JPWO2010016131A1 - Recording medium and recording medium forming method - Google Patents

Abstract

Provided is a recording medium capable of pre-creating a pre-format while maintaining high mass productivity and eliminating the need for pre-format work. In order to record information with high density based on the polarization direction of the ferroelectric material, at least the substrate 11, the electrode film 12 positioned above the substrate 11, and the ferroelectric film positioned above the electrode film 12 13 and the recording / reproducing control signal is recorded by modulating the film thickness of the specific part on the lower layer side of the ferroelectric film 13. A pre-format such as sector information and address information is formed in advance as a film thickness modulation of a specific portion on the lower layer side of the ferroelectric film, so that a ROM function can be provided in a part of a writable recording medium. Work can be made unnecessary.

Description

  The present invention provides at least a substrate, an electrode film located on the upper layer of the substrate, and a ferroelectric located on the upper layer of the electrode film in order to record information at a high density based on the polarization direction of the ferroelectric substance. And a recording medium forming method.

Japanese Patent Laid-Open No. 11-053780 JP 2000-268421 A

  Conventionally, as a recording medium such as a hard disk drive or various recording media, for example, it is possible not only to repeatedly record information by changing polarization, but also to have high durability (high holding power) for repeated recording, An ultra-high density recording medium provided with a ferroelectric layer is known.

  At this time, the recording medium is known as a recording medium comprising at least three layers of a substrate, an electrode film located on the upper layer of the substrate, and a ferroelectric film located on the upper layer of the electrode film. (For example, see Patent Documents 1 and 2).

  In addition, such a multilayer recording medium is formed to have a uniform thickness so that each layer has a flat surface without unevenness or inclination.

  By the way, in the recording medium configured as described above, for example, in a hard disk drive for a personal computer, sector information, address information, drive information, etc. are obtained by initializing or formatting the recording medium (disk). There is a problem that it is necessary to create a pre-format for this, which is troublesome and takes time.

  In order to solve the above problems, an object of the present invention is to provide a recording medium in which a preformat is created in advance while maintaining high mass productivity, and the preformat operation is not necessary.

  In order to achieve the object, a recording medium according to claim 1 is provided with at least a substrate and an electrode positioned on an upper layer of the substrate in order to record information at a high density based on a polarization direction of a ferroelectric substance. In a recording medium comprising a film and a ferroelectric film positioned above the electrode film, a recording / reproduction control signal is recorded by modulating the film thickness of a specific portion on the lower layer side of the ferroelectric film. It is characterized by.

  According to such a configuration, a recording medium using a ferroelectric film for ultra-high density recording as a recording layer, and preformatting such as sector information and address information is performed at a specific portion on the lower layer side of the ferroelectric film. By forming the film thickness in advance as a film thickness modulation, a ROM function can be provided in a part of the writable recording medium, and the preformatting operation can be dispensed with.

  At this time, the film thickness modulation of the specific portion on the lower layer side of the ferroelectric film is constituted by the cross-sectional irregularities formed on the back surface of the ferroelectric film disposed opposite to the upper surface of the electrode film. Features.

  Further, the thickness modulation of the lower layer side specific portion of the ferroelectric film is formed by a groove formed in the upper layer side surface specific portion of the electrode film.

  Furthermore, the groove is a through groove penetrating the electrode film, and the remaining electrode film in which the through groove of the electrode film is not processed is electrically connected.

  According to such a configuration, it is possible to easily form a film thickness modulation at a specific portion on the lower layer side of the ferroelectric film.

  The surface of the ferroelectric film is smoothed in a mirror shape.

  According to such a configuration, it is possible to configure the thickness modulation of the specific portion on the lower layer side of the ferroelectric film while maintaining the smoothness of the surface as the recording medium.

  The substrate is preferably a Si substrate or a glass substrate, and the electrode film includes tantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo), aluminum (Al), copper (Cu). ) Is preferably made of an alloy material or a compound material containing at least one of the main components. At this time, the metal material itself can be used as a substrate material so that the substrate itself also serves as an electrode.

