CN109478012B - Mask blank, phase shift mask, halftone mask, mask blank, and method for manufacturing phase shift mask - Google Patents

Abstract

The mask blank of the present invention comprises: a transparent substrate; a phase shift layer laminated on the surface of the transparent substrate and mainly composed of Cr; an etch stop layer laminated to the phase shift layer; and a light-shielding layer which is laminated on the etching stop layer and contains Cr as a main component. The phase shift layer, the etching stop layer, and the light-shielding layer are etched with the same etchant, whereby a phase shift mask can be manufactured in which the edge of the light-shielding pattern formed on the light-shielding layer is arranged at a position that is set back in a plan view from the edge of the phase shift pattern laminated on the phase shift layer.

Description

Mask blank, phase shift mask, halftone mask, mask blank, and method for manufacturing phase shift mask

Technical Field

The present invention relates to a mask blank (マスクブランクス), a phase shift mask, a halftone mask, a method for manufacturing the mask blank, and a method for manufacturing the phase shift mask, which are capable of forming a fine and highly accurate exposure pattern, and particularly to a technique suitable for use in the manufacture of a flat panel display.

The present application claims priority based on patent application No. 2017-126258, filed in japan on 6/28/2017, the contents of which are incorporated herein by reference.

Background

In a photolithography method used for patterning elements, wirings, and the like such as FPDs (flat panel displays), a phase shift mask is used as a photomask. The phase shift mask is an edge enhancement type mask in which a phase shift layer, an etching stop layer, and a light shielding layer are provided in this order on the surface of a transparent substrate, and can be used when the pattern is made finer.

In addition, in the mask for the FPD, the number of masks required for forming the panel is reduced by using a halftone mask having a semi-transmissive region. By reducing the amount of light transmitted through the semi-transmissive region, the film thickness of the developed photoresist can be controlled to a desired value.

Patent document 1: japanese patent laid-open No. 2010-128003

However, in the above conventional example, the phase shift mask is manufactured by forming a phase shift layer on a transparent substrate, etching and patterning the phase shift layer, forming a light-shielding layer so as to cover the patterned phase shift layer, and etching and patterning the light-shielding layer. If the film formation and patterning are performed alternately in this way, the transfer time between apparatuses and the process waiting time become long, and the production efficiency is significantly reduced. Further, the light-shielding layer and the phase shift layer cannot be etched continuously over a single mask having a predetermined opening pattern, and it is necessary to form the mask (resist pattern) twice, which increases the number of manufacturing steps. Therefore, there is a problem that the phase shift mask cannot be manufactured with high mass productivity.

In addition, it is conceivable that the light-shielding layer and the phase shift layer can be etched with the same etchant at the same time, but in this case, the amount of side etching in the light-shielding layer is not sufficient. Therefore, there is a problem that the dimension of the edge of the light-shielding pattern receding in a plan view from the edge of the phase shift pattern cannot be formed within a predetermined range.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and aims to achieve the following object.

1. The number of manufacturing steps of the phase shift mask in which the edge of the light-shielding pattern formed on the light-shielding layer is disposed at a position that is set back in a plan view from the edge of the phase shift pattern laminated on the phase shift layer can be reduced.

2. The dimension of the edge of the light-shielding pattern that is set back in a plan view from the edge of the phase shift pattern can be formed within a predetermined range.

A mask blank according to an aspect of the present invention includes: a transparent substrate; a phase shift layer laminated on the surface of the transparent substrate and mainly composed of Cr; an etch stop layer laminated to the phase shift layer; and a light-shielding layer laminated on the etching stopper layer, the light-shielding layer, the phase shift layer, the etching stopper layer, and the light-shielding layer being etched with the same etchant, whereby a phase shift mask can be manufactured in which an edge of a light-shielding pattern formed on the light-shielding layer is disposed at a position that is set back in a plan view from an edge of a phase shift pattern laminated on the phase shift layer.

In the aspect of the present invention, it is more preferable that the etching stopper layer contains at least one metal selected from Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, and Hf as a main component.

In the light-shielding layer, the side-face etching amount in the etching of the phase-shift layer, the etching stop layer, and the light-shielding layer may be set to be larger from the etching start time of the light-shielding layer than before the etching start time of the phase-shift layer.

In addition, in the aspect of the present invention, the following means may be adopted: the amount of side etching of the light-shielding layer is set to be greater than or equal to 10 times the etching start time of the phase shift layer.

In the phase shift layer, the etching stop layer, and the light-shielding layer, the light-shielding layer before the etching start time of the phase shift layer may be set to be electrochemically expensive with respect to the etching stop layer, and the light-shielding layer after the etching start time of the phase shift layer may be set to be electrochemically base with respect to the phase shift layer.

The etching stopper layer may have a thickness of 10nm or more.

A method for manufacturing a mask blank according to an aspect of the present invention is a method for manufacturing a mask blank according to any one of the above aspects, including: the phase shift layer, the etching stopper layer, and the light shielding layer are sequentially laminated on the transparent substrate, and the etching stopper layer can be formed by sputtering while containing carbon dioxide as a film forming atmosphere and mainly containing at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, and Hf.

A method for manufacturing a phase shift mask according to an aspect of the present invention is a method for manufacturing a phase shift mask using a mask blank according to any one of the above aspects, and may include: forming a mask having a predetermined opening pattern on the light-shielding layer; and wet-etching the phase shift layer, the etch stop layer, and the light-shielding layer simultaneously with the same etchant over the formed mask.

In the step of simultaneously wet-etching the phase shift layer, the etching stop layer, and the light-shielding layer, the amount of side etching in the light-shielding layer may be set to about 4 to 5 times the amount of side etching in the phase shift layer.

As the etchant, an etchant containing cerium ammonium nitrate is preferably used.

The phase shift mask according to the aspect of the present invention can be manufactured by the manufacturing method according to any one of the above-described aspects.

A mask blank according to an aspect of the present invention includes: a transparent substrate; a halftone layer laminated on the surface of the transparent substrate and mainly composed of Cr; an etch stop layer laminated to the halftone layer; and a light-shielding layer laminated on the etching stopper layer, the halftone layer, the etching stopper layer, and the light-shielding layer being etched with the same etchant, the light-shielding layer being mainly composed of Cr, whereby a halftone mask can be manufactured in which an edge of a light-shielding pattern formed on the light-shielding layer is disposed at a position set back in a plan view from an edge of a halftone pattern laminated on the halftone layer.

In the mask blank according to the aspect of the present invention, in the light-shielding layer, the amount of side etching in the etching of the halftone layer, the etching stop layer, and the light-shielding layer may be set to be larger from the etching start time of the light-shielding layer than before the etching start time of the halftone layer.

A method for manufacturing a mask blank according to an aspect of the present invention is a method for manufacturing a mask blank according to any one of the above aspects, including: the halftone layer, the etching stopper layer, and the light shielding layer are sequentially laminated on the transparent substrate, and the etching stopper layer can be formed by sputtering, in which carbon dioxide is contained as a film forming atmosphere and at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, and Hf is used as a main component.

The halftone mask according to the embodiment of the present invention can be manufactured by the manufacturing method of the above-described embodiment.

