Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1997-03-18
2001-07-17
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S426000, C428S446000, C428S448000
Reexamination Certificate
active
06261696
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical element for constituting an optical system using ultraviolet light, particularly KrF excimer laser light, ArF excimer laser light or the like, and also to a method and apparatus for producing such an optical element.
2. Related Background Art
Light in an ultraviolet region is conventionally used in optical apparatus such as a projection light-exposure apparatus for use in semiconductor device production. As a laser for generating light with a wavelength of 250 nm or less, lasers such as KrF, KrCl, ArF, ArCl, Xe
2
, Kr
2
, Ar
2
, and F
2
lasers are available. Fluorite exhibits a high transmission in the ultraviolet region, and is widely used to constitute optical elements such as a mirror, lens, beam splitter, etc., which constitute an optical system used in a projection light-exposure apparatus.
For example, Japanese Patent Application Laid-Open Nos. 7-261002, 7-218701, and 8-220304, disclose a structure of antireflection film suitable for an optical element. In the optical element for use in a KrF excimer laser, a multilayer is used as an antireflection film, the multilayer comprising aluminum oxide layers having a high refractive index and silicon oxide layers having a low refractive index and being produced by forming the aluminum oxide film first on and in contact with the surface of a quartz substrate, then the silicon oxide film thereon, and further alternately forming the aluminum oxide films and the silicon oxide films.
An optical element for use in shorter-wavelength laser devices such as an ArF excimer laser has been attempted to be produced from fluorite (calcium fluoride) as a substrate material.
However, when an optical element is produced by forming a multilayer film on a fluorite substrate by means of for example sputtering, color centers are generated. As a result, desired spectral characteristics cannot be obtained. Japanese Patent Application Laid-Open Nos. 4-228560 and 5-188203 disclose optical elements in which a 52.0 nm thick silicon oxide film is first formed on a fluorite substrate and then aluminum oxide and silicon oxide films are successively formed thereon, or in which a 62 nm thick silicon oxide film is first formed on a fluorite substrate and then magnesium oxide and silicon oxide films are successively formed thereon.
However, color centers are also generated even in the optical elements produced by these techniques, and thus desired spectral characteristics cannot be obtained.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical element without generating no color centers and with a desired spectral characteristic by using a fluorite substrate and suitably determing the material and thickness of the layer adjacent to the fluorite substrate.
It is another object of the present invention to provide a method and apparatus for forming a film on a fluorite substrate without causing degradation in the characteristics of the fluorite substrate and without generating color centers thereby achieving a desired spectral characteristic.
It is still another object of the present invention to provide an optical element comprising a plurality of films stacked on a fluoride substrate in which a film in contact with and on the substrate is a film having a thickness of 30 nm or less and comprising at least one selected from the group consisting of silicon oxide, beryllium oxide, magnesium oxide, and magnesium fluoride; and to provide a light-exposure apparatus using such an optical element.
(1-1) According to an aspect of the present invention, there is provided a film formation method of forming at least one layered film on a substrate containing fluorite as a main ingredient by using a film formation apparatus which emits electrons or ions, which comprises the step of forming, as a first layered film counted from the side of the substrate, a film having a thickness of 30 nm or less and comprising at least one selected from the group consisting of SiO
2
, BeO, MgO, and MgF
2
.
(1-1-1) Preferably, the thickness of the first layered film is 5 nm or more.
(1-1-2) Furthermore, the first layered film is preferably such a film comprising SiO
2
, and the method preferably further comprises the step of forming a film comprising Al
2
O
3
serving as a second layered film.
(1-1-3) Preferably, the method comprises the step of alternately forming a film comprising SiO
2
and a film comprising Al
2
O
3
to form third and upper layered films.
(1-1-4) Still preferably, the method comprises the steps of: forming films comprising SiO
2
serving as third, fifth and seventh layered films, respectively; and forming films comprising Al
2
O
3
serving as fourth and sixth layered films, respectively, thereby obtaining a multilayered film having the function of antireflection.
(1-1-5) The above multilayered film preferably has the function of antireflection at a wavelength of 193 nm.
(1-1-6) The above film formation apparatus which emits electrons or ions preferably utilizes a vacuum evaporation technique to melt a film material by means of an electron beam.
(1-1-7) Furthermore, the above film formation apparatus which emits electrons or ions preferably utilizes a sputtering technique to sputter a film material.
(1-2) According to another aspect of the present invention, there is provided a film formation method of forming a film on a substrate containing fluorite as a main ingredient by using a film formation apparatus which emits electrons or ions, which comprises the step of forming, as a first layered film counted from the side of the substrate, a film comprising at least one selected from the group consisting of SiO
2
, BeO, MgO, and MgF
2
by a film formation apparatus which emits neither electrons nor ions.
(1-2-1) Preferably the above film formation apparatus which emits electrons or ions utilizes a vacuum evaporation technique to melt a film material by means of an electron beam.
(1-2-2) Furthermore, the film formation apparatus which emits electrons or ions preferably utilizes a sputtering technique to sputter a film material.
(1-2-3) Preferably, the film formation apparatus which emits neither electrons nor ions utilizes a resistance heating technique to melt a film material.
(1-3) According to still another aspect of the present invention, there is provide a film formation method of forming a film at a plurality of positions on a substrate containing fluorite as a main ingredient by using a film formation apparatus which emits electrons or ions, which comprises the step of forming a film, as a first layered film counted from the side of the substrate, at the plurality of positions on the substrate by using a film formation apparatus which emits neither electrons nor ions, the first layered film comprising at least one selected from the group consisting of SiO
2
, BeO, MgO, and MgF
2
.
(2-1) According to a further aspect of the present invention, there is provided a film formation apparatus which emits electrons or ions and is capable of forming a film at a plurality of positions on a substrate containing fluorite as a main ingredient, which comprises a shielding means for blocking the electrons or ions so that when the film is formed at a predetermined position of the plurality of positions, the plurality of positions other than the predetermined position are protected from the incidence of the electrons or ions.
(2-1-1) Preferably, the film formation apparatus which emits electrons or ions utilizes a vacuum evaporation technique to melt a film material by means of an electron beam.
(2-1-2) Furthermore, the film formation apparatus which emits electrons or ions preferably utilizes a sputtering technique to sputter a film material.
REFERENCES:
patent: 4-228560 (1992-08-01), None
patent: 5-188203 (1993-07-01), None
patent: 7-218701 (1995-08-01), None
patent: 7-261002 (1995-10-01), None
patent: 8-220304 (1996-08-01), None
Ando Kenji
Biro Ryuji
Kanazawa Hidehiro
Otani Minoru
Suzuki Yasuyuki
Canon Kabushika Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Jones Deborah
Miranda Lymarie
LandOfFree
Optical element with substrate containing fluorite as main... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical element with substrate containing fluorite as main..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical element with substrate containing fluorite as main... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2519609