JP2007056352A - Target for ion plating used for manufacturing of zinc oxide-based electroconductive film, its manufacturing method, and method for manufacturing zinc oxide-based electroconductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a target which gives a zinc oxide-based electroconductive film having uniformity and high performance in an ion plating method while suppressing the generation of splash or without generating splash, and to provide a useful method for manufacturing the same. <P>SOLUTION: The target for forming the zinc oxide-based electroconductive film comprises a sintered compact mainly containing zinc oxide and is characterized in that the volume ratios of open and closed pores to the volume obtained from the external shape are 15-40% and ≤3.0%, respectively, and the generation of splash is inhibited during ion plating. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a target used when a zinc oxide-based conductive film is manufactured by an ion plating method, a method for manufacturing the target, and a method for manufacturing a zinc oxide-based conductive film, and in particular, a zinc oxide-based conductive film by an ion plating method. The present invention relates to an improved technique for obtaining a homogeneous and high-performance conductive film free from pinhole defects by preventing or suppressing as much as possible the splash phenomenon that occurs during the heating of a target that is an evaporation material. .

  In recent years, the performance improvement of zinc oxide-based conductive films has progressed remarkably, and the specific resistance value, which is one of the main characteristics, is comparable to ITO (indium tin oxide) films at the laboratory level. Low values are starting to be obtained. Therefore, in recent years, when there is concern about the depletion of indium resources, there is an increasing expectation for a zinc oxide-based conductive film as a next-generation conductive film that replaces an ITO film containing expensive indium as an essential component.

  A direct current magnetron sputtering method is known as a representative method for producing a zinc oxide-based conductive film at a mass production level, and this method is excellent in terms of film formation speed and film formation area. However, when a zinc oxide-based conductive film is formed by sputtering, a large resistivity distribution (increase in resistivity at the erosion facing portion) may occur on the substrate.

  On the other hand, the ion plating method described in Patent Documents 1 and 2 irradiates a plasma beam or an electron beam onto an evaporation material (target) with a plasma gun or an electron gun, evaporates the target and ionizes it. It is a method of vapor deposition on a substrate. A large resistivity distribution is not generated, a zinc oxide-based conductive film having a small specific resistance can be obtained at a high film-forming speed, and further, it can cope with a large film-forming area. Has advantages.

  However, in the method in which the zinc oxide-based sintered body, which is the evaporation material (target), is evaporated by ion plating and ionized to form a thin film, the evaporation material splashes during heating and the scattered particles pin the film. There has been a problem that hole defects can occur, and the solution has been desired.

  The splash refers to the following phenomenon. That is, when the evaporation material (target) is irradiated with a plasma beam or an electron beam and heated in vacuum, the evaporation material is vaporized when reaching a certain temperature, and uniform evaporation starts in an atomic state. Splash refers to a phenomenon in which splashes having a visible size of about several μm to 1000 μm mixed with uniform evaporation gas are ejected from the evaporation material and collide with the deposited film. When this phenomenon occurs, it causes pinhole defects and the like in the deposited film due to the collision of the droplets, which not only harms the homogeneity of the deposited film but also significantly deteriorates the performance as the conductive film.

The cause of such a phenomenon is that bubbles contained in the target explode due to thermal shock or static charge charge-up due to high energy such as plasma beam or electron beam, and this induces splash. It is done.
JP 2004-95223 A Japanese Patent Laid-Open No. 10-18026

  The present invention has been made in view of the above circumstances, and a zinc oxide-based conductive film is formed by evaporating and ionizing a zinc oxide-based sintered body used as an evaporation material (target) by an ion plating method. In addition, the present invention provides a target capable of preventing or suppressing splash generated during heating and evaporation, stably obtaining a defect-free zinc oxide-based thin film, and providing a useful method for producing the target. An object of the present invention is to provide a method for producing a high-quality zinc oxide-based conductive film using the above-mentioned.

