JPH10158826A - Mgo target and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an MgO target having a high purity and density and suitable for formation of AC type PDP MgO protective coating by a sputtering method. SOLUTION: This MgO target capable of corresponding to a sputtering coating forming rate of >=600Å/min is composed of a high purity and high density MgO sintered body having >=99.9% purity and >=99.0% relative density. High purity MgO powder is added with 10 to 60wt.% electromelted MgO powder, 1 to 5wt.% MgO fine powder with the average grain size of <=100nm and a binder, and mixing is executed. This mixture is compacted and degreased, is thereafter subjected to primary sintering at 1250 to 1350 deg.C and is next subjected to secondary sintering at >=1500 deg.C. By the blending and two-step sintering, a high purity and high density MgO sintered body can be produced. By the blending of the electromelted MgO powder, MgO coating good in crystallinity can be formed. The MgO coating having good orientation properties, crystalinity and coating characteristics can be formed at a high coating rate by a sputtering method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-purity, high-density M
Related to the gO target and its manufacturing method,
AC PDP (Plasma Display Pan)
e) M suitable for sputtering of the MgO protective film
The present invention relates to a gO target and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, liquid crystals (Liquid Crystal) have been developed.
The research and development and commercialization of various flat displays, including al displays (LCDs), have been remarkable, and their production has been rapidly increasing.

A color plasma display panel (PD)
Regarding P), the development and commercialization of P) have recently been active. PDP is easy to increase in size,
It is at the shortest distance of the large screen wall-mounted TV for HDTV,
Prototyping of a 40-inch diagonal PDP is already underway.

[0004] PDPs are classified into an AC type in which a metal electrode is covered with a dielectric material in terms of an electrode structure, and a DC type in which a metal electrode is exposed in a discharge space.

In the AC type, a protective layer is further formed on the dielectric layer. At the beginning of the development of the AC type PDP, this protective layer was not used, so that the dielectric layer was directly exposed to discharge, and the surface of the dielectric layer was altered by ion bombardment, resulting in an increase in the firing voltage. Was.
In order to solve this problem, attempts have been made to form a protective layer with various oxides having a high heat of sublimation.
DP has a structure in which a protective layer is formed on a dielectric layer.

In an AC type PDP, since the protective layer is in direct contact with the gas, it plays an important role from various aspects. The properties required for this protective layer are (a) low discharge voltage, (b) spatter resistance, (c) fast discharge response, and (d) insulation. MgO is used for the protective layer to satisfy this condition. The MgO protective film protects the surface of the dielectric layer from the impact of sputtering, and plays an important role in extending the life of the PDP.

At present, in an AC type PDP, the MgO
The protective film is formed by an electron beam evaporation method. The optimal MgO film as the protective layer is a film oriented in the (111) plane. If the MgO film is oriented in the (111) plane, it can be driven at the lowest sustain voltage. Also, it exists in the film (11
1) It is said that as the amount of the surface increases, the secondary electron emission ratio increases and the driving voltage also decreases.

[0008] The electron beam evaporation method conventionally used for forming the MgO protective film has a high film forming speed, but has a drawback that splash is generated and the uniformity is lacking for a large area. is there. On the other hand, the sputtering method is easy to introduce from the viewpoint of the manufacturing process, and is suitable for forming the MgO protective film.

AC PDP with good orientation by sputtering
In order to form a protective MgO protective film at a high deposition rate, a high-purity and high-density Mg having a purity of at least 99.9% and a relative density of 99% or more is used as a target.
An MgO target made of an O sintered body is required.

[0010]

A conventional high-density MgO sintered body is manufactured by adding various sintering aids to densify the sintered body. That is, when a commercially available high-purity MgO powder is sintered without a sintering aid, only a sintered body having a relative density of about 93% can be obtained. On the other hand, by adding a sintering aid and sintering, high density can be achieved.

However, in the MgO sintered body obtained by adding the sintering aid, the MgO purity cannot be increased, and the MgO purity is limited to about 98 to 99% and contains a trace amount of impurities. I have.

