JPH11220119A - Ohmic electrode and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal electrode structure of a p-type InP compound semiconductor, having high ohmic characteristic in which a thin reaction layer can be formed at the same time as with an n-type semiconductor electrode through a low-temperature heat treatment of 400 deg.C or lower. SOLUTION: An ohmic electrode is constituted in a multilayered structure, formed by sequentially depositing a plurality of metal layers containing a first layer 21 composed of a transition metal, a second layer 22 composed of Zn, a third layer 23 composed of a transition metal on a single-crystal p-type InP compound semiconductor substrate 1. In the electrode, in addition, a film can be formed together with an n-type semiconductor electrode through low- temperature heat treatment of <=400 deg.C after the metallic layers are deposited. This p-type ohmic electrode 2 can be formed on the substrate at the same time as with the n-type ohmic electrode at a low heat-treating temperature of 400 deg.C or lower. In addition, since the contact specific resistance of the electrode 2 is small at 10<-5> Ωcm<2> and a reaction layer has a uniformly small thickness of 0.1 μm or less, a metal electrode of an InP compound semiconductor can be obtained which is for higher in practicability and reliability, as compared with the conventional p-type ohmic electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ohmic electrode suitable for an InP-based compound semiconductor device, particularly a p-type InP-based compound semiconductor, and a semiconductor device using the same.

[0002]

2. Description of the Related Art Conventionally, ohmic electrodes used for semiconductor devices based on p-type InP-based compound semiconductors, for example, photodiodes, laser diodes, and light-emitting diodes, are usually made of Au-Zn-based metal. I have been. The reason why Au is used in the stacked electrode made of an Au—Zn-based metal is that Au is deposited after deposition of the metal film.
By heating (heat treatment) in the temperature range of 00 to 450 ° C,
Reacts with the InP-based compound semiconductor substrate, penetrates the natural oxide film present on the substrate surface and diffuses into the substrate, thereby obtaining electrical contact between the substrate and the metal film It is. In order to obtain electrical contact between the base material and the metal film as described above, it is necessary to select a material that reacts with the base material at a high temperature and thermally diffuses with the metal constituting the metal film. The reason why Zn is used in this electrode is that Zn acts as a p-type impurity on the base material. That is, the metal diffuses into the substrate by heating after film formation, and a high concentration of p
This is because a type dope layer is formed, and as a result, holes can be tunneled through a Schottky barrier generated at the interface with the substrate after the metal film is deposited, and good ohmic characteristics can be obtained. Only in this case Au, electrical contact as described above can be obtained, but due to the low p-type carrier concentration of the substrate surface (the concentration of normally about 10 ¹⁸ cm ^-3), a metal film and the base material both Electrical contact resistivity at the contact interface of aluminum
(Hereinafter, in the present invention, this electrical contact specific resistance is simply referred to as contact specific resistance.) Characteristics cannot be obtained, and it is necessary to diffuse Zn, which is a p-type impurity, to the substrate surface to increase the carrier concentration on the substrate surface. .

[0003] Sumitomo Electric, No. 141, pp. 100-104
(September, 1992) introduces a p-type InP-based compound semiconductor using an impurity-free InP-based compound semiconductor crystal as a base material and providing an Au / Zn / Au-based metal electrode.
According to the document, the thickness of Au in the first layer and the thickness of Zn in the second layer are 50 nm and 30 nm, respectively, and the thickness of Au in the third layer is 2 nm.
The dependency of the contact specific resistance on the thickness of the third layer is discussed while changing the value between 0 and 500 nm. According to this, only when the thickness of the third layer becomes 100 nm or more, good electrical contact with the substrate is obtained, and Zn of the second layer forms a high carrier concentration layer in the surface of the substrate. to, specific contact resistance is stated to be a 10 ^{over 5} [Omega] cm ² units satisfactory ohmic electrodes. According to the description in the right column on page 100 of the same magazine, a 100 nm-thick T
The contact resistivity is minimized by depositing an Au film having a film thickness of 250 to 350 nm as a fifth layer as a fifth layer and heating the film at a temperature of 435 ° C. in a nitrogen atmosphere to alloy the deposited film. Has also been introduced. However, when the thickness of the deposited film of the third layer is 100 nm or more, a good contact resistivity can be obtained, while the thickness of the alloyed layer (hereinafter referred to as a reaction layer) on the surface of the base material is not good. The layer becomes uniform, and in some places, a protruding portion in which the same layer is deeply penetrated into the base material by about 0.5 μm into a pyramid shape is generated. FIG. 1 schematically shows a cross section in this state. When this protrusion grows, it reaches the operation layer of the semiconductor device and causes the device to fail. As described above, in the Au / Zn-based electrode, by increasing the thickness of the reaction layer, a good ohmic electrode having a small contact specific resistance can be obtained, but the above-described problem still remains.

