JP2020077710A - Manufacturing method of semiconductor substrate for light emitting element and manufacturing method of light emitting element - Google Patents

Abstract

To provide a manufacturing method of a semiconductor substrate for a light emitting element, which enables reuse of a starting substrate by lifting off the starting substrate from an epitaxial functional layer by selectively etching only a selective etching layer and achieving cost reduction.SOLUTION: A manufacturing method of a semiconductor substrate for a light emitting element includes a step S11 of forming a selective etching layer on a starting substrate, a step S12 of forming a light emitting portion by sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer by epitaxial growth, a step S14 of joining a support substrate and the starting substrate to form a joined substrate, and a step S15 of removing the starting substrate from the jointed substrate by removing the selective etching layer by etching, and the support substrate having a warp with a convex bonding surface side is prepared, and the selective etching layer is gradually etched inward from the outer periphery of the joined substrate by using the warp of the support substrate to separate the starting substrate from the joined substrate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a semiconductor substrate for a light emitting device and a method for manufacturing a light emitting device.

  When an active device or a passive device is produced by forming a functional layer (LED or electronic device) on a starting substrate such as GaAs and joining it to a supporting substrate, the starting substrate constituting the joined substrate after joining is Generally, a method of completely dissolving the starting substrate by a wet etching method is used. In this case, when the starting substrate is removed, a method is adopted in which an etching stop layer is provided between the functional substrate (active device portion or passive device portion) and the starting substrate is removed by stepwise selective etching. The etching stop layer may have a thickness of 1 μm or less, and the formation cost is low compared to the total epitaxial cost.

  Since the etching stop layer has etching selectivity, the most efficient method is to lift off the starting substrate by etching only the etching stop layer. If wafer lift-off is realized with the same structure and thickness, cost can be reduced in forming a functional layer using a bonding process. However, in reality, the wafer lift-off method is not adopted for industrial use.

  Patent Document 1 discloses a wafer lift-off method of etching only a selective etching layer. As disclosed in Patent Document 1, in the disclosed technique, the oxide generated in the selective etching layer hinders etching.

Japanese Patent Publication No. 2014-523848

  When an etching stop layer having a thickness of 1 μm or less, which is currently used industrially, is adopted, the etching is stopped due to the influence of the oxide generated by the etching. In the selective etching layer having a thickness of 1 μm or less, the oxide generated in the etched space cannot be removed by physical force such as convection due to ultrasonic waves and temperature. Therefore, the etching of the selective etching layer is hindered, the etching is stopped eventually, and the wafer lift-off is not realized. In order to remove the generated oxide from the space to be etched, the selective etching layer may have a thickness of more than 1 μm. However, the selective etching layer having a thickness of more than 1 μm has the same thickness as the functional layer (active functional layer / passive functional layer) depending on the device. The cost of forming the epitaxial layer is high, and increasing the thickness of the selective etching layer offsets the cost reduction effect of preserving and reusing the starting substrate, or rather increases the cost. This is the reason why wafer lift-off is not adopted in industry.

  The present invention has been made in view of the above problems, and the starting substrate can be reused by lowering the cost by lifting off the starting substrate from the epitaxial functional layer by selectively etching only the selective etching layer. It is an object of the present invention to provide a method for manufacturing a semiconductor substrate for a light emitting device that can achieve the above, and a method for manufacturing a light emitting device from such a semiconductor substrate for a light emitting device.

  In order to achieve the above object, the present invention provides at least a first semiconductor layer, an active layer and a second layer by using a step of forming a selective etching layer on a starting substrate and a material of a lattice matching system that lattice matches the starting substrate. A semiconductor substrate is sequentially formed by epitaxial growth above the selective etching layer to form a light emitting portion including at least the first semiconductor layer, the active layer, and the second semiconductor layer, and a supporting substrate is prepared. A step of joining the supporting substrate and the starting substrate having the light emitting portion to form a joining substrate; and removing the selective etching layer of the joining substrate by etching, thereby removing the starting material from the joining substrate. A light emitting device having at least a step of removing a substrate, a step of forming a first ohmic electrode on the surface of the first semiconductor layer, and a step of forming a second ohmic electrode electrically connected to the second semiconductor layer. In the method for manufacturing a semiconductor substrate for use, in the step of preparing the supporting substrate, a supporting substrate having a warp in which a bonding surface side, which is a surface on the side to be bonded to the starting substrate having the light emitting portion, has a convex shape is prepared. In the step of removing the starting substrate, the starting substrate is separated from the bonding substrate by gradually etching the selective etching layer inward from the outer peripheral portion of the bonding substrate using the warpage of the supporting substrate. The present invention provides a method for manufacturing a semiconductor substrate for a light emitting device, characterized in that

  In this way, after forming a warp on the supporting substrate and joining it to the starting substrate (epitaxial substrate) having the light emitting portion, the selective etching layer is etched by using the warping to separate the starting substrate with almost no etching. it can. As a result, the starting substrate can be reused and the cost can be reduced.

  At this time, it is preferable that the warp of the support substrate is formed by performing mechanical processing on the bonding surface of the support substrate with a grindstone roughness of # 2000 or less to form damage on the surface of the bonding surface.

  By forming damage on the surface of the supporting substrate by such mechanical processing, the warp can be formed relatively easily.

