Semiconductor light emitting device and its manufacture

A ball-up preventive layer is formed on a first substrate. A bonding layer made of eutectic material is formed on the ball-up preventive layer. A semiconductor light emitting structure is formed on a second substrate. A first electrode is formed at least partially on the semiconductor light emitting structure. A barrier layer is formed on the first electrode. A metal layer is formed on the barrier layer. The bonding layer and the metal layer are bonded together. The second substrate is removed from the bonded structure. A second electrode is formed on a partial surface area of the semiconductor light emitting structure exposed on a surface of the bonded structure to obtain a semiconductor light emitting device.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and claims priority of Japanese Patent Application No. 2003-088181 filed on Mar. 27, 2003, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

A) Field of the Invention

The present invention relates to a semiconductor light emitting device and its manufacture.

B) Description of the Related Art

A semiconductor light emitting device is generally formed by a light emitting diode structure formed on a semiconductor substrate of GaAs, InP or the like. Light emitted in a light emitting layer propagates in an omnidirection. If the substrate is absorptive relative to light emission, light directed to the substrate is absorbed and attenuated. In order to efficiently direct emitted light to an external, such a structure is preferable that prevents light absorption in the substrate.

If a high reflectance plane is inserted between a light emitting layer and a substrate, light directed to the substrate is reflected and can be lead to an external. However, if a high reflectance Al layer or Ag layer is formed on the substrate, it becomes very difficult to epitaxially grow a semiconductor light emitting layer on the high reflectance layer.

A semiconductor light emitting device has been proposed which has such a structure that a semiconductor light emitting layer is bonded a conductive substrate through a high reflectance layer (e.g., Japanese Patent Laid-Open Publication No. 2001-189490 which is incorporated herein by reference).

FIGS. 4Ato4C are cross sectional views illustrating an LED manufacture method proposed in the above-mentioned Publication.

As shown inFIG. 4A, on a tentative or temporary substrate42of GaAs or InP, an LED structure41of a pn or np junction is grown. The LED structure may be one of various structures such as a homo pn junction structure, a hetero pn junction structure and a double hetero structure. A metal adhesive layer43is formed on a permanent substrate44, made of a material having a high thermal conductivity, such as silicon, GaAs and alumina, the mental adhesive layer functioning as a reflection mirror. The material of the metal adhesive layer is selected from a group consisting of indium, tin, aluminum, gold, platinum, titanium, zinc, silver, palladium, gold-beryllium alloy, gold-germanium-nickel alloy and zinc-tin alloy. The LED structure41is bonded to the metal adhesive layer43in water, atmospheric air or alcohol and heat treatment is performed.

As shown inFIG. 4B, the tentative substrate42is removed by mechanical polishing or chemical etching. Etchant can be made of hydrochloric acid and phosphoric acid. An etch stopper of, for example, InGaP or AlGaAs, may be formed between the tentative substrate42and LED structure41.

As shown inFIG. 4C, predetermined areas of the LED region are exposed and ohmic contact electrodes411and412are formed. If the metal adhesive layer is made of the same material as that of the ohmic electrode411, such as gold-beryllium alloy, the metal adhesive layer may be used as the ohmic electrode411by etching the LED structure to the metal adhesive layer43.

Light emitted from the LED structure41and directed toward the permanent substrate44is reflected at the metal adhesive layer43and transmits again through the LED structure41to be output to the external. In this manner, an external light emission efficiency can be improved.

If AuZn is used as the material of the metal adhesive layer43and ohmic electrode411, Zn may be diffused into semiconductor so that it becomes difficult to realize an ohmic contact.

Good reflection characteristics are rather incompatible with good ohmic contact. An alloying process is necessary for forming ohmic contact. Morphology of an interface between semiconductor and metal alloy at the ohmic contact may become rough or metal may diffuse to lower the reflectance.

Solder or eutectic may be used for bonding two substrates. In this case, if solder or eutectic impregnates the reflection layer, the reflection characteristics of the reflection layer are degraded. When two substrates are bonded together, solder or eutectic may cause ball-up.

SUMMARY OF THE INVENTION

An object of this invention is to provide a semiconductor light emitting device of a high quality and its manufacture method.

