JP2012022124A - Photomask blank, photo mask and substrate reproduction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo mask and a photomask blank for a liquid crystal display device with which reuse can be performed by reproduction of a substrate of high quality at low cost by omitting a polishing step which was necessary for the reproduction of a substrate as the level difference due to alkali washing occurs.SOLUTION: A photo mask has a light transmission film made from inorganic compound including zirconium and a light shielding film shielding exposure light including metal on a transparent substrate. The light shielding film and a translucent film are removed by etching and the substrate is washed by using alkali solution. Then, the translucent film and the light shielding film are laminated without performing the polishing treatment of the substrate.

Description

  The present invention relates to a photomask blank and a photomask for use in a manufacturing process of a liquid crystal display device, and a method for regenerating a photomask substrate.

  In recent years, the market of liquid crystal panels used in liquid crystal display devices, particularly liquid crystal monitors and liquid crystal televisions, has greatly expanded. Among the manufacturing processes of the liquid crystal display device, a large-sized photomask for a liquid crystal display device (hereinafter, abbreviated as a photomask or a mask), which is a member used in the exposure process, has the following configuration.

  Large photomasks for liquid crystal display devices have different configurations such as a general photomask with a light-shielding film pattern and a halftone mask with a semi-transmissive film pattern formed in addition to the light-shielding film pattern in recent years. There are several types to have.

  A general configuration of the halftone mask is a photomask blank in which a semi-transmissive film 32 (half-tone film) and a light-shielding film 33 are sequentially laminated on a transparent substrate 31 made of a glass material as shown in FIG. As a material, the light shielding film 33 and the semi-transmissive film 32 are respectively patterned using a lithography technique to form a desired pattern, thereby obtaining a photomask 30 having a structure as shown in FIG. (For example, see Patent Document 1)

  The transparent substrate generally uses synthetic quartz glass or soda lime glass as a material, and the light-shielding film and the semi-transmissive film use a metal such as chromium or molybdenum or a metal compound containing a metal and another element.

  By the way, as one of the problems in recent mask manufacturers, there is a problem of disposal of a photomask that is no longer necessary. This is due to the following reasons.

  At present, due to the increase in size and quality of liquid crystal display devices, photomask substrates are also required to be large in size and high in quality, and a large amount of expensive glass substrates are used.

  However, since liquid crystal display devices are frequently changed in recent years, it is said that the usage period of the photomask is almost only a few years and is shortened year by year. Although there is still sufficient durability as a member of the photomask itself, the necessity for use has been eliminated.

  Furthermore, the production quantity of the photomask itself has increased dramatically. As a result, a large number of used photomasks that are no longer needed or defective in the manufacturing process are generated. There was also a problem from the viewpoint of energy consumption and environmental conservation that accompanies it, and from the viewpoint of economy.

  In addition, even if you try to recycle the material, the glass used for the photomask is a special and ultra-high quality material with very few impurities and defects. Can not. Therefore, it can only be used for low quality applications.

Therefore, in recent years, instead of discarding all photomasks that are no longer needed, it has been studied to recycle a substrate and use it again for photomask manufacturing, and has already been implemented by mask manufacturers. That is, after the light shielding film and the semi-transmissive film on the photomask are completely removed by etching to make only the glass substrate, the glass substrate is polished to smooth the surface, and the light shielding film and the semi-transparent film are again applied to the substrate. If a permeable film is laminated, it can be reused as a photomask blank.

(Conventional photomask substrate recycling process)
A commonly practiced photomask reproduction procedure will be described below. FIG. 5 is a flowchart showing the steps of conventional photomask manufacturing and substrate regeneration processing.

  First, in step (T1), a photomask is manufactured. Photomasks are manufactured using known lithography means. In the manufacturing process, for example, mask formation with acid or alkali is performed after pattern formation by etching to remove dust and contaminants adhering to the photomask. . Further, similar mask cleaning is performed after pattern inspection and the like.

  In the procedure (T2), this photomask is used for an exposure process such as a liquid crystal color filter or a liquid crystal panel. In step (T3), after the mask is used, cleaning with acid or alkali is performed. It is also used in the exposure process. In this way, procedures (T2) and (T3) are repeated.