  The target for ion plating according to the present invention, which has been able to solve the above problems, is composed of a sintered body mainly composed of zinc oxide, the ratio of open pores to the volume determined from the outer shape is 15 to 40%, and It is characterized in that the closed pore ratio is 3.0% or less.

  The sintered body is preferably sintered after preforming a zinc oxide-based powder having a zinc oxide content of 80% by mass or more. Among them, at least one selected from 3B group, 4B group, and 7B group is preferable. A zinc oxide-based powder containing 0.003 to 20% by mass of seed elements is preferable because it has higher conductivity due to the doping effect of these elements.

  The production method of the present invention is a method for producing an ion plating target for producing the zinc oxide conductive film, which is fired at 400 to 1000 ° C., has a maximum particle diameter of 150 μm or less and an average particle diameter. A preformed zinc oxide powder of 0.1 to 30 μm is sintered at 500 to 1600 ° C., and the ratio of open pores to the volume determined from the outer shape is 15 to 40%, and the ratio of closed pores is 3 There is a gist where the content is 0% or less.

  Moreover, the method of forming a zinc oxide type electrically conductive film by the ion plating method using the said target is also included by the technical scope of this invention.

  According to the present invention, as an ion plating target composed of a sintered body mainly composed of zinc oxide, the ratio of open holes determined from the outer shape is in the range of 15 to 40%, and the ratio of closed holes is 3.0%. By using a zinc oxide-based sintered body that is suppressed to the following, a zinc oxide-based conductive film having no uniform splash and having a stable performance can be obtained.

  The target of the present invention is a zinc oxide-based sintered body used as an evaporation material for ion plating as described above, and the ratio of open pores determined from the outer shape is in the range of 15 to 40%, and It is characterized in that the closed pore ratio is 3.0% or less.

  In order to investigate the cause of the occurrence of splash that occurs when a zinc oxide-based sintered body is used as a target, the present inventors have some influence on the splash due to the surface properties and internal properties of the sintered body constituting the target. The relationship between the cross-sectional properties observed with a scanning microscope (SEM) and the splash was examined.

  As a result, in a sintered body in which splash is observed, a number of closed holes (holes enclosed inside and not communicating with the surface) are formed at the corners of the grain boundaries formed by adjacent sintered grains. In contrast, in the case of a sintered body without splash, such closed voids are hardly observed, and most of the voids existing between adjacent sintered grains are on the surface of the sintered body. It was confirmed that they existed as so-called open holes.

  As described above, the splash is a phenomenon in which a droplet having a visible size of about several μm to 1000 μm mixed with a uniform evaporation gas jumps out of the evaporation material and collides with the deposited film. Considering the SEM observation results, the cause of the splash is considered as follows.

  That is, zinc oxide begins to evaporate in a zinc oxide-based sintered body heated by an electron beam or the like due to a rapid temperature rise. At this time, the pressure in the closed pores existing near the surface of the sintered body is increased by the evaporated zinc oxide gas, and finally the pressure is explosively released to destroy the sintered body. It seems that the fragments and splashes scattered at this time are observed as splash. In the sintered body that does not cause the splash phenomenon, the evaporated zinc oxide vapor is quickly diffused from the surface of the sintered body through the pores communicating with the surface, that is, the open pores. No pressure increase will occur and no splash will occur.

  In other words, it is considered that the splash phenomenon can be prevented if the pores existing in the sintered body are made as open as possible and the closed pores causing the explosion as described above are reduced as much as possible. In order to make the zinc oxide constituting the sintered body evaporate more smoothly by rapid heating, the sintered body should be made porous, rather than having a high density, and not only the surface layer of the sintered body but also the inside Therefore, it was preferable that the heating and evaporation proceed, and therefore, it was thought that it was best that most of the pores that were porous and existed inside were open pores.