A mask blank according to an aspect of the present invention includes: a transparent substrate; a phase shift layer laminated on the surface of the transparent substrate and mainly composed of Cr; an etch stop layer laminated to the phase shift layer; and a light-shielding layer laminated on the etching stop layer, the light-shielding layer, the phase shift layer, the etching stop layer, and the light-shielding layer being etched with the same etchant, whereby a phase shift mask can be manufactured in which the edge of the light-shielding pattern formed on the light-shielding layer is located at a position that is set back in a plan view from the edge of the phase shift pattern laminated on the phase shift layer. Thus, the light-shielding layer can be etched first, the etching stop layer can be etched, the phase shift layer can be etched, and the light-shielding layer can be etched at the same time. Thus, it is not necessary to perform resist pattern formation twice or more, and the light-shielding pattern and the phase shift pattern can be formed by one continuous etching, and at the same time, the corresponding portions can also be removed from the etching stopper layer. Therefore, it is possible to provide a mask blank and a phase shift mask manufactured from the mask blank, which can reduce the number of manufacturing processes, reduce the number of processes, shorten the manufacturing time, and reduce the cost.

In an embodiment of the present invention, the etching stopper layer contains at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, and Hf as a main component. Thus, the etching stop layer can be etched with the same etchant as that for the phase shift layer and the light-shielding layer containing Cr (chromium) as a main component, and the light-shielding layer can be etched first, then the etching stop layer, then the phase shift layer, and the light-shielding layer can be etched in the side-etching manner. Thus, the light shielding pattern and the phase shift pattern can be formed by one continuous etching.

In the light-shielding layer, the amount of side etching in the etching of the phase shift layer, the etching stop layer, and the light-shielding layer is set to be larger from the etching start time of the light-shielding layer than before the etching start time of the phase shift layer. Thus, the light-shielding layer, the etching stop layer, and the phase shift layer are processed by one continuous etching, and the light-shielding layer is side-etched, whereby a phase shift mask can be manufactured in which the edge of the light-shielding pattern formed on the light-shielding layer is located at a position set back in a plan view from the edge of the phase shift pattern laminated on the phase shift layer so as to have a predetermined size.

In the aspect of the present invention, the amount of side etching of the light-shielding layer is set to be greater than or equal to 10 times the etching start time of the light-shielding layer than before the etching start time of the phase-shift layer. In this way, the light-shielding layer, the etching stop layer, and the phase shift layer are processed by one continuous etching, and the light-shielding layer is side-etched, so that the phase shift mask can be manufactured so that the dimension of the edge of the light-shielding pattern formed on the light-shielding layer, which is disposed at a position set back in a plan view from the edge of the phase shift pattern laminated on the phase shift layer, fits within the range of the edge enhancement mask.

In the phase shift layer, the etching stop layer, and the light-shielding layer, the light-shielding layer before the etching start time of the phase shift layer is set to be electrochemically noble with respect to the etching stop layer, and the light-shielding layer after the etching start time of the phase shift layer is set to be electrochemically base with respect to the phase shift layer. Thus, when the light-shielding layer, the etching stop layer, and the phase shift layer are processed by one continuous etching, the light-shielding layer can be etched first, the etching stop layer can be etched, and then the phase shift layer can be etched.

The etching stopper layer has a film thickness of 10nm or more. Thus, when the light-shielding layer, the etching stop layer, and the phase shift layer are processed by one continuous etching, the light-shielding layer can be etched first, the etching stop layer can be etched, and then the phase shift layer can be etched.

A method for manufacturing a mask blank according to an aspect of the present invention is a method for manufacturing a mask blank described above, including the steps of: the phase shift layer, the etching stopper layer, and the light shielding layer are sequentially laminated on the transparent substrate, and the etching stopper layer is formed by sputtering in which carbon dioxide is contained as a film forming atmosphere and at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, and Hf is used as a main component. Thus, the light-shielding layer before the etching start time of the phase shift layer can be set to be electrochemically expensive with respect to the etching stop layer, and the light-shielding layer after the etching start time of the phase shift layer can be set to be electrochemically less expensive with respect to the phase shift layer. Thus, when the light-shielding layer, the etching stop layer, and the phase shift layer are processed by one continuous etching, the light-shielding layer can be etched first, the etching stop layer can be etched, and then the phase shift layer can be etched.

A method for manufacturing a phase shift mask according to an aspect of the present invention is a method for manufacturing a phase shift mask using any one of the above-described mask blanks, and includes: forming a mask having a predetermined opening pattern on the light-shielding layer; and wet-etching the phase shift layer, the etch stop layer, and the light-shielding layer simultaneously with the same etchant over the formed mask. Thus, the mask pattern is formed at a time, the light-shielding layer can be etched first, the etching stop layer can be etched, and then the phase shift layer can be etched.

In the step of simultaneously wet-etching the phase shift layer, the etching stop layer, and the light-shielding layer, the amount of side etching in the light-shielding layer is set to be about 4 to 5 times the amount of side etching in the phase shift layer. Thus, the light-shielding layer is side-etched by a large amount of side etching, and a predetermined light-shielding pattern and a predetermined phase shift pattern can be easily formed on the basis of an image defined by the mask pattern.

As the etchant, an etchant containing cerium ammonium nitrate was used. Thereby, the phase shift layer, the etching stopper layer, and the light-shielding layer can be wet-etched simultaneously with the same etchant.

The phase shift mask according to the aspect of the present invention can be manufactured by any of the above-described manufacturing methods.

A mask blank according to an aspect of the present invention includes: a transparent substrate; a halftone layer laminated on the surface of the transparent substrate and mainly composed of Cr; an etch stop layer laminated to the halftone layer; and a light-shielding layer laminated on the etching stop layer, the halftone mask being configured such that an edge of a light-shielding pattern formed on the light-shielding layer is located at a position set back in a plan view from an edge of a halftone pattern laminated on the halftone layer by etching the halftone layer, the etching stop layer, and the light-shielding layer with the same etchant, the light-shielding layer being mainly composed of Cr. Thus, the light-shielding layer can be etched first, the etching stop layer can be etched, the halftone layer can be etched, and the light-shielding layer can be etched at the same time. Thus, it is possible to form the light shielding pattern and the halftone pattern by a single continuous etching without forming a resist pattern twice or more, and to remove the corresponding portion of the etching stopper layer, and therefore it is possible to provide a mask blank and a halftone mask manufactured from the mask blank, which can reduce the number of manufacturing steps, the number of processes, the manufacturing time, and the cost.

In the mask blank according to the aspect of the present invention, in the light-shielding layer, the amount of side etching in the etching of the halftone layer, the etching stop layer, and the light-shielding layer is set to be larger from the etching start time of the light-shielding layer than before the etching start time of the halftone layer. Thus, the light-shielding layer, the etching stop layer, and the halftone layer are processed by a single continuous etching process, and the light-shielding layer is subjected to a side etching process, so that a halftone mask can be manufactured in which the edge of the light-shielding pattern formed on the light-shielding layer is disposed at a position that is set back in a plan view from the edge of the halftone pattern formed on the halftone layer so as to have a predetermined size.

A method for manufacturing a mask blank according to an aspect of the present invention is a method for manufacturing a mask blank described above, including the steps of: the halftone layer, the etching stopper layer, and the light shielding layer are sequentially laminated on the transparent substrate, and the etching stopper layer is formed by sputtering while containing carbon dioxide as a film forming atmosphere and mainly containing at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, and Hf. Accordingly, the light-shielding layer before the etching start time of the halftone layer can be set to be electrochemically expensive with respect to the etching stop layer, and the light-shielding layer after the etching start time of the halftone layer can be set to be electrochemically base with respect to the halftone layer, whereby when the light-shielding layer, the etching stop layer, and the halftone layer are processed by one continuous etching, the light-shielding layer can be etched first, the etching stop layer can be etched, and then the halftone layer can be etched, and when the halftone layer is etched, the light-shielding layer can be side-etched by a side-etching amount larger than that of the halftone layer.

