JP5653052B2 - Deposition equipment - Google Patents

Description

  The present invention relates to a film forming apparatus, and more particularly to an apparatus suitable for forming an oxide ferroelectric film.

PZT (Pb (Zr _x Ti _1-x ) O ₃ ), which is an oxide compound containing each element of Pb, Zr, and Ti, and PLZT ((Pb _{1 -x} La _x ) (Zr _y Ti _1-y ) _{1-x / 4} O ₃ ) and other multi-element oxide ferroelectrics have excellent piezoelectricity, pyroelectricity, electro-optical properties, etc. However, these bulk structures have been applied to various electronic devices. Particularly in recent years, thinning of these metal oxides has been studied for the purpose of application to memory materials for non-volatile RAMs, microactuators, integrated sensors, and the like. This thinning makes it possible to lower the drive voltage, integrate elements, omit the polarization process, and the like, and is expected to exhibit device characteristics that cannot be obtained in bulk.

  Conventionally, as a method for producing such a perovskite oxide thin film, a sputtering method, an arc discharge reactive ion plating (ADRIP), or the like is mainly used.

  In the sputtering method, in a rare gas atmosphere such as Ar adjusted to a pressure of several Pa, a rare gas discharge is induced by applying a direct current or a high frequency voltage between a substrate and a target sample facing the substrate. In this method, the sample is repelled by gas molecule collision and deposited on the substrate. In this method, since high energy atoms collide with the substrate and deposit, generally, the adhesion of the thin film is good, and basically a film composition close to the target composition is easily obtained.

  The ADRIP method uses an EB (electron beam) heating evaporation source and a high-density oxygen plasma generation source to deposit a substance produced by the reaction between the evaporation source and the oxygen plasma on the substrate. Since it can be used, there are advantages such as high material efficiency. Also in the production of thin films such as PZT made of perovskite oxide, which required high temperature processing of 600 ° C. or higher in the sputtering method, the high speed of 5 Å / s at a relatively low substrate temperature (500 ° C.) by the ADRIP method. A technique that enables film formation has been proposed (Patent Document 1).

  In both the sputtering method and the ADRIP method, the substrate temperature is an important factor in the film formation conditions. In the sputtering method, a heater is disposed on the back side of the substrate (on the side opposite to the film formation surface) and the back surface is uniform. The temperature is set by arranging a hot plate to make the substrate temperature uniform (Patent Document 2) or by arranging a plurality of heaters on the back side of the substrate, and setting the temperature of the central heater lower than that of the peripheral heater. A technique (Patent Document 3) for making the above uniform has been proposed.

  Further, Patent Document 4 describes that in a sputtering apparatus, a heater is provided on the substrate shutter for the purpose of keeping the substrate temperature during film formation constant before and after opening and closing the shutter. This Patent Document 4 proposes that a heater disposed on the back side of the substrate is usually moved to the shutter, and the substrate is heated by introducing high-temperature gas from the back side of the substrate.

JP 2001-234331 A JP 2005-38914 A JP 2007-327106 A Japanese Patent Laid-Open No. 07-11438

  Normally, in a film formation system, the substrate is shielded from the target, evaporation source, and plasma generation source by the substrate shutter until the substrate temperature and plasma state are stabilized. After stabilization, the shutter is opened and film formation is started. Is configured to do. As the substrate shutter, stainless steel having a high heat insulating property (low heat radiation), more specifically, a SUS 304 silver rough surface is used. There is a problem that the substrate temperature tends to change when the shutter is opened and closed.

  The technique described in Patent Document 4 attempts to solve this problem by combining heating of a substrate with gas and heating with a heater provided in a shutter in a sputtering method. However, since this method has a limit on the temperature rise by gas, it is considered difficult to maintain the substrate temperature at 500 ° C. or higher after the shutter is opened, and the substrate temperature is raised like perovskite oxide. It cannot be applied to the formation of necessary ferroelectrics.

  In addition, the above problem is particularly noticeable in the ADRIP method compared to the sputtering method. In the sputtering method, only the radiant heat from the plasma generated by the magnetron discharge exists on the film formation surface side of the substrate, whereas in the ADRIP method, the radiant heat from the plasma and the radiant heat from the evaporation source exist. This is because there is a large temperature difference between the spaces on both sides of the wall, and it is difficult to maintain an equilibrium state with normal temperature control.

