JP2006336084A - Sputtering film deposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by providing a method by which the lowering of the deposition speed of a thin film, that is caused by densifying the structure of the thin film, is suppressed to be minimum and the change with the passage of time of optical characteristics is suppressed to be minimum. <P>SOLUTION: The method has a process for depositing an oxide thin film by sticking sputtering particles of a target onto a substrate in a reduced pressure atmosphere. In the process, after depositing the thin film under such a condition that gaseous argon and gaseous oxygen are introduced into the reduced pressure atmosphere, moisture is added in addition to the gaseous argon and gaseous oxygen without stopping discharge or changing the conditions and the film deposition is continued, and thereafter the film deposition is completed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a transparent dielectric thin film such as TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and SiO ₂ used for an optical thin film formed on an optical component such as an antireflection film, a low-pass filter, a dichroic filter, or the like. It is related with the film-forming method of.

  Conventionally, it has been considered that the optical properties of optical thin films prepared by vapor deposition or sputtering are inevitably changed to some extent immediately after film formation and immediately after removal from a vacuum bottle. Therefore, for a period of about one week to one month, measures were taken to leave the optical parts in the atmosphere or the like in an environment where they were actually used and incorporate them into the product after the change in optical characteristics had subsided. In addition, quantitative evaluation was performed by leaving it in a high-temperature and high-humidity environment in order to grasp the amount of characteristic fluctuation in a short time. Therefore, time and labor are required for the evaluation, and the productivity is lowered due to the occurrence of a period for which the evaluation is left. It is considered that the cause of the fluctuation of the optical characteristics is often caused by moisture in the air penetrating from the outermost layer of the thin film and adsorbing on the pores existing inside the thin film. For this reason, for example, the ion beam method or the sputtering method is used to increase the packing density of the thin film by a method that increases the kinetic energy when the particles are deposited on the substrate, and to form the film by a method that reduces the voids in the thin film. Attempts have been made to minimize fluctuations in optical characteristics. Although it has become possible to obtain a certain effect by these methods, there have been cases in which the deposition rate of the thin film is reduced in order to produce a dense film.

As a conventional example, for example, Patent Document 1 can be cited.
JP 09-025571 A

  In the present invention, in view of the above problems, productivity is improved by providing a method for minimizing the decrease in the deposition rate of the thin film due to the dense structure of the thin film and minimizing the change in optical characteristics over time. It is for the purpose. The optical thin film obtained by the present invention has excellent environmental durability.

  In order to achieve the above object, a method for forming a transparent dielectric thin film of the present invention includes a step of depositing an oxide thin film by depositing sputtering particles of a target on a substrate in a reduced pressure atmosphere, and the reduced pressure atmosphere. During or after film formation under the condition of introducing argon gas and oxygen gas into the film, without stopping the discharge or changing the conditions, water was added in addition to argon gas and oxygen gas to form the film. It is completed after continuing. At that time, both or at least one of a DC voltage and a high frequency voltage of 10 to 20 MHz, or a DC voltage and a superimposed high frequency of about 1 to 100 kHz are applied to the target to generate sputtered particles.

