first electrode layer of one of the light emitting diode elements and another light emission The second electrode layers of the diode elements are sequentially connected, and the unconnected first electrode layers and the second electrode layers of the light-emitting diode elements at both ends connected in series by the connection, 5. Said 6. connected to said different flip chip electrode or flip chip electrode. Thru 9. The light emitting diode module according to any one of the above.
11. 10. The above-described 11. configuration wherein the light-emitting diode element and the power supply wiring layer are formed on the substrate and then the transparent substrate is removed. The light emitting diode module of description.
12 Further, the exposed surface on the light emitting layer side that was in contact with the removed transparent substrate was processed into a ground surface. The light emitting diode module of description.
13. A phosphor including a fluorescent material is further disposed on the light collecting direction side from the light emitting layer, and the fluorescent material absorbs at least part of the light emitted from each of the light emitting layers and emits light of different wavelengths. Said 1. To 12. The light emitting diode module according to any one of the above.

According to the light emitting diode module of the present invention, a plurality of light emitting diode elements each having a light emitting layer formed of a semiconductor thin film are connected in series, and light emitted from the light emitting layer is extracted in a light collecting direction perpendicular to the light emitting layer. Each light emitting diode element is a light emitting layer formed in a certain area on the substrate, and substantially collects light emitted from the light emitting layer in a direction substantially parallel to the light emitting layer in the vicinity of the side surface of the light emitting layer. And a side reflection part inclined at a predetermined range of angle with respect to the light emitting layer to reflect in the direction, so that not only the light emitted from the light emitting layer in the vertical light collecting direction but also the light emitting layer Light emitted in a substantially parallel direction can be extracted in the condensing direction, and brightness and condensing efficiency can be improved overall even if light emitting diode elements having small sizes are arranged. Also, one substrate, a plurality of light emitting diode elements arranged on the substrate and electrically separated, and a power supply wiring layer electrically connecting at least a part of the plurality of light emitting diode elements in series Therefore, the light emitting diode module can be driven with a high voltage, and a simple power source can be used. Accordingly, it is possible to realize a light emitting means that is excellent in packaging space efficiency, light collection efficiency, and energy efficiency, and that is easy to use with a commercial power source or a vehicle battery. Moreover, this light emitting diode module can be manufactured on one wafer using semiconductor technology. This structure is applicable not only to white light emitting diodes but also to existing single color light emitting diodes.
The side reflecting portion is formed so as to surround all or part of the side surface of the light emitting layer, and is substantially parallel to the light emitting layer when the angle in the predetermined range is not less than 0 degrees and not more than 90 degrees. Most or most of the light emitted in any direction can be extracted and used in a substantially condensing direction.
In the case where a back reflection film is further provided on the side opposite to the light collection direction across the light emitting layer, the light emitted from the light emitting layer to the side opposite to the light collection direction is condensed by the back reflection film. Therefore, the light emitted from the light emitting layer in all directions can be extracted in the light collecting direction, and a light emitting diode module with further excellent luminance and light collecting efficiency can be realized.

When the light emitting diode element and the power supply wiring layer are formed on the surface of the substrate on the light collecting direction side, the light emitting diode element and the power supply wiring layer are easily manufactured using existing semiconductor technology. be able to. In addition, the electrodes and wirings for driving the respective light emitting diode elements can be integrated with a simple structure.
A wall surface formed on the substrate so as to surround the side surface of the light emitting layer and opposed to the side surface of the light emitting layer includes a side wall portion inclined at an angle of the predetermined range, and is formed on at least the wall surface facing the side surface of the light emitting layer. When the reflecting film constitutes the side reflecting portion, the light emitting layer and the side reflecting portion can be formed by a series of processes using the same material, and the light emitting diode having the side reflecting portion built-in The module can be manufactured efficiently.

The substrate is a transparent substrate that transmits light emitted from the light emitting layer, and the light emitting diode element and the power supply wiring layer are formed on a surface of the transparent substrate opposite to the light collecting direction. In this case, the light emitting diode element and the power supply wiring layer can be easily formed using existing semiconductor technology. In addition, it is possible to easily arrange the phosphor so as to cover the condensing direction side of the transparent substrate. When the phosphor is provided, the light reaching the light emitting layer directly or reflected by the phosphor is reflected by the phosphor. Can be captured.
A transmissive membrane layer formed so as to transmit light emitted from the light emitting layer so as to cover at least a side surface of the light emitting layer and to have a thickness that is thick on the substrate side and thin toward the opposite side; When the reflection film formed on the outer surface of the transmission film layer constitutes the side reflection part, a series of steps using the same material for the light emitting layer and the side reflection part on the same substrate surface Thus, it becomes possible to efficiently manufacture a light emitting diode module incorporating a side reflecting portion.
The light emitting layer is formed in a substantially trapezoidal shape that is wide on the substrate side and narrows toward the opposite side, and transmits light emitted from the light emitting layer so as to cover at least the side surface of the light emitting layer. When the reflective film formed on the outer surface of the transmissive film layer constitutes the side reflecting portion, the light emitting layer and the side reflecting portion are made of the same material on the same substrate surface. It can be formed by a series of processes, and it becomes possible to efficiently manufacture a light emitting diode module incorporating a side reflection portion.

  The substrate includes a transparent substrate that transmits light emitted from the light emitting layer and a second substrate, and the light emitting layer formed on a surface of the transparent substrate opposite to the light collecting direction. And the side reflection part formed on the second substrate so as to correspond to the light emitting layer, the transparent substrate and the second substrate are bonded to face each other, and the power wiring layer Is provided, the side reflecting portion having a preferable inclination angle can be formed by etching the silicon substrate or the like, so that a light emitting diode module having excellent light collecting performance can be obtained.

Each of the light emitting diode elements includes a first electrode layer and a second electrode layer electrically connected to the light emitting layer, and further includes a power supply wiring layer formed on the plurality of light emitting diode elements. And at least two flip-chip electrodes or flip-chip electrodes provided on the power wiring layer. In the power wiring layer, the first electrode layer of one light-emitting diode element and the second electrode of another light-emitting diode element are provided. When the first electrode layer and the second electrode layer of the light emitting diode elements at both ends connected in series with each other are sequentially connected to the flip chip electrode or the like, Light emitting layer, electrode layer, power supply wiring layer, flip chip electrode, etc. can be integrally formed, and light emitted in the light collecting direction is not blocked by the electrode, power supply wiring, etc. Because, it is possible to a light emitting diode module with excellent condensing performance compact.
When the transparent substrate is removed after the light emitting diode element and the power supply wiring layer are formed on the substrate, light attenuation in the transparent substrate can be reduced. Increases performance.
Furthermore, when the exposed surface of the first conductive layer that has been in contact with the removed transparent substrate is processed into a ground, the total reflectance of light on the surface can be reduced, The light collecting performance can be further enhanced.

  When a phosphor including a fluorescent material is further disposed on the light collecting direction side of the light emitting layer, and the fluorescent material absorbs at least a part of the light emitted from the light emitting layer and emits light of a different wavelength. The light-emitting layers of a plurality of light-emitting diode elements may be combined to provide a single phosphor. By converting the color of light emitted from each light-emitting layer, or by combining with light emitted from the light-emitting layer, It becomes possible to obtain light of a desired color (for example, white light). The phosphor can capture or pass light emitted from the light emitting layer directly or reflected and emitted in the light collecting direction.

The present invention will now be described in the following detailed description, with reference to the referenced drawings, by way of example of exemplary embodiments according to the present invention. Like reference numerals designate like parts or configurations throughout the several views of the drawings.
It is sectional drawing showing the example of mounting to the package of the light emitting diode module in which the light emitting diode element was connected in series. It is a top view which shows the structural example of the light emitting diode module (optical micromodule) of this invention. It is a top view for demonstrating one light emitting diode element which comprises the light emitting diode module of FIG. It is a top view for demonstrating the electrical connection method between the light emitting diode elements which comprise the light emitting diode module of FIG. It is a top view for demonstrating the electrical connection method of the light emitting diode element which comprises the light emitting diode module of FIG. 3, and an electrode part. It is an equivalent circuit diagram of a light emitting diode module. It is sectional drawing which shows the basic composition of the light emitting diode element (optical microcell) which comprises the light emitting diode module of this invention. It is a top view of the light emitting diode element of FIG. It is sectional drawing which shows another basic structure of a light emitting diode element. It is drawing for demonstrating the relationship between the inclination-angle of the side reflection part (micromirror) incorporated in a light emitting diode element, and the direction of reflected light. FIG. 6 is a cross-sectional view for explaining a first structural example of the light-emitting diode element in the first embodiment (corresponding to a YY ′ cross-section in FIG. 4). FIG. 6 is a cross-sectional view for explaining a first structural example of the light-emitting diode element in the first embodiment (corresponding to the Y ₂ -Y ₂ ′ cross-section in FIG. 4). FIG. 6 is a cross-sectional view for explaining the traveling direction of light in the light-emitting diode element (first structural example) according to the first embodiment. FIG. 8 is a cross-sectional view for illustrating the method for manufacturing the light emitting diode module according to the first embodiment. FIG. 6 is a cross-sectional view for explaining a second structural example of the light-emitting diode element in the first embodiment (corresponding to the YY ′ cross-section in FIG. 4). FIG. 6 is a cross-sectional view for explaining the light traveling direction in the light-emitting diode module (second structural example) according to the first embodiment (corresponding to the XX ′ cross-section in FIG. 3). It is sectional drawing for demonstrating the example which mounts the light emitting diode module of Embodiment 2 in a package. It is sectional drawing for demonstrating the example which mounts the light emitting diode module of Embodiment 2 in a package provided with fluorescent substance. It is a side view for demonstrating the structural example of the light emitting diode module of Embodiment 2, and the advancing direction of light. FIG. 6 is a perspective view for explaining a structural example of a light emitting diode module according to a second embodiment. It is the perspective view which turned down the condensing direction of the light emitting diode module of FIG. 6 is a cross-sectional view for explaining a structural example of a light-emitting diode element portion and a light traveling direction in Embodiment 2. FIG. FIG. 10 is a cross-sectional view for illustrating the method for manufacturing the light emitting diode module according to the second embodiment. It is sectional drawing and the top view which show the structural example of the light emitting diode module of Embodiment 2. It is sectional drawing for demonstrating another manufacturing method of the light emitting diode element (side reflection part) in Embodiment 2. FIG. It is a figure which shows the example which forms the light emitting diode module in Embodiment 2 on a wafer. It is sectional drawing for demonstrating the example which mounts the light emitting diode module of Embodiment 3 in a package. 6 is a side view for explaining a structural example of a light-emitting diode module according to Embodiment 3. FIG. It is a perspective view of the light emitting diode module shown in FIG. FIG. 10 is a side view for explaining the traveling direction of light in the light emitting diode module according to the third embodiment. 10A and 10B are a cross-sectional view and a plan view for explaining a structure example of a light-emitting diode element in Embodiment 3. FIG. 10 is a cross-sectional view for explaining a step of forming a side reflection portion (micromirror) of a light emitting diode element in Embodiment 3 on a wafer. It is a figure for demonstrating the relationship between the surface orientation of a silicon wafer, and an etching characteristic. It is sectional drawing for demonstrating the process bonded together with the 2nd board | substrate (silicon substrate) which formed the structure by the side of the transparent substrate of the light emitting diode element in Embodiment 3, and formed the side reflection part. FIG. 10 is a cross-sectional view for describing a step of forming an electrode structure of a light emitting diode element in a third embodiment. FIG. 10 is a cross-sectional view for explaining the light traveling direction in the light-emitting diode element portion according to the third embodiment. FIG. 3 is a cross-sectional view for explaining a light emitting diode module configured by removing a transparent substrate after a light emitting diode element and the power supply wiring layer are formed on a substrate. It is sectional drawing which bonded another wafer board | substrate with which the penetration conductive via was formed in the wafer state after the light emitting diode element and the power supply wiring layer were formed on the board | substrate. It is sectional drawing for demonstrating the structure of the conventional light emitting diode. It is sectional drawing for demonstrating the structure of another conventional light emitting diode. It is a top view for demonstrating the structure which connects a light emitting diode element only in series. FIG. 42 is a plan view and a cross-sectional view illustrating the structure of one light-emitting diode element in FIG. 41. It is XX 'sectional drawing of FIG. It is sectional drawing for demonstrating the structure of the light emitting diode element mounted in the package.

