Vacuum deposition source for vacuum deposition device and vacuum deposition method

Abstract

Provided is a vapor deposition source for a vacuum vapor deposition apparatus, the vapor deposition source being capable of vapor-depositing an aluminum film at a low cost and at a relatively high film deposition rate without compromising the function of suppressing, as much as possible, the occurrence of splash.　The vapor deposition source comprises a vapor deposition boat 3 installed in a vacuum chamber 1 and a power source Ps for supplying electricity thereto. A vapor deposition material composed of aluminum can be continuously or intermittently supplied to the vapor deposition boat heated by Joule heat to melt and evaporate the vapor deposition material. The vapor deposition boat is composed of ceramics and contains an additive metal material composed of at least one metal element of titanium, tantalum, zirconium, hafnium, or niobium, such that when the vapor deposition material is melted in the crucible, the metal element is incorporated into the melt of the vapor deposition material.

Description

[Technical Field]

[0001] The present invention relates to a vapor deposition source for a vacuum vapor deposition apparatus and a vacuum vapor deposition method, which include a crucible installed in a vacuum chamber and a heating means for heating the crucible, and which deposit an aluminum film on a substrate by continuously or intermittently supplying an aluminum vapor deposition material to the heated crucible and dissolving and evaporating the vapor deposition material in the crucible. [Background technology]

[0002] In recent years, aluminum (Al) films have been used in a wide variety of applications, including electrodes or functional thin films for display devices, wiring on printed circuit boards, and thin films for controlling optical properties and molecular permeability. Vacuum deposition systems are used to deposit Al films. The deposition source installed in the vacuum chamber of the vacuum deposition system typically includes a graphite crucible and a heating means for induction heating the deposition material filled in the crucible, or an evaporation boat and a power supply for supplying electricity to the boat. When depositing Al films on substrates using vacuum deposition systems, not only the quality of the Al film but also the deposition rate (productivity) are highly desired. In such cases, for example, a large current is passed through the evaporation boat, which is heated to high temperatures by the Joule heat generated by the current. However, if bumping (splash) occurs in the molten metal where the deposition material melts and spreads during deposition, high quality Al films cannot be maintained. One known cause of this bumping is the release of elements and compounds contained in the crucible as a gas phase.

[0003] Conventionally, a method for minimizing the occurrence of bumping when forming a gold (Au) film on a deposition target is known, for example, as described in Patent Document 1. In this method, the deposition material is made by adding at least one metal element selected from tantalum (Ta), zirconium (Zr), hafnium (Hf), and niobium (Nb) to Au in a predetermined weight ratio. The deposition material is then placed in a crucible made by sintering a high-melting-point metal such as tungsten or molybdenum, and when the Au is melted by heating the crucible, the metal element is contained in the molten Au. As a result, when impurities such as oxygen and oxides derived from tungsten or molybdenum are released into the molten metal in a gas phase, these impurity gases react with the metal elements that function as gettering materials, and the reaction products that are produced at this time have a vapor pressure that is much lower than that of Au at the heating temperature of the crucible during deposition (for example, 1 / 10,000 or less), making it possible to minimize the occurrence of bumping. Moreover, because the vapor pressure of the metal elements themselves at the heating temperature is much lower than that of Au, there is no problem in that the metal elements or reaction products get mixed into the deposited Au film, degrading its quality.

[0004] The evaporation boats used for depositing Al films are typically made by sintering raw materials containing boron nitride and titanium boride, which provides electrical conductivity to the crucible. It has been confirmed that when such an evaporation boat is heated to high temperatures (1200°C to 1500°C) by applying relatively large amounts of power without any evaporation material, elements contained in the crucible, such as boron, and impurities, such as oxygen, inevitably mixed in during crucible manufacturing, are released as gas phases. Therefore, even when depositing Al films at high deposition rates using a vacuum evaporation system, it is considered to be possible to suppress the occurrence of bumping by applying the above-mentioned conventional techniques.

