JP2012107306A - Method for depositing thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily deposit a fluorine-containing thin film on a substrate without introducing fluorine-based gas.SOLUTION: A method reduces the pressure inside a vacuum film deposition container 1 to a vacuum state and applies a voltage to an electrode 3A disposed inside the vacuum film deposition container 1 to generate plasma from the introduced gas G introduced into the vacuum film deposition container 1. A target 3 is disposed in the electrode 3A so that an ion in the plasma collides with the target 3 and sputter particles are discharged from the target 3. A fluorine-containing solid compound 9 is disposed in the vicinity of the substrate 4 and exposed to the plasma so as to separate fluorine from the compound, and fluorine and sputter particles react with each other, thereby depositing the fluorine-containing thin film on the substrate 4.

Description

  The present invention relates to a thin film forming method for forming a good thin film on a substrate, and relates to a method for forming an element used in a semiconductor device and a thin film forming method used in an optical field.

  In recent years, with the enhancement of functions of optical devices, there is an increasing demand for higher performance of lenses, particularly for improving light transmittance of short wavelengths and for suppressing surface reflection. On the other hand, a vacuum deposition method has been conventionally used as a thin film formation method, but in recent years, a film formation method using plasma, particularly a thin film formation by a sputtering method, has attracted attention from the viewpoint of ease of control. Although it is relatively easy to produce an oxide-based thin film by this sputtering method, the production of a fluoride thin film has recently been desired.

  Therefore, conventionally, a fluorine-based thin film has been prepared without introducing a fluorine-based gas by a sputtering method, and a fluorine-based solid compound is used as a sputtering target as the means (Patent Documents 1 and 2).

JP-A-8-101301 Japanese Patent Laid-Open No. 9-291359

  However, since such a fluorine-based solid compound is vulnerable to heat, it is highly likely to be dissolved when used as a target, and even if it does not go to dissolution, the fluorine gas component in the material is desorbed due to temperature rise, etc. Due to changes in properties, it was difficult to produce a stable thin film.

  In general, in order to produce a fluorine-based thin film by a sputtering method, there is a method of introducing a fluorine-based gas during film formation. There are two types of fluorine-based gases.

The first type of gas is organic fluorine gas such as CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , CHF ₃ , SF _{6 and the} like. These do not require any gas treatment equipment and are not likely to increase the cost in terms of equipment, but because they have a high global warming potential, there are restrictions on their use and the environmental impact in recent years. It is difficult to use from the viewpoint of reducing

The second type of gas is an inorganic fluorine gas, and examples thereof include F ₂ , COF ₂ , SiF ₄ , ClF ₃ , CHF ₃ , WF ₆ , and XeF ₆ . Since these gases are highly toxic, expensive equipment such as cylinder exhaust, emergency exclusion cylinder installation, exhaust gas treatment system is required, and high cost is a problem.

  Therefore, an object of the present invention is to provide a thin film forming method for easily forming a thin film containing fluorine on a substrate without introducing a fluorine-based gas.

  In the present invention, the inside of the vacuum film formation container is depressurized to a vacuum, electric power is applied to an electrode disposed in the vacuum film formation container, plasma is generated from the introduced gas introduced into the vacuum film formation container, A thin film forming method for forming a fluorine-containing thin film on a substrate placed in a vacuum film-forming container, wherein a solid compound containing fluorine desorbed by the plasma is placed in the vicinity of the substrate.

  According to the present invention, by disposing a solid compound containing fluorine in the vicinity of the substrate, fluorine is desorbed from the solid compound exposed to the plasma, so that the concentration of fluorine in the vicinity of the substrate is increased. Then, a thin film containing fluorine is formed on the substrate without introducing a fluorine-based gas into the vacuum film formation container. This eliminates the need for expensive equipment and reduces costs, and also forms a thin film that does not use greenhouse gases and is environmentally friendly.

It is explanatory drawing which shows schematic structure of the sputtering device which is an example of the thin film formation apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of a sputtering apparatus which is an example of a thin film forming apparatus according to an embodiment of the present invention.

  A sputtering apparatus 100 shown in FIG. 1 has a vacuum film formation container 1, and an electrode 3 </ b> A to which electric power is applied from a DC power supply 2 is provided in the vacuum film formation container 1. The target 3 is fixed in contact with the electrode 3A.

  Further, a vacuum preliminary exhaust chamber 6 is disposed adjacent to the vacuum film formation container 1, the substrate 4 is transferred by the transfer rod 8, and the fluorine-based solid compound 9 is transferred by the transfer rod 10. Can be carried in and out.

  The vacuum film formation container 1 and the vacuum preliminary exhaust chamber 6 are partitioned by a gate valve 5, and both chambers 1 and 6 are exhausted by vacuum pumps 12 and 7, respectively. A gas (introduction gas) G is introduced into the vacuum film formation container 1 through a valve 13. The introduced gas G is a different type of gas from the fluorine-based gas, and includes an inert gas or the like for colliding with the target 3.