  The light emitting diode module of the present invention is a light emitting diode module in which a plurality of light emitting diode elements each having a light emitting layer formed of a semiconductor thin film are connected in series, and light emitted from the light emitting layer is extracted in a light collecting direction perpendicular to the light emitting layer. And a plurality of light emitting diode elements arranged on the substrate and electrically separated from each other, and at least a part of the plurality of light emitting diode elements are electrically connected in series. And a power supply wiring layer to be connected. Each of the light emitting diode elements is emitted from the light emitting layer in a direction substantially parallel to the light emitting layer (side of the light emitting layer) in the vicinity of the light emitting layer formed in a certain region on the substrate and the side surface of the light emitting layer. And a side reflecting portion that is inclined with respect to the light emitting layer at an angle within a predetermined range in order to reflect the reflected light in a substantially condensing direction. In the following, the direction of taking out the light emitted from the light emitting layer is referred to as the “light collecting direction”. The “side” is a direction perpendicular to the direction along the surface of the light emitting layer, that is, the light collecting direction. That is, the light emitted to the side means light emitted from the side surface of the light emitting layer.

The first of the gist of the present invention is to form a plurality of light emitting diode elements each having a light emitting layer and a side reflection portion as described above on a single substrate by fine processing using a semiconductor manufacturing technique. . Hereinafter, this side reflection portion is referred to as a “micromirror”, and one light emitting diode element including a light emitting layer and a micromirror formed on a substrate is referred to as an “optical microcell”.
The second aspect of the present invention is that each of the above-described optical microcells is formed by being electrically separated, and at least a part of the plurality of optical microcells can be electrically connected in series. It is a structure. One module configured by connecting at least a part of a plurality of optical microcells formed on one substrate in series is hereinafter referred to as “light emitting diode module” or “optical micromodule”. The optical micromodule includes a power supply wiring layer for electrically connecting the optical microcells to supply power to the optical microcells constituting the optical micromodule. This optical micromodule can be equivalently used as one light emitting diode, and can be operated with a high driving voltage.

The optical micromodule is usually used by being mounted on a package. For example, as shown in FIG. 1, the optical micromodule 201 is placed on a package substrate 976 and accommodated in a package including a cap 977 and a cover glass 981. A phosphor 911 can be enclosed in the package. The power source of the optical micromodule is connected to the lead 856 via the wire bonding 855. The optical micromodule 201 includes a plurality of optical microcells (C ₁₈ , C _17, etc.) on a substrate 301.
An example of the layout of the optical micromodule of the present invention is shown in the plan view of FIG. In this example, the optical micromodule 201 includes 24 elements (cells) arranged in a matrix of 6 rows and 4 columns on one substrate. Among these, the cells C _{1 to} C ₂₂ excluding the P electrode portion 701a and the N electrode portion 701b of the optical micromodule 201 are optical micro cells. Each optical microcell includes a P-type semiconductor region 401a and an N-type semiconductor region 401B.

Each of the C _{1 to} C ₂₂ optical microcells is connected in series between the P electrode and the N electrode. Therefore, the optical micromodule 201 corresponds to one light emitting diode represented by the equivalent circuit diagram of FIG. 6A (n = 22). FIG. 6B is an equivalent circuit diagram of a light-emitting diode composed of a general single chip, and the drive voltage (Vf) is about 4 to 6 V in the case of a white light-emitting diode. Then, in an optical micromodule in which 22 optical microcells are connected in series, if each optical microcell is a white light emitting diode with a driving voltage of 5 V, the driving voltage as a whole is about 100 V (Vf × 22).
However, the number of optical microcells constituting the optical micromodule is not particularly limited, and all the optical microcells may not be connected in series. For example, two of the 22 optical microcells may be connected in parallel, and 11 sets in parallel may be connected in series.

  FIG. 3 is a plan view of one optical microcell constituting the optical micromodule 201. The optical microcell includes a semiconductor layer (eg, GaAlN) formed on a substrate, a micromirror, and the like. In FIG. 3, the semiconductor layer is formed within a boundary 4010 on the substrate, and a P-type (for example, P-type GaAlN) region and an N-type (for example, N-type GaAlN) region are separated by a boundary 4011. . A micromirror 61 is provided so as to surround the region 4010 of the semiconductor layer.

FIG. 4 shows details of the optical microcells C ₄ , C ₅ , C ₆ , and C ₇ . The transparent conductive films 7613 to 7615 are transparent conductive thin films that connect the optical microcells in series in the power supply wiring layer. And N-type region and the P-type region of the optical micro cell C ₅ of the optical micro cell C ₄ is connected by a conductive thin film 7613A. Similarly, the optical micro cell _{C 5,} C 6, each N-type region in the order of _{C 7} and the next P-type region, a conductive film 7613B, are connected by 7613C.
FIGS. 5 (a) represents a state in which the N-type region 401b of the N-electrode of the cell 701b and the light microcell _{C 22} of the optical micromodule 201 are connected by a transparent conductive thin film 7615 in the power supply wiring layer FIG. FIG. 5B shows that the cell 701 a of the P electrode part of the optical micromodule 201 and the P-type region 401 a of the optical microcell C ₁ are connected by a transparent conductive thin film 7614.

  Next, FIG. 7 and FIG. 8 schematically show the basic structure of the optical microcell constituting the optical micromodule of the present invention. FIG. 7 is a cross-sectional view, and the optical microcell 10 is inclined at an angle α in a predetermined range with respect to the light emitting layer 4 in the vicinity of the light emitting layer 4 formed on the substrate 3 and the side surface 4s of the light emitting layer. A side reflector 6 is provided. The light emitting layer 4 is a thin film including semiconductor layers 4a and 4b and an active layer 4c formed between them to emit light, and the thickness of the light emitting layer 4 is about several μm.

The material of the substrate 3 is not particularly limited as long as a thin light emitting layer can be formed. For example, sapphire (Al ₂ O ₃ ), silicon (Si), silicon carbide (SiC), and the like can be given. In this document, a substrate that transmits light emitted from the light emitting layer, such as a sapphire substrate, is referred to as a “transparent substrate”.
The light emitting layer 4 includes semiconductor layers 4a, 4b and 4c. In this document, a light emitting diode that emits ultraviolet light using GaAlN as a material will be described as an example. For example, the semiconductor layer 4a is a P-type GaAlN semiconductor, and the semiconductor layer 4b is an N-type GaAlN semiconductor. A light emitting diode made of GaAlN is known to emit light in the green to ultraviolet range. In addition, there are various semiconductor materials such as GaN, InGaN, ZnSe, and ZnO as light emitting diode semiconductor materials. However, the present invention relates to a structure for condensing light emitted from a light emitting layer composed of a semiconductor, and a structure for electrically connecting a plurality of separated light emitting elements in series. The structure is not particularly limited, and the wavelength of light emitted from the light emitting layer is not limited. That is, the structure of the optical micromodule of the present invention can be applied regardless of the material used for the light emitting layer and the light emission color.

The optical microcell 10 can include a back reflecting film 5 in a direction opposite to the light collecting direction z with respect to the light emitting layer 4. The back reflecting film 5 is a mirror that reflects light emitted from the light emitting layer 4 (active layer 42) in the direction opposite to the light collecting direction z in the light collecting direction z. In the optical microcell 10 shown in FIG. 7, the light emitting layer 4 and the side reflection part (micromirror) 6 are formed on the surface of the substrate 3 on the light collecting direction z side. In this case, the back reflecting film 5 can be provided between the substrate 3 and the light emitting layer 4 as shown in FIG. When a transparent substrate is used as the substrate 3, a back reflecting film may be provided on the lower surface of the transparent substrate, that is, the surface opposite to the surface on which the light emitting layer 4 is formed.
The material of the back reflection film is not particularly limited as long as a thin film that reflects light can be formed. For example, aluminum, silver, nickel, chromium, cobalt, etc. are mentioned.

  As shown in FIG. 7, in the optical microcell 10, light emitted from the active layer 4c in the light collecting direction z can be extracted as it is (p). The light emitted from the active layer 4c in the direction opposite to the light collecting direction z is reflected by the back reflecting film 5 and extracted in the light collecting direction (q). Further, the light traveling from the side surface 4s of the light emitting layer in the direction S substantially parallel to the active layer along the active layer 4c is reflected by the micromirror 6 and extracted in a substantially condensing direction (r).

