ITMI20000893A1 - PROCESS FOR THE PURIFICATION OF ORGANOMETALLIC COMPOUNDS OR HETEROATOMIC ORGANIC COMPOUNDS WITH AN IRON AND MANGANESE BASED CATALYST - Google Patents

Description

DESCRIPTION of the industrial invention entitled:

"PROCESS FOR THE PURIFICATION OF ORGANOMETALLIC COMPOUNDS OR HETEROATOMIC ORGANIC COMPOUNDS WITH AN IRON AND MANGANESE BASED CATALYST SUPPORTED ON ZEOLITES"

The present invention relates to a process for the purification of organometallic compounds or heteroatomic organic compounds with a catalyst based on iron and manganese supported on zeolites.

The organometallic compounds are characterized by the presence of a bond between an atom of a metal (including among the metals also arsenic, selenium and tellurium) and a carbon atom which is part of an organic radical such as for example the saturated or unsaturated, abytic hydrocarbon radicals or aromatic; by extension, the definition of organometallic compounds also generally refers to compounds comprising metal atoms linked to organic radicals through an atom other than carbon, such as alcoholic (-OR) or ester (-O-CO-R) radicals .

Heteroatomic organic compounds (hereinafter also referred to simply as heteroatomic) are those organic compounds which include, in addition to carbon and hydrogen, also atoms such as oxygen, nitrogen, halogens, sulfur, phosphorus, silicon and boron.

Many of these compounds have long been used in traditional chemical applications. In this sector, reagents with very high purities are generally not required, and their purification is generally carried out with techniques such as distillation (possibly at reduced pressure, to decrease the boiling temperature and therefore the risks of thermal decomposition of the compounds) or recrystallization. from solvents.

Recently, however, these compounds have been used in high technology applications, particularly in the semiconductor industry. In these applications, organometallic compounds and heteroatomic compounds are used as reagents in the processes of chemical deposition from a gaseous state (known in the sector with the English definition "Chemical Vapor Deposition" or with the acronym CVD). In these techniques, a gaseous flow of one or more organometallic or heteroatomic compounds (or a flow of a carrier gas containing a known concentration of these) is brought into a process chamber; inside the chamber, the compounds are then made to decompose or react, so as to form on-site materials (generally in the form of thin layers on a substrate) containing said metal atoms or eternatoms. Organometallic or heteroatomic compounds can already be in gaseous form, but they can also be in liquid form. In this second case, the gaseous flow of the compound is obtained either by evaporating the compound, in which case the flow consists only of the compound of interest, or by bubbling a gas in the liquid container, in which case the flow comprises vapors of the compound in the carrier gas.

The main organometallic compounds used in these applications are afiium tethia-t-butoxide, trimethylalummium, triethylaluminium, tri-t-butylaluminium, di-i-butylaluminium hydride, trimethoxyalluminium, dimethylaluminium chloride, diethylaluminium ethoxide, dimethylaluminium hydride, trimethylantimonium , triethylantimony, tri-i-propyl antimony, tris-dimethylamino-antimony, trimethylarsene, tris-dimethylamino-arsenic, t-butylarsine, phenylarsine, barium bistetramethylptanide, bismuth tris-tetramethylpentanion, diethylcadmium, diethylcadmium , iron trisacetylacetonate, iron tris-tetramethylheptanate, trimethylgallo, triethylgallium, tri-ipropylgallium, tri-i-butylgallium, triethoxygallium, trimethylindium, triethylindium, ethyldimethylindium, yttrium-tris-tetramethylgallium, yttrium-tris-tetramethylheptanium magnesium bistetramethylptandionate, dimethylmercury , niobium pentaethoxide, niobium tetraethoxydimethylaminoethoxide, dimethyloro acetylacetonate, lead bis-tetramethylheptanide, bis-hexafluorame acetylacetonate, copper bistetramethylptanediouate, scandium tris-tetramethylethylene oxide, tetramethyltin-tetramethylethyl sulfate, tetramethyl-tetramethylstrandionate, tetramethyl-tetramethyl-tetra, tetramethylstrandionate, tetramethyl-tetramethyl sulfate , tantalum pentoxide, tantalum tetraethoxytetramethylaminoethoxide, tantalum tetraethoxytetramethylpthionate, tantalum tetramethoxytetramethylptanide, tantalum tetra-i-propoxytetramethylptanate, tantalum tri-diethylamido-tantalum-tetraethoxytetramethylpthionate, tantalum tetramethoxytetramethylptanide, tantalum tetra-i-propoxytetramethylptanide, tantalum tri-diethylammido-tantalum bis-i-propoxybis-dimethylaminoethoxide, titanium bis-ethoxy-bis-dimethylaminoethoxide, titanium tetradimethylamide, titanium tetradethylamide, titanium tetra-t-butoxide, titanium tetra-propoxide, vanadyl i-propoxide, dimethylzinc, diethylzinc, zinc methyl heptanionate, zinc bis-acetylacetonate, zirconium tetra-t-butoxide, zirconium tetra-tetramethylptanionate and zirconium tri-i-propoxy-tetramethylheptanate 1 major heteroatomic compounds employed in these applications are trimethylborane, asymmetric dimethylhydrazine (i.e. are bonded to the same nitrogen atom), t-butylamine, phenylhydrazine, trimethylphosphorus, tbutylphosphine and t-butylmercaptan.