Various measures have been considered to solve this problem and make the thickness of the reaction layer relatively small. For example, Electron. Mater. Volume 237 of Volume 20
According to the description on page 1991. G. FIG. Ivey et al., By additionally laminating a Pd layer with a similar metal layer,
Even a shallow reaction layer has good contact resistivity. Au / Pd / Z on a p-type InP-based compound semiconductor substrate.
The n / Pd-based metal electrode provided, by heating at a temperature in the range of four hundred twenty to four hundred twenty-five ° C., to obtain the intended 7 × 10 ^-5 good contact resistivity of [Omega] cm ^2. Also, for example, Appl. Phys
s. Lett. According to the description in Vol. 66, p. 3310 (published in 1995), L. et al. C. Wang et al. Describe Ge / Pd / Zn
/ Pd-based metal layer is formed by heating at a temperature of 420 ° C., to obtain the intended ^{10-2 5} [Omega] cm ² units specific contact resistance. Also, Appl. Phys. Lett. Seventh
According to Volume 0, page 99 (1997), Moon-Ho
Park et al. Provided a Pd / Sb / Zn / Pd-based metal electrode and heated it at 500 ° C. to obtain a thin material having a thickness of 10 to 15 nm and a low contact resistivity.

These ohmic electrodes are reaction layers as thin as 0.1 μm or less from the surface of the base material, but all require heating (heat treatment) at a high temperature exceeding 400 ° C. In many cases, a p-type electrode and an n-type electrode are simultaneously arranged in the same semiconductor wafer, but an Au / Ge / Ni-based metal film widely used as an ohmic electrode for the n-type InP-based compound semiconductor is formed. A suitable temperature for heating at that time is 350 to 400 ° C. Therefore, in such a case, heating must be performed at a high temperature exceeding 400 ° C. in accordance with the heating temperature of the p-type electrode. However, when heated at such a high temperature, the reaction with the base material progresses too much on the n-type electrode side, and the reaction diffusion of the metal layer component into the base material progresses too much, so that the component penetrates deeply into the wafer and the wafer There is a problem that the original practical characteristics deteriorate. In the ohmic electrode, in order to improve the bonderized _Lee ring of the connection wires suppress the sheet resistance at the connection portion with the outside, further provided Au layer on the third layer. However, if the heating temperature during film formation exceeds 400 ° C., Au
Diffusion progresses abnormally, which may cause deterioration of the characteristics of the semiconductor wafer. Thus, for example according to Japanese Patent Laid-Open No. 3-16176, the 10 ^{@ 5} [Omega] cm ² units low specific contact thickness in resistance on Au / Zn / Au system of electrodes 50 to 500 nm, Ti
Alternatively, an attempt has been made to suppress the deterioration of the wafer due to the abnormal diffusion of Au by providing a stopper layer made of Cr and having a thickness of 50 to 500 nm, and arranging a top layer of thick Au thereon. However, this electrode also requires heating at a high temperature of 430-450 ° C.

[0006]

Therefore, according to the above-mentioned prior art, 400 ° C.
A thin reaction layer was formed by the following low-temperature heating, and good ohmic characteristics could not be obtained. An object of the present invention is to solve this problem, ^{10-2 5} [Omega] cm ² units low contact resistance can be obtained, and the reaction layer is less 0.1 [mu] m p
An object of the present invention is to provide a metal electrode structure of a type InP-based compound semiconductor.

