TWI417410B - A manufacturing method of electric conduction film - Google Patents

Description

Conductive film manufacturing method

The present invention relates to a method for fabricating a conductive film, and more particularly to a method for fabricating a conductive film having high carrier mobility and improved electrical conductivity and transmittance.

Since zinc oxide has a wide energy gap and can have a high transmittance in the visible light range, in recent years, zinc oxide has been widely used as a transparent conductive film in an optoelectronic semiconductor industry, such as a flat panel display, a solar cell, and the like.

However, the resistivity of the zinc oxide film is usually between 1 and 100 ohms. Therefore, in order to improve the conductivity of the zinc oxide conductive film, most of the zinc oxide film is usually doped with other metals (such as aluminum). , gallium or indium, etc., in order to reduce the resistivity of the zinc oxide conductive film, and to enhance the conductivity of the zinc oxide conductive film without affecting the optical properties of the zinc oxide conductive film.

Traditionally, cations are mostly doped in the zinc oxide conductive film. However, it is known from the semiconductor physical concept that the substitution of a -1 valence anion with a -2 valent oxygen ion can also improve the conductivity of the zinc oxide conductive film, especially Fluoride ion doping with ionic radii similar to oxygen ions is most noticeable. In the past, chemical vapor deposition was used to deposit a film of fluorine-doped zinc oxide. However, the conductive film obtained has the problem of insufficient conductivity. Therefore, vacuum arc plasma evaporation and magnetron sputtering have been studied. It is desired to grow a zinc oxide conductive film having high quality and excellent conductivity.

For example, the research published by Choi et al. in 2005 pointed out that co-sputtering with aluminum-doped zinc oxide target and fluorine-doped zinc oxide target by magnetron co-sputtering method is used to form co-doped on the substrate. A zinc oxide conductive film having aluminum and fluorine, and after being annealed at 300 ° C for 2 hours in a high vacuum environment of 10 ^-6 Torr, the zinc oxide conductive film co-doped with aluminum and fluorine may have a lower The resistivity confirms that fluorine doping can enhance the conductivity of the aluminum-doped zinc oxide conductive film.

However, when the above-mentioned fluorine-doped zinc oxide target is used for co-sputtering, the fluorine doping amount must be determined before the fluorine-containing zinc oxide target is sintered, so that the process of co-sputtering cannot be performed. The demand changes the deposition concentration of the fluoride ion on the substrate, and it is often necessary to re-sinter a new target to prepare a zinc oxide conductive film doped with different fluoride ion content. Therefore, the method disclosed in the above research is not capable of transmitting fluorine ions. The deposition concentration is changed, and the resistivity of the zinc oxide conductive film is completely changed to have a better conductivity.

Furthermore, since aluminum doping mainly replaces zinc atoms, the difference between aluminum ion radius and zinc ion radius is large, so aluminum doping can increase the carrier concentration, but it is easy to deform the crystal lattice, causing the carrier to move. Scattering occurs, resulting in a decrease in carrier mobility; conversely, fluorine atom doping is mainly to replace the oxygen atom, but the difference between the fluoride ion radius and the oxygen ion radius is not large, so the fluorine doping can increase the carrier concentration, Aluminum doping can also effectively improve carrier mobility. Since the fluorine is easily removed from the surface of the film on the substrate during the sputtering process, the fluorine content of the fluorine-containing target is not sufficiently deposited on the surface of the substrate, so that the zinc oxide conductive film is doped. The fluorine content is insufficient; therefore, the method disclosed in the above research can only increase the carrier concentration in the zinc oxide conductive film by doping with aluminum, and cannot effectively utilize the advantage of fluorine doping.

In view of the above, it is indeed necessary to develop a method of fabricating a conductive film in order to solve the above problems and obtain a conductive film having better light transmittance and conductivity.

The main object of the present invention is to improve the above disadvantages to provide a method for fabricating a conductive film which is capable of arbitrarily adjusting the fluorine content doped in the conductive film to increase the carrier mobility of the conductive film and reduce its resistivity.