As described above, conventionally, a high-purity and high-density MgO sintered body has not been provided, and a high-density but low-purity MgO sintered body or a high-purity but low-density MgO Only a sintered body was obtained.

An MgO film obtained by forming a film by a sputtering method using a MgO sintered body having a high density or an inferior purity or a MgO sintered body having a high purity and a low density as a target is:
It is inferior in orientation and crystallinity, inferior in the function of an AC-type PDP as a MgO protective film, and cannot be formed at a high film forming rate with such a MgO sintered body.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a high-purity and high-density MgO target suitable for forming an MgO protective film of an AC type PDP by a sputtering method and a method of manufacturing the same. .

[0015]

The MgO target of the present invention has an MgO purity of 99.9% or more and a relative density of 99.0%.
This is an MgO target made of the above-described MgO sintered body, and is an MgO target capable of supporting a sputter deposition rate of 600 ° / min or more.

The method of manufacturing the MgO target according to the present invention comprises:
The method for producing an MgO target according to claim 1, wherein the high-purity MgO powder is added to the electro-fused MgO powder 10 to 60.
Wt%, and MgO fine powder 1 having an average particle size of 100 nm or less.
5% by weight and a binder are added, mixed and molded. After the obtained molded body is degreased, it is subjected to primary sintering at 1250 to 1350 ° C, preferably 1250 to 1300 ° C, and then to 150 ° C.
It is characterized by secondary sintering at 0 ° C. or higher.

In the present invention, high purity MgO powder is added to
By adding a small amount of fine MgO fine powder of 10 to 60% by weight of gO powder and performing the two-stage sintering at a low temperature raising / lowering rate, high purity and high density can be obtained without using a sintering aid. Then, an MgO sintered body capable of forming an MgO film having good crystallinity by a sputtering method is manufactured.

That is, the fine MgO fine powder is easily sinterable and can be densified without using a sintering aid. The sintering of the raw material powder to which a small amount of the fine MgO fine powder is added starts from 1200 ° C., and proceeds considerably at 1350 ° C. Therefore, by performing primary sintering at this temperature, uneven sintering between the surface and the inside (difference in microstructure) even in a large product
A MgO sintered body free from slag is obtained. Furthermore, by sintering at a temperature of 1500 ° C. or more, no sintering aid is used,
Therefore, it is possible to obtain a high-density sintered MgO sintered body having a high theoretical purity and containing almost no impurities.

Electrofused MgO has high crystallinity and is similar to a single crystal in this point. Such fused Mg
If the MgO sintered body is manufactured using O as a raw material, an MgO film having good crystallinity can be formed by sputtering.

In the MgO sintered body obtained according to the present invention, small pores are present not in the MgO grain boundaries but in the grains. High-purity, high-density Mg having such a microstructure
When an MgO film is formed by a sputtering method using an O target, the film can be formed at a film formation rate of 600 ° / min or more, which is six times that of a commercially available target.
The film characteristics of the O film are also very good.

[0021]

Embodiments of the present invention will be described below in detail.

Mg constituting the MgO target of the present invention
The O sintered body is made of high-purity MgO having an MgO purity of 99.9% or more.
MgO which is a sintered body but has better orientation and crystallinity
In order to form a film, impurities such as Si, Fe, Cr,
The contents of V, Ca, Al, Mn, Ni, Na, and K are preferably 700 ppm or less in total.

Further, since the MgO sintered body constituting the MgO target of the present invention has a high density of 99.0% or more in relative density, the deposition rate by the sputtering method can be increased, and
High-speed film formation of 0 ° / min or more is possible.

Next, a preferred example of the method for producing the MgO target of the present invention for producing the MgO target of the present invention will be described.