  FIG. 11 is a diagram for explaining radiant heat generated in the vacuum container of the film forming apparatus used in the ADRIP method. As shown in the figure, in the film forming apparatus, a heater 1 for heating the substrate 3 by radiant heat is disposed above the substrate susceptor 2 that supports the substrate 3, and a plasma source, an evaporation source, and the like are disposed below the substrate 3. A radiant heat source 5 is disposed, and a substrate shutter 4 is disposed between the substrate 3 and the radiant heat source 5. From the heater 1 and the radiant heat source 5, as indicated by arrows in FIG. 11A, radiant heat h1 and h5 are radiated toward the substrate 3, and radiant heat h3 is also generated from the substrate 3 heated by the heater 1. The substrate shutter 4 receives the radiant heat h3 from the substrate 3 and is irradiated with the re-radiant heat h41 toward the substrate 3, and receives the radiant heat h5 radiated from the radiant heat source 5 and receives the re-radiant heat h42 toward the radiant heat source 5. Irradiated.

  Here, since the heat radiation from the substrate shutter 4 is smaller than the radiant heat from the substrate 3 and the radiant heat from the radiant heat source 5, the result of combining these is as shown in FIG. It becomes the same state that almost no radiant heat is generated. For this reason, it is considered that the control of the heater 1 is not in time for the inflow of radiant heat from the radiant heat source 5 immediately after the substrate shutter 4 is opened, causing the substrate temperature to fluctuate.

  Due to the fluctuation of the substrate temperature, the initial temperature of the film formation becomes instantaneously higher than the set temperature, which affects the initial nucleation of the PZT film. As a result, the method of forming the initial nucleus fluctuates for each film forming batch, and the reproducibility is lowered. In addition, the ADRIP method requires tuning to determine the optimum conditions. A standard thickness (about 500 μm) substrate used for this tuning and a bonded substrate such as an SOI substrate or an ultrathin substrate of 200 μm or less are used. In this case, the time required to reach thermal equilibrium differs due to the difference in thermal conductivity (thermal resistance) due to the thickness of the substrate and the laminated structure. For this reason, when different substrates are formed simultaneously, a difference occurs in the substrate surface temperature immediately after the shutter is opened, making it difficult to produce films having the same composition and crystal structure. As a result, conditions need to be tuned for each substrate, and the process establishment becomes complicated.

  An object of the present invention is to solve the above-mentioned problems and to provide a film forming apparatus capable of suppressing a temperature variation of a substrate and forming a high quality film with high reproducibility.

  In order to achieve the above object, the present invention employs a high emissivity material that radiates heat from the radiant heat source to the substrate side as a material for the shutter that separates the substrate and the radiant heat source. A thermal equilibrium state of the substrate is realized in an environment including heat from the source.

  That is, the film forming apparatus of the present invention is arranged between a film forming container, a substrate holding part for holding a substrate, a film forming source disposed at a position facing the substrate, and the substrate holding part and the film forming source. The shutter is made of a material that radiates heat generated from the plasma source and the film formation source to the substrate side.

  The film forming apparatus of the present invention may be provided with a plasma source that generates plasma in a space between the substrate and the film forming source. In that case, the shutter is disposed between the substrate and the plasma source. The

The shutter material is preferably made of a metal oxide having an emissivity of 0.70 or more at the film forming temperature and selected from zircon and molybdenum oxide.

  In the film forming apparatus of the present invention, preferably, the substrate holding unit includes a heating unit that heats the substrate, a temperature sensor that detects the temperature of the substrate, and a control unit that feedback-controls the heating unit based on the temperature detected by the temperature sensor. Prepare.

  According to the present invention, the thermal equilibrium state of the substrate can be realized in an environment including heat from a radiant heat source such as a film forming source or a plasma source with the shutter closed, so that the moment when the shutter is opened The fluctuation of the substrate temperature can be suppressed.

  The effect of the present invention will be described with reference to FIG. In FIG. 1, the same elements as those in FIG.

  As shown in FIG. 1A, radiant heat h 1 is radiated from the heater 1 to the substrate 3, and radiant heat h 5 is radiated from the radiant heat source 5 below the shutter 4 to the shutter 4 side. Radiant heat h3 is also radiated from the substrate 3 heated by the heater 1. The shutter 4 is heated by receiving the radiant heat h3 from the substrate 3 and the radiant heat h5 from the radiant heat source 5. Here, since the shutter 4 is made of a highly radioactive material, the heat of the heated shutter 4 is radiated as re-radiant heat h43 and h44 to the substrate side and the radiant heat side, respectively. The re-radiant heat h43 is radiated heat h3 from the substrate 3. Will be bigger.