[0005] On the other hand, to efficiently deposit Al films over a long period of time, the deposition material is formed into a wire shape with a predetermined diameter and supplied from above to a deposition boat, where it is melted. However, adding a metal element that functions as a gettering agent to the raw Al and then forming it into a wire shape to produce a specialized deposition material not only increases production costs but also lacks versatility. Furthermore, it is practically difficult to maintain a constant weight ratio of the metal elements throughout the entire length of the wire during the production of the deposition material. Therefore, when the metal element content in the molten metal is low, bumping in the molten metal may not be effectively suppressed. On the other hand, when the metal element content in the molten metal is high, slag may be generated in the molten Al, which causes fluctuations in the molten metal temperature (and therefore the deposition rate). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6697073 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above, an object of the present invention is to provide a vapor deposition source for a vacuum vapor deposition apparatus and a vacuum vapor deposition method that are capable of depositing an aluminum film at low cost and at a relatively high film formation rate without impairing the function of minimizing the occurrence of bumping. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a deposition source for a vacuum deposition apparatus that includes a crucible installed in a vacuum chamber and a heating means for heating the crucible, and that deposits an aluminum film on a deposition target by continuously or intermittently supplying a deposition material made of aluminum to the heated crucible and melting and evaporating the deposition material in the crucible. The deposition source is characterized in that the crucible is made of ceramic and contains an additive metal material made of at least one metal element selected from the group consisting of titanium, tantalum, zirconium, hafnium, and niobium, and that when the deposition material is melted in the crucible, the metal element is contained in the molten deposition material.

[0009] According to the present invention, a crucible is heated to a predetermined temperature range in a vacuum chamber under a vacuum atmosphere. Aluminum (Al) is continuously or intermittently supplied to the crucible from above. The Al melts and spreads within the crucible. The molten Al evaporates, resulting in the deposition (deposition) of an Al film. Since the molten Al also contains metal elements contained in the crucible, even if elements contained in the crucible or unavoidable impurities are released into the molten aluminum as a gas phase, these impurity gases react with the metal elements functioning as gettering materials. The reaction products produced by the reaction with the impurity gas have a much lower vapor pressure than Al at the heating temperature of the crucible during deposition. This, combined with the suppression of the formation of compounds with a higher vapor pressure than Al (e.g., boron oxide), ensures that bumping is minimized. Furthermore, since the ceramic crucible itself contains the additive metal, there is no need to use a special vapor deposition material as in the conventional example, and costs can be reduced.

[0010] Here, according to the inventors' extensive research, for example, when a metal foil made of the above-mentioned metal elements is laid on a ceramic deposition boat and heated to the above-mentioned temperature range by applying electricity to the deposition boat in a vacuum chamber under a vacuum atmosphere, the metal foil hardly melts. The inventors then discovered that when a deposition material is supplied to the deposition boat to melt Al, and the molten Al comes into contact with the metal foil, the metal foil melts and the metal elements dissolve into the molten metal without changing the pressure in the vacuum chamber or the heating temperature of the deposition boat. Therefore, in the present invention, the additive metal material is formed into a foil, wire, or granular shape and is laid in a crucible prior to deposition onto the deposition target so that the deposition material will come into contact with the molten metal when it melts and spreads. This allows for a simple configuration that minimizes bumping using an existing crucible. Furthermore, if the metal elements that react with the impurity gas become depleted due to repeated deposition on the deposition target over a long period of time, it is advantageous to simply place additional additive metal material in the crucible.

[0011] In the present invention, the additive metal material is preferably titanium, and the crucible is preferably a deposition boat formed by sintering raw materials containing boron nitride and titanium boride. According to the binary phase diagram of Al and Ti, the weight ratio of Ti dissolved in the molten Al is approximately 20 wt% at the maximum within the above temperature range. Therefore, the weight of the metal foil to be applied can be determined based on the volume of the molten Al during deposition. On the other hand, even if a larger weight of additive metal material is applied to prevent depletion of the metal element, no slag is generated in the molten Al. Furthermore, although titanium has a higher vapor pressure than other metal elements within the above temperature range, it has been confirmed that there is no problem of Ti or its reaction products (e.g., titanium oxide) being mixed into the deposited Al film, thereby degrading its quality. Furthermore, if Ti is selected as the metal element to be added, the reaction product generated by the reaction with Ti will be mainly titanium boride, a component of the evaporation boat. This will cover the surface of the evaporation boat where Al is wetted and spreads, thereby further suppressing the generation of compounds with a higher vapor pressure than Al (e.g., boron oxide), and further suppressing the occurrence of bumping.

