JP3141874B2 - Method for manufacturing compound semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a method for producing a transparent conductive film, and more particularly to a method for producing a transparent conductive film at a lower temperature, which is smooth, has low resistance and high transmittance, and reduces costs. The present invention relates to a method for producing a transparent conductive film, which is improved so as to be able to perform. The present invention also relates to a method for manufacturing a compound semiconductor light emitting device using such a method.

[0002]

2. Description of the Related Art At present, transparent conductive films are used for liquid crystal displays.
B) It is used in many fields including solar cells. Transparent
As the bright conductive film, ITO (In_Two O_Three -5wt
% SnO _Two ) Is used. ITO film formation method
In most cases, the sputtering method is the mainstream, and the substrate temperature is 300
At 80 ° C., transmittance is 80% or more, resistivity is 2 × 10^-FourAbout Ωcm
Are obtained with good reproducibility. Organic electrol
Response to luminescence (EL) and light emitting diode (LED)
When considering the use, a transparent conductive film that can be formed at lower temperature
It has been demanded.

[0003] Japanese Patent Application Laid-Open No. 6-318406 discloses that
In which high transmittance and low resistivity can be realized even in film formation_Two O_Three −
A production technique of 10 wt% ZnO has been proposed. This technique
According to the technique, the film was formed at room temperature by sputtering, and the film thickness was 140
nm film with a resistivity of 3 × 10 ^-FourΩcm, transmittance 86%
(At 550 nm).

[0004] In addition, formation of a transparent conductive film has been studied by vapor deposition, ion plating and the like.

[0005]

SUMMARY OF THE INVENTION In a transparent conductive film, the transmittance and conductivity greatly depend on the amount of oxygen. However, the conventional vapor deposition method has a problem that the deposition pressure is limited due to the operation of the vapor deposition source. In addition, in the sputtering method, there are limitations on the film formation pressure and gas for film formation, such as the limitation of the pressure range for using plasma and the use of argon (necessary for generating plasma), and the precise oxygen There was a problem that the amount could not be controlled.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been improved so that the film formation pressure and gas are not limited and the amount of oxygen can be precisely controlled. To provide a method for producing a transparent conductive film.

Another object of the present invention is to improve the transmittance,
And improved so that costs can be reduced,
An object of the present invention is to provide a method for manufacturing a transparent conductive film.

Another object of the present invention is to provide a method of manufacturing a compound semiconductor light emitting device including a step of forming a transparent conductive film improved so as to improve the transmittance and reduce the cost. I do.

[0009]

SUMMARY OF THE INVENTION Compounds according to the invention
In a method for manufacturing a semiconductor light emitting device, first, a transparent electrode
Prepare the compound semiconductor light emitting device substrate immediately before forming
You. This compound semiconductor light emitting device substrate is placed in a vacuum chamber.
At the center of the above-mentioned vacuum chamber, place a tar
Place the get and introduce oxygen into the vacuum chamber. And
Set the film temperature from room temperature to 300 ° C,
Irradiates the light, the source released by ablation
Molecules and molecular ions on the compound semiconductor light emitting device substrate.
Crystal growth of transparent conductive film electrode while depositing and oxidizing
Let it.

This method is called a laser ablation method. In the present invention, a compound semiconductor light emitting device is used.
It is used as a method for forming a transparent conductive film electrode on a substrate . In laser ablation, since an excimer laser serving as an excitation source is guided from outside the film forming apparatus, there is no restriction on the film forming pressure or gas. Further, there is no influence of reverse sputtering due to negative ions, which is a problem in the sputtering method. From such features, there are features such as easy control of the oxygen amount and obtaining a film close to the target composition. Further, a film having excellent surface smoothness as compared with the sputtering method can be obtained. Thus, according to the invention
For example, a transparent conductive film electrode is formed by a laser ablation method.
Therefore, a compound half having low resistance and improved transmittance
A conductor light emitting device is obtained.

In the method for manufacturing a compound semiconductor light emitting device according to claim 2, the target is In ₂ O ₃ -1.
0 Wt% ZnO is used.

[0012]

According to a third aspect of the present invention, in the method of manufacturing a compound semiconductor light emitting device , the film forming pressure is set to 0.3 to ³ × 10 ⁻³ T.
Perform at orr.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a conceptual diagram of a laser ablation film forming apparatus used in a method for manufacturing a transparent conductive film according to the present invention. Laser ablation is a method of irradiating a solid surface with a high-density laser pulse, depositing ions and atoms emitted therefrom on a substrate at an opposite position to form a thin film. This method is very suitable as a process for forming a metal oxide derivative thin film. By using a strong laser pulse, there is an advantage that not only film formation but also fine processing, etching, multi-layering, etc. can be performed in the same experimental chamber. The advantages of the laser ablation method for producing a ferroelectric thin film are as follows.

First, in this method, since a laser beam is introduced from outside the film forming chamber, a thin film can be formed at an arbitrary atmospheric pressure suitable for crystal growth. Also,
Since atoms, molecules, and ions are emitted only from the target, a thin film without impurities is formed.

