TW200525847A - Gallium nitride vertical light emitting diode structure and method of separating a substrate and a thin film in the structure - Google Patents

Abstract

A GaN vertical light emitting device structure and a method of separating a substrate and a thin film thereon in the GaN vertical light emitting device (LED). The structure comprises a metal reflector for reflecting a light. The method comprises the steps: providing a laser array over the substrate wherein a laser light emitted by the laser array may at least partially be transparent to the substrate and its energy may be absorbed by the thin film; irradiating the thin film through the substrate; and then separating the substrate and the thin film.

Description

[Previous technology] The development of semiconductor light-emitting diodes (LEDs) has a history of decades. The improvement of luminous efficiency has always been the key to whether LEDs can be used—the key to further use in people's livelihood. Therefore, the development direction of LEDs over the years is roughly All are in the improvement of luminous efficiency. However, on the way of improving the luminous efficiency, the heat dissipation problem has been a major limiting factor; that is, when the luminous efficiency is continuously increasing, if the heat of the light source cannot be effectively eliminated, lew will be trapped in a situation where it cannot work normally. Therefore, the research and development of LED for many years has been focused on improving luminous efficiency and eliminating heat. In the history of LED development, there are many proposed heat removal technologies, such as replacing traditional printed circuit boards with poor thermal conductivity with gold circuit boards, so that the crystals can be removed from the LED structure by metal. The heat dissipation in the LED structure must also be improved. For example, although sapphire is suitable for growing gallium nitride (. The magic system "Yi," but it is a non-conductive material with poor thermal conductivity, so-often by first To grow a GaN-based LED structure, detach it from the LED structure, and attach another substrate with better thermal conductivity at the back, which is illustrated schematically in the first A and B diagrams. Because of the above sapphire The function of the substrate is only after the formation of multiple layers, and each multilayer film needs to be removed after it is formed, so it is called ^, the transition substrate. In the first A diagram, the one shown is a vertical light-emitting element junction. It is in the unfinished manufacturing stage. In the figure, first use 200525847. V. Description of Invention (2) Substrate 16 is used as a substrate to generate a thin film structure layer. The thin film structure includes a ^ -type gallium nitride system layer 1 5 , Active layer 14, 4, p-type gallium nitride-based layer 3, and metal substrate 11, one end of which has a P-type electrode 17 formed on the metal substrate, because the existence of the transition substrate 16 is to be used The subsequent process has a support, so it can be removed after the vertical light emitting element structure is completed, such as the first B After that, the entire vertical light-emitting element structure 10 is turned by 180 ° to obtain a structure like the first B picture, in which the transition substrate 16 is removed first, and then an n-type The electrode 18 'is then fabricated on the n-type gallium nitride-based layer 15, so that the fabrication of the entire vertical light emitting element structure 10' is completed. Referring again to the first B figure, the entire vertical light emitting element structure at this time 丨 〇, The upper and lower sides must be attached with metal electrodes 17 '(ρ-type electrodes) and 18, (n-type electrodes). Since the entire vertical light-emitting element structure has no lateral structure, it is called a vertical structure LED. The structure thus formed not only improves the above-mentioned heat removal problem, but also has a larger light emitting area than the traditional ones, because neither of the two electrodes is arranged on the side of the structure; therefore, the area of lateral light emission does not need to be reduced, and due to the transparent form It is formed on both sides of the LED structure to allow light to penetrate. As shown in FIG. 1C, it is a first a to a B diagram of the gallium nitride-based vertical light emitting element structure 10 after the transition substrate is removed, ,. Active layer 14 " part of the light emitted The p-type gallium nitride-based layer 1 3 ″ travels, and another part goes to the \ -type gallium nitride-based layer 15 ′, (as shown by the arrow in the figure). If the n-type electrode 18, one side is as desired Where the light exits, the light towards the P-shaped electrode 17 7 is equally wasteful. Regarding the separation between the above-mentioned vertical structure transition substrate and the upper film layer, several technologies have been proposed, such as using sapphire as the substrate (transition Substrate) to form layers of the structure, the transition substrate and the ρ above

