JP2002303965A - Method for producing phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a phase shift mask by which a hollow of a proper shape can be formed in a phase shifter part to a desired depth. SOLUTION: The method for producing a phase shift mask has a step for forming a light shielding film 3 on part of the top of a light transmissive substrate 2 to arrange a light transmissive part and a light shielding part, a step for forming a resist 7 on part of the top of the light transmissive part and on the light shielding part, a step for subjecting a phase shifter 4 forming region to the first etching through the resist 7 as a mask with CHF3 , a step for forming a phase shifter 4 by carrying out the second etching through the resist 7 as a mask with a gaseous CHF3 -He mixture up to such a prescribed depth as to cause the reversal of the phase of light passing through the phase shifter part and the phase of light passing through a light transmissive part other than the phase shifter and a step for removing the resist 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a phase shift mask used in a lithography process in the manufacture of a semiconductor integrated circuit or the like, and more particularly to a method of improving a side wall shape of a dug portion formed in a phase shifter. And a method of manufacturing a phase shift mask capable of controlling the depth of a dug portion with high accuracy.

[0002]

2. Description of the Related Art Semiconductor integrated circuits are becoming ever more highly integrated and finer. In the manufacture of semiconductor integrated circuits,
Lithography technology is particularly important as a key to microfabrication. As such a lithography technique, there is a phase shift method using a phase shift mask proposed by Levenson et al. Of IBM in 1982 in addition to a method using a normal binary mask. The phase shift mask is also called a super-resolution mask.

The phase shift mask includes a halftone type phase shift mask, a chromeless type phase shift mask, a Levenson type phase shift mask, and the like. Of the phase shift masks, the halftone phase shift mask
Because it is relatively easy to manufacture, it has already been put to practical use.

In a halftone type phase shift mask, an absorber corresponding to a light shielding portion partially transmits light. The light transmitted through the light-shielding portion and the light transmitted through portions other than the light-shielding portion (light-transmitting portion) have inverted phases, and this is used to reduce the light intensity at the boundary between the light-shielding portion and the light-transmitting portion. In the case of the halftone type, a mask can be manufactured using only the same mask pattern as the pattern of the light shielding portion or the light transmitting portion, and a pattern for forming a phase shifter is unnecessary. Therefore, the manufacture of the mask is relatively easy.

[0005] However, future design rules will be required.
In the technology of the 13 μm to 0.10 μm generation, it is expected that the demand for mask accuracy will become stricter due to further miniaturization. With the miniaturization of patterns, MEF (mask e
rror factor) tends to be large, which is a problem. On the other hand, a Levenson-type phase shift mask can form a pattern with higher resolution than a halftone-type phase shift mask, so that the MEF can be reduced. Therefore, practical use of a Levenson-type phase shift mask is being studied.

FIG. 6A is a cross-sectional view of a single engraving type Levenson type phase shift mask. As shown in FIG. 6A, the base material 22 of the Levenson-type phase shift mask 21
A light-shielding film 23 is locally formed on the upper surface. Light shielding film 2
The surface of the base material 22 is dug into a part of the portion (light transmitting portion) where the 3 is not formed, and the phase shifter 24 is formed. As a result, the phase of the light transmitted through the phase shifter 24 in the light transmitting portion and the phase of the light transmitted through the other portions are inverted.

The base material 22 is made of quartz glass, and the light shielding film 23 is made of, for example, chromium. Phase shifter 24
Since the part of the base material 22 is thinned by etching,
In order to obtain a desired phase difference, it is necessary to strictly control the etching depth d. In addition, it is required that the cross-sectional shape of the etched portion be vertical so as not to be easily affected by the waveguide effect.

However, in practice, as shown in FIG. 6B, the etching cross section often has a tapered shape, and the bottom of the etched portion often has a convex shape. Alternatively, as shown in FIG. 6C, the etching depth d ′ of the phase shifter 24 may be smaller than the desired depth d.

Hereinafter, a conventional method of manufacturing a one-sided type Levenson type phase shift mask will be described. First, FIG.
As shown in (a), a chromium film 23a is formed on a base material 22 made of quartz glass, and a resist 25a is applied on the chromium film 23a. Thereby, the blanks 26 with resist are formed.

Next, as shown in FIG. 7B, the resist 25a is exposed and developed by a lithography process to form a resist 25 in a pattern of the light shielding film 23 (see FIG. 6A). Subsequently, as shown in FIG.
The chrome film 23a is etched using the resist 25 as a mask to form the light-shielding film 23. Then, FIG.
As shown in (2), the resist 25 is removed.

Next, as shown in FIG. 8E, a resist 27a is applied, and an antistatic film 28 is applied thereon. Next, as shown in FIG. 8F, exposure and development are performed on the resist 27a by a lithography process, and the resist 27a is patterned by the phase shifter 24 (see FIG. 6A).
To form

Subsequently, as shown in FIG. 8G, the base material 22 is etched using the resist 27 as a mask to form a phase shifter 24. For this etching, for example, CHF ₃ which is a fluorine-based gas is used. When etching is performed using CHF ₃ alone, the cross section of the etching is tapered. Thereafter, by removing the resist 27, the Levenson-type phase shift mask 21 shown in FIG. 6A is obtained.

