JP2007308782A - Manufacturing method of titanic acid zirconic acid lead film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably manufacturing a titanic acid zirconic acid lead film having no shortage of lead. <P>SOLUTION: The method for manufacturing the titanic acid zirconic acid lead film on a substrate by an RF-magnetron sputtering method using a target made of a titan acid zirconic acid lead as a raw material comprises a substrate heating step of heating the substrate, and a sputtering film forming step of forming a film on the substrate by the RF-magnetron sputtering method while keeping the substrate temperature heated in the substrate heating step. In the sputtering film forming step, a gas including lead is introduced into ambient gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a lead zirconate titanate film.

  In recent years, lead zirconate titanate (PZT), which is a ferroelectric material, has been widely used as a piezoelectric material constituting actuators for ejecting droplets and micromachines of inkjet recording heads.

When forming a thick film of PZT, it can be manufactured from a ceramic plate using a ceramic polishing method, but it is difficult to manufacture at a low cost because the yield is poor and it is difficult to deal with mass production and is not practical. . Further, for example, when film formation is attempted using a sputtering method that can be formed using a high melting point material and the film thickness is considered to be uniform, the film formation temperature is high, and lead (Pb) after reaching the substrate is high. There is a problem that lead is deficient by re-evaporation. As a means for solving this, for example, when a ferroelectric thin film having a composition of Pb _X La _1-X Ti _1-X / 4O ₃ (0 ≦ X ≦ 0.25) is formed by using a high-frequency magnetron sputtering method. , PbO, LaO ₃ and TiO ₂ powders were blended as targets, calcined at 750 ° C. for 4 hours, pulverized, and further mixed with 20 mol% excess PbO powder to prevent lead shortage (For example, refer to Patent Document 1).
JP-A-6-260018 (page 3-4)

  However, in the target in which the amount of lead is larger than the amount necessary for the composition of the ferroelectric film shown in Patent Document 1, the content of lead gradually decreases as the lead evaporates during sputtering. Since the composition changes, there is a problem that a ferroelectric film having a stable composition cannot be manufactured unless it is periodically replaced with a new target.

  The present invention has been made in view of the above problems, and its object is to provide a lead zirconate titanate film for stably producing a lead zirconate titanate film free of lead. It is to provide a manufacturing method.

  Said subject is solved by the following structures.

1. In the method for producing a lead zirconate titanate film, which uses a target made of lead zirconate titanate as a raw material by an RF magnetron sputtering method to produce a lead zirconate titanate film on a substrate,
A substrate heating step for heating the substrate;
Maintaining the substrate temperature heated in the substrate heating step, and forming a film on the substrate by the RF magnetron sputtering method,
In the sputter deposition step, a lead zirconate titanate film manufacturing method, wherein a gas containing lead is introduced into an atmospheric gas.

  2. 2. The method for producing a lead zirconate titanate film according to 1, wherein the lead-containing gas is introduced into the atmospheric gas by injecting the lead-containing gas onto the surface of the target.

  3. The method for producing a lead zirconate titanate film according to 1 or 2, wherein the lead-containing gas is lead dipivaloylmethane.

  4). The method for producing a lead zirconate titanate film according to any one of claims 1 to 3, wherein the temperature of the heated substrate in the substrate heating step is set to 500 ° C to 670 ° C.

  According to the present invention, the amount of lead zirconate titanate formed on the substrate is determined not only by the amount of lead contained in the target raw material but also by the amount of lead-containing gas introduced into the atmospheric gas. Can be adjusted.

  Therefore, the Pb content caused by evaporation during normal use of the target or the Pb deficiency of lead zirconate titanate film due to re-evaporation of lead from the film deposited on the substrate at the time of film formation is reduced by the gas containing lead. It can be compensated by introducing a gas containing lead by the plasma at the time of discharge by RF magnetron sputtering and mixing it into the sputtered raw material to form a film as ionized lead. Further, the amount of lead supplement can be easily determined by the amount of lead-containing gas introduced into the atmospheric gas.

  Therefore, the manufacturing method of the lead zirconate titanate film | membrane for manufacturing stably the lead zirconate titanate film | membrane which does not lack Pb can be provided.

Embodiments according to the present invention will be described below with reference to the drawings. Lead zirconate titanate Pb (Zr _x Ti _1-x ) O ₃ (hereinafter referred to as a film forming apparatus) using an RF magnetron sputtering film forming apparatus (hereinafter referred to as a film forming apparatus) provided with a lead (Pb) gas injection section shown in FIG. 0.3 ≦ X0.6, hereinafter referred to as PZT.) The production of the film will be described.

