JP2012237043A - METHOD FOR REMOVING Ni FILM FROM MASK MEMBER MADE OF STAINLESS STEEL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively removing an Ni film without eroding a mask member made of stainless steel when removing the Ni film deposited in a thin film pattern forming process from a surface of the mask member made of stainless steel used for pattern forming in the film pattern forming process such as sputtering.SOLUTION: The Ni film is dissolved and removed using mixed acid aqueous solution containing 15-25 wt.% of sulfuric acid and 5-15 wt.% of nitric acid when the Ni film formed on the surface of the mask member is removed from the mask member made of stainless steel used for forming the Ni film in a prescribed pattern on a substrate by a thin film formation technique.

Description

  In the present invention, when a stainless steel is used as a mask member in forming a Ni film with a predetermined pattern on the outer surface of a package such as a piezoelectric vibrator by a thin film forming technique such as sputtering, the surface of the mask member is formed. The present invention relates to a method for removing a formed Ni film.

  As is well known, a so-called external electrode is usually formed on the outer surface of a piezoelectric vibrator glass package using crystal or the like. In this case, in the process of forming the external electrode, a thin film forming technique such as sputtering is used. May form a nickel (Ni) film. In this type of thin film formation technology, a film is formed in a predetermined pattern on a base material such as a glass package. Therefore, the surface of the base material is covered with a mask member having an inverted pattern, and sputtering is performed. It is common to form a thin film having the pattern shape. As mask members in such cases, various materials have been conventionally used. However, as a material of a metal mask (metal mask) when sputtering Ni, heat resistance, corrosion resistance, glass, or the like can be used. From the viewpoint of easy adjustment of the difference in coefficient of thermal expansion with the substrate, stainless steel such as SUS304 and SUS430 is often used as disclosed in Patent Document 1, for example.

By the way, when forming a thin film with a predetermined pattern by a thin film forming technique such as sputtering using the mask member, the thin film material is deposited not only on the surface of the base material but also on the surface of the mask member. If the film of the thin film material (deposited film on the mask member) deposited on the surface of the mask member grows in this way, there is a problem that the pattern formation accuracy by the mask member is lowered. When a thin film is formed with a simple pattern, it has a great adverse effect.
Therefore, in general, when a mask member made of a metal such as stainless steel is used to form a film in a predetermined pattern on the substrate by sputtering or the like, the mask member is removed from the substrate after completion of the thin film forming process such as sputtering, The film deposited on the mask member surface is cleaned and removed to prepare for the next use. That is, every time the mask member is used once, the operation of removing the deposited film from the mask material surface is usually performed.

On the other hand, as described above, stainless steel is often used as a mask member when sputtering a Ni film on a substrate such as glass, but in order to remove the Ni film deposited on the mask member, Conventionally, a halogen-type chemical solution or an iron chloride-type chemical solution is used as an etching agent, and a stainless steel mask member on which a Ni deposited film is formed is immersed in these chemical solutions, and the Ni deposited film is dissolved and removed (etching). )
Although different from the stainless steel mask member which is the subject of the present invention, as a chemical solution for removing the Ni film on the mask member mainly for a mask member made of copper or a copper alloy, sulfuric acid or the like is used. The use of a mixed acid containing various acids such as an inorganic acid and an organic acid is disclosed in, for example, Patent Document 2 and, similarly to the above, for a mask member made of copper, an Ni film on the mask member is formed. For example, Patent Document 3 discloses that a chemical solution for removal includes a solution containing sulfuric acid, hydrogen peroxide solution, and a ketone compound.

