Patent Application
20120319033
The present invention relates to an etching solution for a multilayer thin film having a copper layer and a molybdenum layer contained therein. In particular, the etching solution of the present invention is favorably used for etching a multilayer thin film having a copper layer is provided on a molybdenum layer.
Heretofore, aluminium or an aluminium alloy has been generally used as the wiring material for display devices such as flat panel displays, etc. However, with growing in size and increasing in resolution of displays, there has occurred a problem of RC delay caused by the characteristics such as the wiring resistance of such aluminium-based wiring materials and uniform panel displaying has tended to be difficult.
Given the situation, the recent tendency is toward investigation of employing copper or copper-based wiring with a material having a lower resistance. However, copper has an advantage in that its resistance is low but, on the other hand, has a problem in that, in use for gate wiring, the adhesiveness between the substrate such as glass or the like and copper is not sufficient and that, in use for source/drain wiring, copper may diffuse into the silicon semiconductor underlayer. Consequently, for preventing these, there has been made an investigation of barrier layer lamination with a metal that has high adhesion to a substrate such as glass, etc. and hardly diffuses into the silicon semiconductor underlayer and additionally has a barrier property; and as the metal, molybdenum (Mo) has become specifically noted.
A multilayer film that contains copper or a copper-based copper alloy is formed on a substrate of glass or the like according to a film formation process of a sputtering method or the like, and then processed in an etching process of etching it via a resist serving as a mask to give an electrode pattern. The etching process includes a wet etching mode of using an etching solution and a dry etching mode of using an etching gas of plasma or the like. The etching solution for use in the wet mode is desired to satisfy the following: (i) The processing accuracy is high, (ii) the amount of the etching residue is small, (iii) the etching unevenness level is low, and (iv) an etching performance is stable against dissolution of a metal of a wiring material containing copper which is subjective to etching (a prolonging effect of bath life); and in addition to these, for meeting the size enlargement and the resolution enhancement of displays, (v) the wiring configuration formed after etching could fall within a predetermined range, or that is, a good wiring configuration can be obtained. More concretely, the parameters shown in
As the etching solution to be used in the etching process for the multilayer film containing copper or a copper-based copper alloy, for example, there have been proposed an etching solution containing at least one selected from a neutral salt, an inorganic acid and an organic acid, and hydrogen peroxide and a hydrogen peroxide stabilizer (for example, Patent Reference 1), an etching solution containing hydrogen peroxide, an organic acid and fluorine (for example, Patent Reference 2), etc.
However, these are all unsatisfactory in point of the wiring profile after etching therewith and, as a result, could not often sufficiently meet the size enlargement and the resolution enhancement of displays. Also, the etching solution disclosed in Patent Reference 2 contains a fluorinated compound, so that it was not thoroughly satisfactory from the viewpoint of environmental measure.
The present invention has been made under the circumstances as above, and its object is to provide an etching solution for a multilayer thin film containing a copper layer and a molybdenum layer, and a method of using it for etching a multilayer thin film containing a copper layer and a molybdenum layer.
The present inventors have repeatedly made assiduous studies for attaining the above-mentioned object. As a result, it has been found that the foregoing object can be achieved by an etching solution obtained by blending (A) hydrogen peroxide, (B) a fluorine atom-free inorganic acid, (C) an organic acid, (D) an amine compound, (E) an azole, and (F) a hydrogen peroxide stabilizer in a specified combination and regulating its pH within the range of from 2.5 to 5.
The present invention has been completed on the basis of the finding. Specifically, the gist of the present is as follows:
[1] An etching solution for a multilayer thin film having a copper layer and a molybdenum layer contained therein, which comprises (A) hydrogen peroxide, (B) a fluorine atom-free inorganic acid, (C) an organic acid, (D) an amine compound having a carbon number of from 2 to 10 and having an amino group and a hydroxyl group in a total group number of 2 or more, (E) an azole, and (F) a hydrogen peroxide stabilizer, and which has a pH of from 2.5 to 5.
[2] The etching solution as set forth above in [1], wherein the inorganic acid (B) is sulfuric acid and/or nitric acid.