The halftone mask according to the embodiment of the present invention is manufactured by the above-described manufacturing method, and thus is similarly manufactured by changing the phase shift layer described above to a halftone layer.

According to the aspect of the present invention, the following effects can be exhibited: the phase shift layer, the etching stop layer, and the light-shielding layer are simultaneously wet-etched with the same etchant to thereby laterally etch the light-shielding layer, and a phase shift mask in which the edge of the light-shielding pattern formed on the light-shielding layer is set to a position that is set back in a plan view from the edge of the phase shift pattern laminated on the phase shift layer, and the size of the position is within a range suitable for an edge enhancement mask can be manufactured.

In addition, according to the aspect of the present invention, the following effects can be achieved: the halftone mask is manufactured by performing side etching on the light-shielding layer by simultaneously performing wet etching on the halftone layer, the etching stop layer, and the light-shielding layer with the same etchant, and the halftone mask in which the size of a position where the edge of the light-shielding pattern formed on the light-shielding layer is set to recede in a plan view from the edge of the halftone pattern laminated on the halftone layer is a semi-transmissive region.

Drawings

Fig. 1 is a schematic cross-sectional view showing a mask blank according to a first embodiment of the present invention.

Fig. 2 is a process diagram illustrating a mask blank, a phase shift mask, and a manufacturing method according to a first embodiment of the present invention.

Fig. 3 is a graph showing the temporal change in side etching in each layer of the mask blank, the phase shift mask, and the manufacturing method according to the first embodiment of the present invention.

Fig. 4 is a graph showing changes over time in the electrochemical relationship among the layers of the mask blank, the phase shift mask, and the manufacturing method according to the first embodiment of the present invention.

Fig. 5 is an SEM photograph showing an experimental example of the method for manufacturing the mask blank and the phase shift mask according to the embodiment of the present invention.

Fig. 6 is an SEM photograph showing an experimental example of the method for manufacturing the mask blank and the phase shift mask according to the embodiment of the present invention.

Fig. 7 is an SEM photograph showing an experimental example of the method for manufacturing the mask blank and the phase shift mask according to the embodiment of the present invention.

Fig. 8 is an SEM photograph showing an experimental example of the method for manufacturing the mask blank and the phase shift mask according to the embodiment of the present invention.

Fig. 9 is an SEM photograph showing an experimental example of the method for manufacturing the mask blank and the phase shift mask according to the embodiment of the present invention.

Fig. 10 is a schematic cross-sectional view showing a second embodiment of a mask blank according to an embodiment of the present invention.

Fig. 11 is a process diagram showing a mask blank, a halftone mask, and a manufacturing method according to a second embodiment of the present invention.

Fig. 12 is a graph showing the wavelength dependence of the transmittance in the halftone mask according to the second embodiment of the present invention.

Fig. 13 is data showing the wavelength dependence of the transmittance in the halftone mask according to the second embodiment of the present invention.

Detailed Description

A mask blank, a phase shift mask, and a manufacturing method according to a first embodiment of the present invention will be described below with reference to the drawings.

Fig. 1 is a schematic cross-sectional view showing a mask blank in the present embodiment, and reference numeral MB in the figure denotes the mask blank.

As shown in fig. 1, the mask blank MB according to the present embodiment is composed of a transparent substrate S, a phase shift layer 11 formed on the transparent substrate S, an etching stopper layer 12 formed on the phase shift layer 11, and a light shielding layer 13 formed on the etching stopper layer 12.

In the mask blank MB according to the present embodiment, as described later, the phase shift layer 11, the etching stopper layer 12, and the light shielding layer 13 can be etched with the same etchant.

As the transparent substrate S, a material having excellent transparency and optical isotropy can be used, and for example, a quartz glass substrate can be used. The size of the transparent substrate S is not particularly limited, and is appropriately selected according to a substrate to be exposed using the mask (for example, a substrate for an FPD, a semiconductor substrate). In the present embodiment, a substrate having a diameter of about 100mm, a rectangular substrate having a side of about 50 to 100mm to 300mm or more, a quartz substrate having a vertical length of 450mm, a horizontal length of 550mm and a thickness of 8mm, and a substrate having a maximum side size of 1000mm or more and a thickness of 10mm or more can be used.

In addition, the flatness of the transparent substrate S may be reduced by polishing the surface of the transparent substrate S. The flatness of the transparent substrate S may be set to 20 μm or less, for example. This makes it possible to increase the depth of focus of the mask, and to contribute significantly to fine and highly accurate pattern formation. Further, the flatness is preferably a small value of 10 μm or less.

The phase shift layer 11 contains Cr as a main component, and specifically may be composed of one selected from the group consisting of simple Cr and Cr oxides, nitrides, carbides, oxynitrides, carbonitrides, and oxycarbonitrides, and may be composed of two or more layers of these materials.

The phase shift layer 11 is formed to have a thickness (e.g., 90 to 170nm) that can have a phase difference of about 180 ° with respect to any light in a wavelength region of 300nm to 500nm (e.g., i-ray having a wavelength of 365 nm).

As the etching stopper layer 12, a material containing, as a main component, one or more metals selected from Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, Cu, V, Ta, Zr, and Hf can be used, and for example, a Ni — Ti — Nb — Mo film can be used.

The etching stopper layer 12 can be formed by, for example, sputtering, electron beam deposition, laser deposition, ALD, or the like.

As the film formation conditions of the etching stopper layer 12, whether or not carbon dioxide is contained in the film formation gas can be set. When carbon dioxide is contained in the film forming gas of the etching stopper layer 12, the etching stopper layer 12 can be etched and removed by a chromium etchant described later. When the film forming gas does not contain carbon dioxide, the etching stopper layer 12 can be selectively removed without etching with a chromium etchant described later.

The light-shielding layer 13 contains Cr as a main component, specifically, Cr and nitrogen. Further, the light-shielding layer 13 may also have a different composition in the thickness direction. In this case, the light shielding layer 13 may be formed by one or more layers selected from the group consisting of simple Cr and Cr oxides, nitrides, carbides, oxynitrides, carbonitrides, and oxycarbonitrides.

The light-shielding layer 13 is formed to have a thickness (for example, 80nm to 200nm) that can obtain predetermined optical characteristics.

Here, the light-shielding layer 13 and the phase shift layer 11 are both chromium-based thin films and are oxidized and nitrided, but if compared, the phase shift layer 11 has a higher oxidation degree than the light-shielding layer 13 and is less likely to be oxidized (is less likely to release electrons), and therefore is expensive.

On the other hand, the standard electrode potentials of the light-shielding layer 13 and the etching stopper layer 12 are trivalent chromium (-0.13 ξ 0/V) and divalent nickel (-0.245 ξ)⁰V) is set so that the light-shielding layer 13 (chrome) is noble and the etching stopper layer 12 (nickel) is base.

The mask blank MB according to the present embodiment is applicable to, for example, manufacturing a phase shift mask M, which is a mask for patterning a glass substrate for an FPD.

The phase shift mask M has, for example, a phase shift layer (phase shift pattern) 11 capable of having a phase difference of 180 °, and the aperture width of the light shielding pattern 13b formed on the light shielding layer 13 is set to be wider than the aperture width of the phase shift pattern 11a formed on the phase shift layer 11.