Page 7 200525847 V. Description of the invention (3) Type semiconductor material layer or n-type semiconductor material layer is fabricated with a brittle structure and separated by force. There are also conventional techniques that use laser light to provide energy to separate the transition substrate from the film above it. At this time, the upper film must absorb the laser light energy and be separated from the transition substrate due to melting ', such as in the early US patent application US20030150843. In this application (please refer to the second figure), a linear laser light 2 3 scans the thin film layer 2 1 on the transition substrate 2 2, and the thin film layer 2 1 can absorb the laser light 2 3 energy and then it can communicate with the substrate. The interface 25 of the material melts and separates from the transition substrate 22, where the transition direction of the transition substrate 22 and the film layer 21 during scanning is shown in the figure, S is the scanning area during one scan, and M Is the scanning width of one scan, and t is the thickness of the thin film layer 21, where the value of the scanning width M is approximately equal to or less than the thickness t. However, this application still has its technical disadvantages. For example, after the entire layer of film is scanned by the linear light source, the degree of melting on the film is not the same; therefore, when the transition substrate 22 is detached, the transition substrate 22 and the film layer 21 are affected by each other. The peeling force is not uniform enough. Furthermore, there is a problem of thermal stress during the linear laser scanning. This uneven thermal stress also makes the peeling effect unsatisfactory, and there is a possibility that the film layer is broken. In view of the shortcomings of the conventional GaN-based vertical structure light-emitting diode (LED) element structure and its manufacturing method, a GaN-based vertical light-emitting diode (LED) structure and the It is necessary to put forward a method for separating a substrate from a film on the structure. SUMMARY OF THE INVENTION In view of the above problems, the main purpose of the present invention is to reduce vertical hair.

200525847 V. Description of the invention (4) The problem of uneven thermal stress and melting degree of laser separation between a film and a transition substrate during the manufacture of a photodiode structure. In order to achieve the objective, the first aspect of the present invention is to use a laser array as the melting energy source ', and the size of the irradiation range of the laser array is almost equal to the contact surface between the film to be melted and the transition substrate. Once the power of the laser array is turned on, the laser energy in the array is absorbed by the film surface at the same time, the melting degree of the film surface is equivalent and separated from the transition substrate uniformly, and the film surface is more uniform without thermal stress. Adhesion between release and transition substrate. In addition, because the laser array has a shorter irradiation time on the entire film, the process time can be shortened. A second aspect of the present invention is a gallium nitride-based vertical light-emitting diode element structure with better luminous efficiency, and a metal reflective layer provides reflection of traveling light therein to obtain greater light output efficiency. Aiming at the vertical light emitting diode (LED) structure, the present invention proposes an effective manufacturing method. With this method, the sapphire-based transition substrate in the vertical structure is more uniformly separated from the film layer above it, and the manufacturing process can be reduced. Please refer to the process schematic diagram 3 shown in the third figure. In the figure, the structure 34 shown includes a transition substrate 31 and a thin film layer 32 above. The details of the thin film junction are not shown in the figure. It should include an n-type GaN-based layer, an active layer, and a P-type nitrogen. Gallium-based layers and metal substrates, including one end? Type

surface

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pole. The two materials 3 1, 3 2 need to be separated. The separation method is to provide a laser array 3 3 above the transition substrate 31 and to provide energy through the laser array. Since the laser array is disposed on the entire thin film layer 3 Above 2, the structure 3 4 can irradiate the entire thin film layer 32 without moving. It should be pointed out here that although the laser array 33 in the figure is a ΐχ 3 laser array 33, its form can be any suitable for uniformly projecting on the interface 35, such as the lx η array, 3χ η Array, etc. When the power of the laser array 33 is turned on, the laser array 33 emits energy. Since the laser array 33 is provided to melt the transition substrate 31 and the indirect surface 35 of the thin film layer 32, the wavelength of the laser light of the laser array is selected so that the laser light can be absorbed by the interface 3 5 and The principle of melting is that it can penetrate the substrate. For example, when the thin film layer 32 is a GaN-type layer, the laser light wavelength is about 3 2 7 nm. In order to make the transition substrate 3 1 and the film layer 3 2 indirectly face 3 5 evenly absorb the energy emitted by the laser array 3 3, the design of the laser array should be based on the principle that the energy absorption pattern of the entire interface 3 5 is uniform. . In one embodiment, a light thumb surface (a combination of several slits, not shown in the figure) must be added between the transition substrate 3 and the laser array 33, so that the laser light source becomes a long strip. . After the long laser light is projected on the transition substrate 31, the energy absorption model on the thin film layer 32 should be based on the principle shown in the fourth figure. As shown in the fourth figure, there are several energy absorption patterns on the interface 45 of the thin film layer 42, namely, 1st '2nd ... ·, nth. The strip energy absorption patterns ^ St 'fnd ····, nth is formed by the gaps of the grating surface above it, and each stripe area in the eighth is 1st, 2nd ... ·, nth is close Docking, each zone