JP 2009-221524 A Japanese Patent Laid-Open No. 9-228075 JP-A-6-322559

  In a thin film formation process such as sputtering, stainless steel is used as a mask member for forming a Ni film on a substrate in a predetermined pattern, and the chemical solution for etching and removing the Ni film deposited on the mask member is used as described above. When using a halogen-based chemical solution or an iron chloride-based chemical solution, there are the following problems. That is, if a stainless steel mask member is immersed in these chemical solutions, not only the Ni film on the mask member is dissolved, but also the mask member itself is eroded and the mask member is deformed. The mask member that has been eroded and deformed in this way cannot be used as a mask for pattern formation. Therefore, conventionally, when forming a Ni film using a mask member made of stainless steel, the mask member has to be discarded as it is after the completion of the film forming process such as sputtering. That is, the actual situation is that the mask member made of stainless steel after being used once is discarded without removing the Ni film deposited on its surface and reusing it. This means that the mask member must be replaced with a new one each time a film is formed. Therefore, conventionally, the cost required for the mask member is large, and this has been a major factor that increases the overall cost of the pattern thin film forming process. That is, the mask member made of stainless steel not only has a high raw material cost, but also requires fine and high-precision processing, so the processing cost is also high, and it is impossible to reuse such a stainless steel mask member. This has been a major obstacle to reducing the overall cost of the thin film formation process.

  The present invention has been made in view of the above circumstances, and is deposited in the thin film formation process from the surface of a stainless steel mask member used for pattern formation in a pattern thin film formation process using sputtering or the like. An object of the present invention is to provide a method capable of effectively removing the Ni film without eroding the stainless steel mask member in removing the Ni film formed.

As a result of repeated experiments and studies on the method capable of solving the above-mentioned problems, the present inventors have found that a mixed solution of sulfuric acid and nitric acid is used as a chemical solution for cleaning and removing the Ni film on the surface of the stainless steel mask member. In particular, in order to remove the Ni film while preventing the erosion of the stainless steel mask member, it is possible to use a mixed acid containing 15 to 25 wt% sulfuric acid and 5 to 15 wt% nitric acid, and the balance being substantially made of water. It has been found that it is effective and has led to the present invention.
In addition, using the mixed acid of various places as a chemical | medical solution for removing Ni film | membrane on the mask member which consists of copper or a copper alloy instead of stainless steel is conventionally known by the said patent document 2, patent document 3, etc. However, if the type of metal is different, even if the same chemical solution is used, the dissolution action and erosion action thereof are different. Therefore, the chemical solution shown in Patent Document 2 and Patent Document 3 is directly used as a mask member made of stainless steel. Even if it is applied, it is difficult to predict whether or not the above-described problems can be solved. In other words, the present invention is intended to solve the above-described problems with respect to a mask member made of stainless steel.

  Therefore, the Ni film removing method from the stainless steel mask member of the present invention basically uses a stainless steel mask used for forming a Ni film in a predetermined pattern on a substrate by a thin film forming technique. In removing the Ni film formed on the surface of the member, the Ni film is dissolved and removed using a mixed acid aqueous solution containing 15 to 25 wt% sulfuric acid and 5 to 15 wt% nitric acid. Is.

  Here, the total concentration of sulfuric acid and nitric acid in the mixed acid aqueous solution is preferably in the range of 23 to 40 wt%.

  Further, when the Ni film is dissolved and removed using the above mixed acid aqueous solution, the stainless steel mask member on which the Ni film is formed may be immersed in a mixed acid aqueous solution bath or the mixed acid aqueous solution on the surface of the mask member. May be sprayed by spraying,

  According to the Ni film removal method from the stainless steel mask member of the present invention, when removing the Ni film deposited on the surface of the mask member made of stainless steel, the Ni film can be removed without eroding the mask member. Therefore, it is possible to prevent the occurrence of deformation due to the erosion of the mask member, and it is possible to repeatedly reuse the mask member that has been used once or more in the thin film formation process such as sputtering even on a mass production scale. The cost required for the stainless steel mask member can be greatly reduced, and the overall cost in the pattern thin film forming process can be greatly reduced.

It is a schematic diagram which shows typically an example of the condition which is implementing the Ni film removal method from the stainless steel mask member of this invention.

  The Ni film to be removed in the method of the present invention is a stainless steel mask member used for forming a Ni film in a predetermined pattern on a substrate by a thin film formation technique, and is deposited in the thin film formation process. This is a Ni film.

