JP6969904B2 - Wet etching method and wet etching equipment for photomasks - Google Patents

Description

The present invention relates to a wet etching method and a wet etching apparatus in a process of manufacturing a photomask used for a flat panel display or the like.

A photomask used in a technical field such as a flat panel display has a pattern such as a light-shielding film, a halftone film, and a phase shift film. As the material of these patterns, Cr-based materials, that is, Cr compounds such as Cr (chromium), Cr oxide, and Cr oxynitride are mainly used, and one type or a plurality of types are used in one photomask substrate. Cr-based materials are used.

In the photomask manufacturing process, when a film of Cr-based material (hereinafter referred to as Cr-based material film) is etched using a pattern such as a photoresist as a mask, a wet etching method is often used from the viewpoint of manufacturing cost. When the wet etching method is adopted, the various Cr-based material films are generally etched with an etching solution containing cerium (IV) ions (tetravalent cerium ions).
Hereinafter, for the sake of simplicity, "cerium (IV) ion" may be referred to as "cerium (IV)", and "etching solution containing cerium (IV) ion" may be referred to as "cerium (IV) etching solution".

As the cerium (IV) etching solution, a mixed solution of cerium (IV), an acid (for example, perchloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid) and water is used. As the cerium (IV), a cerium (IV) complex (tetravalent cerium complex) such as, for example, second cerium sulfate, second cerium nitrate or second cerium ammonium nitrate is used.

Patent Document 1 discloses a wet etching apparatus that can be used in a photomask manufacturing process. The Cr film is etched so that it can be immediately washed with pure water after being immersed or sprayed with an etching solution containing dicerium ammonium nitrate as the main component. Therefore, it is said that the wet processing can be controlled reliably.

Japanese Patent Application Laid-Open No. 1-370116

If the etching solution remains in the wet etching step of the photomask, pattern defects may occur. Therefore, it is necessary to sufficiently remove the residue of the wet etching solution.
As disclosed in Patent Document 1, after the treatment with the etching solution, the etching solution is eliminated (washed out) and the wet etching time is accurately controlled by continuously and promptly washing with a pure water spray. It is possible to do.
However, with the miniaturization of patterns due to higher image quality of flat panel displays, fine pattern defects that have not been a problem in the past have also affected the product yield in recent years.

As a result of investigating the pattern after wet etching in detail, the inventor confirmed that fine etching non-uniformity exists even when the pattern is sufficiently washed with pure water, and the fine etching non-uniformity is found. As a result of diligent research on the root cause, it was found that the cause was the cleaning itself with pure water after etching. That is, the etching liquid used for etching the Cr film is hydrolyzed to form hydrate when the liquid approaches neutrality by the washing step with pure water after etching. This hydrate was the cause of the etching non-uniformity.

The present invention has been made based on the above findings, and an object of the present invention is to provide a wet etching method and a wet etching apparatus capable of suppressing etching non-uniformity in a photomask manufacturing process.

The wet etching method according to the present invention is
The first step of supplying an acidic etching solution to a photomask substrate having a Cr-based material film on the surface and etching the Cr-based material film, and
A second step of supplying an acidic first chemical solution that does not etch the Cr-based material film to the photomask substrate, and a second step.
A third step of supplying pure water to the photomask substrate is included in this order. In this way, before cleaning with pure water, which was conventionally performed immediately after the etching process, cleaning with an acidic chemical solution to suppress the formation of hydrate eliminates the cause of etching non-uniformity. be able to. Here, the "acidic etching solution" in the present invention is an example of a solution capable of suppressing the generation of hydrate, and may be another solution as long as it suppresses the generation of hydrate, in particular. Not limited.

Further, the wet etching method according to the present invention is
The etching solution is characterized by containing cerium (IV) ions and a first chemical solution.

Further, the wet etching method according to the present invention is
The cerium (IV) ion is a cerium (IV) ion supplied by one or more acids selected from second cerium sulfate, second cerium nitrate and second cerium ammonium nitrate, and the first chemical solution is It is characterized by being one or more acids selected from perchloric acid, nitric acid, sulfuric acid, phosphoric acid and acetic acid.

