TWI571429B - Transparent conductive film and method of manufacturing the same - Google Patents

Description

Transparent conductive film and method of manufacturing same

The present invention relates to a technique of a transparent conductive film, and more particularly to a transparent conductive film and a method of manufacturing the same.

In the photovoltaic element, since it is necessary to balance the characteristics of light transmission and conduction, a transparent conductive film is often used as an electrode or a wire. At present, it is considered that the material is non-toxic and low-cost, and the aluminum zinc (AZO) film is more commonly used, and its aluminum content ranges from 2 wt% to 10 wt%, due to the close amount of aluminum doping and light penetration and conductivity. Relationship, when the amount of aluminum doping is high, the conductivity is improved, but it tends to aggregate during the sputtering process to produce a precipitated phase, resulting in a decrease in light transmittance, or formation of an oxide of Al ₂ O ₃ , resulting in conductivity. Therefore lower. However, an insufficient amount of aluminum doping will also cause an increase in conductivity.

Therefore, many recent studies have improved the conductivity by placing a metal layer in the AZO film. However, when a very thin metal layer is deposited by sputtering, it is easy to form a micro-structure aggregation, which causes a Mie scattering effect, which in turn causes a decrease in transmittance.

In addition, it has been studied to replace the transparent conductive film with a metal mesh structure or to place it therein, but it needs to be completed by a relatively cumbersome chemical formation method or an etching technique with a mask.

The present invention provides a method for producing a transparent conductive film which can form a transparent conductive film which does not affect the transmittance and enhances its conductive characteristics by a low process cost.

The present invention further provides a transparent conductive film which can have excellent electrical conductivity and transmittance.

A method for producing a transparent conductive film of the present invention comprises forming a zinc oxide (ZnO) seed layer on a surface of a substrate, and dry etching the zinc oxide seed layer to form a plurality of roughened tips on the surface thereof, at the roughening tip Nano metal particles are deposited on the portion, and a transparent conductive layer is formed on the zinc oxide seed layer and the nano metal particles.

In an embodiment of the invention, the gas used in the dry etching includes oxygen and an inert gas.

In an embodiment of the invention, the transparent conductive layer comprises an aluminum zinc oxide (AZO) layer.

In an embodiment of the invention, the time for dry etching the zinc oxide seed layer is, for example, between 150 seconds and 200 seconds.

In an embodiment of the invention, the zinc oxide seed layer is formed to have a thickness between 40 nm and 60 nm.

In an embodiment of the invention, the substrate comprises a glass substrate or a flexible substrate.

The transparent conductive film of the present invention includes a zinc oxide (ZnO) seed layer, a plurality of nano metal particles, and a transparent conductive layer. A plurality of roughened tips are formed on the surface of the zinc oxide seed layer, and the nano metal particles are positioned on the roughened tip portion. The transparent conductive layer is coated on the zinc oxide seed layer and the nano metal particles.

In another embodiment of the invention, the roughened tip portion includes a cylindrical tip.

In another embodiment of the invention, the pitch of the roughened tip portion is between 5 nm and 20 nm.

In another embodiment of the invention, the nano metal particles are formed by a Coulomb force caused by positive and negative charge attraction to form a mesh-like bond.

In another embodiment of the invention, the above-mentioned nano metal particles are not in contact with each other.

In various embodiments of the invention, the nano metal particles include nano silver particles, nano gold particles or nano copper particles.

Based on the above, during the formation of the transparent conductive film, the present invention guides the nano metal particles to be deposited at a near-nano-scale distance by a suitable process design, and then the Coulomb attraction naturally formed by the positive and negative charges existing around the nano metal atoms. In order to form a connection close to a similar mesh, in addition to not affecting its penetration rate, the formation of a network structure of nano metal particles greatly enhances the conductive properties of the transparent conductive film.

The above described features and advantages of the invention will be apparent from the following description.

1A to 1F are schematic views showing a manufacturing process of a transparent conductive film according to an embodiment of the present invention.

Referring to FIG. 1A, a zinc oxide (ZnO) seed layer 102 is formed on the surface of the substrate 100, and the thickness t1 is formed, for example, between 40 nm and 60 nm; preferably between 40 nm and 50 nm, but the present invention is not limited thereto. Can be changed according to needs. Zinc oxide belongs to N-type II-VI semiconductor material, its structure is Wurzite hexagonal structure, belonging to the hexagonal closest packing, and zinc oxide has high melting point and excellent thermal stability, and it is soluble in acid and alkali. But not soluble in water and alcohol. The method of forming the ZnO seed layer 102 includes a sputtering method, an evaporation method, or a spin coating method. Among them, sputtering is preferred. As for the substrate 100 described above, since the sputtering method is a normal temperature process, it may be a glass substrate or a flexible substrate.

