Patent Application
20120082596
The present invention relates to a reactor for moisture generation in which high-purity moisture is generated at a catalytic reaction temperature (i.e., 400° C. or less) that is lower than an ignition point of hydrogen gas and oxygen gas (i.e., 500 to 580° C.), without combustion (approximately 2000° C.) by supplying hydrogen gas and oxygen gas into the reactor that has a platinum catalyst layer to catalyze the reaction of the gases.
Conventionally, a reactor for moisture generation is known that is used for continuously supplying ultra-pure moisture in oxide filming of silicon using a moisture oxidation method in semiconductor manufacturing (for example, as disclosed in Patent Documents 1 to 5).
This kind of reactor for moisture generation is, as shown in
A barrier layer 28a is formed between a stainless-steel base material of the reactor and the platinum catalyst layer 28b, and the barrier layer 28a inhibits impurities in the base material from diffusing in the platinum catalyst layer 28b, which prevents degradation of the platinum catalyst layer.
A thickness of the barrier layer 28a is approximately 0.1 μm to 5 μm, and, for example, the barrier layer 28a is made of TiN and is formed by an ion plating method. Moreover, a thickness of the platinum catalyst layer 28b is approximately 1 nm to 0.5 mm, and is formed by, for example, a vacuum deposition method. In addition, as the method for forming the barrier layer 28a, in addition to the ion plating method, a PVD method, such as an ion sputtering method or a vacuum deposition method, or a chemical vapor deposition method (CVD method), or a hot-pressing method, or a thermal spraying technique, or the like, may be used. Furthermore, as the method for forming the platinum catalyst layer 28b, in addition to the vacuum deposition method, an ion plating method, or an ion sputtering method, or a chemical vapor deposition method, or a hot-pressing method, or the like, may be used, and moreover, a plating method as well may be used when the barrier layer 28a is a conductive substance such as TiN.
Patent Document 1: International Publication WO 97/28085,
Patent Document 2: Japanese Published Unexamined Patent Application No. 2000-169108,
Patent Document 3: Japanese Published Unexamined Patent Application No. 2000-169109,
Patent Document 4: Japanese Published Unexamined Patent Application No. 2000-169110, and
Patent Document 5: Japanese Published Unexamined Patent Application No. 2002-274812.
However, there has been the problem that adhesion strength (e.g., peel strength) of a platinum catalyst layer to a barrier layer is deteriorated when a conventional barrier layer made of TiN, or the like, is used for a long period of time.
Such deterioration with time in adhesion strength is attributed to deterioration in adhesion strength between the barrier layer and the platinum catalyst layer by activated oxygen (i.e., oxygen radicals) due to a catalytic reaction that passes through the platinum catalyst layer to gradually oxidize the vicinity of the interface between the barrier layer and the platinum catalyst layer.
Such deterioration in adhesion strength is not as bad as the platinum catalyst layer being peeled off during normal use. However, the platinum catalyst layer may be partially peeled off by, for example, unanticipated impact, or the like, on the reactor for moisture generation by unintended falling, or the like, during maintenance.
When the platinum catalyst layer is peeled off, the peeled platinum becomes contaminated, which has significant harmful effects on the quality of semiconductors to be manufactured.
Furthermore, when the platinum catalyst layer is peeled off, the peeled platinum has a small heat capacity, and its temperature is increased due to reaction heat generated by a catalytic reaction between hydrogen gas and oxygen gas, which may become an ignition source. This ignition source brings about damage to manufacturing devices and raises safety issues from explosion and combustion.
Therefore, an object of the present invention is to provide a reactor for moisture generation that is capable of maintaining high adhesion strength of the platinum catalyst layer to the barrier layer for a long period of time.
As a result of intensive studies, the inventors have found that a platinum catalyst layer is capable of maintaining high adhesion strength to the barrier layer for a long period of time by forming a barrier layer of Y2O3.
Accordingly, in order to achieve the object of the present invention, the present invention provides a reactor for moisture generation that includes a reactor main body in which a gas inlet and a moisture outlet are provided, a Y2O3 barrier layer that is formed on at least a part or portion of an internal wall surface of the reactor main body, and a platinum catalyst layer formed on at least a part or portion of the Y2O3 barrier layer.