A second object of the present invention is to provide a method for fabricating a conductive film which is capable of stabilizing the carrier concentration of the conductive film with aluminum doping to maintain the transmittance of the conductive film while improving its conductivity.

In order to achieve the above object, the method for fabricating an electroconductive film of the present invention comprises: a plasma generating step, wherein a plasma is generated in a vacuum chamber to generate a gas, and the plasma generating gas is dissociated in the vacuum chamber, and Forming a plasma state rich in high-energy ions; and a bombardment step, in which high-energy ions in the plasma state are simultaneously bombarded with an aluminum-doped zinc oxide target and a zinc fluoride target, so that the two targets are The aluminum atom, the fluorine atom, the zinc atom and the oxygen atom are simultaneously sputtered onto the surface of the target to be co-deposited on a substrate, thereby obtaining a zinc oxide conductive film co-doped with aluminum and fluorine; wherein, a baffle is used After controlling the bombardment of the zinc fluoride target, the fluorine atoms are sputtered and deposited to the content of the substrate.

The conductive film manufacturing method of the present invention may further operate a post-processing step after the bombarding step, wherein the zinc oxide conductive film doped with aluminum and fluorine is subjected to thermal annealing treatment to make the crystal lattice of the zinc oxide conductive film. Rearranged, wherein the temperature of the thermal annealing treatment is 400 to 600 °C.

Moreover, in the manufacturing process of the conductive film of the present invention, the aluminum-doped zinc oxide target is placed in a continuous sputtering gun, and a DC power of 5 to 30 watts is applied to the DC sputtering gun. In addition, the zinc fluoride target is placed in an RF sputtering gun, and the RF sputtering gun is supplied with an RF power of 50 to 150 watts.

The above and other objects, features, and advantages of the present invention will become more apparent from the aspects of the appended claims. It is a reactive magnetron co-sputtering machine 1 , which is provided with a double sputter gun 11 , 12 in a chamber 10 , and the double sputter gun 11 12 are each located at the cathode to supply a suitable DC power of a sputtering gun 11 and an appropriate RF power to another sputtering gun 12, and a substrate 13 is additionally provided at the anode for depositing the conductive material of the present invention. film. The design of the reactive magnetron co-sputtering machine 1 is easily understood by those skilled in the art and is not intended to be emphasized by the present invention. The steps of the method for fabricating the conductive film of the present invention are described in detail below, and thus are not described again, and are not limited to this machine.

Referring to FIGS. 1 and 2, which is a preferred embodiment of the present invention, the reactive magnetron sputtering apparatus 1 is operated. The conductive film manufacturing method includes a plasma generating step S1 and a Bombardment step S2.

The plasma generating step S1 is to pass a plasma generating gas into a vacuum chamber 10 to dissociate the plasma generating gas in the vacuum chamber 10 to form a plasma state rich in high energy ions. More specifically, the chamber 10 is evacuated by a pump 14, so that the chamber 10 is in a vacuum state to ensure that there is no external gas in the chamber 10, and the vacuum chamber 10 is formed. Passing the plasma generating gas G (as shown in FIG. 3a), and slowly increasing the DC and RF power of the two sputtering guns 11, 12 to generate an electric field required for the reaction in the vacuum chamber 10, Free electrons impinge on the plasma generating gas to destroy the plasma to form gas atoms or intermolecular bonds, and dissociate to form a plasma state. Wherein, the pump 14 system can select a mechanical pump or a condensing pump, and the plasma generating gas G can be argon gas, nitrogen gas, hydrogen gas or oxygen gas.