Then, referring to FIG. 1B, the zinc oxide seed layer 102 is dry etched such that the surface 102a forms a plurality of roughened tips. In the present embodiment, the gas used for dry etching such as oxygen (O ₂ ) and an inert gas, wherein the inert gas is preferably argon (Ar). If the etching gases are O ₂ and Ar, the flow rate is about 10 sccm to 20 sccm; the preferred flow ratio is 2:1. The time for the dry etching is determined according to the kind of the etching gas, the thickness of the zinc oxide seed layer 102 to be etched, and the structure of the roughened tip portion to be formed, for example, between several tens of seconds and several minutes; preferably 150 seconds. Between 200 seconds. Since the dry etching is an anisotropic etching, the etching directions are concentrated in the same direction, and a relatively stable upright tip can be formed by appropriate parameter design, and residues are less likely to exist after etching, so the wet etching helps the subsequent nanometer. The deposition of metal particles to form a finer network of such structures.

Since the structure of the roughened tip portion may vary depending on the process parameters of the dry etching, please refer to FIG. 1C, which is an enlarged cross-sectional view of the portion 104 in FIG. 1B.

In FIG. 1C, the roughened tip portion 106 exhibits an irregular distribution on the substrate 100 and may be a topographical tip; however, a structure exhibiting a differently distributed columnar tip may also be obtained by varying the dry etching parameters. In the present embodiment, the pitch d of the roughened tip portion 106 is, for example, between 5 nm and 20 nm; preferably between 5 nm and 10 nm. The longer the dry etching is performed, the finer the sharpened tip portion 106 becomes, resulting in a larger pitch d. If the pitch d of the roughened tip portion 106 is less than 5 nm, aggregation of the cluster structure may be caused; if the pitch d of the roughened tip portion 106 is larger than 20 nm, a network-like structure may not be formed. In addition, the roughened tip portion 102a in the drawing is not drawn to scale, so although the height is different, in fact, the height is not much different from a giant point of view.

Thereafter, referring to FIG. 1D, nano metal particles 108 are deposited on each of the roughened tips 106. A method of depositing the nano metal particles 108 is, for example, a sputtering method. The nano metal particles 108 in the present embodiment are nano silver particles, but the present invention is not limited thereto, and nano gold particles or nano copper particles may also be used. Since the fine roughened tip portion 106 can effectively adsorb the deposited metal ions and appropriately guide them into a nano metal structure packing distribution, there is one nano metal particle 108 at each of the roughened tip portions. By modulating the time of depositing the metal, the size of the nano metal particles 108 adsorbed at the roughened tip portion can be obtained; in general, the longer the deposition time, the larger the particle size of the nano metal particles 108, and the nano metal particles. The distance between 108 is also smaller. In addition, the nano metal particles 108 in the figure are not drawn to scale, so although the sizes are different, in fact, the size is not much different from a giant point of view. The average particle diameter of the nano metal particles 108 is, for example, between 5 nm and 15 nm; preferably between 5 nm and 10 nm. If the average particle diameter of the nano metal particles 108 is less than 5 nm, it may result in the formation of a network-like structure; if the average particle diameter of the nano metal particles 108 is larger than 15 nm, aggregation of the cluster structure may be caused.

Fig. 1E is an enlarged view of a portion where the nano metal particles 108 are formed in Fig. 1D. From FIG. 1E, a Coulomb force between the nano metal particles 108 which can be caused by positive and negative charge attraction can be observed to form a mesh-like junction 110. That is to say, by roughening the distance between the tip portions 106 by the Darney level, the stacked nano metal particles 108 can be brought into close proximity but not in contact with each other, and the electron cloud formed by the positive and negative charges existing around the metal atom , will naturally form a mutual attraction between the Coulomb and make a mesh structure similar to the connection. Since the size of the nano metal particles 108 will affect the distance between the nano metal particles 108, it also affects the Coulomb attraction strength of the mesh junction 110 formed by the positive and negative charges between the atoms, and is also equivalent to the bonding of the mesh connection 110. strength. That is, the larger the nano metal particles 108, the greater the bonding strength of the mesh bonds 110. Since the lattice constant and the ZnO crystal are similar in this embodiment, and the Ag having excellent conductivity is a metal material, the above effects can be achieved through an appropriate process.