FIG. 9A is a cross-sectional view of a double engraving type Levenson type phase shift mask. As shown in FIG. 9A, the base material 22 of the Levenson-type phase shift mask 31
A light-shielding film 23 is locally formed on the upper surface. Light shielding film 2
The light transmitting portions where no 3 is formed are phase shifters 24a and 24b etched at different depths from each other. Thus, the phase of the light transmitted through the phase shifter 24a and the phase of the light transmitted through the phase shifter 24b are inverted.

In the case of the double engraving type, as in the case of the single engraving type, quartz glass is used for the base material 22 and chromium is used for the light shielding film 23, for example. Further, it desired to obtain a phase difference, the etching depth of the etch depth d _a and a phase shifter 24b portion of the phase shifter 24a portion d _b
Strict control is required. Further, in order to suppress the waveguide effect, it is also required that the cross-sectional shape of the etched portion be vertical.

However, in practice, as shown in FIG. 9B, the cross-sectional shape of the etching is often tapered, and the bottom of the etched portion is often convex. Alternatively, as shown in FIG. 9C, the phase shifters 24a and 24
etching depth of part b d _a ', d _b' each desired depth d _a, may become shallower than d _b.

A conventional method of manufacturing a double-dove type Levenson type phase shift mask will be described below. As in the case of the single engraving type, first, as shown in FIG.
A chromium film 23a is formed on a substrate 22 made of quartz glass. A resist 25a is applied on the upper layer to form a blank 26 with a resist.

Next, as shown in FIG. 10B, the resist 25a is exposed and developed by a lithography process, and the resist 25 is formed in a pattern of the light shielding film 23 (see FIG. 9A). Subsequently, as shown in FIG. 10C, the chromium film 23a is etched using the resist 25 as a mask to form the light shielding film 23.

Next, as shown in FIG. 10D, the base material 22 is etched using the resist 25 as a mask to form a phase shifter 24a. At this time, the phase shifter 24
The b formation region is also etched at a predetermined depth of the phase shifter 24a. For this etching, for example, CHF ₃ which is a fluorine-based gas is used. When etching is performed using CHF ₃ alone, the cross section of the etching is tapered. Thereafter, as shown in FIG.
Is removed.

Next, as shown in FIG. 11F, a resist 29a is applied, and an antistatic film 28 is applied thereon. Next, as shown in FIG. 11G, the resist 29a is exposed and developed by a lithography process, and the resist 29 is formed in a pattern of the phase shifter 24b.

Next, as shown in FIG. 11H, the base material 22 is etched using the resist 29 as a mask to form a phase shifter 24b. For this etching, for example, CHF ₃ which is a fluorine-based gas is used. When etching is performed using CHF ₃ alone, the cross section of the etching is tapered. Thereafter, as shown in FIG. 9B, the resist 29 is removed.

[0021]

When the Levenson type phase shift masks 21 and 31 of the single engraving type or the double engraving type are formed by the above-mentioned conventional manufacturing method, the portions of the phase shifters 24, 24a and 24b are formed. A vertical cross section cannot be obtained, or the surface of the phase shifter portion becomes convex.

Alternatively, there arises a problem that the phase shifter portion is etched to a depth smaller than a desired depth. This occurs when the difference in the etching selectivity between the resist 27 (or the resist 29) and the base material 22 is small and the resist 27 (or 29) disappears during the etching of the base material 22. In this case, chromium of the light shielding film 23 reacts with the etching gas, and etching is hindered by a reaction product.

When CHF ₃ which is a fluorine-based gas is used alone for etching for forming a phase shifter,
The cross section of the etching is tapered, and a vertical cross section cannot be obtained. If the cross section is tapered, the effect of the waveguide effect becomes large, and the light intensity transmitted through the phase shifter portion is significantly attenuated. In the case of the single engraving type, as shown in FIG. 6B, the width of the phase shifter 24 is smaller at the lower end than at the upper end. Also, the bottom of the phase shifter 24 is not flat,
It becomes convex.

Similarly, in the case of the double engraving type, FIG.
As shown in (b), the cross sections of the phase shifters 24a and 24b are tapered. Also, the bottoms of the phase shifters 24a and 24b are not flat but convex. When lithography is performed using such a Levenson-type phase shift mask, a defect occurs in the pattern, and high resolution cannot be obtained.

In the case of forming a single engraving type phase shift mask, in the step shown in FIG. 8G, instead of using CHF ₃ alone as an etching gas, He which is an inert gas is added to CHF ₃ . When using the mixed gas shown in FIG.
As shown in (g ′), the side wall of the etched portion can be made almost vertical.

However, the etching selectivity between the quartz glass of the base material 22 and the resist 27 becomes extremely close. Therefore, before the quartz glass is etched to a predetermined depth, the resist 27 is consumed, and as shown in FIG. 6C, the etching depth d 'becomes smaller than the desired depth d. As a result, a desired phase difference cannot be obtained.

Similarly, in the case of the double engraving type, FIG.
By using a mixed gas of CHF ₃ and He as an etching gas in the step shown in FIG. 9D or FIG. 11H, the side wall of the etched portion can be made almost vertical as shown in FIG. However, the etching selectivity between the quartz glass of the base material 22 and the resist 25 or 29 becomes close. Therefore, the etching depth d of quartz glass
_a ', d _b' each predetermined depth d _a, shallower than d _b, not to obtain desired phase difference.

When the resist 25, 27 or 29 is etched to expose the light shielding film 23, the light shielding film 23 is exposed.
May be damaged by etching, and a part of the light shielding film 23 may be peeled off. As a result, a part of the mask pattern is lost, or a light-shielding film material is deposited on the light transmitting portion, so that a defect occurs in the mask pattern.