  Therefore, the total radiant heat radiated from each element is in a state where radiant heat from the shutter 4 toward the substrate 3 is generated as shown in FIG. That is, when the shutter 4 is in the closed state, the substrate 3 achieves substantially the same thermal equilibrium as in the shutter open state.

(A) And (b) is a figure explaining the state of the radiant heat in the film-forming apparatus by this invention. The figure which shows the outline | summary of one Embodiment of the film-forming apparatus of this invention. FIG. 2 is an explanatory view showing details of a substrate susceptor of the film forming apparatus of FIG. 1. It is a figure which shows the detail of the substrate shutter of the film-forming apparatus of FIG. 1, (a) is a perspective view which shows each element, (b) is a sectional side view. The graph which shows the change of the substrate temperature before and behind opening of a substrate shutter measured in Example 1 and Comparative Example 1. FIG. 3 is a graph showing variation in dielectric constant of a PZT film obtained by ten film formations in Example 1. 3 is a graph showing variations in dielectric loss (tan δ) of a PZT film obtained by ten film formations in Example 1. FIG. 6 is a graph showing variations in the composition x of the PZT film obtained by ten film formations in Example 1. 6 is a graph showing X-ray diffraction images of films formed on different types of substrates in Example 2. FIG. The graph which shows the X-ray-diffraction image of the film | membrane formed into a film on the different kind of board | substrate in the comparative example 2. FIG. The figure explaining the state of the radiant heat in the conventional film-forming apparatus.

  Hereinafter, embodiments of the film forming apparatus of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram showing an embodiment of the film forming apparatus of the present invention. This film forming apparatus is an arc discharge plasma type ion plating apparatus, and includes a vacuum vessel 10 connected to a vacuum pump (not shown) and a plasma gun 50 for generating plasma in the vacuum vessel 10.

  A substrate susceptor 13 that supports a substrate 11 to be deposited is disposed in the vacuum vessel 10. As shown in FIG. 3, the substrate susceptor 13 includes a substrate holder 16 for holding the substrate 11 on one surface, and a heater for heating the substrate 11 on the side opposite to the surface on which the substrate 11 is disposed. 12 are installed. The substrate susceptor 13 is provided with a temperature sensor 14 such as a thermocouple. A feedback control circuit 15 is connected to the heater 12 and the temperature sensor 14. The feedback control circuit 15 takes in the output signal of the temperature sensor 12, controls the current value supplied to the heater 12 accordingly, and controls the temperature of the substrate susceptor 13 to a predetermined temperature.

  A plurality of evaporation sources 30 are arranged at positions facing the substrate 11 in the vacuum vessel 10. As the evaporation source 30, various metals and metal oxides are used depending on the composition of the thin film to be formed. Although not shown in FIG. 2, an electron beam source (EB gun) that irradiates the evaporation source 30 with an electron beam is provided in the vacuum vessel 10.

  The vacuum vessel 10 is also provided with a reaction gas supply pipe 17 for supplying a reaction gas to the space between the substrate 11 and the evaporation source 30. A substrate shutter 20 is disposed between the evaporation source 30 and the substrate 11 to block the vapor from the evaporation source 30 from reaching the substrate 11 until the start of film formation. The film forming apparatus of the present invention is characterized by the material of the substrate shutter 20. The substrate shutter 20 will be described in detail later.

  The plasma gun 50 is installed below the substrate shutter 20 in the vacuum vessel 10 and sends out a plasma of an inert gas such as He or Ar to the vacuum vessel 10. The configuration of the plasma gun 50 is not particularly limited, but in the present embodiment, a reflective and pressure gradient type plasma gun that reflects an electron flow is used. This type of plasma gun has a structure in which a cathode 53, an intermediate electrode 55, and an anode 57 are arranged in this order in a cylindrical plasma gun container 51. The cathode 53 is provided with a discharge gas inlet 59. In the figure, one intermediate electrode 55 is shown, but a plurality of intermediate electrodes may be provided.

