High-mobility TCO film and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor materials, and discloses a high-mobility TCO film and a preparation method thereof. The preparation method comprises the following steps: (1) depositing a bottom TCO seed layer film on a cleaned substrate by using a magnetron sputtering technology; (2) depositing a top TCO thin film on the bottom TCO seed layer thin film by using a reactive plasma deposition (RPD) technology; and (3) carrying out annealing treatment on the deposited double-layer thin film to obtain the high-mobility TCO thin film. According to the method, the seed layer is deposited in a magnetron sputtering mode, then the top TCO thin film is deposited through the RPD technology, the advantages of the seed layer and the top TCO thin film are combined through the double-layer TCO thin film technology, the defects of the two technologies are overcome, and the high-performance TCO transparent conductive thin film which is good in adhesiveness, few in defect and high in mobility can be prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor materials, and in particular relates to a high-mobility TCO film and a preparation method thereof. Background Art

[0002] TCO (transparent conductive oxide) film is an important component of thin-film solar cells, with high light transmittance and low resistivity in the visible light wavelength range. High transmittance in the visible spectrum region is conducive to improving photoelectric conversion efficiency and reducing energy loss. The performance of TCO film has an important influence on the efficiency and life of thin-film solar cells. Therefore, the research and optimization of TCO film is one of the keys to improving the performance of thin-film solar cells.

[0003] At present, TCO thin films are mainly prepared on substrates by magnetron sputtering. For example, patent CN 103993279 A discloses that a TCO layer, a metal layer M and a TCO layer are prepared on a cleaned glass substrate in sequence by magnetron sputtering to obtain a TCO / M / TCO multilayer transparent conductive film. However, the film prepared by magnetron sputtering has large stress and many defects due to particle bombardment during the sputtering process, resulting in a low mobility. Patent CN 101974754 A discloses a coating method for a TCO / Ag / TCO composite transparent conductive film, which uses a sol-gel dip coating method or a spray thermal decomposition method to prepare a TCO thin film bottom layer, and then electrodeposit a transparent dense silver film on the TCO thin film bottom layer, and finally uses a sol-gel dip coating method or a spray thermal decomposition method to cover a TCO thin film surface layer on the transparent dense silver film. Although this method overcomes the defect of low mobility of magnetron sputtering film, the bottom layer of TCO film prepared by sol-gel dip coating or spray thermal decomposition has poor adhesion to the substrate and large contact resistance, which is not conducive to carrier transport. Patent CN 106282925 A discloses a method for preparing a TCO / TiW transparent conductive film, which deposits a TiW alloy film layer on the surface of a substrate by radio frequency magnetron sputtering, anneals the TiW alloy film layer / substrate structure, and then deposits TCO transparent conductive oxide on the surface of the annealed TiW alloy film layer by radio frequency magnetron sputtering. This patent uses a TiW alloy film layer as a diffusion barrier to prevent the formation of an intermediate oxide layer, which can significantly improve the contact performance between the TCO film and the substrate, but still cannot solve the problem of low mobility of magnetron sputtering films. Summary of the invention

[0004] In view of the above shortcomings and deficiencies in the prior art, the primary purpose of the present invention is to provide a method for preparing a high-mobility TCO film.

[0005] Another object of the present invention is to provide a high-mobility TCO film prepared by the above method.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a high-mobility TCO film comprises the following preparation steps:

[0008] (1) Depositing a bottom TCO seed layer thin film on the cleaned substrate using magnetron sputtering technology;

[0009] (2) Depositing a top TCO film on the bottom TCO seed layer using reactive plasma deposition (RPD) technology;

[0010] (3) Annealing the deposited double-layer film to obtain a high-mobility TCO film.

[0011] Furthermore, the substrate in step (1) is a glass substrate or a silicon wafer substrate.

[0012] Furthermore, the conditions for depositing the bottom TCO seed layer film in step (1) are as follows:

[0013] The deposition temperature is 25-250° C., the deposition power is 1-10 kW, the deposition pressure is 0.2-0.8 Pa, the oxygen partial pressure is 0%-3%, and the hydrogen partial pressure is 0%-3%.

[0014] Furthermore, the bottom TCO seed layer film in step (1) is an ITO (indium tin oxide), AZO (aluminum-doped zinc oxide), VTTO (doped indium oxide target) or VTZO (indium-free tin oxide target) transparent conductive film.