Many parameters such as pressure, substrate temperature, film forming rate, etc. can be independently selected. In terms of the controllability of the thin film, the film formation can be instantaneously controlled by adjusting the number of laser pulses and the energy.

Further, as recently revealed,
Very high-speed film formation is possible. Thus, it has many excellent points.

The laser ablation apparatus is shown in FIG.
As shown in the figure, a valve consisting of a ferroelectric
Place the target, oxygen or ozone in the vacuum system,
NO _Two Introduce a highly oxidizing gas such as
Irradiates the target to cause ablation. Abu
The atomic and molecular ions released by the
The crystal grows while being deposited and oxidized. Embodiment 1
Then, using such a laser ablation device,
An attempt was made to form a transparent conductive film.

The film forming conditions are described below. Laser: KrF 248 nm ² J / cm ² Target: In ₂ O ₃ -10 wt% ZnO (manufactured by Idemitsu Kosan, high density product, hereinafter abbreviated as IDIXO) Substrate: MGO (transmittance measurement), glass (for resistance measurement) Film formation Temperature: (room temperature (RT) -300 ° C.) RT as standard
Was used.

Film forming pressure: 0.3 to ³ × 10 ^-3 Torr O
₂ (using 3 × 10 ⁻³ TorrO ₂ as a standard) The film forming conditions will be described in more detail.

Oxygen Pressure Dependence First, the oxygen pressure dependence of the transmittance of the transparent conductive film was examined.

In laser ablation, the plume shape changes depending on the film forming pressure. Further, the composition changes depending on where in the plume the sample is positioned under a certain film formation pressure. The inventor has set a target for superconducting device development.
The optimum distance between the substrates was about 60 to 70 mm. In this case, the distance between the target and the substrate was fixed at 70 mm from plume observation, and the oxygen pressure dependency was evaluated. Note that the film thickness of IDIXO was about 120 nm.

FIG. 2 shows the relationship between the resistivity and the oxygen pressure. The resistivity changes greatly with the oxygen pressure and is 3 × 10 ⁻³ Torr
, A characteristic having a dip was obtained. This depends on the amount of oxygen,
This is consistent with previous reports that there is an optimum value for the resistance of the transparent conductive film. The lowest 6.5 × 10 ⁻⁵ Ωc
The value of m is a value that is very difficult to obtain by a conventional sputtering method. For this reason, since the resistivity is lower by about one order of magnitude as compared with the sputtering method, the required film thickness is reduced to 1/10, whereby the transmittance can be increased, and a high quality transparent conductive film can be manufactured at low cost. It becomes possible. In addition, the unevenness of the surface of the film produced under these conditions was very smooth, about 0.5 nm. This value is 1/1 of that of the film formed by the sputtering method.
It is about 10.

FIG. 3 shows the results of evaluating the oxygen pressure dependence of the transmittance of IDIXO. An absorption edge of about 300 nm is observed. The sample for transmittance measurement has a substrate with an absorption edge of 2
It can be seen that MgO of about 00 nm is used, and the absorption of 300 nm is caused by the IDIXO film. Also,
The transmittance of the used MgO substrate at a wavelength of 500 nm is 84.
% And the film forming oxygen pressure and the IDIXO film (12
0 nm) can be calculated as shown in Table 1.

[0031]

[Table 1]

At a film forming pressure of 0.3 Torr, the transmittance is high, but the resistivity is very high. The lowest resistivity was obtained 3
At × 10 ⁻³ Torr, a transmittance of 92% was obtained. In a light emitting element, Au having a small thickness is generally used as a transparent electrode. Since the transmittance of Au having a film thickness of 20 nm is 37%, the use of IDIXO can provide a light output twice or more.

When the reproducibility IDIXO is applied to products, 1) in-plane distribution, 2)
It is necessary to evaluate reproducibility. The ZnSe substrate is currently about 10 mm square, and it is considered that there is no problem from the experience and results of the inventor related to plume shape and superconductivity.
The change in resistivity when the DIXO film was formed three times under the same conditions was evaluated. Table 2 shows the results.

[0034]

[Table 2]

Although an increase in resistivity is observed with RUN, a value of 10 ⁻⁵ Ωcm or less is obtained for all samples.
Stability at such a low value is considered to be no problem for application to products.

The cause of the change in the resistivity can be considered to be 1) a change in the target composition and 2) a change in the film thickness. Regarding 1), it is possible to cope by polishing the target surface and 2) by installing a film thickness monitor.

Dependence on Oxygen Pressure at Temperature Decrease In comparison with the conventional sputtering method, the laser ablation method has
By forming the DIXO film, the resistivity was reduced by about one digit with the best data. This indicates the possibility that the thickness of the conventionally used transparent conductive film can be reduced to about 1/10. In the evaporation method and the sputtering method, an excitation source (evaporation; heat, sputtering; plasma) is provided in the apparatus, and the film forming conditions are limited. In contrast, in the laser ablation method, an excimer laser, which is an excitation source, is introduced from the outside of the apparatus, so the pressure during film formation can easily be changed from near atmospheric pressure to high vacuum, and film formation at the optimal oxygen pressure is performed. Is possible.
Regarding the film composition, a film close to the target composition can be easily obtained by laser ablation. For this reason, according to the present invention, IDIX having a very high resistivity is used.
It is considered that the O film could be formed.

