JP2009139975A - Gray tone mask and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gray tone mask capable of improving a pattern feature and pattern accuracy. <P>SOLUTION: The method for manufacturing a gray tone mask includes steps of: preparing a mask blank having at least a light-semitransmitting film 12, an etching stopper film 13 and a light-shielding film 14 successively formed on a transparent substrate 11 and a resist film 15 formed thereon; exposing and developing the resist film to process the resist film; etching and removing the light-shielding film exposed in a region where the resist is removed; simultaneously removing the light-semitransmitting film in a portion where a light-transmitting portion is to be formed, and the light-shielding film in a portion where a light semitransmitting portion is to be formed; and removing the residual resist film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gray tone mask and a manufacturing method thereof.

In recent years, attempts have been made to reduce the number of masks using a gray-tone mask in the field of large LCD masks (see Non-Patent Document 1, for example).
Here, the gray tone mask includes, for example, a light shielding portion 1, a light transmitting portion 2, and a gray tone portion 3 as shown in FIG. The gray tone part 3 is an area where a fine light-shielding pattern 3a below the resolution limit of a large LCD exposure machine that uses a gray tone mask is formed. The amount of light transmitted through this area is reduced, and It is formed for the purpose of selectively changing the film thickness of the photoresist by reducing the dose. Shading part 1 and fine shading pattern 3
Both a are usually formed from films of the same thickness made of the same material such as chromium or a chromium compound. Both the translucent part 2 and the fine translucent part 3b are portions of the transparent substrate on which the light shielding film or the like is not formed on the transparent substrate.
The resolution limit of a large LCD exposure machine using a gray tone mask is about 3 μm for a stepper type exposure machine and about 4 μm for a mirror projection type exposure machine. For this reason, for example, in FIG. 7A, the space width of the fine light transmitting portion 3b in the gray tone portion is set to less than 3 μm, and the line width of the fine light shielding pattern 3a below the resolution limit of the exposure machine is set to less than 3 μm. Large L above
When exposed with a CD exposure machine, the exposure light that has passed through the gray tone portion 3 has a small amount of exposure as a whole, so the positive photoresist exposed through this gray tone portion 3 only has a thin film thickness. It remains on the substrate. That is, since the resist can have a difference in solubility in the developer between the portion corresponding to the normal light-shielding portion 1 and the portion corresponding to the gray tone portion 3 depending on the exposure amount, the resist shape after development is shown in FIG. ), The portion 1 ′ corresponding to the normal light-shielding portion 1 is about 1.3 μm, for example, and the portion 3 ′ corresponding to the gray tone portion 3 is about 0.3 μm, for example.
The part corresponding to μm and the translucent part 2 is a part 2 ′ where no resist remains. Then, the first etching of the substrate to be processed is performed in the portion 2 ′ where the resist does not remain, the resist of the thin portion 3 ′ corresponding to the gray tone portion 3 is removed by ashing or the like, and the second etching is performed in this portion. Thus, the process for two conventional masks is performed with one mask to reduce the number of masks.

In the above-mentioned gray tone mask, ideally, for example, a fine line & space pattern is around 2 μm to form a gray tone portion with a fine pattern at the resolution limit of a large LCD exposure machine that uses a gray tone mask. Pitch (about 1μm, which is about half of the pitch), and it is necessary to process fine patterns with an accuracy of ± 0.2μm.
From the viewpoint of the accuracy of the large mask for D, the accuracy is very strict.
In addition, it is very difficult to detect defects of 2 μm pitch pattern (especially, defect detection for the edge of the pattern) with the current large mask automatic defect inspection apparatus, and to inspect fine patterns with an accuracy of about ± 0.2 μm. It is also very difficult to do.
Furthermore, since the gray tone part is composed of fine patterns, the
If the data capacity becomes enormous and the capacity of the drawing machine and the data conversion (format conversion) machine attached to the drawing machine is exceeded, drawing may not be possible. Specifically, for example, the data of the gray tone part 3 shown in FIG. 8 (2) is avoided so as not to overlap with the data of the light shielding part 1 and the light transmitting part 2 shown in FIG. 8 (1). Since the data must be created, the creation of the data becomes complicated, and the data of the gray tone part 3 shows a complicated shape along the data of the light shielding part and the light transmitting part. As shown in FIG.
The capacity of the composite data shown in (3) is also enormous.

