JP2000030309A - Sputtering target and production of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make formable a thin film at an increased rate and to reduce the cost by specifying the relative density of an aluminum nitride-base sputtering target. SOLUTION: A calcium compd. such as CaO or Ca3N2 or an yttrium compd. such as Y2O3, YC2 or YN is added as a sintering aid to aluminum nitride powder synthesized by the reduction nitriding reaction of Al2O3 and preferably having <=2 μm primary particle diameter and they are sintered by pressureless sintering, hot pressing, hot isostatic pressing or other method to obtain the objective sputtering target having >=99% relative density and usually having 3-20 mm thickness. The sintering aid is added so as to promote the sintering of the powder less liable to sinter and the added component improves the wettability of the particles with each other by melting at a high temp. and promotes mass transfer to increase the relative density of the resultant sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target used for forming a thin film by forming a vacuum thin film.

[0002]

2. Description of the Related Art Aluminum nitride has high thermal conductivity, high insulation, low dielectric constant, and excellent mechanical strength such as bending strength. For this reason, aluminum nitride is attracting attention as an insulating substrate material for semiconductor mounting that requires high heat dissipation, and its thin film is widely used in various fields such as electronics as optical thin film, dielectric film, insulating film, etc. Used.

[0003] An aluminum nitride thin film can be obtained by high frequency sputtering of an aluminum nitride sputtering target in Ar gas. Since an aluminum nitride sputtering target has a high melting point and is difficult to melt, and it is difficult to obtain a large single crystal of any shape, a polycrystalline sintered body is generally used.

[0004]

SUMMARY OF THE INVENTION Using a conventional sputtering target made of aluminum nitride sintered body,
The problems in producing an aluminum nitride thin film by sputtering are as follows.

When a large power is applied, the temperature rises rapidly from the surface side of the sputtering target, and a large stress is generated due to thermal shock or thermal expansion. Therefore, cracks are easily generated in a target having a low relative density. For this reason, it is difficult to perform high-speed film formation by applying a large amount of power to a sputtering target in production, and thus it is an issue to reduce costs.

An object of the present invention is to provide a sputtering target that can form an aluminum nitride thin film at low cost and at high speed. Another object of the present invention is to provide a method for manufacturing an optical recording medium at low cost by forming an aluminum nitride thin film at a high speed.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a sputtering target containing aluminum nitride as a main component and having a relative density of 98% or more, and to use the sputtering target. This is achieved by the method for manufacturing an optical recording medium described above.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sputtering target of the present invention has aluminum nitride as a main component. Other materials may be mixed, but in order to obtain good characteristics, it is preferable to contain aluminum nitride in a proportion of 60 mol% or more.

If the relative density of the sputtering target is low, cracking of the sputtering target may occur due to high power input for high-speed film formation. This is because when the relative density is low, there are many voids and the area where the particles are in contact with each other is small, so that the bonding strength between the particles is small, and the particles are vulnerable to thermal shock due to heat generation due to large power input. The sputtering target of the present invention has a relative density of 98%.
Due to the above, cracking or the like does not occur even when a large amount of power is supplied. The relative density is more preferably 99% or more from the viewpoint that the applied power density can be ² W / cm ² or more. The relative density in the present invention refers to a relative degree with respect to a true density calculated from a crystal structure.

Although the sputtering target of the present invention can be manufactured by powder sintering, aluminum nitride is a substance that is difficult to sinter, and it is difficult to obtain a dense sintered body with a single composition. Therefore, calcium compounds such as CaO and Ca ₃ N ₂ and yttrium compounds such as Y ₂ O ₃ , YC ₂ and YN are added as sintering aids, and these are added under normal pressure sintering, hot pressing, HIP (hot A dense sintered body can be obtained by sintering under hydrostatic pressure or the like. A sintering aid is a component added to promote the sintering of substances that are unlikely to be sintered.The added component melts at a high temperature, improves the wetting of particles, and promotes mass transfer. To increase the relative density of the sintered body. The heat treatment temperature is not particularly limited, but a temperature of 1800 ° C. or higher is preferable in order to enhance the effect of densification. The synthesis of the raw material powder of aluminum nitride can be obtained by a reduction nitridation reaction of Al ₂ O ₃ .

