JPH07234499A - Phase shift mask and production of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a phase shift mask with which a pattern can be formed equal to designed value on a resist material on a wafer. CONSTITUTION:The phase shift mask consists of a first transmitting area 20, second transmitting area 22 which transmits light of a different phase from the phase of light transmitting through the first transmitting area 20, and light shielding area 12 provided between the fist transmitting area and the second transmitting area. When the width of the first and second transmitting area 20, 22 aredefined Wt, and the width of the pattern formed on a resist material on a base body with light transmitted through the first and second transmitting area through a projecting optical system is defined Wp, and the reducing rate N of the projecting optical system satisfy the relation of Wt<WpXN.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask used for various pattern forming techniques in a semiconductor device manufacturing process, and more particularly to a Levenson type phase shift mask.

[0002]

2. Description of the Related Art A photomask used in a pattern transfer process, that is, a so-called lithography process in manufacturing a semiconductor device is used to transfer a pattern shape on the photomask to a resist material formed on a wafer. A conventional photomask has a pattern area including a light shielding area and a light transmitting area. For example, when the pattern on the photomask is transferred to the resist material formed on the wafer using a projection optical system having a reduction magnification of 5 times,
The size of the pattern on the photomask is 5 times the size of the pattern to be formed on the resist material on the wafer.
When the pattern on the photomask is transferred to the resist material formed on the wafer using the projection optical system of the same size, the size of the pattern on the photomask is the pattern to be formed on the resist material on the wafer. Equal to the size of.

The dimensions of pattern processing in semiconductor devices and the like are becoming finer year by year. A conventional photomask provided with only a pattern region composed of a light-shielding region and a light-transmitting region cannot obtain a resolution of about the wavelength of the exposure light of an exposure apparatus used in a lithography process, and thus a semiconductor device or the like. It is becoming difficult to obtain the required resolution in the manufacture of Therefore, in recent years, so-called phase shift masks having a phase shift region for changing the phase of light have been used in place of such conventional photomasks. By using a phase shift mask, it is possible to form a fine pattern that cannot be formed by a conventional photomask.

For example, a conventional Levenson-type phase shift mask has a first light transmitting region 120 formed on a substrate 10 made of a transparent material, as shown in a partial sectional view of FIG.
And a second light transmitting region 122 and a light shielding region 12 that shields light. The thickness of the substrate 10 in the first light transmission region 120 and the thickness of the substrate 10 in the second light transmission region 122 are different. As a result, the phase of light passing through the first light transmission region 120 and the second light transmission region 12
The phases of light passing through 2 are different by 180 degrees, for example. In the Levenson-type phase shift mask, a plurality of first light transmitting regions 120 and second light transmitting regions 122 are arranged alternately. In the conventional phase shift mask, for example, the width of the light transmitting regions 120 and 122 is Wt ′, and the pattern formed on the resist material on the substrate through the projection optical system by the light transmitted through the light transmitting regions 120 and 122. When the width is Wp ′ and the reduction magnification of the projection optical system is N ′, the width Wt ′ of the first or second light transmission region is designed so that Wt ′ = Wp ′ × N ′.

[0005]

However, the conventional phase shift mask designed as described above has a problem that the pattern shape formed on the phase shift mask is not accurately transferred to the resist material on the wafer. First and second light transmitting regions 12 formed on the phase shift mask
The width (Wt ′) of 0, 122 is 1.5 μm, and the width (Ws ′) of the light shielding region 12 existing between the first light transmitting region 120 and the second light transmitting region 122 is 1.5 μm. Then, for example, a pattern formed on the phase shift mask using a semiconductor exposure apparatus using a KrF excimer laser having a numerical aperture NA = 0.45, a partial coherency of 0.3, a reduction magnification N = 5, and a wavelength of 248 nm. Is transferred to the resist material on the substrate. Regarding the size of the pattern in the resist material thus obtained, the width of the pattern corresponding to the first and second light transmitting regions 120 and 122 is 0.35 μm (the original design value is 0.30 μm), The width of the pattern corresponding to the light shielding area existing between the light transmitting area and the second light transmitting area is 0.25 μm (the original design value is 0.30 μm).