On the other hand, the film thickness of the chromium single layer film provided on the transparent substrate is partially changed, the thick film part is used as a light shielding part, the intermediate film part is used as a gray tone part, and the zero film thickness part is used. A gray-tone mask having a translucent portion is known. However, since the chromium film has a low transmittance (high light-shielding property), the film thickness for obtaining a transmittance of 0% is thin, so that the half film thickness is obtained so that a predetermined intermediate transmittance can be obtained for the intermediate film thickness portion. It is difficult to etch. Therefore, a gray tone mask in which the film thickness of the chromium compound single layer film provided on the transparent substrate is partially changed has been proposed (Patent Document 1). In this case, since the chromium compound single layer film has a thickness of about 4000 angstroms to obtain a transmittance of 0%, half etching to obtain a film thickness at which an intermediate predetermined transmittance can be obtained for the intermediate film thickness portion is not possible. This is easier than in the case of a chromium single layer film. However, in this method, since the film thickness is too thick, the aspect ratio (pattern dimension to height ratio) is high. As a result, the pattern shape and pattern accuracy of the light-shielding portion are deteriorated, and the etching time is also increased. Furthermore, in practice, it is difficult to strictly control the film thickness by half etching, and there is a problem that practicality is difficult.
Monthly FPD Intelligence, May 1999 JP-A-7-49410

An object of the present invention is to provide a gray-tone mask and a method for manufacturing the same, which have solved the above-described problems.

  The present invention has the following configuration.

(Configuration 1) In a gray-tone mask having a light-shielding portion, a light-transmitting portion, and a gray-tone portion that transmits a part of the exposure light, the light-shielding portion is formed on a transparent substrate in sequence, and is etched A gray tone mask comprising a stopper film and a light shielding film, wherein the gray tone portion includes a semi-transparent film or a semi-transparent film and an etching stopper film formed on the transparent substrate.

(Structure 2) The gray-tone mask according to Structure 1, wherein the light-shielding film and the semi-transparent film are formed of a film that can be processed with the same etching solution or the same etching gas.

(Structure 3) The gray-tone mask according to Structure 1 or 2, wherein the light shielding film and the semi-translucent film are made of a material containing chromium.

(Structure 4) The gray tone mask according to any one of structures 1 to 3, wherein the etching stopper film is SiO ₂ or SOG (Spin On Glass).

(Configuration 5) In the graytone mask manufacturing method according to any one of Configurations 1 to 4,
Preparing a mask blank in which at least a semi-transparent film, an etching stopper film, and a light-shielding film are sequentially formed on a transparent substrate;
Forming a resist film on the blank;
The resist film is exposed at an exposure amount at which the resist is completely exposed to the portion where the light-transmitting portion is formed, and at an exposure amount which is smaller than the exposure amount at which the resist is completely exposed to the portion where the gray tone portion is formed. And a process of
Performing a development process, and forming a resist pattern such that the remaining film value of the resist is different between the portion forming the light-shielding portion and the portion forming the gray tone portion;
Etching the semi-transparent film, the etching stopper film, and the light shielding film using the resist pattern as a mask to form a translucent portion;
Removing only the resist pattern remaining on the gray tone portion;
Removing the light-shielding film or the light-shielding film and the etching stopper film using the resist pattern remaining in the previous process as a mask;
And a step of peeling off the remaining resist pattern.

(Configuration 6) A gray tone mask blank for manufacturing the gray tone mask according to any one of configurations 1 to 4,
A gray-tone mask blank comprising a translucent film, an etching stopper film, and a light-shielding film on a transparent substrate.

(Structure 7) The gray tone mask according to any one of structures 1 to 4, wherein the gray tone mask is an LCD mask or a PDP mask.

