JP2010239042A - Electrode forming method, method of manufacturing luminous element, semiconductor device, and luminous element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of reducing costs incurred by increasing the number of processes including the number of evaporations and forming an electrode that has strong adhesion strength at contact bonding between a wire of a wire bonding portion and an electrode during a process of assembling an LED lamp while considering the prevention of the occurrence of defects about a turn or peeling off of the electrode. <P>SOLUTION: The method forms an ohmic electrode on a semiconductor crystal that includes at least an n-type semiconductor crystal, a luminous layer, and a p-type semiconductor crystal, which are formed in this order, wherein at least Au is evaporated on a surface of a p-type semiconductor crystal of the semiconductor crystal as a first metal layer, a mixture of an AuBe alloy material and Au is evaporated on the first metal layer as a second metal layer and forming the AuBe, Au is evaporated on the second metal layer as a third metal layer, and heat treatment is subsequently performed, thus the ohmic electrode being formed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for forming an electrode, a method for manufacturing a light emitting element, a semiconductor element, and a light emitting element.

A light emitting element using a semiconductor crystal in which at least the light emitting layer is represented by (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) (hereinafter also referred to as AlGaInP) Then, AuBe alloy has been used for some time as an ohmic electrode provided on the surface of a p-type semiconductor crystal.

As a method of forming an electrode including the AuBe alloy layer, in the case of a mass production process, a large-sized vapor deposition machine having an advantage in productivity is often used although adhesion is inferior to sputtering.
As a means for heating and evaporating a metal in a vapor deposition apparatus, a method of resistance heating using a boat made of a refractory metal such as tungsten and an EB gun method of heating an electron beam against the surface of a metal target are generally used. (See, for example, Patent Documents 1 and 2).

  Further, when used as a semiconductor light emitting device, the p-type semiconductor crystal side is often the upper surface of the light emitting device due to the order of crystal growth and the convenience of light extraction. Therefore, as shown in FIG. 6, not only the ohmic contact ohmic layer 7 is formed on the surface of the semiconductor crystal 3, but also a relatively thick gold layer is formed thereon as the bonding pad 9. Thus, the ohmic electrode 5 is required. This bonding pad is a so-called bonding pad having a relatively thick gold of about 1 to 2 [mu] m for wire bonding of a gold wire of about 25 [mu] m [phi] during the assembly process of the LED lamp after forming the semiconductor element. FIG. 6 is a diagram illustrating an example of an outline of electrodes formed on a light emitting element or the like.

As an electrode pattern formation method, a resist pattern is formed before vapor deposition, and a lift-off method is used to peel off unnecessary material after vapor deposition. Alternatively, a resist pattern is formed on the surface of a metal film after vapor deposition and etched with chemicals after vapor deposition. However, there is a method using a photolithography process for forming an electrode shape.
Then, heat treatment is performed in an RTA (Rapid Thermal Annealing) or a winding heater heating furnace to obtain ohmic contact.

An electrode with a structure in which a conventional AuBe alloy material is deposited as a basic method for forming an anode electrode having the bonding pad and Au is used as a bonding pad thereon is difficult to wire bond. There are many.
This is presumably because the gold in the bonding pad portion on the electrode surface is altered by the diffusion of Ga, Al, In from the semiconductor crystal and Be in the electrode.

As a countermeasure, there is a method of forming an electrode in two steps and it is actually used (see Patent Document 1).
In this method, first, an ohmic layer is formed once, and Au is vapor-deposited again thereon to form a bonding pad. Specifically, AuBe as an ohmic layer is formed, photolithography, pattern etching, resist stripping, and heat treatment are performed to form an ohmic electrode having a predetermined shape and size, and an Au layer is further formed as a bonding pad layer. Film processing is performed in the order of photolithography, mask alignment, pattern etching, resist stripping, and heat treatment.

In addition, there is a method of forming a metal layer by a single vapor deposition and ensuring wire bondability. In this method, a refractory metal such as Ti, Mo, or W or a metal close thereto is formed between the AuBe alloy layer and the Au pad layer (see, for example, Patent Document 3-5).
The purpose of this technique is to prevent alloying of the Au layer due to interdiffusion during heat treatment. In the case of this manufacturing method, on the dopant layer for taking ohmic such as AuBe, AuZn layer, etc., a high melting point metal such as Ti and Au are successively formed in one vapor deposition in this order. Thereafter, photolithography, pattern etching, resist stripping, and heat treatment are completed in one step.

Japanese Patent Laid-Open No. 06-93443 JP 09-232255 A JP 2000-2000926 A JP 2006-40997 A JP 2007-317913 A

In the method of forming the electrode in two steps as described in Patent Document 1 described above, the upper gold is not affected by the heat treatment for about 30 to 60 minutes at around 500 ° C. when the lower ohmic layer is formed. In the second heat treatment at about 350 ° C., the lower ohmic electrode is alloyed. Therefore, the upper gold has almost no diffusion of Ga, In, Be, etc., and maintains a good gold state. Therefore, the wire bondability is good, and a value of about 80 g is obtained by the shear test.
However, the disadvantage is that each process is repeated twice, which is very disadvantageous in terms of cost. In addition, there is a risk that the AuBe alloy layer and the upper Au layer may be exfoliated without being well alloyed due to a slight amount of dirt therebetween. Further, sudden partial peeling occurs at the interface between the two depositions, and the quality is often not reliable.

And the ohmic electrode obtained with the manufacturing method of the above-mentioned patent documents 3-5 contains a metal layer as a barrier layer, such as Ti, and can prevent diffusion of metal, such as Ga, into gold by heat treatment to some extent. . Therefore, a good state of wire bonding can be obtained, but it is not sufficient. In addition, when LED chips are manufactured with AuBe (Be 1 wt%) / Ti / Au structure, the electrodes are brought into close contact with the adhesive sheet not only in the wire bonding process but also in the element process, and transferred to another sheet. In this case, peeling or turning may occur due to insufficient adhesion to the crystal, which not only lowers the process yield, but also requires additional man-hours such as nonconforming product processing and re-inspection, resulting in increased manufacturing costs. In terms of quality, reliability is reduced, and in process management, re-introduction and delivery time are delayed.
Furthermore, in recent years, since bonding speed has been increased, an electrode structure that facilitates bonding is desired.

  The present invention has been made in view of the above problems, and can also suppress the cost due to an increase in the number of steps such as the number of vapor depositions, while taking into account the prevention of defects such as electrode turning and peeling, An object of the present invention is to provide an electrode forming method, a light emitting device manufacturing method, a semiconductor device, and a light emitting device, in which the adhesion strength of the crimped portion between the wire and the electrode of the wire bond portion in the LED lamp assembly process is stronger than before. To do.

