JP2021157121A - Manufacturing method of lithography mask, lithography mask, and manufacturing method of semiconductor device - Google Patents

Abstract

To provide a method that can apply accurate correction to a lithography mask that has a defect in which a dimension of a transfer pattern deviates from a target dimension to form a transfer image of a normal dimension on a transferee using the obtained corrected lithography mask.SOLUTION: A method of manufacturing a lithography mask 10 for forming a transfer image on a transferee by exposure using an exposure apparatus, in which the lithography mask is provided with a transfer pattern including a thin film forming portion 21 in which a thin film pattern is formed and a light transmitting portion 22 in which a transparent substrate is exposed, comprises: a transfer pattern correction step for correcting a transfer pattern; an inspection step for grasping a dimension of a thin film pattern; a specification step for specifying a correction region to be corrected to a defect in which a dimension of a thin film pattern is deficient to a target dimension; and a correction film deposition step for depositing a correction film of a necessary thickness on a thin film pattern remaining in a correction region so that a transfer image of normal dimension can be formed on the transferee by exposure.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for manufacturing a lithography mask, a lithography mask, and a method for manufacturing a semiconductor device. The present invention particularly relates to a method for manufacturing a lithography mask, a lithography mask, and a method for manufacturing a semiconductor device, which are suitable for semiconductor manufacturing.

Patent Document 1 describes a technique for correcting black defects and white defects of a mask by using an electron beam.

Patent Document 2 describes a technique for modifying a lithography mask by properly using an electron beam and an atomic force microscope probe.

Japanese Unexamined Patent Publication No. 2004-294613 Japanese Unexamined Patent Publication No. 2006-139049

High integration and miniaturization of semiconductor elements are accelerating, and transfer patterns formed on lithography masks (reticles) for transferring patterns to wafers are also being miniaturized. Therefore, in the manufacture of lithography masks, it is important to precisely control the dimensions of the transfer pattern.

However, in the manufacturing process of the lithography mask, it is not easy to match the dimensions of the transfer pattern with the target dimensions (hereinafter, also referred to as the target dimensions d), and it is difficult to completely avoid defects due to the mismatch of dimensions. Met. FIG. 1 shows an example of a defect due to a dimensional mismatch. The upper part of FIG. 1A is a plan view showing an example of a lithography mask having a defect in a state where the dimension of the thin film pattern 13 included in the transfer pattern is insufficient (small) with respect to the target dimension d. The lower part is a cross-sectional view when the lithography mask shown in the plan view is cut along the line AA'. The upper part of FIG. 1B is a plan view showing an example of a lithography mask in which the dimension of the thin film pattern 13 is excessive (large) with respect to the target dimension d, and the lower part is shown in the plan view. It is sectional drawing when the lithography mask is cut along the BB'line.

As a method for correcting defects in the lithography mask, there are a method using a focused ion beam (FIB) and a technique using an electron beam (Electron Beam, EB). In the defect correction method of the lithography mask described in Patent Document 1, the electron beam is tilted with respect to the sample, the lens surface of the objective lens is tilted at a desired angle with respect to the tilted electron beam, and the lens surface is focused by the objective lens. In addition, the correction is performed so that the side surface of the correction portion has a vertical side surface by scanning and irradiating the inclined electron beam.

Further, in the method for correcting a lithography mask described in Patent Document 2, black defects and white defects are corrected by properly using an electron beam and an atomic force microscope depending on the type of material and defect, which is optimal. It is said that the mask can be corrected by the correction method.

A lithography mask for a semiconductor device includes a transfer pattern formed on a substrate, and the transfer pattern is obtained by patterning a thin film formed on a transparent substrate. The dimensions of the transfer pattern may deviate from the target dimensions due to various factors such as an error of the drawing device for patterning. One of the above factors is, for example, insufficient drying after developing the resist film, which causes droplets or the like to remain or adhere to the thin film, resulting in a residue (so-called watermark). , Etching of the thin film may be hindered, and as a result, a defect may occur in which the size of the thin film pattern deviates from the target size d. In order to correct a defect due to such a dimensional deviation, only an unnecessary thin film is removed by using a method such as Patent Document 1 or Patent Document 2, or a correction film is formed in a region where the thin film is missing. It is conceivable to deposit.

However, when the correction is performed by using the correction method described in Patent Document 1 or Patent Document 2, even the necessary thin film in the region other than the black defect is removed, or not only the white defect region but also the surrounding area thereof. However, there is a possibility that the correction film may be deposited, and it was difficult to correct the position accurately. Therefore, it has not been easy to form a transfer image having normal dimensions on the transferred body by using the lithography mask modified by the modification method as described above.

Therefore, the present inventors have made precise corrections to the lithography mask having a defect that the dimensions of the transfer pattern deviate from the target dimension d so that a transfer image having normal dimensions can be formed on the transferred object. Then, the present invention was completed in order to obtain a lithography mask with high dimensional accuracy.

The first aspect of the present invention is
A method for manufacturing a lithography mask for forming a transfer image on a transfer target by exposing it with an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The method for manufacturing a lithography mask includes a transfer pattern correction step of modifying the transfer pattern.
The transfer pattern correction step is
An inspection process for grasping the dimensions of the thin film pattern and
A specific step of specifying a correction area to be corrected for a defect whose dimensions of the thin film pattern are insufficient with respect to the target size, and
A modification film deposition step of depositing a modification film having a required thickness on the thin film pattern remaining in the modification region so that the transfer image having normal dimensions can be formed on the transfer object by the exposure.
It is a method for manufacturing a lithography mask, which comprises.

A second aspect of the present invention is
The method for manufacturing a lithography mask according to the first aspect, wherein the modified film is deposited only on the thin film pattern that remains substantially in the modified region in the modified film deposition step. ..

A third aspect of the present invention is
The method for manufacturing a lithography mask according to the first or second aspect, wherein the modified film does not have a cross section to be etched.

A fourth aspect of the present invention is
The method for manufacturing a lithography mask according to any one of the first to third aspects, wherein the modified film has a film thickness of 1 to 100 nm.

A fifth aspect of the present invention is
A method for manufacturing a lithography mask that forms a transfer image on a transfer target by exposing it with an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The method for manufacturing a lithography mask includes a transfer pattern correction step of modifying the transfer pattern.
The transfer pattern correction step is
An inspection process for grasping the dimensions of the thin film pattern and
A specific step of specifying a correction region to be corrected for a defect in which the size of the thin film pattern is excessive with respect to the target size, and
A film thinning step of removing a required amount of the thin film pattern in the modified region in the film thickness direction so that the transferred image having normal dimensions can be formed on the transferred object by the exposure.
It is a method for manufacturing a lithography mask, which comprises.

A sixth aspect of the present invention is
The method for manufacturing a lithography mask according to the fifth aspect, wherein the dimensions of the thin film pattern in the modified region are substantially maintained in the film thinning step.

A seventh aspect of the present invention is
The lithography according to the fifth or sixth aspect, wherein in the film thinning step, the required amount of the thin film pattern in the modified region is removed by a gas-assisted etching method using a charged particle beam. This is a method for manufacturing a mask.

The eighth aspect of the present invention is
The lithography according to the fifth or sixth aspect, wherein in the film thinning step, the required amount of the thin film pattern in the modified region is removed by using a probe of an atomic force microscope. This is a method for manufacturing a mask.

A ninth aspect of the present invention is
A lithography mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The thin film pattern has a correction area in which a defect that is dimensionally insufficient with respect to the target size is corrected.
A required amount of correction film in the thickness direction is deposited on the thin film pattern remaining in the correction region so that the transfer image having normal dimensions is formed on the transfer target by the exposure. It is a lithography mask characterized by being present.

A tenth aspect of the present invention is
The lithography mask according to the ninth aspect, wherein the modified film is deposited only on the thin film pattern that remains substantially in the modified region.

The eleventh aspect of the present invention is
The lithography mask according to the ninth or tenth aspect, wherein the correction film has a film thickness of 1 to 100 nm.

A twelfth aspect of the present invention is
A lithography mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film of a predetermined film thickness is patterned on a transparent substrate and a translucent portion in which the transparent substrate is exposed. ,
The thin film pattern has a correction area in which defects that are oversized with respect to the target size have been corrected.
The feature is that the film thickness of the thin film pattern in the correction region is made smaller than the predetermined film thickness so that the transfer image having normal dimensions is formed on the transferred body by the exposure. It is a lithography mask.

A thirteenth aspect of the present invention is
The lithography mask according to the twelfth aspect, wherein the film thickness of the thin film pattern in the correction region is 1 to 105 nm smaller than the predetermined film thickness.