For example, in the present invention, the pump 14 is first evacuated to the chamber 10 at a pressure of 2×10 ^-6 Torr, ensuring that the chamber 10 is in an absolute vacuum state, and oxygen is mixed with argon gas. And the flow controller 15 defines the oxygen flow rate of 10-20%, so that the pressure value in the vacuum chamber 10 maintains a working pressure of 5×10 ⁻³ Torr to maintain a better plasma generation rate. And then inputting 5 to 30 watts of DC power and 50 to 150 watts of RF power between the electrodes of the two sputtering guns 11, 12, so that an appropriate electric field can be generated in the vacuum chamber 10 to The high-energy free electrons generated by the site impinge on the argon gas, and the molecular bonds of the argon gas are broken to form a plasma state. The preferred DC power of the embodiment is 10 watts, and the preferred RF power is 90 watts, thereby generating a more suitable plasma generating electric field, and achieving better target bombardment in the subsequent bombardment step S2. effect.

Please cooperate with the 3b and 3c diagrams, the bombardment step S2 is to bombard an aluminum-doped zinc oxide target T1 and a zinc fluoride target T2 by the high-energy ion G in the plasma state, so that the two targets are The aluminum atom A, the fluorine atom F, the zinc atom and the oxygen atom in the material are simultaneously sputtered over the surface of the target to be deposited on a substrate 13 to obtain a zinc oxide conductive film M doped with aluminum and fluorine. Wherein, after a baffle 121 controls the zinc fluoride target T2 to be bombarded, the fluorine atom F is sputtered and deposited to the content of the substrate 13. More specifically, in order to improve the conductivity of the conventional zinc oxide conductive film while maintaining the transparency of the zinc oxide conductive film, the present invention selects the aluminum-doped zinc oxide target T1 and the zinc fluoride target T2. Sputtering, placing the aluminum-doped zinc oxide target T1 on the DC sputtering gun 11, and placing the zinc fluoride target T2 on the RF sputtering gun 12, thereby avoiding the power generation by the DC power source When the high-energy ion G bombards the zinc fluoride target T2, a problem arises in that a positive charge is accumulated in the zinc fluoride target T2; further, when the present invention uses zinc fluoride as a sputtering target T2, The fluorine content of the zinc fluoride target T2 can be arbitrarily changed, and the fluorine content deposited on the substrate 13 is substituted for the oxygen in the zinc oxide conductive film by the ionic radius of the fluoride ion and the oxygen ion; Further, the aluminum-doped zinc oxide target T1 can be used to deposit aluminum ions on the substrate 13 to stabilize the fluorine doping concentration of the zinc oxide conductive film, thereby improving the carrier mobility and increasing the film conductivity.

For example, the present invention is built into the substrate 13 at a working pressure of 5×10 ⁻³ Torr, such that the substrate 13 is located at the anode, and the zinc fluoride target is restricted by the baffle 121 The fluoride ion F of T2 is spattered by sputtering, and is deposited on the substrate 13. The present embodiment controls the opening time of the baffle 121 of the zinc fluoride target T2, which accounts for 25% of the total process time of the conductive film. 50%, 75% and 100%. During the time, the high-energy ion G generated by the plasma simultaneously bombards the aluminum-doped zinc oxide target T1 and the zinc fluoride target T2, so that the energy of the high-energy ion G can be transmitted to the two targets. The surface of T1 and T2 is deposited on the substrate 13 by sputtering the aluminum atom A, the fluorine atom F, the zinc atom and the oxygen atom from the surfaces of the two targets T1 and T2, thereby obtaining different aluminum and fluorine content co-doping. Zinc oxide conductive film. The purity of the aluminum-doped zinc oxide target T1 and the zinc fluoride target T2 is 99.99%, and the diameters of the two targets T1 and T2 are both 3吋, and the two targets T1 and T2 can be used. Obtaining a zinc oxide conductive film with better quality; the substrate 13 can be selected as a glass substrate, and the temperature of the substrate 13 is controlled to be maintained at 150-250 ° C, thereby increasing the aluminum, fluorine, zinc and oxygen atoms or aluminum, fluorine zinc And the uniformity of oxygen ions deposited on the substrate 13.

