JP2015146389A - Oxide crystal film and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide crystal film and such, formed on the same substrate, having a plurality of regions in which principal orientations of the crystal films are different.SOLUTION: An oxide crystal film 10 formed on a same substrate by using a PZT includes: a first region 11; and a second region 12. Principal orientations of the crystal films in the first region and the second region are different. In the oxide crystal film 10, a PZT (111) whose principal orientation is a direction (111) is formed in the first region 11 and a PZT (100) whose principal orientation is a direction (100) is formed in the second region 12.

Description

  The present invention relates to an oxide crystal film and a manufacturing method thereof.

Conventionally, perovskite Pb (Zr, Ti) O ₃ (PZT) is used as a ferroelectric piezoelectric material in sensors, actuators, memory devices, and the like.

  The PZT crystal film has different properties depending on the orientation, and also has different uses. For example, a PZT (111) crystal film whose main orientation is the (111) direction and a PZT (100) crystal film whose main orientation is the (100) direction have the following application differences. That is, since the PZT (111) crystal film has a large remanent polarization, it is suitable for use in FRAM (registered trademark) (Ferroelectric Random Access Memory), and the PZT (100) crystal film has a high relative dielectric constant. Random Access Memory) is suitable.

  However, for example, when integrating FRAM and DRAM manufactured using the same PZT material, conventionally, PZT (111) crystal film and PZT (100) crystal film are formed on different substrates, and a complicated transfer process is performed. They were integrated on a single substrate. That is, in an oxide crystal film such as a PZT crystal film, a technique for forming a plurality of regions having different main orientations of crystal films on the same substrate has not been established.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an oxide crystal film or the like formed on the same substrate and having a plurality of regions having different main orientations of crystal films. .

  The oxide crystal film is an oxide crystal film formed on the same substrate, and includes a first region and a second region, and the first region and the second region It is a requirement that the main orientations of the crystal films are different.

  According to the disclosed technology, an oxide crystal film or the like having a plurality of regions having different main orientations of crystal films formed over the same substrate can be provided.

1 is a cross-sectional view illustrating an oxide crystal film according to a first embodiment. FIG. 3 is a diagram (part 1) illustrating a manufacturing process of an oxide crystal film according to the first embodiment; FIG. 6 is a diagram (part 2) illustrating the manufacturing process of the oxide crystal film according to the first embodiment; It is a figure which illustrates the X-ray-diffraction result of the 1st area | region and 2nd area | region of an oxide crystal film. It is sectional drawing which illustrates the oxide crystal film which concerns on 2nd Embodiment. It is a figure which illustrates the manufacturing process of the oxide crystal film which concerns on 3rd Embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
FIG. 1 is a cross-sectional view illustrating an oxide crystal film according to the first embodiment. Referring to FIG. 1, the oxide crystal film 10 according to the first embodiment is a film manufactured using the same PZT material on the same substrate, and the first region in which the main orientation of the crystal film is different. 11 and a second region 12. In the oxide crystal film 10, a PZT (111) crystal film having a main orientation of (111) is formed in the first region 11, and the main orientation is (100) in the second region 12. A PZT (100) crystal film in the direction is formed. Although the thickness of the oxide crystal film 10 can be determined arbitrarily, it can be set to, for example, about 30 nm to 2 μm.

In FIG. 1, 20 is a silicon substrate, 30 is a silicon oxide film (SiO ₂ film), 40 is a titanium oxide film (TiOx film), 50 is a platinum film (Pt film), and 110 is a PZT amorphous film. That is, the oxide crystal film 10 is an oxide crystal film formed on the same substrate (on the silicon substrate 20), and a plurality of regions (the first region 11 and the first region) having different main orientations of the PZT crystal film. 2 regions 12).

PZT is a solid solution of lead zirconate (PbZrO ₃ ) and lead titanate (PbTiO ₃ ), and the characteristics of PZT differ depending on the ratio of PbZrO ₃ and PbTiO ₃ . For example, the ratio of PbZrO ₃ and PbTiO ₃ is 53:47, and the chemical formula indicates Pb (Zr _0.53 , Ti _0.47 ) O ₃ , PZT generally indicated as PZT (53/47), etc. Can be used.

