Patent Application
20110041759
The present invention relates to a water-reactive Al composite material, a water-reactive Al film, a process for the production of the Al film and a constituent member for a film-forming chamber and in particular to a water-reactive Al composite material comprising 4NAl or 5NAl which contains added In; a water-reactive Al film consisting essentially of this water-reactive Al composite material; a method for the production of this Al film; and a constituent member for a film-forming chamber, which is covered with this Al film.
In a film-forming apparatus for forming a thin film according to, for instance, the sputtering technique, the vacuum deposition technique, the ion-plating technique, or the CVD technique, a film of a metal or a metal compound, as a film-forming material, is inevitably adhered to a constituent member for a film-forming chamber, which is positioned within the film-forming apparatus during the film-forming process. As such constituent members for a film-forming chamber, there can be listed, for instance, an adhesion-preventive plate for inhibiting the adhesion of any film on the inner portions of a vacuum chamber other than a substrate, a shutter, a mask used for forming such a film only on the desired area on the substrate and a tray for conveying the substrate. A film having the same composition as that of the intended thin film (a thin film to be formed on a substrate) is also deposited on or adhered to these members during the film-forming process. In this respect, it is the usual practice that these members are repeatedly used after the removal of the film adhered thereto.
The film inevitably adhered to these constituent members for a film-forming chamber is thickened in proportion to the length of the working time of the film-forming process. Such an adhered film is peeled off, in the form of particles, from the constituent members for a film-forming chamber due to the action of the internal stress of the adhered film or the stress accumulated in the film through the repeated thermal hysteresis, and adhered to the substrate and this would accordingly result in the formation of a film having various defects. For this reason, it is the common practice that the constituent members for a film-forming chamber are subjected to the following cycle, at regular intervals; the removal or dismantlement thereof from the film-forming apparatus at a stage in which the adhered film is not yet peeled off, the washing thereof to remove the film adhered thereto, the subjection thereof to a surface-finishing treatment and the subsequent reuse thereof.
When using a valuable metal such as Al, Mo, Co, W, Pd, Nd, In, Ti, Re, Ta, Au, Pt, Se and Ag, as a film-forming material, there has been desired for the establishment of a processing technique for the recovery of metals which do not take part in the formation of the film thereof on the surface of a substrate and are adhered to the constituent members other than the substrate and for the development of a technique for making the members reusable.
For instance, in the case of the adhesion-preventive plate used for inhibiting the adhesion of any film-forming material onto, for instance, the inner wall of the film-forming apparatus and the surface of a variety of such constituent members for a film-forming chamber, other than the surface of a substrate, the deposit formed during the film-forming process is, in the existing circumstances, peeled off from the foregoing members and/or the inner wall, for the reuse thereof. Currently used as such a method for the peeling off of this deposit include, for instance, the sandblasting technique, the wet etching technique which makes use of an acid or an alkali and the peeling technique which uses the hydrogen embrittlement by the action of, for instance, hydrogen peroxide and even the peeling method which makes use of the electrolysis thereof. In this case, when implementing the treatment for peeling off of the deposit, the adhesion-preventive plate is damaged in a treating liquid in no small quantities and therefore, the adhesion-preventive plate would be limited in the number of reusable times. For this reason, there has been desired for the development of a film-peeling technique which can reduce the occurrence of any damage of the adhesion-preventive plate as low as possible.
In this respect, however, if the concentration of the peeled deposit present in the blasting waste generated during the foregoing sandblasting technique and in the waste liquor generated in the treatment with an agent such as an acid treatment or an alkali treatment is low, the cost required for the recovery of the valuable metals is correspondingly quite high and accordingly, this method is not profitable. In such case, the deposit thus peeled off is accordingly handled as waste, under the present conditions.
In the foregoing treatment with an agent, not only the cost for the agent per se is high, but also the cost required for the post-treatment of the used liquid containing such an agent is high and further the occurrence of any environmental pollution should be prevented. For this reason, there has been desired for the reduction of the amount of the foregoing agent to be used as low as possible. In addition, when carrying out the foregoing treatment with an agent, the film-forming material peeled off from the adhesion-preventive plate would be converted into other new chemical substances and therefore, the cost required for the recovery of only the film-forming material from the peeled deposit would further be piled up. Accordingly, the materials to be recovered are only the film-forming materials whose unit price is balanced with the recovery cost, in the existing circumstances.