[0007]

The ohmic electrode provided by the present invention has a multilayer structure laminated on a p-type InP-based compound semiconductor crystal substrate (hereinafter simply referred to as a substrate). And an ohmic electrode comprising a plurality of metal layers including a first layer made of a transition metal, a second layer made of Zn, and a third layer made of a transition metal in this order from the base material side. Preferably, the thickness of each of these layers is 2 to 10 nm, 5 to 20 nm, 10 to 10 in the order of the first layer, the second layer, and the third layer.
It is of 200 nm.

Further, the ohmic electrode provided by the present invention is such that, based on the above structure, a fourth layer made of a refractory metal and a fifth layer made of Au are sequentially arranged on the third layer. . In this case, preferably, the thicknesses of the fourth layer and the fifth layer are respectively 20 to 200 nm and 100 to 500 nm.
nm.

[0009] Ohmic electrode of the present invention, a compound semiconductor crystal is a target base material which has the above structure, InP or _{Ga x In 1-x As y} P 1-y ( provided that x,
y is a positive number equal to or less than 1 or 0, and y is y = 1-2.
1x). The first and third layers are composed of Pd, Co, Pt, R
h, Ni, or Ir.

In the method of manufacturing an ohmic electrode according to the present invention, a step of depositing a plurality of metal layers including a first layer made of a transition metal, a second layer made of Zn, and a third layer made of a transition metal in order from the substrate side. And then performing a heat treatment at a temperature within the range of 350 to 400 ° C. Further, in the method of manufacturing an ohmic electrode according to the present invention, in the step of depositing the plurality of metal layers, a step of sequentially depositing a fourth layer made of a high melting point metal and a fifth layer made of Au on the third layer. The production method also includes: Hereinafter, the ohmic electrode of the present invention will be described in detail.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The ohmic electrode provided by the present invention has a metal multilayer structure laminated on a p-type InP-based compound semiconductor crystal as a target substrate. Substrates of interest include InP or other III-
Any of p-type semiconductor crystals composed of a mixed crystal composition with a group V semiconductor is available. The latter may be any within the range, a few particularly mixed crystal of GaAs formula _{Ga x In 1-x As y} P 1-y ( provided that x, y is 1 or less positive Among these Or, it is 0, and y is a number satisfying y = 1-2.1x).

The metal multilayer structure provided on the base material includes a plurality of metal layers including a first layer made of a transition metal, a second layer made of Zn, and a third layer made of a transition metal in this order from the base material side. It consists of The transition metal arranged in the first layer reacts with the substrate at a lower temperature through the natural oxide film on the surface of the substrate as compared with Au described above, and can form a uniform reaction layer having a uniform thickness. The thickness of the first layer is preferably 2 to 10 nm. If it is less than 2 nm, the film does not become a uniform film, but becomes an island, and it is difficult to form a film that completely covers the surface of the substrate. On the other hand, Zn hardly adheres directly to the surface of the InP base material, so that the amount of doping may be reduced. For this reason, it may be difficult to develop sufficient ohmic electrode characteristics as an object of the present invention. If it exceeds 10 nm, Zn in the second layer tends to hardly diffuse into the base material. In this first layer, in particular, Pd, Co, Pt, Rh,
Either Ni or Ir metal can be suitably used.

The second layer provided on the first layer is made of Zn. Zn diffuses into the base material, doping the surface of the base material with a high concentration of p-type carriers, and promotes the formation of an ohmic electrode having a low contact resistivity. The thickness of the second layer is preferably 5 to 20 nm. If the thickness is less than 5 nm, it tends to be difficult to exhibit sufficient ohmic electrode characteristics aimed at by the present invention.
Excessive Zn easily reacts with P to form a Zn-P-based compound, which may degrade the properties of the semiconductor.