  In the film forming apparatus 100 shown in FIG. 1, 1 is a chamber, 2 is a magnetron / cathode, 3 is a target having a PZT material, 4 is a substrate holder (anode electrode), 5 is a substrate to be formed, and 6 is a substrate 5. 7 is a Pb (lead) gas injection unit, 8 is a shutter, and 9 is a radio frequency (RF) power source for supplying radio frequency (RF) power to be applied to the magnetron cathode 2. A is a sputtering gas, for example, an argon (Ar) gas inlet, B is an exhaust port connected to a vacuum pump (not shown) for evacuating the chamber 1, and C is a gas containing Pb. Each supply path is shown.

  The substrate holder 4 shows a state of a cross section that allows four disk-shaped substrates 5 to be attached. Further, in order to obtain a uniform film thickness on the substrate surface, the substrate holder 4 is preferably provided with a rotation introduction mechanism (not shown) so that it can rotate within the film formation surface during film formation.

  The Pb gas injection unit 7 is connected to a tank 10 that heats lead dipivaloylmethane, which is liquid at room temperature, and supplies it as a lead-containing gas (Pb gas).

  The tank 11 is heated from about 100 ° C. to about 230 ° C. by the heater 11 provided in the tank 10, the lead dipivaloylmethane liquid in the tank 10 is vaporized to generate lead dipivaloylmethane gas as Pb gas, This Pb gas is guided to the Pb gas injection section 7 through the Pb gas supply path C and the injection section introduction path 12.

  The Pb gas injection unit 7 has a range of about 10 mm to 50 mm above the target surface and from the target surface toward the substrate so that Pb gas can be injected to high-density plasma in a region close to the target generated during sputtering. The injection port 7a is preferably directed toward the target surface. The specific arrangement of the Pb gas injection unit 7 and the direction of the injection port 7a depend on the effect of the magnetron on the injected Pb gas. For example, in the case of a 4-inch target, the Pb gas is generated within a range of about 30 mm from the target surface. It is preferable that the high density plasma can be sufficiently supplied. By providing the Pb gas injection unit 7 so that it can be sufficiently supplied to the high-density plasma region as described above, the introduced Pb gas can be sufficiently decomposed by the plasma and Pb can be ionized and deposited on the substrate. Thus, the shortage of Pb due to re-evaporation in the PZT film deposited on the substrate can be effectively compensated.

  When sputtering gas and Pb gas are mixed and introduced into the chamber, Pb gas does not decompose efficiently, so a large amount of Pb gas is required to compensate for the above Pb deficiency, and Pb gas Insufficient decomposition of is undesirable because it is contained in the PZT film as an organic Pb compound and the purity of the film is poor.

  It is preferable to provide a plurality of injection ports 7a so that the high-density plasma can be uniformly injected. For example, in the case of the ring-shaped Pb gas injection unit 7 shown in FIG. 2 (a view of the target side seen from the substrate 5 side in FIG. 1), the direction of the target 3 is at a position where the inside of the ring is equally divided. It is preferable to provide the injection port 7a facing the direction. Moreover, the injection part introduction path 12 which introduces Pb gas into the ring-shaped Pb gas injection part 7 is provided in the Pb gas injection part 7 so that the Pb gas supplied to the Pb gas injection part 7 can be injected at a uniform pressure. It is preferable to use a plurality of pressure differentials so that the pressure difference does not increase. For example, a Pb gas supply path C from the tank 10, for example, a pipe, is branched into two in the middle, and an injection part introduction provided so as to face the ring-shaped Pb gas injection part 7 as shown in FIG. It is preferable to connect the passages 12-1 and 12-2 so that Pb gas can be supplied. In addition, a plurality of ring-shaped Pb gas injection portions 7 may be stacked so that Pb gas can be injected into the plasma region more efficiently.

  Further, as an example of the Pb gas injection unit, instead of the ring-shaped Pb gas injection unit 7 shown in FIG. 2, as shown in FIG. 3, two ring-shaped pipes 7-1 and 7-2 are connected to a plurality of pipes. What is connected by a cylindrical pipe 7-3 can be provided between the substrate 5 provided on the substrate holder 4 and the target 3. In FIG. 3, the periphery of the film forming apparatus such as a chamber is not shown. A plurality of holes are provided on the target 3 side of the cylindrical pipe 7-3, and these are used as the injection ports 7a. Therefore, the Pb gas guided to the ring pipe 7-1 from the injection unit introduction paths 12-1 and 12-2 passes through the cylindrical pipe 7-3 and reaches the ring pipe 7-2. The high-density plasma generated in the vicinity of the target 3 is injected from the injection port 7a provided in the pipe. In this case, by providing a plurality of cylindrical pipes 7-3 and providing a plurality of injection ports 7a in the cylindrical pipe, a gas containing lead is uniformly injected into high-density plasma. Can be supplied. The direction of the injection port 7a provided in the cylindrical pipe is preferably set to the direction of the target surface having a higher plasma density (the arrow direction shown in FIG. 3).