[0015] Furthermore, the thickness of the bottom TCO seed layer film in step (1) is 5 to 20 nm.

[0016] Furthermore, the conditions for depositing the top TCO film in step (2) are as follows:

[0017] The substrate temperature is 25-300°C, the voltage is 2.5-3kV, the current is 13-15mA, the oxygen partial pressure is 0%-3%, and the hydrogen partial pressure is 0%-3%.

[0018] Furthermore, the top TCO film in step (2) is ITO, AZO, ICO (cerium-doped indium oxide), IWO (tungsten-doped indium oxide), IMO (molybdenum-doped indium oxide) or VTTO transparent conductive film.

[0019] Furthermore, the thickness of the top TCO film in step (2) is 80 to 95 nm.

[0020] Furthermore, the annealing treatment in step (3) refers to annealing treatment in air at 150° C. to 250° C. for 15 to 60 minutes.

[0021] A high-mobility TCO film is prepared by the method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention uses magnetron sputtering to deposit the seed layer, which can improve the adhesion between the bottom TCO film and the substrate material, making the film less likely to fall off; it can also improve the contact characteristics between the bottom TCO and the substrate, reduce the contact resistance, and facilitate the transport of carriers. However, the film prepared by this method alone has high stress and many defects due to the bombardment of particles during the sputtering process, resulting in a low mobility. By using the RPD technology to prepare the top TCO film, since there is no bombardment of high-energy particles on the film, the stress is low and the defects are few, which can greatly improve the mobility of carriers in the film. However, the film prepared by this method alone has poor adhesion to the substrate material, and the film is easy to fall off. The present invention first uses magnetron sputtering to deposit the seed layer, and then deposits the top TCO film by RPD technology. This double-layer TCO film process combines the advantages of the two technologies, overcomes the shortcomings of the two technologies, and can prepare a high-performance TCO transparent conductive film with good adhesion, few defects and high mobility. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0025] Example 1

[0026] (1) Install the ITO target on the PVD equipment, place the cleaned glass substrate inside the equipment, and reach a background vacuum of 5.0E -4 The sputtering process starts after the temperature drops below Pa. The power supply is 5 kW and the working atmosphere is adjusted to 2% O 2 , 1% H 2 The sputtering temperature is room temperature, the sputtering gas pressure is 0.5 Pa, and the sputtering thickness of the bottom ITO seed layer film is 5 nm.

[0027] (2) Place the ICO evaporation material and the substrate with the seed layer deposited inside the RPD device, and the background vacuum reaches 5.0E - 4 After the pressure drops below Pa, evaporation coating begins. The substrate temperature is 300°C, the oxygen flow rate is 0 sccm, the voltage is 2.5-3 kV, the current is 13-15 mA, and a 95 nm thick top ICO film is deposited.

[0028] (3) The obtained double-layer TCO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to finally obtain a high-mobility TCO film.

[0029] Example 2

[0030] (1) Install the ITO target on the PVD equipment, place the cleaned glass substrate inside the equipment, and reach a background vacuum of 5.0E -4 The sputtering process starts after the temperature drops below Pa. The power supply is 5 kW and the working atmosphere is adjusted to 2% O 2 , 1% H 2 The sputtering temperature is room temperature, the sputtering gas pressure is 0.5 Pa, and the sputtering thickness is 10 nm for the bottom ITO seed layer film.

[0031] (2) Place the ICO evaporation material and the substrate with the seed layer deposited inside the RPD device, and the background vacuum reaches 5.0E - 4 Pa, the evaporation coating was started. The substrate temperature was 300°C, the oxygen flow rate was 0 sccm, the voltage was 2.5-3 kV, the current was 13-15 mA, and a 90 nm thick top ICO film was deposited.

[0032] (3) The obtained double-layer TCO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to finally obtain a high-mobility TCO film.

[0033] Example 3

[0034] (1) Install the ITO target on the PVD equipment, place the cleaned glass substrate inside the equipment, and reach a background vacuum of 5.0E -4 The sputtering process starts after the temperature drops below Pa. The power supply is 5 kW and the working atmosphere is adjusted to 2% O 2 , 1% H 2 The sputtering temperature is room temperature, the sputtering gas pressure is 0.5 Pa, and the sputtering thickness of the bottom ITO seed layer film is 15 nm.

