KR20050000836A - Method for manufacturing GaN LED - Google Patents

Abstract

PURPOSE: A method of manufacturing a GaN LED(Light Emitting Diode) device is provided to improve remarkably emissive efficiency of an LED, to perform easily eutectic bonding and to reduce the consumption of a diamond tip in a scribing process by forming a groove with tilted surfaces on a backside of a sapphire substrate. CONSTITUTION: An LED wafer is formed by forming a light emissive structure(23) and electrodes(25,26,27) on a sapphire substrate(21). Lapping is performed on a backside of the LED wafer. A plurality of grooves(32) with tilted surfaces are regularly formed on the backside of the LED wafer by using a laser processing technique. A backside metal made of a reflective coating, a barrier layer(29) and a bonding layer(30) is formed on the backside of the LED wafer. The grooves are used as scribing lines.

Description

Method for manufacturing gallium nitride-based light emitting diode device {Method for manufacturing GaN LED}

The present invention relates to a method of manufacturing a gallium nitride (GaN) light emitting diode, and more specifically, by forming a predetermined inclined surface on the side of the sapphire substrate, it is possible to facilitate eutectic bonding while enhancing the reflection effect to improve the luminance characteristics. The present invention relates to a method for producing a gallium nitride-based light emitting diode.

In general, a light emitting diode (LED) is a semiconductor device that emits light based on recombination of electrons and holes, and is widely used as a light source in optical communication and electronic devices.

The frequency (or wavelength) of light emitted from such a light emitting diode is a band gap function of a material used in a semiconductor device. When using a semiconductor material having a small band gap, low energy and long wavelength photons are generated, and a wide band gap When using a semiconductor material having a photon of a short wavelength is generated. Therefore, the semiconductor material of the device is selected according to the kind of light to be emitted.

For example, an AlGaInP material is used for a red light emitting diode, and silicon carbide (SiC) and a group III nitride semiconductor (particularly, gallium nitride (GaN)) are used for a blue light emitting diode.

Among them, gallium nitride (GaN) -based light emitting diodes cannot form GaN bulk single crystals, so a substrate suitable for the growth of GaN crystals should be used separately, and a representative substrate used is sapphire (aluminum oxide (Al _2). O ₃ ).

The basic structure of such a gallium nitride-based light emitting diode is shown in FIG. As shown in FIG. 1, the GaN light emitting diode 10 basically includes a sapphire substrate 11, a GaN-based light emitting structure 13 formed on the sapphire substrate 11, and a GaN light emitting structure 13. The N-electrode 15, the T-electrode 16 and the B-electrode 17 are formed.

The light emitting structure 13 includes an n-type GaN cladding layer 13a sequentially formed on the sapphire substrate 11, an active layer 13b having a multi-quantum well structure, and a p-type GaN cladding layer. It consists of 13c.

The GaN light emitting structure 13 may be grown using a process such as metal organic chemical vapor deposition (MOCVD). In this case, the n-type GaN cladding layer 13a of the GaN light emitting structure 13 may be formed. In order to improve lattice matching with the sapphire substrate 11 before growing, a buffer layer (not shown) made of AlN / GaN may be formed.

The p-type GaN cladding layer 13c and the active layer 13b are etched in the GaN light emitting structure 13 to expose a portion of the top surface of the n-type GaN cladding layer 13a.

N-electrode 15 and B-electrode 17 for applying a predetermined voltage to the upper surface of the exposed n-type GaN cladding layer 13a and the unetched p-type GaN cladding layer 13c are respectively At this time, in order to increase the current injection area and not lower the brightness characteristic of the light, T- is made of a transparent transparent material before forming the B-electrode 15 on the upper surface of the p-type GaN cladding layer 13c. An electrode 16 (transparent electrode) is formed.

The GaN light emitting diode 10 may be used by simply contacting the N, B-electrodes 15 and 17 with a lead frame by wire bonding technology, or the N, B-electrode of the light emitting diode 10 chip. After forming the micro bumper on the B-electrodes 15 and 17, a flip-chip bonding technique may be applied to the Si substrate.

