JP7305454B2 - How to wash the mask - Google Patents

Description

The present invention relates to a method for cleaning a mask used in a dry film formation method. The present invention relates to a method for cleaning a mask, which is capable of preventing erosion of members constituting the mask when the deposit adhering to the mask is immersed in a cleaning liquid to remove the deposit from the mask.

In recent years, organic films have been utilized as thin films constituting many organic devices such as organic semiconductors, organic thin film solar electrons, and organic electroluminescence (organic EL). In such an organic device, an electrode made of a transparent conductive film is formed. In this case, a film formation method typified by a sputtering method is preferably used to form an electrode having a desired pattern on a predetermined substrate (or a previously formed coating) using a mask. .

In the sputtering method, a transparent conductive film having a desired pattern is deposited on a substrate by allowing sputtered particles flying from a sputtered target to pass through openings provided in a main body of a mask in a deposition chamber. An electrode consisting of is formed. A mask with such openings is also called an open mask.

For this reason, sputtered particles adhere to the outer surface of the main body of the mask other than the openings, and the deposit becomes thicker as the number of film formations (that is, the number of film formation batches) increases. If the film becomes extremely thick, the deposits adhered to the mask will detach and peel off from the main body of the mask, be released into the film forming space, contaminate the film forming environment, and eventually fall and adhere to the object to be processed, resulting in a transparent film. There is a possibility that the electrode made of the conductive film may be adversely affected.

In order to solve this problem, conventionally, cleaning of the mask, that is, cleaning for removing deposits adhering to the mask, has been performed according to the number of film formations (the number of film formation batches). A wet method is generally adopted for mask cleaning processing because it is inexpensive (Patent Document 1).
If the deposit adhering to the mask is a transparent conductive film, the transparent conductive film can be removed from the main body of the mask by using an acidic etching solution.

In recent years, organic EL screens have become even larger, and an object (substrate) to be processed has been required to be larger in size, that is, to have a larger area. Similarly to the organic EL material, the electrode material forming the transparent conductive film is also deposited on the substrate through the openings of the mask. However, if the mask thermally expands significantly due to the temperature of the film formation process, the larger the mask (larger area), the greater the displacement of the film formation position, making it impossible to form an electrode pattern at an accurate position.

Therefore, the mask is required to have "small thermal expansion". In addition, when the area becomes large, "being as light as possible" is also an important factor. In other words, the members constituting the main body of the mask are subject to the restriction that they should not be "stretchable or heavy", and members such as Invar and SUS430 are preferably used.

Examples of the above-mentioned "attached deposits to be removed" include transparent conductive films made of oxide film materials such as IZO, ITO, IGZO, and ZnO.
Here, IZO is indium zinc oxide, ITO is tin oxide doped indium oxide [In2O3-SnO2], IGZO is indium (In), gallium (Ga), zinc (Zn), oxygen (O) and ZnO means zinc oxide, respectively.

As described above, it is possible to remove the deposits from the mask body by immersing the mask body with such deposits in an acidic etching solution. However, the material (Invar and SUS430) constituting the mask body is a ferrous material with low chemical corrosion resistance, and the mask body is easily eroded by the acidic etching solution (i.e., the mask body is damaged). The inventors have found that there is a problem that
Accordingly, the present inventors have developed a method for cleaning a mask that can remove deposits adhering to the main body of the mask and that can suppress erosion of the main body of the mask.

JP 2018-095897 A

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mask cleaning method capable of removing deposits adhering to the main body of the mask and suppressing erosion of the main body of the mask. aim.

In order to solve the above problems, the present invention provides a mask cleaning method for removing deposits adhering to a mask, comprising:
An etching solution containing a chelating agent is used as a cleaning solution, and at least a step of immersing the mask in the cleaning solution is provided, the main body of the mask is made of a ferrous material with low chemical corrosion resistance, and the deposits attached to the mask are IZO and ITO. , IGZO, and ZnO, the etching solution used is a solution having solubility of Zn and In in an alkaline region, and the chelating agent has molecular constituent elements of C, O, H , and Na, using those containing no C other than the main chain,
It is characterized by

In the mask cleaning method,
Preferably, the chelating agent is the hydroxycarboxylic acid sodium gluconate.

