JP2011124455A - Method of manufacturing semiconductor substrate, and laser annealing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method and an apparatus that permit alloying of a semiconductor substrate wherein a metal electrode is formed on one surface side. <P>SOLUTION: A pulse oscillation laser with a wavelength of 500-550 nm and a half width of 300 ns or more that is output from a pulse oscillation laser light source for emitting a pulse oscillation laser beam or a continuous oscillation laser light source for emitting a continuous oscillation laser beam, or a continuous oscillation laser applied to the same position, at a wavelength of 500-550 nm and a half width of 300 ns or longer, is applied to a semiconductor substrate, wherein a metal electrode is formed on one surface side and a metal thin film or a compound semiconductor layer is formed on the other surface side as an option, from the side of the metal electrode, and it is relatively scanned, thus carrying out alloying processing of the semiconductor substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a semiconductor substrate having an ohmic electrode suitable for manufacturing a compound semiconductor, in particular, a semiconductor laser composed of a compound semiconductor layer, a light emitting diode or the like on a GaAs substrate, and the semiconductor. The present invention relates to a laser annealing apparatus suitable for manufacturing a substrate.

  Conventionally, the manufacturing method shown by patent document 1 is proposed as this kind of method. According to the present invention, as shown in FIG. 24, a light emitting element composed of the compound semiconductor layer 2 is formed on the upper layer of the compound semiconductor substrate 1 composed of GaAs, and AuGe (containing 12% Ge), Ni, Au is formed on the back surface of the semiconductor substrate 1. A metal electrode 3 composed of each of the above layers is prepared, and the metal electrode 3 is heated by irradiating a XeCl excimer laser with a wavelength of 308 nm from the metal electrode side 3 to alloy the GaAs substrate 1 and the metal electrode 3. . In this method, the back side of the GaAs substrate can be heated to 400 ° C. or higher without heating a light emitting element made of a ZnSe-based compound semiconductor whose characteristics deteriorate when the temperature is 300 ° C. or higher.

JP-A-7-335985

In the method disclosed in Patent Document 1, irradiation is performed by overlapping an excimer laser with an energy density of 300 mJ / cm ² , a pulse width of 30 ns, and a wavelength of 308 nm in 2 to 10 shots. However, as shown in FIG. 25, when an excimer laser pulse with an energy density of 300 mJ / cm ² , a pulse width of 30 ns, and a wavelength of 308 nm is irradiated to the metal electrode side, the temperature at the interface between the metal electrode and the semiconductor substrate is 600 ° C. The time exceeding 400 ° C. necessary for alloying is very short, about several tens ns, and alloying is insufficient. In addition, there is a problem that the temperature difference between the upper end and the lower end of the electrode portion is about 80 ° C., and this temperature difference acts as a thermal stress on the electrode, causing damage such as peeling of the electrode.

  In addition to the AuGe / Ni / Au metal electrode layer, there is a portion where the GaAs substrate is exposed on the back surface of the GaAs substrate. As described in Patent Document 1, the semiconductor light emitting device chip is 250 μm × 300 μm, for example, and when the GaAs substrate is divided into chips, the entire surface of the semiconductor substrate is covered with metal electrodes. In such a case, it is difficult to divide, and it is necessary to leave a portion where the GaAs substrate is exposed without forming a metal electrode in the portion to be divided. Therefore, the metal electrode and the exposed portion of the GaAs substrate are mixed on the back surface of the GaAs substrate. On the other hand, in the laser annealing using the XeCl excimer laser, the beam size is 0.4 mm × 150 mm, and it is necessary to irradiate the Au electrode portion and the GaAs substrate portion at the same time at the time of laser irradiation. is there.

However, at the time of the batch irradiation, there is a problem that GaAs is heated too much because GaAs tends to increase in temperature more than Au. The absorption coefficient of the excimer laser with a wavelength of 308 nm is 8.45 × 10 ⁵ / cm for GaAs (11.8 nm at the penetration depth where the light intensity is 1 / e), and 7.75 × 10 ⁵ / cm for Au ( The penetration depth is 12.9 nm, and in GaAs with a slightly large absorption coefficient, the irradiated laser is strongly absorbed, the amount of heat absorbed per unit volume of the surface layer increases, and the surface layer is heated intensely. Moreover, the thermal conductivity of both is 0.55 W / (cm · K) for GaAs and 3.18 W / (cm · K) for Au, so when laser is irradiated at the same energy density, the temperature of Au is It is difficult to increase, and the temperature is likely to increase with GaAs. Therefore, when Au is heated by laser irradiation with a wavelength of 308 nm and a pulse width of 30 ns and the boundary between AuGe and GaAs is heated to 400 ° C. or higher, the exposed portion of GaAs becomes high temperature by laser irradiation under the same conditions, and GaAs due to evaporation of GaAs. There are problems such as damage to the substrate and generation of toxic As vapor.

As data showing this, irradiation started when a sample of 700 nm Au deposited on the backside of the GaAs substrate was irradiated from the Au side with a XeCl excimer laser with a wavelength of 308 nm and a pulse width of 30 ns at an energy density of 200 mJ / cm ^2. FIG. 26 shows the temperature distribution in the depth direction after 30 ns. At this time, it can be seen that the temperature reaches 400 ° C. or higher from AuGe having a depth of 700 nm and at a depth of 100 nm from the GaAs surface. FIG. 27 shows a temperature distribution in the depth direction 30 ns after the start of irradiation when the GaAs substrate without the metal electrode is irradiated under the same irradiation conditions. At this time, the surface becomes 1276 ° C. exceeding the melting point of GaAs of 1240 ° C., and it is understood that GaAs is decomposed and evaporated. In general, in a compound composed of an element having a high vapor pressure such as GaAs, As is lost even when the temperature is lower than the melting point, Ga is likely to evaporate when the temperature is raised. Of course, ablation due to instantaneous heating by a pulse laser is likely to occur. Therefore, in an excimer laser having a wavelength of 308 nm, irradiation with an energy density of 200 mJ / cm ² or more causes a great damage to the GaAs substrate, which causes a problem in the process.

Further, FIG. 28 shows a temperature change at the interface between AuGe and GaAs when a GaAs substrate with a metal electrode is irradiated from the metal electrode side at an energy density of 200 mJ / cm ² . As explained above, the 100 nm position from the Au back surface and the GaAs surface is heated to 400 ° C. or more, but the time for the Au back surface to exceed 400 ° C. is about 27 ns, but it exceeds 400 ° C. at the 100 nm position from the GaAs surface. The time is only 4ns. Since the pulse waveform of the excimer laser is about 30 ns, the only way to increase the time for the interface to reach 400 ° C. or higher is to increase the energy density. However, since the pulse width is short, the energy density exceeds 400 ° C. even if the energy density is increased. The time will not be so long. Rather, the effect of increasing the energy density is noticeable in the GaAs exposed portion described above, and there is a problem that the energy density cannot be increased because the GaAs surface is overheated.