The ferroelectric film includes PbTiO ₃ , PLT (La-added PbTiO ₃ ), PZT (PbZrO ₃ —PbTiO ₃ solid solution), PLZT (La-added PbZrO ₃ —PbTiO ₃ solid solution), SrBi ₂ Ta ₂ O ₉ (SBT). ), Bi ₄ Ti ₃ O ₁₂ (BIT), LiTaO ₃ , LiNbO ₃ is preferably used, and in particular, PbTiO ₃ having a large spontaneous polarization value is preferably used.

  Furthermore, the recording medium forming method of the present invention includes an electrode film forming step for forming an electrode film on the upper layer of the substrate, a dielectric film forming step for forming a dielectric film on the upper layer of the electrode film, and an upper layer of the dielectric film. A resist mask forming step for applying a resist to transfer a pattern corresponding to a predetermined uneven shape, an uneven forming step for forming unevenness with a resist pattern by etching, and a polycrystalline film formation and crystallization as a ferroelectric film And a ferroelectric film finishing step for performing processing.

  At this time, the etching process is performed by a reactive ion etching method using a fluorine-based gas so as to penetrate the dielectric film, thereby forming irregularities in the resist pattern.

  Further, the recording medium forming method of the present invention includes an electrode film forming step for forming an electrode film on an upper layer of a substrate, and a resist mask formation for applying a resist on the upper layer of the electrode film and transferring a pattern corresponding to a predetermined uneven shape. A step of forming a groove in the electrode film with a resist pattern by etching, and a ferroelectric film finishing step of forming a polycrystalline film as a ferroelectric film and performing a crystallization process. It is characterized by.

  According to the recording medium of the present invention, a preformat can be created in advance while maintaining high mass productivity, and the preformat work can be made unnecessary.

1A and 1B show a recording medium of the present invention, in which FIG. 1A is a front view of a disk-type recording medium, and FIG. It is an expanded sectional view of an example of a principal part showing a recording medium of the present invention. It is an expanded sectional view of other examples of the important section showing the recording medium of the present invention. It is a flowchart of the work routine of the recording medium shaping | molding method of this invention.

Explanation of symbols

1. Recording medium (disk type)
2. Recording medium (XY scanning type)
DESCRIPTION OF SYMBOLS 11 ... Substrate 12 ... Electrode film 12a ... Groove 13 ... Ferroelectric film

  Next, embodiments of the recording medium of the present invention will be described with reference to the drawings.

  FIG. 1 shows a recording medium of the present invention, FIG. 1 (A) is a front view of a disk-type recording medium, FIG. 1 (B) is a front view of an XY scanning recording medium, and FIG. FIG. 3 is an enlarged cross-sectional view of another example of the main part.

  As shown in FIG. 1, as the recording medium of the present invention, as shown in FIG. 1 (A), a disc-shaped recording medium 1 used for a hard disk drive or the like, and as shown in FIG. 1 (B), The present invention can be applied to the XY scanning type recording medium 2, but is not particularly limited thereto.

  In the following embodiments, the description will be made assuming that the present invention is applied to the recording medium 1 for convenience of explanation.

  As shown in FIG. 2, the recording medium 1 includes at least a substrate 11, an electrode film 12 located on the upper layer (upper side in the drawing) of the substrate 11, and a ferroelectric film 13 located on the upper layer of the electrode film 12. In addition, information can be recorded at high density based on the polarization direction of the ferroelectric film 13.

  Further, a recording / reproduction control signal is recorded by modulating the film thickness in a lower layer side specific portion of the ferroelectric film 13, and the recording / reproduction control signal is formed as a preformat or the like, thereby forming a recording medium. One part can be provided with a ROM function.

At this time, the film thickness modulation of the lower layer side specific portion of the ferroelectric film 13 is performed by the dielectric film (SiO ₂ , Al ₂ O ₃ , Si ₃ N ₄₎ having a concavo-convex shape formed on the upper layer side surface of the electrode film 12. Etc.), it is possible to stably ensure information reading with a signal reading device (not shown).