  Further, it is preferable that the thickness of the supporting substrate is 150 μm or less.

  By setting the thickness of the supporting substrate to 150 μm or less, the supporting substrate can be more easily warped.

  Further, the present invention has a step of, after manufacturing the semiconductor substrate for a light emitting element by any one of the methods for manufacturing a semiconductor substrate for a light emitting element, separating the light emitting element from the semiconductor substrate for a light emitting element into a die shape. A method of manufacturing a light emitting device is provided.

  With such a method for manufacturing a light emitting device, the starting substrate can be reused when manufacturing the semiconductor substrate for a light emitting device, and the manufacturing cost of the light emitting device can be reduced.

  In the method for manufacturing a semiconductor substrate for a light emitting device of the present invention, a warp is formed on a supporting substrate, the substrate is bonded to a starting substrate (epitaxial substrate) having a light emitting portion, and then the selective etching layer is etched using the warp. The starting substrate can be separated with almost no etching. As a result, the starting substrate can be reused and the cost can be reduced. Further, since it is not necessary to thicken the selective etching layer, the cost can be reduced also in this respect. In particular, the thickness of the selective etching layer can be set to 1 μm or less.

6 is a flowchart showing a method for manufacturing a semiconductor substrate for a light emitting device of the present invention. It is a schematic sectional drawing which shows the support substrate which has a curvature as one step in the progress of 1st embodiment of this invention. It is a schematic sectional drawing which shows the starting substrate which formed the selective etching layer and the light emission part as one step in the progress of 1st embodiment of this invention. It is a schematic sectional drawing which shows the starting substrate which formed the ohmic electrode layer, the dielectric material layer, and the 2nd metal layer on the light emission part as one step in the progress of 1st embodiment of this invention. It is a schematic sectional drawing which shows the state before joining of a starting substrate and a support substrate as one step in the progress of 1st embodiment of this invention. It is a schematic sectional drawing which shows the joining board | substrate which joined the starting board | substrate and the support substrate as one step in the progress of 1st embodiment of this invention. It is a schematic sectional drawing which shows the isolation | separation process of a starting board | substrate as one step in the progress of 1st embodiment of this invention. It is a schematic sectional drawing which shows the semiconductor substrate for light emitting elements after isolation | separation as one step in the progress of 1st embodiment of this invention. It is a schematic sectional drawing which shows the support substrate which has a curvature as one step in the progress of 2nd embodiment of this invention. It is a schematic sectional drawing which shows the starting substrate which formed the selective etching layer and the light emitting part as one step in the progress of 2nd embodiment of this invention. FIG. 6 is a schematic cross-sectional view showing a starting substrate on which a second dielectric layer and an adhesive layer are formed on a light emitting portion as one step in the progress of the second embodiment of the present invention. It is a schematic sectional drawing which shows the state before joining of a starting substrate and a support substrate as one step in the progress of 2nd embodiment of this invention. It is a schematic sectional drawing which shows the joining board | substrate which joined the starting board | substrate and the support substrate as one step in the progress of 2nd embodiment of this invention. It is a schematic sectional drawing which shows the isolation | separation process of a starting substrate as one step in the progress of 2nd embodiment of this invention. It is a schematic sectional drawing which shows the semiconductor substrate for light emitting elements after isolation | separation as one step in the progress of 2nd embodiment of this invention. It is a graph which shows the number of the grindstone roughness at the time of carrying out the surface grinding of the silicon wafer of wafer thickness 150 micrometers, and the relationship of the lift-off possible area. It is a graph which shows the relationship between the wafer thickness and the lift-off possible area when the surface of a silicon wafer is surface-ground with a grindstone roughness # 2000.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments, but the present invention is not limited thereto.

  A method for manufacturing a semiconductor substrate for a light emitting device according to the present invention will be described with reference to FIG.

  First, as shown in S11 of FIG. 1, a selective etching layer is formed on a starting substrate (step S11). In this case, in the present invention, the thickness of the selective etching layer can be 1 μm or less.

  Next, as shown in S12 of FIG. 1, a light emitting layer is formed on the starting substrate on which the selective etching layer is formed. At this time, at least the first semiconductor layer, the active layer, and the second semiconductor layer are sequentially formed by epitaxial growth using a lattice-matching material that is lattice-matched with the starting substrate above the selective etching layer. Thus, the light emitting unit including at least the first semiconductor layer, the active layer and the second semiconductor layer is formed (step S12).

  In addition to the steps S11 and S12 for the starting substrate, a supporting substrate is prepared as shown in S13 of FIG. 1 (step S13). The supporting substrate prepared in this step S13 is a supporting substrate having a warp having a convex shape. Further, this support substrate has a convex surface on the side to be joined to the starting substrate having a light emitting portion to be joined to the support substrate in S14 described later.

  Either step S11 or step S12, which is a step for the starting substrate, or step S13 for preparing the supporting substrate may be performed first, or may be performed simultaneously.

  After the steps S12 and S13 are completed, as shown in S14 of FIG. 1, the supporting substrate and the starting substrate having the light emitting portion are bonded to form a bonded substrate (step S14). At this time, as described above, the light emitting portion side (that is, the second semiconductor layer side) of the starting substrate is bonded using the side having the convex warp of the supporting substrate as the bonding surface. This joining step can be performed, for example, after forming a joining layer on one substrate or both substrates.

