JP2010153386A5 - - Google Patents

Description

The mobility of carrier electrons in a conventional low-resistance oxide transparent electrode film is, for example, about 20 to 30 cm ² / Vsec in an ITO film. It is said that the mobility of carrier electrons in n-type semiconductors such as indium oxide (In ₂ O ₃ ) is mainly governed by ionized impurity scattering, neutral impurity scattering, etc. Impurities contained in the state are called ionized impurities, and impurities contained in the neutral state due to excess oxygen adsorbed around are called neutral impurities). When the amount of the impurity element added to increase the carrier electrons increases, the carrier electrons are scattered and the mobility is lowered.

As an oxide transparent electrode film, an indium oxide film to which titanium is added is also conventionally known. For example, the oldest is a document written by JL Vossen (RCA Review, Vol. 32, 1971, pp. 289-296). This document mainly describes the characteristics of the ITO film by RF sputtering, but describes an example of producing an In ₂ O ₃ film to which 20 mol% of TiO ₂ is added as an impurity other than tin. However, the composition of this film is significantly different from that of the present invention, and the electric resistivity (specific resistance) of the film is remarkably high at 7.5 × 10 ⁻¹ Ω · cm.

Japanese Patent Application Laid-Open No. 9-209134 describes the characteristics of an indium oxide target containing titanium and a film produced therefrom by sputtering. In this publication, an oxide transparent electrode film having a high resistivity for a touch panel is aimed at, and in the embodiment, a titanium having a high resistivity of 1.0 × 10 ^{−3 to} 9.4 × 10 ⁻³ Ω · cm is included. An indium oxide film is noted. The indium oxide film containing titanium of the comparative example also has the lowest specific resistance and a specific resistance of 0.6 × 10 ⁻³ Ω · cm. Both have a fairly high specific resistance.

There are also several patent publications relating to film materials in which titanium is added to ITO as a base. However, it is clearly distinguished from the film of the present invention because it contains tin. That is, when tin is contained in the indium oxide film, a large amount of carrier electrons are emitted as conventionally known, so that only a film having a high carrier electron concentration and a low transmittance in the infrared region can be obtained. For example, JP-A-9-161542 describes an indium oxide film to which titanium and tin are added for touch panels. However, the specific resistance described in this publication is as high as 9.6 × 10 ⁻⁴ Ω · cm or more.

Japanese Patent Application Laid-Open No. 7-54132 describes an ITO sintered body target (SnO ₂ content 10 mass%) to which 50 to 500 ppm of Ti is added in order to increase the density of the sintered body. The oxide electrode film having a low resistance of 1.7 to 2.9 × 10 ⁻⁴ Ω · cm produced by sputtering while heating the substrate at 100 to 300 ° C. is described. However, there is no description about the carrier electron concentration and mobility of this film, and the transmission characteristics in the infrared region, and since it is an ITO-based material, most of the additive element contributing to the generation of carrier electrons is tin, which is comparable to conventional ITO. Because of the high carrier electron concentration, the infrared transmittance is judged to be low.

That is, the oxide transparent electrode film according to the first feature of the present invention is a transparent oxide conductive film formed on a substrate containing indium oxide as a main component, titanium, and heated to 150 ° C. or higher and 350 ° C. or lower. Indium oxide indium is replaced by titanium at a titanium / indium atomic ratio of 0.003 to 0.120, the indium oxide is crystalline, and the ratio of the oxide transparent electrode film The resistance is 5.7 × 10 ⁻⁴ Ω · cm or less, the carrier electron concentration by Hall effect measurement is 5.5 × 10 ²⁰ cm ⁻³ or less, and the mobility of carrier electrons by Hall effect measurement is 40 cm ^2. / Vsec or more. It can also be said that the oxide transparent electrode film is made of indium oxide containing titanium.

More preferably, the titanium / indium atomic ratio is 0.003 to 0.050, and the specific resistance of the oxide transparent electrode film is 4.0 × 10 ⁻⁴ Ω · cm or less.

As a result, a crystalline oxide transparent electrode film in which indium oxide is the main component and indium in the indium oxide is replaced with titanium at a ratio of 0.003 to 0.120 in terms of the number of titanium / indium atoms, Conventional electron ITO with carrier electron concentration of 5.5 × 10 ²⁰ cm ⁻³ or less
A low electrical resistivity with a specific resistance of 1.9 to 5.7 × 10 ⁻⁴ Ω · cm can be realized.

More preferably, when an oxide transparent electrode film in which indium oxide is a main component and indium in the indium oxide is substituted with titanium in a ratio of 0.003 to 0.050 in terms of the number ratio of titanium / indium is carrier electrons, A low electrical resistivity with a concentration of 5.5 × 10 ²⁰ cm ⁻³ or less, which is lower than that of a conventional ITO film, and a specific resistance of 1.9 to 4.0 × 10 ⁻⁴ Ω · cm can be realized.