The primary particle is a minimum unit that maintains continuity of the crystal plane orientation. If the primary particle diameter is larger than 2 μm, it becomes difficult to obtain a high relative density target unless heat treatment at an extremely high temperature is performed. Therefore, the primary particle diameter is preferably 2 μm or less. It is more preferable that the primary particle diameter be 1 μm or less, because it becomes easy to increase the relative density and the strength of the sputtering target.

The backing plate is a high thermal conductivity material bonded to the back surface for cooling so that the sputtering target is not heated to a high temperature due to cation bombardment during sputtering. Therefore, a material containing copper, which is a material having high thermal conductivity, is effective. Further, by cooling the backing plate with water, a higher cooling effect can be obtained.

The shape of the sputtering target can be selected depending on the sputtering apparatus to be used, and may be a circle having a diameter of about 2 to 8 inches, or (4 to 8 inches).
6) A square of about (5 to 20 inches) or the like is generally used. As the thickness of the sputtering target, usually,
It is about 3 to 20 mm.

A typical layer constitution of the constituent members of the optical recording medium of the present invention is such that a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are laminated in this order on a transparent substrate. However, it is not limited to this.

The material of the reflection layer of the present invention includes metals such as Al and Au having light reflectivity, alloys containing these as main components and containing additional elements such as Ti, Cr and Hf, and Al and Au. Mixed with a metal compound such as a metal nitride such as Al or Si, a metal oxide, or a metal chalcogenide. Metals such as Al and Au and alloys containing these as main components are preferable because of high light reflectivity and high heat conductivity. As an example of the above alloy, Al, Si, Mg, Cu, Pd, T
i, Cr, Hf, Ta, Nb, Mn, and the like, in which at least one element in total is added at 5 atomic% or less and 1 atomic% or more, or Au is added to Cr, Ag, Cu, Pd, P
There is a material in which at least one element such as t or Ni is added in a total amount of 20 atomic% or less and 1 atomic% or more. In particular, an alloy containing Al as a main component is preferable because the price of the material can be reduced, and A is particularly preferable because it has good corrosion resistance.
An alloy in which at least one or more metals selected from Ti, Cr, Ta, Hf, Zr, Mn, and Pd are added to 1 in an amount of 5 atomic% or less and 0.5 atomic% or more in total. Above all,
Al—Hf—Pd alloy, Al—H alloy containing the reflective layer in a total amount of 0.5 atomic% or more and less than 3 atomic% because the corrosion resistance is good and hillocks and the like hardly occur.
f alloy, Al-Ti alloy, Al-Ti-Hf alloy, Al
-Cr alloy, Al-Ta alloy, Al-Ti-Cr alloy,
It is preferable to use any one of Al-Si-Mn alloys mainly containing Al.

The recording layer of the present invention is not particularly limited, but may be a Ge—Te alloy, a Ge—Sb—Te alloy, a Pd—Ge—Sb—Te alloy, an Nb—Ge—Sb—
Te alloy, Pd-Nb-Ge-Sb-Te alloy, Pt-
Ge-Sb-Te alloy, Co-Ge-Sb-Te alloy,
In-Sb-Te alloy, Ag-In-Sb-Te alloy,
Ag-V-In-Sb-Te alloy, In-Se alloy, and the like. Because the record can be rewritten many times,
e-Sb-Te alloy, Pd-Ge-Sb-Te alloy, N
b-Ge-Sb-Te alloy, Pd-Nb-Ge-Sb-
Te alloys and Pt-Ge-Sb-Te alloys are preferred. In particular, Pd-Ge-Sb-Te alloy, Nb-Ge-Sb-
Te alloy, Pd-Nb-Ge-Sb-Te alloy, Pt-
Ge-Sb-Te alloys are preferable because they have a short erasing time and are excellent in recording many times. As the material of the substrate of the present invention, various transparent synthetic resins, transparent glass, and the like can be used. To avoid the effects of dust and scratches on the board,
It is preferable to use a transparent substrate and perform recording from the substrate side with a focused light beam. Examples of such a transparent substrate material include glass, polycarbonate, polymethyl methacrylate, polyolefin resin, epoxy resin, and polyimide resin. In particular, a polycarbonate resin and an amorphous polyolefin resin are preferable because they have low optical birefringence, low hygroscopicity, and are easy to mold.

