JP2015098631A - Manufacturing method for lead-compound thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent lead-compound thin film.SOLUTION: There is prepared a lead-compound thin film manufacturing method comprising: a chamber; a plurality of evaporation sources arranged in said chamber and including a Pb evaporation source having a Pb material; and a substrate holder arranged in said chamber and above said evaporation sources and capable of holding a substrate. Before the substrate is arranged in the substrate holder, the inside of the chamber is evacuated, and the Pb material of the Pb evaporation source is heated to 900°C or higher. While the inside of the chamber being evacuated, the substrate is arranged in the substrate holder. After the substrate is arranged in the substrate holder, a plurality of evaporation materials containing the Pb material are evaporated from the evaporation sources so that a lead compound thin film is evaporated on said substrate surface.

Description

  The present invention relates to a method for producing a compound thin film containing lead by physical vapor deposition.

  Multi-element oxide ferroelectrics containing lead (Pb), such as lead zirconate titanate (PZT) and lead lanthanum zirconate titanate (PLZT), have excellent piezoelectricity, pyroelectricity, and electro-optics. It has characteristics and is applied to various electronic devices. Such a multi-element oxide ferroelectric can be formed on a substrate by using, for example, a vacuum deposition method or an ion plating method. For example, in Patent Documents 1 and 2, various source gases evaporated from an evaporation source are activated by high-density plasma generated by a pressure gradient arc discharge plasma gun, and a multi-component oxide strong oxide is formed on a substrate in an oxygen atmosphere. An arc discharge reactive ion plating method for depositing a thin film made of a dielectric has been proposed.

Japanese Patent No. 4138196 JP 2011-204776 A

  An object of the present invention is to provide a high-quality lead compound thin film.

  According to the main aspect of the present invention, a) a chamber, a plurality of evaporation sources including a Pb evaporation source disposed in the chamber and comprising a Pb raw material, and above the plurality of evaporation sources in the chamber A step of preparing a deposition apparatus comprising at least a substrate holder capable of holding the substrate; and b) reducing the pressure in the chamber before disposing the substrate on the substrate holder, A step of heating the Pb source of the Pb evaporation source to 900 ° C. or higher, c) a step of disposing the substrate in the substrate holder while reducing the pressure in the chamber, and d) arranging the substrate in the substrate holder. And a step of evaporating a plurality of evaporation materials including a Pb material from the plurality of evaporation sources and depositing a lead compound thin film on the surface of the substrate.

  A high-quality lead compound thin film can be obtained.

FIG. 1A is a schematic view showing a configuration example of an arc discharge reactive ion plating apparatus, and FIG. 1B is a cross-sectional view showing a substrate disposed in the apparatus and a lead compound thin film formed on the substrate. FIG. 2A is a flowchart showing a method for producing a lead compound thin film according to a reference example, and FIGS. 2B and 2C are photomicrographs obtained by photographing the surface of the produced lead compound thin film. FIG. 3A is a flowchart showing a method of manufacturing a lead compound thin film according to an example, and FIG. 3B is a graph comparing particle densities of lead compound thin films according to a reference example and an example.

  Hereinafter, a method for forming a PZT film as a lead compound thin film will be described. The lead compound thin film is not limited to the PZT film but may be a PLZT film or the like.

  FIG. 1A is a schematic side view showing an arc discharge reactive ion plating (ADRIP) apparatus 100 used when producing a PZT film. The ADRIP apparatus 100 is configured such that a substrate holder 104, various evaporation sources 106 to 108, a gas supply mechanism 109, a plasma gun 110, a sub chamber 120, and the like are attached to a reaction chamber (main chamber) 101.

The reaction chamber 101 is connected to a vacuum exhaust device 130, and the inside of the reaction chamber 101 can be evacuated to a high vacuum (a vacuum degree of 1 × 10 ⁻⁴ Pa or higher and a pressure of 1 × 10 ⁻⁴ Pa or lower).

  A rotation shaft 102 is provided through the upper surface of the reaction chamber 101, and a substrate holder 104 provided with a radiant heating type heater 103 is connected to the rear surface. The substrate holder 104 is configured to hold the substrate 105.

