Vacuum film deposition apparatus and vacuum film deposition method

Abstract

To provide a vacuum film deposition apparatus capable of stably and continuously monitoring the film thickness of a predetermined thin film being even a low density thin film when depositing the thin film on a substrate Sg in a vacuum chamber 1 having a vacuum atmosphere.SOLUTION: Two film deposition sources 31 and 32 and film thickness monitors 51 and 52 are arranged in a vacuum chamber. When setting the scattering areas of film deposition materials discharged according to a predetermined cosine rule from respective film deposition sources to normal scattering areas Re1 and Re2 and setting a scattering area formed by overlapping the film deposition materials discharged according to the predetermined cosine rule from the two deposition sources to an overlapping scattering area Ce, arranging one film thickness monitor 51 in the normal scattering area and arranging the other film thickness monitor 52 in the overlapping scattering area, the second thickness monitor detects a film thickness on the basis of a difference with a film thickness detected by the first film thickness monitor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum film-forming apparatus and a vacuum film-forming method, and more particularly to an apparatus and method that enable stable detection of the film thickness of a so-called low-density thin film during film formation. [Background technology]

[0002] A vacuum deposition apparatus as a vacuum film forming apparatus is usually equipped with a film thickness monitor to detect the film thickness of a thin film formed on a substrate to be processed during deposition (film formation) or to feedback control a deposition source (e.g., the amount of heat generated by a heater) from the amount of deposition per unit time. Such a film thickness monitor generally uses a quartz oscillator (see, for example, Patent Document 1). This apparatus includes a quartz oscillator having excitation electrodes formed on both the front and back sides of a quartz substrate, an excitation means for applying an AC voltage of a predetermined frequency between the front excitation electrode and the back excitation electrode to excite the quartz oscillator by the potential difference, and a detection means for detecting the film thickness from the amount of change in resonance frequency associated with a change in the weight of the quartz oscillator.

[0003] In the above-mentioned film thickness monitor, when the film material discharged from the film source according to a predetermined cosine law adheres to the quartz oscillator vibrating at a predetermined vibration frequency, its mass increases and it becomes difficult to vibrate. In other words, the resonance frequency decreases with the increase in mass. Since there is a correlation between the change in resonance frequency and the change in weight at this time, the mass of the attached film material can be determined from the change in resonance frequency. Then, the film thickness (Å, nm) on the surface of the quartz oscillator is calculated based on the adhesion area of ​​the film material to the quartz oscillator and the density of the attached film material, and this film thickness is converted into the film thickness on the substrate, thereby continuously detecting (monitoring) the film thickness of the thin film, or detecting the film formation rate based on this film thickness (Å / sec). At this time, the film thickness monitor is usually provided with a correction coefficient experimentally determined in advance according to the film material so that the film thickness can be stably monitored regardless of the difference in the film material.

[0004] Incidentally, it is known that some film-forming materials, such as low-molecular-weight organic materials, have a relatively low film density when formed on the surface of a substrate to be processed, and the film density varies depending on the crystallinity (crystal growth direction) even when formed to the same film thickness (hereinafter, these are also referred to as "low-density thin films"). When forming such a film-forming material to a thickness of 10 Å or less, for example 1 Å, even if an attempt is made to monitor the film thickness by attaching it to the quartz crystal oscillator of a film thickness monitor, there are frequent cases where the film thickness is detected as thinner or thicker than the actual film thickness, resulting in a false detection that makes it impossible to stably monitor the film thickness. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-117397 A Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, an object of the present invention is to provide a vacuum film-forming apparatus and a vacuum film-forming method that enable stable monitoring of the film thickness even when forming a low-density thin film. [Means for solving the problem]

[0007] In order to solve the above problems, the vacuum film formation apparatus of the present invention for forming a predetermined thin film on a substrate to be processed in a vacuum chamber in a vacuum atmosphere comprises at least two film formation sources arranged in the vacuum chamber and at least two film thickness monitors for monitoring the film thickness of the thin film, each film thickness monitor having a quartz oscillator with excitation electrodes formed on both the front and back sides of a quartz substrate, and a detection means for applying a voltage between the front excitation electrode and the back excitation electrode to excite the quartz oscillator by the potential difference, and detecting the film thickness based on the amount of change in resonance frequency associated with a change in weight of the quartz oscillator, characterized in that the scattering region of the film formation material discharged from each film formation source according to a predetermined cosine law is defined as a normal scattering region, and the scattering region where the film formation material discharged from any two deposition sources according to the predetermined cosine law overlaps with each other is defined as an overlapping scattering region, a first film thickness monitor selected from each film thickness monitor is disposed in the normal scattering region and a second film thickness monitor is disposed in the overlapping scattering region, and the second film thickness monitor detects the film thickness based on the difference with the film thickness detected by the first film thickness monitor.

