The present invention is related to a method of fabricating a magnetic device having a dry etching process. More specifically, the present invention is related to a method of fabricating a magnetic device having a process for performing dry etching at a high etching rate and a high selectivity when the micro-work of a magnetic thin film is carried out.
An MRAM (magnetic random access memory), which is an integrated magnetic memory, has attracted attention as a memory having an integration density similar to a DRAM and a high speed similar to an SRAM, and that can be limitlessly rewritten. Furthermore, a thin-film magnetic head, magnetic sensor and the like constituting magnetic resistance devices, such as GMR (gigantic magnetic resistance) and TMR (tunneling magnetic resistance), have been rapidly developed.
Heretofore, in the etching process of magnetic materials, ion milling has been frequently used. However, since ion milling is physical sputter etching, selectivity to various materials for the mask is difficult to obtain, and problems wherein the bottom of the material to be etched was tapered have been caused. Therefore, it is the present situation that ion milling is not suited for the fabrication of large-capacity MRAM, which requires especially fine processing techniques, that it is difficult to uniformly process large-area 300 mm substrates, and that the yield cannot be raised.
In place of such ion milling, techniques cultivated in the semiconductor industry have been introduced.
Among these, RIE (Reactive Ion Etching) technology, which can secure uniformity in large-area 300 mm substrates, and excels in micro-work characteristics, is anticipated.
However, even with the RIE technology widely used in the semiconductor industry, the reactivity to magnetic materials, such as FeNi, CoFe and CoPt was poor, and it was difficult to process them without producing etching residues and sidewall depositions.
As methods for fabricating magnetic devices using a process for the dry etching of magnetic films, for the selective etching of a magnetic material of transition elements, Japanese Patent Application Laid-Open No. H8-253881 proposes carbon monoxide (CO) gas to which a nitrogen-containing compound gas, such as ammonia (NH3) and amine gas, is added, as the reaction gas for dry etching; Japanese Patent Application Laid-Open No. 2005-42143 proposes alcohols having at least one hydroxyl group as the etching gas for dry etching of a magnetic material using a non-organic material as a mask; and Japanese Patent Application Laid-Open No. 2005-268349 proposes a gas containing at least methane and oxygen as the dry etching gas for the magnetic material of difficult-to-etch elements, such as Pt and Ir.
An object of the present invention is to provide a dry etching process on the basis of high-rate etching and high selectivity, wherein no after-corrosion treatment or no corrosion resistant treatment is required when a mask material (non-organic material mask) formed of a non-organic material, such as a metal atom material selected from a metal group consisting of III group, IV group, V group and VI group in a periodic table, or a material formed of these metal atoms and non-metal atoms is used.
Another object of the present invention is to provide a method of fabricating a magnetic device using the above-described dry etching process.
To achieve the above-described objects, the present invention is, firstly a method of fabricating a magnetic device characterized by including the steps of etching a magnetic film or diamagnetic film which includes at least one kind of metal selected from a metal group consisting of VIII group, IX group and X group elements in a periodic table by using a non-organic material mask, in an atmosphere of plasma generated by using at least one kind of compound selected from a gasifying compound group consisting of ethers, aldehydes, carboxylic acids, esters, diones and amines; and secondly a method of fabricating a magnetic device characterized by including the steps of etching a magnetic film or diamagnetic film which includes at least one kind of metal selected from a metal group consisting of VIII group, IX group and X group element in a periodic table by using a non-organic material mask, in an atmosphere of plasma generated by using at least one kind of compound selected from a gasifying compound group consisting of ethers, aldehydes, carboxylic acids, esters, diones and amines, and at least one kind of gas selected from a gas group consisting of oxygen, ozone, nitrogen, H2O, N2O, NO2 and CO2.
In the fabricating method of the present invention, as the ethers, at least one kind of ether selected from a compound group consisting of dimethyl ether, diethyl ether and ethylene oxide can be cited.
In the fabricating method of the present invention, as the aldehydes, at least one kind of aldehyde selected from a compound group consisting of formaldehyde and acetaldehyde can be cited.
In the fabricating method of the present invention, as the carbonic acids, at least one kind of carboxylic acid selected from a compound group consisting of formic acid and acetic acid can be cited.
In the fabricating method of the present invention, as the esters, at least one kind of ester selected from a compound group consisting of ethyl chloroformate and ethyl acetate can be cited.
In the fabricating method of the present invention, as the amines, at least one kind of amine selected from a compound group consisting of dimethylamine and triethylamine can be cited.
In the fabricating method of the present invention, as the diones, at least one kind of dione selected from a compound group consisting of tetramethylheptadione, acetylacetone and hexafluoroacetylacetone can be cited.
The mask material (non-organic material mask) used in the present invention is a non-organic material composed of a single-layer film or a laminated film formed of a substance produced by mixing a metal atom material selected from a metal group consisting of III group, IV group, V group and VI group in a periodic table, for example, Ta, Ti Al or Si, or a mixed material of such metal atoms and non-metal atoms, for example, a non-organic mask material composed of a single-layer film or a laminated film formed of a metal such as Ta, Ti and Al or a non-metal such as Si, or the oxide or nitride of these metals or non-metals, can be used.