  In this way, it is possible to stably perform the alloy by extending the reaction time for performing the alloy, to reduce the temperature difference between the front and back of the metal electrode to reduce the damage due to the thermal stress of the metal electrode, and at the same time, the laser beam is irradiated. There is a need for a processing method that reduces the damage on the surface of the GaAs substrate, keeps the light emitting element formed on the upper surface of the GaAs substrate below a predetermined temperature, and simultaneously satisfies these conditions.

  The present invention has been made to solve the above-described conventional problems. Laser irradiation is performed on the metal electrode side made of AuGe (containing 12% Ge), Ni, Au, etc. on one surface of a semiconductor substrate. In the case of a semiconductor substrate having a metal film or a semiconductor layer on the other side, the alloy processing is effectively suppressed by suppressing the temperature rise of the metal film or the semiconductor layer. An object of the present invention is to provide a semiconductor substrate manufacturing method and a laser annealing apparatus that can be performed.

That is, according to the first aspect of the method for manufacturing a semiconductor substrate of the present invention, a semiconductor substrate having a metal electrode formed on one side is irradiated with a laser having a wavelength of 500 to 550 nm from the metal electrode side at a half width of 300 ns or more. However, the alloy processing is performed on the substrate by relatively scanning.
The method for manufacturing a semiconductor substrate according to a second aspect of the present invention is the method according to the first aspect, wherein a metal film is formed on the other surface side of the semiconductor substrate, and a wavelength of 500 from the metal electrode side with respect to the semiconductor substrate. An alloying process is performed on the substrate by relatively scanning while irradiating a laser having a wavelength of ˜550 nm with a half width of 300 ns or more.
According to a third aspect of the present invention, there is provided a method for manufacturing a semiconductor substrate, wherein the compound semiconductor layer is formed on the other surface side of the semiconductor substrate in the first aspect of the invention, and the wavelength from the metal electrode side with respect to the semiconductor substrate. An alloy process is performed on the substrate by relatively scanning while irradiating a laser of 500 to 550 nm with a half width of 300 ns or more.

  The laser irradiating with the above half-value width uses a pulsed laser beam oscillated from a pulsed laser light source, or adjusts a continuous wave laser oscillated from a continuous wave laser light source so that Irradiation may be performed for a time width of 300 ns or more.

A laser having a wavelength of 500 to 550 nm is selected. If this wavelength is too short, the light absorption coefficient of GaAs or the like increases and the surface of the semiconductor substrate tends to be overheated. On the other hand, if the wavelength is too long, the light absorption of the metal is lowered, and the energy use efficiency of the laser is lowered. For this reason, the wavelength of the laser is defined above.
In addition, the laser is applied to the metal electrode side of the semiconductor substrate with a half width of 300 ns or more. In the pulsed laser, the pulse half width is set to 300 ns or more. The irradiation time is adjusted with a continuous wave laser. By increasing the half-value width, evaporation and damage of a semiconductor substrate such as GaAs can be significantly suppressed. If the full width at half maximum is too short, it is difficult to keep the metal electrode and the semiconductor substrate long at a temperature at which alloying proceeds. The half width is preferably 1000 ns or more.

As described above, the present invention can be applied to a semiconductor substrate having a metal electrode formed on one side. Examples of the semiconductor substrate include those in which Ni—Si or Al—Si is alloyed in a Si semiconductor substrate on which a Ni electrode is formed.
In the present invention, a semiconductor substrate in which a metal electrode is formed on one side and a metal film is formed on the other side can be targeted. Examples of the semiconductor substrate include various III-V group semiconductors, such as GaAsS, GaN, GaP, InP, InAs, and AlN, which are likely to cause evaporation of constituent elements, but are not limited thereto, and are not limited to Si, SiC, ZnTe. And various substrates. Examples of the metal electrode include Au, Ni, Co, Ti, Pd, Pt, Fe, Cu, Mo, and W. A metal having a low melting point is usually used for the metal film. The low melting point material has a relatively lower melting point than the metal electrode material, and examples thereof include Al and Cu.
In the present invention, a semiconductor substrate in which a metal electrode is formed on one side and a compound semiconductor layer is formed on the other side can be targeted. Examples of the semiconductor substrate include various III-V group semiconductors, such as GaAs, GaN, GaP, InP, InAs, and AlN, which easily cause evaporation of constituent elements. However, the present invention is not limited thereto, and Si, SiC, ZnTe. Examples of the metal electrode include AuGe (containing 12% Ge) / Ni / Au, Au, Ni, Co, Ti, Pd, Pt, Fe, Cu, Mo, W, and the like.
The metal electrode, metal film, and compound semiconductor layer may be either a single layer or a multilayer, and the metal may be an alloy with an element not exemplified here or a laminated film, and is a metal irradiated with laser light. By using the above-mentioned metal electrode as the outermost surface of the electrode, the laser beam is absorbed. Therefore, an Al / Ti / Ni / Au laminated film, Al / Mo / Ni / Au, or the like can be used from the semiconductor substrate side, and Al can also be used on the semiconductor substrate side. Further, another layer may be formed on the upper layer.
In the semiconductor substrate, for example, a low melting point metal film or a compound semiconductor layer is formed on one surface side of the semiconductor substrate, and then a metal electrode is formed on the other surface side.

The metal electrode may be formed on a semiconductor substrate by patterning, and may have a portion where the surface of the semiconductor substrate is exposed and a portion of the metal electrode. The semiconductor substrate can be irradiated with the pulsed laser in a lump on the exposed portion of the semiconductor substrate surface and the metal electrode portion.
However, the semiconductor substrate and the metal electrode have a high laser absorption rate of the semiconductor substrate, and it is necessary to irradiate the laser with an energy density that suppresses overheating of the semiconductor substrate.
For the above, a material such as SiO ₂ that transmits light having a wavelength of 500 to 550 nm may be formed on the metal electrode side, and the pulsed laser may be irradiated from above the transmissive material. . Since the reflection / absorption rate varies depending on the thickness of the transmissive material due to light interference between the transmissive material and the semiconductor substrate or the metal electrode, the absorption amount of the semiconductor substrate and the metal electrode can be adjusted. At this time, it is desirable that the transmissive material is formed in the same thickness on each upper layer across the portion where the semiconductor substrate surface on the metal electrode side is exposed and the portion of the metal electrode. The film thickness is set so that the degree of reduction of the reflectance of the metal electrode is larger than the degree of reduction of the reflectance of the semiconductor substrate due to the transmissive material.
Further, the transmissive material may be formed only above the metal electrode. In that case, the film thickness is set so that the reflectance of the metal electrode is minimized. Furthermore, in this case, the reflectance can be greatly reduced by forming an antireflection film made of a multilayer film as a transmission material on the metal electrode.

