Method for manufacturing light-emitting element

Abstract

The present invention is a method for manufacturing a light-emitting element, which is characterized by comprising: a step for growing, on at least a starting substrate, an epitaxial layer that includes a light-emitting layer having (AlxGa1-x) yIn1-yP as an active layer (0 < = xlt); 0 < = y < = 0.6; and a step of forming a separation groove for forming an element on the light-emitting layer by an ICP dry etching method performed by inductively coupled plasma, the temperature of the substrate including the epitaxial layer is set to 40 DEG C or less during the process of forming the separation groove by the ICP dry etching method. Therefore, it is possible to provide a method for manufacturing a light-emitting element capable of preventing a decrease in luminance when forming a light-emitting element of a micro-LED size by processing an epitaxial layer having an AlGaInP-based light-emitting layer by an ICP dry etching method.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a light-emitting element, and in particular to a method for manufacturing an aluminum indium gallium phosphide (AlGaInP)-based micro-light-emitting diode (micro-LED). Background Art

[0002] The technology of separating only the epitaxial functional layer from the starting substrate and transferring it to another substrate is an important technology for alleviating the limitations due to the physical properties of the starting substrate and improving the design freedom of the device system.

[0003] During transfer, by designing the bonding material with different types of substrates to be a material that can be peeled off in a subsequent step, the device can be further transferred to other substrates after it is formed.

[0004] In the method for manufacturing an LED using an AlGaInP-based epitaxial substrate, since the starting substrate is a light-absorbing substrate, it is necessary to remove the starting substrate and transfer the epitaxial layer for high brightness.

[0005] During the transfer, there are multiple options for the transfer target substrate and the bonding material or bonding method between the transfer target substrate and the transfer target substrate. According to the technology used, the transfer target substrate, bonding material and bonding method suitable for the transfer of micro light emitting diodes, that is, micro LEDs, can be selected.

[0006] For example, in the case of a gallium nitride (GaN)-based epitaxial substrate with a transparent substrate as a starting substrate, the micro-LED element is bonded to a donor substrate (donor substrate) having a polysilicone adhesive with a patterned protruding shape on the surface, and then the LED element is separated from the starting substrate by irradiating a laser from the back side of the starting substrate and the micro-LED element is further transferred from the donor substrate to the mounting substrate. This technology is an excellent technology that increases the freedom of micro-LED installation and reduces installation costs.

[0007] However, the aforementioned mounting method is a method of irradiating a laser to melt the interface between the starting substrate and the epitaxial layer so as to peel off the epitaxial layer from the starting substrate. The starting substrate is transparent to the laser, and it is necessary to design a material and structure in which the laser is absorbed only in a predetermined melting layer. Therefore, even if it is the most suitable for a GaN-based epitaxial layer using sapphire as a starting substrate, it cannot be applied to an AlGaInP-based epitaxial layer using gallium arsenide (GaAs) which is not transparent to laser as a starting substrate. Therefore, for an AlGaInP-based epitaxial substrate using GaAs as a starting substrate, the same process as that of a GaN-based epitaxial layer cannot be applied.

[0008] In order to make the above-mentioned process suitable for GaN-based epitaxial layers generally applicable to AlGaInP-based epitaxial layers, it is necessary to realize a structure in which the AlGaInP-based epitaxial layer is transferred onto a laser transmissive substrate and a laser absorption layer is provided between the AlGaInP-based epitaxial layer and the laser transmissive substrate.

[0009] Patent Document 1 discloses a technique for thermally pressing a semiconductor epitaxial substrate and a temporary support substrate via a dielectric layer, and a technique for separating a starting substrate and an epitaxial functional layer by wet etching. In this technique, by designing the temporary support substrate as a laser-transmitting substrate and designing the dielectric layer as a laser-absorbing layer, it is possible to achieve the same transfer as the above transfer suitable for a GaN-based epitaxial layer.

[0010] By using the technology of Patent Document 1, the same transfer as that suitable for GaN-based epitaxial layers can be achieved, but new problems accompanying downsizing will occur in micro LEDs.

[0011] As shown in Non-Patent Document 1, in the structure of GaN-based light-emitting elements, the brightness decreases more significantly as the size decreases due to defects or interface states and surface states generated on the side of the element during element shape processing.

[0012] Non-Patent Document 1 discloses dry etching processing conditions for a GaN-based epitaxial layer, but does not disclose conditions for an AlGaInP-based epitaxial layer.

[0013] In addition, Patent Document 2 discloses a technique for processing the shape of a light-emitting portion by applying inductively coupled plasma (ICP) dry etching to a light-emitting portion including an AlGaInP-based active layer, but does not disclose a technique regarding dry etching conditions.