For example, according to the phase shift mask M, in the exposure process, by using light in a wavelength region, particularly, a composite wavelength including g-ray (436nm), h-ray (405nm), and i-ray (365nm) as exposure light, a region with the minimum light intensity can be formed by a phase inversion action, and the exposure pattern can be made clearer. By such a phase shift effect, the pattern accuracy is greatly improved, and a fine and highly accurate pattern can be formed. The phase shift layer may be formed of chromium oxide, chromium oxynitride, chromium oxynitrides, or the like, or may be formed of an oxide film, a nitride film, or an oxynitride film containing Si. In addition, the thickness of the phase shift layer may be set to a thickness having a phase difference of about 180 ° with respect to the i-ray. Further, the above-described phase shift layer may also be formed in a thickness capable of having a phase difference of about 180 ° for h-rays or g-rays. By "about 180" is meant herein 180 or about 180, such as 180 ± 10 or less. According to the phase shift mask, by using the light in the wavelength region, the pattern accuracy can be improved by the phase shift effect, and a fine and highly accurate pattern can be formed. Thus, a flat panel display with high image quality can be manufactured.

Next, a method for manufacturing the mask blank MB according to the present embodiment will be described.

Fig. 2 is a cross-sectional view showing a phase shift mask manufacturing process using a mask blank according to the present embodiment, fig. 3 is a graph showing a change in side etching with time in the mask blank according to the present embodiment, and fig. 4 is a graph showing a change in electrochemical relationship with time in the mask blank according to the present embodiment.

As shown in fig. 1, the mask blank MB according to the present embodiment is formed by sequentially forming a phase shift layer 11 mainly composed of Cr and an etching stopper layer 12 mainly composed of Ni on a glass substrate S by a DC sputtering method or the like. In the formation of the etching stopper layer 12, it is preferable to use a gas atmosphere containing carbon dioxide and to contain carbon such as methane.

Next, a light-shielding layer 13 containing Cr as a main component is formed on the etching stopper layer 12.

At this time, as film forming conditions, DC sputtering using chromium as a target was performed, and argon and nitrogen (N) were contained as a sputtering gas₂) And the like, sputtering can be performed.

Further, as the sputtering proceeds, the light-shielding layer 13 may be formed in a state of having a chromium layer on the glass substrate S side and a chromium oxide layer thereon by changing the conditions thereof.

Next, a method of manufacturing a phase shift mask from the mask blank MB according to the present embodiment manufactured in this manner will be described.

Next, as shown in fig. 2 (a), a photoresist layer PR1a is formed on the uppermost layer of the mask blank MB, i.e., on the light-shielding layer 13. The photoresist layer PR1a may be positive or negative, but may be positive. As the photoresist layer PR1a, a liquid-like resist was used.

Next, as shown in fig. 2 (b), the photoresist layer PR1a is exposed to light, and as shown in fig. 2 (c), development is performed, thereby forming a resist pattern PR1 on the light-shielding layer 13. The resist pattern PR1 functions as an etching mask for the light-shielding layer 13, the etching stopper layer 12, and the phase shift layer 11, and has an appropriate shape according to the etching pattern of each of these layers 11, 12, and 13. As an example, the resist pattern PR1 is set to have a shape having an opening width corresponding to the opening width dimension of the phase shift pattern 11a formed in the phase shift region PS.

Next, as shown in fig. 2 (d), the following steps are started: the light-shielding layer 13, the etching stopper layer 12, and the phase shift layer 11 are wet-etched with a predetermined etchant over the resist pattern PR 1.

As this etching step, the three layers 11, 12, and 13 are successively patterned by a single etching process, but the etching of the light shielding layer 13 is started first from the lamination order of the glass substrate S.

As the etching liquid, an etching liquid containing cerium ammonium nitrate can be used, and for example, cerium ammonium nitrate containing an acid such as nitric acid or perchloric acid is preferably used.

Here, since the etching stopper layer 12 has higher resistance to the etching liquid than the light shielding layer 13, first, only the light shielding layer 13 is patterned to form the light shielding pattern 13 a. The light-shielding pattern 13a is provided in a shape having an opening width corresponding to the resist pattern PR 1.

At this time, in the region corresponding to the resist pattern PR1 of the light-shielding layer 13, the etching stopper layer 12 is wet-etched by continuing to use the same etching solution as shown in fig. 2 (e) after the portion removed in the entire region in the thickness direction.

Here, the etching of the etching stopper layer 12 is started using the same etching solution while crossing the resist pattern PR1, that is, without removing the resist pattern PR1, from the time when the light-shielding layer 13 is etched and the etching stopper layer 12 is exposed.

Further, since the etching rate of the etching stopper layer 12 is smaller than that of the light shielding layer 13, the light shielding pattern 13a can be formed and the etching stopper pattern 12a can be formed by appropriately selecting the film thickness of the etching stopper layer 12.

Next, after the light-shielding pattern 13a is formed, as shown in fig. 2 (e), from the time when the etching stopper layer 12 is etched and the phase shift layer 11 is exposed, the etching of the phase shift layer 11 is started using the same etching liquid over the resist pattern PR1, that is, in a state where the resist pattern PR1 is not removed.

Thus, since the light-shielding pattern 13a is made of the same Cr-based material as the phase shift layer 11 and the side surface of the light-shielding pattern 13a is exposed, the phase shift layer 11 is patterned to form the phase shift pattern 11 a. The phase shift pattern 11a has a predetermined opening width dimension.

Here, as shown in fig. 2 (f), the side etching rate of the light-shielding layer 13 increases while the phase shift layer 11 is etched.

That is, from the time when the phase shift layer 11 is exposed, that is, the etching start time of the phase shift layer 11, the side etching amount of the light-shielding layer 13 is increased by about 10 times as much as the side etching amount up to now (the side etching amount before the phase shift layer 11 is exposed).

Therefore, simultaneously with the formation of the phase shift pattern 11a, the light-shielding pattern 13a is further side-etched than the phase shift pattern 11a so that a high side-etched amount is obtained from the time when the etching of the phase shift layer 11 starts. As shown in fig. 2 (f), the light-shielding pattern 13b having a shape with an opening width larger than the opening width dimension of the phase shift pattern 11a is formed.

In this case, the light-shielding layer 13 or the light-shielding pattern 13a obtains a high side etching amount from the etching start time of the phase shift layer 11, thereby shortening the etching processing time and reducing damage to the phase shift layer 11 or the phase shift pattern 11 a.

Next, as shown in fig. 2 (g), the resist pattern PR1 is removed. Since a known resist stripping liquid can be used for removing the resist pattern PR1, a detailed description thereof will be omitted.

Next, as shown in fig. 2 (h), the etching stopper pattern 12a exposed from the side surface of the light-shielding pattern 13b is wet-etched using a second etching solution to form an etching stopper pattern 12b having an opening width corresponding to the light-shielding pattern 13 b. As the second etching solution, an etching solution in which at least one selected from acetic acid, perchloric acid, hydrogen peroxide water, and hydrochloric acid is added to nitric acid can be suitably used.

In addition, other methods may be used to remove the exposed etching stopper pattern 12a after the removal of the resist pattern PR 1.

As described above, as shown in fig. 2 (h), the edge-enhanced phase shift mask M is obtained, that is, the opening width of the light-shielding region LR formed as the light-shielding pattern 13b (and the etching stopper pattern 12b) is wider than the opening width of the phase shift region PS formed as the phase shift pattern 11 a.

Next, a change in the amount of side etching (side etching rate) in the present embodiment will be described.

In the etching in the present embodiment, the light-shielding layer 13, the etching stopper layer 12, and the phase shift layer 11 are continuously etched with the same etchant.