Some typical examples of application of these methods are the production of semiconductors of the ΠΙ-V type, such as GaAs or InP, or of the Π-VI type such as ZnSe; the use for p (for example with boron) or n (for example with phosphorus) doping of traditional silicon semiconductor devices; the production of materials with a high dielectric constant (for example, compounds such as PbZrxTi1-x03) used in ferroelectric memories; or the production of materials with a low dielectric constant (such as Si02) for the insulation of electrical contacts in semiconductor devices

For these applications extremely high purity reagents are required, with levels of the order of 10'1-10'2 ppm, while traditional chemical techniques do not generally allow to go down to impurity levels lower than ten ppm. Furthermore, even in the case in which organometallic or heteroatomic compounds of very high purity are produced, the storage is a source of contamination due to the release of gas from the walls of the container, which in any case makes it necessary to use a purifier immediately upstream of the application. (so-called "point of use" purifiers).

US patent 5,470,555 describes the removal from organometallic compounds of the gaseous oxygen present as an impurity through the use of a catalyst consisting of metal copper or nickel, or the relative oxides activated by reduction with hydrogen, deposited on a support such as alumina, silica or silicates. According to the patent, with this method it is possible to obtain the removal of gaseous oxygen from a flow of the organometallic compound up to values of 10 "2 ppm.

However, oxygen is not the only impurity that must be removed from organometallic or heteroatomic compounds. Other harmful impurities in CVD processes are for example water and, in particular, the species derived from the alteration of the organometallic or heteroatomic compound itself, following undesired reactions generally with water or oxygen. For example, in the case of a generic organometallic compound MRn, in which M represents the metal, R an organic radical and n the valence of the metal M, there can be contamination by species MRn-x (-OR) x, in which x is an integer that can vary between 1 and u. These oxygenated species are harmful in CVD processes because they introduce oxygen atoms into the material being formed, significantly altering its electrical properties.

The object of the present invention is to provide a process for the purification of organometallic compounds or heteroatomic organic compounds from oxygen, water and from the compounds derived from the reaction of water and oxygen with the organometallic or heteroatomic compounds whose purification is to be carried out.

This object is achieved according to the present invention with a process in which the organometallic or heteroatomic compound to be purified is brought into contact with an iron and manganese-based catalyst deposited on zeolites. The purification can be carried out on the organometallic or heteroatomic compound both in the liquid state and in the vapor state.

It is also possible to use, in addition to the iron and manganese-based catalyst, other impurity-absorbing materials, such as for example a hydrogenated getter alloy or a palladium-based catalyst.

The invention will be described below with reference to the Figures in which:

- Fig. 1 shows a cut-away view of a purifier with which it is possible to practice a first embodiment of the process of the invention;

- Fig. 2 shows a cross section of a purifier with which it is possible to implement a second embodiment of the process of the invention.

