JP2001068707A - Conductive material, manufacture thereof, conductive thin-film, and composite film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a p-conductivity type zinc oxide, by using a p- conductivity type conductive material including nitrogen as its impurity. SOLUTION: First, a substrate 3 to form thereon a conductive thin-film is stored in a chamber 2. After reducing the pressure of the chamber 2, an excitation gas 10 is fed from an excitation-gas generating apparatus 11 onto the surface of the substrate 3. For example, by exciting the gas beam of nitrogen oxide through using an ECR, the excitation gas 10 is outputted. The excitation gas 10 generated in this way contains nitrogen and oxygen ions, etc. Then, after so controlling for the pressure of the excitation gas 10 in the chamber 2 as to have a predetermined value, an ArF excimer laser beam 9 is projected on a ZnO target 4 disposed in the chamber 2 oppositely to the substrate 3. Therefore, the oxygen-deficiency of zinc oxide is sufficiently compensated and the enough amount of nitrogen can be doped in a thin film. As a result, a p- conductivity type conductive thin-film having zinc oxide as its parent material can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive material, a conductive thin film, a composite film, and a method for producing a conductive material. -Type conductive material, a p-type conductive thin film made of the p-type conductive material, a composite film having the p-type conductive thin film and an n-type conductive thin film, and the p-type conductive material And a method for producing the same.

[0002]

2. Description of the Related Art A semiconductor technology using silicon as a base material has the greatest feature that a p-type conductivity and an n-type conductivity can be arbitrarily realized by doping. Has brought. However, since a semiconductor using silicon as a base material is weak to heat, it is difficult to operate a device using such a semiconductor at a high temperature. Therefore, a material that can easily control the conductivity type and has high heat resistance has been desired.

[0003] A conductive oxide is known as a material having high heat resistance. However, most of the conductive oxides are of the n-conductivity type, and very few exhibit the p-conductivity type. Moreover, such p-conductivity-type oxides are not practical.

For example, p-type oxides include YB
a ₂ Cu ₃ O _7-y , (La, Sr) MnO ₃ , (La, S
r) ₂ CuO _{4 and the} like are known. However, all of these materials have a black color and cannot be used for transparent electrodes such as solar cells.

[0005] Further, as a p-type transparent oxide, Cu
AlO ₂ and SrCu ₂ O ₂ have been reported. These materials are colorless and transparent, but have a carrier density of 10 ¹⁶ (pieces / c).
m ³ ), and sufficient conductivity has not been obtained.

Incidentally, zinc oxide is widely used for transparent electrodes of solar cells and the like. Zinc oxide is not only a transparent material having high heat resistance, but also has a large band gap (3.2 eV) and a low optical transition probability.
Therefore, realization of both n-conductivity type and p-conductivity type is desired for zinc oxide, but zinc oxide of p-conductivity type has not yet been obtained.

One of the reasons zinc oxide cannot be of p conductivity type is its oxygen deficiency. Therefore, if oxygen deficiency of zinc oxide is prevented, p-type conductivity can be realized. However, simply forming a zinc oxide thin film in an atmosphere containing O ₂ gas cannot sufficiently prevent oxygen deficiency of zinc oxide, resulting in an n-type conductivity.

For example, in order to prevent oxygen deficiency of zinc oxide and to introduce a p-type acceptor, a zinc oxide thin film is formed in an excited gas atmosphere obtained by exciting a mixed gas of nitrogen gas and oxygen gas. Filming is being considered. According to this method, it is considered that oxygen deficiency of zinc oxide can be prevented and nitrogen that makes the conductivity type of zinc oxide p-type can be introduced. However, in fact, the zinc oxide obtained by this method is of the n conductivity type, and the p conductivity type is not realized.

[0009]

As described above, many companies and research institutes have been focusing on the development of p-type zinc oxide, but none of them has been able to obtain p-type zinc oxide. .

The present invention has been made in view of the above problems, and has as its object to realize a p-conductive type zinc oxide. That is, the present invention provides a p-conductive type conductive material having zinc oxide as a base material, a conductive thin film made of this conductive material,
It is an object of the present invention to provide a composite film formed by laminating a p-type conductive thin film and an n-type conductive thin film, and a method for producing the conductive material.

