JP2013157059A - Recording medium and sputtering system manufacturing recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium capable of reducing degradation of cross erasing characteristic caused by a heat which is given to a pillar and is conducted to a neighboring pillar during recording operation.SOLUTION: The recording medium includes: a substrate having plural projections each disposed in an island shape; and a thin film of one or more layer including a recording layer of a recording material formed over the substrate. Among the neighboring projections, in the side wall of the projection excluding the upper face of the projection and in the bottom face among the projections, there is an area in which the film thickness of at least the recording layer in the thin film is 2% or less of the film thickness of the thin film deposited over the upper face of the projection.

Description

  The present invention relates to a recording medium that records and reproduces information by arranging convex portions including a recording material on a substrate, and a sputtering apparatus for manufacturing the recording medium.

  Various studies have been carried out in the field of information recording. In particular, optical information recording media have been extensively studied and developed as information recording media that can be stored stably for a long period of time. To date, CDs, DVDs, Blu-ray discs, and the like have been developed as products and are widely used in the world.

  With further progress in the information recording field, higher density optical memories are being demanded. CDs, DVDs, and Blu-ray discs have achieved higher densities by reducing the shortest mark lengths to 0.83 μm, 0.40 μm, and 0.15 μm, respectively. However, in the current optical recording system, it is considered difficult to make the recording mark much smaller than this because of the diffraction limit of light.

  In recent years, optical recording methods using near-field light have attracted much attention as a technology that breaks this diffraction limit. The near-field light refers to light that is generated in a form that is localized in the vicinity of light when the light is incident on an aperture, nanoparticle, or the like having a size that is smaller than the wavelength of the light. The spot diameter formed by the near-field light does not depend on the wavelength of the incident light, but is determined by the size of the incident aperture or fine particles.

  As a conventional recording method using near-field light, many methods have been adopted in which light is incident on a sharpened fiber loop or the like, and near-field light is generated in a minute opening provided at the tip thereof. There was a problem that the use efficiency of the was low. In recent years, a near-field light generating element using metal surface plasmon resonance has been proposed as a technique for greatly improving the light utilization efficiency (see, for example, Patent Document 1).

  In this technique, a minute metal film is irradiated with light of an appropriate wavelength to induce surface plasmon resonance, and near-field light is generated in the vicinity of the metal film to perform recording / reproduction. In order to improve the recording density, many methods for performing stable recording and reproduction by forming a pattern on a substrate in advance have been proposed (see, for example, Patent Document 2 and Patent Document 3).

  By using these to record finer recording marks, it is possible to realize further higher density and larger capacity of the optical memory. Particularly in rewritable CDs, DVDs, and Blu-ray discs, phase change recording materials are widely used as recording films (see, for example, Patent Document 4). In this case, the mark is recorded by, for example, making the phase change recording material amorphous by heating / quenching with a light spot or crystallizing by heating / slow cooling. The research and development of this phase change recording material has been extensively conducted so far. The limit of density increase in the current optical recording medium is not due to the phase change recording material, but is determined by the diffraction limit (the size of the formed light spot) of the current optical recording system. Therefore, if a smaller light spot or a smaller heating region can be formed, the phase change recording material still has great potential as a high-density recording material. Therefore, it is considered that the phase change recording material is a promising material for further high density recording in the future.

  As a medium suitable for the above method, for example, a medium including a substrate and a particle portion including an information recording material arranged in an isolated state on the substrate, and having a width in the information recording direction of the particle portion of 30 nm or less. It has been proposed (see, for example, Patent Document 5). In other words, it is a proposal to achieve high density and large capacity by setting the size of the recording area to the nano order, and nano-order fine particles (hereinafter referred to as “nanoparticles”) including the information recording medium are isolated on the substrate. It has been proposed to arrange in such a state.

  In order to form nanoparticles containing such an isolated information recording material, an etching method and a sputtering method are effective.

  By the way, as a method of continuously forming a thin film on a concavo-convex substrate, a method in which sputtering is performed in a state where a substrate provided with concavo-convex of submicron order and a sputtering target are opposed to each other is DVD or Blu-ray. This method has been widely known. For example, a method has been proposed in which the film thickness deposited on the sidewalls of the concavo-convex surface of the substrate is made uniform and thinned on the left and right sides by appropriately setting sputtering conditions (see, for example, Patent Document 6).

By controlling the film thickness on the side surfaces in this way, the amount of heat transmitted between adjacent tracks is reduced, and the deterioration of the signals of adjacent tracks (so-called cross erase characteristics) is suppressed.
In addition, for example, in a DVD or Blu-ray disc, as a device for suppressing thermal interference between recording marks, when recording one mark, the light emission pulse is set to multi and continuously. A recording method that suppresses distortion of a recording mark by optimizing a so-called recording strategy that irradiates light in accordance with the recording mark length is widely known.

JP 2003-114184 A Japanese Patent No. 2584122 Japanese Patent No. 3793040 Japanese Patent No. 2574325 WO2010 / 116707A1 JP 2001-143318 A

  As described above, an etching method and a sputtering method are effective as methods for forming isolated nanoparticles containing an information recording material. Among these, the etching method is, for example, continuously forming one or more thin films containing a recording material on a flat substrate, then applying a mask on the surface to etch the surface, In this method, the recording material in a portion not covered with the mask is etched to isolate the recording material in the portion covered with the mask.

  However, the formation of isolated nanoparticles by an etching method includes complicated processes such as an etching process and a mask formation process for etching, and therefore is inferior in mass productivity when compared with an optical disk formed by a sputtering method described later. There is a problem.

  On the other hand, the sputtering method, for example, is a method of continuously forming a thin film containing one or more recording materials by sputtering on a substrate on which island-shaped irregularities previously arranged in an isolated state on the substrate are formed, Since the formation method is less complicated than the etching method, the method is excellent in mass productivity.

