CN110967919A

CN110967919A - Method for manufacturing photomask substrate, method for manufacturing photomask, and photomask

Info

Publication number: CN110967919A
Application number: CN201910915865.3A
Authority: CN
Inventors: 宫崎由宽
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2018-09-28
Filing date: 2019-09-26
Publication date: 2020-04-07
Also published as: TW202032263A; KR20200036754A; JP2020056815A

Abstract

The invention provides a method for manufacturing a photomask substrate, a method for manufacturing a photomask and a photomask, aiming at reducing the generation of defects of the photomask and improving the production efficiency and quality of photomask manufacturing. A method for manufacturing a photomask substrate having a light-shielding film (3) on a transparent substrate (1) for forming a transfer pattern including a light-transmitting portion and a light-shielding portion by patterning at least the light-shielding film (3) to form a photomask, wherein the light-shielding film (3) includes an upper layer (3b) and a lower layer (3a) each having a light-shielding property with an optical density OD of 1.5 or more, the method comprising: a step for forming a lower layer (3a) on a transparent substrate (1); a step of performing a 1 st foreign matter removal treatment on the surface of the lower layer (3 a); and a step of forming an upper layer (3b) on the lower layer (3 a).

Description

Method for manufacturing photomask substrate, method for manufacturing photomask, and photomask

Technical Field

The present invention relates to a method for manufacturing a photomask blank and a photomask blank using the same, and more particularly, to a photomask blank which is particularly advantageous for reducing defects in a photomask for manufacturing a display device.

Further, the present invention relates to a method of manufacturing a photomask and a photomask.

Background

The following is disclosed with respect to a photomask substrate processing technique, particularly, reduction of defects generated in a photomask.

Patent document 1 describes the following: even if the light-shielding film having an antireflection layer on the upper layer has an optical density of 3.0 or more, there is a problem that pinholes are generated in the antireflection layer by the falling-off of foreign matters entering the antireflection layer, and the optical density of the light-shielding film is locally lowered. In patent document 1, in order to solve this problem, the film material and film thickness of the light-shielding film are set so that the optical density of the light-shielding portion after removal of the antireflection layer is 3.0 or more.

Patent document 2 describes a method for manufacturing a photomask, in which a mask defect correction step can be omitted because of a problem of an increase in manufacturing cost when correcting a pinhole or the like generated in a chromium film. The following are also described: based on the above method, defect inspection of the mask blank is performed to find out a pinhole defect existing in the chrome film, and the position and size thereof are recorded in the form of defect coordinate data, and the relative coordinate position is shifted so as not to overlap with the actual pattern coordinate data of the mask.

Patent document 3 describes a correction method for correcting a white defect generated in a mask pattern, in which a source gas introduced into a processing chamber is decomposed by near-field light existing in the vicinity of the white defect portion, and a thin film is formed on the white defect portion.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012 and 3152

Patent document 2: japanese laid-open patent publication No. 10-186635

Patent document 3: japanese patent laid-open publication No. 2011-186394

Disclosure of Invention

Problems to be solved by the invention

In order to manufacture a photomask, the following steps are performed: a photomask blank (for example, a photomask blank) having at least 1 optical film formed on a transparent substrate is subjected to photolithography to form a desired pattern.

According to the method described in patent document 1, there are the following advantages: when the antireflection layer is formed on the light-shielding film, sufficient optical density can be obtained even if the surface of the antireflection layer is recessed due to the falling-off of foreign matters entering the antireflection layer. However, the thickness of the optical film of the photomask is less than 0.5 μm, more typically less than 0.1 μm (about 50 to 200nm in the case of a light-shielding film including an antireflection layer), whereas the size of foreign matters generated in the formation of the antireflection layer is related to the generation cause described later, and the number of foreign matters is much larger than the thickness of the optical film, and the number of foreign matters exceeding 1 μm is not so small.

Therefore, if such foreign matter enters the film and falls off in the photomask manufacturing process or the photomask using process, the risk of falling-off defects (white defects) cannot be effectively reduced even if the optical density OD of the light-shielding film is adjusted as described above.

According to the method described in patent document 2, there is an advantage that the correction process can be omitted even if a defect occurs. However, the ability to apply this method depends on the number and location of defects, and the pattern design of the photomask to be fabricated. In particular, there is a limit to the application of this method to a photomask for manufacturing a display device in which a substrate has a large size (one side of the main surface is about 300 to 2000 mm) and a plurality of panel patterns are densely arranged as a countermeasure against defects.