However, in the former method, the light emitting direction becomes the upper direction in the structure of FIG. 1, and reflects the light emitted in the lower direction to be directed upward, thereby improving the luminance characteristic of the reflective layer on the lower surface of the sapphire substrate 11. Should be formed.

By the way, in the case of forming a reflective layer on the back of the sapphire substrate 11 as described above, after depositing a metal on the back for chip mounting, alignment problems during the scribing process, a diamond tip for scribing (diamond) The consumption of tip) increases, and the chip breaks.

In order to solve this problem, conventionally, a metal mask is deposited on the back side of a light emitting diode having a structure as shown in FIG. 1, and then a scribing process is performed, or a metal mask is deposited on the back side of the light emitting diode. A method using a steel mask has been proposed.

However, this conventional method has a problem that the manufacturing process is complicated and the consumption of diamond tips, which occupies a large part of the manufacturing cost, is considerably large. In addition, the conventional method has a problem that it is difficult to form the bonding layer required for mounting the chip by eutectic bonding on the lead frame being studied for high reliability.

The present invention has been proposed in order to solve the above-described problems, and an object thereof is to provide a method of manufacturing a gallium nitride-based light emitting diode which can increase a reflection effect by forming a predetermined inclined surface on the side of the sapphire substrate.

Another object of the present invention is to provide a method of manufacturing a gallium nitride-based light emitting diode in which eutectic bonding is facilitated by forming a predetermined inclination angle on the side of the sapphire substrate.

In addition, another object of the present invention is to form a cutting groove having a predetermined inclination angle on the back surface of the sapphire substrate in the wafer state, and then to form metal deposition only in the required area through the photo process and deposition, diamond chip consumption during the scribing process It is to provide a method of manufacturing a gallium nitride-based light emitting diode that can reduce the.

1 is a cross-sectional view showing a basic structure of a gallium nitride-based light emitting diode.

2 is a cross-sectional view showing the basic structure of a gallium nitride-based light emitting diode manufactured by the present invention.

3A to 3E are cross-sectional views showing gallium nitride based light emitting diodes according to the present invention for each manufacturing step.

Fig. 4 is a schematic diagram showing the bottom surface of a gallium nitride based light emitting diode according to the present invention in a wafer state.

5 is a schematic diagram showing a state in which a gallium nitride-based light emitting diode according to the present invention is bonded.

Explanation of symbols on the main parts of the drawings

21 sapphire substrate 23 light emitting structure

25-27: electrode 28: reflective layer

29 barrier layer 30 bonding layer

31: LED Wafer 32: Groove

32a: inclined surface 33: cutting line

As a construction means for achieving the above object of the present invention, the present invention comprises a wafer forming step of forming an LED wafer by forming a light emitting structure and an electrode on the sapphire substrate; A wrapping step of wrapping a back side of the LED wafer; A laser processing step of forming a groove having an inclination angle at a cutting position on a rear surface of the wrapped LED wafer by a laser processing technique; And a rear metal forming step of sequentially forming a reflective layer, a barrier layer, and a bonding layer on a rear surface of the laser processed LED wafer, wherein the groove having the inclination angle formed in the laser processing step is used as a cutting line. Provided is a method of manufacturing a gallium nitride-based light emitting diode device.

In addition, the method of manufacturing the gallium nitride based light emitting diode device according to the present invention described above may display a cutting line by not performing metal deposition at the cutting position through patterning in the back metal forming step.

The present invention also provides a wafer forming step of forming an LED wafer by forming a light emitting structure and an electrode on a sapphire substrate; A wrapping step of wrapping a back side of the LED wafer; A laser processing step of forming a groove having an inclination angle at a cutting position on a rear surface of the wrapped LED wafer by a laser processing technique; Forming a pattern through a photoresist at each cutting position of the rear surface of the LED wafer; The present invention provides a method of manufacturing a gallium nitride-based light emitting diode device comprising a cutting line forming step of sequentially depositing a reflective layer, a barrier layer, and a bonding layer on a rear surface of the patterned LED wafer, and then lifting off a pores register.

In addition, in the method of manufacturing the gallium nitride-based light emitting diode device of the present invention, the laser processing step preferably irradiates beams of predetermined power in predetermined directions in both directions, respectively, based on the cutting position of the LED wafer. As a result, a groove having an inclination angle α having a '∧' shape can be formed.

