JP2015133401A - Film deposition method and film deposition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deposit on a metal surface, a film of a barrier layer having an improved cutoff function.SOLUTION: A film deposition method includes a step of depositing on a metal surface, a film of a barrier layer by plasma atomic layer deposition using oxygen gas and gaseous starting material forming an oxide film by reacting with oxygen plasma. In at least an initial stage of the film deposition step, the oxygen plasma containing hydrogen atoms in a composition is used.

Description

  The present invention relates to a film forming method and apparatus for forming a barrier layer on a metal surface.

  In recent years, LEDs (Light Emitting Diodes) have been used for light emitting devices in various fields. The LED chip is die-bonded on a substrate, the LED chip and the electrode are electrically connected by a wire, and the periphery is covered with a translucent resin that protects the LED chip.

  In order to improve the light extraction efficiency of the LED chip, a silver film may be used for applications such as a reflective film, a reflective electrode film, an electrode film, or a wiring. However, when a silver film is used, silver sulfidation becomes a big problem. Although the LED chip is sealed with a translucent resin, hydrogen sulfide or the like in the atmosphere enters through the resin, and the silver film is sulfided to become black, so that the light output of the LED is lowered. For example, Patent Document 1 discloses that a barrier layer is formed on a silver film for the purpose of preventing blackening of the silver film.

Although not related to the LED chip, for example, Patent Document 2 discloses forming a coating that protects the discoloration of silver by using an atomic layer deposition (ALD) method. Non-Patent Document 1 describes the ALD film formation of Al ₂ O ₃ at a low temperature. Furthermore, a technique called plasma atomic layer deposition (hereinafter referred to as “PE-ALD”) in which an organic metal gas and oxygen plasma are reacted to form an oxide film is also known.

JP 2010-239043 A Special table 2009-525406 gazette

M.M. D. Groner, F.A. H. Fabregette, J.A. W. Elam, and S.M. M.M. George, “Low-Temperature Al 2 O 3 Atomic Layer Deposition”, Chem. Mater. 2004, 16, 639-645

  In Patent Document 1, a metal oxide film is formed as a barrier layer so as to cover the entire silver. As disclosed in the example of Patent Document 1, by forming a metal oxide film (barrier layer) by a sputtering method, it is possible to reduce permeation of a sulfide gas such as hydrogen sulfide as compared with a resin film. Become. However, the barrier layer formed by sputtering cannot completely block the permeation of sulfide gas, and it is inevitable that the silver film becomes black over time.

  For the purpose of improving the barrier property, it is conceivable to form a barrier layer at a high temperature. Even in the ALD method described in Patent Document 2, only a low-density film can be obtained at a low temperature as shown in Non-Patent Document 1, so that it is necessary to process at a high temperature in order to obtain a stable film. is there. However, since the LED cannot withstand a high temperature environment, formation of a barrier layer by high temperature film formation on the LED chip is not realistic.

  Although the metal oxide film can be formed at a relatively low temperature by using reactive sputtering, there is a problem that the silver film is oxidized by oxygen gas introduced during the film formation. If the silver film is blackened due to the formation of a barrier layer for the purpose of preventing blackening, there is no point in forming the barrier layer. Similarly, PE-ALD using oxygen plasma cannot avoid oxidation of the silver film.

  In order to solve the above problems, the present inventor forms a first barrier layer by ALD using the source gas and water shown in Patent Document 1 and Non-Patent Document 1, and thereafter, the source gas and A method and apparatus for forming a second barrier layer by oxygen plasma was invented, and a patent application was filed earlier (Japanese Patent Application No. 2013-096384, unpublished at the time of filing this application, hereinafter referred to as “previous application”).

  An object of the present invention is to provide a new film forming method and apparatus capable of forming a barrier layer having a high blocking function, and an electronic device on which such a barrier layer is formed.

  According to a first aspect of the present invention, the method includes a step of forming a barrier layer on the surface of a metal by plasma atomic layer deposition using a source gas that reacts with oxygen plasma to form an oxide film and oxygen gas. There is provided a film forming method characterized by using, as an oxygen plasma, one containing a hydrogen atom in the composition (hereinafter referred to as “hydrogen-containing oxygen plasma”) at least in the initial stage of the film forming step.

  This film forming method is particularly effective when the metal to be formed is silver Ag, or at least a part of which is silver Ag. By adjusting the amounts of oxygen and hydrogen during film formation, While preventing silver blackening, a barrier layer can be formed on the surface. In addition, a barrier layer having a high blocking function can be formed on a metal other than silver while preventing oxidation of the metal. Further, since the temperature during film formation can be suppressed to a relatively low temperature, deterioration of the resin can be suppressed even when a resin package is used.