  From this viewpoint, as a result of quantitatively examining the influence of the degree of porosity of the sintered body and the existence ratio of open pores on the splash phenomenon, as described above, the ratio of open pores required from the outer shape of the sintered body is as follows. When the ratio is 15 to 40% and the ratio of closed pores is suppressed to 3.0% or less, there is almost no splash during heating for ion plating, and a stable and uniform evaporation state is exhibited. It was found that a uniform and high performance conductive film without pinhole defects was formed.

The volume ratio of the closed holes and the open holes of the sintered body can be determined, for example, as follows. For example, when water is used as a liquid and measurement is performed at a temperature of 25 ° C., it is obtained by the following formulas (1) and (2).
Open pore volume ratio (O) = [(Ww−W) × density of water at 25 ° C./V]×100 (1)
Closed pore volume ratio (C) = [(1-O) / (100) − (W / V · ρ)] × 100 (2)

  In the above formula, V is a volume determined from the outer shape of the sintered body; W is a mass of the sintered body; Ww is immersed in water, depressurized to a pressure of 3500 Pa or less, held for 12 hours, and then taken out. The mass after wiping off the water on the surface of the sintered body; ρ represents the theoretical density of the sintered body.

  Incidentally, if the ratio of open pores is less than 15%, the density as a whole of the sintered body is too high, and the porosity is insufficient, and the evaporation of zinc oxide due to rapid heating is difficult to occur. When a meat target is used, a splash phenomenon is likely to occur. On the other hand, if the ratio of open holes exceeds 40% and becomes too high, the target material becomes insufficient in strength, causing problems such as cracking of the target material due to thermal shock caused by high energy such as a plasma beam or an electron beam. .

  From such a viewpoint, a more preferable value of open pores is 16% or more, more preferably 18% or more, 30% or less, and further preferably 28% or less.

  Further, as described above, the closed hole is directly connected to the splash due to the pressure increase and explosion in the closed hole, and when it exceeds 3.0%, the splash becomes obvious. Therefore, in order to achieve the object of the present invention, it is an absolute condition to suppress the closed pores to 3.0% or less, preferably 2.5% or less. Regardless of ion plating conditions and the like, a more preferable closed hole for preventing even a slight splash is 2.0% or less.

  The zinc oxide-based sintered body used as a target in the present invention may be one obtained by doping zinc oxide with a conductivity-imparting component and imparting conductivity, or an element selected from 3B group, 4B group and 7B group Specifically, a material doped with one or more of B, Al, Ga, In, Si, Ge, Sn, Pb, F, Cl, Br, and I is used. The doping amount of these elements varies depending on the kind of element and the required degree of conductivity and cannot be determined uniformly, but the standard is 0.003% by mass or more and 20% by mass or less, more preferably Is 0.01 mass% or more and 10 mass% or less.

  Next, a useful manufacturing method for obtaining an ion plating target having the above characteristics will be described.

  In the production method of the present invention, as a method for obtaining a target having the above characteristics, a method of sintering a zinc oxide powder having a specified firing temperature and particle diameter at a predetermined temperature as described in detail below is employed. .

  Specifically, a zinc oxide powder that has been fired at 400 to 1000 ° C. and has a maximum particle size of 150 μm or less and an average particle size of 0.1 to 30 μm is used. After preforming by any method such as isostatic pressing, sintering is performed at 500 to 1600 ° C.

  The biggest aim of the above manufacturing method is to advance the crystal growth by firing at a high temperature in advance, and to use a zinc oxide-based powder that is less likely to cause volume shrinkage in the subsequent sintering step. In addition to increasing the open pore volume ratio as a ligation), the closed pore volume ratio is minimized.

  In order to realize such an aim, the production method of the present invention defines the specifications and sintering temperature of the zinc oxide-based powder to be used, and the reasons for determining them are as follows.

