TWI447820B - Preparation of P - type Zinc Oxide Thin Films - Google Patents

Description

P-type zinc oxide film manufacturing method

The invention relates to a method for preparing a P-type zinc oxide film, which can prepare a P-type zinc oxide film different from the traditional n-type by a simple process, and can improve the electrical properties of the film.

Zinc oxide is a compound semiconductor with a potential gap of 3.37 eV between the conduction band and the valence band at room temperature. It is a promising short-wavelength optoelectronic material such as blue light, ultraviolet light and white light. Another compound semiconductor gallium nitride also has an extremely high energy gap value of 3.4 eV. Since zinc oxide also has a very high exciton binding energy of 60 meV, and a relatively simple fabrication method, the more zinc oxide is produced. The more attention you receive.

Since zinc oxide is essentially an n-type semiconductor, it is necessary to convert the zinc oxide originally belonging to the n-type conductivity into the zinc oxide of the P-type conductivity by doping with an appropriate element, thereby oxidizing the P-type conductivity. Zinc can be applied to more photovoltaic elements. The P-type conductive zinc oxide may be doped with a Group I element such as lithium, sodium, potassium, copper, silver, or a Group V element such as nitrogen, phosphorus or arsenic. The advantage of using a Group I element is that the formed energy level of the receptor is a shallow layer, but since the atom is small, it is easy to run to the position of the gap to form a donor body. The bonding of sodium, potassium and oxygen is longer than the zinc-oxygen bond (0.193 nm), causing lattice strain and forming self-defects such as oxygen vacancies, resulting in a counter-effect of compensation. For a group V element with a longer bond length, it is easy to cause lattice strain, and a misalignment defect is formed, which also has a compensation effect. From the above arguments, the nitrogen in the group V element is the best P-type doping element, has a small dissociation energy, and is not easy to form a misalignment defect and an AX center. The AX center is a defect complex that contributes electrons to offset the holes created by the dopant.

Whether the energy level of the receptor formed by nitrogen is shallow or not, but the low solubility is a problem, and can be solved by co-doping. The group III element is co-doped with nitrogen, wherein the two nitrogen atoms doped by pure nitrogen are 0.614 nm apart, and after co-doping, one zinc atom is replaced by a group III element, and the positions of the two oxygens are Nitrogen substitution, the distance between the two nitrogen atoms is 0.457 nm, the closer the distance is, the better the solubility; the Madelung energy (related to the potential energy between the ions), the addition of n-type dopants can help reduce energy, which is why One of the reasons why n-type zinc oxide is easy to manufacture is that the addition of P-type doping increases energy. Therefore, from the energy point of view, it is difficult to make P-type zinc oxide by using nitrogen alone, and the doping of a group III element can increase the solubility of nitrogen. Moreover, the co-doping is theoretically calculated to produce a shallower layer. Receptor energy level. For the doping of nitrogen, in addition to the compensation of the self-defect of zinc oxide, the donor form of the double nitrogen-substituted oxygen is also a problem.

From the above, it is found that the current zinc oxide film is relatively complicated in process, and must be subjected to subsequent heat treatment to complete the preparation of the P-type zinc oxide film, or the formed film resistivity cannot meet the requirements, so the method for preparing the P-type zinc oxide film There is still room for simplification, and the electrical properties of the film have yet to be improved in order to reduce the cost of fabrication and increase the efficiency of application to photovoltaic components.

In view of the above, the present invention is a method for preparing a P-type zinc oxide film, using a zinc-, aluminum-, and magnesium-containing oxide target and a zinc-metal target, and using a magnetron RF sputtering device, the plating atmosphere is argon gas. It is mixed with nitrogen gas and directly plated into P-type zinc oxide film, which can effectively reduce the complexity of the process and enhance the electrical properties of the film.

In view of the above disadvantages of the prior art, the main object of the present invention is to provide a method for preparing a P-type zinc oxide film, which simultaneously uses an oxide target containing zinc, aluminum, magnesium and a zinc metal target, and is co-doped by aluminum-nitrogen. Miscellaneous way to achieve the purpose of plating a better P-type zinc oxide film.

Another object of the present invention is to provide a method for fabricating a P-type zinc oxide film by using a magnetron RF sputtering device for P-type zinc oxide film plating, thereby obtaining a large range of P-type zinc oxide film.

A further object of the present invention is to provide a method for fabricating a P-type zinc oxide film, which is subjected to P-type zinc oxide film plating by a magnetron RF sputtering device, thereby obtaining a P-zinc oxide film having good uniformity and high flatness.

Another object of the present invention is to provide a method for fabricating a P-type zinc oxide film by using a magnetron RF sputtering device for P-type zinc oxide film plating, thereby obtaining a P-zinc oxide film having low resistivity and high optical transmittance.