  The Pb gas injection unit 7 is preferably made of a non-magnetic material because there is no magnetic coupling due to the magnetic field generated from the magnetron / cathode 2 and no unstable operation of sputtering occurs. As a specific material constituting the Pb gas injection unit 7, SUS316 and SUS304 are preferable because they are heat-resistant, corrosion-resistant, workable, and inexpensive in addition to the above non-magnetic materials. Compared to the glass, it is difficult to break, but a glass such as quartz that is easy to manufacture can be obtained.

The Pb gas is preferably a gas obtained by vaporizing lead dipivaloylmethane Pb (C ₁₁ H ₁₉ O ₂ ) ₂ in the range of 100 ° C. to 230 ° C. This Pb gas is preferably introduced into an atmosphere gas in a chamber into which an inert gas, for example, argon (Ar) gas is introduced as a sputtering gas. The atmospheric gas pressure after lead gas introduction is in the range of 0.13 Pa to 1.3 Pa where discharge is efficient and easy, and the ratio of the supply amount of lead dipivaloylmethane gas in the atmospheric gas is 5 volume% to 30 volume% Is preferred. If the ratio of lead dipivaloylmethane gas is 40% by volume or more, the film formation rate becomes slow due to lack of sputtering gas or plasma instability, and if it is less than 5% by volume, Pb composition compensation and film stress relaxation are achieved. The action is weakened.

The Pb gas thus introduced into the mixed gas is decomposed by obtaining energy from the plasma, and the carbon (C) contained in the lead dipivaloylmethane Pb (C ₁₁ H ₁₉ O ₂ ) ₂ is CO or CO ₂ , hydrogen (H ₂ ) and oxygen (O ₂ ) are exhausted as water or water vapor (H ₂ O), and lead (Pb) is ionized and deposited on the substrate 5 together with the sputtered PZT particles. it can.

  The supply amount of the Pb gas can be easily adjusted by controlling the heating temperature of the tank 10 by the heater 11 or adjusting the gas flow rate in the supply path C of the Pb gas. Therefore, the amount of Pb gas in the mixed gas can be easily adjusted as appropriate, and the amount of Pb in the PZT film formed on the substrate 5 can be easily made appropriate.

  The film formed by the deposition of PZT particles and Pb ions reaching the substrate 5 is slightly Pb-excess, but re-evaporates at a high substrate temperature to obtain a stoichiometrically matched lead zirconate titanate film. It is done. In addition, since Pb is a raw material supplied by gas, the sputtering load can be reduced, so that the film formation rate is improved, and Pb gas is appropriately supplied so that Pb of the PZT film is not insufficient. Thus, a film with reduced film stress can be obtained.

  The film formation rate is preferably in the range of 50 Å / min to 200 Å / min, and the substrate temperature during film formation is preferably in the range of 500 ° C. to 670 ° C. A film formation rate of 50 成膜 / min or more is preferable from the viewpoint of film formation efficiency. On the other hand, if it is 200 A / min or less, the film on the substrate is charged to cause abnormal discharge and does not become a rough film in which pinholes are present, so that a good piezoelectric film can be obtained.

In order for the PZT film deposited on the substrate to be a stoichiometrically Pb (Zr _0.52 Ti _0.48 ) O ₃ crystallized and have a preferentially oriented perovskite structure having a piezoelectric function, the substrate temperature is set to 500 ° C. The temperature is preferably 670 ° C. or lower, and more preferably 550 ° C. or higher and 600 ° C. or lower can provide a more preferred orientation. When the substrate temperature is lower than 500 ° C., Pb gas is hardly re-evaporated from the deposited PZT film, and Pb gas is supplied using a target that stoichiometrically matches Pb (Zr _0.52 Ti _0.48 ) O _3. The PZT film can be formed without this, but the preferential orientation is difficult to achieve and the piezoelectric function cannot be achieved. When the substrate temperature is higher than 670 ° C., preferential orientation is facilitated, but the amount of Pb re-evaporation increases, and the deposited PZT film stoichiometrically _matches Pb (Zr _0.52 Ti _0.48 ) O ₃ . If the supply amount of Pb gas is increased to make up for the deficiency of Pb due to re-evaporation, the amount of Pb gas in the mixed gas increases too much, and the mixed gas pressure increases and the plasma becomes unstable. Therefore, it becomes difficult to form a film.

