Indium tin oxide film with low surface roughness and preparation method thereof

Abstract

The invention belongs to the technical field of ITO (indium tin oxide) films, and discloses an indium tin oxide film with low surface roughness and a preparation method thereof, in the indium tin oxide film, the molar content of In2O3 is 88-92%, the molar content of SnO2 is 8-12%, and the molar content of SnO2 is 8-12%. The indium tin oxide thin film is prepared from an indium tin oxide target material under the condition that Ar-H2 gas and Ar-O2 gas are continuously introduced at the sputtering power of 800-1000 w; the thickness of the indium tin oxide film is 100-110 nm, the flow rate of the Ar-H2 gas is 80-90% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2-3%, and the volume content of O2 in the Ar-O2 gas is 10-11%. The invention discloses an indium tin oxide thin film with low surface roughness, the surface roughness of the indium tin oxide thin film is far lower than 3nm required by high-end thin film application and reaches the level lower than 1nm, and the transmission effect of electrons on the surface of the thin film in the thin film application process is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of ITO thin films, and in particular to an indium tin oxide thin film with low surface roughness and a preparation method thereof. Background Art

[0002] ITO film, or indium tin oxide film, is a material that is both transparent and highly conductive. ITO film plays an important role in screen technologies such as tablet computers and smartphones; through a high-precision sputtering process, ITO film can ensure that the screens of these devices have high clarity and sensitivity; it has shown broad application prospects in various fields, such as electronic displays, solar cells, antistatic coatings, etc.

[0003] Among them, high-end ITO is mainly used in flat panel display, integrated circuit semiconductor, solar photovoltaic, magnetic recording and optical recording, especially in large-area and large-size TFT-LCD, OLED and other fields, with the characteristics of high density, high purity and high uniformity.

[0004] Regarding the preparation of ITO thin films, a number of prior arts have been disclosed, thereby obtaining ITO thin films with better performance. For example, prior art 1: Chinese patent application 202310476452.6 discloses a low-temperature magnetron sputtering ITO transparent conductive film and a preparation method thereof. The preparation method of the low-temperature magnetron sputtering ITO transparent conductive film comprises the following steps: (1) the background vacuum of the sputtering chamber is less than 1.0×10 -5 Pa; (2) under a pure Ar working pressure of 0.2 Pa, pre-sputtering the In2O3·SnO2 composite target at a sputtering power of 20 W for 5-10 minutes to remove surface impurities, the In2O3 molar content of the target is 90%, the SnO2 molar content is 10%, and the purity of In, Sn, and O elements in the target is 99.99%; (3) then under a pure Ar working pressure of 0.2 Pa, depositing an ITO thin film on the substrate described in step ① at a sputtering power of less than 20 W, the deposition rate is less than 2 nm / min, the substrate temperature is 20°C-100°C, and the deposition thickness is about 80-100 nm, thereby obtaining an ITO transparent conductive film.

[0005] The preparation method of prior art 1 can prepare an indium tin oxide film with high transmittance and low resistivity. According to Examples 1-3 of prior art 1, it can be known that the surface roughness of the indium tin oxide film prepared by prior art 1 is less than 5 nm, but the surface roughness is difficult to meet the requirements of higher-end ITO films.

[0006] In the display industry, if the roughness of the film is large, it will have a greater impact on its surface contact resistance. After a large number of experiments, it was found that the roughness of the film is 3nm, which is a very important critical point. When the roughness is less than 3nm, the electron transmission effect on the film surface is better, which can better meet the requirements for the preparation of high-end optoelectronic devices and can exert better performance. Summary of the invention

[0007] One of the purposes of the present invention is to provide an indium tin oxide film with low surface roughness, wherein the surface roughness is less than 3 nm, which can significantly reduce the surface contact resistance, make the transmission effect of electrons on the surface of the film more excellent, and meet the preparation requirements of high-end optoelectronic devices.

[0008] Another object of the present invention is to provide a method for preparing an indium tin oxide film with low surface roughness. The indium tin oxide film prepared by the preparation method has the advantages of low surface roughness and excellent optical and electrical properties.

[0009] To achieve the above-mentioned object, the present invention provides an indium tin oxide film with low surface roughness, wherein the molar content of In2O3 in the indium tin oxide film is 88-92%, and the molar content of SnO2 is 8-12%. The indium tin oxide film is prepared by sputtering an indium tin oxide target with a sputtering power of 800-1000w under the condition of continuous introduction of Ar-H2 gas and Ar-O2 gas; the thickness of the indium tin oxide film is 100-110nm, the flow rate of the Ar-H2 gas is 80-90% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2-3%, and the volume content of O2 in the Ar-O2 gas is 10-11%.