In one of its embodiments, the process of the invention consists in putting the compound to be purified in the liquid state in contact with the iron and manganese-based catalyst deposited on zeolites. This can be achieved simply by introducing the catalyst into the container of the liquid compound, from which the same will then be evaporated by heating or with a carrier gas.

In a preferred embodiment, however, the purification is carried out by contacting the iron and manganese-based catalyst with vapors, pure or in a carrier gas, of the organometallic or heteroatomic compound. In the following, the invention will be described with particular reference to purification in the vapor state, since this is the condition most commonly used in industry.

The sum of the metals preferably constitutes about 10 to 90% of the total weight of the catalyst. The ratio of iron to manganese varies between about 7: 1 and 1: 1 and is preferably about 2: 1.

A catalyst suitable for the purposes of the invention is marketed by the Japanese company Nissan Girdler Catalyst Co. Ltd. for the purification of inert gases such as helium, argon or nitrogen. This product contains iron and manganese in a weight ratio of approximately 1.8.

If it is desired to have a different ratio between the two materials, the catalyst can be produced by depositing metal iron and manganese in the desired ratio on zeolites H deposition of metals on zeolites is generally formed with coprecipitation techniques from a solution in which soluble compounds have been dissolved (indicated hereafter as precursors) of iron and manganese, and in which the zeolites which will form the support of the catalyst are present. The starting solvent and the precursors can be chosen from a wide range of possibilities, with the only constraint that the precursors are soluble in the chosen solvent. For example, it is possible to use organic solvents such as alcohols or esters with preclusols in which the metals are complexed with an organic binder: typically in this case the complexes of metals with acetylacetone are used. Preferably, however, one works in an aqueous solution. In this case the precursors used are soluble salts of metals, such as chlorides, nitrates or acetates. The precipitation of the compounds that form the first deposit on the zeolites is generally made by increasing the pH of the solution; a first deposit is thus obtained formed by compounds of the metals, generally oxides or hydroxides or more generally intermediate species of the oxo-hydroxides type. Once this first deposit has been obtained, the solution is centrifuged or filtered and the wet powders are first dried and then treated at high temperature for the conversion of iron and manganese compounds to metals. The reduction of the oxo-hydroxides to the metallic form takes place with a two-stage heat treatment, in which in the first stage a flow of hydrogen is passed over the intermediate product at a temperature above 200 ° C for a time of at least 4 hours; in the second stage, which immediately follows the first, a stream of purified argon is passed over the reduced intermediate product at a temperature of at least 200 ° C for at least 4 hours.

The catalyst support is generally in the form of tablets or cylinders, with dimensions between 1 and 3 millimeters.

The temperature range useful for the purification of organometallic or hetero atomic compounds with the iron and manganese-based catalyst is between about -20 and 100 ° C; at lower temperatures the removal of oxygen is limited, while at temperatures above about 100 ° C decomposition reactions of the gas to be purified could take place. The preferred temperature range is between room temperature and about 50 ° C.

The flow of the gas to be purified can vary between about 0.1 and 20 slpm (liters of gas, measured under standard conditions, per minute), at absolute pressures preferably between about 1 and 10 bar.

This flow can be constituted only by the vapors of the compound to be purified, or by said vapors within a flow of a carrier gas. The carrier gas can be any gas that does not interfere either with the iron and manganese-based catalyst (or with any other gas-absorbing materials used), or with the deposition process in which the organometallic or heteroatomic compound is used. . Argon, nitrogen, or even hydrogen are commonly used.

= Figure 1 shows a cut-away view of a possible purifier to be used in the first embodiment of the process of the invention. The purifier 10 consists of a body 11, generally cylindrical; at the two ends of the body 11 there are a pipe 12 for the gas inlet to the purifier, and a pipe 13 for the gas outlet. Inside the body 11 there is the catalyst 14 based on iron and manganese on zeolites (the case in which the support is cylindrical in shape is exemplified). The gas inlet 12 and outlet 13 are preferably provided with standard connections of the VCR type known in the field (not shown in the figure) for connection with the gas lines upstream and downstream of the purifier. The purifier body can be made of various metallic materials; the preferred material for this purpose is AISI 316 steel. The internal surfaces of the purifier body, which come into contact with the gas, are preferably electropolished until a surface roughness of less than about 0.5 µm is obtained. In order to prevent traces of catalyst dust from being transported downstream of the purifier by the outgoing gas flow, inside the purifier body at the outlet 13, particulate retention means can be arranged, such as rings or generally metallic porous septa with dimensions of the "ports" or pores such as to retain particles without causing an excessive pressure drop in the gas flow; the dimensions of these openings can generally vary between about 10 and 0.003 µm.