  Among the laser annealing apparatuses of the present invention that implement the above manufacturing method, the first aspect of the present invention is that a pulsed laser is used to perform an alloy process by irradiating a semiconductor substrate with a laser having a wavelength of 500 to 550 nm and a half width of 300 ns or more. A pulse oscillation laser light source that emits, a stage that holds the semiconductor substrate on which a metal electrode is formed on one side, and that can move the semiconductor substrate along at least the semiconductor substrate surface direction; An optical system that makes the laser incident on the metal electrode side of the held semiconductor substrate, and a control device that controls the stage so as to move the semiconductor substrate held on the stage.

  Further, the present invention of the second laser annealing apparatus includes a continuous wave laser light source that emits a continuous wave laser to irradiate a semiconductor substrate with a laser having a wavelength of 500 to 550 nm at a half-value width of 300 ns or more at the same location and perform an alloy process. An adjustment means for adjusting the continuous wave laser to the laser and the semiconductor substrate having a metal electrode formed on one surface side can be held, and the semiconductor substrate can be moved at least along the semiconductor substrate surface direction A stage, an optical system for making the laser incident on the metal electrode side of the semiconductor substrate held on the stage, and a control device for controlling the stage so as to move the semiconductor substrate held on the stage And have.

  The laser annealing apparatus of the present invention includes either a pulsed laser light source or a continuous wave laser light source. In an apparatus provided with a pulsed laser source, the semiconductor substrate may be irradiated without changing the half-value width of the oscillated pulsed laser, or more than 300 ns by changing the half-value width of the oscillated pulsed laser. Any of those that irradiate the metal electrode side of the semiconductor substrate in this state. The laser can shape the beam shape by an optical system. The optical system is configured by an appropriate homogenizer, lens, mirror, and the like, and the configuration of the present invention is not limited to a specific one. The stage that holds the semiconductor substrate may hold one semiconductor substrate, or may hold a plurality of semiconductor substrates.

Various adjustment means may be used as the adjustment means for adjusting the continuous wave laser and irradiating the metal electrode side of the semiconductor substrate at the same position with an irradiation time of a half width of 300 ns or more. For example, the irradiation time can be adjusted by a shutter. However, while the laser is shut off, energy is not used effectively and lost and energy efficiency is lowered. Therefore, a configuration that can apply all of the irradiation energy to the semiconductor substrate side is desirable.
In addition, the adjustment means can irradiate the same position intermittently by irradiating the semiconductor substrate side so that the irradiation position is repeatedly switched in a short time of 300 ns or more. Further, the irradiation position may be gradually moved when switching the irradiation position. At this time, the irradiation position may be further moved by cooperating with the movement on the substrate side. As the irradiation position is switched, overlap irradiation can be performed at the same position, and energy can be effectively applied to the semiconductor substrate even by a continuous wave laser with low power intensity.

For example, a polygon mirror and an fθ lens that are rotation-controlled by a control device are used, and the rotation of the polygon mirror and the above-described time are continuously increased by 300 ns or more by the control device. The movement of the stage can be controlled. In this case, if the scan width by the polygon mirror exceeds the width of the semiconductor substrate, the stage can be a one-dimensional movement mechanism, otherwise the stage can be a two-dimensional movement mechanism. Irradiation can be performed on the entire surface of the semiconductor substrate.
Further, the stage holds one or more of the semiconductor substrates on a circumference, and a rotation mechanism capable of rotating the stage in a plane parallel to the substrate surface of the semiconductor substrate, and a rotation And a moving mechanism capable of moving the stage along the semiconductor substrate surface direction. Then, the rotational speed of the stage and the movement of the stage so that the time that the laser incident on the semiconductor substrate held on the stage by the control device is continuously irradiated to one point of the substrate is 300 ns or longer. Can be controlled.
The control device can be configured by a CPU, a program that operates the CPU, a ROM that stores the program, a storage unit that has a nonvolatile memory that stores operating conditions of the device, and the like.

In the present invention, a semiconductor substrate having a metal electrode formed on one surface is irradiated with a laser having a wavelength of 500 to 550 nm and a half-value width of 300 ns or more from the electrode side to perform the alloying process on the substrate. The region where alloying near the interface between the semiconductor and the metal electrode is caused by heating for a long time can be controlled over a long period of time to an alloyable temperature, so that uniform and high-quality alloy processing can be performed. Alloying between metal electrodes proceeds effectively. As a result, an ohmic electrode having a low contact resistance can be formed. In addition, by using a laser having a longer wavelength than the ultraviolet light source of excimer laser such as 308 nm or 248 nm, the absorption coefficient to the metal electrode is reduced, thereby reducing the temperature difference between the front and back of the metal electrode and reducing damage. There is.
Further, when a metal thin film or a compound semiconductor layer is formed on the other surface side of the semiconductor substrate, the metal electrode side can be alloyed while maintaining these at a predetermined temperature or lower, and the ohmic electrode can be formed. The formed semiconductor substrate can be manufactured satisfactorily.

  In addition, the metal electrode formed on one surface of the semiconductor substrate is patterned, and the portion where the semiconductor substrate is exposed and the portion of the metal electrode are collectively irradiated with laser on the metal electrode side, so that the wavelength is 500 to 550 nm. With laser irradiation, the absorption coefficient of the surface of the semiconductor is smaller than that of the ultraviolet laser, so that the temperature of the substrate is hardly raised, and the alloying can be performed without being damaged by decomposition or evaporation of the semiconductor. This has an excellent effect of enabling high-throughput processing because it is not necessary to control the irradiation position or perform masking so that the surface of the semiconductor substrate is not irradiated with laser.

  Furthermore, if the half width is 1000 ns or more, the alloy process can be performed in a time of 1 μs or more, so that the alloying between the semiconductor and the metal electrode is sufficiently advanced, and the ohmic electrode having a stable and low contact resistance. There is a very excellent effect that can be formed. Furthermore, since the temperature difference between the front and back surfaces of the metal electrode can be reduced, it is possible to suppress the peeling of the metal electrode and the occurrence of cracks.

Further, if the semiconductor substrate is made of GaAs and the electrode is made of a metal containing Au, GaAs has a small absorption coefficient for light having a wavelength of 500 to 550 nm, and can suppress excessive heating. . In addition, metals usually have a large amount of reflection and little absorption of visible light, but in the present invention, even in visible light, metals including Au, Ni, Co, Ti, Fe, Cu, Mo, W and the like have light absorption, Au absorbs light at a wavelength of 500 to 550 nm or less, and thus the metal can be sufficiently heated even with light in a wavelength band in which metal reflection exists. That is, there is an effect that Au can be sufficiently heated while controlling the temperature of the GaAs substrate.
In addition, if a semiconductor light emitting device is formed by a compound semiconductor layer formed on the other surface of the semiconductor substrate, a semiconductor light emitting device that is sufficiently alloyed and uses a low contact resistance electrode can be manufactured. is there.