  In the mask cleaning, for example, a strong acid such as a mixture of hot concentrated sulfuric acid and hydrogen peroxide solution is used for acid cleaning, and a strong alkali such as a potassium hydroxide solution or a sodium hydroxide solution is used for alkali cleaning. Use. (See Patent Document 1 below)

  However, when washing with strong alkali, there is an action of dissolving and removing resist residues and contaminants firmly adhered to the glass substrate surface with alkali, but at the same time, there is a problem that the glass substrate is slightly dissolved with alkali. there were. Since the glass dissolution rate is about several tens of nanometers per hour, the substrate surface dissolves little by little even in a short cleaning process.

At this time, there is a difference that the exposed part of the glass substrate on the photomask, that is, the part without the pattern is dissolved by strong alkali, and the pattern part covered with the light shielding film or the semi-transmissive film is not dissolved. An uneven step is generated along the edge.
Since this step is due to dissolution by alkali, it is proportional to the concentration of the strong alkali or the cleaning time and the total number of cleanings, and the step gradually becomes deeper every time cleaning is repeated.

  The process up to the step (T3) was a process using a photomask, but when the liquid crystal product was completed, when a substitute photomask was produced, or the photomask itself increased defects, etc. If the photomask becomes unusable for the reason, a reproduction process for returning the photomask to the photomask blank state and manufacturing the photomask again is performed according to the following procedure.

The following is the conventional substrate recycling process.
In step (T4), the light-shielding film pattern and the semi-transmissive film pattern provided on the photomask are respectively etched and removed entirely so that only the glass substrate is obtained. At this time, the step of the glass substrate remains as it is.

Therefore, it is necessary to polish the glass substrate in the procedure (T5) so as to reduce the level difference to obtain a smooth substrate surface. The polishing process requires precise polishing using a dedicated glass polishing apparatus, and particularly requires advanced techniques for processing a large-sized substrate.
Furthermore, the surface of the substrate must be inspected after the polishing process to confirm that there are no glass scratches or surface irregularities due to polishing.

  Next, in step (T6), a semi-transmissive film is laminated on a polished and smoothed glass substrate, and a light shielding film is further laminated. Thereby, the photomask blank is reproduced.

  In step (T7), a photomask is produced using the regenerated photomask blank. The photomask manufactured in this way returns to the procedure (T1) again, and is repeatedly used through a similar reproduction process.

  Of course, even when this regeneration processing procedure is repeated, the glass is gradually damaged by the strong alkali used in the mask cleaning process as described above. And in order to eliminate the level | step difference which arises and to make it smooth, a glass grinding | polishing process will be repeated.

  However, the substrate becomes thinner by polishing, and eventually, when a photomask is loaded into the exposure apparatus, a defect such as a defective loading due to a difference in substrate thickness may occur. In addition, scratches or smoothness did not meet the standards even after polishing, and in many cases, they were defective after polishing.

  Further, the polishing process needs to be provided with a dedicated processing facility separately from the photomask manufacturing process, resulting in a large cost depending on the polishing facility and processing time.

JP-A-2-247650 Japanese Patent Laid-Open No. 61-267054

  The present invention has been made in order to solve the above-described problems, and an object of the present invention relates to a photomask and a photomask blank for a liquid crystal display device, and it is ensured that low-cost and high-quality substrate regeneration is performed. An object of the present invention is to provide a photomask and a photomask blank that can be reused.

  In the present invention, in order to achieve the above object, the photomask blank according to claim 1 is a light-transmitting film made of an inorganic compound containing zirconium on a transparent substrate, and a light-shielding material that contains a metal and blocks exposure light. And a membrane.

The photomask blank according to claim 2,
The light transmission film is made of a compound containing at least zirconium, silicon, and oxygen.

The photomask blank according to claim 3,
A semi-transmissive film that transmits part of the exposure light is provided between the light transmissive film and the light shielding film.

The photomask according to claim 4,
A pattern is formed on the light shielding film by using the photomask blank according to claim 1.

The photomask according to claim 5,
A pattern is formed on each of the light shielding film and the semi-transmissive film by using the photomask blank according to claim 3.

The photomask substrate recycling method according to claim 6,
A method for regenerating a photomask substrate in which a light transmissive film made of a compound containing zirconium, silicon, and oxygen, a semi-transmissive film, and a light shielding film are laminated on a transparent substrate, and etching the light shielding film and the semi-transmissive film And after the substrate is washed with an alkali solution, the semi-transmissive film and the light-shielding film are laminated without polishing the substrate.

