CN1316057C - Sputtering target and production method therefor - Google Patents

Abstract

A transparent, conductive film-forming IZO sputtering target containing 100 to 2000 ppm of Sn and mainly consisting of In and Zn oxides, and a production method for the transparent, conductive film-forming IZO sputtering target containing 100 to 2000 ppm of Sn and mainly consisting of In and Zn oxides obtained by sintering at 1100 to 1500 DEG C powder in which In2O3 and ZnO are mixed so as to provide 0.5 to 25 wt. % of ZnO. Obtained constantly and with a good reproducibility are a transparent, conductive film-forming IZO sputtering target and the transparent, conductive film, wherein the IZO transparent, conductive film mainly consisting of In and Zn oxides is improved without compromise in the film's characteristics, a bulk resistance is reduced by adding a slight amount of Sn, and a stable discharge is possible at sputtering.

Description

sputtering target

technical field of invention

The present invention relates to an IZO sputtering target mainly composed of In and Zn oxides for producing transparent conductive films.

Background technique

Transparent conductive films composed of some intermetallic oxides have high electrical conductivity and visible light transmittance, and they have various applications such as liquid crystal display devices, thin film electroluminescent display devices, radiation sensors, transparent graphic inputs for terminal devices panels, heating films to prevent dew condensation on window panes, selectively permeable membranes for antistatic films or solar heat collectors, and electrodes for touch panels.

Among such transparent conductive films composed of intermetallic oxides, the most commonly used transparent conductive film is composed of indium oxide and tin oxide, commonly called ITO.

Other known transparent conductive films include those composed of indium oxide and zinc oxide, antimony-added tin oxide, or aluminum-added zinc oxide. Since these transparent conductive films vary in ease of production, price, and characteristics, their use depends on the application.

Among these transparent conductive films, it has been proposed to use a transparent conductive film mainly composed of In and Zn oxide (IZO), which has an etching rate higher than that of an ITO film. However, since the bulk resistance of IZO is higher than that of ITO, the discharge during sputtering may become unstable, especially during DC magnetron sputtering.

In an indium oxide-based sintered body, it is known that addition of about 5% tin reduces bulk resistance, and similar effects are obtained in indium oxide-zinc oxide.

However, adding such a large amount of tin can be dissociated from the IZO component system mainly composed of In and Zn oxides, but can produce transparent In-Zn-Sn oxide (ITZO) which is basically different from IZO transparent conductive films. conductive film.

Therefore, the ITZO transparent conductive film does not necessarily satisfy the purpose since the characteristics of the IZO transparent conductive film mainly composed of In and Zn oxides are lost.

Contents of the invention

After considering the above-mentioned various aspects, the present invention attempts to improve the IZO transparent conductive film that is mainly composed of In and Zn oxides without losing its characteristics, and also provides IZO for producing transparent conductive films that reduce bulk resistance by adding a very small amount of Sn. A sputtering target capable of stabilizing the discharge during sputtering.

That is, the present invention provides (1) an IZO sputtering target for producing a transparent conductive thin film mainly containing In and Zn oxides, characterized in that it contains 100-2000 ppm tin, and its volume resistance is 1-5 milliohm. cm; (2) a kind of IZO sputtering target that is used to produce the transparent conductive film that mainly contains In and Zn oxide, it is characterized in that it contains 100-1000ppm tin, and its volume resistance is 1-5 milliohm cm; ( 3) a kind of IZO sputtering target that is used to produce the transparent conductive thin film that mainly contains In and Zn oxide, it is characterized in that it contains 100-500ppm tin, and its bulk resistance is 1-5 milliohm cm; (4) according to The IZO sputtering target for producing a transparent conductive film described in any one of (1)-(3), it is characterized in that containing such as Fe, Al and Si each unavoidable impurity content is less than 10ppm; (5) The IZO sputtering target for producing a transparent conductive film according to any one of (1)-(4), characterized in that the crystal grain size is 4 microns or less; (6) according to (1)-(4) The IZO sputtering target for producing transparent conductive film described in any one, it is characterized in that crystal grain size is 3 microns or less; (7) according to any one of (1)-(4) using IZO sputtering target for producing transparent conductive thin films, characterized in that the crystal grain size is 2 microns or less.

Brief description of the drawings

FIG. 1 is a graph showing the relationship between bulk resistance and Sn content in IZO sputtering target examples and comparative examples containing In and Zn oxides as main components.