[0011]

SUMMARY OF THE INVENTION The present inventors have found that a p-type conductivity cannot be realized when a zinc oxide thin film is formed in an excited gas atmosphere formed by exciting a mixed gas of nitrogen gas and oxygen gas. Thought that nitrogen gas is a reducing gas, which promotes oxygen deficiency, and that both nitrogen and oxygen cannot be simultaneously excited into ions, atoms, or active species thereof. Therefore, instead of using a mixed gas of a nitrogen gas and an oxygen gas, when a nitrogen oxide gas is used, for both nitrogen and oxygen, ions, atoms, or active species thereof can be obtained simultaneously and with high efficiency,
Furthermore, they have found that by using a mixed gas containing these, it is possible to realize a p-conductivity-type zinc oxide which has not been realized until now.

That is, according to the present invention, there is provided a conductive material comprising zinc oxide and an impurity contained in the zinc oxide, wherein the conductive material is of p-conductivity type and the impurity contains nitrogen. Materials are provided. Further, according to the present invention, there is provided a p-type conductive thin film comprising the above-mentioned conductive material.

Further, according to the present invention, there is provided a composite film comprising the p-type conductive thin film and an n-type conductive thin film joined to the p-type conductive thin film. Provided.

According to the present invention, at least one chemical species selected from the group consisting of nitrogen ions, nitrogen atoms, and active species thereof, and at least one chemical species selected from the group consisting of oxygen ions, oxygen atoms, and active species thereof. A method for producing a p-type conductive material is provided, which comprises a step of bringing a mixed gas containing one kind of chemical species into contact with zinc oxide.

Usually, the conductive material and the conductive thin film of the present invention are transparent. In these transparent conductive materials and transparent conductive thin films, the carrier density is preferably 1 × 10 ¹⁸ / cm or more. In order to increase the carrier density, for example, an element which acts as a donor in addition to nitrogen may be further contained as the impurity. Thereby, the carrier density can be greatly increased.

When the conductive material and the conductive thin film of the present invention contain gallium and nitrogen as impurities, N1s
Is, for example, 406.5 ± 3 eV.
On the other hand, when the conductive material and the conductive thin film of the present invention contain only nitrogen as an impurity, the binding energy of N1s is about 397 ± 3 eV.

In the method of the present invention, the mixed gas is
For example, nitrous oxide (N ₂ O) gas or nitrogen dioxide (N
It can be obtained by exciting a nitrogen oxide (NO _x ) gas such as an O ₂ ) gas. ECR or a plasma generator can be used to excite this nitric oxide gas.
In addition, photoexcitation using ultraviolet light or the like or electron beam excitation may be used for the excitation of the nitric oxide gas. Further, these can be used in combination.

In the method of the present invention, the step of bringing the mixed gas and the zinc oxide into contact is usually to deposit zinc oxide on the surface of the substrate by a gas phase deposition method such as a pulse laser deposition method in a mixed gas atmosphere. including. in this case,
Preferably, the zinc oxide deposited on the substrate surface constitutes a conductive thin film.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a view schematically showing an apparatus for manufacturing a conductive thin film according to an embodiment of the present invention. This device 1
Is for forming a thin film on the surface of the substrate 3 by a pulse laser deposition method.

In the apparatus 1 shown in FIG.
Accommodates a base 3 and a target 4. The chamber 2 has an exhaust system (not shown), and the inside of the chamber 2 can be controlled to a desired gas pressure. The target 4 is held by a holding member 6 rotatably connected to the pulse motor 5, and is arranged to face the base 3. The chamber 2 is provided with a window, and a laser beam 9 output from the ArF excimer laser 7 and transmitted through the lens 8 is irradiated on the target 4 through the window. Also,
An excitation gas generator 11 that supplies an excitation gas 10 to the vicinity of the surface of the base 3 is connected to the chamber 2. The pulse motor 5 and the ArF excimer laser 7 include:
A computer 12 for controlling these operations is connected.