  According to the photomask blank and the photomask of the present invention, by providing the substrate with a light transmission film made of an inorganic compound containing zirconium, the surface of the glass substrate can be obtained even when a strong alkali or strong acid is used in the mask cleaning process. Since it has a protective function and there is no step at the boundary between the light-shielding film pattern or the semi-transmissive film pattern part and the non-pattern part, the substrate can be regenerated without polishing the substrate. .

It is sectional drawing which shows the Example of the photomask blank of this invention. It is sectional drawing which shows the Example of the photomask of this invention. It is sectional drawing which shows the manufacture procedure of the photomask of this invention. It is a flowchart which shows the Example of the photomask substrate reproduction | regeneration processing procedure of this invention. It is a flowchart which shows the conventional photomask substrate reproduction | regeneration processing procedure. It is sectional drawing which shows the conventional photomask blank and photomask.

  Hereinafter, embodiments of a photomask blank according to the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing an embodiment of the photomask blank of the present invention.
As a configuration of the photomask 10, a light transmissive film 12 that is transparent to exposure light, a semi-transmissive film 13 that transmits a part of the exposure light, and a light shielding film 14 that shields the exposure light are laminated on a transparent substrate 11. Yes.
As the laminating means, a known film forming means is used. For example, a thin film is formed by a sputtering method or a vapor deposition method. In particular, the sputtering method is preferable because it can form a high-quality compound thin film that is homogeneous and has few defects.

  Here, the light-transmitting film 12 has a protective layer effect on the transparent substrate 11 and prevents erosion of the substrate surface when the substrate is cleaned by using a material having alkali resistance. be able to.

  Specifically, by using an inorganic compound containing zirconium as a film material, a light transmissive film 12 having high transparency, high resistance to acids and alkalis, and good adhesion and smoothness to the substrate can be obtained. It was.

  In particular, zirconium silicate (ZrSiOx) (x is the number of oxygen atoms and is determined by the valence and composition ratio of other components) is an etching solution or chemical solution cleaning (acid, alkali) used in the photomask manufacturing process. It is suitable because it has the characteristics that it has high resistance to heat and has high hardness and resistance to physical cleaning.

  In the photomask manufacturing process, for example, an acid-based etching solution such as a cerium nitrate ammonium nitrate solution or a permanganate solution is used as an etching solution, and a strong acid such as hot concentrated sulfuric acid or a strong alkali such as potassium hydroxide as a cleaning solution, A chemical solution such as tetramethylammonium hydroxide (TMAH) is used as a developer, and the zirconium silicate has high resistance to any chemical solution.

Therefore, even if the film thickness is very thin, the light transmission film 12 using zirconium silicate has no risk of being eroded and has an action of protecting the glass substrate.
The film thickness of the light transmission film 12 is preferably thin so as not to reduce the transmittance so much, and is 10 nm in this embodiment. Of course, depending on the purpose, the thickness of the light transmission film 12 may be increased to improve the resistance, or conversely, the light transmission film 12 may be thinned to minimize the decrease in transmittance.

  In this embodiment, the semi-transmissive film 13 is made of chromium oxide (CrOx), and the light shielding film 14 is made of chromium (Cr). As these materials, those generally used as photomask film materials can be used, but they are formed so that the optical density of the semi-transmissive film 13 and the light-shielding film 14 satisfies the required specifications. Further, the transmissivity of the semi-permeable film 13 is also formed so as to meet the specifications.

  The transparent substrate 11 is made of glass that is highly transparent to the exposure light, and soda glass is also used. In particular, synthetic quartz glass that has low defects, a low coefficient of thermal expansion, and high transparency is preferable. In this example, synthetic quartz glass was used.

Next, FIG. 2 shows a configuration of an embodiment of the photomask of the present invention.
In the configuration of the photomask 20, a light transmission film 12 is laminated on a transparent substrate 11, and a semi-transmission film pattern 13a and a light shielding film pattern 14a are formed thereon.

  In order to manufacture the photomask 20, normal pattern forming means may be used. For example, a photosensitive resist is coated on the photomask blank 10, and the light shielding film 14 and the semi-transmissive film 13 are formed by predetermined exposure, development and etching. Each is obtained by forming a pattern.