  In the conventional sputtering method, the side wall surface of the convex portion on the pillar substrate (hereinafter also referred to as “pillar”) and the plane between the pillar and the pillar are as described in Patent Document 6 above. A film having a certain thickness is deposited. That is, the recording layers made of one recording material are continuously connected over the entire surface of the pillar substrate. This means that when recording is performed on one pillar, thermal energy given to the pillar is easily transmitted in the film surface, and there is a problem in that signal deterioration is caused by changing the recording state of the adjacent pillar by cross erase. .

  An object of the present invention is to provide a recording medium that can suppress signal deterioration due to cross erase caused by heat applied to a pillar during recording being transferred to an adjacent pillar.

The recording medium according to the present invention includes a substrate having a plurality of convex portions arranged in an island shape,
One or more thin films including a recording layer made of a recording material provided on the substrate;
With
The film thickness of at least the recording layer of the thin film is deposited on the upper surface of the convex portion on the side wall surface of the convex portion excluding the upper surface of the convex portion and the bottom surface between the convex portions between adjacent convex portions. A region having a thickness of 2% or less of the thickness of the thin film exists.

  Further, even if the height difference between the top surface and the bottom surface of the convex portion is 1 nm or more and 150 nm or less, and the distance between the centers of the adjacent convex portions is 2 nm or more and 100 nm or less. Good.

  Furthermore, on the side wall surface of the convex portion between adjacent convex portions, there may be a region where at least the recording layer is not formed in the thin film.

  Furthermore, at least a region of the thin film where the recording layer is not formed may exist on the bottom surface between adjacent convex portions.

  The recording layer on the upper surface of the convex portion may be capable of thermal recording with near-field light.

  Further, the film thickness of the recording layer on the upper surface of the convex portion may be 3 nm or more and 30 nm or less.

  Still further, in the side wall surface of the convex portion between adjacent convex portions, an area having a thickness of 2% or less of the thickness of the thin film on the upper surface of the convex portion is an area of the side wall surface of the convex portion. May be present in the range of 10% to 50%.

  Moreover, in the bottom face between adjacent convex parts, the area | region used as the film thickness of 2% or less of the film thickness of the said thin film of the upper surface of the said convex part is the range of 5% or more and 30% or less with respect to the area of the said bottom face. May be present.

  Furthermore, the recording layer may be formed by laminating the recording material by sputtering from a direction in an angle range of 15 ° or more and 65 ° or less with respect to the normal of the surface of the substrate. .

A sputtering apparatus for producing a recording medium according to the present invention produces a recording medium in which one or more thin films including a recording layer made of a recording material are formed on a substrate having a plurality of convex portions arranged in an island shape. Because
A substrate holder for mounting the substrate;
A cathode on which a target made of the recording material is placed;
With
The angle formed between the normal of the surface of the substrate holder and the normal of the surface of the target is θ, and the normal of the surface of the substrate holder is projected with respect to an xy plane parallel to the surface of the target. And an angle adjustment mechanism capable of independently adjusting the angle θ and the angle φ of the substrate holder, where φ is an angle formed by a line segment and the positive direction of the x-axis of the xy plane. To do.

  The angle adjustment mechanism may be capable of adjusting the angle θ in the range of 0 ° to 75 °.

  Further, the distance between the cathode and the substrate holder may be 200 mm or more and 1000 mm or less.

  According to the recording medium and the manufacturing apparatus of the present invention, a region having a film thickness of 2% or less of the film thickness deposited on the upper surface of the pillar is formed between adjacent convex portions or adjacent concave portions. By providing, it is possible to suppress the amount of heat transferred between the thin films formed on the substrate protrusions. Thereby, it is possible to suppress signal deterioration of adjacent pillars due to cross erase during recording, and it is possible to provide a recording medium having excellent recording characteristics.

Partial sectional view of the recording medium in Embodiment 2 of the present invention The schematic diagram which shows the external appearance of the pillar board | substrate in Embodiment 2 of this invention. Partial sectional view of a sputtering apparatus for forming a recording medium in Embodiment 2 of the present invention Schematic diagram of polar display of the inclination of the substrate holder surface relative to the reference surface Sectional TEM sectional view of a recording medium in Example 1 of the present invention Schematic diagram showing a recording method of a recording medium in Embodiment 2 of the present invention

Embodiments of the present invention will be described below.
(Embodiment 1)
First, for the purpose of verifying the effect of the present invention, when one isolated pillar including a recording material continuously arranged in nano order is heated, the amount of heat transferred to the recording material of the pillar adjacent to the pillar is The result of the simulation will be described.

As a simulation model, a diameter of 25 nm, a height of 35 nm, an average distance between the center position of the pillar upper surface and the center position of the pillar upper surface closest to the pillar is 40 nm, on the pillar substrate arranged in an island shape, The recording material is continuously provided between adjacent pillars, each having a film thickness of 1) the recording material is uniformly formed to 20 nm on the upper surface of the pillar, and the film thickness of 0.1 nm is formed on the pillar side wall surface. When the film thickness is 0.1 nm on the plane (bottom surface) between the pillar and the pillar,
2) The case where the recording material is uniformly formed to 20 nm on the upper surface of the pillar, the film thickness of 10 nm is uniformly formed on the bottom surface between the pillars, and the film thickness of 0.1 nm is formed on the pillar side wall surface. ,
3) When the recording material is uniformly formed to 20 nm on the top surface of the pillar, the film thickness is uniformly formed to 10 nm on the bottom surface between the pillars, and the film thickness is uniformly formed to 5 nm on the pillar side wall surface. ,
The three cases were examined. In any of the cases 1) to 3), a film is uniformly formed on the pillar side wall surface extending 360 ° around the pillar. In these cases, when the central temperature of the recording material on the upper surface of any pillar is set to 500 ° C. from room temperature (20 ° C.) to 50 p (pico) seconds, the central temperature of the recording material on the upper surface of the adjacent pillar is Examined. The thermal simulation was carried out using Ge ₁₀ Sb ₉₀ (mol%) as the recording material, quartz glass as the pillar material, and air between the pillars.