As described above, the design of the conventional phase shift mask (for example, Wt '= Ws' = 1.5 μm, where N
= 5), a desired pattern cannot be formed on a resist material on a wafer, and when such a phase shift mask is used, the characteristics of a semiconductor device such as a manufactured semiconductor device are significantly deteriorated, This leads to a decrease in manufacturing yield of semiconductor devices and a decrease in productivity. Further, in extreme cases, the manufacture of semiconductor devices is hindered.

Therefore, an object of the present invention is to provide a phase shift mask capable of making a pattern formed on a resist material on a wafer equal to a design value. A further object of the present invention is to provide a method of manufacturing a semiconductor device using such a phase shift mask.

[0008]

The above object is to provide a first light transmitting region, a second light transmitting region for transmitting light having a phase different from the phase of light passing through the first light transmitting region, and First
Of the light-shielding region provided between the light-transmitting region and the second light-transmitting region, the width of the first or second light-transmitting region is Wt, and the width of the first or second light-transmitting region is Wt. When the width of the pattern formed on the resist material on the substrate by the light transmitted through the transmission region through the projection optical system is Wp and the reduction ratio of the projection optical system is N, Wt and Wp are Wt <Wp × N Can be achieved by the phase shift mask of the present invention.

The phase shift mask of the present invention has 0.8 <W.
A Levenson-type phase shift mask that satisfies t / (Wp × N) <0.9 can be obtained. In this case, when the distance between the center of the first light transmission region and the center of the second light transmission region is D, 1.5 ≦ D / (Wp × N) ≦ 3.0 is more preferable. Preferably satisfies 1.5 ≦ D / (Wp × N) ≦ 2.5.

A method of manufacturing a semiconductor device according to the present invention for achieving the above object uses a phase shift mask of the present invention described above to expose a resist material formed on a wafer to form a phase shift mask. It is characterized in that the formed pattern shape is transferred to a resist material.

[0011]

In the conventional phase shift mask, the size (width) of the first and second light transmitting regions is determined based on the relationship of Wt '= Wp * N as in the conventional photomask. In the phase shift mask, for example, the light passing through the first light transmitting region interferes with the light passing through the adjacent second light transmitting region, and a light intensity profile having a sharp shape can be obtained. . This light intensity is higher than the light intensity obtained with a conventional photomask. Therefore, in the phase shift mask, when the same exposure amount as that of the conventional photomask is used, for example, the pattern formed on the resist material on the substrate through the projection optical system by the light transmitted through the first light transmission region. The width Wp 'of the pulse width becomes larger than the desired value. This state is schematically shown in FIG.
It should be noted that FIG. 10 shows a light transmission region (Wt ′ = 1.5) having the same width in the conventional phase shift mask and the conventional photomask.
μm. However, it is a graph showing the light intensity distribution on the resist material of the light passing through N = 5).

On the other hand, in the phase shift mask of the present invention, the relationship of Wt <Wp × N is satisfied by the width Wt of the first or second light transmitting region and the width Wp of the pattern formed on the resist material on the substrate. Meet Therefore, as schematically shown in FIG. 10, in the phase shift mask of the present invention,
Even when using the same exposure amount as a conventional photomask,
The width Wp of the pattern formed on the resist material on the substrate via the projection optical system can be exactly matched with a desired value by the light transmitted through the first or second light transmitting region.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings. In the drawings, the same reference numerals mean the same elements.

When a transfer pattern shape or the like is formed on a resist material formed on a wafer by exposure light, one used for reduction projection is called a reticle, and one used for one-to-one projection is called a mask. Alternatively, a master corresponding to a master may be referred to as a reticle, and a duplicate thereof may be referred to as a mask. In this specification, the reticle and the mask having various meanings are collectively referred to as a mask.

(Embodiment 1) As shown in FIG. 1, the phase shift mask of the embodiment 1 has a substrate 1 made of a transparent material.
It has a light-shielding region 12 formed in 0, a first light-transmitting region 20 and a second light-transmitting region 22. Incidentally, FIG.
1A is a schematic partial plan view, and FIG.
FIG. 2 is a schematic partial cross-sectional view taken along the line BB of FIG.

