JP4990835B2 - Convex structure manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a convex structure, and more particularly to a method for producing a convex structure for manufacturing an optical information recording medium such as an optical disk.

  In ROM (Read Only Memory) type optical discs, data is pre-recorded by pre-pits formed on the substrate in the manufacturing stage, and in write-once and rewritable optical discs, pre-pits and tracks are formed in advance, on which organic dyes, etc. And a recording material layer made of a phase change material or the like is formed, and data is recorded using a change in optical characteristics based on a chemical physical change in the recording material layer. In these optical discs other than ROM type, signals such as rotation control information such as a wobbling signal used for optical disc rotation control and address information necessary for position search at the time of data recording are generally concaved in advance when the master disc is manufactured. Or it is recorded on a track (groove or land) which is a convex portion. Both optical discs are manufactured by replication, and a concave / convex pattern (convex structure) such as prepits and tracks is recorded on the master, a disc stamper is formed from the master disc, and synthetic resin is heated and pressed using the disc stamper. Alternatively, it is obtained by injection molding and forming a translucent substrate having a recording surface on which the pattern is transferred from the master.

  In recent years, research and development of higher-density recording media exceeding the recording density of BD (Blu-ray Disc (registered trademark)) has progressed, and in order to realize high-resolution patterning of prepits and tracks, As a master production method, a combination of an organic resist and LBR (Laser beam recording), an inorganic resist and PTM (Phase transition mastering), or a combination of an inorganic resist and EBR (Electronic beam recording) is generally used. .

  Currently, the mainstream of BD-ROM (single-sided capacity 25GB / diameter 120cm) master disk is the one that uses LBR and PTM. A technique using PTM and EBR that can be easily resolved is employed.

  In high-resolution patterning of convex structures such as prepits and tracks, there are the following proposals.

For example, in Patent Document 1 and Patent Document 2, using a heat mode, a medium having a laminated structure of a light absorption layer and a thermal reaction layer such as ZnS-SiO ₂ is irradiated with laser light, and then the medium is used. A structure manufacturing method and an optical information recording medium manufacturing method are described in which a concavo-convex pattern of a convex structure made of ZnS-SiO _{2 is} manufactured by etching.

  Patent Document 3 also uses a heat-sensitive material layer that changes its state by exposure and a recording master having a recording auxiliary layer arranged so as to be in contact therewith, and the thermal conductivity, optical constant and A master manufacturing method for an optical information recording medium, wherein the exposure state of a heat-sensitive material layer is controlled thermally and optically by arbitrarily selecting a thickness and the like, and the cross-sectional shape of a concavo-convex pattern formed on the master is controlled. Disclosure.

In Patent Document 4, an inorganic resist layer made of a transition metal oxide or the like is formed on an intermediate layer such as ZnS-SiO ₂ formed on a substrate, and an uneven pattern is formed on the inorganic resist layer by exposure and development processing. None, a method for producing an optical disc master is disclosed in which the transition metal oxide convex pattern is reduced to reduce the inclination angle of the convex pattern by utilizing the difference in volume shrinkage between the convex surface and the intermediate layer on the lower surface. ing.
JP2007-179607 JP 2006-252712 A JP 2005-011489 A JP 2007-287261 A

  The concave or convex structure in the master disk formed using heat mode recording has a cross-sectional shape with inclined side surfaces. Therefore, when the optical information recording medium is replicated directly using the master of the convex structure, or the metal stamper is manufactured based on the master and the optical information recording medium is replicated using the stamper, the cross-sectional aspect of the structure is obtained. There is a problem that the ratio is not sufficient and the amplitude of signals from the guide grooves and signal pits of the optical information recording medium becomes small. Therefore, in order to form a desired structure of an optical information recording medium, it is important to form a master having a structure having an optimum cross-sectional inclination angle according to replication.

  However, Patent Document 1 and Patent Document 2 both disclose heat mode recording, materials and methods, but do not mention control of the tilt angle of the structure.