  Next, as shown in S15 of FIG. 1, the starting substrate is removed from the bonded substrate by removing the selective etching layer of the bonded substrate by etching (step S15). Regarding the step S15 of removing the starting substrate, in the present invention, the selective etching layer is gradually etched inward from the outer peripheral portion of the bonding substrate by utilizing the warp of the supporting substrate. As a result, the starting substrate is separated from the bonded substrate.

  Next, as shown in S16 of FIG. 1, a first ohmic electrode is formed on the surface of the first semiconductor layer (step S16). Further, as shown in S17 of FIG. 1, a second ohmic electrode electrically connected to the second semiconductor layer is formed (step S17). Either step S16 or step S17 may be performed first. Further, the ohmic electrode can be formed on the starting substrate before the etching of the selective etching layer (step S15).

  The semiconductor substrate for a light emitting device can be manufactured as described above. In addition, after the semiconductor substrate for a light emitting element is manufactured in this manner, the light emitting element can be manufactured by a step of separating the light emitting element from the semiconductor substrate for a light emitting element into a die shape.

  Hereinafter, the method for manufacturing a semiconductor substrate for a light emitting device of the present invention will be described with reference to more specific examples (first embodiment and second embodiment).

(First embodiment)
The first embodiment of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 2, a support substrate 101 made of, for example, a silicon substrate is prepared. This step corresponds to step S13 in FIG. As shown in FIG. 2, the support substrate 101 is a support substrate having a convex warp. The convex surface (upper surface in FIG. 2) of the supporting substrate 101 becomes a surface (bonding surface 101a) on the side that is bonded to the starting substrate (having a light emitting portion and the like). Note that, in FIG. 2, a state in which a first metal layer 104 (first contact layer 102 and first bonding layer 103) used for bonding in the bonding step shown in S14 of FIG. 1 is formed on the support substrate 101. The (bonding support substrate 105) is shown.

  The warped shape of the support substrate 101 (the convex surface of the bonding surface 101a) can be formed by machining the bonding surface 101a of the supporting substrate 101 and forming damage on the surface of the bonding surface 101a. it can. For example, it is possible to form the warp of the support substrate 101 by performing surface grinding with a grindstone roughness of a surface grinder of # 3000 or less to leave processing damage. Further, the thickness of the support substrate 101 after the surface grinding can be set to, for example, 200 μm or less. At this time, the roughness of the grindstone for surface grinding is preferably # 2000 or less. It is sufficient if the grindstone roughness is # 200 or more. Further, the thickness of the support substrate 101 after the surface grinding is more preferably 150 μm or less. In addition, the thickness of the support substrate 101 after the surface grinding is more preferably 70 μm or more for reasons of substrate strength and easiness of handling.

  Here, FIG. 16 shows the relationship between the number of grindstone roughness when a 150 μm-thick silicon wafer is surface-ground and the lift-off possible area when the ground silicon wafer is used as a support substrate. The relationship is that the thickness after processing is constant, the roughness of the processing grindstone is changed to process the silicon wafer, and after bonding to the starting substrate having the light emitting portion, the selective etching layer is selectively etched to obtain the starting substrate. It was obtained from the experiment of investigating the lifted-off area ratio when trying to lift off. Here, 100% of the lift-off possible area in the figure means that the selective etching layer was completely etched, and the starting substrate and the light emitting part were separated, and the data of less than 100% means that the selective etching layer was partially etched. This means that the starting substrate and the light emitting unit were not completely separated. From the results of FIG. 16, it can be seen that as the count of the abrasive grains used for surface grinding becomes finer (as the number increases), the warp decreases, so that the lift-off possible area decreases. As can be seen from this figure, it is more preferable to carry out the surface grinding with the grindstone roughness of the surface grinder being # 2000 or less.

  FIG. 17 shows the relationship between the wafer thickness when the surface of a silicon wafer is surface-ground with an abrasive grain roughness of # 2000 and the lift-off possible area when the ground silicon wafer is used as a support substrate. This is also an experiment similar to that shown in FIG. 16 but performed with various wafer thicknesses. As the wafer thickness decreases, the warp increases, so that the lift-off possible area increases.

  As described above, by the surface grinding, a convex warp is generated on the bonding surface 101a side of the support substrate 101. Wafer warpage after grinding becomes more likely to occur as the thickness decreases, but it is preferable that the wafer has a predetermined thickness in order to prevent wafer damage during bonding. Therefore, it is preferable to control the thickness of the support substrate 101 after the surface grinding to a thickness in the range of 70 to 200 μm (particularly 150 μm or less).

  When the processed surface of the support substrate 101 needs to be a mirror surface, processing such as polishing can be applied to the surface. By performing polishing to such an extent that the warp is not lost, it is possible to perform mirror finishing while maintaining the warp of the support substrate 101. For example, when the warp generation processing is performed on the support substrate 101 by surface grinding with an abrasive grain roughness of # 2000, if the polish thickness is less than 0.2 μm, the surface should be mirror-finished while maintaining the warp. Is possible.