[0010] During sputtering, hydrogen doping can promote the crystallization process of the film, making the crystal structure of the film more complete and orderly; at the same time, hydrogen doping makes the stoichiometric ratio of the film closer to the ideal stoichiometric ratio, thereby improving the quality and performance of the film.

[0011] The introduction of an appropriate amount of oxygen can reduce defects and pores in the film, make the film structure denser, and improve its hardness, wear resistance and corrosion resistance. At the same time, the introduction of oxygen can affect its electrical properties, change its carrier concentration, adjust resistivity, etc. At the same time, it can also adjust its optical properties, adjust the film's refractive index, extinction coefficient and other optical constants, thereby changing its optical transmittance.

[0012] The present invention has found that under the supply of specific hydrogen flow and oxygen flow, the crystallization growth of the film during the sputtering process is well controlled. Combined with a specific sputtering power, the probability of crystal structure mutation during film growth can be effectively reduced, so that the surface roughness of the indium tin oxide film is controlled to be far below the critical point of 3nm, effectively improving the transmission effect of electrons on the film surface.

[0013] The present invention also discloses a method for preparing an indium tin oxide film with low surface roughness, comprising the following steps:

[0014] Step 1: Remove impurities from the surface of the indium tin oxide target;

[0015] Step 2: Continuously introduce Ar-H2 gas and Ar-O2 gas, and prepare an indium tin oxide film using the indium tin oxide target obtained in step 1 at a sputtering power of 800-1000w.

[0016] Furthermore, the specific operation of step 1 is: pre-sputtering the indium tin oxide target at a sputtering power of 600 W for 5-20 minutes under 3 mtorr of pure Ar gas.

[0017] Furthermore, the sputtering pressure in step 2 is 2.5-5.2 mtorr.

[0018] Furthermore, in step 2, the target spacing is 45-100 mm.

[0019] In the technical field, the target spacing is the distance between the target and the substrate.

[0020] Furthermore, the deposition rate of the indium tin oxide film in step 2 is less than 4 nm / s.

[0021] Preferably, the specific operation of step 2 is: installing the substrate and the indium tin oxide target obtained in step 1, continuously introducing Ar-H2 gas and Ar-O2 gas, and depositing an indium tin oxide film on the substrate with the indium tin oxide target obtained in step 1 at a sputtering power of 800-1000w, and maintaining the substrate temperature at 25-200°C during the process.

[0022] More preferably, the material of the substrate can be selected from one of glass, quartz, sapphire, silicon, polyimide PI, and polyethylene terephthalate PET.

[0023] Preferably, the method further comprises step 3: annealing the indium tin oxide film obtained in step 2 at a temperature of 200-350°C.

[0024] In actual production and research and development, technical personnel in this field currently tend to optimize the vacuum coating system and conduct in-depth research on the physical process of the film to continuously improve the quality and performance of magnetron sputtered ITO films and further promote the development of transparent conductive technology.

[0025] In particular, with respect to the technical solution of the present invention, when a DC magnetron sputtering PVD coating machine is used to prepare an indium tin oxide thin film, a more preferred specific preparation method includes the following steps:

[0026] Step a: Pump the background vacuum of the sputtering chamber to below 6E -6 Torr;

[0027] Step b: installing an indium tin oxide target, and pre-sputtering the indium tin oxide target at a sputtering power of 600 W for 5-20 minutes under 3 mtorr of pure Ar gas to remove impurities on the surface of the indium tin oxide target;

[0028] Step c: ultrasonically cleaning and drying the substrate with nitrogen in sequence, and then placing the substrate in a waiting chamber;

[0029] Step d: introducing pure Ar gas into the sputtering chamber to make the vacuum degree in the sputtering chamber between 2.5-5.2 mtorr;

[0030] Step e: placing the substrate into a sputtering chamber, continuously introducing Ar-H2 gas and Ar-O2 gas to maintain the vacuum degree in the sputtering chamber between 2.5-5.2 mtorr, setting the target spacing to 45-100 nm, and then depositing an indium tin oxide film on the substrate at a sputtering power of 800-1000 w; during the process, maintaining the substrate temperature at 25-200 ° C, and maintaining the deposition rate of the indium tin oxide film <4 nm / s; wherein the flow rate of the Ar-H2 gas is 80-90% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2-3%, and the volume content of O2 in the Ar-O2 gas is 10-11%;

[0031] Step f: annealing the indium tin oxide film at a temperature of 200-350° C. for 30 minutes.

