JP3582973B2 - Method for manufacturing compound semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a compound semiconductor device such as an LED (Light Emitting Diode) and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, as an electrode structure of a compound semiconductor element, an Au-based alloy layer as a contact layer is provided between a compound semiconductor layer and a TiN layer and a Ti layer as barrier layers are provided thereon, and further thereon. A device provided with an Al layer as a bonding pad layer is known (for example, JP-A-57-117284). A structure in which a Ti layer is further provided between the Au-based alloy layer and the TiN layer is also known. Here, the TiN layer was formed by a reactive sputtering method using a mixed gas of Ar and N ₂ or an N ₂ gas as an atmosphere gas.
[0003]
[Problems to be solved by the invention]
By the way, in the production of a compound semiconductor element, a heat treatment step for obtaining an ohmic contact is performed after a pattern of an electrode structure is formed. In the barrier layer such as the TiN layer or the Ti layer described above, in the heat treatment process, impurities such as Ga that lower the wire bonding property such as Ga diffuse from the Au-based alloy layer serving as the wafer or the contact layer to the Al layer serving as the bonding pad layer. It is provided to suppress
[0004]
However, since the barrier properties of the barrier layer cannot be said to be sufficient in the above-described conventional technology, the Au alloy layer and the Al layer react with each other and precipitates appear on the Al surface. As a result, there has been a problem that barrier flattening of flattening of the electrode surface is impaired and bonding performance is reduced.
[0005]
Further, in the above-described conventional technique, there is a problem that overetching occurs because the etching of the TiN layer cannot be stabilized.
[0006]
The present invention has been made in order to solve such problems of the related art, and provides a compound semiconductor device capable of improving the barrier properties of a barrier layer and stabilizing etching workability, and a method of manufacturing the same. With the goal.
[0007]
[Means for Solving the Problems]
In the method for manufacturing a compound semiconductor device of the present invention, a contact layer made of a material capable of making ohmic contact with the compound semiconductor layer is provided on the compound semiconductor layer containing Ga, and TiN, TiO, and A method for manufacturing a compound semiconductor device, comprising: a first barrier layer having a mixed composition of TiON, a second barrier layer made of Ti, and a bonding pad layer made of Al, which is a wire bondable material, stacked in this order, A step of forming the first barrier layer by a reactive sputtering method using a mixed gas in which O ₂ gas is mixed with N ₂ gas in a mixed amount of 20% or less , wherein the first barrier layer is formed by: the intermittent reactive sputtering, by laminating the following thin film 25nm is intended to a predetermined thickness, the objective is achieved by the That.
[0008]
The contact layer may be made of Au-based alloy.
[0009]
A Ti layer may be provided between the contact layer and the first barrier layer.
[0010]
It is desirable that the thickness of the first barrier layer is 50 nm to 150 nm.
[0011]
It is desirable that the thickness of the second barrier layer is 100 nm to 500 nm.
[0015]
Preferably, the first barrier layer is formed by a reactive sputtering method with a sputtering pressure of 1.0 Pa to 1.5 Pa.
[0016]
The first barrier layer is preferably formed by a reactive sputtering method with a sputtering power of 2.5 kW or less.
[0017]
Hereinafter, the operation of the present invention will be described.
[0018]
In the present invention, by providing a first barrier layer made of a mixed composition of TiN, TiO and TiON and a second barrier layer made of Ti between the contact layer and the bonding pad layer, the TiN layer The barrier property can be improved as compared with a conventional compound semiconductor device provided with a Ti layer as a barrier layer. Although the reason for this is not clear at present, it has been confirmed by experiments by the present inventors. Therefore, it is possible to prevent impurities from diffusing from a wafer or a contact layer made of an Au-based alloy or the like to a bonding pad layer made of Au, Al, or an alloy thereof.
[0019]
By the way, depending on the material of the contact layer to be used, the adhesion to the first barrier layer composed of a mixed composition of TiN, TiO and TiON may be deteriorated. Therefore, by providing a Ti layer having good adhesion to both the contact layer and the first barrier layer between the contact layer and the first barrier layer, the adhesion between the contact layer and the first barrier layer is improved. It is possible to prevent the peeling or the like by improving it.
[0020]
The thickness of the first barrier layer is desirably 50 nm or more to suppress barrier destruction, and desirably 150 nm or less from the viewpoint of film stress.