The formation of a conductive thin film using the apparatus 1 shown in FIG. 1 is performed, for example, by the following method. First, the substrate 3 on which the conductive thin film is formed is housed in the chamber 2. No particular limitation is imposed on the base body 3, but for example, SiO ₂
/ Si substrate, glass substrate (Corning # 7059)
And the like, and a sapphire single crystal substrate with the (0001) plane exposed.

After the pressure in the chamber 2 is reduced, the excited gas 10 is supplied from the excited gas generator 11 to the surface of the base 3. The excitation gas generator 11 excites, for example, a nitric oxide gas beam by using the ECR to generate the excitation gas 10.
Is output. Further, the excitation gas 10 thus generated contains nitrogen ions, nitrogen atoms, or active species thereof, and oxygen ions, oxygen atoms, or active species thereof.

Next, the gas pressure in the chamber 2 is reduced to 1 × 10
^{-5 to} 5 × 10 ⁻¹ Torr, and a ZnO target 4 disposed in the chamber 2 so as to face the substrate 3,
For example, ArF excimer laser light 9 having a wavelength of 193 nm is irradiated. At this time, the temperature of the substrate 3 is set to 80 from room temperature.
It is about 0 ° C. The driving of the pulse motor 5 and the ArF
The output of the excimer laser 7 is appropriately controlled by the computer 12. By the above operation, a zinc oxide thin film containing nitrogen as an impurity is formed on the surface of the substrate 3 as a conductive thin film.

In the above-described method, since nitrogen oxide gas is used as a raw material of the excitation gas 10, unlike the case where a mixed gas of nitrogen gas and oxygen gas is used, ions and atomic Alternatively, the active species can be efficiently generated. Therefore, according to the above-described method, oxygen deficiency of zinc oxide can be sufficiently compensated and a sufficient amount of nitrogen can be doped. Therefore, by using such a method, a p-type conductive thin film using zinc oxide as a base material can be obtained.

In the above method, it is preferable to control the gas pressure in the chamber 2 to 10 ^-3 Torr or more.
By increasing the gas pressure, oxygen deficiency of zinc oxide can be better compensated.

In the above method, only nitrogen is contained as an impurity. However, other elements may be further contained in addition to nitrogen. For example, in addition to nitrogen as an impurity,
Elements that act as acceptors, such as phosphorus, lithium, sodium, and potassium can be used. In addition, as an impurity, an element which behaves as a donor such as indium, gallium, aluminum, boron, fluorine, chlorine, or bromine can be used in addition to nitrogen.

These acceptors or donors include, for example, Z containing the donor or acceptor as an impurity.
By using the nO target 4, it can be easily introduced into the conductive thin film. The ZnO target 4
Usually, those containing impurities of 0 to 30% by weight are used, and those containing impurities of 10 to 20% by weight are preferably used.

It is preferable that an element acting as a donor be introduced into the conductive thin film in addition to nitrogen. Since nitrogen is an acceptor, it is more energetically stabilized in the presence of an element that acts as a donor. for that reason,
By using an element that behaves as a donor, more nitrogen can be introduced into the conductive thin film, that is, the carrier density can be increased. For example, when the impurities are nitrogen and gallium, a high carrier density can be realized by making gallium of about 1/2 to 1/3 (atomic ratio) of nitrogen exist in the conductive thin film. Note that when an element that behaves as a donor is used as one of the impurities, it is necessary to control the content of the conductive thin film so that the conductivity type is p-type.

The above-mentioned conductive thin film is usually 1 × 10 ¹⁷
Particles / cm ³ or more, preferably 1 ×
It has a carrier density of 10 ¹⁸ / cm ³ or more. The thickness of the conductive thin film varies depending on the application, but is generally about 0.1 to 2 μm.

The p-type conductive thin film described above is made of n
It can be used in combination with a conductive type conductive thin film.
This will be described with reference to FIG.

FIG. 2 is a perspective view schematically showing a composite membrane according to one embodiment of the present invention. The composite membrane 20 shown in FIG.
Are formed on one main surface of a substrate 21 by a p-type conductive thin film 22 according to the present embodiment and a well-known n-type conductive thin film 23.
Are sequentially laminated. Reference number 2
Reference numeral 4 denotes an electrode.