The present invention has been made in view of the above problems, and accordingly, the present invention provides a method of manufacturing a phase shift mask capable of forming a dug portion with a good shape and a desired depth in a phase shifter portion. The purpose is to provide.

[0030]

In order to achieve the above object, a method of manufacturing a phase shift mask according to the present invention comprises forming a light-shielding film on a part of a light-transmitting substrate and forming a light-shielding film on the substrate. Providing a transmitting portion and a light shielding portion, forming a resist on a part of the light transmitting portion and on the light shielding portion, and using the resist as a mask and performing light transmission using a first etching gas. Performing a first etching on the phase shifter forming region of the portion, and using the resist as a mask and a second etching gas to form a second etching on the phase shifter forming region.
In the step of forming a phase shifter, wherein the phase of light transmitted through the phase shifter portion and the phase of light transmitted through the light transmitting portion other than the phase shifter are inverted. A step of performing the second etching to a predetermined depth; and a step of removing the resist.

Preferably, the first etching gas is
An etching gas capable of sufficiently increasing the etching selectivity of the base material relative to the etching selectivity of the resist, wherein the second etching gas forms an etching cross section of an end of the phase shifter using the base material. An etching gas that can be made substantially perpendicular to the surface and that can flatten the phase shifter surface substantially parallel to the substrate surface. More preferably, the second etching gas is an etching gas in which a difference between an etching selectivity of the resist and an etching selectivity of the base material is smaller than when the first etching gas is used.

Preferably, a fluorine-based gas is used as the first etching gas, and a gas obtained by adding an inert gas to the fluorine-based gas is used as the second etching gas. The fluorine-based gas is CHF ₃ , CF ₄ and SF
_At least one of the _six . Further, the inert gas is at least one of He, Ar, Xe and N _2.
Including seeds.

In the step of forming the light shielding film, preferably,
Forming a light-shielding material layer on the base material, forming a second resist having the pattern of the light-shielding portion on the light-shielding material layer, and using the second resist as a mask to form the light-shielding material layer Forming the light-shielding film, and removing the second resist.

In the step of forming the resist on a part of the light transmitting part and on the light shielding part, preferably, a resist material is applied on the light transmitting part and the light shielding part, and a resist material layer is formed. Forming, forming an antistatic film on the resist material layer, and exposing and developing the resist material layer via the antistatic film to form the resist.

This makes it possible to make the etching cross section at the end of the phase shifter substantially perpendicular to the surface of the base material and to process the surface of the phase shifter flat substantially parallel to the surface of the base material. Therefore, if lithography is performed using the phase shift mask manufactured by the manufacturing method of the present invention,
The effect of the waveguide effect is reduced, and a fine pattern can be transferred with high accuracy.

Further, according to the method of manufacturing a phase shift mask of the present invention, since the etching rate of the resist can be adjusted, it is possible to prevent the resist from disappearing before the phase shifter is formed. Therefore, the base material of the phase shifter can be etched to a desired depth. This makes it possible to set a desired phase difference between the phase of light transmitted through the phase shifter and the phase of light transmitted through the light transmitting portion other than the phase shifter.

In order to achieve the above object, a method of manufacturing a phase shift mask according to the present invention comprises a step of forming a light-shielding material layer on a light-transmitting substrate, and a step of forming a portion on the light-shielding material layer. Forming a first resist, etching the light-shielding material layer using the first resist as a mask,
Forming a light-shielding film on a part of the base material, providing a light-transmitting portion and a light-shielding portion on the base material, and using the first resist as a mask, Performing a first etching on the transmitting portion, and performing a second etching on the light transmitting portion by using the first resist as a mask and using a second etching gas to form a second portion having a first depth. Forming a first resist, removing the first resist, forming a second resist on a part of the first phase shifter and on the light-shielding portion, Using the third resist as a mask, performing a third etching on a second phase shifter formation region of the first phase shifter using a third etching gas; and performing a third etching using the second resist as a mask. Using the etching gas of No. 4, the second Perform a fourth etching phase shifter forming region, and forming a second phase shifter, and the phase of light transmitted through the first phase shifter portion,
A step of performing the fourth etching to a second depth such that a phase of light transmitted through the second phase shifter is inverted, and a step of removing the second resist. I do.

Preferably, the first etching gas is
An etching gas capable of sufficiently increasing an etching selectivity of the base material than an etching selectivity of the first resist, and the second etching gas is used for etching an end of the first phase shifter. An etching gas capable of making a cross section substantially perpendicular to the surface of the base material and processing the surface of the first phase shifter to be flat and substantially parallel to the surface of the base material. More preferably, the second
Is an etching gas in which the difference between the etching selectivity of the first resist and the etching selectivity of the base material is smaller than when the first etching gas is used.

Preferably, the third etching gas is:
An etching gas capable of sufficiently increasing an etching selectivity of the base material than an etching selectivity of the second resist, and the fourth etching gas is used to etch an end of the second phase shifter. An etching gas capable of making a cross section substantially perpendicular to the surface of the base material and processing the surface of the second phase shifter to be flat and substantially parallel to the surface of the base material. More preferably, the fourth
Is an etching gas in which the difference between the etching selectivity of the second resist and the etching selectivity of the base material is smaller than when the third etching gas is used.