In order to generate hydrogen-containing oxygen plasma, it is desirable to use hydrogen gas H ₂ in addition to oxygen gas. Water H ₂ O can also be used.

As the source gas, an organometallic compound can be used. For example, a barrier layer of aluminum oxide Al ₂ O ₃ can be formed using an organoaluminum compound such as trimethylaluminum (TMA). Further, by using an organic titanium compound as the raw material gas can deposit a titanium oxide TiO ₂ barrier layer. By using an organic silicon compound as a source gas, a silicon oxide SiO ₂ barrier layer can be formed.

  According to the second aspect of the present invention, a film forming chamber for storing an object having a metal layer provided on at least a part of its surface, an exhaust device for maintaining the film forming chamber in a vacuum atmosphere, and a reaction with oxygen plasma. A gas introducing means for introducing a source gas for forming an oxide film and an oxygen gas as a reaction gas into the film forming chamber; a hydrogen introducing means for introducing a material containing a hydrogen atom in the composition into the film forming chamber; A high-frequency power source that applies high-frequency power to generate plasma, and a control unit that controls the gas introduction unit, the hydrogen introduction unit, and the high-frequency power source, and the control unit controls the gas introduction unit to supply a source gas to the film formation chamber And oxygen gas are introduced, and the high-frequency power source is controlled to control the deposition of the barrier layer on the surface of the metal layer by plasma atomic layer deposition, and at least at the initial stage of the deposition control With the introduction of oxygen gas into the film forming apparatus is provided which is characterized in that performs a control process for introducing a material containing hydrogen atoms in the composition to control the hydrogen introducing means into the deposition chamber.

  According to the present invention, a barrier layer having a high blocking function can be formed, and an electronic device provided with such a barrier layer can be provided.

It is a figure which shows the structure of the ALD apparatus which concerns on the 1st Embodiment of this invention. 2 is a flowchart showing a flow of film formation control by a control unit of the ALD apparatus shown in FIG. 1. It is a figure which shows the structure of the ALD apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the example of a measurement result of the water-vapor-permeation rate of the barrier layer from which the film-forming method differs. It is a figure which shows the example of a measurement result of the reflectance of Ag in which the flow rate ratio of oxygen gas and hydrogen gas was changed and the barrier layer was formed. It is sectional drawing of the electronic device which has a barrier layer formed with the apparatus shown in FIG. 1 or FIG.

FIG. 1 is a diagram showing a configuration of an ALD apparatus as a film forming apparatus according to the first embodiment of the present invention. Hereinafter, it will be explained as an example the case of forming aluminum oxide Al ₂ O ₃ as a barrier layer on the silver film.

An ALD apparatus shown in FIG. 1 includes a film formation chamber 1, a substrate 2 to be formed (including a silver film on a film formation surface), an exhaust device 3, a gas shower 4, and a high-frequency power source for generating plasma. 5, air supply units 6 to 9, and control unit 10. The film forming chamber 1 accommodates a substrate 2 that is an object provided with a metal layer on at least a part of its surface. The exhaust device 3 is connected to the film forming chamber and maintains the inside of the film forming chamber 1 in a vacuum atmosphere. The high frequency power source 5 applies high frequency power to the film forming chamber 1 to generate plasma. The gas supply units 6 and 7 are connected to the film forming chamber 1 and introduce gas into the film forming chamber 1 for introducing a source gas that reacts with oxygen plasma to form an oxide film and an oxygen O ₂ gas as a reactive gas. Configure the means. The air supply unit 8 is connected to the film forming chamber 1 and constitutes hydrogen introduction means for introducing a material containing hydrogen atoms in the composition into the film forming chamber 1. The air supply unit 9 is connected to the film forming chamber 1 and introduces an inert gas into the film forming chamber 1. In this embodiment, the source gas is trimethylaluminum (TMA), and hydrogen H ₂ is used as a material containing hydrogen. For example, argon is used as the inert gas. The control unit 10 includes a CPU, a RAM, a ROM, and the like, and controls the overall operation of the ALD apparatus including the high frequency power supply 5 and the intake units 6 to 9.

  The gas shower 4 is disposed to face the substrate 2 and is connected to the high frequency power source 5. By the gas shower 4 facing the film formation target, a gas flow can be evenly generated with respect to the film formation target surface. Further, plasma is generated inside the film forming chamber 1 by applying high frequency power to the gas shower 4. In the embodiment shown in FIG. 1, the film formation chamber 1 and the substrate 2 are grounded. However, a new high frequency power source may be provided to apply high frequency power to the substrate 2.