In the step of immersing the mask in the cleaning liquid,
It is preferable that the temperature of the cleaning liquid is in the range of 50°C or higher and 60°C or lower.

The step of immersing the mask in the cleaning solution includes:
a step A of preparing pure water as a base of the cleaning liquid in a cleaning container;
A step B of adding an alkaline first chemical solution (solution) to the cleaning solution of the step A;
Step C of adding a second chemical solution (solution) made of sodium gluconate to the washing solution of step B;
a step D of stirring the cleaning liquid of the step C;
a step E of heating and maintaining the cleaning liquid of the step D at a predetermined temperature;
A step F of immersing the mask in the cleaning solution of the step E and performing ultrasonic cleaning at a frequency of 80 kHz to 12 kHz,
It is preferable to prepare in order.

The step of immersing the mask in the cleaning solution includes:
A step G of removing the chemical solution by rinsing the mask taken out from the cleaning solution of the step F with pure water;
a step H of removing contamination by rinsing again with pure water the mask that has undergone the step G;
A step I of drying the mask that has undergone the step H,
Furthermore, it is preferable to prepare in order.

In the mask cleaning method according to the present invention, an etching solution containing a chelating agent is used as a cleaning liquid in order to remove deposits adhering to the mask. For example, Zn, In) and its ions (Ion) are incorporated. This action can prevent the phenomenon of saturation of dissolution.
Moreover, by using a chelating agent whose molecular constituent elements are composed of C, O, H, and Na, and which does not contain C other than the main chain, the effect of the residue on the main body of the mask is reduced. Therefore, erosion of the main body of the mask is suppressed.
Therefore, the present invention simultaneously solves the two problems described above (that is, the problem that the dissolution of the deposit stops in the middle and the deposit cannot be completely removed, and the problem that the main body of the mask is eroded). It contributes to the provision of a mask cleaning method that enables

5 is a graph showing the effect of the mask cleaning method according to the present invention. 1 is a flowchart of a mask cleaning method according to the present invention. Potential-pH diagram of zinc (Zn). Potential-pH diagram of indium (In). Potential-pH diagram for tin (Sn). FIG. 4 is a schematic diagram illustrating a state in which deposits adhere to a mask;

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 is a schematic diagram illustrating a state in which deposits adhere to a mask.
In FIG. 6, reference numeral 10 denotes a target (for example, ITO) for a transparent conductive film, and reference numeral 20 denotes sputtered particles sputtered from the target 10 and flying.
The sputtered particles 20 that have passed through the openings provided in the main body of the mask 30 are deposited on the substrate 40 to form an electrode composed of a transparent conductive film 50 having a desired pattern, for example. In FIG. 5 , the spaces between the main bodies of the mask 30 represent openings provided in the main body of the mask 30 .

At that time, sputtered particles adhere to the outer surface of the main body of the mask 30 other than the openings. Reference numeral 60 represents deposits adhering to this mask 30 . The deposit 60 becomes thicker as the number of film formations (that is, the number of film formation batches) increases.

If the deposit 60 adhering to the mask 30 becomes extremely thick, there will be a problem with the film formation atmosphere. That is, the deposit 60 separates and peels off from the main body of the mask 30 and is released into the film forming space, contaminating the film forming environment. As a result, a phenomenon occurs in which the detached/peeled deposit 60 falls and adheres to the substrate 40, which is the object to be processed. If the falling/adhering matter composed of such deposits 60 mixes with the transparent conductive film 50 formed on the substrate 40, the conductivity of the electrode composed of the transparent conductive film 50 is deteriorated, or the surface thereof is damaged. There arises a problem that various properties of the film are degraded, such as the profile being roughened.