The gas stream to be purified can be put in contact, in addition to the iron and manganese-based catalyst, with at least one additional material, selected from a hydrogenated geter alloy and a palladium-based catalyst deposited on γalumina, or both.

The use of hydrogenated geter alloys for the purification of gases in the field of microelectronics is known from the patent EP-B-470936, but limited to the purification of simple hydrides, such as SiHU, PH3 and As3⁄4.

The getter alloys useful for the invention are alloys based on titanium and zirconium with one or more elements selected from the transition metals and aluminum, and mixtures between one or more of these alloys with titanium and / or zirconium. In particular, the alloys ZrM2 are useful for the invention, where M is one or more of the transition metals Cr, Mn, Fe, Co or Ni, described in US 5,180,568; the Zr-V-Fe alloys described in US patent 4,312,669 and in particular the alloy with a percentage composition by weight Zr 70% - V 24.6% - Fe 5.4%, produced and sold by the Applicant under the name St 707; the Zr-Co-A alloys, in which with A we mean any element selected from yttrium, lanthanum, Rare Earths or mixtures of these elements, described in US 5,961,750; Ti-Ni alloys; and the Ti-V-Mn alloys described in US patent 4,457,891.

The hydrogen loading of the alloys listed above is carried out at a hydrogen pressure lower than 10 bar, and preferably higher than atmospheric pressure, at temperatures ranging from room temperature to about 400 ° C. The optimum temperature range for the use of hydrogenated getter alloys in this application is between room temperature and about 100 ° C. More details on the method of loading getter alloys with hydrogen can be found in the cited patent EP-B-470936.

The catalyst based on palladium on γ-alumina preferably contains from 0.3 to 4% of palladium on the total weight of the catalyst. At lower values of palladium content, the impurity removal activity is limited, while quantities of palladium higher than 4% by weight lead to a strong increase in the cost of the catalyst without significant increases in the purification yield. The optimum temperature range for the use of this material is between about -20 and 100 ° C, and preferably between room temperature and 50 ° C.

The catalysts based on palladium on γ-alumina are available on the market, and are sold for the catalysis of chemical reactions (for example, hydrogenation reactions) by the companies Sud-Chemie, Degussa or Engelhard. Alternatively, the catalyst can be produced by impregnating the y-alumina in solution with an amount of a palladium salt or complex, for example palladium chloride (PdCl2), calculated on the basis of the desired amount of palladium in the final catalyst; drying of the γ-alumina thus impregnated; decomposition (for example, thermal) of the precursor; possible calcination, for example at temperatures of about 400-500 ° C of the product thus obtained.

The additional material (or the additional materials) can be indifferently upstream or downstream of the iron-manganese-based catalyst along the direction of the gas flow. It is also possible, when both of the aforementioned additional materials are used, that one of these is located upstream and the other downstream of the iron and manganese-based catalyst.

The additional material (or additional materials) can be present in a separate body, connected to the purifier body 11 containing the iron and manganese-based catalyst by means of pipes and fittings, for example of the type VCR mentioned above. This second body will also preferably be made with the materials and with the finishing level of the surfaces described for the body 11.

Preferably, the additional material (or additional materials) are arranged in the same purifier body in which the iron and manganese-based catalyst is present. In this case, the different materials can be mixed, but are preferably separated in the purifier body.