  The intermediate electrode 55 has a through-hole having a predetermined diameter in the center, and the pressure of the plasma gun container 51 is maintained at a positive pressure as compared with the vacuum container 10 by this through-hole, thereby forming a pressure gradient. In the intermediate electrode 55, a permanent magnet or an electromagnet that generates a magnetic field for converging the generated plasma and passing through the through hole is incorporated as necessary.

  By flowing a discharge gas at an appropriate flow rate from the cathode 51 and applying a voltage between the cathode 53 and the anode 57 by a DC power source 52, a DC arc discharge plasma is generated between the cathode 53 and the anode 57 and in the vacuum vessel 10. be able to.

Next, the substrate shutter 20 that is a feature of the present invention will be described. The film forming apparatus of the present invention is characterized in that the substrate shutter 20 is made of a substance that can radiate radiant heat at a high rate (hereinafter, a high emissivity material). As the high emissivity material, a substance having an emissivity of ε0.70 or more is preferable, and in particular, a substance having an emissivity of ε0.70 or more that easily radiates heat at a film forming temperature (for example, 500 ° C. to 700 ° C.) is preferable. Such high emissivity material, specifically, zircon _{(ZrO 2 · SiO 2, ε} = 0.92~0.8), acid molybdenum (epsilon = 0.8), carbon graphite (epsilon = 0 .85), titanium oxide (ε = 0.8), and the like, and in particular, metal oxides selected from zircon and molybdenum oxide having ε = 0.8 to 0.9 are used. High emissivity materials made of these metal oxides have high thermal emissivity and can be removed by washing even when an evaporation material adheres, and are excellent in handleability.

  The substrate shutter 20 can be entirely composed of the above-described high emissivity material, but is a high thermal conductivity support with a shutter made of a high emissivity material attached to a region facing the substrate 11. May be used. As the highly heat-conductive support, a plate-like material such as an aluminum alloy or SUS304 can be used.

  As shown in FIGS. 4A and 4B, the substrate shutter 20 has a structure in which a shutter plate 22 made of a high emissivity material is detachably fixed to a metal frame 21 such as SUS. It is preferable to adopt. The shutter plate 22 has a possibility that the thermal emissivity may decrease due to the adhering evaporation material, but in the normal maintenance cycle (every 3 batches), the thickness of the PZT film to be formed is about several tens of μm. There is not enough adhesion to reduce the thermal emissivity. In addition, since the shutter plate can be replaced, only the shutter plate 22 can be replaced with a cleaned shutter plate during a maintenance cycle, so that it is possible to reliably prevent a decrease in thermal emissivity due to adhering evaporant.

  The thickness of the shutter plate 22 is usually 1 to 2 mm. This is because if it is too thick, it may hang down due to its own weight and the mobility of the substrate shutter 20 may be deteriorated, or the heat capacity may be increased and the heat may be cut off.

  A procedure for forming a film using the film forming apparatus of this embodiment will be specifically described.

  One or more substrates 11 are set on the substrate susceptor 13. When a plurality of substrates 11 are set, the same type may be used, or the thickness and type may be different. As the evaporation source 30, one or more desired evaporation sources are set. The vacuum vessel 10 and the plasma gun vessel 51 are evacuated to a predetermined degree of vacuum. A predetermined reaction gas (for example, oxygen) is supplied from the reaction gas supply pipe 17.

  An arc discharge plasma is generated from the plasma gun 50 with the substrate shutter 20 closed, and the plasma is drawn out to the vacuum vessel 10. The evaporation source 30 is irradiated with an electron beam from an EB gun (not shown) to heat the evaporation sources 30 respectively.

  The control circuit 15 is operated, and the substrate 11 is heated from the back side by the heater 12 and controlled so as to reach the set temperature. Here, since the substrate shutter 20 is made of a high emissivity material, heat from the evaporation source 30 is radiated to the substrate 11 through the substrate shutter 20 to heat the substrate 11. The control circuit 15 controls the heater 12 so that the temperature of the substrate 11 heated by the sum of the heat from the heater 12 and the heat from the evaporation source 30 re-radiated by the substrate shutter 20 becomes the set temperature. . Therefore, even when a plurality of types of substrates 11 having different materials and structures are set, all of them reach thermal equilibrium at the start of film formation, and the same substrate surface temperature can be obtained.

