TW201418164A - Metal oxide film - Google Patents

Abstract

A metal oxide film comprises indium, zinc, tin, and oxygen, wherein based on the total atomic content of indium, zinc and tin as 100%, the atomic content range of indium is 60 to 80at%, the atomic content range of zinc is 10 to 25at%, and the atomic content range of tin is 1 to 20at%, and the ratio of the zinc atomic content to the tin atomic content is greater than 1.1. In addition to being able to replace the existing ITO film, the metal oxide film of the present invention is high in the crystallization temperature to still maintain the non-crystalline state after being heated under a temperature not higher than 250 DEG C, so as to maintain the film's surface evenness degree and high etching efficiency.

Description

Metal oxide film

The present invention relates to a metal oxide film, and more particularly to a metal oxide film having a high crystallization temperature.

Among the metal oxide films used in the field of optoelectronics and semiconductors, the most commonly used and relatively mature ones are indium tin oxide (ITO) films.

The reason why ITO film is widely used in the field of optoelectronics and semiconductors is because of its good conductivity and excellent light transmittance under visible light irradiation. Furthermore, its work function can be combined with thin film solar cells and light-emitting diodes. The matching of the active layers, especially the energy levels of the organic thin film solar cell and the active layer of the organic light emitting diode, is suitable as an electrode layer therein.

However, the indium content is low and is a rare metal, but the percentage of indium in the ITO film is higher than 70%; therefore, if a large amount of indium-based metal oxide is still relied on in the future, it is bound to cause depletion of indium. Therefore, other types of metals have been developed to replace all or part of the indium in the ITO film to reduce the content of indium in the metal oxide film while maintaining the characteristics of the metal oxide film similar to those of the ITO film, and directly replacing the photovoltaic element. The ITO thin film in the semiconductor element is an object of research by a person skilled in the art.

Furthermore, in addition to the development of metal oxide films which have a low indium content and can replace the ITO film, due to the current manufacture of photovoltaic elements and semiconductor elements After the formation of the metal oxide film, a number of processes, such as high temperature heating, are required. Therefore, the stability of the metal oxide film also needs special attention.

Accordingly, it is an object of the present invention to provide a metal oxide film having a high crystallization temperature.

Thus, the metal oxide film of the present invention comprises indium, zinc, tin and oxygen, wherein the atomic content of indium ranges from 60 to 80 at.% based on the total atomic content of indium, zinc and tin of 100 at.%, the atom of zinc The content ranges from 10 to 25 at.%, the atomic content of tin ranges from 1 to 20 at.%, and the ratio between the atomic content and the atomic content of tin is greater than 1.1.

Preferably, the atomic content of indium ranges from 67 to 80 at.%, the atomic content of zinc ranges from 12 to 18 at.%, and the atomic content of tin ranges from 5 to 12 at.%.

Preferably, the atomic content of indium ranges from 73 to 79 at.%, the atomic content of zinc ranges from 14.5 to 16.5 at.%, and the atomic content of tin ranges from 6 to 10.5 at.%.

Preferably, the ratio between the atomic content of zinc and the atomic content of tin ranges from 1.6 to 2.4.

Preferably, the metal oxide film is amorphous and has a crystallization temperature of greater than 250 °C.

Preferably, the refractive index is between 1.6 and 2.4 at a wavelength of 455 nm.

Preferably, under illumination from a source having a wavelength in the range of 400 to 800 nm, Its average light transmittance is greater than 88%.

Preferably, the metal oxide film has a work function between 5 and 6 eV.

Preferably, the metal oxide film has a carrier concentration of between 1 x 10 ²⁰ and 1 x 10 ²¹ cm ^-3 .

The effect of the invention is that, in addition to being able to replace the current ITO film, since the metal oxide film of the invention has a high crystallization temperature, it is still amorphous after being heated at a high temperature of not higher than 250 ° C, and the film surface can be maintained. The degree of flatness.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

A preferred embodiment of the metal oxide film of the present invention comprises indium, zinc, tin and oxygen, wherein the atomic content of indium ranges from 60 to 80 at.%, based on the total atomic content of indium, zinc and tin of 100 at.%, zinc The atomic content ranges from 10 to 20 at.%, the atomic content of tin ranges from 1 to 20 at.%, zinc is greater than tin, and the ratio of the atomic content of zinc to the atomic content of tin must be greater than 1.1.

The inventors have found that the partial characteristics of the film obtained according to the preferred embodiment of the above composition ratio are very similar to those of the ITO film, particularly resistivity, work function, and refractive index under visible light irradiation. In addition, the transmittance, crystallization temperature and etching characteristics of the preferred embodiment are superior to those of the currently used ITO film, and have high transmittance, high crystallization temperature, and high etching rate.