Next, the etching start time is considered over time.

First, if an etchant is supplied to the mask blank MB, the light-shielding layer 13 located at the uppermost position exposed from the opening of the resist pattern PR1 comes into contact with the etchant, and the light-shielding layer 13 is etched in that portion. In this case, the side etching of the light-shielding layer 13 by the etchant is, for example, about 0.005 μm/10 sec.

Next, the etching proceeds, and the upper light-shielding layer 13 is etched to the lowermost portion in the film thickness direction, and the etching stopper layer 12 at the intermediate position in the film thickness direction is brought into contact with the etchant.

In this case, the upper light-shielding layer 13 and the lower etching stopper layer 12 are wet-etched at the same time. Here, since there is a difference in composition between the lower etching stopper layer 12 and the upper light shielding layer 13, there is a relationship that it is electrochemically inexpensive.

As in the present embodiment, when the upper light-shielding layer 13 is electrochemically expensive relative to the lower etching stopper layer 12, that is, when the lower etching stopper layer 12 is electrochemically less expensive relative to the upper light-shielding layer 13, the etching of the etching stopper layer 12 is performed less expensive relative to the expensive light-shielding layer 13.

However, since the etching stopper layer 12 is originally made of a material having a large etching resistance against the chrome etchant, the etching of the etching stopper layer 12 is not performed much more than the light shielding layer 13. Therefore, for example, the etching amount of the side surface of the etching stopper layer 12 is about 0.001 μm/10sec smaller than the side surface etching amount of the light shielding layer 13 about 0.005 μm/10sec, and the etching of the etching stopper layer 12 does not proceed so much.

Here, a mechanism of removing a film made of metal or the like by etching, that is, corrosion will be described.

Most of the corrosion is caused by electrochemical reactions (oxidation and reduction).

The ease of redox reaction varies depending on the metal, and is represented by a standard electrode potential. The standard electrode potential causes a reduction reaction when it is equal to or higher than the standard electrode potential, and causes an oxidation reaction when it is equal to or lower than the standard electrode potential. Therefore, the metal having a lower standard electrode potential is more easily oxidized (base metal), and the metal having a higher standard electrode potential is more hardly oxidized (noble metal). In the present embodiment, the standard electrode potentials measured with the standard hydrogen electrode as a reference are compared, and a high metal is set to be expensive and a low metal is set to be base.

When metals having different standard electrode potentials are brought into contact with each other, the oxidation reaction of the base metal is promoted, and the reduction reaction of the noble metal is promoted. This corrosion is referred to as dissimilar metal contact corrosion. Base metals become metal ions during oxidation reactions, promoting corrosion. That is, base metals are susceptible to corrosion.

In addition, dissimilar metal contact corrosion is related to the area of the precious and base metals. If the area of the metal which is less noble than the noble metal is large, the electrons required for the reduction reaction are small, and therefore, the oxidation proceeds slowly, whereas if the area of the metal which is less noble than the noble metal is small, the electrons required for the reduction reaction increase, and therefore, the oxidation proceeds rapidly.

The dissimilar metal contact corrosion is caused not only by a simple metal but also by a metal compound (for example, an oxide, nitride, carbide, or fluoride of a metal). In this case, the metal compound to be oxidized is difficult to be further oxidized than a compound of the same metal not to be oxidized. That is, it is difficult to release electrons and to form cations, and therefore, the tendency to ionize decreases, which is expensive.

In this manner, the multilayer film is etched with high accuracy by wet etching using a redox reaction, and it is important to use a difference between the standard electrode potentials of the metals contained in the upper layer and the lower layer and a difference between the corrosion difficulty of the upper layer and the lower layer (it can be said that the flow difficulty of current is increased when the film is an electrode with an etchant as an electrolyte).

Here, when the standard electrode potential of the metal contained in the upper layer and the lower layer is "upper layer < lower layer (the standard electrode potential of the lower layer is higher than the standard electrode potential of the upper layer)", that is, "the upper layer is base and the lower layer is expensive", the etching rate of the lower layer is lower than the etching rate of the upper layer in wet etching.

Therefore, there are cases where: when etching the lower layer, the etching rate to the lower layer becomes too small to be etched substantially, and when etching the upper layer, the etching rate to the upper layer becomes too large to be formed into a predetermined shape.

On the other hand, in contrast to the above case, when the standard electrode potential of the metal contained in the upper layer and the lower layer is "upper layer > lower layer (the standard electrode potential of the lower layer is lower than the standard electrode potential of the upper layer)", that is, "the upper layer is expensive and the lower layer is base", the etching rate of the lower layer is higher than that of the upper layer in wet etching.

Therefore, there are cases where: when the lower layer is to be etched, the etching rate to the lower layer becomes too high to form a predetermined shape, and when the upper layer is to be etched, the etching rate to the upper layer becomes too low to be substantially etched.

Therefore, it is considered that, when the standard electrode potentials of the upper layer and the lower layer are "upper layer > lower layer", that is, when the upper layer is electrochemically expensive relative to the lower layer, the side etching in the lower layer can be prevented from becoming excessively small, and the lower layer can be appropriately etched by wet etching.

In the present embodiment, it is considered that the light-shielding layer 13 is directly laminated on the etching stopper layer 12, whereby the etching stopper layer 12 becomes a sacrificial electrode (base), and electrons are received from the light-shielding layer 13 (base), thereby increasing the etching rate of the etching stopper layer 12.

By using a material containing as a main component at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W, Cu, V, Ta, Zr, and Hf as the etching stopper layer 12, for example, a Ni — Ti — Nb — Mo film, the above-described electrochemically noble and base relationship is set, and the above-described amount of side etching can be controlled to be about 0.005 μm/10sec in the etching of the light shielding layer 13.

Further, the etching proceeds, the etching of the etching stopper layer 12 in the middle of the film thickness direction reaches the lowermost portion in the film thickness direction, and the phase shift layer 11 on the lower side is brought into contact with the etchant, and the state after the etching of the phase shift layer 11 is started is considered.

Here, the upper light-shielding layer 13, the middle etching stopper layer 12, and the lower phase shift layer 11 are wet-etched at the same time.

In this case, the middle etching stopper layer 12 of the three layers functions as a conductor, and there is an electrochemically inexpensive relationship between the upper light shielding layer 13 and the lower phase shift layer 11.

Here, as in the present embodiment, when the upper light-shielding layer 13 is electrochemically less expensive than the lower phase-shift layer 11, that is, when the lower phase-shift layer 11 is electrochemically more expensive than the upper light-shielding layer 13, etching of the less expensive light-shielding layer 13 is greatly performed with respect to the more expensive phase-shift layer 11. Further, as the etching in the film thickness direction in the light-shielding layer 13 progresses, the difference in lateral side etching in the corresponding direction increases.

That is, contrary to the case described with the relation between the light-shielding layer 13 and the etching stopper layer 12, when the standard electrode potential of the metal contained in the upper layer and the lower layer is "upper layer < lower layer", that is, "upper layer is base and lower layer is expensive", when the upper layer is to be etched by wet etching, the etching rate of the upper layer can be increased.

Here, since only the side wall portion of the light-shielding layer 13 is in contact with the etchant as the light-shielding pattern 13a, the light-shielding layer 13 on the upper side is etched in a direction perpendicular to the side wall portion, that is, in a lateral direction, and the amount of side etching becomes extremely large.

It is considered that the increase in the amount of side etching in the light-shielding pattern 13a is started at the time when the etching stopper layer 12 is etched in the film thickness direction and the phase shift layer 11 is exposed, that is, at the same time as the etching start time of the phase shift layer 11.

