JP2002294439A - Sputtering target and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target useful for forming a protective film of a phase-change recording medium, which does not crack or break when manufacturing the sintered compact, has a high manufacturing yield, and does not cause cracks even when being sputtered in high power, and to provide a manufacturing method therefor. SOLUTION: The sputtering target of a sintered compact consisting of Zn, S, Si, and O, is characterized in that the distribution of density in the sintered body is a predetermined value or less, in other words, an absolute value of difference of relative density between arbitrary two points in the sintered compact is 3% or less. The method for manufacturing the sintered compact includes pressure sintering with a step-by-step increasing sintering pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly comprises zinc sulfide and silicon dioxide which are used for forming a protective film of a phase change recording medium on which information can be recorded, reproduced and erased by using a light beam. The present invention relates to a sputtering target made of a sintered body and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, information is recorded using a light beam,
A mixed film of zinc sulfide (ZnS) and silicon dioxide (SiO ₂ ) is often used as a protective film for an optical disc that can be reproduced and erased. A sputtering method using a compact as a sputtering target is often used.

The production of a sintered body composed of zinc sulfide and silicon dioxide used for a sputtering target used for forming a protective film of a phase change recording medium represented by such an optical disk is performed by a hot press method, a CIP (low temperature) method. It is performed by a method using a combination of a hydrostatic pressing (HIP) method and a HIP (high-temperature isostatic pressing) method, and among others, a hot pressing method that is simple in industrial production is mainly employed.

[0004] However, in the case of a ceramic sintered body composed of zinc sulfide and silicon dioxide, cracks and cracks are easily generated during the process of manufacturing a sputtering target, and these are known as the main factors that lower the yield. I have. It is also known that cracking and cracking are apt to occur when trying to sputter with high output. There has been an urgent need to prevent cracks and cracks occurring during the production and sputtering of these sputtering targets.

[0005]

In recent years, in order to improve the production efficiency of the phase change recording medium, it has been attempted to improve the production efficiency of the phase change recording medium by performing high-speed film formation by high-output sputtering. Further, phase change recording media are required to have higher densities and higher capacities, and required characteristics such as reliability and film quality uniformity are becoming increasingly severe. However, when high-output sputtering is performed using a conventional sputtering target for forming a protective film of a phase-change recording medium, the sputtering target is cracked and cannot be continuously sputtered.
In addition, when high-speed film formation is performed using a sputtering target formed of a sintered body having a non-uniform density and a density distribution, the variation in the thickness of the formed protective film increases, and the uniformity of the film quality increases. The properties of the protective film are not sufficient, and the characteristics of the protective film become non-uniform depending on the in-plane position of the phase change recording medium.

SUMMARY OF THE INVENTION The present invention has been made to address such problems, and can prevent cracking of a target during production of a sintered body or sputtering, and can improve the uniformity of film quality of a protective film. It is an object of the present invention to provide a sputtering target.

[0007]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies. As a result, in a sintered body having a relative density of 93% or more, the sintered body By producing a homogeneous sputtering target so that the difference between the maximum value and the minimum value is within 3%, cracking of the sintered body during sintering and cracking during high-power sputtering do not occur. It has been found that high-speed and stable sputtering can be performed.

[0008] The present invention has been made based on the above research results.

[0009] The sputtering target of the present invention is a sputtering target characterized by using a homogeneous sintered body having a density distribution not exceeding a predetermined value in the sintered body. The difference between the maximum value and the minimum value of the relative density is within 3%. That is, the sputtering target of the present invention,
A sputtering target comprising a sintered body containing zinc sulfide and silicon dioxide as main components, wherein an absolute value of a difference between relative densities at arbitrary two points of the sintered body is within 3%. is there.
In the sputtering target of the present invention,
It is preferable that the relative density of the entire sintered body constituting the sputtering target is 93% or more.

In order to obtain a sintered body having a small density distribution as described above, for example, it is useful to apply pressure stepwise during sintering. It is also useful to add a small amount of zinc oxide powder as a sintering aid.

That is, the sputtering target of the present invention is a sputtering target obtained by subjecting a mixed powder of zinc sulfide powder and silicon dioxide powder to pressure sintering by gradually increasing the sintering pressure. And the mixed powder further includes a zinc oxide powder.