A fourteenth aspect of the present invention is
The step of preparing the lithography mask according to the manufacturing method according to any one of the first to eighth aspects or the lithography mask according to any one of the ninth to thirteenth aspects.
A step of exposing the lithography mask using an exposure apparatus and forming the transfer image on the transfer target.
It is a manufacturing method of a semiconductor device including.

According to the present invention, it is possible to precisely correct a lithography mask having a defect that the dimensions of the transfer pattern deviate from the target dimensions, and the obtained corrected lithography mask can be used on the transferred object. A transfer image of normal dimensions can be formed.

The upper part of FIG. 1A is a plan view showing an example of a lithography mask having a defect in a state where the dimension of the thin film pattern 13 included in the transfer pattern is insufficient (small) with respect to the target dimension d. The lower part is a cross-sectional view when the lithography mask shown in the plan view is cut along the line AA'. The upper part of FIG. 1B is a plan view showing an example of a lithography mask in which the dimension of the thin film pattern 13 is excessive (large) with respect to the target dimension d, and the lower part is shown in the plan view. It is sectional drawing when the lithography mask is cut along the BB'line. FIG. 2A is a cross-sectional view of a lithography mask model (referred to as a mask model) in which the target pattern 12 to be formed is provided on the transparent substrate 11. FIG. 2B is a cross-sectional view of a lithography mask having a defect in which the dimension of the thin film pattern 13 included in the transfer pattern 20 is insufficient (small) with respect to the target dimension d. FIG. 2C is a cross-sectional view of a lithography mask in which the correction film 14 is deposited on the thin film remaining in the correction region Z2. FIG. 3A is a cross-sectional view of a model of a lithography mask (referred to as a mask model) in which the target pattern 12 to be formed is provided on the transparent substrate 11. FIG. 3B is a cross-sectional view of a lithography mask having a defect in which the dimension of the thin film pattern 13 is excessive (large) with respect to the target dimension d. FIG. 3C is a cross-sectional view of a lithography mask in which a thin film in the correction region Z2 is partially removed in the film thickness direction. The upper part of FIG. 4A is a plan view of the lithography mask 10 before modification, and the lower part is a cross-sectional view when the lithography mask 10 before modification shown in the plan view is cut along the AA'line. Is. The upper part of FIG. 4B is a plan view of the corrected lithography mask 10, and the lower part is a cross-sectional view when the corrected lithography mask 10 shown in the plan view is cut along the AA'line. Is. FIG. 5 is an image captured by a scanning electron microscope of a part of the transfer pattern 20 of the uncorrected mask. FIG. 6 is a graph showing a light intensity curve of the transfer pattern 20 before modification and a light intensity curve of a normal pattern. FIG. 7A is an image captured by a scanning electron microscope of a part of the modified transfer pattern 20. FIG. 7B is a diagram showing the results of measuring the surface shape of the modified lithography mask 10 (modified mask) with an atomic force microscope. FIG. 8 is a graph showing a light intensity curve of the corrected transfer pattern 20 and a light intensity curve of a normal pattern. FIG. 9 shows the line widths of the corrected transfer pattern 20 on which the correction film 14 is deposited and the pattern transferred onto the wafer (transferred body) of the normal pattern (the correction film 14 is not deposited). It is a graph which shows the result of having obtained the relationship with a focus position by a simulation. The upper part of FIG. 10A is a plan view of the lithography mask 10 before modification, and the lower part is a cross-sectional view when the lithography mask 10 before modification shown in the plan view is cut along the AA'line. Is. The upper part of FIG. 10B is a plan view of the corrected lithography mask 10, and the lower part is a cross-sectional view when the corrected lithography mask 10 shown in the plan view is cut along the AA'line. Is. FIG. 11 is an image captured by a scanning electron microscope of a part of the transfer pattern 20 of the uncorrected mask. FIG. 12 is a graph showing a light intensity curve of the transfer pattern 20 before modification and a light intensity curve of a normal pattern. FIG. 13A is an image captured by a scanning electron microscope of a part of the modified transfer pattern 20. FIG. 13B is a diagram showing the results of measuring the surface shape of the modified lithography mask 10 (modified mask) with an atomic force microscope. FIG. 14 is a graph showing a light intensity curve of the corrected transfer pattern 20 and a light intensity curve of a normal pattern. FIG. 15 shows the line width and focus of the corrected transfer pattern 20 in which the film thickness of the thin film is reduced and the pattern transferred onto the wafer (transferred body) of the normal pattern (not reduced). It is a graph which shows the result of having obtained the relationship with a position by a simulation.

In lithography masks for semiconductor devices, the transfer pattern is becoming finer, and the dimensions of the transfer pattern approach the wavelength of the exposure light (for example, the wavelength of 193 nm, which is the exposure light of the ArF excimer laser), or It is becoming smaller than the wavelength of the exposure light. For this reason, due to the influence of the three-dimensional structure (three-dimensional structure) of the transfer pattern, a discrepancy can be seen between the transfer characteristics obtained by the two-dimensional simulation and the transfer characteristics of the actual lithography mask. Therefore, in the development of the lithography mask, in order to reduce the above deviation, a method of reducing the influence of the three-dimensional structure (three-dimensional structure, height) of the thin film pattern included in the transfer pattern is being studied.

On the other hand, the present inventors correct the defect due to the above-mentioned dimensional deviation by positively using the thin film pattern instead of reducing the influence of the three-dimensional structure which is the cause of the above deviation. I found out what I could do. That is, according to the study by the present inventors, the defect due to the dimensional deviation of the thin film pattern grasped on the plane (two-dimensional) is not corrected on the plane, but is transferred normally by changing the three-dimensional structure of the thin film pattern. It became clear that a pattern can be obtained.

2 (a) and 3 (a) show a cross section of a model (referred to as a mask model) of a lithography mask having a target pattern 12 to be formed on a transparent substrate 11. The dimension of the target pattern 12 is the target dimension d. FIG. 2B shows a cross section of a lithography mask having a defect in which the dimension of the thin film pattern 13 included in the transfer pattern 20 is insufficient (small) with respect to the target dimension d, and is shown in FIG. 3B. Shows a cross section of a lithography mask having a defect in which the dimension of the thin film pattern 13 is excessive (large) with respect to the target dimension d.

When a defect as shown in FIGS. 2 (b) or 3 (b) is corrected by using a conventional correction method as described in Patent Document 1 or Patent Document 2, the dimension itself is corrected, that is, It is conceivable to deposit a correction film at a place where the necessary thin film is missing, or to remove the unnecessary thin film.

However, as described above, even if the correction method as described in Patent Document 1 or Patent Document 2 is used, it is difficult to make a precise correction so as to match the target dimension d. This is because when the dimensional deviation amount Δd is very fine, for example, 3 to 20 nm, the area and dimensions for depositing the correction film or the area and dimensions for the thin film to be removed are also very fine, and the correction position. This is because it is difficult to precisely control. In this specification, "A to B" means a numerical range of "A or more and B or less".

By the way, in FIGS. 2 (a) and 3 (a), the curve at the upper part of the mask model is a region surrounded by a broken line in the figure (referred to as a reference region Z1) assuming that the mask model is exposed. ) Shows a schematic diagram of the light intensity distribution. Further, in FIGS. 2 (b) and 3 (b), the curve at the top of the lithography mask represents a schematic diagram of the light intensity distribution in the region corresponding to the reference region Z1 when the lithography mask is exposed. There is.

In the lithography mask before modification in FIG. 2B, the dimension of the thin film pattern 13 in the region corresponding to the reference region Z1 is insufficient with respect to the target dimension d, and the peak of the light intensity distribution in the region is reached. Is higher than the peak of the light intensity distribution in the reference region Z1 of the mask model shown in FIG. 2 (a).

In the lithographic mask before modification of FIG. 3B, the dimension of the thin film pattern 13 in the region corresponding to the reference region Z1 is excessive with respect to the target dimension d, and the peak of the light intensity distribution in the region is It is lower than the peak of the light intensity distribution in the reference region Z1 of the mask model shown in FIG. 3 (a).

In order to form a transfer image of normal dimensions on the transferred object, the light intensity distribution of the lithography mask as shown in FIG. 2 (b) or FIG. 3 (b) is measured in FIG. 2 (a) or FIG. It is useful to match the light intensity distribution of the mask model as shown in a).

Therefore, the present inventors have conducted diligent studies and found that the light intensity distribution of the lithography mask can be controlled by adjusting the three-dimensional shape (height) of the thin film pattern 13. Specifically, the region to be modified is specified as the modification region Z2, and as shown in FIG. 2 (c), the modification film 14 is deposited on the thin film remaining in the modification region Z2, or FIG. 3 (c). As shown in the above, it has been found that the light intensity distribution in the modified region Z2 can be controlled by partially removing (reducing) the thin film in the modified region Z2 in the film thickness direction.