Fig. 3 and 4 show how the amount of side etching and the electrochemical relationship between base and noble in the three layers 11, 12, 13 change as the etching progresses.

Fig. 3 is a graph showing a change with time of side etching in each layer 13, 12, 11 of the present embodiment, and fig. 4 shows a change with time of electrochemical relationship in each layer 13, 12, 11 of the present embodiment.

As shown in the left side of fig. 3, during a period immediately after the start of etching in which only the light shielding layer 13 is etched, the light shielding layer 13 is not a comparison target which is electrochemically inexpensive or expensive, as shown in the left side column of fig. 4. Therefore, the light-shielding layer 13 is etched by a predetermined amount of side etching based on the relationship between the film composition and the etchant.

In this embodiment, the amount of side etching in the light-shielding layer etching is 0.005 μm/10 sec.

Next, as shown in the center of fig. 3, the light-shielding layer 13 is etched over the entire length in the film thickness direction, and after the etching of the etching stopper layer 12 is started, the light-shielding layer 13 and the etching stopper layer 12 are etched at the same time. In this way, when etching is performed, the light-shielding layer 13 becomes electrochemically expensive with respect to the etching stopper layer 12, as shown in the central column of fig. 4. Therefore, the etching of the light-shielding layer 13 is performed by the side etching amount in the etching of only the light-shielding layer 13, and the etching of the etching stopper layer 12 is performed by the small side etching amount at a low etching rate.

In this embodiment, the amount of side etching in the etching of the etching stopper layer is a value less than 0.005 μm/10 sec.

Next, as shown in the right side of fig. 3, the light-shielding layer 13 is etched over the entire length in the film thickness direction, and the etching stopper layer 12 is etched over the entire length in the film thickness direction, so that after the etching of the phase shift layer 11 is started, the etching stopper layer 12 can be regarded as a conductor connecting the light-shielding layer 13 and the phase shift layer 11, and the light-shielding layer 13 and the phase shift layer 11 can be etched at the same time.

When etching proceeds in this way, the light-shielding layer 13 becomes electrochemically base with respect to the phase shift layer 11 as shown in the right column of fig. 4. Therefore, the light-shielding layer 13 is etched by a side etching amount that is very large compared to the side etching amount in etching of only the light-shielding layer 13, and the phase shift layer 11 is etched by a small side etching amount because it is expensive.

In the present embodiment, the side etching amount in the increased light-shielding layer etching is 0.066 μm/10 sec.

The amount of side etching in the phase shift layer etching was about 0.005 μm/10 sec.

In fig. 3 and 4, the chromium light-shielding film represents the light-shielding layer 11, the nickel thin film (ES film) represents the etching stopper layer 12, and the chromium PSM film represents the phase shift layer 11.

In addition, as in the present embodiment, in order to form the phase shift mask by processing the three layers 11, 12, and 13 by one etching, the film thickness of the etching stopper layer 12 needs to be set within a predetermined range.

When the film thickness of the etching stopper layer 12 is not set within the predetermined range, particularly when the film thickness of the etching stopper layer 12 is too thin, there is a possibility that the etching stopper layer 12 is removed in the film thickness direction to generate a portion where etching of the phase shift layer 11 starts before the light-shielding pattern 13a is formed into a predetermined shape corresponding to the resist pattern PR1 in the initial etching of only the light-shielding layer 13, and a pattern of the predetermined shape cannot be formed. Alternatively, after the etching of the phase shift layer 11 is started, the etching of the phase shift layer 11 may become too large compared to a predetermined amount, and a pattern having a predetermined shape may not be formed. The film thickness of the phase shift layer 11 becomes thinner as it approaches the pattern edge, and the film thickness cannot reach a predetermined film thickness, and the phase angle becomes smaller. In this case, the transmittance may increase, which is not preferable.

If the etching stopper layer 12 is too thick, the etching of the phase shift layer 11 may be started too late, the opening width of the light-shielding pattern 13a may become too large, or the etching of the phase shift layer 11 may be terminated at the lower portion, and the phase shift effect may not be exhibited.

According to the present embodiment, the width of the exposed phase shift pattern 11a in comparison with the light-shielding pattern 13b in a plan view can be set according to the amount of side etching in the light-shielding layer 13 after the start of etching of the phase shift layer 11, the amount of side etching in the phase shift layer 11, the film thickness of the etching stopper layer 12, the amount of change in the amount of side etching in the light-shielding layer 13 and the light-shielding pattern 13a, and the like.

Here, the etching rate (lateral etching amount) in the lateral direction in the light-shielding layer 13 and the phase shift layer 11 can be realized by setting an electrochemically base-to-noble relationship. The film formation conditions in the light-shielding layer 13 and the phase-shift layer 11 for setting the electrochemically base-noble relationship include film formation conditions based on the relationship among the specific materials in the two layers (oxide film and chromium film), the presence or absence of nitrogen or the increase or decrease in the amount of nitrogen, the presence or absence of carbon dioxide or the increase or decrease in the amount of carbon dioxide, the presence or absence of methane (carbon) or the increase or decrease in the amount of methane, the film formation pressure, and the film formation rate.

As described above, in addition to the electrochemically base and expensive relationship between the phase shift layer 11 and the light-shielding layer 13, the amount of side etching in the light-shielding layer 13 with respect to the amount of etching in the phase shift layer 11 is set so that the amount of etching in the light-shielding layer 13 changes in the substrate in-plane direction (lateral direction).

When the etching processing time is increased, the rate of increase in the etching amount of the light-shielding layer 13 becomes larger than the rate of increase in the etching amount of the phase-shift layer 11. Therefore, the width dimension of the light-shielding pattern 13b receding from the phase shift pattern 11a, that is, the width dimension of the exposed phase shift region SP of the phase shift pattern 11a with respect to the light-shielding pattern 13b can be changed with a change in the etching amount of these layers.

At this time, in addition to the above-described setting of the film thickness of the etching stopper layer 12, the position in the width direction of the upper end of the phase shift pattern 11a and the position in the width direction of the lower end of the phase shift pattern 11a at the end of the etching stopper pattern 12a are also changed. Therefore, the etching treatment time is set in consideration of these.

As a result, as shown in fig. 1, the width of the phase shift pattern 11a that is set back with respect to the light-shielding pattern 13b in a plan view can be set within a predetermined range.

According to the present embodiment, a mask blank MB is formed by laminating a phase shift layer 11, an etching stopper layer 12, and a light shielding layer 13 in this order on a transparent substrate S.

By forming the resist pattern PR1 on the light-shielding layer 13 of the mask blank MB, performing only continuous wet etching, setting the film thickness of the etching stopper layer 12, and setting the electrochemically inexpensive relationship between the phase shift layer 11 and the light-shielding layer 13, it is possible to manufacture the edge-enhanced phase shift mask M while controlling the side etching rate of each layer 11, 13 and the etching processing time in each layer.

Therefore, the pattern width dimension of the three layers can be set with high accuracy by performing resist formation only once, and a high-definition phase shift mask M with high visibility can be manufactured in a short time with a small number of steps.

The light shielding layer 13 is made of at least one selected from the group consisting of Cr oxides, nitrides, carbides, oxynitrides, carbonitrides, and oxycarbonitrides, and has a film thickness that sufficiently exhibits a light shielding effect.