As the non-organic material mask used in the present invention, for example, a single-layer film or a laminated film of simple elements Ta, Ti, Al or Si can be used as the mask material. Alternatively, a single-layer film or a laminated film of oxides or nitrides of Ta, Ti, Al or Si such as, Ta oxides, Ti oxides, Al oxides such as Al2O3, Si oxides such as SiO2, and TaN, TiN, AlN, SiN or the like can be used as the mask material. When the above-described single-layer film is used, the thickness thereof is 2 to 300 nm, preferably 15 to 30 nm. When the above-described laminated film is used, the laminated thickness thereof is 2 to 300 nm, preferably 15 to 30 nm.
In the fabricating method according to the present invention, as a magnetic film or a diamagnetic film composed of at least one kind of metal selected from a metal group consisting of VIII group, IX group and X group in a periodic table to be subjected to etching process, an FeN film, NiFe film, CoFe film, CoFeB film, PtMn film, IrMn film, CoCr film, CoCrPt film, NiFeCo film, NiFeMo film, CoFeB film, FeMn film, CoPt film, NiFeCr film, CoCr film, CoPd film, CoFeB film or NiFeTb film can be used. These magnetic films or diamagnetic films may be ferromagnetic or soft magnetic. Although the content of magnetic substance contained in these magnetic films or diamagnetic films is 10 atomic % or more, preferably 50 atomic % or more, it is not limited to these values.
In the fabricating method according to the present invention, the magnetic film or diamagnetic film to be subjected to the etching process may be a single-layer film or a laminated film. When the single-layer film is used, the thickness thereof is 2 to 300 nm, preferably 15 to 30 nm. When the laminated film is used, the laminated thickness thereof is 2 to 300 nm, preferably 15 to 30 nm.
In the fabricating method according to the present invention, the etching temperature when etching a magnetic film or diamagnetic film is preferably maintained within a range of 250° C. or lower. If the temperature exceeds 250° C., undesired thermal damage is given to the magnetic film. The preferable temperature range of the present invention is 20 to 100° C.
Also in the fabricating method according to the present invention, the vacuum during etching is preferably a range between 0.05 and 10 Pa. Within this pressure range, the magnetic device can be anisotropically processed by the formation of high-density plasma.
In the fabricating method according to the present invention, an oxidation gas or a nitriding gas (adding gas), such as oxygen, ozone, nitrogen, H2O, N2O, NO2 CO2 can be added to the above-described gasified compound within a range not exceeding 50 atomic %.
Also in the present invention, it is preferable to add an inert gas to the above-described gasified compound within a range not exceeding 90 atomic %. As the inert gas, Ar, Ne, Xe, Kr or the like can be used. At this time, a mixed gas of the above-described adding gas and an inert gas may also be used. Also at this time, it is preferable that the quantity of the mixed gas is within the range of the above-described quantity.
According to the fabricating method of the present invention, if the above-described adding gas or inert gas is added to the above-described gasifying compounds within the above-described range, the etching rate can be further increased, and at the same time, the selectivity to the mask can be significantly enhanced. However, if more than 50 atomic % of the adding gas is used, decrease in the etching rate will occur, and the lowering of selectivity for the non-organic material mask will also be caused.
In the dry etching method used in the fabricating method of the present invention, when the magnetic material is etched using the mask material composed of non-organic material, no after-corrosion treatment is required, and the consideration of corrosion resistance to the etching apparatus is unnecessary. According to the present invention, as described above, a high etching rate and a large selectivity could be achieved, and by the high etching rate and large selectivity, a high degree of micro-work of a magnetic thin film composed of a single-layer film or a laminated film can be realized. Thereby, the yield of highly integrated MRAM could be significantly improved.
In
The fundamental structure of a TMR element fabricated by the fabricating method according to the present invention will be shown in
The structure of the apparatus viewed from the top is shown in
The etching conditions for the Ta film by the above-described CF4 using the photoresist film 209 as a mask were as follows:
Next, after removing photoresist 209, an etching process wherein acetic acid gas and oxygen gas were used as etching gases, and Ta formed by the above-described process is used as a masking material for etching NiFe film 207, CoFe film 206, Al2O3 film 205 and CoFeB/PtMn film 204, was carried out to fabricate a magnetic film shown in
At this time, by operating the gas-introducing system 3, from a vessel 31 wherein acetic acid was stored shown in
An element shown in
As described above, the dry etching method used in the fabricating method according to the present invention exhibited an unexpectedly significant effect.
An element shown in
Among ethers, aldehydes, carboxylic acids, diones and amines, ethers and aldehydes are not corrosive, and especially advantageous in safety.
Although a certain number of examples and comparative test examples of the present invention have been described, the present invention is not limited to the described embodiments, but can be changed to various embodiments within a technical range grasped from the description of claims. For example, the etching apparatus is not limited to the ICP-type plasma apparatus having a 1-turn antenna shown in
This application is a continuation application of International Application No. PCT/JP2007/057689, filed on Mar. 30, 2007, the entire contents of which are incorporated by reference herein.
Number | Date | Country | |
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Parent | PCT/JP2007/057689 | Mar 2007 | US |
Child | 12556987 | US |