Preferably, the third etching gas is:
An etching gas capable of sufficiently increasing an etching selectivity of the base material than an etching selectivity of the second resist, and the fourth etching gas is used to etch an end of the second phase shifter. An etching gas capable of making a cross section substantially perpendicular to the surface of the base material and processing the surface of the second phase shifter to be flat and substantially parallel to the surface of the base material.

More preferably, the fourth etching gas has a difference between the etching selectivity of the second resist and the etching selectivity of the base material smaller than when the third etching gas is used. Etching gas. Preferably, the first etching gas and the third etching gas have the same composition, and the second etching gas and the fourth etching gas have the same composition.

Preferably, a fluorine-based gas is used as the first and third etching gases, and the second and fourth etching gases are used.
As the etching gas, a gas obtained by adding an inert gas to the fluorine-based gas is used. More preferably, the fluorine-based gas contains at least one of CHF ₃ , CF ₄ and SF ₆ . The inert gas is He, A
at least one of r, Xe and N ₂ .

In the step of forming the second resist on a part of the first phase shifter and on the light-shielding portion, preferably, a resist material is formed on the first phase shifter and the light-shielding portion. Applying, forming a resist material layer, forming an antistatic film on the resist material layer, exposing and developing the resist material layer via the antistatic film, the second resist And forming a.

Thus, the etched sections at the ends of the first and second phase shifters are made substantially perpendicular to the surface of the base material, and the surfaces of the first and second phase shifters are made substantially parallel to the surface of the base material. It can be processed flat. Therefore, when lithography is performed using the phase shift mask manufactured by the manufacturing method of the present invention, the influence of the waveguide effect is reduced, and a fine pattern can be transferred with high accuracy.

Further, according to the method of manufacturing the phase shift mask of the present invention, since the etching rate of the resist can be adjusted, the first resist disappears before the first phase shifter is formed. Can be prevented. Therefore, the base material of the first phase shifter can be etched to a desired depth.

Similarly, the loss of the second resist before the formation of the second phase shifter can be prevented. Therefore, the base material of the second phase shifter can be etched to a desired depth. Thus, the phase difference between the phase of the light passing through the first phase shifter and the phase of the light passing through the second phase shifter can be set to a desired phase difference.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a phase shift mask according to the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1A is a cross-sectional view of a single engraving type Levenson type phase shift mask 1 manufactured by the phase shift mask manufacturing method of the present embodiment. FIG. 1 (a)
As shown in FIG. 1, a light-shielding film 3 is locally formed on a base material 2 of a Levenson-type phase shift mask 1. Light shielding film 3
A part of the part (light transmitting part) in which is not formed is the base material 2
Are dug down, and the phase shifter 4 is formed.
As a result, the phase of the light transmitted through the phase shifter 4 in the light transmitting portion and the phase of the light transmitted through the other portions are inverted.

The substrate 2 is made of quartz glass, and the light shielding film 3 is made of, for example, chromium. The Levenson-type phase shift mask 1 shown in FIG. 1A is processed so that the wall surface of the phase shifter 4 is perpendicular to the surface of the base material at the boundary between the phase shifter portion 4 and the light shielding film 3 portion. I have. The surface of the phase shifter 4 is flattened substantially parallel to the surface of the base material. Thereby, the influence of the waveguide effect is suppressed.

The phase shifter 4a is formed at a desired depth d controlled with high precision. This makes it possible to obtain a desired phase difference. For example, when the Levenson-type phase shift mask 1 is used for photolithography using a KrF laser as a light source, the phase difference can be made 180 ° by setting the depth d of the phase shifter 4 to 244 nm.

Next, a method of manufacturing the phase shift mask of the present embodiment will be described. First, as shown in FIG. 1B, a chromium film 3a is formed on a base material 2 made of quartz glass, and a resist 5a is applied on the chromium film 3a. As the substrate 2, for example, a quartz glass wafer having a thickness of 0.25 inches and a diameter of 6 inches is used. The chromium film 3a is formed by, for example, sputtering, and the thickness of the chromium film is, for example, several tens nm.
Degree. An electron beam resist is used as the resist 5a. Thus, blanks 6 with electron beam resist are formed.

Here, a single-layer chromium film 3a is used as the material of the light-shielding film 3, but a layer made of tungsten or molybdenum silicide may be formed instead of the chromium film 3a. Alternatively, a layer formed of these materials may be stacked to form a multilayer film. For example, a chromium oxide film may be formed on the surface of the chromium film, and a light-shielding film having a two-layer structure may be formed.

Next, as shown in FIG. 1C, the resist 5a is exposed and developed by a lithography process,
A resist 5 is formed in a pattern of the light shielding film 3 (see FIG. 1A). Subsequently, as shown in FIG. 1D, the chrome film 3a is etched using the resist 5 as a mask to form the light shielding film 3.

The chromium film 3a is etched by dry etching or wet etching. In the case of wet etching, nitric acid
Cerium ammonium ((NH ₄ ) ₂ Ce (NO ₃ )
A solution containing ₆ ) can be used. The composition of the etchant, for example, ceric ammonium nitrate 13 to 18 wt%, 3-5 wt% perchloric acid (HClO _4), and purified water 77-84 wt%. After etching the chromium film 3a, the resist 5 is removed as shown in FIG.