[3] The etching solution as set forth above in [1] or [2], wherein the organic acid (C) is at least one member selected among succinic acid, glycolic acid, lactic acid, malonic acid, and malic acid.
[4] The etching solution as set forth above in any one of [1] to [3], wherein the amine compound (D) is at least one member selected among ethanolamine, 1-amino-2-propanol, and N,N-diethyl-1,3-propanediamine.
[5] The etching solution as set forth above in any one of [1] to [4], wherein the azole (E) is 5-amino-1H-tetrazole.
[6] The etching solution as set forth above in any one of [1] to [5], wherein the hydrogen peroxide stabilizer (F) is phenylurea.
[7] The etching solution as set forth above in any one of [1] to [6], comprising from 4.5 to 7.5% by mass of the hydrogen peroxide (A), from 0.01 to 3% by mass of the inorganic acid (B), from 5 to 13% by mass of the organic acid (C), from 2 to 7% by mass of the amine compound (D), from 0.001 to 0.5% by mass of the azole (E), and from 0.01 to 0.5% by mass of the hydrogen peroxide stabilizer (F).
[8] The etching solution as set forth above in any one of [1] to [7], further comprising 200 ppm or more of a copper ion.
[9] The etching solution as set forth above in any one of [1] to [8], wherein the multilayer thin film is one having a copper layer laminated on a molybdenum layer.
[10] A method for etching a multilayer thin film containing a copper layer and a molybdenum layer, which comprises bringing a subject to be etched into contact with the etching solution of any of the above [1] to [8].
[11] The etching method of the above [10], wherein the multilayer thin film is one formed by laminating a copper layer on a molybdenum layer.
According to the present invention, there are provided an etching solution which secures, in an etching process for a multilayer thin film containing a copper layer and a molybdenum layer, high processing accuracy, little etching residue and unevenness and a long bath life, and realizes a good wiring profile after etching therewith, and which therefore can meet the requirement of size enlargement and resolution enhancement of displays, and an etching method using it for a multilayer thin film containing a copper layer and a molybdenum layer. According to the etching method, a wiring material that contains a multilayer thin film containing a copper layer and a molybdenum layer can be etched all at a time, and therefore, after etching therewith, a good wiring profile can be realized at high producibility.
The etching solution of the present invention is used for etching of a multilayer thin film having a copper layer and a molybdenum layer contained therein, and it comprises (A) hydrogen peroxide, (B) a fluorine atom-free inorganic acid, (C) an organic acid, (D) an amine compound having a carbon number of from 2 to 10 and having an amino group and a hydroxyl group in a total group number of 2 or more, (E) an azole, and (F) a hydrogen peroxide stabilizer, and has a pH of from 2.5 to 5.
<<(A) Hydrogen peroxide>>
Hydrogen peroxide which is used in the etching solution of the present invention has a function to oxidize a copper wiring as an oxidizing agent and also has a function to oxidize and dissolve molybdenum. A content of hydrogen peroxide in the etching solution is preferably from 3 to 10% by mass, and more preferably from 4.5 to 7.5% by mass. The content of hydrogen peroxide falling within the above range is preferred, the control of hydrogen peroxide is easy, and also as securing a suitable etching rate and facilitating good control of the etching amount. Thus, such is preferable.
The fluorine atom-free inorganic acid which is used in the etching solution of the present invention contributes to the dissolution of copper which has been oxidized with the hydrogen peroxide (A). In the present invention, from the viewpoint of environmental measure, a fluorine atom-free acid is adopted. As the fluorine atom-free inorganic acid, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, hypophosphorous acid, carbonic acid, sulfamic acid, boric acid, and the like are preferably exemplified. These can be used alone or in admixture of a plurality thereof. Above all, sulfuric acid and nitric acid are preferable.
A content of the inorganic acid (B) in the etching solution is preferably from 0.01 to 5% by mass, and more preferably from 0.01 to 3% by mass. When the content of the inorganic acid falls within the above range, a suitable etching rate can be secured and a good wiring profile can be obtained after etching.