According to one aspect of the present invention, there is provided a method of manufacturing a semiconductor light emitting device, comprising the steps of: (a) preparing a first substrate; (b) forming a ball-up preventive layer on the first substrate; (c) forming a bonding layer made of eutectic material on the ball-up preventive layer to obtain a support substrate; (d) preparing a second substrate; (e) forming a semiconductor light emitting structure on the second substrate; (f) forming a first electrode in at least a partial surface area of the semiconductor light emitting structure; (g) forming a barrier layer on a surface including an upper surface of the first electrode; (h) forming a metal layer on the barrier layer to obtain a device substrate; (i) bonding together the bonding layer of the support substrate and the metal layer of the device substrate to obtain a bonded structure; (j) removing the second substrate from the bonded structure; and (k) forming a second electrode in a partial surface area of the semiconductor light emitting structure exposed on a surface of the bonded structure at the step (j) to obtain the semiconductor light emitting device, wherein: in the step (i), eutectic material of the bonding layer forms eutectic with the metal layer to bond together the support substrate and the device substrate; the ball-up preventive layer prevents ball-up of the bonding layer; and the barrier layer prevents a composition of a material of the first electrode from diffusing into the side of the barrier layer and prevents the eutectic material of the bonding layer from intruding into the first electrode.

With this semiconductor light emitting device manufacture method, the ball-up can be prevented during bonding in the step (i). It is possible to prevent a reflectance of the reflection layer of the semiconductor light emitting device from being lowered by diffusion of the bonding (eutectic) material.

According to another aspect of the present invention, there is provided a semiconductor light emitting device comprising: a substrate; a ball-up preventive layer formed on the substrate; a bonding layer made of eutectic material and formed on the ball-up preventive layer; a metal layer formed on the bonding layer; a barrier layer formed on the metal layer; a first electrode formed on or in the barrier layer; a semiconductor light emitting structure formed on a surface including an upper surface of the first electrode; and a second electrode formed on a partial surface of the semiconductor light emitting structure, wherein: eutectic material of the bonding layer forms eutectic with the metal layer to bond together the bonding layer and the metal layer; the ball-up preventive layer prevents ball-up of the bonding layer; and the barrier layer prevents a composition of a material of the first electrode from diffusing into the barrier layer and prevents the eutectic material of the bonding layer from intruding into the first electrode.

This semiconductor light emitting device can prevent ball-up and loweing in reflectance and has a high quality.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1Ato1G are schematic cross sectional views illustrating a method of manufacturing a semiconductor light emitting device according to a first embodiment.

Reference is made to FIG.1A. On both sides of a conductive substrate11, an Au layer12is vapor-deposited and alloyed at 400° C. in a nitrogen atmosphere. For example, the substrate is made of Si doped with n- or p-type impurities at a high concentration. The thickness of the Au layer12is 150 to 600 nm for example. With the alloying process, the conductive substrate11and Au layer12form eutectic and are integrated to form ohmic contact. The Au layer12will not therefore be peeled off from the conductive substrate11. The conductive substrate11may be made of material other than Si, such as Cu, having an electrical conductivity and a high thermal conductivity and becoming alloy with Au.

Reference is made to FIG.1B. On one of the Au layers12, a Ti layer13, an Ni layer14and an AuSn eutectic layer15are sequentially vapor-deposited by an electron beam evaporation method (EB method). The Ti layer13is 100 to 200 nm thick, the Ni layer14is 50 to 150 nm thick, and the AuSn eutectic layer15is 600 to 1200 nm thick. The composition of the AuSn eutectic layer15is Au:Sn=about 20 wt %: about 80 wt %. Deposition of the Ti layer13, Ni layer14and AuSn eutectic layer15may also be done by resistance heating evaporation or sputtering method, instead of the EB method.

The lamination structure of the conductive substrate11, Au layer12, Ti layer13, Ni layer14and AuSn eutectic layer15is called a support substrate30. Since the support substrate30has the Ti layer13and Ni layer14, even if the support substrate30is heated to about 280° C. (eutectic temperature) at which the AuSn eutectic layer15is melted, a ball-up of the AuSn eutectic layer15on the support substrate30can be prevented. Namely, the Ti layer and Ni layer have a function of preventing the ball-up. The “ball-up” is the phenomenon that AuSn once liquidized at the eutectic temperature or higher is solidified again as the temperature lowers, and during the solidification, AuSn is segregated on the support substrate30and locally protrudes upwards.