In addition to the method for peeling off of the deposit, as has been discussed above, there has been known a technique for recovering valuable metals which comprises the steps of implementing a film-forming process in an apparatus provided with constituent members covered with an Al film consisting of a water-reactive Al composite material having such characteristic properties that it can undergo a reaction in a moisture-containing atmosphere and can thus be converted into substances soluble or active in water; peeling off and separating the film adhered to the Al film, during the film-forming process, through the reaction and/or dissolution of the Al film; and then recovering the valuable metals included in the film-forming material present in the adhered film thus peeled off (see, for instance, Patent Document 1 specified below). In this water-reactive Al composite material, the surface of small or fine lumps composed of Al crystalline grains is covered with a film of In and/or Sn.
Patent Document 1: JP-A-2005-256063 (Claims).
Accordingly, it is an object, in a broad sense, of the present invention to solve the foregoing problems associated with the conventional techniques and more specifically to provide an Al composite material containing added In, which can be made soluble through the reaction with water in a moisture-containing atmosphere; an Al film essentially consisting of this Al composite material; a method for the production of such an Al film; and a constituent member for a film-forming chamber, which is covered with this Al film.
Thus, the water-reactive Al composite material of the present invention comprises 4NAl or 5NAl and added In in an amount ranging from 2 to 5% by mass on the basis of the mass of Al, wherein In is uniformly dispersed in Al crystalline grains.
If the Al composite material has such a composition, the Al film prepared from this material can easily react with water in a moisture-containing atmosphere with the generation of hydrogen gas and the resulting products can thus be dissolved in water.
If the amount of the added In is less than 2% by mass, the reactivity of the resulting Al film with water is reduced, while if the amount of the added In is higher than 5% by mass, the reactivity of the resulting Al film with water becomes considerably high and the Al film may sometimes react with the moisture present in the atmospheric air.
The method for the production of a water-reactive Al film according to the present invention comprises the steps of melting a material prepared by adding In to 4NAl or 5NAl in an amount ranging from 2 to 5% by mass on the basis of the mass of Al such that the resulting material has a uniform composition; thermally spraying the molten material on the surface of a base material; and solidifying the sprayed molten material through quenching to thus form a thermally sprayed Al film in which In is uniformly dispersed in Al crystalline grains.
The water-reactive Al film according to the present invention is characterized in that it consists essentially of the foregoing water-reactive Al composite material.
The constituent member for a film-forming chamber of a film-forming apparatus according to the present invention is characterized in that the constituent member is provided, on the surface, with the foregoing water-reactive Al film.
The constituent member for a film-forming chamber according to the present invention is further characterized in that the constituent member is an adhesion-preventive plate, a shutter or a mask.
The thermally sprayed Al film consisting essentially of the water-reactive Al composite material according to the present invention would show the effects described below. More specifically, the Al film can easily be produced by a simple process while lowering the cost of production; the Al film has such characteristic properties that it can be dissolved in water through the reaction with water present in a moisture-containing atmosphere, even after the film experiences a thermal hysteresis phenomenon as a result of the film-forming process carried out at a temperature ranging from about 300 to 350° C.; and the Al film is highly active and highly soluble in water before the film experiences thermal hysteresis (upon the formation of the thermally sprayed film) and after the film experiences thermal hysteresis as compared with those produced using Al raw materials having low purities (2NAl and 3NAl), since the Al film of the present invention is produced using an Al raw material having a high purity (4NAl and 5NAl).
This Al film can undergo a reaction with water in the presence of moisture and can effectively be dissolved in water while generating hydrogen gas. Accordingly, the following effects can be achieved by the Al composite film of the present invention: If the film-forming operation is carried out using a film-forming apparatus provided with constituent members for a film-forming chamber (for instance, an adhesion-preventive plate, a shutter and a mask), which are covered with the water-reactive Al film of the present invention, the inevitably adhered film consisting essentially of the film-forming material and adhered to the surface of, for instance, an adhesion-preventive plate during the film-forming process can be peeled off and/or separated from the surface of the constituent members for the film-forming chamber through the reaction and/or dissolution of this Al film and the valuable metals included in the film-forming material can be easily recovered from the adhered film peeled off from the surface of the constituent members and the constituent members can thus be reused over an increased number of times.