[0012] Furthermore, in order to solve the above-mentioned problems, the vacuum deposition method of the present invention for depositing an aluminum film on an object to be deposited by heating a crucible placed in a vacuum chamber, continuously or intermittently supplying a deposition material made of aluminum into the crucible, and melting and evaporating the deposition material in the crucible, is characterized in that the crucible is made of ceramics, and the method includes a step of laying an additive metal material made of at least one metal element selected from titanium, tantalum, zirconium, hafnium, and niobium in the crucible prior to deposition on the object to be deposited, so that the additive metal material comes into contact with the molten metal when the deposition material melts and spreads. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view illustrating the configuration of an in-line vacuum deposition apparatus including a deposition source according to an embodiment of the present invention. [Figure 2] 2(a) is an enlarged plan view of the deposition source shown in FIG. 1, and FIG. 2(b) is an enlarged cross-sectional view thereof. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, with reference to the drawings, an embodiment of a deposition source BS for a vacuum deposition apparatus and a vacuum deposition method of the present invention will be described using as an example a case in which a crucible is a deposition boat, a heating means is a power source that applies electricity to the deposition boat to heat it with Joule heat, and an object to be deposited is a rectangular glass substrate (hereinafter referred to as "substrate Sg"), and a wire-shaped deposition material Em made of aluminum is continuously supplied and evaporated in a vacuum chamber under a vacuum atmosphere to deposit an aluminum (Al) film on the film formation surface of the substrate Sg. In the following, terms indicating directions such as up and down are based on Figure 1, which shows the installation position of the deposition source BS.

[0015] 1, the in-line vacuum deposition apparatus Es includes a vacuum chamber 1, to which a vacuum pump is connected via an exhaust pipe (not shown), and the inside of the vacuum chamber 1 can be evacuated to a predetermined pressure (vacuum level) to form a vacuum atmosphere. In this case, the inside of the vacuum chamber 1 during deposition is 1×10 -2 Pa~5×10 -4 The pressure in the vacuum chamber 1 is maintained within a pressure range of 10 Pa. A substrate transfer device 2 is provided in the space above the vacuum chamber 1. The substrate transfer device 2 has a carrier 21 that holds the substrate Sg with its lower surface, which serves as the film formation surface, open, and can transfer the carrier 21, and therefore the substrate Sg, in one direction within the vacuum chamber 1 at a predetermined speed by a drive device not shown. As a known substrate transfer device can be used, further description will be omitted. An evaporation source BS of this embodiment is provided in the space below the vacuum chamber 1, facing the substrate Sg being transferred in one direction.

[0016] Referring also to FIG. 2, the deposition source BS includes a ceramic deposition boat 3. The deposition boat 3 includes a boat body 31 having a recess 31a with a flat inner bottom surface, and the portions of the boat body 31 extending on both sides of the recess 31a in the longitudinal direction (the left-right direction in FIG. 1) form electrode mounting plate portions 31b. The deposition boat 3 is made by sintering raw materials containing boron nitride (BN) and titanium boride (TiB2), which provides electrical conductivity, as main components, in a predetermined weight ratio. In this case, a metal compound such as aluminum nitride can also be added to provide wettability. Since known sintering methods can be used, further explanation is omitted.

[0017] Two support bases 4, 4 made of an insulating material are installed on the inner surface of the lower wall 1 a of the vacuum chamber, spaced apart in the longitudinal direction. A pair of left and right electrode clamps 5, 5 made of a highly conductive metal such as copper are installed on the upper surfaces of the support bases 4, 4, respectively, and these clamps can detachably hold the deposition boat 3 by pressing the electrode mounting plate portions 31 b of the boat body 31 from both longitudinal sides. When the deposition boat 3 is held, the bottom surface of the boat body 31 is horizontal, and the deposition boat 3 is installed at a predetermined height from the inner surface of the lower wall 1 a of the vacuum chamber.