Hereinafter, a method of manufacturing a gallium nitride-based light emitting diode according to the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a cross-sectional view of a GaN LED chip of a final stage manufactured according to the present invention. Referring to this, the GaN LED 20 manufactured according to the present invention has a sapphire substrate 21 similar to a structure of a general LED. ), A GaN-based light emitting structure 23 formed on the sapphire substrate 21, and an N-electrode 25, a T-electrode 26, and a B-electrode 27 formed on the GaN light emitting structure 23. In addition, an inclined surface having a predetermined slope is formed at a lower edge of the sapphire substrate 21, and a reflective layer 28, a barrier layer 29, and a bonding layer 30 are sequentially formed under the sapphire substrate 21. In addition, a cutting line A on which the reflective layer 28, the barrier layer 29, and the bonding layer 30 are not deposited is formed.

The light emitting diode may be directly mounted on the lead frame of the package by eutectic bonding technology.

When the current is supplied to the light emitting diodes 20 through the N-electrode 25 and the B-electrode 27, the active layer 23b of the light emitting structure 23 is activated to form light. The light emitted in the direction in which the electrodes 25 and 27 are formed is emitted as it is, on the contrary, the light emitted in the sapphire substrate 21 is reflected by the reflective layer 28 formed on the lower surface of the sapphire substrate 21 so as to face in the opposite direction. do. In addition, the light reaching the side inclined surface of the sapphire substrate 21 among the light emitted in the side direction is reflected by the reflective layer formed on the inclined surface. Therefore, most of the light generated by the light emitting structure 23 is emitted in the direction in which the electrodes 25 and 26 are formed (upward in the drawing), and as a result, the luminance characteristic may be improved.

The manufacturing process for the GaN light emitting diode of the present invention will be described in detail with reference to the step-by-step process diagram shown in Figures 3a to 3e.

After the light emitting structure 23 is grown on the sapphire substrate 21 in the order of the n-type GaN cladding layer, the active layer, and the p-type GaN cladding layer, the predetermined region of the light emitting structure 23 is etched to the active layer, and the etched structure is etched. Electrodes are formed on the n-type GaN cladding layer and the p-type GaN cladding layer, respectively, to produce an LED wafer 31 in which a plurality of light emitting diodes are integrated.

The present invention is characterized by a method of forming a cutting line on the back surface of the LED wafer 31, the process of forming the LED wafer may be made by other methods in addition to the above-described method.

When the LED wafer 31 is provided as described above, the back surface of the LED wafer 31, that is, the back surface of the sapphire substrate 21 is flatly wrapped, and then the back surface of the wrapped LED wafer 31 ( That is, grooves having a triangular cross section having a predetermined inclination and depth are formed at cutting positions between the light emitting diode elements on the rear surface of the sapphire substrate 21.

That is, by irradiating a laser with a predetermined inclination with respect to the cut portion between the respective light emitting diodes on the back surface of the wrapped wafer 31, the groove 32 having a predetermined angle of inclination at the rear edge of each light emitting diode element is formed. To form.

First, as shown in FIG. 3A, a laser beam having a predetermined power is irradiated in a direction in which the reference line P corresponding to the cutout portion between the light emitting diode elements on the rear surface of the LED wafer 31 is inclined to the left by an angle α. Next, as illustrated in FIG. 3B, a groove having an inclined angle of '∧' is irradiated by irradiating a laser beam having the same power as the previous power in a direction inclined by an angle α to the right with respect to the reference line P. 32). In this case, when the inclination of the inclined surface 32a of the sapphire substrate 21 formed by the groove 32 is y / x, the luminance characteristic of the light emitting diode manufactured by the method is inclined y / of the inclined surface 32a. The relationship between the inclination of the inclined surface 32a and the characteristics of the device will be described later through simulation results.

Next, as a next step, metal deposition is performed on the back surface of the LED wafer 31 on which the grooves 32 are formed, and as shown in FIG. 3C, the reflective layer 28, the barrier layer 29, and the bonding layer 30 are formed. Form sequentially.