When producing a thin film in a film-forming apparatus according to a variety of film-forming techniques such as the sputtering technique, the interior of the film-forming chamber is subjected to the influence of repeated thermal hysteresis. For this reason, the surface of the constituent members such as an adhesion-preventive plate, which are positioned within the film-forming chamber and which are coated with the Al film of the present invention, is also subjected to the influence of repeated thermal hysteresis. Accordingly, it would be necessary that the film, at the time of the film-formation through the thermal spraying technique before the film is subjected to the influence of the thermal hysteresis, is not only stable, but also easy to handle. At the same time, the Al film provided thereon with adhered film inevitably attached thereto during the film-forming process should have such a solubility (or activity) that the Al film can easily be peeled off from the base material such as the constituent members along with the adhered film and further should be stable, even after the Al film is influenced by the thermal hysteresis experienced in the film-forming process. In the case of the water-reactive Al film according to the present invention, such requirement for the solubility or activity would sufficiently be satisfied.
The upper limit of the thermal hysteresis temperature within the foregoing film-forming chamber is on the order of about 300 to 350° C. when the film is formed according to, for instance, the sputtering technique, the vacuum deposition technique, the ion-plating technique or the CVD technique. Therefore, it would in general be sufficient, from the practical standpoint, that the Al film has reactivity with water even after it is subjected to the influence of the thermal hysteresis up to a temperature of 300° C. and it would be more suitable that the Al film preferably has reactivity with water even after the Al film experiences the thermal hysteresis up to a temperature of 350° C. In the case of the water-reactive Al film according to the present invention, such requirement for the solubility would certainly be satisfied, as will be explained below more in detail.
The foregoing solubility or activity of the Al composite film of the present invention is evaluated on the basis of the current density (in the present invention, also referred to as “reaction current density (mA/cm2)”) as determined by immersing a base material covered with the Al film in warm water maintained at a predetermined temperature (ranging from 40 to 130° C. and preferably 80 to 100° C.) and then determining the current density of the immersion liquid. This determination method is one which comprises the steps of determining the loss in weight observed for each sample before and after the immersion thereof in the treating liquid and then converting the result into the current density value while taking into consideration, for instance, the surface area of the sample and the immersion time of the same in the treating liquid. It can be said that the Al film provided thereon with adhered film inevitably attached thereto during the film-forming process has such a solubility (or activity) that the Al film can easily be peeled off from the base material along with the adhered film even after the Al film is subjected to the influence of thermal hysteresis experienced in the film-forming process, so long as the reaction current density as determined according to this method is not less than 50 mA/cm2.
The present invention will hereunder be described with reference to the following embodiments.
In the Al film consisting essentially of the water-reactive Al composite material according to the present invention, In is highly uniformly dispersed or distributed within the 4NAl or 5NAl matrix and accordingly, the Al film can easily react with water within a moisture-containing atmosphere such as water, water vapor or an aqueous solution and as a result, it can thus be made soluble or active in water. Usable in the present invention as Al raw materials are, for instance, those having purities of 4N (99.99%) and 5N (99.999%) and each of them can be obtained by further treating an Al raw material having a low purity and prepared by the electrolytic process such as 2N (99%) Al or 3N (99.9%) Al according to the three layer electrolytic process or a method according to the partial solidification technique (the segregation technique) which makes use of the temperature difference between the solid and liquid phases upon the solidification. The principal impurities present in the 4NAl and 5NAl include Fe and Si and these Al raw materials further include, for instance, Cu, Ni and C as impurities other than the foregoing principal ones.
In the Al—In system, the electrochemical potential difference between Al and In is in general quite high, but if the spontaneous oxide film of Al is present on the surface thereof, the ionization of Al is not advanced at all. However, when the spontaneous oxide film is once broken or removed and Al directly comes in close contact with In, the ionization of Al can be promoted very rapidly due to the potential difference between them. At this stage, In is, in the as-is status thereof, highly dispersed throughout the Al crystalline grains without causing any chemical change. In has a low melting point (157° C.) and never forms any solid-solution with Al. Accordingly, a desired Al film can be obtained by melting Al and In in such a manner that the composition thereof becomes uniform while taking care of the density difference between them and then thermally spraying the resulting molten material on the surface of a base material according to the thermal spraying technique to thus give an Al film, as a result of the solidification of the deposited molten material through quenching as well as the compressive effect of the solidification.