  Here, the thin film formation technique typically includes sputtering, but also includes PVD methods such as vacuum deposition and ion plating, or chemical vapor deposition (CVD). As the stainless steel of the mask member, for example, there are many SUS304, which is typical as an austenitic stainless steel, or SUS430, which is typical as a ferritic stainless steel, but other austenitic stainless steel, ferritic stainless steel, and martens There is no particular limitation as long as it is stainless steel that can be used as a mask member, such as site stainless steel. The Ni film is not particularly limited as long as it is a Ni film formed in a predetermined pattern in the process of forming electrodes in various ordinary electronic components. In addition to a pure Ni film, a Ni alloy mainly composed of Ni A membrane is also included.

Hereinafter, an example of an embodiment for carrying out the method of the present invention will be described with reference to FIG.
In FIG. 1A, reference numeral 1 denotes a mask member on which a Ni film 2 is deposited and formed on the surface. In carrying out the present invention, a mixed acid aqueous solution 4 containing 15 to 25 wt% sulfuric acid and 5 to 15 wt% nitric acid is prepared, and the mixed acid aqueous solution 4 is poured into the treatment tank 3.
Then, as shown in FIG. 1B, the mask member 1 is immersed in the mixed acid aqueous solution 4 in the treatment tank 3, and the chemical dissolution action (etching action) by the mixed acid aqueous solution 4 causes the (C) in FIG. As shown in FIG. 2, the Ni film 2 on the surface of the mask member 1 is dissolved and removed.

  Here, a mixed acid aqueous solution of sulfuric acid and nitric acid is used as an etching solution for removing the NI film, and the sulfuric acid concentration in the mixed acid aqueous solution is adjusted to 15 to 25 wt% and the nitric acid concentration is adjusted to a range of 5 to 15 wt%. Thus, only the Ni film can be effectively removed while preventing the mask member from eroding into the stainless steel. That is, since stainless steel generally contains Cr in a high concentration, if the surface of the stainless steel of the mask member is in contact with a mixed acid aqueous solution of sulfuric acid and nitric acid, the surface of the stainless steel is mainly oxidized by nitric acid having strong oxidizing power. A passive film is formed on the surface, and the passive film exhibits an erosion prevention function, thereby preventing the mask member from being eroded. On the other hand, almost no passivation is formed in the Ni film at a nitric acid concentration of the level specified in the present invention, and the Ni film is dissolved and removed by the chemical dissolution action (etching action) of sulfuric acid and nitric acid.

When the concentration of nitric acid in the above mixed acid aqueous solution is less than 5 wt%, a passive film is not sufficiently formed on the surface of the stainless steel of the mask member, so that the effect of forming a passive film and preventing the erosion of the mask member is sufficient. I can't get it. On the other hand, when the concentration of nitric acid exceeds 15 wt%, the Ni film dissolution and removal action is large at the beginning, but the Ni film is gradually formed with a passive state and the solubility is lowered. As a result, the Ni film is completely removed. The portion that cannot be completely removed or the portion that is partially dissolved and the portion that is not dissolved are unevenly formed (that is, the Ni film is not uniformly dissolved and removed).
In addition, when the sulfuric acid concentration in the mixed acid aqueous solution is less than 15 wt%, the scientific dissolution action of the Ni film is lowered, and the latter passive formation and passive action of the Ni film on the Ni film as described above is relatively strong. Thus, the Ni film is not uniformly dissolved and removed. On the other hand, if the sulfuric acid concentration in the mixed acid aqueous solution exceeds 25 wt%, even if nitric acid is added, it becomes difficult to prevent the mask member from being eroded and the mask member is eroded.
Therefore, from the above, the mixed acid aqueous solution of sulfuric acid and nitric acid, which is an etching solution for removing the NI film in the stainless steel mask member, has a sulfuric acid concentration of 15 to 25 wt% and a nitric acid concentration of 5 to 15 wt%. It is necessary to use what is in.

  The total concentration of sulfuric acid and nitric acid in the mixed acid aqueous solution is not basically limited, but it is usually preferably in the range of 23 to 40 wt%. When the total concentration of the sulfuric acid concentration and the nitric acid concentration is less than 23 wt%, the chemical dissolution action with respect to the Ni film as the whole mixed acid aqueous solution becomes small, and there is a possibility that the time required for dissolution and removal of the NI film becomes long. On the other hand, if the total concentration of sulfuric acid concentration and nitric acid concentration exceeds 40 wt%, the mask member made of stainless steel may be eroded.