In the wet etching method according to the present invention, since the etching solution is removed from the photomask substrate by an acidic chemical solution, the formation of hydrate due to the hydrolysis of cerium (IV) can be prevented. As a result, non-uniform etching of the Cr-based material film can be suppressed.

Further, the wet etching method according to the present invention is
It is characterized in that the pH of the etching solution and the pH of the first chemical solution are the same.

Further, the wet etching method according to the present invention is
The acid contained in the etching solution is the same as the acid in the first chemical solution.

By using such a chemical solution, the generation of the hydrate can be suppressed more effectively.

Further, the wet etching method according to the present invention is
Prior to the first step, an acidic second chemical solution that does not etch the Cr-based material film is supplied to the photomask substrate.

Further, the wet etching method according to the present invention is
The second chemical solution is the same as the first chemical solution.

By adopting such a wet etching method, it is possible to prevent the etching solution from scattering and adhering to the surface of the photomask substrate, and further suppress non-uniform etching of the Cr-based material film.
Further, even in a fine etching mask pattern, the wettability and permeability of the etching solution can be improved, and the etching non-uniformity can be suppressed.

The wet etching apparatus according to the present invention is
It is equipped with a first processing tank, a second processing tank, a third processing tank, and a transfer device for a photomask substrate.
The first processing tank includes a supply unit that supplies an acidic etching solution for etching a Cr-based material film to the photomask substrate.
The second treatment tank includes a supply unit for supplying an acidic first chemical solution that does not etch the Cr-based material film to the photomask substrate.
The third treatment tank includes a supply unit that supplies pure water to the photomask substrate.
The transport device is characterized in that the photomask substrate is transported to the first processing tank, the second processing tank, and the third processing tank in this order.

With such a wet etching apparatus configuration, while suppressing the generation of cerium hydrate, the etching of the Cr-based material film by the etching solution is controlled, and the wet etching process of the Cr-based material with good uniformity can be performed. Can be executed.

Further, the wet etching apparatus according to the present invention is
Further equipped with a fourth processing tank
The fourth treatment tank includes a supply unit for supplying an acidic second chemical solution that does not etch the Cr-based material film to the photomask substrate.
The transfer device is characterized in that the photomask substrate is transferred to the fourth processing tank, the first processing tank, the second processing tank, and the third processing tank in this order.

With such a wet etching apparatus configuration, it is possible to prevent the etching solution from scattering and adhering to the photomask substrate surface on the photomask substrate surface, and further suppress non-uniform etching of the Cr-based material film. Wet etching processing can be performed.

According to the present invention, by suppressing the etching non-uniformity in the etching process of the photomask, it is possible to suppress the occurrence of fine pattern defects and prevent the product yield from being lowered due to the suppression.

The flow chart which compares and shows the main steps of the conventional wet etching method and the wet etching method of Embodiment 1. The cutaway perspective view which shows the main structure of the wet etching apparatus for performing the wet etching by Embodiment 1. FIG. The cutaway perspective view which shows the main structure of the wet etching apparatus for performing the wet etching by Embodiment 1. FIG. The cutaway perspective view which shows the main structure of the wet etching apparatus for performing the wet etching by Embodiment 1. FIG. The flow chart which shows the main process of the wet etching method of Embodiment 2. The cutaway perspective view which shows the main structure of the wet etching apparatus for performing the wet etching by Embodiment 2. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, none of the following embodiments give a limiting interpretation in finding the gist of the present invention. Further, the same or the same kind of members may be designated by the same reference numerals and the description thereof may be omitted.

(Embodiment 1)
1 (a) and 1 (b) show the main steps of the conventional wet etching method and the wet etching method of Embodiment 1, respectively.