[0018] A material supplying means 6 is provided within the vacuum chamber 1 to continuously supply a wire-shaped deposition material Em to the recess 31a. The material supplying means 6 has a housing 61 installed on the side of the deposition shield 11 disposed within the vacuum chamber 1 facing away from the deposition source BS. The housing 61 houses a feed roller 62, a motor 63 that rotates and drives the feed roller 62, and a pair of upper and lower guide rollers 64, 64. A protruding pipe portion 61a is formed on the side wall of the housing 61 located on the deposition source BS side, and the housing 61 is installed within the vacuum chamber 1 so that the protruding pipe portion 61a passes through a through hole 11a formed in the deposition shield 11. A guide pipe 65 curved in a V-shape and having a predetermined length is attached to the tip of the protruding pipe portion 61a to guide the wire-shaped deposition material Em toward the recess 31a. The deposition material Em is aluminum having a purity appropriate for the quality of the aluminum film to be formed, formed into an outer diameter of 1 mm to 5 mm, and is wound around the feed roller 62 in advance. Then, the tip portion Em1 of the wire-shaped vapor deposition material Em wound around the payout roller 62 is pulled out and passed between a pair of upper and lower guide rollers 64, 64, and then inserted from the space inside the protruding tube portion 61a into the guide tube 65. The tip portion Em1 of the vapor deposition material Em protruding from the guide tube 65 is brought into contact with the inner bottom surface of the recess 31a from above in the longitudinal central region thereof, thereby preparing the wire-shaped vapor deposition material Em.

[0019] When an Al film is deposited on the underside of a substrate Sg in a vacuum chamber 1 under a vacuum atmosphere using the vacuum evaporation method of this embodiment, a power source Ps installed outside the vacuum chamber 1 applies current between the electrode mounting plates 31b, 31b via electrode clamps 5, 5. This heats the boat body 31 with Joule heat. The input power is set according to the film formation rate required to deposit an Al film on the underside of the substrate Sg. In this embodiment, the input power is set to a range of 4 kW to 6 kW so that the evaporation boat 3 can be heated to a temperature range of 1200°C to 1500°C, which allows for a high film formation rate. At temperatures below 1200°C, the wire-shaped evaporation material Em cannot be efficiently melted to achieve a high film formation rate. However, at temperatures above 1500°C, the ambient temperature becomes too high, causing the wire-shaped evaporation material Em to soften and clog the guide tube 65, potentially preventing smooth and continuous supply. When the evaporation boat 3 reaches a predetermined temperature, the motor 63 rotates the feed roller 62 to feed the wire-shaped evaporation material Em. As a result, the deposition material Em melts in the recess 31a, and the deposition material Em in the melted and spread molten Al evaporates, so that an Al film is deposited on the lower surface of the substrate Sg moving in one direction. The supply rate of the wire-shaped deposition material Em is set to, for example, a range of 2 g / min to 5 g / min (per unit area (cm) on the surface of the molten metal) depending on the film formation rate. 2 The supply rate per ) is set to be in the range of 0.1 g / min to 0.5 g / min, preferably 0.2 g / min.

[0020] When the deposition boat 3 is heated to the above temperature range, impurities such as boron contained in the deposition boat 3 and oxygen inevitably contained during the manufacturing of the deposition boat 3 are released as a gas phase. Therefore, it is necessary to prevent bumping due to the release of impurity gases during deposition. Therefore, in this embodiment, the additive metal material 7, which is at least one metal element selected from titanium, tantalum, zirconium, hafnium, and niobium, is formed into a foil having a thickness ranging from 0.1 mm to 0.5 mm. The foil-shaped additive metal material 7 is laid on the inner bottom surface of the recess 31a prior to deposition so as to come into contact with the molten metal when the deposition material Em melts and spreads upon heating of the deposition boat 3 (the step of laying the additive metal material 7 in the crucible in the vacuum deposition method of this embodiment). Specifically, two sheets of the additive metal material 7 are laid on both longitudinal sides of the inner bottom surface of the recess 31a, avoiding the peripheral area of ​​the inner bottom surface where the tip Em1 of the deposition material Em contacts (see FIG. 2). In this case, the weight ratio of each metal element that can be dissolved in molten Al in the above temperature range can be obtained from the binary phase diagram of Al and each metal element, and the weight of the foil-shaped added metal material 7 to be laid can be set based on the volume of molten Al in the recess 31a during deposition. However, it is preferable to lay the added metal material 7 at a weight greater than this in order to prevent depletion of the metal elements when deposition on the substrate Sg is repeated over a long period of time.