Further, in order to examine the relationship between the amount of oxygen and the resistivity, an experiment was performed in which the temperature-reducing atmosphere after film formation was changed at about 300 ° C. The film formation pressure was set to 3 × 10 ⁻³ Torr which exhibited the lowest resistivity at room temperature. Table 3 shows the results.

[0039]

[Table 3]

At a temperature decrease of 100 Torr, oxygen is supplied to the sample, and the resistivity increases. At the film forming pressure and the temperature drop in vacuum, there is not much change in the resistivity. In this pressure range,
This indicates that the oxygen taken up does not change drastically.
It is considered that the IDIXO film has a characteristic that oxygen is easily introduced and hardly deficient in combination with the experiment on the oxygen pressure dependency.

Evaluation of Au-Added IDIXO Film The transparent conductive film is generally an n-type semiconductor, and may form a junction when formed as a p-electrode of a ZnSe-based LED. In order to prevent this, an IDIXO / Au structure in which an Au film is formed before forming an IDIXO film was studied. Table 4 shows the results regarding the resistivity.

[0042]

[Table 4]

At 3 nm, compared to a smooth glass substrate,
At a somewhat higher resistivity, 10 nm, a similar resistivity is obtained. The reason that the resistance increases at 3 nm is that the presence of Au (which does not contribute to electric conduction) grown in an island shape prevents the IDIXO from growing as a continuous film at the initial stage of film formation.
It is considered that the resistivity increased. Further, when the thickness becomes 10 nm, Au becomes a continuous film, which indicates that the decrease in electric conductivity of IDIXO is compensated.

FIG. 4 shows the transmittance characteristics of the IDIXO / Au electrode structure. A decrease in transmittance is observed due to the presence of Au. At a wavelength of 500 nm, IDIXO (120
nm) / Au (3 nm) has a transmittance of about 80%.
The reason why the transmittance is lower than that of the thin Au film is considered to be that the transmittance of the IDIXO itself is reduced due to the presence of Au.

Embodiment 2 FIG. 5 is a sectional view of a compound semiconductor light emitting device manufactured by applying the method for manufacturing a transparent conductive film according to Embodiment 1. Referring to FIG. 5, an n-type electrode 2 is provided on the back surface of n-type semiconductor layer 1. An active layer 3 is provided on the n-type semiconductor layer 1. A p-type semiconductor layer 4 is provided on the active layer 3. The contact layer 5 is provided on the p-type semiconductor layer 4. On the contact layer 5, a p-electrode 6 which is a transparent electrode is provided. Pad 7 is provided on p electrode 6. A current is sent to the pad 7 from an external power supply (not shown) through a wiring 8.

As a method for forming the transparent electrode 6 of the compound semiconductor light emitting device as shown in FIG. 5, by using the laser ablation method described in the first embodiment, the transmittance is high and the electric conductivity is low. Further, an electrode having a light output twice or more that of a conventionally used Au electrode was obtained. The electrode structure of the ZnSe-based LED is IDIXO (200 nm) / Au in order to maximize the light output.
(3 nm) is desirable.

It should be noted that the embodiment disclosed this time is an example in all respects and is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a laser ablation film forming apparatus.

FIG. 2 is a diagram showing the relationship between the resistivity and the oxygen pressure of an IDIXO film having a thickness of 120 nm.

FIG. 3 is a diagram showing the oxygen pressure dependence of the transmittance of an IDIXO film having a thickness of 120 nm.

FIG. 4 is a diagram showing the wavelength dependence of the transmittance of IDIXO (120 nm) / Au.

FIG. 5 is a cross-sectional view of a compound semiconductor light emitting device obtained according to the present invention.

[Explanation of symbols]

 6 p electrode

Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI H01B 13/00 503 H01B 13/00 503B // H01B 5/14 5/14 A (58) Field surveyed (Int.Cl. ⁷ , DB name H01L 33/00 C23C 14/00-14/58 H01B 13/00 JICST file (JOIS)

Claims (3)

(57) [Claims] And 1. A process of preparing a compound semiconductor light-emitting device substrate immediately before forming the transparent electrode, a step of placing said compound semiconductor light-emitting device substrate in a vacuum chamber, in the center of the vacuum chamber, the transparent conductive film electrode A step of placing a target to be a material; a step of introducing oxygen into the vacuum chamber; a film formation temperature of room temperature to 300 ° C . ; irradiating the target with laser light; and atoms and molecular ions emitted by ablation. Depositing the compound on the compound semiconductor light emitting device substrate, and crystallizing the transparent conductive film electrode while oxidizing the compound semiconductor light emitting device substrate. 2. The method according to claim 1, wherein the target is In ₂ O ₃ -10 wt.
The method for manufacturing a compound semiconductor light-emitting device according to claim 1 , wherein the compound semiconductor light-emitting device contains% ZnO. 3. A film forming pressure of 0.3 to ³ × 10 ⁻³ Torr.
in the r, performing said crystal growth method of manufacturing a compound semiconductor light-emitting device according to claim 1.