[0014] In addition, Patent Document 3 discloses a technique for using a mixed gas of a gas such as chlorine (Cl2) and argon (Ar) for dry etching of an AlGaInP-based laser element. Patent Document 3 discloses performing a first dry etching and a second dry etching. However, although Patent Document 3 discloses making the ratio of Ar gas to the total gas supply of the second dry etching condition lower than the ratio of Ar gas to the total gas supply of the first dry etching condition, it does not disclose other conditions of the mixed gas of Cl2 and Ar.

[0015] Patent Document 4 discloses a method for manufacturing an electronic device including an LED chip, but does not disclose dry etching conditions for forming the LED chip.

[0016] Patent Document 5 discloses a light emitting device including a light emitting element. However, Patent Document 5 does not mention an etching process for forming the light emitting element.

[0017] Patent Document 6 discloses a light emitting element and a light emitting device using the light emitting element. However, Patent Document 6 does not mention an etching process for forming the light emitting element.

[0018] The prior art does not disclose a technique for the processing conditions for preventing or suppressing the decrease in brightness accompanying the reduction in size in the ICP etching process used when forming a micro LED having an AlGaInP-based light-emitting element structure.

[0019] [Prior Technical Literature]

[0020] (Patent Document)

[0021] Patent Document 1: Japanese Patent Application Publication No. 2021-27301

[0022] Patent Document 2: Japanese Patent Application Publication No. 2017-50406

[0023] Patent Document 3: Japanese Patent Application Publication No. 2014-103161

[0024] Patent Document 4: Japanese Patent Application Publication No. 2022-13195

[0025] Patent Document 5: Japanese Patent Application Publication No. 2021-36623

[0026] Patent Document 6: Japanese Patent Application Publication No. 2017-34231

[0027] (Non-patent literature)

[0028] Non-patent document 1: JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS, Vol. 20, No. 5, (2002), 1566-1573 Summary of the invention

[0029] [Problems to be solved by the invention]

[0030] Conventionally, when an epitaxial layer having an AlGaInP-based light-emitting layer is processed by an ICP dry etching method to form a light-emitting element of a micro-LED size, there is a problem that the brightness of the formed light-emitting element decreases.

[0031] The present invention is to solve the above-mentioned problem and aims to provide a method for manufacturing a light-emitting element, which can prevent the brightness from decreasing when forming a light-emitting element of micro-LED size by processing an epitaxial layer having an AlGaInP-based light-emitting layer by ICP dry etching.

[0032] [Technical means used to solve the problem]

[0033] In order to solve the above problems, the present invention provides a method for manufacturing a light emitting element, which is characterized by comprising:

[0034] At least a step of growing an epitaxial layer including a light emitting layer on a starting substrate, the light emitting layer (Al x Ga 1-x ) y In 1-y P is used as an active layer, where 0≦x<1, 0.4≦y≦0.6; and

[0035] forming a separation groove for forming an element on the light emitting layer by an ICP dry etching method using inductively coupled plasma;

[0036] In the process of forming the separation grooves by the ICP dry etching method, the temperature of the substrate including the epitaxial layer is set to 40° C. or less.

[0037] In this way, when forming the separation groove by the ICP dry etching method, the temperature of the substrate including the epitaxial layer is set to 40°C or less, so that even if the processing surface temperature rises, it is difficult to reach the phosphorus (P) separation temperature, so it is difficult to generate defects on the processing surface, and the brightness of the light-emitting element can be prevented from decreasing. As a result, the brightness of the manufactured light-emitting element will be improved.

[0038] One side of the element to be formed by the ICP dry etching method is preferably 100 μm or less.

[0039] In the case of a micro LED in which one side of an element formed by the aforementioned ICP dry etching method is 100 μm or less, the influence of the surface state is greater, so the brightness is further improved.

[0040] The reaction gas used in the above-mentioned ICP dry etching method is preferably a gas composed of Cl2 and Ar, or Cl2 gas.

[0041] When the Cl2 gas flow rate is greater than the Ar gas flow rate and the peak-to-peak voltage V pp The separation grooves were formed under the condition of 800 V or more.

[0042] Under such conditions, the ICP dry etching time can be shortened.

[0043] In this case, the gas flow rate of the Ar in the reaction gas is preferably set to be greater than 0 sccm and less than 1 / 3 of the gas flow rate of the Cl 2 .

[0044] Under such conditions, the ICP dry etching time can be reliably shortened.