  The intake section 6 is connected to a supply source of TMA that is a raw material gas. The intake section 7 is connected to a supply source of oxygen gas that is a reaction gas. The intake unit 8 is connected to a hydrogen supply source. The intake section 9 is connected to an argon supply source that is an inert gas. Source gas, reaction gas, hydrogen gas, and inert gas are all supplied from the gas shower 4 into the film forming chamber 1. The supply and stop of the source gas is performed by opening / closing the intake section 6.

  The control unit 10 controls the air supply units 6 and 7 to introduce the source gas and the oxygen gas into the film forming chamber, and also controls the high frequency power source 5 to barrier the metal layer surface of the substrate 2 by plasma atomic layer deposition. Control to form a layer is executed. Further, the control unit 10 controls the air supply unit 8 with the introduction of oxygen gas into the film forming chamber 1 at least in the initial stage of the film forming control so that the material containing hydrogen atoms in the composition is formed in the film forming chamber. The control introduced to 1 is executed. In these controls, the control unit 10 transmits signals to the air supply units 6 to 9 and the high frequency power source 5 to control the application time of high frequency power and the timing of gas supply.

Next, the film formation process of a barrier layer is demonstrated. First, the substrate 2 is set, the air supply unit 6 and the air supply unit 9 are opened, and TMA which is a source gas containing Al and argon as an inert gas are introduced into the film forming chamber 1. In this embodiment, the substrate 2 is heated to 120 ° C. After the TMA molecules are adsorbed on the surface of the substrate 2, the intake portion 6 is closed and the source gas is purged. Thereafter, the intake portions 7 and 8 are opened, and oxygen gas and hydrogen gas are supplied into the film forming chamber 1. Next, high frequency power is applied to the gas shower 4 to generate oxygen plasma containing active hydrogen (hydrogen-containing oxygen plasma), and the TMA molecules of the substrate 2 are oxidized to form Al ₂ O ₃ . By containing hydrogen radicals in the oxygen plasma, the silver film is not blackened and a dense film having a high barrier function can be formed. The oxidation of TMA molecules is controlled by the application time of high frequency power. After the intake section 7 is closed and the oxidizing gas and the hydrogen gas are purged from the film forming chamber 1, the introduction of the source gas, the purge, the oxidizing gas and the hydrogen gas are continued until the desired thickness is obtained while the intake section 9 is kept open. The introduction, high-frequency electrode application, and purge cycles are repeated and continued.

  FIG. 2 is a flowchart showing a control flow of the control unit 10 in the barrier layer forming process.

When there is an instruction to start film formation from the operator, the control unit 10 instructs the air supply units 6 and 9 to introduce the source gas and the inert gas into the film formation chamber 1 (steps S1 and S2). In FIG. 2, the air supply unit 9 is instructed before the air supply unit 6 in order to clarify the loop in the flowchart. The timing of the instructions to the air supply units 6 and 9 may be simultaneous, or the air supply unit 6 may be first. Subsequently, after the time until the TMA molecules are adsorbed on the surface of the substrate 2 has elapsed, the control unit 10 instructs the intake unit 6 to stop supplying gas (step S3). Subsequently, the control unit 10 instructs the intake units 7 and 8 to supply oxygen gas and hydrogen gas into the film forming chamber 1 (step S4). Next, the control unit 10 turns on the high frequency power source 5 and applies high frequency power to the gas shower 4 (step S5). As a result, the TMA molecules of the substrate 2 are oxidized to form Al ₂ O ₃ . Subsequently, the control unit 10 instructs the intake units 7 and 8 to stop supplying oxygen gas and hydrogen gas (step S6). Thereby, oxygen gas and hydrogen gas are purged from the film forming chamber 1. The control unit 10 repeats the processes in steps S2 to S6 until a desired film thickness is obtained (step S7). When the desired film thickness is obtained, the control unit 10 instructs the air supply unit 9 to stop supplying the inert gas (step S8), and the film formation control ends.

  According to the present embodiment, the film thickness can be accurately controlled by opening / closing the intake portions 6 to 9 and applying time of the high frequency power. Moreover, even when the film formation surface of the substrate 2 is not a flat surface but has an uneven surface, the film is well-fitted and a uniform film can be formed. Here, the introduction of hydrogen gas into the film formation chamber 1 is performed every time the oxygen gas is introduced, but it may be performed only at the initial stage of film formation.