[0008] In addition, in order to solve the above-mentioned problems, the vacuum film formation method of the present invention for forming a predetermined thin film on a substrate to be processed in a vacuum chamber in a vacuum atmosphere includes at least two film formation sources arranged in the vacuum chamber and at least two film thickness monitors that detect the film thickness of the thin film based on the amount of change in resonant frequency associated with a change in weight of a quartz oscillator, and is characterized in that the scattering area of ​​the film formation material released from each film formation source according to a predetermined cosine law is defined as a normal scattering area, and the scattering area where the film formation material released from any two film formation sources according to the predetermined cosine law overlaps is defined as an overlapping scattering area, and the film thickness of the thin film is detected by a first film thickness monitor arranged in the normal scattering area, and the second film thickness monitor arranged in the overlapping scattering area detects the film thickness based on the difference from the film thickness detected by the first film thickness monitor.

[0009] According to the above, for example, a film material (hereinafter also referred to as "first film material") discharged from one of the deposition sources into the normal scattering region is assumed to have a small change in film density on the surface of the attached quartz crystal oscillator and a correlation between the change in resonance frequency and the change in weight, and is co-deposited on a second quartz crystal oscillator arranged in the overlapping scattering region. As a result, even if a low-density thin film is formed using a film material (hereinafter also referred to as "second film material") discharged from another deposition source, the mass of the attached film material can be determined from the change in resonance frequency. Then, the mass of each second film material can be determined from the difference between the mass of the first film material detected by the first film thickness monitor. As a result, it becomes possible to stably monitor the film thickness. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating a vacuum deposition apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a graph showing a deposition rate measured using a film thickness monitor. [Diagram 3] FIG. 13 is an enlarged view showing a main part of a vacuum deposition apparatus according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, with reference to the drawings, an embodiment of the vacuum film formation apparatus and the vacuum film formation method of the present invention will be described by taking as an example a case where a substrate to be processed is a glass substrate (hereinafter referred to as "substrate Sg"), a film formation source is an evaporation source for vacuum evaporation, and two of these evaporation sources are used to form a predetermined thin film on the substrate Sg by co-evaporation in a vacuum chamber in a vacuum atmosphere. In the following, terms indicating directions such as up and down are based on Figure 1, which shows the installation posture of the vacuum evaporation apparatus DM.

[0012] Referring to FIG. 1, a vacuum deposition apparatus DM as a vacuum film forming apparatus includes a vacuum chamber 1, and although not shown or described, a vacuum pump is connected to the vacuum chamber 1 via an exhaust pipe, and a vacuum atmosphere can be formed by evacuating the vacuum chamber 1 to a predetermined pressure. A substrate transport device 2 is provided on the upper part of the vacuum chamber 1. The substrate transport device 2 has a carrier 21 that holds a substrate Sg with its lower surface as a film forming surface open, and can move the carrier 21 and thus the substrate Sg in one direction in the vacuum chamber 1 at a predetermined speed by a driving device not shown. A known device can be used as the substrate transport device 2, so further description will be omitted. Two deposition sources 31 and 32 as film forming sources are provided on the bottom surface of the vacuum chamber 1 facing the substrate Sg.

[0013] Each deposition source 31, 32 has the same structure and includes a crucible 31 that contains different film forming materials 41, 42. The crucible 31 has a bottomed cylindrical outline with an opening at the top in the vertical direction, and is made of a material with good thermal conductivity and high melting point, such as molybdenum, titanium, stainless steel, or carbon, and can be filled with, for example, powdered film forming materials 41, 42 from the opening at the top. A heating means 32 made of a known device such as a sheath heater or a lamp heater is provided around each crucible 31. When the film forming materials 41, 42 contained in each crucible 31 are heated by the heating means 32 in the vacuum chamber 1 in a vacuum atmosphere, the sublimated or evaporated film forming materials 41, 42 are discharged from the top opening of each crucible 31 according to a predetermined cosine law. At this time, the scattering regions of the film forming materials 41, 42 respectively released from the first and second evaporation sources 31, 32 in accordance with a predetermined cosine law are defined as normal scattering regions Re1, Re2, and the overlapping scattering regions of the film forming materials 41, 42 respectively released from the first and second evaporation sources 31, 32 in accordance with a predetermined cosine law are defined as overlapping scattering regions Ce.