The third layer provided on the second layer is composed of a transition metal. Specifically, for example, Pd, Co, Pt, R
Metals such as h, Ni, and Ir. The layer has a function of reacting with the surface of the base material in relation to the Zn of the second layer and controlling the diffusion of Zn of the second layer. The thickness of this layer is
Preferably it is 10 to 200 nm. If the thickness is less than 10 nm, the lower layer made of Zn is easily oxidized by the heat treatment atmosphere, and as a result, the diffusion of the same component into the base material tends to be inhibited. That is, the function of protecting the Zn layer from the atmosphere may be reduced. When it exceeds 200 nm,
Zn tends to diffuse in the electrode surface direction opposite to the substrate direction.

According to the ohmic electrode of the present invention, the first to third metal layers are sequentially laminated, and particularly preferably, the thickness of each layer is controlled within the above-mentioned range. The above-described functions of the respective layers are synergistically combined with each other to provide an n-type metal electrode and
0 ℃ together allowing granted in the following heat treatment, 10 ^{@ 5} Omega
It is possible to provide a metal electrode of a p-type InP-based compound semiconductor having a contact specific resistance of the order of cm ² and a reaction layer of 0.1 μm or less and excellent in practicality, which has not been achieved conventionally.

Further, according to the ohmic electrode provided by the present invention, in the basic structure comprising the first to third layers, a fourth layer made of a refractory metal is further provided on the third layer.
One in which a fifth layer made of u is sequentially arranged is also included. The refractory metals forming the fourth layer include Nb, W, Mo, Ta,
Examples include Ti and Pt. In this case, the fourth refractory metal layer serves to prevent contact between the uppermost Au layer provided thereon and the third transition metal layer, and to prevent mutual diffusion during the heat treatment. I do. The preferred thickness of this layer is between 20 and 200 nm. If it is less than 20 nm, it becomes difficult to suppress the interdiffusion between Au in the fifth layer and the transition metal in the third layer. If the thickness exceeds 200 nm, the thickness of the entire electrode becomes large, so that the pattern is not easily removed by the lift-off method frequently used for fine processing, and the efficiency of vapor deposition tends to decrease. Uppermost Au layer, as well as functions to reduce the sheet resistance of the electrode, there is a function of improving the wire Bonde _Lee ring properties, in order to sufficiently exhibit their functions, the range that the film thickness of 10~500nm It is desirable to control with.

According to the ohmic electrode of the present invention, the above-described fourth and fifth metal layers are additionally laminated on the first to third electrodes sequentially, and particularly preferably, the film of each additional layer is further laminated. When the thickness is controlled within the above range, the functions of the respective layers described above are synergized, and the application of the n-type metal electrode and the application of the p-type metal electrode by heat treatment at 400 ° C. or lower can be performed simultaneously. , 10 ^{over 4 Ωc}
has a specific contact resistance of less than m ^2, and the reaction layer is not more 0.1μm or less, wire Bonde _Lee in yet low sheet resistance
It is possible to provide a metal electrode of a p-type InP-based compound semiconductor, which is excellent in the conventional technology, and which is not excellent in the past.

Next, the method for manufacturing the ohmic electrode of the present invention will be described in detail. In manufacturing the ohmic electrode of the present invention, first, a p-type InP-based compound semiconductor crystal is prepared as a target substrate. The p-type InP-based compound semiconductor substrate is as described above. First, a plurality of metal layers including a first layer made of a transition metal, a second layer made of Zn, and a third layer made of a transition metal are sequentially deposited from the substrate side. Deposition is performed one by one in order from the first layer from the viewpoint of controlling the individual film thickness, but any method may be used as long as it is an existing thin film forming method. Example, a vacuum deposition method, a sputtering method, can be applied a method such as ion plating _Lee ring method, usually is preferably performed in a vacuum deposition layer by layer. Note that, in this case, the source material of the metal layer is a material such as a metal wire or a metal particle when vapor-deposited by a resistance heating method, and a particle, a rod, or an ingot when vapor-deposited by an electron beam vapor deposition method. Use a metal lump. In any case, the purity is preferably 3N or more.