The organic acid which is used in the etching solution of the present invention contributes to the etching of copper and molybdenum and the removal of a residue to be caused due to molybdenum, and the content thereof in the etching solution is preferably from 1 to 15% by mass, more preferably from 5 to 13% by mass. When the content of the organic acid falls within the above range, etching of copper and molybdenum and the removal of a residue to be caused due to molybdenum can be sufficiently achieved, and also, a good wiring profile can be obtained after etching. Also, the organic acid functions as a masking agent of a copper ion to be contained in the etching solution after etching and is able to inhibit the decomposition of hydrogen peroxide with copper.
As the organic acid, in addition to aliphatic carboxylic acids having a carbon number of from 1 to 18 and aromatic carboxylic acids having a carbon number of from 6 to 10, amino acids having a carbon number of from 1 to 10 and the like are preferably exemplified.
As the aliphatic carboxylic acid having a carbon number of from 1 to 18, formic acid, acetic acid, propionic acid, lactic acid, glycolic acid, diglycolic acid, pyruvic acid, malonic acid, butyric acid, hydroxybutyric acid, tartaric acid, succinic acid, malic acid, maleic acid, fumaric acid, valeric acid, glutaric acid, itaconic acid, adipic acid, caproic acid, adipic acid, citric acid, propanetricarboxylic acid, trans-aconitic acid, enanthic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and the like are preferably exemplified.
As the aromatic carboxylic acid having a carbon number of from 6 to 10, benzoic acid, salicylic acid, mandelic acid, phthalic acid, isophthalic acid, terephthalic acid, and the like are preferably exemplified.
Also, as the amino acid having a carbon number of from 1 to 10, carbamic acid, alanine, glycine, asparagine, aspartic acid, sarcosine, serine, glutamine, glutamic acid, 4-aminobutyric acid, iminodibutyric acid, arginine, leucine, isoleucine, nitrilotriacetic acid, and the like are preferably exemplified.
Of the foregoing organic acids, acetic acid, succinic acid, alanine, citric acid, malic acid, lactic acid, glycolic acid, tartaric acid, malonic acid, glycine, glutaric acid, maleic acid, and trans-aconitic acid are preferable as the organic acid, with succinic acid, malic acid, lactic acid, glycolic acid, and malonic acid being especially preferable. These can be used alone or in combination of a plurality thereof.
The amine compound which is used in the etching solution of the present invention contributes to the favorable wiring profile after etching and is a compound having a carbon number of from 2 to 10 and having an amino group and a hydroxyl group in a total group number of 2 or more.
As such an amine compound, polyamines such as ethylenediamine, trimethylenediamine, tetramethylenediamine, 1,2-propanediamine, 1,3-propanediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, 1,3-diaminobutane, 2,3-diaminobutane, pentamethylenediamine, 2,4-diaminopentane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, N-methylethylenediamine, N,N-dimethylethylenediamine, trimethylethylenediamine, N-ethylethylenediamine, N,N-diethylethylenediamine, triethylethylenediamine, 1,2,3-triaminopropane, hydrazine, tris(2-aminoethyl)amine, tetra(aminomethyl)methane, diethylenetriamine, triethylenetetramine, tetraethylpentamine, heptaethyleneoctamine, nonaethylenedecamine, diazabicycloundecene, etc.; and alkanolamines such as ethanolamine, N-methylethanolamine, N-methyl diethanolamine, N-ethylethanolamine, N-aminoethylethanolamine, N-propylethanolamine, N-butylethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, N-methylisopropanolamine, N-ethylisopropanolamine, N-propylisopropanolamine, 2-aminopropane-1-ol, N-methyl-2-amino-propane-1-ol, N-ethyl-2-amino-propane-1-ol, 1-aminopropane-3-ol, N-methyl-1-aminopropane-3-ol, N-ethyl-1-aminopropane-3-ol, 1-aminobutane-2-ol, N-methyl-1-aminobutane-2-ol, N-ethyl-1-aminobutane-2-ol, 2-aminobutane-1-ol, N-methyl-2-aminobutane-1-ol, N-ethyl-2-aminobutane-1-ol, 3-aminobutane-1-ol, N-methyl-3-aminobutane-1-ol, N-ethyl-3-aminobutane-1-ol, 1-aminobutane-4-ol, N-methyl-1-aminobutane-4-ol, N-ethyl-1-aminobutane-4-ol, 1-amino-2-methylpropane-2-ol, 2-amino-2-methylpropane-1-ol, 1-aminopentane-4-ol, 2-amino-4-methylpentane-1-ol, 2-aminohexane-1-ol, 3-aminoheptane-4-ol, 1-aminooctane-2-ol, 5-aminooctane-4-ol, 1-aminopropane-2,3-diol, 2-aminopropane-1,3-diol, tris(oxymethyl)aminomethane, 1,2-diaminopropane-3-ol, 1,3-diaminopropane-2-ol, 2-(2-aminoethoxy)ethanol, 2-(2-aminoethylamino)ethanol, diglycolamine, etc. are preferably exemplified. These can be used alone or in combination of a plurality thereof. Of these, ethanolamine, 1-amino-2-propanol, and N,N-diethyl-1,3-propanediamine are especially preferable.