[0045] [Effects of the Invention]

[0046] As described above, according to the method for manufacturing a light emitting element of the present invention, it is possible to prevent the brightness of the manufactured light emitting element from decreasing. As a result, it is possible to improve the brightness of the manufactured light emitting element. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic cross-sectional view showing one step of one example of a method for manufacturing a light-emitting element of the present invention.

[0048] Figure 2 This is a schematic cross-sectional view showing one step of one example of a method for manufacturing a light-emitting element of the present invention.

[0049] Figure 3 This is a schematic cross-sectional view showing one step of one example of a method for manufacturing a light-emitting element of the present invention.

[0050] Figure 4 This is a schematic cross-sectional view showing an example of a dry etching apparatus used in an example of a method for manufacturing a light-emitting element of the present invention.

[0051] Figure 5 This is a schematic cross-sectional view showing one step of one example of a method for manufacturing a light-emitting element of the present invention.

[0052] Figure 6 This is a schematic cross-sectional view showing one step of one example of a method for manufacturing a light-emitting element of the present invention.

[0053] Figure 7 This is a schematic cross-sectional view showing one step of one example of a method for manufacturing a light-emitting element of the present invention.

[0054] Figure 8 This is a graph showing the luminous efficiency of the light-emitting elements manufactured in Example 1 and Comparative Example 1.

[0055] Fig. 9 This is a graph showing the relationship between the substrate temperature and the luminous efficiency in Example 2 and Comparative Example 2. DETAILED DESCRIPTION

[0056] As described above, a method for manufacturing a light emitting element is sought to be developed which can prevent a decrease in brightness when forming a light emitting element of a micro LED size by processing an epitaxial layer having an AlGaInP-based light emitting layer by an ICP dry etching method.

[0057] The inventors of the present invention have repeatedly studied the above problems and found that when forming separation grooves by ICP dry etching, the temperature of the substrate including the epitaxial layer is set to 40° C. or less, thereby preventing the brightness of the light-emitting element from decreasing, thereby completing the present invention.

[0058] That is, the present invention is a method for manufacturing a light emitting element, characterized by comprising:

[0059] At least a step of growing an epitaxial layer including a light emitting layer on a starting substrate, the light emitting layer (Al x Ga 1-x ) y In 1-y P is used as an active layer, where 0≦x<1, 0.4≦y≦0.6; and

[0060] forming a separation groove for forming an element on the light emitting layer by an ICP dry etching method using inductively coupled plasma;

[0061] In the process of forming the separation grooves by the ICP dry etching method, the temperature of the substrate including the epitaxial layer is set to 40° C. or less.

[0062] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

[0063] In such Figure 1 On the first conductivity type GaAs starting substrate 2 shown in the figure, after laminating the first conductivity type GaAs buffer layer (not shown), a first conductivity type gallium indium phosphide (GaInP) first etching stop layer with a thickness of, for example, 0.1 μm and a first conductivity type GaAs second etching stop layer with a thickness of, for example, 0.1 μm are grown to form an etching stop layer 3. Subsequently, as shown in FIG. Figure 1 As shown, a first conductive type AlGaInP first cladding layer (lower cladding layer) 11 with a thickness of, for example, 1.0 μm, an undoped AlGaInP active layer 12 with a thickness of, for example, 0.3 μm, a second conductive type AlGaInP second cladding layer (upper cladding layer) 13 with a thickness of, for example, 1.0 μm, a second conductive type GaInP intermediate layer (not shown) with a thickness of, for example, 0.1 μm, and a second conductive type gallium phosphide (GaP) window layer 14 with a thickness of, for example, 4.0 μm are sequentially grown on the etching stop layer 3 as an epitaxial layer (epitaxial functional layer) 1 to prepare an epitaxial wafer 10 having a light-emitting element structure. Here, the portion from the first cladding layer 11 to the second cladding layer 13 is referred to as a double heterogeneous (DH) structure portion (light-emitting layer) 15. This series of steps is an example of the steps of growing an epitaxial layer 1 including a light-emitting layer 15 on a starting substrate 2, wherein the light-emitting layer 15 is (Al x Ga 1-x ) y In 1-y P is used as the active layer 12, wherein 0≦x<1, 0.4≦y≦0.6.

[0064] Then, benzocyclobutene (BCB) is spin-coated on the epitaxial wafer 10 as a thermosetting bonding member to form Figure 2 The bonding film (BCB bonding film) 4 is shown. Subsequently, the epitaxial wafer 10 and the bonding target wafer 5 (for example, a sapphire wafer) are overlapped and thermally pressed together via the bonding film 4. Figure 2 The epitaxially bonded substrate 20 shown is formed by bonding an epitaxial wafer 10 and a sapphire wafer 5 via a BCB bonding film 4. When BCB is applied by spin coating, the designed film thickness can be set to 0.6 μm, for example.