A film thickness of the Y2O3 barrier layer is preferably 50 nm to 5 μm, and is more preferably 100 to 300 nm.
The reactor main body is preferably formed of a material that is catalytically inactive to hydrogen and oxygen.
The reactor for moisture generation further includes at least one reflector inside the reactor main body, and the reflector is preferably formed of a material that is catalytically inactive to hydrogen and oxygen.
The reflector is fixed to the reactor main body via spacers with fixation screws so as to block up at least one of the gas inlet and the moisture outlet via a predetermined space, and the spacers and the fixation screws are preferably formed of a material that is catalytically inactive to hydrogen and oxygen.
A material, which is catalytically inactive to hydrogen and oxygen, is preferably used for members such as reactor main body members and reflectors having surfaces exposed to gas inside the reactor.
The material, which is catalytically inactive, is preferably an iron-chromium-aluminum alloy, an aluminum alloy, or a copper alloy.
An area of the reactor main body, other than the portion on which the platinum catalyst layer is provided inside an internal space, is preferably coated with a barrier layer formed of a material that is catalytically inactive to hydrogen and oxygen.
Moreover, the reactor for moisture generation further includes at least one reflector disposed inside the reactor main body, and the reflector is preferably coated with a barrier layer formed of a material that is catalytically inactive to hydrogen and oxygen.
Furthermore, the reflector is fixed to the reactor main body via spacers with fixation screws so as to block up at least one of the gas inlet and the moisture outlet via a predetermined space, and the spacers and the fixation screws are preferably coated with a barrier layer formed of a material that is catalytically inactive to hydrogen and oxygen.
The barrier layer formed of the material that is catalytically inactive is preferably formed of at least one material selected from the group consisting of TiN, TiC, TiCN, TiAlN, Al2O3, Cr2O3, SiO2, CrN, and Y2O3.
In accordance with the present invention, a Y2O3 barrier layer is formed on an internal wall surface of a reactor main body, and a platinum catalyst layer is formed on the Y2O3 barrier layer, which makes it possible to inhibit deterioration with time in adhesion strength of the platinum catalyst layer to the Y2O3 barrier layer.
An embodiment of a reactor for moisture generation according to the present invention will be hereinafter described with reference to
In the reactor for moisture generation of
As a base material of the reactor main body, for example, stainless steel, such as SUS316L, nickel alloy steel, or nickel steel, may be used. In the case where the reactor main body is formed of a material, such as stainless steel, nickel alloy steel, or nickel steel, which is catalytically active to O2 or H2, it is particularly preferable that, for the portion where the platinum catalyst layer is not formed inside the reactor, a noncatalytic barrier layer, which is catalytically inactive to oxygen and hydrogen, is formed as a barrier layer for preventing catalytic activity by the base material. As such a material of the barrier layer, TiN, TiC, TiCN, TiAlN, Al2O3, Cr2O3, SiO2, or CrN may be used, and Y2O3 as well may be used. In addition, two or more types of those among these materials listed may be used.
This is the same as for the reflectors 26 and 27 in the case where reflectors 26 and 27 are provided in the reactor main body. That is, in the case where the base material of the reflectors 26 and 27 is a material that is catalytically active to O2 or H2, a noncatalytic barrier layer that is catalytically inactive to oxygen and hydrogen is preferably formed on the reflectors 26 and 27.
In addition, in the case where Y2O3 is used as a barrier layer for preventing catalytic activity by the base material, the barrier layer may be used in common as the barrier layer that inhibits impurities in the base material from diffusing inside the platinum catalyst layer 28b. That is, after the barrier layer 28c of Y2O3 is formed on the entire internal surface of the reactor main body members 22 and 23, the platinum catalyst layer 28b may be formed only on a desired portion on the barrier layer.