  On the other hand, Patent Document 3 also discloses a method of controlling the cross-sectional shape of the structure on the master by utilizing the heat mode and controlling the thermal conductivity that hardly changes due to the composition of the recording auxiliary layer in contact with the heat-sensitive material layer. However, in addition to the heat-sensitive material layer, a recording auxiliary layer is essential, the layer structure is complicated, and a developer suitable for each layer is required, which complicates the process.

  Patent Document 4 utilizes a difference in volume shrinkage between the convex surface of the convex pattern structure made of a transition metal oxide and the intermediate layer on the lower surface by uniform reduction treatment. It is difficult to adjust the taper angle of the structure to an arbitrary taper angle, and a phenomenon in which the difference in volume shrinkage hardly appears in the taper angle control is utilized.

  In the conventional technique for controlling the cross-sectional inclination angle of the side surface of the structure, the physical property of the inorganic material constituting the structure remaining on the substrate after the formation of the convex structure by etching is not sufficiently controlled, and the desired structure inclination angle is set. It was difficult to get.

  Thus, the problem to be solved by the present invention is to provide a method for producing a convex structure that can control the inclination angle of the side surface of the convex structure as an example.

The convex structure manufacturing method of the present invention includes a first material mainly composed of at least one of zinc oxide, zinc sulfide, and zinc selenide, silicon oxide, and silicon nitridation. , Aluminum oxide, aluminum nitride, tin oxide, tin nitride, germanium oxide, and a second material mainly composed of germanium nitride Providing an inorganic resist layer on the substrate;
Exposing the inorganic resist layer with a laser beam to form a latent image;
Developing the inorganic resist layer to form a pattern of openings reaching the substrate in the remaining inorganic resist layer according to the latent image;
And performing a dry etching on the substrate through the opening of the inorganic resist layer to form a convex structure corresponding to the latent image on the substrate.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  As shown in FIG. 1, the master for manufacturing an optical information recording medium according to the embodiment is a circular substrate 12 made of, for example, silicon. An inorganic resist layer 16 is provided on the substrate 12, and data recording is performed by condensing and irradiating a laser beam from the inorganic resist layer side, and etching is performed so as to have a convex structure as a master. .

  The thickness of the substrate 12 is set so that the substrate 12 serves as a base for ensuring the mechanical strength required for the master, and the material is SiC, GaN, AlN or glass in addition to silicon. It is possible to use.

As a base material of the inorganic resist layer 16, an oxide, sulfide, nitride, or a combination thereof can be used as a main component. Specifically, the base material includes a first material mainly composed of at least one of a zinc oxide such as ZnO, a zinc sulfide such as ZnS, and a zinc selenide such as ZnSe, SiO, SiO Silicon oxide such as ₂ ; silicon nitride such as SiN; aluminum oxide such as Al ₂ O ₃ ; aluminum nitride such as AlN; tin oxide such as SnO ₃ , SnO ₂ and SnO; SnN And a second material mainly composed of at least one of germanium oxides such as GeN and GeCrN and tin nitrides such as GeO ₂ and GeO. The main component mentioned here preferably accounts for 50 atomic% or more of the material constituting the inorganic resist layer 16, and more preferably 80 atomic%. Furthermore, the inorganic resist layer 16 is more preferably composed mainly of a mixture of ZnS-SiO _2, SiO ₂ of the second material is also possible at 5 mol% to 90 mol% composition ratio is 10 mol% 25 mol% desirable.

  Next, an example of a method for manufacturing an unrecorded blank optical information recording medium manufacturing master will be described.

  First, as shown in FIG. 1, an inorganic resist layer 16 is formed on a flat circular substrate 12 such as silicon. The inorganic resist layer 16 can be formed using a vapor phase growth method.

  Next, a method for manufacturing a high-density disk stamper using the blank master will be described.