  After forming the warp in the support substrate 101, as shown in FIG. 2, the first metal layer 104 can be formed on the bonding surface 101a. The material and thickness of the first metal layer 104 are not particularly limited. The first metal layer 104 can have a laminated structure made of, for example, Ti / Au. In this case, the Ti thickness of the first contact layer 102 can be set to 100 nm, for example. The Au thickness of the first bonding layer 103 can be set to, for example, 500 nm. The first bonding layer 103 may be replaced by a metal containing Ag, In, Ga, and a high melting point such as Pt, Mo, W, Pd, or Ir may be formed between the first contact layer 102 and the first bonding layer 103. You may use the laminated structure which steps on a metal.

  Next, as shown in FIG. 3, an epitaxial substrate 120 in which a light emitting portion (functional layer) 119 is laminated on a starting substrate 111 is prepared. A selective etching layer 112 and a layer having an etching property different from that of the selective etching layer 112 are provided between the starting substrate 111 and the light emitting portion (functional layer) 119. 113 is inserted. These steps correspond to step S11 and step S12 in FIG.

  The starting substrate 111 may be GaAs, for example, and the light emitting portion (functional layer) 119 may have a light emitting diode structure. The light emitting diode structure may include a first semiconductor layer (n-type AlGaInP layer) 114, an active layer (AlGaInP active layer) 115, and a second semiconductor layer (p-type AlGaInP layer) 116 from the side of the starting substrate 111. The light emitting unit 119 may have layers other than these. Each of the first semiconductor layer (n-type AlGaInP layer) 114, the active layer (AlGaInP active layer) 115, and the second semiconductor layer (p-type AlGaInP layer) 116 has a thickness of about 0.5 to 2 μm. It is possible to have a laminated structure of a plurality of composition layers. The light emitting portion (functional layer) 119 can be manufactured by a metal organic chemical vapor deposition (MOVPE) method, a molecular beam epitaxy (MBE) method, an actinic ray epitaxy (CBE) method, or the like. Further, the selective etching layer 112 can be made of AlAs and the selective etching layer 113 can be made of GaAs, and the thickness of each can be set to 0.5 μm, for example. The material of the selective etching layer is not limited to these, and may be any combination as long as it is a material that is selective to the etching solution and can grow, for example, AlInP or AlGaAs or GaAs instead of AlAs. A material such as GaInP, ZnSe, or Ge may be selected.

  The light emitting portion (functional layer) 119 is not limited to a light emitting diode structure containing AlGaInP as a main component, and has a light emitting diode structure having an AlGaAs system or a strained InGaAs system as an active layer, which uses the starting substrate 111 as GaAs. be able to.

  Further, the starting substrate 111 is not limited to GaAs, and materials such as InP and Si can be similarly applied, and the material of each epitaxial layer can also be applied as long as it can be epitaxially grown on the starting substrate 111. is there.

  Next, as shown in FIG. 4, the ohmic electrode layer 131 can be formed on a part of the surface of the epitaxial substrate 120. Further, the dielectric layer 132 can be formed on a part of the region other than the region where the ohmic electrode layer 131 is formed on the surface of the epitaxial substrate. It is preferable that the ohmic electrode layer 131 and the dielectric layer 132 have substantially the same thickness, but a thickness difference of about 50% can be allowed. The ohmic electrode layer 131 serves as a second ohmic electrode electrically connected to the second semiconductor layer 116. That is, this step corresponds to step S17 in FIG.

  Next, a second metal layer 137 that covers at least a part of both the ohmic electrode layer 131 and the dielectric layer 132 can be formed on the surface of the epitaxial substrate 120. Thereby, the epitaxial substrate for bonding 140 can be obtained. The second metal layer 137 has a laminated structure made of, for example, Ti / Au, and can have a Ti thickness of 100 nm and an Au thickness of 500 nm, for example. FIG. 4 shows an example in which the second metal layer 137 includes the second contact layer (for example, Ti layer) 135 and the second bonding layer (for example, Au layer) 136. The second metal layer 137 may be made of Au, or a relatively soft metal such as Ag, In, or Ga, or a metal alloy.

Next, as shown in FIG. 5, the bonding epitaxial substrate 140 and the bonding support substrate 105 are opposed to each other so that at least a part of the first metal layer 104 and the second metal layer 137 are in contact with each other, and heat and pressure are applied. To join. This step corresponds to step S14 in FIG. The temperature at the time of joining can be, for example, 300 ° C. and the pressure can be 10 N / cm ² . The joining temperature and pressure are not limited to these conditions, and any temperature and pressure can be selected as long as the joining can be realized.

  Next, as shown in FIG. 6, by joining the first metal layer 104 and the second metal layer 137, the joining substrate 150 in which the joining supporting substrate 105 and the joining epitaxial substrate 140 are joined is obtained. At this time, it is preferable that the support substrate 101 is relatively thinner than the starting substrate 111. In that case, the warp on the support substrate 101 side is reduced, and the bonding substrate 150 is substantially the same as the warp of the epitaxial substrate 120. Can be.

  Next, as shown in FIG. 7, the selective etching layers 112 and 113 are etched. The selective etching layers 112 and 113 can be etched using a hydrofluoric acid-containing liquid. The selective etching layers 112 and 113 are etched and removed from the outer peripheral portion of the wafer of the bonding substrate 150. This step corresponds to step S15 in FIG.

