JP2007158100A - Manufacturing method of nitride semiconductor light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a nitride semiconductor light-emitting element capable of easily separating chips without adding any special processes, reducing manufacturing process time, and preventing a light emitting region from being damaged when separating the chips. <P>SOLUTION: After a dielectric mask 2 is formed on a substrate 1 for growth, a nitride semiconductor crystal 10 is grown. The nitride semiconductor crystal 10 comprises an n-type nitride semiconductor layer 3, an active layer 4, a p-type nitride semiconductor layer 5, and the like. The dielectric mask 2 has an opening bored in a rectangular shape to the chip shape. The nitride semiconductor crystal 10 is grown on the substrate 1 for growth at the region of the opening, and crystal growth is completed while adjacent chips are being separated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a nitride semiconductor light emitting device capable of obtaining a device separated into a rectangular shape in a short time.

  Nitride semiconductors are used in blue LEDs used as light sources for lighting, backlights, etc., LEDs used in multicoloring, LDs, and the like. Since it is difficult to manufacture a bulk single crystal in a nitride semiconductor, GaN is grown on a heterogeneous substrate such as sapphire or SiC by using MOCVD (metal organic chemical vapor deposition). A sapphire substrate is particularly used as a growth substrate because it is excellent in stability in a high-temperature ammonia atmosphere in an epitaxial growth process. Since the sapphire substrate is an insulating substrate and cannot conduct, the nitride semiconductor on the sapphire substrate is etched until the n-type gallium nitride layer is exposed after epitaxial growth, and an n-type contact is formed on the etched surface. , Two electrodes of p-type and n-type are provided on the same surface side.

  However, when two p-type and n-type electrodes are provided on the same surface as described above, the current is likely to concentrate on the mesa portion close to the n-electrode, thereby increasing the ESD (electrostatic breakdown) voltage. I can't. In addition, it is difficult to uniformly inject current into the active layer, and it becomes difficult to cause the active layer to emit light uniformly. In addition, since wire bonding electrodes are required for both the p-electrode and the n-electrode on the same surface side, light emission is more effective than a nitride semiconductor on a conductive substrate, which may be provided with either wire-bonding electrode. As the area is reduced, the chip (element) area is increased, and the number of chips that can be taken from the same wafer is reduced. In addition, since sapphire has a high hardness and a hexagonal crystal structure, when sapphire is used as a growth substrate, it is necessary to separate the sapphire substrate by scribing, and the manufacturing process becomes complicated and the yield is poor.

  On the other hand, if the nitride semiconductor layer is grown on the conductive substrate and the electrodes are provided so as to face each other, the above problem can be solved, but the SiC of the conductive substrate that can be used for gallium nitride at present is expensive. If the substrate is doped with impurities in order to have high electrical conductivity, light absorption will increase.

  Therefore, a method is used in which the sapphire substrate is peeled off, the n-type gallium nitride layer is exposed, an n-electrode is formed in that portion, and the n-electrode and the p-electrode are arranged to face each other.

  The nitride semiconductor device in which the sapphire substrate is peeled off as described above and the n-electrode and the p-electrode are opposed to each other is separated before the sapphire substrate is removed in order to separate the nitride semiconductor for each chip (device). A separation groove for separating the nitride semiconductor into chips is formed.

For example, as shown in FIG. 14, a GaN buffer layer 22 formed on a sapphire substrate 21 and also serving as a separation layer, and a nitride semiconductor 23 having a light-emitting region grown thereon are formed for each element. A separation groove 24 is formed by dry etching until reaching the sapphire substrate 21 in accordance with the size that can be separated. Next, excimer laser light of about 300 nm or less is irradiated from the back of the sapphire substrate 21 at several hundred mJ / cm ² to decompose the GaN buffer layer 22 and peel off the sapphire substrate 21. This method is called Laser Lift Off (hereinafter abbreviated as LLO) (see, for example, Patent Document 1).

Further, after forming the chip separation groove 24 by dicing without forming it by dry etching, the sapphire substrate is peeled off using LLO as described above.
JP 2003-168820 A

  However, in the above-described conventional method, in order to form the chip isolation groove 24, the chip-shaped markings are vertically and horizontally inserted into the planarized nitride semiconductor layer, and then dry etching or dicing is performed. Since it is necessary to form the separation groove 24, the longer the number of chips to be separated and the larger the nitride semiconductor layer to be divided, the longer it takes to complete the formation of the separation groove 24. The work process time until the end of production was long.

  Further, when the separation groove 24 is formed by dry etching, it is necessary to form the separation groove 24 until it reaches the sapphire substrate 21 with a predetermined width. Therefore, the etching time becomes long, and the side surface of the light emitting region of the nitride semiconductor 23 is etched gas (plasma). ), The light emitting region is damaged, and the leakage current increases, resulting in ESD degradation and luminance degradation.