The reflectors 26 and 27 may be disposed so as to face each other inside the reactor. The reflectors 26 and 27 are formed to be discoid in the example illustrated. However, the shapes of the reflectors 26 and 27 are not limited as long as the shapes thereof are capable of improving the efficiency of diffusing mixed gas by colliding with mixed gas flowing into an internal space P of the reactor. The inlet side reflector 26 is fixed to the reactor main body member 22 via spacers 31 with fixation screws 30 so as to block up the raw material gas inlet 24 via a given gap from the reactor main body member 22 on the inlet side. The outlet side reflector 27 as well is fixed to the reactor main body member 23 via the spacers 31 with the fixation screws 30 so as to block up the moisture gas inlet 25 via a given gap from the reactor main body member 23 on the outlet side. The reflectors may be fixed not only by screw clamps, but also by another fixing means such as by welding. In addition, the example illustrated shows the example provided with the pair of reflectors. However, one reflector may be provided, and in that case, it is preferable that only the outlet side reflector 27 may be provided.
A mixed gas G jetted toward the reflector 26 through the raw material gas inlet 24 collides with the reflector 26 to be diffused inside the internal space P, and the diffused mixed gas G makes contact to roughly evenly collide over the entire surface of the platinum catalyst layer 28b, to be so-called “catalytically activated,” which induces a reaction of H2 and O2 to generate moisture gas. Furthermore, the moisture gas formed inside the internal space P is guided out to the moisture gas outlet 25 through the gap L between the outlet side reflector 27 and the reactor main body member 23 on the outlet side.
As the base material of the reactor main body members 22 and 23 of the reactor and the base material of the reflectors 26 and 27, in place of a material such as stainless steel, nickel alloy steel, or nickel steel, which is catalytically active to O2 or H2 gas, a substantially different material that is catalytically inactive to O2 or H2 gas, that is, for example, an iron-chromium-aluminum alloy, an aluminum alloy, or a copper alloy, may be used.
In the case where the base materials of the reactor main body members 22 and 23 of the reactor are formed of a material, as described above, which is catalytically inactive, the outer surface of the noncatalytic material thereof on the portion other than the portion on which the Y2O3 barrier layer 28c is provided inside the internal space is preferably subjected to an appropriate surface treatment for preventing external release of the internal gas, or the internal metal composition material. As the surface treatment, a barrier layer may be formed that is noncatalytic and that has excellent resistance to corrosion, resistance to reduction, and resistance to oxidation. As such a barrier layer, TiN, TiC, TiCN, TiAlN, Al2O3, Cr2O3, SiO2, or CrN may be used, and Y2O3 as well may be used. In addition, two or more types of those among these listed materials may be used together. In this case as well, in the case where a Y2O3 barrier layer is used as the surface treatment, the barrier layer may be used in common as the above-described barrier layer that inhibits impurities in the base material from diffusing inside the platinum catalyst layer 28b. The reflectors 26 and 27 as well are preferably subjected to the same surface treatment described above.
The Y2O3 barrier layer may be appropriately formed by a sol-gel process. For example, the base material of the reactor main body, formed of stainless steel or the like, may be coated with an organic solvent solution of yttrium alkoxide by spin coating, dip coating, spray coating, or the like, and after the coated film is dried, the film is fired at 500 to 600° C. for 1 to 5 hours in an oxygen atmosphere to form the Y2O3 barrier layer. In addition, a TiN, TiC, TiCN, TiAlN, Al2O3, Cr2O3, SiO2, or CrN barrier layer may be formed to be 0.1 to 5 μm thick by use of a PVD method, such as an ion plating method, a sputtering method, or a vacuum deposition method, a chemical vapor deposition method (CVD method), a hot-pressing method, a thermal spraying technique, or the like.
In a case where the Y2O3 barrier layer is formed by a wet process, such as the above-described sol-gel process, because a coating film provided with a film thickness of approximately 50 nm may be obtained by one coating and firing, coating and firing are repeated several times as needed so as to make a desired film thickness (for example, 100 nm, 300 nm).
In order to improve the barrier performance regarding preventing impurities in the stainless steel base material from diffusing in the platinum catalyst layer, the film thickness of the barrier layer may be preferably thicker. However, a dense film free of defects, such as pinholes, is formed with precisely controlled particle diameters of the raw material, and the process of film formation of the Y2O3 barrier layer is able to obtain an equivalent barrier performance with a film thickness that is thinner than that of a conventional TiN barrier layer. In view of the increase in cost due to increases in the number of times of coating and firing to produce a thicker Y2O3 barrier layer, the film thickness of the Y2O3 barrier layer is preferably 300 nm or less.
