JP2005064015A - Method for manufacturing semiconductor device and light emitting diode element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device wherein damage to a substrate is reduced and substrate deterioration can be reduced when a film is formed physically in an atmosphere where ions are present like a sputtering method, and to provide a light emitting diode element of high reliability which is manufactured by the method for manufacturing. <P>SOLUTION: The method for manufacturing a semiconductor device is provided which includes a process (A) for forming an insulating amorphous natural oxide film which contains constitution element of the surface of a semiconductor lamination film on the surface of the semiconductor lamination film laminated on the semiconductor substrate; and a process (B) for forming a metal film turning to a surface electrode, by a physical film formation method under an atmosphere where ions are present, on the amorphous natural oxide film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a semiconductor device and a light emitting diode manufactured by the manufacturing method, and in particular, an insulating amorphous natural oxide film is formed on the surface of a light emitting element and applied to the element in the manufacturing process. The present invention relates to a light emitting diode that is improved in reliability by reducing damage and accompanying deterioration.
[0002]
[Prior art]
A conventional light emitting diode element made of a compound semiconductor material has, for example, a multilayer structure in which a p-type GaAlAs clad layer, a GaAlAs active layer, and an n-type GaAlAs clad layer are stacked on a p-type GaAs substrate. And an n-type GaAlAs cladding layer are formed with electrodes (see, for example, Patent Document 1). As a method of forming this electrode, a vapor deposition method or a sputtering method is used. In particular, the sputtering method is a widely used technique because it has the excellent advantage that the adhesion of the material is relatively low and the compound-based material can be deposited by a high melting point material or a reactive gas. is there.
[0003]
The most basic sputtering apparatus (see FIG. 5) is a bipolar DC voltage glow discharge type. When forming an electrode, the material is used in an atmosphere of an inert gas such as argon gas (about 10 ⁻² Torr). A voltage is applied between the (target) and the substrate on which the film is formed, and ionized argon ions collide with the target to knock out atoms (or molecules) constituting the target toward the substrate and attach them to the substrate. Recently, in addition to the glow discharge type, there are a number of sputtering methods that have progressed with improvements in equipment such as magnetron sputtering and ion beam sputtering.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-298341
[Problems to be solved by the invention]
However, since the sputtering apparatus generates plasma between the target and the semiconductor substrate, there is a problem that the substrate surface is damaged by the plasma or the substrate temperature rises.
In order to solve these problems, improvements have been made in equipment, and a magnetron sputtering method has been developed in which a magnet is installed near the target and a magnetic field is applied to confine electrons and ions in the vicinity of the target. For this reason, damage to the substrate could not be completely eliminated. Further, there is a method such as ion beam sputtering as an improved type, but it is possible to avoid the entry of particles into the substrate, but the structure of the apparatus becomes complicated and expensive, and the deposition rate of target atoms (or molecules) on the substrate However, there are problems such as slow processing and difficulty in processing a large-area substrate.
[0006]
One of the main objects of the present invention is a method for manufacturing a semiconductor device, which can reduce damage to a substrate and reduce substrate deterioration when a film is physically formed in an atmosphere in which ions exist, such as sputtering. And providing a highly reliable light emitting diode device manufactured by this manufacturing method.
[0007]
[Means for Solving the Problems]
Thus, according to the present invention, the step (A) of forming an insulating amorphous natural oxide film containing the constituent elements on the surface of the semiconductor multilayer film on the surface of the semiconductor multilayer film laminated on the semiconductor substrate; ,
There is provided a method of manufacturing a semiconductor device including a step (B) of forming a metal film to be a surface electrode by a physical film forming method in an atmosphere where ions are present on the amorphous natural oxide film.
Here, in the present invention, the physical film forming method performed in an atmosphere in which ions are present is a method in which plasma is generated in an atmosphere in which ions of an inert gas are present so that material atoms (or material molecules) are formed on a semiconductor substrate. It means a method of forming a film by colliding, and examples thereof include a sputtering method and an ion plating method. In the present invention, a sputtering method is particularly applied.