In other words, when the content of indium in the metal oxide film is more than 80 at.%, and the ratio between the atomic content of zinc and the atomic content of tin is not more than 1.1, the resistivity is too high except for the lower crystallization temperature of the film. High and cannot be used as an electrode layer in a photovoltaic element or a current diffusion layer for laterally uniform diffusion of current, and also because the work function is too high to match the active layer of the current solar cell or the active layer of the organic light-emitting diode and supply electrons The hole transition; in addition, its light transmittance and refractive index in visible light are also low and cannot be effectively penetrated by light and applied as an anti-reflection film.

Preferably, the indium of the preferred embodiment has an atomic content ranging from 67 to 80 at.%, an atomic content of zinc ranging from 12 to 18 at.%, and an atomic content of tin ranging from 5 to 12 at.%. More preferably, the indium of the preferred embodiment has an atomic content ranging from 73 to 79 at.%, the atomic content of zinc ranges from 14.5 to 16.5 at.%, and the atomic content of tin ranges from 6 to 10.5 at.%; The preferred embodiment may have better film properties when in the above range.

In particular, when the relationship between the atomic content of zinc and the atomic content of tin indicates a more precise composition ratio between the elements of the preferred embodiment, the ratio of the atomic content of zinc to the atomic content of tin is less than 3, more preferably The ratio ranges from 1.6 to 2.4; in addition, the difference between the atomic content of zinc and the atomic content of tin is not less than 1 at.% and less than 9 at.%, and the preferred embodiment is suitable for replacing the photovoltaic element. The ITO film, and some of the film properties are better and more stable than the ITO film.

It should be noted that the characteristics of the film referred to herein mainly include resistivity, transmittance of visible light, refractive index of visible light, carrier concentration, work function, and crystallization temperature.

Wherein, the resistivity of the preferred embodiment is not more than 7×10 ^-4 Ω-cm; in the positive embodiment, when the light source having a wavelength range of 400 to 800 nm is irradiated in the forward direction, the average transmittance of the substrate having a thickness of 100 nm is greater than 88%, and the preferred embodiment has a film refractive index between 1.6 and 2.4 when illuminated by a light source having a wavelength of 455 nm. Further, the work function of the preferred embodiment ranges from 5 to 6 eV, and the carrier concentration of the preferred embodiment ranges from 1 x 10 ²⁰ to 1 x 10 ²¹ cm ^-3 . In addition, the crystallization temperature of the preferred embodiment is greater than 250 ° C, that is, the preferred embodiment is still amorphous after annealing at 220 ° C, so that it has a heating temperature of at least higher than 220 ° C. Can be crystalline.

In order to make the composition ratio and characteristics of the above-mentioned metal oxide thin film of the present invention more specific, the specific examples of how the present invention is produced will be described in detail below, and the characteristics between the specific examples and the comparative examples will be compared.

[Specific example 1]

First, a sputtering target is prepared, the sputtering target containing indium, zinc, tin and oxygen, wherein the atomic content of indium is 69.3 at.% based on the total atomic content of indium, zinc and tin of 100 at.%, The atomic content of zinc is 15.8 at.%, and the atomic content of tin is 14.8 at.%.

Then, the sputtering target is subjected to a sputtering process to form a metal oxide film. The working parameter of the sputtering process is to use a 900 W DC power source, the flow rate of the argon gas is 70 sccm, and the flow rate of the oxygen gas is 2.5 sccm. The metal oxide film is formed on a substrate at room temperature. Finally, the post anneal was carried out at a temperature of 220 ° C to prepare the specific example 1.

[Specific example 2]

This specific example 2 is similar to the manufacturing method of the specific example 1, and the difference is The sputtering target contains indium, zinc, tin and oxygen, wherein the atomic content of indium is 76.5 at.% and the atomic content of zinc is 12.1 at. based on the total atomic content of indium, zinc and tin of 100 at.%. %, the atomic content of tin is 11.4 at.%.

[Comparative Example 1]

The comparative example 1 is similar to the production method of the specific example 1, except that the sputtering target contains indium, zinc, tin and oxygen, wherein the indium, zinc and tin are based on the total atomic content of 100 at.%, indium. The atomic content is 78.2 at.%, the atomic content of zinc is 9.8 at.%, and the atomic content of tin is 11.6 at.%.

[Comparative Example 2]

First, a sputtering target is prepared. The sputtering target contains indium oxide and tin oxide. The content of indium oxide is 90% by weight and the content of tin oxide is 10% by weight based on 100% by weight of indium oxide and tin oxide. .

Next, the sputtering target was subjected to a sputtering process to form a metal oxide film; and a post anneal at 280 ° C was further performed to prepare Comparative Example 2.