[0065] In the present embodiment, spin coating of BCB is exemplified, but the method of forming the BCB bonding film 4 is not limited to the spin coating method as long as the BCB can be uniformly formed on the epitaxial wafer 10. The BCB bonding film 4 may be formed by dipping or other methods.

[0066] In addition, in this embodiment, the case where BCB is applied in a layered state is exemplified, but the present invention is not limited to the layered state. The same result can be obtained by patterning photosensitive BCB into isolated islands, lines, or other shapes and performing a bonding step using the BCB bonding film thus formed.

[0067] In addition, in the present embodiment, the thickness of the BCB bonding film 4 is set to 0.6 μm, but this film thickness is only for illustration and is not limited to this film thickness. As long as the thickness is 0.1 μm or more, sufficient bonding can be obtained, so it is better. Regarding the thickness of the BCB bonding film 4, any film thickness can be selected, but after the light-emitting element is formed, before it is transferred to the mounting substrate, the formed BCB bonding film 4 will eventually need to be removed. Therefore, if the BCB bonding film 4 is too thick, the removability of the BCB will decrease. From the above point of view, it is more appropriate to make it less than 3 μm, but even if the film thickness is above this, the same effect can be obtained.

[0068] In addition, any conditions may be selected for the bonding conditions. For example, 1.2 N / cm 2 The temperature is set to be 200°C or higher and 400°C or lower.

[0069] In this embodiment, the wafer 5 to be bonded is exemplified as a sapphire wafer, but the wafer 5 to be bonded is not limited to a sapphire wafer, and any material may be selected as long as laser transmittance and flatness are ensured. Quartz or glass may be used instead of sapphire.

[0070] Then, the GaAs starting substrate 2 is removed by wet etching to expose the first etching stop layer, and then the etchant is switched to remove the first etching stop layer and the second etching stop layer, respectively, to expose the first cladding layer 11. Figure 3As shown, an epitaxial bonding substrate 30 is produced in which the bonded wafer 5 holds (supports) only the light emitting layer 15 and the window layer 14 via the BCB bonding film 4. The epitaxial bonding substrate 30 may be a substrate including the epitaxial layer 1.

[0071] Subsequently, a mask pattern is formed on the epitaxial layer 1 by, for example, optical lithography, and element separation processing is performed by inductively coupled plasma (ICP) dry etching. In short, a step of forming element separation grooves on the light emitting layer 15 by ICP dry etching using inductively coupled plasma is performed.

[0072] The size of the formed element is arbitrary, but for example, the present invention is more effective for a micro LED having a side of 100 μm or less (eg, 1 μm or more and 100 μm or less). The reaction gas used for ICP dry etching can be, for example, a gas composed of chlorine (Cl2) and argon (Ar), or Cl2 gas.

[0073] In the present embodiment, the ICP dry etching process is performed twice: a step of exposing a portion of the surface of the BCB bonding film 4 and a step of exposing a portion of the surface of the GaP window layer 14 .

[0074] The reaction gas conditions during ICP dry etching processing are, for example, suitable processing conditions where Cl2 is set to 30 to 50 sccm, Ar is set to 0 to 20 sccm, and the amount of Cl2 gas is normally greater than the amount of Ar gas.

[0075] The pressure in the etching chamber where ICP dry etching is performed can be set to 0.7 Pa, for example.

[0076] In the present invention, when forming the separation groove by ICP dry etching, the temperature of the substrate (epitaxial bonding substrate) 30 including the epitaxial layer 1 is set to 40° C. or less. When forming the separation groove by ICP dry etching, the temperature of the substrate (epitaxial bonding substrate) 30 including the epitaxial layer 1 is set to 35° C. or less.

[0077] Under the conventional substrate processing temperature condition (200°C), if the temperature of the processed surface rises, damage is likely to occur. The reason is that under a reduced pressure environment, the detachment of P starts at 250-300°C, and defects are formed on the processed surface due to the detachment of P. Even if protective agents such as boron trichloride (BCl3) and silicon tetrachloride (SiCl4) are introduced to prevent the detachment of P, it is difficult to completely prevent the detachment of P on the processed surface. According to the present invention, by setting the substrate temperature to below 40°C, even if the temperature of the processed surface rises, the detachment temperature of P is not easily reached. As a result, defects are not easily generated on the processed surface. As a result, it is possible to prevent the brightness of the light-emitting element manufactured by the method for manufacturing a light-emitting element of the present invention from decreasing. As a result, the brightness of the manufactured light-emitting element is improved. The lower limit of the temperature of the substrate including the epitaxial layer during the processing of forming the separation groove by the ICP dry etching method is not particularly limited, but can be set to 30°C, for example.