In addition, as shown in FIG. 4, after the bombardment step S2, a post-processing step S3 may be further performed, and the post-processing step S3 is performed by thermally annealing the zinc oxide conductive film doped with aluminum and fluorine. The lattice of the zinc oxide conductive film is rearranged. More specifically, the vacuum chamber 10 is evacuated to a pressure of 1×10 ^-3 Torr, and the temperature of the vacuum chamber 10 is raised to 400-600 ° C. This embodiment preferably controls the vacuum. The temperature of the chamber 10 is 500 ° C, and the zinc oxide conductive film doped with aluminum and fluorine is thermally annealed, and the annealing time is 10 to 20 minutes at a rate of 6 ° C per second. Thereby, the photoelectric characteristics of the zinc oxide conductive film doped with aluminum and fluorine can be changed to obtain a zinc oxide conductive film having better transmittance and conductivity.

Further, referring to FIG. 4 again, the present invention may further operate a pre-step S01 before the plasma generating step S1. The pre-step S01 washes off the deposit on the surface of the substrate 13. More specifically, in this embodiment, the substrate 13 is immersed in acetone, subjected to ultrasonic vibration for 5 to 10 minutes to complete the first cleaning; then, the substrate 13 is placed in a methanol solution to repeat the super The sound wave is shaken for 5~10 minutes to complete the second cleaning; finally, the substrate 13 is moved to the deionized water for the third ultrasonic shock for 5-10 minutes, thereby completely removing the surface attached to the substrate 13 Dirty, dust or oil stains, etc., and then dried under high pressure nitrogen, and placed in a precision oven at 120 ° C for 1 hour to remove moisture on the surface of the substrate 13, thereby maintaining the zinc oxide formed on the surface of the substrate 13. The quality of the conductive film. Even in the plasma generating step S1, the pre-sputtering means can be used to remove the pollution source on the two targets T1 and T2 to achieve a better effect of stabilizing the subsequent coating process.

According to the above, the conductive film manufacturing method of the present invention can not only sputter aluminum atoms or aluminum ions through the aluminum-doped zinc oxide target T1, but also can sputter a sufficient amount of fluorine by the zinc fluoride target T2. Atom or fluoride ion, forming a zinc oxide conductive film co-doped with aluminum and fluorine; since the difference between the radius of the fluoride ion and the radius of the oxygen ion is small, by sufficiently doping with fluorine, in addition to increasing the concentration of the carrier, Can improve carrier mobility. According to the Hall effect measurement principle, the resistivity system has a negative correlation with the product of the carrier mobility and the carrier concentration. Therefore, in the case where the electron concentration is maintained stable, the present invention is capable of mobility through the carrier. The electrical resistivity of the zinc oxide conductive film doped with aluminum and fluorine is increased to improve the conductivity of the zinc oxide conductive film without changing the transmittance of the zinc oxide conductive film. In addition, the present invention can arbitrarily change the fluorine content of the zinc fluoride target sputtered onto the surface of the substrate, and can adjust the preferred fluorine content in the zinc oxide conductive film without re-making a new fluorine-containing target. In order to facilitate the better ratio of co-doped aluminum and fluorine, the time and cost required for the fluorine target to be purchased or prepared again is omitted.

In order to confirm that the conductive film of the present invention can be co-sputtered through the aluminum-doped zinc oxide target and the zinc fluoride target, a zinc oxide conductive film co-doped with aluminum and fluorine is deposited on the substrate, and the present invention The conductive film has better conductivity and light penetration efficiency. Here, the zinc oxide conductive film deposited with different concentrations of fluorine atoms is analyzed to obtain the measured values of carrier concentration, carrier mobility, resistivity and light transmittance. The results are detailed in 5 and 8. Figure.

Please refer to FIG. 5 , which is a graph of the concentration of the conductive film carrier of the present invention and the percentage of the opening time of the baffle of the zinc fluoride target. The percentage of the baffle opening time of the zinc fluoride target may represent that after the bombardment of the zinc fluoride target by the high-energy plasma ion, the fluorine atom is sputtered from the zinc fluoride target and deposited on the substrate. content. From the results of FIG. 5, regardless of the percentage of the baffle opening time of the zinc fluoride target, the carrier concentration of the zinc oxide conductive film doped with aluminum and fluorine is about 3.34×10 ²⁰ /cm ^{3 .} Between 3.62 × 10 ²⁰ /cm ³ , the different fluorine atom deposition concentrations shown on the substrate are not sufficient to affect the carrier concentration of the electroconductive thin film of the present invention.