  As shown in FIG. 9, the optical microcell may have a structure in which a transparent substrate 31 is used and the light emitting layer 41 and the micromirror 61 are provided on the substrate surface opposite to the light collecting direction z. In the optical microcell 11, a back reflection film 51 is formed on the lower surface of the light emitting layer 41. The micromirror 61 can be formed simultaneously with the light emitting layer 41 on the surface of the transparent substrate 31. Alternatively, the optical microcell 11 can be configured by forming the light emitting layer 41 on the surface of the transparent substrate 31 and forming the micromirror 61 on the second substrate and bonding the two substrates together. In any case, the light emitted in each direction from the light emitting layer (active layer) can be extracted in the light condensing direction through the transparent substrate 31 (p, q, r).

  The micromirror (6, 61) may be a surface of a structure (side wall portion) formed in the vicinity of the side surface of the light emitting layer or covering the side surface of the light emitting layer. That is, the micromirror can be configured by inclining the wall surface of the side wall portion facing the side surface of the light emitting layer at an angle α with respect to the active layer and using the surface of the wall surface as a light reflecting surface. As shown in the embodiment, the side wall portion may be formed of the same material as the material forming the light emitting layer (for example, GaAlN), or may be formed of a different material (for example, silicon, silicon oxide, or the like). Good. Further, the reflection surface may be the surface of the sidewall part itself, or a reflection film may be formed on the surface of the sidewall part. The material of the reflective film is not particularly limited as long as a thin film that reflects light can be formed. For example, aluminum, silver, nickel, chromium, cobalt, etc. are mentioned.

  FIG. 8 is a plan view of the optical microcell 10 as viewed from the light collecting direction z side. The light emitting layer 4 is formed in a certain region on the substrate 3, and is configured such that the micromirror 6 surrounds the periphery of the light emitting layer 4. The size of one optical microcell is not particularly limited. For example, one side can have a size of about several tens to several hundreds of μm (for example, 200 μm). Further, the width of the portion where the micromirror 6 is formed can be about several μm to several tens of μm. Smaller optical microcells can also be formed by microfabrication technology.

The size of one optical microcell is preferably small in order to minimize attenuation of light traveling in the direction along the light emitting layer (direction S shown in FIG. 7). This is because if the attenuation of light in the direction along the light emitting layer is small, the amount of collected light per current injected for light emission can be increased. In order to suppress attenuation of light emitted to the side of the light emitting layer, it is desirable that the space between the light emitting layer and the micromirror is narrow.
On the other hand, it is known that if the size of the light emitting layer is made too small, the area ratio of the interface increases and the light emission efficiency decreases. Further, since the micromirror and its peripheral portion do not directly contribute to light emission, the light emission amount is limited by the area of the micromirror peripheral portion and the presence of the micromirror itself. Therefore, in order to obtain a sufficient amount of light collection, the area of the light emitting layer must be increased.

In general, one light emitting diode is provided with one light emitting layer. There is no need to intentionally separate the light emitting layer, and element space is wasted if it is separated, and therefore, one light emitting diode is not separated into a plurality of light emitting layers. However, the light emitting elements on the substrate can be separated into a plurality of electrically independent optical microcells, and these optical microcells can be connected in series on the substrate so that they can be directly driven at a high voltage.
If the size of one optical microcell is reduced, the number of optical microcells increases, and the degree of freedom of combination in which optical microcells are connected in series or in parallel is increased. On the other hand, if it is made smaller, the occupation ratio of the space for separating the optical microcells becomes higher, and since this portion does not contribute to light emission, it is a loss in terms of the element area.

The aim of the present invention is to realize an optical micromodule with high energy efficiency by maximizing the amount of light collected per injection current into the optical micromodule. Therefore, the optical microcell constituting the optical micromodule has an optimum size in consideration of the size of the light emitting layer, the size of the micromirror part that does not contribute to light emission, the distance between the light emitting layer and the micromirror, and the like. It is necessary to Optimum conditions vary depending on the thickness of the light emitting layer and the light emitting material, but in any size of optical microcell, the light collection efficiency is maximized in units of optical microcells. The idea of maximizing the luminous efficiency of the optical micromodule is the same.
Rather than increasing the size of the light-emitting layer to increase brightness, even if the light-emitting layer is separated into a plurality of light-emitting layers on one substrate, the optical microcell structure with a built-in micromirror compensates for the loss caused by the separation. The merit of maximizing the amount of light emission that can be used per drive current, that is, the light emission efficiency, can be created. Furthermore, since the optical microcells can be connected in series or in parallel, it is possible to take advantage of the ability to freely set the drive voltage.

  In order to embody the above advantages, the optical microcell used in the optical micromodule of the present invention forms a micromirror that faces the side surface of the light emitting layer and is inclined with respect to the light emitting layer in the vicinity of the side surface of the light emitting layer. It has a possible structure. The micromirror may be provided so as to surround the entire periphery in the side surface direction of the light emitting layer, or may be provided on a part of the entire periphery. In order to capture as much light emitted to the side of the light emitting layer as possible and collect it in the light collecting direction by the micromirror, the micromirror is preferably formed in most of the periphery of the light emitting layer, as shown in FIG. More preferably, the light emitting layer 4 is formed all around.

Next, the inclination angle α of the micromirror will be described.
In FIG. 10, the lateral direction is the direction S parallel to the light emitting layer, the upward direction is the light collecting direction z, and the surface M is the reflecting surface of the micromirror. The light (in) emitted from the light emitting layer in the direction along the light emitting layer is reflected by the micromirror surface M in a substantially condensing direction (out).
As shown in FIG. 5A, when the tilt angle α of the micromirror is 45 °, the light reflected by the micromirror is most preferable because it goes in the light collecting direction z perpendicular to the light emitting layer. Further, as shown in FIGS. 4B and 4C, when the inclination angle α is 60 ° or 30 °, the light is reflected in a direction deviating 30 ° with respect to the light collecting direction z. In this case, the vector intensity of light in the condensing direction is about 1.73 / 2, and about 86% of the light intensity can be extracted in the condensing direction. Further, as shown in FIGS. 4D and 4E, when the inclination angle α is 67.5 ° or 22.5 °, the light is deviated by 45 ° with respect to the light collecting direction z. Reflect on. In this case, although the vector intensity of light in the condensing direction is about ½, about 50% of the light intensity can still be extracted in the condensing direction.
Therefore, the micromirror whose inclination angle α of the micromirror with respect to the light emitting layer is approximately 45 ° (for example, 22.5 ° to 67.5 °, preferably 30 ° to 60 °, most preferably 45 °). If it is formed, it becomes possible to take out the light of the intensity | strength according to the inclination angle to a condensing direction.

The reflection surface of the micromirror does not necessarily have to be a flat surface as a whole, and may be composed of a curved surface. As will be described later in Examples, the micromirror can be formed into various shapes by various manufacturing methods. However, in any case, it is a common configuration to direct light traveling in a direction substantially parallel to the light emitting layer in the light collecting direction by the micromirror.
The light traveling in a direction substantially parallel to the light emitting layer is refracted, reflected, scattered, etc. due to the difference in the refractive index of the structure and material inside the light emitting layer and between the light emitting layer and the micromirror. And each layer and surface irregularities are complicatedly affected. Therefore, in practice, the inclination angle of the entire micromirror (from the skirt portion contacting the substrate side to the top portion on the opposite side) facing the side surface of the light emitting layer is in the range of 0 ° or more and 90 ° or less. If the angle of inclination of the central portion of the reflecting surface with the portion facing the active layer in the layer is set to be approximately 45 °, a light collecting effect can be obtained.

The optical microcell can be configured by integrally forming electrodes for supplying power to the light emitting layer. The material used for the electrode is not particularly limited as long as it has conductivity, and for example, aluminum can be used. Further, in a portion where light needs to be transmitted, indium oxide (ITO) or the like can be used as a transparent conductive film.
As the electrode of the light emitting layer, a first electrode layer and a second electrode layer that are electrically the same as or electrically connected to either the N-type semiconductor layer or the P-type semiconductor layer, respectively, It can be formed integrally. In this document, a negative electrode (cathode) connected to the N-type semiconductor layer is referred to as an N-type electrode or N electrode, and a positive electrode (anode) connected to the P-type semiconductor layer is referred to as a P-type electrode or P electrode.

The optical micromodule of the present invention enables high-voltage driving by connecting a plurality of optical microcells in series with the above-described optical microcell as one unit, or combining serial connection and parallel connection. It is a feature. Therefore, each optical microcell is configured to be electrically separated. That is, the electrodes (N-type electrode and P-type electrode) of one optical microcell are configured separately from the electrodes of other optical microcells.
The electrodes of each optical microcell are connected in the power supply wiring layer. The power supply wiring layer can be composed of a conductive thin film that connects the electrodes. As shown in FIGS. 4 and 5, the power wiring layer of the optical micromodule in which the optical microcells are connected in series includes an N-type electrode of one optical microcell and a P-type electrode of the next optical microcell. A plurality of conductive thin films that are sequentially connected are provided. The N-type electrode that is not connected to the other optical microcell at one end thereof becomes the negative electrode (“N” shown in FIG. 2) of the entire optical micromodule, and the optical microcell at the other end. The P-type electrode that is not connected to other optical microcells of the cell becomes the positive electrode (“P” shown in FIG. 2) of the entire optical micromodule.
The material of the conductive thin film constituting the power wiring layer can be the same as the material used for the electrode of the optical microcell. Further, the conductive thin film of the power wiring layer can be configured in common with the electrode of the optical microcell.

  The connection method between the optical micromodule and the outside (package substrate, main substrate, lead terminal, etc.) is not limited. For example, wire bonding may be used, and flip-chip mounting is possible by providing protruding electrodes (bumps). May be. In order to perform flip chip mounting, the optical micromodule is electrically connected to the negative electrode of the entire optical micromodule when the light emitting layer of the optical microcell is formed on the surface of the transparent substrate opposite to the light collecting direction. And a flip chip electrode or flip chip electrode electrically connected to a positive electrode of the entire optical micromodule. The shape of the flip chip electrode (bump) is not particularly limited, and may be, for example, a columnar shape, a spherical shape, a plate shape, or the like. The above-mentioned flip chip electrode refers to an electrode for flip chip mounting, and any shape such as a film shape or a flat plate shape may be used. Bumps may be provided on the flip chip electrodes, or the optical micromodule may be mounted on a package substrate provided with the bumps using the flip chip electrodes. The flip chip electrode or the like may be formed in a wafer state, or a stud bump may be formed after dividing the wafer into individual optical micromodules.