(Function)
According to Configuration 1, a three-layer structure of a semi-transparent film, an etching stopper film, and a light-shielding film that are sequentially formed on a transparent substrate is used to form a light-shielding film in a gray tone part (semi-transparent part) by etching. At the time of removal, the etching stopper film can avoid a reduction in the thickness of the semi-transparent film, and thus a gray-tone mask having a very high uniformity in the thickness of the semi-transparent film can be easily obtained. Further, since the light shielding film can be composed of a thin film such as chromium with a high light shielding property, the etching time can be shortened and the aspect ratio is low, and as a result, the pattern shape and pattern accuracy of the light shielding portion are improved. Further, since the etching stopper layer is provided, the light-shielding film and the semi-transparent film can be composed of the same material film or the same main component film.
In the case of using a SiO ₂ or SOG (Spin On Glass) or the like as an etching stopper film, SiO ₂ or SOG is to have a transmission characteristic equivalent to the transparent substrate, interposed gray tone portion (semi-light-transmitting portion) Since the transmission characteristics are not affected, the etching stopper film in the gray tone portion (semi-transmissive portion) may not be removed.
In the present invention, as the light shielding film and / or the semi-transparent film, Cr, chromium compound, MoSi
It is preferable to use any one selected from Si, W, and Al.

According to Configuration 2, the light shielding film and the semi-transparent film can be processed simultaneously by configuring the light shielding film and the semi-transparent film with a film that can be processed with the same etching solution or the same etching gas.

According to Configuration 3, since the light shielding film and the semi-transparent film are made of a material containing chromium, the light shielding film and the semi-transparent film can be simultaneously processed with the same etching solution or the same etching gas. Examples of such a film include a film made of the same material (for example, semi-transparent film: Cr, light-shielding film: Cr) and a film having the same main component (for example, semi-transparent film: chromium compound, light-shielding film: Cr). . In particular, when the semi-transparent film is made of a chromium compound or the like and the semi-transparent film is made of a chromium compound or the like, the following effects are obtained. First, when the semi-transparent film is made of a chromium compound or the like, the film thickness of the chromium compound having a predetermined transmittance can be increased, and the uniformity of the film thickness and thus the uniformity of the transmittance can be made with high accuracy. Can be controlled. On the other hand, when the semi-transparent film is made of Cr or the like, the film thickness of Cr having a predetermined transmittance is very thin, and the transmittance varies greatly even if the film thickness slightly varies. In addition, it is difficult to control the uniformity of the Cr semi-transparent film and thus the uniformity of the transmittance with high accuracy as compared with the case of a chromium compound or the like. When the light shielding film is made of Cr or the like, the film thickness of Cr having a predetermined light shielding property (optical density) can be reduced.
As a result, the thickness of the entire light shielding portion can be suppressed, and the pattern shape and pattern accuracy of the light shielding portion are improved. On the other hand, when the light shielding film is made of a chromium compound or the like, the film thickness of the chromium compound having a predetermined light shielding property (optical density) is increased, and as a result, the thickness of the entire light shielding portion cannot be suppressed. The pattern shape and pattern accuracy of the part are inferior.
In the above-described configurations 1 to 3, as the chromium compound, chromium oxide (CrOx),
Examples thereof include chromium nitride (CrNx), chromium oxynitride (CrOxNy), chromium fluoride (CrFx), and those containing carbon or hydrogen in these films.

According to the configuration 4, as the etching stopper film, SiO ₂ or SOG (Spin On Gla
By using ss), since SiO ₂ and SOG have the same transmission characteristics as the transparent substrate, even if they are interposed in the light shielding part or the gray tone part (semi-transmissive part), their transmission characteristics are not affected. SiO ₂ and SOG are preferable because they function as an etching stopper layer with respect to many light shielding film materials or semi-transparent film materials. Furthermore, SiO ₂ and SOG have high adhesion to a light shielding film material or a semi-transparent film material.
If the etching stopper layer is not provided, the semi-transparent film and the light-shielding film must be made of a material that can take an etching selectivity, and the material is limited, and the adhesion between the semi-transparent film and the light-shielding film is a problem. It may become.
The thickness of the etching stopper layer made of SiO ₂ or SOG is preferably in the range of 100 to 1000 Å.

According to the configuration 5, the resist process (resist application, drawing (exposure), development) is not required in the subsequent steps by making the resist film thickness different in accordance with the exposure amount for each region.
In addition, it is preferable to perform simultaneously the process of removing the etching stopper film | membrane on the part which should form a translucent part, and the process of removing the resist on the part which should form a semi-translucent part.
Further, it is preferable that the step of removing the semi-transparent film on the portion where the light-transmitting portion is to be formed and the step of removing the light-shielding film on the portion where the semi-transparent portion is to be formed are performed simultaneously.