  The film thickness modulation of the lower layer side specific portion of the ferroelectric film 13 can also be configured by forming a groove 12a in the upper layer side surface specific portion of the electrode film 12, as shown in FIG.

  At this time, the groove 12a is an annular through groove penetrating the electrode film 12, and the remaining electrode film 12 where the through groove 12a is not processed is ensured to be electrically connected.

  Further, the surface of the ferroelectric film 13 is subjected to a mirror-like smoothing process in order to maintain the smoothing of the surface when the concave-convex shape is formed by etching or the like as shown in FIG. Is preferred. In addition, the board | substrate 11 is comprised by the film thickness of 0.1 mm-5 mm from the Si substrate.

  The electrode film 12 is an alloy material or compound containing at least one of tantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo), aluminum (Al), and copper (Cu) as a main component. The material is formed to a (maximum) film thickness of 20 nm to 200 nm. The material of the electrode film 12 is not limited to these, for example, when the groove 12a is formed as shown in FIG.

The ferroelectric film 13 includes PbTiO ₃ , PLT (La-added PbTiO ₃ ), PZT (PbZrO ₃ —PbTiO ₃ solid solution), PLZT (La-added PbZrO ₃ —PbTiO ₃ solid solution), SrBi ₂ Ta ₂ O ₉ (SBT), A film thickness of 20 nm to 200 nm is used from any one of Bi ₄ Ti ₃ O ₁₂ (BIT), LiTaO ₃ , and LiNbO ₃ , and in particular, it is considered to ensure a large spontaneous polarization value. Then, PbTiO ₃ is preferably used as the material.

  In the present embodiment, the recording medium 1 having such a configuration is formed through the following procedure (step) as shown in the flowchart of FIG.

  In the following description, a case will be described in which a dielectric film having a concavo-convex shape is formed on the upper layer side surface of the electrode film 12 in order to modulate the film thickness of a specific portion on the lower layer side of the ferroelectric film 13.

(Step S1)
That is, in step S1, for example, when manufacturing a disk-type (see FIG. 1) recording medium 1 using glass as a substrate material, a known manufacturing method similar to a magnetic disk or optical disk is used. A glass substrate having a concentric hole for fixing to a spindle for rotating the disk is prepared at the center of the polished circular glass plate, and the process proceeds to step S2.

(Step S2)
In step S2, a Ta film as the electrode film 12 is formed on the entire surface of the substrate 11 with a thickness of 50 nm as an upper layer of the substrate 11, and the process proceeds to step S3.

(Step S3)
In step S3, a SiO2 film as a dielectric film is formed on the entire surface of the electrode film 12 with a thickness of 30 nm as an upper layer of the electrode film 12, and the process proceeds to step S4.

(Step S4)
In step S4, a resist is applied to the upper layer of the dielectric film, and a resist mask is formed by performing pattern transfer corresponding to a predetermined uneven shape by a photolithography technique, and the process proceeds to step S5.

(Step S5)
In step S5, the resist pattern is transferred to the SiO2 film as irregularities by reactive ion etching with a fluorine-based gas so as to penetrate the SiO2 film, and the process proceeds to step S6.

(Step S6)
In step S6, a polycrystalline film of PZT is formed with a thickness of 100 nm on the SiO2 film by using, for example, the MOCVD method, and the process proceeds to step S7.

(Step S7)
In step S7, the PZT polycrystalline film is heat-treated at 500 ° C. for 10 minutes to perform PZT crystallization, and the process proceeds to step S8.

(Step S8)
In step S8, the entire surface to be the recording surface of the disk is flattened, including a portion where the previously formed dielectric film pattern is transferred to the PZT film and is uneven by CMP processing on the polished surface of PZT. Can be finished as.