[0078] The specific process of setting the temperature of the substrate (epitaxial bonding substrate) 30 including the epitaxial layer 1 to 40° C. or less when forming the separation groove by the ICP dry etching method is not particularly limited, but an example is referred to as Figure 4 The specific explanation is as follows.

[0079] Figure 4 The dry etching apparatus 100 shown in the figure includes an ICP chamber 101 surrounded by a quartz wall 102. A coil 103 is wound around the outer periphery of the quartz wall 102.

[0080] A wafer fixing table and electrode 104 is disposed in the ICP chamber 101. The wafer fixing table and electrode 104 can fix the processing object, that is, the epitaxial bonding substrate 30. The fixing means is not particularly limited, but for example, two types of fixing methods can be selected, namely mechanical fixing (chuck method) and electrostatic fixing (electrostatic chuck). Figure 4 In the illustrated example, the wafer holding table / electrode 104 is configured to hold the epitaxial bonding substrate 30 by an electrostatic chuck method.

[0081] In addition, the dry etching apparatus 100 further includes a bias electrode 105, an antenna power supply 106, a reaction gas inlet 107, and a reaction gas outlet 108. Figure 4 In the dry etching apparatus 100 of the structure shown, plasma can be generated in the ICP chamber 101 while the reaction gas 200 is introduced into the ICP chamber 101 through the reaction gas inlet 107. The plasma can perform ICP dry etching of the epitaxial layer 1 along the mask pattern formed on the epitaxial layer 1.

[0082] In this example, during the ICP dry etching process, a constant temperature helium (He) gas 300 is sprayed from a fixed stage, that is, a wafer holding stage and electrode 104, toward the bottom of a substrate to be processed, that is, an epitaxial bonding substrate 30.

[0083] The thermostatic helium gas 300 is a temperature-controlled gas. More specifically, the thermostatic helium gas 300 is introduced from the thermostatic helium gas inlet 109 and passes through the temperature-controlled helium thermostatic cooler 110 to be temperature-controlled at, for example, about 35°C.

[0084] The temperature-controlled constant-temperature helium gas 300 is injected from the wafer holding stage / electrode 104 toward the bottom of the substrate to be processed, that is, the epitaxial bonding substrate 30 , and flows along the flow direction 301 of the constant-temperature helium gas.

[0085] By adjusting the amount of the thermostatic helium gas 300 sprayed on the bottom of the epitaxial bonding substrate 30 , the temperature of the back surface of the workpiece, that is, the bottom of the epitaxial bonding substrate 30 can be adjusted to about 35° C. The back surface temperature can be confirmed by monitoring the temperature of the wafer mounting table and electrode 104 .

[0086] The entire workpiece is cooled by heat conduction. The thermal resistance of the sapphire substrate 5 of the epitaxial bonding substrate 30 is not 0, so the temperature of the back side of the workpiece is not strictly consistent with the temperature of the surface. In addition, the part of the surface of the epitaxial bonding substrate 30 that is subjected to plasma becomes locally high temperature. However, the heat of the surface of the epitaxial bonding substrate 30 is transferred to the back side by heat conduction, and as a result, it is cooled, so the surface of the epitaxial bonding substrate 30 can be fixed and maintained below 40°C on average. The temperature difference between the back side and the surface can be about 2 to 3°C.

[0087] By adjusting the temperature and flow rate of the thermostatic helium gas 300 to be sprayed, the temperature of the substrate (epitaxial bonding substrate) 30 including the epitaxial layer 1 during the process of forming the separation grooves by the ICP dry etching method can be adjusted.

[0088] In ICP dry etching, it is expected that the peak voltage V pp Set it to 800V or more, more preferably 1,000V or more. pp By setting the peak voltage V to 800 V or higher, a high etching rate can be achieved and the etching time can be shortened. pp However, in the method for manufacturing a light-emitting element of the present invention, when processing is performed by ICP dry etching, the temperature of the substrate 30 including the epitaxial layer 1 is set to 40°C or less, thereby suppressing the generation of defects on the processed surface as described above. In the ICP dry etching process, the peak-to-peak voltage V pp For example, it can be set to 1,400 V or less.

[0089] In addition, the amount of the reaction gas 200 will increase or decrease according to the size of the ICP chamber 101 and the processing area of ​​the epitaxial bonding substrate 30, and is therefore not limited to the aforementioned flow rate range. What is important is the flow rate ratio rather than the absolute value of the flow rate. The Cl2 flow rate is normally greater than the Ar flow rate, which is an appropriate condition from the perspective of the ICP dry etching rate.