  When the plasma generation and the evaporation amount from the evaporation source 30 are stabilized and the temperature of the substrate 11 reaches thermal equilibrium at the set temperature by feedback control, the substrate shutter 20 is opened and film formation is started. The vapor from the evaporation source 30 passes through a mixed plasma of a discharge gas (for example, helium) and a reaction gas (for example, oxygen), and is deposited on the substrate 11 at a set temperature while causing a predetermined reaction.

  After opening the substrate shutter 20, the amount of heat from the evaporation source and the plasma source is directly incident on the substrate, but the substrate temperature is already in a thermal equilibrium state by taking into account the radiation heat from these, so the shutter is opened. Even at the moment, the temperature of the substrate 11 is hardly affected.

  Thus, since the substrate temperature fluctuation at the start of film formation can be suppressed, nucleation at the initial stage of film formation in which vapor from the evaporation source 30 is deposited on the substrate 11 can be stabilized. In addition, since the substrate temperature does not change, the film can be formed under the same growth conditions every time. Thereby, for example, in the case of forming a ferroelectric film, the film formation reproducibility is improved and the occurrence of defects due to the disturbance of the initial nucleus can be suppressed. A decrease in the adhesion of the film to the substrate 11 can also be suppressed.

  Further, in the conventional film forming apparatus, when the substrate size is increased, the film thickness and film characteristics are often distributed. This is because, as shown in FIG. 3, there is a difference in heat dissipation between the center of the substrate 11 and the vicinity of the substrate presser 16 where the substrate is installed, but the film forming apparatus of this embodiment has the susceptor 13 side. The total amount of heat from the evaporation source via the substrate shutter as well as the heater of the substrate is feedback controlled to reach a thermal equilibrium state. Therefore, even for a large-diameter wafer (8 inches), for example, regardless of the substrate size. It becomes possible to form a ferroelectric film such as a PZT film showing good piezoelectric characteristics.

  In the above embodiment, the arc discharge ion plating apparatus has been described. However, the present invention is not limited to this apparatus, and an apparatus in which a heat source of radiant heat exists in a space separated from the substrate 11 by the substrate shutter 20, for example, a vapor deposition apparatus or a sputtering apparatus. The structure of the substrate shutter 20 of the present embodiment can be similarly applied to such a physical vapor deposition apparatus.

  As described above, according to the present invention, the substrate temperature fluctuation can be suppressed before and after the start of film formation (after opening and closing the substrate shutter), and a high-quality film can be obtained. It is suitable for the production of ferroelectric thin films that are safe and environmentally friendly. For example, a MEMS optical scanner or an ink jet printer head that is driven by using a PZT film as a piezoelectric thin film can be manufactured.

<Example 1, comparative example 1>
<Changes in substrate temperature>
Using a reflective pressure gradient arc discharge ion plating apparatus to which a plasma gun 50 having intermediate electrodes (three) is attached as shown in FIG. A lead zirconate titanate PZT (Pb (Zr _x Ti _1-x ) O ₃ ) thin film having the characteristics described above was formed. At that time, the substrate temperature from the start to the end of the reaction was monitored by a thermocouple.
As the substrate shutter of the ion plating apparatus, in Example 1, zircon (plate thickness: 1 mm) having an emissivity ε = 0.8 to 0.9 is used, and in Comparative Example 1, SUS304 silver having an emissivity ε = 0.4. A rough surface plate (plate thickness 1 mm) was used. Other conditions and film forming methods were the same as in Example 1 and Comparative Example 1 as described below.

  The substrate 11 was formed by depositing constituent materials in the order of SiO 2 / Ti / Pt on a (100) plane Si wafer, and Pb, Zr, and Ti metals were used as the material of the evaporation source 30.

First, 100 sccm of He gas was introduced into the pressure gradient arc discharge plasma gun 50 as a carrier gas, and a DC bias voltage was applied to generate arc discharge. The discharge voltage was controlled at 120V and the discharge current at 70A. High-density plasma (plasma density of 10 ¹² cm ³ or more) generated by this arc discharge was introduced into the vacuum vessel by a magnetic field of about 300 gauss generated by a magnetic field generation source for plasma control.

In this state, high-density oxygen plasma and oxygen radicals were generated in the vacuum vessel by introducing 250 sccm of O ₂ gas as a reaction gas from the gas introduction tube.