Next, as shown in FIG. 2F, a resist 7a is applied, and an antistatic film 8 is applied thereon. An electron beam resist is used as the resist 7a. FIG.
When the resist 5 is formed by performing electron beam lithography on the resist 5a in the step shown in (c), the charging of the blanks can be ignored since the chromium film 3a is grounded. On the other hand, when drawing an electron beam on the resist 7a shown in FIG. 2F, the quartz glass of the base material 2 is locally exposed on the drawing surface. Therefore, the exposed portion of the quartz glass is charged, and the position of the subsequently incident electrons may be shifted (charge-up).

For the purpose of preventing such charge-up, an antistatic film 8 is formed. As an antistatic film,
A water-soluble or organic solvent-soluble conductive polymer is used. A solution containing such a polymer is applied on the resist 7a to a thickness of about 20 to 30 nm by, for example, spin coating. Next, as shown in FIG. 2G, exposure and development are performed on the resist 7a by a lithography process, and the resist 7a is patterned by the phase shifter 4 (see FIG. 1A).
To form

Subsequently, as shown in FIG. 2H, the first stage etching is performed on the base material 2 using the resist 7 as a mask. For this etching, CHF ₃ which is a fluorine-based gas is used alone, and the etching is stopped before the etching depth reaches a desired depth d of the phase shifter 4 (see FIG. 1A).

As a result, the cross section of the etched portion becomes tapered, and the bottom of the etched portion becomes convex. However, the etching selectivity of the substrate 1 can be made sufficiently higher than the etching selectivity of the resist 7, and the resist 7 can be left.

Next, as shown in FIG. 2I, a second stage etching is performed on the base material 2 using the resist 7 as a mask. For this etching, He, which is an inert gas, is mixed with CHF.
Using the mixed gas added to ₃ , etching is performed until the etching depth reaches a desired depth d of the phase shifter 4.

When He is mixed with the etching gas, the etching selectivity of the base material 1 and the etching selectivity of the resist 7 become closer, and the etching rate of the resist 7 increases.
However, since the etching rate of the resist 7 is kept low in the first stage etching, the second stage etching can be completed before the resist 7 is completely consumed.

Further, by adding He to the etching gas and performing the second stage of etching, the cross-sectional shape of the etched portion can be made vertical and the bottom of the etched portion can be made flat. The flow ratio between CHF ₃ and He is not particularly limited, and either flow rate may be higher. In consideration of the type and thickness of the resist or the depth of the etched part,
The flow ratio between CHF ₃ and He is determined appropriately. After that, the resist 7 is removed to obtain the single-cavity Levenson-type phase shift mask 1 shown in FIG.

According to the method for manufacturing the phase shift mask of the present embodiment, the side wall of the phase shifter 4 is processed almost perpendicularly to the substrate 2 at the boundary between the phase shifter 4 and the light shielding film 3. It is possible to do. Therefore, when performing lithography using the Levenson-type phase shift mask 1, the effect of the waveguide effect is reduced, and the pattern is transferred with high accuracy. Further, the phase shifter 4 can be processed flat and parallel to the surface of the substrate 2.

Further, according to the method of manufacturing the phase shift mask of the present embodiment, the resist can be prevented from disappearing before the completion of the etching, and the substrate 1 can be etched to a desired depth. . Therefore, a desired phase difference is obtained between the light transmitted through the phase shifter 4 and the light transmitted through the other light transmitting portions.

With respect to the phase shift mask manufactured by the method of manufacturing the phase shift mask according to the present embodiment, the light intensity of transmitted light was measured using a light intensity simulation microscope. The light intensity simulation microscope includes a light source that irradiates the mask with ultraviolet light, and a CCD (charge coupled device) that detects light transmitted through the mask. As a result of the measurement, it was confirmed that the waveguide effect was reduced and the light intensity of the transmitted light became uniform in the mask plane.

(Embodiment 2) FIG. 3A is a cross-sectional view of a double engraving type Levenson type phase shift mask 11 manufactured by the mask manufacturing method of this embodiment. FIG.
As shown in (a), the Levenson-type phase shift mask 1
A light-shielding film 3 is locally formed on one base material 2.

The surface of the substrate 2 is dug relatively shallowly in a part of the portion (light transmitting portion) where the light shielding film 3 is not formed, and the phase shifter 4a is formed. A phase shifter 4b in which the surface of the base material 2 is dug relatively deep is formed in the other light transmitting portions. As a result, the phase of the light transmitted through the phase shifter 4a in the light transmitting portion and the phase of the light transmitted through the phase shifter 4b are inverted.

The substrate 2 is made of quartz glass, and the light shielding film 3 is made of, for example, chromium. The Levenson-type phase shift mask 11 shown in FIG.
At the boundary between a and the light-shielding film 3 or at the boundary between the phase shifter 4b and the light-shielding film 3, the wall surface of the phase shifter 4a or 4b is processed so as to be perpendicular to the substrate surface. Thereby, the influence of the waveguide effect is suppressed. Further, the surfaces of the phase shifters 4a and 4b are flattened substantially in parallel with the substrate surface.

[0067] Also, the phase shifter 4a, 4b are desired depth d _a that is controlled in each high accuracy, and is formed with d _b. This makes it possible to obtain a desired phase difference. For example, in photolithography using a KrF laser as a light source, a Levenson-type phase shift mask 1 is used.
When using 1, the phase shifter 4a depth d _a 310
nm, 554 nm depth d _b of the phase shifter 4b, and the difference between them by a 244 nm, the phase difference may be 180 °.

