TWI443212B - A method of manufacturing an oxide based target for physical vapor deposition - Google Patents

Description

Method for preparing oxide target suitable for physical vapor deposition

The invention relates to a method for preparing a target, in particular to a method for preparing an oxide target suitable for physical vapor deposition, by which a low bulk resistance, a high density and a suitable crystal can be obtained. Particle size target.

Transparent conductive oxides have been widely used in flat panel displays such as liquid crystal, plasma, and electroluminescence, and in transparent electrode layers (films) of thin film solar cells such as amorphous germanium, microcrystalline germanium, and copper indium gallium selenide (CIGS). . At present, the most common transparent conductive film layer in commercial use is a DC magnetron sputtering method, which uses a plasma ionized argon ion to bombard a film forming material (ie, a sputtering target), so that a large number of atoms in the target are The film layer is formed by striking and splashing deposition on the substrate. Therefore, it is necessary to have a sputtering target having good characteristics and stable film formation at the time of sputtering. In the prior art, a target for sputtering a transparent conductive film is formed by molding a raw material powder, and then forming a bulk sintered target by a heating and sintering method. Conventional techniques start from the target process, and the two main points that can improve the abnormal discharge are to increase the resistivity and density of the sintered body target. The most commonly used transparent conductive sintered target is Indium Tin Oxide (ITO) whose main component is indium oxide and added with tin oxide. Its commercial target resistivity can reach 2 x 10 ^-4 Ω. Below -cm, and the relative density of the target has reached 99% or more. However, since ITO contains a large amount of rare metal indium, which is expensive to manufacture and has a tendency to be depleted, a zinc oxide-based transparent conductive material rich in mineral resources and low in cost is proposed (Journal: Thin Solid Films, v. 124, 1985) , p. 4 3-47). The zinc oxide-based transparent conductive material is mainly composed of zinc oxide, and an n-type doping element (for example, boron (B), aluminum (Al), gallium (Ga), indium (In), ytterbium (Y), A transparent conductor formed by strontium (Sc), bismuth (Si), germanium (Ge), etc., wherein the best doping is AZO (Aluminum Doped Zinc Oxide) formed by doping with aluminum (Al) or GZO (Gallium Doped Zinc Oxide) formed by doping with gallium (Ga).

Referring to Japanese Laid-Open Patent Publication No. 02-149459, it is disclosed that sintering of AZO in an argon (Ar) atmosphere can achieve higher sintered target density and electrical resistivity than sintering in air, and the sintered density reaches 5.6 g/cm ³ , and the resistivity It reaches 5 × 10 ^-3 Ω-cm. Although its density can reach 99%, the resistivity is still far less than that of ITO, and its powder preparation source needs to be purified to 4N or above.

Referring to Japanese Laid-Open Patent Publication No. 07-258836, it is disclosed that AZO is doped and mixed with alumina powder of a relatively fine particle diameter, and can achieve a density of 5.65 g/cm ³ and a resistivity of 3 × 10 ^-3 Ω-cm after sintering. And the powder preparation source needs to be purified to 4N (99.99%) or above powder sintering can be achieved.

Referring to Taiwan Patent Publication No. 200602460, No. 200706664 and No. 200730646, it is disclosed that the addition of alumina, zirconia or zirconia having a particle size of 20 to 250 ppm and a particle diameter of 1 μm or less can be improved in sintering. Density and resistivity. The best sintered density of the embodiment is 5.64 g/cm ³ and the resistivity is 1.48×10 ^-3 Ω-cm, and the resistivity is still far less than that of ITO, and the powder preparation source needs to be purified to 4N or above. Powder sintering can be achieved.

In summary, the technique disclosed in the above patent document has a slight increase in the density and electrical resistivity of the zinc oxide-based transparent conductive sintered target, but its resistivity is still much higher than that of ITO, which is still a poor sputtering target. From the above, it is necessary to provide an innovative and progressive zinc oxide target to solve the above problems.

As a result of the job, the applicant has carefully studied and researched, and has been working hard to finally develop a method for preparing an oxide target suitable for physical vapor deposition, which can solve the above problems.

SUMMARY OF THE INVENTION A primary object of the present invention is to provide a method for preparing an oxide target suitable for physical vapor deposition by sintering a zinc oxide raw powder mixed with uniform carbon to increase the carrier concentration and reduce the electrical resistivity.