  In this photomask manufacturing, as described above, there is a chemical treatment process that immerses in an acid or alkaline chemical such as an etching solution or a cleaning solution. When the conventional photomask blank 30 is used, the transparent substrate 31 The exposed portion of the surface is eroded by strong alkali (potassium hydroxide or the like) and a step is formed at the boundary with the non-exposed portion. In order to regenerate the substrate, it is necessary to perform a polishing process.

  On the other hand, in the photomask 20 of the present invention, even when the same strong alkali cleaning is performed, the light transmission film 12 made of zirconium silicate laminated on the substrate functions as a protective layer, and the substrate surface is almost the same. Since it was not eroded, there was no level difference and a smooth surface could be maintained.

  In addition to zirconium silicate, materials with high chemical resistance, such as indium tin oxide (ITO), can be used as the light transmissive film material. In particular, zirconium silicate is not limited to acids and alkaline cleaning solutions, but is also an alkali developer and acid etching. Since it has high tolerance also to the liquid agent used at mask manufacturing processes, such as a liquid and a resist peeling liquid, it is preferable.

FIG. 3 is a cross-sectional view showing a manufacturing procedure in the embodiment of the photomask of the present invention.
First, in (a), after a photosensitive resist is applied on the photomask blank 10 having the structure shown in FIG. 1, a predetermined mask pattern is drawn and exposed using a laser drawing apparatus, and development processing is performed to form a resist pattern 15a. Formed. Here, the opening part p1 is illustrated as a pattern example.

Next, in FIG. 3B, the light shielding film 14 exposed at the opening p1 was etched using a ceric ammonium nitrate solution to form a light shielding film pattern 14a.
Subsequently, in (c), the semipermeable membrane 13 was etched using an aqueous potassium permanganate solution to form a semipermeable membrane pattern 13a.

  In addition, the etching conditions are tested in advance in the etching process of (b), and in the etching of the light shielding layer 14 made of chromium, the etching process time is set by measuring the time to reach the etching end point (bottom surface of the light shielding layer). It is.

In the etching of the translucent film 13 made of chromium oxide (c), the light shielding film pattern 14a is utilized by utilizing the fact that the aqueous potassium permanganate solution selectively etches only chromium oxide and hardly etches metal chromium. Was etched in the width direction (= side etching) so that the pattern end faces of the semi-transmissive film pattern 13a and the light shielding film pattern 14a were aligned.
At this time, the light transmission film 12 made of zirconium silicate is not etched because it is resistant to an acid-based etching solution such as a potassium permanganate aqueous solution.

Next, in (d), the resist remaining in (c) was again drawn and exposed, and development processing was performed to form a resist pattern 15b having an opening p2.
Further, in (e), the light shielding film 14 exposed at the opening p2 was etched using a ceric ammonium nitrate solution to form a light shielding film pattern 14b.

  Then, in (f), the remaining resist was stripped and removed with a stripper to obtain a photomask 20. Finally, the photomask 20 was cleaned using a hot concentrated sulfuric acid cleaning solution and a potassium hydroxide cleaning solution to remove contaminants and deposits on the mask and clean it.

  The configuration of such a photomask blank is an example, and is not limited to the present configuration. Depending on the intended use, such as adding a film having other functions, or forming each film in a multilayer configuration. It can be appropriately selected and used.

For example, it is possible to use a light shielding film as a multilayer film and provide a low reflective layer on the surface side, or to add a barrier film as an etching blocking layer between the light shielding film and the semi-transmissive film.
In addition, the photomask manufacturing procedure is not limited to the above-described procedure. For example, a known material such as a semi-transmissive film using a metal silicide compound with a hydrofluoric acid-based etching solution or a pattern formation using a dry etching method is used. And an etching method may be appropriately combined.

  Next, referring to FIG. 4, a procedure for regenerating the photomask substrate of the present invention is shown in a flowchart, and the contents will be described in detail below.

(Photomask playback processing procedure)
First, in step (S1), a photomask blank having the configuration of the present invention described above was manufactured, and then, using this photomask blank, a photomask having the configuration of the present invention was manufactured.

  The photomask manufacturing means uses a known lithography technique, and the photomask was manufactured by the manufacturing process shown in FIG. At this time, mask cleaning with acid and alkali was performed in the manufacturing process and the inspection process to remove dust and contaminants adhering to the mask.