  In the laser annealing apparatus of the present invention, a pulse oscillation laser light source that emits a pulse oscillation laser to irradiate a semiconductor substrate with a laser having a wavelength of 500 to 550 nm and a half-value width of 300 ns or more to perform alloy processing, and a metal on one side A stage capable of holding the semiconductor substrate on which an electrode is formed and moving the semiconductor substrate along at least the surface direction of the semiconductor substrate, and the metal substrate side of the semiconductor substrate held on the stage And an optical system for injecting the laser, and a control device for controlling the stage so as to move the semiconductor substrate held on the stage, so that a half-value width is formed on the metal electrode formed on one surface side of the semiconductor substrate. By irradiating a pulsed laser of 300 ns or longer, the electrode can be alloyed with respect to the substrate. Excellent Tsu bets, which can include formation of a stable alloy and the ohmic electrode device is obtained.

  Further, in another laser annealing apparatus of the present invention, a continuous wave laser light source that emits a continuous wave laser to irradiate a semiconductor substrate with a laser beam having a wavelength of 500 to 550 nm at a half-value width of 300 ns or more at the same position and perform an alloy process; An adjusting means for adjusting the continuous wave laser to the laser, and the semiconductor substrate having a metal electrode formed on one surface side can be held, and the semiconductor substrate can be moved at least along the semiconductor substrate surface direction A stage, an optical system that causes the laser to be incident on the metal electrode side of the semiconductor substrate held by the stage, and a control device that controls the stage to move the semiconductor substrate held by the stage; Therefore, using a continuous wave laser, a single point of the metal electrode formed on one side of the semiconductor substrate is continuously irradiated. Time by irradiating laser over 300 ns, alloying process of the electrode can be performed with respect to the substrate, excellent throughput, which can be such as formation of a stable alloy and the ohmic electrode device is obtained.

It is sectional drawing which shows the outline of the semiconductor substrate used for this invention. It is a figure which shows the laser annealing state of one Embodiment of this invention, and the laser irradiation state with respect to a semiconductor substrate. Similarly, it is a figure which shows the laser irradiation state with respect to the laser annealing apparatus and semiconductor substrate of other embodiment. Similarly, it is the schematic which shows a part of laser annealing apparatus. Similarly, it is a figure which shows the laser irradiation state with respect to the laser annealing apparatus and semiconductor substrate of other embodiment. It is a graph which shows the wavelength dependence of the reflectance of Au in the Example of this invention. Similarly, it is a graph showing the wavelength dependence of the absorption coefficient of GaAs. Similarly, it is a graph which shows the wavelength dependence of the penetration depth of GaAs. Similarly, it is a graph showing a temperature distribution in the depth direction after 300 ns when a laser is irradiated to Au / GaAs at a wavelength of 515 nm, a pulse width of 300 ns, and an energy density of 580 mJ / cm ² . Similarly, it is a graph showing the temperature change of the interface position when GaAs is irradiated at a wavelength of 515 nm, a pulse width of 300 ns, and an energy density of 580 mJ / cm ² . Similarly, it is a graph showing the temperature distribution in the depth direction after 300 ns irradiated with Au / GaAs at a wavelength of 515 nm, a pulse width of 300 ns, and an energy density of 580 mJ / cm ² . Similarly, it is a graph showing the temperature distribution in the depth direction after 1000 ns after irradiation with Au / GaAs at a wavelength of 515 nm, a pulse width of 1000 ns, and an energy density of 890 mJ / cm ² . Similarly, it is a graph showing the temperature change of the interface position when Au / GaAs is irradiated at a wavelength of 515 nm, a pulse width of 1000 ns, and an energy density of 890 mJ / cm ² . Similarly, it is a graph showing the temperature distribution in the depth direction after 1000 ns when GaAs is irradiated with a wavelength of 515 nm, a pulse width of 1000 ns, and an energy density of 890 mJ / cm ² . Similarly, it is a graph showing the temperature distribution in the depth direction after 1000 ns irradiated with a wavelength of 515 nm, a pulse width of 1000 ns, and an energy density of 1000 mJ / cm ² Au / GaAs. Similarly, it is a graph showing the temperature change of the interface position when Au / GaAs is irradiated at a wavelength of 515 nm, a pulse width of 1000 ns, and an energy density of 1000 mJ / cm ² . Similarly, it is a graph showing the temperature distribution in the depth direction after 1000 ns when GaAs is irradiated with a wavelength of 515 nm, a pulse width of 1000 ns, and an energy density of 1000 mJ / cm ² . Similarly, it is a graph which shows the irradiation time dependence of the temperature difference of the surface of an Au electrode immediately after irradiation of a continuous wave laser, and a back surface. Similarly, it is a graph which shows the laser reflectivity of each material at the time of permeable film formation. Similarly, it is a graph which shows the laser reflectivity of each material when it does not have a permeable film. Similarly, it is a figure which shows the wavelength dependence of the reflectance by the presence or absence of a permeable film. Similarly, it is a figure which shows the temperature change in each irradiation condition in 10 micrometers depth from a laser irradiation surface. Similarly, it is a figure which shows the wavelength dependence of the reflectance of various metals. It is a figure which shows the cross section of the semiconductor substrate used as laser annealing object. It is a figure which shows the temperature distribution in the depth direction of the semiconductor substrate at the time of laser annealing in a prior art example. It is a graph which shows the depth dependence of the temperature of GaAs at the time of laser irradiation. Similarly, it is a graph which shows the temperature in a depth position. Similarly, it is a graph which shows the temperature change of AuGe (metal electrode) and GaAs (semiconductor substrate) interface.

Hereinafter, a semiconductor substrate which is an object of the manufacturing method of the present invention will be described with reference to FIG.
FIG. 1A shows a structure in which a metal electrode 3 is formed on one surface side of a semiconductor substrate 1. In the manufacturing method of the present invention, the semiconductor substrate 1 and the metal electrode 3 are alloyed by irradiating the laser 10 with a wavelength of 500 to 550 nm and a half width of 300 ns or more from the metal electrode 3 side.
FIG. 1B shows a structure in which the metal electrode 3 is formed on one surface side of the semiconductor substrate 1 and the low melting point metal film 4 is formed on the other surface side. In the semiconductor substrate 1, for example, after the low melting point metal film 4 is formed on one surface side of the semiconductor substrate 1, the metal electrode 3 is formed on the other surface side of the semiconductor substrate 1. The semiconductor substrate 1 is irradiated with a laser 10 from the metal electrode 3 side, and the semiconductor substrate 1 and the metal electrode 3 are alloyed. A semiconductor circuit may be formed on one surface side of the semiconductor substrate 1 and the low melting point metal film 4 may be patterned as the metal wiring.
FIG. 1C shows a structure in which the metal electrode 3 is formed on one surface side of the semiconductor substrate 1 and the compound semiconductor layer 2 is formed on the other surface side. Note that another layer may be formed on the upper side of the compound semiconductor layer 2. In the semiconductor substrate 1, for example, after forming the compound semiconductor layer 2 on one surface side of the semiconductor substrate 1, the metal electrode 3 is formed on the other surface side of the semiconductor substrate 1. The semiconductor substrate 1 is irradiated with a laser 10 from the metal electrode 3 side, and the semiconductor substrate 1 and the metal electrode 3 are alloyed.
FIG. 1D shows a structure in which the metal electrode 3 is formed on one surface side of the semiconductor substrate 1 and the compound semiconductor layer 2 is formed on the other surface side. In the semiconductor substrate 1, for example, after forming the compound semiconductor layer 2 on one surface side of the semiconductor substrate 1, the metal electrode 3 is formed on the other surface side of the semiconductor substrate 1. The metal electrode 3 is patterned, and a part of the semiconductor substrate 1 is not covered with the metal electrode 3 but exposed. A transmissive layer 5 through which the laser passes is provided with the same thickness over the metal electrode 3 and the exposed semiconductor substrate 1. The transmission layer 5 can be composed of SiO ₂ , SiON, Si ₃ N ₄ , TiO ₂ , ZnO ₂ , Al ₂ O ₃ , MgO, Y ₂ O ₃ , or the like.
The semiconductor substrate 1 is irradiated with a laser 10 from the metal electrode 3 side, and the semiconductor substrate 1 and the metal electrode 3 are alloyed.