  Next, a method for manufacturing the oxide crystal film 10 will be described. 2 and 3 are diagrams illustrating the manufacturing process of the oxide crystal film according to the first embodiment.

  First, in the step shown in FIG. 2A, a silicon substrate 20 having a thickness of about 650 μm serving as a support is prepared. Then, a silicon oxide film 30, a titanium oxide film 40, and a platinum film 50 are sequentially stacked on the surface of the silicon substrate 20.

  Specifically, a silicon oxide film 30 having a thickness of about 600 nm is formed on the surface of the silicon substrate 20 by, for example, a CVD (Chemical Vapor Deposition) method or a thermal oxidation method. Then, a titanium oxide film 40 having a thickness of about 50 nm is stacked on the silicon oxide film 30 by, for example, a sputtering method or a CVD method. Further, a platinum film 50 having a thickness of about 100 nm is laminated on the titanium oxide film 40 by, for example, a sputtering method or a CVD method.

Next, in the step shown in FIG. 2B, the PZT coating film 100 is formed on the platinum film 50. Specifically, for example, starting materials such as lead acetate, zirconium alkoxide, and titanium alkoxide compound are dissolved in methoxyethanol, which is a common solvent, to synthesize a PZT precursor solution (PZT sol-gel solution), which is a uniform solvent. Then, for example, a seed layer is formed on the platinum film 50 using PbTiO ₃ by a spin coating method, and then a synthesized PZT precursor liquid (PZT sol-gel liquid) is applied on the seed layer to form the PZT coating film 100. To do. In addition, the composite oxide solid content concentration of the synthesized PZT precursor solution can be, for example, about 0.5 mol / liter or less. However, the formation of the seed layer is not essential, and the PZT coating film 100 may be formed directly on the platinum film 50 without forming the seed layer.

  Next, in the step shown in FIG. 2C, the silicon substrate 20 with the PZT coating film 100 formed on the platinum film 50 is placed on, for example, a hot plate (not shown), and the thermal decomposition start temperature ( For example, it is heated to a predetermined temperature (for example, about 220 ° C.) of about 100 ° C. or more and less than 300 ° C. As a result, the solvent evaporates and the PZT coating film 100 is thermally decomposed into a solid PZT amorphous film 110 (amorphous oxide film). Then, it cools to room temperature. In the present application, the thermal decomposition start temperature means the lowest temperature at which thermal decomposition is possible. The thermal decomposition start temperature is determined depending on the boiling point of the main solvent used for the synthesis of the PZT precursor liquid.

  Said predetermined temperature (for example, about 220 degreeC) can be calculated | required experimentally beforehand, for example. For example, a plurality of PZT amorphous films are produced by changing the temperature at which the PZT coating film is heated, cooled to room temperature, and then each PZT amorphous film is further heated to a crystallization temperature or higher to produce a plurality of PZT crystal films. Then, the Lotgering factor of each PZT crystal film is measured to determine the relationship between the heating temperature and the Lotgering factor.

  Here, the Lotgering factor represents the ratio of each orientation when the sum of the peak intensities of each orientation obtained by X-ray diffraction is 1, the denominator is the sum of the peak intensities of each orientation, and the numerator is arbitrary. It is an average orientation degree when it is set as the peak intensity of orientation. Here, the (111) Lotgering factor is determined when the molecules are in the (111) orientation.

  Next, the target (111) lotgering factor is determined. For example, when the goal is that the (111) lot-galling factor is 0.9 or more (90% or more), the goal is achieved based on the relationship between the heating temperature and the (111) lot-galling factor. Select the temperature. The selected temperature is the predetermined temperature (for example, about 220 ° C.).

Then, in the process shown in FIG. 3 (a), irradiated locally laser beam _{L 1} to the PZT amorphous film 110 (laser annealing), the main orientation direction (111) PZT (111) crystal film The first region 11 in which is formed is formed.

Specifically, for example, the structure shown in FIG. 2C is placed on a stage, and continuously oscillating laser light L ₁ (for example, near a wavelength of 980 nm) having a flat top is moved locally while moving the stage. And the PZT amorphous film 110 is crystallized. The region not irradiated with the laser beam _{L 1} will remain PZT amorphous film 110.