As a result of thermal simulation, it was 190 ° C. when the center temperature of the adjacent pillar was 1), 240 ° C. in the case of 2), and 290 ° C. in the case of 3).
That is, from the result of thermal simulation, when heat is applied to an arbitrary pillar upper surface including a recording material with a nano-order film thickness in a very short time of the order of several picoseconds, a film other than the pillar upper surface, that is, the pillar side wall surface is exposed. It can be seen that heat is transferred to the upper surface of the adjacent pillar through the provided film and the film provided on the bottom surface. Further, in these cases, it is understood that the amount of heat transmitted to the adjacent pillars becomes smaller as the film thickness of the film other than the pillar upper surface, that is, the film provided on the pillar side wall surface and the film provided on the bottom surface is thinner.
From these results, it was found that the thinner the film other than the upper surface of the pillar, the more the cross erase caused by the heat transferred to the pillar during recording is transferred to the adjacent pillar.

(Embodiment 2)
FIG. 1 is a schematic diagram showing a configuration of a recording medium 100 according to Embodiment 2 of the present invention. As shown in FIG. 1, this recording medium 100 includes a substrate 102 in which a plurality of pillars 101 are isolated in advance in an island shape on a glass substrate, and a phase change film provided thereon. I have. Here, among the phase change films, the phase change film formed on the pillar upper surface 106 is referred to as a pillar upper surface film 103. Further, the phase change film formed on the bottom surface 107 between the pillars 101 is referred to as a bottom film 104. Further, the phase change film deposited on the side wall surface 108 of the pillar 101 is referred to as a side wall film 105. FIG. 1 schematically shows the side wall film 105 partially attached to the side wall surface 108.
The phase change film for recording / reproducing information by near-field light is mainly the pillar upper surface film 103.
Further, the recording medium 100 may have a protective layer for protecting the phase change films 103 to 105 as described later.

  Below, each structural member which comprises this recording medium is demonstrated.

<Board>
The substrate 102 may be either a disk shape or a polygonal shape, and the material constituting the substrate 102 is preferably a material having high flatness and high stability when the information recording medium 100 is moved for recording and reproduction. . In this embodiment, 5 mm square glass having excellent flatness is used. However, the present invention is not limited to this, and a metal such as aluminum or a fractal material such as polycarbonate may be used.

<Pillar>
The shape of the pillar 101 on the substrate 102 is preferably generally a cylindrical shape, but may be a quadrangular column as long as the pillar 101 is isolated in an island shape. The diameter 201 is approximately 25 nm. The interval 203 between adjacent pillars 101 is approximately 40 nm, the average distance between the center position of the pillar upper surface 106 and the center position of the bottom surface 107 is 15 nm, and the average height 204 of the pillar 101 is 35 nm. Is formed.

  The smaller the size of the pillar 101 and the smaller the distance 203 between the adjacent pillars 101, the larger the recording capacity per unit area. This is preferable, but if it is too small, the nanoparticles are formed stably and uniformly. Difficult to do. Therefore, the pillar diameter 201 and the interval 203 between the pillars 101 are preferably 2 nm or more. Further, if the pillar diameter 201 or the interval 203 between the pillars 101 is too large, high-density recording becomes difficult. Therefore, the diameter 201 and the interval between the pillars 101 are preferably 100 nm or less.

  As a method of forming the pillar 101 on the substrate 102, for example, a method of performing etching with a gas such as Ar after appropriately masking the substrate 102 is used. In the case where the substrate is made of a plastic material such as polycarbonate, in addition to the etching method, a method of transferring the substrate 102 by pressing it against a mold in which fine holes are formed in advance can be used.

The lower limit of the pillar height 204 is described in detail later, but is preferably 1/3 or more with respect to the pillar diameter 201 in order to effectively use the sputtering shielding effect. If the pillar height 204 is too high, when the pillar 101 is formed by the etching method, if the pillar height 204 is high, the etching time becomes long and mass productivity becomes poor.
Further, in the case where the pillar 101 is formed by the above-described mold transfer method, if the pillar height 204 is high, peeling unevenness is likely to occur, resulting in poor mass productivity. Therefore, the pillar height 204 has an upper limit, and considering mass productivity, the upper limit is preferably three times the diameter of the pillar 101.

<Thin film>
The thin film is composed of one or more layers including at least a recording layer (recording film) made of a recording material.
In the present invention, the pillar top film 103, the bottom film 104, and the sidewall film 105 have different thicknesses, and the pillar top film 103 preferably has a thickness of 3 nm to 30 nm. The difference between the optical properties of the thin film when the phase change material is crystalline and the optical properties of the thin film when the phase change material is amorphous is reduced by multiplying the film thickness. For this reason, if the thickness of the pillar upper surface film 103 is less than 3 nm, it is difficult to obtain a sufficiently stable recording signal.

  When the pillar upper surface film 103 is thicker than 30 nm, the side wall film formed on the side wall surface 108 in proportion to the thickness of the pillar upper surface film 103 when the distance between the convex portions of the pillar 101 is narrow. The film thickness of 105 increases. For this reason, there is a possibility that the sidewall film 105 is connected to the pillar upper surface film 103 of the adjacent pillar 101, and it is difficult to isolate the pillar upper surface film 103 in an island shape.

  The thickness of the pillar upper surface film 103 is preferably uniform on the pillar upper surface 106 in order to stabilize the recording signal, but is not necessarily uniform. For example, film thickness unevenness may occur in one direction, or the film thickness may be inclined. In that case, if all the pillar upper surfaces 106 on the substrate 102 have the same film thickness unevenness, recording and reproduction can be performed on the individual pillar upper surface films 103 under the same light irradiation conditions.