Further, the method for producing a sputtering target of the present invention comprises the steps of uniformly mixing zinc sulfide powder and silicon dioxide powder, or uniformly mixing zinc sulfide powder, silicon dioxide powder and zinc oxide powder, This is a method for manufacturing a sputtering target, characterized in that the sintering pressure is increased stepwise and pressure sintering is performed.

More specifically, the method for manufacturing a sputtering target of the present invention comprises a step of obtaining a sintered body by sintering a mixed powder of zinc sulfide powder and silicon dioxide powder under pressure. In the pressure sintering, the first stage pressing is started after reaching a predetermined temperature of 800 ° C. or more and 900 ° C. or less, and the sintering temperature (sintering temperature) of 1020 ° C. or more and 1200 ° C. or less is reached. A method for producing a sputtering target, wherein the second stage of pressurization is started after the arrival, and a method for producing a sputtering target, wherein the mixed powder further contains zinc oxide powder. .

Hereinafter, the present invention will be described in more detail.

In a sputtering target composed of a sintered body containing zinc sulfide and silicon dioxide as main components,
By making the variation in density within the sintered body equal to or less than a predetermined value, cracking of the sintered body that occurs during sintering and cracking that occurs during high-power sputtering can be prevented, and high-speed and stable sputtering can be performed. Not only is it possible,
It is also possible to improve the uniformity of the quality of the obtained protective film.

That is, in the sintered body constituting the sputtering target of the present invention, the absolute value of the difference between the relative densities at any two points is within 3%. In addition, a sputtering target using a sintered body having a small variation in density within the sintered body can be sputtered at a high speed and stably without causing cracks. The absolute value of the relative density difference at a point is 2%
Is preferably within 1.5%, and more preferably within 1.5%.

The relative density of the entire sintered body constituting the sputtering target of the present invention is preferably at least 93%, more preferably at least 96%. This is because, as compared with a sputtering target using a sintered body having a large density of the entire sintered body, cracking does not occur and high-speed and stable sputtering can be performed.

The sintered body containing zinc sulfide and silicon dioxide as main components in the present invention means a sintered body having a total content of zinc sulfide and silicon dioxide of 90% or more.

Further, a sputtering target is constituted.
The relative density of the sintered body can be determined, for example, by the Archimedes method.
It can be calculated from the measured bulk density. This and
The theoretical density of the sintered body is less than zinc sulfide and silicon dioxide.
Sintered bodies can be made of zinc sulfide and
And silicon dioxide only
good. Specifically, the theoretical density of zinc sulfide and silicon dioxide
4.09 g / cm for each^Three, 2.20 g / cm^Threeof
Values, for example, zinc and silica obtained by chemical analysis, etc.
Of zinc sulfide and silicon dioxide calculated from the silicon content
As the weighted average weighted by the content, the theoretical density of the sintered body
Is calculated. For example, the molar ratio of zinc sulfide to silicon dioxide is
In the case of a 80:20 sintered body, the theoretical density is 3.67.
g / cm ^ThreeBecomes

The relative density at an arbitrary point of the sintered body is calculated by cutting out a sintered body piece having a predetermined size centered on the point, for example, a 30 mm square, and calculating the relative density by the above method.

In order to produce a sintered body having a small density distribution, it is useful to add a sintering aid to improve the sinterability. It is also important to adopt sintering conditions that do not leave stress in the sintered body.

When a sintering aid is added, zinc sulfide powder, silicon dioxide powder and zinc oxide powder as a sintering aid are uniformly mixed, and the obtained mixed powder is sintered to obtain a sintered body. Make it. In addition, it is preferable that the addition amount of the zinc oxide powder in the mixed powder is 0.6 to 5 wt%. That is, in order to obtain a sufficient effect of zinc oxide addition, the addition amount is set to 0.6.
wt% or more, and the addition amount is preferably 5 wt% or less in order to prevent an adverse effect on the thin film due to generation of a double oxide of zinc and silicon. In particular,
Considering the effect on the properties of the protective film of the phase change recording medium obtained by sputtering and the effect of the addition, the content is more preferably 1 to 3 wt%.