In order to solve the above problems, in the present invention, at least an n-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more, (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) and (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) A method of forming an ohmic electrode on a semiconductor crystal in which a p-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more is formed in this order, the surface of the p-type semiconductor crystal of the semiconductor crystal being At least Au is vapor-deposited as a first metal layer, and a mixture of AuBe alloy material and Au is vapor-deposited as a second metal layer on the first metal layer to form an AuBe alloy. Au is vapor-deposited as a third metal layer, It provides a method of forming an electrode and forming an ohmic electrode by performing heat treatment.

In this manner, Au, AuBe alloy, and Au are sequentially deposited on the surface of the p-type semiconductor crystal, and then heat treatment is performed. As a result, the first metal layer becomes Au instead of AuBe, adhesion strength at the time of vapor deposition is improved, Be is diffused after heat treatment to obtain ohmic contact, and the Be concentration in the electrode can be lowered. Further, by providing Au also on the AuBe alloy layer, the Be concentration can be further reduced. Therefore, the strength of the second metal layer made of an AuBe alloy that is harder and more brittle than Au can be made stronger than before.
In addition, the Be concentration in the electrode can be further reduced as compared to the conventional case by depositing a mixture of AuBe alloy material and Au instead of directly depositing the AuBe alloy material as the second metal layer. It is possible to stably add Be.
With these effects, the Be concentration can be maintained to such an extent that an ohmic contact can be obtained, and the adhesion strength between the wire or the p-type semiconductor crystal and the electrode and the strength of the electrode itself are stronger than before. Can be. Accordingly, it is possible to manufacture an ohmic electrode with reduced wire bondability and reduced generation of electrode defects.

Here, it is preferable to use a material having a Be concentration of 1 to 2 wt% as the AuBe alloy material.
As will be described in detail later, since the AuBe alloy has a eutectic point around Be 1.1 wt%, when using a material having a reduced Be concentration in the AuBe alloy material, Be is not uniformly distributed. The Be concentration may be excessive or insufficient. Depending on the batch, the Be may be excessive, and another batch may cause a shortage of Be. For this reason, the Be concentration in the ohmic electrode can be stabilized even between batches by using an AuBe alloy material having a Be concentration of 1 to 2 wt% in which the Be concentration is stable as the alloy material.

Further, the amount of the AuBe alloy material is adjusted so that the total Be concentration of the first metal layer, the second metal layer, and the third metal layer after the heat treatment is 0.1 to 0.5 wt%. be able to.
Thus, by adjusting the amount of AuBe alloy material so that the total Be concentration of the first metal layer, the second metal layer, and the third metal layer after heat treatment is 0.1 to 0.5 wt%, The Be concentration in the formed ohmic electrode can be easily controlled within a range where the ohmic property can be obtained, and the risk of occurrence of defects in the adhesion between the wire and the electrode during bonding is reduced as much as possible. The Be concentration can be suppressed in a concentration range that can be obtained.

The thickness of the first metal layer is 5 to 100 nm, the thickness of the second metal layer is 10 to 200 nm, the thickness of the third metal layer is 5 to 100 nm, and the total thickness is 300 nm or less. It is preferable that
By forming each metal layer so as to have a thickness in the above range, the productivity can be made sufficiently high, and the effect of the role that each layer plays can be fully exhibited. it can.

Further, when the first metal layer, the second metal layer, and the third metal layer are formed, a fourth metal layer made of Ti is formed immediately above the third metal layer, and the fourth metal layer is directly above. It is preferable to form a fifth metal layer made of Au.
Thus, by forming the fourth metal layer made of Ti on the third metal layer, the constituent elements such as Ga from the p-type semiconductor crystal and the Be from the AuBe layer are made of Au formed on the top. Diffusion to the fifth metal layer can be strongly suppressed, and an increase in impurity concentration in the fifth metal layer on the outermost surface layer can be prevented.
Further, by forming the fifth metal layer made of Au on the fourth metal layer, it is possible to obtain better wire bondability characteristics.

Moreover, the thickness of the fourth metal layer can be set to 50 to 150 nm.
In this way, by setting the thickness of the fourth metal layer in the above-described range, it is possible to more strongly prevent impurities such as Ga and Be from diffusing into the upper fifth metal layer without impairing productivity. The thickness range can be made.

And the thickness of the said 5th metal layer can be 1.5-2 micrometers.
Thus, by setting the thickness of the fifth metal layer within the above-described range, it is possible to obtain a thickness that can provide higher adhesion strength when bonding the wire.

Furthermore, the electrode pattern can be formed by either a lift-off method or an etching method.
With the lift-off method, the accuracy of the electrode pattern can be made sufficiently high. In addition, since an etching process is unnecessary, it is possible to avoid using an acid or alkaline chemical solution with a large environmental load.
Moreover, if it is an etching method, an electrode pattern can be formed in a short time and with high precision.

Moreover, it is preferable that the heat processing conditions of the said heat processing shall be 400 to 500 degreeC and 10 to 100 minutes in inert gas atmosphere.
By alloying the metal layers formed under such heat treatment conditions, Be can be diffused to the first metal layer to such an extent that ohmic resistance can be obtained, and each metal layer reacts with the heat treatment atmosphere. Deterioration can be surely avoided.

In the present invention, at least an n-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1,0) ≦ y ≦ 1) and the carrier concentration represented by (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1). Forming a semiconductor crystal by forming a p-type semiconductor crystal of 1 × 10 ¹⁷ atoms / cm ³ or more in this order, and forming the semiconductor crystal on the surface of the p-type semiconductor crystal using the electrode forming method according to the present invention; There is provided a method for manufacturing a light-emitting element, comprising a step of forming an electrode and a step of dicing the semiconductor crystal on which the electrode is formed.

  As described above, in the ohmic electrode formed by the electrode forming method of the present invention, the adhesion strength between the wire and the ohmic electrode or between the ohmic electrode and the p-type semiconductor crystal is stronger than before. For this reason, in the light emitting element in which the ohmic electrode is formed by using such an electrode forming method, the ohmic electrode formed on the surface is in close contact with the wire or the p-type semiconductor crystal. The number of defects can be reduced as compared with the prior art. That is, a high-quality light-emitting element can be manufactured with a high yield.

Here, the surface area of the electrode can be 50% or less of the surface area of the p-type semiconductor crystal after the dicing.
If the electrode has such an area, a sufficient amount of light can be extracted from the light-emitting layer, and thus a light-emitting element with high emission luminance can be manufactured.

In the present invention, at least an n-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1,0) ≦ y ≦ 1) and the carrier concentration represented by (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1). A semiconductor element in which an ohmic electrode is formed on a semiconductor crystal in which a p-type semiconductor crystal of 1 × 10 ¹⁷ atoms / cm ³ or more is formed in this order, and the electrode is at least close to the p-type semiconductor crystal The first metal layer is composed of a first metal layer, a second metal layer, and a third metal layer in order from the side. The first metal layer is an Au vapor deposition layer, and the second metal layer is an AuBe alloy obtained by vapor deposition of a mixture of AuBe alloy material and Au. Layer, the third metal layer is made of an Au vapor deposition layer To provide a semiconductor device which is characterized in that plus the heat treatment.