When the light emitting layer is formed on the surface of the transparent substrate opposite to the light collecting direction, the optical micromodule has a structure (optical microcell, power wiring layer, flip chip electrode or flip chip) formed on the transparent substrate. After the chip electrode or the like is physically fixed, the transparent substrate may be removed (lifted off). That is, after the flip chip electrode or the like is disposed on the power wiring layer of the optical micromodule, the transparent substrate can be removed. For example, as described in the embodiments, the transparent substrate can be removed after the optical micromodule is mounted on another wafer substrate, a package substrate, or the like.
Further, when the optical microcell and the power supply wiring layer are formed on the surface of the transparent substrate opposite to the light collecting direction, the optical micromodule has the above-described power supply wiring on the optical micromodule as described in the embodiments. The transparent substrate may be removed (lifted off) after the layer (or the power supply wiring layer and the flip chip electrode) is formed. Further, the exposed surface on the light emitting layer side after the transparent substrate is removed can be processed into a textured surface by blasting or the like. Here, the term “null” means that the surface is evenly presented so that the light inside the light emitting layer is not totally reflected on the surface. By making the surface evenly rough, it is possible to reduce loss due to total reflection of light in the light emitting layer on the surface.

  In addition, a phosphor including a fluorescent material such as a fluorescent pigment or a fluorescent dye can be disposed above the optical micromodule (condensing direction). When the phosphor is provided, the light emitted from the light emitting layer hits the fluorescent material directly or reflected, and the fluorescent material is excited to emit light having a longer wavelength. For this reason, in particular, when a phosphor is provided in the light collecting direction, the range in which light can be captured by the phosphor even if the direction of the light reflected by the micromirror is out of the light collecting direction. It suffices if light is reflected in the direction.

  Further, the optical micromodule can be mounted on a package in the same manner as shown in FIG. The optical micromodule can also be mounted on a known package (see, for example, FIGS. 39 and 40). A phosphor can be provided in the package. When visible light is emitted from the light emitting layer of the optical microcell and the visible light is used as it is, a phosphor is unnecessary.

(Embodiment 1)
An optical micromodule can be configured by forming a plurality of optical microcells and a power supply wiring layer on the surface of the substrate on the light collecting direction side. An optical microcell constituting the optical micromodule will be described based on a specific embodiment. In this example, a structure (side wall part) is made of the same material as that of the light emitting layer on the periphery of the light emitting layer on one substrate, and an inclined wall surface is formed on the side wall part, and the inclined wall surface is made of silver or nickel. A micromirror is formed by covering with a reflective film made of a film or the like. Thereby, the micromirror inclined with respect to the light emitting layer can be formed all around or part of the light emitting layer. Further, a back reflecting film is provided on the back surface of the light emitting layer as viewed from the light collecting direction.

FIG. 11 is a cross-sectional view showing the structure of the optical microcell 102 having the above configuration (corresponding to the YY ′ cross section of the optical microcell shown in FIG. 3). In the optical microcell 102, a light emitting layer 402 including an N-type GaAlN semiconductor layer 402b, an active layer 402c, and a P-type GaAlN semiconductor layer 402a is formed on a sapphire substrate 302. In the vicinity of the side surface of the light emitting layer, a side wall portion made of the same GaAlN semiconductor as the light emitting layer and processed so that the side surface 6021 facing the light emitting layer is inclined is formed. The side wall portion can be processed simultaneously with the light emitting layer. The side wall portion is covered with a thin film 6022 using silver, nickel, or the like. Furthermore, an insulating layer 562 made of SiO ₂ or the like and a transparent electrode layer (P-type electrode portion 702a, N-type electrode portion 702b) made of indium oxide or the like are formed on the semiconductor layer. A back reflection film 502 is formed on the back surface of the sapphire substrate 302.
The thin film layer 6022 becomes a reflective film of the micromirror 602, and light in the direction along the active layer 402c is reflected by the micromirror 602 provided in the vicinity of the side surface and emitted in the light collecting direction.

FIG. 12 is a cross-sectional view of another part of the optical microcell 102 (corresponding to the Y ₂ -Y ₂ ′ cross section of the optical microcell shown in FIG. 3). Except that the N-type electrode portion 702b is not formed in this portion, it is the same as the structure and operation described with reference to FIG.

FIG. 13 shows a state in which light emitted from the light emitting layer (active layer) is reflected by the micromirror and the back reflecting film in the optical microcell having the above structure (the power supply wiring layer is not formed). Yes. In this figure, the light emitted from the active layer in the surface direction (condensing direction z) is emitted as it is (p). The light emitted from the active layer in the back surface direction is reflected in the light collecting direction by the back reflection film (q). Light emitted from the active layer in a direction substantially parallel to the active layer is reflected by the micromirror 602 and emitted toward the surface (r ₁ , r ₂ , r ₃ , r ₄ ). Among these, r ₁ and r ₄ indicate light substantially parallel to the active layer, and r ₂ indicates light in a slightly oblique direction. r ₃ indicates a light that has transmitted while being totally reflected, such as a semiconductor layer, shows a state released to substantially condensing direction is reflected by the micromirror.
The light emitted from the light emitting layer is slightly refracted due to the difference in refractive index at the interface with the silicon oxide film, the transparent conductive film or the like, but is not shown in the figure because it is explained mainly by reflection. Similarly, it is refracted when the reflected light comes out of the silicon oxide film or the like into the atmosphere, but it is not shown. The existence of refraction does not change the principle of reflection by the micromirror surface.

The optical micromodule 201 including the optical microcell 102 having the above structure can be manufactured by, for example, a manufacturing method as shown in FIG.
14A shows a step of forming a semiconductor layer including a N-type GaAlN semiconductor 402b, an active layer 402c, and a P-type GaAlN semiconductor 402a on a sapphire substrate 302 (substrate manufacturing process), and then a semiconductor layer is formed thereon. A state in which a photoresist 1611 for etching is formed is shown.
FIG. 14B shows a state in which a pattern of a photoresist 1612 for further processing is formed after the step of dry etching the semiconductor layers 402b, 402c and 402a (semiconductor layer etching step). By the semiconductor layer etching process, the semiconductor layer is formed as indicated by the interface 4021.
FIG. 14C shows a state in which the inclined surface 4022 is formed in the semiconductor layer by an etching process (taper etching process) in which the portion of the interface 4021 of the semiconductor layer is inclined. The slope 4022 can be formed by wet etching using a photoresist 1612. After the etching process, the photoresist is removed.

FIG. 14D shows a process of forming a reflective film on the inclined surface 4022 (side reflective film forming process). After depositing a thin film 6023 of silver or nickel, a photoresist is applied, and the pattern of the photoresist is formed. 1613 is formed. Thereafter, the thin film 6023 is etched to form a micromirror (602). In order to adjust the shape of the inclined portion of the micromirror, the thin film 6023 is etched by wet etching. After the etching process, the photoresist is removed.
When the above wet etching method is used, the positional relationship between the end surface of the photoresist 1613 provided in the micromirror portion shown in FIG. 14D and the inclined portion of the thin film 6023 formed of silver, nickel, or the like is is important. By performing wet etching in this state, the thin film 6023 is etched while the photoresist 1613 is peeled off from the end face in contact with the thin film 6023 at the bottom skirt. As a result, underetching occurs at the bottom of the thin film 6023. As a result, the inclined surface of the thin film 6023 has a gentle shape up to the sapphire substrate surface.
FIG. 14E shows a state in which a photoresist pattern 1614 is formed in order to expose the N-type semiconductor portion after the micromirror 602 is formed in the side reflection film forming step.
FIG. 14F shows a state in which the step of removing the P-type semiconductor portion and the active layer (P-type semiconductor etching step) is performed. After removing the P-type layer 402a and the active layer 402c of the GaAlN semiconductor by etching to expose the N-type layer 402b, the photoresist is removed. The removal of the P-type region and the active layer of the GaAlN semiconductor can be performed using a known method that utilizes the management of the etching time or changes in the etching rate of the N-type semiconductor layer. As a result, the surface 4025 of the N-type semiconductor and the surface 4024 of the P-type semiconductor are exposed.

FIG. 14G shows a state in which after forming a silicon oxide film layer on the entire surface, a step of forming an opening for an electrode by etching (protective film forming step) is performed, and the photoresist is removed. . By this step, a silicon oxide film 561 for insulation and protection, a contact portion 4026 for the P-type electrode, and a contact portion 4027 for the N-type electrode are formed.
In FIG. 14 (h), after forming a transparent conductive film such as indium oxide (ITO) over the entire surface, an etching process is performed to form an indium oxide film on the electrode (electrode formation process), and then the photoresist is removed. Shows the state. By this step, a P-type electrode portion 702a and an N-type electrode portion 702b are formed. Further, as shown in FIG. 14 (h), the back reflection film 502 is formed by evaporating silver or the like on the back surface of the sapphire substrate 302 in the final process (back reflection film forming process).
Simultaneously with or after the formation of the electrodes, a power supply wiring layer for connecting the optical microcells with a conductive thin film is formed. This conductive thin film can be formed of the same material as the electrode portion.

The optical microcell can also be configured using an opaque silicon substrate or the like as the substrate. FIG. 15 shows a cross-sectional structure of an optical microcell 103 using a silicon substrate, which is different from the optical microcell 102. Note that a description of points common to the above-described structure example of the optical microcell will be omitted. In this example, a low-cost silicon substrate is used as the substrate, and a back reflective film is provided on the lower surface of the light emitting layer (GaAlN layer).
In this case, the YY ′ cross section of one optical microcell shown in FIG. 3 can have a structure as shown in FIG. The optical microcell 103 includes a conductive thin film 503 that reflects light, such as a nickel thin film, a chromium thin film, or a silver thin film, on a silicon substrate 303. A light emitting layer 403 including an N-type GaAlN semiconductor layer 403b and a P-type GaAlN semiconductor layer 403a is formed on the conductive thin film. An active layer 403c is present at the interface between the N-type GaAlN semiconductor 403b and the P-type GaAlN semiconductor 403a (not shown because it is a thin layer). In the vicinity of the side surface of the light emitting layer 403, a side wall portion is formed that is made of the same GaAlN semiconductor as the light emitting layer and is processed by inclining the side surface 6031 facing the light emitting layer. The side wall portion can be formed simultaneously with the light emitting layer. The side wall is covered with a thin film layer 6032 using silver, nickel or the like. Furthermore, an insulating layer 563 made of SiO ₂ or the like and a transparent electrode layer (P-type electrode portion 703a or N-type electrode portion 703b) made of indium oxide or the like are formed on the semiconductor layer. The structure of the optical microcell 103 corresponding to the Y ₂ -Y ₂ ′ section of the optical microcell shown in FIG. 3 can also be formed in the same manner as described above.
The thin film layer 6032 becomes a reflective film of the micromirror 603, and light in the direction along the active layer is reflected by the micromirrors 603 provided on both sides of the light emitting layer 403 and is emitted in a substantially condensing direction.