Thereafter, a heat treatment is performed at a temperature in the range of 350 to 400.degree. In this case, the atmosphere is a non-oxidizing gas atmosphere or a reduced pressure atmosphere containing such a gas in order to prevent oxidation of the metal deposition layer and the substrate. As the atmosphere gas, for example, an inert gas such as argon, nitrogen, and helium,
A reducing gas such as hydrogen is usually used. The pressure of the atmospheric gas is preferably in the range of ^{10-2 2} Torr to atmospheric pressure. 10 ^{- 2}
If the pressure is less than Torr, if the container is not sufficiently airtight, the influence of oxygen from the outside may appear, and if the pressure exceeds atmospheric pressure, it becomes necessary to increase the pressure resistance of the container. There is. Note In and atmosphere prepared cases, in order to prevent oxidation of the metal deposited layer and the substrate, once a vacuum of up to about 10 ^{over 3} Torr, and a method of subsequently introducing a predetermined atmospheric gas at a predetermined pressure It is desirable. Keep in the above temperature range
The (heat treatment) time may be usually about 30 seconds to 10 minutes.

[0020]

(Embodiment 1) An embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a diagram schematically showing the basic structure of the cross section of the ohmic electrode according to the embodiment of the present invention. In the figure, reference numeral 1 denotes a base made of a p-type InP-based compound semiconductor crystal, reference numeral 2 denotes a first layer 21 made of a transition metal provided on the base, and a first layer 21 made of Zn provided thereon. The ohmic electrode of the present invention is composed of two layers 22 and a third layer 23 made of a transition metal provided thereon.

First, as Sample 1, an electrode having the above basic structure, in which the first layer was composed of Pd, the second layer was composed of Zn, and the third layer was composed of Pd. InP compound semiconductor crystals having lengths, widths and thicknesses of 9 mm, 18 mm and 0.4 mm, respectively, are prepared as a base material, and 99.95% pure Pd and 99.999% Zn are used as a source of each electrode layer. did. After arranging the substrate in a vacuum evaporation apparatus, first, a first layer is formed to a thickness of 3 nm by a Pd source, and then a second layer is formed to a thickness of 10 nm by a Zn source, and a third layer is formed to a thickness of 30 nm by a Pd source. , Respectively. Next, in the nitrogen atmosphere containing 5% of hydrogen gas, the base material on which the metal layer was laminated was adjusted to a gas pressure such that the total pressure was 1 atm, and 340 ° C, 350 ° C, 375 ° C, 400 ° C, 420
Heat treatment was performed at each temperature of 2 ° C. for 2 minutes. FIG. 3 shows the relationship between the contact resistivity of the obtained electrode and the heat treatment temperature.
The numerical values attached to the respective data are the values of the contact specific resistance. 375 Contact resistivity of 7 × 10 ^{over 5} [Omega] cm ² in the heat treatment of ℃ was obtained. Note that the contact resistivity is determined by the transmission line model method.
(Transmission Line Model). FIG. 4 schematically shows an enlarged cross section of the ohmic electrode of Sample 1. In the figure, 2 is an ohmic electrode, and 3 is a reaction layer. It can be seen that the reaction layer has a thickness of less than 0.1 μm and a uniform thickness, unlike the reaction layer shown in FIG.

The same substrate is used, the above-mentioned p-type deposition layer is provided, and n-type AuGeN
When an i-type deposited layer was provided and subjected to a simultaneous heat treatment at 375 ° C. in the same atmosphere as above, the reaction layer on the n-type side also had a uniform thickness similar to that of the p-type, and a contact resistivity of 1: 1.
0 ^{over 5 Ωcm 2} units of what normal was obtained. The base material is I
G, which is a mixed crystal composition of InP and GaAs instead of nP
a _0.15 In _0.85 As _0.33 P _0.67 (x = 0.15, y = 0.15
The same metal layer deposition as Sample No. 1 except that 33) was used.
When an ohmic electrode was manufactured under the heat treatment conditions, each evaluation result comparable to that of Sample No. 1 was obtained.