[0035] (2) Place the ICO evaporation material and the substrate with the seed layer deposited inside the RPD device, and the background vacuum reaches 5.0E - 4 Pa, the evaporation coating was started. The substrate temperature was 300°C, the oxygen flow rate was 0 sccm, the voltage was 2.5-3 kV, the current was 13-15 mA, and a top ICO film of 85 nm thickness was deposited.

[0036] (3) The obtained double-layer TCO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to finally obtain a high-mobility TCO film.

[0037] Example 4

[0038] (1) Install the AZO target on the PVD equipment, place the cleaned glass substrate inside the equipment, and reach a background vacuum of 5.0E -4 The sputtering process starts after the temperature drops below Pa. The power supply is 5 kW and the working atmosphere is adjusted to 2% O 2 , 1% H 2 The sputtering temperature is room temperature, the sputtering gas pressure is 0.5 Pa, and the sputtered bottom AZO seed layer film has a thickness of 20 nm.

[0039] (2) Place the AZO evaporation material and the substrate with the seed layer deposited inside the RPD device, and the background vacuum reaches 5.0E - 4 Pa, the evaporation coating was started. The substrate temperature was 300°C, the oxygen flow rate was 0 sccm, the voltage was 2.5-3 kV, the current was 13-15 mA, and a top AZO film with a thickness of 80 nm was deposited.

[0040] (3) The obtained double-layer AZO film is placed in an air annealing furnace for annealing at 250°C for 20 min to finally obtain a high-mobility TCO film.

[0041] Example 5

[0042] (1) Install the VTTO target on the PVD equipment, place the cleaned glass substrate inside the equipment, and reach a background vacuum of 5.0E -4 The sputtering process starts after the temperature drops below Pa. The power supply is 5 kW and the working atmosphere is adjusted to 2% O 2 , 1% H 2 The sputtering temperature is room temperature, the sputtering gas pressure is 0.5 Pa, and the sputtering thickness of the bottom VTTO seed layer film is 10 nm.

[0043] (2) Place the IWO evaporated material and the substrate with the seed layer deposited inside the RPD device, and the background vacuum reaches 5.0E - 4 After the pressure drops below Pa, evaporation coating begins. The substrate temperature is 300°C, the oxygen flow rate is 0 sccm, the voltage is 2.5-3 kV, the current is 13-15 mA, and a 90 nm thick top IWO film is deposited.

[0044] (3) The obtained double-layer TCO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to finally obtain a high-mobility TCO film.

[0045] Comparative Example 1

[0046] Compared with Example 2, this comparative example directly prepares a single-layer ITO film by PVD equipment, and the specific steps are as follows:

[0047] (1) Install the ITO target on the PVD equipment, place the cleaned glass substrate inside the equipment, and reach a background vacuum of 5.0E -4 The sputtering process starts after the temperature drops below Pa. The power supply is 5 kW and the working atmosphere is adjusted to 2% O 2 , 1% H 2 , the sputtering temperature is room temperature, the sputtering gas pressure is 0.5 Pa, and a single-layer ITO film with a sputtering thickness of 100 nm is obtained.

[0048] (2) The obtained single-layer ITO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to obtain a TCO film.

[0049] Comparative Example 2

[0050] Compared with Example 2, this comparative example directly prepares a single-layer ICO film by RPD equipment, and the specific steps are as follows:

[0051] (1) Place the ICO evaporation material and the cleaned glass substrate in the RPD equipment, and the background vacuum reaches 5.0E -4 After the pressure drops below Pa, evaporation coating begins. The substrate temperature is 300°C, the oxygen flow rate is 0 sccm, the voltage is 2.5-3 kV, the current is 13-15 mA, and a single-layer ICO film with a thickness of 100 nm is deposited.

[0052] (2) The obtained single-layer ICO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to obtain a TCO film.

[0053] Comparative Example 3

[0054] Compared with Example 4, this comparative example directly prepares a single-layer AZO film by PVD equipment, and the specific steps are as follows:

[0055] (1) Install the AZO target on the PVD equipment, place the cleaned glass substrate inside the equipment, and reach a background vacuum of 5.0E -4 The sputtering process starts after the temperature drops below Pa. The power supply is 5 kW and the working atmosphere is adjusted to 2% O 2 , 1% H 2 , the sputtering temperature is room temperature, the sputtering gas pressure is 0.5 Pa, and a single-layer AZO film with a sputtering thickness of 100 nm is obtained.