In the conventional wet etching method shown in FIG. 1 (a), a photomask substrate (hereinafter, may be simply referred to as a substrate) having an etching mask pattern such as a Cr-based material film and a photoresist is prepared.
S01 (etching liquid treatment): A step of supplying a cerium (IV) etching liquid to a substrate by spraying or the like to etch a Cr-based material film.
S02 (pure water treatment): A step of supplying pure water to a substrate by spraying or the like to remove a cerium (IV) etching solution.
S03 (Drying): The steps of blowing air onto the substrate, removing pure water, and drying the substrate are executed in the above order.

Immediately after the step of S01, the cerium (IV) etching solution remains on the surface of the substrate. In the step of S02, pure water is supplied to the surface of the substrate by spraying or the like to wash away the cerium (IV) etching solution, and pure water is used. Performs the process of replacing with. Since the cerium (IV) etching solution is removed by this step, the etching of the Cr-based material film on the substrate surface can be stopped.
As a result, the etching time can be controlled, the Cr-based material film can be prevented from being unnecessarily etched, and the pattern of the Cr-based material film defined by the etching mask pattern can be formed.

When the pattern of the Cr-based material film formed by the above method was investigated in detail, it was found that even when the etching time was accurately controlled, minute non-uniformity of etching remained. This minute non-uniformity can cause a CD error of the pattern as the miniaturization progresses.

As a result of detailed research on the cause of this non-uniformity, it was found that it was caused by the S02 process, contrary to the conventional wisdom. That is, cerium (IV) exists stably in an acidic liquid, but when the liquid approaches neutrality, it hydrolyzes to become a hydrate. As a result of investigating the pH dependence of the acidic liquid, it was found that the cerium (IV) etching solution also depends on the added acid, but typically starts hydrolysis when the pH exceeds 1.0. ..
In the step S02, since pure water is supplied to the cerium (IV) remaining on the substrate surface, cerium hydrate is generated on the surface. As a result, cerium (IV) and hydrate are mixed on the substrate.
In particular, as the screen size of the display device increases and the photomask substrate becomes larger (for example, the long side is 1.5 [m] or more), the flow rate of pure water used for pure water cleaning increases, so that cerium is used. The generation of hydrate tends to increase.

The mixture of cerium (IV) and hydrate causes a slight difference in the etching amount of the Cr-based material film, that is, non-uniformity. As a result, a CD error may occur in the pattern of the formed Cr-based material film, which may be visually recognized as pattern unevenness. As the required tolerance for CD error becomes stricter (smaller) with miniaturization, there is a risk that the product yield of the photomask will decrease.

Hereinafter, a method of suppressing the generation of the above-mentioned hydrate and stopping the etching of the Cr-based material film will be described with reference to FIG. 1 (b).

As shown in FIG. 1 (b), in the wet etching method according to the present embodiment, a photomask substrate having an etching mask pattern such as a Cr-based material film and a photoresist is prepared.
S11 (etching liquid treatment): A step of supplying a cerium (IV) etching liquid to a substrate by spraying or the like to etch a Cr-based material film.
S12 (acid treatment): An acidic liquid (hereinafter referred to as the first chemical solution) that does not contain cerium (IV) and does not etch the Cr-based material film is supplied to the substrate by spraying or the like, and cerium (IV) etching is performed. The process of removing the liquid,
S13 (pure water treatment): A step of supplying pure water to the substrate by spraying or the like to remove the first chemical solution.
S14 (drying): A step of blowing air onto the substrate, removing pure water, and drying the substrate.
Are executed in the above order.

The S11 step is the same as the above S01 step.
Here, the cerium (IV) etching solution is as described above, and is an etching solution containing cerium (IV) and the first acid. The cerium (IV) is supplied by, for example, one or more acids selected from secondary cerium sulfate, secondary cerium nitric acid and ammonium secondary cerium nitrate, and the first acid is perchloric acid, nitric acid and sulfuric acid. , Phosphoric acid and one or more acids selected from acetic acid. The etching solution is a mixture of an acid that supplies cerium (IV), a first acid, and water, and is adjusted to a pH at which cerium (IV) is stably present. Specifically, the pH of the cerium (IV) etching solution is preferably 1.0 or less. The cerium (IV) etching solution may contain a surfactant.