As described above, the p-type conductive thin film 22 of the present embodiment and the well-known n-type conductive thin film 23 form a pn layer.
A bond can be formed. n-type conductive thin film 2
Although there is no particular limitation on the material used for 3, it is preferable that the n-type conductive thin film 23 is made of a material whose base material is an oxide such as zinc oxide. In this case, only oxide
Joining can be realized.

The p-type conductive thin film described above can be used for an electrode requiring light transmission, such as a transparent electrode of a solar cell or the like. Further, as shown in FIG. 2, a pn junction can be obtained only with an oxide by combining with a conductive oxide thin film of an n conductivity type, so that an all-oxide transistor can be realized. Further, the p-type conductive thin film according to the present embodiment is a monolithic element having a piezoelectric vibration element, a ferroelectric memory element, and the like,
Also, it can be used as a surface light emitting element or the like instead of a light emitting diode or a fluorescent lamp. In particular, zinc oxide is known to have good piezoelectric properties by adding copper and good ferroelectricity by adding lithium, and a monolithic element can be constituted only by zinc oxide. .

In the embodiment described above, the conductive material is manufactured as a conductive thin film, but this conductive material is not always obtained as a thin film. The conductive material according to the present embodiment can be obtained as a bulk by, for example, the same method as in the production of ceramics.

[0036]

Embodiments of the present invention will be described below. [Electrical Characteristics] First, using the apparatus 1 shown in FIG. 1, under the conditions shown in the following table, a conductive thin film having a thickness of 100 to 300 nm and made of zinc oxide as a base material was formed on one main surface of the substrate 3. Formed. The output of the ArF excimer laser 7 was controlled so that the fluence was 0.5 J / cm ^2, and the film was formed at a rate of 10 Å / min. The conductive thin films obtained as described above were respectively subjected to Samples (1) to (1).
(8).

The Ga concentration shown in the following table means the gallium concentration in the ZnO target 4. Samples (1) and (8) were formed under an atmosphere obtained by exciting nitrogen gas using ECR, and sample (2) was formed under an atmosphere of dinitrogen monoxide gas. Samples (3) to (7) were formed under an atmosphere obtained by exciting nitrous oxide gas using ECR.

Sample (1) obtained as described above
About (8), the resistivity, the carrier density, the mobility, and the conductivity type were examined. The results are shown in the following table.

[0039]

[Table 1]

As shown in the above table, samples (3) to (3)
In (5), the p conductivity type was realized. That is, when the gas pressure was set relatively high in an atmosphere obtained by exciting nitric oxide, p-type conductivity could be realized. Further, as is clear from the comparison of the samples (3) to (5), when Ga as a donor was contained in the ZnO target 4, the carrier density could be significantly increased.

Further, as shown in the above table, the samples (1), (2), (6) to (8) were able to realize the n conductivity type. That is, when the nitrogen oxide gas is not used, when the oxygen-nitrogen gas is not excited, or when the gas pressure is lower than 1 × 10 ⁻⁴ Torr, the n-type conductivity can be realized.

Therefore, the samples of the p-conductivity type (3) to
(5) and n-conductivity type samples (1), (2), (6)-
It was confirmed that the combination of (8) and the above could form a pn junction of all oxides.

[Crystallographic Properties] Next, samples (1),
X-ray diffraction patterns were obtained for (3) and (5) using an X-ray diffractometer. The result is shown in FIG.

FIG. 3A shows the X-ray diffraction pattern obtained for the sample (1), and FIG. 3B shows the X-ray diffraction pattern obtained for the sample (3). FIG. 3C shows the X-ray diffraction pattern obtained for the sample (5). As is clear from the comparison of FIGS. 3A to 3C, even in the case of the p-conductivity type, crystallinity almost equivalent to that in the case of the n-conductivity type is obtained, and there is no generation of impurities or foreign phases. Was confirmed.

[Binding Energy] Next, the samples (3) and (5) were subjected to XPS analysis. FIG. 4 shows the results.

FIG. 4B shows the result of XPS analysis of nitrogen of the sample (3). In addition, FIG.
(C) shows X for nitrogen and gallium of sample (5).
Each of the PS analysis results is shown. FIG. 4 (a),
As is clear from the comparison of (b), the sample (3) and the sample (5) have significantly different nitrogen binding energies.