Next, referring to FIG. 1F, a transparent conductive layer 112 is formed on the zinc oxide seed layer 102 and the nano metal particles 108, and the thickness t2 is, for example, between 40 nm and 60 nm. However, the present invention is not limited thereto, and may be changed according to requirements. . The transparent conductive layer 112 is, for example, an aluminum zinc oxide (AZO) layer, indium tin oxide (ITO), gallium zinc oxide (GZO) or fluoro tin oxide (FTO); preferably an AZO layer. The method of forming the transparent conductive layer 112 includes RF magnetron sputtering, vapor deposition, or spin coating. In the present embodiment, since the mesh structure is composed of the nano metal particles 108, the conductive property of the film layer can be improved while maintaining a good transmittance, and the transparent conductive film such as AZO is applied to the relevant photovoltaic element. Very important.

Some experiments are listed below to verify the efficacy of the present invention, but the present invention is not limited to the following.

experiment

A layer of ZnO seed having a thickness of about 40 nm was formed on the BK-7 glass and then dry etched at different times. The gases used for the dry etching were O ₂ (40 sccm) and Ar (20 sccm), and the times were 0 seconds, 30 seconds, 180 seconds, 330 seconds, 480 seconds, and 630 seconds, respectively. The nano-Ag particles were then deposited for about 50 seconds and observed to have a particle size of about 10-15 nm by SEM. 2A shows that the nano-Ag particles deposited on the ZnO seed layer are agglomerated without dry etching (dry etching time = 0 sec); FIG. 2B shows that nano-Ag particles are observed through a 180-second dry etching process. There are guided accumulations and the particle size is also reduced.

Finally, an AZO target with a doping amount of 2 wt% aluminum was used to form an AZO layer of about 40 nm thick on the ZnO seed layer and the nano Ag particles by RF magnetron sputtering to obtain ZnO (40 nm)/Ag (50 seconds). ) / AZO (40 nm) film. Figure 3 is an X-ray diffraction pattern of all the test pieces in the experiment, which scans the entire ZnO/Ag/AZO film at an incident angle of 1°. It can be observed from Fig. 3 that the characteristic front of ZnO(002) is not obvious after the dry etching time is increased to 330 seconds, indicating that the seed layer structure is over-etched, resulting in a decrease in crystallinity and deviation from the (002) direction; When the etching time is 180 seconds, the crystal characteristics of Ag(111) are less obvious due to the uniform distribution of nano-Ag particles and smaller particle size.

Further analysis will be conducted to further obtain whether or not to improve the photoelectric properties of the film.

Detection

The transmittance and resistivity of the ZnO/Ag/AZO film obtained in the above experiment were respectively measured.

4 is an overall film average transmittance (abbreviated as Avg) of a ZnO/Ag/AZO film completed by different dry etching times of a ZnO seed layer. It can be seen from the results of FIG. 4 that the ZnO seed layer is effective for improving the light transmittance of the film for the entire film layer after being treated at different dry etching times. When the ZnO seed layer is structured by a dry etching for 180 seconds, it should be ideal for the deposition of nano-Ag. The overall transmittance of the ZnO seed layer is not etched (dry etching time = 0 seconds). %, while the overall penetration of the ZnO seed layer after etching for 180 seconds was increased to 85.5%. However, when the etching time continues to increase, it is found that there is a decrease in the transmittance, which may be because once the dry etching time is elongated, the roughened tip portion becomes finer, resulting in a larger space between the roughened tip portions, and The deposition of nano-Ag particles in such a space results in the formation of a cluster structure of metal particles, and possibly also because the structure of the seed layer is destroyed. As a result, the penetration rate deteriorates. In other words, in addition to changing the dry etching time, the size of the nanoparticle can be adjusted to control the size of the transmittance. Therefore, for the current experimental parameters, the etching time can be higher than 150 to 200 seconds, but the range of etching time will vary as long as the experimental parameters are changed.

Figure 5 shows the results of measuring the resistivity of the ZnO/Ag/AZO film by the Hall measurement system. The dry etching time of the ZnO seed layer is 0 seconds, 30 seconds, 180 seconds, 330 seconds, 480 seconds, and 630 seconds, respectively. The resistivity of the overall ZnO/Ag/AZO film is 5×10 ^-5 Ω-cm, 3.31×10 ^-5 Ω-cm, 2.25×10 ^-5 Ω-cm, 4.03×10 ^-5 Ω-cm, 4 × 10 ^-5 Ω-cm and 4.2 × 10 ^-5 Ω-cm. Therefore, the resistivity of all films which have been subjected to dry etching of ZnO is lowered. Especially after the dry etching of the ZnO seed layer for 180 seconds, the overall film layer has the lowest resistivity, which is due to the construction of a better network structure, which will facilitate the uniform distribution of the nano-Ag particles, so that the nano-Ag particles The distance between them facilitates the mutual transfer of electrons, which in turn reduces the resistivity.