Thus, the ohmic electrode formed on the surface of the p-type semiconductor crystal is at least a first metal layer, a second metal layer, and a third metal layer in order from the side close to the p-type semiconductor crystal, and the first metal layer is It is assumed that the Au vapor deposition layer, the second metal layer is composed of an AuBe alloy layer obtained by vapor deposition of a mixture of AuBe alloy material and Au, the third metal layer is composed of an Au vapor deposition layer, and these layers are subjected to heat treatment.
Thus, by providing an Au vapor deposition layer instead of directly contacting an AuBe alloy layer with a p-type semiconductor crystal, an AuBe alloy layer that is difficult to adhere to the p-type semiconductor crystal is directly attached to the semiconductor crystal. Therefore, the adhesion strength between the p-type semiconductor crystal and the electrode can be made sufficiently stronger than before.

In addition, since the heat treatment is applied, Be diffuses to the first metal layer side during the heat treatment, so that the resistance between the p-type semiconductor crystal and the electrode can be made sufficiently small to make an ohmic contact. .
Since an Au vapor deposition layer (third metal layer) is also provided on the AuBe alloy layer, Be diffuses into this third metal layer during the heat treatment, so that the total Be concentration in the ohmic electrode is reduced. The strength of the AuBe alloy layer, which is harder and more brittle than Au, can be made stronger than before.
With these results, the Be concentration in the electrode can be maintained at a level where ohmic contact can be obtained, and the bondability with the wire and the electrode strength are better than before, and the defect is not good. The number of semiconductor elements is significantly smaller than that of the prior art.

Further, it is preferable that a material having a Be concentration of 1 to 2 wt% is used as the AuBe alloy material.
As described above, if an AuBe alloy having a Be concentration of 1 to 2 wt% with a stable Be concentration is used as the AuBe alloy material, a semiconductor element having a stable Be concentration in the electrode can be obtained.

The total Be concentration of the first metal layer, the second metal layer, and the third metal layer after the heat treatment is preferably 0.1 to 0.5 wt%.
Thus, by forming the total Be concentration of the first metal layer, the second metal layer, and the third metal layer after heat treatment to be 0.1 to 0.5 wt%, the formed electrode and the p-type semiconductor crystal In addition, the Be concentration in a range in which the risk of occurrence of defects in the adhesion between the wire and the electrode during bonding can be reduced as much as possible can be achieved.

Furthermore, the thickness of the first metal layer is 5 to 100 nm, the thickness of the second metal layer is 10 to 200 nm, the thickness of the third metal layer is 5 to 100 nm, and the total thickness is 300 nm. The following is preferable.
Thus, by setting the thickness of each metal layer and the total thickness in the above-mentioned range, the time required for vapor deposition is not long, and the thickness can be surely exhibited. It is possible to achieve both reduction in manufacturing cost and improvement in quality.

The electrode further includes a fourth metal layer made of Ti immediately above the third metal layer and a fifth metal layer made of Au directly on the fourth metal layer, and heat-treated. It is preferable that
Thus, by assuming that the fourth metal layer made of Ti is formed on the third metal layer, impurities such as Be from the AuBe layer and Ga from the p-type semiconductor crystal are diffused to the fifth metal layer. Since the diffusion of Ga and Be is suppressed by the fourth metal layer, the fifth metal layer made of Au on the fourth metal layer further improves the wire bondability characteristics. The ohmic electrode can be obtained.

The fourth metal layer preferably has a thickness of 50 to 150 nm.
As described above, by setting the thickness of the fourth metal layer to 50 to 150 nm, it is possible to reliably suppress the diffusion of impurities such as Ga and Be into the upper fifth metal layer without impairing the productivity. The thickness can be made.

Furthermore, the fifth metal layer preferably has a thickness of 1.5 to 2 μm.
If the fifth metal layer is as described above, sufficient adhesion strength can be ensured when bonding the wire.

Furthermore, the present invention provides a light-emitting element that is diced from the semiconductor element described in the present invention.
As described above, since the ohmic electrode of the semiconductor element of the present invention is in close contact with a wire or a p-type semiconductor crystal, a light-emitting element diced from a semiconductor element having such an ohmic electrode is Since the electrode formed on the surface is in close contact with the wire or the p-type semiconductor crystal, the number of defects around the electrode is remarkably smaller than that in the prior art.

Here, the area of the electrode is preferably 50% or less of the surface area of the p-type semiconductor crystal after the dicing.
Thus, when the area of the electrode is 50% or less of the surface area of the p-type semiconductor crystal after dicing, the amount of light extracted from the light emitting layer can be made sufficiently high.

  As described above, according to the present invention, the cost due to an increase in the number of processes such as the number of vapor depositions can be suppressed, the occurrence of defects such as electrode turning and peeling can be prevented, and the LED lamp assembly process There are provided a method for forming an electrode, a method for manufacturing a light emitting element, a semiconductor element, and a light emitting element.

It is the figure which showed an example of the outline of the semiconductor element (a) of this invention, and the ohmic electrode (b) formed in the surface. It is the process flow which showed an example of the formation method of the electrode of this invention. It is a phase diagram of an AuBe alloy. FIG. 3 is a diagram showing an outline of ohmic electrodes of light emitting elements of Example 1 and Comparative Example 1. It is the image which observed the mode of the ohmic electrode of the light emitting element of Example 1 and Comparative Example 1. FIG. It is the figure which showed an example of the outline of the electrode formed in a light emitting element etc. FIG. It is the figure which showed an example of the flow of the manufacturing process of a common light emitting element.

Hereinafter, the present invention will be described more specifically.
First, an example of a method for manufacturing a light emitting element using a general compound semiconductor element will be described with reference to the drawings. FIG. 7 is a diagram showing an example of a flow of a general light emitting device manufacturing process.

  First, as shown in FIG. 7A, a light emitting layer 22 made of AlGaInP and a p-type GaP epitaxial layer (p-GaP layer) 23 are formed on an n-type GaP substrate (n-GaP layer) 21. Formed by phase growth.

  Thereafter, as shown in FIG. 7B, an AuSiNi alloy layer 24 is formed on the back side of the n-type GaP substrate 21 by a vapor deposition apparatus. Thereafter, the electrode shape is formed by a photolithography process and an etching process after being taken out from the vapor deposition apparatus, and then heat-treated to form an ohmic electrode to form the n-side electrode 24.