  In the structure of the optical microcell 103 shown in FIG. 15, since light in the back surface direction from the active layer is reflected by the reflective film layer 503 directly below, the sapphire is compared with the case of the optical microcell 102 shown in FIG. Attenuation due to reciprocation of light at the substrate is improved. In the vicinity of the active layer, since it is surrounded by a reflective film layer in the back direction and micromirrors in the side direction, it is extremely preferable as a reflective structure built in the optical microcell. Further, when the back reflection film layer 503 and the micromirror 603 are arranged close to each other, the periphery of the light emitting layer 403 can be covered with a reflection film except for the light collection direction, and the light collection rate can be ideally increased. This is possible by shortening the distance between the reflective film layer 503 and the micromirror 603 in FIG.

FIG. 16 is a cross-sectional view of an optical micromodule configured by arranging the optical microcells 103 and providing a power supply wiring layer for connecting the optical microcells. This corresponds to the XX ′ cross section of the optical micromodule 201 shown in FIG. 2, and each optical microcell corresponds to the optical microcells C ₁₈ , C ₁₇ , C ₆ , C ₅ in FIG. 2 in order from the left. Micromirrors 603 are formed on both sides of the light emitting layer of each optical microcell.
The optical microcells are connected in series using the same transparent conductive film as the electrodes of the optical microcell. An N-type electrode 703b of the P-type electrode 703a and the light microcell _{C 17} light microcells _{C 18} is connected with a transparent conductive thin film 7621 that is integrated with the electrodes. Similarly, the N-type electrode 703b of the P-type electrode 703a and the light microcell _{C 5} light microcell _{C 6} are connected with a transparent conductive thin film 7622 that is integrated with the electrodes.
In FIG. 16, p, q, r, and r ′ indicate the traveling direction of the light emitted from the active layer. Since the optical microcell 103 includes the back reflecting film 503 on the silicon substrate 303, the light emitted from the active layer in the direction opposite to the collecting direction z is reflected by the back reflecting film 503 and collected. (Q).
Light emitted directly or reflected from the active layer in the light collecting direction z excites light with a long wavelength by arranging a phosphor (not shown) above the light microcell (light collecting direction). Thus, white light can be obtained by the combination of the lights.

  An optical micromodule configured by forming a plurality of optical microcells and a power supply wiring layer on the surface of the substrate on the light collecting direction side can be manufactured by various manufacturing methods by modifying the above structure. However, explanation is omitted.

(Embodiment 2)
As shown in FIG. 9, the optical micromodule of the present invention uses a transparent substrate as the substrate, and the optical microcell and the power wiring layer are placed on the surface of the transparent substrate opposite to the light condensing direction. It can also be formed and configured. In this case, for example, a light-transmitting film layer that transmits light emitted from the light emitting layer and covers at least the side surface of the light emitting layer is formed. The permeable membrane layer can be formed with a thickness inclined so as to be thick on the substrate side and thin toward the opposite side. And a micromirror can be comprised by forming a reflecting film in the outer surface of the permeation | transmission film | membrane layer.

FIG. 17 is a cross-sectional view showing an example in which the optical micromodule is mounted on a package. The light collecting direction z is above the package in the figure. In FIG. 17, an optical micromodule 231 is housed in a package including a protective transparent cap 971 and a package substrate 941. In the optical micromodule 231, an N-type semiconductor layer 431 b, an active layer 431 c, and a P-type semiconductor layer 431 a are formed on the lower surface (surface opposite to the light collection direction z) of a transparent substrate 331 (for example, a sapphire substrate). A light emitting layer 431 is provided, and a back reflecting film 531 is provided on the lower surface of the light emitting layer with an insulating layer interposed therebetween. Further, on the side surface side of the light emitting layer 431, a micromirror 631 inclined with a predetermined range of angle with respect to the active layer is formed.
The micromirror 631 can be formed so as to surround the side surface of the light emitting layer 431. As described above, one unit including one light emitting layer and a micromirror surrounding the side is called an optical microcell. In the cross section of the optical micromodule 231 shown in FIG. 17, the cross sections of two optical microcells can be seen.
Of the light emitted from the active layer 431 c included in the optical micromodule 231, the light emitted toward the transparent substrate 331 side, that is, in the light collecting direction z, is emitted through the transparent substrate 331 in the light collecting direction. Light emitted from the active layer to the side opposite to the transparent substrate 331 is reflected by the back reflecting film 531 and is emitted through the transparent substrate 331 in the light collecting direction. Light emitted from the active layer in the side surface direction (a direction perpendicular to the light collecting direction z) is reflected by the micromirror 631 and is emitted through the transparent substrate 331 in a substantially light collecting direction. The relationship between the inclination angle α of the micromirror with respect to the active layer and the light reflection direction is as described above (see FIG. 10).

  The optical micromodule includes an electrode for supplying power to each light emitting layer, power supply wiring, and the like. In FIG. 17, the electrodes of the optical micromodule 231 are installed on the side opposite to the light collecting direction z and wired in the power supply wiring layer 771. Then, the power source is concentrated on the flip chip electrode 801, and is electrically connected to the lead 851 through this. The lead 851 is drawn out of the package substrate 941 and used for external connection.

  FIG. 18 shows a case where a phosphor 901 containing a phosphor is provided on the light collecting direction side from the optical micromodule 231. As in FIG. 17, the optical micromodule 231 is mounted on the package substrate 942 via the flip chip electrode 802. A phosphor 901 is filled in a cap 972 having a reflecting portion whose inner surface is inclined, and the whole is sealed with a transparent cap 983. As described above, the light emitted from the active layer included in the optical micromodule 231 is collected in the light collecting direction z and excites the fluorescent material contained in the phosphor 901. Most of the light emitted by the fluorescent material is directly emitted in the light collecting direction z, and the light scattered in the package is reflected by the inclined side surface inside the cap 972 and collected in the light collecting direction.

Next, an example of an optical micromodule configured by arranging the optical microcells in a matrix will be described.
19 and 20 are a side view and a perspective view of the optical micromodule 232. In both figures, the light collection direction z is shown upward. The optical micromodule 232 includes an optical microcell layer 132 in which a light emitting layer and a micromirror are arranged on the lower surface of one sapphire substrate 332. In the illustrated side S _A, and optical micro-cell 1321 in which a light-emitting layer in the light microcell layer 132 is formed in parallel four, at both ends of each optical micro-cell 1321 is provided with a micro mirror 632 Yes. One optical microcell 1321 can be formed so that the four directions on the side surface of the light emitting layer are surrounded by the micromirror 632. A back reflection film 532 is provided on the lower surface of the optical microcell layer 132.

  As shown in FIG. 19, among the light emitted from the light emitting layer in the optical microcell, the light directed in the light collecting direction z travels straight in the light collecting direction through the transparent substrate 332 (p). The light emitted in the direction opposite to the light collecting direction z is reflected by the back reflecting film 532 and collected in the light collecting direction through the transparent substrate 332 (q). Further, light in a direction perpendicular to the light collecting direction z is reflected in a substantially light collecting direction by a micromirror 632 formed around the side surface of the light emitting layer and inclined at an angle of about 45 ° with respect to the light emitting layer. Then, they are collected in a substantially condensing direction through the transparent substrate 332 (r). The light perpendicular to the condensing direction z propagates along the thin film of the light emitting layer. In order to avoid attenuation during propagation, it is preferable that the size of the light emitting layer is as small as possible, the area occupied by the micromirror in the optical microcell is as small as possible, and the distance between the light emitting layer and the micromirror is as short as possible. When the optical microcells are arranged, the size of each optical microcell, that is, the pitch of the micromirrors can be formed with a width and a depth of about 200 μm, for example.

Further, a power wiring layer 772 and a flip chip layer 802 for supplying power to each optical microcell are provided under the back reflecting film 532. The electrodes (N-type electrode and P-type electrode) of each optical microcell are configured to be electrically separated from the electrodes of other optical microcells in the micromirror 632, and between the electrodes of each optical microcell. Are connected in the power supply wiring layer 772. The power supply wiring layer can be composed of a conductive thin film that connects the electrodes. In order to connect the optical microcells in series, the N-type electrode of one optical microcell and the P-type electrode of the next optical microcell are sequentially connected by a conductive thin film in the power wiring layer. The N-type electrode of one end of the optical microcell that is not connected to the other optical microcell serves as the negative electrode of the entire optical micromodule and is electrically connected to the flip chip electrode 802. In addition, the P-type electrode of the other end optical microcell connected in series and not connected to another optical microcell serves as the positive electrode of the entire optical micromodule, and is electrically connected to another flip chip electrode 802. Connected. Power can be supplied to the optical microcells connected in series in the power wiring layer through the flip chip electrode.
The power supply wiring layer 772 and the flip chip electrode 802 are provided on the side opposite to the condensing direction so as not to interfere with condensing.

In Figure 20, the side surfaces _{S A} side of the optical micro-module 232, the micromirror 632 has five represented by, four optical microcells 1321 sandwiched the micromirrors 632 are arranged. Further, the side surface S _B side, the micromirror 632 has six represented by the five optical microcells 1321 sandwiched the micromirrors 632 are arranged. That is, the optical micromodule 232 is composed of 4 × 5 = 20 optical microcells. FIG. 21 is a perspective view showing the optical micromodule 232 shown in FIG. 20 with the light collecting direction z facing down. As described above, power to the 20 optical microcells is supplied from the flip chip electrode 802 via the power supply wiring layer 772.
One optical microcell can be configured to have a size of about 200 μm in both width and depth, for example. It is also possible to reduce the size by applying semiconductor processing technology. The light collection efficiency per unit drive current is more efficient when the size is small. On the other hand, the area ratio of the micromirror part is relatively large, and the area utilization factor of the light emitting element is inefficient. The optimum value is determined while looking at these pros and cons.