  By etching the selective etching layers 112 and 113, the light emitting portion (functional layer) 119 and the starting substrate 111 are physically separated. The support substrate 101 has a curvature with a substantially constant curvature due to processing damage on the surface, and even if a part of the support substrate 101 is separated from the starting substrate 111, the separation region is wider than the selective etching layers 112 and 113 and the starting substrate 111. And separate. In the process of removing the selective etching layers 112 and 113, an oxide of the material to be etched is formed and etching inhibition starts. However, due to the distance from the supporting substrate 101, the width of the selective etching layers 112 and 113 (for example, 1 μm or less) or more. Since the width is formed, the oxide is removed by the invasion of the etching solution, and the etching inhibition does not stop the etching of the selective etching layers 112 and 113.

  As a result, the starting substrate 111 and the light emitting portion (functional layer) 119 are separated by removing the selective etching layers 112 and 113, and the starting substrate 111 can be lifted off from the light emitting portion (functional layer) 119.

  Next, as shown in FIG. 8, after lift-off of the starting substrate 111, an electrode (first ohmic electrode 163) is formed on the lift-off surface. This step corresponds to step S16 in FIG. Further, an electrode connected to the ohmic electrode layer 131 (second ohmic electrode) can be formed on the back surface side of the support substrate 101 to realize a light emitting device structure. Further, the protective film 165 can be formed as appropriate. In this way, the semiconductor substrate 160 for a light emitting device can be manufactured. After the semiconductor substrate 160 for a light emitting element is manufactured, the light emitting element can be separated from the semiconductor substrate for a light emitting element in a die shape to manufacture the light emitting element.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 9, a support substrate 201 made of, for example, sapphire is prepared. This step corresponds to step S13 in FIG. As shown in FIG. 9, the support substrate 201 is a support substrate having a convex warp. The convex surface (the upper surface in FIG. 9) of the supporting substrate 201 is the surface (bonding surface 201a) on the side to be bonded to the starting substrate (having the light emitting portion and the like). Note that FIG. 9 shows a state in which the first dielectric layer 202 to be used for bonding in the bonding step shown in S14 of FIG. 1 is formed on the supporting substrate 201 (bonding supporting substrate 205).

  The warp shape of the support substrate 201 (the convex surface of the bonding surface 201a) can be obtained by machining the bonding surface 201a of the supporting substrate 201 and forming damage on the surface of the bonding surface 201. This step can be performed under the same conditions as in the first embodiment. For example, the surface grinding is performed by setting the grindstone roughness of the surface grinder to # 200 to # 3000 to leave processing damage, and the thickness after the surface grinding is set to 70 to 200 μm. More preferably, the grindstone roughness is # 2000 or less, and the thickness after surface grinding is 150 μm or less. As described above, by the surface grinding, a convex warp is generated on the joint surface 201a side. Wafer warpage after grinding is more likely to occur as the thickness becomes thinner, but if it is too thin, wafer damage will occur at the time of bonding. Therefore, it is preferable to control the thickness after the surface grinding to a thickness in the range of 70 to 200 μm.

When the surface after processing needs to be a mirror surface, processing such as polishing can be added to the surface. By performing polishing to the extent that the warp is not lost, it is possible to perform mirror finishing while maintaining the warp. For example, when the warpage generation process is performed with # 2000 and the polish thickness is less than 0.2 μm, the surface can be mirror-finished while maintaining the warpage. The first dielectric layer 202 is formed on the bonding surface 201a side of the support substrate 201. The first dielectric layer 202 can use SiO ₂ and can have a thickness of, for example, 300 nm. Other than SiO ₂ as the dielectric layer 202, another transparent insulating film such as SiN _x may be used.

  Next, as shown in FIG. 10, an epitaxial substrate in which a light emitting portion (functional layer) 219 is laminated on a starting substrate 211 is prepared. Between the starting substrate 211 and the light emitting portion (functional layer) 219, a selective etching layer 212 and a layer having an etching property different from that of the selective etching layer 212 are provided. 213 is inserted. These steps correspond to step S11 and step S12 in FIG.

  The starting substrate 211 can be, for example, GaAs, and the light emitting portion (functional layer) 219 can have a light emitting diode structure. The light emitting diode structure has, for example, a first semiconductor layer (n-type AlGaInP layer) 214, an active layer (AlGaInP active layer) 215, and a second semiconductor layer (p-type AlGaInP layer) 216 from the side of the starting substrate 211, and the thickness of each layer. It has a thickness of about 0.5 to 2 μm, and may have a laminated structure of a plurality of composition layers. The light emitting portion (functional layer) 219 can be manufactured by a metal organic chemical vapor deposition (MOVPE) method, a molecular beam epitaxy (MBE) method, an actinic ray epitaxy (CBE) method, or the like. Further, the selective etching layer 212 can be made of AlAs and the selective etching layer 213 can be made of GaAs, and the thickness of each can be set to 0.5 μm, for example. The material of the selective etching layer is not limited to these, and may be any combination as long as it is a material that is selective to the etching solution and can grow, for example, AlInP or AlGaAs or GaAs instead of AlAs. A material such as GaInP, ZnSe, or Ge may be selected.

  The light emitting portion (functional layer) 219 is not limited to one having AlGaInP as a main component, and may have a light emitting diode structure having an AlGaAs type or a strained InGaAs type active layer.