The phase of light passing through the first light transmitting area 20 and the phase of light passing through the second light transmitting area 22 are different by 180 degrees, for example. In Example-1, by changing the thickness of the base 10 in the first light transmission region 20 and the thickness of the base 10 in the second light transmission region 22, specifically, the recess is formed in the base 10. As a result, the phase of light passing through the first and second light transmitting regions 20 and 22 is relatively changed. When the wavelength of the exposure light is λ and the refractive index of the material forming the substrate 10 is n,
The value of the depth d of the recess is a value satisfying d = λ / (2 (n-1)).

In the first embodiment, the plurality of first and second light transmitting regions 20 and 22 have a band-shaped pattern shape and are arranged in parallel at equal intervals. In the phase shift mask of the present invention, patterns having various light transmissive regions are formed in regions other than the light transmissive regions that characterize the phase shift mask of the present invention, but the shapes of these various patterns are arbitrary. is there.

Numerical aperture NA = 0.45, partial coherency 0.3, reduction ratio N = 5, wavelength 248 nm K
Using a semiconductor exposure apparatus that uses an rF excimer laser,
A test of transferring the pattern formed on the phase shift mask of Example-1 to the resist material on the substrate was conducted. The pattern transferred to the resist material has strip-shaped line and space shapes and is arranged in parallel at equal intervals. The line width (W of a band-shaped pattern to be formed on the resist material
(corresponding to p) is 0.30 μm, and the width of the space is 0.3
It was set to 0 μm. The width (Wt) of the first and second light transmitting regions 20 and 22 and the central portion (center line in this case) of the first light transmitting region 20 and the first and second light transmitting regions 20 and 22 for forming the pattern of the resist material. The relationship of the distance D between the center of the second light transmission region 22 (also the center line) was obtained. The results were as follows. The unit is μm. Wp Wp × N D Wt Wt / (Wp × N) D / (Wp × N) 0.30 1.50 2.40 1.35 0.90 1.6 0.30 1.50 2.55 1.30 0.87 1.7 0.30 1.50 2.70 1.25 0.83 1.8 0.30 1.50 2.85 1.25 0.83 1.9 0.30 1.50 3.00 1.25 0.83 2.0 0.30 1.50 3.15 1.25 0.83 2.1 0.30 1.50 3.30 1.30 0.87 2.2 0.30 1.50 3.45 1.30 0.87 2.3 0.30 1.50 3.60 1.35 0.90 2.4 0.30 1.50 3.75 1.35 0.90 2.5

The above result is an example, and the value of Wt may be appropriately changed depending on the semiconductor exposure apparatus used, the exposure conditions, the exposure amount, the width (Wp) of the pattern to be formed on the resist material, and the like. obtain.

Hereinafter, a method of manufacturing the phase shift mask of Example-1 will be described with reference to FIGS.

[Step-100] A light-shielding layer 12 made of, for example, chromium is provided on a substrate 10 made of a transparent material such as quartz.
A is deposited by a sputtering method. After that, the light shielding layer 1
A resist sensitive to an electron beam is applied onto 2A by, for example, a spin coating method to form a photosensitive layer 30, and the structure shown in FIG. 2A is obtained. A positive resist was used as the photosensitive layer 30.

[Step-110] Next, in the first drawing step with the electron beam from the drawing apparatus, the drawing area shown in FIG. 2A is set, and the drawing with the electron beam with the acceleration voltage of 20 kV is performed. A desired resist pattern is formed on the photosensitive layer 30. The drawing area corresponds to the first light transmission area formation scheduled area and the second light transmission area formation scheduled area.
After that, the structure shown in FIG. 2B is obtained through a developing process of the photosensitive layer 30.

[Step-120] Next, the light shielding layer 1 is formed by a mixed gas of chlorine and oxygen using a reactive ion etching method.
After etching 2A, the photosensitive layer 30 is peeled off (see FIG. 2).
(See (C)). As a result, the first light transmission region 20
And the second light transmission region formation scheduled region 22A is formed. At the same time, the light shielding region 12 made of, for example, chrome is formed.