Next, on the same base material as above, the respective layers were deposited in the same procedure as in Example 1 using the first layer, second layer, and third layer sources made of the same metal as above. . Thereafter, the substrate on which the metal film was deposited was subjected to a heat treatment at 375 ° C. for 2 minutes under the same atmosphere as in Example 1 to form a film having the thickness shown in Table 1. Table 1 shows the resulting contact resistivity and the state of the reaction layer of each sample including the sample 1. Sample Nos. 15, 16, 17, and 18 are samples in which the metals of the first and third layers are replaced with Rh, Ni, Ir, and Au, respectively (the film thickness is the same as that of the Pd sample). From these results, the thicknesses of the first layer, the second layer, and the third layer were 2 to 2, respectively.
10 nm, 5 to 20 nm, by controlling the range of 10 to 200 nm, at 10 ^{over 5} [Omega] cm ² units low contact resistivity, thickness of the reaction layer is as thin as 0.1μm or less, the range the thickness of each layer It can be seen that an excellent ohmic electrode having a reaction layer with a more uniform thickness can be obtained as compared with the case where no control is performed.

[0024]

[Table 1]

(Example 2) In the same procedure as in Example 1, first, second and third metal films having the same metal type and thickness as those of Sample Nos. 1, 12, and 17 were deposited. Fourth and fifth layers of metal films having various metal types and thicknesses shown in Table 2 were deposited.
Heat treatment was performed at 5 ° C. for 1 hour. The numerical values in the lower layer base material number column of Table 2 are the corresponding sample numbers of Example 1 in which the first, second, and third metal films are the same. When the contact resistivity and the state of the reaction layer of each of the obtained electrode samples were confirmed, each of the samples of the present invention of Sample Nos. 19 to 33 was almost the same as the corresponding lower layer base material sample. For a more Bonde _Lee ring of wire, a method of pulling the Au wire having a diameter of 20μm by thermocompression attached to the top layer of Au Sogai surface, in a direction perpendicular to the fixed electrode outermost surface of the same wire to the substrate side Confirmed. As a result, it was confirmed that each of the samples can withstand a tensile load exceeding 2 g, which is a practical level. In particular the thickness of the fourth layer and fifth layer, respectively 20 to 200 nm, by controlling the range of 100 to 500 nm, the sheet resistance value is small, in particular obtained with ohmic electrode excellent in wire bonderized _Lee ing properties You can see that. In the table, the symbol ○ in the column of wire bonding properties indicates a load exceeding 4 g, and the symbol □ indicates a load exceeding 3 g and 4 g.
△ indicates that the wire peeled off under a load of 2 g or more and less than 3 g.

In addition, using a substrate on which the same first to third layers as the sample No. 26 in Table 2 were deposited, an n-type Au / Ge / Ni-based deposited layer was applied to another portion of the substrate, Further, Nb as the fourth layer and Au as the fifth layer were deposited at the same film thickness as that of Sample No. 26, and were simultaneously heat-treated at 375 ° C. in the same atmosphere as described above. A p-type electrode having the same thickness as that of the mold and having the same contact resistivity as that of the sample 26 is obtained, and the reaction layer on the n-type side has the same thickness as that of the p-type and has a contact resistivity. but 10 ^{over 5 Ωcm 2}
A normal one was obtained. Further, Ga _0.15 In which is a mixed crystal composition of InP and GaAs instead of InP
_An ohmic electrode was prepared under the same metal layer deposition and heat treatment conditions as in Sample No. 26 except that _0.85 As _0.33 P _0.67 (x = 0.15, y = 0.33) was used. Approximately the same evaluation results were obtained.

[0027]

[Table 2]

Example 3 Using the ohmic electrode of Sample No. 26 manufactured in Example 2, a light receiving element shown in FIG.
(InGaAs / InP photodiode).
In FIG. 5, 1 is an InP substrate, 2 is the p-type ohmic electrode of the present invention, 4 is a passivation film, and 5 is InP
Window layer, 6 is a p-type semiconductor region, 7 is an InGaAs light receiving layer,
8 is an InP buffer layer, 9 is Au / Ge / Ni on the substrate.
This is an n-type ohmic electrode on which a base metal film is formed. As shown in the figure, this device has a buffer layer 8 made of n-type InP, an n-type InGa
It is formed by laminating a light receiving layer 7 made of As and a window layer 5 made of n-type InP. A p-type semiconductor region 6 is formed in a predetermined region in this layer by diffusion of Zn. A pair of the p-type ohmic electrodes 2 of the present invention are formed on the p-type semiconductor region 6, and n
A mold ohmic electrode 9 is formed. An antireflection film 10 is formed inside the p-type ohmic electrode 2, and a passivation film 4 is formed outside the same. The electrode of the sample number 26 of the present invention is mounted on the p-type ohmic electrode 2.