The data shown in FIGS. 4A and 4C relate to the sample (5).
, Almost the same data can be obtained.

[Optical Characteristics] Next, the sample (5),
Regarding (8), the visible-ultraviolet absorption characteristics were examined. The result is shown in FIG.

FIG. 5 is a graph showing the visible state of the samples (5) and (8).
It is a graph which shows an ultraviolet absorption characteristic. In the figure, curve 15 shows the data obtained for sample (5) and curve 16
Indicates the data obtained for sample (8).

As is clear from the comparison between the curves 15 and 16, the sample (5) exhibiting the p conductivity type has a light transmittance comparable to that of the sample (8) having the n conductivity type. That is, it can be said that the sample (5) has optical characteristics sufficiently usable as a transparent electrode.

[0051]

As described above, according to the present invention, ions and atoms or active species thereof are generated simultaneously and with high efficiency for both nitrogen and oxygen, and a mixed gas containing these is used. Thus, p-type zinc oxide, which has not been realized until now, is obtained. That is, according to the present invention, a p-type conductive material having zinc oxide as a base material,
A conductive thin film made of the conductive material, a composite film formed by laminating the p-type conductive thin film and the n-type conductive thin film, and a method for manufacturing the conductive material are provided.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an apparatus for manufacturing a conductive thin film according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing a composite membrane according to one embodiment of the present invention.

3A is a diagram showing an X-ray diffraction pattern of a conductive thin film according to a comparative example, and FIGS. 3B and 3C are diagrams each showing an X-ray diffraction pattern of a conductive thin film according to an example of the present invention. FIG.

FIGS. 4 (a) and (b) are diagrams showing XPS analysis results on nitrogen of a conductive thin film according to an example of the present invention, and (c).
FIG. 3 is a view showing an XPS analysis result on gallium of the conductive thin film according to the example of the present invention.

FIG. 5 is a view showing visible-ultraviolet absorption characteristics of conductive thin films according to Examples and Comparative Examples of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Device 2 ... Chamber 3 ... Substrate 4 ... Target 5 ... Pulse motor 6 ... Holding member 7 ... ArF excimer laser 8 ... Lens 9 ... Laser light 10 ... Excited gas 11 ... Excited gas generator 12 ... Computer 15, 16 ... Curve Reference Signs List 20 composite film 21 substrate 22 23 conductive thin film 24 electrode

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) H01L 21/28 301 H01L 21/28 301Z 5G307 21/285 21/285 B 5G323 301 301Z 33/00 33/00 D 31 / 04H F term (reference) 4M104 BB36 BB40 CC01 DD34 DD55 GG04 GG05 5F041 CA41 CA49 CA55 5F051 FA02 5F103 AA08 AA10 BB22 DD28 HH04 JJ01 JJ03 KK10 LL04 NN04 NN05 5G301 CA27 CD03 CE01 5G307 FB02 FC01 5G307 FB02

Claims (9)

[Claims] 1. A conductive material comprising zinc oxide and impurities contained in the zinc oxide, wherein the conductive material is p-type and the impurity includes nitrogen. 2. The conductive material according to claim 1, wherein the impurity further contains an element acting as a donor. 3. A conductive thin film of p-conductivity type, comprising the conductive material according to claim 1. 4. A composite film comprising: the p-type conductive thin film according to claim 3; and an n-type conductive thin film joined to the p-type conductive thin film. 5. The composite film according to claim 4, wherein the n-type conductive thin film is made of an oxide as a base material. 6. A chemical species selected from the group consisting of nitrogen ions, nitrogen atoms, and active species thereof, and at least one chemical species selected from the group consisting of oxygen ions, oxygen atoms, and active species thereof. And a step of contacting a mixed gas containing the following with zinc oxide. 7. The method according to claim 6, wherein the mixed gas is generated using a nitrogen oxide gas as a raw material. 8. The conductive material according to claim 6, wherein the step of contacting the mixed gas with the zinc oxide includes depositing zinc oxide on a substrate surface by a vapor deposition method in the mixed gas atmosphere. Manufacturing method of conductive material. 9. The method according to claim 8, wherein the zinc oxide deposited on the surface of the base forms a conductive thin film.