[0090] In addition, the reaction gas 200 used in the ICP dry etching method can be set to be only a gas composed of Cl2 and Ar or only Cl2 gas, without introducing SiCl4 or BCl3 and other processing side protection gases, and processed in an atmosphere with more normality of reactive gas, that is, Cl2. Ar gas is introduced to stabilize the plasma, so if the plasma ignites and the state of the processing work is stabilized, even if the introduction (Ar = 0 sccm) is stopped and processed, it can be processed without any problems. As for Ar, its plasma is easy to stabilize and is a suitable gas type compared to other sputtering gases.

[0091] By setting the Ar gas flow rate of the reaction gas 200 to be greater than 0 sccm and less than 1 / 3 of the Cl 2 gas flow rate, the ICP dry etching rate can be reliably shortened.

[0092] In addition, although 0.7Pa is illustrated as an example of atmosphere, any condition can be selected as long as plasma can be stably generated. However, if the pressure is increased, the stability of Cl2 plasma will decrease, so too high a pressure is not good. In addition, if it is too low, the reactive species will decrease and the processing speed will decrease, so too low a pressure is not good. It is more appropriate to process in the range of 0.05 to 5Pa and preferably in the range of 0.1 to 2Pa.

[0093] Processing performed by ICP dry etching, such as Figure 5 As shown, the light emitting element 7 separated from other elements by the separation groove 6 can be obtained. Figure 5 The light emitting element 7 shown includes a GaP window layer 14 with a portion of the surface exposed and a DH structure 15 located thereon. The light emitting element 7 is bonded to a bonding target wafer 5 via a BCB bonding film 4 .

[0094] In this embodiment, a case where a part of the surface of the GaP window layer 14 is exposed is exemplified, but the present invention is not limited to the case where the GaP window layer 14 is exposed, and at least the active layer 12 may be separated from other elements. For example, even if a part of the surface of the second cladding layer 13 is exposed instead of a part of the surface of the GaP window layer 14, the same effect can be obtained.

[0095] Then, if Figure 5 As shown, after the components are separated and processed, Figure 6 As shown in FIG. 1 , as an end surface treatment, a protective film 8 is formed on the surface of the light emitting element 7. The material of the protective film 8 can be, for example, silicon dioxide (SiO2), but is not limited to SiO2. Any material can be selected as long as it can protect the end surface of the light emitting element 7 and has insulating properties. Silicon nitride (SiN x ) and titanium oxide, magnesium oxide, etc. In the protective film 8, openings 8A and 8B are provided in order to form the electrodes described in the following paragraphs.

[0096] Then, if Figure 6 After forming the protective film 8 as shown, Figure 7 As shown, electrodes are formed in contact with the first conductive type layer and the second conductive type layer, and heat treatment is performed to form ohmic contacts. For example, the first conductive type can be set to n-type, the second conductive type can be set to p-type, and the n-type layer (in Figure 7 The material of the electrode 9A connected to the first cladding layer 11 is made of a metal containing gold (Au) and silicon (Si). Figure 7 The material of the electrode 9B connected to the window layer 14 in the middle is a metal containing Au and beryllium (Be). In addition, the material of the n-type electrode is not limited to Au and Si, and the same result can be obtained even if a metal containing Au and germanium (Ge) is used. In addition, the material of the p-type electrode is not limited to Au and Be, and the same result can be obtained even if a metal containing Au and zinc (Zn) is used.

[0097] According to an example of the method for manufacturing a light-emitting element of the present invention described above, a light-emitting element 7 can be obtained, which is bonded to a bonded wafer 5 via a BCB bonding film 4 and provided with electrodes 9A and 9B. The manufactured light-emitting element 7 suppresses the occurrence of defects caused by the ICP dry etching process for forming a separation groove for separating the element, and thus even when the element size is small and, for example, when one side of the element is 100 μm or less, it is possible to suppress the decrease in brightness and show high luminous efficiency.

[0098] The above shows an example of processing the separation groove 6 by the ICP dry etching method on the epitaxial bonding substrate 30, but in the manufacturing method of the light-emitting element of the present invention, the substrate to be processed by the ICP dry etching method can be any substrate as long as it includes the epitaxial layer 1, and is not limited to the epitaxial bonding substrate 30.

[0099] [Example]

[0100] Hereinafter, the present invention will be specifically described using Examples and Comparative Examples, but the present invention is not limited thereto.

