Dielectric film having high refractive index and method for preparation thereof

• US 6,872,452 B2
• Filed: 11/15/2002
• Issued: 03/29/2005
• Est. Priority Date: 03/19/2001
• Status: Active Grant

• Current Assignee: Nippon Sheet Glass Company Limited (Nippon Telegraph and Telephone Corporation)
• Original Assignee: Nippon Sheet Glass Company Limited (Nippon Telegraph and Telephone Corporation)
• Inventors: Taninaka, Yasunori, Enjoji, Katsuhisa
• Primary Examiner(s): Jones, Deborah
• Assistant Examiner(s): Blackwell-Rudasill, G.
• Application Number:
  US10/298,071
• Publication Number:
  US 20030170504A1
• Time in Patent Office: 865 Days
• Field of Search: 428/428, 428/432, 428/433, 428/689, 428/697, 428/699, 428/701, 428/702, 359/359, 359/580, 359/586, 359/588, 204/192.1
• US Class Current: 428/432
• CPC Class Codes: C23C 14/083 of refractory metals or yttrium
• CPC Class Codes: C23C 14/352 using more than one target C23C14/56 takes precedence
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: Y10T 428/31851 Natural oil

Abstract

The high refractive dielectric film which can be used stably as a constituent material of an optical multi-layer film, namely, and which does not cause change over time in optical properties and has small film stress, is an amorphous material having no columnar structure, obtained by adding to a main component titanium oxide (TiOx: 1≦x≦2) another metal oxide (MOw: M represents a metal such as niobium, tantalum, 1≦w). Though titanium oxide is a material which tends to manifest a crystalline structure even in the form of a thin film, a mixed high refractive dielectric film can be obtained, containing titanium oxide causing little change over time in optical properties by rendering the resulting thin film amorphous by inhibiting growth of a crystal of titanium oxide by adding another metal oxide.

Claims

1. A high refractive dielectric film constructing a dielectric multi-layer film in which a high refractive dielectric film having a relatively high refractive index and a low refractive dielectric film having a relatively low refractive index are alternately laminated on a transparent substrate,

wherein the high refractive dielectric film is made of an amorphous material having no columnar structure, obtained by adding to titanium oxide (TiOx:

1<

x<

2) another metal oxide (MOy;

1≦

y≦

5/2) selected from the group consisting of niobium oxide (NbOy), and tantalum oxide (TaOy) and the ratio of the other metal component to the total amount of metal components (M/(Ti+M)) is 30 atom % or more and the low refractive dielectric film is made of an amorphous material having no columnar structure, obtained by adding to silica.

4. The high refractive dielectric film according to claim 1 wherein said high refractive dielectric film has a film stress of 0.30 Gpa or less.

2. A high refractive dielectric film constructing a dielectric multi-layer film prepared by the method in the chamber in which a pair of cathodes for magnetron sputtering, a pair of targets placed on the pair of cathodes and a substrate, which is a film forming object, placed at a location opposite to said pair of targets are prepared in a vacuum chamber capable of producing a reduced atmosphere, and a film is formed on the surface of said substrate by a reactive neutralization sputtering method using oxygen as a reactive gas while applying alternating voltage so as to change the polarities of said pair of cathodes alternately, wherein two steps of

a step in which a first pair of cathodes made of an alloy of titanium (Ti) and another metal (M) or a mixture of titanium (Ti) and said another metal (M) selected from niobium (Nb) and tantalum (Ta) are placed at mutually adjacent positions in parallel, and alternating voltage is applied to said pair of cathodes using as a process gas an oxygen-containing gas of a first given concentration, to form on the surface of the substrate a relatively high refractive dielectric film which is an amorphous material having no columnar crystal, made of titanium oxide (TiOx:

1≦

x≦

2) and another metal oxide (MOy;

1≦

y≦

5/2) selected from niobium oxide (NbOy) and tantalum oxide (TaOy) and

a step in which a second pair of targets made of silicon (Si) metal are placed at mutually adjacent positions in parallel, apart from said first pair of targets, the substrate surface on which said high refractive dielectric film is formed is shifted to a location opposite to said second pair of targets and alternating voltage is applied using as a process gas an oxygen-containing gas of a second given concentration, to form a relatively low refractive dielectric film on the substrate surface carrying thereon said high refractive dielectric film formed

are repeated a given number of times in the order as described above or in the reverse order, to form on the surface of the substrate an optical multi-layer film.

3. A high refractive dielectric film constructing a dielectric multi-layer film according to claim 2 wherein said high refractive dielectric film has a film stress of 0.30 GPa or less.

5. A high refractive dielectric film constructing a dielectric multi-layer film prepared in the chamber by a method in which a pair of cathodes for magnetron sputtering, a pair of targets placed on the pair of cathodes and a substrate, which is a film forming object placed at a location opposite to said pair of targets, are prepared in a vacuum chamber capable of producing a reduced atmosphere, and a film is formed on the surface of said substrate by a reactive neutralization sputtering method using oxygen as a reactive gas while applying alternating voltage so as to change the polarities of said pair of cathodes alternately,

wherein the method comprises repeating the following two steps a given number of times in the order as set forth or in the reverse order, to form on the surface of the substrate an optical multi-layer film:

a first step in which a first pair of cathodes made of an alloy of titanium (Ti) and another metal (M) or a mixture of titanium (Ti) and said another metal (M) selected from niobium (Nb) and tantalum (Ta) are placed at mutually adjacent positions in parallel, and alternating voltage is applied to said pair of cathodes using as a process gas an oxygen-containing gas of a first given concentration, to form on the surface of the substrate a relatively high refractive dielectric film which is an amorphous material having no columnar crystal, made of titanium oxide (TiOx;

1≦

x≦

2) and another metal oxide (MOy;

1≦

y≦

5/2) selected from niobium oxide (NbOy) and tantalum oxide (TaOy); and

a second step in which a second pair of targets made of silicon (Si) metal are placed at mutually adjacent positions in parallel, apart from said first pair of targets, the substrate surface on which said high refractive dielectric film is formed is shifted to a location opposite to said second pair of targets and alternating voltage is applied using as a process gas an oxygen-containing gas of a second given concentration, to form a relatively low refractive dielectric film on the substrate surface carrying thereon said high refractive dielectric film formed.

6. The high refractive dielectric film according to claim 5 wherein said high refractive dielectric film has a film stress of 0.30 GPa or less.