A content of the amine compound in the etching solution of the present invention is preferably from 1 to 10% by mass, and more preferably from 2 to 7% by mass. When the content of the amine compound falls within the above range, a good wiring profile can be obtained after etching.
As the azole which is used in the etching solution of the present invention, triazoles such as 1H-benzotriazole, 5-methyl-1H-benzotriazole, 3-amino-1E-triazole, etc.; tetrazoles such as 1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, 5-amino-1H-tetrazole, etc.; imidazoles such as 1H-imidazole, 1H-benzoimidazole, etc.; thiazoles such as 1,3-thiazole, 4-methylthiazole, etc.; and the like are preferably exemplified. Of these, tetrazoles are preferable, and 5-amino-1H-tetrazole is especially preferable.
The content of the azole in the etching solution is preferably from 0.001 to 1% by mass, more preferably from 0.001 to 0.5% by mass. When the content of the azole falls within the above range, a good wiring profile can be obtained while suppressing an increase of CD loss after etching.
The etching solution of the present invention contains a hydrogen peroxide stabilizer. Not specifically defined, any one generally used as a hydrogen peroxide stabilizer is usable here with no limitation; however, as the hydrogen peroxide stabilizer for use herein, preferably mentioned are urea-based hydrogen peroxide stabilizers such as phenylurea, allylurea, 1,3-dimethylurea, thiourea, etc., as well as phenylacetamide, phenylethylene glycol, etc. Above all, preferred is phenylurea.
The content of the hydrogen peroxide stabilizer (F) in the etching solution of the present invention is preferably from 0.01 to 0.5% by mass, more preferably from 0.01 to 0.3% by mass from the viewpoint of sufficiently securing the addition effect thereof.
<<pH>>
The etching solution of the present invention is required to have a pH of 2.5 to 5. When its pH is less than 2.5, a residue derived from a molybdenum oxide, which is hardly dissolved, which is formed at the time when molybdenum is etched and dissolved, is remained after etching, and as a result, there is a concern that the residue can bring on a lowering of electrical characteristics caused by leak current. Also, when the pH is larger than 5, then the stability of the hydrogen peroxide (A) may lower whereby the etching rate for copper wiring may lower and the bath life of the etching solution may shorten. From such viewpoints, the pH of the etching solution of the present invention is preferably from 2.5 to 5.
For the purpose of enhancing an etching performance from the beginning of use, it is preferable to allow the etching solution of the present invention to contain a copper ion in advance. The copper ion can be contained in the etching solution by adding a copper powder or a copper salt such as copper sulfate, copper nitrate, etc. to the etching solution.
A concentration of the copper ion in the etching solution is preferably 100 ppm or more, and more preferably 200 ppm or more. Also, though an upper limit of the concentration is not restricted so far as the etching performance is not lowered, taking into consideration a bath life and the like, it is preferably not more than 2,000 ppm, and more preferably not more than 1,000 ppm.
The etching solution of the present invention may contain, in addition to the foregoing components (A) to (F), water and other various additives which are usually used in etching solutions, within the range where the effects of the etching solution are not impaired. The water is preferably one from which metal ions or organic impurities, particles, and the like have been removed by means of distillation, ion exchange treatment, filter treatment, adsorption treatment of every kind, or the like, and pure water and ultra-pure water are especially preferable.