[0056] (2) The obtained single-layer AZO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to obtain a TCO film.

[0057] Comparative Example 4

[0058] Compared with Example 4, this comparative example directly prepares a single-layer AZO film by RPD equipment, and the specific steps are as follows:

[0059] (1) Place the AZO evaporation material and the cleaned glass substrate in the RPD equipment, and the background vacuum reaches 5.0E -4 The evaporation coating was started after the pressure dropped below Pa. The substrate temperature was 300°C, the oxygen flow rate was 0 sccm, the voltage was 2.5-3 kV, the current was 13-15 mA, and a single-layer AZO film with a thickness of 100 nm was deposited.

[0060] (2) The obtained single-layer AZO film is placed in an air annealing furnace for annealing at 250° C. for 20 min to obtain a TCO film.

[0061] The mobility and contact resistance of the TCO films obtained in the above examples and comparative examples were tested, and the results are shown in Table 1 below.

[0062] Table 1

[0063]

[0064]

[0065] From the data of Example 2 and Comparative Examples 1-2 in the above table, it can be seen that the mobility of the ICO film plated by full RPD is much higher than that of the ITO film plated by magnetron sputtering. On the one hand, it is because of the different types of materials, and on the other hand, it is because the defect density of the evaporated film is much lower than that of the sputtered film. Therefore, the mobility of Comparative Example 2 is much higher than that of Comparative Example 1, but the adhesion of the sputtered film to the substrate is better than that of the evaporated film, so the contact resistance is relatively small. Example 2 combines the two processes. The bottom layer uses magnetron sputtering to increase the contact with the substrate, and the upper layer uses RPD technology to evaporate the film, which can not only improve the contact with the substrate, but also reduce the defects of the magnetron sputtered film, thereby greatly improving the mobility of the film.

[0066] From the data of Example 4 and Comparative Examples 3-4 in the above table, it can be seen that the mobility of the pure sputtered AZO film is only 13.71 cm 2 / V·s, contact resistance is 32.6mΩ·cm 2 ; The mobility of the evaporated AZO film reached 36.13cm 2 / V·s, the contact resistance reached 35.7mΩ·cm 2 ; The mobility of the film combined with sputtering and evaporation can reach 30.11cm 2 / V·s, the contact resistance also decreased to 33.1mΩ·cm 2 .

[0067] It can be seen that the thin film prepared by combining sputtering and evaporation can combine the advantages of both, which can not only improve the mobility of the film, but also increase the contact characteristics with the substrate material.

[0068] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a high mobility TCO film, characterized in that: The method comprises the following preparation steps: (1) Depositing a bottom TCO seed layer thin film on the cleaned substrate using magnetron sputtering technology; (2) Depositing a top TCO film on the bottom TCO seed layer using reactive plasma deposition (RPD) technology; (3) Annealing the deposited double-layer film to obtain a high-mobility TCO film.

2. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The substrate in step (1) is a glass substrate or a silicon wafer substrate.

3. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The conditions for depositing the bottom TCO seed layer film in step (1) are as follows: The deposition temperature is 25-250° C., the deposition power is 1-10 kW, the deposition pressure is 0.2-0.8 Pa, the oxygen partial pressure is 0%-3%, and the hydrogen partial pressure is 0%-3%.

4. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The bottom TCO seed layer film in step (1) is an ITO, AZO, VTTO or VTZO transparent conductive film.

5. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The thickness of the bottom TCO seed layer film in step (1) is 5 to 20 nm.

6. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The conditions for depositing the top TCO film in step (2) are as follows: The substrate temperature is 25-300°C, the voltage is 2.5-3kV, the current is 13-15mA, the oxygen partial pressure is 0%-3%, and the hydrogen partial pressure is 0%-3%.

7. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The top TCO film in step (2) is a transparent conductive film of ITO, AZO, ICO, IWO, IMO or VTTO.

8. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The thickness of the top TCO film in step (2) is 80 to 95 nm.

9. The method for preparing a high-mobility TCO thin film according to claim 1, characterized in that: The annealing treatment in step (3) refers to annealing treatment in air at 150°C to 250°C for 15 to 60 minutes.

10. A high mobility TCO film, characterized in that: It is prepared by the method according to any one of claims 1 to 9.

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