  The film thickness of at least one of the bottom film 104 formed on the bottom surface 107 between the pillars 101 and the side wall film 105 formed on the side wall surface 105 of the pillar 101 is formed on the pillar upper surface 106. It is preferable that there is a region having a thickness of 2% or less of the thickness of the pillar upper surface film 103 to be formed. Furthermore, it is preferable that the bottom film 104 or the sidewall film 105 includes a portion where the recording film is not partially attached.

  FIG. 1 shows, as an example, a bottom film 104 in which a recording film is deposited on a part of the bottom surface 107 between the pillars 101, and a sidewall in which a film is deposited on a part of the left and right side wall surfaces 108 of the pillar 101. The membrane 105 is shown.

  As a film formation method for the recording medium 100 shown in FIG. 1, it is preferable to use a sputtering apparatus in which the distance between the sputtering target 302 and the substrate 303 (TS distance) is long. By increasing the distance between the sputtering target 302 and the substrate 303, the straightness of the sputtering particles can be improved. This can be achieved by using such a sputtering apparatus having excellent rectilinearity of the sputtered particles and tilting the substrate 303 at an arbitrary angle with respect to the target surface to form a thin film.

  During sputtering discharge, particles sputtered from the target 302 are sputtered with various angular distributions with respect to the target surface. The longer the distance between the target 302 and the substrate 303, the more sputtered particles are deposited on the substrate 303. Is likely to be particles that travel in a direction perpendicular to the surface of the target 302 and the film is less likely to adhere to the side wall of the pillar 101. Therefore, the longer the distance between the target 302 and the substrate 303, the more sputtered particles It is preferable in terms of straightness. The distance between the sputtering target 302 and the substrate 303 (“TS distance”) is determined by the area of the sputtering material to be used and the generation of high-density plasma by a so-called magnetron sputtering method in which a magnet is installed on the back surface of the target to promote sputter discharge. Although it depends on the region (referred to as erosion), it is preferably at least 4 times the erosion diameter in consideration of straightness. For example, when the target size is φ100 mm and the erosion diameter is φ60 mm, the distance between the sputtering target 302 and the substrate 303 is preferably 240 mm or more, more preferably 200 mm, from the viewpoint of straightness. The above is preferable.

  On the other hand, if the distance between the target 302 and the substrate 303 is too long, the number of sputtered particles deposited on the substrate 303 is reduced, and the sputter rate is significantly slowed down. Further, since the sputtering apparatus becomes large, the apparatus cost tends to be high, and the apparatus maintenance becomes difficult, so the distance (TS distance) between the target 302 and the substrate 303 is preferably 1000 mm or less from the viewpoint of the sputtering rate. There is no particular upper limit.

  That is, by utilizing the effect (sputter shadowing) that the individual pillars 101 block the straightness of the sputtered particles, a part of the bottom film 104 formed on the bottom surface 107 between the adjacent pillars 101 and the side wall surface 108 are formed. It is preferable that a part of the sidewall film 105 has a region that is 2% or less of the thickness of the pillar upper surface film 103. Furthermore, it is more preferable that the bottom film 104 or the sidewall film 105 includes a region having a thickness of 0 nm. This is because if the thickness is greater than 2%, heat is easily transferred to the adjacent pillar upper surface film 103 through the bottom film 104 or the sidewall film 105.

<About bottom film>
The maximum film thickness of the bottom film 104 formed on the bottom surface 107 is preferably 20 nm or less, which is the upper limit film thickness range of the pillar upper film 103.
The bottom of a region (more preferably, a region where no film is deposited) that is 2% or less of the film thickness of the pillar upper surface film 103 due to the shadowing effect with respect to the area occupied by the entire bottom surface 107 between the pillars 101 and 101. The ratio of the area varies depending on the pillar shape, the area of the pillar upper surface 106, the pillar height 204, and the inclination angle between the substrate 102 and the target surface, and the ratio is preferably 5% or more and 30% or less. Furthermore, 10% or more and 30% or less are more preferable.

  In the simulation 3) described above, a part of 10 nm which is the film thickness of the bottom area is a region where the film thickness of the bottom film is 1% (0.2 nm) of the film thickness of the pillar upper surface. The thermal simulation was carried out by changing the ratio of the bottom area of. As a result, it was found that the temperature of the adjacent pillar can be lowered as the ratio increases. Specifically, when the ratio is 5%, the heating temperature of the adjacent pillar is 280 ° C., and when the ratio is 10%, the heating temperature of the adjacent pillar is 270 ° C., and the ratio is 0. %, The temperature is lower than 290 ° C.

  The reason for setting the upper limit to 30% is, for example, that if the pillar shape is a rectangle and the sputtering is performed so that the long side of the rectangle is a shadow of sputtering, the ratio can be higher than 30%. This is because it is disadvantageous from the viewpoint of recording capacity.

<About sidewall film>
The maximum film thickness of the sidewall film 105 formed on the sidewall surface 108 is preferably as thin as possible within the range where the pillar 101 is kept in an isolated state. Although depending on the interval between the pillars 101, if the sidewall film 105 is thick, the pillar 101 and the pillar 101 may be connected by the film, and heat is easily transmitted through the sidewall surface 108. Further, when the pillar interval 203 is narrow, it is difficult to isolate the pillar 101 if the sidewall film 105 is thick. Specifically, the maximum film thickness of the sidewall film 105 is preferably 20 nm or less, and more preferably 10 nm or less. This is because it is difficult to deposit a film on the side wall surface 108 beyond the upper limit film thickness (20 nm) of the pillar upper surface 106.
Similarly to the bottom surface film 104, the side wall film 105 is provided with a portion (more preferably, a portion where the side wall film 105 is not partially attached) having a thickness of 2% or less with respect to the thickness of the pillar upper surface film 103. Therefore, it is preferable that the thermal interference of the pillar upper surface film 103 can be cut off and the signal deterioration of the adjacent pillar due to the cross erase can be suppressed.