On the other hand, because yttrium is an expensive material, it is preferable that the film thickness of the Y2O3 barrier layer is further reduced to achieve a reduction in cost. However, when the film thickness of the Y2O3 barrier layer is too thin, the barrier performance may be degraded, and it is difficult to control the film thickness. Therefore, although the film thickness of the Y2O3 barrier layer is usually 100 nm or more, it is possible to adequately fulfill the barrier function with a film thickness of 50 nm or more.
In addition, the Y2O3 barrier layer is preferably formed by a sol-gel process from the standpoint of reducing the cost of manufacturing facilities. However, the method is not limited thereto, and the Y2O3 barrier layer may be formed by a thermal spraying technique, a PVD method, a vacuum deposition method, a sputtering method, an ion plating method, or the like. By a dry process, such as a thermal spraying technique, it is possible to increase the film thickness of the Y2O3 barrier layer without repeating the same processes as in the wet process. However, even in the case of a dry process, in view of the material cost, the film thickness of the Y2O3 barrier layer is preferably 5 μm or less.
A platinum catalyst layer is formed on the Y2O3 barrier layer. The platinum catalyst layer may be formed by a vacuum deposition method, an ion plating method, a sputtering method, a chemical vapor deposition method, a hot-pressing method, or the like.
The film thickness of the platinum catalyst layer is preferably 0.1 μm to 3 μm (100 nm to 3000 nm). That is, when the film thickness is too thin, the platinum catalyst layer is unable to adequately perform both the function as a catalyst and the function as a protective film. Therefore, the film thickness of the platinum catalyst layer is preferably 0.1 μm (100 nm) or more. On the other hand, in view of the function as a catalyst and the function as a protective film of the barrier layer, as will be described later, the film thickness of the platinum catalyst layer is preferably increased. However, when the film thickness is too thick, the cost thereof is increased. Therefore, the film thickness of the platinum catalyst layer is preferably 3 μm (3000 nm) or less, and is more preferably 0.5 μm (500 nm) or less.
The adhesion strength of the platinum catalyst layer to the Y2O3 barrier layer was tested according to the following procedure.
First, a circular substrate made of SUS316L (35 mm in diameter×3 mm in thickness) was prepared. A Y2O3 coating material (YYK01LBY-03: Brown liquid) manufactured by Kojundo Chemical Lab. Co., Ltd. was sprayed and coated onto the substrate by a spray nozzle, and was dried. Thereafter, this Y2O3 coating was subjected to heat treatment (firing) at 500° C. for one hour in an oxidant atmosphere at an O2/N2 ratio of 20%. A Y2O3 film, with a film thickness of approximately 50 nm, was formed by a one-time coating and heating treatment, and a Y2O3 barrier layer with a film thickness of approximately 100 nm was formed by repeating the coating and heating treatments twice.
Next, a platinum catalyst layer was formed on the Y2O3 barrier layer by use of an ion plating apparatus (AAIF-T12100SB series manufactured by Shinko Seiki Co., Ltd.) as follows.
That is, after any oxidized film, and the like, formed on the surface of the Y2O3 barrier layer were removed by bombardment with argon ions (Ar bombardment), the platinum catalyst layer was formed by ion plating processing. The Ar bombardment was set under the conditions that an Ar flow rate was 260 sccm, a substrate bias was −1500V, and a processing time was 10 minutes. The platinum catalyst layer with a film thickness of 0.23 μm (230 nm) was formed using this process of film formation wherein the substrate bias was −500V, the ionized electrode was set at 50V, the film formation rate was 0.025 μm/min., and the EB voltage was 9 kV.
An adhesion strength test was carried out on the example of film formation described above. As a testing device, an adhesion tester (i.e., coating film adhesion strength tester; Type 0610 series, manufactured by COTEC Corporation) was used.
A dolly attached to the testing device was bonded to the platinum catalyst layer by use of a predetermined epoxy resin adhesive. While the sample, to which the dolly was bonded, was heated for 400 hours in an air atmosphere of 500° C. to increase the severity of the environment, peel strength measurement by the adhesion tester was carried out every 50 hours.