[0014] The film forming materials 41, 42 are appropriately selected according to the thin film to be formed on the substrate Sg, and metal materials or organic materials are used. Some of the film forming materials 41, 42, such as allylamine (low molecular weight organic material), tend to have a relatively low film density when formed on the surface of the substrate Sg, and the film density varies depending on the crystallinity (direction of crystal growth) even when the film is formed to the same thickness (low density thin film). Even if one of the film forming materials 41, 42 becomes such a low density thin film (hereinafter, this is referred to as the "second film forming material 42"), first and second film thickness monitors 51, 52 are provided at predetermined positions in the vacuum chamber 1 so that the film thicknesses of the film forming materials 41, 42 when vapor-deposited on the surface of the substrate Sg can be stably and continuously monitored. In this case, the other film formation material (hereinafter referred to as the "first film formation material 41"), when formed on the surface of the substrate Sg, does not matter as long as the film density does not change significantly depending on its crystallinity (direction of crystal growth) even if the film is formed to the same thickness, and there is a correlation between the change in resonant frequency and the change in weight.

[0015] Each film thickness monitor 51, 52 has the same structure and includes a sensor head 51 installed in the vacuum chamber 1 and a controller 52 as a detection means installed outside the vacuum chamber 1. The sensor head 51 is not shown in detail because a known sensor head can be used, but it has a holder 54 on which a plurality of quartz crystal oscillators 53 are installed at intervals on the same circumference and which is rotated by a stepping motor. A mask body 55 is installed on the holder 54 so as to cover each of the quartz crystal oscillators 53, and a film formation window 55a is opened at a predetermined position of the mask body 55 so as to face one of the quartz crystal oscillators 53. The quartz crystal oscillator 53 has excitation electrodes 53b, 53c formed on both the front and back sides of a quartz crystal substrate 53a.

[0016] The controller 52 includes an excitation circuit 52a that alternately applies an AC voltage of a predetermined frequency between the front excitation electrode 53b and the back excitation electrode 53c to excite the crystal oscillator 53 by the potential difference, and a control unit 52b that controls the operation of a frequency detector that measures the resonance frequency and the excitation circuit, and detects the amount of change in the resonance frequency measured by the frequency detector. For example, even when a film is formed at a deposition rate in the range of 0.1 Å / s to 10 Å / s, the frequency of the AC voltage is set in the range of 4 to 100 MHz so that the deposition rate can be stably and continuously monitored. For example, when the measured resonance frequency changes beyond a predetermined range as the thickness of the film-forming materials 41 and 42 increases, it is determined that the crystal oscillator 53 has reached the end of its life, and the stepping motor rotates the holder 54 again until the next crystal oscillator 53 faces the film-forming window 55a.

[0017] The vacuum deposition apparatus DM includes a control unit Cb including a computer, a memory, a sequencer, and the like, and controls the operation of, for example, the heating means 32 and the vacuum pump. The control unit Cb and the control unit 52b of the controller 52 are connected via a communication line, and the amount of change in the resonance frequency calculated (detected) by the control unit 52b is output to the control unit Cb. The control unit Cb can continuously monitor the thickness of the first film-forming material 41 by, for example, calculating the thickness of the film on the surface of the quartz oscillator 53 using a known method from the amount of change in the first film-thickness monitor 51 and converting this thickness into the thickness on the substrate Sg. In this embodiment, the first film-thickness monitor 51 is disposed in the normal scattering region Re1 (region excluding the overlapping scattering region Ce), and the second film-thickness monitor 52 is disposed in the overlapping scattering region Ce.

[0018] When the vacuum film formation method of this embodiment is carried out to monitor the film thickness of the second film formation material 42 when it is evaporated on the surface of the substrate Sg, the control unit Cb calculates the film thickness on the surface of the quartz crystal oscillator 53 from the amount of change in the second film thickness monitor 52. A difference is taken between this calculated film thickness and the amount of change in the first film thickness monitor 51, and the film thickness on the surface of the quartz crystal oscillator 53 is calculated (detected) based on this difference, and this film thickness is converted into a film thickness on the substrate Sg, thereby making it possible to stably and continuously monitor the film thickness when the second film formation material 42 is evaporated on the surface of the substrate Sg.

[0019] According to the above embodiment, by co-evaporating the first film forming material 41 and the second film forming material 42 on the second film thickness monitor 52, even if the film density of the second film forming material 42 is relatively small when the second film forming material 42 is formed on the surface of the substrate Sg, the film thickness can be stably and continuously monitored. In the experiment by the inventor, it was confirmed that the film formation rate of the first film forming material 41 and the second film forming material 42 could also be stably and continuously monitored as shown in FIG. 2. In FIG. 2, the dotted line indicates the deposition rate of the first film forming material 41, and the dashed line indicates the deposition rate when the first film forming material 41 and the second film forming material 42 are co-evaporated. The solid line indicates the deposition rate of the second film forming material 42 obtained by carrying out the vacuum deposition method of the present embodiment.