In this case, the reflective layer 28 is formed of a material selected from the group consisting of Ag, Al, Pd, Rh and alloys thereof, and the barrier layer 29 is a group consisting of Ti, W, Cr, Pt, Ni and alloys thereof. It is formed of a material selected from, the bonding layer 30 is made of a material selected from the group consisting of Au, Sn, In and alloys thereof.

In addition, since the reflective layer 28, the barrier layer 29, and the bonding layer 30 are each formed to have a uniform thickness along the rear surface of the wafer 31, the rear surface of the wafer 31 after deposition is in a '∧' shape. A concave portion appears.

Next, as shown in FIG. 3D, the reflective layer 28, the barrier layer 29, and the bonding layer 30 are formed by using the transparent characteristics of the wafer 31 and the photoresist PR. The portion to be deposited is patterned to form a cutting line 33. The cutting line 33 appears at the cutting position of the rear surface of the LED wafer 31 and is located at the center of the '32' shaped groove 32.

Fig. 4 shows the bottom surface of the light emitting diode wafer after the completion of the process shown in Fig. 3d, wherein concave cut lines 33 are formed between the plurality of light emitting diode chips.

Subsequently, the wafer 31 is cut along the cutting line 33 formed as described above, thereby finally forming the light emitting diode device 20 having the inclined surface 32a formed at the corner of the sapphire substrate 21 as shown in FIG. 2. .

That is, the cutting line 33 can be formed through the above laser process and metal deposition, and the wafer thickness at the cutting line 33 thus formed is reduced, thereby cutting the wafer 31 into a plurality of light emitting diodes. This can reduce the diamond tip consumption in the process.

One light emitting diode formed by cutting along the cutting line 33 formed as described above is shown in FIG. 2, and the light emitting diode 20 manufactured as described above has a bonding layer 30 and a substrate formed on the bottom surface thereof. The bonding material of is eutectic (eutectic) and bonded, the bonding state is shown as Figure 3e.

The light emitting diode 20 manufactured as described above can be collected by reflecting the light emitted from the side surface, as compared with the conventional deposition of a reflective film or a bonding layer only on the rear surface, thereby obtaining higher luminance.

The effect of improving the reflection characteristics can be seen more clearly from the simulation results.

Figure 4 is a schematic diagram showing the bonded state of the LED device according to the present invention, wherein the width of the light emitting diode is 347㎛, the height is 80㎛. And the thickness of the eutectic bonding material is about 20 micrometers. In this case, luminous flux and luminous intensity generated in each case were measured while adjusting the inclination (y / x) of the inclined surface of the side surface. The results are shown in Table 1 below. . In the simulation results of Table 1 below, the depth y of the grooves 32 is equally set to 40 μm, which is 1/2 of the total height of the light emitting diodes.

Condition Farfield receiver Plane receiver Lumen Luminance (cad) % Increase Lumen Luminance (cad) % Increase One 0.12288 0.00978 100% 0.03038 212365 100% 2 0.15129 0.01204 123% 0.06008 519713 245% 3 0.16912 0.01346 135% 0.06933 599733 282% 4 0.16627 0.01323 138% 0.07368 637384 300% 5 0.18552 0.01476 151% 0.09084 785778 370% 6 0.19546 0.01555 159% 0.10208 883026 416%

The measurement data of Table 1 is a simulation result obtained by die-bonding the LED chip corresponding to each condition described above to a flat lead frame using Ag paste, where condition 1 is x = 0, y = 0 when the slope (y / x) is 0, the back metal (that is, the case that does not form a reflective layer), condition 2 is the reflective layer with the slope (y / x) is 0 Condition 3 is x = 20 μm, y = 40 μm, and the reflection layer is formed while the inclination (y / x) is 2, and condition 4 is the slope as x = 40 μm and y = μm40. y / x) is 1 and the reflective layer is formed, condition 5 is x = 60 µm and y = µm40, and the slope (y / x) is 2/3 and the reflective layer is formed, and condition 6 is x = In the case where the reflective layer is formed while the inclination (y / x) is 1/2 with 80 µm and y = µ40,

When comparing the measured luminous flux and luminous intensity according to the above conditions, when the luminance characteristic of the condition 1 without forming the inclined surface and forming the reflective layer as 100% is 100%, the inclined surface is not formed and only the reflective layer is formed on the rear surface. In this case, the luminance characteristic is increased by about 2 times, and in addition, when the inclined surface is formed and the reflective layer is formed, it can be seen that the inversely proportional to the inclination of the inclined surface is increased up to 4 times.