Although the thickness of the substrate is not particularly limited, it is practically 0.01 mm to 5 mm. 0.01m
If it is less than m, even when recording with a light beam focused from the substrate side, it is easily affected by dust, and if it is 5 mm or more,
It becomes difficult to increase the numerical aperture of the objective lens, and the spot size of the irradiation light beam becomes large, so that it becomes difficult to increase the recording density. The substrate may be flexible or rigid. The flexible substrate is used in the form of a tape, a sheet, or a card. The rigid substrate is used in the form of a card or a disk. Further, these substrates may be formed into an air sandwich structure, an air incident structure, or a close bonding structure using two substrates after forming a recording layer and the like.

The light source used for recording on the optical recording medium of the present invention is a high-intensity light source such as a laser beam or a strobe light. Particularly, a semiconductor laser beam has a small light source, low power consumption, Is preferred because of the simplicity.

In the case of a phase-change type optical recording medium, recording is performed by irradiating a crystalline recording layer with a laser light pulse or the like to form an amorphous recording mark. Alternatively, a recording mark in a crystalline state may be formed on a recording layer in an amorphous state.
Erasing can be performed by irradiating a laser beam to crystallize an amorphous recording mark or to make a crystalline recording mark amorphous. Since the recording speed can be increased and the recording layer is hardly deformed, it is preferable to form an amorphous recording mark during recording and crystallize during erasing.

In addition, when forming a recording mark, the light intensity is high.
One-beam overwriting, in which rewriting is performed slightly by irradiating a single light beam at the time of erasing is slightly weak, is preferable because the time required for rewriting is reduced.

The present invention can be used for the production of various optical recording media, and can be particularly preferably used for the production of phase-change optical recording media. In a phase change optical recording medium,
Since recording / erasing is performed by a phase change of the recording layer, a large temperature change occurs in the recording layer. This is because a large temperature change occurs in the dielectric layer accompanying this, so that the formation of the dielectric layer is important.

As a method for forming a reflective layer, a recording layer, and the like on a substrate, a thin film forming method in a vacuum, for example, a vacuum deposition method, an ion plating method, a sputtering method and the like can be mentioned. In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled during film formation.

The thickness of each layer to be formed is controlled by monitoring the state of deposition using a quartz crystal film thickness meter or the like.
Easy to do. The formation of the recording layer or the like may be performed while the substrate is fixed, or may be moved or rotated.

Further, as long as the effects of the present invention are not significantly impaired, an ultraviolet curable resin may be provided as necessary after forming a reflective layer or the like to prevent scratches and deformation. After the formation of the reflection layer or the like, or after the formation of the above-mentioned resin protective layer, the two substrates may be bonded to each other with an adhesive.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. (Analysis and Measurement Method) The metal element composition ratio was confirmed by ICP emission analysis (SPS4000 manufactured by Seiko Instruments Inc.). Observation of particle size was made by scanning electron microscope observation (S-
800).

Example 1 1.0% by weight of Y ₂ O ₃ was added to AlN powder obtained by a reductive nitridation reaction of Al ₂ O ₃ , and the mixture was uniformly mixed by a ball mill. This was sintered at 1800 ° C. for 5 hours by a normal pressure sintering method to obtain a sintered body. The relative density of this sintered body was measured and found to be 99.5%. When the particle size was observed with a scanning electron microscope, the primary particle size within the observation range was all 0.8 μm or less.