Further, the oxide transparent electrode film of the present invention has a carrier electron concentration lower than that of the conventional oxide transparent electrode film, but the mobility of carrier electrons is 40 cm ² / Vsec or more, and depending on the production conditions, 60 cm ² / Vsec or more. Also, a film having a thickness of 70 cm ² / Vsec or more can be realized, and the electric resistivity is higher than that of a conventional low resistance oxide transparent electrode film (for example, about 20 to 30 cm ² / Vsec for an ITO film). It becomes as low as a low resistance oxide transparent electrode film. Therefore, since the transparent oxide electrode film of the present invention is a material exhibiting high mobility in a low carrier electron concentration state, it has high transmittance of not only visible light but also infrared light, and has a low electric power as described above. Conductivity can be realized.

By the way, the composition of the In ₂ O ₃ film to which 20 mol% of TiO ₂ is added in the literature written by JL Vossen (RCA Review, 1971 Volume 32, p.289-296) is greatly different from the composition of the present invention. The electric resistivity of the film is as high as 7.5 × 10 ⁻¹ Ω · cm, which is clearly different from the electric resistivity of the film of the present invention.

Moreover, the specific resistance of the membrane in JP-9-209134 Patent Publication, as high as ^{1.0 × 10 -3 ~9.4 × 10 -3} Ω · cm, 0.6 × 10 -3 Ω · to the comparative example Although there is a specific resistance of cm, both are higher than the specific resistance of the film of the present invention.

Furthermore, the specific resistance of the indium oxide film disclosed in Japanese Patent Application Laid-Open No. 9-161542 is as high as 9.6 × 10 ⁻⁴ Ω · cm or more, which is clearly the film of 5.7 × 10 ⁻⁴ Ω · cm or less in the present invention. Different.

Furthermore, the low-resistance oxide transparent electrode film of 1.7 to 2.9 × 10 ⁻⁴ Ω · cm described in JP-A-7-54132 contributes to generation of carrier electrons because it is an ITO-based material. Most of the additive elements to be added are tin, and it is judged that infrared transmittance is low, and the characteristics are clearly different from the film of the present invention.

As described above, an oxide transparent electrode film having high transmittance in the infrared region as well as the visible light region and having a low resistance of 5.7 × 10 ⁻⁴ Ω · cm or less is composed of titanium as indium oxide, Although it has become possible to easily realize it by containing it in the composition range of the present invention, it is difficult by itself, and it is necessary to form a film under suitable sputtering conditions. In particular, it is essential to optimize the amount of oxygen in the deposition gas, the gas pressure, and the substrate temperature during sputtering deposition.

(Electrical characteristics)
As is apparent from Table 1, the indium oxide transparent electrode film of indium oxide containing titanium having a Ti / In atomic ratio of 0.003 to 0.120 according to the present invention has a carrier electron concentration of 5.5 × 10 ²⁰ cm. ^{Although the} resistivity was as low as ⁻³ or less, the resistivity was 5.7 × 10 ⁻⁴ Ω · cm or less, which was very low. The mobility of carrier electrons is as high as 41 cm ² / Vsec or more, and it can be said that low electrical resistivity is realized.

Further, the oxide transparent electrode film of indium oxide containing titanium having a Ti / In atomic ratio of 0.003 to 0.050 according to the present invention (Examples 1 to 9) has a carrier electron concentration of 4.5 × 10 ^20. Although it was as low as cm ⁻³ or less, it had a low electrical resistivity of 4.0 × 10 ⁻⁴ Ω · cm or less. Although not shown in Table 1, even in the oxide transparent electrode film of indium oxide containing titanium having a Ti / In atomic ratio of 0.003 to 0.050, the oxygen amount in the deposition gas is increased to 2 to 3%. As a result, it was found that an oxide transparent electrode film having a specific resistance of 4.0 × 10 ^{−4 to} 5.5 × 10 ⁻⁴ Ω · cm can be produced. Similarly, these films had high transmittance in the infrared region due to the low carrier electron concentration.

(Electrical characteristics)
As is apparent from Table 2, the specific resistivity of the conventional ITO film is as low as 2.4 × 10 ⁻⁴ Ω · cm or less, but the carrier electron concentration is as high as 1.1 × 10 ²¹ cm ⁻³ or more.

(Electrical characteristics)
When the same evaluation as in the example was performed, the specific resistance was 2.2 × 10 ⁻⁴ Ω · cm, the carrier electron concentration was 1.2 × 10 ²¹ cm ⁻³ , and the carrier mobility was 23 cm ² / Vsec. .