[0021]
When the second barrier layer is formed with a thickness of 100 nm or more over the first barrier layer, barrier destruction can be suppressed, and when the thickness is 500 nm or less, device damage due to film stress can be prevented. desirable.
[0022]
According to the method for manufacturing a compound semiconductor device of the present invention, the first barrier layer made of a mixed composition of TiN, TiO, and TiON is formed by a reactive sputtering method using a mixed gas of N ₂ gas and O ₂ gas. It is possible to film. According to this method, the first barrier layer and the second barrier layer can be formed simply by switching the gas, and the manufacturing efficiency can be improved.
[0023]
At this time, if the mixing amount of the O ₂ gas is set to 20% or less, a general reactive sputtering apparatus which is not an explosion-proof specification can be used, so that a compound semiconductor element can be manufactured using existing equipment. .
[0024]
Each of the first barrier layer and the second barrier layer can be further improved in barrier properties by laminating thin films by discontinuous sputtering to a predetermined thickness. It has been confirmed that the properties are stable.
[0025]
At the time of sputtering the first barrier layer, the sputtering pressure is desirably set to 1.0 Pa to 1.5 Pa. When the pressure is higher than this range, the barrier property is improved, but overetching is likely to occur at the time of etching the second layer, and the mean free pass is reduced, the deposit is reduced, and the deposition time to a predetermined thickness is increased. This is because there is a fear. Also, when the pressure is lower than this range, over-etching is less likely to occur, but the barrier property is lowered.
[0026]
At the time of sputtering the first barrier layer, the lower the sputtering power, the higher the barrier property tends to be. However, in order to obtain a stable discharge, the power is preferably 1 kW to 2.5 kW.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Here, as one embodiment of the present invention, GaP which is a III-V compound semiconductor device is used.
The LED will be described.
[0028]
FIG. 1E is a cross-sectional view showing an LED according to the embodiment of the present invention.
[0029]
In this compound semiconductor device, an N-type semiconductor layer 2 and a P-type semiconductor layer 1 are provided on an N-type GaP substrate 3, a cathode electrode 4 is provided below the N-type substrate 3, and a P-type semiconductor layer 1 is provided on the P-type semiconductor layer 1. An anode electrode 5 is provided.
[0030]
FIG. 2 shows a sectional view of the anode electrode 5.
[0031]
Here, a contact layer 6 made of an Au-based alloy such as AuBe or AuZn is provided on the P-type semiconductor layer 1, and a first barrier layer 7 made of a mixed composition of TiN, TiO, and TiON and a first barrier layer 7 made of Ti. A second barrier layer 8 is provided, and a bonding pad layer 9 made of Au, Al, or an alloy thereof is further provided thereon.
[0032]
This compound semiconductor device can be manufactured through the steps shown in FIGS.
[0033]
First, as shown in FIGS. 1A and 1B, lapping or the like is performed on a wafer in which an N-type semiconductor layer 2 and a P-type semiconductor layer 3 are epitaxially grown on an N-type GaP substrate 3 to form a PN junction. Then, grinding is performed to a predetermined thickness, for example, about 280 μm.
[0034]
Next, as shown in FIG. 1C, a cathode electrode 4 made of AuSi or the like is formed on the N-type substrate 3 side.
[0035]
Subsequently, as shown in FIG. 1D, an anode electrode 5 is formed on the P-type semiconductor layer 1 side. This step is performed as follows.
[0036]
First, as shown in FIG. 3A, before forming a contact layer, pretreatment by wet etching is performed to remove impurities on the wafer surface.
[0037]
Next, as shown in FIG. 3B, the contact layer 6 is immediately formed on the preprocessed wafer by vapor deposition or sputtering. As the contact layer 6, an Au-based alloy such as AuBe or AuZn to which Be or Zn is added, which can easily obtain an ohmic contact with the P-type epitaxial layer 1, can be used.
[0038]
Subsequently, as shown in FIG. 3C, a first barrier layer 7 made of a mixed composition of TiN, TiO and TiON and a second barrier layer 8 made of Ti are formed by reactive sputtering.
[0039]
Here, the condition of the reactive sputtering at the time of forming the first barrier layer 7 is an important point for improving the barrier.
[0040]
First, according to the experiments of the present inventor, it is desirable to use a gas in which O ₂ gas is mixed with N ₂ gas at a mixing amount of 20% or less, and more preferably, about 5 to 20% as a sputtering gas. It is a mixed gas.