  Further, the starting substrate 211 is not limited to GaAs, and materials such as InP and Si can be similarly applied, and the material of the epitaxial layer can also be applied as long as it can be epitaxially grown on the starting substrate 211. ..

  Next, as shown in FIG. 11, a second dielectric layer 231 may be formed on at least a part of the surface of the epitaxial substrate 220. Further, an adhesive layer 232 made of, for example, BCB (benzocyclobutene) can be formed on the second dielectric layer 231. The adhesive layer 232 is not limited to BCB, and any material can be selected as long as it is a transparent and bondable material. For example, an epoxy resin can be selected instead of BCB. Further, in the joining process, a direct joining method of the first dielectric layer 202 and the second dielectric layer 231 may be used instead of the adhesive layer 232 (without using the adhesive layer 232).

Next, as shown in FIG. 12, the epitaxial substrate and the supporting substrate are bonded to each other by facing the first dielectric layer 202 and the adhesive layer (BCB adhesive layer) 232 and applying heat and pressure. This step corresponds to step S14 in FIG. The temperature at the time of joining can be, for example, 300 ° C., and the pressure can be 10 N / cm ² . The joining temperature and pressure are not limited to these conditions, and any temperature and pressure can be selected as long as the joining can be realized.

  Then, as shown in FIG. 13, by joining the first dielectric layer 202 and the adhesive layer (BCB adhesive layer) 232, the joining substrate 250 in which the supporting substrate 205 and the joining epitaxial substrate 240 are joined is obtained.

  It is preferable that the support substrate 201 is relatively thinner than the starting substrate 211. In that case, the warp on the support substrate 201 side is reduced, and the bonding substrate 250 is substantially the same as the warp of the epitaxial substrate 220. You can

  Next, as shown in FIG. 14, the selective etching layers 212 and 213 are etched. The selective etching layers 212 and 213 can be etched using a hydrofluoric acid-containing liquid. The selective etching layers 212 and 213 are etched and removed from the outer peripheral portion of the wafer. This step corresponds to step S15 in FIG.

  By etching the selective etching layers 212 and 213, the light emitting portion (functional layer) 219 and the starting substrate 211 are physically separated. The support substrate 201 has a warp with a substantially constant curvature due to processing damage on the surface, and even if a part of the support substrate 201 is separated from the starting substrate 211, the separation region is separated from the starting substrate 211 by a width equal to or larger than the selective etching layer. .. In the process of removing the selective etching layers 212 and 213, an oxide of the material to be etched is formed and etching inhibition starts, but due to the distance from the supporting substrate 201, the width of the selective etching layers 212 and 213 (for example, 1 μm or less) or more. Therefore, the oxide is removed by the invasion of the etching solution and the etching inhibition does not stop the etching of the selective etching layers 212 and 213.

  As a result, the starting substrate 211 and the light emitting portion (functional layer) 219 are separated by removing the selective etching layers 212 and 213, and the starting substrate 211 can be lifted off from the light emitting portion (functional layer) 219.

  Next, as shown in FIG. 15, after lift-off of the starting substrate, electrodes having different polarities (first ohmic electrode 263 and second ohmic electrode 261) are formed on the lift-off surface to realize a light emitting device structure. Further, the protective film 265 can be formed as appropriate. In this way, the semiconductor substrate 260 for a light emitting element can be manufactured. After the semiconductor substrate 260 for a light emitting element is manufactured, the light emitting element can be separated from the semiconductor substrate for a light emitting element in a die shape to manufacture the light emitting element.

  As described above, in the present invention, by using the wafer with the warp remaining as the supporting substrate, the epitaxial lift-off can be realized regardless of the material. The material most suitable for the device structure (low electrical resistance, low thermal resistance, low light absorption coefficient, etc.) can be selected as the supporting substrate as long as the warpage is left.

  Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples of the present invention, but the present invention is not limited thereto.

(Example 1)
As shown in FIG. 2, the supporting substrate 101 was subjected to surface grinding with a grindstone roughness of # 2000 to prepare a supporting substrate 101 made of silicon having a convex warp on the bonding surface side and having a thickness of 100 μm (see FIG. 1). Step S13). On this support substrate 101, a first metal layer 104 including a first contact layer 102 made of Ti and having a thickness of 100 nm and a first bonding layer 103 made of Au and having a thickness of 500 nm was formed, and a support substrate 105 for bonding was prepared. ..

Next, as shown in FIG. 3, a starting substrate 111 made of GaAs was prepared. On this starting substrate 111, a selective etching layer 112 made of AlAs having a thickness of 0.5 μm and a selective etching layer 113 made of GaAs having a thickness of 0.5 μm were formed (step S11 in FIG. 1). Further, on the selective etching layers 112 and 113 formed on the starting substrate 111, (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, by metal organic chemical vapor deposition (MOVPE) method. 0.4 ≦ y ≦ 0.6), and (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ _1, 0.4 ≦) having a bandgap larger than that of the active layer 115. A light emitting portion (double hetero (DH) structure) 119 in which a cladding layer (first semiconductor layer 114, second semiconductor layer 116) composed of y ≦ 0.6 is arranged on both sides of the active layer 115 was produced (FIG. 1). Step S12). In this way, the selective etching layer 112 made of AlAs having a thickness of 0.5 μm and the selective etching layer 113 made of GaAs having a thickness of 0.5 μm were formed between the starting substrate 111 and the light emitting portion (DH structure) 119.