  As shown in FIG. 2, as a laser cutting process, a laser beam LB having a predetermined numerical aperture NA, wavelength, and output blinking so as to correspond to a signal to be recorded is applied to a rotating blank master 11 by an inorganic resist. The light is incident from the layer 16 side, and the inorganic resist layer 16 is irradiated and exposed. The laser beam LB to be exposed is exposed over a wide range, but is converged with a predetermined NA, so that the bottom surface of the inorganic resist layer in the cross section (perpendicular to the optical axis) is thinner than the top surface. A first material (based on zinc oxide or / and sulfide or / and selenide) and a second material (silicon oxide or / and nitride or / and aluminum) constituting the inorganic resist layer 16 Oxide or / and nitride or / and tin oxide or / and nitride or / and germanium oxide or / and nitride as a main component) Changes, and the solubility in an acid solution changes.

  By irradiation with the laser beam LB, the irradiated portion of the inorganic resist layer 16 is changed in physical properties by the laser beam LB, and a latent image laM having a spiral pattern is formed. The physical properties of the portion where the latent image is formed have solubility sufficiently different from the physical properties of the other portion (unrecorded area). Therefore, development can be performed due to the difference in dissolution rate between the latent image portion and the other portion. For example, since the temperature at the bottom of the inorganic resist layer is higher than that at the top, the solubility also changes in the thickness direction of the inorganic resist layer.

  Next, as a development step, as shown in FIG. 3, the exposed master 11 is mounted on a developing device (not shown), the master 11 is developed to remove the inorganic resist layer other than the latent image laM portion, and the substrate 12. A pattern of the opening OP reaching the position, that is, a reverse taper mask pattern 161 corresponding to a signal to be recorded is formed on the substrate 12 from an inorganic resist layer material. Here, it should be noted that, in the manufacture of the blank master, the width of the thermal conductivity and the bonding state can be increased by changing the mixing ratio of the first material and the second material. It is possible to control the cross-sectional shape (tilt angle) of 161. By increasing the mixing ratio of the first material and the second material and the ratio of the mixing of the second material to the first material, the end portion of the latent image portion is inversely tapered, that is, the surface of the substrate 12 and the inversely tapered mask. The angle θ formed with the side surface of the opening of the pattern 161 can be less than 90 degrees. Here, the reverse tapered cross-sectional shape refers to an overhang shape in which the inorganic resist gradually protrudes toward the opening space side as the inorganic resist layer is separated in the thickness direction from the substrate 12 contact side.

  Here, when the inclination angle of the cross section at the opening OP of the reverse taper mask pattern 161 is less than 90 degrees, the bottom surface B of the pattern 161 is narrower than the upper surface U, and therefore a pattern (thinner than the exposure surface (upper surface U)) ( The bottom surface B) will be drawn.

  Next, as a dry etching process, as shown in FIG. 4, the master 11 is placed in a chamber of a reactive ion etching apparatus (not shown), and reactive ion etching is performed.

  In the chamber of the reactive ion etching apparatus, a planar cathode connected via a blocking capacitor to a grounded high-frequency power source RF having a predetermined frequency and a grounded anode spaced apart and parallel to the cathode are installed. ing. The master 11 is mounted on the cathode.

  The inside of the chamber is supplied with an etching gas and exhausted to maintain the degree of vacuum at about 1 to 10 Pa. When power of a predetermined high frequency is applied to the cathode by a high frequency power source, discharge occurs between the cathode and anode, and the etching gas can be ionized (plasma).

  Electrons and positive ions in the plasma generated in the chamber are fast and positive ions move slowly due to the difference in mass. Therefore, the electrons quickly reach the cathode and anode. That is, electrons can follow high-frequency direction movement, but ions cannot follow and hardly move.

  Electrons that reach the cathode charge the cathode with a blocking capacitor. Since the anode is grounded, electrons that reach the anode flow to ground. The voltage charged on the cathode reaches 400 to 1000 V (cathode drop), and as shown by the arrow in FIG. 4, positive ions are incident on the master 11 (cathode) along the vertical electric field generated by the cathode drop, It is possible to perform anisotropic etching chemically and chemically.