In addition, the method of manufacturing a light emitting diode according to the present invention patterns the portion of the metal to be deposited using the transparent properties of the LED wafer and the photoresist that are wrapped during deposition of the metal for reflection, barrier, and bonding, thereby depositing the metal only on the desired portion. It is also possible to form a cutting line through this.

In addition, the method of manufacturing a light emitting diode according to the present invention enables the LED chip manufactured by simultaneously depositing the reflective layer 28 and the bonding layer 30 as described above to be directly connected to the lead frame by a eutectic bonding method when mounted on a package. do.

For example, when the light emitting diodes 20 of FIG. 2 are placed on a lead frame covered with a material such as Ag or Au, and then heated to a predetermined temperature, the chips are vibrated horizontally, and the bonding layer 30 At the eutectic point of Ag or Au of the leadframe, the alloy between the two materials is uniformly bonded.

In this case, the bonding layer 30 may be formed of a thin intermediate brazing material (Au + Si) to be connected at the eutectic point.

As described above, the GaN light emitting diode manufacturing method according to the present invention can increase the luminance characteristics of the light emitting diode device, and by forming a cutting line through a laser processing and a lift-off process, a diamond tip occupies a large part of the manufacturing cost. There is an excellent effect to reduce the manufacturing cost by reducing the consumption.

In addition, it is easy to directly mount the light emitting diode elements on the lead frame through eutectic bonding.

Claims (7)

Forming a light emitting structure and an electrode on the sapphire substrate to form an LED wafer; A wrapping step of wrapping a back side of the LED wafer; A laser processing step of forming a groove having an inclination angle at a cutting position on a rear surface of the wrapped LED wafer by a laser processing technique; And Back metal forming step of sequentially forming a reflective layer, a barrier layer, a bonding layer on the back of the laser processed LED wafer And a groove having an inclination angle formed in the laser processing step as a cutting line. The method of claim 1, wherein the laser processing step A method of manufacturing a gallium nitride-based light emitting diode device, characterized in that a groove having a '∧' shape is formed by irradiating a beam having a predetermined power by inclining the predetermined angle α in both directions based on the cutting position of the LED wafer. The method of claim 1, wherein the forming of the back metal is Method for producing a gallium nitride-based light emitting diode device characterized in that the cutting line is displayed by not performing metal deposition at the cutting position through the patterning. The method of claim 1 wherein the method is Cutting each of the LED wafers along the formed cutting lines to form respective light emitting diode chips; And Mounting the light emitting diode chip on a lead frame through eutectic bonding; Method of manufacturing a gallium nitride-based light emitting diode device further comprising. Forming a light emitting structure and an electrode on the sapphire substrate to form an LED wafer; A wrapping step of wrapping a back side of the LED wafer; A laser processing step of forming a groove having an inclination angle at a cutting position on a rear surface of the wrapped LED wafer by a laser processing technique; Forming a pattern through a photoresist at each cutting position of the rear surface of the LED wafer; After forming a reflective layer, a barrier layer, and a bonding layer sequentially on the back surface of the patterned LED wafer, the cutting line forming step of lifting off the fore register Method of manufacturing a gallium nitride-based light emitting diode device characterized in that it further comprises. The method of claim 5, wherein the laser processing step A method of manufacturing a gallium nitride-based light emitting diode device, characterized in that a groove having a '∧' shape is formed by irradiating a beam having a predetermined power by inclining the predetermined angle α in both directions based on the cutting position of the LED wafer. The method of claim 5, wherein the method Cutting each of the LED wafers along the formed cutting lines to form respective light emitting diode chips; And Mounting the light emitting diode chip on a lead frame through eutectic bonding; Method of manufacturing a gallium nitride-based light emitting diode device further comprising.