  In addition, as shown in FIG. 3, when forming the groove | channel 12a in the upper layer side surface specific site | part of the electrode film 12, the process of step S5 is performed after the process of step S3 mentioned above.

  Further, when the Ta film is used as an electrode film, the Ta film can be etched in the same step S6. Therefore, the desired disk-shaped recording medium is obtained by performing the steps S7 and S8. be able to.

  According to the present invention, it is possible to provide a recording medium that can eliminate the need for preformatting work.

In order to achieve the object, a recording medium according to claim 1 is provided with at least a substrate and an electrode positioned on an upper layer of the substrate in order to record information at a high density based on a polarization direction of a ferroelectric substance. In a recording medium comprising a film and a ferroelectric film positioned above the electrode film, a recording / reproduction control signal is recorded by modulating the film thickness of a specific portion on the lower layer side of the ferroelectric film. The film thickness modulation of the lower layer side specific portion of the ferroelectric film is formed by a groove formed in the upper layer side surface specific portion of the electrode film .

At this time , the film thickness modulation of the lower layer specific portion of the ferroelectric film is formed by a groove formed in the upper layer surface specific portion of the electrode film.

Claims (11)

In order to record information with high density based on the polarization direction of the ferroelectric material, at least a substrate, an electrode film located on the upper layer of the substrate, a ferroelectric film located on the upper layer of the electrode film, In a recording medium comprising
A recording medium in which a recording / reproducing control signal is recorded by modulating a film thickness of a specific portion on a lower layer side of the ferroelectric film. The film thickness modulation of the specific portion on the lower layer side of the ferroelectric film is constituted by a cross-sectional unevenness formed on the back surface of the ferroelectric film disposed opposite to the upper surface of the electrode film. The recording medium according to claim 1. 2. The recording medium according to claim 1, wherein the film thickness modulation of the lower layer side specific portion of the ferroelectric film is formed by a groove formed in the upper layer side specific portion of the electrode film. The said groove | channel is a through-groove which penetrated the said electrode film, and the said remaining electrode film in which the said through-groove of the said electrode film is not processed is electrically connected. Recording media. 5. The recording medium according to claim 1, wherein the surface of the ferroelectric film is smoothed into a mirror surface. The recording medium according to claim 1, wherein the substrate is a Si substrate or a glass substrate. The electrode film is an alloy material or compound containing at least one of tantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo), aluminum (Al), and copper (Cu) as a main component. The recording medium according to claim 1, wherein the recording medium is made of a material. The ferroelectric film includes PbTiO ₃ , PLT (La-added PbTiO ₃ ), PZT (PbZrO ₃ —PbTiO ₃ solid solution), PLZT (La-added PbZrO ₃ —PbTiO ₃ solid solution), SrBi ₂ Ta ₂ O ₉ (SBT), 8. The recording medium according to claim 1, wherein any one of Bi ₄ Ti ₃ O ₁₂ (BIT), LiTaO ₃ , and LiNbO ₃ is used. An electrode film forming step for forming an electrode film on the upper layer of the substrate, a dielectric film forming step for forming a dielectric film on the upper layer of the electrode film, and applying a resist to the upper layer of the dielectric film to cope with a predetermined uneven shape A resist mask forming step for transferring the pattern, an unevenness forming step for forming unevenness in the resist pattern by etching, a ferroelectric film finishing step for forming a polycrystalline film as a ferroelectric film and a crystallization process, A recording medium forming method comprising: The unevenness is formed in the resist pattern by performing an etching process so that the etching process penetrates the dielectric film using a reactive ion etching method using a fluorine-based gas. Recording medium molding method. An electrode film forming step for forming an electrode film on the upper layer of the substrate, a resist mask forming step for applying a resist to the upper layer of the electrode film and transferring a pattern corresponding to a predetermined uneven shape, and an electrode film with a resist pattern by etching A method for forming a recording medium, comprising: a groove forming step for forming a groove on the substrate; and a ferroelectric film finishing step for forming a polycrystalline film as a ferroelectric film and performing a crystallization process.

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