In order to solve the above problems, the present inventors have developed a “potential-pH diagram of zinc (Zn)” shown in FIG. 3, a “potential-pH diagram of indium (In)” shown in FIG. 4, and FIG. From the "potential-pH diagram of tin (Sn)" shown in , it was conceived that the following mechanism might work.
(a1) Zn and In hydroxides are soluble in the Alkaline region.
(a2) However, since the solubility product is small, the dissolution is saturated.
(a3) Then, how about adding a material having a chelate effect to the alkaline solution?
(a4) This may enable the incorporation of dissolved Zn, In, and Ion.
(a5) As a result, is it possible to prevent saturation?

Specifically, when the Alkaline concentration is "1 to 10%", the Alkaline type is "NaOH, KOH", the sodium gluconate concentration is "0.1 to 5%", and the treatment liquid temperature is "25 to 60°C" ,
Based on Figure 4,
[Sn2+][OH-]2 = 6.3 x 10-27 (mol/l)3 (at 25°C, ionic strength 0)
was calculated.
It was expected that such action would also be effective for the ITO material.

FIG. 1 is a graph showing the effects of the present invention (mask cleaning method). This is the result of application to deposit 60 adhering to mask 30 .
Here, as the cleaning liquid, pure water was added with KOH as an alkaline solution (first chemical solution) and sodium gluconate as a chelating agent (second chemical solution) and stirred. As a sample, a mask body (open mask material) made of Invar and a deposit made of an IZO film was used.

FIG. 1 shows the results of evaluating the weight change of the main body of the mask before and after deposits adhere. From FIG. 1, it was found that the main body of the mask was not dissolved because it was before deposits adhered (Before: 0.8238 g) and after deposits adhered (After: 0.8237 g). . At that time, it was confirmed that the removal rate of the IZO film was 90% or more.

In order to be applied to the cleaning of large area masks, the following two points are required for the treatment liquid.
(b1) The treatment liquid should be inexpensive.
(b2) High safety.
Sodium gluconate used as a chelating agent (second chemical solution) is also used in foods and satisfies the above two conditions.

In order to confirm the actions and effects described above, 5 processing conditions (Experimental Examples 1 to 5) shown in Table 1 were performed. As the samples of Experimental Examples 1 to 5, the same samples as those evaluated in FIG. 1 were used.
In Experimental Example 1, the treatment liquid is 5% KOH and the temperature of the treatment liquid is 50.degree. The aim of Experimental Example 1 is to protect the base material (main body of the mask).
In Experimental Example 2, the treatment liquid is 10% KOH and the temperature of the treatment liquid is 50.degree. The aim of Experimental Example 1 is to protect the base material (main body of the mask).
In Experimental Example 3, the treatment liquid is composed of 5% KOH and Al(NO3)3, and the temperature of the treatment liquid is 50.degree. The aim of Experimental Example 3 is to impart oxidizing properties.
In Experimental Example 4, the treatment liquid is composed of 5% KOH, Al(NO3)3 and H2O2, and the temperature of the treatment liquid is 50.degree. The aim of Experimental Example 4 is to impart oxidizing properties.
In Experimental Example 5, the treatment liquid is 5% KOH and 1% sodium gluconate (abbreviated as "GA" in Table 1), and the temperature of the treatment liquid is 50.degree. The aim of Experimental Example 5 is to confirm the chelate effect.
In Experimental Example 6, the treatment liquid is 10% KOH and 1% sodium gluconate (abbreviated as "GA" in Table 1), and the temperature of the treatment liquid is 50.degree. The aim of Experimental Example 6 is to confirm the chelate effect.

Table 1 summarizes the evaluation results along with the processing conditions and aims of Experimental Examples 1 to 5. In Table 1, the film removability is the rate at which the deposited film is removed from the main body of the mask, where ◯ indicates 90% or more, and X indicates less than 90%. Base material wear is the weight change of the main body of the mask, and the ◯ mark indicates the case where there is no weight change as shown in FIG.