The etching method of the present invention is a method for etching a multilayer thin film that contains a copper layer and a molybdenum layer, and is characterized in that the etching solution of the present invention, or that is, the etching solution for a multilayer thin film containing a copper layer and a molybdenum layer, which comprises (A) hydrogen peroxide, (B) a fluorine atom-free inorganic acid, (C) an organic acid, (D) an amine compound having a carbon number of from 2 to 10 and having an amino group and a hydroxyl group in a total group number of 2 or more, (E) an azole, and (F) a hydrogen peroxide stabilizer, and which has a pH of from 2.5 to 5 is used and that the method comprises a step of bringing a subject to be etched into contact with the etching solution of the present invention. According to the etching method of the present invention, a multilayer thin film containing a copper layer and a molybdenum layer can be etched all at a time to give a good wiring profile after etching.
In the etching method of the present invention, the subject to be etched with the etching solution is one, for example, as shown in
Not specifically defined, the copper wiring may be formed of copper or a copper-based material, and as the molybdenum-based material to form the barrier film, there may be mentioned molybdenum (Mo) metal, an Mo based alloy, and so on.
The method of bringing the subject to be etched into the etching solution is not specifically defined; and herein employable is a wet etching method, for example, a method of dripping the etching solution onto the subject (sheet-fed spin treatment) or spraying it thereonto, or a method of dipping the subject into the etching solution, etc. In the present invention, preferably employed is the method of dripping the etching solution onto the subject (sheet-fed spin treatment) or spraying it thereonto, or the method of dipping the subject into the etching solution.
The temperature at which the etching solution is used is preferably from 20 to 60° C., more preferably from 30 to 50° C. When the temperature of the etching solution is not lower than 20° C., then the etching rate is not so much lowered and the production efficiency is not extremely lowered. On the other hand, when the temperature is not higher than a boiling point, then the solution composition change could be prevented and the etching condition could be kept constant. Elevating the temperature of the etching solution could increase the etching rate, but in consideration of the object of reducing the composition change of the etching solution, the best treatment temperature may be suitably determined.
In the etching method of the present invention, the hydrogen peroxide (A) contained in the etching solution is consumed by oxidation and dissolution of copper or molybdenum as described above, or the like, and the dissolved copper or molybdenum accelerates the decomposition of hydrogen peroxide. Therefore, there is a concern that a lowering of the performance of the etching solution to be caused due to a lowering of the hydrogen peroxide concentration. In such a case, hydrogen peroxide (A) and the organic acid (B) may be simultaneously or separately added so as to prolong the bath life of the etching solution.
Next, the present invention is described in more detail by reference to the following Examples, but it should be construed that the present invention is not limited by these Examples at all.
(Observation of Cross Section of Multilayer Thin Film Having Copper Layer and Molybdenum Layer Contained Therein after Etching)
A sample of the etched multilayer thin film containing a copper layer and a molybdenum layer, as obtained in Examples and Comparative Examples, was cut and observed with a 30000 magnification through scanning electronic microscope (“S5000H
Type (Model Number)”, by Hitachi) (acceleration voltage 2 kV, acceleration current 10 μA). On the thus-taken SEM image, the taper angle and the CD loss (μm) as shown in
When the taper angle and the CD loss (μm) fell within the standard ranges shown in Table 1, the sample was considered to be acceptable for the etching performance.
A surface of a multilayer thin film sample having a copper layer and a molybdenum layer contained thereon after etching, as obtained in each of the Examples and Comparative Examples, was observed using a scanning electron microscope (S5000 Model (model number), manufactured by Hitachi, Ltd.) in an observation magnification of 50,000 times (accelerating voltage: 2 kV, accelerating current: 10 μA), and a residue of the sample was evaluated according to the following criteria.
A: A residue was not confirmed at all.
B: Though a residue was slightly confirmed, the wiring performance was not influenced, so that no problem was caused from the standpoint of practical use.
C: A remarkable residue was confirmed.