An example of a partial cross-sectional structure of the optical micromodule 232 is shown in FIG. In this figure, the power supply wiring layer is omitted. The optical microcell 133 has a transparent electrode layer 733, a light emitting layer 433 including an N-type GaAlN layer 433b, an active layer 433c, and a P-type GaAlN layer 433a, a conductive film (back reflective film) 533, silicon on the lower surface of the sapphire substrate 333. An oxide film 573, a P-type electrode 733a, and an N-type electrode 733b are provided. The P-type electrode and the N-type electrode are formed of a material that reflects light, such as Al. The silicon oxide film 573 covers the light emitting layer 433, and the N-type electrode 733b formed on the silicon oxide film functions as a micromirror.
As shown in the drawing, among the light emitted from the active layer 433c in the light emitting layer, the light emitted in the light collecting direction z passes straight through the sapphire substrate 333 in the light collecting direction (p). The light emitted in the direction opposite to the light collecting direction z is reflected by the back reflecting film 533 and passes through the sapphire substrate 333 and gathers in the light collecting direction (q). Further, the light emitted along the direction perpendicular to the condensing direction, that is, along the active layer, is reflected by the micromirror (N-type electrode 733b) and gathers in the substantially condensing direction (r).

An example of a method for manufacturing the optical microcell 133 will be described with reference to FIG.
FIG. 23A shows a transparent electrode layer 7331 such as indium oxide (ITO), an N-type GaAlN layer 433b, an active layer 433c, a P-type GaAlN layer 433a, and a reflective conductor film 533 on a 3 inch sapphire substrate 333, for example. They are stacked in order. The substrate thus laminated is formed by forming a P-type GaAlN semiconductor layer, an active layer, an N-type GaAlN semiconductor layer, and an indium oxide film on a sapphire substrate, and transferring them onto a sapphire substrate 333 serving as a base material. It may be realized by a method.
In FIG. 23B, the reflective conductor film 533, the P-type GaAlN layer 433a, the active layer 433c, and the N-type GaAlN layer 433b are removed with the width of 100 μm and the pitch of about 200 μm, for example, leaving the transparent electrode 7331 on the substrate. State. This can be formed by photolithography and etching processes. In this case, ITO serves as an etching stopper.
FIG. 23C shows a state where the silicon oxide film 573 is deposited on the entire surface. The silicon oxide film is doped with high-concentration phosphorus so that a sloped wall surface can be easily provided by subsequent processing. In this case, a silicon oxide film containing high-concentration phosphorus is used, but when phosphorus affects the light emitting layer, a thin transparent insulating film having a high barrier property against phosphorus is deposited as a barrier film, It is also possible to deposit a silicon oxide film containing high-concentration phosphorus.

FIG. 23D shows a case where the silicon oxide film 573 is semi-melted at a relatively low temperature to form a gradient in film thickness. That is, the silicon oxide film covering the side surface of the semiconductor layer (light emitting layer) is formed so as to be inclined so that it is thick on the substrate 333 side and thins upward. It is a well-known technique for processing a silicon semiconductor that the silicon oxide film contains phosphorus at a high concentration and is semi-melted at a low temperature of several hundred degrees to have a slope.
FIG. 23E is a diagram in which an opening (contact portion) for taking out an electrode is provided by etching the silicon oxide film 573.
FIG. 23F shows a state in which an Al thin film is deposited on the entire surface in the above state, and then the Al thin film is etched to form a P-type electrode 733a and an N-type electrode 733b. Following the Al thin film, the transparent electrode layer 7331 such as ITO is etched to electrically separate the N-type electrode 733b of the optical microcell between the adjacent optical microcells.

FIG. 24 shows a cross section of the optical microcell 133 manufactured by the process shown in FIG. 23 and a plane on which the semiconductor layer is formed. The configuration of the cross section shown in FIG. 24A is the same as that in FIG. In the plan view of FIG. 24B, a region indicated by “P” is a P-type electrode 733a, and a region “N” surrounding the P-type electrode with a gap is an N-type electrode 733b. In the drawing, a broken line 1331 indicates a boundary between the semiconductor layers (433a to 433c) and the reflective conductor film 533. The semiconductor layer and the electrode of each optical microcell may be formed so as to have rounded corners. By using a light emitting layer (semiconductor layer) with rounded corners, electric field concentration that occurs when the four corners of the light emitting layer are formed at right angles can be prevented, and current does not contribute to light emission. It is possible to minimize the wasteful flow.
A broken line 1332 indicates the boundary of the optical microcell. At the boundary of the optical microcell, there is no electrode such as Al or a transparent electrode, and only the sapphire substrate which is an insulator. As a result, each optical microcell is in an independent state on the sapphire substrate, and each optical microcell is electrically isolated and isolated.
Thereafter, a power supply wiring layer for connecting the electrodes of each optical microcell in series with a conductive thin film is formed.

  The N-type electrode 733b also serves as a micromirror. Since the electrode material becomes a material component of the micromirror, it is preferable that the electrode has a laminated structure containing chromium, nickel, silver or the like rather than simply using an aluminum material. For example, a structure in which a thin chrome, nickel, or silver layer is provided for the role of a micromirror and an aluminum layer is provided thereon can be used.

The micromirror is formed in a substantially trapezoidal shape so that the shape of the light emitting layer is narrow toward the opposite side widely on the substrate side, and includes a transmission film layer formed so as to cover at least the side surface of the light emitting layer, You may comprise by providing a reflecting film in the outer surface of the permeable film layer. The substantially trapezoidal shape refers to a shape in which a cross section perpendicular to the substrate of the light emitting layer is a substantially trapezoid with a long base in contact with the substrate. That is, the side surface of the light emitting layer itself is formed to be inclined at an angle within the predetermined range.
The manufacturing example of the micromirror shown in FIG. 25 shows a structure in which the light emitting layer (semiconductor layer) itself is subjected to taper etching. FIG. 25 shows a state in which the side surface of the GaAlN semiconductor layer constituting the light emitting layer is taper etched using a wet etching method that causes under-etching when etching GaAlN that is the light emitting layer. Thereafter, similarly to FIG. 23F, the Al thin film 734b is etched, and the transparent electrode layer 7341 is further etched to be electrically separated from the adjacent optical microcell.

FIG. 26 shows an example in which an optical micromodule configured by arranging the optical microcells is formed on a wafer. The S _A surface shown in FIG. 26 corresponds to the S _A surface (FIG. 21) of the optical micromodule 232. In this example, optical micromodules 232 of about 1.0 × 1.2 mm are formed on a 3-inch wafer 271, and each optical micromodule 232 is formed with a pitch of about 200 μm. Twenty (4 × 5) optical microcells 1321 are formed.
In addition, as shown in FIG. 26, a power wiring layer 772 of the optical micromodule can be formed, and further, a flip-chip structure electrode 802 for supplying power to each microcell can be formed. The flip-chip structure electrode can be formed, for example, by performing copper plating or solder plating in a wafer state. The flip chip electrode may be formed in a columnar shape or the like in the wafer state as described above, or simply provided with a planar electrode (flip chip electrode) for flip chip mounting and divided into each optical micromodule and then stud bumps. It may be formed by such a method. In addition, a flip chip electrode may be provided on the optical micromodule, and the optical micromodule may be bonded to a protruding electrode provided on the side of the package substrate or the like.
In order to cut out each optical micromodule from the wafer into a chip state, an optical microcell adjacent to a 4 × 5 optical microcell constituting one optical micromodule can be used as a scribe line. Each optical microcell is electrically and optically independent until the power supply wiring layer is formed, so that it can be used as a scribe line without being used as a light emitting portion. Further, the optical micromodule is not limited to a 4 × 5 cell configuration, and the number of cells can be freely selected by changing the pattern after the power supply wiring layer.

  In this example, an example of an optical microcell having a pitch of 200 μm has been described. However, if the optical microcell has a pitch of 50 μm, 20 optical microcells can be formed per side of 1 mm. 20 × 20 = 400 optical microcells are built. A high drive voltage can be freely set although it is discrete by connecting a part in series and a part in parallel.

(Embodiment 3)
The substrate of the optical micromodule of the present invention may be composed of a transparent substrate that transmits light emitted from the light emitting layer and a second substrate. In this case, a light emitting layer formed on a surface of the transparent substrate opposite to the light condensing direction and a micromirror formed on the second substrate so as to correspond to the light emitting layer, and emitting light An optical micromodule can be configured by attaching a transparent substrate on which a layer is formed and a second substrate on which a micromirror is formed to face each other and then providing the power supply wiring layer.

  If the second substrate is a silicon substrate, a micromirror tilted at an angle within the predetermined range using silicon as a base material can be formed. The inclination angle (α) of the micromirror is, for example, an angle of 54 ° by using silicon having a (110) plane orientation as the second substrate and etching the silicon with an alkaline aqueous solution such as potassium hydroxide. Can be formed. The above angle can be easily formed with good reproducibility by utilizing the selective etching property of the plane orientation of silicon. In this way, a micromirror is formed on a silicon wafer, a light emitting layer is formed on a sapphire wafer having the same diameter, and the silicon wafer and the sapphire wafer are bonded to each other so that the side surface of the light emitting layer is surrounded by the micromirror. Thus, an optical micromodule with a built-in micromirror can be realized.

FIG. 27 is a cross-sectional view showing an example in which the optical micromodule is mounted on a package. The light collecting direction z is above the package in the figure. In FIG. 27, an optical micromodule 251 is mounted in a package including a protective transparent cap 973 and a package substrate 951. The optical micromodule 251 includes, for example, an active layer 451c sandwiched between an N-type semiconductor layer and a P-type semiconductor layer on the lower surface of the sapphire substrate 351 (the surface opposite to the condensing direction z), and below that A back reflection film 551 is provided. A micromirror 651 is formed on the silicon substrate 361, and the optical micromodule 251 is configured by bonding the substrate 351 on which a semiconductor layer or the like is formed to the silicon substrate 361. The micromirror 651 is inclined at an angle within the predetermined range, and is disposed in the vicinity of the side surface of the active layer 451c.
The micromirror 651 can be formed so as to surround the side surface of the active layer 451c. In the cross section of the optical micromodule 251 shown in FIG. 27, the cross sections of two optical microcells are visible.
Of the light emitted from the active layer 451 c included in the optical micromodule 251, the light emitted toward the transparent substrate 351 side, that is, in the light collecting direction z, is emitted through the transparent substrate 351 in the light collecting direction. Light emitted from the active layer to the side opposite to the transparent substrate 351 is reflected by the back reflecting film 551 and is emitted through the transparent substrate 351 in the light collecting direction. Light emitted from the active layer in the side surface direction (a direction perpendicular to the light collecting direction z) is reflected by the micromirror 651 and is emitted in a substantially light collecting direction through the transparent substrate 351. The relationship between the inclination angle α of the micromirror and the light reflection direction is as described above (see FIG. 10).