From Table 1, the following points became clear.
(c1) When the treatment liquid is only KOH, the substrate wear can be achieved, but the film removability is insufficient (Experimental Examples 1 and 2).
(c2) When the treatment liquid consists of KOH and Al(NO3)3, the base material wear can be achieved, but the film removability is insufficient (Experimental Example 3).
(c3) When the treatment liquid consists of KOH, Al(NO3)3 and H2O2, the substrate wear can be achieved, but the film removability is insufficient (Experimental Example 4).
(c4) When the treatment liquid is composed of KOH and sodium gluconate, it is possible to reduce the wear of the base material and to have sufficient film removability (Experimental Examples 5 and 6).

From the above evaluation results, by using an etching solution containing a chelating agent as a treatment liquid (cleaning liquid), the chelating agent has a chelating effect, and elements (for example, Zn, In) dissolved from the deposit and their ions (Ion) can be incorporated, and it was confirmed that this action prevents the phenomenon of saturation of dissolution.
That is, according to Experimental Examples 5 and 6, it was found that the film can be removed with an acidic etching solution, but the problem that the open mask material (Invar) is eroded can be solved. The solution is to use an Alkaline solution as a base and add sodium gluconate to suppress base material erosion and make it possible to remove the IZO film. As a result, the open mask material is prevented from being eroded, and the IZO film can be removed in about 1 hour.

In order to obtain such effects, it is preferable to use, as the chelating agent, one whose molecular constituent elements are C, O, H, and Na, and which does not contain C other than the main chain. As a result, the effect of the residue on the mask body is reduced, and erosion of the mask body is suppressed.
Therefore, the present invention simultaneously solves the two problems described above (that is, the problem that the dissolution of the deposit stops in the middle and the deposit cannot be completely removed, and the problem that the main body of the mask is eroded). To provide a mask cleaning method that can be eliminated.

The present invention has been achieved by the following mechanism.
(d1) Zn and In hydroxides are soluble in the Alkaline region.
(d2) However, since the solubility product is small, the dissolution is saturated.
(d3) Therefore, a material having a Chelate effect was added.
(d4) This takes in dissolved Zn, In, and Ion.
(d5) As a result, saturation can be prevented.

Preferred processing conditions in the present invention are as follows.
・ Alkaline concentration: 1 to 10%
・Alkaline types: NaOH, KOH
・Sodium gluconate concentration: 0.1 to 5%
・Processing liquid temperature: 25 to 60°C

Examples of the base material (main body of the mask) to which the present invention is applied include ferrous materials with low chemical corrosion resistance such as Invar and SUS430.

Chelate materials to which the present invention is applied include aminocarboxylic acids, hydroxycarboxylic acids, and inorganic materials.
・In this alkaline range (including pH 14 or higher), sodium gluconate, which is a hydroxycarboxylic acid, is effective in the pH range.
・C is not included except for the main chain of the Chelate material, and the effect of residue on the base material is the least. The molecular structure elements are C, O, H, and Na, and Na can be removed as Ion in the final precision cleaning.
・Inorganic systems are often used, but Ion phosphate attracts attention as a contaminant element, so it is not preferable in the present invention.

The processing procedure (procedure of the step of immersing the mask in the cleaning solution) of the present invention is as follows.
・Pure water→Introducing Alkaline→Injecting sodium gluconate→Stirring→Warming (up to 60℃)
→ US (80-120 kHz) → Rinse with pure water (remove chemicals) → Rinse with pure water (remove contaminants) → Dry Please refer to the flowchart (Fig. 2) of the mask cleaning method according to the present invention for details of each treatment process. , are described below.

That is, the step of immersing the mask in the cleaning solution includes:
a step A of preparing pure water as a base of the cleaning liquid in a cleaning container;
A step B of adding an alkaline first chemical solution to the cleaning solution of the step A;
A step C of adding a second chemical solution made of sodium gluconate to the washing solution of the step B;
a step D of stirring the cleaning liquid of the step C;
a step E of heating and maintaining the cleaning liquid of the step D at a predetermined temperature;
A step F of immersing the mask in the cleaning solution of the step E and performing ultrasonic cleaning (also abbreviated as US) at a frequency of 80 kHz to 12 kHz;
Prepare in order.