Figure 2 is a graph of bulk resistance versus Sn content plotted on a logarithmic scale up to 100000 ppm.

Best Mode for Carrying Out the Invention

When producing a sputtering target mainly composed of In and Zn oxides, for example, weigh indium oxide powder with an average particle size of 2 μm and zinc oxide powder with the same average particle size so that their weight ratio is 90:10, and weigh Take 100-2000ppm, preferably 100-1000ppm, more preferably 100-500ppm tin, add molding adhesive thereto, and mix together evenly.

Next, put the mixed powder into a mold, press molding, and then sinter at a high temperature of 1100-1500°C for 0-20 hours. The crystal grain size of the sintered IZO sputtering target is adjusted to 4 microns or less, preferably 3 microns or less, more preferably 2 microns or less.

The sintered IZO sputtering target thus obtained was ground with a surface grinder to an IZO target material having a surface roughness Ra of 5 micrometers or less.

Here, the sputtering surface of the IZO sputtering target may be mirror-polished to obtain a surface roughness Ra of 1000°C or less.

For such mirror finishing (polishing), known polishing techniques such as mechanical polishing, chemical polishing, and mechano-chemical polishing (combination of mechanical polishing and chemical polishing) can be used.

For example, polishing with #2000 fixed abrasive grain polisher (polishing liquid: water), or grinding with free abrasive grains (abrasive: SiC slurry, etc.), followed by grinding with diamond slurry, can perform mirror polishing.

There is not any particular limitation on such a polishing method, but other polishing methods may be used as long as the above-mentioned average surface roughness Ra of the present invention is achieved. The IZO sputtering target thus obtained was bonded to a base plate.

Next, implement a cleaning process such as blowing off air or washing with running water. When the air is used to blow out the foreign matter, the air can be sucked by a vacuum cleaner to effectively remove the foreign matter from the face facing the nozzle. However, when there are limitations to blowing off with air or washing with running water as described above, ultrasonic cleaning or the like may be further performed. Ultrasonic cleaning is effective when multiple vibrations are performed at a frequency of 25-300 kHz. From 25 kHz to 300 kHz, it is preferable to select 12 frequencies at intervals of 25 kHz to perform multiple vibrations.

Therefore, the bulk resistance of the thus-produced IZO sputtering target for producing a transparent conductive thin film can be controlled within 1-5 milliohm·cm.

As mentioned above, the use of Sn content as low as 2000 ppm or less without changing the composition of IZO can reduce the bulk resistance of IZO sputtering targets.

In addition, after bonding to obtain an IZO transparent conductive film mainly composed of In and Zn oxides, sputtering is performed using an IZO sputtering target containing 100-2000ppm, preferably 100-1000ppm, more preferably 100-500ppm Sn. Therefore, the resistivity of the transparent conductive film is 1.0×10 ^-4 to 1.0×10 ^-3 ohm·cm.

Examples and Comparative Examples

The present invention will be described in comparison with Examples and Comparative Examples.

In the production of IZ0 sputtering targets, indium oxide powder with an average particle size of 2 µm, zinc oxide powder with the same average particle size, and tin (Sn) were weighed to achieve the weight ratios listed in Table 1, and molded adhesive was added thereto. Agents, mixed together evenly, and then granulated.

Then, the mixed powder is evenly filled into a mold, and compressed using a cold press. The molding thus obtained was sintered in a sintering furnace at 1430° C. for 7 hours. In addition, the surface of the sintered body thus obtained was ground with a surface grinder, and the edge was cut off with a diamond knife to obtain an IZO target material.

The IZO target material density is 6.90 g/cm ³ and the average crystal grain size is 1.5 microns.

Table 1

sample number Sn content (ppm) Bulk resistance In ₂ O ₃ content (weight%) ZnO content (weight%) 1 0 5.28 89.3 10.7 2 0 4.97 89.3 10.7 3 0 4.37 89.3 10.7 4 0 4.86 89.3 10.7 5 179 4.11 89.3 10.7 6 179 4.11 89.3 10.7 7 179 4.19 89.3 10.7 8 179 4.57 89.3 10.7 9 210 3.32 89.3 10.7 10 210 3.76 89.3 10.7 11 210 3.31 89.3 10.7 12 210 3.39 89.3 10.7 13 210 3.24 89.3 10.7 14 210 3.2 89.3 10.7 15 210 3.69 89.3 10.7 16 345 2.79 89.3 10.7 17 345 2.59 89.3 10.7