[0041]
At this time, the lower the sputtering power, the higher the barrier property tends to be, and the sputtering power is desirably 2.5 kW or less. However, although it depends on the performance of the sputtering apparatus to be used, it is desirable to set it to 1 kW to 2.5 kW in order to obtain a stable discharge.
[0042]
Further, the pressure during sputtering is desirably 1.0 Pa to 1.5 Pa. When the pressure is higher than this range, the barrier properties are improved, but overetching is likely to occur during the etching of the first barrier layer 7, and the mean free pass is reduced to lower the deposit, and the deposition time until the predetermined thickness is reached. Becomes longer. On the other hand, if the pressure is lower than this range, over-etching hardly occurs and stable etching workability can be obtained, but the barrier property is low.
[0043]
The thickness of the first barrier layer 7 is desirably 50 nm to 150 nm. If the thickness of the first barrier layer 7 is smaller than this, the barrier properties are reduced, and if it is larger than this, the film stress is increased, and there is a possibility that the element may be damaged. The thickness of the second barrier layer 8 is desirably 100 nm to 500 nm in consideration of the thickness of the first barrier layer 7.
[0044]
Here, the first barrier layer 7 and the second barrier layer 8 are not sputtered continuously to a predetermined thickness at a stretch, but are formed by laminating thin films (preferably 25 nm or less) by discontinuous sputtering. By setting the thickness, the barrier property can be further improved and the workability at the time of etching can be stabilized.
[0045]
Incidentally, depending on the material of the contact layer 6, the adhesion to the first barrier layer 7 made of a mixed composition of TiN, TiO, and TiON may be deteriorated. In such a case, if a Ti layer 10 having a thickness of about 5 nm to 10 nm is provided between the contact layer 6 and the first barrier layer 7 as shown in FIG. 4, the adhesion can be improved.
[0046]
Thereafter, as shown in FIG. 3C, a bonding pad layer 9 is formed on the second barrier layer 8 by sputtering or vapor deposition. For the bonding pad layer 9, a material capable of wire bonding such as Al, Au, or an alloy thereof can be used.
[0047]
Next, as shown in FIG. 3D, an electrode pattern 11 is formed by a normal photolithography process.
[0048]
Subsequently, as shown in FIG. 3E, patterns of the contact layer 6, the first barrier layers 7, 8 and the bonding pad layer 9 are sequentially formed by wet etching, the resist is removed, and a heat treatment is performed. An anode electrode 5 is formed.
[0049]
After forming the anode electrode in this manner, as shown in FIG. 1E, the wafer is divided into individual elements by dicing to complete the LED.
[0050]
In the LED thus obtained, the barrier property of the first barrier layer 7 is good, so that barrier destruction does not occur in a heat treatment step for obtaining an ohmic contact performed after patterning of the electrode structure, and the bonding performance is improved. Did not decrease. Further, overetching did not occur at the time of etching the first barrier layer 7 made of a mixed composition of TiN, TiO, and TiON and the second barrier layer 8 made of Ti, and the yield was improved.
[0051]
On the other hand, (1) when only the Ti layer was formed by the reactive sputtering method using Ar gas as the barrier layer, the barrier property was not sufficient, and the barrier was broken, and the bonding performance was lowered.
[0052]
Also, (2) when only the TiN layer was formed by a reactive sputtering method using N ₂ gas as the barrier layer, the barrier properties were not sufficient, and barrier destruction occurred to lower the bonding performance.
[0053]
(3) In the case where a TiN layer is formed as the first barrier layer and a Ti layer is formed as the second barrier layer, the barrier property is insufficient and the etching of the TiN layer is stabilized. And over-etching occurred.
[0054]
In the above-described embodiment, an example in which the barrier property is improved for the anode electrode on the P-type semiconductor layer is described. However, the cathode electrode on the N-type semiconductor layer is similarly formed from a contact layer made of an Au-based alloy and Al. By providing a barrier layer made of a mixed composition of TiN, TiO, and TiON and a barrier layer made of Ti between the bonding pad layer and the bonding pad layer, the barrier properties can be improved. In the above embodiment, a GaP LED that is a III-V group compound semiconductor device has been described, but the present invention is also applicable to a compound semiconductor device using another material system.
[0055]
【The invention's effect】
As described above in detail, in the case of the present invention, by providing the first barrier layer made of a mixed composition of TiN, TiO and TiON and the second barrier layer made of Ti, the TiN layer and the Ti layer The barrier property can be improved as compared with a conventional compound semiconductor device having a barrier layer, and an electrode having good bonding characteristics can be obtained. Further, the yield can be improved by preventing over-etching of the first barrier layer made of a mixed composition of TiN, TiO, and TiON and the second barrier layer made of Ti.