Next, as shown in FIG. 7C, an AuBe layer is formed on the upper surface of the p-type GaP epitaxial layer 23 by 300 nm, a Ti layer is formed by 80 nm, and an Au layer is formed by 1.5 μm on the deposition apparatus. Film.
Subsequently, photolithographic etching, Au layer etching, Ti layer etching, AuBe alloy layer etching, electrode shape etching treatment are performed, resist stripping, a heat treatment step at a temperature of 400 to 500 ° C., and ohmic contact p. The side electrode 25 is formed, and the semiconductor element 26 is manufactured.
For example, the p-side electrode 25 includes an AuBe layer (300 nm) as a lower layer in contact with a semiconductor crystal of a p-GaP layer and an Au layer as an upper layer. Here, the thickness of the p-side electrode 25 is usually about 1 to 2 μm.

Then, as shown in FIG. 7D, the semiconductor element 26 is cut and element-separated by a method such as dicing or braking for each element to obtain a light-emitting element 27.
In the above example, the case of using an n-type GaP substrate has been described. However, not only an n-type GaP substrate but also an n-type GaAs substrate can be used.

Here, when using an AuBe alloy for the p-type ohmic electrode, it is essential to perform a heat treatment in order to obtain an ohmic contact from the layered structure after the vapor deposition, whereby the p-type semiconductor inside or below the ohmic electrode is required. Interdiffusion occurs with the crystal, and Ga, Al, In, etc. and Be in the crystal reach the electrode surface.
The tendency of this diffusion is remarkable when a Ti layer is not provided in the ohmic electrode.

As a result, even if the outermost Au layer is made as thick as 1 to 2 μm, the wire bondability of the ohmic electrode is impaired as a result.
In addition, cracks may occur. This results in a state of roughness of the electrode surface, white cloudiness, and the like, and also reduces the image recognizability for picking up the chip in the lamp assembly process.

The AuBe alloy layer forms an alloy layer with the p-type semiconductor crystal by heat treatment.
However, peeling may occur in wire bonding during lamp assembly from the alloy layer portion. In appearance, a crack is formed in which the crystal below the electrode is removed together with the electrode. That is, the phenomenon that the crystal breaks into an electrode shape along the alloy layer under the electrode, not the electrode peeling, becomes a fatal failure for the LED lamp. Further, peeling between the AuBe alloy layer and the Ti layer may occur after the lamp is formed. Also, the Ti layer itself is side-etched with an etching solution, which causes turning and peeling.

That is, Be diffuses as a dopant for obtaining ohmic contact from the AuBe alloy layer to the p-type semiconductor crystal side, and Be also diffuses in the opposite direction, that is, the Au layer side for wire bonding of the electrode surface layer.
Even with an ohmic electrode having a structure in which a Ti layer is placed in a barrier layer, it was found from SIMS analysis that diffusion could not be completely prevented.
Here, when impurities such as Ga and Be are mixed in Au, the Au layer is cured, and it becomes difficult to attach by ultrasonic thermocompression bonding of wire bonding. This indicates that it is desirable to reduce the Be concentration in the ohmic electrode.

In mass production of light-emitting elements, particularly light-emitting diodes, about 10,000 to 40,000 elements can be obtained from a single semiconductor element wafer depending on the size of the chip. In actual mass production, light emitting diodes in units of 10 million to several hundred million units are mass-produced per month. As lamps used for industrial and consumer use, when used for signals, large outdoor displays, etc., the number of units used is from several hundred to ten thousand units.
Therefore, when the forward voltage VF is high due to failure or high ohmic contact resistance, it may lead to problems such as variations in the amount of light in the display. In addition, the failure rate is proportional to the number used and increases greatly, and the cost of reworking is also large.
Accordingly, it is desired that the ohmic electrode portion has a low contact resistance and is stable. In addition, even if the contact resistance is good, if it peels off, it becomes a fatal failure, so that the adhesion strength is required to be as strong as possible.

Actually, in order to ensure quality in the mass production process, the vapor deposition apparatus and the film formation process have been managed by various means in order to ensure a uniform film thickness in the vapor deposition process.
For example, in a large-scale vapor deposition machine, the substrate holder on which several hundred wafers are attached is rotated and revolved so that the physical position in the vapor deposition system, the incident angle of vapor evaporated from the vapor deposition material, and the like are uniform. Efforts have been made to equalize and stabilize by optimizing the operation. However, since there is a limit to this, other improvement methods are naturally required.

Therefore, the inventors of the present invention have made extensive studies in order to lower the Be concentration in the ohmic electrode as compared with the prior art, and in particular to improve wire bondability.
As a result, when forming the AuBe alloy layer, it was found that the AuBe alloy material is not used as it is as a vapor deposition source, but a mixture of AuBe alloy material and Au is used.

In addition, Au is continuously deposited before and after the AuBe alloy material and Au mixture is deposited, and Be is diffused into the upper and lower Au layers during the heat treatment to obtain ohmic contact and as a whole in the electrode. It has been found that the Be concentration can be reduced.
Based on this knowledge, the present inventors have completed the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a diagram showing a schematic example of a semiconductor element of the present invention and an ohmic electrode formed on the surface thereof.

As shown in FIG. 1A, the semiconductor element 10 of the present invention has, for example, at least each of (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ expressed by 1), and a carrier concentration of 1 × ¹⁰ 17 atoms / cm ³ or more n-type semiconductor crystal 11, and the light-emitting layer 12, a carrier concentration of 1 × ¹⁰ 17 atoms / cm ³ or more p-type semiconductor crystal 13 in this order, a p-type ohmic electrode 15 formed on the surface of the p-type semiconductor crystal 13, and an n-type ohmic electrode 14 formed on the surface of the n-type semiconductor crystal 11. It consists of
Here, in the above example, an example of a semiconductor crystal represented by AlGaInP is shown as the n-type semiconductor crystal, but the present invention is not limited to this, and GaAs can be used as the n-type semiconductor crystal.

  As shown in FIG. 1B, the p-type ohmic electrode 15 includes at least a first metal layer 16, a second metal layer 17, and a third metal layer 18 in order from the side closer to the p-type semiconductor crystal 13. The first metal layer 16 is an Au vapor deposition layer, the second metal layer 17 is an AuBe alloy layer obtained by vapor deposition of a mixture of AuBe alloy material and Au, and the third metal layer 18 is an Au vapor deposition layer. It is a thing.

As described above, the AuBe alloy material is not directly deposited on the p-type semiconductor crystal, but the Au deposition layer is first provided, so that the adhesion with the p-type semiconductor crystal is weaker than that of Au. Direct contact between AuBe and the p-type semiconductor crystal can be avoided. Thereby, the adhesion strength between the p-type semiconductor crystal and the electrode can be made stronger than before.
Further, since heat treatment is applied, Be diffuses from the second metal layer to the first metal layer side during this heat treatment, and the contact between the p-type semiconductor crystal and the electrode can be an ohmic contact, The resistance can be small.

Furthermore, since the Au vapor deposition layer (third metal layer) as the diffusion destination of Be is also provided on the AuBe alloy layer, the Be concentration in the ohmic electrode as a whole becomes lower than that of the prior art. ing.
From these results, it is possible to obtain a semiconductor element in which an ohmic electrode is formed which is in ohmic contact with the p-type semiconductor crystal and has better bondability and electrode strength with the wire than in the past.