  In the above description, silver has been described as an example of the target for forming the barrier layer. However, a similar barrier layer is formed on other oxidizable or corrosive metals, and an oxidizing gas or a corrosive gas is used. It can block well.

  In the above description, aluminum oxide is formed as the barrier layer, but a metal oxide film such as titanium oxide or silicon oxide may be formed. The source gas is not limited to trimethylaluminum (TMA) and can be appropriately selected according to the target barrier layer. Further, the inert gas is not limited to argon, and for example, nitrogen may be used.

  In order to set the substrate 2 in the film formation chamber 1, the substrate 2 is carried into the film formation chamber 1 while maintaining the vacuum atmosphere in the film formation chamber 1 using a transfer device (not shown). Alternatively, the substrate 2 may be manually carried into the film formation chamber 1 and installed, and then the inside of the film formation chamber 1 may be evacuated to a predetermined degree of vacuum.

  FIG. 3 is a diagram showing a configuration of an ALD apparatus according to the second embodiment of the present invention. The ALD apparatus includes a film forming chamber 20, a substrate 2 to be formed, an exhaust device 3, a high frequency coil 21, a high frequency power source 5 for generating plasma, air supply units 6 to 9, and a control unit 10. And comprising. The air supply units 6 to 9 and the exhaust device 3 are connected to the film forming chamber 1.

  The ALD apparatus shown in FIG. 1 generates capacitively coupled plasma in order to form a barrier layer. On the other hand, the ALD apparatus shown in FIG. 3 arranges the coil 21 instead of the gas shower 4 as a high frequency electrode and generates inductively coupled plasma. In other words, the present embodiment can form a barrier layer in substantially the same film formation process as that of the first embodiment, except that the plasma generation method is different.

FIG. 4 is a diagram showing an example of measurement results of water vapor permeability of barrier layers with different film forming methods. The vertical axis represents the water vapor transmission rate. As the barrier layer, an Al ₂ O ₃ film having a thickness of 20 nm on a 100 μm thick PET (Polyethylene terephthalate) film (one surface) is used. As a film formation method,
(1) ALD using source gas and water (referred to as “H2O-ALD”),
(2) PE-ALD (referred to as “PE-ALD (O2)”) using source gas and oxygen plasma,
(3) PE-ALD (referred to as “PE-ALD (O2 / H2)”) using source gas and hydrogen-containing oxygen plasma,
(4) A method of forming a film by PE-ALD using a source gas and hydrogen-containing oxygen plasma, and then forming a film using PE-ALD using a source gas and oxygen plasma (referred to as “PE-ALD (O2 / H2 → O2)”).
The following four types were used. For comparison, a case without a barrier layer is also shown (shown as “PET” in the figure).

As shown in FIG. 4, the water vapor transmission rate of PET without a barrier layer is 6.04 g / m ² · day, whereas the water vapor transmission rate is 0.47 g / m ² by providing a barrier layer of H 2 O-ALD. It decreases to m ² · day. Furthermore, in the barrier layer made of PE-ALD (O2), the water vapor transmission rate is 0.09 g / m ² · day, and in PE-ALD using hydrogen gas, the water vapor transmission rate is 0.08 g / m ² · day. It has become. No difference in water vapor transmission rate was observed between PE-ALD (O2 / H2) and PE-ALD (O2 / H2-> O2). By performing PE-ALD while reacting with a hydrogen-containing oxygen plasma, the barrier exhibits an excellent barrier property against water vapor as compared to an Al ₂ O ₃ barrier layer having the same thickness formed by another method. It can be seen that a layer is obtained. The measurement results shown in FIG. 4 do not indicate the barrier property against sulfur gas such as hydrogen sulfide. However, it is considered that the same tendency exists for gases other than water vapor.

FIG. 5 is a diagram showing an example of measurement results of the reflectance of Ag in which a barrier layer is formed by changing the flow rate ratio of oxygen gas and hydrogen gas. The vertical axis represents the reflectance at a wavelength of 460 nm, and the horizontal axis represents the flow ratio of oxygen gas to hydrogen gas. The total flow rate of oxygen gas and hydrogen gas was 200 sccm, and an Al ₂ O ₃ barrier layer was formed to a thickness of 25 nm. FIG. 5 also shows the reflectance (shown as “2Step” in the figure) when an Al ₂ O ₃ barrier layer having the same thickness is formed in two stages of H 2 O-ALD and PE-ALD (O 2). The reflectivity of Ag alone without a barrier layer is also shown.