  The fluorine-based solid compound 9 is a fluorine-based resin such as polytetrafluoroethylene (PTFE). The fluorine-based solid compound 9 is formed in a larger area than the substrate 4 and is disposed in the vicinity of the substrate 4. Specifically, if the surface of the substrate 4 on which the thin film is formed by sputtering is the front surface, the fluorine-based solid compound 9 is disposed so as to face the back surface of the substrate 4.

  With the above configuration, when forming a film on the substrate 4, first, the vacuum pumps 12 and 7 are operated, and the inside of the vacuum film forming container and the vacuum pre-evacuation chamber are decompressed to a vacuum. Next, the gate valve 5 is opened, the substrate 4 is carried into the vacuum film formation container 1 by the transfer rod 8, and the fluorine-based solid compound 9 is carried by the transfer rod 10. Although this fluorine-type solid compound 9 is arrange | positioned in the vicinity of the board | substrate 4 and the position facing the back surface of the board | substrate 4, it is not this limitation.

  Next, the valve 13 is opened, and the introduction gas G is introduced into the vacuum film formation container 1. Direct current power is applied to the electrode 3A from the direct current power source 2 to generate plasma in which gas is ionized. Then, ions (positive ions) in the generated plasma collide with the target 3, and sputtered particles are emitted to the substrate 4.

  Since the fluorine-based solid compound 9 is installed in the vicinity of the substrate 4 that is the film formation target, the fluorine-based solid compound 9 is exposed to plasma, and fluorine is gasified and desorbed from the fluorine-based solid compound 9. As a result, the concentration of the fluorine gas in the vicinity of the substrate 4 is increased, and the fluorine desorbed from the fluorine-based solid compound 9 reacts with the sputtered particles released from the target 3 by the sputtering method to form a fluorine-based thin film on the substrate 4. It is formed.

  By the above thin film formation method, a fluorine-containing thin film is formed on the substrate 4 without introducing a fluorine-based gas into the vacuum film formation container 1. This eliminates the need for expensive equipment for treating fluorine gas, reduces costs, and forms an environmentally friendly thin film without using fluorine gas as a warming gas. Further, by adjusting the timing of insertion of the fluorine-based solid compound 9 into the vacuum film formation container 1, an arbitrary thickness and amount of fluorine can be introduced into the thin film.

  Although the film formation method in the sputtering method has been described in the above embodiment, even in the plasma CVD method in which a film is formed using plasma, fluorine is contained in the thin film by disposing a fluorine-based solid compound in the vicinity of the substrate. It is captured. More specifically, when a metal-containing target is not placed in a vacuum film-forming container, a gas containing metal is introduced into the vacuum film-forming container, and the introduced gas is converted into plasma to form a film on the substrate. Even if it exists, this invention is applicable.

[Example 1]
After evacuating the vacuum film formation container 1 and the vacuum pre-evacuation chamber 6 to a pressure of 10 ⁻⁴ Pa, the gate valve 5 is opened, the substrate 4 is carried into the vacuum film formation container 1 by the transfer rod 8, and the transfer rod 10 is fluorinated. The solid compound 9 is carried into the vacuum film formation container 1. Ar gas was introduced at 50 sccm and oxygen was introduced at 50 sccm as the introduction gas G, DC power of 100 W was applied to the Si target 3, and a film containing SiO ₂ was formed on the substrate 4 to a thickness of about 100 nm.

And when the board | substrate 4 was taken out and the optical characteristic was measured, the refractive index was 1.38. Considering that the refractive indexes of SiO ₂ and the fluorine-based solid compound 9 are about 1.46 and 1.32 respectively, fluorine in the fluorine-based solid compound 9 is desorbed and mixed in the SiO ₂ thin film to be refracted. The rate is thought to have declined. When this thin film was analyzed by TDS (temperature-programmed desorption method), it was confirmed that fluorine was desorbed from the thin film by heating.

Next, a fluorine resin liquid was formed by dipping on the fluorine thin film produced by inserting the fluorine solid compound, and the thin film was laminated. When this laminated film was wiped with a soft cloth soaked in alcohol from above, the film was not peeled off. On the other hand, when this fluororesin thin film was laminated on the SiO ₂ film formed by the usual sputtering method and the same wiping was performed, a phenomenon that the fluororesin thin film was peeled was observed. . Therefore, in order to improve the adhesion by forming a thin film with low wettability such as a fluorine-based resin on the oxide thin film such as SiO ₂ film, the film formation of the base thin film is performed as in this embodiment. At this time, it is effective to insert the fluorine-based solid compound 9 into the vacuum film formation container 1. As a result, fluorine is taken into the thin film, the difference in wettability between the thin film interfaces can be eliminated, and the adhesion can be improved.

