JPH04371951A - Phase shift mask and production thereof - Google Patents

Abstract

PURPOSE:To provide the phase shift mask which exhibits an excellent phase shift effect to stress the contrast of pattern edges by the inversion of phases and the method for production thereof. CONSTITUTION:This mask has a light shielding region formed of a light shielding layer 4, a 1st transmission region A adjacent to the light shielding region and a 2nd transmission region B which is adjacent to the 1st transmission region A and has 180 deg. phase different of the transmitted light with the 1st transmission region A. The light shielding region and the 1st transmission region A are formed in the recessed part provided on a transparent substrate 1. The mask has otherwise the light shielding region formed of the light shielding layer 4, the 1st transmission region A adjacent to the light shielding region and the 2nd transmission region B which is adjacent to the 1st transmission region A and has 180 deg. phase difference of the transmitted light with the 1st transmission region A. The 2nd transmission region B is formed of a transparent shifter layer 13 provided on the transparent substrate 11 and further, an etching stop layer 12 is provided among the transparent substrate 11 and the transparent shifter layer 13 and the light shielding layer 4.

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 of the so-called self-alignment type or edge enhancement type and a method of manufacturing the same.

0002

2. Description of the Related Art Conventional photomasks have had the problem that when patterns are close together, light leaking from the transparent portions of the mask interferes with each other, resulting in poor resolution. Therefore, a phase shift mask using a phase shift technique that inverts the phase of projection light transmitted through adjacent patterns by 180 degrees to improve the resolution of fine patterns has been developed and is attracting attention. That is, at the pattern edge portion of the phase shift layer, the phase is sharply reversed by 180 degrees, so that the contrast of light at the edge portion is emphasized, and extremely fine patterns such as isolated patterns can be resolved.

By the way, in the conventional self-aligned phase shift mask, as shown in FIG. 4(a), a shifter pattern 23 is formed in a self-aligning manner on a light-shielding pattern 22 on a transparent substrate 21. 22 side etching to create an overhang shape, or as shown in the same figure (
As shown in b), a method was used in which a light shielding pattern 22 was formed on a shifter pattern 23 and side etching was performed.

0004

[Problems to be Solved by the Invention] However, in conventional structures, the surface cut by dry etching is rough, and the transmitted light in this area is scattered, reducing the coherency of the light and weakening the light intensity. There was a problem.

The present invention was devised in view of these conventional problems, and its purpose is to exhibit an excellent phase shift effect that emphasizes the contrast of pattern edges by inverting the phase, and to achieve an excellent phase shift effect that emphasizes the contrast of pattern edges. It is an object of the present invention to provide a phase shift mask that does not cause such disadvantages as a decrease in light coherency and a weakening of light intensity, and a method for manufacturing the same.

[0006]

Means for Solving the Problems In order to achieve the above object, a phase shift mask according to claim 1 includes a light-shielding region, a first transmission region adjacent to the light-shielding region, and a first transmission region adjacent to the light-shielding region. The phase difference of transmitted light with the adjacent first transmission region is 1
and a second transmitting region at an angle of 80 degrees, and the light shielding region and the first transmitting region are formed in a recess provided in a transparent substrate.

[0007] The phase shift mask of claim 2 further includes a light-shielding region, a first transmission region adjacent to the light-shielding region, and a transmission region adjacent to the first transmission region and the first transmission region. and a second transmission region where the phase difference of light is 180 degrees,
The second transmission region is formed by a transparent shifter layer provided on a transparent substrate, and further includes an etching stop layer between the transparent substrate and a light shielding layer forming the transparent shifter layer and the light shielding region. It is characterized by:

[0008] Furthermore, in the method of manufacturing a phase shift mask according to claim 3, a concave portion is formed in a transparent substrate by etching through a lithography process, a light-shielding pattern is formed in the concave portion by lift-off, and further, exposure is performed from the back side of the transparent substrate. The method is characterized in that a resist pattern is formed on the light-shielding pattern, and side etching of the light-shielding pattern is performed.

[0009] Furthermore, in the method of manufacturing a phase shift mask according to claim 4, at least an etching stop layer and a transparent shifter layer are provided in this order on a transparent substrate, the transparent shifter layer is patterned by etching through a lithography process, and then A light shielding pattern is formed in the recessed portion of the formed transparent shifter layer by lift-off, a resist pattern is further formed on the light shielding pattern by exposure from the back side of the transparent substrate, and side etching of the light shielding pattern is performed.