(Electrical characteristics)
As is clear from Table 3, the oxide transparent electrode film of indium oxide containing titanium of Examples 13 to 15 of the present invention, the oxide transparent electrode film of indium oxide containing titanium and tungsten of Reference Examples 1 to 6, Although the substrate temperature is sputtered by low-temperature heating at 150 ° C., the specific resistance is as low as 4.5 × 10 ⁻⁴ Ω · cm or less. This is because the electron mobility is high as shown in Table 3.

Although the film | membrane of Comparative Examples 5-7 has a low density | concentration of a carrier electron and high transmittance | permeability also in an infrared region, specific resistance is 5.3-5.9 * 10 < ^-4 > ohm * cm, Examples 13-15, Higher than the films of Reference Examples 1-6. This is because the mobility of carrier electrons is 28 to 32 cm ² / Vsec, which is lower than the films of Examples 13 to 15 and Reference Examples 1 to 6. When the crystallinity of the film was evaluated from X-ray diffraction measurement and film structure observation with a scanning electron microscope, the films of Examples 13 to 15 and Reference Examples 1 to 6 had a grain size as compared with the films of Comparative Examples 5 to 7. Since the half width of the X-ray diffraction peak is small, it was found that the crystallinity is superior to the films of Comparative Examples 5 to 7 doped with only tungsten. Thus, since the film | membrane of Examples 13-15 and Reference Examples 1-6 is excellent in crystallinity, it is thought that mobility is high. Therefore, in comparison with the conventional indium oxide thin film containing tungsten, the indium oxide thin film containing titanium or the indium oxide thin film containing tungsten and titanium of the present invention has low resistance and visible light even at low temperature substrate heating at 150 ° C. A film having a high infrared transmittance can be obtained. In the production of the oxide transparent electrode film by sputtering, the lower the substrate temperature, the shorter the heating time and the less the substrate heating power can be realized, and the production cost and productivity can be increased. Therefore, it can be said that it is a very useful material in industry.

(Comparative Example 8)
An oxide transparent electrode film having a titanium / indium atomic ratio of 0.130 under the same conditions as in Example 1 from a target prepared by changing only the mixing ratio of the raw materials under the same production conditions as in Example 1. Obtained. As a result, a film having a specific resistance of 6.5 × 10 ^{−4 to} 7.5 × 10 ⁻⁴ Ω · cm and a specific resistance of 5.7 × 10 ⁻⁴ Ω · cm or less was not realized.

(Comparative Example 9)
An oxide transparent electrode film having a titanium / indium atomic ratio of 0.002 under the same conditions as in Example 1 from a target prepared by changing only the mixing ratio of raw materials under the same manufacturing conditions as in Example 1. Obtained. As a result, a specific resistance of 6.0 × 10 ^{−4 to} 1.2 × 10 ⁻³ Ω · cm was exhibited, and a film having a specific resistance of 5.7 × 10 ⁻⁴ Ω · cm or less was not realized.

Production of solar cell (Example 16)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 is a schematic sectional view showing an embodiment of the present invention. On the glass substrate (12), the oxide transparent electrode film (11) of Example 5 was formed to a thickness of about 500 nm under the same film formation conditions as in Example 5 by DC magnetron sputtering. A ZnO target was used thereon, a ZnO target was used, Ar was used as the sputtering gas, and a ZnO thin film having a thickness of about 150 nm was formed as the window layer (10). To form a hetero pn junction thereon, a solution precipitation method CdS thin film as a semiconductor having an intermediate layer _{(9), CdI 2, NH} 4 Cl 2, NH 3, using a mixed solution of thiourea, of about 50nm Formed to a thickness. On top of this, a CuInSe ₂ thin film was formed to a thickness of 2 to 3 μm by vacuum deposition as a p-type semiconductor light absorption layer (8). An Au film was formed thereon as a back metal electrode (7) to a thickness of about 1 μm by vacuum deposition. These solar cells AM1.5 (100 mW
/ Cm ² ) was irradiated from the oxide transparent electrode film side and the characteristics were examined. The conversion efficiency was 12%.