Instead of the Ni layer14, an NiV layer may be formed on the Ti layer13to prevent the ball-up.

Reference is made toFIG. 1C. Asemiconductor substrate21such as a GaAs substrate is prepared which can lattice-match a semiconductor light emitting layer capable of emitting light having a target wavelength. A semiconductor light emitting structure22is formed on a semiconductor substrate21. When current is injected into the semiconductor light emitting structure22, it emits light having a wavelength specific to the semiconductor. The semiconductor light emitting structure22, for example, includes a quantum well structure. It may also be structured including a homo pn junction, a double hetero (DH) structure or a single hetero (SH) structure. The semiconductor light emitting structure22will be described later in detail.

An ohmic electrode23is formed on the semiconductor light emitting structure22. The ohmic electrode23is made of metal capable of forming ohmic contact with the semiconductor light emitting structure. For example, if a surface layer of the semiconductor light emitting structure22is made of p-type compound semiconductor, e.g., p-AlGaInP, the p-type electrode23can be made of AuZn. The ohmic electrode23can be formed on the semiconductor light emitting structure22by vacuum vapor deposition such as resistance heating evaporation, an EB method and sputtering.

The ohmic electrode23of a manufactured semiconductor light emitting device functions also as a reflection layer for reflecting light emitted from the semiconductor light emitting structure22and improving the external light emission efficiency of the semiconductor light emitting device.

On the ohmic electrode23, a conductive diffusion barrier layer24is formed, for example, by reactive sputtering method. The diffusion barrier layer24is made of Ti—W-nitride for example. The conductive diffusion barrier layer24is 100 to 200 nm thick for example. The diffusion barrier layer24is required to have a thickness of at least 100 nm. The function of the conductive diffusion barrier layer24will be later described.

After the conductive diffusion barrier layer24is formed, an alloying process is performed to form good ohmic contact between the semiconductor light emitting structure22and ohmic electrode23. For example, if the surface layer of the semiconductor light emitting structure22is made of p-type AlGaInP and the ohmic electrode23is made of AuZn, heat treatment for alloying is performed at about 500° C. in a nitrogen atmosphere.

After the alloying process, on the conductive diffusion barrier layer24, a first intrusion barrier layer25made of, for example, Al and a second intrusion barrier layer26made of, for example, Ta are vapor-deposited in this order. The thickness of the first intrusion barrier layer25made of Al is preferably 600 nm to 1000 nm. Vapor deposition may be EB method, resistance heating evaporation or sputtering. Although different names, the diffusion barrier layer and intrusion barrier layer, are used, both the layers have the same barrier function against diffusing species.

The thickness of the second intrusion barrier layer26made of Ta is preferably 100 nm to 200 nm. EB method may be used for vapor deposition. Since Ta is a refractory metal, it is difficult to vapor-deposit it by resistance heating evaporation. By using the EB method, a Ta layer can be formed easily. The second intrusion barrier layer26may be made of another refractory metal material such as Mo and W, instead of Ta. The function of the first and second intrusion barrier layers25and26will be later described.

On the second intrusion barrier layer26, a low resistivity metal layer27made of, for example, Au is formed. A lamination structure of the semiconductor substrate21, semiconductor light emitting structure22, ohmic electrode23, diffusion barrier layer24, first intrusion barrier layer25, second intrusion barrier layer26and metal layer27is called a device substrate31.

Reference is made toFIG. 1E, the support substrate30and device substrate31are bonded together by thermocompression bonding (hot press or metal bonding) for example. With the thermocompression bonding method, the support substrate30with the eutectic layer15and the device substrate31are heated to a temperature at which eutectic material melts and pressured to bond the substrates together. They are bonded together by eutectic material (AuSn) contained in the AuSn eutectic layer15. Bonding is performed by tightly contacting the AuSn eutectic layer15and metal layer27under the conditions of, for example, a nitrogen atmosphere, 10 minutes at 300° C. and a pressure of about 1 MPa.

The first and second intrusion barrier layers25and26have a function of preventing eutectic material (AuSn) of the eutectic layer15from intruding into the ohmic electrode23during the thermocompression bonding. The present inventors have found that the use of Al as the material of the first intrusion barrier layer25and Ta as the material of the second intrusion barrier layer26is effective among other materials. The diffusion barrier layer24has a function of preventing Zn of AuZn of the ohmic electrode23from diffusing into the first and second intrusion barrier layers25and26.