As a sintering condition for reducing the occurrence of residual stress in the sintered body, it is useful to apply pressure stepwise during sintering. That is, after the temperature reaches a sintering temperature at which sintering starts to advance, the first stage of pressurization is started to promote densification. Next, it is useful to start the second-stage pressurization after the temperature reaches the sintering holding temperature to further advance the sintering. In the present invention, 1
Approximately 70% of the total pressurized amount at the time of pressurization in the second stage
Some pressurization is implemented.

When zinc oxide is used as a sintering aid to be added, since zinc oxide is composed of only zinc and oxygen, which are constituent elements of zinc sulfide and silicon dioxide, other sintering aids such as The effect of the addition on the properties of the formed thin film as a protective film of the phase-change recording medium can be greatly reduced as compared with the addition of.

The molar ratio of the zinc sulfide powder to the silicon dioxide powder in the mixed powder is preferably from 90:10 to 70:30. This is because a film having the most preferable characteristics such as the rate can be obtained as the protective film of the phase change recording medium.

The sintering temperature (sintering holding temperature) is preferably set to a transition temperature of zinc sulfide from a zinc blende structure to a wurtzite structure, that is, from 1020 ° C. to 1200 ° C. If the temperature is lower than 1020 ° C., high-temperature zinc sulfide having a wurtzite structure cannot be obtained, and in order to obtain the effect of improving the sintering density, a very high pressure and a long firing time are required.
If the temperature exceeds 00 ° C., the composition of the sintered body may change due to sublimation of zinc sulfide. The sintering temperature was set to 1100
By setting the temperature to be higher than or equal to 1200 ° C., a sintered body having a higher density can be easily obtained.

It is preferable that the pressing start temperature is 800 ° C. or higher. The purpose of this is to remove the residual gas components contained in the raw material powder in a trace amount. If the pressurization is started from a low temperature and sintering is advanced, the gas components in the raw material powder may remain. It is. Further, it is preferable to start the second stage pressing after reaching the sintering holding temperature. If the second-stage pressurization is started immediately after the first-stage pressurization, the sintering does not proceed uniformly at this stage because the fluidity of the raw material powder is not good. This is because there is a possibility that this will occur. Normally, in the hot pressing method, sintering proceeds from the outer peripheral portion due to heat conduction. Therefore, if the flowability of the raw material powder is low during sintering, sintering hardly proceeds in the central portion. In that case, it is known that a density distribution occurs in the in-plane direction in the obtained sintered body.

As a more detailed manufacturing method of the sintered body of the present invention, when a sintering aid is added, raw material powders of zinc sulfide, silicon dioxide and zinc oxide are blended so as to have a predetermined composition. After mixing uniformly in a ball mill, the obtained mixed powder is filled into, for example, a hot-pressed graphite mold and heated in an argon atmosphere or vacuum to a temperature of 1020.
~ 1200 ° C, time: 1 ~ 10hr, first stage pressing start temperature: 800 ~ 900 ° C, pressure: 100 ~ 210kg / c
m ² , second-stage pressurization start temperature: 1,200 to 1,200, pressure: 150 to 300 kg / cm ² , heating rate: 200 to
300 ° C./hr, cooling rate: 100 to 300 ° C./hr,
Sintering rate: The sintering is performed under hot pressing conditions in the range of 1 to 5 ton / min. Here, the cooling rate is 30
If the temperature is higher than 0 ° C./hr, residual stress is generated in the sintered body during the cooling process, and defects such as cracks and cracks are generated in the sintered body. Therefore, the cooling rate is preferably 200 ° C./hr or less. If the pressure rise rate is higher than 5 ton / min, the stress remains, so it is preferable to set the pressure to 3 ton / min or less.

The zinc sulfide powder, silicon dioxide powder and zinc oxide powder used as the raw material powder for producing the sintered body of the present invention are not particularly limited, and commercially available powders can be used. In order to obtain a uniform and high-density sintered body, it is preferable to use a powder having an average particle diameter of 10 μm or less for zinc sulfide powder and silicon dioxide powder, and a powder having an average particle diameter of 5 μm or less for zinc oxide powder. Preferably, it is used.