200525847 V. Description of the invention (6) The energy absorption intensity in the domains 1st, 2nd ... ,, nth is almost uniform, and the energy absorption intensity in each region 1st, 2nd, ..., nt h is also nearly uniform. It is also proposed here that the grating surface can be replaced by other optical components, as long as the laser light projected on the film 42 can be uniformly distributed. The fifth figure shows another embodiment of the energy absorption intensity distribution model. There are multiple absorption patterns on the thin film layer 52. The absorption pattern is different from that in the fourth figure. At this time, the surface of the thin film layer 52 can also absorb energy uniformly. And it is uniformly separated from the transition substrate, of course, any other embodiment of the intensity absorption model capable of uniformly absorbing the surface of the film layer 52 can be used. To achieve a uniformly distributed energy absorption intensity uniform distribution model, the laser light needs to be processed before it can be achieved, as described above, the grating surface is added; in addition, other characteristics of the laser light must be more uniformly distributed due to adjustments, such as adjusting each laser Focusing of the projection of light. In short, the final film absorption laser light intensity distribution model is based on the principle as close to that shown in the sixth figure, where the sixth chart shows that the X-axis and y-axis of the film interface have the same absorbed energy intensity at each point. Compared with the conventional technology, because the energy projected on the film interface of the present invention is uniform, there is no problem of uneven thermal stress on the entire film interface, and there is no problem of non-uniform separation caused by different completion time points of laser irradiation before separation. Therefore, the laser array energy source design proposed by the present invention can be an invention that can effectively solve the shortcomings of conventional technology. In addition, since the laser irradiation on the thin film surface does not need to be scanned in a conventional manner as in conventional technology, and the entire thin film surface is irradiated at one time, the process time can be greatly shortened. The seventh figure shows a gallium nitride-based vertical diode device structure 70 of the present invention, which includes a multilayer thin film structure and a p-type electrode 7 7. An n-type electrode

200525847 V. Description of the invention (7) 78, in which a metal reflective layer 72 is made. When the active layer 74 emits light, 'part of the light travels toward the p-type nitride nitride system layer 73, and the metal reflective layer 72 reflects the far part of the light, so that the reflected light is directed to the n-type gallium nitride-based layer 7 5— The lateral structure 70 emits light, so the luminous efficiency is improved. In addition, the positions of the n-type gallium nitride-based layer 75 of the structure 70 and the p-type gallium nitride-based layer 73 are interchangeable, and constitute another embodiment (not shown) of the present invention. As for the material of the metal reflective layer 7 2, it can be selected to match the metal substrate 7 1 with a good matching degree, and the reflection ability is good. Among them, copper tungsten alloy (CuW) can be a metal substrate, and silver (Ag) at this time , Aluminum (A1), and rhodium (Rh) can be the material of the metal reflective layer 72. ^ The basic embodiment of the present invention has been described in detail above. Those skilled in the art can derive various embodiments by reading and understanding the above embodiments # For example, the size of the laser array and the emitted laser The number of beams can be increased by 3: the intensity absorption distribution model of the interface can be changed, the grating surface must be changed, such as I parts, and the combination of the laser light source and the thin film material can be made ... The invention says that M ^ 1 ^ The examples are all μ a a 0 ′ The white that is easily deduced belongs to the spirit scope of the present invention, and the scope of these patent applications is in the section. I wish W Yi Yi to be described later