  An object of the present invention is to provide means for easily producing an optical thin film having excellent environmental durability by forming a thin film by the above method. The optical thin film obtained by the present invention has excellent environmental durability.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples at all. FIG. 1 shows a film forming apparatus used for a method of forming an optical thin film according to an embodiment, which includes a decompression chamber 1 evacuated by a vacuum pump (not shown) and substrates disposed inside thereof in opposition to each other. Holder 2 and target 3, RF power source 4 and DC power source 5 that apply high-frequency voltage and DC voltage to target 3, and argon gas that is a sputtering gas and an oxygen gas that is a reactive gas are introduced into decompression chamber 1. The oxygen introduction line 6 and the water vapor introduction line 7 which is moisture in the decompression chamber 1 are provided. The high frequency voltage of the RF power source 4 is applied to the target 3 via the matching network 4a, and the DC voltage of the DC power source 5 is applied to the target 3 via the low pass filter 5a. Next, a process for forming an oxide thin film on the substrate W ₁ will be described. First, the substrate W ₁ is held on the substrate holder 2, the decompression chamber 1 is depressurized to a predetermined degree of vacuum, argon gas and oxygen gas are introduced from the argon / oxygen introduction line 6, and the RF power source 4 is supplied to the target 3. Is applied to generate a plasma 1 by so-called magnetron sputtering discharge. The target 3 is sputtered by positive ions and released toward the substrate W ₁ in a state where it is partially oxidized by the oxidizing active species near the surface of the target 3. The sputtered particles that have reached the substrate W ₁ in this way are oxidized by the oxidizing active species in the plasma P1 or in the vicinity of the surface of the substrate W ₁ , and an oxide thin film is formed on the surface of the substrate W ₁ . The target thin film thickness is calculated in advance as the deposition rate per unit time when the thin film is created in a separate process, and this thin film deposition rate is sufficiently stable to the required specifications. Make sure that. In this examination, it was 0.202 nm / sec. After completing 95% of the desired film thickness in this way, water vapor is introduced from the water vapor introduction line 7 to form the remaining 5%. In general, the rate of thin film deposition is reduced by introducing water vapor. As a result of our verification, it was found that the deposition rate of the thin film was reduced by 15% compared to the case where water vapor was not introduced, and was 0.173 nm / sec in this study. In this way, when the film thickness of 100% is formed with respect to the desired film thickness, the discharge is terminated, or a measure is taken so that particles from the target are not deposited on the substrate by a shutter unit or the like. The relationship between the film formation time at this time and the set thin film deposition rate is shown in FIG. Here, the film formation time in the figure will be described. If the desired film thickness is d (nm) and the film formation rate when water vapor is not introduced is r (nm / sec), the film formation rate when water vapor is introduced can be 0.85 r (nm / sec). Further, if the respective film formation times are t1 and t2 (sec), the following two equations are established. rt1 + 0.85rt2 = d, rt1 = 0.95d. From this equation, t1: t2 = 323: 20, and the film formation time can be set. Accordingly, when the total film formation time is set to 1000 seconds, the time for film formation without introducing water vapor is 942 seconds, and the time for film formation with water vapor introduction is 58 seconds. After the film formation is completed by such means, the film formation process is completed by taking out the formed substrate into the atmosphere. In the first process where water vapor is not introduced, there are relatively many vacancies in the thin film structure itself, and it is easy to obtain a low-density structure. The optical characteristics are likely to change with time by being fixed to the holes. FIG. 3 shows the spectral characteristics of an optical thin film formed without introducing water vapor. In the graph, the thick solid line represents the reflectance immediately after being taken out of the vacuum chamber after film formation, and the thin solid line represents the reflectance after 10 days. It can be seen that the characteristics are different between the two despite the same sample. On the other hand, by introducing water vapor into the thin film outermost layer in a layer corresponding to 5% and laminating it, it is possible to suppress changes with time in optical characteristics. This is because the layer into which water vapor is introduced has a high density of thin film, and even when left in the atmosphere, moisture is fixed, so that there are few vacancies necessary, and as a result it is difficult for optical properties to change over time. is there. In addition, the presence of this layer on the outermost layer of the thin film has the effect of preventing moisture in the atmosphere from entering the film structure, so it has a structure with relatively many vacancies inside the thin film. However, the entire thin film hardly changes over time. In addition, when water vapor is introduced, the deposition rate of the thin film is reduced, and the productivity is likely to be lowered. However, by using this layer only for the outermost layer 5%, the decrease in the deposition rate of the thin film is minimized and the optical performance is reduced. It is possible to minimize changes with time of characteristics. FIG. 4 shows the spectral characteristics of the optical thin film formed by providing the outermost layer with water vapor introduced therein. As in FIG. 3, the thick solid line represents the reflectance immediately after being taken out of the vacuum chamber after film formation, and the thin solid line represents the reflectance after 10 days. Both are very consistent and it can be seen that the change in optical properties over time is minimized. In addition, it is not necessary to change discharge conditions and the like because a desired effect can be exhibited by simply introducing water vapor without stopping the discharge process in which the film is formed. Furthermore, since the optical constants hardly change regardless of the presence or absence of the introduction of water vapor, both can be handled as optical thin films having uniform characteristics, and there is an advantage that the load during designing is not increased.

It is a figure explaining the film-forming apparatus used for the manufacturing method of the optical thin film by one Example. Represents the relationship between the film formation time and the set thin film deposition rate according to one embodiment. Represents the reflectance immediately after and 10 days after deposition of an optical thin film deposited without introducing water vapor according to one embodiment. According to one embodiment, the reflectance is shown immediately after and 10 days after the optical thin film formed by introducing water vapor into the outermost layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Decompression chamber 2 Substrate holder 3 Target 4 RF power supply 5 DC power supply 6 Argon and oxygen line 7 Water vapor introduction line

Claims (2)

  In the method of forming a metal compound thin film by depositing target sputtering particles on a substrate in a reduced pressure atmosphere, a sputtering gas and a reactive gas are introduced into the reduced pressure atmosphere during or after the formation of the thin film. A sputtering film forming method, wherein a thin film layer having a film quality different from that of the thin film is formed by introducing an additional gas while maintaining the introduction of the sputtering gas and the reactive gas.   2. The sputter deposition method according to claim 1, wherein argon is used as the sputtering gas, oxygen is used as the reactive gas, and water vapor is used as the additive gas.

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