In order to achieve the above object, a method for fabricating a P-type zinc oxide film according to the present invention includes providing a substrate, a first metal, and a second metal, and forming a metal film on the substrate, the metal film having a first metal And a second metal, wherein the first metal system comprises zinc oxide, aluminum oxide and magnesium oxide metal, and the concentration of the aluminum oxide metal is 0.5 to 2%, and the concentration of the magnesium oxide metal is 0.01 to 5%, The second metal is zinc metal. When the metal film is formed, a sputtering gas of argon gas and nitrogen gas is mixed, and the first metal and the second metal are uniformly distributed on the substrate through the sputtering gas. The metal thin film is formed into a metal film having P-type conductivity by the sputtering gas, so as to improve the conductivity of the metal film and the uniformity and flatness of the surface of the metal film, and The preparation method of the P-type zinc oxide film reduces the metal film process steps, thereby reducing the cost of the metal film process.

The above summary, the following detailed description and the accompanying drawings are intended to further illustrate the manner, the Other objects and advantages of the present invention will be described in the following description and drawings.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily appreciate other advantages and functions of the present invention from the disclosure herein.

The target used in the present invention is a MgxZn1-xO:Al0.01 (x=0, 0.025, 0.05) (mole ratio) ceramic target, and the method is to mix ZnO, MgO, and Al2O3 in proportion, and use zirconium balls and ethanol. The first wet ball mill, the time is controlled at 8hr. Then, the slurry was placed in an oven at 120 ° C for 12 hr to remove ethanol and moisture, and the dried powder was uniformly sieved to make the powder particles uniform in size, and then calcined at 1200 ° C in an air atmosphere for 4 hours. The temperature is kept at 2 hr and the temperature is naturally lowered. The calcined powder was then subjected to a second ball milling again in a wet ball milling time for 12 hrs in order to make the powder particles finer to facilitate the subsequent process. Then, the coarse screening and drying operations are repeated. After completion, the PVA is uniformly added to the powder, and again placed in an oven at 120 ° C for 1 hr. After drying, the action of the mash and the target can be performed. Before the target is pressed, the powder must first pass through the mesh No. 120 standard analysis sieve, and the target is pressed with a hydraulic press at a pressure of 1500 kgf/cm 2 for one minute and thirty seconds, and pressed into a circular target having a diameter of two turns. Next, the pressed target was sintered at 300 ° C, 550 ° C, and 1000 ° C under an oxygen atmosphere, that is, a target of MgxZn1-xO:Al0.01 (x=0, 0.025, 0.05) was completed.

The plating parameter of the magnetron RF sputtering system of the present invention can be set as follows, the plating power is 75 watts, the plating atmosphere is a mixed gas of argon gas and nitrogen gas (ratio 80/20), and the working pressure is plated (that is, the cavity pressure) ) is 10 mTorr, the plating time is 25 minutes, and the substrate temperature is 525 °C.

Please refer to FIG. 1 , which is a schematic diagram of a method for fabricating a P-type zinc oxide film according to the present invention. As shown in the figure, the method includes providing a substrate 1 , a first metal 2 and a second metal 3 , and the second metal 3 . Is disposed on the first metal 2, and forms a metal thin film on the substrate 1, the metal thin film having a first metal 2 and a second metal 3, wherein the first metal 2 system comprises zinc oxide, aluminum oxide and a magnesium oxide metal, wherein the concentration of the aluminum oxide metal is 0.5 to 2%, the concentration of the magnesium oxide metal is 0.01 to 5%, and the second metal 3 is a zinc metal, and a mixed argon is formed when the metal thin film is formed. The gas and nitrogen sputtering gas 4 uniformly distributes the first metal 2 and the second metal 3 on the substrate 1 through the sputtering gas 4, and the metal thin film is formed into a film by the sputtering gas 4. A metal film having a P-type conductivity characteristic for the purpose of improving the conductivity of the metal film and the uniformity and flatness of the surface of the metal film, and reducing the process of the metal film by the above-mentioned method for producing a P-type zinc oxide film Steps to reduce the cost of the metal film process The purpose.

Please refer to Table 1, which is an electrical property of the method for producing a P-type zinc oxide film of the present invention, wherein A is an electrical property plated using an oxide target containing zinc, aluminum, and magnesium, and B is used simultaneously. The electrical properties of zinc oxide, aluminum, and magnesium oxide targets and zinc metal targets, and the electrical analysis results of different magnesium oxide ratios (x=0, 0.025, 0.05) are compared. It can be seen from the data that the zinc oxide, aluminum, and magnesium oxide targets and the zinc metal target plating (B) are compared with the zinc oxide film not coated with the zinc metal target (A), p The -type resistivity decreased from 20.43 Ωcm to 7.03 Ωcm, and the carrier concentration increased from 4.43 x 1016 cm-3 to 1.7 x 1017 cm-3.