It should be noted that this Comparative Example 2 is also an ITO film which is known to those skilled in the art.

[Component Analysis and Measurement Results]

Table 1 below shows the film composition of the specific examples and the comparative examples, and the characteristic measurement results of the specific examples and comparative examples; and the "ITO film" mentioned next is Comparative Example 2.

First, the composition ratio of the film and the relationship between the elements are analyzed: It can be understood from the specific examples 1 and 2 of Table 1, that the atomic content of indium of the specific examples 1 and 2 of the present invention is in the range of 73 to 79 at.%, and the atomic content of zinc. The range is 14.5 to 16.5 at.%, the atomic content of tin ranges from 6 to 10.5 at.%, and the ratio of the atomic content of zinc to the atomic content of tin ranges from 1.6 to 2.4. Furthermore, the atomic content of zinc and tin The difference in atomic content ranges from greater than 5 at.% and less than 9 at.%.

Referring to Figure 1, secondly, the proportional relationship between the sputtering target and the specific example is analyzed: the target composition and the film composition of the specific examples 1 and 2 can be known, the target The composition ratio of the material is not the same as the composition ratio of the formed film specific example, and there is a difference value, and the difference value is not predictable by a specific formula.

Hereinafter, the characteristics of Specific Examples 1 and 2 and Comparative Examples 1 and 2 will continue to be analyzed.

(1) Resistivity

Referring to Table 1, the specific examples 1 and 2 have a specific resistance of not more than 7 × 10 ^-4 Ω-cm.

When the atomic content of indium is not more than 80 at.%, and the ratio between the atomic content of zinc and the atomic content of tin is greater than 1.1, the resistivity closer to that of Comparative Example 2 may be obtained, indicating that the specific example 1 and the specific example 2 are in the resistance. The characteristics exhibited by the ratio are similar to those of the current ITO film; and the difference between the resistivity of Comparative Example 1 and the resistivity of the ITO film is large, that is, the conductivity is poor.

(2) Average transmittance

The average light transmittance referred to herein refers to an average light transmittance value obtained by measuring a film having a film thickness of 100 nm when the light source wavelength range is from 400 to 800 nm (i.e., a wavelength range of visible light).

As can be understood from Table 1, the average light transmittance of Specific Example 1 and Specific Example 2 was more than 88%, and was close to the average light transmittance of Comparative Example 2, and was higher than the average light transmittance of Comparative Example 1.

(3) Light transmittance:

The light transmittance referred to herein means a light transmittance value obtained by measuring a film having a film thickness of 100 nm when the light source wavelength range is 455 nm.

It can be understood from Table 1 that the specific examples 1 and 2 have high light transmittance. In addition to the average light transmittance of Comparative Example 1, the light transmittance of Specific Example 1 and Specific Example 2 was higher than that of the ITO film.

(4) Refractive index:

The refractive index referred to herein refers to a refractive index value obtained by measuring a film having a film thickness of 100 nm when the light source wavelength range is 455 nm.

It can be understood from Table 1 that the refractive index of Specific Example 1 and Specific Example 2 is between 1.6 and 2.4, and is similar to the refractive index of the ITO film, indicating that Specific Example 1 and Specific Example 2 can be substituted for the ITO film for refractive use, and It is not limited to replace the ITO film used for refractive purposes.

(5) Carrier concentration:

As can be understood from Table 1, the carrier concentration of Specific Example 1 and Specific Example 2 is in the range of 1 × 10 ²⁰ to 1 × 10 ²¹ cm ^-3 , and is similar to the carrier concentration of the ITO film, and shows specific examples 1 and specific examples. 2 can replace the ITO film used in the semiconductor process, and is not limited to replace the ITO film used in the semiconductor process.

(6) Work function

When a metal oxide is applied to a photovoltaic element, the metal oxide needs to match the energy level of one of the adjacent actuation layers, so the work function is one of the important parameters for the transition and transmission of electrons and holes.

It can be understood from Table 1 that the work functions of the specific example 1 and the specific example 2 are between 5 and 6 eV, and compared with the work function of the comparative example 1, the work function closer to the ITO film indicates the specific example 1 and specific Example 2 is more suitable for replacing an ITO film applied to a photovoltaic element.

(7) Crystalline state:

When a metal oxide film is amorphous, its surface is flat to a higher extent than a crystalline metal oxide.

As can be understood from Table 1, after the specific examples 1, 2 and the comparative examples 1 and 2 were subjected to post-tempering, the specific examples 1 and 2 were still amorphous, and the comparative examples 1 and 2 were still in a crystalline state.

Further, it is worth mentioning that since the crystallization temperature of Comparative Example 2 (i.e., the ITO film) is about 150 ° C, when tempered at 220 ° C, a crystalline ITO film can theoretically be obtained. The reason why the comparative example 2 uses a tempering temperature of 280 ° C is because the tempering temperature of 280 ° C is usually used for the ITO film in the industry.