[0021] According to the above, when the wire-shaped deposition material Em is supplied from above to the recess 31a of the deposition boat 3 heated in the vacuum chamber 1 under a vacuum atmosphere, Al melts and spreads in the recess 31a. When this molten Al comes into contact with the foil-shaped additive metal material 7, the additive metal material 7 melts, and the metal element dissolves in the molten metal. As a result, even if impurities such as boron contained in the deposition boat 3 and unavoidably mixed oxygen are released as a gas phase into the molten metal due to heating, this impurity gas reacts with the metal element functioning as a gettering material. The reaction product generated by the reaction with the impurity gas has a much lower vapor pressure than Al as the deposition material Em in the above temperature range. This, combined with the suppression of the formation of compounds with a higher vapor pressure than Al (e.g., boron oxide), minimizes the occurrence of bumping. At this time, it is sufficient to lay the foil-shaped additive metal material 7 on the inner bottom surface of the recess 31a, and therefore there is no need to manufacture a wire-shaped deposition material Em specifically containing the metal element, and an existing material can be used, which reduces costs and also allows the use of an existing deposition boat 3. Furthermore, if the metal element that reacts with the impurity gas becomes depleted due to repeated deposition on the substrate Sg, it is sufficient to lay additional additive metal material 7 on the deposition boat 3.

[0022] Furthermore, even when titanium (Ti) was selected as the additive metal material 7 and a larger weight of the additive metal material 7 was added to prevent Ti depletion, no slag was observed in the molten Al, and although titanium as a metallic element has a higher vapor pressure than other metallic elements in the above temperature range, it was confirmed that there was no problem such as Ti or its reaction products (titanium oxide, etc.) being mixed into the deposited Al film and degrading its quality. Moreover, the reaction products generated by the reaction with Ti are mainly titanium boride, a component of the deposition boat 3, which covers the inner bottom surface of the recesses 31a where Al wets and spreads, thereby further suppressing the generation of compounds with a higher vapor pressure than Al (e.g., boron oxide), and thus further suppressing the occurrence of bumping.

[0023] To confirm the above effects, the following experiment was conducted using the vacuum deposition apparatus Es shown in Figure 1. A square stainless steel substrate measuring 200 mm on a side was attached directly above and a specified distance from the deposition boat 3 in the vacuum chamber 1. Al was continuously deposited for 4 hours under the following deposition conditions, and the amount of bumping was confirmed. Two types of deposition boats 3 were used: one made by mixing and sintering the main raw materials BN and TiB2 at a specified weight ratio (Boat 1), and the other made by mixing and sintering the main raw materials BN and TiB2 with the additive AlN at a specified weight ratio (Boat 2) (external dimensions: 38 mm x 150 mm x 9 mm thick).

[0024] Four types of additive metal material 7 were prepared: 1.5 g of Nb foil, 3.7 g of Ta foil, 1.0 g of Ti foil, and 1.9 g of Zr foil, and each was laid in advance in the recess 31a of the deposition boat 3. The deposition conditions were as follows: the power input to the deposition boat 3 was 5 kW (the heating temperature of the deposition boat 3 was approximately 1350°C); the aluminum deposition material Em had an outer diameter of 2 mm and was fed from the feed roller 62 at a feed rate of 3 g / min. The pressure inside the vacuum chamber 1 during deposition was 5 × 10 -3 The temperature was maintained at Pa.