Next, this was ground and polished to form a sputtering target having a diameter of 6 inches and a thickness of 6 mm, and bonded to an oxygen-free copper backing plate using an indium alloy.

Thickness 0.6 mm, diameter 12 cm, 1.48
μm pitch (land width 0.74 μm, groove width 0.7
Sputtering was performed while rotating a polycarbonate substrate having a spiral groove of 4 μm) at 30 revolutions per minute.

6.5 × 10 ^-4 P in the sputtering apparatus
After evacuation to a, Ar gas was introduced, the internal pressure of the apparatus was set to 0.5 Pa, and RF magnetron sputtering was performed. First, ZnS to which 20 mol% of SiO ₂ was added was sputtered to form a first dielectric layer having a thickness of 95 nm on a substrate. Then sputtered AlN-Y ₂ O ₃ target described above to form a layer of 2 nm. Then, Ge, Sb, T
Sputtering alloy target consisting of e
Thus, a recording layer having a composition of Ge _17.1 Sb _27.6 Te _55.3 was obtained. Furthermore, the same ZnS-S as the first dielectric layer is used as the second dielectric layer.
TiO ₂ is sputtered to form a film having a thickness of 16 nm.
A reflective layer having a thickness of 150 nm was formed by sputtering an lHfPd alloy to obtain an optical recording medium of the present invention.

The AlN-Y ₂ O ₃ target of the present invention did not show any cracks or deformation other than the dents in the erosion portion even after 5 hours of sputtering at an input power of 2000 W.

(Example 2) CaO was added to AlN powder in an amount of 1.0
%, And a sintered body was obtained in the same manner as in Example 1. The relative density of this sintered body was 99.0%. When the particle size was observed with a scanning electron microscope, the primary particle size in the observation range was all 0.8 μm or less.

When a sputtering target was prepared and bonded to a backing plate in the same manner as in Example 1, and sputtering was performed under the same conditions, the AlN-CaO target of the present invention exhibited cracks and deformations other than the depressions in the erosion portion. I was not able to admit.

(Comparative Example) A sintered body was obtained by the normal pressure sintering method under the same conditions as in Example 1 except that the sintering aid was not added and only AlN powder was used. When the relative density of this sintered body was measured, 8
3.0%. Further, when the particle size was observed with a scanning electron microscope, the primary particle size within the observation range was all 0. 1.
It was 9 μm or less. Bonding to the backing plate was performed after grinding and polishing in the same manner as in Example 1.

When sputtering was performed in the same manner as in Example 1, the target was cracked by sputtering for 30 minutes.

[0035]

According to the present invention, a sputtering target capable of forming an aluminum nitride thin film at a high speed can be provided. As a result, an optical recording medium could be manufactured at low cost.

Continued on the front page F term (reference) 4G001 BA07 BA09 BA36 BA67 BB07 BB09 BB36 BB67 BD03 BD04 BD36 BE22 BE32 BE33 4K029 AA11 AA24 BA21 BA43 BA46 BA51 BA58 BA64 BB02 BB08 BC10 BD12 CA05 DC05 DC09 DC24 5D121 AA01 EE03 EE03 EE03

Claims (7)

[Claims] 1. A sputtering target containing aluminum nitride as a main component and having a relative density of 98% or more. 2. The sputtering target according to claim 1, wherein the relative density is 99% or more. 3. The sputtering target according to claim 1, comprising at least one of a calcium compound and an yttrium compound. 4. The primary particle diameter of aluminum nitride is 2 μm.
The sputtering target according to claim 1, wherein: 5. The sputtering target according to claim 1, wherein the sputtering target is bonded to a metal backing plate. 6. The sputtering target according to claim 5, wherein the backing plate is made of a metal containing copper. 7. A method for manufacturing an optical recording medium capable of recording or reproducing information by irradiating a recording layer formed on a substrate with light, wherein the optical recording medium contains aluminum nitride as a main component. 7. A method for manufacturing an optical recording medium, comprising a thin film to be formed, and using the sputtering target according to claim 1 when forming the thin film by sputtering film formation.