[0056]
Further, by forming a contact layer made of an Au-based alloy that is a material capable of making ohmic contact with the P-type and N-type compound semiconductor layers, Au, Al, or a material thereof that can be wire-bonded to the contact layer is used. It is possible to improve the yield of the compound semiconductor device by preventing impurity diffusion between the semiconductor device and the bonding pad layer.
[0057]
Further, by providing a Ti layer between the contact layer and the first barrier layer, the adhesion between them can be improved.
[0058]
Further, it is possible to prevent damage of devices due to the film stress suppresses the barrier disruption by the thickness of the first barrier layer to 50 nm to 150 nm.
[0059]
Further, by setting the thickness of the second barrier layer to 100 nm to 500 nm, barrier destruction can be suppressed and element damage due to film stress can be prevented.
[0060]
According to the method for manufacturing a compound semiconductor device of the present invention, it is possible to form the first barrier layer made of a mixed composition of TiN, TiO, and TiON by a reactive sputtering method using a mixed gas of N ₂ and O _2. Therefore, the manufacturing process is not complicated, and a compound semiconductor element having excellent characteristics can be provided at low cost.
[0061]
In addition, by setting the mixed amount of the O ₂ gas in the mixed gas to 20% or less, a general sputtering apparatus which is not an explosion-proof specification can be used, so that the manufacturing apparatus does not become complicated.
[0062]
Further, a first barrier layer made of a mixed composition of TiN, TiO and TiON and a thin film formed by intermittent sputtering of a second barrier layer made of Ti are laminated to a predetermined thickness to further increase the barrier. And the stability of etching can be improved.
[0063]
In addition, by setting the sputtering pressure at the time of sputtering the first barrier layer to 1.0 Pa to 1.5 Pa, the barrier property can be improved and over-etching can be prevented.
[0064]
Further, by setting the sputtering power to 2.5 kW or less during the sputtering of the first barrier layer, the barrier properties can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a process for manufacturing a compound semiconductor device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a step of forming an anode electrode in the compound semiconductor device according to the embodiment of the present invention.
FIG. 3 is a cross-sectional view showing an anode electrode portion in the compound semiconductor device according to the embodiment of the present invention.
FIG. 4 is a cross-sectional view showing another anode electrode portion in the compound semiconductor device according to the embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 P-type semiconductor layer 2 N-type semiconductor layer 3 N-type GaP substrate 4 Cathode electrode 5 Anode electrode 6 Contact layer 7 First barrier layer 8 composed of a mixed composition of TiN, TiO, and TiON Second barrier layer 9 composed of Ti Bonding pad layer 10 Ti layer

Claims (7)

A contact layer made of a material capable of ohmic contact with the compound semiconductor layer is provided on the compound semiconductor layer containing Ga, and a first barrier layer having a mixed composition of TiN, TiO, and TiON is provided on the contact layer. A method for manufacturing a compound semiconductor device, comprising: a second barrier layer made of Ti; and a bonding pad layer made of Al which is a wire bondable material, stacked in this order,
Forming the first barrier layer by a reactive sputtering method using a mixed gas obtained by mixing O ₂ gas with N ₂ gas in a mixed amount of 20% or less,
A method of manufacturing a compound semiconductor device, wherein a thin film having a thickness of 25 nm or less is laminated on the first barrier layer to a predetermined thickness by intermittent reactive sputtering. Method of manufacturing a compound semiconductor device according to claim 1, wherein the contact layer is made of Au-based alloy. Method of manufacturing a compound semiconductor device according to between said contact layer and the first barrier layer, in claim 2 in which the Ti layer is provided. Method of manufacturing a compound semiconductor device according to any one of claims 1 to 3 the thickness of the first barrier layer is 50 nm to 150 nm. The method for manufacturing a compound semiconductor device according to claim 1, wherein the thickness of the second barrier layer is 100 nm to 500 nm. 2. The method according to claim 1 , wherein the first barrier layer is formed by a reactive sputtering method at a sputtering pressure of 1.0 Pa to 1.5 Pa. 3. 2. The method according to claim 1 , wherein the first barrier layer is formed by a reactive sputtering method with a sputtering power of 2.5 kW or less. 3.

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