Beam shape of the laser light L ₁ irradiated to PZT amorphous film 110, for example, may be substantially rectangular. Beam size of the laser beam _{L 1} can be, for example, a 1 mm × 0.35 mm. Scan width of the laser beam _{L 1} is, for example, can be set to 1 mm. Since the laser light L ₁ having a wavelength of about 980 nm is hardly absorbed by the PZT amorphous film 110, it reaches the platinum film 50 that is the lower layer of the PZT amorphous film 110.

On the other hand, the platinum film 50 has a very large absorption coefficient in the vicinity of a wavelength of 980 nm, which is approximately 7 × 10 ⁵ cm ⁻¹ . Further, for example, in the platinum film 50 having a film thickness of 100 nm, the light transmittance in the vicinity of the wavelength of 980 nm is 1% or less. Accordingly, the platinum film 50 absorbs almost all of the light energy of the laser light L ₁ having a wavelength of about 980 nm irradiated to the platinum film 50.

Light energy of the platinum film 50 laser light L _1, which is absorbed into the change in thermal heating the platinum film 50. The heat of the platinum film 50 is transmitted (diffused) to the PZT amorphous film 110 formed on the platinum film 50, and the PZT amorphous film 110 is crystallized to become a PZT (111) crystal film. The thickness of the PZT (111) crystal film that can be formed by a single treatment is about 30 nm to 80 nm.

In general, the crystallization temperature of the PZT amorphous film is about 600 ° C. to 850 ° C., which is considerably lower than the melting point of platinum (1768 ° C.). Thus, by controlling the energy density and irradiation time of the laser light L ₁ incident on the platinum film 50, without damaging the platinum film 50, it can be crystallized by heating the PZT amorphous film 110. Energy density of the laser beam _{L 1} is, for example, can be set to 100 to 1000 W / cm ² approximately. The irradiation time of the laser beam L1 can be, for example, about ₁ ms to 200 ms.

Next, in the step shown in FIG. 3B, the PZT amorphous film 110 is heat-treated. After cooling to room temperature, irradiated locally laser beam _{L 1} to the PZT amorphous film 110 (laser annealing), the main orientation is (100) direction PZT (100) a crystal film is formed Two regions 12 are formed.

  Specifically, first, the structure shown in FIG. 3A is placed on, for example, a hot plate (not shown) and heated to a temperature of 300 ° C. or higher and lower than 500 ° C. (for example, about 350 ° C.). . Then, it cools to room temperature. The first region 11 where the PZT (111) crystal film is formed is also heated to the same temperature, but does not adversely affect the PZT (111) crystal film. In addition, although the upper limit of heating temperature should just be the temperature (less than about 600 degreeC) which does not crystallize, it is less than 500 degreeC here in the meaning which has a margin with respect to crystallization temperature (about 600 degreeC-850 degreeC). .

  A suitable temperature for heating in this step can also be determined based on the aforementioned Lotgering factor. However, here, the difference is that the (100) Lotgering factor is obtained when the molecule is in the (100) orientation, and the temperature at which the (100) Lotgering factor is equal to or higher than the target value is selected.

Next, similarly to the step shown in FIG. 3A, the PZT amorphous film 110 after the heat treatment is locally irradiated with a laser beam L ₁ (for example, near a wavelength of 980 nm) to crystallize the PZT amorphous film 110. I do. The irradiation conditions of the laser light L ₁ may be the same as the step shown in FIG. 3 (a).

In PZT amorphous film 110 was heat treated at temperatures below 300 ° C. or higher 500 ° C., the laser beam _{L 1} to the locally irradiated region (second region) of PZT (100) crystal film is formed. The region not irradiated with the laser beam _{L 1} will remain PZT amorphous film 110.

  Through the above steps, the oxide crystal film 10 can be formed. That is, the oxide crystal film is formed on the same substrate (on the silicon substrate 20) and has a plurality of regions (first region 11 and second region 12) having different main orientations of the PZT crystal film. The oxide crystal film 10 can be formed. In the step of FIG. 3B, the PZT amorphous film 110 may not be left and all the regions other than the first region 11 may be used as the second region 12.