According to the method described in patent document 3, in order to correct a defect generated in a photomask pattern, first, rough scanning is performed to temporarily specify a correction region, and then, position information of a white defect to be corrected is accurately acquired. Then, a source gas for defect correction is introduced into the processing chamber, and when a white defect position is irradiated with light such as laser light, the source gas is decomposed by the near-field light, and a film is formed at the white defect position.

In general, defects inevitably occur in a photomask pattern, and a pattern defect inspection process for specifying the positions and sizes of the defects is required to correct the defects. In the pattern defect inspection step, the inspection device scans the entire transfer area of the photomask and compares a transmission image or a reflection image of the formed pattern with a normal pattern to specify the position, shape, and size of the defect. With the recent high definition of patterns for manufacturing display devices, the difficulty of pattern defect inspection techniques has increased, and a large amount of time and man-hours have been required.

The invention aims to reduce the generation of defects of a photomask and improve the production efficiency and quality of photomask manufacturing.

Means for solving the problems

According to an aspect of the present invention, there is provided a method of manufacturing a photomask substrate having a light-shielding film on a transparent substrate, the photomask substrate being used for manufacturing a photomask by patterning at least the light-shielding film to form a transfer pattern including a light-transmitting portion and a light-shielding portion, wherein the light-shielding film includes an upper layer and a lower layer each having a light-shielding property with an optical density OD of 1.5 or more, the method comprising: forming the lower layer on the transparent substrate; a step of performing a 1 st foreign matter removal treatment on the surface of the lower layer; and forming the upper layer on the lower layer.

Preferably, the step of performing the 2 nd foreign matter removal treatment is performed after the step of forming the upper layer.

The light-shielding film may further include an antireflection layer on the upper layer.

The upper layer and the lower layer are preferably made of a material etched with the same etchant.

The film thickness of the light-shielding film is preferably 200nm or less.

The light shielding film may have any one of an additional film and an additional film pattern on an upper side or a lower side thereof.

The upper layer and the lower layer are preferably both made of a material containing Cr.

The present invention includes a photomask substrate in which a light-shielding film is formed on a transparent substrate and a transfer pattern including a light-shielding portion and a light-transmitting portion is formed by patterning at least the light-shielding film, wherein the light-shielding film has a film thickness of 200nm or less and includes an upper layer and a lower layer made of a material etched with the same etchant, the upper layer and the lower layer each have a light-shielding property with an optical density OD of 1.5 or more, the light-shielding film has a lower layer defective portion in which a defective portion of 0.5 to 10 μm generated in the lower layer is covered with the upper layer, and the optical density OD is 1.5 or more over the entire surface of the light-shielding film.

The upper layer may have a defect portion in which a defect of 0.5 to 10 μm is generated in the upper layer.

The light shielding portion may be formed by forming at least the light shielding film on the transparent substrate, and may have an antireflection layer on the upper layer.

The present invention includes a method of manufacturing a photomask, comprising: a step of preparing a photomask blank manufactured by the method for manufacturing a photomask blank; and patterning the light-shielding film.

The present invention includes a method of manufacturing a photomask, comprising: preparing the photomask substrate; and patterning the light-shielding film.

According to another aspect of the present invention, there is provided a photomask including a transfer pattern including a light-shielding portion and a light-transmitting portion, the transfer pattern being formed by forming a light-shielding film on a transparent substrate and patterning at least the light-shielding film, wherein the light-shielding portion is formed by forming the light-shielding film on the transparent substrate, the light-transmitting portion is exposed through the transparent substrate, the light-shielding film has a film thickness of 200nm or less and includes an upper layer and a lower layer, the upper layer and the lower layer are formed of a material etched with the same etchant and have light-shielding properties with a light density OD of 1.5 or more, the light-shielding film has a lower layer defect portion in which a 0.5 to 10 μm-sized defect portion generated in the lower layer is covered with the upper layer, and the light density OD of 1.5 or more over the entire surface of the light-shielding portion.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the photomask blank before the photomask pattern is formed is substantially defect-free, thereby reducing the occurrence of defects in the photomask and improving the production efficiency and quality of photomask production.

Drawings

Fig. 1(a) is a flowchart showing a reference diagram showing an example of a photomask manufacturing process, and fig. 1(b) is a flowchart showing an example of a photomask manufacturing process according to an embodiment of the present invention.

Fig. 2 is a diagram for explaining the cause of the peeling defect in the photomask manufacturing process.

Fig. 3 is a diagram for explaining an example of the method for manufacturing a photomask blank of the present invention.

Fig. 4 is a diagram for explaining another example of the method for manufacturing a photomask blank of the present invention.