In each of the semiconductor substrates 1, in the irradiation of the laser 10 from the metal electrode 3 side, the metal electrode 3 and the semiconductor substrate 1 are appropriately heated without excessively heating the semiconductor substrate 1, and the metal electrode 3, the semiconductor substrate 1, Is effectively made into an alloy. Moreover, in what has a low melting-point metal film and a compound semiconductor layer in the other surface side of the metal electrode 3, the said alloying can be performed suppressing these temperature rising.
Further, when the metal electrode is patterned, by providing the transmission layer, the reflectance on the metal electrode side can be further reduced, and the semiconductor substrate 1 side can be prevented from being preferentially heated.

Next, an apparatus for performing a laser annealing process on the semiconductor substrate will be described.
FIG. 2A is a diagram schematically showing a laser annealing apparatus 100 having a pulsed laser light source 101.
The laser annealing apparatus 100 includes a pulsed laser light source 101 of a solid-state laser that outputs a pulsed laser having a wavelength of 500 to 550 nm and a half width of 300 ns or more. The output destination of the pulsed laser light source 101 is provided with an attenuator 103 for adjusting the laser intensity of the pulsed laser, and the transmission destination of the pulsed laser adjusted to the desired laser intensity by the attenuator 103 is A shaping optical system 104 for shaping the pulsed laser 102 into a line beam 105 is provided, and a sample stage 106 is located at the emission destination of the shaping optical system 104.
The sample stage 106 is installed on a stage 110. The stage 110 can be moved two-dimensionally in the horizontal direction, and the movement is controlled by a control device 115 including a CPU. .
In the laser annealing apparatus 100, the transfer robot 111 and the cassette 112 are provided. The cassette 112 accommodates the semiconductor substrate 107. The semiconductor substrate 107 is provided with a metal electrode on a laser incident surface (not shown). Further, a compound semiconductor layer or a metal electrode having a low melting point may be provided on the back side of a laser incident surface (not shown).

Next, the operation of the laser annealing apparatus 100 will be described.
The semiconductor substrate 107 accommodated in the cassette 112 is taken out by the transfer robot 111 and placed on the sample stage 106.
The pulsed laser light source 101 oscillates a pulsed laser 102 having a wavelength of 515 nm, a pulse width of 300 ns or more, and an oscillation frequency of 10 kHz. The pulsed laser 102 passes through the attenuator 103 and is adjusted to a desired laser intensity, and is shaped into a line beam 105 of long axis × short axis = 2 mm × 40 μm in the shaping optical system 104. As shown in FIG. 2B, the line beam 105 irradiates the semiconductor substrate 107 placed on the sample stage 106 from the metal electrode side.

  The stage 110 on which the sample stage 106 is installed moves at a constant feed rate of 80 mm / second in the direction of the minor axis 108 and the major axis 109 of the line beam during laser irradiation. The movement at this time is controlled by the control device 115, and the substrate is assumed to be irradiated with the line beam five times. After completing the irradiation in the scanning direction, next, the stage 110 is moved 2 mm in the long axis direction, and the line beam is scanned again at a feed rate of 80 mm / second, thereby irradiating the entire surface of the substrate with a pulsed laser, Alloying the metal electrode and the semiconductor substrate can be performed uniformly over the entire surface of the substrate.

Next, a laser annealing apparatus according to another embodiment will be described.
FIG. 3A is a diagram showing an outline of a laser annealing apparatus 200 having a continuous wave laser light source 201.
The laser annealing apparatus 200 includes a continuous wave laser light source 201 that outputs a continuous wave laser having a wavelength of 500 to 550 nm. The output destination of the continuous wave laser light source 201 is provided with an attenuator 203 that adjusts the laser intensity of the continuous wave laser. The attenuator 203 for adjusting the laser intensity can be omitted when the output is controlled by the continuous wave laser light source 201.

A polygon mirror 204 and an fθ lens 213 made of a polyhedron are arranged at the transmission destination of the continuous wave laser that is adjusted to a desired laser intensity by the attenuator 203 or whose output is controlled by the continuous wave laser light source 201. A sample stage 206 is located at the transmission destination of the fθ lens 213.
The sample stage 206 is installed on a stage 210. The stage 210 can be moved two-dimensionally in the horizontal direction, and the movement is controlled by a control device 215 including a CPU. . The control device 215 also controls the rotation of the polygon mirror 204.
Further, the laser annealing apparatus 200 is provided in the transfer robot 211 and the cassette 212, and the semiconductor substrate 207 is accommodated in the cassette 212. The semiconductor substrate 207 is provided with a metal electrode on a laser incident surface (not shown). Further, a compound semiconductor layer or a metal electrode having a low melting point may be provided on the back side of a laser incident surface (not shown).

Next, the operation of the laser annealing apparatus 200 will be described.
The semiconductor substrate 207 accommodated in the cassette 212 is taken out by the transfer robot 211 and placed on the sample stage 206.
The continuous wave laser light source 201 outputs a continuous wave laser 202 of a solid state laser having a wavelength of 532 nm. The continuous wave laser 202 passes through the attenuator 203 and is adjusted to a desired laser intensity, modulates the beam angle after reflection by the polygon mirror 204, and then condenses, for example, a circular spot beam 205 through the fθ lens 213. Then, as shown in FIG. 3B, the semiconductor substrate 207 placed on the sample stage 206 is irradiated.

As shown in FIG. 4, the spot beam 205 is deflected in the scanning direction 209 by the rotation of the polygon mirror 204. The beam scanning speed is controlled by the size, rotation speed, and beam diameter of the polygon mirror 204 so that the continuous irradiation time is 300 ns or more for the irradiation point on the substrate. The sample stage 206 is installed on a stage 210 that moves in the scanning direction 209 of this beam and in a moving direction 208 that is substantially perpendicular to this direction. The stage moves in the direction 208. The scan width by the polygon mirror 204 is 10 mm, and the feed rate of the sample stage 210 is such that the next scan position is shifted by 1/5 of the half width of the beam so that the spot beam is scanned five times at one place on the substrate. Irradiate while moving at a high speed. If the scan width is less than the width of the semiconductor substrate 207, the stage 210 is moved by the length of the scan width in the scan direction 209 of the spot beam 205, and the scan in the scan direction 209 by the polygon mirror 204 is performed again. Irradiate the entire surface by moving.
Next, the entire surface of the substrate is scanned by moving 5 mm in the scanning direction and scanning the spot beam, and the metal film on the irradiation surface of the semiconductor substrate or the alloy of the electrode on the substrate is uniformly performed on the entire surface of the substrate.