[0101] (Example 1)

[0102] In Example 1, by referring to Figures 1 to 7 Here, a light emitting element is manufactured by describing an example of a method for manufacturing a light emitting element of the present invention. Specific conditions and the like are as follows.

[0103] exist Figure 1 After a first conductivity type GaAs buffer layer (not shown) is stacked on the first conductivity type GaAs starting substrate 2 shown in the figure, a first conductivity type GaInP first etching stop layer with a thickness of 0.1 μm and a first conductivity type GaAs second etching stop layer with a thickness of 0.1 μm are grown to form an etching stop layer 3. Subsequently, as shown in FIG. Figure 1 As shown, a first conductive type AlGaInP first cladding layer 11 with a thickness of 1.0 μm, a non-doped AlGaInP active layer 12 with a thickness of 0.3 μm, a second conductive type AlGaInP second cladding layer 13 with a thickness of 1.0 μm, a second conductive type GaInP intermediate layer (not shown) with a thickness of 0.1 μm, and a second conductive type GaP window layer 14 with a thickness of 4.0 μm are sequentially grown on the etching stop layer 3 to produce an epitaxial wafer 10, which has a light-emitting element structure as an epitaxial layer (epitaxial functional layer) 1.

[0104] Subsequently, benzocyclobutene (BCB) is spin-coated on the epitaxial wafer 10 as a thermosetting bonding member to form Figure 2 The bonding film 4 is shown. Subsequently, the epitaxial wafer 10 and the sapphire wafer 5 to be bonded are placed opposite each other via the bonding film 4 and heated at 2 N / cm 2 The bonding is performed under the conditions of 250°C. Figure 2 As shown, an epitaxial bonding substrate 20 is prepared in which an epitaxial wafer 10 and a sapphire wafer 5 are bonded via a bonding film 4. When BCB is applied by spin coating, the designed film thickness is set to 0.6 μm.

[0105] Subsequently, the GaAs starting substrate 2 is removed by wet etching to expose the first etching stop layer, and then the etchant is switched to remove the first etching stop layer and the second etching stop layer respectively. Figure 3 The first coating layer 11 is exposed as shown. Figure 3 The epitaxially bonded substrate 30 is shown.

[0106] Subsequently, a mask pattern of 50 μm on one side was formed on the epitaxial layer 1 by photolithography, and the epitaxial bonded substrate 30 including the epitaxial layer 1 was subjected to device separation processing by ICP dry etching.

[0107] In ICP dry etching, use reference Figure 4The dry etching apparatus 100 described above uses chlorine (Cl2) and argon (Ar) as reaction gases. The ICP dry etching process is performed twice: a step of exposing a portion of the surface of the BCB bonding film 4 and a step of exposing a portion of the surface of the GaP window layer 14, thereby forming Figure 5 The light emitting elements 7 are shown separated by separation trenches 6 .

[0108] The Cl2 flow rate was set to 30 sccm, the Ar flow rate was set to 10 sccm, and the pressure was set to 0.7 Pa. During ICP dry etching, the temperature of the epitaxial bonding substrate 30 was kept constant at 30°C by spraying the thermostatic helium gas 300 adjusted to 25°C at a flow rate of 20 to 30 sccm to the bottom of the epitaxial bonding substrate 30.

[0109] In addition, the peak voltage V pp The antenna power and the bias power were adjusted so as to be within the range of 1,000 to 1,200 V, and the ICP dry etching process was performed.

[0110] Then, after the components are separated and processed, Figure 6 As shown, a protective film 8 composed of SiO2 is formed on the surface of the light emitting element 7 as an end surface treatment.

[0111] After forming the protective film 8, as Figure 7 As shown, ohmic contacts are formed by forming electrodes 9A and 9B connected to the first conductivity type layer and the second conductivity type layer, respectively, and performing heat treatment.

[0112] Specifically, the first conductivity type is designed to be n-type, and the second conductivity type is designed to be p-type. A metal containing Au and Si is used for the electrode 9A connecting the n-type layer, i.e., the first cladding layer 11, and a metal containing Au and Be is used for the electrode connecting the p-type layer, i.e., the window layer 14.

[0113] Through the above process, such as Figure 7 As shown, a light emitting element 7 is manufactured, which is bonded to a bonded wafer 5 via a BCB bonding film 4 and provided with electrodes 9A and 9B.

[0114] (Comparative Example 1)

[0115] In Comparative Example 1, the conditions for ICP dry etching are as follows: the temperature of the epitaxial bonding substrate 30 is set to 200° C., the reaction gas used is a mixed gas of Cl2, SiCl4, and Ar, the flow rates are set to Cl2=2.5 sccm, SiCl4=1 sccm, and Ar=15 sccm, respectively, the pressure in the chamber is set to 0.7 Pa, and the peak-to-peak voltage V is set to 1.15 sccm. pp The light emitting element was manufactured in the same manner as in Example 1 except that the voltage was set to about 400 to 500 V.