  As shown in FIG. 5, the reflectance when the barrier layer was formed only with oxygen gas without using hydrogen gas was 58.4. On the other hand, when the barrier layer was formed with a hydrogen gas flow rate of 20 sccm (oxygen gas flow rate of 180 sccm), the reflectivity increased significantly to 91.0. The respective reflectances when the flow rate of hydrogen gas was 30, 40, 50, 60, and 70 were 91.7, 93.8, 94.5, 94.1, and 93.8. The reflectivity when the film was formed in two stages of H 2 O-ALD and PE-ALD (O 2) was 93.9. The reflectance of Ag alone was 96.3. From this measurement result, it can be seen that the flow rate ratio of oxygen gas to hydrogen gas is preferably 160/40 or more. That is, it is preferable to react hydrogen gas with oxygen gas in a range of 1/4 or more. Hydrogen gas is preferably reacted with oxygen gas in a range of 3/4 or less.

  In the above embodiment, the barrier layer is formed at a substrate temperature of 120 ° C., but the barrier layer is desirably formed at 200 ° C. or less, more preferably 150 ° C. or less.

  FIG. 6 is a cross-sectional view of an electronic device having a barrier layer formed using the above-described embodiment. Here, the LED light source 30 will be described as an example of the electronic device. The basic structure of the LED light source 30 is the same as that shown in Patent Document 1 except that the barrier layer is formed using hydrogen-containing oxygen plasma. That is, the LED light source 30 includes Ag electrodes 32 and 33 on the substrate 31. These Ag electrodes 32 and 33 are connected to external electrodes not shown. An LED element 36 is mounted on the Ag electrodes 32 and 33. A barrier layer 34 is provided on the upper surface of the LED element 36. One of the two electrodes of the LED element 36 is electrically connected to the Ag electrode 32 via a wire 37, and the other is electrically connected to the Ag electrode 33 via a wire 38. A package frame 40 is provided around the LED light source 30, and the package frame 40 is embedded with a sealing material 41 in which phosphors are uniformly kneaded so as to surround the LED element 36. .

DESCRIPTION OF SYMBOLS 1,20 Film-forming chamber 2 Substrate 3 Exhaust device 4 Gas shower 5 High frequency power supply 6-9 Air supply unit 10 Control unit 21 High frequency coil 30 LED light source 31 Substrate 32, 33 Ag electrode 34 Barrier layer 36 LED element 37, 38 Wire 40 Package frame 41 Sealing material

Claims (8)

Using a source gas that reacts with oxygen plasma to form an oxide film and oxygen gas, and includes forming a barrier layer on the surface of the metal by plasma atomic layer deposition;
A film forming method comprising using at least the initial stage of the film forming process, the oxygen plasma containing hydrogen atoms in the composition. In the film-forming method of Claim 1,
A hydrogen deposition gas is used in addition to the oxygen gas when the oxygen plasma is generated.   The film forming method according to claim 2, wherein the hydrogen gas is reacted with the oxygen gas in a range of ¼ or more.   4. The film forming method according to claim 1, wherein the metal is a metal film formed on a substrate together with an electronic element, and the function of the electronic element is maintained in the film forming step. 5. The film forming method is performed at a substrate temperature lower than a limit temperature.   5. The film forming method according to claim 4, wherein the electronic element is a light emitting diode.   The film forming method according to claim 1, wherein at least a part of the metal is silver Ag. 7. The film forming method according to claim 1, wherein at least one compound selected from an organoaluminum compound, an organotitanium compound, and an organosilicon compound is used as the source gas, and aluminum oxide Al ₂ O ₃ , A film forming method comprising forming the barrier layer with one or more oxides selected from titanium oxide TiO ₂ and silicon oxide SiO ₂ . A film forming chamber for storing an object provided with a metal layer on at least a part of its surface;
An exhaust device for maintaining the film forming chamber in a vacuum atmosphere;
A gas introduction means for introducing a source gas that reacts with oxygen plasma to form an oxide film and an oxygen gas as a reaction gas into the film formation chamber;
A hydrogen introduction means for introducing a material containing a hydrogen atom into the film formation chamber;
A high frequency power source for generating plasma by applying high frequency power to the film forming chamber;
A controller for controlling the gas introduction means, the hydrogen introduction means, and the high-frequency power source,
The control unit controls the gas introduction unit to introduce the source gas and the oxygen gas into the film formation chamber, and also controls the high-frequency power source to barrier the surface of the metal layer by plasma atomic layer deposition. In addition, at least in the initial stage of the film formation control, the hydrogen introduction unit is controlled to introduce hydrogen atoms into the composition by introducing the oxygen gas into the film formation chamber. The film forming apparatus is characterized in that control is performed to introduce a material containing the material into the film forming chamber.

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