  Here, since the cross section of the opening portion of the mask pattern 161 is reversely tapered, the upper surface of the opening portion constricts the flow of positive ions, and the exposed substrate 12 has a pattern from the center of the surface as shown in FIG. The nearby part is excavated so that it gradually becomes shallower.

  Thus, since the mixed inorganic material of the first and second materials is used as the inorganic resist layer 16 and the bonding state is changed by laser light irradiation (heating) depending on the mixing ratio, the mixing ratio changes to the acid solution. In the dry etching, the etching rate of the surface portion of the substrate 12 that is covered with the reverse taper mask pattern 161 and appears from the opening by changing the inclination of the end of the reverse taper mask pattern 161 using the phenomenon that the solubility can be controlled. In particular, the etching rate of the end portion of the inverse taper mask pattern 161 is controlled.

  As a result, when the step of removing the inorganic resist layer (reverse taper mask pattern) with an alkaline aqueous solution is executed after the dry etching step, the substrate 12 after the dry etching has a desired inclination angle θ1 as shown in FIG. A convex structure Pt can be obtained.

  By controlling the inclination of the cross-sectional shape of the inorganic resist layer by selecting the numerical aperture NA of the laser light and the mixing ratio of the first and second materials, the bottom surface of the inorganic resist layer pattern is narrower than the wide range of the laser light exposure part. It is possible to draw a thin pattern.

  In order to facilitate the control of the cross-sectional shape, a metal layer (not shown) may be provided between the substrate 12 and the inorganic resist layer 16 to expand the control range of the thermal conductivity. For example, an Ag alloy or an Al alloy is formed between the substrate 12 and the inorganic resist layer 16, and the thickness of the film can be changed to widen the variable range of the cross-sectional inclination angle.

  Furthermore, in the replication process, a disk stamper is created from the substrate 12 having the convex structure Pt by electroforming, the disk stamper is mounted on a mold of an injection molding apparatus, and the mold is closed to form a cavity. Then, after injecting a molten resin such as polycarbonate (PC) into the cavity, it is cured and taken out from the mold, thereby obtaining an optical disk substrate onto which the convex structure Pt of the disk stamper is transferred.

(Example)
A plurality of blank masters were produced as follows. First, set the silicon substrate with a diameter of 120mm in the sputtering apparatus, on a substrate, then a film thickness of 50 nm, change the composition ratio 2～25Mol% of SiO ₂ the first material of ZnS and second materials as SiO ₂ A plurality of layers having an inorganic resist layer formed by mixing them were prepared.

  Thereafter, information was recorded on the blank master as follows. By laser beam exposure, a single mark and space pattern was recorded with a constant linear velocity, a track pitch of 320 nm, a pit length of 150 nm, and a duty ratio of 50%.

  The exposed master was immersed and developed with an aqueous sulfuric acid solution.

  In this way, by applying a laser beam or the like to the mixture of the first material and the second material and heating (exposure), the bonding state of the first material and the second material changes, and the portion that has not been heated (exposed) Since the solubility of the heated (exposed) portion in the acid changes, when exposed to a 1% sulfuric acid aqueous solution for 60 seconds, the heated (exposed) portion remains, and the unheated (exposed) portion dissolves. That is, the mixture of the first material and the second material behaves as a photosensitive (heat sensitive) substance that reacts with light or heat and acts as a material for the inorganic resist layer, and sulfuric acid acts as a developer.

  After development, the master was washed with pure water and dried by air blow to leave an exposed portion, and the unexposed portion was removed to form a convex pattern, thereby obtaining a silicon master.

7 and 8 are SEM photographs of a cross section of a silicon substrate recorded with a single mark space, respectively. 7 is when the inclination angle of the inorganic resist layer end is less than 90 degrees (SiO ₂ composition ratio 20 mol%), and FIG. 8 is when the inclination angle of the inorganic resist layer end is 90 degrees (SiO ₂ composition ratio 10 mol%). belongs to.