For the steps A to E described above, for example, the following conditions are selected.
Step A: Pure water (for example, semiconductor cleaning grade) is used.
Step B: Add a semiconductor cleaning grade NaOH solution.
Step C: Use sodium gluconate with a purity of 95% or more.
Step D: Stir with a circulation pump.
Step E: The treatment liquid is heated to a predetermined temperature using a heater or the like.
Process F: U.S.A. provided in the washing tank while operating the circulation pump. S. Irradiate at 80 kHz.

Further, the step of immersing the mask in the cleaning solution includes:
A step G of removing the chemical solution by rinsing the mask taken out from the cleaning solution of the step F with pure water;
a step H of removing contamination by rinsing again with pure water the mask that has undergone the step G;
A step I of drying the mask that has undergone the step H,
Prepare further.

For the steps G to I described above, for example, the following conditions are selected.
Step G: The chemical solution is removed by pure water immersion or pure water shower.
Process H: pure water U.S. S. Perform rinsing treatment (2 to 3 tanks).
Step I: Using HFE (Hydro Fluoro Ether) or IPA (Isopropyl Alcohol)
Remove moisture and mask dry.

The method for cleaning a mask according to the present invention achieves the effects of the present invention by including the step of immersing the mask in the cleaning liquid, which consists of Steps A to I.

In the above experimental example, the deposited film is the IZO film, but the present invention is not limited to the IZO film. The present invention is also effective when the deposited film is an ITO film, an IGZO film, or a ZnO film.
It does not depend on the deposition method for forming the deposited film. A sputtering method, a vapor deposition method, a CVD method, and the like can be used as the film forming method.

INDUSTRIAL APPLICABILITY The present invention can be widely applied to a mask cleaning method. In particular, it is effective for a mask having an opening (open mask), but the present invention applies to parts other than masks (parts that are placed inside a film deposition apparatus and are expected to have the effect of removing deposited films), For example, it can be used to clean parts such as shower plates and shutters.

Claims (5)

A mask cleaning method for removing deposits adhering to a mask, comprising:
Using an etching solution containing a chelating agent as a cleaning solution,
comprising at least the step of immersing the mask in the cleaning solution ;
The main body of the mask is an iron-based material with low chemical corrosion resistance,
the deposit adhering to the mask is an oxide film material selected from IZO, ITO, IGZO, and ZnO;
As the etching solution, a solution having solubility of Zn and In in an alkaline region is used,
A method of cleaning a mask, wherein the chelating agent is composed of C, O, H, and Na as molecular constituent elements, and contains no C other than the main chain. wherein the chelating agent is the hydroxycarboxylic acid sodium gluconate;
The mask cleaning method according to claim 1 , characterized in that: In the step of immersing the mask in the cleaning liquid,
2. The method of cleaning a mask according to claim 1, wherein the temperature of said cleaning liquid is in the range of 50[deg.] C. or more and 60[deg.] C. or less. The step of immersing the mask in the cleaning solution includes:
a step A of preparing pure water as a base of the cleaning liquid in a cleaning container;
A step B of adding an alkaline first chemical solution to the cleaning solution of the step A;
A step C of adding a second chemical solution made of sodium gluconate to the washing solution of the step B;
a step D of stirring the cleaning liquid of the step C;
a step E of heating and maintaining the cleaning liquid of the step D at a predetermined temperature;
A step F of immersing the mask in the cleaning solution of the step E and performing ultrasonic cleaning at a frequency of 80 kHz to 12 kHz,
2. The method of cleaning a mask according to claim 1, wherein the masks are provided in order. The step of immersing the mask in the cleaning solution includes:
A step G of removing the chemical solution by rinsing the mask taken out from the cleaning solution of the step F with pure water;
a step H of removing contamination by rinsing again with pure water the mask that has undergone the step G;
A step I of drying the mask that has undergone the step H,
5. The method of cleaning a mask according to claim 4 , further comprising sequentially providing.

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