Please refer to FIG. 6 , which is a graph showing the mobility of the conductive film carrier of the present invention and the percentage of the opening time of the baffle of the zinc fluoride target. Wherein, the percentage of the baffle opening time of the zinc fluoride target, that is, after the zinc fluoride target is bombarded by the high-energy plasma ion, the fluorine atom is sputtered from the zinc fluoride target and deposited on the substrate. content. From the results of Fig. 6, it is known that when the baffle plate of the zinc fluoride target is not opened, the carrier mobility of the zinc oxide conductive film is only 18.3 cm ² /Vs, with the blocking of the zinc fluoride target. The percentage of plate opening time increases, and the carrier mobility of the zinc oxide conductive film doped with aluminum and fluorine is gradually increased, and when the percentage of baffle opening time of the zinc fluoride target reaches 75%, the system can obtain up to Carrier mobility of 30.3 cm ² /Vs.

Please refer to FIG. 7 , which is a graph of the resistivity of the conductive film of the present invention and the percentage of the baffle opening time of the zinc fluoride target. Wherein, the percentage of the baffle opening time of the zinc fluoride target, that is, after the zinc fluoride target is bombarded by the high-energy plasma ion, the fluorine atom is sputtered from the zinc fluoride target and deposited on the substrate. content. From the results of Fig. 7, it is known that when the baffle plate of the zinc fluoride target is not opened, the resistivity of the zinc oxide conductive film is only 1.02 × 10 ^-3 Ω-cm, along with the target of the zinc fluoride target. The percentage of the opening time of the baffle is increased, and the resistivity of the zinc oxide conductive film doped with aluminum and fluorine is gradually decreased gradually, and when the percentage of the baffle opening time of the zinc fluoride target is 75%, the lowering time can be obtained. 5.69 × 10 ^-4 Ω-cm resistivity.

According to the Hall effect measurement principle, it is confirmed that the resistivity system has a negative correlation with the product of the carrier mobility and the carrier concentration, and it is confirmed that the present invention is co-doped with the zinc oxide conductive film of aluminum and fluorine. The carrier mobility of the conductive film can be improved by doping with fluorine atoms, and the carrier concentration of the conductive film is stabilized by doping with aluminum atoms, thereby reducing the resistivity of the conductive film, thereby effectively improving the conductivity. The effect of film conductivity.

Please refer to FIG. 8 , which is a graph showing the light transmittance of the conductive film of the present invention and the percentage of the shutter opening time of the zinc fluoride target. Wherein, the percentage of the baffle opening time of the zinc fluoride target, that is, after the zinc fluoride target is bombarded by the high-energy plasma ion, the fluorine atom is sputtered from the zinc fluoride target and deposited on the substrate. content. From the results of Fig. 8, it is known that regardless of the percentage of the baffle opening time of the zinc fluoride target, when the wavelength of the light is 360 nm, there is a significant absorption boundary, and the energy system at the absorption boundary Similar to the energy gap of 3.3 eV of zinc fluoride, the absorption boundary of the conductive film of the present invention is the result of direct absorption of zinc oxide. Moreover, at a wavelength of 300 to 900 nm, regardless of the percentage of the baffle opening time of the zinc fluoride target, the average light transmittance is maintained above 93%, thereby confirming that the co-doped aluminum And the fluorine zinc oxide conductive film has better light penetration efficiency.

The method for preparing a conductive film of the present invention is capable of arbitrarily adjusting the fluorine content doped in the conductive film to improve the carrier mobility of the conductive film and to reduce the resistivity of the conductive film.