As the silicon dioxide powder to be used, a powder composed of spherical particles can be used. However, an irregular shape having many corners obtained by crushing relatively large particles having no specific shape can be used. By using a powder having particles having an average particle diameter of 10 μm or less, it is possible to effectively prevent the silicon dioxide particles from falling off from the sintered body, and to more effectively generate particles during sputtering. Can be prevented.

The sintered body obtained as described above is processed into a predetermined shape by dry or wet machining and, if necessary, is made of Cu for effectively cooling the heat during sputtering. Alternatively, the sputtering target of the present invention is manufactured by bonding to a backing plate made of Mo.

The shape of the sputtering target can be appropriately selected depending on the sputtering apparatus to be used. For example, a circular target having a diameter of about 3 to 9 inches is generally used. Also, (4-6 inches) × (5-2
A square of about 0 inch) is also observed. The thickness of the sputtering target is usually about 3 to 20 mm.

[0033]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 5 ZnS powder having an average particle size of 5 μm, SiO ₂ powder having an average particle size of 5 μm, and Zn having an average particle size of 0.5 μm were used as raw material powders.
O powder was used.

The ZnS powder and the SiO ₂ powder are mixed in a molar ratio of 8
0:20 was added, and ZnO powder was added thereto in an amount of 1.0 wt% (Examples 1 to 4) based on the total amount, and this was put into a resin pot together with zirconia balls.
The mixture was mixed in a ball mill for 16 hours. In Example 5, no sintering aid was added. The obtained mixed powder is filled in a hot-pressed graphite mold, and the temperature is 1150 ° C. (Examples 1 and 3) or 1180 ° C. (Examples 2, 4, and 5) and the pressure is 2 in vacuo.
Performs a hot press sintering at 00kg / cm ² of the conditions,
A sintered body was produced. The first-stage pressurization start temperature is 850.
° C (Examples 1, 2) or 900 ° C (Examples 3, 4, 5)
And the second-stage pressurization start temperature was 1150 ° C. (Examples 1, 3) or 1180 ° C. (Examples 2, 4, 5). Further, the temperature raising rate and the temperature decreasing rate were 200 ° C./hr, the pressure increasing rate and the pressure decreasing rate were 3 ton / min, and the holding time was 6 hours.

Each of the obtained sintered bodies is processed by machining.
After processing into a disk shape (200mmφ, thickness 5mm), C
A sputtering target was obtained by bonding to a u backing plate.

(Comparative Examples 1 and 2) The same raw material powder as in the Example was used, but in Comparative Examples 1 and 2, ZnO powder as a sintering aid was not added. ZnS powder and SiO ₂ powder in molar ratio of 8
0:20, and this was put into a resin pot together with zirconia balls.
Mix for 6 hours. The obtained mixed powder is filled in a hot-pressed graphite mold, and the temperature is 1150 ° C. and the pressure is 200 k in vacuum.
Hot press sintering was performed under the conditions of g / cm ² to produce a sintered body. In Comparative Example 1, the pressure was not increased in a stepwise manner, and when the sintering temperature reached 900 ° C., the pressure was 200 kPa.
g / cm ² . In Comparative Example 2, the first-stage pressurization start temperature was 900 ° C., and the second-stage pressurization start temperature was 950 ° C. Here, the temperature raising rate and the temperature decreasing rate were 200 ° C./hr, the pressure increasing rate and the pressure decreasing rate were 3 ton / min, and the holding time was 6 hours.

Table 1 shows the presence or absence of ZnO and the sintering conditions for Examples 1 to 5 and Comparative Examples 1 and 2. Two types of sintered bodies were prepared under the same conditions, one for density measurement and one for sputtering target production.

[0039]

[Table 1] Regarding the in-plane density distribution of the sintered body, the density of a disk-shaped (200 mmφ, 5 mm thick) sintered body processed first was measured by the Archimedes method. Thereafter, as shown in FIG. 1, samples of 30 mm square were cut out from each of the five positions of up, down, left, right, and center, and the sintered body density of each sample was measured in the same manner.