Further, a reaction gas supply mechanism 109 is provided through the upper surface of the reaction chamber 101, and a reaction gas such as oxygen (O ₂ ) can be supplied from the reaction gas supply mechanism 109 to the surface of the substrate 105.

  Various evaporation sources 106 to 108 are provided at the bottom of the reaction chamber 101. The various evaporation sources 106 to 108 have a configuration in which, for example, various evaporation raw materials are filled in a carbon crucible. Various evaporation materials are heated and evaporated by, for example, electron beam irradiation. When a PZT film is formed on the surface of the substrate 105, evaporation sources containing lead (Pb) raw material, zirconium (Zr) raw material, and titanium (Ti) raw material are used as the various evaporation sources 106 to 108, respectively.

  A plasma gun 110 having an anode, a cathode, a magnetic field generating coil, and the like is provided on the side surface of the reaction chamber 101. The plasma gun 110 ionizes and activates an inert gas (discharge gas) such as Ar or He by arc discharge. Then, the plasma 118 is led out between the substrate 105 and the various evaporation sources 106 to 108 in the chamber 101 by the pressure gradient of the magnetic field / discharge gas generated by the magnetic field generating coil.

  Various raw material vapors evaporated from the evaporation sources 106, 107 and 108 are activated when passing through the plasma 118 and reach the substrate 105. By introducing oxygen gas from the reactive gas supply mechanism 109, high-density oxygen plasma and active species of oxygen are generated, and react with the raw material vapor evaporated from the evaporation sources 106, 107, 108 in the vicinity of the substrate 105 to oxidize. Form things.

  A sub chamber 120 is provided on the side surface of the reaction chamber 101. The sub-chamber 120 can be evacuated to a high vacuum and can accommodate the substrate 105. By including the sub-chamber 120 that can be evacuated to a high vacuum, the substrate 105 can be taken in and out of the reaction chamber 101 while the inside of the reaction chamber 101 is maintained at a high vacuum.

  FIG. 1B is a cross-sectional view showing the substrate 105 and the PZT film 15 formed on the substrate 105.

  The substrate 105 has a structure in which, for example, a support substrate including the Si substrate 11 and the silicon oxide layer 12 and a lower electrode including the Ti layer 13 and the Pt layer 14 are stacked. The substrate 105 can be produced, for example, by forming a silicon oxide film 12 on the surface of the Si substrate 11 by thermal oxidation, and forming a Ti layer 13 and a Pt layer 14 on the silicon oxide film 12 by a sputtering method.

  The PZT film 15 is formed on the surface of the lower electrode (Pt layer 16) of the substrate 105 using the ADRIP apparatus 100. In addition, by forming, for example, a Pt layer 16 as an upper electrode on the surface of the manufactured PZT film 15, the device 20 including the lower electrode, the PZT film 15 and the upper electrode can be used as a piezoelectric element. The Pt layer 16 can be formed by sputtering, for example.

  FIG. 2A is a flowchart showing a film forming process of the PZT film 15 according to the reference example. Hereinafter, the process of forming the PZT film 15 will be described with reference to the configuration of the ADRIP apparatus 100 shown in FIG. 1A.

First, before disposing the substrate 105 on the substrate holder 104, the inside of the reaction chamber 101 is evacuated to a high vacuum of, for example, 1 × 10 ⁻⁴ Pa or more (step S101). At this time, the substrate 105 is accommodated in the sub-chamber 120, and the sub-chamber 120 is also evacuated to the same degree of vacuum as in the reaction chamber 101.

  Next, the substrate 105 is moved from the sub-chamber 120 to the reaction chamber 101 and disposed on the substrate holder 104 in the reaction chamber 101 (step S102). Subsequently, the substrate 105 is heated by the radiant heating type heater 103 so that the temperature of the substrate 105 becomes 500 ° C. (step S102).

  After the temperature of the substrate 105 reaches about 500 ° C., Ar gas is introduced into the plasma gun 118 at 1 sccm to 100 sccm (10 sccm in the embodiment), He gas is introduced at 5 sccm to 300 sccm (100 sccm in the embodiment), and the cathode of the plasma gun 110 is introduced. An arc discharge plasma 118 is generated by applying a DC voltage between the anode and the anode. Then, the plasma 118 is introduced into the chamber 101 by the pressure gradient of the magnetic field / discharge gas generated by the magnetic field generating coil (step S103). Subsequently, oxygen gas is introduced at 50 sccm to 400 sccm (250 sccm in the embodiment) from the reaction gas supply mechanism 109 to generate high-density oxygen plasma and active species of oxygen (step S104).