The atmosphere, bonding temperature and time of the thermocompression bonding are selected so that eutectic material can be melted, that the characteristics of the eutectic material are not changed (e.g., lowered bonding strength due to oxidation or the like) and that the support substrate30and device substrate31are bonded reliably.

Reference is made to FIG.1F. After the support substrate30and device substrate31are bonded together, the semiconductor substrate21of GaAs is removed by, for example, wet etching. Etchant may be NH4OH containing etchant for example. The semiconductor substrate21may also be removed by dry etching or mechanical polishing. At least one of wet etching, dry etching and mechanical polishing and another method may be combined to remove the semiconductor substrate21.

Reference is made to FIG.1G. After the semiconductor substrate21is removed, a front electrode28is formed on the semiconductor light emitting structure22in ohmic contact with the surface layer of the semiconductor light emitting structure22exposed on the surface of the semiconductor light emitting device. The front electrode28is made of material such as AuSnNi and AuGeNi which can form ohmic contact with n-type semiconductor if this is the material of the surface layer of the semiconductor light emitting structure22.

The front electrode28is formed by lift-off, for example. In lift-off, a photoresist layer is coated on the semiconductor light emitting structure22and exposed by using a photomask to form an opening of a desired electrode shape, electrode material is vapor-deposited and thereafter the photoresist layer together with the upper deposited metal layer is removed. As a method of vapor-depositing electrode material, resistance heating evaporation, EB method, sputtering or the like may be used.

With the processes described above, a semiconductor light emitting device32can be manufactured.

Description will be made on the merits of the Ti layer13and Ni layer14(ball-up preventing layer) included in the support substrate30.

If the thermocompression bonding is performed for bonding the device substrate31and a support substrate not provided with the ball-up preventive structure, eutectic material of the eutectic layer15balls up during the thermocompression bonding so that the device substrate cannot be bonded horizontally (in parallel) to the support substrate. If the thermocompression bonding does not form a horizontal bonding, it becomes difficult to perform photolithography at a later process after the thermocompression bonding. For example, in the process described with reference toFIG. 1G, the surface coated with the photoresist film cannot be in tight contact with the photomask because of the ball-up phenomenon, so that it is difficult to form the surface electrode28having a desired shape and a size of 10 μm or smaller.

The influence of the ball-up phenomenon exists as long as the photolithography process is included, even if the electrode material layer28is vapor-deposited on the semiconductor light emitting structure22, thereafter a resist pattern of a desired electrode shape is made using photoresist, and the unnecessary electrode region is removed by etching or the like. There is a shadow mask vapor deposition method well known as a simple electrode forming method. With this method, however, it is difficult to form an electrode having a size of 10 μm or smaller with a high precision. If the semiconductor light emitting device32is manufactured by using the support substrate30having the Ti layer13and Ni layer14(ball-up preventive layers), the above problem can be solved and the semiconductor light emitting device of a high quality can be manufactured.

With reference toFIGS. 2Ato2C, description will be made on examples of the semiconductor light emitting structure22of the device substrate31shown in FIG.1D.

Reference is made to FIG.2A. The semiconductor light emitting structure22has the configuration that a potential barrier layers22band a potential well layer22ware alternately laminated on a low resistivity n-type clad layer22n, and a low resistivity p-type clad layer22pis stacked on the uppermost potential barrier layer22b. The lamination of the potential barrier layers22band potential well layers22wconstitutes a multiple quantum well structure. The number of quantum well layers22wcan be increased or decreased as desired.

Reference is made to FIG.2B. The semiconductor light emitting structure22has the single hetero (SH) structure that on an n-type semiconductor layer22n, a p-type semiconductor layer22phaving a different composition is stacked. The n-type semiconductor layer22nand p-type semiconductor layer22peach may be made of a plurality of sub layers. For example, low impurity concentration layers may be used for forming a pn junction, and high impurity concentration layers are formed on both sides of the low impurity concentration layer. Material having a large band gap may be used as the material of the high impurity concentration layer to form guide and clad layers.