Therefore, the substrate temperature during film formation is preferably 500 ° C. or more and 670 ° C. or less, more preferably 550 ° C. or more and 600 ° C. or less. By setting the temperature within this range, the PZT film has a stoichiometric amount. A film having a perovskite structure of Pb (Zr _0.52 Ti _0.48 ) O ₃ is obtained. Pb (Zr _0.52 Ti _0.48 ) O ₃ is a composition having the largest piezoelectric constant among lead zirconate titanates, and is preferably used as an actuator or the like as a piezoelectric material. When the piezoelectric material is used for an actuator or the like, the film thickness is preferably about 0.5 μm to about 100 μm. However, when the film is formed by the RF magnetron sputtering method, if the film thickness is 10 μm or more, substrate deformation occurs due to the film stress, or the manufacturing process. From the point that it takes a long time, a practical film thickness is preferably about 0.5 μm to 10 μm.

In the above embodiment, PZT (lead zirconate titanate _{Pb (Zr X Ti 1-X} ) O 3 (0.3 ≦ X0.6)) Although the film production method according to the present invention, for example, PLZT ((Pb, La) (Zr, Ti) O ₃ : lead zirconate titanate to which La (lanthanum) is added) may contain an additive in PZT. Examples of the additive include La (lanthanum), nb (niobium), Mg, Ni and the like, also is not a lead zirconate titanate, applied to the manufacture of _{PLT (Pb 1-X La X} Ti 1-X / 4O 3) and PT (PbTiO ₃₎ be able to.

Further, as a raw material of the gas containing Pb, it is vaporized in a temperature range of about 200 ° C. which can be easily heated from room temperature, and depending on the pressure in the chamber, a vapor pressure of about 10 ⁻³ Pa to 10 Pa. Other than the above lead dipivaloylmethane, tetramethyl lead ((Pb (CH ₃ )) ₄ ), tetraethyl lead ((Pb (C ₂ H ₅ )) ₄ ), beta-diketone compounds (For example, dipiparoyl methanate lead (Pb (C ₁₁ H ₁₉ O ₂ ) ₂ ), acetyl acetonate lead (Pb (C ₅ H ₇ O ₂ ) ₂ ), dimethyl heptafluoro acetyl acetonate lead (Pb (C ₁₀ H ₁₀ F ₇ O ₂ ) ₂ ) and the like are preferable materials.

  Even in the case of solids at room temperature, such as the beta-diketone compound dipipaloyl methanate lead, it is stored in the tank and heated with a heater in the same way as the lead dipivaloylmethane liquid shown in FIG. By vaporizing, it can be used as Pb gas.

Example 1
A ferroelectric film containing lead composed of lead zirconate titanate was produced using a film deposition apparatus 100 by RF magnetron sputtering provided with a lead gas injection unit 7 shown in FIG. FIG. 4 schematically shows the produced film. In the substrate 5 (FIG. 1) on which the ferroelectric film is fabricated, 1 μm of thermally oxidized SiO ₂ 22 is previously formed on Si on the substrate 21 (FIG. 4), and a Ti film 23 is formed thereon by RF magnetron sputtering. 0.03 μm and a Pt film 24 formed with 0.3 μm were used.

The target 3 used was a sintered fine powder of lead zirconate titanate Pb (Zr _0.52 Ti _0.48 ) O ₃ .

Lead dipivaloylmethane Pb (C ₁₁ H ₁₉ O ₂ ) ₂ was introduced into an atmospheric gas whose sputtering gas was Ar. The lead dipivaloyl methane gas is vaporized by heating the lead dipivaloyl methane liquid in the supply tank 10 to about 200 ° C. with the heater 11, and introducing this gas into the Pb gas injection unit 7. Was sprayed on the surface.

  The atmospheric gas pressure consisting of Ar and lead dipivaloylmethane in the chamber 1 was 0.67 Pa, and the supply rate of lead dipivaloylmethane was 15% by volume. Film formation was performed with the substrate temperature heated and maintained at 600 ° C. The film formation rate was 100 Å / min, and a good PZT film having a thickness of 5 μm and no warpage due to film stress was obtained.