Further, if the mixing ratio (composition ratio mol%) of the first material and the second material is changed in a range where the composition ratio of the first material is larger than the composition ratio of the second material, the mixture remains heated (exposure). The cross-sectional shape (tilt) of the portion changed depending on the mixing ratio. When the first material is ZnS and the second material is SiO ₂ , the inclination angle of the end portion of the inorganic resist layer exceeds 90 degrees in the range of ₂ to 10 mol% of SiO ₂ , but 90% at 10 to 25 mol% of SiO _2. It became less than degree.

As shown in FIG. 7, a mixture of ZnS and SiO ₂ (SiO ₂ composition ratio 20 mol%) is formed on a Si substrate, the inorganic resist layer 16 is exposed with a laser beam or the like to form a pattern, and 1% sulfuric acid is formed. When developed with an aqueous solution, portions other than the exposed portion are removed, and an inorganic resist mask having an inclination of less than 90 degrees, that is, a reverse tapered cross section is formed on the Si substrate.

  When etching is performed by RIE or the like using the inorganic resist mask of the example, the conditions such as the etching gas type and the etching rate are not adjusted (although the adjustment is possible), depending on the inclination angle of the cross section of the inorganic resist mask. Thus, a convex structure having an inclined cross section could be formed on the Si substrate. The cross-sectional inclination angle of the Si convex structure can be controlled while the etching conditions are kept constant. That is, after a pattern is produced by etching, the inorganic resist layer is removed with an alkaline aqueous solution to obtain a convex structure having a desired inclination.

It is a general | schematic fragmentary sectional view which shows the convex structure manufacturing method which concerns on embodiment by this invention. It is a general | schematic fragmentary sectional view for demonstrating the convex-structure manufacturing method of embodiment by this invention. It is a general | schematic fragmentary sectional view for demonstrating the convex-structure manufacturing method of embodiment by this invention. It is a general | schematic fragmentary sectional view for demonstrating the convex-structure manufacturing method of embodiment by this invention. It is a general | schematic fragmentary sectional view for demonstrating the convex-structure manufacturing method of embodiment by this invention. It is a general | schematic fragmentary sectional view for demonstrating the convex-structure manufacturing method of embodiment by this invention. It is a SEM photograph which shows the cross section of the silicon substrate by which the pattern recording of the Example by this invention was carried out. It is a SEM photograph which shows the cross section of the silicon substrate by which the pattern recording of the Example by this invention was carried out.

Explanation of symbols

11 Master 12 Substrate 16 Inorganic resist layer LB Laser beam
laM latent image Pt convex structure

Claims (5)

Providing on the substrate an inorganic resist layer in which a first material of zinc sulfide and a second material of silicon oxide are mixed;
Exposing the inorganic resist layer with a laser beam to form a latent image;
Developing the inorganic resist layer to form a pattern of openings reaching the substrate in the remaining inorganic resist layer according to the latent image;
See containing and forming a convex structure in accordance with the latent image on the substrate is subjected to dry etching to the substrate through the opening of the inorganic resist layer,
The step of providing the inorganic resist layer on the substrate controls the angle formed by the surface of the substrate and the side surface of the opening of the inorganic resist layer by changing the mixing ratio of the first material and the second material. A process for producing a convex structure , comprising the step of :   The method for producing a convex structure according to claim 1, wherein an angle formed between the surface of the substrate and a side surface of the opening of the inorganic resist layer is less than 90 degrees. The method for producing a convex structure according to claim 1 , wherein the inorganic resist layer contains 10 to 25 mol% of silicon oxide.   The method for producing a convex structure according to claim 1, further comprising a step of removing the inorganic resist layer with an alkaline aqueous solution after the step of dry etching the substrate. The step of forming the convex structure includes a step of controlling an etching rate by controlling an angle formed between a surface of the substrate and a side surface of the opening of the inorganic resist layer. Item 2. A method for producing a convex structure according to Item 1 .