According to the mask blank of structure 6, a gray tone mask can be manufactured only by the film removal process of each layer and the resist film reduction process. In addition, a high-quality gray-tone mask having excellent uniformity in the thickness of the gray tone portion (semi-transparent film) and thus uniformity in transmission characteristics can be obtained.

In the above configurations 1 to 6, the optical density of the light shielding film and the semi-transparent film may be 3.0 or more. That is, even if the light shielding film itself does not have an optical density of 3.0 or more, the optical density when the semi-transparent film is combined may be 3.0 or more. In this case, the light shielding film can be made thinner by the optical density of the semi-transmissive film.

According to Configuration 7, in the case of a gray-tone mask blank for LCD, since the substrate size is large and it is difficult to ensure film thickness uniformity, the method of half-etching a single layer film to an intermediate film thickness requires a film in the mask blank. In consideration of the thickness variation, it is necessary to strictly control the film thickness by half etching (specifically, it is necessary to suppress the in-plane variation of the etching amount by half etching to almost zero). Since it is difficult to strictly control the film thickness, such a method has difficulty in practical use. On the other hand, the graytone mask manufacturing method of the present invention does not have such a problem. Therefore, the present invention is for producing a large graytone mask (color filter or thin film transistor (TFT)) for LCD (liquid crystal display device). Etc.) and large gray-tone masks for PDP (Plasma Display Panel) etc. are indispensable.

In addition, according to the gray tone mask of the present invention and the manufacturing method thereof, the following effects can be obtained.
Since it is not necessary to form a gray tone portion with a fine pattern at the resolution limit of a large LCD exposure machine that uses a gray tone mask, there is no problem in processing accuracy of the fine pattern in the gray tone portion.
By controlling the gray tone part (semi-transparent part) with the thickness of the semi-transparent film, the detection waveform is stabilized, so that the defect appearance is easier than when the gray tone part is formed with a fine pattern. is there.
Since a semi-transparent film whose transmittance is controlled in advance is used, it is easy to control the transmittance.
Even if the pattern shape of the light-shielding part and the light-transmitting part is complicated, the gray tone part (semi-transparent part) draws uniformly on the entire surface of the gray tone part by adjusting the exposure amount (so-called solid exposure). The drawing data amount in the gray tone portion is smaller than that in the case of drawing the gray tone portion composed of a fine pattern, and drawing becomes easy.

Embodiments of the present invention will be described below.
As shown in FIG. 1A, the combined data when all the pattern data of the light-shielding part, the light-transmitting part, and the gray tone part are incorporated is the light-shielding part 1 and the light-transmitting part 2 (for example, an amorphous silicon pattern of TFT). And a gray tone portion 3 (semi-transparent portion) formed in the periphery thereof. In this case, the data of the light shielding part 1 and the light transmitting part 2 shown in FIG.
The data is separated into the data of the gray tone part 3 shown in (3). Then, after drawing the light-transmitting portion 2 with an exposure amount (100%) at which the resist can be completely removed, the semi-transparent portion 3 is drawn with an exposure amount that is about half of the exposure amount at which the resist is completely exposed. The pattern shown in FIG. 1A can be drawn. With the drawing pattern shown in FIG. 1 (1), it is not necessary to form a fine pattern below the resolution limit in the gray tone part 3, and the problem of data capacity when a fine pattern is formed in the gray tone part is solved. The Note that the drawing order of the translucent part 2 and the semi-translucent part 3 is random, and either one may be the first.
The exposure dose distribution when the drawing pattern shown in FIG. 1A is drawn on a resist (an example of drawing with a positive resist) is as shown in FIG. That is, the exposure amount of the translucent part 2 is 100.
%, The exposure amount of the gray tone portion 3 is 50%, and the exposure amount of the light shielding portion 1 is 0% (not exposed).

Next, a manufacturing procedure of the gray tone mask will be described.
3 and 4 are partial cross-sectional views showing a gray-tone mask manufacturing procedure, taken along II of FIG.
A line section is shown.