[0008]
That is, the present invention does not improve a film forming apparatus such as a sputtering apparatus in order to solve the above problem, but forms an insulating amorphous natural oxide film on the surface of the semiconductor laminated film of the semiconductor substrate. Due to the amorphous natural oxide film formed on the surface of the semiconductor substrate, for example, electrons ionized during sputtering stay on the surface of the amorphous natural oxide film, causing a charge-up (charging) phenomenon. When the surface of the amorphous natural oxide film is charged up, thermionic electrons during sputtering are difficult to enter the semiconductor multilayer film, suppressing the temperature rise of the semiconductor substrate and reducing damage to the semiconductor multilayer film due to electron impact. It becomes possible to do. In addition, even for electrically neutral atoms that do not have ions or charges, the substrate can be effectively used regardless of the presence or absence of atomic charges to prevent the amorphous natural oxide film from directly entering the semiconductor multilayer film. Can be protected. Such an effect is obtained by the fact that the natural oxide film is amorphous. In the case of crystallinity, oxidation, dislocation, and defect (damage) from the element surface to the inside of the crystal progress inside the crystal. There's a problem.
[0009]
Here, as the semiconductor device manufactured by the manufacturing method of the present invention, various semiconductor devices manufactured by performing physical film formation in an atmosphere in which ions exist in the manufacturing process, such as sputtering, are used. The semiconductor device is not particularly limited, and examples thereof include a semiconductor device such as a light emitting diode element, a light receiving element, and an IC.
[0010]
In the present invention, the semiconductor substrate may be an elemental semiconductor such as silicon (Si) or a compound semiconductor such as gallium arsenide (GaAs), InP, ZnTe, AlGaInP, or AlGaAsP. A desired semiconductor substrate can be used.
[0011]
In the present invention, the semiconductor laminated film on the semiconductor substrate may be composed of one layer or two or more layers. For example, when a gallium arsenide based semiconductor substrate is used, an amorphous natural oxide film and As a constituent element (crystal component) on at least the surface side (surface layer) of the semiconductor laminated film in contact with the semiconductor laminated film, aluminum is preferably included.
In this case, the surface of the semiconductor multilayer film containing aluminum as a crystal component is treated with, for example, a mixed solution of ammonia, hydrogen peroxide, and pure water to oxidize the surface of the semiconductor multilayer film. An oxide film (insulating oxide protective film) can be obtained. However, since the thickness of the amorphous natural oxide film obtained depends on the aluminum mixed crystal ratio of the semiconductor multilayer film, an amorphous natural oxide film intended to reduce damage to the semiconductor multilayer film in the semiconductor device manufacturing process is required. In order to obtain it, it is desirable that the constituent element on the surface side of the semiconductor multilayer film has an elemental composition ratio of aluminum of 0.5 or more, and more preferably 0.5 or more and 0.7 or less. Further, considering that the semiconductor laminated film and the metal film (electrode material) are alloyed through the amorphous natural oxide film by heating the semiconductor substrate to ensure conductivity, the amorphous natural oxide film The film thickness is desirably 100 nm or less, and more desirably 20 to 50 nm. Since the amorphous natural oxide film is formed by the solution as described above, an expensive device is unnecessary, and the cost and simplification of the manufacturing of the semiconductor device can be achieved.
If the aluminum elemental composition ratio of the semiconductor multilayer film is less than 0.5, an amorphous natural oxide film having a thickness that can sufficiently reduce damage to the semiconductor multilayer film cannot be formed. On the other hand, if it exceeds 0.7, the amorphous natural oxide film tends to be formed thick, and it becomes difficult to alloy the semiconductor laminated film and the metal film (electrode material), so that sufficient conductivity cannot be secured. Further, if the thickness of the amorphous natural oxide film is less than 20 nm, the amorphous natural oxide film cannot sufficiently reduce the damage to the semiconductor multilayer film. It becomes difficult to alloy the film and the metal film, and sufficient conductivity cannot be secured.
[0012]
In the present invention, after the step (B) of forming the metal film on the amorphous natural oxide film, the semiconductor substrate is subjected to a heat treatment so that the surface of the semiconductor multilayer film is interposed through the amorphous natural oxide film as described above. And a step (C) of alloying the metal film. By this step (C), conductivity between the metal film to be an electrode and the semiconductor laminated film is ensured.
[0013]
Furthermore, after the step (B), a step (D) may be included in which only the metal film is patterned into an arbitrary shape while leaving the amorphous natural oxide film. In this case, the step (D) may be either between the step (B) and the step (C) or after the step (C). In this step (D), when an electrode is formed by patterning a metal film, an amorphous natural oxide film is intentionally left so that the surface of the semiconductor device is formed by the amorphous natural oxide film when the chip is formed thereafter. It can be protected from the outside and more reliable.