The light emitting unit (DH structure) 119 is (Al _x Ga _1-x ) _y In _1-y P (x = 1, y≈0. 1) as the first semiconductor layer (n-type cladding layer) 114 from the side of the starting substrate 111. 5) is about 1.0 μm, the active layer 115 is (Al _x Ga _1-x ) _y In _1-y P (x≈0.1, y≈0.5) is about 0.5 μm, and the second semiconductor layer is As the (p-type cladding layer) 116, (Al _x Ga _1-x ) _y In _1-y P (x≈0.85, y≈0.5) is set to about 1.0 μm, and the epitaxial substrate 120 having a thickness of 450 μm is formed. Obtained.

  Next, as shown in FIG. 4, an ohmic electrode layer (second ohmic electrode) 131 is formed on a part of the surface of the epitaxial substrate 120, and the first dielectric is formed in a region other than the region where the ohmic electrode layer 131 is formed. The layer 132 was formed (formation of the second ohmic electrode in step S17 of FIG. 1).

Next, as shown in FIGS. 5 and 6, a bonding metal epitaxial layer having a thickness of 450 μm, in which a second metal layer 137 covering both the surface of the epitaxial substrate 120 and the ohmic electrode layer 131 and the first dielectric layer 132 is formed. The substrate 140 was formed. The second metal layer 137 was formed by sequentially forming the second contact layer 135 as the Ti layer 100 nm and the second bonding layer 136 as the Au layer 500 nm. Next, the bonding epitaxial substrate 140 and the bonding support substrate 105 are opposed to each other so that at least a part of the first metal layer 104 and the second metal layer 137 are in contact with each other, and they are bonded together by applying heat and pressure (see FIG. 1). Step S14). The temperature at the time of joining was 300 ° C. and the pressure was 10 N / cm ² . By joining the first metal layer 104 and the second metal layer 137, the joining substrate 150 in which the joining supporting substrate 105 and the joining epitaxial substrate 140 are joined was obtained.

  Next, as shown in FIG. 7, the selective etching layer 112 was etched using a hydrofluoric acid-containing liquid. The etching of the selective etching layer 112 proceeds from the outer peripheral portion of the bonding substrate 150, the selective etching layer 112 is gradually removed, and the starting substrate 111 changes so as to restore the warp. The width was increased, and the light emitting portion (DH structure) 119 and the starting substrate 111 were physically separated (step S15 in FIG. 1). After lift-off of the starting substrate 111, electrodes were formed on the lift-off surface (step S16 in FIG. 1). An electrode (second ohmic electrode) connected to the electrode (ohmic electrode layer 131) was formed on the back surface side of the support substrate 101 to manufacture a light emitting device (FIG. 8).

(Comparative Example 1)
A light emitting device was manufactured in the same manner as in Example 1 except that the surface of the supporting substrate 101 was not ground. In this case, since the separation width of the selective etching layer 112 removed by the selective etching does not change, the oxide during etching cannot be removed, and the oxide inhibits the etching, so that the starting substrate 111 cannot be separated.

(Example 2)
As shown in FIG. 9, the supporting substrate 201 was subjected to surface grinding with a grindstone roughness of # 2000 to prepare a supporting substrate 201 made of sapphire having a thickness of 100 μm and having a convex warp on the bonding surface side (see FIG. 1). Step S13). Next, a supporting substrate 205 for bonding, in which the first dielectric layer 202 made of SiO ₂ and having a thickness of 300 nm was formed on the supporting substrate 201, was prepared.

Next, as shown in FIG. 10, the starting substrate 211 was GaAs. On the starting substrate 211, a selective etching layer 212 made of AlAs having a thickness of 0.5 μm and a selective etching layer 213 made of GaAs having a thickness of 0.5 μm were formed (step S11 in FIG. 1). From (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0.4 ≦ y ≦ 0.6) by metalorganic vapor phase epitaxy (MOVPE) method on the starting substrate 211. And a clad layer 214 composed of (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0.4 ≦ y ≦ 0.6) having a larger bandgap than the active layer. A light emitting portion (DH structure) 219 having 216 arranged on both sides of the active layer 215 was produced (step S12 in FIG. 1). Thus, the selective etching layer 212 made of AlAs having a thickness of 0.5 μm and the selective etching layer 213 made of GaAs having a thickness of 0.5 μm were formed between the starting substrate 211 and the light emitting portion (DH structure) 219.

The light emitting part (DH structure) 219 is (Al _x Ga _1-x ) _y In _1-y P (x = 1, y≈0.) As the first semiconductor layer (n-type cladding layer) 214 from the side of the starting substrate 211. 5) is about 1.0 μm, (Al _x Ga _1-x ) _y In _1-y P (x≈0.1, y≈0.5) is about 0.5 μm as the active layer 215, and the second semiconductor layer ( As (p-type clad layer) 216, (Al _x Ga _1-x ) _y In _1-y P (x≈0.85, y≈0.5) is set to about 1.0 μm to obtain an epitaxial substrate 220 having a thickness of 450 μm. It was

  Next, as shown in FIG. 11, a second dielectric layer 231 was formed on the surface of the epitaxial substrate 220, and an adhesive layer 232 made of BCB was formed on the second dielectric layer 231.

Next, as shown in FIGS. 12 and 13, the first dielectric layer 202 and the adhesive layer 232 were opposed to each other, and heat and pressure were applied to bond them (step S14 in FIG. 1). The temperature at the time of joining was 300 ° C. and the pressure was 10 N / cm ² . By joining the first dielectric layer 202 and the adhesive layer 231, a joining substrate 250 in which the joining supporting substrate 205 and the joining epitaxial substrate 240 are joined was obtained.

  Next, as shown in FIG. 14, the selective etching layer 212 was etched. The selective etching layer 212 was etched using a hydrofluoric acid-containing liquid. The etching of the selective etching layer 212 progresses from the outer periphery of the bonding substrate 250, the selective etching layer 212 is gradually removed, and the starting substrate 211 undergoes a change in an attempt to restore the warp. The width was increased and the light emitting portion (DH structure) 219 and the starting substrate 211 were physically separated (step S15 in FIG. 1).

  After lift-off of the starting substrate 211, electrodes having different polarities were formed on the lift-off surface to manufacture a light emitting device (steps S16 and S17 in FIG. 1).

(Comparative example 2)
A light emitting device was manufactured in the same manner as in Example 2 except that the surface grinding of the surface of the supporting substrate was not carried out. However, since the separation width of the selective etching layer 212 removed by the selective etching does not change, the oxide during etching is not changed. It could not be removed, and the oxide could hinder the etching to separate the starting substrate.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has the same operational effect It is included in the technical scope of the invention.

101 ... Support substrate, 101a ... Bonding surface,
102 ... 1st contact layer, 103 ... 1st joining layer, 104 ... 1st metal layer,
105 ... Support substrate for bonding,
111 ... Starting board,
112 ... Selective etching layer, 113 ... Selective etching layer,
114 ... First semiconductor layer, 115 ... Active layer, 116 ... Second semiconductor layer,
119 ... a light emitting part,
120 ... Epitaxial substrate (starting substrate having light emitting portion),
131 ... Ohmic electrode layer (second ohmic electrode), 132 ... Dielectric layer,
135 ... Second contact layer, 136 ... Second bonding layer, 137 ... Second metal layer,
140 ... Epitaxial substrate for bonding,
150 ... Bonding substrate,
160 ... Semiconductor substrate for light emitting element, 163 ... First ohmic electrode,
165 ... Protective film,
201 ... Support substrate, 201a ... Bonding surface, 202 ... First dielectric layer,
205 ... Support substrate for bonding,
211 ... Starting board,
212 ... Selective etching layer, 213 ... Selective etching layer,
214 ... First semiconductor layer, 215 ... Active layer, 216 ... Second semiconductor layer,
219 ... a light emitting part,
220 ... Epitaxial substrate (starting substrate having light emitting portion),
231 ... Second dielectric layer, 232 ... Adhesive layer,
240 ... Epitaxial substrate for bonding,
250 ... Bonding substrate,
260 ... Semiconductor substrate for light emitting element,
261 ... Second ohmic electrode, 263 ... First ohmic electrode,
265 ... Protective film.

Claims (4)

Forming a selective etching layer on the starting substrate,
At least the first semiconductor layer, by forming at least a first semiconductor layer, an active layer and a second semiconductor layer above the selective etching layer by sequential epitaxial growth using a material of a lattice-matching system that is lattice-matched with the starting substrate. Forming a light emitting portion comprising the active layer and the second semiconductor layer;
A step of preparing a supporting substrate,
A joining step of joining the supporting substrate and the starting substrate having the light emitting unit to form a joining substrate;
Removing the starting substrate from the bonding substrate by removing the selective etching layer of the bonding substrate by etching,
Forming a first ohmic electrode on the surface of the first semiconductor layer;
In a method for manufacturing a semiconductor substrate for a light emitting device, which comprises at least a step of forming a second ohmic electrode electrically connected to the second semiconductor layer,
In the step of preparing the support substrate, a support substrate having a warp in which the bonding surface side, which is a surface on the side to be bonded to the starting substrate having the light emitting portion, has a convex shape is prepared,
In the step of removing the starting substrate, the starting substrate is separated from the bonding substrate by gradually etching the selective etching layer inward from the outer peripheral portion of the bonding substrate using the warpage of the supporting substrate. A method for manufacturing a semiconductor substrate for a light emitting device, which is characterized by the above.   The warp of the support substrate is formed by subjecting the joint surface of the support substrate to machining with a grindstone roughness of # 2000 or less to form damage on the surface of the joint surface. 1. A method for manufacturing a semiconductor substrate for a light emitting device according to 1.   The method for manufacturing a semiconductor substrate for a light emitting device according to claim 1, wherein the thickness of the support substrate is 150 μm or less.   A step of manufacturing the semiconductor substrate for a light emitting element by the method for manufacturing a semiconductor substrate for a light emitting element according to any one of claims 1 to 3 and then separating the light emitting element from the semiconductor substrate for a light emitting element in a die shape. A method for manufacturing a light-emitting element, comprising:

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