[Step-130] After that, a resist which is exposed to an electron beam is applied to the entire surface to form a photosensitive layer 32, and an antistatic layer (not shown) is applied thereon, and then, as shown in FIG. A drawing area as shown in A) is set. This drawing area includes a second light transmission area forming planned area 22A. still,
A positive resist was used as the photosensitive layer 32. And
In the second drawing step using the electron beam from the drawing device,
Drawing with an electron beam with an acceleration voltage of 20 kV,
2, a desired resist pattern is formed.

[Step-140] Next, the step of peeling the antistatic layer, the step of developing the photosensitive layer 32 (see FIG. 3B),
After forming a recess in the substrate 10 by etching the substrate 10 in plasma with a mixed gas of carbon tetrafluoride and oxygen (see (C) of FIG. 3) and peeling the photosensitive layer 32, the final step is performed. The phase shift mask of Example 1 having the structure shown in FIG. 1 can be obtained. The value of the depth d of the etched substrate 10 is λ where the wavelength of exposure light is
When the refractive index of the material forming 0 is n, d = λ /
It is a value that satisfies (2 (n-1)).

(Embodiment 2) As shown in FIG. 4, the phase shift mask of Embodiment 2 has a substrate 1 made of a transparent material.
It has a light-shielding region 12 formed in 0, a first light-transmitting region 20 and a second light-transmitting region 22. Incidentally, FIG.
1 is a schematic partial plan view, and is a line BB in FIG.
FIG. 3 is a schematic partial cross-sectional view taken along the line.

As in Example 1, the first light transmitting region 2
The phase of the light passing through 0 and the phase of the light passing through the second light transmitting region 22 are different by 180 degrees, for example. In Example-2, for example, SOG is provided on the second light transmission region 22.
The phase shift layer 14 made of (Spin On Glass) is formed, whereby the first and second light transmitting regions 2 are formed.
The phase of light passing through 0 and 22 is relatively changed. When the wavelength of the exposure light is λ and the refractive index of the material forming the phase shift layer 14 is n ′, the value of the thickness d ′ of the phase shift layer 14 is d ′ = λ / (2 (n′−1) )) Is satisfied.

Also in the second embodiment, the plurality of first and second light transmitting regions 20 and 22 have a band-shaped pattern shape and are arranged in parallel at equal intervals.

A method of manufacturing the phase shift mask of Example-2 will be described below with reference to FIGS.

[Step-200] [Step-1 of Example-1]
00], a substrate 10 made of a transparent material such as quartz.
After forming the light shielding layer 12A on the upper surface by a sputtering method,
The photosensitive layer 30 is formed on the light shielding layer 12A ((A) of FIG. 2).
reference). Next, as in the case of [Process-110] of Example-1, writing is performed with an electron beam having an acceleration voltage of 20 kV to form a desired resist pattern on the photosensitive layer 30 (see FIG. 2B). Then, [Process-120] of Example-1
Similarly to the above, after the light shielding layer 12A is etched, the photosensitive layer 3
0 is peeled off (see FIG. 2C). As a result, the first light transmission region 20 and the second light transmission region formation scheduled region 22A are formed, and the light shielding region 12 is also formed.

[Step-210] Next, a phase shift layer 14 made of SOG is formed on the entire surface by spin coating, and a resist sensitive to an electron beam is applied on the entire surface to form a photosensitive layer 32. Then, an antistatic layer (not shown) is further applied thereon. Then, a drawing area as shown in FIG. 5A is set, and drawing is performed with an electron beam having an acceleration voltage of 20 kV. This drawing area includes a second light transmission area forming planned area 22A. A positive resist was used as the photosensitive layer 32.

[Step-220] Next, a step of removing the antistatic layer, a step of developing the photosensitive layer 32 (see FIG. 5B),
S in a plasma with a mixed gas of carbon tetrafluoride and oxygen
The phase shift layer 14 made of OG is etched to leave the phase shift layer 14 on the second light transmission region 22 (see FIG. 5C). Then, the photosensitive layer 32 is removed, and finally the phase shift mask of Example-2 having the structure shown in FIG. 4 can be obtained.