  The ratio of the region of the sidewall film 105 that is 2% or less of the thickness of the pillar upper surface film 103 to the area of the sidewall surface 108 is the pillar shape, the area of the pillar upper surface 106, and the pillar height 204. , And the inclination angle θ between the substrate 102 and the target surface, the ratio is preferably 10% or more and 50% or less. More preferably, it is 20% or more and 40% or less.

  In the simulation 3) described above, a part of the film thickness of 5 nm which is the film thickness of the sidewall surface is set to 1% (0.2 nm) of the film thickness of the pillar upper surface, and the ratio is changed. A thermal simulation was performed. As a result, it was found that the temperature of the adjacent pillar can be lowered as the ratio of the film thickness of the side wall surface to 0.2 nm increases. Specifically, when the ratio is 10%, the heating temperature of the adjacent pillar is 280 ° C., and when the ratio is 20%, the heating temperature of the adjacent pillar is 270 ° C., and the ratio is The temperature is lower than 290 ° C. when 0%.

  The reason why the upper limit is set to 50% is due to the restriction in principle that the sidewall film 105 and the bottom film 104 are deposited by sputtering from the direction inclined with respect to the normal direction of the pillar substrate 102. In other words, in the side wall film 105 formed on the side wall surface 108, a region (more preferably, a region where no film is deposited) of the pillar upper surface film 103 is used by utilizing the sputtering shielding effect of the pillar 101 itself. In the case of forming, it is theoretically difficult to make it higher than 50%.

<Recording material>
In order to increase the writing speed of the information recording medium 100, the pillar upper surface film 103, the bottom surface film 104, and the side wall film 105 that bear information recording preferably have a high crystallization speed. In particular, the material includes a mixed material of GeTe—Bi ₂ Te _3, a mixed material with GeTe—Sb ₂ Te ₃ , a mixed material of SnTe—Bi ₂ Te _3, a mixed material of SnTe—Sb ₂ Te ₃ , Sb or The main component is Bi, Ge, Te, In, Mn, Sn, Ga, C, W, Mo, Ag, Pt, Au, etc., or Ag-In-Sb-Te is used. May be.
In the present embodiment, a material containing 90 mol% Sb and 10 mol% Ge is used as the material of the pillar upper surface film 103, but the present invention is not limited to this.

<Protective layer>
Although the protective layer for the pillar upper surface film 103 is not particularly shown in the drawing, it may be formed on the upper side of the pillar upper surface film 103, the bottom surface film 104, and the sidewall film 105 (on the opposite side to the substrate as viewed from the phase change film). Alternatively, it may be formed in the lower part (substrate side). Moreover, you may form in any of upper and lower sides.
In this manner, by protecting the pillar upper surface film 103 with the protective layer, information can be recorded or rewritten on the pillar upper surface film 103 more stably.

As a material for the protective layer, a dielectric material is desirable. Examples of the material for the protective layer include TiO ₂ , ZrO ₂ , HfO ₂ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , SiO ₂ , SnO ₂ , Al ₂ O ₃ , B ₂ O ₃ , Cr ₂ O _3. , Ga ₂ O ₃ , In ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Yb ₂ O ₃ , CaO, MgO, CeO ₂ , TeO _{2 and the} like. One or more kinds of oxides can be used. In addition, as a material for the protective layer, C—N, T—N, Zr—N, Nb—N, Ta—N, S—N, Ge—N, Cr—N, Al—N, Ge—S—N, One or a plurality of nitrides selected from Ge—Cr—N and the like can also be used. Further, as a material for the protective layer, carbides such as sulfide SiC such as ZnS, fluorides such as LaF3, CeF3, and MgFz, and C can also be used. The protective layer may be formed using a mixture of one or more materials selected from the above materials.

The thickness of the protective layer is preferably 10 nm or less. If the thickness of the protective layer is greater than 10 nm, near-field light is less likely to concentrate on the phase change nanoparticles, and recording may become unstable. By making the thickness of the protective layer 10 nm or less, stable recording can be performed, and the thickness of the protective layer is more preferably 5 nm or less.
In this example, a ZnS-20 mol% SiO ₂ film was formed to 5 nm on the upper and lower portions of the pillar upper surface film 103, the bottom surface film 104, and the sidewall film 105, respectively.

<Recording method>
FIG. 6 is a schematic diagram illustrating a recording method on the recording medium 100. The metal antenna 502 is brought close to an arbitrary pillar 501, and the metal antenna 502 is irradiated with a polarized laser beam, for example, on a part of the metal antenna 502 (not shown), and close to the vicinity 503 of the metal antenna 502. Information can be recorded by generating a field and heating the recording material provided on the pillar 501 and then causing the recording material to undergo phase transition by cooling.

  Embodiments of the present invention will be described below with reference to the drawings. The following examples are merely examples, and the present invention is not limited to the following examples. Further, in the following embodiments, the same portions may be denoted by the same reference numerals and redundant description may be omitted.

Example 1
FIG. 2 shows the appearance of the pillar substrate 102 used in the first embodiment. A pillar substrate 102 in which pillars 101 are periodically arranged in a 5 mm square region was used. The pillar shape seen from the film surface side was circular, and the average diameter 201 was φ25 nm. As a result of observing the cross section at the center of the pillar substrate 102, it has a generally trapezoidal shape, and its average base length 202 is 30 nm. The average distance 203 between the adjacent pillars 101 was 40 nm, and the average height 204 of the pillars 101 was 35 nm.