  First, the zinc oxide-based powder must be pre-fired at 400 to 1000 ° C. This zinc oxide-based powder is a skeletal component of the sintered body (target) as described above, and itself needs to be sufficiently crystallized. For this purpose, at least 400 ° C. or more, preferably Is preferably fired at a temperature of 500 ° C. or higher. However, if the firing temperature is too high, the molded body is liable to crack when pre-fired. Therefore, it is preferable to use a product fired at a temperature of 1000 ° C. or less, preferably 950 ° C. or less.

  Next, the preferable particle size constitution of the zinc oxide-based powder has a maximum particle size of 150 μm or less and an average particle size of 0.1 to 30 μm. This particle size structure is important for effectively exhibiting the action as a skeletal component of the zinc oxide-based powder. When the maximum particle size exceeds 150 μm or the average particle size exceeds 30 μm, coarse particles are used as the skeletal component. As a result, the target becomes insufficient in homogeneity and the strength tends to be insufficient, resulting in poor quality stability. On the other hand, if the average particle size is too small, the target is too dense because it is too fine as a skeletal component, the volume ratio of open holes is small, and the volume ratio of closed holes is large. In order to obtain a sintered body having a homogeneous and appropriate open void volume ratio and closed void volume ratio, a more preferable particle size constitution is that the maximum particle size is 130 μm or less, more preferably 110 μm or less, and the average particle size is 0.00. It is 3-25 micrometers, More preferably, it is 0.5-20 micrometers.

  There is no restriction on the mixing method when mixing elements selected from Group 3B, Group 4B, and Group 7B, and one or more selected from the above elements are blended in an appropriate amount with respect to the zinc oxide powder. Then, they may be mixed using a known mixing device such as a ball mill, a homogenizer, a Henschel mixer. The above-mentioned selective elements are mixed in order to increase the conductivity of the zinc oxide sintered body by adding appropriate amounts of these elements and to improve the properties as a conductive material. In order to exhibit, it is preferably 0.003 mass% or more, more preferably 0.01 mass% or more with respect to the zinc oxide powder. However, if the content of these elements is too large, an increase in the effect according to the added amount is not recognized, and conversely, obstacles such as acting as impurities and inhibiting conductivity appear, so at most 20 masses. % Or less, more preferably 15% by mass or less.

  The zinc oxide powder or zinc oxide powder containing the above-mentioned selective element in the zinc oxide powder is preformed by an arbitrary method such as a mechanical press or an isostatic press, and then heated and sintered at a predetermined temperature to obtain an appropriate strength. The target which consists of an oxide which has and has a predetermined open pore volume ratio and a closed pore volume ratio can be obtained.

  The sintering temperature after preforming is preferably 500 ° C to 1600 ° C. If the sintering temperature is less than 500 ° C., sufficient sintering does not occur, and the sintered body (target) itself tends to collapse. However, if the sintering temperature exceeds 1600 ° C. and becomes too high, the volume ratio of closed pores of the sintered body tends to increase and splash tends to occur, which is not preferable. From such a viewpoint, a more preferable sintering temperature is 600 ° C. or higher and 1500 ° C. or lower, more preferably 700 ° C. or higher and 1400 ° C. or lower. The sintering time is not particularly limited, but usually about 2 hours or more is sufficient, and typically about 3 hours or more. Although there is no upper limit to the time, it is useless to extend the time to 5 hours or more, so normally about 5 hours or less is adopted. The sintering atmosphere may be an air atmosphere, a reducing atmosphere, or an inert gas atmosphere.

  The target of the present invention thus obtained does not crack or collapse due to thermal shock even when heated with a high energy beam such as a plasma beam or an electron beam as described above, and may cause a splash phenomenon. Therefore, the obtained zinc oxide-based conductive film will be homogeneous and high-performance without pinhole defects, and in the near future, it can be expected to be put into practical use as an inexpensive conductive film material that can be replaced with an ITO film or the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

  In the following examples, the volume ratio of open holes and closed holes was determined as follows.