On the other hand, while the substrate shutter 20 is closed, the substrate 11 is heated to about 550 ° C. by the heater 12, and the evaporation source 30 is independently heated by electron beam heating in the presence of the above mixed plasma of He and O _2. Evaporated. The evaporation amount of each metal was monitored by a quartz vibration type film thickness sensor, and the output of the electron beam heating source was feedback-controlled to control the evaporation amount to be a constant amount. Specifically, the output of the evaporation source so that the Pb evaporation amount is in the range of 10 to 20 times the total evaporation amount of Zr and Ti, and the evaporation amount of Zr and Ti is substantially equal. Controlled. Thus, the film composition of the PZT film was adjusted to x = 0.5, that is, Pb (Zr _0.5 Ti _0.5 ) O ₃ .

  After about 20 minutes had passed in this state, the substrate shutter was opened, and the reaction of each raw metal vapor and oxygen radicals in the mixed plasma was deposited on the substrate 11 to start film formation on the substrate. The pressure during film formation was 0.1 Pa, the film formation rate was 1 nm / s or more, and film formation was performed for about 60 minutes. Finally, a PZT film having a film thickness of 4 μm was formed.

  Changes in the substrate temperature from 20 minutes before opening the substrate shutter to the end of film formation are shown in FIG. 5 (in the figure, the results of Example 1 are indicated by white circles and the results of Comparative Example 1 are indicated by black circles). As can be seen from the comparison with Example 1 and Comparative Example 1, in Comparative Example 1 using a material having low thermal radiation, the substrate temperature temporarily increased by about 100 ° C. after the substrate shutter was opened. In Example 1, the substrate temperature hardly changed before and after the substrate shutter. In Comparative Example 1, the heat from the evaporation source is cut off when the substrate shutter is closed, and the substrate is kept at a temperature of 550 ° C. exclusively by the heat from the heater. Then, the substrate is further heated by the heat from the evaporation source, and the temperature rises. In contrast, in the embodiment, a high thermal radiation material is used as the substrate shutter. This is because the substrate temperature is maintained in total with heat, so that a rapid temperature change does not occur before and after the substrate shutter is opened and closed. Thus, according to Example 1, it was confirmed that there was no temperature change before and after the opening and closing of the substrate shutter, and stable nucleation was possible.

<Confirmation of reproducibility>
Each of the PZT films was formed ten times by the film forming method of Example 1 and Comparative Example 1, and the reproducibility of the composition and characteristics (dielectric constant and dielectric loss) of the PZT film obtained each time was confirmed. The composition of the target PZT film is Pb (Zr _0.5 Ti _0.5 ) O ₃ , and the target dielectric constant and dielectric loss are 1050 and 3.00%, respectively.

  The composition of the obtained PZT film was measured by EDX analysis. The characteristics were measured for dielectric constant and dielectric loss. Furthermore, the crystal phase of the obtained PXT film was analyzed with an X-ray diffraction image.

  The difference in the reproducibility of the dielectric constant is shown in FIG. As a result of forming a PZT film by the method of Comparative Example 1 using a low radioactive substrate shutter, the dielectric constant varies within a range of 500 to 1100 after 10 film formations with respect to the target dielectric constant 1050, and the variation rate between the rods is It was 30% or more. On the other hand, the PZT film of Example 1 had a dielectric constant in the range of 1000 to 1100 after 10 depositions, and the variation rate between rods could be suppressed to within 5%.

  In addition, FIG. 7 shows variation in dielectric loss (tan δ) between rods. In the film forming method of Comparative Example 1, the variation in the range of tan δ = 3.30% to 8.30% with respect to the target dielectric loss of 3.00% was 10% or more, and the variation rate between the 10 film forming rods was 40% or more. It was. On the other hand, in Example 1, it was in the range of tan δ = 2.95% to 3.15%, and the variation rate between the ten film forming rods could be suppressed within 5%.

Moreover, the dispersion | variation in a composition is shown in FIG. When the composition of PZT was x = 0.5, that is, when Pb (Zr _0.5 Ti _0.5 ) O ₃ was targeted, in Comparative Example 1, x = 0.33 to 0.75, which was a variation of 35% or more. . On the other hand, in Example 1, x = 0.48 to 0.52, and the composition could be stabilized within 5%.