When the composition analysis of the obtained PZT film 25 is performed, it is confirmed that it is stoichiometrically Pb (Zr _0.52 Ti _0.48 ) O ₃ , Pb deficiency is not recognized, and the result of X-ray diffraction is shown in FIG. As a result of the X-ray diffraction pattern, the film had a perovskite structure.

  The PZT film 25 thus obtained was further overlapped to form an Al film 26 with a thickness of 0.3 μm by RF magnetron sputtering, and the relative dielectric constant was measured as an electrode.

As shown in FIG. 4, a capacitance meter 27 (Digital Hi Tester, model 3233, manufactured by Hioki Electric Co., Ltd.) is connected to a Pt film (electrode) 24 and an Al film (electrode) 26 and electrostatically charged at room temperature. The capacity C was measured. Using the measured value of the capacitance C, the relative dielectric constant εr was obtained from the following equation (1).
εr = C / (εo × electrode area / dielectric film thickness) (1)
εo: dielectric constant of vacuum (8.854 × 10 ⁻¹² F / m)
The relative dielectric constant was 1260, which was a sufficient value for a PZT film.

(Comparative Example 1)
Film formation was performed under the same conditions as in Example 1 except that Pb gas was not introduced into the atmospheric gas. As a result of analyzing the composition of the obtained film, it was Pb _0.9 (Zr _0.52 Ti _0.48 ) O _3, which was clearly in a Pb-deficient state. Further, the obtained film showed minute cracks, and the relative dielectric constant could not be measured.

(Example 2)
A PZT film was manufactured with the same settings as in Example 1 except that the heating temperature of the substrate 5 was 450 ° C., 500 ° C., 550 ° C., 600 ° C. (Example 1), 650 ° C., and 700 ° C. Further, when the heating temperature was set to 700 ° C., Pb was insufficient, so the supply amount of Pb gas was increased so as to have the same composition as other films. In addition, signs of unstable plasma discharge during film formation due to an increase in the supply amount of Pb gas were occasionally observed. For each of the manufactured films, the surface of the film was observed by SEM and the same dielectric constant as in Example 1 was measured. The results are shown in Table 1. The compositions of the PZT films were all the same Pb (Zr _0.52 Ti _0.48 ) O ₃ .

“◎”, “◯”, “Δ”, and “X” shown in the table represent the following, respectively.
In SEM observation, it was as follows. ○: The film was dense and the surface was smooth. ×: The relative dielectric constant where the film was not dense and the surface was rough was as follows. ◎: 1000 or more ○: 500 or more and less than 1000 Δ: can be measured and less than 500 ×: In the Pb gas supply amount that could not be measured, the ratio of the lead dipivaloylmethane supply amount in Example 1 was 15% by volume (1) The ratio is shown as.

It is a figure which shows typically the RF sputtering film-forming apparatus which provided the Pb gas injection part which injects the gas containing lead. It is a figure which shows an example of a Pb gas injection part. It is a figure which shows an example of a Pb gas injection part. It is a figure which shows typically a mode that the electrostatic capacitance in the ferroelectric film manufactured in the Example is measured. 2 is a diagram showing an example of an X-ray diffraction pattern of a PZT film manufactured in Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 2 Magnetron cathode 3 Target 4 Substrate holder 5 Substrate 6 Heater 7 Lead gas injection part 7a Injection port 8 Shutter 9 RF power supply 10 Pb gas raw material supply tank 11 Vaporization heater 12 Injection part introduction path 13 Lead dipivaro Irmethane liquid 100 RF sputtering film forming apparatus provided with Pb gas injection part A Sputtering gas introduction path B Exhaust path C Pb gas supply path

Claims (4)

In the method for producing a lead zirconate titanate film, which uses a target made of lead zirconate titanate as a raw material by an RF magnetron sputtering method to produce a lead zirconate titanate film on a substrate,
A substrate heating step for heating the substrate;
Maintaining the substrate temperature heated in the substrate heating step, and forming a film on the substrate by the RF magnetron sputtering method,
In the sputter deposition step, a lead zirconate titanate film manufacturing method, wherein a gas containing lead is introduced into an atmospheric gas. The lead zirconate titanate film according to claim 1, wherein the lead-containing gas is introduced into the atmospheric gas by injecting the lead-containing gas onto the surface of the target. Method. The method for producing a lead zirconate titanate film according to claim 1 or 2, wherein the lead-containing gas is lead dipivaloylmethane. The method for producing a lead zirconate titanate film according to any one of claims 1 to 3, wherein a temperature of the substrate heated in the substrate heating step is set to 500 ° C or more and 670 ° C or less.

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