A secondary object of the present invention is to provide a method for preparing an oxide target suitable for physical vapor deposition by adding a doping element to thereby increase the carrier concentration and reduce the resistivity.

In order to achieve the above main object, the present invention provides a method for preparing an oxide target suitable for physical vapor deposition, which comprises at least the steps of: dissolving a metal zinc in a melting furnace to melt the metal zinc; and performing an oxidation step Obtaining a zinc oxide powder; collecting the zinc oxide powder; performing the forming step of the zinc oxide powder; and performing a sintering step to form an oxide target suitable for physical vapor deposition.

In order to achieve the above secondary object, the present invention provides a method for preparing an oxide target suitable for physical vapor deposition, which comprises at least the steps of: melting a metal zinc; performing an oxidation step to obtain a zinc oxide powder; Collecting the zinc oxide powder; mixing the zinc oxide powder with at least one doping element and performing a forming step; and performing a sintering step to form an oxide target suitable for physical vapor deposition.

According to a feature of the invention, the zinc oxide powder contains a carbon element distribution, and the carbon element has a weight content of between 50 ppm and 500 ppm of the zinc oxide powder.

According to another feature of the invention, the relative density of the oxide target suitable for physical vapor deposition is between 80% and 99%.

According to still another feature of the present invention, the oxide target suitable for physical vapor deposition has a resistivity of between 1 × 10 ^-2 Ω-cm and 1 × 10 ^-4 Ω-cm.

According to still another feature of the invention, the doping element is selected from an n-type doping element.

The preparation method of the oxide target suitable for physical vapor deposition of the present invention has the following effects:

1. The zinc oxide powder of the present invention contains a carbon element distribution which increases the concentration of the carrier and lowers the volume resistivity;

2. The target of the present invention has low bulk resistance, high density and appropriate grain size;

3. The zinc oxide powder of the invention is easy to manufacture and can be further reduced in production cost without further scouring, and has better commercial utilization value;

4. The zinc element is a mineral-rich substance, and therefore, the target preparation of the present invention can effectively reduce the price.

The above and other objects, features and advantages of the present invention will become more apparent and understood.

While the invention may be embodied in various forms, the embodiments illustrated in the drawings It is not intended to limit the invention to the particular embodiments illustrated and/or described.

Referring now to Figure 1, there is shown a method of preparing an oxide target suitable for physical vapor deposition of the present invention. It contains the following steps:

Step 110: placing a metal zinc in a melting furnace to melt the metal zinc;

Step 120: performing an oxidation step to obtain zinc oxide powder;

Step 130: collecting the zinc oxide powder;

Step 140: performing a molding step of the zinc oxide powder;

Step 150: Perform a sintering step to form an oxide target suitable for physical vapor deposition.

Among them, the metal zinc is selected from one of pure zinc or a waste zinc raw material. In one embodiment, it is selected from the waste zinc raw material, and the waste zinc raw material is melted in a graphite crucible at a high temperature of 1000 ° C or higher and converted into zinc vapor. Thereby, the zinc oxide powder contains a uniform carbon element distribution which increases the carrier concentration and lowers the volume resistivity. The entrained air is then oxidized to form zinc oxide and collected after cooling the tube to obtain zinc oxide powder. It is to be noted that the zinc oxide powder has a purity of between 99.0% and 99.8%, preferably 99.8%. Moreover, an important feature of the present invention is that the zinc oxide powder contains a carbon element distribution, and the weight content of the carbon element is between 50 ppm (50 parts per million) and 500 ppm (parts per million) of the zinc oxide powder. Between five). The function of carbon element is to form more conductive carrier concentration with zinc oxide to reduce the volume resistivity. The obtained zinc oxide transparent conductive target not only has high density and low resistivity, but the resistivity is not lowered. As a result of a decrease in the sintered density, the zinc oxide-based transparent conductive target has a preferable coating property, which is very close to the level of the ITO target.

Further, in the forming step in step 140, the present invention selectively performs the forming step in a dry pressing, cold equalizing or cast forming manner. Among them, when forming the block, it is still necessary to pay attention to whether the zinc oxide powder is flat in the mold, so as to avoid unevenness of the raw embryo density caused by the uneven pressure of the test piece.