[0032] Beneficial Effects

[0033] Compared with the prior art, the present invention has at least the following advantages:

[0034] (1) The present invention discloses an indium tin oxide film with low surface roughness. The surface roughness of the indium tin oxide film is far lower than the 3nm required for high-end film applications and reaches a level lower than 1nm, which greatly improves the transmission effect of electrons on the film surface during the film application process;

[0035] (2) The present invention discloses a method for preparing an indium tin oxide film with low surface roughness, wherein the concentration and flow rate of hydrogen and the concentration and flow rate of oxygen in the introduced gas, as well as the sputtering power, are controlled during the process of preparing the indium tin oxide film by sputtering an indium tin oxide target material, thereby sputtering an indium tin oxide film with a surface roughness of less than 1 nm;

[0036] (3) The method for preparing an indium tin oxide film with low surface roughness disclosed in the present invention provides hydrogen and oxygen for the sputtering process via Ar-H2 gas and Ar-O2 gas, respectively. Compared with the gas supply method of directly using a mixture of oxygen, hydrogen and argon at a specific partial pressure, it is more conducive to the role of hydrogen and oxygen in the sputtering process, thereby further reducing the surface roughness of the indium tin oxide film. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the embodiments, but it does not constitute any limitation to the present invention. Any limited number of modifications made within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0038] In order to explain the technical content of the present invention in detail, further description is given below in conjunction with the implementation modes.

[0039] In the following embodiments and comparative examples, glass substrates are used as substrates, and the glass substrates are ultrasonically cleaned using deionized water, acetone, and ethanol in sequence, and then blown dry using nitrogen. Since cleaning and drying of glass substrates belong to the prior art in this field, the specific process details will not be described in detail here.

[0040] In the following examples and comparative examples, the following steps were performed before the indium tin oxide film was prepared:

[0041] Step a: Pump the background vacuum of the sputtering chamber to below 6E -6 Torr;

[0042] Step b: installing an indium tin oxide target, and pre-sputtering the indium tin oxide target at a sputtering power of 600 W for 15 minutes under 3 mtorr of pure Ar gas to remove impurities on the surface of the indium tin oxide target;

[0043] Step c: Pure Ar gas is introduced into the sputtering chamber to make the vacuum degree in the sputtering chamber between 3.5±0.2 mtorr, a glass substrate is placed in the sputtering chamber, and the target spacing is set to 90 nm.

[0044] Example 1

[0045] An indium tin oxide film with low surface roughness is prepared by using an indium tin oxide target material with a molar content of In2O3 of 88% and a molar content of SnO2 of 12% as a sputtering target material through the following steps:

[0046] Step 1: Continuously introduce Ar-H2 gas and Ar-O2 gas with a total flow rate of 85 sccm, and deposit a 100 nm thick indium tin oxide film with low surface roughness on a glass substrate at a deposition rate of 3 nm / s with a sputtering power of 900 w, wherein the flow rate of the Ar-H2 gas is 80% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2%, and the volume content of O2 in the Ar-O2 gas is 10%; during the process, the temperature of the glass substrate is maintained at 28°C, and the sputtering pressure is maintained at 3±0.2 mtorr.

[0047] Example 2

[0048] An indium tin oxide film with low surface roughness is prepared by using an indium tin oxide target material with a molar content of In2O3 of 88% and a molar content of SnO2 of 12% as a sputtering target material through the following steps:

[0049] Step 1: Continuously introduce Ar-H2 gas and Ar-O2 gas with a total flow rate of 85 sccm, and deposit a 100 nm thick indium tin oxide film on a glass substrate at a deposition rate of 3 nm / s with a sputtering power of 900 w. The flow rate of the Ar-H2 gas is 80% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas. The volume content of H2 in the Ar-H2 gas is 2%, and the volume content of O2 in the Ar-O2 gas is 10%. During the process, the temperature of the glass substrate is maintained at 28°C, and the sputtering pressure is maintained at 3±0.2 mtorr.

[0050] Step 2: Anneal the indium tin oxide film obtained in step 1 at a temperature of 250° C. for 30 minutes.