  Thereafter, Pb, Zr, and Ti materials are evaporated from the various evaporation sources 106, 107, and 108, respectively (step S105). The evaporation amounts of the various evaporation materials are such that the Pb evaporation amount is in the range of up to 10 times the total evaporation amount of Zr and Ti, and the evaporation amounts of Zr and Ti are substantially equal. It is preferable to control. The amount of evaporation of the various evaporation materials can be controlled by adjusting the intensity of the electron beam applied to the various materials, and can be detected and monitored by using a crystal oscillator type film thickness sensor or the like.

Thus, the PZT film 15 having a perovskite crystal structure is formed on the surface of the substrate 105 held by the substrate holder 104. In addition, the area of the PZT film | membrane 15 produced in the Example is about 15000 mm < ² >.

  2B is an optical micrograph obtained by photographing a part of the surface of the produced PZT film 15, and FIG. 2C is an electron micrograph obtained by enlarging a part of a region surrounded by a circle in FIG. 2B. As shown in these photographs, it was confirmed that many small particles (particles) were formed on the surface of the produced PZT film 15. For example, the diameter of the particles shown in FIG. 2C is about 9 μm.

  According to the inventor of the present application, it is confirmed that the Pb raw material bumps (splashes) when the Pb raw material is heated and evaporated in various raw material evaporation steps (step S105). It has also been confirmed that bumping occurs only with the Pb raw material and does not occur with the Zr raw material and the Ti raw material.

  Such bumping of the Pb raw material occurs when the gas (air, etc.) contained in the Pb raw material or the gas (air, etc.) adsorbed on the crucible containing it is released from the heated and melted Pb raw material. It is thought that it occurs. Further, it is considered that the particles formed on the PZT film 15 are adhered to the substrate 105 by the melted Pb material being scattered by bumping of the Pb material. Therefore, it is considered that the particles observed by the micrograph are composed of Pb which is one of the evaporation raw materials.

  Such particles may deteriorate the crystallinity of the PZT film at the time of film formation, and may become a starting point of dielectric breakdown when a voltage is applied to the manufactured PZT film. Therefore, it is preferable to reduce the number of particles in the PZT film as much as possible.

  FIG. 3A is a flowchart illustrating a film forming process of the PZT film 15 according to the embodiment. Hereinafter, the difference between the film forming process of the PZT film 15 according to the embodiment and the film forming process of the PZT film 15 according to the reference example (FIG. 2A) will be described.

  The film forming process of the PZT film 15 according to the embodiment includes a Pb raw material heating process (process S111) between the exhaust process (process S101) and the substrate disposing process (process S102). That is, before disposing the substrate 105 on the substrate holder 104, the inside of the reaction chamber 101 is evacuated to a high vacuum (step S101), and only the Pb raw material is heated to a temperature of, for example, 900 ° C. or more (step S111). Thereafter, the substrate 105 is disposed on the substrate holder 104 while maintaining the degree of vacuum in the reaction chamber 101 (step S102), and the PZT film 15 is formed on the surface of the substrate 105 in the same manner as the PZT film 15 forming process according to the reference example. Are formed (steps S103 to S105).

  When a Pb source material is heated and evaporated in various source evaporation steps (step S105) by providing a Pb source heating step (step S111) between the exhaust step (step S101) and the substrate placement step (step S102). Bumping of the Pb raw material is suppressed. This is presumably because most of the gas mixed in the Pb raw material that induces bumping has already been released in the Pb raw material heating step (step S111). For this reason, the PZT film produced by carrying out the Pb raw material heating step (by the film forming method according to the example) was prepared without performing the Pb raw material heating step (step S111) (by the film forming method by the reference example). The number of particles is reduced compared to the film.