Reference is made to FIG.2C. The semiconductor light emitting structure22has the double hetero (DH) structure that on an n-type semiconductor layer22n, an intrinsic (i) semiconductor layer22ihaving a narrow band gap and a different composition is stacked, and on this intrinsic (i) semiconductor layer22i, a p-type semiconductor layer22phaving a wide band gap and a different composition is stacked. A carrier confinement effect of confining electrons and holes in the (i) layer22ican be obtained by disposing the n- and p-type semiconductor layers22nand22phaving a wide band gap on both sides of the (i) layer22i. Since the material having a wide band gap has generally a low reflactive index, a light confinement effect can also be obtained.

According to the method of manufacturing a semiconductor light emitting device described above, the ball-up of AuSn can be prevented when the support substrate30and device substrate31are bonded together, because the support substrate30includes the ball-up preventive layers (Ti layer13and Ni layer14) under the AuSn eutectic layer15.

If a support substrate not provided with the ball-up preventive layer is used, AuSn lumps having a height of about 10 to 30 μm are formed. The support substrate30provided with the ball-up preventive layers was used and lumps were not observed with an optical microscope. It can be considered from this that the ball-up preventive layers can prevent the ball-up perfectly. Even if some ball-up exist, the height of a lump is considered to be not more than 2 μm which is a recognition threshold value of an optical microscope.

It can be considered that the Ti layer13functions as a layer having a high adhesion or tight contact with the underlying Au layer12. By forming the Ni layer13on the Ti layer14, it can be expected that wettability of the eutectic layer formed on the Ni layer can be improved. Improvement on the wettability by the Ni layer14can be considered as preventing segregation of the eutectic material AuSn.

The Au layer not easy to be peeled off from the conductive substrate11can be formed by vapor-depositing Au on both sides of the conductive substrate and preforming an alloying process. By making alloy of the conductive substrate11and Au layer12, the semiconductor light emitting device32can be formed which is excellent in tight contact, has a good ohmic contact, a long life time and a high reliability. During the processes of manufacturing a semiconductor light emitting device, durability in processes after the alloying process can be improved.

Zn in AuZn can be prevented from diffusing into the first and second intrusion barrier layers25and26during bonding of the support substrate30and device substrate31by forming the diffusion barrier layer24made of Ti—W-nitride on the p-side ohmic electrode23made of AuZn.

The diffusion preventing effect by the diffusion barrier layer results in, for example, a lowered contact resistance value. The present inventors have confirmed from the following experiment that the diffusion barrier layer prevents diffusion of Zn.

Two structures, one having no diffusion barrier (Ti—W-nitride) layer and the other having the diffusion barrier layer24, were prepared. The one structure had the configuration that an AuZn layer of 200 nm thick was vapor-deposited on a p-InGaP substrate, and that an Al layer of 300 nm thick was vapor-deposited on the AuZn layer, and the alloying process was performed at 500° C. The other structure had the configuration that an AuZn layer of 200 nm thick was vapor-deposited on a p-InGaP substrate, that a diffusion barrier (Ti—W-nitride) layer of 100 to 200 nm thick was formed on the AuZn layer, and that an Al layer of 300 nm thick was vapor-deposited on the diffusion barrier layer, and the alloying process was performed at 500° C.

Contact resistance between the p-InGaP substrate and AuZn layer of the two structures was measured. The former structure had a contact resistance value of 2.7×10−4(Ωcm2), and the latter structure with the diffusion barrier layer had a contact resistance value of 5×10−6to 6×10−5(Ωcm2).

The contact resistance value of the structure with the diffusion barrier layer is smaller by one to two orders of magnitude. It can be judged that ohmic characteristics are better if the contact resistance value is smaller. It can therefore be judged that existence of the diffusion barrier layer realizes good ohmic contact characteristics, because the diffusion barrier (Ti—W-nitride) layer prevents diffusion of Zn.

By forming the first intrusion barrier layer25made of Al and the second intrusion barrier layer26made of Ta, it becomes possible to prevent eutectic material (AuSn) from intruding into the ohmic electrode23functioning as a reflection layer of the semiconductor light emitting device32, during bonding of the support substrate30and device substrate31, and to prevent a reflectance value from being lowered.