In the same way as in Example 1, a Y2O3 barrier layer with a film thickness of 0.3 μm (300 nm) was formed on a substrate, and a platinum catalyst layer with a film thickness of 0.23 μm (230 nm) was formed on the Y2O3 barrier layer, and an adhesion strength test by the adhesion tester was then carried out under the same conditions as in Example 1.
A sample, which is the same as that in Example 1 except for the point that the film thickness of the platinum catalyst layer is 0.28 μm (280 nm), was prepared.
A dolly attached to the testing device was bonded to the platinum catalyst layer by use of a predetermined epoxy resin adhesive. While the sample, to which the dolly was bonded, was heated for 1000 hours in an air atmosphere of 500° C., in order to increase the severity of the environment, peel strength measurement by the adhesion tester was carried out every 50 hours.
The same kind of sample as in Example 3 was used. A dolly attached to the testing device was bonded to the platinum catalyst layer by use of a predetermined epoxy resin adhesive. While the sample, to which the dolly was bonded, was heated for 1000 hours in an air atmosphere of 550° C. in order to increase the severity of the environment, peel strength measurement by the adhesion tester was carried out every 50 hours.
A TiN film was formed as the barrier layer in place of the Y2O3 film, and a platinum catalyst layer was formed on the TiN barrier layer in accordance with a comparative example. The TiN barrier layer was formed by use of a cathodic arc ion plating apparatus so as to have a film thickness of 3 μm. A platinum catalyst layer of 0.3 pm (300 nm) was formed on the TiN barrier layer by use of an ion plating apparatus (AAIF-T12100SB series manufactured by Shinko Seiki Co., Ltd.). In the same way as in Examples 1 to 3, while the sample was heated in an air atmosphere of 500° C. in order to accelerate the severity of the environment, the peel strength test by the adhesion tester was carried out.
Graphs of the test results in the above-described examples and the comparative example are shown in
With reference to the graphs of
By comparison between Example 1 and Example 2, there was no effect on adhesion strength even when the film thickness of the Y2O3 barrier layer was changed. However, by comparison between Example 1 and Example 3, from the fact that the platinum catalyst layer having the thicker film thickness in Example 3 maintains higher adhesion strength than Example 1, it is clear that a platinum catalyst layer having a thicker film thickness maintains higher adhesion strength. This may be because the vicinity of the interface between the Y2O3 barrier layer and the platinum catalyst layer is difficult to oxidize when the platinum catalyst layer is thicker. That is, the platinum catalyst layer may function as a protective film for protecting the Y2O3 barrier layer from oxidization as well. However, because adhesion strength between the platinum catalyst layer and the Y2O3 barrier layer is 5 kgf/cm2 or more, no practical problem is caused by this difference in the thickness of the platinum catalyst layer. Because deterioration with time in adhesion strength of the Y2O3 barrier layer to the platinum catalyst layer is hardly found in the test results in Examples 1 to 4, from the standpoint of adhesion strength, no practical problem occurs when the film thickness of the Y2O3 barrier layer is 0.1 μm (100 nm) or more as in Example 1.
Furthermore, by comparison between the examples of the present invention and the comparative example, it is clear that even when the Y2O3 barrier layer had a film thickness (0.3 μm, 0.1 μm), which is less than or equal to 1/10th of the film thickness of the TiN barrier layer (3 μm) of the comparative example, the Y2O3 barrier layers maintained their adhesion strengths higher than that of the much thicker TiN barrier layer. This result may be because the Y2O3 barrier layer is a stable substance whose standard Gibbs energy of formation is higher than that of the TiN barrier layer, and has excellent resistance to oxidation. Accordingly, by controlling the film thickness of a Y2O3 barrier layer even if yttrium, which is more expensive than titanium, is used, it is possible to form a Y2O3 barrier layer having more excellent adhesion strength performance at a cost equivalent to or less than that for a TiN barrier layer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-107139 | Apr 2009 | JP | national |
This is a Continuation-in-Part Application in the United States of International Patent Application No. PCT/JP2010/002914 filed Apr. 22, 2010, which claims priority on Japanese Patent Application No. 2009-107139, filed Apr. 24, 2009. The entire disclosures of the above patent applications are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2010/002914 | Apr 2010 | US |
| Child | 13274446 | US |