First, as shown in FIG. 3 (1), on a substrate in which a semi-transparent film 12, an etching stopper film (barrier film) 13, a light-shielding film 14 and a novolac positive resist film 15 are sequentially formed on a transparent substrate 11. When drawing is performed with the exposure distribution shown in FIG. 2, area B is unexposed,
In the area A, the exposure amount at the time of drawing is adjusted so that the film thickness after exposure / development is about half of the remaining film value of the area B. Area C gives an exposure amount sufficient for resist patterning (residual film value is zero). The drawing method at this time is to draw the area A with a laser drawing machine with a light amount of 100% exposure, and then draw the rear A with a light amount of about 50% exposure. Area A,
As for the drawing order of C, any one may be first.

Next, as shown in FIG. 3B, the resist film 1 has a thickness difference by wet processing.
5 is processed (development / thinning treatment).
At this time, the film thickness of the resist film 15 is about half of the area B in the area A, and the area C
Then, it is in a completely removed state. The wet processing is performed with a developer such as inorganic alkali (for example, KOH, concentration 0.63N) or organic alkali (for example, TMAH, concentration 2.3%).

Next, as shown in FIG. 3C, the light shielding film 14 exposed in the area C where the resist is completely removed is completely removed by wet etching or dry etching.

Next, as shown in FIG. 3D, the etching stopper film 13 (SiO ₂ film or SOG) in the area C is removed by wet etching using a fluorine-based aqueous solution or dry etching using a fluorine-based gas.
When the etching stopper film 13 is processed by dry etching, the resist removal in the area A (semi-translucent portion) performed in the next process (FIG. 4A) may be performed simultaneously.

Next, as shown in FIG. 4A, the area A is subjected to dry processing (for example, O ₂ ashing).
The resist is completely removed. As a result, the film thickness of the resist film 15 in the area B (light shielding portion) is about half of the initial film thickness.
If the etching of the etching stopper film 13 is processed by dry etching in the previous step (FIG. 3 (4)), this step may be omitted.

Next, as shown in FIG. 4B, the light shielding film 14 in the area A and the semi-transparent film 12 in the area C are removed by wet etching or dry etching, so that the translucent part and the semi-transparent part are simultaneously formed. Form. At this time, the semi-transparent film 12 in the area A is not etched because it is protected by the etching stopper film.

Next, as shown in FIG. 4 (3), the remaining resist is treated with organic alkali or dry treatment (
O ₂ ashing) to remove the light shielding part in area B, the semi-transparent part in area A,
As a result, a gray-tone mask in which translucent portions are formed in area C is obtained.

When removing the etching stopper film 13 in the semi-translucent portion, the etching stopper film in the area A (semi-transmissive portion) can be removed by wet etching or dry etching, for example (FIG. 4 (4)).

In the above embodiment, the mask blank for producing the gray-tone mask is, for example, Cr or a chromium compound (for example, CrO) on a transparent substrate such as a quartz substrate.
A semi-transparent film having a controlled thickness such as a sputtering film is formed by sputtering, etc., and an etching stopper layer is formed by SiO ₂ film (formed by sputtering or vapor deposition) or SOG (spin-on-glass). A (barrier layer) is formed, a light-shielding film having a light-shielding property such as Cr is formed by sputtering or the like, and a resist is applied on the light-shielding film in a range of 5000 to 10,000 angstroms.
Thus, the light shielding film and the semi-transparent film are made of a Cr-based material, and the etching stopper layer is made of SiO _2.
With system material, Cr-based materials such as nitric acid aqueous solution was added perchloric acid can be etched by dry etching using wet etching or chlorine-based gas by the ceric ammonium, SiO ₂ material of the fluorine-containing aqueous solution Etching can be performed by wet etching or dry etching using a fluorine-based gas, and these are highly selective to each other's etching solution or etching gas, and thus are not easily etched against each other's etching.
It should be noted that the etching stopper film made of SiO ₂ film or SOG has almost no influence on the transmittance, so it may not be removed.
At this time, the optical density of the light shielding film and the semi-transparent film is set to 3.0 or more.
The thickness of the etching stopper layer is in the range of 100 to 1000 angstroms.
The thickness of the semi-transparent film is set such that the transmissivity of the semi-transparent film is 20% to 50%. For example, when Cr is used for the semi-transparent film, the thickness of the semi-transparent film is in the range of 100 to 200 angstroms (FIG. 5), and when CrO is used for the semi-transparent film, the semi-translucent film is used. The film thickness is 650-14
The range is 00 angstrom (FIG. 6).