<Example 2, comparative example 2>
A PZT film was formed on the substrate by the same film forming method as in Example 1 and Comparative Example 1 with different types of substrates used, and changes in the crystal structure due to differences in the substrate types were measured. Three types of substrates were used: bare Si (thickness 500 μm), SOI (thickness 50 μm / 2.0 μm / 450 μm), and bare Si (thickness 625 μm). The X-ray diffraction image of the obtained PZT film of Example 2 is shown in FIG. 9, and the X-ray diffraction image of the PZT film of Comparative Example 2 is shown in FIG. 9 and 10, (a) shows the case where bare Si (thickness 500 μm) is used, (b) shows the case where SOI is used, and (c) shows the case where bare Si (thickness 625 μm) is used. .

  As shown in FIGS. 9A, 9B, and 9C, in Example 2, it was confirmed that perovskite single-phase PZT films having the same crystal structure were formed on three types of substrates. . As a result, in the film forming method of Example 2, even when the heat capacity varies depending on the thickness and material of the substrate, the substrate temperature is balanced by the sum of the heat from the heater and the heat from the evaporation source when the substrate shutter is opened. Therefore, it is proved that the temperature change and its influence on the initial nucleation are not affected. Therefore, it was found that by forming a film by the film forming method of Example 1, it is not necessary to tune the film forming conditions for each type of substrate.

In Comparative Example 2, it was confirmed that the PZT film formed on the bare Si substrate (500 μm) had crystallinity strongly oriented to (001) as shown in FIG. In addition, in the PZT film formed on the SOI substrate, it was confirmed that perovskite was formed because (001) and (110) were observed as shown in FIG. A heterogeneous phase of PbO appeared around 30 degrees. That is, unlike the bare Si substrate, it was not a perovskite single phase. This is because the SOI substrate has a SiO ₂ layer of 2.0 μm inserted in the intermediate layer, and the SiO ₂ layer has a thermal conductivity 100 times smaller than that of Si, so the amount of heat incident from the evaporation source and the plasma source is reduced. It is presumed that a phenomenon occurs in which the surface temperature of the substrate 11 instantaneously increases when the SiO ₂ layer is thermally insulated on the substrate 11 and the substrate shutter 20 is opened. This phenomenon is thought to have affected the growth of initial nuclei.

  As apparent from the diffraction image of FIG. 10C, the PZT film formed on the bare Si substrate having a thickness of 625 μm did not become a perovskite single phase. This is because the thickness of the substrate is 125 μm thicker than that of 500 μm, so the 625 μm thick substrate has a higher thermal resistance than the 500 μm thick substrate, and as a result, the surface temperature has risen. It is thought that a heterogeneous peak of PbO appeared.

According to the present invention, in a film forming apparatus for forming a substrate, in which a shutter for controlling the start of film formation is provided between a film forming material and the substrate, temperature fluctuations before and after opening and closing the shutter As a result, it is possible to stably perform initial nucleation of the film and to provide a film forming apparatus with excellent reproducibility of film characteristics.
The film forming apparatus of the present invention is suitable for manufacturing a ferroelectric thin film excellent in safety and environmental friendliness.

10 ... Vacuum container, 11 ... Substrate, 12 ... Heater, 13 ... Substrate susceptor, 14 ... Temperature sensor, 15 ... Control circuit, 20 ... Substrate shutter, 30 ... Evaporation source, 50 ... Plasma gun

Claims (5)

A film forming container, a substrate holding unit for holding the substrate, a film forming source disposed at a position facing the substrate, a plasma source for generating plasma in a space between the substrate and the film forming source, A film forming apparatus having an openable and closable shutter disposed between the substrate holding unit and the plasma source,
The shutter is made of a material that radiates heat generated from the plasma source and the film forming source toward the substrate, and the material is made of a metal oxide selected from zircon and molybdenum oxide. .   2. The film forming apparatus according to claim 1, wherein the shutter material has an emissivity of 0.70 or more at a film forming temperature.   3. The film forming apparatus according to claim 1, wherein the shutter material has an emissivity of 500 to 600 ° C. of 0.70 or more.   4. The film forming apparatus according to claim 1, wherein the substrate holding unit detects a heating unit that heats the substrate, a temperature sensor that detects a temperature of the substrate, and the temperature sensor. And a control unit that feedback-controls the heating unit according to temperature. A film forming container, a substrate holding unit for holding the substrate, a film forming source disposed at a position facing the substrate, and an openable / closable shutter disposed at a position separating the film forming source and the substrate And
The film forming apparatus, wherein the shutter is made of a material that radiates heat generated from the film forming source to the substrate side, and the material is made of a metal oxide selected from zircon and molybdenum oxide.

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