The present invention will now be described in further detail with reference to the accompanying drawings.

FIG. 1(a) is a sectional view showing the structure of one embodiment of the phase shift mask of the present invention, and FIG. 1(b) is a sectional view showing the structure of another embodiment.

In the configuration shown in FIG. 1(a), a light-shielding region by a light-shielding layer 4 and a first transmitting region A adjacent to this light-shielding region are formed in a recess formed by etching a transparent substrate 1. , and another region adjacent thereto forms a second transmission region B. In addition, in the configuration shown in FIG. 6(b), an etching stop layer 12 is provided on a transparent substrate 11, and a patterned transparent shifter layer 13 is provided on the etching stop layer 12. The transparent shifter layer 13 forms a light-shielding region A and a first transmissive region A adjacent thereto, and the transparent shifter layer 13 forms a second transmissive region B
is formed. That is, the difference from (a) is that the shifter is not formed by etching a transparent substrate, but the phase shifter is formed by providing a transparent shifter layer on the substrate and etching this.

In both the configurations shown in FIGS. 1(a) and 1(b), the phase shift effect is caused by a phase difference of 180 degrees between the first transmission area A and the second transmission area B. By doing so, the effect as a phase shift mask similar to that of the conventional structure shown in FIG. 4 can be obtained. In the conventional structure, as described above, the surface roughening caused by dry etching caused problems such as a decrease in light coherency and a weakening of light intensity, but in the present invention, as described later, the second transmission region is not etched. Therefore, such inconvenience does not occur. Further, the role of the first transmission region adjacent to the light-shielding pattern in the phase shift is only to emphasize the contrast of the pattern edge by reversing the phase, and defects caused by surface roughness have almost no effect.

[0014] Here, the conditions for the phase difference of transmitted light to be 180 degrees between the first transmission area A and the second transmission area B are as follows.
In FIG. 1(a), let the refractive index of the glass be n, the exposure light source wavelength be λ, and the etching depth of the recess be d, then d=λ/
It is sufficient that the recessed portion is formed in the transparent substrate 1 with an etching depth of {2(n-1)}. In addition, in FIG. 2B, when the refractive index of the shifter layer 13 is n', the exposure light source wavelength is λ, and the thickness of the shifter layer 13 is d', d'=λ/
The shifter layer 13 has a thickness of {2(n'-1)}.
should be formed.

Next, a method for manufacturing a phase shift mask according to the present invention will be explained.

First, a method for manufacturing a phase shift mask having the structure shown in FIG. 1(a) will be explained with reference to FIG.
A conductive layer 2 is formed thereon using a known thin film forming method, and an electron beam resist 3 is applied thereon (see figure (a)).
. By providing the conductive layer 2, it is possible to prevent a charge-up phenomenon from occurring during electron beam lithography. As the conductive layer 2,
For example, a thin film of indium tin oxide (ITO), tantalum, or the like can be used, and although the thickness is not particularly limited, it is preferably about 2 to 10 nm thick. The transparent substrate 1 is made of an optically transparent material such as soda glass or quartz glass, which has been conventionally used as a mask substrate, and its thickness is usually 0.2 to 6 mm, although there are no essential restrictions. A certain degree is used.

Next, a resist pattern is formed by electron beam lithography, and then the transparent substrate 1 is dry etched to form a shifter (see FIGS. 3(b) and 3(c)). The etching depth at this time is determined as described above.

FIGS. 3(d) and 3(e) show that a light shielding layer 4 is formed on the entire surface by a method called lift-off, and a resist pattern 3 is formed.
At the same time, the light-shielding layer on the resist is removed to form a light-shielding pattern in the recessed portions of the transparent substrate 1. The light shielding layer 4 is typically made of chromium or the like, but it is also possible to form a low antireflection layer by laminating chromium oxide or the like thereon. In order to have light blocking properties, a certain optical density (generally 2.6 to 3
．． (approximately 0) is required. The thickness of the light shielding layer 4 is approximately 0.02 to 0.2 μm in order to provide a constant optical density.