<Sputtering equipment>
FIG. 3 shows a part of a sputtering apparatus for sputtering a thin film including a recording layer on the pillar substrate 102. The sputtering apparatus is provided with a substrate holder 304 on which a cathode 301, a target 302, and a substrate 303 are installed, and a transport plate 305 for moving the substrate holder 304 directly below a plurality of cathodes.
Although not particularly shown in the drawing, the sputtering apparatus may have a plurality of cathodes 301. For example, as a cathode type, one cathode that can apply an RF wave and two cathodes that can apply a DC voltage may be provided in parallel.
In addition, each cathode 301 is attached with a target 302 having a diameter of φ100 as a target 302 to be attached. At the time of film formation, the center of the substrate 303 is positioned on a perpendicular line from the center of the target. Form a film.
In this way, by mounting the substrate 303 on the substrate holder 304, sequentially forming a film on each cathode 301, and transporting the substrate 303 after the film formation, thin films having different materials or film formation conditions are sequentially stacked. It is possible to

  FIG. 4 is a schematic diagram in the case of displaying the inclination of the surface 309 of the substrate holder 304 with respect to the reference surface 310 in polar coordinates. The substrate holder 304 is provided with a jig 306 for fixing the substrate and a jig 307 that can arbitrarily change the angle of the substrate holder 304. A plane parallel to the surface of the target 302 is defined as a reference plane 310, an xy plane is defined, and a normal direction from the reference plane 310 toward the plane of the target 302 is defined as a z-axis. The angle formed by the normal line of the surface 308 of the substrate holder 304 with respect to the z-axis of the reference surface 310 is defined as θ. This angle θ represents the inclination of the surface 309 of the substrate holder 304 with respect to the reference surface 310. Further, the angle from the positive direction of the x-axis of the line segment OB obtained by projecting the normal line OA of the surface 309 of the substrate holder 304 onto the reference surface 310 is defined as φ. The angles θ and φ are polar coordinates representing the inclination of the substrate holder 304. In this sputtering apparatus, the angles θ and φ of the surface 309 of the substrate holder 304 with respect to the reference surface 310 can be controlled from the outside of the sputtering apparatus. In addition, by controlling not only the angle θ with the normal direction of the reference surface 310 but also the angle φ with respect to the xy plane of the reference surface 310, the formation direction of the sidewall film 105 and the bottom film 104 can be appropriately controlled. Furthermore, the formation direction of the protective layer and the recording layer can be changed as appropriate.

When the surface of the target 302 and the surface of the substrate 303 face each other, an angle θ between a perpendicular line perpendicular to the target surface and a perpendicular line perpendicular to the substrate holder surface 309 is 0 °. In this sputtering apparatus, the angle θ can be changed within a range of 0 ° to 75 °. That is, it is possible to adjust the angle between the straight traveling direction of the sputtered particles and the direct upward direction of the pillar 101 formed on the substrate 102.
The substrate 303 is installed so as to be horizontal with the substrate holder surface 309, and is installed at the center of the substrate holder 304.

A distance from the center of the target 302 to the center of the substrate holder 304 (hereinafter abbreviated as a TS distance) can be arbitrarily set by exchanging a sputtering apparatus housing provided therebetween. A casing was installed so that the TS distance was 300 mm.
The sputtering gas flows from the periphery of the target 302 and is exhausted by a vacuum pump 308 installed at the lower part of the substrate 303 in the drawing.
A port is provided in a casing located approximately between the target 302 and the substrate holder 304, and the degree of vacuum is measured from the port.

<Method for creating thin film>
The thin film was prepared by sequentially forming a ZnS-20 mol% SiO ₂ layer as a first protective layer, a Ge ₁₀ Sb ₉₀ (at%) layer as a phase change recording layer, and a _second protective layer on the pillar substrate 102. A ZnS-20 mol% SiO ₂ layer was formed as a protective layer.
The first protective layer was formed by depositing ArS at a flow rate of 3 sccm using a ZnS-20 mol% material as a target 302 and supplying RF400W for 45 seconds to the cathode electrode so that the thickness of the pillar upper surface 106 becomes 5 nm. Formed. The discharge gas pressure during film formation was 1.2E-2 Pa.
As the film formation conditions of the phase change recording layer, Ge ₁₀ Sb ₉₀ (at%) material was used as the target 302, Ar gas was flowed at 3 sccm, DC 100 W was supplied to the cathode electrode for 55 seconds, and the film thickness of the pillar upper surface 106 was 10 nm. It formed so that it might become. The discharge gas pressure during film formation was 1.2E-2 Pa.
The film formation conditions for the second protective layer were ZnS-20 mol% material as the target 302, Ar gas was flowed at 3 sccm, and RF400W was supplied to the cathode electrode for 45 seconds so that the film thickness on the top surface of the pillar was 5 nm. Formed. The discharge gas pressure during film formation was 1.2E-2 Pa.
When all these films were formed, the substrate 303 was sputtered without rotating.
When forming the recording film, various samples were prepared by changing the angle of the substrate holder 304.

<Evaluation of sample>
After the sample is prepared, the sample is cut along a plane including a perpendicular drawn from the target surface and a perpendicular drawn from the substrate holder surface 309, and the cross section is observed with a transmission electron microscope (TEM) and deposited on the pillar 101. The film thickness of the recording film was evaluated.
FIG. 5 is a schematic diagram of a cross-sectional TEM image observed at this time. In the figure, a layer denoted by reference numeral 401 corresponds to a recording film.