In the step of S12, the cerium (IV) etching solution remaining on the substrate is washed away with the first chemical solution, and the cerium (IV) etching solution on the substrate is replaced with the first chemical solution.
As the first chemical solution, for example, one or more acids selected from perchloric acid, nitric acid, sulfuric acid, phosphoric acid and acetic acid can be used. More specifically, an acidic liquid having the same pH (for example, 1.0 or less) as the cerium (IV) etching solution, for example, nitric acid having a concentration of 0.1 [mol / L] or more, perchloric acid or a concentration of 0.05. Sulfuric acid of [mol / L] or more can be preferably used, but the present invention is not limited thereto.

Since cerium (IV) is stably present in an acidic liquid, hydrate is not generated in the S12 step. As a result, even in a state where the cerium (IV) etching solution and the first chemical solution are mixed, the CD error due to the cerium hydrate does not occur.
Further, since the cerium (IV) etching solution is removed by the first chemical solution, the etching of the Cr-based material film is stopped by the step of S12.

As the first chemical solution, the same acid as that used in the cerium (IV) etching solution can be preferably used. For example, when the cerium (IV) etching solution is a mixed solution of nitric acid secondary cerium ammonium nitrate, perchloric acid and water, a mixed solution of nitric acid or perchloric acid or nitric acid and perchloric acid can be used. It is not limited to. It may not be mixed with a cerium (IV) etching solution to generate hydrate.

Further, as the first chemical solution, an acidic liquid having the same pH as the cerium (IV) etching solution can be preferably used as described above in order to prevent hydrolysis of cerium (IV), but the first chemical solution is not limited to this. No. The pH may be the same as that of the cerium (IV) etching solution, and the pH may be such that the pH is in a range that does not leave hydrate on the substrate when mixed with the cerium (IV) etching solution.
By mixing the cerium (IV) etching solution and the first chemical solution in advance and investigating the presence or absence of hydrate generation and the hydrate formation rate, the acid that can be used as the first chemical solution can be used. The type and concentration can be determined. Further, even if the hydrolysis of cerium (IV) may be started in the first chemical solution, it may be flushed together with the first chemical solution so that no hydrate remains on the substrate.

In the step S13, pure water is supplied to the surface of the substrate, but at this stage, cerium (IV) does not remain on the surface of the substrate, so that no hydrate is generated.

Conventionally, the etching with the cerium (IV) etching solution was stopped by using pure water, but in this embodiment, the cerium is mixed with the cerium (IV) etching solution to form an acidic liquid that does not form a hydrate. (IV) By stopping the etching with the etching solution, the non-uniformity of etching of the Cr-based material film can be suppressed.

(Etching device)
Next, a wet etching apparatus for carrying out the wet etching method of the present embodiment will be described.
FIGS. 2, 3 and 4 are notched perspective views showing the main configuration of the wet etching apparatus 1 for performing the wet etching according to the present embodiment.

As shown in FIG. 2, the wet etching apparatus 1 includes a first processing tank 2 for processing S11, a second processing tank 3 for processing S12, and a third processing tank 4 for processing S13. Be prepared.
A separation barrier for separating each treatment tank is provided between the first treatment tank 2 and the second treatment tank 3 and between the second treatment tank 3 and the third treatment tank 4. May be good. In this case, the separation wall is provided with an opening with a shutter for transporting the photomask substrate 5. When the photomask substrate 5 is conveyed, the shutter is opened and the opening is passed through the opening to move the photomask substrate 5 from the first processing tank 2 to the second processing tank 3 and from the second processing tank 3 to the third processing tank 4. By transporting the photomask substrate 5 of the above and closing the shutter after the transport is completed, it is possible to prevent the chemical solution from being mixed between the treatment tanks.

The first treatment tank 2 includes a first chemical liquid pipe 6 for transferring the cerium (IV) etching liquid. The first chemical liquid pipe 6 is connected to a chemical liquid tank and a liquid pump (not shown), and the cerium (IV) etching solution stored in the chemical liquid tank is made to flow into the first chemical liquid pipe 6 by the liquid pump.