  On the other hand, in order to shorten the manufacturing process time, it is conceivable to reduce the thickness of the n-type nitride semiconductor layer and the like to shorten the epitaxial growth time. However, when the thickness of the n-type nitride semiconductor layer and the like is reduced, The lateral current spread is reduced, and problems such as the active layer being unable to shine sufficiently occur.

  The present invention was devised to solve the above-described problems, facilitates chip separation without adding a special process, and shortens the manufacturing process time. An object of the present invention is to provide a method for manufacturing a nitride semiconductor light emitting device capable of preventing damage.

  In order to achieve the above object, according to a first aspect of the present invention, a nitride semiconductor crystal including a light emitting region and a first electrode layer are formed on a growth substrate, and the nitride semiconductor crystal and the first electrode layer are supported. In the method for manufacturing a nitride semiconductor light emitting device, after the transfer to the substrate, the second electrode layer is formed on the nitride semiconductor crystal so as to face the first electrode layer. A rectangular opening is formed on the growth substrate. A method of manufacturing a nitride semiconductor light emitting device, comprising: patterning a dielectric mask having a portion, and then selectively growing the nitride semiconductor crystal and terminating the crystal growth in a state of being separated into a rectangular shape.

  The invention according to claim 2 is the method for manufacturing a nitride semiconductor light emitting element according to claim 1, wherein the opening portion of the dielectric mask has a square shape.

  The invention according to claim 3 is characterized in that the nitride semiconductor crystal is composed of an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor. It is a manufacturing method of the nitride semiconductor light emitting element given in any 1 paragraph.

  The invention according to claim 4 is characterized in that the n-type nitride semiconductor layer is grown at a temperature in the range of 1000 ° C. to 12000 ° C. and a pressure of 100 Torr or more. Is the method.

  The invention of claim 5 is characterized in that the p-type nitride semiconductor layer is grown at a temperature in the range of 1000 ° C. to 1100 ° C. and a pressure of 100 Torr or more. The method for producing a nitride semiconductor light emitting device according to 1).

  The invention according to claim 6 is characterized in that the active layer is grown at a temperature in the range of 700 ° C. to 900 ° C. and a pressure of 200 Torr or more, and the nitriding according to any one of claims 3 to 5. 1 is a method for manufacturing a semiconductor light emitting device.

  According to the present invention, chip separation can be facilitated without adding a special process, and the manufacturing process time can be shortened. In addition, since it is not necessary to create a chip separation groove, the light emitting region or the like is not exposed to the etching gas for a long time, and the light emitting region or the like can be protected.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a nitride semiconductor light emitting device manufacturing method according to the present invention.

  A nitride semiconductor crystal 10 is grown on the substrate 1 on which the dielectric mask 2 is formed. As the growth surface of the growth substrate 1, a C-plane is usually used. The nitride semiconductor crystal 10 includes, for example, an n-type nitride semiconductor layer 3, an active layer 4, a p-type nitride semiconductor layer 5, and the like.

  As shown in FIG. 4, the dielectric mask 2 has an opening 12 that is hollowed out in a rectangular shape in accordance with the chip shape. Nitride semiconductor crystal 10 is epitaxially grown on growth substrate 1 in the region of opening 12. The growth direction is performed in the direction of the arrow in FIG. 1, and when the shape of the opening 5 is rectangular, as shown in FIG. 2, a die-shaped or rectangular parallelepiped chip (nitride semiconductor crystal 10) is separated. Thus, it is not necessary to perform operations such as dicing for chip separation and dry etching. If the shape of the opening 5 is a square, the nitride semiconductor crystal 10 can be grown in a cubic shape.

  By the way, since the growth substrate such as a sapphire substrate and GaN have different lattice constants, the GaN-based semiconductor layer grown on the growth substrate has dislocations (lattice defects) extending vertically from the substrate. Yes. As a method for reducing such dislocations, selective lateral growth (ELO: Epitaxial Lateral Overgrowth) is well known.

  In order to separate the nitride semiconductor crystal 10 into a die shape, the above-described selective lateral growth method is used. By reducing the area where the growth substrate 1 and the nitride semiconductor crystal 10 are in contact with each other, all the dislocations existing in the growth substrate are not transmitted to the nitride semiconductor crystal 10. By covering the growth substrate 1 with the dielectric mask 2 as a selective growth mask, growth first occurs from the opening 12 of the dielectric mask 2 (selective growth), and then a growth layer is also formed on the dielectric mask 2. By spreading, crystal growth is formed in the lateral direction. In order to form separated chips, it is desirable that the opening 12 of the dielectric mask 2 has a square shape so that it grows in the horizontal and vertical directions in the growth surface of the growth substrate 1 in the same manner. .