Separately, a sample without the second protective layer was prepared, and the coverage of the recording film was examined by observing the surface with a scanning electron microscope (SEM).
From the cross-sectional TEM image, the average film thickness of the pillar upper surface film 103 is t1, the average film thickness of the sidewall film 105 deposited on one side of the sidewall surface 108 is t2, and the average of the sidewall film 105 deposited on the other side. The typical film thickness was t3, the minimum film thickness of the bottom film 104 deposited on the bottom surface 107 was t4, and the maximum film thickness was t5.
Since it is difficult to measure a film thickness thinner than 0.1 nm in terms of resolution from the cross-sectional TEM image, a film is deposited when the film thickness is considered to be 0.1 nm or less from the observed image. Assuming that there was no, it was measured as 0.0 nm.
Further, from the SEM image, the non-coverage ratio of the sidewall film 105 deposited on the pillar sidewall surface 108 and the deposition on the bottom surface 107 between the pillars 101 within a range surrounding the center of any four pillars 101. The uncovered ratio of the bottom film 104 to be examined is examined, respectively (area where the sidewall film 105 is not deposited on the sidewall surface 108 / pillar sidewall area), (area where the bottom film 104 is not deposited on the bottom face 107 / bottom area). As sought.

<Creation conditions>
At the time of forming the first protective layer, the angle θ of the substrate holder 304 is formed at 0 °. At the time of forming the recording film, the angle of the substrate holder 304 is formed at 35 °. At the time of forming the second protective layer, The substrate holder 304 was formed with an angle θ of 0 °.
The film thicknesses of the first protective layer and the second protective layer deposited on the pillar substrate 102 were t1 = 5 nm, t2 = t3 = 0.4 nm, and t4 = t5 = 4.6 nm.
The thickness of the recording film deposited on the pillar substrate 102 was t1 = 9.8 nm, t2 = 0.0 nm, t3 = 2.0 nm, t4 = 0 nm, and t5 = 9.1 nm.
The non-cover ratio of the film on the side wall surface 108 was 28%, and the non-cover ratio of the film on the bottom face 107 was 14%.
That is, by tilting the substrate 102 at an appropriate angle θ, the thickness of the sidewall film 105 deposited on the pillar sidewall surface 108 and the thickness of the bottom film 104 deposited on the bottom surface 107 can be partially set to 0 nm. It turned out to be.

(Example 2)
When forming the first protective layer, the angle θ of the substrate holder 304 is formed at 0 °, and when forming the recording film, the angle θ of the substrate holder 304 is formed at 15 °, and when forming the second protective layer. The recording medium 100 was formed in the same manner as in Example 1 except that the angle θ of the substrate holder 304 was set to 0 °.
The film thicknesses of the first protective layer and the second protective layer deposited on the pillar substrate 102 were t1 = 5 nm, t2 = t3 = 0.4 nm, and t4 = t5 = 4.6 nm.
The film thickness of the recording film deposited on the pillar substrate 102 was t1 = 9.8 nm, t2 = 0.0 nm, t3 = 0.6 nm, t4 = 0 nm, and t5 = 9.3 nm.
The uncovered rate of the sidewall film 105 on the sidewall surface 108 was 20%, and the uncovered rate of the bottom film 104 on the bottom surface 107 was 10%.

(Example 3)
The recording medium 100 was formed in the same manner as in Example 1 except that the angle θ of the substrate holder 304 was set to 65 ° when forming the recording film. The film thicknesses of the first protective layer and the second protective layer deposited on the pillar substrate 102 were t1 = 5 nm, t2 = t3 = 0.4 nm, and t4 = t5 = 4.6 nm.
The film thickness of the recording film deposited on the pillar substrate 102 was t1 = 8.4 nm, t2 = 0.0 nm, t3 = 8.3 nm, t4 = 0.0 nm, and t5 = 5.2 nm.
The uncovered rate of the sidewall film 105 on the sidewall surface 108 was 34%, and the uncovered rate of the bottom film 104 on the bottom surface 107 was 26%.
The film thickness deposited on the pillar upper surface and the film thickness deposited on the pillar side wall surface 108 are partially equal. In this embodiment, the film is deposited on the sidewall film 105 and the bottom surface 107 deposited on the pillar side wall surface 108. It was possible to partially set the thickness of the bottom film 104 to be 0.0 nm.

(Comparative Example 1)
At the time of forming the recording film, the angle θ of the substrate holder 304 was set to 0 °. That is, the film was formed such that the target surface and the substrate surface were parallel.
The film thicknesses of the first protective layer and the second protective layer deposited on the pillar substrate 102 were t1 = 5.0 nm, t2 = t3 = 0.4 nm, and t4 = t5 = 4.6 nm. The film thickness of the recording film deposited on the pillar substrate 102 was t1 = 10.0 nm, t2 = t3 = 0.3 nm, and t4 = t5 = 9.0 nm.
The uncovered rate of the sidewall film 105 on the sidewall surface 108 was 0%, and the uncovered rate of the bottom film 104 on the bottom surface 107 was 0%.
That is, in the case where the film is formed so that the target surface and the substrate surface are parallel, the film thickness of the film deposited around the pillar cannot be set to 0.0 nm.

(Comparative Example 2)
At the time of forming the recording film, the angle θ of the substrate holder 304 was set to 10 °. The film thicknesses of the first protective layer and the second protective layer deposited on the pillar substrate 102 were t1 = 5.0 nm, t2 = t3 = 0.4 nm, and t4 = t5 = 4.6 nm.
The thickness of the recording film deposited on the pillar substrate 102 was t1 = 10.0 nm, t2 = 0.1 nm, t3 = 0.5 nm, t4 = 2.4 nm, and t5 = 8.8 nm.
The uncovered rate of the sidewall film 105 on the sidewall surface 108 was 6%, and the uncovered rate of the bottom film 104 on the bottom surface 107 was 4%.
That is, when the angle θ of the substrate holder 304 is 10 °, the thickness of the sidewall film 105 and the bottom film 104 deposited around the pillar cannot be 0.0 nm, and the non-coverage ratio is also increased. I could not.