Finally, a sintering step is performed in step 150. The sintering step of the present invention may be carried out by atmospheric pressure sintering, positive pressure sintering, hot press sintering or hot pressure sintering. Further, the sintering step is performed at a sintering temperature of 1100 ° C to 1500 ° C, and the sintering densification step is carried out in an atmosphere of nitrogen, nitrogen or an inert gas (for example, argon (Ar)). Finally, the relative density of the oxide target suitable for physical vapor deposition is between 80% and 99%, and the volume resistivity is from 1×10 ^-2 Ω-cm to 1×10 ^-4 Ω-cm. Between and the grain size is between 2 μm and 5 μm. The relative density refers to the ratio of the true density obtained by the Archimedes measurement to the theoretical density measured by XRD.

Referring now to Figure 2, there is shown another method of preparing an oxide target suitable for physical vapor deposition of the present invention. It is not much different from FIG. 1, mainly by changing step 140 to step 240, that is, mixing the zinc oxide powder with at least one doping element by dry ball milling or wet ball milling and performing a molding step. The doping element is an n-type doping element selected from the group consisting of boron (B), aluminum (Al), gallium (Ga), indium (In), ytterbium (Y), strontium (Sc), cerium (Si), germanium. The group consisting of (Ge) and a mixture thereof, preferably doped with alumina, has a doping concentration of 1.0 to 10.0 weight percent (wt%). Finally, the relative density of the oxide target suitable for physical vapor deposition is between 80% and 99%, and the volume resistivity is from 1×10 ^-2 Ω-cm to 1×10 ^-4 Ω-cm. Between and the grain size is between 2 μm and 5 μm.

The oxide target suitable for physical vapor deposition of the present invention can be applied to a physical plating process such as vacuum evaporation, sputtering, and ion plating.

<Example 1>

First, a metal pure zinc is placed in a melting furnace to melt the metal zinc, and then melted in a graphite crucible at a high temperature of 1000 ° C and converted into zinc vapor. Thereby, the zinc oxide powder contains a uniform carbon element distribution which increases the carrier concentration and lowers the volume resistivity. The air that was blown in was then oxidized to form zinc oxide, and after cooling the tube, zinc oxide powder having a purity of 99.8% was collected. Next, zinc oxide powder and deionized water (DI-Water) were placed in a grinding pot containing zirconia balls, and ball mixing was performed at a number of revolutions of 300 (rad/sec) using a ball mill for 12 hours. Thereafter, the ball milled zinc oxide solution was placed in an oven and the solution was dried at 70 °C. Subsequently, the dried powder was placed in a mortar and ground into a powder, and sieved by a sieve machine (200 mesh). Then, the sieved powder was placed in a glass beaker, and shaken up and down for about half an hour to perform simple granulation. Among them, this action can still increase the fluidity of the powder. Next, the granulated powder is added to a 1 wt% binder (polyvinyl alcohol, Polyvinyl Alcohol, PVA), ground in a mortar, and uniformly mixed, and then 3 g of the powder is placed in a cylindrical abrasive having a diameter of 15 mm; A test piece was prepared using a dry molding machine (dry pressure) at a load pressure of 1000 psi. After the test, the test piece was placed in a high-temperature box furnace and sintered in the atmosphere; the temperature of the sintering parameter was 1100 ° C and the temperature was held for two hours. The target is finally completed and the target is subjected to material analysis. The results of the analysis by the X-ray diffraction analyzer are shown in Fig. 3. The target is indeed pure phase zinc oxide; the result of electron microscopy analysis is shown in Fig. 4. The grain size of the target is 0.8 μm; four-point probe measurement method The measured volume resistivity was 1.0 × 10 ^-3 Ω-cm; and the relative density of the Archimedes measurement was 97%. The relative density refers to the ratio of the true density obtained by the Archimedes measurement to the theoretical density measured by XRD.

<Example 2>

Example 2 is substantially the same as the step of Example 1, the main difference is that the zinc oxide powder and the alumina are mixed by dry ball milling, and the alumina doping concentration is 3.0 weight percent (wt%), that is, zinc oxide and The ratio of alumina is: 97%: 3%. Finally, the obtained target was a pure phase zinc oxide having a relative density of 94%, a volume resistivity of 1.2 × 10 ^-4 Ω-cm, and a crystal grain size of 3 μm.