Next, after removing the conductive layer 2 on the surface of the substrate,
Apply photoresist 5 to the entire surface and expose to light 6 from the back side of the substrate.
Then, a resist pattern is formed using the light-shielding pattern itself as a mask (see (f) and (g) in the same figure). At this time, if the exposure amount is slightly excessive, the resist pattern size becomes smaller than the light shielding pattern. By etching this, a pattern similar to that obtained by side-etching the light-shielding pattern is formed, completing the phase shift mask (see (h) in the same figure). The amount of etching at this time varies depending on the dimensions of the light shielding pattern itself, but if the width is 2 to 4 μm, the appropriate amount of side etching is about 0.3 to 0.4 μm on one side.

Next, a method for manufacturing a phase shift mask having the configuration shown in FIG. 1(b) will be explained with reference to FIG.
As shown in a), an etching stop layer 12, a transparent shifter layer 13, and a conductive layer 14 are formed in this order on a transparent substrate 11 using a known thin film forming method, and an electron beam resist 15 is coated thereon. do. The transparent substrate 11 and the conductive layer 14 are the same as those described above.

Furthermore, the etching stop layer 12 literally serves to prevent the underlying substrate from being etched during the dry etching of the shifter layer 13, and as a matter of course, the etching stop layer 12 is used to prevent the underlying substrate from being etched during the dry etching of the shifter layer 13. A material with a large ratio and a transparent material is selected. For example, when the shifter layer 13 is made of SiO2, the etching stop layer 12 is made of alumina (Al2
O3), silicon nitride (Si3N4), zirconia (Z
rO2), magnesia spinel (MgO・Al2O3)
Materials such as The thickness of the etching stop layer 12 is not particularly limited, but a thickness of about 5 to 20 nm is desirable.

The shifter layer 13 may be made of a transparent material, but SiO2, SOG, etc. are usually used. The shifter layer 13 is for inverting the phase of transmitted light by 180 degrees, and the thickness of the shifter layer 13 is set as described above so that the transmitted light has a phase difference of 180 degrees with respect to the substrate 1. is set. For example, the refractive index n of the shifter layer is 1.47 (
SiO2), and the exposure light source wavelength λ is 365 nm, the thickness of the shifter layer is 390 nm according to the above formula.

Next, a resist pattern is formed by electron beam drawing, and then the conductive layer 14 and the transparent shifter layer 13 are dry-etched to form a shifter (FIG. 3(b),
(see (c)).

Next, a light-shielding pattern made of the light-shielding layer 16 is formed in the concave portion of the shifter layer 13 by the above-mentioned lift-off (see (d) and (e) in the same figure), and then a photoresist 17 is applied to the entire surface. A resist pattern is formed on the light-shielding pattern by exposure 18 from the back side of the substrate (see (f) in the same figure).
), (g)), and by etching this, a phase shift mask as shown in (h) of the same figure is completed.

[0025]

[Examples] The present invention will be explained in more detail with reference to Examples below.

Example-1 On a cleaned synthetic quartz glass substrate (thickness 2.3 mm),
A tantalum film with a thickness of 5 nm was formed as a conductive layer by sputtering, and a positive electron beam resist (manufactured by Chisso Corporation, trade name: PBS) was applied to a thickness of about 500 nm on the tantalum film, and after a prescribed baking process. , using a raster scan type electron beam lithography system, with an acceleration voltage of 10 KV and a dose of approximately 2.
．． A predetermined pattern was drawn at 5 μC/cm 2 and developed to obtain a resist pattern. After a predetermined baking process, using the resist pattern as a masking pattern, the glass substrate was dry-etched using C2F6 and H2 gas in a parallel plate reactive etching apparatus. The dry etching was performed under conditions that had high anisotropy and a high selectivity with respect to the resist. Etching conditions were gas ratio C2F6:H2=10:1, power 300W, gas pressure 0.
．． It was set to 03 Torr. The etching depth at this time is 3
It was set to 90 nm.