18 345 2.8 89.3 10.7 19 345 2.78 89.3 10.7 20 345 2.79 89.3 10.7 twenty one 345 2.57 89.3 10.7 twenty two 345 2.73 89.3 10.7 twenty three 345 2.39 89.3 10.7 twenty four 345 2.68 89.3 10.7 25 345 2.52 89.3 10.7 26 345 2.92 89.3 10.7 27 345 2.72 89.3 10.7 28 2100 1.88 89.3 10.4 29 2700 1.66 89.3 10.4 30 3400 1.73 89.3 10.3 31 3400 1.66 89.3 10.3 32 39000 0.72 89.3 5.7 33 78800 0.14 90 0

Then, the surface was blown with air, and then ultrasonically cleaned for 3 minutes at 12 multiple vibration frequencies selected at intervals of 25 kHz from 25 kHz to 300 kHz. The surface was then dried to obtain IZO sputtering targets of Examples of the present invention and Comparative Examples.

As shown in table 1, sample 1-4 does not contain any tin (Sn) (comparative example), and sample 5-8 contains the Sn (embodiment) of 179ppm; Sample 9-15 contains the Sn (embodiment) of 210ppm; Sample 16-27 contained 345 ppm Sn (example); and samples 28-31 contained 2100-3400 ppm Sn (comparative example).

However, samples 32 and 33 contained 39000 and 78800 ppm of Sn (comparative example), respectively, and the added amount was changed so that the total amount of Zn+Sn was not changed. If the Sn content exceeds 2000 ppm, the object of the present invention cannot be achieved due to the loss of IZ0 characteristics.

The bulk resistance measurements of the IZO sputtering targets are also listed in Table 1. Figures 1 and 2 show plots of these data for easy viewing.

Figure 1 shows the data graph from never adding any Sn to adding 345ppm of Sn; Figure 2 shows the bulk resistance graph from adding 179ppm of Sn to adding 78800ppm of Sn (Figure 2 omits the data without adding any Sn). (The amount of added Sn is shown on a logarithmic scale).

As shown in Table 1 and Fig. 1, when the Sn addition amount is from 179ppm to 345ppm, the bulk resistance is 1-5 ohm·cm (1-5×10 ^-3 ohm·cm), indicating a low resistance value.

However, without adding any Sn, the bulk resistance is about 5 milliohm·cm or more, and it is impossible to achieve a stable low bulk resistance value of 5 milliohm·cm or less. In order to keep the bulk resistance value stably at or below 5 milliohm·cm, it has been proved that the Sn content should be 100 ppm or more.

On the other hand, when the Sn content is increased (adding a large amount of Sn), a lower volume resistance value can be achieved, however, if the Sn content exceeds 2000ppm, the decrease in the volume resistance value is slowed down, and it is impossible to see improvement by increasing the Sn content. significant effect on the bulk resistance value.

As mentioned above, if Sn is added in excess of 2000 ppm, the characteristics of IZO will deteriorate, so it is not preferable to add an excessive amount of Sn.

It can be seen from the above facts that in order to reduce the bulk resistance value and maintain the IZO characteristics, it is desirable that the Sn content in the sintered IZO target is within 100-2000ppm, which can be confirmed by the examples shown in Table 1 and Figures 1 and 2 .

(Evaluation of properties of the formed thin film)

Next, thin films were fabricated using the IZO sputtering targets of the present invention having different Sn contents, and the characteristics of the thin films were also evaluated.

Three types of 4-inch diameter IZO sputtering targets with different Sn contents manufactured as described above were used as sputtering targets. The Sn content, density and volume resistance (characteristic values) of the targets are listed in Table 2.

That is, the Sn content of sample 101 is 0 ppm, the density is 6.84 g/cm ³ , and the bulk resistance is 5.22 milliohm·cm; the Sn content of sample 102 is 465 ppm, the density is 6.79 g/cm ³ , and the bulk resistance is 2.44 milliohm • cm; sample 103 had a Sn content of 2000 ppm, a density of 6.78 g/cm ³ , and a bulk resistance of 1.93 milliohm·cm.