  After measuring the diameter, height and mass of the sample sintered body, it is placed in a separable flask. A pipe connected to the diffusion pump and a dropping funnel containing pure water are arranged on the lid of the separable flask, and a pipe connected to the rotary pump is connected to the upper part of the dropping funnel.

First, the inside of the dropping funnel is depressurized with a rotary pump, and the air dissolved in the water is sufficiently exhausted, then the inside of the separable flask is first used with a rotary pump and then with a diffusion pump, The pressure is reduced until the internal pressure becomes 10 ⁻³ Pa or less, and this state is continued for 2 hours. Next, the decompression is stopped, water from which the air has been sufficiently removed from the dropping funnel is dropped into the separable flask, and the sample sintered body previously charged completely absorbs the water while completely absorbing the water. Add water until pickled. Thereafter, the inside of the separable flask was sucked with a rotary pump, and the pressure was reduced to 3500 Pa or less to confirm that no bubbles were generated from the sintered body. Leave in the room for 12 hours.

  A beaker containing pure water is placed in the electronic balance for a whole day and night, and the humidity in the balance is increased in advance. Then, the sintered body that has sufficiently absorbed water is taken out from the separable flask, the surface water is quickly wiped off with a wiper, and the weight of the sintered body is immediately measured with a balance. All temperatures during this period are 25 ° C. From the measured values, the volume ratio (O) of open pores and the volume ratio (C) of closed pores of each sample sintered body were obtained by the above formulas (1) and (2).

Example 1
A zinc oxide powder having a maximum particle size of 110 μm or less and an average particle size of 5 μm, which has been calcined at about 900 ° C. for 3 hours, is preformed at a pressure of 20 MPa by a mechanical press, and then calcined at 1100 ° C. for 5 hours in an air atmosphere. As a result, a zinc oxide sintered body having a diameter of 29 mm and a thickness of 20 mm was produced.

  The obtained zinc oxide sintered body had an open void volume ratio of 16% and a closed void volume ratio of 2.8%. Moreover, when this zinc oxide sintered body was loaded into an ion plating apparatus and evaporated by irradiating with a 6 kV electron beam, the state of splash was observed when observed for 2 minutes from the observation window on the side of the chamber. There wasn't.

Example 2
With a ball mill, a maximum particle size of 75 μm or less, an average particle size of 3 μm, a zinc oxide-based calcined powder of 97 parts by mass and calcined at about 650 ° C. for 3 hours, and 3 parts by mass of gallium oxide powder (manufactured by Kishida Chemical Co., Ltd.) After mixing sufficiently, it was preformed at a pressure of 20 MPa by a mechanical press. Subsequently, it sintered at 1100 degreeC in air | atmosphere for 3 hours, and obtained the zinc oxide type sintered compact of diameter 30.5mm x thickness 20mm.

  The obtained zinc oxide-based sintered body had an open void volume ratio of 24% and a closed void volume ratio of 2.3%. When this zinc oxide-based sintered body is loaded into an ion plating apparatus and evaporated by irradiating it with a 6 kV electron beam, it is observed from the observation window on the side of the chamber for 2 minutes, and no splash is observed. It was.

Example 3
A ball mill fully mixes 97 parts by mass of zinc oxide powder having a maximum particle size of 75 μm or less and an average particle size of 4 μm, and heated and fired at about 800 ° C. for 3 hours, and 3 parts by mass of gallium oxide powder (manufactured by Kishida Chemical). Then, it was preformed at a pressure of 20 MPa by a mechanical press. Next, sintering was performed at 1300 ° C. for 2 hours in an air atmosphere to obtain a zinc oxide-based sintered body having a diameter of 30.7 mm and a thickness of 20 mm.

  The obtained zinc oxide-based sintered body had an open void volume ratio of 32% and a closed void volume ratio of 1.9%. When this zinc oxide-based sintered body is loaded into an ion plating apparatus and evaporated by irradiating it with a 6 kV electron beam, it is observed for 2 minutes from a viewing window on the side of the chamber, and a splash is observed. There wasn't.

Comparative Example 1
A zinc oxide powder having a maximum particle size of 250 μm or less and an average particle size of 35 μm, heated and fired at about 950 ° C. for 3 hours, preformed at a pressure of 20 MPa by a mechanical press, and then 5 ° C. at 1100 ° C. in an air atmosphere. Time-sintering was performed to obtain a zinc oxide sintered body having a diameter of 31 mm and a thickness of 20 mm.

  The obtained zinc oxide sintered body had an open pore volume ratio of 25% and a closed void volume ratio of 3.7%. When this zinc oxide sintered body was loaded into an ion plating apparatus and evaporated by irradiating it with a 6 kV electron beam and observed through a viewing window on the side of the chamber for 2 minutes, the occurrence of splash was observed 26 times. It was.

Comparative Example 2
97 parts by mass of zinc oxide powder having a maximum particle size of 250 μm or less and an average particle size of 35 μm, heated and fired at about 950 ° C. for 3 hours, and 3 parts by mass of gallium oxide powder (manufactured by Kishida Chemical Co., Ltd.) are sufficiently mixed with a ball mill. Then, it was preformed at a pressure of 20 MPa by a mechanical press. Next, sintering was performed at 1100 ° C. for 3 hours in an air atmosphere to obtain a zinc oxide-based sintered body having a diameter of 32 mm and a thickness of 20 mm.

  The obtained zinc oxide-based sintered body had an open void volume ratio of 35% and a closed void volume ratio of 3.5%. Further, when this zinc oxide-based sintered body was loaded in an ion plating apparatus and evaporated by irradiating with a 6 kV electron beam, it was observed for 2 minutes from a viewing window on the side of the chamber. Observed once.

Comparative Example 3
The maximum particle size is 180 μm or less, the average particle size is 31 μm, and 97 parts by mass of zinc oxide powder heated and fired at about 800 ° C. for 3 hours and 3 parts by mass of gallium oxide powder (manufactured by Kishida Chemical Co., Ltd.) are used. After using and mixing well, it was preformed at a pressure of 20 MPa by a mechanical press. Next, a zinc oxide-based sintered body having a diameter of 30.5 mm and a thickness of 20 mm was manufactured by sintering at 1100 ° C. for 3 hours in an air atmosphere.

  The resulting zinc oxide-based sintered body had an open void volume ratio of 14% and a closed void volume ratio of 4.0%. In addition, when this zinc oxide-based sintered body was loaded into an ion plating apparatus and evaporated by irradiating with a 6 kV electron beam, it was observed from a viewing window on the side of the chamber for 2 minutes. Observed 30 times.

Claims (5)

  A zinc oxide-based conductive material comprising a sintered body mainly composed of zinc oxide, wherein the ratio of open pores to the volume determined from the outer shape is 15 to 40%, and the proportion of closed pores is 3.0% or less. Target for ion plating for film production.   The target according to claim 1, wherein the sintered body is obtained by preforming and sintering a zinc oxide-based powder having a zinc oxide content of 80% by mass or more.   The target according to claim 1 or 2, wherein the zinc oxide-based powder contains 0.003 to 20 mass% of at least one element selected from Group 3B, 4B, and 7B.   A method for producing the target for ion plating according to any one of claims 1 to 3, wherein the target is fired at 400 to 1000 ° C, the maximum particle size is 150 µm or less, and the average particle size is 0.1 to 0.1. A method for producing a target for producing a zinc oxide-based conductive film, wherein a zinc oxide-based powder having a thickness of 30 μm is preformed and sintered at 500 to 1600 ° C.   A method for producing a zinc oxide-based conductive film, wherein the target according to any one of claims 1 to 3 is used to form a zinc oxide-based conductive film by an ion plating method.