Next, a 100 nm thick low anti-reflection light shielding film consisting of a chromium film and a chromium oxide film is formed on the entire surface of the substrate by sputtering, and then a hot concentrated sulfuric acid solution is used to A light-shielding pattern was obtained by dissolving the resist pattern and removing the light-shielding film on the resist. Furthermore, after removing the conductive layer exposed on the substrate surface,
A photoresist (manufactured by Hoechst, trade name AZ1350J) was applied to a thickness of approximately 500 nm on the entire surface side of the substrate.
After a predetermined baking process, the entire surface was exposed to ultraviolet light from the back side of the substrate at a slightly overexposure dose, and a predetermined development process was performed to form a resist pattern using the light-shielding pattern as a mask. Subsequently, side etching of the light shielding pattern was performed by wet etching using a cerium ammonium sulfate etching solution, and finally the resist pattern was peeled off to obtain a phase shift mask having a structure as shown in FIG. 1(a).

Example 2 An Al2O3 film with a thickness of 20 nm was formed as an etching stop layer on a cleaned glass substrate by sputtering, and a Si film with a thickness of 390 nm was formed on top of it as a shifter layer.
An O2 layer was similarly formed by sputtering. On top of that, a tantalum film with a thickness of 5 nm was formed as a conductive layer by a sputtering method, and then a positive electron beam resist similar to that in Example-1 was applied, and the electron beam resist was applied in the same manner as in Example-1. A resist pattern was obtained by drawing. Next, the shifter layer was dry etched using the resist pattern as a masking pattern. The etching conditions were the same as in Example-1.

After the etching is completed, a light shielding film is formed on the entire surface in exactly the same manner as in Example 1, the resist pattern is removed to obtain a light shielding pattern, and a photoresist is applied on the entire surface. A photoresist pattern was formed on the light-shielding pattern by full-surface exposure, and then wet-etched to obtain a phase shift mask having the structure shown in FIG. 1(b).

[0030]

As described in detail above, according to the present invention, it is possible to exhibit an excellent phase shift effect that emphasizes the contrast of pattern edges by reversing the phase. Since the second transmission region of the shift mask is not etched, problems such as a decrease in light coherency and a weakening of light intensity due to surface roughening caused by dry etching do not occur as in conventional methods.

[Brief explanation of drawings]

FIGS. 1A and 1B are cross-sectional views showing the configurations of one embodiment and another embodiment of a phase shift mask of the present invention, respectively.

FIGS. 2(a) to 2(h) are cross-sectional views showing, in order of steps, a method for manufacturing a phase shift mask according to an embodiment of the present invention.

FIGS. 3A to 3H are cross-sectional views showing a method for manufacturing a phase shift mask according to another embodiment of the present invention in order of steps;

FIGS. 4(a) and 4(b) are cross-sectional views showing the structure of a conventional phase shift mask, respectively.

[Explanation of symbols]

1,11 Transparent substrate 2,14 Conductive layer 3,15 Electron beam resist layer 4,16 Light shielding layer 5, 17 Photoresist layer 6,18 Ultraviolet exposure 12 Etching stop layer 13 Transparent shifter layer

Claims (4)

[Claims] 1. A light-shielding region, a first transmissive region adjacent to the light-shielding region, and a first transmissive region adjacent to the first transmissive region.
and a second transmitting region whose transmitted light has a phase difference of 180 degrees with respect to the transmitting region, and the light shielding region and the first transmitting region are formed in a recess provided in a transparent substrate. phase shift mask. 2. A light-shielding region, a first transmissive region adjacent to the light-shielding region, and a first transmissive region adjacent to the first transmissive region.
and a second transmission area in which the phase difference of transmitted light is 180 degrees with respect to the transmission area, the second transmission area is formed by a transparent shifter layer provided on the transparent substrate, and A phase shift mask comprising an etching stop layer between a substrate and a light shielding layer forming the transparent shifter layer and the light shielding region. 3. Forming a recess in a transparent substrate by etching through a lithography process, then forming a light-shielding pattern in the recess by lift-off, and further forming a resist pattern on the light-shielding pattern by exposing from the back side of the transparent substrate, A method for manufacturing a phase shift mask, comprising performing side etching of the light shielding pattern. 4. At least an etching stop layer and a transparent shifter layer are provided in this order on a transparent substrate, the transparent shifter layer is patterned by etching through a lithography process, and then light is shielded by lift-off into the recesses of the formed transparent shifter layer. A method for manufacturing a phase shift mask, comprising forming a pattern, further forming a resist pattern on the light-shielding pattern by exposing from the back side of a transparent substrate, and performing side etching of the light-shielding pattern.