Next, a method of manufacturing the mask of this embodiment will be described. First, as shown in FIG. 3B, a chromium film 3a is formed on a substrate 2 made of quartz glass, and a resist 5a is applied on the chromium film 3a. As the substrate 2, for example, a quartz glass wafer having a thickness of 0.25 inches and a diameter of 6 inches is used. The chromium film 3a is formed by, for example, sputtering, and the thickness of the chromium film is, for example, about several tens nm. An electron beam resist is used as the resist 5a. Thus, blanks 6 with electron beam resist are formed.

Here, a single-layer chromium film 3a is used as the material of the light-shielding film 3, but a layer made of tungsten or molybdenum silicide may be formed instead of the chromium film 3a. Alternatively, a layer formed of these materials may be stacked to form a multilayer film. For example, a chromium oxide film may be formed on the surface of the chromium film, and a light-shielding film having a two-layer structure may be formed.

Next, as shown in FIG. 3C, the resist 5a is exposed and developed by a lithography process,
A resist 5 is formed in a pattern of the light shielding film 3 (see FIG. 3A). Subsequently, as shown in FIG. 3D, the chrome film 3a is etched using the resist 5 as a mask to form the light shielding film 3. The etching of the chromium film 3a can be performed by wet etching as in the first embodiment.

Next, as shown in FIG. 4E, a first stage etching for forming the phase shifter 4a on the base material 2 is performed using the resist 5 as a mask. At this time, the substrate 2 in the phase shifter 4b formation region is etched to the same depth as the substrate 2 in the phase shifter 4a formation region. Using CHF ₃ in this etching is a fluorine-based gas alone, the desired depth d _a of the etching depth phase shifter 4a (FIG. 3
Etching is stopped before (a) is reached.

As a result, the cross section of the etched portion becomes tapered, and the bottom of the etched portion becomes convex. However, the etching selectivity of the substrate 1 can be made sufficiently higher than the etching selectivity of the resist 5, and the resist 5 can be left.

Next, as shown in FIG. 4F, a second stage etching for forming the phase shifter 4a on the substrate 2 is performed using the resist 5 as a mask. In this etching, a mixed gas obtained by adding He, which is an inert gas, to CHF ₃ is used until the etching depth reaches _a desired depth da of the phase shifter 4a.

When He is mixed in the etching gas, the etching selectivity of the substrate 2 and the etching selectivity of the resist 5 become close to each other, and the etching rate of the resist 5 increases.
However, since the etching rate of the resist 5 is kept low in the first-stage etching, the second-stage etching can be completed before the resist 5 is completely consumed.

By adding He to the etching gas and performing the second stage of etching, the cross-sectional shape of the etched portion can be made vertical and the bottom of the etched portion can be made flat. The flow ratio between CHF ₃ and He is not particularly limited, and either flow rate may be higher. In consideration of the type and thickness of the resist or the depth of the etched part,
The flow ratio between CHF ₃ and He is determined appropriately. Then, FIG.
As shown in (g), the resist 5 is removed.

Next, as shown in FIG. 4H, a resist 9a is applied, and an antistatic film 8 is applied thereon. Next, as shown in FIG. 5I, exposure and development are performed on the resist 9a by a lithography process, and the phase shifter 4b is exposed.
The resist 9 is formed in the pattern (see FIG. 3A).

Subsequently, as shown in FIG. 5J, a first-stage etching for forming the phase shifter 4b on the base material 2 is performed using the resist 9 as a mask. This etching using CHF ₃ as a fluorine-based gas alone, the desired depth of etching depth phase shifter 4b d _b (FIG. 3
Etching is stopped before (a) is reached.

As a result, the cross section of the etched portion becomes tapered, and the bottom of the etched portion becomes convex. However, the etching selectivity of the substrate 2 can be made sufficiently higher than the etching selectivity of the resist 9, and the resist 9 can be left.

Next, as shown in FIG. 5K, a second stage etching for forming the phase shifter 4b on the substrate 2 is performed using the resist 9 as a mask. The use of a mixed gas obtained by adding He is an inert gas to CHF ₃ in this etching, etching is performed until the etching depth reaches a desired depth d _b of the phase shifter 4b.

When He is mixed with the etching gas, the etching selectivity of the base material 2 and the etching selectivity of the resist 9 become close, and the etching rate of the resist 9 increases.
However, since the etching rate of the resist 9 is kept low in the first-stage etching, the second-stage etching can be completed before the resist 9 is completely consumed.

By adding He to the etching gas and performing the second-stage etching, the cross-sectional shape of the etched portion can be made vertical and the bottom of the etched portion can be made flat. The flow ratio between CHF ₃ and He is not particularly limited, and either flow rate may be higher. In consideration of the type and thickness of the resist or the depth of the etched part,
The flow ratio between CHF ₃ and He is determined appropriately. Thereafter, the resist 9 is removed to obtain a double-drilled Levenson-type phase shift mask 11 shown in FIG.

According to the mask manufacturing method of the present embodiment, the phase shifter 4a or the boundary between the phase shifter 4b and the light shielding film 3 or the boundary between the phase shifter 4b and the light shielding film 3 is used. The side wall 4b can be processed substantially perpendicularly to the substrate 2. Further, the phase shifters 4a and 4b can be processed flat and parallel to the surface of the substrate 2. Therefore, the effect of the waveguide effect in the Levenson-type phase shift mask 11 is reduced.