It can be considered that the two intrusion barrier layers can prevent almost perfectly the eutectic material (AuSn) from intruding into the ohmic electrode23. AuSn is also used as the material of the n-side electrode. Sn functions also as an n-type dopant. If the ohmic electrode23is made of the p-side electrode (AuZn) and AuSn transmits through the intrusion barrier layer and reaches the AuZn layer, the ohmic characteristics are degraded, or in a worse case, a Schottky junction is formed. However, the experiment made by the present inventors using the intrusion barrier layers showed no change in the ohmic characteristics. It can therefore be considered that intrusion of AuSn into the ohmic electrode23can be prevented almost perfectly.

Because of these effects and reasons, the semiconductor light emitting device32having a high quality can be manufactured.

Additional remark will be given on the alloy process between the conductive substrate11and Au layer12. The alloying process between the conductive substrate11and the Au layer12on the side to be bonded to the device substrate31is a more effective alloying process. The material of the electrode on the opposite surface may be different material such as Ti/TiN/Al since this electrode is used as a lead electrode for such as die bonding. However, the front and back electrodes are preferably made of the same material in order to simplify the process. Since the eutectic temperature of Au with Si is as low as about 400° C., it can be said that these materials are adequate materials in terms of mass production. For example, the eutectic temperature with Si is 600 to 800° C. for Pt, about 900° C. for Ni, and about 900° for Ti.

FIGS. 3Ato3F are schematic cross sectional views illustrating a method of manufacturing a semiconductor light emitting device according to a second embodiment.

FIG. 3Ashows the support substrate30whose structure and manufacture method have been described with reference toFIGS. 1A and 1B. This support substrate30is prepared by the processes shown inFIGS. 1A and 1B.

Reference is made to FIG.3B. Similar to the first embodiment, a semiconductor substrate, e.g., a GaAs substrate, is prepared. On this semiconductor substrate21, a semiconductor light emitting structure22is formed. By injecting current into the semiconductor light emitting structure22, this structure emits light having a wavelength specific to the material of its semiconductor light emitting layer. As described with the first embodiment, the semiconductor light emitting structure22is made of, for example, a multiple quantum well structure, a simple (homo) pn junction, a double hetero (DH) structure, a single hetero (SH) structure or the like.

In a partial surface area of the semiconductor light emitting structure22, an ohmic electrode23is formed. The material and forming method of the ohmic electrode23may be similar to those of the first embodiment.

Next, a first barrier (diffusion barrier) layer41is formed on the ohmic electrode23by using Ti—W-nitride for example. The first barrier layer41has a thickness of, for example, 100 to 200 nm and is required to be at least 100 nm. For example, a reactive sputtering method is used to form the first barrier layer. The first barrier layer41and ohmic electrode layer23are etched and patterned by using a resist pattern as a mask. A lift-off method may be used to pattern the ohmic electrode layer.

After patterning the first barrier layer41and ohmic electrode23, an alloying process is performed to form good ohmic contact between the semiconductor light emitting structure22and ohmic electrode23. For example, if the surface layer of the semiconductor light emitting structure22is made of p-AlGaInP and the ohmic electrode23is made of AuZn, heat treatment is performed at about 500° C. in a nitrogen atmosphere.

After the alloying process, a conductive reflection layer is formed. Al is vapor-deposited to form a metal reflection layer42on the first barrier layer41and on the semiconductor light emitting structure22where the first barrier layer (ohmic electrode23) is not formed. The metal reflection layer42is made thicker than a total thickness of the ohmic electrode23and the first barrier layer41formed on the ohmic electrode23. The thickness is preferably 600 nm to 1000 nm for example. The metal reflection layer42can be formed, for example, by EB method, resistance heating evaporation, sputtering or the like.

The metal reflection layer42has the structure that Al of the first intrusion barrier layer25of the semiconductor light emitting device32manufactured by the first embodiment method is also used as the reflection electrode. Namely, the metal reflection layer42of a manufactured semiconductor light emitting device has also a function of reflecting light emitted from the semiconductor light emitting structure22to improve the external light emission efficiency of the semiconductor light emitting device.

The metal reflection layer42made of Al can reflect incidence light at a reflectance of about 80% or higher if the wavelength of light emitted by the semiconductor light emitting structure22is near 650 nm. The metal reflection layer42made of Al can reflect light having a wavelength of 700 nm or shorter at a reflectance of about 80% or higher. Additional description of the metal reflection layer42will be later given.