Please refer to Table 2, which is the electrical value of the P-type zinc oxide film of the present invention. As shown in Table 1, when the proportion of magnesium oxide is increased by 2.5% (x = 0.025), the plating results are shown in Table 2.

When only an oxide target is used, the resistivity is lower than that of no MgO, but it is an n-type semiconductor and a non-P type. At the same time, zinc oxide films coated with zinc, aluminum, and magnesium oxide targets and zinc metal targets showed a slight increase in carrier concentration, a slight decrease in carrier mobility, and a slight decrease in overall resistivity compared with those without MgO. The most important result is that the process of adding a zinc metal target has been converted to p-type.

When the proportion of magnesium oxide is increased by 5% (x=0.05), the results are shown in Table 3. Regardless of whether or not zinc metal target is used for plating, the electrical properties of zinc oxide film are beyond the scope of Hall measuring instruments. It is measured, that is, the resistivity is increased. It is speculated that the cause may be that Mg plays a defective role, such as a scattering center, causing a decrease in carrier mobility.

Please refer to FIG. 2 , which is a schematic diagram of the light transmittance of the P-type zinc oxide film of the present invention, as shown in the figure, simultaneously coated with a zinc-, aluminum-, and magnesium-containing oxide target and a zinc metal target, and The optical transmittance of different magnesium oxide ratios (x=0, 0.025, 0.05) was compared with the energy band analysis results. It can be seen from the spectrum that the three different magnesium oxide ratio test pieces have an average visible light transmittance of over 78%. . As the magnesium oxide concentration in the target increases to 5%, the transmittance in the visible range tends to increase. Magnesium oxide (x = 0) was 77.95%, magnesium oxide (x = 0.025) was 81.11%, and magnesium oxide (x = 0.05) was 81.54%. The light transmittance meets the needs of general optoelectronic applications.

Referring to FIG. 3, it is a schematic diagram of the energy band analysis result of the P-type zinc oxide film of the present invention. As shown in the figure, the absorption edge in the UV-vis spectrum gradually decreases as the concentration of magnesium oxide increases. The wavelength shift (blue shift), that is, the film band becomes larger, which means that MgO can successfully regulate the film band. The energy band values (Eg) were calculated as: magnesium oxide (x = 0) of 3.38 eV, magnesium oxide (x = 0.025) of 3.43 eV, and magnesium oxide (x = 0.05) of 3.47 eV.

The above-described embodiments are merely illustrative of the features and functions of the present invention, and are not intended to limit the scope of the technical scope of the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

1. . . Substrate

2. . . First metal

3. . . Second metal

4. . . Sputter gas

1 is a schematic view showing a method of fabricating a P-type zinc oxide film of the present invention;

2 is a schematic view showing the light transmittance of the P-type zinc oxide film of the present invention;

Fig. 3 is a view showing the results of energy band analysis of the P-type zinc oxide thin film of the present invention.

1. . . Substrate

2. . . First metal

3. . . Second metal

4. . . Sputter gas

Claims (8)

A method for fabricating a P-type zinc oxide film includes: providing a substrate; providing a first metal and a second metal; and forming a metal film on the substrate, wherein the metal film has a first metal and a second metal When the metal thin film is formed, a sputtering gas is passed through, and the first metal and the second metal are uniformly distributed on the substrate through the sputtering gas, and the metal thin film is formed into a single layer by the sputtering gas. The P-type conductive metal film can improve the conductivity of the metal film and the uniformity and flatness of the surface of the metal film. A method for producing a P-type zinc oxide thin film according to claim 1, wherein the substrate is a glass substrate. The method for producing a P-type zinc oxide thin film according to claim 1, wherein the first metal comprises zinc oxide, aluminum oxide and magnesium oxide metal. A method for producing a P-type zinc oxide film according to claim 3, wherein the alumina concentration is 0.5 to 2%. A method for producing a P-type zinc oxide film according to claim 3, wherein the magnesium oxide has a concentration of 0.01 to 5%. The method for producing a P-type zinc oxide film according to claim 1, wherein the second metal is zinc metal. The method for producing a P-type zinc oxide film according to claim 1, wherein the sputtering gas system is a mixed gas of argon gas and nitrogen gas. A method for producing a P-type zinc oxide film according to claim 7 wherein the ratio of the argon gas to the nitrogen gas mixture is 70/30 to 90/10.