(Comparative Example 3)
A thin film was formed in the same manner as in Example 1 except that the housing of the sputtering apparatus was changed and the TS distance was 100 mm. At the time of forming the first protective layer, the angle θ of the substrate holder 304 is formed at 0 °. At the time of forming the recording film, the angle θ of the substrate holder 304 is formed at 35 °, and at the time of forming the second protective layer. The substrate holder 304 was formed with an angle θ of 0 °.
At this time, the film formation time for forming the first protective layer and the second protective layer to 10 nm was 10 seconds, and the film formation time for forming the recording layer to 10 nm was 15 seconds.
The film thicknesses of the first protective layer and the second protective layer deposited on the pillar substrate 102 were t1 = 5 nm, t2 = t3 = 1.3 nm, and t4 = t5 = 3.9 nm.
The film thickness of the recording film deposited on the pillar substrate 102 was t1 = 9.8 nm, t2 = 0.2 nm, t3 = 4.3 nm, t4 = 0.6 nm, and t5 = 7.2 nm.
Further, the uncovered rate of the sidewall film 105 on the sidewall surface 108 was 0%, and the uncovered rate of the bottom film 104 on the bottom surface 107 was 0%.
That is, when the TS distance is 100 mm, since the distance between the target 302 and the substrate 303 is short, the rectilinearity of the sputtered particles is bad, and even if the substrate holder 304 is tilted, the film thickness of the film deposited around the pillar can be reduced. It turned out that it cannot be 0.0 nm.

  As described above, by adjusting the angle θ of the substrate holder 304 within the range of 15 ° to 65 ° and setting the TS distance to 300 mm, the film thickness of the film deposited around the pillar is 0 as shown in the embodiments. It was found that the thickness could be 0.0 nm.

  The recording medium according to the present invention relates to a recording medium in which a recording layer is formed on a substrate having convex portions provided in an island shape, and information is recorded on a thin film formed on the convex portion on the substrate by near-field light. . In this recording medium, at least the film thickness of the recording layer of the thin film is deposited on the upper surface of the convex portion on the side wall surface of the convex portion excluding the upper surface of the convex portion and the bottom surface between the convex portions between adjacent convex portions. A region having a thickness of 2% or less of the thickness of the thin film is provided. Thereby, the amount of heat transmitted between the thin films formed on the convex portions on the substrate can be suppressed. Therefore, it is possible to suppress signal deterioration of adjacent convex portions due to cross erase due to heat transfer through a thin film during recording on one convex portion, and it is possible to provide a recording medium having excellent recording characteristics. .

DESCRIPTION OF SYMBOLS 100 Recording medium 101 Pillar 102 Substrate 103 Pillar upper surface film 104 Bottom surface film 105 Side wall film 106 Pillar upper surface 107 Bottom surface 108 Side wall surface 201 Pillar upper surface diameter 202 Pillar bottom length 203 Pillar distance 204 Pillar height 301 Cathode 302 Target 303 Substrate 304 Substrate holder 305 Transport plate 306 Substrate fixing jig 307 Substrate holder angle adjustment jig 308 Vacuum pump 309 Substrate holder surface 310 Reference plane (xy plane)
401 Recording film 501 Pillar 502 Metal antenna 503 Near tip of metal antenna

Claims (12)

A substrate having a plurality of convex portions arranged in an island shape;
One or more thin films including a recording layer made of a recording material provided on the substrate;
With
The film thickness of at least the recording layer of the thin film is deposited on the upper surface of the convex portion on the side wall surface of the convex portion excluding the upper surface of the convex portion and the bottom surface between the convex portions between adjacent convex portions. A recording medium comprising a region having a thickness of 2% or less of the thickness of the thin film.   The height difference between the top surface and the bottom surface of the convex portion is 1 nm or more and 150 nm or less, and the distance between the centers of the adjacent convex portions is 2 nm or more and 100 nm or less. The recording medium described in 1.   The recording medium according to claim 1, wherein at least the recording layer is not formed in the thin film on the side wall surface of the convex portion between adjacent convex portions.   The recording medium according to claim 1, wherein at least a region in which the recording layer is not formed exists in the thin film on a bottom surface between adjacent convex portions.   The recording medium according to claim 1, wherein the recording layer on the upper surface of the convex portion is capable of thermal recording with near-field light.   The recording medium according to claim 1, wherein a film thickness of the recording layer on an upper surface of the convex portion is 3 nm or more and 30 nm or less.   On the side wall surface of the convex portion between adjacent convex portions, a region having a film thickness of 2% or less of the thickness of the thin film on the upper surface of the convex portion is relative to the area of the side wall surface of the convex portion. The recording medium according to claim 1, wherein the recording medium is present in a range of 10% to 50%.   In the bottom surface between adjacent convex portions, a region having a thickness of 2% or less of the thickness of the thin film on the top surface of the convex portion exists in a range of 5% to 30% with respect to the area of the bottom surface. The recording medium according to claim 1, wherein:   The recording layer is formed by laminating the recording material by sputtering from a direction in an angle range of 15 ° or more and 65 ° or less with respect to the normal line of the substrate surface. The recording medium according to claim 1. A sputtering apparatus for producing a recording medium in which one or more thin films including a recording layer made of a recording material are formed on a substrate in which a plurality of convex portions are arranged in an island shape,
A substrate holder for mounting the substrate;
A cathode on which a target made of the recording material is placed;
With
The angle formed between the normal of the surface of the substrate holder and the normal of the surface of the target is θ, and the normal of the surface of the substrate holder is projected with respect to an xy plane parallel to the surface of the target. And an angle adjustment mechanism capable of independently adjusting the angle θ and the angle φ of the substrate holder, where φ is an angle formed by a line segment and the positive direction of the x-axis of the xy plane. A sputtering apparatus for producing a recording medium.   The sputtering apparatus according to claim 10, wherein the angle adjustment mechanism can adjust the angle θ in a range of 0 ° to 75 °.   The sputtering apparatus according to claim 10, wherein a distance between the cathode and the substrate holder is 200 mm or more and 1000 mm or less.

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