Further, a power wiring layer 781 and a plurality of flip chip electrodes 821 are provided on the lower surface of the silicon substrate 361. The electrodes (N-type electrode and P-type electrode) of each optical microcell are configured to be electrically separated from the electrodes of other optical microcells in the micromirror 651, and between the electrodes of each optical microcell. Are connected in the power supply wiring layer 781. The power supply wiring layer can be composed of a conductive thin film that connects the electrodes. In order to connect the optical microcells in series, the N-type electrode of one optical microcell and the P-type electrode of the next optical microcell are sequentially connected by a conductive thin film in the power wiring layer. Then, the N-type electrode of one end of the optical microcell that is not connected to the other optical microcell becomes the negative electrode of the entire optical micromodule and is connected to the flip chip electrode 821. In addition, the P-type electrode of the other end optical microcell connected in series and not connected to another optical microcell serves as the positive electrode of the entire optical micromodule, and is electrically connected to another flip chip electrode 821. Connected. With this power supply wiring layer, power can be supplied from the flip chip electrode to the optical microcells connected in series. The power supply wiring layer 781 and the flip chip electrode 821 are provided on the side opposite to the condensing direction so as not to interfere with condensing.
Further, as in the case of the optical micromodule shown in FIG. 18, a phosphor can be provided on the light collecting direction side from the optical micromodule.

Next, an example of an optical micromodule configured by arranging optical microcells in a matrix will be described.
28 and 29 are a side view and a perspective view of the optical micromodule 252. FIG. In both figures, the light collecting direction z is shown downward. The optical micromodule 252 includes an optical microcell layer 152 including a light emitting layer and a micromirror on the upper surface of one sapphire substrate 352. The optical microcell layer 152 is formed with a large number of optical microcells 1521 each having a light emitting layer, and micromirrors 652 are provided at both ends of each optical microcell 1521. One optical microcell 1521 can be formed so that the four directions on the side surface of the light emitting layer are surrounded by the micromirror 652. A back reflection film 552 is provided on the upper surface of the optical microcell layer 152.

In the example shown in FIG. 28, nine micromirrors 652 are provided on one side of the optical micromodule 252, and eight optical microcells 1521 sandwiched between the micromirrors 652 are configured. 29, is represented the S _A surface S _B 8 pieces each surface of the optical micro-cell, the optical micromodule 252 will be composed of 8 × 8 = 64 pieces of light microcells . As described above, the number of optical microcells and the connection method between the optical microcells can be arbitrarily designed.

FIG. 30 is a side view showing the optical micromodule 252 with the light collecting direction z facing upward. Of the light emitted from the active layer in the optical microcell 1521, the light directed in the light collecting direction z travels straight in the light collecting direction through the transparent substrate 352 (p). The light emitted in the direction opposite to the light collecting direction z is reflected by the back reflecting film 552 and collected in the light collecting direction through the transparent substrate 352 (q). Further, light in a direction perpendicular to the condensing direction z is substantially condensed by the micromirror 652 formed in four directions and inclined at an angle of about 45 ° (for example, 30 ° to 60 °) with respect to the active layer. The light is reflected in the direction and collected in the light collecting direction through the transparent substrate 352 (r). As described above, when the angle (α) with respect to the active layer of the micromirror is 54 °, the direction of the reflected light r is 18 ° with respect to the light collecting direction z as shown in the figure.
The light perpendicular to the light collecting direction z propagates along the thin film of the light emitting layer. In order to avoid attenuation during propagation, it is preferable that the size of the light emitting layer is as small as possible, the area occupied by the micromirror in the optical microcell is as small as possible, and the distance between the light emitting layer and the micromirror is as short as possible. When the optical microcells are arranged, the size of each optical microcell, that is, the pitch of the micromirrors can be formed with a width and a depth of about 100 μm, for example.

FIG. 31 is a cross-sectional view (a) and a plan view (b) showing in detail the structure of one optical microcell. In order to explain the structure of the optical microcell and its electrode, the plan view of FIG. 31 (b) is drawn with the semiconductor layer and the micromirror portion combined with the view seen from the electrode surface.
An optical microcell 153 shown in FIG. 31A includes a sapphire substrate 353, a transparent electrode 7531 such as ITO, an N-type semiconductor layer 453b, an active layer 453c, a P-type semiconductor layer 453a, a Ni thin film 5531 on the sapphire substrate side, and a silicon substrate. A Ni thin film 5532, a silicon layer 363, and a PIQ film (insulating polyimide film) 583 are provided.
As shown in FIG. 31 (b), the regions of the P-type electrode 753a and N-type electrode 753b made of Al or the like, and the region where the semiconductor layers (453a to 453c) and the like are stacked have four corners at right angles. Instead, it is rounded. Thereby, average light emission can be promoted while avoiding concentration of the electric field.

A method of manufacturing the optical microcell (optical micromodule) having the above structure in a wafer state will be described with reference to FIGS.
The substrate shown in FIG. 32A is obtained by epitaxially growing a high-concentration P-type silicon layer 3632 having a thickness of about 3 μm using an N-type silicon 363 having a (110) plane orientation as a substrate, and further, an N-type silicon having a thickness of about 5 μm. This is a substrate on which a layer 3633 is epitaxially grown. An oxide film 584 having a thickness of about 0.5 μm is formed on this substrate, and a pattern is formed by photolithography. FIG. 33 (a) is a perspective view of the N-type silicon wafer, in which an oxide film (SiO ₂ ) 584 having a width of about 2 μm is left by photolithography like a grid, and the pitch is about 100 μm. ing. The N-type silicon layer 3633 is etched by placing the substrate in an alkaline (eg, potassium hydroxide) etchant. FIGS. 32B and 33B show that the etching of the N-type silicon layer 3633 stops at the (111) plane due to the anisotropic etching characteristic that the etching rate of the (111) plane orientation of silicon is slow. , Showing a state in which a slope inclined at 54 ° is formed. The inclined surface of the N-type silicon layer 3633 is formed in all four directions.
In the state shown in FIG. 32C, a Ni thin film 5532 is formed thereafter. The silicon mirror surface can be used in this state as it is, or it can be used to facilitate covalent bonding when an oxide film is formed and merged with a later sapphire substrate. The Ni thin film is formed to facilitate covalent bonding with the Ni thin film formed on the sapphire substrate side.
A silicon wafer having a micromirror formed in this shape is completed.

Next, an example of a manufacturing method on the transparent substrate (sapphire substrate) side will be described.
34A includes a 3-inch sapphire substrate 353, a transparent electrode layer 7531 such as ITO, an N-type GaAlN layer 453b, an active layer 453c, a P-type GaAlN layer 453a, a total reflection conductor (Ni thin film) 5531. Are stacked. In the figure, the thicknesses of these layers are shown enlarged.
FIG. 34B shows a state where a groove 3531 having a depth of 10 μm and a width of 20 μm is formed on the substrate. This groove can be formed by photolithography and etching processes.
FIG. 34C shows a state immediately before the silicon substrate (the state of FIG. 48C) on which the micromirror is formed is bonded to the sapphire substrate 353 on which the groove is formed. The two wafers are bonded to each other so that the apex of the micromirror formed on the silicon wafer is positioned at the center of the groove on the sapphire substrate.
FIG. 34 (d) shows a state where both wafers are combined. The surface layers of the two wafers are mirror surfaces. In this case, since both are Ni thin film layers (5531, 5532), they are completely integrated at the molecular level by intermolecular attractive force. As a result, the micromirror part is completely isolated from the outside, and a stable mirror can be formed. This technique is similar to the silicon bonding technique that has recently become popular. In the case of silicon bonding, the silicon surface and the silicon oxide surface are bonded together. In this case, the Ni thin film on the silicon wafer and the Ni thin film on the sapphire substrate are bonded together.

The above is an example in which a silicon substrate and a sapphire substrate are bonded together via a Ni thin film. Depending on the difference, an organic adhesive layer may be used for bonding.
FIG. 34E shows a state in which the silicon substrate side of the bonded wafer is etched, leaving only a thickness of about 3 μm. In the figure, 3362 is a silicon layer. By utilizing the low etching rate of the high-concentration P-type silicon layer 3362, an accurate thickness can be left. The silicon layer having a thickness of about 3 μm is a part that supports the micromirror as a structure.

A process of forming the electrode of the optical microcell from the state in which the silicon substrate and the sapphire substrate are bonded together as described above will be described with reference to FIG.
FIG. 35A shows a state in which a pattern of a photoresist 181 is formed on the substrate shown in FIG. In this state, etching of the silicon layer 3632, etching of the silicon side reflective conductor (Ni thin film) 5532, etching of the sapphire side reflective film (Ni thin film) 5531, and etching of the semiconductor layers 453a to 453c are performed, and a transparent electrode layer (ITO) Etching is completed using 7531 as a stopper.
FIG. 35B shows a state after the etching. Since the silicon layer 3632 has a (110) plane orientation, the etched wall surface is tapered with an inclination of 54 °. Etching leaving behind.
FIG. 35 (c) is a diagram showing a state in which the PIQ of the P-type electrode portion and the N-type electrode portion is removed after the PIQ (insulating polyimide film) 583 is applied.
FIG. 35D shows a state in which a P-type electrode 753a and an N-type electrode 753b are formed by depositing an electrode material made of Al or the like from the above state and then etching.
Through the above steps, the micromirror, the light emitting layer, and the electrode layer of the optical microcell were formed. Furthermore, an optical micromodule can be completed by forming a power supply wiring layer for connecting the optical microcells on the electrode layer of the optical microcell.

FIG. 36 shows how light is reflected in the optical microcell formed as shown in FIG. The micromirror is a Ni film 5532 on the surface of the inclined portion of the convex portion formed on the silicon substrate. In FIG. 36, the light emitted in the active layer 453c in the horizontal direction, that is, along the thin film, is reflected by the micromirrors formed in the four directions and travels in the substantially condensing direction (r). In this example, since the inclination angle of the micro mirror is 54 °, the light is reflected by the micro mirror in a direction inclined by 18 ° with respect to the light collection direction z. Further, the light emitted from the active layer in the direction opposite to the micromirror, that is, in the direction of the N-type electrode 753b is reflected by the PIQ film or reflected by the negative electrode Al, and returns to the light emitting layer. Head to. A part of the light is internally reflected (r ′) in the light collecting direction by the inclination of the negative electrode Al thin film.
As described above, in view of the relationship between the tilt angle (α) of the micromirror and the light collection, α = 45 ° is preferable. The micromirror formed using a predetermined plane orientation of silicon is α = 54 °, and the direction of light reflected by the micromirror can be inclined by 18 ° with respect to the light collection direction z. A highly preferred micromirror can be realized.