(8) Etching rate:

The etching rate referred to herein is wet etching using oxalic acid in an amount of 3.6 wt.% as an etchant and measuring the etching rate.

Since the amorphous metal oxide film does not have a specific lattice structure and lattice growth direction, the amorphous metal oxide phase is easier to be etched and removed than the crystalline metal oxide. That is, the etching rate is high.

According to Table 1, the etching rates of Specific Example 1 and Specific Example 2 were 1.5 to 2 times higher than those of the ITO film.

(9) Crystallization temperature:

It has been experimentally found that the crystallization temperature of the specific example 1 is 260 ° C, and the crystallization temperature of the specific example 2 is 330 ° C; indicating that the specific example 1 and the specific example 2 are applied to a photovoltaic device process or a semiconductor process to form the metal oxide film. After that, when the step of heating at a high temperature is required, since the crystallization temperature is high, it is not easy to self- The amorphous state was crystallized to form a crystalline state; in contrast, in Comparative Example 1, the crystallization temperature was similar to that of the ITO film, and was only 150 °C. It is shown that when Comparative Example 1 and the ITO film are subjected to a step of heating at a subsequent high temperature, they are easily crystallized.

Integrally, in (1) to (9), when the atomic content of indium of the metal oxide film is more than 80 at.%, and the ratio between the atomic content of zinc and the atomic content of tin is not more than 1.1, the film crystallization temperature is removed. In addition, the resistivity is higher than that of the ITO film, the conductivity is poor, the average light transmittance is low, and the work function is too high, which is not suitable for replacing the current ITO film; further, due to the metal oxide film of the present invention Based on the total atomic content of indium, zinc and tin of 100 at.%, the atomic content of indium ranges from 60 to 80 at.%, the atomic content of zinc ranges from 10 to 20 at.%, and the atomic content of tin ranges from 1 to 20 at.%. And the ratio of the atomic content of zinc to the atomic content of tin is greater than 1.1, the crystallization temperature is higher than the crystallization temperature of the ITO film, and is more suitable for a process requiring high temperature heating, and the etching rate is also higher than that of the ITO film. The etching rate, in turn, can be followed by a process after forming a metal oxide film, such as a patterning process, with better etching efficiency.

In summary, the metal oxide film of the present invention has a resistivity, a light transmittance, a refractive index, a carrier concentration, and a work function equivalent to that of the ITO film, and is suitable for replacing the ITO film; in particular, the crystallization temperature of the metal oxide film of the present invention. Above 250 ° C, it is suitable for the technical field of subsequent processes requiring high temperature heating and the like than the ITO film, so that the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are Still It is within the scope of the patent of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a line diagram showing the composition ratio of a target which is sputtered to form a metal oxide of the present invention to a ratio of a composition of a metal oxide film produced.

Claims (10)

A metal oxide film comprising: indium, zinc, tin and oxygen, wherein the atomic content of indium ranges from 60 to 80 at.% based on the total atomic content of indium, zinc and tin of 100 at.%, and the atomic content range of zinc For 10 to 25 at.%, the atomic content of tin ranges from 1 to 20 at.%, and the ratio of the atomic content of zinc to the atomic content of tin is greater than 1.1. The metal oxide film according to claim 1, wherein the indium has an atomic content ranging from 67 to 80 at.%, the zinc has an atomic content ranging from 12 to 18 at.%, and the tin has an atomic content ranging from 5 to 12 at. .%. The metal oxide film according to claim 2, wherein the indium has an atomic content ranging from 73 to 79 at.%, the zinc atomic content ranges from 14.5 to 16.5 at.%, and the tin atomic content ranges from 6 to 10.5 at.%. The metal oxide film according to claim 2, wherein a ratio between an atomic content of zinc and an atomic content of tin ranges from 1.6 to 2.4. The metal oxide film according to claim 1, wherein the metal oxide film is amorphous and has a crystallization temperature of more than 250 °C. A metal oxide film according to claim 5, wherein the electrical resistivity is not more than 7 × 10 ^-4 Ω-cm. The metal oxide film according to claim 5, wherein the average transmittance of the light source is in the range of 400 to 800 nm. The light rate is greater than 88%. The metal oxide film according to claim 5, wherein the refractive index of the light source at a wavelength of 455 nm is between 1.6 and 2.4. The metal oxide film according to claim 5, wherein the metal oxide film has a work function of between 5 and 6 eV. The metal oxide film according to claim 5, wherein the metal oxide film has a carrier concentration of between 1 × 10 ²⁰ and 1 × 10 ²¹ cm ^-3 .