[0051] Example 3

[0052] It is generally the same as Example 2, except that an indium tin oxide target with a molar content of In2O3 of 92% and a molar content of SnO2 of 8% is used as the sputtering target.

[0053] Example 4

[0054] It is generally the same as Example 2, except that an indium tin oxide target material having a molar content of In2O3 of 90% and a molar content of SnO2 of 10% is used as the sputtering target material.

[0055] Example 5

[0056] It is generally the same as Example 2, except that the sputtering power of step 1 is 800 W, the flow rate of the Ar-H2 gas is 90% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2%, and the volume content of O2 in the Ar-O2 gas is 10%.

[0057] Example 6

[0058] It is generally the same as Example 2, except that the sputtering power of step 1 is 1000W, the flow rate of the Ar-H2 gas is 85% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 3%, and the volume content of O2 in the Ar-O2 gas is 11%.

[0059] Comparative Example 1

[0060] It is generally the same as Example 2, except that an indium tin oxide target with a molar content of In2O3 of 86% and a molar content of SnO2 of 14% is used as the sputtering target.

[0061] Comparative Example 2

[0062] It is generally the same as Example 2, except that an indium tin oxide target material with a molar content of In2O3 of 95% and a molar content of SnO2 of 5% is used as the sputtering target material.

[0063] Comparative Example 3

[0064] It is generally the same as Example 2, except that the gas introduced in step 1 is pure Ar gas.

[0065] Comparative Example 4

[0066] It is generally the same as Example 2, except that the gas introduced in step 1 is Ar-O2 gas, and the volume content of O2 in the Ar-O2 gas is 10%.

[0067] Comparative Example 5

[0068] It is generally the same as Example 2, except that the gas introduced in step 1 is Ar-H2 gas, and the volume content of H2 in the Ar-H2 gas is 2%.

[0069] Comparative Example 6

[0070] It is generally the same as Example 2, except that the flow rate of the Ar-H2 gas is 70% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2%, and the volume content of O2 in the Ar-O2 gas is 10%.

[0071] Comparative Example 7

[0072] It is generally the same as Example 2, except that the flow rate of the Ar-H2 gas is 95% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2%, and the volume content of O2 in the Ar-O2 gas is 10%.

[0073] Comparative Example 8

[0074] It is generally the same as Example 2, except that the sputtering power of step 1 is 600W.

[0075] Comparative Example 9

[0076] It is generally the same as Example 2, except that the sputtering power of step 1 is 1100W.

[0077] The indium tin oxide films obtained in Examples 1-6 and Comparative Examples 1-9 were tested by ultra-precision atomic force microscopy to test the clean points of the films and obtain the roughness of the indium tin oxide films. The results are shown in Table 1.

[0078] Table 1 Surface roughness results of indium tin oxide films obtained in Examples 1-6 and Comparative Examples 1-9

[0079] Surface roughness Ra(nm) Example 1 0.282 Example 2 0.435 Example 3 0.679 Example 4 0.784 Example 5 0.563 Example 6 0.994 Comparative Example 1 2.745 Comparative Example 2 1.945 Comparative Example 3 3.517 Comparative Example 4 3.448 Comparative Example 5 3.294 Comparative Example 6 1.943 Comparative Example 7 2.041 Comparative Example 8 2.517 Comparative Example 9 1.547

[0080] According to the results in Table 1, we can see that:

[0081] According to the data comparison between Example 1 and Example 2, it can be seen that the annealing treatment of the film will cause the surface roughness of the film to increase significantly, but overall the indium tin oxide film prepared by the present invention after annealing still has an extremely low surface roughness, which can greatly reduce the surface contact resistance of the film and improve the transmission effect of electrons on the surface of the film.

[0082] According to the data comparison between Example 2, Example 3 and Example 4, it can be seen that the component composition of the target material will also have a certain influence on the surface roughness of the film. The reason is that different component compositions will cause certain changes in the growth process of the crystal during sputtering; but in general, the technical solutions of the present invention can control the surface roughness of the indium tin oxide film to below 1 nm.

[0083] According to the data of Example 2, Example 5 and Example 6, the sputtering power and the flow rate control of hydrogen and oxygen in the gas supply system will also affect the surface roughness of the indium tin oxide film, but in general, the technical solutions of the present invention can control the surface roughness of the indium tin oxide film to below 1 nm.