[Example 2]
After evacuating the vacuum film formation container 1 and the vacuum pre-evacuation chamber 6 to a pressure of 10 ⁻⁴ Pa, the gate valve 5 is opened, the substrate 4 is carried into the vacuum film formation container 1 by the transfer rod 8, and the transfer rod 10 is fluorinated. The solid compound 9 is carried into the vacuum film formation container 1. In Example 2, the fluorinated solid compound 9 is polytetrafluoroethylene (PTFE). Ar gas was introduced at 50 sccm and oxygen was introduced at 50 sccm as the introduction gas G, DC power of 100 W was applied to the Si target 3, and a film containing SiO ₂ was formed on the substrate 4 to a thickness of about 100 nm. And when the board | substrate 4 was taken out and the optical characteristic was measured, the refractive index was 1.39. Considering that the refractive indexes of SiO ₂ and PTFE are about 1.46 and 1.30, respectively, fluorine in the fluorine-based solid compound 9 is desorbed and mixed into the SiO ₂ thin film, and the refractive index is lowered. it is conceivable that. This thin film was also analyzed by TDS (temperature-programmed desorption method), and it was confirmed that fluorine was desorbed from the thin film by the temperature increase.

[Example 3]
In Examples 1 and 2 described above, a method for forming a thin film by incorporating fluorine in the fluorine-based solid compound into the thin film is described. However, instead of the fluorine-based solid compound, an oxygen-based solid compound or a nitrogen-based solid compound is used. In the same manner, if an oxide film is installed near the substrate, an oxide-based thin film or a nitride-based thin film can be formed.

In Example 3, after the vacuum film formation container 1 and the vacuum preliminary exhaust chamber 6 are exhausted to a pressure of 10 ⁻⁴ Pa, the gate valve 5 is opened, and the substrate 4 is carried into the vacuum film formation container 1 by the transfer rod 8. Then, the nitrogen-based solid compound is carried into the vacuum film formation container 1 by the transfer rod 10. As the introduction gas G, Ar was introduced at 50 sccm, TEOS (tetraethoxysilane) was introduced at 50 sccm, and oxygen was introduced at 50 sccm. A DC power of 100 W was applied to the electrode 3A, and a film containing SiO ₂ was formed on the substrate 4 to a thickness of about 100 nm. And when the board | substrate 4 was taken out and the optical characteristic was measured, the refractive index was 1.71. Considering that the refractive indexes of SiO ₂ and nitrogen-based solid compound are about 1.46 and 2.00, respectively, nitrogen in the nitrogen-based solid compound is desorbed and taken into the SiO ₂ thin film, increasing the refractive index. It is considered a thing. Actually, when this thin film was analyzed by TDS (temperature-programmed desorption method), it was confirmed that nitrogen was desorbed from the thin film by the temperature rise.

[Example 4]
After evacuating the vacuum film formation container 1 and the vacuum preliminary exhaust chamber 6 to a pressure of 10 ⁻⁴ Pa, the gate valve 5 is opened, the substrate 4 is loaded with the transfer rod 8, and the oxygen-based solid compound is loaded with the transfer rod 10. Ar was introduced at 50 sccm as the introduction gas G, DC power of 100 W was applied to the Si target 3, and a film containing Si was formed on the substrate 4 to a thickness of about 100 nm. When the substrate 4 was taken out and the optical characteristics were measured, a dielectric film having a refractive index of 1.48 was formed. Usually, when a film is formed using Si as a target 3, a Si metal film is formed. However, considering that the dielectric film is formed, it is considered that oxygen in the oxygen-based solid compound is desorbed and mixed into the Si thin film. When this thin film was also analyzed by TDS (temperature-programmed desorption method), it was confirmed that oxygen was desorbed from the thin film by heating.

DESCRIPTION OF SYMBOLS 1 ... Vacuum film-forming container, 2 ... DC power supply, 3 ... Target, 3A ... Electrode, 4 ... Substrate, 9 ... Fluorine-type solid compound, G ... Introducing gas

Claims (3)

The vacuum film-forming container is depressurized to a vacuum, electric power is applied to an electrode disposed in the vacuum film-forming container, and plasma is generated from the introduced gas introduced into the vacuum film-forming container, and the vacuum film-forming container A thin film forming method for forming a thin film containing fluorine on a substrate disposed inside,
A thin film forming method, wherein a solid compound containing fluorine desorbed by the plasma is disposed in the vicinity of the substrate.   2. The thin film formation according to claim 1, wherein a target is disposed on the electrode, and a thin film is formed on the substrate with sputtered particles released from the target by a sputtering method and fluorine desorbed from the solid compound. Method.   The thin film forming method according to claim 1, wherein the solid compound is a fluororesin.

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