  However, in the present invention, since it is necessary to perform crystal growth so as to finally form a chip separated into a rectangular shape, the growth is performed under conditions where the vertical growth is strong. In general, when a nitride semiconductor crystal is grown at a high temperature of 1000 ° C. or higher and a low pressure of less than 100 Torr, the lateral growth becomes strong. Therefore, the temperature and pressure conditions are set in appropriate ranges as described later.

Hereinafter, a method for manufacturing a nitride semiconductor light emitting device will be described. First, as shown in FIG. 3, the dielectric mask 2 having an opening 12 in which a region for growing the nitride semiconductor crystal 10 is formed in a rectangular shape on the growth substrate 1 is patterned. As the growth substrate 1, an insulating sapphire substrate or SiC can be used. In this embodiment, a sapphire substrate is used, and the nitride semiconductor crystal 10 is grown on the C plane. The dielectric mask 2 functions as a selective growth mask, and SiO ₂ or SiN is used.

  Further, the size L of the opening of the dielectric mask 2 is formed such that L = W− (50 μm to 100 μm), where W is the size of the completed chip in the same direction. As an example, the size L of the opening can be about 150 μm to 1 mm.

  Next, an n-type nitride semiconductor layer 3 is grown on the growth substrate 1 as shown in FIG. FIGS. 5 to 13 show manufacturing process diagrams in which the portion A surrounded by a broken line in FIG. 1, that is, one chip is enlarged. In the first stage, since the semiconductor crystal does not grow on the dielectric mask 2, the semiconductor crystal stacked in the opening 12 grows upward and laterally, and has a rectangular parallelepiped shape as shown in FIG. It becomes. For example, a Si-doped n-GaN contact layer is formed as the n-type nitride semiconductor layer 3. The substrate temperature is raised to 1000 to 1200 ° C., preferably 1050 to 1100 ° C., and grown by a known HVPE method (halide vapor phase growth method) under a pressure of 100 Torr to atmospheric pressure, preferably 200 Torr to atmospheric pressure.

  After the n-type nitride semiconductor layer 3 is formed, an active layer 4 is formed as shown in FIG. The active layer 4 is made of, for example, InGaN, and the temperature is lowered to 700 ° C. to 900 ° C., and the pressure is grown at 200 Torr to atmospheric pressure. As shown in the drawing, the active layer 4 is formed on the outside so as to wrap the entire n-type nitride semiconductor layer 3.

  Thereafter, as shown in FIG. 7, a p-type nitride semiconductor layer 5 is formed. The p-type nitride semiconductor layer 5 is composed of, for example, an Mg-doped p-GaN contact layer, and the temperature is increased to 1000 to 1100 ° C., preferably 1010 to 1070 ° C., and is desirably in a pressure range of 100 Torr to atmospheric pressure. Is grown in the range of 200 Torr to atmospheric pressure. The p-type nitride semiconductor layer 5 is formed outside so as to wrap the entire active layer 4.

Next, as shown in FIG. 8, in order to obtain a complete stacked structure in the vertical direction, the mask 6 is patterned on the region of the semiconductor layer that must be left, and dry etching is performed on the edge of the chip. The excess region of the nitride semiconductor crystal 10 is deleted. For the mask 6, in addition to SiO ₂ and SiN that are dielectric masks, Pt, Ni, and the like that are metal masks are used.

  After that, when the mask 6 is removed as shown in FIG. 9, the n-type nitride semiconductor layer 3, the active layer 4, and the p-type nitride semiconductor layer 5 are formed in a rectangular shape, and adjacent chips are separated from each other. Become. This overall state is shown in FIG.

  Next, as shown in FIG. 10, a p-electrode 7 is laminated as a first electrode layer by vapor deposition, and a conductive fusion layer 8 is formed thereon. For example, a laminated body of Ni and Au can be used as the p-electrode 7. However, in the case of a structure considering light extraction efficiency, it is desirable to use a transparent electrode, for example, ohmic contact using ZnO. Electrode.

  The conductive fusion layer 8 joins the p-electrode 7 and the support substrate 9 shown in FIG. 11 and may be a brazing material such as solder. In the case of thermocompression bonding, a multilayer of Ti and Au is used. Only a metal film or Au, a multilayer metal film of an alloy of Au and Sn and Ti, or the like is used. The p-electrode 7 and the support substrate 9 are electrically connected by the conductive fusion layer 8.