The first chemical solution pipe 6 transfers the cerium (IV) etching solution. The first chemical liquid pipe 6 is provided with an outlet 7, for example, a nozzle for flowing out the cerium (IV) etching liquid.
The first chemical liquid pipe 6 and the outflow port 7 form a supply unit for the cerium (IV) etching liquid to the surface of the photomask substrate 5.
The cerium (IV) etching solution is sprayed or showered onto the photomask substrate 5 from the outlet 7 to execute the S11 step.
After a predetermined etching time calculated from the film thickness of the Cr-based material film and the etching rate has elapsed, the outflow of the cerium (IV) etching solution is stopped.

The cerium (IV) etching solution that has flowed out is collected via a chemical solution discharge port (not shown) provided at the bottom of the first treatment tank 2, and is transferred by a liquid circulation pump to filter foreign substances. It is returned to the first chemical solution pipe 6 through the filter of. That is, the cerium (IV) etching solution is used in a circulating manner.

Further, the cerium (IV) etching solution may flow out from the outlet 7 to the photomask substrate 5 while moving the first chemical solution pipe 6 in parallel with the transport direction of the photomask substrate 5.

Next, as shown in FIG. 3, in order to execute the S12 step, the photomask substrate 5 is transferred to the second processing tank 3 by a transfer device 8, for example, a belt conveyor.
The transport device 8 may be a crane-type transport device that lifts and transports the photomask substrate 5. In this case, it is not necessary to provide an opening for passing the photomask substrate 5 in the separation wall that separates each treatment tank.

The second treatment tank 3 includes a second chemical liquid pipe 9 for transferring the first chemical liquid.
The second chemical liquid pipe 9 is connected to a liquid tank and a liquid pump (not shown), and the liquid pump causes the first chemical liquid stored in the liquid tank to flow into the second chemical liquid pipe 9.

The second chemical liquid pipe 9 is provided with an outlet 10, for example, a nozzle for letting out the first chemical liquid.
The second chemical solution pipe 9 and the outflow port 10 form a supply unit for the first chemical solution to the surface of the photomask substrate 5.
The first chemical solution is sprayed or showered onto the photomask substrate 5 from the outlet 10 to execute the S12 step. The first chemical solution is discharged for a predetermined time, and after the cerium (IV) etching solution is removed from the photomask substrate 5, the outflow of the first chemical solution is stopped.

Next, as shown in FIG. 4, in order to execute the S13 step, the photomask substrate 5 is transported to the third processing tank 4 by the transport device 8.
The third treatment tank 4 includes a third chemical liquid pipe 11 for transferring pure water.
The third chemical liquid pipe 11 is connected to a liquid tank and a liquid pump (not shown), and the pure water stored in the liquid tank is made to flow into the third chemical liquid pipe 11 by the liquid pump.

The third chemical liquid pipe 11 is provided with an outlet 12, for example, a nozzle for allowing pure water to flow out.
The third chemical liquid pipe 11 and the outlet 12 form a pure water supply unit to the surface of the photomask substrate 5.
Pure water is sprayed or showered onto the photomask substrate 5 from the outlet 12 to execute the S13 step. Pure water is discharged for a predetermined time, and after the first chemical solution is removed (washed out) from the photomask substrate 5, the outflow of pure water is stopped.

Next, the air transferred by the pipe 13 is ejected from the ejection port 14, for example, an air knife to the photomask substrate 5, and the S14 process is executed.
Although the ejection port 14 is arranged only on the upper surface side of the photomask substrate 5 in FIG. 4, it may be arranged on the back surface side and the back surface of the photomask substrate 5 may be dried at the same time.

However, for example, when the next step is a wet treatment, it is not always necessary to dry the photomask substrate 5 by the S14 step. The step S14 may be executed according to the processing content of the next step.

In the above embodiment, the photomask substrate 5 is held horizontally and transported, but the photomask substrate 5 may be tilted or held vertically and transported. The liquid or air may be ejected while being held at an angle or vertically.
Further, although an example in which the liquid flows out to the photomask substrate 5 is shown, it may be immersed in the liquid, for example, as in Patent Document 1, immersion in a cerium (IV) etching solution and a first acid and pure. It may be combined with the outflow of water.

The wet etching apparatus 1 can continuously perform wet etching processing of the photomask. In the above embodiment, an example of processing one photomask substrate 5 is shown, but a plurality of photomask substrates 5 may be continuously processed. However, in this case, it is necessary to set the processing time in each processing tank so that the S12 process processing can be performed promptly after the S11 process processing.

Although the wet etching apparatus 1 is provided with the second processing tank 3 and the third processing tank 4 independently, the second processing tank 3 may be omitted. In the third chemical liquid pipe 11 of the third treatment tank 4, the first chemical liquid and pure water may be switched and transferred.
That is, the first chemical solution is allowed to flow through the third chemical solution pipe 11 of the third treatment tank 4, the first chemical solution is discharged onto the substrate 5 for a predetermined time, then stopped, and after the S12 step is executed, the third chemical solution is executed. Pure water may flow through the third chemical solution pipe 11 of the treatment tank 4, the pure water may flow out onto the substrate 5, and the S13 step may be executed. Such processing can be performed by installing a switching valve between the third chemical liquid pipe 11 and the first chemical liquid tank and the pure water tank, and selecting the liquid to be flowed through the third chemical liquid pipe 11. Will be.
By omitting the second processing tank 3, the apparatus can be miniaturized.

(Embodiment 2)
FIG. 5 shows the main steps of the wet etching method of the second embodiment.
In the wet etching method according to the present embodiment, a photomask substrate having an etching mask pattern such as a Cr-based material film and a photoresist is prepared.
S21 (pretreatment): A step of supplying an acidic liquid (hereinafter referred to as a second chemical solution) that does not etch the Cr-based material film to the substrate by spraying or the like.
S22 (etching liquid treatment): A step of supplying a cerium (IV) etching liquid to a substrate by spraying or the like to etch a Cr-based material film.
S23 (acid treatment): An acidic liquid (hereinafter referred to as the first chemical solution) that does not contain cerium (IV) and does not etch the Cr-based material film is supplied to the substrate by spraying or the like, and cerium (IV) etching is performed. The process of removing the liquid,
S24 (pure water treatment): A step of supplying pure water to the substrate by spraying or the like to remove the first chemical solution.
S25 (drying): The steps of blowing air onto the substrate, removing pure water, and drying the substrate are performed in the above order.

The difference from the first embodiment is that the S21 step is added before the S22 step, which is the treatment step with the cerium (IV) etching solution.
The step S21 is a step of supplying the surface of the photomask substrate with the second chemical solution by spraying or showering, and covering (wetting) the surface of the photomask substrate with the second chemical solution.

As the second chemical solution, the same chemical solution as the first chemical solution can be used, and the details are as described in the first embodiment.
That is, the second chemical solution is as follows.
An acidic liquid having the same pH as the cerium (IV) etching solution, for example, perchloric acid, nitric acid, sulfuric acid, phosphoric acid or acetic acid, can be preferably used, but is not limited thereto. The pH may be the same as that of the cerium (IV) etching solution.
The same acid as that used in the cerium (IV) etching solution can be preferably used, but is not limited thereto.
It may not be mixed with a cerium (IV) etching solution to generate hydrate.

The S21 step prevents the cerium (IV) etching solution from scattering (adhering) to the photomask substrate and causing etching unevenness.
That is, when the cerium (IV) etching solution flows out onto the photomask substrate while the substrate surface is not covered with the liquid, the cerium (IV) etching solution splashes on the substrate surface and the etching is non-uniform at the reattached portion. (Unevenness) may occur.
By covering the surface of the photomask substrate with the second chemical solution, it is possible to prevent the etching non-uniformity due to the splashing and reattachment of the cerium (IV) etching solution.
Further, the second chemical solution prevents hydrolysis of the cerium (IV) etching solution, so that hydrate does not occur on the surface of the photomask substrate.
Further, by covering the surface of the photomask substrate with a second chemical solution in advance, the wettability and permeability of the cerium (IV) etching solution between the fine photomask patterns on the photomask substrate are enhanced, and the dimensions of the fine pattern are improved. It also has the effect of preventing the occurrence of variations.

FIG. 6 is a notched perspective view showing the main configuration of the wet etching apparatus 21 for performing the wet etching according to the second embodiment.
As shown in FIG. 6, the wet etching apparatus 21 has a configuration in which a fourth processing tank 15 is added to the wet etching apparatus 1 shown in FIG.
That is, the wet etching apparatus 21 processes the fourth processing tank 15 for processing the above S21, the first processing tank 2 for processing the above S22, and the second processing tanks 3 and S24 for processing the S23. The third processing tank 4 to perform is provided.

The fourth treatment tank 15 includes a fourth chemical liquid pipe 16 for transferring the second chemical liquid. The fourth chemical liquid pipe 16 is connected to a chemical liquid tank and a liquid pump (not shown), and the liquid pump causes the second chemical liquid stored in the chemical liquid tank to flow into the fourth chemical liquid pipe 16.

The fourth chemical solution pipe 16 transfers the second chemical solution. The fourth chemical solution pipe 16 is provided with an outlet 17, for example, a nozzle for allowing the second chemical solution to flow out.
The fourth chemical solution pipe 16 and the outflow port 17 form a second chemical solution supply unit to the surface of the photomask substrate 5.
The second chemical solution is sprayed or showered onto the photomask substrate 5 from the outlet 17, and the S21 step is executed.
After that, the transport device 8 transports the photomask substrate 5 to the first processing tank 2.

Since the following is the same as the step S11 of the first embodiment, the description thereof will be omitted.

The second chemical solution may be the same liquid as or different from the first chemical solution used in the S23 step. If the same liquid is used, the liquid tank can be shared, and the device can be miniaturized.

(Other embodiments) -Spin method-
In the above embodiment, an example of a spray method in which an etching solution or various chemical solutions is supplied by spraying has been described, but even in a spin type etching apparatus in which a substrate is rotated horizontally to supply chemical solutions, the etching solution or It is possible to carry out the present invention by appropriately providing supply pipes for various chemicals and pure water, and sequentially performing etching treatment, acid treatment, and pure water treatment in the same manner as in the first or second embodiment described above. ..

For example, when the process corresponding to the first embodiment is executed, the cerium (IV) etching solution is supplied from the first nozzle to the rotating substrate surface, and the entire substrate surface is covered with the cerium (IV) etching solution to perform the etching process. After that, the supply of the cerium (IV) etching solution is stopped.
After that, the first chemical solution is supplied from the second nozzle to the rotating substrate surface, and the cerium (IV) etching solution on the entire substrate surface is replaced with the first chemical solution to remove the cerium (IV) etching solution. , Stop the supply of the first chemical solution.
After that, pure water is supplied from the third nozzle to the surface of the rotating substrate, and the first chemical solution on the entire surface of the substrate is replaced with pure water to remove the first chemical solution, and then the supply of pure water is stopped. ..
After that, the substrate is rotated at high speed to shake off the pure water and spin dry.
A step of supplying a second chemical solution from the fourth nozzle and covering (wetting) the entire surface of the substrate with the second chemical solution is added before performing the etching process with the cerium (IV) etching solution, according to the second embodiment. The process corresponding to may be executed.

When supplying pure water or various chemicals to a rotating substrate, it is preferable to supply the substrate while rotating at a low speed. The reason is to suppress the mist generated by the rotation of the substrate in the spin cup as much as possible. Further, high-speed rotation may prevent a certain amount of chemical solution from being present on the substrate, and in that sense, low-speed rotation is preferable.
Further, in the case of performing the etching process, after forming a liquid film of the cerium (IV) etching solution on the entire surface of the substrate, the rotation of the substrate may be stopped at one end and the etching process may be performed. The amount of the cerium (IV) etching solution used can be reduced.

Further, the second, third, and fourth nozzles can be shared. By supplying pure water or chemical solution from the tank of chemical solution or pure water to the shared nozzle via the switching valve, the pure water or chemical solution required for the processing process may be supplied to the shared nozzle.
Further, when sharing the first, second, third, and fourth nozzles, it is necessary to prevent the cerium (IV) etching solution and pure water from continuously flowing through the shared nozzles. For example, immediately after the cerium (IV) etching solution is flowed through the nozzle, the first chemical solution is flowed through the nozzle, and after the pure water is flown through the nozzle, the second chemical solution is supplied to the nozzle. This process is possible when the process corresponding to the second embodiment is executed. Alternatively, when performing the process corresponding to the first embodiment, after supplying pure water to the shared nozzle, the substrate is discharged from the cleaning device, and the first chemical solution is applied to the shared nozzle in a state where the substrate is not in the device. The pure water remaining in the shared nozzle may be discharged by the first chemical solution.

Further, a cup may be provided under the substrate, and the cerium (IV) etching solution may be recovered and circulated in the step of performing the etching process.

According to the present invention, in a wet etching step of forming a pattern of a Cr-based material film on a photomask substrate used for manufacturing a flat panel display or the like, a pattern-sized CD is obtained by suppressing etching non-uniformity. The error can be reduced. In particular, it contributes to the realization of precise patterns in large flat panel displays with high image quality, and has high industrial applicability.

1 Wet etching device 2 1st processing tank 3 2nd processing tank 4 3rd processing tank 5 Photomask substrate 6 1st chemical liquid pipe 7 Outlet 8 Transfer device 9 2nd chemical liquid pipe 10 Outlet 11 3rd Chemical solution piping 12 Outlet 13 Air piping 14 Air knife 15 Fourth processing tank 16 Fourth chemical solution piping 17 Outlet 21 Wet etching equipment

Claims (7)

The first step of supplying an acidic etching solution to a photomask substrate having a Cr-based material film on the surface and etching the Cr-based material film, and
A second step of supplying an acidic first chemical solution that does not etch the Cr-based material film to the photomask substrate, and a second step.
The photomask substrate, and a third step of supplying pure water, containing Mutotomoni in this order,
A wet etching method characterized in that the pH of the etching solution and the pH of the first chemical solution are the same. The wet etching method according to claim 1, wherein the etching solution contains cerium (IV) ions and the first chemical solution. The cerium (IV) ion is a cerium (IV) ion supplied by one or more acids selected from second cerium sulfate, second cerium nitrate and second cerium ammonium nitrate, and the first chemical solution is The etching method according to claim 2 , wherein the acid is one or more selected from perchloric acid, nitric acid, sulfuric acid, phosphoric acid and acetic acid. The etching method according to any one of claims 1 to 3 , wherein the acid contained in the etching solution and the acid of the first chemical solution are the same. The etching method according to any one of claims 1 to 4 , wherein an acidic second chemical solution that does not etch the Cr-based material film is supplied to the photomask substrate before the first step. .. The etching method according to any one of claims 1 to 5 , wherein the second chemical solution is the same as the first chemical solution. The first treatment tank, the second treatment tank, and the third treatment tank
It is equipped with a fourth processing tank and a transfer device for the photomask substrate.
The first processing tank includes a supply unit that supplies an acidic etching solution for etching a Cr-based material film to the photomask substrate.
The second treatment tank includes a supply unit for supplying an acidic first chemical solution that does not etch the Cr-based material film to the photomask substrate.
It said third treatment tank is provided with a supply section for supplying pure water to the photomask substrate,
The fourth treatment tank includes a supply unit for supplying an acidic second chemical solution that does not etch the Cr-based material film to the photomask substrate.
The transfer device is characterized in that the photomask substrate is transferred to the fourth processing tank, the first processing tank, the second processing tank, and the third processing tank in this order. Etching device.

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