The present invention is not limited to the above-described embodiment.
For example, an antireflection layer can be provided on the light shielding film at the mask blank stage. In this case, since the light shielding film and the antireflection film can be etched at the same time, there is no increase in the number of processes.
The antireflection layer is made of, for example, chromium oxide (CrOx), chromium nitride (CrNx), chromium oxynitride (
CrOxNy) or the like.
Further, dry etching or dry processing can be performed instead of wet processing, and wet processing can be performed instead of dry etching or dry processing. Moreover, it is not limited to the exposure by a laser drawing machine, You may use another exposure apparatus.
The light irradiation amount of the gray tone portion (semi-translucent portion) is not limited to 50% of the light irradiation amount necessary to sufficiently expose the photoresist having a predetermined film thickness.

(The invention's effect)
As described above, according to the present invention, it is possible to easily obtain a gray-tone mask in which the uniformity of the thickness of the semi-translucent film is very high. Further, since the light shielding film can be formed of a thin film having high light shielding properties such as chromium, the etching time can be shortened and the aspect ratio is low, and as a result, the pattern shape and pattern accuracy of the light shielding portion are improved.
In particular, the present invention is indispensable for putting a large graytone mask for LCD into practical use.

FIGS. 1A and 1B are diagrams for explaining drawing data according to an embodiment of the present invention, FIG. 1A is composite data when all pattern data is incorporated, and FIG. 1B is a light shielding portion and a light transmitting portion. Drawing data of FIG. 1 and FIG. 1 (3) respectively show the drawing data of the gray tone portion. It is a figure which shows distribution of the light irradiation amount after drawing. It is a fragmentary sectional view which shows a part of manufacturing procedure of the gray tone mask concerning one embodiment of this invention. It is a fragmentary sectional view which shows a part (continuation) of the manufacturing procedure of the gray tone mask concerning one embodiment of this invention. It is a figure which shows the relationship between the film thickness of a Cr semi-transparent film, and the transmittance | permeability. It is a figure which shows the relationship between the film thickness of a CrO semi-transparent film, and the transmittance | permeability. It is a figure for demonstrating a gray tone mask, (1) is a fragmentary top view, (2) is a fragmentary sectional view. It is a figure for demonstrating the conventional drawing data, FIG. 8 (1) is drawing data of a light-shielding part and a translucent part, FIG. 8 (2) is drawing data of a gray tone part, FIG. The composite data when pattern data is incorporated is shown respectively.

DESCRIPTION OF SYMBOLS 1 Light-shielding part 2 Light-transmitting part 3 Gray tone part 3a Fine light-shielding pattern 3b Fine light-transmitting part 11 Transparent substrate 12 Semi-light-transmitting film 13 Etching stopper film (barrier film)
14 light shielding film 15 resist film

Claims (1)

A light shielding part;
A light-transmitting portion having a portion adjacent to the light-shielding portion;
A gray-tone mask manufacturing method having a gray-tone portion that transmits a part of exposure light,
After reducing the light passing through the gray tone portion and selectively changing the film thickness of the exposed photoresist, first etching of the substrate to be processed is performed on the portion where the photoresist does not remain, and the gray tone portion The gray tone for large LCDs that can be etched by two masks with one mask by removing the thin photoresist portion corresponding to the above by ashing and performing the second etching on this portion In the mask manufacturing method,
On the transparent substrate, at least a semi-transparent film, an etching stopper film, a light shielding film are sequentially formed, and a step of preparing a mask blank in which a resist film is formed;
Exposing the resist film, developing the resist film, and processing the resist film;
Etching and removing the light shielding film exposed in the region where the resist has been removed;
Removing the semi-transparent film on the portion where the translucent portion is to be formed and the light-shielding film on the portion where the semi-transparent portion is to be formed simultaneously;
Including a step of removing the remaining resist film,
A method for manufacturing a gray-tone mask.

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