  After forming the conductive fusion layer 8, as shown in FIG. 11, a support substrate 9 is bonded, and laser light is irradiated from behind the growth substrate 1 to form one of the GaN layers of the n-type nitride semiconductor layer 3. The part is disassembled and the growth substrate 1 is peeled off.

  The support substrate 9 is used to replace (transfer) the nitride semiconductor crystal 10 and the p-electrode 7 grown on the growth substrate 1, and a conductive substrate is used. A material such as GaN, silicon, or SiC is used as the conductive substrate, and Cu or the like is also used as the high thermal conductivity submount. An external connection terminal or the like is provided on the surface of the support substrate 9 opposite to the surface on which the conductive fusion layer 8 is formed, and is connected to an external electrical terminal.

  When the growth substrate 1 is removed as shown in FIG. 11, the dielectric mask 2 is also removed together with the growth substrate 1, so that the shape shown in FIG. 12 is obtained.

  After peeling off the growth substrate 1, excess Ga is flowed by acid etching or the like, and as shown in FIG. 13, an n-electrode 11 is formed as a second electrode layer by vapor deposition. The n electrode 11 is composed of a laminate of Ti and Al, Al, or the like, and is in ohmic contact with the n-type nitride semiconductor layer 3.

  Thereafter, the support substrate 9 is cut by dicing or the like and completely separated into chips. As described above, a nitride semiconductor crystal is selectively grown using a dielectric mask having a rectangular opening, the crystal growth conditions are adjusted appropriately, and vertical growth is also taken into consideration. A chip having a shape (die shape) can be formed, and crystal growth can be completed in a state where adjacent chips are separated.

  Therefore, it is not necessary to create the chip separation groove by etching or dicing, and the manufacturing process time can be shortened. In particular, after a nitride semiconductor is epitaxially grown on a sapphire substrate, etching is performed until the n-type gallium nitride layer is exposed, an n-type contact is formed on the etched surface, and p-type and n-type are formed on the same surface side. In the case of a nitride semiconductor light emitting device having a structure in which two electrodes are provided, it takes a long time because it includes a step of mesa etching until the n-type gallium nitride layer is exposed, but the p electrode and the n electrode as in the present invention. In the nitride semiconductor light emitting device having a structure in which the two are opposed to each other, the shape of the nitride semiconductor crystal 10 grown in a dice shape can be used almost as it is, so that the chip manufacturing time can be shortened.

Further, the dry etching of the chip end portion performed to remove the excess region of the nitride semiconductor crystal 10 in the step of FIG. 8 is the same as the dry etching for forming the chip isolation groove shown in FIG. In contrast, since the work is completed in a short time, the semiconductor layer such as the active layer 4 is hardly damaged.

It is a figure which shows the concept of the nitride semiconductor light-emitting device manufacturing method of this invention. It is a figure which shows the state which the growth complete | finished in the state isolate | separated by the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows 1 process of the nitride semiconductor light-emitting device manufacturing method. It is a figure which shows the state of the conventional chip separation process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Growth substrate 2 Dielectric mask 3 N-type nitride semiconductor layer 4 Active layer 5 P-type nitride semiconductor layer 6 Mask 7 P electrode 8 Conductive fusion layer 9 Support substrate 10 Nitride semiconductor crystal 11 N electrode

Claims (6)

A nitride semiconductor crystal including a light emitting region and a first electrode layer are formed on a growth substrate, and the nitride semiconductor crystal and the first electrode layer are transferred to a support substrate, and then face the first electrode layer. In the method for manufacturing a nitride semiconductor light emitting device, wherein the second electrode layer is formed on the nitride semiconductor crystal,
After nitriding a dielectric mask having a rectangular opening on the growth substrate, the nitride semiconductor crystal is selectively grown and crystal growth is terminated in a state of being separated into a rectangular shape. For manufacturing a semiconductor light emitting device.   The method for manufacturing a nitride semiconductor light emitting device according to claim 1, wherein the opening of the dielectric mask has a square shape.   The nitride semiconductor according to claim 1, wherein the nitride semiconductor crystal includes an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor. Manufacturing method of light emitting element.   4. The method of manufacturing a nitride semiconductor light emitting device according to claim 3, wherein the n-type nitride semiconductor layer is grown at a temperature in the range of 1000 [deg.] C. to 1200 [deg.] C. and a pressure of 100 Torr or more.   5. The nitride semiconductor light-emitting element according to claim 3, wherein the p-type nitride semiconductor layer is grown at a temperature in a range of 1000 ° C. to 1100 ° C. and a pressure of 100 Torr or more. Production method. 6. The method for manufacturing a nitride semiconductor light emitting device according to claim 3, wherein the active layer is grown in a temperature range of 700 ° C. to 900 ° C. and a pressure of 200 Torr or more.

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