Fig. 5 is a sectional view showing an example of a configuration of a photomask manufactured using the photomask blank according to the embodiment of the present invention.

Detailed Description

The present inventors have conducted detailed investigations on the kind of photomask defects and the cause of the defects, and as a result, have found that a photomask manufacturing process can be further shortened and production efficiency can be improved by forming a light-shielding film constituting a photomask substrate substantially without defects.

Accordingly, the present inventors have conducted intensive studies to reduce defects generated in a photomask and to improve the production efficiency and quality of the photomask, thereby completing the present invention.

Hereinafter, a photomask substrate processing technique and the like according to an embodiment of the present invention will be described in detail with reference to the drawings.

In this embodiment, a method for manufacturing a photomask substrate in which at least a light-shielding film is formed on a transparent substrate and a peeling defect of the light-shielding film or a potential peeling defect (a peeling defect in a photomask manufacturing process or a process of a photomask treatment thereafter) is eliminated will be described in detail with reference to the drawings.

In the present specification, the photomask blank is a photomask blank in which at least a light-shielding film is directly or indirectly formed on a transparent substrate. The light-shielding film is an unpatterned film. The photomask blank may include another film (an optical film, a functional film, or the like) or a film pattern on or under the light-shielding film.

The following reference example steps (see fig. 1(a)) can be mainly applied to the production of a photomask using a photomask substrate.

I. Preceding Process

(1) Process for forming optical film

Referring to fig. 2, in step S1, a light-shielding film 3 as an optical film is formed on a transparent substrate 1.

The transparent substrate 1 is a plate material for forming a photomask substrate, and a substrate made of a transparent material and processed to have a predetermined flatness and smoothness on the front and back sides is used. As the transparent material, quartz (SiO) is preferable₂). For example, synthetic quartz is suitably used.

A light-shielding film 3 is formed on one main surface of the transparent substrate 1. The surface on which the light shielding film 3 is formed is defined as the 1 st main surface, and the main surface on the opposite side is defined as the 2 nd main surface. The light shielding film 3 is made of a film material having predetermined physical and chemical properties, and is formed to have a desired film thickness by a known film forming means such as a sputtering method.

In addition, in order to confirm the film formation quality, defect inspection of the optical film (here, the light shielding film 3) is performed as necessary. For example, when there is a specification of a photomask blank product, it is checked before shipment whether the specification is satisfied.

(2) Cleaning (cleaning before coating) step 1

In step S2, the photomask blank with the light-shielding film 3 obtained above is cleaned to remove the foreign matter 11 and clean the surface to remove dirt that interferes with the adhesion of the resist.

(3) Resist coating process

In step S3, a resist is applied to the photomask substrate using, for example, a resist coater, thereby forming a resist film having a desired thickness (e.g., 500 to 1000 nm). As the resist material, either a positive type resist or a negative type resist can be used, and a positive type resist is suitably used for a photomask substrate for manufacturing a display device. The resist coating step produces a photomask blank with a resist film.

(4) Drawing step

In step S4, the resist film is drawn by the drawing device based on desired pattern data. A laser drawing apparatus is preferably used for drawing by using an energy beam such as an electron beam or a laser beam when manufacturing a photomask for manufacturing a display device.

(5) Developing/etching process

In step S5, a resist pattern is formed by developing the resist film. Then, the light shielding film 3 is etched using the resist pattern as an etching mask. Examples of the etching method include a wet etching method and a dry etching method, and the wet etching method is suitably applied to the production of a photomask for the production of a display device. Through this developing/etching process, a light-shielding film pattern is formed. As described later, the unnecessary resist pattern is removed by the stripper in the cleaning step 2 (step S6).

The light shielding film pattern may be a single pattern for transfer of the photomask. Alternatively, the transfer pattern of the photomask may be formed together with another film or another film pattern.

II. post-procedure

(6) Cleaning step 2

In step S6, the resist pattern of the photomask blank having the light-shielding film pattern formed on the 1 st main surface is peeled off, followed by cleaning to remove foreign matter. Dirt such as fine resist residue that is not completely removed by the resist remover, and residue resulting from hydrolysis of the etchant of the light-shielding film 3 (if the light-shielding film is a Cr-based film, the etchant for Cr (cerium ammonium nitrate, etc.)) is removed, and the cleanliness required for defect detection in pattern defect inspection and for obtaining information on the position thereof, which is performed later, is obtained.

(7) Pattern defect inspection process

In step S7, the optical unit is scanned over the photomask pattern formed in the process up to step S6, and information on the presence or absence of a defect generated in the pattern, the type of the generated defect, the defect generation position or size, and the like is acquired.

(8) Correction procedure

In step S8, if the defect detected in step S7 can be corrected, the defect is corrected. For example, as a correction unit for the defect, a CVD laser apparatus or a focused ion beam apparatus is used to remove the remainder of the pattern, and/or a correction film is deposited on the peeled portion of the pattern.

(9) Cleaning step 3

In step S9, the photomask having the pattern is cleaned again.

(10) Foreign matter inspection step

In step S10, a foreign matter inspection step is performed to confirm that the pattern surface is free of foreign matter.

(11) Pellicle attaching step

In step S11, a Pellicle is attached to the pattern formation surface (1 st main surface) of the photomask requiring a Pellicle (Pellicle).

(12) Foreign matter inspection step

In step S12, a foreign matter inspection is further performed from the top film. Here, if a foreign substance is found, the foreign substance can be removed from the pellicle by irradiation with an energy ray (e.g., laser beam).

Through the above steps, a photomask can be manufactured.

In addition, defects generated in the photomask are mainly classified into the following two types.

The peeling defect as the 1 st defect is a defect in which the light transmittance exceeds a predetermined value due to peeling of the light-shielding film 3 at a position where the light-shielding film 3 should remain in the transfer pattern, or the like, and is also referred to as a white defect.

The remaining defect 2 is a defect in which the transmittance is lower than a predetermined value (including zero) due to the unnecessary light-shielding film remaining or the foreign material adhering to the transparent substrate or the formed transfer pattern, and is also referred to as a black defect.

Among these defects, the remaining defects are removed and corrected by means such as sublimation of unnecessary residual films or foreign substances by irradiating them with energy such as laser light. On the other hand, regarding the peeling defect, correction is performed by depositing a correction film (made of a material different from the light-shielding film) in the defective portion so as to function as in a normal light-shielding film pattern. However, the burden on the process is large, such as difficulty in correction after the pellicle is attached.

Further, according to the study of the present inventors, many defects generated in the production of a photomask are peeling defects, and most of the peeling defects are caused by a film formation step such as a light shielding film.

Therefore, if the correction load of the peeling defect can be reduced, it can be said that the efficiency of the photomask manufacturing process can be improved.

Fig. 2 is a diagram schematically showing the cause of the occurrence of the peeling defect.

As shown in fig. 2 (a), a transparent substrate 1 made of a transparent material such as glass is prepared for manufacturing a photomask substrate. As described above, quartz (SiO) is preferable as the material of the transparent substrate 1₂) Synthetic quartz is suitably used.

As shown in fig. 2 (b), the light shielding film 3 is formed by the film forming apparatus. The light-shielding film 3 may have an antireflection layer 5 on its surface.

The film forming process is performed in a state where the central value and the deviation of the film thickness are accurately managed. However, in this case, foreign matter may be mixed into the film.

For example, when a film material deposited (adhered) inside a vacuum chamber of a film forming apparatus (sputtering apparatus or the like) grows to some extent, the film material may detach due to its own weight or film stress, become foreign matter, fall, and adhere to a transparent substrate during film formation. Which remains as foreign matter 11 in the film on the photomask substrate.

Fig. 2(c) shows the following states: in the lamination of the light-shielding film 3 and the antireflection layer 5, foreign matter (film foreign matter 11) falls off in any subsequent process, and a fall-off defect 15 is generated.

The size of the foreign matter generated in the vacuum chamber is usually about 0.5 to 10 μm. As the film grows, detachment of foreign matter from the inner wall of the apparatus or the like easily occurs, and therefore it is not uncommon for the size to exceed 1 μm.

The film thickness of the light-shielding film 3 is preferably not more than 200nm (preferably 50 to 200 nm). If the film thickness of the light-shielding film 3 is too large, the accuracy of patterning (particularly, wet etching) is likely to deteriorate. For example, there is a risk that the etching cross section of the light-shielding film 3 is inclined and a fine pattern cannot be formed precisely. In particular, in a difficult pattern such as a hole pattern having a CD (pattern width) of 2 μm or less, a line pattern of a line-space pattern, or the like, the film thickness of the light-shielding film is limited.

In this case, since the size of the foreign matter is larger than the film thickness of the light shielding film 3, part of the foreign matter is buried in the film, but the other part is often exposed from the film surface. If they fall off the light-shielding film 3 at any stage of the photomask manufacturing process or during the processing of the photomask after the manufacturing, pinholes are generated in the light-shielding film 3 as shown in fig. 2 (c). The peeling defect 15 becomes conspicuous as a photomask.

In the transparent substrate 1 for a photomask on which the light-shielding film 3 is formed, if the light-shielding film 3 does not have the peeling defect (including a potential peeling defect) 15, it is considered that the occurrence of the peeling defect in the photomask is substantially suppressed. In this case, the mask manufacturing process shown in fig. 1(a) can be shortened. This is because the three steps of the pattern defect inspection, correction, and cleaning 3 in fig. 1(a) may not be necessary.

Therefore, the present inventors have studied a method of forming the light-shielding film 3 on the transparent substrate 1 and reducing the peeling defect of the light-shielding film 3 to approach zero in a state before patterning the light-shielding film 3.

That is, a method for manufacturing a photomask blank according to the present invention is a method for manufacturing a photomask blank having a light-shielding film on a transparent substrate, the photomask blank being formed by patterning at least the light-shielding film to form a transfer pattern including a light-transmitting portion and a light-shielding portion.

The light-shielding film includes an upper layer and a lower layer each having a light-shielding property with an optical density OD of 1.5 or more, and the method for manufacturing the photomask substrate includes the steps of: forming a lower layer directly or indirectly on the transparent substrate; a step of performing a foreign matter removal treatment on the surface of the lower layer; and a step of forming the upper layer directly or indirectly on the lower layer.

The method for manufacturing a photomask blank according to the present embodiment will be described below with reference to fig. 1(b) and 3.

(1) Formation of an underlayer on a transparent substrate

In step S1, the transparent substrate 1 is prepared (see fig. 3a), and the lower layer 3a is formed. The material of the transparent substrate 1 is the same as in the case of fig. 1 (a).

That is, the lower layer 3a is formed on one main surface of the transparent substrate 1. The lower layer 3a is a film constituting the light-shielding film 3 together with an upper layer 3b described later.

The lower layer 3a has light-shielding properties with an optical density OD of 1.5 or more. The optical density OD is preferably 2.0 or more, and more preferably 2.5 or more. The film material and the film thickness of the lower layer 3a are determined so as to satisfy the optical density OD, and these are reflected in the film formation conditions.

The material of the lower layer 3a satisfies the above-described optical density OD value according to a predetermined film thickness, and examples thereof include a material containing chromium (Cr) or a material containing a transition metal and Si (silicon).

Examples of the material of the lower layer 3a include Cr and compounds thereof (oxides, nitrides, carbides, oxynitrides, or oxynitrides). Alternatively, the material of the lower layer 3a may be a material containing Si and at least one of Ta (tantalum), Mo (molybdenum), and Ti (titanium), or a material composed of an oxide, nitride, oxynitride, carbide, or oxynitride of these materials.

More specifically, examples of the material of the lower layer 3a include molybdenum silicon nitride (MoSiN), molybdenum silicon oxynitride (MoSiON), molybdenum silicon oxide (MoSiO), silicon oxynitride (SiON), titanium oxynitride (TiON), and the like.

The lower layer 3a preferably contains a material that can be wet-etched. The film thickness of the lower layer 3a may be, for example, 5nm or more and 190nm or less.

In the film forming step of the lower layer 3a, foreign matter 11 may be mixed in the film of the lower layer 3a (see fig. 3 (b)).

(2) Foreign matter removal treatment

In the present embodiment, as shown in step S1-2, the photomask blank with the foreign matter 11 mixed therein is subjected to a foreign matter removal process.

The foreign matter removal treatment is a cleaning treatment performed while applying a mechanical force to the surface to be cleaned (here, the surface of the lower layer 3a), and is a cleaning accompanied by so-called physical cleaning. Specifically, the cleaning is performed by applying a mechanical force to the surface to be cleaned with a cleaning tool 21 (brush, sponge, or the like) or a liquid flow (liquid flow by ultrasonic waves, liquid flow by jet flow, shower, bubbling, or the like) while using a cleaning liquid (water or reagent) 31. This promotes the shedding of foreign matter in the film, which may cause the shedding defect, and thus promotes the visualization of the defect.

In order to effectively remove foreign matter from the photomask substrate, contact cleaning is more preferably performed by bringing the cleaning tool 21 such as the brush or the sponge mentioned above into physical contact with the surface to be cleaned (see fig. 3 c).

In addition, it is preferable to use the cleaning liquid 31 in combination in cleaning, and in this case, as a reagent to be used, a diluent of an alkaline reagent such as TMAH (tetramethylammonium hydroxide) or KOH, a surfactant, or the like can be used as an example.

By the above treatment, the foreign matter 11 is detached, and a defective portion (pinhole) 15 of the lower layer 3a is generated (see fig. 3 d). If the lower layer 3a is a single layer, the peeling defect is clearly evident. The size of the defect 15 of the lower layer 3a reflects the size of the foreign matter, and is 0.5 to 10 μm, more specifically, about 1 to 10 μm. In addition, the size of the defect (here, the size of the defective portion 15 of the film) can be grasped from the distance between a plurality of intersection points where the straight line intersects the outer edge of the region and the distance to the maximum when the straight line is overlapped with the defective region of the film.

At this time, the defective portion 15 of the lower layer is likely to be in a state of not satisfying the value of the optical density OD1.5 required as the light-shielding film.

In this embodiment, defect correction processing such as pattern defect inspection and deposition of a correction film on a defective portion of the lower layer is not performed at this stage.

(3) Formation of the upper layer

In step S1-3, the upper layer 3b is formed on the lower layer 3a having the defective portion 15 (see fig. 3 (e)). The defective portion 15 is covered with the upper layer 3b as the lower defective portion 3 c.

The upper layer 3b also has light-shielding properties with an optical density OD of 1.5 or more. The optical density OD of the upper layer 3b is preferably 2.0 or more, more preferably 2.5 or more. The optical density OD of the upper layer 3b also satisfies the above range depending on the film material and film thickness, as in the lower layer 3 a.

The material of the upper layer 3b may be selected from the same group as the material of the lower layer 3 a. The upper layer 3b and the lower layer 3a may have the same or different composition, and may have the same or different composition.

However, in the patterning in the photomask manufacturing process, the upper layer 3b and the lower layer 3a are preferably etched with the same etchant (etching solution in the case of wet etching), and therefore, the etching characteristics of the upper layer 3b and the lower layer 3a are preferably common.

The upper layer 3b and the lower layer 3a more preferably contain the same component, and the composition may be the same. For example, when the lower layer 3a contains Cr, the upper layer 3b preferably contains Cr in the same manner.

The film thickness of the upper layer 3b may be, for example, 5nm to 190nm, similarly to the film thickness of the lower layer 3 a.

Preferably, the photomask blank in the state in which the upper layer 3b is formed may be as follows.

That is, the photomask blank of the present embodiment is a photomask blank for forming a light-shielding film on a transparent substrate and forming a transfer pattern including a light-shielding portion and a light-transmitting portion by patterning at least the light-shielding film,

the light-shielding film has a film thickness of 200nm or less and includes an upper layer and a lower layer made of a material etched with the same etchant,

the upper layer and the lower layer each have a light-shielding property with an optical density OD of 1.5 or more,

the light-shielding film has a lower layer defective portion in which a defective portion of 0.5 to 10 μm size generated in the lower layer is covered with the upper layer,

the light-shielding film has an optical density OD of 1.5 or more over the entire surface thereof.

In the photomask blank of the present embodiment, after the formation of the upper layer 3b, the antireflection layer 5 may be further formed on the upper layer 3b (see fig. 3 (f)). The antireflection layer 5 can prevent stray light generated in the exposure apparatus during exposure, and can suppress generation of a standing wave due to reflection of a laser beam for drawing during pattern drawing.

The anti-reflection layer 5 preferably has etching characteristics common to the upper layer 3b and the lower layer 3 a. Therefore, when the upper layer 3b and the lower layer 3a contain Cr, the antireflection layer 5 also preferably contains Cr.

The antireflection layer 5 may be a film having an optical density OD of about 1.0.

Note that, during the film formation of the upper layer 3b or the film formation of the antireflection layer 5, it is also assumed that foreign matter is mixed.

Fig. 4 is a diagram showing a state in which foreign matter is mixed in at the time of forming the upper layer 3b or at the time of forming the antireflection layer 5.

The steps (a) to (d) of fig. 4 are the same as the steps (a) to (d) of fig. 3. Therefore, only the steps after fig. 4 (e) will be described below.

Fig. 4 (e) is a diagram showing a state in which foreign matter 41 is mixed in the upper layer 3 b. The foreign matter 41 may fall off in any process (e.g., a cleaning process) of manufacturing the photomask, and may cause a defect in the upper layer 3 b.

However, the probability that the defect position of the upper layer 3b matches the defect position of the lower layer 3a is extremely low and is substantially zero. Therefore, even if a defect is formed in the upper layer 3b, the light-shielding property having an optical density OD1.5 or more required as a light-shielding film can be satisfied over the entire surface of the light-shielding film. The optical density OD is preferably 2.0 or more, and more preferably 2.5 or more.

The upper limit of the optical density OD of the light-shielding film is preferably 6.0. This makes it possible to avoid the problem of the film thickness being excessively large (exceeding 200nm) and the patterning accuracy being deteriorated in order to improve the light-shielding property.

The photomask blank according to the present embodiment shown in fig. 4 (e) has the foreign matter 41 on the surface thereof, and even if the foreign matter 41 is removed in any subsequent step, the defect of removal of the photomask blank is not generated, as described above.

However, if the photomask manufacturing process (patterning) is performed while the foreign matter 41 is held, there is a possibility that the foreign matter 41 falls off and adheres to the pattern surface.

Therefore, as shown in fig. 4 (f), it is preferable to remove the foreign matter 41 that may have come off by performing the foreign matter removal treatment by the cleaning tool 21 and the cleaning liquid 31 again on the surface of the upper layer 3b in the same manner as described above. This may be performed simultaneously with the step S2a of cleaning 1' (pre-application cleaning) in fig. 1 (b).

The photomask blank of fig. 4 (g) in which the upper layer 3b and the lower layer 3a have defects may have the antireflection layer 5 in the uppermost layer of the light-shielding film.

Then, the photomask blank provided with the light-shielding film including the lower layer 3a and the upper layer 3b may be subjected to the Resist (Resist) application process of step S3 in fig. 1(a),

Rendering processing of step S4

Development, etching treatment in step S5,

Similarly to the cleaning 2 process of step S6, the process shown in FIG. 1(b) is performed

Resist coating processing in step S3,

The drawing processing in step S4,

Development, etching treatment in step S5,

Cleaning 2' processing of step S6 a.

After that, the pattern defect inspection of step S7 performed after the cleaning 2 of step S6 in fig. 1(a) may be performed.

However, in the photomask blank manufacturing method of the present embodiment, the pattern defect inspection process may be omitted. This is because the cause of the peeling defect is removed in advance by using the defect-free photomask substrate.

Next, it is confirmed that there is no foreign substance through the foreign substance inspection in step S7a, a pellicle is attached in step S11, and the final foreign substance inspection is performed in step S12, thereby completing the photomask product.

In the above step, a film (additional film) having an additional property or an additional film pattern obtained by patterning the additional film may be provided on the upper side or the lower side of the light-shielding film within a range not to impair the object of the present invention. That is, the photomask blank of the present invention may be a binary mask formed by patterning the light-shielding film, or may be a photomask having an additional film pattern.

Here, the additional film may be an optical film or a functional film other than the light-shielding film. The optical film is a semi-transparent film that transmits a part of the exposure light, and includes an optical film having a predetermined exposure light transmittance (for example, 3 to 60%) and a phase shift amount of the exposure light of 90 degrees or less. Such an additional film is used in a process of forming a multi-tone photomask. Alternatively, the semi-transparent film may be a semi-transparent film having the above exposure transmittance and having a phase shift amount of exposure light of 180 ± 20 degrees. Such additional films are suitable for use in the formation of phase shift masks.

As the functional film, a conductive film, an insulating film, and an etching stopper film can be exemplified.

In addition, other films may be interposed between the upper layer and the lower layer and between the upper layer and the antireflection layer within a range not to impair the effects of the present invention. Other films may also be interposed between the transparent substrate and the lower layer.

As described above, the photomask substrate is a substrate in which at least a light-shielding film is formed on a transparent substrate.

For example, the photomask blank may be used for manufacturing a binary mask, or may be a photomask intermediate in which an optical film pattern and a light-shielding film for forming a light-shielding film pattern are formed on a transparent substrate.

Fig. 5 is a sectional view showing an example of a configuration of a photomask manufactured using the photomask substrate of the present embodiment.

As shown in fig. 5, the photomask manufactured by using the photomask substrate of the present embodiment is a photomask including a transfer pattern including a light-shielding portion 61 and a light-transmitting portion 63, the transfer pattern being formed by patterning a light-shielding film 3 formed on a transparent substrate 1. Here, the light-shielding portion 61 is formed by forming the light-shielding film 3 on the transparent substrate 1, and the light-transmitting portion 63 is formed by exposing the transparent substrate 1.

The light-shielding film 3 has a film thickness of 200nm or less, and includes an upper layer 3b and a lower layer 3 a. The upper layer 3b and the lower layer 3a are made of a material etched with the same etchant, and have light-shielding properties with an optical density OD of 1.5 or more, respectively.

The light-shielding film 3 in the light-shielding portion 61 has: a lower layer defective portion 3c in which a defective portion caused by the foreign matter mixed in the lower layer 3a is covered with the upper layer 3 b; and a portion where the upper layer 3b is broken due to the foreign matter mixed into the upper layer 3b and only the lower layer 3a remains where the upper layer broken portion 45 is formed, but the optical density OD can be maintained at 1.5 or more over the entire surface of the light shielding portion 61.