<Example 3>

Example 3 is substantially as in the procedure of Example 2, the main difference being that the zinc oxide powder and alumina were mixed by dry ball milling with an alumina doping concentration of 2.0 weight percent (wt%). Finally, the obtained target was a pure phase zinc oxide having a relative density of 93%, a volume resistivity of 1.0 × 10 ^-4 Ω-cm, and a grain size of 3.2 μm.

<Example 4>

Example 4 is roughly as the procedure of Example 1. The main difference is that the test piece is placed in a high temperature box furnace and sintered in nitrogen; the sintering parameter temperature is 1200 ° C and the temperature is maintained for two hours. The target is finally completed and the target is subjected to material analysis. The target was obtained as pure phase zinc oxide, having a relative density of 92%, a volume resistivity of 0.5 × 10 ^-4 Ω-cm, and a grain size of 4 μm.

<Example 5>

Example 5 is substantially the same as the procedure of Example 1. The main difference is that the test piece is placed in a high-temperature box furnace and sintered in argon; the temperature of the sintering parameter is 1300 ° C and the temperature is maintained for two hours. The target is finally completed and the target is subjected to material analysis. The target obtained was a pure phase zinc oxide having a relative density of 93%, a volume resistivity of 1.5 × 10 ^-4 Ω-cm, and a grain size of 4.2 μm.

<Example 6>

Example 6 is substantially the same as the procedure of Example 1, the main difference is that zinc oxide powder and DI-Water are placed in a grinding jar containing zirconia balls, and ball milling is performed at a rotation speed of 600 (rad/sec) using a ball mill (Ball mixing) ) and lasted for 12 hours; the temperature of the sintering parameters was changed to 1400 ° C and held for three hours. The target is finally completed and the target is subjected to material analysis. The target was pure phase zinc oxide by X-ray diffraction analyzer; the grain size of the target was 5 μm as determined by electron microscopy; the volume resistivity measured by four-point probe measurement was 1.3×10. ^-4 Ω-cm; and the Archimedes measurement results have a relative density of 95%.

<Example 7>

Example 7 is substantially as the step of Example 2, the main difference being: mixing the zinc oxide powder with alumina, the alumina doping concentration is 4.0 weight percent (wt%); the ball mill is changed to the rotation speed 800 (rad/sec) Ball mixing was carried out for 24 hours; and the temperature of the sintering parameters was changed to 1500 ° C and held for three hours. The target was obtained as pure phase zinc oxide, having a relative density of 93%, a volume resistivity of 1.3 × 10 ^-4 Ω-cm, and a grain size of 4.3 μm.

<Example 8>

Example 8 is substantially as in the step of Example 7, the main difference being: mixing the zinc oxide powder with indium oxide with an indium oxide doping concentration of 10.0 weight percent (wt%). The target was obtained as pure phase zinc oxide, having a relative density of 92.5%, a volume resistivity of 1.1 × 10 ^-4 Ω-cm, and a grain size of 5.3 μm.

<Example 9>

Example 9 is substantially the same as the step of Example 8, the main difference is: mixing the zinc oxide powder with gallium oxide, the gallium oxide doping concentration is 5.0 weight percent (wt%); the ball mill is changed to the rotation speed 1000 (rad/sec) Ball mixing was carried out for 2 hours; and the temperature of the sintering parameters was changed to 1500 ° C and held for two hours. The target was obtained as pure phase zinc oxide, having a relative density of 94%, a volume resistivity of 1.35 × 10 ^-4 Ω-cm, and a grain size of 3.1 μm.

In summary, the method for preparing an oxide target suitable for physical vapor deposition of the present invention has the following effects:

1. Melting the metal zinc in a melting furnace, the zinc oxide powder containing a uniform carbon element distribution, which can increase the carrier concentration and reduce the volume resistivity;

2. The target of the present invention has low bulk resistance, high density and appropriate grain size;

3. The zinc oxide powder of the invention is easy to manufacture and can be further reduced in production cost without further scouring, and has better commercial utilization value;

4. The zinc element is a mineral-rich substance, and therefore, the target preparation of the present invention can effectively reduce the price.

While the present invention has been described in its preferred embodiments, it is not intended to limit the scope of the invention, and various modifications and changes can be made without departing from the spirit and scope of the invention. As explained above, various modifications and variations can be made without departing from the spirit of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100. . . Flow chart of preparation method of oxide target suitable for physical vapor deposition (1)

200. . . Flow chart of preparation method of oxide target suitable for physical vapor deposition (2)

Figure 1 shows a method of preparing an oxide target suitable for physical vapor deposition of the present invention.