This diode was heated at a temperature of 200.degree.
As a result of conducting a high-temperature continuous energization test with a 5 V bias, 200
No deterioration of the element occurred after 0 hours, and it was found that the electrode was a highly practical electrode that surpassed the AuZn-based ohmic electrode.

[0030]

As described above, the p-type ohmic electrode of the present invention has a 400
It can be applied simultaneously with the n-type ohmic electrode at a heat treatment temperature of not more than ℃. Further the specific contact resistance is 10 ^{@ 5} .omega.c
Since the thickness of the reaction layer is as small as 0.1 m ² and the thickness of the reaction layer is 0.1 μm or less, it is possible to provide a metal electrode of an InP-based compound semiconductor with much higher practical reliability than a conventional p-type ohmic electrode. .

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a cross section of a conventional p-type ohmic electrode.

FIG. 2 is a diagram schematically showing a basic configuration of a p-type ohmic electrode of the present invention.

FIG. 3 is a view showing a relationship between a heat treatment temperature for forming an ohmic electrode of a sample 1 of the present invention and a contact specific resistance.

FIG. 4 is a diagram schematically showing a cross section of an ohmic electrode of Sample 1 of the present invention.

FIG. 5 is a diagram showing a light receiving element using the p-type ohmic electrode of the present invention.

[Explanation of symbols]

 1, InP-based compound semiconductor substrate 2, p-type ohmic electrode 3, reaction layer 4, passivation film 5, InP window layer 6, p-type semiconductor region 7, InGaAs light-receiving layer 8, InP buffer layer 9, n-type ohmic electrode 10 , Anti-reflection film 21, first layer 22 of p-type ohmic electrode, second layer 23 of p-type ohmic electrode, third layer of p-type ohmic electrode

Claims (9)

[Claims] 1. An ohmic electrode laminated on a p-type InP-based compound semiconductor crystal, comprising a first layer made of a transition metal, a second layer made of Zn, and a third layer made of a transition metal in order from the substrate side. An ohmic electrode comprising a plurality of metal layers including a layer. 2. The first layer, the second layer, and the third layer each have a thickness of:
2 to 10 nm, 5 to 20 nm, 10 to 200 n respectively
The ohmic electrode according to claim 1, wherein m is m. 3. The ohmic according to claim 1, wherein a fourth layer made of a high melting point metal and a fifth layer made of Au are further disposed on the third layer. electrode. 4. The ohmic electrode according to claim 3, wherein the fourth layer and the fifth layer have a thickness of 20 to 200 nm and 100 to 500 nm, respectively. Wherein said compound semiconductor crystal is a InP or _{Ga x In 1-x As y} P 1-y ( provided that x, y is 1 or less positive or 0, y is y = 1-2. The ohmic electrode according to any one of claims 1 to 4, wherein the ohmic electrode comprises a number satisfying 1x. 6. The method according to claim 1, wherein the first layer and the third layer are Pd, C
The ohmic electrode according to any one of claims 1 to 5, wherein the ohmic electrode is made of a metal selected from the group consisting of o, Pt, Rh, Ni, and Ir. 7. A method of manufacturing an ohmic electrode laminated on a p-type InP-based compound semiconductor crystal, comprising, in order from the crystal side, a first layer made of a transition metal, a second layer made of Zn,
A method for manufacturing an ohmic electrode, comprising: depositing a plurality of metal layers including a third layer made of a transition metal; and thereafter performing a heat treatment at a temperature in the range of 350 to 400C. 8. The method according to claim 7, wherein in the step of depositing the plurality of metal layers, a fourth layer made of a refractory metal and a fifth layer made of Au are further deposited on the third layer. The method for producing the ohmic electrode according to the above. 9. A semiconductor device using the ohmic electrode according to claim 1.