[0116] [Results of Example 1 and Comparative Example 1]

[0117] Figure 8 The results are shown for comparing the light emitting device 7 with a 50 μm square grain manufactured in Example 1 with the light emitting device with the same size manufactured in Comparative Example 1 at a current density of 3.2 A / mm. 2 The result of the luminous efficiency when the current flows. Figure 8 It can be judged that the light emitting element 7 manufactured in Example 1 has a higher light emitting efficiency than the light emitting element manufactured in Comparative Example 1. From this result, it can be seen that Example 1, which is an example of the present invention, can suppress the brightness reduction more than Comparative Example 1.

[0118] (Example 2)

[0119] In Example 2, the peak-to-peak voltage V pp The voltage is set to be fixed at about 900 V, the flow rate of the reaction gas 200 is set to Cl2=30 sccm, Ar=10 sccm, and the temperature of the epitaxial bonding substrate 30 maintained fixed during ICP dry etching is changed within the range of above 20°C and below 40°C for ICP dry etching. Except for this, the light-emitting element 7 with 50 μm square grains is manufactured under the same conditions as in Example 1.

[0120] (Comparative Example 2)

[0121] In Comparative Example 2, the light emitting element 7 having 50 μm square grains was manufactured under the same conditions as in Example 2 except that the temperature of the epitaxial bonding substrate 30 maintained fixed during ICP dry etching was changed within a range of more than 40° C. and less than 200° C. to perform ICP dry etching.

[0122] In Example 2 and Comparative Example 2, the temperature of the thermostatic helium gas 300 is adjusted and the flow rate of the thermostatic helium gas 300 is controlled to change the temperature of the epitaxial bonding substrate 30 maintained constant during the ICP dry etching.

[0123] [Results of Example 2 and Comparative Example 2]

[0124] Fig. 9 The results show that the light emitting elements 7 manufactured in Example 2 and the light emitting elements manufactured in Comparative Example 2 have a current density of 3.2 A / mm. 2 The result of luminous efficiency when Fig. 9As shown, in Comparative Example 2 in which the temperature of the epitaxial bonding substrate 30 during the ICP etching process is set to be higher than 40°C and lower than 200°C, the external quantum efficiency (luminous efficiency) tends to increase as the temperature of the epitaxial bonding substrate 30 during the ICP etching process is reduced, but the efficiency is at a very low level up to about 110°C, and the efficiency is also low at 50°C. On the other hand, if the temperature of the epitaxial bonding substrate 30 during the ICP etching process is set to 40°C, a significant tendency to improve the luminous efficiency is confirmed, and in Example 2 in which the temperature of the epitaxial bonding substrate 30 during the ICP etching process is set to be lower than 40°C, a generally good tendency is shown.

[0125] That is, in Example 2 in which the temperature of the epitaxial bonding substrate 30 during the ICP etching process was set to 40° C. or less, the luminance reduction was more suppressed than in Comparative Example 2.

[0126] Furthermore, the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same configuration and exerting the same effects as the technical concept described in the claims of the present invention are included in the technical scope of the present invention.

Claims

1. A method for manufacturing a light emitting element, characterized in that: have: At least a step of growing an epitaxial layer including a light emitting layer on a starting substrate, the light emitting layer (Al x Ga 1-x ) y In 1-y P is used as an active layer, where 0≦x<1, 0.4≦y≦0.6; and forming a separation groove for forming an element on the light emitting layer by an ICP dry etching method using inductively coupled plasma; During the process of forming the separation grooves by the ICP dry etching method, the temperature of the substrate including the epitaxial layer is set to 40° C. or less.

2. The method for manufacturing a light emitting element according to claim 1, wherein: One side of the element to be formed by the ICP dry etching method is 100 μm or less.

3. The method for manufacturing a light-emitting element according to claim 1 or 2, wherein: The reaction gas used in the ICP dry etching method is a gas composed of Cl2 and Ar, or Cl2 gas; When the Cl2 gas flow rate is greater than the Ar gas flow rate and the peak-to-peak voltage V pp Under the condition of 800 V or more, a separation groove is formed.

4. The method for manufacturing a light emitting element according to claim 3, wherein: The gas flow rate of the Ar in the reaction gas is greater than or equal to 0 sccm and less than or equal to 1 / 3 of the gas flow rate of the Cl 2 .

Images