Figure 2 shows a method of preparing an oxide target suitable for physical vapor deposition of the present invention.

Fig. 3 is a view showing the analysis results of the x-ray diffraction analyzers of Examples 1 to 5 of the present invention.

Fig. 4 is a graph showing the results of electron microscope analysis of Example 1 of the present invention.

100. . . Flow chart of preparation method of oxide target suitable for physical vapor deposition (1)

Claims (19)

A method for preparing an oxide target suitable for physical vapor deposition, comprising at least the following steps: (a) placing a metal zinc in a graphite crucible and melting at a high temperature of 1000 ° C or higher to convert into a zinc vapor; (b) introducing air, oxidizing the zinc vapor into zinc oxide powder, the purity of the zinc oxide powder being between 99.0% and 99.8%; (c) collecting the zinc oxide powder in a cooling tube; (d) The zinc oxide powder is subjected to a molding step; and (e) performing a sintering step to form an oxide target suitable for physical vapor deposition; wherein the zinc oxide powder contains a carbon element distribution, and the weight of the carbon element The content is between 50 ppm and 500 ppm of the zinc oxide powder. The preparation method of claim 1, wherein the metal zinc of the step (a) is selected from one of a pure zinc or a waste zinc raw material. The preparation method of claim 1, wherein the oxide target of the step (e) has a grain size of between 2 μm and 5 μm. The preparation method of claim 1, wherein the sintering temperature of the sintering step of the step (e) is between 1100 ° C and 1500 ° C. The preparation method of claim 1, wherein the oxide target of the step (e) has a density of between 80% and 99%. The preparation method of claim 1, wherein the oxide target of the step (e) has a bulk resistivity of from 1 × 10 ^{2 -2} Ω-cm to 1 × 10 ^-4 Ω-cm. The preparation method of claim 1, wherein the step (d) further comprises first mixing the zinc oxide powder with at least one doping element, and then performing the molding step. The preparation method of claim 7, wherein the doping element is selected from an n-type doping element. The preparation method of claim 8, wherein the n-type doping element is selected from the group consisting of boron (B), aluminum (Al), gallium (Ga), indium (In), ytterbium (Y), and cerium (Sc). One of the groups consisting of 矽(Si), 锗(Ge), and mixtures thereof. The preparation method of claim 8, wherein the n-type doping element has a doping concentration of 1.0 to 10.0% by weight (wt%). A method for preparing an oxide target suitable for physical vapor deposition, comprising the steps of: (a) melting a metal zinc in a graphite crucible at a high temperature of 1000 ° C or higher to convert it into a zinc vapor; (b) introducing air to oxidize the zinc vapor to a zinc oxide powder, the purity of the zinc oxide powder Between 99.0% and 99.8%; (c) collecting the zinc oxide powder in a cooling tube; (d) mixing the zinc oxide powder with at least one doping element and performing a forming step; and (e) performing a sintering step And forming an oxide target suitable for physical vapor deposition; wherein the zinc oxide powder contains a carbon element distribution, and the carbon element has a weight content of between 50 ppm and 500 ppm of the zinc oxide powder. The preparation method of claim 11, wherein the metal zinc of the step (a) is selected from one of a pure zinc or a waste zinc raw material. The preparation method of claim 11, wherein the oxide target of the step (e) has a grain size of between 2 μm and 5 μm. The preparation method of claim 11, wherein the doping element of the step (d) is selected from an n-type doping element. The preparation method of claim 14, wherein the n-type doping element is a group selected from the group consisting of boron (B), aluminum (Al), gallium (Ga), indium (In), yttrium (Y), strontium (Sc), cerium (Si), germanium (Ge), and mixtures thereof One. The preparation method of claim 14, wherein the n-type doping element has a doping concentration of 1.0 to 10.0% by weight (wt%). The preparation method of claim 11, wherein the sintering temperature of the sintering step of the step (e) is between 1100 ° C and 1500 ° C. The preparation method of claim 11, wherein the density of the oxide target suitable for physical vapor deposition in step (e) is between 80% and 99%. The preparation method of claim 11, wherein the oxide resistivity of the oxide target suitable for physical vapor deposition in step (e) is between 1×10 ^-2 Ω-cm and 1×10 ^-4 Between Ω-cm.