  By repeating the steps of FIG. 2B to FIG. 3B, the oxide crystal film 10 can be thickened. Here, a thick oxide crystal film 10 is manufactured by repeating the steps of FIGS. 2B to 3B three times, and X-ray diffraction of the first region 11 and the second region 12 is performed. went. The result is shown in FIG.

  FIG. 4A shows the X-ray diffraction result of the first region 11. From FIG. 4A, it can be confirmed that a PZT (111) crystal film having a main orientation of the (111) direction is formed in the first region 11. FIG. 4B shows the X-ray diffraction result of the second region 12. From FIG. 4B, it can be confirmed that a PZT (100) crystal film having a main orientation of the (100) direction is formed in the second region 12.

  Note that the process of FIGS. 2B to 3B is repeated three times to increase the thickness, and the processes of FIGS. 2B to 3B may be repeated any number of times. Absent.

  Thus, when the PZT coating film is heated to a temperature equal to or higher than the thermal decomposition start temperature and lower than the first temperature to form a PZT amorphous film and then cooled, and further, the PZT amorphous film is locally heated above the crystallization temperature, A PZT (111) crystal film is formed. Further, the PZT amorphous film on which the PZT (111) crystal film is locally formed is further heated to a second temperature that is equal to or higher than the first temperature and lower than the crystallization temperature, and then cooled to locally crystallize the PZT amorphous film. When heated above the crystallization temperature, a PZT (100) crystal film is formed.

  Note that the PZT (100) crystal film can be formed without going through the step of heating the PZT coating film to a temperature not lower than the thermal decomposition start temperature and lower than the first temperature. That is, when the PZT coating film is heated to a second temperature that is equal to or higher than the first temperature and lower than the crystallization temperature to form a PZT amorphous film, and then cooled, and further, the PZT amorphous film is locally heated above the crystallization temperature, A PZT (100) crystal film is formed.

  In the method according to the present embodiment, since the PZT amorphous film 110 is heat-treated at a relatively low temperature of less than 500 ° C., there is little thermal shock to the silicon substrate 20 and each film stacked on the silicon substrate 20, and other devices Easy to integrate. In addition, since devices having different functions can be formed using the same material on the same substrate, the degree of integration can be improved.

In the above description, an example in which a continuous wave laser beam L ₁ (for example, near a wavelength of 980 nm) that is not absorbed by PZT is used as a light source has been described. However, the present invention is not limited to this. For example, a continuous wave laser beam having another wavelength that is not absorbed by PZT may be used as a light source, or a continuous wave laser beam having a wavelength that is absorbed by PZT may be used as a light source. Alternatively, pulsed laser light may be used as the light source.

In the above description, PZT is used as the material of the oxide crystal film. However, other ABO ₃ type materials may be used, for example. The ABO ₃ type material is a composite oxide described by the general formula ABO ₃ and having A = Pb, Ba, Sr B = Ti, Zr, Sn, Ni, Zn, Mg, and Nb as main components. For example, when barium titanate is used as an ABO ₃ type material, it is possible to prepare a barium titanate precursor solution by dissolving barium alkoxide and a titanium alkoxide compound in a common solvent. is there.

  In the above description, the platinum film 50 is used as the lower layer of the PZT amorphous film 110. However, instead of the platinum film 50, for example, a metal film or metal containing at least one of Ir, Rh, Ru, Pd, and Cr is used. An oxide film may be used.

<Second Embodiment>
In the second embodiment, an example of an oxide crystal film having a linear alignment pattern is shown. In the second embodiment, the description of the same components as those already described is omitted.

  FIG. 5 is a cross-sectional view illustrating an oxide crystal film according to the second embodiment. Referring to FIG. 5, an oxide crystal film 10A according to the second embodiment is a film manufactured using the same PZT material, and includes a first region 11 in which a PZT (111) crystal film is formed. , PZT (100) crystal films formed on the second regions 12 are alternately arranged. For example, the first region 11 and the second region 12 may have a substantially parallel pattern with the depth direction in the drawing being the longitudinal direction. Although the thickness of the oxide crystal film 10A can be determined arbitrarily, it can be set to, for example, about 30 nm to 2 μm.

