JPH06148863A - Phase shift pattern - Google Patents

Abstract

PURPOSE:To enable a designer of mask patterns to engage solely in circuit design regardless of the layout of phase shift patterns so that the fine patterning having high reliability can be executed. CONSTITUTION:The patterns which are the phase shift patterns 10 to be used for a photoexposing process and are equally spaced by phase shift layers 12 are formed on one surface of a transparent substrate 11. The light past the phase shift patterns 10 makes the uniform irradiation of mask patterns 13 possible with the light having a specified angle with zero order light. The light with which the edges of the mask patterns 13 is irradiated is diffracted by the edges of the mask patterns 13 and the zero order light and first order light thereof are eventually imaged through the inside of the pupil plane of a projecting optical system, by which the fine patterns improved in resolution are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift pattern, and more particularly to a phase shift pattern formed on an exposure mask and a pellicle used in a photolithography process for semiconductor manufacturing.

[0002]

2. Description of the Related Art With the recent trend toward higher density and smaller semiconductor integrated circuits, various patterns in the manufacturing process thereof are required to be further miniaturized. Therefore, in order to perform such fine pattern processing, it is required to perform finer and more accurate patterning of the resist film used as an etching mask in photolithography.

Conventionally, the mask 6 as shown in FIG.
When exposure is performed using 0, the incident light 14 is diffracted by the mask 60 patterned with a light shielding film, for example, chromium 18 on the glass substrate 17 in the projection exposure apparatus as shown in FIG. Next, ± 1st order, ± 2nd order ...). Of these light fluxes, two or more diffracted light rays pass through the pupil plane of the projection optical system 15 of the projection exposure apparatus to form an image on the wafer 16 to resolve the pattern.

However, with the miniaturization of the pattern, when the mask 61 whose pattern width is less than the resolution limit is used, the diffraction angle θ ₁ with respect to the incident light 14 becomes large as shown in FIG. The primary light cannot pass through the pupil plane of the projection optical system 15, and as a result, the pattern is no longer resolved on the wafer 16. Therefore, as a countermeasure against this, as shown in FIG. 13, a phase shift mask or a phase shift pattern is proposed in which the 0th order light is extinguished and the resolution of the pattern is improved by two light beams of ± first order light.
As an example of such a phase shift mask 62, as shown in, for example, FIG. 14, one surface of the glass substrate 17 on which the chrome pattern 18 is formed and the surface on the opposite side to the chrome pattern 18 is repeated. , The phase shifter 19 is formed every other section.

Further, as shown in FIG. 15, the mask 61
On the other hand, an oblique-incidence illumination method has been developed in which the exposure light 14 is obliquely incident to pass the 0th-order light and the 1st-order light into the pupil plane of the projection optical system 15 and form an image on the wafer 16. It was

In these phase shift masks or the grazing incidence illumination method, the resolution limit can be greatly increased. However, since the LSI pattern is complicated, the pattern dependency is large, and it is necessary to consider the layout of the shifter that maximizes the resolution in consideration of the LSI pattern. Further, especially in the case of a phase shift mask, its manufacturing process is very difficult, and an automatic shifter pattern layout device has been devised, but there is a problem that it is not at a practical level due to the limitation of the pattern. In addition, the method of inspecting and correcting the formed shift pattern has not been developed yet.

The present invention has been made in view of the above problems, and the 0th-order light disappears in the light incident on the phase shift mask in which the repetitive pattern having the same opening area as the π retarder is formed. This property is applied to a photomask, a pellicle, or the like, paying attention to the fact that the diffraction angle of the primary light is equal to the diffraction angle of the incident light when passing through a normal mask.

[0008]

According to the present invention, there is provided a phase shift pattern used in a light exposure process, wherein a pattern of equal intervals formed by a phase shift layer is formed on one surface of a transparent substrate. Provided.

The phase shift pattern of the present invention is preferably a pattern in which the phase shift layer is formed in a repeating pattern at regular intervals, and the shifter is a material that does not absorb the exposure light and inverts the phase by about 180 °. If there is, it is not particularly limited. Specifically, it is preferable to use SOG, resist or the like. The film thickness of the shifter at this time is preferably about λ / {2 (n-1)}. Where λ
Is the wavelength and n is the refractive index. Further, the width of the pattern of the phase shifter formed as the repeating pattern and the interval between the adjacent pattern are preferably about 1.5 to 2.0 μm.

Further, in the phase shift pattern of the present invention, the light shielding layer is formed in a repetitive pattern at regular intervals, and the phase shift layer is formed in at least one of the openings arranged between adjacent light shielding layers. Good. The light shielding layer in this case is not particularly limited as long as it is a material capable of absorbing light having a wavelength of approximately 248 to 436 nm, and chromium, Mo
Si, aluminum, etc. can be used. In addition, the width of the light-shielding layer formed in a repeating pattern at regular intervals and the distance between the light-shielding layer and the adjacent light-shielding layer pattern are preferably about 1 to 2 μm and about 1 to 2 μm, respectively. The thickness of the light shielding layer is not particularly limited, but is preferably about 80 to 120 nm, more preferably about 100 nm.

In the present invention, the transparent substrate on which the phase shift pattern is formed is a transparent substrate such as a quartz substrate, and is preferably a substrate which does not affect the transmission of light in the wavelength region used in a normal exposure light process or the like. . The transparent substrate can be used by patterning a phase shifter on one surface and arranging it between the mask and the exposure light. The thickness of the transparent substrate at this time is not particularly limited, but 2.28 to
It is preferably about 6.35 mm.

On the transparent substrate, a phase shifter is patterned on one surface of the transparent substrate to form a phase shift pattern, while a mask pattern is formed on the surface opposite to the side on which the phase shift pattern is formed with a light shielding material. And can be used as a mask. The thickness of the transparent substrate in this case is not particularly limited, but 2.28 to 6.35.
About mm is preferable. As a light shielding material, a wavelength of about 248
The material is not particularly limited as long as it can absorb light of ˜436 nm, and chromium, MoSi, aluminum or the like can be used.

Further, the transparent substrate may be structured as a pellicle with a phase shifter patterned on one surface thereof to cover the surface of the photomask opposite to the side where the mask pattern is formed. The thickness of the transparent substrate in this case is not particularly limited, but is 2.5 to 3.0 μm.
It is preferably about m, and more preferably about 2.85 μm.

The exposure light used when using the phase shift pattern of the present invention is not particularly limited, but i-line, g-line,
An excimer line or the like can be used, and when exposure is performed using them, the resolution can be improved by about 20%.

[0015]

The phase shift pattern according to the present invention is a phase shift pattern used in a light exposure process. Since a pattern of a plurality of phase shift layers at equal intervals is formed on one surface of the transparent substrate, this phase shift pattern The 0th-order light disappears from the light passing through the pattern, and the mask pattern is uniformly irradiated with the light having a certain angle with respect to the 0th-order light. The light applied to the edge portion of the mask pattern is diffracted at the edge portion of the mask pattern, and the 0th-order light and the 1st-order light thereof pass through the pupil plane of the projection optical system.
Further, since the light that has not resolved the mask pattern travels straight, it passes through the pupil plane of the projection optical system to form an image with a certain angle with respect to the 0th-order light.

Further, a pattern of a plurality of light shielding layers is formed on one surface of the transparent substrate at equal intervals, and a phase shift layer is formed in at least one of the openings arranged between adjacent light shielding layers. If so, the mask pattern creation process is performed more easily.

[0017]

Embodiments of the phase shift pattern of the present invention will be described below with reference to the drawings. Example 1 First, as shown in FIG. 1, a transparent substrate having a thickness of 2.28 is used.
A mask pattern 13 made of Cr is formed on one surface of a quartz substrate 11 of mm. Then, on the other surface of the quartz substrate 11, fine and evenly spaced repetitive patterns of SOG are formed as the phase shift layer 12. The SOG pattern in this case is SOG as shown in FIG.
Has a line width of about 1.5 μm, and an interval between SOG and SOG is about 1.5 μm. Further, the SOG film thickness at that time is about 545 assuming that the exposure is performed using the g-line.
nm.

Embodiment 2 As shown in FIG. 2, as a pellicle for coating on the substrate on the side opposite to the surface on which the mask pattern is formed,
A repetitive pattern of SOG is formed as the phase shift layer 22 on the pellicle film 21 made of quartz glass having a thickness of 2.28 mm, which is a transparent substrate, as in the first embodiment.

Example 3 As shown in FIG. 3, the thickness of the transparent substrate was 2.28 mm.
The phase shift layer 32 is formed on the quartz substrate 31 of the same as in the first embodiment.
As a result, a repeating pattern of SOG is formed. This phase shift pattern is used by being arranged above the substrate on which the mask pattern is formed and at a position where the exposure light is irradiated in parallel.

Embodiment 4 As shown in FIG. 5, a mask pattern 13 made of Cr is formed on one surface of a quartz substrate 11 having a thickness of 2.28 mm. Then, the light shielding layers 44 are repeatedly arranged on the other surface of the quartz substrate 11 at equal intervals. At this time, the light shielding layer 44 is formed of chromium to a thickness of about 100 nm, and the pattern of the light shielding layer 44 is as shown in FIG.
The line width of the light-shielding layer 44 is about 1.5 μm, and the distance between the light-shielding layers 44 and 44 is about 1.5 μm. Further, a pattern of SOG is formed as the phase shift layer 42 in at least one of the openings adjacent to the light shielding layer 44. The film thickness of SOG at this time is set to about 545 nm on the assumption that the exposure is performed using the g-line. This is a so-called Levenson type.

When exposure is performed using g-line using the phase shift pattern 40 in which the light shielding layer and the phase shift pattern are formed on the surface opposite to the side where the mask pattern is formed, as shown in FIG. As shown in the figure, the light 14 incident on the phase shift pattern 40 is reduced to 0 by the phase shift layer 42.
Since the secondary light disappears and the diffraction angle of the ± 1st order light becomes equal to the diffraction angle of the 1st order light with respect to the incident light when passing through a normal mask, only the ± 1st order light is the pupil plane of the projection optical system 15. It is possible to improve the pattern that passes through the inside and is resolved on the wafer 16.

Embodiment 5 As shown in FIG. 6, a transparent substrate for covering a substrate on which a mask pattern is formed has a thickness of 2.85 m.
On the pellicle film 21 of m, the light shielding layers 54 are repeatedly arranged at equal intervals as in the fourth embodiment, and the phase shift layer 5 is provided in at least one of the openings adjacent to the light shielding layer 54.
2, a pattern of SOG is formed.

The pellicle having the pattern of the light-shielding layer 54 and the phase shift layer 52 formed on the surface opposite to the side where the mask pattern is formed in this way is covered with a mask and exposed to the g-line (436 nm) exposure light. When the exposure is performed, as shown in FIG.
The 0th-order light disappears due to the phase shift layer 52 formed on the pellicle, and the diffraction angle of the ± 1st-order light becomes equal to the diffraction angle of the 1st-order light with respect to the incident light when passing through a normal mask. Only the ± first-order light passes through the pupil plane of the projection optical system 15 and the pattern resolved on the wafer 16 can be improved. Specifically, the resolution limit of 0.8 μm is 0.6 μ
It has improved to m.

Example 6 Similar to Example 4, light-shielding layers were repeatedly arranged on a transparent substrate at equal intervals, and a SOG pattern was formed as a phase shift layer in at least one of adjacent openings of the light-shielding layer. Has been formed. This phase shift pattern is used by being arranged above the substrate on which the mask pattern is formed and at a position where the exposure light is irradiated in parallel.

Even when a transparent substrate having such a phase shift pattern is disposed between the exposure light and the mask for exposure, the resolution is basically the same as when the mask and pellicle are used. It is possible to improve the pattern.

[0026]

According to the phase shift pattern of the present invention, the phase shift pattern used in the light exposure process is formed on one surface of the transparent substrate by a pattern of a plurality of phase shift layers at equal intervals. , The 0th-order light disappears in the light passing through this phase shift pattern,
It is possible to uniformly irradiate the mask pattern with light having a certain angle with respect to the 0th-order light. Then, the light irradiated to the edge portion of the mask pattern is diffracted at the edge portion of the mask pattern, and the 0th-order light and the 1st-order light thereof pass through the pupil plane of the projection optical system, and at the same time, the mask pattern is resolved. Since the light that did not exist travels straight, it will pass through the pupil plane of the projection optical system and form an image with a certain angle with respect to the 0th-order light.
A fine pattern with improved resolution can be formed.

Further, a pattern of a plurality of light-shielding layers at equal intervals is formed on one surface of the transparent substrate, and a phase shift layer is formed in at least one of the openings arranged between adjacent light-shielding layers. If so, the mask pattern creation process can be performed more easily. Therefore, by forming the phase shift pattern according to the present invention,
Since the designer of the mask pattern can concentrate only on the circuit design regardless of the layout of the phase shift pattern, it becomes possible to perform fine and highly reliable pattern processing.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an essential part showing a first embodiment of a phase shift pattern according to the present invention.

FIG. 2 is a schematic cross-sectional view of a main part showing a second embodiment of the phase shift pattern.

FIG. 3 is a schematic cross-sectional view of a main part showing a third embodiment of the phase shift pattern.

FIG. 4 is a plan view of first to third embodiments of a phase shift pattern.

FIG. 5 is a schematic cross-sectional view of a main part showing a fourth embodiment of the phase shift pattern.

FIG. 6 is a schematic cross-sectional view of a main part showing a fifth embodiment of the phase shift pattern.

FIG. 7 is a plan view of fourth and fifth embodiments of a phase shift pattern.

FIG. 8 is a schematic diagram for explaining an optical path of a projection exposure apparatus using the phase shift pattern of the fourth embodiment.

FIG. 9 is a schematic diagram for explaining an optical path of a projection exposure apparatus using the phase shift pattern of the fifth embodiment.

FIG. 10 is a schematic cross-sectional view of a main part showing a conventional mask.

FIG. 11 is a schematic diagram for explaining an optical path of the projection exposure apparatus when a mask having a relatively large pattern width is used.

FIG. 12 is a schematic diagram for explaining an optical path of a projection exposure apparatus when a mask having a pattern width equal to or smaller than a resolution limit is used.

FIG. 13 is a schematic diagram for explaining an optical path of a projection exposure apparatus when a phase shift pattern is used.

FIG. 14 is a schematic cross-sectional view of a main part showing a conventional mask having a phase shift pattern formed therein.

FIG. 15 is a schematic diagram for explaining the optical path of the projection exposure apparatus when obliquely incident illumination is used.

[Explanation of symbols]

 10, 20, 30, 40, 50 Phase shift pattern 11, 31 Quartz substrate (transparent substrate) 21 Pellicle film (transparent substrate) 12, 22, 32, 42, 52 Phase shift layer 13 Mask pattern

Claims (5)

[Claims] 1. A phase shift pattern used in a light exposure process, wherein a pattern of phase shift layers at equal intervals is formed on one surface of a transparent substrate. 2. The phase shift pattern according to claim 1, wherein each phase shift layer is formed in a repeating pattern at regular intervals. 3. A pattern of light-shielding layers at equal intervals is formed on one surface of a transparent substrate, and further, a phase shift layer is formed in at least one of openings provided between adjacent light-shielding layers. Item 1. The phase shift pattern according to item 1. 4. The phase shift pattern according to claim 1, wherein a mask pattern is formed of a light shielding material on the other surface of the transparent substrate. 5. The pellicle provided on the surface of the transparent substrate opposite to the pattern forming surface of the mask.
The phase shift pattern according to any one of 1.