Further, as the AuBe alloy material in the mixture used as the vapor deposition source for the second metal layer 17, a material having a Be concentration of 1 to 2 wt% can be used.
As described above, if an AuBe alloy having a stable Be concentration of 1 to 2 wt% is used as the AuBe alloy material, the Be concentration in the ohmic electrode can be further reduced and a stable semiconductor element can be obtained. .

And the total Be density | concentration of the 1st metal layer 16, the 2nd metal layer 17, and the 3rd metal layer 18 after heat processing can be 0.1-0.5 wt%.
As described above, the semiconductor element in which the ohmic electrode having the total Be concentration of 0.1 to 0.5 wt% of the first metal layer, the second metal layer, and the third metal layer after the heat treatment is formed is an ohmic electrode and p. The resistance between the semiconductor crystal and the type semiconductor crystal is small, and the risk of occurrence of defects in the adhesion between the wire and the electrode during wire bonding is minimized.

Furthermore, the thickness of the first metal layer 16 is 5 to 100 nm, the thickness of the second metal layer 17 is 10 to 200 nm, the thickness of the third metal layer 18 is 5 to 100 nm, and the thickness of these three layers. Can be made 300 nm or less.
Thus, if the thickness of each metal layer and the total thickness of the metal layers are within the above-mentioned ranges, the productivity is good because the deposition is not a long time, and the role as described above is sufficient. The thickness can be achieved.

In addition, the p-type ohmic electrode is further provided with a fourth metal layer 19 made of Ti just above the third metal layer 18 and a fourth metal layer 19 just above the third metal layer 18, as shown by 15 'in FIG. And a fifth metal layer 20 made of Au.
As described above, the ohmic electrode in which the fourth metal layer made of Ti is formed on the third metal layer has an element such as Ga or Al diffused from the p-type semiconductor crystal, or Be diffused from the AuBe layer. However, it is more strongly suppressed from reaching the fifth metal layer formed thereon.
Further, since the diffusion of impurities such as Ga and Be is suppressed by the fourth metal layer made of Ti, the purity of the fifth metal layer made of Au formed thereon can be increased, thereby further improving the wire bondability. It is a characteristic ohmic electrode.

The fourth metal layer 19 can have a thickness of 50 to 150 nm.
Thus, if the thickness of the fourth metal layer is 50 to 150 nm, the productivity is sufficiently high, and it is possible to reliably suppress the diffusion of impurities such as Ga and Be into the upper fifth metal layer. The thickness can be as large as possible.

Furthermore, the fifth metal layer 20 can have a thickness of 1.5 to 2 μm.
If the thickness of the fifth metal layer is 1.5 to 2 μm, the adhesion strength can be sufficiently high when bonding the wire.

A light emitting element can be obtained by dicing from the semiconductor element 10 as described above. Dicing can be performed as shown in FIG.
The p-type ohmic electrode of such a light-emitting element is in close contact with a wire or a p-type semiconductor crystal. For this reason, it is a light emitting element in which the defect around an electrode is remarkably few compared with the past.

Here, the area of the p-type ohmic electrode in the light-emitting element can be 50% or less of the surface area of the p-type semiconductor crystal after dicing.
Thus, if the area of the p-type ohmic electrode is 50% or less of the surface area of the p-type semiconductor crystal after dicing, the amount of light from the light-emitting layer shielded by the electrode can be reduced. The amount of light extracted can be made sufficiently high. The surface area here means the area on the side of the surface on which the electrode is formed.

The ohmic electrode on the semiconductor element or the light emitting element as described above can be formed by the electrode forming method of the present invention as described below, but the present invention is not limited thereto.
Hereinafter, although the formation method of the electrode of this invention is demonstrated with reference to figures, this invention is not limited to this.
FIG. 2 is a process flow showing an example of the electrode forming method of the present invention.

First, each is represented by (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and the carrier concentration is 1 × 10 ¹⁷ atoms / cm ³ or more. The n-type semiconductor crystal, the light emitting layer, and the p-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more are manufactured by a method such as vapor phase growth.
The n-type semiconductor crystal, the light-emitting layer, and the p-type semiconductor crystal may be manufactured by a general method. For example, after the light-emitting layer is vapor-phase grown on the n-type semiconductor crystal by the MOVPE method, the p-type semiconductor crystal is converted into HVPE. It can be formed by the method.

Thereafter, an n-type ohmic electrode is formed on the surface of the n-type semiconductor crystal.
The formation method and the composition of the electrodes may be appropriately selected according to the semiconductor element to be manufactured.
Thereafter, an electrode pattern of the n-side electrode is formed.
As a method for forming the electrode pattern, a general method can be used.

Thereafter, heat treatment is performed to make ohmic contact.
This heat treatment can also be a heat treatment under general conditions.

  Then, first, Au is vapor-deposited as a first metal layer on the surface of the p-type semiconductor crystal to form an Au vapor-deposited layer.

Thereafter, a mixture of AuBe alloy material and Au is deposited on the first metal layer as a second metal layer to form an AuBe alloy layer.
For example, the AuBe alloy material and Au may be deposited in the same resistance heating boat, for example, a tungsten boat.

  Here, an AuBe alloy material having a Be concentration of 1 to 2 wt% can be used. This is for the reason explained below.

In order to reduce the Be concentration in the ohmic electrode, it seems to be sufficient to lower the concentration of Be in the AuBe alloy material used during vapor deposition. However, there are some problems in using AuBe alloy materials.
Conventionally used AuBe alloy materials have Be concentrations of about 1 wt% and about 2 wt%. This is a concentration derived from the stability as an alloy material.

FIG. 3 shows an outline of the phase diagram of the AuBe alloy. The horizontal axis indicates that the ratio of Be on the right side and Au on the left side is large. This time, the case where the Be concentration is around 1 to 2 wt% will be described.
There is an eutectic point per Be20 at% in terms of the number of atoms. In terms of weight%, there is a eutectic point near 1.1 wt%. Below that, there is no eutectic point, and it can be seen that this is a so-called eutectic type I phase diagram with a liquidus line descending to the right from around the melting point of gold of 1060 ° C.
From the figure, it can be seen that near the eutectic point where Be is 20 at%, that is, per Be concentration of 1.1 wt%, the alloy is solidified while the Be concentration is stable. Below this, Au and AuBe 1.1 wt% are mixed and present in the eutectic state. AuBe 1 wt% close to the eutectic point can provide an alloy with few eutectics and a relatively stable Be concentration.