(Embodiment 3) As shown in FIG. 6, the phase shift mask of Embodiment 3 has a substrate 1 made of a transparent material.
It has a light-shielding region 12 formed in 0, a first light-transmitting region 20 and a second light-transmitting region 22. Incidentally, FIG.
1 is a schematic partial plan view, and is a line BB in FIG.
FIG. 3 is a schematic partial cross-sectional view taken along the line.

As in Example 1, the first light transmitting region 2
The phase of the light passing through 0 and the phase of the light passing through the second light transmitting region 22 are different by 180 degrees, for example. In Example-3, the substrate 10 in a region other than the first light transmission region 20.
A phase shift layer 14 made of, for example, SOG is formed on the top. That is, the light blocking area 12 and the second light transmitting area 2
2 has a phase shift layer 14 formed thereon. As a result, the phase of light passing through the first and second light transmitting regions 20 and 22 is relatively changed. The wavelength of the exposure light is λ,
When the refractive index of the material forming the phase shift layer 14 is n ′, the value of the thickness d ′ of the phase shift layer 14 is d ′ = λ /
It is a value that satisfies (2 (n'-1)).

Also in the third embodiment, the plurality of first and second light transmitting regions 20 and 22 have a band-shaped pattern shape and are arranged in parallel at equal intervals.

Hereinafter, a method of manufacturing the phase shift mask of Example-3 will be described with reference to FIGS.

[Step-300] After the phase shift layer 14 made of, for example, SOG is formed on the substrate 10 made of a transparent material such as quartz by the spin coating method, the light shielding layer 12A made of chromium or the like is formed thereon. A film is formed by a sputtering method. Then, a resist sensitive to an electron beam is applied on the light shielding layer 12A to form the photosensitive layer 30, and the structure shown in FIG. 7A is obtained. A positive resist was used as the photosensitive layer 30.

[Step-310] Next, in the first drawing step using an electron beam from the drawing apparatus, the drawing area shown in FIG. 7A is set, and drawing is performed with an electron beam having an acceleration voltage of 20 kV. A desired resist pattern is formed on the photosensitive layer 30. The drawing area corresponds to the first light transmission area formation scheduled area and the second light transmission area formation scheduled area.
Then, the structure shown in FIG. 7B is obtained through a developing process of the photosensitive layer 30.

[Step-320] Then, the light-shielding layer 1 is formed using a mixed gas of chlorine and oxygen by using the reactive ion etching method.
After etching 2A, the photosensitive layer 30 is peeled off (FIG. 7).
(See (C)). As a result, the first light transmission region formation scheduled region 20A and the second light transmission region formation scheduled region 22 are formed.
A is formed, and the light shielding region 12 is also formed.

[Step-330] After that, a resist which is exposed to an electron beam is applied to the entire surface to form a photosensitive layer 32, and an antistatic layer (not shown) is applied thereon, and then, as shown in FIG. A drawing area as shown in A) is set. This drawing area includes a second light transmission area forming planned area 22A. still,
A positive resist was used as the photosensitive layer 32. And
In the drawing area shown in FIG. 8A, the acceleration voltage 20
Drawing with an electron beam of kV is performed.

[Step-340] Next, a step of peeling the antistatic layer, a step of developing the photosensitive layer 32 (see FIG. 8B),
Through the formation of the first light transmission region 20 by etching the phase shift layer 14 in plasma with a mixed gas of carbon tetrafluoride and oxygen (see FIG. 8C), and the peeling process of the photosensitive layer 32. Finally, an example of the structure shown in FIG.
3 phase shift mask can be obtained.

In the method of manufacturing a semiconductor device of the present invention, the phase shift mask of the present invention described in Examples-1 to 3 is used. Then, the phase shift mask is set in a semiconductor exposure apparatus, the resist material formed on the wafer is exposed, and the pattern shape formed on the phase shift mask is transferred to the resist material. In this way, a desired pattern can be formed on the resist on the wafer.