Next, the configuration of another laser annealing apparatus according to the present invention including a continuous wave laser light source will be described.
FIG. 5A is a diagram showing an outline of a laser annealing apparatus 300 having a continuous wave laser light source 301.
The laser annealing apparatus 300 includes a continuous wave laser light source 301 that outputs a continuous wave laser having a wavelength of 500 to 550 nm. The output destination of the continuous wave laser light source 301 is provided with an attenuator 303 for adjusting the laser intensity of the continuous wave laser. The attenuator 303 for adjusting the laser intensity can be omitted when the output is controlled by the continuous wave laser light source 301.

An optical that focuses the continuous wave laser 302 into, for example, a circular spot beam 305 at the transmission destination of the continuous wave laser 302 that is adjusted to a desired laser intensity by the attenuator 303 or whose output is controlled by the continuous wave laser light source 301. A system 304 is arranged. A rotating sample stage 306 is located at the emission destination of the optical system 304.
The rotating sample table 306 is installed on a table 313 provided with a rotating mechanism for rotating the rotating sample table 306, and the table 313 is installed on a stage 310 that can be moved one-dimensionally in the horizontal direction. Has been. The rotation of the rotating sample stage 306 and the movement of the stage 310 are controlled by a control device 315 configured by a CPU or the like.
The laser annealing apparatus 300 is provided in the transfer robot 311 and the cassette 312, and the semiconductor substrate 307 is accommodated in the cassette 312. The semiconductor substrate 307 is provided with a metal electrode on a laser incident surface (not shown). Further, a compound semiconductor layer or a metal electrode having a low melting point may be provided on the back side of a laser incident surface (not shown).

Next, the operation of the laser annealing apparatus 300 will be described.
The semiconductor substrate 307 accommodated in the cassette 312 is taken out by the transfer robot 311, and a plurality of semiconductor substrates 307 are placed on the circumference of the rotating sample stage 306.
The continuous wave laser light source 301 outputs a continuous wave laser 302 of a solid state laser having a wavelength of 532 nm. The continuous wave laser 302 passes through the attenuator 303 and is adjusted to have a desired laser intensity, and is condensed into a spot beam 305 having a diameter of 30 μm in the optical system 304. As shown in FIG. Irradiation is performed on the semiconductor substrate 307 installed on the table 306.

  The spot beam 305 is scanned in the rotation direction 309 on the semiconductor substrate 307 by the rotation of the rotating sample stage 306. At this time, the irradiation point on the substrate is controlled by the rotation speed, beam size, and rotation radius of the rotating sample stage 306 so that the continuous irradiation time is 300 ns or longer. The rotation speed of the rotating sample stage 306 is adjusted by a stage 313 that is provided with a rotation mechanism and is controlled by a control device 315. The entire surface is irradiated by moving the stage 313 on the stage 310 in the direction 308 shown in the figure.

Examples of the present invention will be described below.
The structure of the substrate in the example was the same as the structure in FIG. That is, an Au electrode of 700 nm is formed on the back surface of a GaAs substrate having a thickness of 100 μm, and this substrate is sufficient to see the influence on the compound semiconductor on the back surface.

  In the present invention, light having a wavelength of 500 to 550 nm is irradiated as described above. One reason for this is that the metal has a wavelength band with low light reflectance. For a metal having a large absorption coefficient, since a light transmission component does not exist in a film sufficiently thicker than the light penetration length, all components other than reflection are absorbed. Therefore, it is important for the light reflectance to be low in order to heat the metal efficiently. FIG. 6 shows the wavelength dependence of the light reflectance of Au. From the figure, it can be seen that the reflectance rapidly decreases at a wavelength of 550 nm or less. From this, it is understood that the light absorption of the metal is improved at a wavelength of 550 nm or less, and the energy of the laser beam is efficiently given to the metal.

  In addition, another reason for irradiating light with a wavelength of 500 to 550 nm in the present invention is that the absorption coefficient of the semiconductor substrate is not too large. FIG. 7 shows the wavelength dependence of the light absorption coefficient of GaAs. If the wavelength is less than 500 nm, it is presumed that the absorption coefficient increases rapidly and the substrate surface is easily overheated.

  Further, FIG. 8 shows the wavelength dependence of the light penetration depth indicating the depth at which the intensity of incident light becomes 1 / e. From the figure, it can be seen that the penetration depth is about 50 to 100 nm or more when the wavelength is 500 nm or more, and that the absorption of the laser light becomes moderate to some extent and is not easily overheated.

The embodiment of the present invention will now be described with reference to the results obtained when laser light having a wavelength of 515 nm and a pulse width of 300 ns is irradiated. In this test, irradiation was performed at an energy density of 580 mJ / cm ² . FIG. 9 shows the temperature distribution in the depth direction after 300 ns after irradiation with Au / GaAs under the above conditions. From the figure, it can be seen that the temperature at the position of 100 nm from the Au back surface and the GaAs surface near the Au / GaAs interface exceeds 400 ° C. and reaches the temperature at which the alloy proceeds. Further, FIG. 10 shows the time change of the Au / GaAs interface temperature at this time.

From the figure, it can be seen that the interface was 400 ° C. or higher over a long period of 47 ns, and the time exceeding 400 ° C. was 8 ns at the 100 nm position from the GaAs surface, and it was at the optimum temperature for a long time for compound formation. Thus, a good quality compound was formed and the contact resistance could be lowered.
Next, FIG. 11 shows the temperature distribution in the depth direction after 300 ns after irradiation of the GaAs substrate under the same irradiation conditions as described above. From the figure, the surface temperature of the GaAs substrate is the highest 1236 ° C., seen to be kept below 1240 ° C. the melting point, wavelength 308nm of the temperature XeCl excimer laser, pulse width 30 ns, the energy density of 200 mJ / cm ² It can be seen that the evaporation and damage of GaAs can be suppressed lower than when irradiated.

Further, examples of the present invention will be described below with reference to results obtained when laser light having a wavelength of 515 nm and a pulse width of 1000 ns is irradiated. In this test, irradiation was performed with an energy density of 890 mJ / cm ² . FIG. 12 shows the temperature distribution in the depth direction after 1000 ns after irradiation with Au / GaAs under the above conditions. From the figure, it can be seen that the temperature at the position of 100 nm from the Au back surface and the GaAs surface near the Au / GaAs interface exceeds 400 ° C. and reaches the temperature at which the alloy proceeds.