Further, as the low Be side, which is the object of the present invention, for example, when considering an AuBe alloy material having a Be concentration of 0.5 wt%, when melting AuBe from about 1000 ° C. to 0.5 wt% is solidified by cooling. From about 940 ° C., Au begins to precipitate as a solid as a primary crystal. However, until about 580 ° C., the concentration of Be in the liquid phase increases while solid of 100% Au is precipitated from the liquid phase side. Then, AuBe having a Be concentration of 20 at% is eutectic at 580 ° C.
That is, it becomes a eutectic state of Au and AuBe20at%. As a whole, it is 0.5 wt%, but Be partially contains 0 wt% and 2 wt%. The actual alloy is about 1 mmφ, and it cannot be said that the eutectic in the case of 0.5 wt% is uniformly mixed and solidified, and Be is not uniformly distributed. Therefore, if an AuBe alloy material having a Be concentration of 0.5 wt% is used, the Be concentration in the deposited AuBe alloy layer may not be stable.

Therefore, it is not very desirable to use an alloy material in such a state for forming an ohmic electrode that requires stability.
Further, the absolute amount of the ohmic electrode alloy used for one deposition is several g or less, and Au having a large specific gravity is further undesirable because the number of atoms is further reduced and the specific gravity is further reduced.

In the case of Be 2 wt%, it can be seen that it has a liquidus line with a reverse slope and is also difficult to produce in a region having no eutectic point. Therefore, it can be seen that even if the Be concentration is 2 wt%, the material is not guaranteed.
Incidentally, the next eutectic point is around 40 at% in terms of the number of atoms and 3 wt% in terms of the weight ratio. Any eutectic point is in the vicinity of 580 to 600 ° C.

As described above, since the AuBe alloy has a eutectic point around Be 1.1 wt%, if the Be concentration in the AuBe alloy material is reduced (for example, 0.5 wt%), the Be concentration becomes excessive or insufficient. There is a fear.
Thus, by using an AuBe alloy material having a stable Be concentration of 1 to 2 wt% as the alloy material, the Be concentration in the ohmic electrode can be more reliably stabilized at a low concentration.

Also, the amount of AuBe alloy material and the amount of Au mixed with it are adjusted so that the total Be concentration of the first metal layer, the second metal layer, and the third metal layer is 0.1 to 0.5 wt% after the heat treatment. can do.
As described above, the AuBe alloy is deposited when the second metal layer is deposited so that the total Be concentration of the first metal layer, the second metal layer, and the third metal layer is 0.1 to 0.5 wt% after the heat treatment. By adjusting the material and the amount of Au mixed therewith, the Be concentration in the ohmic electrode is within a range where ohmic properties can be obtained, and an ohmic electrode having a lower Be concentration than conventional ones can be further facilitated. Can be formed.
Accordingly, it is possible to more easily form an ohmic electrode having better wire bonding characteristics and adhesion to the semiconductor crystal and having a sufficiently small resistance between the semiconductor crystal and the electrode.

  Furthermore, Au is vapor-deposited as a third metal layer on the second metal layer.

The thickness of the first metal layer is 5 to 100 nm, the thickness of the second metal layer is 10 to 200 nm, the thickness of the third metal layer is 5 to 100 nm, and the total thickness is 300 nm or less. Can do.
By forming the thickness of each metal layer to be in the above range, it is not necessary to make the deposition time long, and the productivity can be improved. In addition, it is possible to sufficiently exhibit the effects required for each layer to exhibit.

Further, when forming the first metal layer, the second metal layer, and the third metal layer, the fourth metal layer made of Ti just above the third metal layer, and the second metal layer made of Au just above the fourth metal layer. Five metal layers can be formed.
Thus, by forming the fourth metal layer made of Ti on the third metal layer, Ga, Al, In, and Be from the AuBe layer from the p-type semiconductor crystal are formed up to the fifth metal layer. A barrier layer that strongly suppresses diffusion can be provided, and the concentration of impurities such as Ga and Be in the fifth metal layer that is the outermost surface layer can be further reduced.
Further, by forming the fifth metal layer made of Au on the fourth metal layer, even better wire bondability characteristics can be obtained.

The thickness of the fourth metal layer can be 50 to 150 nm.
By setting the thickness of the fourth metal layer to 50 to 150 nm, it is possible to achieve a thickness that can further suppress the diffusion of impurities such as Ga and Be into the fifth metal layer, and to deposit for a long time. This is unnecessary, and the manufacturing time can be shortened.

And the thickness of a 5th metal layer can be 1.5-2 micrometers.
Thus, a better wire bonding characteristic can be obtained by setting the thickness of the fifth metal layer to 1.5 to 2 μm.

Thereafter, an electrode pattern is formed.
As a method for forming the electrode pattern, a general method can be used, and it is particularly preferable to use either a lift-off method or an etching method.

By using an etching method for forming the electrode pattern, the electrode pattern can be formed with high accuracy in a short time.
Further, with the lift-off method, an electrode pattern can be formed with high accuracy, and an etching process using an acid or alkaline chemical having a large environmental load is not required.

Thereafter, by performing a heat treatment, the metal layer and the semiconductor crystal are brought into ohmic contact to form an ohmic electrode, whereby a semiconductor element can be manufactured.
In this example, the case where a semiconductor crystal represented by AlGaInP is used as the n-type semiconductor crystal has been described. However, the present invention is not limited to this, and the n-type semiconductor crystal may include GaAs in addition to AlGaInP. Can be used.

Here, the heat treatment conditions of this heat treatment can be set to 400 ° C. to 500 ° C. for 10 to 100 minutes in an inert gas atmosphere.
Under such heat treatment conditions, Be can be diffused to such an extent that the first metal layer and the p-type semiconductor crystal can be brought into ohmic contact, and each metal layer reacts with the heat treatment atmosphere or is heated. It is possible to reliably prevent the deterioration.

  As described above, first, the AuBe alloy material is not vapor-deposited alone, but the AuBe alloy material and Au are placed on the same boat, and the Be concentration in the AuBe alloy layer is made lower than in the prior art. Moreover, Au was vapor-deposited on both sides of the AuBe alloy layer as a destination where Be diffuses.

Thereby, since the first layer is not an AuBe alloy layer but an Au layer, the degree of adhesion at the time of vapor deposition is improved, and the Be concentration can be made lower than before after the heat treatment.
Also, by providing Au layers above and below, Be diffuses to the lower Au layer (first metal layer) side during the heat treatment, and reaches the p-type semiconductor crystal through it. That is, the Be concentration can be lowered, and an increase in ohmic resistance can be prevented.

The AuBe alloy itself is harder and more brittle than Au. That is, it is considered that the stress of the film remaining in the deposited AuBe alloy layer after vapor deposition is stronger than that in the pure Au layer. Actually, peeling may occur when the AuBe alloy material is directly deposited, but the peeling is drastically reduced when Au is vapor-deposited and then a mixture of AuBe alloy material and Au is vapor-deposited.
With these effects, good wire bondability can be obtained, adhesion after heat treatment is good, peeling is difficult, and ohmic electrodes with good reproducibility can be formed.