The added In is highly dispersed throughout the Al crystalline grains due to the action of the thermal spraying process and it is maintained in the state in which it comes in direct contact with Al. The added In never forms a stable phase along with Al and therefore, the Al/In interface is maintained in its high energy state and can undergo a vigorous reaction with water within a moisture-containing atmosphere at the contact surface with water. In addition, In as an added element is in a highly dispersed condition and the H2 gas bubbles generated during the reaction undergo expansion to thus generate a mechanical action. Therefore, the reaction products mainly comprising AlOOH are finely pulverized on the surface, due to the mechanical action, without forming any film thereon and dispersed in the liquid and the reaction or the dissolution reaction continuously and explosively proceeds at the successively renewed reaction boundary.
The higher the purity of an Al raw material, the more conspicuous the behavior of the Al—In system described above and, in other words, the behavior is particularly conspicuous in the case of 4NAl and 5NAl as compared with 2NAl and 3NAl.
Now the thermally sprayed Al film obtained using this composite material will hereunder be described in more detail, while taking a water-reactive Al composite material consisting essentially of 4NAl—In by way of example.
More specifically, the method for the preparation of the thermally sprayed Al film comprises the steps of preparing 4NAl and In; combining the Al raw material with In, in an amount ranging from 2 to 5% by mass to thus uniformly dissolve and disperse In into Al; forming the resulting uniform mixture into a form of a rod or a wire to thus give a material for thermal spray; then covering the surface of a base material, for instance, a constituent member for a film-forming chamber of a film-forming apparatus such as an adhesion-preventive plate used in the chamber by spraying the material in its molten state on the surface of the base material according to the flame-thermal spraying technique; and subsequently quenching and solidifying the sprayed material to thus give a base material provided thereon with a desired water-reactive thermally sprayed Al film. The thermally sprayed Al—In film thus formed is one in which In is present in Al crystalline grains (grain diameter: not more than 10 nm) in its highly, uniformly dispersed state.
When immersing the base material covered with the thermally sprayed Al film in warm water or spraying water vapor on the base material, as has been discussed above, for instance, when immersing the same in warm water whose temperature is set at a predetermined level, the reaction of the film with water is initiated immediately after the immersion, which is accompanied by the generation of hydrogen gas, the water is blackened as the reaction further proceeds because of the presence of, for instance, deposited In, finally the thermally sprayed film is completely dissolved and precipitates consisting of, for instance, Al, In and Si remain in the warm water. This reaction vigorously proceeds with the increase in the temperature of the water.
The foregoing thermally sprayed film has been described above while taking, by way of example, one formed using a material having a rod-like or wire-like shape according to the flame-thermal spraying technique, but the Al film may likewise be formed using a powdery material according to the flame-thermal spraying technique. The film may further be formed according to the electric arc spraying technique, or the plasma spraying technique. In the present invention, the raw material described above is molten, followed by the spray of the molten material on the surface of a base material, quenching and solidifying the same to thus form a thermally sprayed film, according to one of these thermal spraying techniques, while using the known process conditions.
If using a base material, whose surface is covered with the foregoing water-reactive Al film, as a constituent member for a film-forming chamber such as an adhesion-preventive plate or a shutter which is positioned within the film-forming chamber of a film-forming apparatus, as has been discussed above, the film composed of the film-forming material inevitably adhered to the constituent member for a film-forming chamber can easily be peeled off from the constituent member after the completion of the film-forming process carried out over a predetermined number of times or cycles and accordingly, the valuable metals can be recovered from the peeled Al film provided thereon with the deposited film of the film-forming material, with ease.
In this case, used as a liquid for peeling off of the Al composite film is not any chemical reagent, but is water such as pure water, water vapor or an aqueous solution. Accordingly, it is possible to prevent the occurrence of any damage of the constituent member for a film-forming chamber such as an adhesion-preventive plate due to the dissolution of the latter in the liquid and these constituent members can be reused over a substantially increased number of times, as compared with that observed for the case in which a chemical reagent is used as such a liquid for peeling. Moreover, any chemical reagent is not used in the present invention and therefore, this would result in the considerable reduction of the cost required for the post-treatment and in the preservation of the environment. Furthermore, most of the film-forming materials adhered to the constituent members for a film-forming chamber such as an adhesion-preventive plate is never dissolved in water and accordingly, the present invention has such an advantage that a material can be recovered in the form of a solid having a composition and a shape substantially identical to those observed for the film-forming material. In addition, the present invention shows such an advantage that not only the recovery cost can be dramatically reduced, but also the process to be used for the recovery can be simplified and accordingly, wide variety of materials can be recovered according to the present invention. For instance, if the film-forming materials are expensive metals such as precious metals and rare metals, the use of a constituent member for a film-forming chamber such as an adhesion-preventive plate, which is provided, on the surface thereof, with a film consisting of the water-reactive Al composite material of the present invention, would permit the removal or peeling off of the film inevitably adhered to the constituent member during the film-forming operations and consisting of the film-forming material, simply by immersing the member in water or spraying water vapor on the same. This in turn permits the recovery of precious metals and rare metals without being accompanied by any contamination. Thus, the recovery cost can be reduced and the film-forming material can likewise be recovered while they are still in their high quality conditions.