Molybdenum (Mo) was sputtered onto a substrate of glass to thereby form a barrier film of molybdenum (molybdenum layer) thereon, then a copper-based material was sputtered thereonto to form a wiring material film (copper layer), then a resist was applied onto it, a pattern mask was transferred through exposure thereonto, and developed to form a wiring pattern, thereby fabricating a multilayer thin film containing a copper layer and a molybdenum layer in which the copper layer was laminated on the molybdenum layer.
The multilayer thin film having a copper layer and a molybdenum layer as obtained in the Fabrication Example was repeatedly subjected to an operation of etching with an etching solution shown in Table 2 at 35° C. by means of shower spraying; and with respect to the obtained multilayer thin film having a copper layer and a molybdenum layer after etching, a taper angle and a CD loss (μm) were obtained in a low-concentration region of a copper ion concentration in the etching solution (also expressed as “Cu concentration”) (from 200 to 1,000 ppm; also expressed as “low Cu concentration region”) and a high-concentration region of a copper ion concentration in the etching solution (from 3,000 to 4,000 ppm; also expressed as “high Cu concentration region”) by means of SEM observation.
Also, a time at which an etching subject of an area where the resist had not been patterned was determined to be etched by means of visual inspection was set up as a just etching time; and a time at which an etching treatment (overetching) was performed in an arbitrary proportion within the range of from 110 to 300% of the just etching time was set up as an etching time (for example, when the just etching time is 100 seconds, so far as overetching of 50% is concerned, its etching time is 150 seconds). These results of evaluations are shown in Table 2.
As Examples 6 and 7, etching was performed in the same manner as that in Example 4, except that in Example 4, a copper powder was previously added in a copper ion concentration of 200 ppm and 6,000 ppm, respectively to the Etching Solution 4 to be used. A taper angle, a CD loss (μm), and evaluation of residue of the multilayer thin film having a copper layer and a molybdenum layer contained therein, as obtained in the first etching are shown in Table 3. Also, a taper angle, a CD loss (μm), and evaluation of residue of the multilayer thin film having a copper layer and a molybdenum layer of Example 4 as obtained in the first etching are shown in Table 3.
Samples were etched in the same manner as in Example 1, except that the etching solution comprising the components shown in Table 4 was used in Example 1. A taper angle, a CD loss (μm), and evaluation of residue of each of the obtained multilayer thin films having a copper layer and a molybdenum layer are shown in Table 4.
The Examples using the etching solution of the present invention were favorable in the wiring cross-sectional shape after etching and also exhibited excellent results in view of the evaluation of residue. On the other hand, in Comparative Example 1 using an etching solution not containing the component (B), in the wiring cross-sectional shape, so-called undercut in which molybdenum as the lower layer was more selectively etched than copper as the upper layer was generated. In Comparative Examples 2 and 3 using an etching solution not containing the components (B) to (F), the etching did not proceed, or the resist was peeled, so that it was confirmed that these etching solutions cannot be put into practical use. Also, in Comparative Example 4 using an etching solution having a pH falling outside the range specified in the invention of the present application, the CD loss was large; and in Comparative Example 5 using an etching solution not containing the component (D), molybdenum as the lower layer was selectively etched, and the etched edge face was not formed in a forward tapered shape but a reversely tapered shape in which the taper angle partially exceeded 90°, so that it was confirmed that a problem was caused from the standpoint of wiring cross-sectional shape.
The wiring cross-sectional shape after first etching in Examples 6 and 7 using an etching solution previously containing 200 ppm and 6,000 ppm of a copper ion, respectively was favorable as compared with the wiring cross-sectional shape after first etching in Example 4, so that it was confirmed that the evaluation of residue was favorable. That is, it was confirmed that when a copper ion is previously added in the etching solution of the present invention, a favorable performance is revealed from the beginning of use of the etching solution.
The etching solution of the present invention can be favorably used for etching of a copper layer and a molybdenum layer contained therein; and according to the etching method of using the etching solution, a multilayer thin film containing a copper layer and a molybdenum layer can be etched all at a time to have a good wiring profile after etching, therefore realizing high producibility.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-030377 | Feb 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP11/53151 | 2/15/2011 | WO | 00 | 8/15/2012 |