  In the above description, when removing the Ni film, a so-called dipping method is applied to immerse the mask member having the Ni film in a mixed acid aqueous solution bath for removing the Ni film (for etching). In some cases, the mixed acid aqueous solution may be sprayed on the surface of the mask member, and even if the spray method is applied instead of the dipping method in this way, the sulfuric acid concentration of the mixed acid aqueous solution is 15 to 25 wt% and the nitric acid concentration is 5 to 5. If the content is within the range of 15 wt%, the same effect as in the dipping method can be obtained.

  1 shows that the Ni film 2 is directly formed on the surface of the mask member 1 made of stainless steel, the Ni film 2 is formed directly on the surface of the mask member 1 in the method of the present invention. In the case where a thin layer of dissimilar metal such as Cr is formed on the surface of the mask member 1 made of stainless steel, for example, and a Ni film is formed on the dissimilar metal thin layer, Of course, the present invention can also be applied to the removal of the Ni film on the thin metal layer.

  Examples of the present invention will be described below. In addition, each following Example is for showing the effect of this invention, and of course, the conditions described in these Examples do not limit the technical scope of this invention.

  First, the Ni film removability test was performed as follows. That is, a 1 mm thick rectangular plate (length 30 mm, width 40 mm) mask member made of SUS304, which is an austenitic stainless steel, is prepared, and a Ni film with a thickness of 0.5 μm is preliminarily formed on one surface thereof by a normal sputtering method. It was formed by. On the other hand, as a mixed acid aqueous solution composed of sulfuric acid, nitric acid and water, No. 1 in Table 1 was obtained. 1-No. 15 having various sulfuric acid concentrations and nitric acid concentrations as shown in FIG. Then, an experiment for removing the Ni film was performed by immersing the mask base material on which the Ni film was formed as described above in a mixed acid aqueous solution bath. Here, the temperature (bath temperature) of the mixed acid aqueous solution at the time of immersion was 25 ° C. ± 5 ° C., and the immersion time was 5 minutes. After immersion for 5 minutes, the mask member was taken out of the mixed acid aqueous solution bath, washed with water and dried, and then the removal state of the Ni film on the mask member surface was observed visually and under a microscope. The result is shown in the column of “Ni film removability” of “Evaluation” in Table 1. In this case, the mark “◯” for “Ni film removability” indicates the case where the Ni film is uniformly and almost completely removed, and the mark “X” indicates that the Ni film is not completely removed and the removal state is not satisfactory. The case where the Ni film remains uniform and uneven is shown. Furthermore, Δ marks indicate the case where the removal situation is uniform, but the Ni film could not be completely removed by the above immersion time (that is, when a long time exceeding 5 minutes is required for complete removal).

Next, an experiment (SUS corrosion resistance test) for examining the corrosion resistance of the mask member against the mixed acid aqueous solution was performed. That is, for the same SUS304 mask member as described above, No. 1-No. 15 was immersed in a mixed acid aqueous solution bath (bath temperature 25 ° C. ± 5 ° C.) shown in FIG. 15 for 24 hours, taken out, washed with water and dried, and the erosion status of the mask member was observed visually and under a microscope. The result is shown in the column of “SUS corrosion resistance” of “Evaluation” in Table 1. Here, the mark “◯” regarding “SUS erosion resistance” indicates that the mask member made of SUS304 is not eroded at all, or even if it is slightly eroded, its maximum erosion width is 5 μm or less, and there is no practical problem. In this case, the mark X indicates a case where the maximum erosion width exceeds 5 μm and has been eroded.
Furthermore, as a comprehensive evaluation, a case where both the above-mentioned “Ni film removability” and “SUS erosion resistance” are good is judged as a good general evaluation (marked with a circle), and at least one of the other cases. When one of the performances was inferior, it was judged that the overall evaluation was poor (Δ mark, × mark), and these comprehensive evaluations are shown in FIG.