Further, according to the mask manufacturing method of the present embodiment, the resist can be prevented from disappearing before the completion of the etching, and the substrate 2 can be etched to a desired depth. Therefore, a desired phase difference is obtained between the light transmitted through the phase shifter 4a and the light transmitted through the phase shifter 4b.

With respect to the phase shift mask manufactured by the method of manufacturing the phase shift mask according to the present embodiment, the light intensity of transmitted light was measured using a light intensity simulation microscope. As a result of the measurement, it was confirmed that the waveguide effect was reduced and the light intensity of the transmitted light became uniform in the mask plane.

The embodiment of the method for manufacturing a phase shift mask of the present invention is not limited to the above description. For example, the fluorine-based gas and the inert gas can be changed to gases other than those described above. In addition, various changes can be made without departing from the spirit of the present invention.

[0086]

According to the method of manufacturing a phase shift mask of the present invention, it is possible to form a dug portion with a good shape and a desired depth in a phase shifter portion. Therefore,
It is possible to increase the resolution of photolithography.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a single-drilled Levenson-type phase shift mask manufactured by a method for manufacturing a phase shift mask according to Embodiment 1 of the present invention.
FIGS. 4B to 4E are cross-sectional views illustrating manufacturing steps of a method for manufacturing a phase shift mask according to Embodiment 1 of the present invention.

FIGS. 2 (f) to 2 (i) are cross-sectional views illustrating manufacturing steps of a method for manufacturing a phase shift mask according to Embodiment 1 of the present invention, and show steps subsequent to FIG. 1 (e).

FIG. 3A is a cross-sectional view of a double-drilled Levenson type phase shift mask manufactured by the method for manufacturing a phase shift mask according to Embodiment 2 of the present invention.
(B) to (d) are cross-sectional views illustrating manufacturing steps of a method for manufacturing a phase shift mask according to Embodiment 2 of the present invention.

FIGS. 4 (e) to 4 (h) are cross-sectional views showing manufacturing steps of a method for manufacturing a phase shift mask according to Embodiment 2 of the present invention, and show steps subsequent to FIG. 3 (d).

FIGS. 5 (i) to 5 (k) are cross-sectional views showing manufacturing steps of a method for manufacturing a phase shift mask according to Embodiment 2 of the present invention, and show steps subsequent to FIG. 4 (h).

FIG. 6A is a cross-sectional view of a single engraving type Levenson type phase shift mask, and FIGS. 6B and 6C.
FIG. 2 is a cross-sectional view of a single-cavity Levenson type phase shift mask manufactured by a conventional phase shift mask manufacturing method.

FIGS. 7A to 7D are cross-sectional views illustrating manufacturing steps of a conventional method for manufacturing a phase shift mask.

8 (e) to 8 (g ′) are cross-sectional views showing a manufacturing process of a conventional method for manufacturing a phase shift mask, and FIGS.
The step following (d) is shown.

FIG. 9A is a cross-sectional view of a double engraving type Levenson type phase shift mask, and FIGS. 9B and 9C.
FIG. 2 is a cross-sectional view of a double engraving type Levenson type phase shift mask manufactured by a conventional phase shift mask manufacturing method.

FIGS. 10A to 10D are cross-sectional views showing manufacturing steps of a conventional method for manufacturing a phase shift mask.

11 (e) to 11 (h) are cross-sectional views showing manufacturing steps of a conventional method for manufacturing a phase shift mask.
The step following (d) is shown.

[Explanation of symbols]

1, 21: single-sided Levenson-type phase shift mask, 2, 22: base material, 3, 23: light shielding film, 3a, 23a
... Chromium film, 4, 4a, 4b, 24, 24a, 24b ...
Phase shifter, 5, 5a, 7, 7a, 9, 9a, 25, 2,
5a, 27, 27a, 29, 29a ... resist, 6, 2
6 Blanks with electron beam resist, 8, 28 Antistatic film, 11, 31 Double-drilled Levenson type phase shift mask.

Continued on the front page F-term (reference) 2H095 BB03

Claims (20)

