Formation of thin metallic fluoride film

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a technique for forming an optical thin film material having a low refractive index by sputtering.

【0002】

[Conventional technology]

In recent years, attempts have been made to carry out an optical thin film by sputtering because it is advantageous for simplification and automation in the process of forming an optical thin film. Among them, since it is difficult to form a film by sputtering a low refractive index material, for example, the following invention is disclosed in Japanese Patent Application Laid-Open No. 4-223401 in order to solve this problem. The above invention is MgF₂And Si are targeted, and RF sputtering is performed using a mixed gas of argon gas and oxygen gas to obtain an MgSiOF film having a refractive index of 1.40 to 1.41.

【0003】

[Problems to be Solved by the Invention]

However, the above-mentioned prior art has a drawback that it takes a long time to form a film and is not practical. This is due to the slow film formation rate according to RF sputtering. For example, the film formation rate is about 7 nm / min. Therefore, it takes several tens of minutes to form one layer of a normal optical film.

【0004】

Therefore, the present invention has been made in view of the above drawbacks, and an object of the present invention is to provide a method for forming a metal fluoride thin film capable of forming an optical thin film material having a low refractive index at a high film forming speed by sputtering. To do.

【0005】

[Means for solving problems]

In order to achieve the above object, the present invention has adopted the following configuration. That is, a metal fluoride thin film was formed by reactive DC sputtering with a mixed gas of at least an inert gas and a gas containing a fluorine atom using a metal target.

【0006】

[Action]

The operation of the present invention will be described below with reference to FIGS. 1 and 2. The target 1 is a metal, and by DC sputtering, the metal atom 2 is efficiently knocked out by the inert gas ion 7 (see Fig. 1). Then, the knocked-out metal atom 2 is bonded to the fluorine atom 4 or the fluorine ion 5 generated by the dissociation of the gas molecule 3 containing the fluorine atom on the substrate 8 in flight or to form a film, and is combined with the metal fluoride 6. It is formed and formed (see Fig. 2). Therefore, the metal fluoride thin film can be formed by sputtering at a high film forming speed.

【0007】

[Example 1]

Set the magnesium target and the substrate to be filmed in the chamber, 1 x 10^-3Argon and CF with partial pressures of 0.2 Pa and 0.1 Pa, respectively, exhausted to Pa₄Introduce a mixed gas with. Then, 500W of DC power is applied to the target. Argon ion and CF₄CF generated by dissociation₃⁺The magnesium target is hit by ions and the like, and magnesium atoms pop out. The magnesium atom that pops out is CF₄Is bonded to fluorine atoms and fluorine ions generated by dissociation during flight or on the substrate, and is formed on the substrate as a magnesium fluoride thin film.

【0008】

According to this example, a magnesium fluoride thin film could be formed at a film forming rate of 70 nm / min. The refractive index of the film formed at a wavelength of 550 nm was 1.38 when measured with an ellipsometer.

【0009】

[Example 2]

Set the aluminum target and the substrate to be filmed in the chamber, 1 x 10^-3Exhaust to Pa, Argon and F with partial pressures of 0.2 Pa and 0.1 Pa, respectively₂Introduce a mixed gas with. Then add 800W DC power to the target. The aluminum target is hit by the argon ion and the aluminum atom pops out. The aluminum source that popped out is F₂Is bonded to fluorine atoms and fluorine ions generated by dissociation during flight or on the substrate, and is formed on the substrate as an aluminum fluoride thin film.

【0010】

According to this example, an aluminum fluoride thin film could be formed at a film forming rate of 100 nm / min. Moreover, when the film film was measured with an ellipsometer, the refractive index at a wavelength of 550 nm was 1.37.

【0011】

[Example 3]

Set the magnesium target and the substrate to be filmed in the chamber, 1 x 10^-3Exhaust to Pa, xenon and SF with partial pressures of 0.2 Pa and 0.1 Pa, respectively₆Introduce a mixed gas with. Then add 1kW of DC power to the target. Argon ion and SF₆SF generated by dissociation₅⁺The magnesium target is hit by ions and the like, and magnesium atoms pop out. The magnesium atom that popped out is SF₆Is bonded to fluorine atoms and fluorine ions generated by dissociation during flight or on the substrate, and is formed on the substrate as a magnesium fluoride thin film.

【0012】

According to this example, an aluminum fluoride thin film could be formed at a film forming rate of 120 nm / min. Moreover, when the film film was measured with an ellipsometer, the refractive index at a wavelength of 550 nm was 1.38.

【0013】

[Example 4]

Set the magnesium target and the substrate to be filmed in the chamber, 1 x 10^-3Exhaust to Pa, with partial pressures of 0.2Pa, 0.1Pa and 0.1Pa, argon, oxygen and CF, respectively.₄Introduce a mixed gas with. Then add 1kW of DC power to the target. Argon ion, oxygen ion and CF₄CF generated by dissociation₃⁺The magnesium target is hit by ions and the like, and magnesium atoms pop out. The magnesium atom that pops out is CF₄Is bonded to fluorine atoms and fluorine ions generated by dissociation during flight or on the substrate, and is formed on the substrate as a magnesium fluoride thin film.

【0014】

According to this example, a magnesium fluoride thin film could be formed at a film forming rate of 120 nm / min. Moreover, when the film film was measured with an ellipsometer, the refractive index at a wavelength of 550 nm was 1.40.

【0015】

[Effect of the invention]

As described above, according to the method for forming a metal fluoride thin film according to the present invention, it has become possible to form an optical thin film material having a low refractive index by sputtering at a high film forming speed.

[Simple explanation of drawings]

[Figure 1]

It is explanatory drawing of the operation of this invention.

[Figure 2]

It is explanatory drawing of the operation of this invention.

[Explanation of symbols]

1 target 2 metal atoms 3 gas molecules 4 Fluorine atom 5 Fluoride ion 6 Metal fluoride 7 Inert gas ion 8 board