The present invention will now be described in more detail below with reference to the following Working Examples.
The following Al—In compositions were prepared and then inspected for the relation between the Al purity, the In concentrations and the solubility or activity of the resulting thermally sprayed films and the results thus obtained were investigated and compared with one another, while using 3NAl, 4NAl and 5NAl as the Al raw materials. In this connection, the added amount of In is expressed in terms of that relative to the mass (weight) of the Al raw material used.
3NAl-2% by mass (wt %) of In;
3NAl-3% by mass of In;
3NAl-4% by mass of In;
4NAl-2% by mass of In;
4NAl-3% by mass of In;
4NAl-4% by mass of In;
5NAl-1.5% by mass of In;
5NAl-2.5% by mass of In;
5NAl-3.5% by mass of In;
There were combined Al and In with each other in the rates specified above to thus uniformly dissolve or disperse In in Al and then each resulting blend was formed into a rod-like article and this article was used as a material for the thermal spraying process. Then a thermally sprayed film was formed by melting the rod-like article and then thermally spraying the resulting melt of the article on the surface of a base material made of aluminum in the atmosphere according to the rod flame spraying technique (heat source: C2H2—O2 gas; temperature: about 3,000° C.). Each of the thermally sprayed films thus produced was subjected to a heat-treatment at a temperature ranging from 0 to 350° C. (the film was treated in the atmosphere for one hour and subsequently cooled within a furnace) in place of subjecting the film to the influence of thermal hysteresis possibly experienced during the film-forming process. Thereafter, the base material provided thereon with the thermally sprayed film prior to the heat-treatment (0° C.) and the same base material used above and obtained after the heat-treatment each were immersed in 300 mL of pure water maintained at 80° C., followed by the determination of the current density of each immersion liquid to obtain the solubility of each thermally sprayed film. The results thus obtained were investigated. The results thus obtained are plotted on
The data plotted on
It was found that when immersing, in warm water maintained at 80° C., the base material covered with a thermally sprayed Al film having a good solubility in water and obtained after the foregoing heat-treatment, the reaction of the film with water is initiated immediately after the immersion, which is accompanied by the vigorous generation of hydrogen gas, the water undergoes blackening as the reaction further proceeds because of the presence of, for instance, deposited In, finally the thermally sprayed film cannot maintain the state such that it is firmly adhered to the base material, due to the reaction with water and the film begins to be peeled off from the base material with dissolution.
Platinum (Pt) film-forming operations were repeated over 30 cycles using a sputtering apparatus provided with an adhesion-preventive plate whose surface had been covered with a thermally sprayed film (film thickness: 200 μm) of the 4NAl-3% by mass of In prepared in Example 1 and then the adhesion-preventive plate to which the Pt film had been adhered was disassembled from the sputtering apparatus and treated with warm water maintained at 80° C. As a result, it was found that the thermally sprayed film is completely dissolved within 30 minutes and that the adhered film of Pt is peeled off from the adhesion-preventive plate. Thus, Pt as the film-forming material could easily be recovered. At this stage, it was found that AlOOH is precipitated in the warm water.
If coating, with an Al film consisting of the water-reactive Al composite material according to the present invention, the surface of constituent members for a film-forming chamber of a vacuum film-forming apparatus, which is used in forming a thin film of a metal or a metal compound according to the sputtering technique, the vacuum deposition technique, the ion-plating technique and the CVD technique, the film inevitably adhered, during the film-forming process, to the surface of such a constituent member for a film-forming chamber can be peeled off therefrom in a moisture-containing atmosphere and can easily be recovered. Therefore, the present invention can be used in the fields in which these film-forming apparatuses are employed, for instance, in the technical fields related to semiconductor elements and electronics-related machinery and tools for the purpose of increasing the number of reuse times of the constituent members for a film-forming chamber of a film-forming apparatus and of recovering the film-forming materials which contains valuable metals.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-118855 | Apr 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/058259 | 4/27/2009 | WO | 00 | 10/28/2010 |