  As is apparent from Table 1, the sample No. of the present invention in which the sulfuric acid concentration in the mixed acid aqueous solution for etching is in the range of 15 wt% to 25% and the nitric acid concentration is in the range of 15 wt% to 25%. 5-No. 9, no. 12, no. In the case of No. 13, both “Ni film removability” and “SUS erosion resistance” were both good, and it was confirmed that they were also good overall.

  On the other hand, in the comparative example No. 1 in which the nitric acid concentration exceeds 15 wt% and the sulfuric acid concentration is less than 15 wt%. 1-No. In the case of No. 4, the Ni film removal property was inferior, and not only the Ni film could not be completely removed by the immersion time of 5 minutes, but also the Ni film removal situation was uneven. On the other hand, in the comparative example No. 1 in which the sulfuric acid concentration exceeds 25 wt% and the nitric acid concentration is less than 15 wt%. 10, no. In the case of No. 11, the SUS erosion resistance was poor, and the mask member made of SUS304 was eroded. In the case of 11, the Ni film can be removed, but it has been found that the removal takes a long time. Furthermore, No. of the comparative example. No. 14 is an example in which the sulfuric acid concentration is less than 15 wt% and the nitric acid concentration is less than 5 wt%. As in the case of 11, the Ni film can be removed, but it has been found that the removal takes a long time. The comparative example No. No. 15 is an example in which the sulfuric acid concentration exceeds 25 wt% and the nitric acid concentration exceeds 15 wt%. In this case, the SUS erosion resistance is inferior, and it has been found that the mask member made of SUS304 is eroded.

  Therefore, from these experimental results, the Ni film removal property and the SUS resistance can be obtained by setting the sulfuric acid concentration in the etching mixed acid aqueous solution within the range of 15 wt% to 25% and at the same time the nitric acid concentration within the range of 15 wt% to 25%. It is clear that both erodibility and satisfaction can be satisfied.

  The stainless steel of the mask member is changed to a ferritic SUS430 different from the case of Example 1, and 1-No. In the same manner as in Example 15, the nitric acid concentration and sulfuric acid concentration of the mixed acid aqueous solution were changed, and the Ni film removal test and SUS erosion resistance were performed in the same manner as in Example 1. As a result, it was confirmed that substantially the same result as that shown in Table 1 was obtained for Example 1.

  In the Ni film removal test in Example 1, the Ni film was removed by the dipping method. In Example 3, the Ni film removal was performed by spraying the mixed acid aqueous solution on the mask member by the spray method. A sex test was performed. Others were the same as in Example 1. The nitric acid concentration and sulfuric acid concentration of the mixed acid aqueous solution were also the same as in Example 1 No. 1-No. 15 was changed. As a result, it was confirmed that substantially the same results as those shown in Table 1 for Example 1 were obtained.

DESCRIPTION OF SYMBOLS 1 ... Mask member, 2 ... Ni film | membrane, 3 ... Treatment tank, 4 ... Mixed acid aqueous solution

Claims (4)

In removing the Ni film formed on the surface of the stainless steel mask member used for forming the Ni film in a predetermined pattern on the substrate by the thin film formation technique,
A method for removing a Ni film from a stainless steel mask member, comprising dissolving and removing the Ni film using a mixed acid aqueous solution containing 15 to 25 wt% sulfuric acid and 5 to 15 wt% nitric acid. In the Ni film removal method from the stainless steel mask member according to claim 1,
A method for removing a Ni film from a stainless steel mask member, characterized in that a total concentration of sulfuric acid and nitric acid in the mixed acid aqueous solution is within a range of 23 to 40 wt%. In the Ni film removal method from the stainless steel mask member according to any one of claims 1 and 2,
A method for removing a Ni film from a stainless steel mask member, comprising immersing the stainless steel mask member on which a Ni film is formed in a bath of the mixed acid aqueous solution. In the Ni film removal method from the stainless steel mask member according to any one of claims 1 and 2,
A method for removing a Ni film from a stainless steel mask member, comprising spraying the mixed acid aqueous solution onto a surface of the mask member made of stainless steel on which a Ni film is formed.

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