  The manufacturing process of the oxide crystal film 10A is basically the same as the manufacturing process of the oxide crystal film 10 according to the first embodiment. For example, a line pattern is formed as follows. Can be formed.

  First, similarly to the step shown in FIG. 2C, the silicon substrate 20 having the PZT coating film 100 formed on the platinum film 50 is placed on a hot plate and heated to, for example, about 220 ° C. to form a PZT amorphous material. A film 110 is formed. Then, it cools to room temperature.

  Next, for example, a continuous wave laser beam having a wavelength of 1470 nm and a beam width of 50 μm is irradiated while scanning the PZT amorphous film 110 in a line shape, and the first regions 11 (line regions arranged at predetermined intervals) ( PZT (111) crystal film) is formed. The pitch (scan pitch) of the first regions 11 can be set to about 40 μm, for example. Note that the PZT amorphous film 110 remains in the region not irradiated with laser light.

  Next, the PZT amorphous film 110 in which the first region 11 is formed is placed on a hot plate, heated to about 350 ° C., for example, and then cooled to room temperature. Then, a laser beam similar to the above is irradiated while scanning in a line between the adjacent first regions 11, and the second region 12 (PZT (100) crystal film) between the adjacent first regions 11. Form.

  Thus, the oxide crystal film 10A in which the first region 11 in which the PZT (111) crystal film is formed and the second region 12 in which the PZT (100) crystal film is formed are alternately arranged in a line shape. Is formed. The oxide crystal film 10A may be thickened by repeating the above steps.

  In this manner, an arbitrary alignment pattern can be formed by selecting the laser beam width and the scan pitch and scanning the laser beam aiming at a predetermined position.

  Since the silicon substrate 20, the silicon oxide film 30, and the titanium oxide film 40 are transparent to laser light having a wavelength of 1470 nm, the laser light may be irradiated from the back side of the silicon substrate 20. Also in this case, the PZT amorphous film 110 formed on the platinum film 50 is heated by the platinum film 50 absorbing laser light irradiated from the back side of the silicon substrate 20.

  In addition, instead of the method of selecting the laser beam width and scan pitch and forming the target alignment pattern, the target alignment pattern is formed by irradiating the laser beam through a mask having a predetermined opening. Also good.

<Third Embodiment>
In the third embodiment, an example in which an oxide crystal film in which a PZT (111) crystal film and a PZT (100) crystal film are formed over the same substrate is manufactured without irradiation with laser light is described. Note that in the third embodiment, description of the same components as those of the already described embodiments is omitted.

  FIG. 6 is a diagram illustrating an oxide crystal film manufacturing process according to the third embodiment. First, the PZT coating film 100 is formed on the platinum film 50 in the same manner as the process shown in FIGS. 2A and 2B of the first embodiment.

Next, in the step shown in FIG. 6A, the structure shown in FIG. 2B is placed on the hot plate 500 which is the first heat source, and the thermal decomposition start temperature (for example, about 100 ° C.). Heat to a temperature lower than 300 ° C. (for example, about 220 ° C.). Then, at the same time, irradiating infrared rays _{L 2} from the infrared light source is a second heat source (not shown) to the PZT coating film 100.

However, the PZT (111) region to form a crystalline film (corresponding to the first region 11), the infrared _{L 2} is arranged a mask 600 for infrared shielding so as not to be irradiated. The intensity of the infrared ray L ₂ is determined so that the temperature of the region where the PZT (100) crystal film is to be formed (corresponding to the second region 12) is 300 ° C. or higher and lower than 500 ° C. For example, the temperature is adjusted to about 350 ° C. As a result, the solvent evaporates, the PZT coating film 100 is thermally decomposed, and a first PZT amorphous film 120 and a second PZT amorphous film 130 having different thermal histories are formed. Then, it cools to room temperature.

  Next, in the step shown in FIG. 6B, the structure shown in FIG. 6A is heated to the crystallization temperature or higher by external heating with an electric furnace, an RTA (Rapid Thermal Annealing) apparatus or the like. That is, the entire PZT amorphous film is heated to the crystallization temperature or higher. As a result, the first PZT amorphous film 120 is crystallized to become a PZT (111) crystal film, and at the same time, the second PZT amorphous film 130 is crystallized to become a PZT (100) crystal film, thereby forming the oxide crystal film 10B. Is done.