[0020] Although the embodiment of the present invention has been described above, various modifications are possible without departing from the scope of the technical concept of the present invention. In the above embodiment, the vacuum deposition apparatus DM having the deposition sources 31 and 32 has been described as an example of a vacuum film forming apparatus, but the present invention can be widely applied to cases where a film is formed by a sputtering method, an ion plating method, or the like. In addition, in the above embodiment, the deposition sources 31 and 32 are two, and a predetermined thin film is formed on the surface of the substrate Sg by co-deposition, but the present invention is not limited to this. For example, when only the second film forming material 42 is formed on the surface of the substrate Sg, a deposition source of the first film forming material 41 may be installed in the vacuum chamber 1, and an anti-adhesion plate (not shown) for preventing adhesion to the substrate Sg may be provided so that the first film forming material 41 does not adhere to the substrate Sg (does not contribute to film formation), but adheres to the second film thickness monitor 52, so that the thickness of the thin film made of the second film forming material 42 can be stably and continuously monitored.

[0021] On the other hand, in the case where a predetermined thin film is formed on the surface of the substrate Sg by co-evaporation by evaporating the third film material 43 in addition to the first film material 41 and the second film material 42, as shown in Fig. 3, a restricting means 6 that allows the first film material 41 and the second film material 42 to scatter from the deposition sources 31, 32 to the surface of the substrate Sg but restricts the third film material 43 from the deposition source 33 to the surface of the substrate Sg may be provided on the deposition source 31, 32, 33 side of the second film thickness monitor 52 arranged in the overlapping scattering region Ce. This allows only the first film material 41 and the second film material 42 to be selectively attached to the second film thickness monitor 52 with a simple configuration, and the film thickness of the second film material 42 can be monitored in the same manner as described above. [Explanation of symbols]

[0022] DM...vacuum deposition apparatus (vacuum film formation apparatus), Sg...substrate to be processed (substrate), 1...vacuum chamber, 31, 32...evaporation source (film formation source), 41, 42...film formation material, 51, 52...film thickness monitor, 52...controller (detection means), 53...quartz oscillator, 53a...quartz substrate, 53b...front excitation electrode, 53c...rear excitation electrode, Re1, Re2...normal scattering area, Ce...overlapping scattering area.

Claims

1. A vacuum deposition apparatus for depositing a predetermined thin film on a substrate to be processed in a vacuum chamber having a vacuum atmosphere, At least two film formation sources are disposed in a vacuum chamber, and at least two film thickness monitors are provided for monitoring the film thickness of the thin film; Each film thickness monitor has a quartz crystal unit having excitation electrodes formed on both the front and back sides of a quartz crystal substrate, and a detection means for applying a voltage between the front excitation electrode and the back excitation electrode to excite the quartz crystal unit by the potential difference, and detecting the film thickness based on the amount of change in resonance frequency accompanying the weight change of the quartz crystal unit, A vacuum film forming apparatus characterized in that a scattering region of film forming material discharged from each film forming source in accordance with a predetermined cosine law is defined as a normal scattering region, and a scattering region where film forming materials discharged from any two evaporation sources in accordance with the predetermined cosine law overlap each other is defined as an overlapping scattering region, a first film thickness monitor selected from each film thickness monitor is disposed in the normal scattering region and a second film thickness monitor is disposed in the overlapping scattering region, and the second film thickness monitor is configured to detect a film thickness based on a difference from the film thickness detected by the first film thickness monitor.

2. 1. A vacuum film forming method for forming a predetermined thin film on a substrate to be processed in a vacuum chamber having a vacuum atmosphere, comprising: At least two film formation sources are arranged in a vacuum chamber, and at least two film thickness monitors are arranged to detect the film thickness of the thin film based on the amount of change in resonance frequency caused by a change in weight of a quartz crystal oscillator; A vacuum film forming method characterized in that a scattering area of ​​film forming material released from each film forming source in accordance with a predetermined cosine law is defined as a normal scattering area, and a scattering area where film forming material released from any two film forming sources in accordance with the predetermined cosine law overlaps is defined as an overlapping scattering area, a first film thickness monitor arranged in the normal scattering area detects the thickness of the thin film, and a second film thickness monitor arranged in the overlapping scattering area detects the thickness of the thin film based on the difference from the film thickness detected by the first film thickness monitor.

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