The film thickness that sufficiently exhibits such a light-shielding effect may increase the etching time of the light-shielding layer 13 with respect to the etching time of the phase-shift layer 11, but the film thickness of the etching stopper layer 12 and the electrochemically inexpensive relationship between the phase-shift layer 11 and the light-shielding layer 13 are set as described above, and the side etching rate of the light-shielding layer 13 can be sufficiently increased.

This makes it possible to set the etching rates of the light-shielding layer 13 and the phase shift layer 11 within an appropriate range. Further, by controlling the etching amount, the line roughness of the phase shift layer 11 and the light blocking layer 13 is substantially linear, and the pattern cross section of these layers is substantially vertical, and a good pattern is formed as a photomask, so that the CD accuracy of the formed light blocking pattern 13b and the phase shift pattern 11a can be improved. In addition, the cross-sectional shape of the film can be made to be a shape close to a good perpendicular as a photomask.

Further, by using the above-described Ni-containing film as the etching stopper layer 12, the adhesion strength between the Cr-containing light-shielding layer 13 and the phase shift layer 11 can be sufficiently improved, and the light-shielding layer 13 and the phase shift layer 11 can be etched by a wet etching solution common thereto.

Therefore, all the patterning can be performed in one etching process in succession. When the light-shielding layer 13, the etching stopper layer 12, and the phase shift layer 11 are etched by a wet etching solution, the etching solution does not penetrate through the interface between the light-shielding layer 13 and the etching stopper layer 12 and the interface between the etching stopper layer 12 and the phase shift layer 11. Therefore, the CD accuracy of the light-shielding pattern 13b and the phase shift pattern 11a to be formed can be improved, and the sectional shape of the film can be made to be a shape close to a good vertical shape as a photomask.

According to the present embodiment, the phase shift mask M has the phase shift pattern 11a capable of having a phase difference of 180 ° with respect to any light in a wavelength region of 300nm to 500nm inclusive, for example, g-ray, h-ray, or i-ray. Here, the width dimension of the phase shift pattern 11a formed adjacent to the edge of the light shielding pattern 13b may be set to about 0.5 μm to 2.0 μm.

In the above-described embodiment, the case where the etching rate of the phase shift layer 11 is set by controlling the grain size has been described, but the etching rate can be set by other factors such as the film formation conditions and the film composition.

In addition, although the green mask MB and the phase shift mask M according to the above-described embodiments have been described as the layer containing chromium as the phase shift layer 11, the present invention is not limited to the above-described layer as long as the electrochemical base and noble relationship between the phase shift layer 11 and the light shielding layer 13 can be set as described above and etching can be performed by a common wet etching solution.

In addition, the phase shift layer 11 can be formed of a plurality of layers.

A mask blank, a halftone mask, and a manufacturing method according to a second embodiment of the present invention will be described below with reference to the drawings.

Fig. 10 is a schematic cross-sectional view showing a mask blank in the present embodiment, and fig. 11 is a cross-sectional view showing a halftone mask manufacturing process based on the mask blank in the present embodiment.

The present embodiment differs from the first embodiment described above in that a halftone layer is provided instead of the phase shift layer, and the same reference numerals are given to the other components corresponding to the first embodiment described above, and the description thereof is omitted.

As shown in fig. 10, the mask blank MB according to the present embodiment is composed of a transparent substrate S, a halftone layer 15 formed on the transparent substrate S, an etching stopper layer 12 formed on the halftone layer 15, and a light shielding layer 13 formed on the etching stopper layer 12.

In the mask blank MB according to the present embodiment, the halftone layer 15, the etching stopper layer 12, and the light shielding layer 13 are set to be etchable by the same etchant.

The semi-transmissive layer 15 can be a semi-transmissive layer having a transmittance of 10% to 70% for any light in a wavelength region of 300nm to 500nm, for example, g-ray, h-ray, or i-ray. The halftone layer 15 and the light-shielding layer 13 preferably contain Cr as a main component, and specifically may be composed of one selected from the group consisting of simple Cr and Cr oxides, nitrides, carbides, oxynitrides, carbonitrides, and oxycarbonitrides, or may be composed of two or more selected from the above materials laminated.

In the method of manufacturing the halftone mask M5 according to the present embodiment, as shown in fig. 11, the phase shift layer 11 according to the first embodiment can be changed to the halftone layer 15, and the manufacturing can be performed in the same manner.

Here, the halftone layer 15 can be formed by a DC sputtering method using a Cr target in general. At this time, O of a reactive gas is introduced together with Ar (argon) gas, He (helium) gas, or the like of an inert gas₂(oxygen) gas, N₂O (nitrous oxide) gas, NO (nitric oxide) gas, N₂(Nitrogen) gas, CO₂(carbon dioxide) gas, CO (carbon monoxide) gas, CH₄(methane) gas, etc., and can form Cr oxides, nitrides, carbides, oxynitrides, carbonitrides, oxycarbonitrides, etc.

The transmittance of the halftone mask M5 according to the present embodiment is determined by the optical characteristics of each film of a simple Cr substance containing Cr as a main component, Cr oxide, nitride, carbide, oxynitride, carbonitride, oxycarbonitride, or a laminated film of two or more selected from the above materials, and the film thickness of each film. Therefore, the transmittance can be controlled by controlling the film formation parameters and the film thickness at the time of sputter film formation.

In particular, by forming the halftone layer 15 with a film containing Cr as a main component, the wavelength dependence of the transmittance can be made very small. Specifically, the difference in transmittance among g-ray (426nm), h-ray (405nm), and i-ray (365nm) in the region having a wavelength of 300nm to 500nm can be reduced to approximately 2% or less. Therefore, the mask blank MB and the halftone mask M5 suitable for multicolor wavelength exposure used in the FPD exposure machine can be provided.

Fig. 12 shows spectral transmittance characteristics of a mask a having a transmittance of 45.9% and a mask B having a transmittance of 28.2% in h-rays (405nm), as an example of forming the halftone mask M5 with a film containing Cr as a main component according to the present embodiment.

Fig. 13 shows the transmittances of g-ray (426nm), h-ray (405nm), and i-ray (365nm) of the mask a and the mask B shown in fig. 12 as an example of the halftone mask M5 formed by the film mainly containing Cr according to the present embodiment.

From the above results, it is understood that when the halftone mask M5 is formed using a film containing Cr as a main component, the values of the transmittance differences Δ T obtained by subtracting the transmittance of h-rays from the transmittance of g-rays are 0.4% and-1.4%, respectively, and the magnitude of Δ T is 2% or less. From this, it is understood that since the wavelength dependency of the transmittance of both the mask a and the mask B formed by the film containing Cr as the main component is small, it is possible to form a mask suitable for multi-wavelength exposure among g-ray (426nm), h-ray (405nm), and i-ray (365nm) used in the exposure machine for the FPD.

Examples

Next, examples according to the present invention will be explained.

< Experimental example >

In order to confirm the above effects, the following experiments were performed. That is, on the glass substrate S, an oxynitride film of chromium constituting the phase shift layer 11 was formed by a sputtering method to a thickness of 122.0nm, an Ni — Ti — Nb — Mo film constituting the etching stopper layer 12 was formed to a thickness of 14.3nm, and a film composed of a layer of a chromium oxynitride main component and a layer of a chromium oxynitride main component constituting the light shielding layer 13 was formed to a total thickness of about 105.0nm, thereby obtaining a mask blank MB.

At this time, the etching stopper layer 12 was formed to contain carbon under the conditions that methane and carbon dioxide were contained as sputtering gas, and NiO was contained_xTr is used for film formation.

Further, the light-shielding layer 13 is made to contain nitrogen (N) as a sputtering gas so as to contain nitrogen₂) The conditions of (1).