The relative density of the sintered body was calculated from the bulk density measured by the Archimedes method. Note that the theoretical density of the sintered body was calculated on the assumption that the sintered body was composed of only zinc sulfide and silicon dioxide. Specifically, the theoretical densities of zinc sulfide and silicon dioxide are 4.09 g / cm ³ ,
Using a value of 2.20 g / cm ³ , a composition ratio (molar ratio) of 8
A value of 3.67 g / cm ³ obtained as a weighted average using the weight ratio obtained from 0:20 as a weight was used as the value of the theoretical density of the sintered body.

In addition to observing the occurrence of cracks and cracks during the production of the sintered body, the obtained sputtering target was evaluated for film formation.

For film formation evaluation, pre-sputtering was performed for 1 minute at an argon pressure of 0.4 Pa and an input power of 300 W using an RF magnetron sputtering apparatus, and then an argon pressure of 0.4 Pa and an input power of 300 were applied.
Sputtering under the condition of W until the target life,
It was examined whether cracks or cracks occurred in the sputtering target.

Table 1 shows the above Examples and Comparative Examples.
The measurement results of the density of the entire sintered body, the density at each position in the sintered body, the presence or absence of cracking during the production of the sintered body, and the presence or absence of cracking in the film formation evaluation are shown.

As is evident from Table 1, in the sputtering target of the present invention (Examples 1 to 5) in which the second-stage pressurization start temperature was the sintering holding temperature, no crack was generated both during sintering and during sputtering. Did not occur. Further, the density distribution of the sintered body was suppressed to within 1.5%. In contrast, Z
In the sintered body in which stepwise pressure sintering was not performed without adding nO (Comparative Example 1), cracks occurred during sintering, and the in-plane density distribution also exceeded 3%. Although stepwise pressure sintering was performed, in the sintered body (Comparative Example 2) in which the second-stage pressure start temperature was 950 ° C., no crack occurred during sintering, but the in-plane density distribution was 3%. 0.0%, and cracks occurred during sputtering.

[0045]

As described above, the sputtering target of the present invention has a very small density distribution of the sintered body, so that no cracks or cracks occur during its production, and the production yield can be greatly improved. Even when high-power sputtering is performed using this, a film can be formed at high speed and stably without generating cracks or cracks.

[Brief description of the drawings]

FIG. 1 is a diagram showing sampling positions when measuring the in-plane density distribution of a sintered body.

Claims (10)

[Claims] 1. A sputtering target comprising a sintered body containing zinc sulfide and silicon dioxide as main components,
The absolute value of the difference between the relative densities at any two points of the sintered body is within 3%. 2. The sputtering target according to claim 1, wherein the relative density of the sintered body is 93% or more. 3. A sintered body obtained by subjecting a mixed powder of zinc sulfide powder and silicon dioxide powder to pressure sintering while gradually increasing the sintering pressure. The sputtering target according to claim 1 or 2. 4. The sputtering target according to claim 3, wherein the mixed powder of the zinc sulfide powder and the silicon dioxide powder further includes a zinc oxide powder. 5. The method according to claim 1, wherein the ratio of the zinc oxide powder in the mixed powder is 0.1%.
The sputtering target according to claim 4, wherein the content is 6 wt% or more and 5 wt% or less. 6. The sputtering target according to claim 1, wherein after the zinc sulfide powder and the silicon dioxide powder are mixed, the sintering pressure is increased stepwise and pressure sintering is performed. Production method. 7. The method according to claim 1, wherein after the zinc sulfide powder, the silicon dioxide powder and the zinc oxide powder are mixed, the sintering pressure is increased stepwise and pressure sintering is performed.
3. The method for producing a sputtering target according to item 1. 8. A method for producing a sputtering target, comprising a step of pressure-sintering a mixed powder of zinc sulfide powder and silicon dioxide powder to obtain a sintered body, wherein the pressure-sintering is performed at 800 ° C. to 900 ° C. The first-stage pressurization is started after reaching the following predetermined temperature, and 1020 ° C. or more and 1200 ° C.
A method for manufacturing a sputtering target, wherein the second stage pressurization is started after reaching the following sintering holding temperature. 9. The method according to claim 8, wherein the mixed powder of the zinc sulfide powder and the silicon dioxide powder further includes a zinc oxide powder. 10. The method for producing a sputtering target according to claim 9, wherein a ratio of the zinc oxide powder in the mixed powder is 0.6 wt% or more and 5 wt% or less.