The phase shift mask of the present invention has been described above based on the preferred embodiments, but the present invention is not limited to these embodiments. The various numerical values, the size of the pattern, the phase difference, and the like described in the embodiments are examples, and can be changed to desired values or appropriate values as appropriate. The planar shape of the first and second light transmitting regions is not limited to a linear strip shape, and for example, the planar shapes of the first and second light transmitting regions are formed in order to form contact holes arranged at equal intervals. Is a rectangle, and the first and second light transmission regions are 2
The elements can be arranged in a zigzag pattern alternately, or can be appropriately changed.

Various materials used in the manufacturing process of the phase shift mask can be appropriately changed. The substrate 10 can be made of not only quartz but also ordinary glass, glass to which various components are appropriately added, and the like. The material forming the light-shielding layer 12 is not limited to chromium, but chromium oxide, chromium oxide laminated on chromium, refractory metal (W, Mo, Be, etc.),
It is possible to use a material capable of blocking an appropriate amount of light, such as tantalum, aluminum, or metal silicide such as MoSi ₂ . Further, the phase shift layer 14 may be made of a transparent material such as polymethylmethacrylate, magnesium fluoride, titanium dioxide, polyimide resin, silicon dioxide, indium oxide, SiN, and various resists instead of being composed of SOG. When forming the photosensitive layers 30 and 32,
A negative resist may be used instead of the positive resist. In this case, the electron beam drawing area is different from that of the positive type resist.

[0045]

According to the phase shift mask of the present invention, the width of the pattern to be formed on the resist material on the wafer can be made equal to the design value. The width of the pattern formed on the phase shift mask depends on the pattern arrangement state, for example, the distance D between the center of the first light transmitting region and the center of the second light transmitting region. Since it is properly set, a pattern having a desired width can be formed on the resist material on the wafer. Therefore, it is possible to prevent deterioration of characteristics of a semiconductor device such as a manufactured semiconductor device, and to prevent a decrease in manufacturing yield of the semiconductor device and a decrease in productivity.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a phase shift mask of Example-1.

FIG. 2 is a schematic partial cross-sectional view of a base body and the like for explaining a manufacturing process of the phase shift mask of Example-1.

FIG. 3 is a schematic partial cross-sectional view of the substrate etc. for explaining the manufacturing process of the phase shift mask of Example-1 following FIG. 2;

FIG. 4 is a diagram showing a structure of a phase shift mask of Example-2.

FIG. 5 is a schematic partial cross-sectional view of a base body and the like for explaining a manufacturing process of the phase shift mask of Example-2.

FIG. 6 is a diagram showing a structure of a phase shift mask of Example-3.

FIG. 7 is a schematic partial cross-sectional view of a base body and the like for explaining a manufacturing process of a phase shift mask of Example-3.

FIG. 8 is a schematic partial cross-sectional view of the substrate etc. for explaining the manufacturing process of the phase shift mask of Example-3, following FIG. 7;

FIG. 9 is a partial cross-sectional view of a conventional Levenson-type phase shift mask.

FIG. 10 is a graph schematically showing the light intensity distributions of the phase shift mask of the present invention, the conventional phase shift mask, and the conventional photomask.

[Explanation of symbols]

 Reference Signs List 10 substrate 12 light-shielding region 14 phase shift layer 20 first light transmitting region 22 second light transmitting region 30, 32 photosensitive layer

Claims (4)

[Claims] 1. A first light transmission region, a second light transmission region for transmitting light having a phase different from the phase of light passing through the first light transmission region, and the first light transmission region and the second light transmission region. Of the light-shielding region provided between the first and second light-transmitting regions, and the width of the first or second light-transmitting region is Wt. When the width of the pattern formed on the resist material on the substrate through the projection optical system is Wp and the reduction ratio of the projection optical system is N, Wt and Wp satisfy Wt <Wp × N. Phase shift mask. 2. The phase shift mask according to claim 1, wherein the phase shift mask satisfies the condition 0.8 <Wt / (Wp × N) <0.9 and is a Levenson type phase shift mask. 3. When the distance between the center of the first light transmitting region and the center of the second light transmitting region is D, 1.5 ≦ D / (Wp × N) ≦ 2.5 The phase shift mask according to claim 2, wherein 4. A pattern shape formed on a phase shift mask by exposing a resist material formed on a wafer using the phase shift mask according to claim 1 or 2. Is transferred to the resist material.