This makes it possible to match the light intensity distribution of the modified lithography mask with the light intensity distribution of the mask model, and as a result, by using this modified lithography mask, transfer of normal dimensions on the transferred object. An image can be formed.

In the present specification, the dimension refers to the dimension on the plane when the lithography mask is viewed in a plan view from the main surface side on which the transfer pattern is formed, and is perpendicular to the main surface like the film thickness of the thin film. Dimensions in the direction (thickness direction, film thickness direction) are not included unless otherwise specified.

<First Embodiment>
Hereinafter, the correction step included in the method for manufacturing the lithography mask 10 according to the first embodiment of the present invention will be specifically described. First, the defects of the lithography mask 10 and the transfer pattern 20 according to the present embodiment will be described. explain. In the present specification, the transfer pattern before the modification and the transfer pattern after the modification are collectively referred to as a transfer pattern 20, and the same applies to the thin film pattern 13.

The lithography mask 10 according to the present embodiment has a transfer pattern 20 obtained by applying lithography to a mask substrate described later and by patterning a thin film formed on the transparent substrate 11 (). (See FIG. 4A), the transfer pattern 20 is a transparent region (thin film forming portion 21) in which a thin film pattern 13 is formed by patterning a thin film on a transparent substrate 11 and a transparent substrate 11 is exposed. The light unit 22 and the like can be included. The lithography mask 10 of the present invention includes a transmissive photomask used for forming a transfer image on a transfer target by applying photolithography. Further, the lithography mask 10 of the present invention is a reflective mask (so-called EUV mask) used for forming a transfer image on an object to be transferred using extreme ultraviolet rays (Extreme Ultra Violet, EUV) having a wavelength in the vicinity of 13.5 nm. ) May be included.

In the present specification, the mask substrate refers to a transparent substrate 11 having a thin film formed on the main surface, and includes a so-called mask blank. Another film may be formed between the main surface of the transparent substrate 11 and the thin film. The mask substrate also includes a mask blank with a resist in which a resist film is formed on a thin film. Further, the mask substrate may be a lithography mask intermediate in which a part of the thin film is already patterned for the purpose of manufacturing a lithography mask having a film pattern having a laminated structure.

In this embodiment, for example, as shown in FIGS. 4A and 4B, a lithography mask 10 formed in a state where the thin film is in contact with the main surface of the transparent substrate 11 will be described as an example.

As the transparent substrate 11 used for the mask substrate, a transparent substrate such as synthetic quartz, which is polished flat and smooth, is used. For example, the main surface is a quadrangle having a side of about 5 to 6 inches and a thickness of about 2 to 7 mm.

The thin film of the mask substrate is formed on one of the two main surfaces of the transparent substrate 11 by a known film forming method such as a sputtering method.

The thin film can be a light-shielding film (optical density OD: Optical Density of 2 or more, preferably 3 or more with respect to the exposure light when the lithography mask 10 is used). This light-shielding film may be provided with a light-shielding layer and an antireflection layer described later on the surface thereof.

Further, the thin film may be a semipermeable membrane that partially transmits the exposure light. At this time, the exposure light transmittance of the semipermeable membrane can be 5 to 80% based on the exposure light transmittance of the transparent substrate 11 (100%).

Such a semipermeable membrane can be usefully applied to a so-called multi-gradation mask (also referred to as a gradation mask or a halftone mask), a halftone type phase shift mask, or the like.

When the semipermeable membrane is applied to the above-mentioned multi-gradation mask, the exposure light transmittance is preferably 20 to 70%, more preferably 30 to 60%. The phase shift amount of the semipermeable membrane with respect to the exposure light can be preferably 90 degrees or less, more preferably 60 degrees or less.

When the semipermeable membrane is applied to a halftone type phase shift mask, the exposure light transmittance is preferably 5 to 40%, more preferably 5 to 30%. Further, the phase shift amount of the semipermeable membrane with respect to the exposure light can be preferably within the range of 180 ± 20 degrees.

When the exposure light consists of a single wavelength, the transmission rate and the phase shift amount with respect to the exposure light shall be for that wavelength, and when a broad wavelength light source is used, any wavelength included in the wavelength range of the light source (representative). (Wavelength).

The film thickness of the thin film is determined by its function, but is preferably 23 to 105 nm. For example, if the thin film is a light-shielding film, the film thickness can be 44 to 105 nm.

As the thin film, a thin film capable of wet etching or dry etching can be used, but from the viewpoint of dimensional control, it is preferable to use a thin film capable of dry etching having anisotropic etching characteristics. The thin film material can include, for example, chromium (Cr). When the thin film is a light-shielding film, chromium or a compound thereof can be used, and when the thin film is a semipermeable membrane, one made of a chromium compound can be preferably used. The chromium compound can be, for example, a film containing any of an oxide of chromium, a nitride, a carbide, a nitride oxide, and a carbide of oxide.

Further, when the thin film is a light-shielding film or a translucent film, a metal other than chromium, for example, molybdenum (Mo), tantalum (Ta), tungsten (W), zirconium (Zr), niobium (Nb), titanium ( A material consisting of Ti) or a compound thereof may be applied. For example, the material may be a material containing metal silicide, its oxide, nitride, carbide, oxynitride, and carbide oxynitride. Examples of the metal silicide that can be used as the material of the thin film include molybdenum silicide and tantalum silicide. Further, the thin film may be a material containing silicon nitride (silicon nitride, Si ₃ N _{4 or simply Si N).} Further, these materials may be used alone or in combination of two or more.

When the thin film is a light-shielding film, the surface may be provided with an antireflection layer for suppressing light reflectance. In that case, for example, the antireflection layer arranged on the surface of the light-shielding film containing chromium as a main component can be a chromium compound (oxide, nitride, carbide, etc.). The antireflection layer can be formed by changing the composition of the light-shielding film including the antireflection layer in the film thickness direction. The composition change may be a gradual change or a slow change. The antireflection layer has a function of suppressing reflection on the drawing light in the process of manufacturing the lithography mask, and also has a function of suppressing reflection on the exposure light when exposing the lithography mask. The thickness of the antireflection layer can be, for example, 4 to 40 nm.

The lithography mask 10 according to the present embodiment includes a transfer pattern 20 on a transparent substrate 11, first prepares a mask substrate having a thin film formed on the transparent substrate 11, and patterns the thin film to form a thin film pattern 13. By doing so, it is obtained. The patterning of this thin film may be performed a plurality of times, if necessary. When the transfer pattern 20 including the thin film pattern 13 has a defect, the lithography mask 10 is completed by applying the correction step (correction method) of the transfer pattern 20 described later to correct the defect. Can be done.

The defects to be corrected by using the method for correcting the transfer pattern 20 of the lithography mask 10 according to the present embodiment are the target pattern 12 to be formed on the lithography mask 10 and the thin film pattern actually formed on the lithography mask 10. Including those having a shape different from that of 13. Specifically, as shown in FIG. 4A, the defect to be corrected by using the correction method of the lithography mask 10 of the present embodiment lacks the dimension of the thin film pattern 13 with respect to the target dimension d. A state defect and a state defect in which the size of the thin film pattern 13 is excessive with respect to the target dimension d as shown in FIG. 10A are included. In FIG. 4A, the upper row shows a plan view of the lithography mask 10 before modification, and the lower row is a cross-sectional view when the lithography mask 10 before modification shown in the plan view is cut along the AA'line. Is shown. In FIG. 4B, the upper row shows a plan view of the corrected lithography mask 10, and the lower row is a cross-sectional view when the corrected lithography mask 10 shown in the plan view is cut along the AA'line. Is shown. FIG. 10 is the same as that of FIG.

In FIGS. 4 and 10, a so-called line-and-space pattern is illustrated as the transfer pattern 20, but the transfer pattern is not limited to this, and for example, a hole pattern, a dot pattern, and the like are also transfer patterns according to the present embodiment. Included in 20.

Next, the correction step (correction method) included in the method for manufacturing the lithography mask 10 according to the present embodiment will be described in detail with reference to the drawings.

First, a method of correcting the lithography mask 10 including defects in a state where the dimensions of the thin film pattern 13 included in the transfer pattern 20 are insufficient (small) with respect to the target dimension d will be described.

FIG. 4 is a schematic view illustrating a method for modifying the lithography mask 10 according to the first embodiment of the present invention, and FIG. 4A shows a lithography mask 10 provided with a transfer pattern 20 on a transparent substrate 11. , FIG. 4B shows the lithography mask 10 modified by the modification method according to the present embodiment.

The method for manufacturing a lithography mask according to this embodiment is
A method for manufacturing a lithography mask for forming a transfer image on a transfer target by exposing it with an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The method for manufacturing a lithography mask includes a transfer pattern correction step of modifying the transfer pattern.
The transfer pattern correction step is
An inspection process for grasping the dimensions of the thin film pattern and
A specific step of specifying a correction area to be corrected for a defect whose dimensions of the thin film pattern are insufficient with respect to the target size, and
A modification film deposition step of depositing a modification film having a required thickness on the thin film pattern remaining in the modification region so that the transfer image having normal dimensions can be formed on the transfer object by the exposure.
including.

The transfer pattern correction step according to the present embodiment will be described below in the order of the steps.

(Inspection process)
First, a lithography mask 10 (lithographic mask 10 before modification) including a transfer pattern 20 obtained by patterning a thin film formed on a transparent substrate 11 to form a thin film pattern 13 is prepared, and an inspection device is used. Then, the dimensions of the thin film pattern 13 are grasped. In the present specification, grasping the dimensions is not limited to the case of measuring the dimensions, but also the thin film pattern 13 formed on the above-mentioned uncorrected lithography mask 10 and the target pattern to be formed on the lithography mask 10. It also includes obtaining information on the tendency of excess or deficiency of the dimension of the thin film pattern 13 with respect to the dimension of the target pattern 12 (referred to as the target dimension d) by comparing with 12 (details will be described later).

When the transfer pattern 20 includes a repeating pattern consisting of a plurality of regularly arranged unit patterns, the target pattern 12 and the thin film pattern 13 of the lithography mask 10 before modification are compared with each other. The unit patterns to be used may be compared with each other. For example, the thin film pattern 13 included in one unit pattern (first unit pattern) may be compared with the thin film pattern 13 included in another unit pattern (second unit pattern). At this time, the first unit pattern corresponds to the thin film pattern 13 formed on the lithography mask 10 before the correction, and the second unit pattern corresponds to the target pattern 12. Each of the plurality of unit patterns can include a thin film forming portion 21 (thin film pattern 13) and a translucent portion 22. The same applies hereinafter.

(Specific process)
As shown in FIG. 4A, when the lithography mask 10 before correction includes a defect in which the dimension of the thin film pattern 13 is insufficient with respect to the dimension of the target pattern 12, the region to be corrected is the correction region. Specified as Z2. In FIG. 4A, for example, the region surrounded by the alternate long and short dash line is defined as the correction region Z2.

The target pattern 12 is obtained in advance by simulation based on, for example, design data used for drawing the thin film pattern 13 on the mask substrate and optical conditions such as the wavelength of the inspection light used for inspection by the inspection device. Can be kept.

Further, when the target pattern 12 and the thin film pattern 13 are compared and it is confirmed that there is a region where the dimension of the thin film pattern 13 is insufficient with respect to the target dimension d, the transfer pattern including the thin film pattern 13 is confirmed. A transfer image obtained by transferring 20 to a transfer target is obtained by simulation, and correction is necessary only when it is determined that the dimensions of the obtained transfer image (referred to as a predicted transfer image) are not normal. It may be determined that there is, and the correction area Z2 may be specified. The same applies when comparing the first unit pattern and the second unit pattern. In the present embodiment, by confirming that the dimensions of the predicted transfer image are normal, it can be determined that a transfer image having normal dimensions can be formed on the transferred body. The method for confirming whether or not the dimensions of the predicted transfer image are normal will be described later.

(Modified membrane deposition process)
Next, as shown in FIG. 4B, the correction film 14 is deposited on the thin film existing in the correction region Z2. For the deposition of the modified film 14, a method using a charged particle beam such as FIB or EB can be used. For example, the modified region Z2 is in a state where the raw material gas atmosphere as the raw material of the modified film 14 is used. By irradiating the region with a charged particle beam, the correction film 14 can be deposited.

The required film thickness (required thickness) of the modified film 14 to be deposited can be appropriately determined depending on the amount of dimensional deviation (also referred to as defect size) of the thin film pattern 13 from the target dimension d, and is, for example, 1 to 100 nm. It can be preferably 20 to 100 nm. If the film thickness of the correction film 14 is too small, it is insufficient to adjust the light intensity distribution, and if it is too large, inconveniences such as collapse of the accumulated correction film 14 may occur. When the film thickness of the correction film 14 is within the above range, the light intensity distribution can be precisely controlled.

The thickness of the correction film 14 that does not cause overcorrection is obtained in advance by simulation or the like, and after the correction film 14 is deposited by the obtained thickness, the light intensity distribution of the correction region Z2 is confirmed. If necessary, the correction film 14 may be further deposited.

The correction film 14 only needs to be deposited substantially on the thin film pattern 13 remaining in the correction region Z2, and even if the edge position of the correction film 14 coincides with the edge position of the thin film pattern 13 remaining in the correction region Z2. Alternatively, the edge of the correction film 14 is located inside the outer edge of the formation region of the thin film pattern 13 remaining in the correction region Z2 in consideration of the possibility of misalignment when the correction film 14 is deposited. You may do so. When the edge of the correction film 14 is located inside the outer edge, for example, the edge of the correction film 14 is preferably located inside within a range of 25 nm or less from the outer edge, 15 to 25 nm. Within the range of, even if the position shift occurs when the correction film 14 is deposited, the edge of the correction film 14 can be contained in the formation region of the thin film pattern 13 remaining in the correction region Z2, which is more preferable.

Note that depositing only on the thin film pattern 13 remaining in the modified region Z2 means that the deposition is not only on the thin film pattern 13 remaining in the modified region Z2, but also using the modified lithography mask 10. It also includes a state in which the edge of the correction film 14 is deposited so as to be located outside the outer edge of the thin film to the extent that a normal transfer image can be formed on the transferred body. When the edge of the correction film 14 is located outside the outer edge of the thin film, for example, the edge of the correction film 14 can be located outside within a range of 25 nm or less from the outer edge.

Further, the correction film 14 is not formed only on a necessary region after being formed on the entire main surface of the transparent substrate 11 and then patterned by drawing and etching, and as described above, for example, under a raw material gas atmosphere. By irradiating the thin film in the modified region Z2 with a charged particle beam, it is deposited only on the thin film. Therefore, in the modified lithography mask 10, the edge of the modified film 14 does not have a cross section due to etching (cross section to be etched).

The raw material gas used as the raw material of the correction film 14 can be appropriately selected depending on the required optical characteristics in the correction region Z2 of the lithography mask 10, and can be appropriately selected, for example, metal carbonyl or tetraethoxysilane (TEOS). It is possible to use a material containing silicon. Examples of the metal carbonyl include chromium carbonyl (Cr (CO) ₆ ), molybdenum carbonyl (Mo (CO) ₆ ), and tungsten carbonyl (W (CO) ₆ ).

(Correction result confirmation process)
The correction result of the lithography mask 10 that has undergone the above steps is confirmed. For example, a transfer image obtained by transferring the transfer pattern 20 including the thin film pattern 13 of the lithography mask 10 that has undergone the above steps to the transfer target is obtained by simulation, and the target transfer image and the simulation are obtained. If the dimensions of the predicted transfer image are normal by comparing with the transferred image (predicted transfer image), it can be considered that the modification of the lithography mask 10 is completed.

When determining whether or not the dimensions of the predicted transfer image are normal, for example, when the light intensity in the region where the transparent substrate 11 is exposed is 1, the light intensity of the target transfer image (target light intensity). ) And the light intensity of the predicted transfer image, and the amount of deviation of the light intensity at the positions corresponding to each other is ± 8% or less, preferably ± 5% or less, more preferably ± with respect to the target light intensity. If it is within the range of 3% or less, it may be determined that the size of the predicted transfer image is normal. Alternatively, the dimensions of the target transfer image (referred to as the target transfer image dimensions) and the dimensions of the predicted transfer image are compared, and the amount of dimensional deviation is ± 8% or less, preferably ± 5 of the target transfer image dimensions. If it is within the range of% or less, more preferably ± 3% or less, it may be determined that the dimensions of the predicted transfer image are normal.

Here, the target transfer image size and the predicted transfer image size have specific light intensities in their respective light intensity distributions (the vertical axis is the light intensity and the horizontal axis is the position on the transferred object such as a wafer). When a straight line parallel to the horizontal axis is drawn so as to pass through this threshold value, it can be determined by finding the distance between the intersections of this straight line and the light intensity distribution. By the above method, it can be determined that the dimensions of the transferred image formed on the transferred body by exposing the modified lithography mask 10 are normal.

When comparing the first unit pattern and the second unit pattern, which is a normal pattern without modification, in the above-mentioned inspection step, a transfer image obtained by transferring each unit pattern to the transfer target. Is obtained by simulation, and the obtained transfer images may be compared with each other. Specifically, the light intensities of the transferred image obtained by transferring the first unit pattern and the second unit pattern to the transfer target are defined as the first light intensity and the second light intensity, respectively, and these light intensities are set to each other. In comparison, if the amount of deviation of the light intensity at the positions corresponding to each other is within the range of ± 8% or less, preferably ± 5% or less, more preferably ± 3% or less with respect to the second light intensity, the dimensions are large. It may be determined that it is normal. Alternatively, the dimensions of the transferred images of the first unit pattern and the second unit pattern obtained by simulation are compared, and the amount of dimensional deviation is preferably ± 8% or less with respect to the dimensions of the transferred image of the second unit pattern. May be determined that the dimensions are normal if is within ± 5%, more preferably ± 3% or less. The dimensions of these transfer images can also be obtained in the same manner as described above for comparing the dimensions of the target transfer image and the dimensions of the predicted transfer image.

If it is determined by the above correction result confirmation step that the correction is insufficient, the correction film deposition step is performed until the dimensions of the predicted transfer image or the dimensions of the transfer image of the first unit pattern by simulation become normal. The process from to the correction result confirmation step may be repeated.

As described above, the defect of the lithography mask 10 can be corrected.

According to the method for modifying the lithography mask 10 according to the present embodiment, the dimension of the transfer pattern 20 (the dimension of the thin film pattern 13) is increased or decreased without processing to match the target dimension d (the dimension of the transfer pattern 20 is increased or decreased). This defect can be precisely corrected (without) and the desired transcription result can be obtained.

An example in which a defect is corrected by the correction method according to the present embodiment is shown below as a first embodiment.

<First Example>
The lithographic mask 10 (pre-correction mask) before modification, which is the target of modification in this embodiment, is for transfer including a thin film pattern 13 obtained by patterning a thin film containing molybdenum silicide (MoSi) formed on a transparent substrate 11. The pattern 20 is provided. The transfer pattern 20 was a 1: 1 line-and-space pattern with a pitch of 360 nm on the lithography mask 10. Further, in the thin film forming portion 21 where the thin film was formed, the light transmittance was 6% and the phase shift amount was 180 degrees.

FIG. 5 shows an image captured by a scanning electron microscope of a part of the transfer pattern 20 of the uncorrected mask. In this image, the gray region is the line portion (thin film forming portion 21) and the black region is the space portion (space portion). It represents the translucent portion 22). As shown in FIG. 5, in a part of the middle line portion of the five line portions of the uncorrected mask, the dimension is insufficient with respect to the target dimension d, and the light intensity curve is as shown in FIG. .. In the light intensity curve, the wavelength of the exposure light is 193 nm, the NA of the exposure light source is 1.35, the Sigma is outer 0.98 / inner 0.735, the illumination shape is bipolar illumination, and the polarization is TE. It was obtained by simulation as polarized light.

In FIG. 6, the dotted line shows the light intensity curve of the transfer pattern 20 before correction, and the solid line shows the light intensity curve of the normal pattern. As is clear from FIG. 6, in a part of the transfer pattern 20 before modification, the light intensity was higher than that of the normal pattern. Specifically, at the peak of the light intensity curve indicated by the arrow in FIG. 6, the light intensity is 0.468 in the normal pattern, and 0.492 (+ 5.1% with respect to 0.468) in the uncorrected mask. )Met.

The amount of deviation in light intensity is not necessarily large enough to be called a defect, and correction may not be necessary depending on the specifications required for the lithography mask. However, in this embodiment, as an example, it is indicated by an arrow in FIG. It was decided to modify the transfer pattern 20 corresponding to the location.

_{Specifically, the film containing SiO 2} is modified on the thin film pattern 13 existing in the specified modification region Z2 by irradiating the electron beam in an atmosphere of a raw material gas containing tetraethoxysilane and oxygen. It was deposited as a film 14. The film thickness of the deposited correction film 14 was 78 nm.

FIG. 7A shows a part of the corrected transfer pattern 20 captured by a scanning electron microscope, and each line portion shown in gray corresponds to each line portion in FIG. As can be seen from FIG. 7A, the correction film 14 was deposited in the region where the dimensions were insufficient in FIG. 5 (a part of the middle line portion of the five line portions). FIG. 7B shows the results of measuring the surface shape of the modified lithography mask 10 (modified mask) with an atomic force microscope. In FIG. 7B, the gray region represents the line portion (thin film forming portion 21), and the black region represents the space portion (translucent portion 22). With reference to FIG. 7B, it can be seen that the correction film 14 is formed on the sixth white line portion from the right end, and the film thickness is increased.

FIG. 8 shows the light intensity curve of the modified mask. The light intensity curve of FIG. 8 was obtained by the same method as the light intensity curve before correction. In FIG. 8, the broken line shows the light intensity curve of the corrected transfer pattern 20, and the solid line shows the light intensity curve of the normal pattern. The part indicated by the arrow in FIG. 6 corresponds to the part indicated by the arrow in FIG. As is clear from FIG. 8, at the peak of the light intensity curve at the location indicated by the arrow, the light intensity was 0.468 in the normal pattern, but 0.461 (relative to 0.468) in the corrected mask. -1.5%), and it was found that the transfer pattern 20 including the thin film pattern 13 could be precisely modified.

Next, the influence of the focus shift on the pattern size (line width) formed on the transferred body when the film thickness of the thin film constituting the thin film pattern 13 is changed will be described. FIG. 9 shows the line widths of the corrected transfer pattern 20 on which the correction film 14 is deposited and the pattern transferred onto the wafer (transferred body) of the normal pattern (the correction film 14 is not deposited). The result of obtaining the relationship with the focus position by simulation is shown. The simulation conditions are the same as the conditions when the above-mentioned light intensity curve is obtained.

Referring to FIG. 9, even if the focus position is changed in the state where the correction film 14 is deposited, the shift amount of the focus position is within the range of ± 80 nm as in the normal pattern in which the correction film 14 is not deposited. , The line width of the pattern on the wafer is almost unchanged. That is, even if the correction film 14 is deposited and the total thickness of the film formed on the transparent substrate 11 is changed so as to be large as in the correction method according to the present embodiment, the correction film 14 is deposited. It can be seen that the same dimensional accuracy as that of the normal pattern is obtained.

According to the correction method of the lithography mask 10 as described above, the dimension of the transfer pattern 20 is increased or decreased without processing to match the dimension of the transfer pattern 20 (the dimension of the thin film pattern 13) with the target dimension d (the dimension of the transfer pattern 20 is increased or decreased). This defect can be precisely corrected and the desired transcription result can be obtained.

<Lithography mask obtained by the correction method according to this embodiment>
The lithographic mask obtained by the above correction method is a lithographic mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The thin film pattern has a correction area in which a defect that is dimensionally insufficient with respect to the target size is corrected.
A required amount of correction film in the thickness direction is deposited on the thin film pattern remaining in the correction region so that the transfer image having normal dimensions is formed on the transfer body by the exposure. Can be

The correction film 14 only needs to be deposited substantially only on the thin film pattern 13 remaining in the correction region Z2, and the edge position of the correction film 14 coincides with the edge position of the thin film pattern 13 remaining in the correction region Z2. Alternatively, the edge of the correction film 14 may be located inside the outer edge of the formation region of the thin film pattern 13 remaining in the correction region Z2. When the edge of the correction film 14 is located inside the outer edge, for example, the edge of the correction film 14 is preferably located inside within a range of 25 nm or less from the outer edge, 15 to 25 nm. Within the range of, even if the position shift occurs when the correction film 14 is deposited, the edge of the correction film 14 can be contained in the formation region of the thin film pattern 13 remaining in the correction region Z2, which is more preferable.

Further, the edge of the correction film 14 does not have a cross section by etching (cross section to be etched).

The method for correcting the lithography mask 10 according to the present embodiment is to correct a defect by changing the three-dimensional shape of the thin film pattern 13 included in the transfer pattern 20, and to correct the defect by changing the transmittance. It is not intended to be done. Therefore, the transmittance of the exposure light of the correction film 14 is not particularly limited. That is, the correction film 14 may be substantially transparent to the exposure light, and may have a semipermeable or light-shielding property that transmits a part of the irradiated light. Here, when the transmittance of the exposure light of the transparent substrate 11 is 100%, the case where the transmittance is 80 to 100% is substantially transparent, and the case where the transmittance is 5 to 80% is semi-translucency, 5%. If it is less than, the light-shielding property is defined.

As the material of the correction film 14, for example, silicon (SiO ₂₎ alone or dioxide include those in combination with silicon dioxide (SiO ₂₎ and chromium oxide. Silicon dioxide (SiO ₂ ) is preferable because it has high chemical resistance and light resistance when properly deposited.

<Second Embodiment>
Next, the correction step (correction method) included in the method for manufacturing the lithography mask 10 according to the second embodiment of the present invention will be described in detail with reference to the drawings.

In the present embodiment, a method of correcting the lithography mask 10 including defects in a state in which the thin film pattern 13 included in the transfer pattern 20 is excessive (large) with respect to the target dimension d will be described.

FIG. 10 is a schematic view illustrating a method for modifying the lithography mask 10 according to the second embodiment of the present invention, and FIG. 10A shows a lithography mask 10 provided with a transfer pattern 20 on a transparent substrate 11. , FIG. 10B shows the lithography mask 10 modified by the modification method according to the present embodiment.

The lithography mask 10 according to the present embodiment has a transfer pattern 20 obtained by applying lithography to the mask substrate described above and obtained by patterning a thin film formed on the transparent substrate 11 (). (See FIG. 10), the transfer pattern 20 includes a region (thin film forming portion 21) in which a thin film is formed on the transparent substrate 11, that is, a thin film pattern 13 and a translucent portion 22 in which the transparent substrate 11 is exposed. Can include. In this embodiment, as shown in FIG. 10, a lithography mask 10 formed in a state where the thin film is in contact with the main surface of the transparent substrate 11 will be described as an example.

The method for manufacturing a lithography mask according to this embodiment is
A method for manufacturing a lithography mask that forms a transfer image on a transfer target by exposing it with an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The method for manufacturing a lithography mask includes a transfer pattern correction step of modifying the transfer pattern.
The transfer pattern correction step is
An inspection process for grasping the dimensions of the thin film pattern and
A specific step of specifying a correction region to be corrected for a defect in which the size of the thin film pattern is excessive with respect to the target size, and
A film thinning step of removing a required amount of the thin film pattern in the correction region in the film thickness direction is included so that the transfer image having normal dimensions can be formed on the transferred object by the exposure.

The transfer pattern correction step according to the present embodiment will be described below in the order of the steps.

(Inspection process)
Similar to the first embodiment, first, a lithography mask 10 having a transfer pattern 20 obtained by patterning a thin film having a predetermined film thickness on a transparent substrate 11 to form a thin film pattern 13 (lithographic mask 10 before modification). ) Is prepared, and the dimensions of the thin film pattern 13 are grasped by using an inspection device.

When the thin film pattern 13 includes a repeating pattern in which the same pattern is repeated a plurality of times, instead of comparing the target pattern 12 and the thin film pattern 13 of the lithography mask 10, as in the first embodiment, instead of comparing the target pattern 12 with the thin film pattern 13 of the lithography mask 10. Corresponding patterns (first unit pattern and second unit pattern) may be compared in the repeating pattern. In this case, the following steps are the same as those in the first embodiment except for the film thinning step, and thus details may be omitted.

(Specific process)
As shown in FIG. 10A, when the lithography mask 10 before correction includes a defect in which the dimension of the thin film pattern 13 is larger than the target dimension d, the region to be corrected is specified as the correction region Z2. In FIG. 10A, for example, the region surrounded by the alternate long and short dash line is defined as the correction region Z2.

Further, when the target pattern 12 and the thin film pattern 13 are compared and it is confirmed that there is a region where the dimension of the thin film pattern 13 is excessive with respect to the target dimension d, the same as in the first embodiment, Only when the transfer image obtained by transferring the transfer pattern 20 including the thin film pattern 13 to the transfer target is obtained by simulation and it is determined that the dimensions of the obtained transfer image (predicted transfer image) are not normal. , It may be determined that correction is necessary, and the correction area Z2 may be specified. The same applies when comparing the first unit pattern and the second unit pattern.

(Film reduction process)
Next, as shown in FIG. 10B, the required amount of the thin film pattern 13 existing in the correction region Z2 is removed in the film thickness direction, and the film thickness is reduced (reduced). At this time, the film can be reduced so that a part of the thin film pattern 13 of the correction region Z2 remains on the transparent substrate 11. That is, in the film thinning step, the thin film pattern 13 of the correction region Z2 is partially removed in the film thickness direction, and not all of it is removed. In FIG. 10B, in the cross-sectional view of the lithography mask 10, the thin film pattern 13 in the range from one edge to the other edge of the thin film pattern 13 in the correction region Z2 is reduced in the film thickness direction. However, only a part of the thin film pattern 13 within the range may be reduced in the film thickness direction. The thin film pattern 13 modified by undergoing the film thinning step includes the film thickness reducing portion 15 (see FIG. 13).

For thinning the thin film pattern 13, for example, a gas-assisted etching method using a charged particle beam, a method of physically grinding a residual thin film using an atomic force microscope probe, a laser beam or a focused ion beam (a laser beam or a focused ion beam). A method of removing by Focused Ion Beam (FIB) can be applied.

The amount of reducing the thin film pattern 13 in the film thickness direction (film thickness reduction amount) can be appropriately determined depending on the amount of dimensional deviation (defect size) of the thin film pattern 13 from the target pattern 12, and is, for example, 1 to 105 nm. It can be preferably 2 to 70 nm, more preferably 5 to 30 nm. When the amount of film thinning is within the above range, the light intensity distribution can be precisely controlled. It should be noted that the amount of film reduction that does not cause overcorrection is obtained in advance by simulation or the like, and after the thin film pattern 13 is thinned in the correction area Z2 by the obtained amount of film reduction, the light intensity distribution in the correction area Z2 is determined. It may be confirmed and further thinning may be performed if necessary.

Further, in the film thinning step, it is preferable that the dimensions of the thin film pattern 13 of the correction region Z2 are substantially maintained. Here, "substantially retained" means that the thin film pattern 13 in the correction region Z2 is removed only in the film thickness direction, and the dimensions of the thin film pattern 13 do not change before and after the film thickness reduction, as well as after the correction. It also includes a state in which the dimension of the thin film pattern 13 after film thickness reduction is smaller than the dimension before film thickness reduction to the extent that a normal transfer image can be formed on the transferred object using the lithography mask 10.

(Correction result confirmation process)
The correction result of the lithography mask 10 that has undergone the above steps is confirmed. Similar to the first embodiment, for example, the target transfer image and the transfer image obtained by simulation (predicted transfer image) are compared, or two single patterns (first unit pattern and 1st unit pattern) of the repeating pattern are compared. The transfer images of the second unit pattern) are compared with each other, and if the dimensions of the predicted transfer image (or the transfer image of the first unit pattern) are normal, it can be considered that the correction of the lithography mask 10 is completed.

Specifically, as in the first embodiment, the light intensity of the target transfer image and the light intensity of the predicted transfer image are compared, or the dimensions of the target transfer image and the dimensions of the predicted transfer image By comparing, it can be determined that the dimensions of the predicted transfer image are normal. The same applies when comparing the transferred images of the first unit pattern and the second unit pattern. As a result, it can be determined that the dimensions of the transferred image formed on the transferred body by exposing the corrected lithography mask 10 are normal.

If it is determined that the correction is insufficient, the process from the film thinning step to the correction result confirmation step may be repeated until the dimensions of the predicted transfer image become normal.

As described above, the defect of the lithography mask 10 can be corrected.

According to the method for modifying the lithography mask 10 according to the present embodiment, the dimension of the transfer pattern 20 (the dimension of the thin film pattern 13) is increased or decreased without processing to match the target dimension d (the dimension of the transfer pattern 20 is increased or decreased). This defect can be precisely corrected (without) and the desired transcription result can be obtained.

An example in which a defect is corrected by the correction method according to the present embodiment is shown below as a second embodiment.

<Second Example>
The lithography mask 10 (pre-correction mask) to be modified in this embodiment includes a transfer pattern 20 including a thin film obtained by patterning a thin film containing molybdenum silicide (MoSi) formed on the transparent substrate 11. And said. The transfer pattern 20 is a 1: 1 line-and-space pattern with a pitch of 360 nm on the lithography mask 10. In the portion where the thin film was formed (thin film forming portion), the light transmittance was 6% and the phase shift amount was 180 degrees.

FIG. 11 shows an image captured by a scanning electron microscope of a part of the transfer pattern 20 of the uncorrected mask. In the image, the gray region is the line portion (thin film forming portion 21) and the black region is the space portion (translucency). Part 22) is represented. As shown in FIG. 11, in a part of the middle line portion of the five line portions of the uncorrected mask, the dimension is excessive with respect to the target dimension d, and the light intensity curve is as shown in FIG. rice field. The light intensity curve was obtained by the same method as in the first embodiment.

In FIG. 12, the dotted line shows the light intensity curve of the transfer pattern 20 before correction, and the solid line shows the light intensity curve of the normal pattern. As is clear from FIG. 12, in a part of the transfer pattern 20 before modification, the light intensity was lower than that of the normal pattern. Specifically, at the peak of the light intensity curve indicated by the arrow in FIG. 12, the light intensity is 0.459 in the normal pattern, whereas in the uncorrected mask, it is 0.422 (-8. 1%).

The amount of deviation in light intensity is not necessarily large enough to be called a defect, and correction may not be necessary depending on the specifications required for the lithography mask. However, in this embodiment, as an example, it is indicated by an arrow in FIG. It was decided to modify the transfer pattern 20 corresponding to the location.

_{Specifically, XeF 2} was used as the assist gas, and by irradiating the electron beam, a part of the thin film pattern 13 existing in the specified correction region Z2 was etched in the film thickness direction. The amount of film thickness (amount of film reduction) removed by etching was 14 nm.

FIG. 13A shows an image of the corrected transfer pattern 20 captured by a scanning electron microscope, and each line portion (thin film forming portion 21) shown in gray corresponds to the line portion in FIG. The same applies to the space section. With reference to FIG. 13A, the color is darkened in the vicinity of the edge of a part of the middle line portion among the five line portions, and the darkened region is the region where the thin film is etched (the region where the thin film is etched (a). The film thickness reduction portion 15). FIG. 13B shows the results of measuring the surface shape of the modified lithography mask 10 (modified mask) with an atomic force microscope. In FIG. 13B, the gray region represents the line portion (thin film forming portion 21), and the black region represents the space portion. With reference to FIG. 13B, it can be seen that there is a region where the film thickness is reduced (film thickness reduction portion 15) in the vicinity of the edge of the sixth line portion from the right end.

FIG. 14 shows the light intensity curve of the modified mask. The light intensity curve of FIG. 14 was obtained by the same method as the light intensity curve before modification. In FIG. 14, the broken line shows the light intensity curve of the corrected transfer pattern 20, and the solid line shows the light intensity curve of the normal pattern. The portion indicated by the arrow in FIG. 12 corresponds to the portion indicated by the arrow in FIG. As is clear from FIG. 14, at the peak of the light intensity curve at the location indicated by the arrow, the light intensity was 0.459 in the normal pattern, but 0.456 (relative to 0.459) in the corrected mask. -0.7%), and it was found that the transfer pattern 20 including the thin film pattern 13 could be precisely modified.

In this embodiment, only the thin film near the edge of the line portion is etched while maintaining the film thickness of the region near the center in the width direction of the line portion (thin film forming portion 21) to be corrected. Is not limited to this. That is, the thin film may be etched in the film thickness direction in the region from one edge of the line portion to be corrected to the other edge.

Next, the influence of the focus shift on the pattern size (line width) formed on the transferred body when the film thickness of the thin film constituting the thin film pattern 13 included in the transfer pattern 20 is reduced will be described. FIG. 15 shows the line width and focus of the corrected transfer pattern 20 in which the film thickness of the thin film is reduced and the pattern transferred onto the wafer (transferred body) of the normal pattern (not reduced). The result of obtaining the relationship with the position by simulation is shown. The simulation conditions are the same as the conditions when the above-mentioned light intensity curve is obtained.

Referring to FIG. 15, even if the focus position is changed in the state where the film thickness is reduced, the shift amount of the focus position is within the range of ± 80 nm as in the case of the normal pattern in which the film thickness is not reduced. The line width of the pattern on the wafer remains almost unchanged. That is, it can be seen that by applying the correction method according to the present embodiment, even if the thickness of the thin film is reduced, the same dimensional accuracy as that of the normal pattern in which the film is not reduced can be obtained.

According to the correction method of the lithography mask 10 as described above, the dimension of the transfer pattern 20 is increased or decreased without processing to match the dimension of the transfer pattern 20 (the dimension of the thin film pattern 13) with the target dimension d (the dimension of the transfer pattern 20 is increased or decreased). This defect can be precisely corrected and the desired transcription result can be obtained.

<Lithography mask obtained by the correction method according to this embodiment>
The lithographic mask obtained by the above correction method is a lithographic mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film of a predetermined film thickness is patterned on a transparent substrate and a translucent portion in which the transparent substrate is exposed. ,
The thin film pattern has a correction area in which defects that are oversized with respect to the target size have been corrected.
The film thickness of the thin film pattern in the correction region is made smaller than the predetermined film thickness so that the transfer image having normal dimensions is formed on the transferred body by the exposure.

The thin film pattern 13 in the correction region Z2 may be smaller than a predetermined film thickness to the extent that a normal transfer image can be formed on the transferred object using the corrected lithography mask 10, and is, for example, larger than the predetermined film thickness. It can be reduced by 1 to 105 nm, preferably 2 to 70 nm, and more preferably 5 to 30 nm. If the film thickness of the thin film pattern 13 in the correction region Z2 is within the above range, the light intensity distribution can be precisely controlled, and the corrected lithography mask 10 is used for normal transfer onto the transferred object. An image can be formed.

<Manufacturing method of lithography mask>
The present invention includes a method for manufacturing a lithography mask modified by the above-mentioned modification method. That is, the method for manufacturing a lithography mask of the present invention can include the above-mentioned method for modifying a lithography mask.

An example of a method for manufacturing a lithography mask will be described below.

First, a mask substrate is prepared. The mask substrate can be the same as the above-mentioned mask substrate, but the mask substrate here is the one in which the above-mentioned thin film is formed on the transparent substrate and the photoresist film is further formed on the thin film. do. The photoresist film may not be formed on the thin film of the mask substrate. In this case, a step of applying the photoresist film may be added before the drawing step described later.

Using a drawing machine, the photoresist film is drawn and developed to form a resist pattern. For drawing, for example, an electron beam (EB) drawing machine can be used.

Then, using the resist pattern as a mask, the thin film is etched to form the thin film pattern. As a result, a transfer pattern including a thin film forming portion and a translucent portion can be formed. Either wet etching or dry etching may be used for etching the thin film, but dry etching is preferable because the dimensions can be precisely controlled. When dry etching is applied, the etching gas can be appropriately selected depending on the material of the thin film, and for example, a gas containing chlorine (Cl), a gas containing fluorine (F), or the like can be used.

After that, the resist pattern is peeled off to create a lithography mask before modification.

Next, the lithographic mask before modification can be modified by the above-mentioned modification method, and the obtained lithography mask can be used as a finished product.

There are no particular restrictions on the use of the lithography mask. This lithography mask can be particularly advantageously used as a lithography mask for semiconductor devices in which the pattern is being miniaturized. That is, the method of the present invention can be suitably used for a lithography mask or the like having a transfer pattern including fine portions having a size of 50 to 400 nm.

The present invention includes a method for manufacturing a semiconductor device using a lithography mask manufactured by the above-mentioned manufacturing method. For example, the method for manufacturing a semiconductor device of the present invention includes a step of preparing a lithography mask manufactured by the above-mentioned manufacturing method or the above-mentioned lithography mask, and using an exposure apparatus to expose the lithography mask to obtain the transfer pattern. , The step of transferring to the transferred body and forming the transferred image on the transferred body can be included.

The modification method included in the method for manufacturing a lithography mask according to the present invention can be suitably used for modifying a pattern resolved on a transfer target, and when the defect size is 3 to 20 nm, the present invention The effect of the invention is remarkable. In particular, in the dimensional abnormality defect (defect due to dimensional deviation) of the transfer pattern generated in the lithography mask, the effect of the present invention is effective when, for example, the defect size included in the region where one side is 2 to 4 μm is 3 to 20 nm. It is remarkable.

Since the conventional method is a method of correcting the dimension itself, the correction must be performed so that the position does not deviate from the target correction position, and in particular, the defect size is several nm (for example, less than 10 nm). ), It was necessary to deposit a correction film or remove unnecessary thin films within a region of several nm, which made correction very difficult. On the other hand, in the modification method according to the present invention, the thickness of the modified film to be deposited or the amount of the thin film to be reduced in the film thickness direction (film reduction amount) can be 10 nm or more, and irradiation with charged particle beams or the like can be performed. Since the film thickness and the amount of film reduction of the correction film can be precisely controlled only by controlling the time, the correction can be performed much more easily and accurately than the conventional correction method.

Further, the correction method according to the present invention has dimensions caused by overcorrection (removing even a necessary thin film or depositing a correction film in an unnecessary region) when the correction is performed by a conventional defect repair method. It is also very useful as a method for correcting abnormal defects.

As the exposure machine used when transferring the transfer pattern included in the lithography mask manufactured by the manufacturing method according to the present invention to the transfer target, a reduction projection exposure apparatus or an EUV exposure apparatus can be used.

As the optical system of the exposure apparatus, in the case of a reduction projection exposure apparatus, the NA (numerical aperture) is in the range of 0.8 to 1.4 and the coherency factor (σ) value is in the range of 0.8 to 1.0. Can be preferably used. Further, the effect of the present embodiment is particularly remarkable when deformed lighting (ring band lighting, double pole lighting, quadrupole lighting, etc.) is used as the exposure light source.

The exposure light of the exposure apparatus can be, for example, 250 nm or less, preferably 200 nm or less. For example, when a KrF excimer laser is used as the light source of the exposure apparatus, the wavelength of the exposure light can be 248 nm, and when an ArF excimer laser is used, the wavelength of the exposure light can be 193 nm. When light of these wavelengths is used as the exposure light, a transfer pattern including a fine portion of 50 to 400 nm can be transferred onto the transferred body, and the effect of the present invention becomes remarkable. Therefore, it is preferable to use light of these wavelengths.

According to the above-described embodiment, since the correction film is deposited on the thin film or the film thickness of the thin film is reduced in the correction region, the light transmittance and the phase shift amount in the correction region are corrected. It may change before and after, but this is not a particular problem. This is because, according to the modification method of the present invention, the light intensity distribution of the transfer pattern can be matched with the light intensity curve of the target pattern to be formed, so that a normal transfer image is formed on the transferred object. Because it can be done.

Further, in the above-described embodiment, when the thin film is composed of a light-shielding film and the light-shielding film includes a light-shielding layer and an antireflection layer, a correction film is deposited on a part of the antireflection layers, or a part of the correction film is deposited. The antireflection layer will disappear from the surface side. However, the width at which the correction film is deposited or the width at which the antireflection layer disappears is the width of the region to be modified, and is very small, for example, 3 to 20 nm. That is, it is only a small part of the antireflection layer. Therefore, the reflection of the exposure light in this portion does not interfere with the transferability of the transfer pattern.

The lithography mask according to the present invention may include the following first and second lithography masks.

The first lithographic mask is a lithographic mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a repeating pattern consisting of a plurality of regularly arranged unit patterns on a transparent substrate.
Each of the plurality of unit patterns has a thin film forming portion in which a thin film pattern is formed on the transparent substrate, and a translucent portion in which the transparent substrate is exposed.
When one of the plurality of unit patterns is a first unit pattern and the other one is a second unit pattern,
In the first unit pattern, a correction film different from the thin film is formed on a part of the thin film patterns, and the dimensions of the part of the thin film patterns correspond to those in the second unit pattern. Smaller than the dimensions of the thin film pattern
The first light intensity, which is the light intensity of the transferred image obtained by transferring the first unit pattern to the transferred body, and the second unit pattern obtained by transferring the second unit pattern to the transferred body, which are obtained by simulation. The difference from the second light intensity, which is the light intensity of the transferred image, may be ± 8% or less with respect to the second light intensity.

The modified membrane can be different in composition or material from the thin film. Specifically, the same ones as those of the first embodiment and the second embodiment can be used.

The correction film need only be deposited on a part of the thin film patterns in the first unit pattern, and the edge position of the correction film may coincide with the edge position of the thin film pattern, or the correction film may be deposited. The edge may be located inside the outer edge of the formation region of the thin film pattern. When the edge of the correction film is located inside the outer edge, for example, the edge of the correction film is preferably located inside within a range of 25 nm or less from the outer edge, and is preferably in the range of 15 to 25 nm. If it is inside, even if the position shift occurs when the correction film is deposited, the edge of the correction film can be contained within the formation region of the thin film pattern, which is more preferable.

The second lithographic mask is a lithographic mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a repeating pattern consisting of a plurality of regularly arranged unit patterns on a transparent substrate.
Each of the plurality of unit patterns has a thin film forming portion in which a thin film having a predetermined film thickness is patterned on the transparent substrate, and a translucent portion in which the transparent substrate is exposed. death,
When one of the plurality of unit patterns is a first unit pattern and the other one is a second unit pattern,
The thin film pattern in the first unit pattern includes a film thickness reduction portion smaller than the predetermined film thickness, and the dimensions of the thin film pattern including the film thickness reduction portion are the corresponding said in the second unit pattern. Larger than the dimensions of the thin film pattern,
The first light intensity, which is the light intensity of the transferred image obtained by transferring the first unit pattern to the transferred body, and the second unit pattern obtained by transferring the second unit pattern to the transferred body, which are obtained by simulation. The difference from the second light intensity, which is the light intensity of the transferred image, may be ± 8% or less with respect to the second light intensity.

The film thickness of the thin film pattern in the region corresponding to the film thickness reduction portion may be smaller than the predetermined film thickness so that a normal transfer image can be formed on the transferred object using the corrected lithography mask, for example. The film thickness can be 1 to 105 nm, preferably 2 to 70 nm, and more preferably 5 to 30 nm smaller than the predetermined film thickness. If the film thickness of the thin film pattern is within the above range, the light intensity distribution can be finely controlled, and a normal transfer image can be formed on the transferred object by using the modified lithography mask. can.

The conditions of the above simulation can be the same for both the first light intensity and the second light intensity.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

10 Lithography mask 11 Transparent substrate 12 Target pattern 13 Thin film pattern 14 Correction film 15 Film thickness reduction part 20 Transfer pattern 21 Thin film formation part 22 Translucent part Z1 Reference area Z2 Correction area

Claims (14)

A method for manufacturing a lithography mask for forming a transfer image on a transfer target by exposing it with an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The method for manufacturing a lithography mask includes a transfer pattern correction step of modifying the transfer pattern.
The transfer pattern correction step is
An inspection process for grasping the dimensions of the thin film pattern and
A specific step of specifying a correction area to be corrected for a defect whose dimensions of the thin film pattern are insufficient with respect to the target size, and
A modification film deposition step of depositing a modification film having a required thickness on the thin film pattern remaining in the modification region so that the transfer image having normal dimensions can be formed on the transfer object by the exposure.
A method for manufacturing a lithography mask, which comprises. The method for manufacturing a lithography mask according to claim 1, wherein in the modified film deposition step, the modified film is deposited only on the thin film pattern that remains substantially in the modified region. The method for manufacturing a lithography mask according to claim 1 or 2, wherein the modified film does not have a cross section to be etched. The method for producing a lithography mask according to any one of claims 1 to 3, wherein the modified film has a film thickness of 1 to 100 nm. A method for manufacturing a lithography mask that forms a transfer image on a transfer target by exposing it with an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The method for manufacturing a lithography mask includes a transfer pattern correction step of modifying the transfer pattern.
The transfer pattern correction step is
An inspection process for grasping the dimensions of the thin film pattern and
A specific step of specifying a correction region to be corrected for a defect in which the size of the thin film pattern is excessive with respect to the target size, and
A film thinning step of removing a required amount of the thin film pattern in the modified region in the film thickness direction so that the transferred image having normal dimensions can be formed on the transferred object by the exposure.
A method for manufacturing a lithography mask, which comprises. The method for manufacturing a lithography mask according to claim 5, wherein in the film thinning step, the dimensions of the thin film pattern in the modified region are substantially maintained. The production of the lithography mask according to claim 5 or 6, wherein in the film thinning step, the required amount of the thin film pattern in the modified region is removed by a gas-assisted etching method using a charged particle beam. Method. The production of the lithography mask according to claim 5 or 6, wherein in the film thinning step, the required amount of the thin film pattern in the modified region is removed by using a probe of an atomic force microscope. Method. A lithography mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film pattern is formed on a transparent substrate and a translucent portion in which the transparent substrate is exposed.
The thin film pattern has a correction area in which a defect that is dimensionally insufficient with respect to the target size is corrected.
A required amount of correction film in the thickness direction is deposited on the thin film pattern remaining in the correction region so that the transfer image having normal dimensions is formed on the transfer target by the exposure. A lithography mask characterized by being present. The lithography mask according to claim 9, wherein the modified film is deposited only on the thin film pattern that remains substantially in the modified region. The lithography mask according to claim 9, wherein the correction film has a film thickness of 1 to 100 nm. A lithography mask for forming a transfer image on a transfer target by exposure using an exposure apparatus.
The lithography mask includes a transfer pattern including a thin film forming portion in which a thin film of a predetermined film thickness is patterned on a transparent substrate and a translucent portion in which the transparent substrate is exposed. ,
The thin film pattern has a correction area in which defects that are oversized with respect to the target size have been corrected.
The feature is that the film thickness of the thin film pattern in the correction region is made smaller than the predetermined film thickness so that the transfer image having normal dimensions is formed on the transferred body by the exposure. The lithography mask. The lithography mask according to claim 12, wherein the film thickness of the thin film pattern in the correction region is 1 to 105 nm smaller than the predetermined film thickness. A step of preparing a lithography mask according to the manufacturing method according to any one of claims 1 to 8 or a lithography mask according to any one of claims 9 to 13.
A step of exposing the lithography mask using an exposure apparatus and forming the transfer image on the transfer target.
A method for manufacturing a semiconductor device, including.

Images