A resist pattern PR1 was formed on the mask blank MB, and the light-shielding layer 13, the etching stopper layer 12, and the phase shift layer 11 were successively etched by the resist pattern PR1 using a mixed etching solution of ammonium cerium nitrate and perchloric acid to form a light-shielding pattern 13a, and the etching stopper layer 12 was further etched to form a phase shift pattern 11a and a light-shielding pattern 13b, thereby obtaining an edge-enhanced phase shift mask M.

The weight ratio of the etching solution is 13-18: 3-5: 77-84% of cerium ammonium nitrate, perchloric acid and pure water. That is, if the weight of the etching solution is 100%, the weight of the cerium ammonium nitrate is 13 to 18%, the weight of the perchloric acid is 3 to 5%, and the weight of the pure water is 77 to 84%.

The etching time by the etching solution is changed in three steps so that the etching time exceeding the standard etching time, that is, the etching time exceeding the standard etching time is 60sec, 180sec, or 300 sec. Under these conditions, films shown in experimental examples 1 to 3 were produced, and cross sections of the films were photographed to obtain SEM photographs.

The results are shown in fig. 5 to 7.

In fig. 5 to 7, the PS step represents the distance from the end of the phase shift pattern 11a to the end of the side face of the light shielding pattern 13 b. The ES film thickness represents the film thickness of the etching stopper layer 12.

From the results, it is understood that the amount of side etching of the light-shielding layer 13 can be controlled by controlling the etching time to exceed the total etching time.

That is, it is understood that the PS step length dimension in the figure, that is, the distance from the end of the phase shift pattern 11a to the end of the side face of the light shielding pattern 13b can be set by controlling the etching time.

In addition, although it is needless to say that the three-layer structure having the step is formed by one etching process in this experimental example, it is shown by an image.

In addition, films shown in experimental examples 4 to 5 were produced while changing the film thickness of the etching stopper layer 12 described in the above experimental example 1, that is, while setting the film thicknesses to 9.5nm and 6.7nm, and cross sections of the films were photographed to obtain SEM photographs. The over-etching time was set to 60 sec.

These results are shown in fig. 8 to 9.

In addition, similarly to fig. 5 to 7, the PS step portion indicates the distance from the end of the phase shift pattern 11a to the end of the side face of the light shielding pattern 13b, and the ES film thickness indicates the film thickness of the etching stopper layer 12.

From these results, it is important to set the film thickness of the etching stopper layer 12 when the phase shift mask M having the three-layer structure with the step is formed by one etching process, and if the film thickness is not set to the predetermined range, it is difficult to form the three-layer structure with the standing edge by one etching process.

Description of the symbols

MB … … mask blank

M … … phase shift mask

S … … glass substrate (transparent substrate)

PR1a … … photoresist layer

PR1 … … resist pattern

11 … … phase shift layer

11a … … phase shift pattern

12 … … etch stop layer

12a, 12b … … etch stop pattern

13 … … light-shielding layer

13a, 13b … … light blocking pattern

M5 … … halftone mask

15 … … halftone layer

15a … … halftone pattern

Claims (15)

1. A mask blank is characterized by comprising:

a transparent substrate;

a phase shift layer laminated on the surface of the transparent substrate and mainly composed of Cr;

an etch stop layer laminated to the phase shift layer; and

a light-shielding layer laminated on the etching stop layer and containing Cr as a main component,

etching the phase shift layer, the etching stop layer, and the light-shielding layer with the same etchant, thereby making it possible to manufacture a phase shift mask in which the edge of the light-shielding pattern formed on the light-shielding layer is disposed at a position that is set back in a plan view from the edge of the phase shift pattern laminated on the phase shift layer by one continuous etching,

in the phase shift layer, the etch stop layer, and the light-shielding layer,

the light-shielding layer before the etching start time of the phase shift layer is set to be electrochemically expensive with respect to the etching stop layer,

the light-shielding layer after the etching start time of the phase shift layer is set to be electrochemically base with respect to the phase shift layer.

2. The mask blank according to claim 1,

the etching stop layer contains at least one metal selected from Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W and Hf as a main component.

3. Mask blank according to claim 1 or claim 2,

in the light-shielding layer, the amount of side etching in the etching of the phase shift layer, the etching stop layer, and the light-shielding layer is set to be larger from the etching start time of the light-shielding layer than before the etching start time of the phase shift layer.

4. The mask blank according to claim 3,

the amount of side etching of the light-shielding layer is set to be greater than or equal to 10 times the etching start time of the phase shift layer.

5. The mask blank according to claim 1 or claim 2,

the etching stop layer has a film thickness of 10nm or more.

6. The mask blank according to claim 3,

the etching stop layer has a film thickness of 10nm or more.

7. A method for manufacturing a mask blank according to any one of claims 1 to 6,

comprises the following steps: laminating the phase shift layer, the etch stop layer, and the light-shielding layer in this order on the transparent substrate,

the etching stopper layer is formed by sputtering while containing carbon dioxide as a film forming atmosphere and mainly containing at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W and Hf.

8. A method for manufacturing a phase shift mask, using the mask blank according to any one of claims 1 to 6, comprising:

forming a mask having a predetermined opening pattern on the light-shielding layer; and

the phase shift layer, the etch stop layer, and the light-shielding layer are simultaneously wet-etched with the same etchant over the formed mask.

9. The method for manufacturing a phase shift mask according to claim 8,

in the step of simultaneously performing wet etching on the phase shift layer, the etching stop layer and the light-shielding layer,

the amount of side etching in the light-shielding layer is set to be 4-5 times of the amount of side etching in the phase shift layer.

10. The method for manufacturing a phase shift mask according to claim 8 or claim 9,

as the etchant, an etchant containing cerium ammonium nitrate was used.

11. A phase shift mask, characterized in that,

is manufactured by the manufacturing method according to any one of claim 8 to claim 10.

12. A mask blank is characterized by comprising:

a transparent substrate;

a halftone layer laminated on the surface of the transparent substrate and mainly composed of Cr;

an etch stop layer laminated to the halftone layer; and

a light-shielding layer laminated on the etching stop layer and containing Cr as a main component,

etching the halftone layer, the etching stop layer, and the light-shielding layer with the same etchant, thereby making it possible to manufacture a halftone mask in which the edge of the light-shielding pattern formed on the light-shielding layer is disposed at a position set back in a plan view from the edge of the halftone pattern laminated on the halftone layer by one continuous etching,

in the halftone layer, the etch stop layer, and the light-shielding layer,

the light-shielding layer before the etching start time of the halftone layer is set to be electrochemically expensive with respect to the etching stopper layer,

the light-shielding layer after the etching start time of the halftone layer is set to be electrochemically base with respect to the halftone layer.

13. The mask blank according to claim 12,

in the light-shielding layer, the amount of side etching in the etching of the halftone layer, the etching stop layer, and the light-shielding layer is set to be greater from the etching start time of the light-shielding layer than before the etching start time of the halftone layer.

14. A method for manufacturing a mask blank according to claim 12 or claim 13,

comprises the following steps: laminating the halftone layer, the etch stop layer, and the light-shielding layer in this order on the transparent substrate,

the etching stopper layer is formed by sputtering while containing carbon dioxide as a film forming atmosphere and mainly containing at least one metal selected from the group consisting of Ni, Co, Fe, Ti, Si, Al, Nb, Mo, W and Hf.

15. A halftone mask characterized in that,

manufactured by the manufacturing method of claim 14.

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