[0084] According to the data comparison between Examples 2-4 and Comparative Examples 1 and 2, when the component composition of the target material exceeds the scope of the present invention, too much or too little indium oxide will also make it difficult to fully control the growth process of the crystal during the sputtering process, thereby causing the surface roughness of the indium tin oxide film prepared in Comparative Examples 1 and 2 to be significantly improved, and the surface contact resistance of the indium tin oxide film is greatly improved. Although the critical point of the surface roughness of 3nm is broken through, the effect of improving the transmission of electrons on the surface is significantly reduced compared with the technical solution of the present invention.

[0085] According to the data of Comparative Examples 3-5, if pure Ar gas, Ar-O2 gas or Ar-H2 gas is used to sputter the indium tin oxide film, the surface roughness of the indium tin oxide film will not exceed the critical point below 3nm, which means that in the technical solution of the present invention, the selection of gas is particularly important; however, according to the data of Comparative Examples 6 and 7, if only the technical solution of Ar-O2 gas and Ar-H2 gas is used, and the flow ratio of Ar-O2 gas and Ar-H2 gas is not controlled, the crystal growth of the indium tin oxide film cannot be stably and effectively controlled during the sputtering process. Although the finally obtained indium tin oxide film breaks through the critical point below 3nm, the indium tin oxide film with a surface roughness lower than 1nm cannot be obtained, and the influence on the electron transmission effect on the film surface at the application end is particularly obvious.

[0086] Similarly, according to the data comparison between Example 2 and Comparative Examples 8 and 9, it can be seen that the sputtering power in the technical solution of the present invention is complementary to the selection of gas, and is intended to control the crystal growth of the indium tin oxide film during the sputtering process, thereby obtaining an indium tin oxide film with lower surface roughness.

[0087] The embodiments presented herein are only embodiments selected according to the combination of all possible embodiments. The appended claims should not be limited by the embodiments describing the present invention. Some numerical ranges used in the claims include sub-ranges therein, and the changes in these ranges should also be covered by the appended claims.

Claims

1. An indium tin oxide film with low surface roughness, wherein the molar content of In2O3 in the indium tin oxide film is 88-92%, and the molar content of SnO2 is 8-12%, characterized in that: The indium tin oxide film is prepared by sputtering an indium tin oxide target at a sputtering power of 800-1000w under the condition of continuous introduction of Ar-H2 gas and Ar-O2 gas; the thickness of the indium tin oxide film is 100-110nm, the flow rate of the Ar-H2 gas is 80-90% of the total flow rate of the Ar-H2 gas and the Ar-O2 gas, the volume content of H2 in the Ar-H2 gas is 2-3%, and the volume content of O2 in the Ar-O2 gas is 10-11%.

2. A method for preparing an indium tin oxide thin film with low surface roughness as claimed in claim 1, characterized in that: The steps include: Step 1: Remove impurities from the surface of the indium tin oxide target; Step 2: Continuously introduce Ar-H2 gas and Ar-O2 gas, and prepare an indium tin oxide film using the indium tin oxide target obtained in step 1 at a sputtering power of 800-1000w.

3. The method for preparing an indium tin oxide thin film with low surface roughness according to claim 2, characterized in that: The specific operation of step 1 is: pre-sputtering the indium tin oxide target at a sputtering power of 600 W for 5-20 minutes under 3 mtorr of pure Ar gas.

4. The method for preparing an indium tin oxide thin film with low surface roughness according to claim 2, characterized in that: The sputtering pressure in step 2 is 2.5-5.2 mtorr.

5. The method for preparing an indium tin oxide thin film with low surface roughness according to claim 2, characterized in that: In step 2, the target spacing is 45-100 mm.

6. The method for preparing an indium tin oxide thin film with low surface roughness according to claim 2, characterized in that: The deposition rate of the indium tin oxide film in step 2 is less than 4 nm / s.

7. The method for preparing an indium tin oxide thin film with low surface roughness according to any one of claims 2 to 6, characterized in that: The specific operation of step 2 is: installing the substrate and the indium tin oxide target obtained in step 1, continuously introducing Ar-H2 gas and Ar-O2 gas, and depositing an indium tin oxide film on the substrate with the indium tin oxide target obtained in step 1 at a sputtering power of 800-1000w, and maintaining the substrate temperature at 25-200°C during the process.

8. The method for preparing an indium tin oxide thin film with low surface roughness according to any one of claims 2 to 6, characterized in that: The method further comprises step 3: annealing the indium tin oxide film obtained in step 2 at a temperature of 200-350°C.