Table 2

(target nature)

sample number Sn content (ppm) Density (g/ ^cm3 ) Bulk resistance (millohm cm) 101 0 6.84 5.22 102 465 6.79 2.44 103 2000 6.78 1.93

In addition, the above-mentioned target was installed in a DC magnetron sputtering device to grow thin films on SCG substrates at room temperature. During sputtering, the pressure is pre-reduced to 1.2×10 ^-3 Pascal or lower, and then Ar gas (purity: 99.9%) and Ar+1%O ₂ mixed gas (purity: 99.99%) are added respectively to reach a vacuum pressure of 1.0 Pascal, under the conditions of voltage 360V and current 0.11A, a film with a thickness of 150 nanometers was made.

The characteristics of the thin films made under Ar atmosphere are listed in Table 3, and the characteristics of the thin films made in Ar+1%O ₂ mixed gas are listed in Table 4.

table 3

(Properties of thin film formed in Ar atmosphere)

sample number Sn content ppm) X-ray diffraction results Transmittance coefficient e(%) Resistivity (mOhm cm) 101 0 Amorphous 93.0 0.64 102 465 Amorphous 94.4 0.51 103 2000 Amorphous 94.3 0.59

Table 4

(Properties of films made in Ar+1%O ₂ mixed gas)

Sample No. Sn content (ppm) X-ray diffraction results Light transmittance e(%) Resistivity (mOhm cm) 101 0 Amorphous 96.4 0.59 102 465 Amorphous 94.5 0.60 103 2000 Amorphous 96.8 0.59

As evident from the above Table 3, when the film was produced in an Ar atmosphere while the Sn content of the IZO target was 0 (not added), 465 ppm and 2000 ppm, the transmittance of the film was 93.0%, 94.4% and 94.3 %; Resistivity is 0.64 milliohm·cm, 0.51 milliohm·cm and 0.59 milliohm·cm. Therefore, no great change in the characteristics of the film formed in the Ar atmosphere was found.

Also as evident from Table 4 above, when the thin film was produced in Ar+1%O _mixed gas

Also as evident from the above Table 4, when the thin film is produced in Ar+1%O _mixed gas, and the Sn content of the IZO target is 0 (not added), 465ppm and 2000ppm respectively, the transmission coefficient of the thin film is 96.4%, 94.5%, and 96.8%; the resistivities are 0.59 milliohm.cm, 0.60 milliohm.cm, and 0.59 milliohm.cm. Therefore, no great change was found in the characteristics of the films produced in the mixed gas of Ar+1%O ₂ .

The above results confirmed that when 100-2000ppm of Sn was added, a film with the same quality as that of the IZO sputtering target without Sn was obtained, and the addition of 100-2000ppm of Sn did not affect the characteristics of the film.

As described above, the volume resistance value of IZO is lowered by adding a trace amount of Sn, and a thin film is stably formed without changing general IZO characteristics.

Industrial applicability

The IZO sputtering target used to produce the transparent conductive film of the present invention can considerably and effectively reduce the bulk resistance by adding a very small amount of Sn without significantly losing the transparent conductive film mainly composed of In and Zn oxide (IZO) characteristics. In addition, with such a target production method, the above-mentioned low bulk resistance target can be obtained stably and with high reproducibility.

Claims (8)

1. indium-zinc oxide sputtering target that is used to produce transparent conductive film, this target mainly contains indium oxide and zinc oxide, it is characterized in that, and this target contains 100-2000ppm tin, and its body resistance is the 1-5 m ohm cm.

2. the indium-zinc oxide sputtering target that is used to produce transparent conductive film according to claim 1 is characterized in that this target contains 100-1000ppm tin.

3. the indium-zinc oxide sputtering target that is used to produce transparent conductive film according to claim 1 is characterized in that this target contains 100-500ppm tin.

4. according to each described indium-zinc oxide sputtering target that is used to produce transparent conductive film among the claim 1-3, it is characterized in that the content of every kind of unavoidable impurities is all less than 10ppm.

5. the indium-zinc oxide sputtering target that is used to produce transparent conductive film according to claim 4, wherein said unavoidable impurities is selected from Fe, Al and Si.

6. according to each described indium-zinc oxide sputtering target that is used to produce transparent conductive film in claim 1-3 and 5, it is characterized in that the crystal size of described sputtering target is 4 microns or littler.

7. according to each described indium-zinc oxide sputtering target that is used to produce transparent conductive film in claim 1-3 and 5, it is characterized in that the crystal size of described sputtering target is 3 microns or littler.

8. according to each described indium-zinc oxide sputtering target that is used to produce transparent conductive film in claim 1-3 and 5, it is characterized in that the crystal size of described sputtering target is 2 microns or littler.