Further, FIG. 13 shows the time change of the Au / GaAs interface temperature at this time. From the figure, it can be seen that the interface was 400 ° C. or higher over a long period of 72 ns, and the time exceeding 400 ° C. at the position of 100 nm from the GaAs surface was 14 ns, and it was at the optimum temperature for a long time for compound formation. Thus, a high-quality compound was formed, and the contact resistance could be further reduced. Next, FIG. 14 shows the temperature distribution in the depth direction after 1000 ns after irradiating the GaAs substrate under the same irradiation conditions as described above.
From the figure, it can be seen that the surface temperature of the GaAs substrate is suppressed to about 1050 ° C., and the temperature is lower than that when the XeCl excimer laser is irradiated at a wavelength of 308 nm, a pulse width of 30 ns, and an energy density of 200 mJ / cm ^2. It can be seen that the evaporation and damage of GaAs can be greatly suppressed compared to the case of irradiation at a wavelength of 515 nm, a pulse width of 300 ns, and an energy density of 580 mJ / cm ² .

Thus, with a pulse width of 1000 ns, damage to the GaAs surface can be greatly reduced, so that irradiation with an energy density of 890 mJ / cm ² or more can keep the vicinity of the interface at a temperature at which alloying proceeds for a longer time. Can do.
As an example, FIG. 15 shows a state when irradiation is performed with an energy density of 1000 mJ / cm ² and a pulse width of 1000 ns. From FIG. 16, the time when the interface temperature is 400 ° C. or higher is 330 ns, and the time exceeding 400 ° C. is several 274 ns at the position of 100 nm from the GaAs surface. The maximum temperature of the GaAs substrate surface irradiated under the same conditions is from FIG. The temperature was about 0 ° C., and the alloying could be performed while maintaining the temperature suitable for the alloy for a longer time while suppressing the temperature rise on the surface of the GaAs substrate. Thus, it can be understood that the effect of the present invention is further exhibited when the irradiation time is 1000 ns.

  FIG. 18 shows the irradiation time dependence of the temperature difference between the front and back surfaces of the Au electrode immediately after continuous light irradiation and the temperature difference at a position of 100 nm from the back surface and the GaAsGaAs surface. As can be seen from the figure, compared to the XeCl excimer laser, the implementation conditions of the present invention show that the temperature difference between the electrodes and the interface is remarkably reduced, and the thermal stress acting on the electrodes and the interface can be reduced. It was possible to prevent electrode peeling and cracking.

Further, examples of the present invention will be described. Here, a SiO ₂ / Au / GaAs substrate and a SiO ₂ / GaAs substrate are prepared. The Au film thickness remains unchanged at 700 nm, and the SiO ₂ film thickness corresponding to the permeable film of the present invention is 40 nm or 220 nm as described below.
FIG. 19 shows the dependency of the reflectance on the SiO ₂ film thickness with respect to the wavelength of 515 nm when the SiO ₂ film is formed on the Au / GaAs and GaAs substrates with an arbitrary thickness. From the figures, it can be seen that the reflectance periodically decreases at a specific thickness, and the decreasing film thicknesses are different from each other.

FIG. 20 shows how much the absorptance changes with each SiO ₂ thickness, assuming that (incident light rate−reflectance) = absorptivity when the SiO ₂ film is not formed = 100%. This figure shows that when there is SiO _{2 of} that thickness and the comparative numerical value of Au / GaAs is 150%, even if the same energy density is irradiated, 150% of energy is substantially absorbed by Au / GaAs. It is shown that. _If the gain amount of the SiO 2 / Au / GaAs _is larger than the gain amount of the SiO 2 / GaAs, when irradiated with _SiO 2 / GaAs at an energy density capable of Au / GaAs interface 400 ° C., SiO ₂ film without It is obvious that the temperature can be kept lower than in the case of.

When SiO ₂ is formed with a film thickness of 40 nm or 220 nm, etc., with a high magnification of (SiO ₂ / Au / GaAs) / (SiO ₂ / GaAs) shown in FIG. Absorption occurs, and the Au / GaAs interface can reach a temperature at which the alloy can be alloyed while keeping the temperature of the GaAs surface lower.
This will be described in the above embodiment. The reflectances when irradiated with the pulse width of 1000 ns and 890 mJ / cm ² are 65.6% for Au and 40.3% for GaAs, respectively. At this time, the energy density absorbed is about 531mJ / cm ² at about 306mJ ^/ cm 2, GaAs with Au, respectively.
Here, when a 40 nm or 220 nm SiO ₂ film is formed on the surface, the reflectance decreases to 48% for Au and 32% for GaAs, respectively. Therefore, as in the case of 890 mJ / cm ² irradiation without the SiO ₂ film, irradiation with an energy density of 589 mJ / cm ² is required to obtain the same alloy effect at the Au / GaAs interface exceeding 400 ° C. In addition, the energy density absorbed by the GaAs substrate at this time is 401 mJ / cm ² , and the maximum temperature of the GaAs substrate surface can be greatly reduced.
FIG. 21 shows the wavelength dependence of the reflectance of Au / GaAs and SiO ₂ / Au / GaAs in this example. As can be seen from the figure, the reflectance is reduced due to the effect of the SiO ₂ film. In addition, since the reflectance of Au is reduced, energy incident on Au can be saved and the energy density required for the process is lowered. Therefore, when a laser oscillator having the same output is used, the beam area can be increased. As a result, throughput is also improved.

In the present invention, the thickness of the metal electrode on the back surface is not limited to 700 nm, and can be implemented and has an effect. When the metal film becomes thicker, it is possible to uniformly heat the vicinity of the interface between the electrode and the semiconductor substrate while suppressing the temperature difference between the front and back of the metal by increasing the energy density by increasing the continuous irradiation time, The effect of the present invention becomes more prominent.
In the present invention, the compound semiconductor layer formed on the surface of the semiconductor substrate can have various structures regardless of the structure shown in FIGS. Further, examples of the low melting point metal formed on the surface side of the semiconductor substrate include Al (aluminum), but are not limited thereto.

Furthermore, the temperature change in each irradiation condition mentioned in description of this invention in the 10 micrometer depth from a laser irradiation surface is shown in FIG. As can be seen from the figure, the maximum temperature is 100 ° C. or less, and the thickness of the GaAs substrate is 10 μm or more, so that no damage is caused to the compound semiconductor or the low melting point metal on the front surface side. It can be seen that the metal and semiconductor substrate can be alloyed by laser irradiation.
As for the metal that is alloyed with the semiconductor substrate, it can be said that Au and Cu are particularly effective in the present invention. FIG. 23 shows the wavelength change of the reflectance of various metals. From the figure, it can be seen that the reflectance of Au and Cu decreases at a wavelength of 550 nm or less, and the light absorption is improved. Metals such as Ni, Co, Ti, Pd, Pt, Fe, Cu, Mo, and W, which are not taken up here, can also be used in the present invention, and a high-quality alloy with the Si substrate is possible.

