Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-09-12
2004-07-13
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
Reexamination Certificate
active
06762000
ABSTRACT:
This application claims the Paris convention priority of Japanese patent application 2000 277260 filed on Sep. 12, 2000, the entire disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
i) Field of the Invention
The present invention relates to a phase shift mask blank which is suitable particularly for ArF or F
2
excimer laser, and a manufacturing apparatus and method of the phase shift mask blank.
ii) Description of the Related Art
In recent years, it has been clarified that high resolution and focus depth are two important properties required for photolithography but are in a contradictory relation with each other, and that a practical resolution cannot be enhanced only by high NA and short wavelength of a lens of an exposure apparatus (Monthly Semiconductor World 1990.12, Applied Physics Vol. 60, Nov. 1991, and the like).
Under such situation, phase shift lithography has been noted as the next-generation photolithography technique, and partially brought to practical use. The phase shift lithography is a method for enhancing the resolution of photolithography by change only of a mask without changing an optical system. When a phase difference is applied between exposure lights transmitted through the photo mask, mutual interference of the transmitted lights can be utilized to rapidly enhance the resolution.
The phase shift mask is a mask for using light strength information together with phase information. Various types of the masks are known such as Levenson type, auxiliary pattern type, and self-matching type (edge emphasizing type). These phase shift masks have a complicated constitution and require a high degree of manufacturing technique as compared with the conventional photo mask which has only the light strength information.
In recent years, a so-called halftone type phase shift mask has been developed as one of the phase shift masks.
In the halftone phase shift mask, a light semi-transmission portion has two functions: a shield function of substantially shielding the exposure light; and a phase shift function of shifting (usually reversing) a light phase. Therefore, it is unnecessary to separately form a shield film pattern and phase shift film pattern. This type of phase shift mask is simple in constitution and easy in manufacturing.
For the halftone phase shift mask, as shown in
FIG. 4
, a mask pattern formed on a transparent substrate
100
is constituted of a light transmission portion (transparent substrate exposed portion)
200
for transmitting a light which is strong enough to substantially contribute to exposure, and a light semi-transmission portion (shield and phase shifter portion)
300
for transmitting a light which is not strong enough to substantially contribute to the exposure (FIG.
4
A). Additionally, the phase of the light transmitted to the light semi-transmission portion is shifted, and the light semi-transmission portion is brought to a substantially reversed relation with respect to the phase of the light transmitted through the light transmission portion (FIG.
4
B). The lights transmitted in the vicinity of a boundary between the light semi-transmission portion and the light transmission portion and turned to the opposite portions by diffraction phenomenon cancel each other. Thereby, light strength in the boundary is substantially set to zero, and contrast, that is, resolution of the boundary is enhanced (FIG.
4
C).
The light semi-transmission portion (phase shift layer) in the halftone phase shift mask or blank needs to have a required optimum value with respect to both transmittance and phase shift amount. Concretely, (1) the transmittance in an exposure wavelength of KrF, ArF, or F
2
excimer laser, or the like can be adjusted in a range of 3 to 20%, (2) a phase angle can be adjusted usually to a value in the vicinity of 180° in the exposure wavelength, and (3) the transmittance needs to be usually testable in a range of 65% or less in test wavelengths such as 257 nm, 266 nm, 364 nm, and 488 nm.
In recent years, there has been a demand for a finer processing of a device, or the like, and shortening of an exposure wavelength for use in the device has been advanced. On the other hand, influences of a particle adhering to the mask blank and a pinhole formed in the mask have been increasingly regarded as problems. That is, for example, by generation of arc in a film formation apparatus during film formation, or other causes, a particle with a particle diameter of about one micron or less is sometimes mixed in the light semi-transmission film at a ratio of about 0.05 to 0.5 particle per one square centimeter. Moreover, when there is a fine groove or hole in the surface of a target, the particle with a particle diameter of about several microns or less is sometimes mixed in the light semi-transmission film. When the particle mixed in the light semi-transmission film falls out in a cleaning process, the pinhole is generated. Therefore, in order to prepare the mask blanks having less pinholes, it is necessary to reduce the number of particles during formation of the light semi-transmission film.
Additionally, in conventional mask blanks for i-ray, or KrF excimer laser, in which a relatively long wavelength is used as the exposure wavelength, there are many particles or pinholes. Therefore, the blanks cannot be applied to some of photo mask blanks for KrF, in which a pattern finer than a conventional pattern is formed, or mask blanks for a short wavelength of ArF or F
2
excimer laser.
With the shortening of the exposure wavelength, a property of the particle or the pinhole, required for the mask blanks, becomes stricter. It is necessary for practical use of the mask blanks for the short wavelength of the ArF or F
2
excimer laser to reduce the number of particles or pinholes having a diameter larger in size than about a half of the exposure wavelength as much as possible.
SUMMARY OF THE INVENTION
The present invention has been developed under the aforementioned background, and a first object thereof is to provide a phase shift mask blank in which the number of particles or pinholes each having a diameter larger than a diameter substantially equivalent in size to an exposure wavelength is reduced as much as possible.
Moreover, a second object of the present invention is to provide a manufacturing apparatus and method able to manufacture the phase shift mask blank in which the number of particles or pinholes each having the diameter larger than the diameter equivalent in size to the exposure wavelength is reduced as much as possible.
Furthermore, a third object of the present invention is to provide a photo mask blank in which the number of particles or pinholes is reduced as much as possible.
Additionally, a fourth object of the present invention is to provide a manufacturing apparatus and method which can manufacture the photo mask blank having the number of particles or pinholes reduced as much as possible.
To achieve the aforementioned objects, the present invention has the following constitutions.
(Constitution 1) A manufacturing method of a photo mask blank having a thin film for forming a pattern on a transparent substrate,
wherein during sputtering formation of the thin film, the surface of a target is directed downwards and the surface of a substrate is directed upwards with respect to a gravity direction, and a peripheral edge of the substrate is shielded in order to prevent film formation.
Particularly, a manufacturing method of a halftone phase shift mask blank having a light semi-transmission film on a transparent substrate,
wherein during sputtering formation of the light semi-transmission film, the surface of a target is directed downwards and the surface of a substrate is directed upwards with respect to a gravity direction, and a peripheral edge of the substrate is shielded in order to prevent film formation.
(Constitution 2) A manufacturing method of a photo mask blank having a thin film for forming a pattern on a transparent substrate, comprising a step of:
manufacturing the thin film using a
Mitsui Hideaki
Mitsui Masaru
Nozawa Osamu
Ootsuka Hitoshi
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Hoya Corporation
Huff Mark F.
Mohamedulla Saleha
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