In summary, the present invention utilizes dry etching to obtain a suitable roughened tip portion, thereby guiding the nano metal particles to be deposited at a near nanometer scale distance, and then naturally attracted by the positive and negative charges existing around the metal atom. Force to form a connection close to a mesh. Therefore, the transparent conductive film of the present invention can greatly reduce the resistivity of the transparent conductive film due to the formation of the network structure of the nano metal particles without affecting the transmittance thereof. In addition, compared with the current literature requiring a cumbersome chemical generation method or an etching technique with a photomask, the present invention obtains a transparent conductive film having high penetration and low electrical resistivity at a low process cost, and thus the present invention The method is competitive in the photovoltaic element application market in terms of improving the photoelectric characteristics of the transparent conductive film.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Substrate
102‧‧‧Zinc oxide seed layer
102a‧‧‧ surface

104‧‧‧ parts

106‧‧‧Roughening tip

108‧‧‧Nano metal particles

110‧‧‧ mesh connection

112‧‧‧Transparent conductive layer

D‧‧‧ spacing

T1, t2‧‧‧ thickness

1A is a schematic illustration of the formation of a zinc oxide (ZnO) seed layer in accordance with an embodiment of the present invention. Fig. 1B is a schematic view showing the formation of a roughened tip portion in the embodiment. Figure 1C is an enlarged cross-sectional view of a portion of Figure 1B. Fig. 1D is a schematic view showing the formation of nano metal particles in the examples. Fig. 1E is a partial enlarged view of Fig. 1D. Fig. 1F is a schematic view showing the formation of a transparent conductive layer in the embodiment. 2A is an SEM plan view of the deposition of nano-Ag particles on the surface of a ZnO seed layer which has not been subjected to dry etching. 2B is an SEM plan view of the surface deposition of nano-Ag particles on a ZnO seed layer after 180 seconds of dry etching. Figure 3 is an X-ray diffraction pattern of all ZnO/Ag/AZO films in the experiment. Figure 4 is a graph showing the transmittance of all ZnO/Ag/AZO films in the experiment. Figure 5 is a graph showing the resistivity of all ZnO/Ag/AZO films in the experiment.

100‧‧‧Substrate

102‧‧‧Zinc oxide seed layer

108‧‧‧Nano metal particles

112‧‧‧Transparent conductive layer

T2‧‧‧ thickness

Claims (10)

A method for manufacturing a transparent conductive film, comprising: forming a zinc oxide (ZnO) seed layer on a surface of a substrate; dry etching the zinc oxide seed layer such that a surface of the zinc oxide seed layer has a plurality of roughened tips The time during which the zinc oxide seed layer is dry etched is between 150 seconds and 200 seconds; a plurality of nano metal particles are deposited on the roughened tip portion; and the zinc oxide seed layer and the nano A transparent conductive layer is formed on the metal particles. The method for producing a transparent conductive film according to claim 1, wherein the gas used for the dry etching includes oxygen and an inert gas. The method for producing a transparent conductive film according to claim 1, wherein the transparent conductive layer comprises an aluminum zinc oxide layer. The method for producing a transparent conductive film according to claim 1, wherein the zinc oxide seed layer is formed to have a thickness of between 40 nm and 60 nm. The method for producing a transparent conductive film according to claim 1, wherein the substrate comprises a glass substrate or a flexible substrate. A transparent conductive film comprising: a zinc oxide (ZnO) seed layer having a plurality of roughened tips formed on a surface thereof, the roughened tip portion including a columnar tip; and a plurality of nano metal particles formed only on the column The top of the tip; and a transparent conductive layer covering the zinc oxide seed layer and the nano metal particles. The transparent conductive film according to claim 6, wherein the pitch of the roughened tip portion is between 5 nm and 20 nm. The transparent conductive film according to claim 6, wherein the nano metal particles form a mesh-like bond by a Coulomb force caused by positive and negative charge attraction. The transparent conductive film according to claim 6, wherein the nano metal particles are not in contact with each other. The transparent conductive film according to claim 6, wherein the nano metal particles comprise nano silver particles, nano gold particles or nano copper particles.