  In this manner, an oxide crystal film in which a PZT (111) crystal film and a PZT (100) crystal film are formed over the same substrate can be manufactured without irradiation with laser light. This method is effective in that a PZT (111) crystal film and a PZT (100) crystal film can be formed at the same time, but the PZT (111) crystal film and the PZT (100) are more effective than a method of irradiating a laser beam. The interface of the crystal film tends to be unclear (blurred state). Therefore, when producing a linear alignment pattern of about several tens of μm, it is preferable to use a method of irradiating a laser beam.

  The preferred embodiment has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and replacements are made to the above-described embodiment without departing from the scope described in the claims. Can be added.

  For example, the light with which the object to be heated is irradiated is not limited to laser light, and any light may be used. For example, a flash lamp or the like can be used. Further, as the support, a sapphire substrate or the like may be used instead of the silicon substrate.

  The manufacturing method of the oxide crystal film according to the above-described embodiment can be applied to the case where FRAM and DRAM are integrated on the same substrate. However, the temperature sensing method in which different orientation patterns are formed on the same substrate. You may apply, for example when producing a sensor.

10, 10A, 10B Oxide crystal film 11 First region 12 Second region 20 Silicon substrate 30 Silicon oxide film 40 Titanium oxide film 50 Platinum film 100 PZT coating film 110 PZT amorphous film 120 First PZT amorphous film 130 First 2 PZT amorphous film 500 Hot plate 600 Mask L ₁ , L ₂ laser light

JP2013-226818A

Claims (9)

An oxide crystal film formed on the same substrate,
Having a first region and a second region;
An oxide crystal film, wherein a main orientation of the crystal film is different between the first region and the second region. The oxide crystal film according to claim 1, wherein the crystal film is of ABO ₃ type.   3. The oxide crystal film according to claim 2, wherein the crystal film contains a composite oxide containing lead (Pb), titanium (Ti) and zirconium (Zr) as a main component. A method for producing an oxide crystal film formed on the same substrate,
Forming an amorphous film on the substrate;
Providing different thermal histories to the first region and the second region of the amorphous film, and forming crystal films having different main orientations in the first region and the second region. A method for producing an oxide crystal film. In the step of forming the amorphous film,
Forming a coating film on the substrate, and heating the coating film to a temperature not lower than the first decomposition temperature and lower than the first temperature to form the amorphous film;
The step of forming the crystal film includes
Heating the first region of the amorphous film locally above the crystallization temperature to form a crystal film in the first region of the amorphous film;
Heating the amorphous film having a crystal film formed in the first region to a second temperature not lower than the first temperature and lower than the crystallization temperature;
Heating the second region of the amorphous film locally to a temperature equal to or higher than the crystallization temperature to form a crystal film having a main orientation different from that of the first region in the second region of the amorphous film; The method for producing an oxide crystal film according to claim 4, comprising: In the step of forming the crystal film,
6. The method for producing an oxide crystal film according to claim 5, wherein the first region and the second region of the amorphous film are locally heated to a temperature equal to or higher than a crystallization temperature by irradiating light. In the step of forming the amorphous film,
A coating film is formed on the substrate, and the first region of the coating film is heated to a temperature not lower than the first decomposition temperature and lower than the first temperature, and at the same time, the second region of the coating film is heated to the first temperature. The amorphous film is heated to a second temperature lower than the crystallization temperature.
In the step of forming the crystal film,
5. The oxide crystal film according to claim 4, wherein the entire amorphous film is heated to a temperature equal to or higher than a crystallization temperature to form crystal films having different main orientations in the first region and the second region. Production method. In the step of forming the amorphous film,
The first region and the second region of the coating film are heated by a first heat source, and at the same time, the second region of the coating film is heated by a second heat source to heat the first region of the coating film. The oxide crystal film manufacturing method according to claim 7, wherein the temperature is set to a temperature not lower than a decomposition start temperature and lower than a first temperature, and the second region of the coating film is set to a second temperature not lower than the first temperature and lower than a crystallization temperature. Method.   The method for producing an oxide crystal film according to claim 5, wherein the coating film is formed by coating a sol-gel solution on the substrate.

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