  Optical microcells can be formed on a wafer, a power wiring layer 782 for connecting the P-type electrode and N-type electrode of each optical microcell 1521 can be provided, and a flip chip electrode layer 822 can be formed. The flip chip electrode may be formed in a wafer state, or may be formed by a method such as a stud bump after being divided into each optical micromodule. Further, when the optical micromodule shown in FIG. 30 is cut out from the state of the wafer, the optical microcell adjacent to the 8 × 8 optical microcell can be used as the scribe line. Each optical microcell is electrically and optically independent until the power supply wiring layer is formed, so that it can be used as a scribe line without being used as a light emitting portion.

  The present invention is not limited to the examples detailed in the first, second and third embodiments. The basic element of the present invention is to extract as much light as possible from the light emitting layer and the light reflected from the semiconductor layer in the light collecting direction. Therefore, it is important to configure the reflecting portion with a material having as high a reflectance as possible and to minimize the absorption and attenuation of light in the optical microcell. For this purpose, for example, in the case of an optical micromodule having a structure in which a light emitting layer is formed on a transparent substrate (sapphire substrate) and light from the light emitting layer is collected through the transparent substrate, a power wiring layer (or power wiring) After the layer and the flip chip electrode or flip chip electrode) are formed, that is, after the structure of the optical micromodule is physically fixed, the transparent substrate layer can be removed.

For example, as shown in FIG. 37, a power wiring layer is formed on the optical micromodule 237, a flip chip electrode 802 and the like are further formed, and the optical micromodule is mounted on a package substrate 942, and then serves as a substrate. The sapphire layer can be removed by a lift-off method. Similarly, the sapphire substrate can be removed after mounting the optical micromodule on another substrate made of ceramic, silicon, or the like having substantially the same size as the optical micromodule and having through-conductive vias. Thereby, attenuation of the light in a sapphire layer can be eliminated. Furthermore, since the surface of the light-emitting element on the light-collecting direction side (the surface on the light-emitting layer side that was in contact with the sapphire substrate) is exposed by removing the sapphire layer, the surface is roughened like a blank by blasting or the like. The total reflection in the light emitting layer can be reduced, and as a result, the light collection efficiency can be increased.
FIG. 38B is a cross-sectional view showing a state in which the optical micromodules 238 are formed on the wafer 273 (transparent substrate 338) shown in FIG. In the optical micromodule 238, optical microcells 1381 having micromirrors 638 are formed in an array, and after the power supply wiring layer 783 is formed, the flip chip electrode 803 is formed. In another wafer 943, a through conductive via 9431 and a surface electrode 9432 are formed. The electrode of the optical micromodule 238 is connected to the surface electrode 9432 on another wafer 943 through the flip chip electrode 803 and the through conductive via 9431. In such a state, since the structure on the substrate (light emitting layer, micromirror, power supply wiring layer, etc.) constituting the optical micromodule 238 is physically fixed, the transparent substrate 338 can be removed. . The transparent substrate 338 may be removed after being separated into individual optical micromodules. FIG. 38C is a diagram showing the optical micromodule 239 in which the optical micromodules 238 on the wafer 273 are individually separated and the transparent substrate 338 is removed, upside down.

The above is an example, and the selection and combination of materials for the optical micromodule is an important factor. In the examples, nickel, cobalt, and the like have been described as examples of the reflective film, but it is also possible to use a material having higher reflectivity such as silver. Moreover, although GaAlN was mentioned and demonstrated as a semiconductor material, it is applicable also to GaN and other semiconductor materials.
Furthermore, the structure of the present optical micromodule is not limited to a light emitting diode using a phosphor, but can be commonly used for a light emitting diode that emits visible light.
Each of the optical microcells is formed by being electrically separated, and at least a part of the plurality of optical microcells is electrically connected in series to constitute an optical micromodule. The number of optical microcells connected in series can be set to an arbitrary number according to the voltage value of the power supply used by changing the pattern after the power supply wiring layer.
In addition, the present invention is not limited to the embodiments described in detail above, and various modifications or changes can be made within the scope of the claims of the present invention.

  Applications of light emitting diodes are expanding for energy saving. In the automobile field, it is used in a wide range of fields such as lamps including headlights, lamps using LEDs for home use, backlights for liquid crystal TV receivers, and traffic lights for industrial use. Light-emitting diodes that are easy to use with high-voltage drive will be important components in the future.

10, 11, C _{1 to} C ₂₂ , 102, 103, 1321, 133, 1381, 1521; Optical microcells (light emitting diode elements), 1611 to 1614, 1711, 1721; Photoresist, 201, 231, 232, 237 238, 239, 251, 252; optical micromodule (light emitting diode module), 271, 273; wafer, 3, 31, 302, 303, 331, 332, 333, 338, 351, 352, 353; substrate, 361; Second substrate (silicon substrate), 363; N-type silicon layer, 3632; High-density P-type silicon layer, 3633; N-type silicon layer, 4, 41, 402, 403, 431; Light emitting layer (semiconductor layer), 401a 402a, 403a, 431a, 433a, 434a, 435a; P-type semiconductor layer (P-type Region), 431c, 433c, 434c, 451c, 453c; active layer, 401b, 402b, 403b, 431b, 433b, 434b, 453b; N-type semiconductor layer (N-type region), 5, 51, 502, 503, 531, 532, 533, 551, 552; back reflective film, 562, 563, 573; insulating film (SiO ₂ film), 583; insulating film (PIQ film), 584; SiO ₂ film, 6, 61, 602, 603, 631 , 632, 638, 651, 652, 653; micromirror (side reflection part), 701a, 702a, 703a, 733a, 753a; P (P type) electrode, 701b, 702b, 703b, 733b, 753b; N (N Type) electrode, 7613, 7614; transparent conductive film, 771, 772, 781, 782, 783; power wiring layer, 801, 8 2, 803, 821, 822; flip chip electrode, 851, 852, 856; lead, 901, 911, 921; phosphor, 941, 942; package substrate, 943; another substrate (wafer), 971, 972, 973 , 977; cap, 983; cover glass, p, q, r, r ′; light traveling direction, S: direction parallel to the light emitting layer (active layer), z: light collecting direction, α: inclination angle of the micromirror .

Claims (13)

A plurality of light emitting diode elements each having a light emitting layer formed of a semiconductor thin film, connected in series, and taking out light emitted from the light emitting layer in a light collecting direction perpendicular to the light emitting layer;
Each of the light emitting diode elements substantially collects light emitted from the light emitting layer in a direction substantially parallel to the light emitting layer in the vicinity of the side surface of the light emitting layer formed in a certain region on the substrate. A side reflecting portion inclined at an angle within a predetermined range with respect to the light emitting layer in order to reflect in the direction,
One substrate,
A plurality of the light emitting diode elements arranged on the substrate and electrically separated from each other; and
A power supply wiring layer for electrically connecting at least a part of the plurality of light emitting diode elements in series;
A light emitting diode module comprising: The side reflecting portion is formed so as to surround all or part of the side surface of the light emitting layer,
The light emitting diode module according to claim 1, wherein the angle in the predetermined range is not less than 0 degrees and not more than 90 degrees. Further comprising a back reflection film on the opposite side of the light collection direction across the light emitting layer,
3. The light emitting diode module according to claim 1, wherein light emitted from the light emitting layer to the side opposite to the light collecting direction is reflected in the light collecting direction by the back reflecting film.   4. The light emitting diode module according to claim 1, wherein the light emitting diode element and the power supply wiring layer are formed on a surface of the substrate on the light collecting direction side. 5. A wall surface formed on the substrate so as to surround the side surface of the light emitting layer and facing the side surface of the light emitting layer is provided with a side wall portion inclined at an angle of the predetermined range,
The light emitting diode module according to claim 4, wherein at least a reflective film formed on the wall surface facing the side surface of the light emitting layer constitutes the side reflecting portion. The substrate is a transparent substrate that transmits light emitted from the light emitting layer,
4. The light emitting diode module according to claim 1, wherein the light emitting diode element and the power supply wiring layer are formed on a surface of the transparent substrate opposite to the light collecting direction. 5. A transmissive membrane layer formed so as to transmit light emitted from the light emitting layer so as to cover at least a side surface of the light emitting layer and to have a thickness that is thick on the substrate side and thin toward the opposite side; ,
The light emitting diode module according to claim 6, wherein a reflection film formed on an outer surface of the transmission film layer constitutes the side reflection portion. The light emitting layer is formed in a substantially trapezoidal shape that is wide on the substrate side and narrows toward the opposite side, and transmits a light emitted from the light emitting layer so as to cover at least the side surface of the light emitting layer. With layers,
The light emitting diode module according to claim 6, wherein a reflection film formed on an outer surface of the transmission film layer constitutes the side reflection portion. The substrate comprises a transparent substrate that transmits light emitted from the light emitting layer, and a second substrate,
The light emitting layer formed on the surface of the transparent substrate opposite to the light condensing direction;
The side reflection part formed on the second substrate so as to correspond to the light emitting layer;
With
The said transparent substrate in which the said light emitting layer was formed, and the said 2nd board | substrate in which the said side reflection part was formed are bonded together, and the said power supply wiring layer is further provided, and is comprised. The light emitting diode module according to any one of the above. Each of the light emitting diode elements includes a first electrode layer and a second electrode layer electrically connected to the light emitting layer,
And a power wiring layer formed on the plurality of light emitting diode elements, and at least two flip chip electrodes or flip chip electrodes provided on the power wiring layer,
In the power supply wiring layer, the first electrode layer of one of the light emitting diode elements and the second electrode layer of another of the light emitting diode elements are sequentially connected,
The unconnected first electrode layer and the second electrode layer of the light emitting diode elements at both ends connected in series by the connection are connected to different flip chip electrodes or flip chip electrodes, respectively. The light emitting diode module according to claim 6.   The light emitting diode module according to claim 6, wherein the transparent substrate is removed after the light emitting diode element and the power supply wiring layer are formed on the substrate.   The light emitting diode module according to claim 11, wherein the exposed surface on the light emitting layer side that has been in contact with the removed transparent substrate is processed into a ground surface. A light emitter containing a fluorescent material is further disposed from the light emitting layer to the light collecting direction side,
The light emitting diode module according to claim 1, wherein the fluorescent material absorbs at least a part of light emitted from each light emitting layer and emits light having a different wavelength.

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