Moreover, the process of dicing the semiconductor crystal (semiconductor element) in which the electrode was formed can be performed after that.
Then, a light emitting element can be manufactured by performing arbitrarily the etching for removing the damage by dicing, the roughening process for high brightness, etc.

  The ohmic electrode formed by the electrode forming method of the present invention has good wire bondability characteristics and high adhesiveness, so that peeling does not easily occur and the structure is stable. For this reason, the light emitting element in which the ohmic electrode is formed using such an electrode forming method has remarkably fewer defects around the electrode as compared with the conventional case. Therefore, a high-quality light-emitting element with high yield can be manufactured at a lower cost than in the past.

Here, the surface area of the electrode can be 50% or less of the surface area of the p-type semiconductor crystal after dicing.
By setting the surface area of the electrode to 50% or less of the surface area of the p-type semiconductor crystal after dicing, the area of the electrode that obstructs light extraction can be made sufficiently small, so the amount of light extracted from the light emitting layer Can be secured sufficiently. Therefore, a light-emitting element with high emission luminance can be manufactured.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
Example 1
First, a semiconductor crystal composed of an n-type GaP layer, an AlGaInP light emitting layer, and a p-type GaP layer was produced.
Thereafter, the surface of the n-type GaP layer was washed with sulfuric acid / hydrogen peroxide and then washed with pure water.
Then, vacuum deposition of AuSi / Ni electrodes was performed at a vacuum degree of about 1 × 10 ⁶ Torr.
Thereafter, an n-side electrode was formed in the order of photolithography, pattern etching, resist stripping, and heat treatment.

Next, the surface of the p-type GaP layer was washed with sulfuric acid / hydrogen peroxide 3: 1: 1 and then washed with pure water.
Thereafter, Au was vacuum-deposited as a first metal layer by 20 nm under a vacuum degree of about 1 × 10 ⁶ Torr.
Next, as a second metal layer, a mixture of AuBe alloy material with a Be concentration of 1 wt% and Au mixed at a ratio of 2: 1, that is, Be diluted to about 0.6 to 0.7 wt%, is set in a tungsten boat. Then, the mixture was heated and melted, melted and evaporated at a low vapor pressure, and an AuBe alloy layer was deposited to a thickness of 60 nm.
And Au was vacuum-deposited as a third metal layer by 20 nm. The total Be concentration of these three layers was about 0.4 wt%.

On the Au layer as the third metal layer, Ti was vacuum-deposited by 70 nm as a fourth metal layer by EB gun vapor deposition. When the Ti layer is formed, the Ti ingot is heated with an electron beam for about 10 minutes with a current that does not evaporate while the shutter is closed, and is adsorbed by Ti such as moisture, oxygen, and nitrogen in the film formation. Ti was evaporated after degassing to release the components that would be.
Then, Au was vacuum-deposited as a fifth metal layer on the Ti layer by 1.5 μm.

Next, a 120 μm square electrode was formed by photolithography.
Thereafter, heat treatment was performed to obtain ohmic contact. When the resistance between the produced ohmic electrode and the pGaP layer was evaluated, it was about 5Ω between adjacent electrodes. Moreover, the outline of the produced ohmic electrode was as shown to 15 'of Fig.4 (a).

Thereafter, the semiconductor element was diced at a pitch of 280 μm, and a square light emitting element chip having a side of about 250 μm was cut out.
After that, as a dicing strain removal, etching was performed for 4 minutes with sulfuric acid / hydrogen peroxide at a liquid temperature of 40 ° C. to manufacture a light emitting device.
Thereafter, roughening etching was performed on the element surface to improve the light extraction efficiency.

An evaluation experiment as shown below was performed on the manufactured light-emitting element.
First, shear strength was evaluated in order to evaluate the adhesion between the produced ohmic electrode and the p-type GaP layer.
In addition, it was evaluated whether or not the electrodes were peeled off or turned up by appearance inspection during the process or at the final stage.
And the resistance between electrodes at the time of energizing 20 mA was evaluated using the curve tracer. These results are shown in Table 1.
Furthermore, in order to evaluate the external appearance of the electrode, an image of the produced electrode was taken. The result is shown in FIG.

(Comparative Example 1)
A light emitting device was manufactured in the same manner as in Example 1 except that an electrode having a structure as shown in FIG.
The electrode is formed by vacuum-depositing an AuBe alloy material having a Be concentration of 1 wt% on the first layer to form an AuBe layer 37 having a thickness of 200 nm, and then Ti is formed in the same manner as the fourth metal layer of Example 1. A Ti layer 39 was formed by vapor deposition with a thickness of 80 nm, and Au with a thickness of 1.5 μm was vapor-deposited on the surface to form an Au layer 40, and a p-side electrode 35 was formed.

And evaluation similar to Example 1 was performed with respect to the produced light emitting element.
The results of shear strength, appearance inspection, and interelectrode resistance are shown in Table 1, and the electrode image is shown in FIG.

The peel shear strength of the ball bond portion of wire bonding was 40 g for the electrode of Comparative Example 1, whereas the electrode of Example 1 was sufficiently strong at 60 g, which was improved by about 20 g compared to the conventional structure. I found out.
The electrode of Example 1 was in a good state with no peeling or turning. This is considered to be an effect of the Au layer that hits the base of the AuBe alloy layer. Moreover, since the Be concentration in Au became low, it is considered that gold was hardened and approached pure gold.
Furthermore, the electrode of Example 1 had better surface visibility than the electrode of Comparative Example 1, and the camera was well recognized by the apparatus.

FIG. 5A shows the appearance of the ohmic electrode of Example 1 observed.
As can be seen from this figure, the p-side ohmic electrode of the light-emitting element of Example 1 was peeled off from the underlayer, and peeled between the AuBe alloy layer and the Ti layer, even after etching with two strong acids and mixed acids. In addition, defects such as turning up of the outer periphery of the electrode due to side etching of the Ti layer itself did not occur.
On the other hand, as shown in FIG. 5B, some of the ohmic electrodes of Comparative Example 1 were turned up. Moreover, it turned out that the surface is also rough compared with the electrode of Example 1.

(Example 2-4, Comparative Example 2-4)
In Example 1, the shape and size of the electrode were changed (the electrode width was 100 μm (Example 2), the electrode was circular with a diameter of 80 μm (Example 3), and the electrode was circular with a diameter of 60 μm (implementation) A light emitting device was produced in the same manner as in Example 1 except for Example 4)).
In Comparative Example 1, the shape and size of the electrode were changed (the electrode width was 100 μm (Comparative Example 2), the electrode was circular with a diameter of 80 μm (Comparative Example 3), and the electrode was circular with a diameter of 60 μm. A light emitting device was manufactured in the same manner as in Comparative Example 1 except that (Comparative Example 4)).
And in order to evaluate the adhesiveness with the p-type GaP layer of the produced ohmic electrode, the following evaluation experiment was done with respect to the semiconductor element and light emitting element of Examples 1-4 and Comparative Examples 1-4.