The method for fabricating the conductive film of the present invention is capable of stabilizing the carrier concentration of the conductive film with aluminum doping to maintain the transmittance of the conductive film and at the same time achieving the effect of improving the conductivity thereof.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

[this invention]

S1. . . Plasma generation step

S2. . . Bombardment step

S3. . . Post processing step

S01. . . Pre-step

1. . . DC reactive magnetron co-sputtering machine

10. . . Chamber

11. . . Sputter gun

111. . . Baffle

12. . . Sputter gun

121. . . Baffle

13. . . Substrate

14. . . Pump

15. . . Flow controller

T1. . . Aluminum-doped zinc oxide target

T2. . . Zinc fluoride target

G. . . Plasma generated gas/plasma high energy particles

A. . . Aluminum atom

F. . . Fluorine atom

M. . . Conductive film

Figure 1: Schematic diagram of a DC reactive magnetron co-sputtering machine used in the present invention.

Figure 2: Flow chart of the operation of the present invention.

3a-3c: Schematic diagram of the operational flow of the present invention.

Fig. 4 is a flow chart showing the operation of the present invention.

Fig. 5 is a graph showing the concentration analysis of the conductive film carrier of the present invention.

Fig. 6 is a graph showing the mobility analysis of the conductive film of the present invention.

Figure 7 is a graph showing the electrical resistivity analysis of the conductive film of the present invention.

Fig. 8 is a graph showing the transmittance of a conductive film of the present invention.

S1. . . Plasma generation step

S2. . . Bombardment step

Claims (10)

A method for fabricating a conductive film, comprising: a plasma generating step, introducing a plasma into a vacuum chamber to generate a gas, dissolving the plasma generating gas in the vacuum chamber, and forming a plasma rich in high energy ions And a bombardment step, in which the high-energy ions in the plasma state are simultaneously bombarded with an aluminum-doped zinc oxide target and a zinc fluoride target, such that the aluminum atom A and the fluorine atom F in the two targets The zinc atom and the oxygen atom are simultaneously sputtered onto the surface of the target to be co-deposited on a substrate to obtain a zinc oxide conductive film co-doped with aluminum and fluorine; wherein the zinc fluoride target is controlled by a baffle After the material is bombarded, the fluorine atoms are sputtered and deposited to the content of the substrate. According to the method for manufacturing a conductive film according to the first aspect of the patent application, after the bombardment step, a post-processing step is performed, and the zinc oxide conductive film doped with aluminum and fluorine is subjected to thermal annealing treatment to cause the oxidation. The lattice realignment of the zinc conductive film. The method for producing a conductive film according to claim 2, wherein the temperature of the thermal annealing treatment is 400 to 600 °C. The method for producing a conductive film according to claim 1 or 2, wherein the aluminum-doped zinc oxide target is placed in a continuous sputtering gun, and 5 to 30 watts are introduced into the DC sputtering gun. For DC power, the zinc fluoride target is placed in an RF sputtering gun, and the RF sputtering gun is supplied with RF power of 50 to 150 watts. The method for producing an electroconductive thin film according to claim 1 or 2, wherein the aluminum-doped zinc oxide target has a purity of 99.99%, and the aluminum-doped zinc oxide target has a diameter of 3 Å. The method for producing a conductive film according to claim 1 or 2, wherein the zinc fluoride target has a purity of 99.99%, and the zinc fluoride target has a diameter of 3 Å. The method for producing an electroconductive film according to claim 1 or 2, wherein the pressure in the vacuum chamber is 5 × 10 ^-3 Torr. The method for producing a conductive film according to claim 1 or 2, wherein the temperature of the substrate is maintained at 150 to 250 °C. According to the method for manufacturing a conductive film according to claim 1 or 2, in the plasma generating step, a pre-sputtering method is further adopted to remove the pollution source on the target and stabilize the subsequent bombardment step. According to the method for producing a conductive film according to claim 1 or 2, before the plasma generating step, a pre-step is performed, which washes off the deposit on the surface of the substrate.