[0014]
According to another aspect of the present invention, a light-emitting diode element manufactured by the above-described method for manufacturing a semiconductor device can be provided.
Specifically, the semiconductor substrate is a p-type GaAs substrate,
The semiconductor stacked film is formed by sequentially stacking a p-type GaAlAs cladding layer, a GaAlAs active layer, an n-type GaAlAs cladding layer, and a p-type GaAlAs window layer on the p-type GaAs substrate,
Provided is a red light emitting diode device with improved reliability in which a front electrode is formed on the p-type GaAlAs window layer through an amorphous natural oxide film and a back electrode is formed on the back surface of a p-type GaAs substrate. can do.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.
[0016]
FIG. 1 is a perspective view showing a light-emitting diode element according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of the light-emitting diode element according to the embodiment, and FIGS. FIG. 4 is a schematic explanatory view of a manufacturing process of the light-emitting diode element of the embodiment, and FIG. 4 is a relationship between the aluminum mixed crystal ratio of the semiconductor laminated film and the film thickness of the amorphous natural oxide film in the light-emitting diode element of the embodiment. FIG. 5 is a schematic explanatory view showing a process of forming a metal film in the manufacture of the light-emitting diode element of the embodiment, and FIG. 6 is a semiconductor in the manufacture of the light-emitting diode element of the embodiment. It is principal part sectional drawing which shows the process of alloying a film layer and a metal film.
[0017]
As shown in FIGS. 1 and 2, the light-emitting diode device 1 of the present invention includes a p-type GaAs substrate 10 having a thickness of 150 μm as a semiconductor substrate, a p-type GaAlAs cladding layer 11 and a GaAlAs active layer on the p-type GaAs substrate 10. A semiconductor laminated film 15 in which a layer 12, an n-type GaAlAs cladding layer 13, and a p-type GaAlAs window layer 14 are laminated in order, an amorphous natural oxide film 16 formed on the semiconductor laminated film 15, and this amorphous This is a red light-emitting diode composed of an n-type electrode 17 which is a front electrode formed on the natural oxide film 16 and a p-type electrode 18 which is a back electrode formed on the back surface of the p-type GaAs substrate 10.
[0018]
More specifically, each semiconductor layer of the semiconductor multilayer film 15 is composed of a crystal component represented by Ga _1-X Al _X As, and includes a p-type Ga _0.4 Al _0.6 As clad layer 11, Ga _0.8 Al _0.2 As active layer 12, n-type Ga _0.6 Al _0.4 As cladding layer 13, and p-type Ga _0.4 Al _0.6 As window layer 14 are 20 μm, 1 μm, 10 μm, and 20 μm, respectively. It is formed with the film thickness. Further, magnesium is used as the p-type dopant, and tellurium is used as the n-type dopant.
[0019]
Next, a method for manufacturing the light emitting diode element 1 will be described.
First, on the p-type GaAs substrate 10 shown in FIG. 3A, as shown in FIG. 3B, a p-type GaAlAs cladding layer 11, a GaAlAs active layer 12, an n-type GaAlAs cladding layer 13, and a p-type GaAlAs window. The layer 14 is sequentially crystal-grown by a liquid layer epitaxial growth method to form the semiconductor laminated film 15. Here, aluminum mole ratio of the GaAlAs epitaxial layer _{(Ga 1-X Al X As} : mixed crystal ratio X) is set to 0.6,0.2,0.4,0.6, the film thickness Is set to 20 μm, 1 μm, 10 μm, and 20 μm, magnesium is used as the p-type dopant, and tellurium is used as the n-type dopant.
[0020]
Subsequently, a part or all of the p-type GaAs substrate 10 of the epitaxial wafer obtained in the above process is removed by performing wet etching for about 20 minutes using, for example, an etchant made of phosphoric acid, hydrogen peroxide, and water, Processing is performed to a predetermined thickness (in this case, 150 μm).
[0021]
Next, the epitaxial wafer processed to a predetermined thickness is immersed in a mixed solution of ammonia water, hydrogen peroxide solution, and pure water, and the surface of the epitaxial wafer, that is, the surface of the p-type GaAlAs window layer 14 that is the surface layer of the semiconductor laminated film 15 is obtained. Then, an amorphous natural oxide film (GaAlAs oxide film) 16 which is an insulating oxide protective film is formed with a predetermined film thickness T (see FIG. 3B).