First, before the heat treatment, a peel-off test using an adhesive sheet (SPV-224 tape (manufactured by Nitto Denko)) and a peel-off test using an adhesive sheet (TR-20 tape (manufactured by Tsukasa Corporation)) were performed. In addition, a scratch test was performed after the heat treatment. The results are summarized in Table 2.
In Table 2, ◎, ○, Δ, × in the column of the peel-off test results: ◎: No peeling, ○: No turning at the edge, Δ: Turning at the edge, ×: Some peeling Is. In the scratch test column, ◎, ○, Δ, × indicate ◎: not easily peeled off, ○: partly cut, Δ: electrode edge turned up, ×: easily peeled off.

As shown in Table 2, the ohmic electrodes of the light-emitting elements of Examples 1 to 4 are good results in all of the two types of peel-off tests before heat treatment and the scratch test after heat treatment, and the adhesion to the p-type GaP layer. Was found to be very good. Moreover, even if the electrode size was reduced, no decrease in adhesion was observed.
On the other hand, it has been found that the electrodes of the light emitting elements of Comparative Examples 1 to 4 have weaker adhesion with the p-type GaP layer as the electrode area becomes smaller.
From these results, it was found that the electrode forming method of the present invention is more effective as the size of the electrode is reduced.

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

3 ... Semiconductor crystal, 5 ... Ohmic electrode, 7 ... Ohmic layer, 9 ... Bonding pad layer,
10: Semiconductor element,
11 ... n-type semiconductor crystal, 12 ... light emitting layer, 13 ... p-type semiconductor crystal,
14 (n-type) ohmic electrode, 15, 15 '... (p-type) ohmic electrode,
16 ... 1st metal layer, 17 ... 2nd metal layer, 18 ... 3rd metal layer, 19 ... 4th metal layer, 20 ... 5th metal layer,
21 ... n-GaP layer (n-type semiconductor crystal), 22 ... light emitting layer, 23 ... p-GaP layer (p-type semiconductor crystal),
24 ... n-side electrode, 25 ... p-side electrode,
26 ... Semiconductor device, 27 ... Light emitting device,
35 ... Ohmic electrode (p-side electrode), 37 ... AuBe layer, 39 ... Ti layer, 40 ... Au layer.

Claims (20)

At least an n-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) And a carrier concentration represented by (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is 1 × 10 ¹⁷ atoms / A method of forming an ohmic electrode on a semiconductor crystal in which a p-type semiconductor crystal of cm ³ or more is formed in this order,
Au at least as a first metal layer is vapor-deposited on the surface of the p-type semiconductor crystal of the semiconductor crystal, and a mixture of AuBe alloy material and Au is vapor-deposited as a second metal layer on the first metal layer. And forming an ohmic electrode by depositing Au as a third metal layer on the second metal layer and then performing a heat treatment.   2. The method of forming an electrode according to claim 1, wherein the AuBe alloy material is one having a Be concentration of 1 to 2 wt%.   Adjusting the amount of the AuBe alloy material so that the total Be concentration of the first metal layer, the second metal layer, and the third metal layer after the heat treatment is 0.1 to 0.5 wt%. The method for forming an electrode according to claim 1, wherein the electrode is formed.   The thickness of the first metal layer is 5 to 100 nm, the thickness of the second metal layer is 10 to 200 nm, the thickness of the third metal layer is 5 to 100 nm, and the total thickness is 300 nm or less. The method for forming an electrode according to any one of claims 1 to 3, wherein:   When forming the first metal layer, the second metal layer, and the third metal layer, a fourth metal layer made of Ti is formed immediately above the third metal layer, and Au is formed directly on the fourth metal layer. 5. The method of forming an electrode according to claim 1, wherein a fifth metal layer is formed.   The method for forming an electrode according to claim 5, wherein the thickness of the fourth metal layer is 50 to 150 nm.   The thickness of the said 5th metal layer shall be 1.5-2 micrometers, The formation method of the electrode of Claim 5 or Claim 6 characterized by the above-mentioned.   8. The electrode forming method according to claim 1, wherein the electrode pattern is formed by any one of a lift-off method and an etching method.   The electrode forming method according to any one of claims 1 to 8, wherein a heat treatment condition of the heat treatment is 400 ° C to 500 ° C for 10 to 100 minutes in an inert gas atmosphere. . At least an n-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) And a carrier concentration represented by (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is 1 × 10 ¹⁷ atoms / forming a semiconductor crystal by forming a p-type semiconductor crystal of cm ³ or more in this order;
Forming an electrode on the surface of the p-type semiconductor crystal using the method for forming an electrode according to any one of claims 1 to 9;
And a step of dicing the semiconductor crystal on which the electrode is formed.   The method of manufacturing a light emitting element according to claim 10, wherein a surface area of the electrode is 50% or less of a surface area of the p-type semiconductor crystal after the dicing. At least an n-type semiconductor crystal having a carrier concentration of 1 × 10 ¹⁷ atoms / cm ³ or more and (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) And a carrier concentration represented by (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is 1 × 10 ¹⁷ atoms / A semiconductor element in which an ohmic electrode is formed on a semiconductor crystal in which a p-type semiconductor crystal of cm ³ or more is formed in this order,
The electrode comprises at least a first metal layer, a second metal layer, and a third metal layer in order from the side close to the p-type semiconductor crystal,
The first metal layer is an Au vapor deposition layer, the second metal layer is an AuBe alloy layer on which a mixture of AuBe alloy material and Au is vapor-deposited, and the third metal layer is composed of an Au vapor deposition layer and a heat treatment. There is a semiconductor element.   The semiconductor element according to claim 12, wherein a material having a Be concentration of 1 to 2 wt% is used as the AuBe alloy material.   The total Be concentration of the first metal layer, the second metal layer, and the third metal layer after the heat treatment is 0.1 to 0.5 wt%. The semiconductor element as described.   The thickness of the first metal layer is 5 to 100 nm, the thickness of the second metal layer is 10 to 200 nm, the thickness of the third metal layer is 5 to 100 nm, and the total thickness is 300 nm or less. The semiconductor device according to claim 12, wherein the semiconductor device is provided.   The electrode further includes a fourth metal layer made of Ti just above the third metal layer and a fifth metal layer made of Au just above the fourth metal layer and subjected to heat treatment. 16. The semiconductor element according to claim 12, wherein the semiconductor element is any one of the above.   The semiconductor element according to claim 16, wherein the fourth metal layer has a thickness of 50 to 150 nm.   18. The semiconductor device according to claim 16, wherein the fifth metal layer has a thickness of 1.5 to 2 μm.   A light-emitting element that is diced from the semiconductor element according to any one of claims 12 to 18.   The light emitting device according to claim 19, wherein an area of the electrode is 50% or less of a surface area of the p-type semiconductor crystal after the dicing.

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