  The inventor produced seven PZT films according to the flowchart shown in FIG. 2A (deposition method according to the reference example), and produced six PZT films according to the flowchart shown in FIG. 3A (deposition method according to the example). Sample numbers 1 to 7 are assigned to the seven PZT films manufactured by the manufacturing method according to the reference example, and sample numbers 8 to 13 are assigned to the six PZT films manufactured by the manufacturing method according to the examples. And

FIG. 3B is a graph showing the particle density of the produced PZT film. The horizontal axis of the graph indicates sample numbers 1 to 13 of the produced PZT film, and the vertical axis of the graph indicates the average number of particles (particle density) per mm ^{2 on the} surface of the PZT film.

  From this graph, it can be seen that the particle density tends to be lower in the PZT films of sample numbers 8 to 13 than in the PZT films of sample numbers 1 to 7. That is, it can be seen that the particle density tends to be lower in the PZT film produced by the film forming method according to the example (FIG. 3A) than in the PZT film produced by the film forming method according to the reference example (FIG. 2A).

  From these results, in the method of forming the PZT film, the Pb raw material heating step (step S111) is provided between the exhaust step (step S101) and the substrate disposing step (step S102). It was found that the particle density of the PZT film can be reduced. In addition, according to the further study by the present inventors, in the Pb raw material heating step (step S111), it is preferable to heat the Pb raw material at 900 ° C. or higher, and more preferably 1000 ° C. or higher for 5 minutes from the viewpoint of reducing the particle density. It has been found that heating is more preferable. Further, from the viewpoint of suppressing spillage of the melted Pb material, it is preferable to heat the Pb material at 1700 ° C. or lower in the Pb material heating step (step S111).

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not restrict | limited to these. For example, the thin film formed on the substrate surface is not limited to the PZT film, but may be a compound thin film containing Pb. The thin film formation method is not limited to the ADRIP method, and any method may be used as long as the Pb raw material is heated and evaporated, such as a vacuum evaporation method or an ion plating method. It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 11 ... Si substrate, 12 ... Silicon oxide layer, 13 ... Ti layer, 14 ... Pt layer (lower electrode), 15 ... PZT film, 16 ... Pt layer (upper electrode), 20 ... Piezoelectric element, 100 ... ADRIP device, DESCRIPTION OF SYMBOLS 101 ... Reaction chamber (main chamber), 102 ... Rotating shaft, 103 ... Heater, 104 ... Substrate holder, 105 ... Substrate, 106-108 ... Evaporation source, 109 ... Reaction gas supply mechanism, 110 ... Plasma gun, 118 ... Plasma, 120 ... sub chamber, 130 ... evacuation device.

Claims (4)

a) a plurality of evaporation sources including a chamber, a Pb evaporation source disposed in the chamber and including a Pb raw material, and disposed in the chamber and above the plurality of evaporation sources to hold a substrate; A step of preparing a vapor deposition apparatus comprising at least a substrate holder capable of;
b) before disposing the substrate on the substrate holder, reducing the pressure in the chamber and heating the Pb raw material of the Pb evaporation source to 900 ° C. or higher;
c) disposing the substrate in the substrate holder while reducing the pressure in the chamber;
d) after disposing the substrate on the substrate holder, evaporating a plurality of evaporation materials including a Pb material from the plurality of evaporation sources, and depositing a lead compound thin film on the substrate surface;
For producing a lead compound thin film comprising:   2. The method for producing a lead compound thin film according to claim 1, wherein in step b), the Pb raw material of the Pb evaporation source is heated at 1000 ° C. or more for 5 minutes or more. The vapor deposition apparatus further supplies a reactive gas to a plasma gun capable of introducing plasma between the plurality of evaporation sources and the substrate held by the substrate holder, and a substrate surface held by the substrate holder A reactive gas supply mechanism capable of
In the step d), the lead compound thin film evaporates a plurality of evaporation materials containing Pb from the plurality of evaporation sources, activates the evaporated evaporation materials by the plasma, and converts the activated evaporation materials into the substrate. The method for producing a lead compound thin film according to claim 1 or 2, wherein the lead compound thin film is formed by reacting with the reaction gas on the surface.   In addition to the Pb evaporation source, the plurality of evaporation sources include a Zr evaporation source including a Zr raw material and a Ti evaporation source including a Ti raw material, the reaction gas includes oxygen gas, and the lead compound thin film includes PZT The method for producing a lead compound thin film according to claim 3 which is a film.