[0022]
Here, as shown in FIG. 4, the thickness T of the amorphous natural oxide film 16 to be formed is related to the mixing ratio of ammonia water, hydrogen peroxide water and pure water, and the aluminum mixed crystal ratio X. For example, when the mixing ratio of ammonia water, hydrogen peroxide water, and pure water is 1: 1: 4, and the aluminum mixed crystal ratio X is 0.6, the film thickness T is about 100 nm. The film thickness T is about 50 nm when the mixing ratio of hydrogen peroxide water and pure water is 1: 1: 10 and the aluminum mixed crystal ratio X is 0.6. That is, when the aluminum mixed crystal ratio X is constant, the film thickness T decreases as the ratio of pure water increases. Furthermore, the film thickness T is also related to the time (processing time) for immersing the wafer in the mixed solution. The shorter the processing time, the thinner the film thickness T.
In the present embodiment, the mixing ratio of ammonia water, hydrogen peroxide water, and pure water was 1: 1: 10, and the treatment time was 50 seconds. The film thickness T of the amorphous natural oxide film 16 thus obtained is 50 nm. The processing conditions for forming the amorphous natural oxide film are not limited to this. As described above, the film thickness T of the amorphous natural oxide film 16 depends on the aluminum mixed crystal ratio X, the solution composition, and the processing time. Therefore, it may be processed so that the film thickness T of the amorphous natural oxide film 16 is finally 100 nm or less, preferably 20 or more and 50 nm or less.
[0023]
Next, the epitaxial wafer on which the amorphous natural oxide film 16 is formed is heat-treated in a nitrogen atmosphere at 400 ° C. for 10 minutes. As a result, the amorphous natural oxide film 16 becomes strong.
[0024]
Next, as shown in FIG. 3C, a metal film 117 serving as an electrode is formed as a thin film with a film thickness of 400 nm on the surface of the amorphous natural oxide film 16 of the epitaxial wafer by sputtering. At this time, a metal film 117 is formed by sequentially depositing an AuSi alloy layer 117a having a thickness of 100 nm and an Au layer 117b having a thickness of 300 nm as electrode materials (see FIG. 6).
[0025]
In forming the metal film 117 by this sputtering method, an epitaxial wafer W is set in a bipolar DC voltage glow discharge type sputtering apparatus S as shown in FIG. 5, and an inert gas such as argon gas (about 10 ⁻² Torr). ) To generate a plasma 23 by applying a voltage between the target (electrode material) 20 and the epitaxial wafer W, and to cause the ionized argon ions 21 to collide with the target to form atoms (or molecules) constituting the target 20. ) 22 is struck out toward the wafer and attached to the surface of the wafer W. In FIG. 5, 24 represents electrons in plasma, 25 represents γ electrons, and 26 represents a DC power source.
At the time of sputtering, the ionized electrons stay on the surface of the amorphous natural oxide film 16 and cause a charge-up (charging) phenomenon. When the surface of the amorphous natural oxide film 16 is charged up, it becomes difficult for the thermoelectrons being sputtered to enter the semiconductor laminated film 15, suppressing the temperature rise of the p-type GaAs substrate 10, and epitaxially growing by electron impact. Damage to the crystal (semiconductor laminated film 15) is reduced. Further, even for electrically neutral atoms having no ions or charges, the amorphous natural oxide film 16 is prevented from entering the semiconductor laminated film 15 directly. To protect the board.
[0026]
Subsequently, as shown in FIG. 3D, a metal film (p-type electrode) 18 made of an AuZn alloy is also formed on the back side of the p-type GaAs substrate 10 by sputtering. Thereafter, a photosensitive resist film having an electrode-shaped pattern opening is formed on the surface of the metal film 117 by photolithography, and wet etching is performed for 30 to 60 seconds using an etchant made of iodine and ammonium iodide. A portion of the metal film 117 exposed in the opening is removed and patterning is performed, and then the resist film is removed to form a plurality of n-type electrodes 17. The amorphous natural oxide film 16 may also be removed by etching, but it is left for the purpose of further improving the reliability by protecting the element surface during subsequent processes or during handling after chip formation. preferable.