[Claims] A step of forming a light-shielding film on a part of a light-transmitting substrate and providing a light-transmitting part and a light-shielding part on the substrate; a part of the light-transmitting part and the light-shielding part; Forming a resist thereon, using the resist as a mask, performing a first etching on a phase shifter formation region of the light transmitting portion using a first etching gas, and using the resist as a mask, Performing a second etching on the phase shifter formation region using a second etching gas to form a phase shifter, wherein a phase of light transmitted through the phase shifter portion and a portion other than the phase shifter are A method of manufacturing a phase shift mask, comprising: a step of performing the second etching to a predetermined depth such that a phase of light transmitted through the light transmitting portion is inverted; and a step of removing the resist. 2. The etching gas according to claim 1, wherein said first etching gas is an etching gas capable of sufficiently increasing an etching selectivity of said base material relative to an etching selectivity of said resist, and said second etching gas is: The etching cross section of the end of the phase shifter is substantially perpendicular to the substrate surface,
2. The method of manufacturing a phase shift mask according to claim 1, wherein the etching gas is an etching gas capable of processing the surface of the phase shifter into a plane substantially parallel to the surface of the base material. 3. The etching gas according to claim 2, wherein a difference between an etching selectivity of said resist and an etching selectivity of said base material is smaller than when said first etching gas is used. Item 3. A method for manufacturing a phase shift mask according to Item 2. 4. The phase shift mask according to claim 3, wherein a fluorine-based gas is used as the first etching gas, and a gas obtained by adding an inert gas to the fluorine-based gas is used as the second etching gas. Method. 5. The method according to claim ₄ , wherein said fluorine-based gas contains at least one of CHF ₃ , CF ₄ and SF ₆ . 6. The method according to claim 4, wherein the inert gas contains at least one of He, Ar, Xe and N ₂ . 7. The step of forming the light-shielding film includes a step of forming a light-shielding material layer on the base material, and a step of forming a second resist having the pattern of the light-shielding portion on the light-shielding material layer. 2. The method of manufacturing a phase shift mask according to claim 1, further comprising: etching the light-shielding material layer using the second resist as a mask to form the light-shielding film; and removing the second resist. Method. 8. The step of forming the resist on a part of the light transmitting part and on the light shielding part includes applying a resist material on the light transmitting part and the light shielding part to form a resist material layer. The method according to claim 1, further comprising: forming an antistatic film on the resist material layer; and exposing and developing the resist material layer via the antistatic film to form the resist. A method for manufacturing a phase shift mask. 9. A step of forming a light-shielding material layer on a light-transmitting substrate, a step of forming a first resist on a part of the light-shielding material layer, and using the first resist as a mask. Etching the light shielding material layer, forming a light shielding film on a part of the base material,
Providing a light transmitting part and a light shielding part on the base material; performing a first etching on the light transmitting part using a first etching gas using the first resist as a mask; Using the first resist as a mask and performing a second etching on the light transmitting portion using a second etching gas;
Forming a first phase shifter having a first depth; removing the first resist; forming a second resist on a part of the first phase shifter and on the light-shielding portion; Forming, using the second resist as a mask, performing a third etching in a second phase shifter formation region of the first phase shifter using a third etching gas; Using the fourth resist as a mask and performing a fourth etching on the second phase shifter formation region using a fourth etching gas to form a second phase shifter, wherein the first phase shifter is formed. Performing the fourth etching to a second depth such that the phase of the light transmitted through the shifter portion and the phase of the light transmitted through the second phase shifter portion are inverted; Removing step Method of manufacturing a phase shift mask. 10. The method according to claim 1, wherein the first etching gas is the first etching gas.
Is an etching gas capable of sufficiently increasing the etching selectivity of the base material from the etch selectivity of the resist, wherein the second etching gas is an etching cross section of the end of the first phase shifter, 10. The manufacturing method of a phase shift mask according to claim 9, wherein the etching gas is an etching gas which is substantially perpendicular to the surface of the base material and is capable of processing the surface of the first phase shifter to be flat and substantially parallel to the surface of the base material. Method. 11. The first etching gas according to claim 1, wherein
11. The method for manufacturing a phase shift mask according to claim 10, wherein the difference between the etching selectivity of the resist and the etching selectivity of the base material is an etching gas that is smaller than when the first etching gas is used. 12. The second etching gas according to claim 2, wherein
Is an etching gas capable of sufficiently increasing the etching selectivity of the base material from the etching selectivity of the resist, wherein the fourth etching gas is formed by etching an etching cross section of an end of the second phase shifter. 10. The manufacturing method of a phase shift mask according to claim 9, wherein the etching gas is an etching gas that is substantially perpendicular to the surface of the base material and is capable of processing the surface of the second phase shifter to be flat and substantially parallel to the surface of the base material. Method. 13. The method according to claim 12, wherein the fourth etching gas comprises the second etching gas.
13. The method for manufacturing a phase shift mask according to claim 12, wherein the difference between the etching selectivity of the resist and the etching selectivity of the base material is an etching gas that is smaller than when the third etching gas is used. 14. The method according to claim 11, wherein the third etching gas is the second etching gas.
Is an etching gas capable of sufficiently increasing the etching selectivity of the base material from the etching selectivity of the resist, wherein the fourth etching gas is formed by etching an etching cross section of an end of the second phase shifter. The manufacturing method of a phase shift mask according to claim 11, wherein the etching gas is an etching gas that is substantially perpendicular to the surface of the base material and is capable of processing the surface of the second phase shifter to be flat and substantially parallel to the surface of the base material. Method. 15. The method according to claim 15, wherein the fourth etching gas is the second etching gas.
15. The method for manufacturing a phase shift mask according to claim 14, wherein the difference between the etching selectivity of the resist and the etching selectivity of the base material is an etching gas that is smaller than when the third etching gas is used. 16. The phase shift mask according to claim 15, wherein said first etching gas and said third etching gas have the same composition, and said second etching gas and said fourth etching gas have the same composition. Manufacturing method. 17. A fluorine-based gas as the first and third etching gases, and a gas obtained by adding an inert gas to the fluorine-based gas as the second and fourth etching gases.
6. The method for manufacturing a phase shift mask according to 5. 18. The method according to claim 17, wherein the fluorine-based gas contains at least one of CHF ₃ , CF ₄ and SF ₆ . 19. The method according to claim 17, wherein said inert gas contains at least one of He, Ar, Xe and N ₂ . 20. The step of forming the second resist on a part of the first phase shifter and on the light-shielding portion includes applying a resist material on the first phase shifter and the light-shielding portion. Forming a resist material layer; forming an antistatic film on the resist material layer; exposing and developing the resist material layer via the antistatic film to form the second resist 10. The method of manufacturing a phase shift mask according to claim 9, comprising the steps of: