JP6065549B2 - Photomask manufacturing method - Google Patents

Description

The present invention relates to a photomask using arbitrary transparency and phase shift effect, by blocking or reducing light other than a predetermined phase shift amount, which causes transferability deterioration at the time of wafer transfer. the method of manufacturing a photomask for realizing the improvement of sexual.

  A photomask having a phase shift effect includes a Levenson mask having a shifter dug to a predetermined depth by etching a quartz substrate as a support substrate, and a phase shift film having a predetermined amount of transmittance on the support substrate. There is a halftone mask that uses a phase shift effect by forming a pattern.

  In addition, in illumination systems used for wafer transfer, a high numerical aperture NA of 1.35 is often used by using immersion exposure, and an arbitrary phase shift as shown in FIG. Obliquely incident light other than the amount becomes noise, and in the photomask using the phase shift effect, the phase shift effect cannot be obtained sufficiently, which affects wafer transfer.

  FIG. 4 is an explanatory view of a part of an example of a conventional phase shift type photomask as seen in cross section. The photomask of FIG. 4 includes a phase shift pattern 21 in which only the phase shift film 12 is formed in a pattern on the substrate 11 and a light shielding portion 20 in which the light shielding film 13 is formed on the phase shift film 12. When light 16 is incident on such a photomask in an oblique direction from the substrate 11 side, the light 16 irradiated to the phase shift film is reflected or transmitted outside the phase shift pattern 21 and is opposite to the substrate 11. Light emitted to the side is generated and becomes noise. For this reason, the shift effect cannot be obtained sufficiently.

  For photomasks that have a shifter that has a quartz substrate etched to an arbitrary depth, such as a Levenson mask, a photomask that blocks or reduces noise caused by obliquely incident light by providing a light-shielding film on the inner wall of the shifter. There is a mask.

Japanese Patent No. 3750312

  However, by forming a phase shift pattern consisting of a phase shift film having a predetermined amount of transmittance on the support substrate, such as the latter, an effective solution for obliquely incident light in a halftone mask using the phase shift effect No law has been proposed.

An object the present invention provides a halftone mask having a predetermined transmittance and phase shift effect and decreased noise due to the oblique incident light, to provide a method for manufacturing a photo mask to achieve improved wafer transferability And

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The photomask manufacturing method of the present invention has been made in view of the above problems, and the invention according to claim 1 includes a phase shift film having a predetermined transparency and phase shift effect on a support substrate, and a phase shift film. In a photomask manufacturing method in which a light-shielding film laminated thereon is formed, a pattern is formed on a mask blank in which a phase-shift film and a light-shielding film are laminated on a support substrate, and then a resist is applied to draw and write A resist pattern is formed by performing development, and the light shielding film is removed by etching using the resist pattern as a mask to form a phase shift pattern and a light shielding film pattern, and the oxygen plasma etching is left on the sidewall of the light shielding film pattern. The resist is removed, and a material to be a side wall film is formed, and the side wall of the phase shift pattern and the side by the anisotropic etching After removal of the material except for the side wall of the light pattern, a method for manufacturing a photomask, and removing the remaining portions of the resist.

According to a second aspect of the invention, the claim 1, wherein the material is a manufacturing method of a photomask, characterized in that deposited by PVD or CVD.

The photomask manufactured by the present invention is a halftone mask having a predetermined transmittance and a phase shift effect, and a phase shift having a phase shift effect on both side surfaces of a phase shift pattern made of a phase shift film having a phase shift effect. The side wall film is formed of a material different from that of the film. With such a configuration, in particular, the side wall film is formed of a material different from the phase shift film having the phase shift effect, so that the obliqueness other than the predetermined phase shift amount causes deterioration of transferability during wafer transfer. A photomask in which incident light is blocked or reduced to reduce noise can be obtained.

It is explanatory drawing which looked at a part of embodiment of the photomask manufactured by this invention in the cross section. It is explanatory drawing which looked at an example of the flow of the manufacturing method of the photomask of this invention in the cross section. It is the example of calculation by the simulation using the embodiment example of the photomask manufactured by this invention, (a) It is a result of NILS, (b) It is a result of DOF. It is explanatory drawing which looked at a part of example of the conventional phase shift type photomask in the cross section.

  Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view showing a part of an embodiment of a photomask manufactured according to the present invention in a sectional view. In the present embodiment, in the figure, the transmittance is 10% or less in a state where the support substrate (11) made of quartz, the phase shift film (12) having predetermined transparency and phase shift effect, and the phase shift film are in contact with each other. A halftone mask composed of a light shielding film (13) is assumed. As shown in FIG. 1A, sidewall films (15) are provided on both side surfaces of a pattern (14) made of a phase shift film having a phase shift effect by using a material different from that of the phase shift film having a phase shift effect. ing. As shown in FIG. 1B, when transferring the wafer by obliquely incident light (16), it is possible to block or reduce light other than a predetermined phase shift amount that causes deterioration of transferability. Thus, improvement in wafer transfer property can be realized. In the conventional structure in which the sidewall film (15) is not formed, the oblique incident light (16) other than the predetermined phase shift amount cannot be blocked as shown in FIG. 4, and the wafer transfer is affected as noise.

  The sidewall film (15) preferably has a refractive index of 1.2 or less with respect to the wafer exposure wavelength light. When the refractive index exceeds 1.2, the DOF is deteriorated. In this way, reflection of exposure light from the pattern side surface can be suppressed, and oblique incident light (16) other than an arbitrary phase shift amount can be blocked or reduced more effectively.

  Further, the sidewall film (15) has a refractive index of 1.2 or less and an extinction coefficient of 1 or more with respect to the wafer exposure wavelength light, thereby suppressing reflection of exposure light from the side surface of the pattern and the exposure. A light blocking effect can also be obtained, and obliquely incident light (16) other than an arbitrary phase shift amount can be blocked or reduced more effectively.

  Further, the sidewall film (15) has a reflectance of 30% or less with respect to the wafer exposure wavelength, and the reflection from the sidewall film (15) is reduced to prevent irregular reflection between patterns or within the pattern. Thus, more stable wafer transfer properties can be realized.

  By setting the thickness of the side wall film (15) to 2 nm or more, a more stable light shielding effect can be obtained.

  Examples of the material of the sidewall film include a film containing one or a plurality of film materials of chromium, chromium oxide, chromium nitride, chromium oxynitride, zirconium, zirconium oxide, indium, indium oxide, indium tin oxide, and tantalum. it can.

  FIG. 2 is an explanatory view showing, in section, an example of the flow of the photomask manufacturing method of the present invention.

  In the present embodiment, a support substrate (11) made of quartz, a phase shift film (12) having arbitrary transparency and phase shift effect, and a transmittance of 10% or less in contact with the phase shift film. It is assumed that the method is a halftone mask manufacturing method comprising the light shielding film (13).

  After forming a pattern (20) composed of a phase shift film and a light shielding film on a mask blank in which a phase shift film and a light shielding film are laminated on the support substrate 11, a resist (17) is applied as shown in FIG.

  Next, a resist pattern is formed by performing drawing and development, and the light shielding film is removed by etching using the resist pattern as a mask. At this time, as shown in FIG. 2B, since the resist (18) remains on the side surface of the pattern (20) made of the phase shift film and the light shielding film, oxygen plasma etching is used (FIG. 2C). ), The resist (18) is removed (FIG. 2D). However, the resist (18) adhering to the side surface of the pattern (20) composed of the phase shift film and the light shielding film is removed, but not all the resist (19) adhering to the light shielding film is removed.

  Next, as shown in FIG. 2E, the material to be the sidewall film is formed on the pattern (14) made of the phase shift film having the phase shift effect and the pattern (20) made of the phase shift film and the light shielding film. Form a film. Next, after removing the phase shift film and the material deposited on the transmission part by anisotropic etching, the resist is removed to form a sidewall film as shown in FIG. It becomes possible.

  The material may be formed by a PVD method or a CVD method.

An example of the structure of the photomask manufactured by the present invention is shown below.
(Photomask structure and simulation conditions)
Phase shift film: 6% halftone film Phase shift film thickness: 720 mm
Side wall film refractive index: 1.0
Side wall film extinction coefficient: 1.7
Side wall thickness: 160 mm
Mask pattern dimension: 160 nm (including sidewall film)
Mask pattern pitch dimension: 320 nm
Exposure wavelength: 193nm
NA: 1.35 (immersion exposure)
Lighting system: Double
σ (In / Out): 0.85 / 0.97
Exposure magnification: × 4
Polarized light: TE polarized light

  EM-Suite (manufactured by Panoramic Technology) was used as a simulator. The grid is 1 nm (dimension on the mask), and evaluation is performed by Aero. In the calculation of the aerial, the calculation is performed by Non Hopkins that does not use Hopkins (paraxial approximation), which enables a highly accurate transfer simulation.

FIG. 1A shows a photomask manufactured by the present invention . By setting the side wall film (15) to 160 mm, it is possible to reduce the oblique incident light (16) other than the arbitrary phase shift amount transmitted from the side wall.

From the result of the simulation shown in FIG. 3 (a), it was confirmed that the use of the photomask manufactured according to the present invention improved 11% in NILS compared to the structure without the sidewall film.

The example which formed the resist pattern on the wafer using the photomask manufactured by this invention is shown. An antireflection film and a resist were coated on the silicon substrate, and the resist was exposed using an exposure apparatus. The exposure conditions are as follows.
Light-shielding film: Chromium oxide and chromium (multilayer)
Shading film thickness: 440 mm
Side wall film material: Chrome oxide side wall film thickness: 100 mm
Resist: Chemical amplification type positive resist resist Film thickness: 1500mm
Exposure wavelength: 193nm
NA: 1.35 (immersion exposure)
σ (In / Out): 0.85 / 0.97
Exposure magnification: × 4
Polarized light: TE polarized light

A pattern was formed on a mask blank in which a phase shift film and a light-shielding film were laminated on a support substrate, a resist was applied, and a resist pattern was formed by drawing and developing. After removing the light shielding film by etching using the resist pattern as a mask, the resist adhered to the phase shift film and the side wall of the light shielding film was removed by oxygen plasma etching. Next, a material to be a sidewall film is formed on the resist, the material formed on the phase shift film and the transmission part is removed by anisotropic etching, and then the resist is removed to remove the film . A photomask was manufactured.

Mounting the silicon substrate off Otomasuku and resist produced is applied to the exposure apparatus, exposure was performed.

  Also in the wafer transfer, the NILS improvement was confirmed as in the simulation.

An example of the structure of the photomask manufactured by the present invention is shown below.
(Photomask structure etc.)
Phase shift film: 6% halftone film Phase shift film thickness: 720 mm
Side wall film refractive index: 1.0
Side wall film extinction coefficient: 2.2
Side wall thickness: 160 mm
Mask pattern dimension: 160 nm (including sidewall film)
Mask pattern pitch dimension: 640 nm
Exposure wavelength: 193nm
NA: 1.35 (immersion exposure)
Lighting system: Double
σ (In / Out): 0.85 / 0.97
Exposure magnification: × 4
Polarized light: TE polarized light

FIG. 1A shows a photomask manufactured by the present invention . By setting the chromium oxide of the side wall film (15) to 160 mm, it is possible to reduce the oblique incident light (16) other than the arbitrary phase shift amount transmitted from the side wall.

From the result of the simulation shown in FIG. 3 (b), a 6% improvement in DOF was confirmed by using the photomask manufactured according to the present invention as compared with the structure without the sidewall film.

The example which formed the resist pattern on the wafer using the photomask manufactured by this invention is shown. An antireflection film and a resist were coated on the silicon substrate, and the resist was exposed using an exposure apparatus. The exposure conditions are as follows.
Light-shielding film: Chromium oxide and chromium (multilayer)
Shading film thickness: 440 mm
Side wall film material: Chromium oxide resist: Chemically amplified positive resist film thickness: 1500mm
Exposure wavelength: 193nm
NA: 1.35 (immersion exposure)
σ (In / Out): 0.85 / 0.97
Exposure magnification: × 4
Polarization: TE polarization The same improvement effect as in the simulation was confirmed in wafer transfer.

DESCRIPTION OF SYMBOLS 11 ... Support substrate 12 ... Phase shift film 13 ... Light shielding film 14 in which transmittance is 10% or less in contact with phase shift film ... Pattern 15 made of phase shift film having phase shift effect ... Side wall film 16 ... Arbitrary Obliquely incident light 17 other than the phase shift amount ... resist 18 ... resist 19 attached to the side surface of the pattern made of the phase shift film and the light shielding film ... resist 20 attached on the light shielding film ... pattern 21 made of the phase shift film and the light shielding film Obliquely incident light with an arbitrary amount of phase shift

Claims (2)

  In a photomask manufacturing method in which a phase shift film having predetermined transparency and a phase shift effect and a light shielding film laminated on the phase shift film are formed on a support substrate, the phase shift film is formed on the support substrate. After forming a pattern on the mask blank on which the light shielding film is laminated, a resist is applied, and a resist pattern is formed by drawing and developing, and the light shielding film is removed by etching using the resist pattern as a mask to perform phase shift Forming a pattern and a light-shielding film pattern, removing the resist remaining on the side wall of the light-shielding film pattern by oxygen plasma etching, forming a material to be a side-wall film, and forming the side wall of the phase shift pattern by anisotropic etching And after removing the material except for the side wall of the light shielding pattern, the remaining portion of the resist is removed. Manufacturing method of a photomask to be. A method for producing a photomask, comprising depositing the material according to claim 1 by a PVD method or a CVD method.

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