Next, in step (S2), this photomask was used for the exposure process of the liquid crystal display panel, and in step (S3), this photomask was washed with acid or alkali.
Procedures (S2) and (S3) were repeated each time a liquid crystal display panel product was manufactured.

In this cleaning process, the photomask is laminated with a light transmissive film 12 made of zirconium silicate on the entire lower layer, and the light transmissive film 12 is exposed at a portion without the semi-transmissive film pattern 13a.
At this time, since the light-transmitting film has resistance to acid and alkali, the glass substrate is protected, and the glass exposed portion is dissolved by the cleaning liquid as in the conventional case, so that no step occurs in the substrate.

The next steps (S4) to (S5) are steps for performing a photomask substrate regeneration process.
First, in step (S4), a used photomask was picked up, and the light-shielding film pattern 14a and the semi-transmissive film pattern 13a on the photomask were each etched and removed. At this time, the lower light transmissive film 12 is not etched and is not changed by cleaning, so that the light transmissive film 12 remains on the glass substrate, and naturally there is no step in the substrate, and the surface is smooth. there were.

  Here, the etching method of the light shielding film and the semi-transmissive film may be appropriately selected according to the film material. For example, if the light shielding film uses chromium, the method described in Patent Document 2 may be used. .

Next, in step (S5), the semi-transmissive film 13 and the light-shielding film 14 were laminated on the light transmissive film 12, and the photomask blank 10 was reproduced.
Further, if the photomask 20 is produced through the manufacturing process shown in FIG. 3 in the procedure (S6), the photomask is reproduced.

  The photomask regenerated in this way can be returned to the procedure (S1) and used in the manufacture of the liquid crystal display, and the procedure of reproducing is repeated.

  As is apparent from the above, according to the photomask substrate regeneration processing method of the present invention, the light transmission film is made of zirconium silicate, so that it is possible to perform the regeneration processing without polishing the glass substrate as in the prior art. A significant cost reduction effect was obtained.

  In the photomask and photomask blank of the present invention, the configuration of the light-shielding film and the semi-transmissive film is not limited to this example, and different materials may be used. Also, the photomask manufacturing method is not limited to this embodiment, and a pattern forming method using, for example, a dry etching method may be used.

  Furthermore, in the present embodiment, the substrate size is kept as it is as a substrate regeneration processing method. However, when the substrate size is large, the substrate may be cut and divided and reused as a plurality of small-sized substrates. it can.

  According to the photomask blank, the photomask, and the substrate reproduction method according to the present invention, not only a large-sized photomask for a liquid crystal display device, but also a photomask for manufacturing a semiconductor, a photomask for manufacturing a printed circuit board, a photomask for manufacturing a MEMS device, etc. It can be used for various applications.

10, 30 ... Photomask blanks 11, 31 ... Transparent substrate 12 ... Light transmissive films 13 and 32 ... Semi-transmissive films 13a and 32a ... Semi-transmissive film patterns 14 and 33 ... Light shielding Films 14a, 33a ... Light-shielding film patterns 15a, 15b ... Resist patterns 20, 40 ... Photomasks S1-S6 ... Photomask substrate regeneration processing procedure T1-T7 of the present invention ... Conventional photo Mask substrate recycling process

Claims (6)

  A photomask blank comprising: a light-transmitting film made of an inorganic compound containing zirconium; and a light-shielding film containing a metal and shielding exposure light on a transparent substrate.   The photomask blank according to claim 1, wherein the light transmission film is made of a compound containing at least zirconium, silicon, and oxygen.   3. The photomask blank according to claim 1, further comprising a semi-transmissive film that transmits part of exposure light between the light transmissive film and the light shielding film.   A photomask, wherein a pattern is formed on the light shielding film using the photomask blank according to claim 1.   The photomask blank according to claim 3, wherein a pattern is formed on each of the light-shielding film and the semi-transmissive film. A method for regenerating a photomask substrate in which a light transmissive film made of a compound containing zirconium, silicon, and oxygen, a semi-transmissive film, and a light shielding film are laminated on a transparent substrate,
The light shielding film and the semi-transmissive film are removed by etching, the substrate is washed with an alkaline solution, and then the semi-transmissive film and the light-shielding film are stacked without polishing the substrate. Substrate regeneration method.

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