[0025] Table 1 shows the measurement results of the number of bumps adhering to the stainless steel substrate at a size of 0.05 mm or more. The number of bumps adhering was measured using a 10x magnifying glass. First, when deposition was carried out without laying down the additive metal material 7, it was confirmed that more than 10,000 bumps adhered (comparative example). In contrast, it was confirmed that if the additive metal material 7 made of any metal element was laid down in advance, the adhesion of bumps could be significantly reduced, and in particular, in the case of relatively inexpensive Ti, bumps of 0.05 mm or more were not observed. [Table 1]

[0026] Next, the presence of metal elements Al, Nb, Ta, Ti, and Zr in the Al film was confirmed by XRF. As shown in Table 2, the presence of metal elements was below the detection limit, confirming that there was no contamination. [Table 2]

[0027] Although the above describes an embodiment of the present invention, various modifications are possible without departing from the scope of the technical concept of the present invention. In the above embodiment, a foil-shaped additive metal material 7 is laid in the recess 31a of the deposition boat 3 prior to deposition onto the substrate Sg so that the molten metal contains at least one metal element selected from titanium, tantalum, zirconium, hafnium, and niobium when the deposition material Em is melted in the deposition boat 3. However, the present invention is not limited to this. For example, the metal element may be sprayed onto the inner bottom surface of the recess 31a, avoiding the peripheral area of ​​the inner bottom surface of the recess 31a where the tip Em1 of the deposition material Em contacts. Furthermore, the deposition material Em may be linear or granular, shaped to a predetermined wire diameter or particle size. Furthermore, in the above embodiment, the deposition material Em is wire-shaped and supplied to the deposition boat 3. However, the present invention is not limited to this. For example, the present invention can be widely applied to a system in which the deposition material Em is granular and periodically (intermittently) added to a crucible. Furthermore, in the above embodiment, the crucible is described as an evaporation boat 3 made of ceramics, but the present invention is not limited to this, and can also be applied to a graphite crucible (especially one whose inner surface is coated with PBN) that is heated by induction heating. [Explanation of symbols]

[0028] BS...evaporation source for vacuum evaporation device, Em...evaporation material (aluminum wire), Es...vacuum evaporation device, Sg...substrate (evaporated object), 1...vacuum chamber, 3...evaporation boat (crucible), 7...additive metal material.

Claims

1. A vapor deposition source for a vacuum vapor deposition apparatus includes a crucible disposed in a vacuum chamber and a heating means for heating the crucible, and is configured to continuously or intermittently supply an aluminum vapor deposition material to the heated crucible, and melt and evaporate the vapor deposition material in the crucible to vapor-deposit an aluminum film on an object to be vapor-deposited, the vapor deposition source comprising: A deposition source for a vacuum deposition apparatus, characterized in that the crucible is made of ceramic and contains an additive metal material made of at least one metal element selected from the group consisting of titanium, tantalum, zirconium, hafnium, and niobium, which is placed in the crucible prior to deposition onto an object to be deposited so that the additive metal material will come into contact with the molten metal when the deposition material is supplied to a heated deposition boat and melts and spreads therein, and the metal element dissolves in the molten metal of the deposition material when the additive metal material comes into contact with the molten metal of the deposition material.

2. 2. The evaporation source for a vacuum evaporation apparatus according to claim 1, wherein the additive metal material is formed into a foil, wire or granule shape.

3. 3. The evaporation source for a vacuum evaporation apparatus according to claim 2, wherein the additive metal material is titanium, and the crucible is an evaporation boat made by sintering raw materials containing boron nitride and titanium boride.

4. A vacuum deposition method for depositing an aluminum film on a deposition target by heating a crucible placed in a vacuum chamber, continuously or intermittently supplying an aluminum deposition material to the crucible, and melting and evaporating the deposition material in the crucible, comprising: A vacuum deposition method using a ceramic crucible, comprising a step of laying in the crucible, prior to deposition on an object, an additive metal material formed into a foil, wire, or granule shape and made of at least one metal element selected from the group consisting of titanium, tantalum, zirconium, hafnium, and niobium, so that when the deposition material melts and spreads, the additive metal material comes into contact with the molten metal, and the metal element dissolves in the molten metal of the deposition material.

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