Production of photodetection element (Example 20, Comparative Example 18)
An example of manufacturing a light detection element using a CaS material doped with Eu and Sm as the detection material layer will be described below. FIG. 8 is a schematic cross-sectional view showing the configuration of the photodetecting element of Example 20. The indium oxide thin film doped with titanium of Example 5 is formed on the glass substrate (14) as a transparent electrode (15) on the light incident side by sputtering to a thickness of about 200 nm. A CaS light doped with about 1 μm of Eu and Sm at a substrate temperature of 500 ° C. by electron beam evaporation using a sintered pellet of CaS added with 200 ppm of Eu ₂ O ₃ and Sm ₂ O ₃ thereon. A sensing material layer (16) was formed. Finally, an aluminum film was formed as a back electrode (17) on the photodetecting material layer (16) by a sputtering method.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Front side (light-receiving part side) Transparent electrode film 3 P-type amorphous silicon film 4 Amorphous silicon film not containing impurities 5 N-type amorphous silicon film 6 Back side transparent electrode 7 Back side metal electrode 8 Light absorption layer 9 Semiconductor intermediate layer DESCRIPTION OF SYMBOLS 10 Window layer 11 Oxide transparent electrode film 12 Glass substrate 13 Lower electrode 14 Glass substrate 15 Light-incident side transparent electrode 16 Photodetection material layer 17 Back electrode

Claims (17)

An oxide transparent conductive film formed on a substrate containing indium oxide as a main component and containing titanium and heated to 150 ° C. or higher and 350 ° C. or lower, wherein indium oxide indium is titanium, titanium / indium The indium oxide is substituted at an atomic ratio of 0.003 to 0.120, the indium oxide is crystalline, and the specific resistance of the oxide transparent electrode film is 5.7 × 10 ⁻⁴ Ω · cm or less. A transparent oxide electrode film characterized in that a carrier electron concentration by a measurement effect is 5.5 × 10 ²⁰ cm ⁻³ or less and a carrier electron mobility by a Hall effect measurement is 40 cm ² / Vsec or more. The titanium / indium atomic ratio is 0.003 to 0.050, and the specific resistance of the oxide transparent electrode film is 4.0 × 10 ⁻⁴ Ω · cm or less. The oxide transparent electrode film described in 1.   3. The oxide transparent electrode film according to claim 1, wherein an average light transmittance at a wavelength of 1000 to 1400 nm is 60% or more. 4. The oxide transparent electrode film according to claim 1, wherein a carrier electron concentration by Hall effect measurement is 4.0 × 10 ²⁰ cm ⁻³ or less. 5. The oxide transparent electrode film according to claim 1, wherein the mobility of carrier electrons by Hall effect measurement is 60 cm ² / Vsec or more. 6. The oxide transparent electrode film according to claim 5, wherein the mobility of carrier electrons by Hall effect measurement is 70 cm ² / Vsec or more.   Using a sputtering target made of an oxide sintered body whose constituent elements are substantially indium, titanium, and oxygen, the substrate temperature is set to 150 ° C. to 350 ° C., and oxygen is added to the sputtering gas by 0.25% or more 4 The method for producing an oxide transparent electrode film according to claim 1, wherein a film is formed by a sputtering method using a mixed gas of argon and oxygen that is contained in an amount of not more than%.   The transparent conductive base material which formed the oxide transparent electrode film in any one of Claims 1-6 on the transparent substrate.   9. The transparent conductive substrate according to claim 8, wherein an average light transmittance at a wavelength of 1000 to 1400 nm is 60% or more, and a surface resistance is 30 Ω / □ or less.   A solar cell using the oxide transparent electrode film according to claim 1.   On a substrate provided with an electrode layer or a metal substrate having electrode properties, a p-type semiconductor light absorbing layer, an n-type semiconductor intermediate layer thereon, a semiconductor window layer thereon, and an n-type transparent layer thereon The solar cell of the structure which laminated | stacked the electrode layer sequentially WHEREIN: The solar cell characterized by using the oxide transparent electrode film in any one of Claims 1-6 for this transparent electrode layer.   In a solar cell having a structure in which a transparent electrode layer on a transparent substrate, a semiconductor window layer thereon, an n-type semiconductor intermediate layer thereon, and a p-type semiconductor light absorption layer thereon are sequentially laminated, A solar cell using the oxide transparent electrode film according to claim 1 for the transparent electrode layer. Light absorbing _{layer, CuInSe 2, CuInS 2, CuGaSe} 2, CuGaS 2 and a solar cell according to claim 11 or 12 of these solid solutions, and at least one selected from CdTe.   The solar cell according to claim 11, wherein the intermediate layer is a solution-deposited CdS layer or a (Cd, Zn) S layer.   The solar cell according to claim 11, wherein the window layer is ZnO or (Zn, Mg) O.   A photodetecting element having a pair of electrodes and a photodetecting material layer sandwiched between the electrodes, wherein the oxide transparent electrode film according to any one of claims 1 to 6 is formed on at least one of the electrodes. A photodetecting element characterized by being used.   The light detection element according to claim 16, wherein the light detection material layer is an infrared detection material layer.