  As an alloy with a Si substrate, for example, an Al—Si alloy of an Al / Ti / Ni / Au electrode on a p-type Si layer of the Si substrate, a Ni—Si alloy of a Ni / Ti / Ni / Au electrode, etc. are known. As for such an electrode alloy, high-quality alloying is possible by irradiation with pulsed laser light having a wavelength of 500 to 550 nm and a half width of 300 ns or more, more preferably 1000 ns or more. Even when the metal electrode is patterned, the present invention can suppress overheating of the Si substrate. The ohmic contact electrode substrate of the Si substrate can be used as, for example, an IGBT (insulated gate bipolar transistor) that is a power semiconductor element.

As an example, an alloy with a GaN substrate includes a Ti / GaN alloy of Ti / Ni / Au electrodes on an n-type GaN layer of a GaN substrate, and a GaN film epitaxially grown on a sapphire substrate, which is a wide band gap semiconductor substrate. An Au-GaN alloy of Au / Ni electrodes on a substrate with a substrate or a substrate with a GaN film epitaxially grown on a Si substrate is known. Similarly, by irradiation with pulsed laser light having a length of 300-1000 ns or more, A quality alloy is possible. Also, even when the metal electrode is patterned, GaN does not absorb light having a wavelength of 500 to 550 nm, so that only the electrode is heated and the GaN substrate is exposed to transmit light without being absorbed. Become. Similarly, light is transmitted through the GaN film on the sapphire substrate, and no adverse effect is exerted. The GaN film on the Si substrate passes through the GaN film and is absorbed by the Si substrate, but the Si substrate with the GaN film is not adversely affected by the effect of the present invention. As a GaN ohmic contact electrode substrate of a GaN substrate or a substrate with a GaN film, for example, it can be used as a light emitting element such as an LED (light emitting diode) or LD (laser diode), or a power semiconductor element.
The semiconductor substrate manufactured by the alloy according to the present invention is a substrate having an electrode having low contact resistance and good adhesion, and can be used as a high-quality product.

  As described above, the present invention has been described based on the embodiment and the previous examples. However, the present invention is not limited to the above description, and appropriate modifications can be made without departing from the present invention. is there.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Compound semiconductor layer 3 Metal electrode 4 Metal film 100 Laser annealing apparatus 101 Pulse oscillation laser light source 106 Sample stage 107 Semiconductor substrate 110 Stage 200 Laser annealing apparatus 201 Continuous oscillation laser light source 204 Polygon mirror 206 Sample stage 207 Semiconductor substrate 210 Stage 213 fθ lens 300 laser annealing apparatus 301 continuous wave laser light source 306 rotating sample stage 307 semiconductor substrate 310 stage

Claims (15)

  A semiconductor substrate having a metal electrode formed on one side thereof is subjected to alloy processing by relatively scanning while irradiating a laser having a wavelength of 500 to 550 nm from the metal electrode side with a half width of 300 ns or more. A method for manufacturing a semiconductor substrate.   A metal film is formed on the other surface side of the semiconductor substrate, and the semiconductor substrate is relatively scanned while being irradiated with a laser having a wavelength of 500 to 550 nm from the metal electrode side at a half-value width of 300 ns or more. 2. The method of manufacturing a semiconductor substrate according to claim 1, wherein an alloying process is performed on the semiconductor substrate.   A compound semiconductor layer is formed on the other surface side of the semiconductor substrate, and the semiconductor substrate is relatively scanned while irradiating a laser having a wavelength of 500 to 550 nm from the metal electrode side with a half width of 300 ns or more. 2. The method of manufacturing a semiconductor substrate according to claim 1, wherein an alloy process is performed on the substrate.   4. The laser according to claim 1, wherein the laser is adjusted so that a pulsed laser having a half-width of 300 ns or more or a continuous-wave laser is irradiated to the same portion at a time of a half-width of 300 ns or more. The manufacturing method of the semiconductor substrate in any one.   The method for manufacturing a semiconductor substrate according to claim 1, wherein the half width is 1000 ns or more.   6. The method of manufacturing a semiconductor substrate according to claim 1, wherein the semiconductor substrate is made of GaAs and the metal electrode is made of a metal containing Au.   The said metal electrode is patterned and formed on the said semiconductor substrate, The said laser is irradiated to the part which the semiconductor substrate surface exposed, and the part of the said metal electrode collectively. 7. A method for producing a semiconductor substrate according to any one of 6 above.   8. The method of manufacturing a semiconductor substrate according to claim 7, wherein a material that transmits light having a wavelength of 500 to 550 nm is formed on the metal electrode side, and the laser is irradiated from the transmissive material.   9. The method of manufacturing a semiconductor substrate according to claim 8, wherein the transmissive material is formed in an upper layer over a portion where the surface of the semiconductor substrate on the metal electrode side is exposed and a portion of the metal electrode.   The method of manufacturing a semiconductor substrate according to claim 1, wherein a semiconductor light emitting element is formed by a compound semiconductor layer formed on the semiconductor substrate.   A pulse oscillation laser light source that emits a pulse oscillation laser to perform an alloy process by irradiating a semiconductor substrate with a laser having a wavelength of 500 to 550 nm and a half width of 300 ns or more, and the semiconductor substrate on which a metal electrode is formed on one side A stage capable of holding and moving the semiconductor substrate along at least the semiconductor substrate surface direction, and an optical system for allowing the laser to be incident on the metal electrode side of the semiconductor substrate held on the stage; A laser annealing apparatus, comprising: a control device that controls the stage so as to move the semiconductor substrate held on the stage.   A continuous wave laser light source for emitting a continuous wave laser to irradiate a semiconductor substrate with a laser having a wavelength of 500 to 550 nm at the same location at a half width of 300 ns or more to perform an alloy process, and an adjusting means for adjusting the continuous wave laser to the laser A stage capable of holding the semiconductor substrate having a metal electrode formed on one side thereof and moving the semiconductor substrate along at least the semiconductor substrate surface direction, and the semiconductor substrate held on the stage An laser annealing apparatus, comprising: an optical system that makes the laser incident on the metal electrode side; and a control device that controls the stage so as to move the semiconductor substrate held on the stage.   The adjusting means includes a polygon mirror and an fθ lens that are rotationally controlled by the control device, and the control device is configured so that the time for continuously irradiating one spot on the semiconductor substrate is 300 ns or longer. The laser annealing apparatus according to claim 12, wherein the rotation and the movement of the stage are controlled. The stage holds one or more of the semiconductor substrates on a circumference, and a rotating mechanism capable of rotating the stage in a plane parallel to the substrate surface of the semiconductor substrate, and the rotating A moving mechanism capable of moving the stage along the semiconductor substrate surface direction,
The control device adjusts the rotational speed of the stage and the movement of the stage so that the laser beam incident on the semiconductor substrate held on the stage is continuously irradiated to one point of the substrate for 300 ns or longer. The laser annealing apparatus according to claim 12, wherein the laser annealing apparatus is controlled.   The laser annealing apparatus according to claim 11, wherein the control device performs control so that a continuous irradiation time per point on the substrate becomes 1000 ns or more.

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