200525847 Brief description of the drawings. Figures 1 A and 1 B are schematic diagrams of a conventional process for separating a substrate from a thin film layer. Figure 1 C is a schematic diagram of a vertical light emitting diode structure of a conventional technique. A schematic diagram of a process for separating a substrate and a thin film layer; the third diagram is a schematic diagram of an embodiment of a process for separating a film and a substrate with a laser array in the present invention; the fourth diagram is the intensity of energy absorbed on a thin film layer in the present invention A schematic diagram of an embodiment of a distribution model; the fifth diagram is a schematic diagram of an embodiment of a distribution model of absorbed energy intensity on another thin film layer in the present invention; the sixth diagram is a schematic diagram of a distribution model of ideal absorbed energy intensity at each point of the film junction in the present invention And FIG. 7 is a schematic diagram of a gallium nitride-based vertical light-emitting diode structure of the present invention. 10 Vertical light-emitting element structure 11 Transition substrate 13 p-type hafnium nitride-based layer 14 Active layer 1 5 n-type gallium nitride-based layer 16 Metal substrate I 0 ', 1 0' 'Vertical light-emitting element structure II', 1 Γ '' Transition substrate

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Schematic illustrations on page 14, 13, 13, 3 '' p-type GaN-based layer 14, 14, 14 '' active layer 15, 1, 15''n-type gallium nitride-based layer 16, 16, 16 '' metal Substrate 17, 1 7 ', 1 7' 'ρ-type electrode 18, 1 8' 'η-type electrode 21 Thin film layer 22 Transition substrate 23 Laser light 25 Junction 31 Transition substrate 32 Film 33 Laser matrix light source 35 Interface between substrate and film layer 42 film 45 substrate and film indirect surface 52 film 55 substrate and film indirect surface 70 gallium nitride-based vertical light-emitting diode structure 71 metal substrate 72 metal reflective layer 73 p-type nitride Gallium-based layer 74 Active layer 75 η-type GaN-based layer 200525847 Brief description of the diagram 77 p-type electrode 7 8 η-type electrode mil Page 15

Claims (1)

200525847 VI. Scope of patent application 1. A method for separating a sapphire material and a crystalline thin film layer in a gallium nitride-based vertical light-emitting diode element, wherein the thin crystal layer is attached to a sapphire substrate, The method includes at least the following steps. A laser array is provided above the sapphire substrate, and the laser light emitted by the laser array at least partially penetrates the sapphire substrate 2. It can absorb the crystal thin film layer; % ^ Irradiating the crystalline film layer through the sapphire substrate with the laser array; and separating the sapphire substrate and the crystalline film layer from each other. 2. The method for separating a sapphire substrate and a crystalline thin film layer in a gallium nitride-based vertical light emitting diode device as described in item 1 of the scope of patent application, wherein the wavelength of the laser light is about 3 2 7 nm . ', 3. The method for separating a sapphire substrate and a crystalline thin film layer in a gallium nitride-based vertical light emitting diode element as described in item 1 of the scope of the patent application, wherein the irradiated crystalline thin film layer is irradiated on The interface between the sapphire substrate and the crystal & film layer. '/ 4 · The method for separating a sapphire substrate and a crystalline thin film layer in a gallium nitride-based vertical light-emitting diode device as described in item 1 of the scope of patent application, wherein the laser array is a laser in an arbitrary array form Shoot light. 5 · A method of separating a substrate from a thin film layer, wherein the film is above the substrate 'The method includes at least the following steps: A laser array is provided above the substrate, and the laser array emits The laser light at least partially penetrates the substrate and can be absorbed by the thin film layer; the laser array irradiates the thin film layer through the substrate; Page 16 200525847 6. Scope of patent application Separate the substrate from the film layer. 6. The method for separating a substrate and a thin film layer as described in item 5 of the scope of the patent application, wherein the absorption of the thin film layer is the absorption of the substrate and the interface with the thin film layer. 7. The method for separating a substrate and a thin film layer as described in item 5 of the scope of patent application, wherein the laser array is laser light in an arbitrary array form. 8. A gallium nitride-based vertical light emitting element structure, comprising: a metal substrate; a metal reflective layer on the metal substrate; a P-type gallium nitride layer on the metal reflective layer; an active Layer on the p-type gallium nitride-based layer; and an n-type gallium nitride-based layer on the active layer, wherein the positions of the p-type gallium nitride-based layer and the n-type gallium nitride layer are interchangeable . 9. The gallium nitride-based vertical light-emitting device structure according to item 8 of the scope of patent application, wherein the metal substrate is at least CuW, and the metal reflective layer is at least Ag, A1 and Rh. Page 17