[0027]
Next, as shown in FIG. 3E, the wafer on which the n-type electrode 17 and the p-type electrode 18 are formed on both front and rear surfaces is heat-treated at 400 to 500 ° C. for 15 minutes. As a result, as shown in FIG. 6 (the portion within the dotted circle in FIG. 3E), the p-type GaAlAs window layer 14 and the n-type electrode 17 on the surface of the semiconductor laminated film 15 are interposed via the amorphous natural oxide film 16. The AuSi layer 117a is alloyed to ensure conductivity between the semiconductor laminated film 15 and the n-type electrode 17.
[0028]
Next, as shown in FIG. 3 (f), the wafer obtained in the above process is divided into chip units by a known method such as dicing to obtain the light emitting diode element 1.
[0029]
【The invention's effect】
According to the present invention, an insulating amorphous natural oxide film (insulating oxide protective film) is formed on the surface of an epitaxial wafer to be a semiconductor device, and an electrode material is formed thereon by a physical film forming method such as sputtering. Therefore, a semiconductor device such as a light emitting diode with improved element reliability can be manufactured without damaging the epitaxially grown crystal (semiconductor laminated film). Further, by controlling the film thickness of the amorphous natural oxide film to 100 nm or less, it is possible to form an ohmic contact between the metal film and the crystal by heating even with the amorphous natural oxide film attached. Since the amorphous natural oxide film is formed using a solution, a semiconductor device can be easily manufactured without using an expensive or complicated device.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a light emitting diode device according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of the light-emitting diode element according to the embodiment.
FIG. 3 is a schematic explanatory diagram of a manufacturing process of the light-emitting diode element according to the embodiment;
FIG. 4 is a graph showing the relationship between the aluminum mixed crystal ratio of the semiconductor laminated film and the film thickness of the amorphous natural oxide film in the light emitting diode element of the same embodiment.
5 is a schematic explanatory view showing a step of forming a metal film in the manufacture of the light-emitting diode element according to the embodiment. FIG.
6 is a fragmentary cross-sectional view showing a step of alloying a semiconductor film layer and a metal film in the manufacture of the light-emitting diode element of the embodiment; FIG.
[Explanation of symbols]
1 Light-Emitting Diode Element 10 p-type GaAs Substrate (Semiconductor Substrate)
11 p-type GaAlAs cladding layer 12 GaAlAs active layer 13 n-type GaAlAs cladding layer 14 p-type GaAlAs window layer 15 semiconductor laminated film 16 amorphous natural oxide film 17 n-type electrode (surface electrode)
18 p-type electrode (back electrode)
117 Metal film

Claims (9)

Forming an insulating amorphous natural oxide film containing constituent elements on the surface of the semiconductor multilayer film on the surface of the semiconductor multilayer film laminated on the semiconductor substrate;
And (B) forming a metal film to be a surface electrode by a physical film-forming method in an atmosphere in which ions are present on the amorphous natural oxide film. The method of manufacturing a semiconductor device according to claim 1, wherein the amorphous natural oxide film is formed with a film thickness of 100 nm or less. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the amorphous natural oxide film is formed on the surface of the semiconductor multilayer film by immersing the semiconductor substrate in a solution containing ammonia and hydrogen peroxide. The method for manufacturing a semiconductor device according to claim 1, wherein aluminum is included as a constituent element on at least the surface side of the semiconductor multilayer film in contact with the amorphous natural oxide film. 5. The method for manufacturing a semiconductor device according to claim 4, wherein the constituent element on the surface side of the semiconductor laminated film has an elemental composition ratio of aluminum of 0.5 or more. 6. The method according to claim 1, further comprising a step (C) of alloying the surface of the semiconductor laminated film and the metal film through the amorphous natural oxide film by heat-treating the semiconductor substrate after the step (B). The manufacturing method of the semiconductor device as described in one. The manufacturing of the semiconductor device according to claim 1, further comprising a step (D) of patterning only the metal film into an arbitrary shape while leaving the amorphous natural oxide film after the step (B). Method. A light emitting diode element manufactured by the method for manufacturing a semiconductor device according to claim 1. The semiconductor substrate is a p-type GaAs substrate;
The semiconductor stacked film is formed by sequentially stacking a p-type GaAlAs cladding layer, a GaAlAs active layer, an n-type GaAlAs cladding layer, and a p-type GaAlAs window layer on the p-type GaAs substrate,
9. The light emitting diode element according to claim 8, wherein a surface electrode is formed on the p-type GaAlAs window layer through an amorphous natural oxide film, and a back electrode is formed on the back surface of the p-type GaAs substrate.

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