Reference is made to FIG.3C. On the metal reflection layer42, a second barrier (intrusion barrier) layer43is formed which is made of refractory metal such as Ta, Mo and W. The second barrier layer43has a thickness of 100 to 200 nm for example. The refractory metal such as Ta, Mo and W is hard to be vapor-deposited by resistance heating evaporation so that EB method or the like is used for example. By using the EB method, the second barrier layer43can be formed easily. The function of the second barrier layer43will be later described.

On the second barrier layer43, a low resistance metal layer27is formed which is made of, for example, Au. A lamination structure of the semiconductor substrate21, semiconductor light emitting structure22, ohmic electrode23, first barrier layer41, metal reflection layer42, second barrier layer43and metal layer27is called a device substrate44.

Reference is made to FIG.3D. The support substrate30and device substrate44are bonded together by thermocompression bonding (hot press or metal bonding) for example. The atmosphere, bonding temperature and time during bonding are similar to those of the first embodiment described with reference to FIG.1E.

The first barrier layer41has a function of preventing Zn of AuZn of the ohmic electrode23from diffusing into the metal reflection layer42. If the first barrier layer41is not formed and the ohmic electrode23and metal reflection layer42contact each other in their main areas, Zn of AuZn of the ohmic electrode23diffuses into the metal reflection layer42and the ohmic characteristics between the semiconductor light emitting structure22and ohmic electrode23are degraded. Namely, the ohmic characteristics may be lost and the Schottky characteristics may appear.

The second barrier layer43has a function of preventing eutectic material (AuSn) of the eutectic layer15from intruding into the metal reflection layer42. If the eutectic material (AuSn) intrudes into the metal reflection layer42, the reflectance of the metal reflection layer42lowers.

It is not preferable to use Au as the material of the metal reflection layer42. Au mixes with the eutectic material (AuSn) of the eutectic layer15and a reflectance is lowered, even if the second barrier layer43is formed. For example, a reflectance of a reflection layer made of single Au is 90% or higher if the light wavelength of a semiconductor light emitting device is near 650 nm, whereas a reflectance of an Au reflection layer mixed with AuSn is 60% or lower.

The reflection layer42is a metal reflection layer using metal because it must be electrically conductive.

Reference is made to FIG.3E. After the support substrate30and device substrate44are bonded together, the semiconductor substrate21of GaAs is removed. The removing method is similar to that of the first embodiment described with reference to FIG.1F.

Reference is made to FIG.3F. After the semiconductor substrate21is removed, a front electrode28is formed on the semiconductor light emitting structure22, the front electrode forming ohmic contact with the n-type semiconductor22nexposed on the surface of a semiconductor light emitting device. The material and forming method for the front electrode28are similar to those of the first embodiment described with reference to FIG.1G.

With the above-described processed, a semiconductor light emitting device45can be manufactured.

The second embodiment has the effects common to those of the first embodiment. In addition, since the semiconductor light emitting device of the second embodiment has the second barrier layer43made of Ta or the like and formed on the metal reflection layer42made of Al, the eutectic material (AuSn) of the eutectic layer15can be prevented from intruding into the reflection layer when the support substrate30and device substrate44are bonded together. It is therefore possible to prevent the reflectance of the metal reflection layer42of a manufactured semiconductor light emitting device45from being lowered.

As described earlier, the semiconductor light emitting device45manufactured by the second embodiment manufacture method, has the structure that Al of the first intrusion barrier layer25of the semiconductor light emitting device32manufactured by the first embodiment is used also as the reflection electrode. Both a high reflectance and an excellent ohmic contact are therefore possible even if the ohmic electrode23is made of a low reflectance material other than AuZn and ohmic characteristics between Al and the semiconductor light emitting structure are poor.

From these effects and reasons, the semiconductor light emitting device45of a high quality can be manufactured.

Since arsenic is not contained in semiconductor light emitting devices manufactured by the semiconductor light emitting device manufacture methods of the first and second embodiments, there is only a small load on environments. For example, the invention is applicable to various display devices not desired to use environment load substance, such as a vehicle lamp, a portable telephone back light, an electric bulletin board light source.

The present invention has been described in connection with the preferred embodiments. The invention is not limited only to the above embodiments. For example, instead of forming lead electrodes on both sides of a semiconductor light emitting device, they may be formed on one side as shown in FIG.4C. In this case, an insulating substrate may be used as the support substrate. The semiconductor light emitting structure may have well-known various structures. The material of the ohmic electrode may be well-known various materials. It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.