Figure 2 shows a cut-away view of a possible purifier containing more than one material (the case of two materials is exemplified); in particular, the figure shows a purifier made according to the preferred method in which the different materials are kept separate inside the body of the purifier. D purifier 20 is composed of a body 21, a gas inlet 22 and an outlet for the gas 23; inside the body 21, on the side of the inlet 22 the iron and manganese-based catalyst 24, and on the side of the outlet 23 a material 25 chosen from a hydrogenated getter alloy or a palladium-based catalyst on γ -alumina; preferably, a mechanical element 26 easily permeable to gases, such as a metal mesh, is arranged between the two materials to help maintain the separation and the original geometric arrangement of the materials themselves

In the case of the simultaneous presence of two different materials in the same body (situation exemplified in figure 2), the purifier must be kept at a temperature compatible with the operating temperatures of all the materials present, consequently preferably between room temperature and about 50 ° C.

Finally, it is also possible to add to the various materials mentioned also a chemical water absorber, for example calcium oxide or boron oxide prepared according to the teachings of patent application EP-A-960647 in the name of the Applicant.

The invention will be further illustrated by the following example. This example is not limitative of the scope of the invention, and serves to illustrate a possible embodiment intended to teach those skilled in the art how to put the invention into practice and to represent the best way considered for its realization.

EXAMPLE 1

A purifier of the type shown in figure 1 is produced. The purifier has a body in AISI 316 steel and an internal volume of 30 cm3. The catalyst is inserted into the purifier, consisting of zeolite cylinders (total volume of 15 cm'1) on which iron and menganese are deposited, respectively 56 and 31% of the total weight of the catalyst. The purifier is then connected, via connections of the VCR type, upstream to a nitrogen cylinder containing 10 ppm by volume (ppmv) of water and 100 ppmv of oxygen, and downstream to an APIMS mass spectrometer (mass spectrometer ionization at atmospheric pressure) mod. TOF 2000 by Sensar, which has a detection threshold of 10'4 ppmv for both water and oxygen. The test is carried out in nitrogen rather than in a vapor stream of an organometallic compound, because the analysis instrument used (APIMS) has a reduced sensitivity in the vapors of these compounds, such that a test with an organometallic compound would not allow obtaining significant data. The gas to be purified is passed at 5 bar in the purifier maintained at room temperature, with a flow of 0.1 slpm. At the beginning of the test the quantity of water and oxygen in the gas leaving the purifier is below the sensitivity threshold of the analyzer, indicating the functioning of the hydrogenated getter alloy in the removal of these species. The test is continued until the analyzer detects in the gas leaving the purifier a quantity of contaminant equal to 10'3 ppmv; this contamination value of the outgoing gas is adopted as an indicator of the exhaustion of the purifier. From the knowledge of the test data, it appears that the purifier has a capacity of 20 1/1 (liters of gas measured at standard conditions on the volume of the getter alloy) for both oxygen and water.

Claims (19)