By the technique for processing a photomask blank according to the present embodiment, the photomask blank subjected to the photomask manufacturing process is substantially free of defects. Since most of the peeling defects generated in the photomask are caused by the film forming process, the defect correcting process of the photomask can be significantly reduced by the photomask substrate processing technique of the present embodiment, and the production efficiency and yield of the photomask can be improved.

In the above-described embodiments, the illustrated configuration and the like are not limited thereto, and may be appropriately modified within a range in which the effects of the present invention are exhibited. In addition, the present invention may be modified as appropriate without departing from the intended scope of the present invention.

Further, each component of the present invention may be arbitrarily selected, and an invention having a selected structure is also included in the present invention.

Industrial applicability

The present invention can be used as a method for manufacturing a photomask substrate.

Description of the symbols

1 transparent substrate

3 light-shielding film

3a lower layer

3b upper layer

3c lower layer defect

5 anti-reflection layer

11. 41 foreign matter

15 defective part

21 cleaning tool

31 cleaning liquid

45 upper layer defect part

61 light-shielding part

63 light transmission part

Claims

1. A method of manufacturing a photomask substrate having a light-shielding film on a transparent substrate, the photomask substrate being used for forming a pattern for transfer including a light-transmitting portion and a light-shielding portion by patterning at least the light-shielding film to thereby produce a photomask, wherein,

the light-shielding film comprises an upper layer and a lower layer each having a light-shielding property with an optical density OD of 1.5 or more,

the method for manufacturing the photomask blank comprises the following steps:

forming the lower layer on the transparent substrate;

a step of performing a 1 st foreign matter removal treatment on the surface of the lower layer; and

and forming the upper layer on the lower layer.

2. The method of manufacturing a photomask substrate according to claim 1, wherein the step of performing the 2 nd foreign substance removal treatment is performed after the step of forming the upper layer.

3. The method for manufacturing a photomask substrate according to claim 1 or 2, wherein the light-shielding film further has an antireflection layer on the upper layer.

4. The method of manufacturing a photomask-blank according to claim 1 or 2, wherein the upper layer and the lower layer are composed of a material etched with the same etchant.

5. The method for manufacturing a photomask substrate according to claim 1 or 2, wherein the film thickness of the light-shielding film is 200nm or less.

6. The method of manufacturing a photomask substrate according to claim 1 or 2, wherein any one of an additional film and an additional film pattern is provided on an upper side or a lower side of the light-shielding film.

7. The method of manufacturing a photomask substrate according to claim 1 or 2, wherein the upper layer and the lower layer are each composed of a material containing Cr.

8. A method for manufacturing a photomask, comprising the steps of:

a step of preparing a photomask blank manufactured by the method for manufacturing a photomask blank according to any one of claims 1 to 7; and

and patterning the light shielding film.

9. A photomask blank having a light-shielding film formed on a transparent substrate, the photomask blank being used for forming a transfer pattern including a light-shielding portion and a light-transmitting portion by patterning at least the light-shielding film, wherein,

the light-shielding film has a lower layer defective portion in which a defective portion of 0.5 to 10 μm generated in the lower layer is covered with the upper layer,

10. The photomask substrate according to claim 9, wherein the photomask substrate has an upper layer defect portion in which a defect of 0.5 to 10 μm is generated in the upper layer.

11. The photomask substrate according to claim 9 or 10, wherein the light-shielding portion is formed by forming at least the light-shielding film on the transparent substrate and has an antireflection layer on the upper layer.

12. A method of manufacturing a photomask, comprising:

a step of preparing the photomask substrate according to any one of claims 9 to 11; and

and patterning the light shielding film.

13. A photomask comprising a transfer pattern including a light-shielding portion and a light-transmitting portion, the transfer pattern being formed by forming a light-shielding film on a transparent substrate and patterning at least the light-shielding film, wherein the photomask comprises a photomask having a light-shielding layer and a light-transmitting portion,

the light shielding portion is formed by forming the light shielding film on the transparent substrate,

the light-transmitting part is formed by exposing the transparent substrate,

the light-shielding film has a film thickness of 200nm or less and includes an upper layer and a lower layer,

the upper layer and the lower layer are made of materials etched by the same etchant, and have light shielding properties with optical density OD of 1.5 or more,

the light-shielding film has a lower layer defective portion in which a defective portion having a size of 0.5 to 10 μm generated in the lower layer is covered with the upper layer,

the light-shielding portion has an optical density OD of 1.5 or more over the entire surface thereof.