RIVEND IC SHARES 1. Process for the purification of organometallic compounds or heteroatomic organic compounds from oxygen, water and compounds derived from the reaction of water and oxygen with the compounds whose purification is to be carried out, comprising the operation of putting the organometallic compound or organic heteroatomic to be purified with a catalyst consisting of metallic iron and manganese supported on zeolites. 2. Process according to claim 1 wherein the iron and manganese-based catalyst is contacted with the organometallic or heteroatomic organic compound in the form of pure vapor or in a carrier gas. 3. Process according to claim 1 wherein the sum of the weights of iron and manganese is between 10 and 90% of the total weight of the catalyst. 4. Process according to claim 1 wherein the weight ratio of iron to manganese is between 7: 1 and 1: 1. 5. The process of claim 4 wherein said ratio is about 2: 1. 6. Process according to claim 2 wherein said operation is carried out at a temperature comprised between about -20 and 100 ° C. 7. Process according to claim 6 wherein said operation is carried out at a temperature comprised between room temperature and 50 ° C. 8. Process according to claim 2 wherein said operation is carried out with a flow of gas to be purified between about 0.1 and 20 slpm, at absolute pressures comprised between about 1 and 10 bar. 9. Process according to claim 1 wherein the organometallic compound is selected from hafhium tetra-t-butoxide, trimethylaluminium, triethylaluminium, tri-tbiitylaluminium, di-i-butylaluminium hydride, trimethoxyalluminium, dimethylaluminium chloride, diethylaluminium ethoxide, dimethylaluminium hydride, trimethylantimony, triethylantimony, tri-i-propyl antimony, tris-dimethylaminoantimony, trimethylarsenic, tris-dimethylamino-arsenic, t-butylarsine, phenylarsine, barium bis-tetramethylptanionate, diethyl dimethyl methyl methyl methyl methyl methyl methyl methyl methyl methyl acetate bis-cyclopentadienyl-iron, iron trisacetylacetonate, iron tris-tetramethylheptanionate, trimethylgallium, triethylgallium, tri-ipropylgallium, tri-i-butylgallium, triethoxygallium, trimethylindium, triethylindium, ethyl dimethylindium, yttrandedionate, lyldimethyl methylptylindionate, yttrandedionate bis-methylcyclopentadienyl-magnesium magnesium bistetramethylptanionate, dimethylmercury, niobium pentaethoxide, tetraethoxydimethylaminoethoxide of niobium, dimethyloro acetylacetonate, lead bis-tetramethylptanionate, bis-hexafluoram acetylacetonate, copper bistetramethylheptanide, tannin tris-tetramethylethylethylene diethylene, tetramethylethylene-diethylene, tetramethylethylene-diethylene, tetramethylethylene-diethylene, tetramethylethylene-diethio-diethio strontium bistetramethylptanate, tantalum pentoxide, tantalum tetraethoxydimethylaminoethoxide, tantalum tetraethoxytetramethylptanate, tantalum tetramethoxytetramethylheptanate, tantalum tetra-i-propoxytetramethylptanate, tantalum tri-ethoxyethylaminoethylenate, tantalum tri-diethylamethylammide-tantalum , titanium bis-i-propoxybis-dimethylaminoethoxide, titanium bis-ethoxy-bis-dimethylaminoethoxide, titanium tetradimethylamide, titanium tetradethylamide, titanium tetra-t-butoxide, titanium tetra-propoxide, vanadyl i-propoxide, dimethylzdinco, diethyl co, zinc bistetramethylptanionate, zinc bis-acetylacetonate, zirconium tetra-t-butoxide, zirconium tetra-tetramethylptanionate and zirconium tri-i-propoxy-tetramethylptanionate. 10. Process according to claim 1 wherein the heteroatomic organic compound is selected from trimethylborane, asymmetric dimethylhydrazine, t-butylamine, phenylhydrazine, trimethylphosphorus, t-butylphosphine and t-butylmercaptan. 11. Process according to claim 1 further comprising the operation of contacting the organometallic or heteroatomic organic compound to be purified, with at least a second material selected from a hydrogenated getter alloy and a palladium-based catalyst supported on γ-alumina. 12. The process of claim 11 wherein the organometallic or heteroatomic compound is in the form of pure vapor or in a carrier gas. 13. Process according to claim 11 wherein the second material is a hydrogenated getter alloy selected from alloys based on titanium and / or zirconium with one or more elements selected from transition metals and aluminum, and mixtures between one or more of these alloys with titanium and / or zirconium. 14. Process according to claim 13 wherein the getter alloy is selected from ZrM2 alloys, where M is one or more of the transition metals Cr, Mn, Fe, Co or Ni; the Zr-V-Fe alloys and in particular the alloy with a percentage composition by weight Zr 70% - V 24.6% - Fe 5.4%; the Zr-Co-A alloys, in which with A we mean any element chosen from among yttrium, lanthanum, Rare Earths or mixtures of these elements; Ti-Ni alloys; and Ti-V-Mn alloys. 15. Process according to claim 12 wherein the contact between the gas to be purified and the hydrogenated getter alloy occurs at a temperature ranging from room temperature to about 100 ° C. 16. Process according to claim 11 wherein the second material is a palladium-based catalyst supported on γ-alumma with a weight content of 0.3 to 4% palladium. 17. Process according to claim 12 wherein the contact between the gas to be purified and the supported palladium occurs at a temperature comprised between about -20 and 100 ° C. 18. Process according to claim 17 wherein said contact takes place at a temperature comprised between room temperature and 50 ° C. 19. Process according to claim 1 further comprising the operation of contacting the organometallic or heteroatomic organic compound to be purified, in the form of pure vapor or in a carrier gas, with a chemical water absorber.