First, a high-purity MgO powder having an average particle diameter of 0.1 μm or more, preferably 0.2 to 2 μm and a purity of 99.9% or more, preferably 99.99% or more, and an electro-fused MgO powder of 10 to 60% MgO with weight% and average particle size of 100 nm or less
A binder is mixed at a predetermined ratio with 1 to 5% by weight of fine powder and a binder, and a slurry having a concentration of 70% or more, preferably 70 to 75% is prepared using a dispersion medium such as ethanol, and granulated by a spray dryer according to a conventional method. I do. Then, the obtained granulated powder is press-molded in a mold, degreased, and then in the air, in a vacuum,
Alternatively, primary sintering is performed at 1250 to 1350 ° C. in an inert atmosphere, and 1500 ° C. or higher, preferably 1550 to 160 ° C.
Secondary sintering at a temperature of 0 ° C. The electrofused MgO powder also has an average particle size of 0.1 μm or more, preferably 0.2 to 2 μm, like the high-purity MgO powder.

In the present invention, high purity M
The reason why the MgO fine powder having an average particle size of 100 nm or less is added to the gO powder and used is to improve the sinterability and control the microstructure. The reason for this is that if it exceeds 5% by weight, it is difficult to prepare a high-concentration slurry, the density of the obtained compact is low, and even if it is sintered, it does not become close to the theoretical density. MgO
If the added amount of the fine powder is less than 1% by weight with respect to the high-purity MgO powder, the above-mentioned effect by adding the MgO fine powder cannot be sufficiently obtained. It is important that the MgO fine powder also has high purity.
It is preferably at least 9%.

The reason for adding the electro-fused MgO powder is that electro-fused MgO is similar to a single crystal in that the crystallinity is advanced.
This is because the O film can be formed by sputtering. However, the electrofused MgO powder has low sinterability, and if the addition amount is increased, a dense sintered body cannot be obtained. In addition, since the fused MgO powder is manufactured using arc discharge, it has many pores,
It is not a preferred target material in that it contains adsorbed impurities. However, when a sputtered film is formed by using an electrofused MgO sintered body as a target, an MgO film having good crystallinity can be formed as described above, although the film forming speed is low. Due to the balance between the sinterability of MgO, the film characteristics of the obtained MgO film, and the film formation rate, the amount of the electrofused MgO powder should be 1
0 to 60% by weight.

If the average particle size of the electro-fused MgO powder and the high-purity MgO powder is less than 0.1 μm, the handling of the powder is poor, and it is difficult to prepare a high-concentration (70% or more) slurry. Granular powder cannot be produced, and as a result, a high-density compact and sintered body cannot be obtained. Particularly, in the case of manufacturing a large product, in addition to the problem of the density, the warpage increases, and the post-processing takes time. If the average particle size of the electrofused MgO powder and the high-purity MgO powder exceeds 2 μm, it is difficult to control the microstructure, and a dense sintered body cannot be obtained.

The binder to be used is a non-aqueous binder.
The content is preferably 0.5 to 3% by weight based on the total of the gO powder and the MgO fine powder.

In the present invention, the two-stage sintering of the primary sintering and the secondary sintering is performed to reduce the rate of temperature rise / fall during sintering, thereby preventing unevenness in sintering and reducing the fineness of the sintered body. Control the structure, AC
Suitable for sputter deposition of MgO protective film for type PDP
Obtain a sintered body. In this sintering, the primary sintering temperature was 12
If it is lower than 50 ° C., sintering does not proceed. If it exceeds 1350 ° C., it is difficult to control the microstructure by two-stage sintering. If the secondary sintering temperature is lower than 1500 ° C., it is not possible to sufficiently densify by normal pressure sintering. The temperature of this secondary sintering is 15
When the temperature is 00 ° C. or higher, a high-density sintered body can be obtained by ordinary normal pressure sintering even for a large product without performing special sintering such as a HIP method or a hot press method.

In the present invention, from the viewpoint of controlling the microstructure, the rate of temperature rise at 1000 ° C. or more in the primary sintering and the secondary sintering is 50 ° C./hr or less, particularly 40 to 20 ° C./hr.
And the temperature decreasing rate is 100 ° C./hr or less, especially 70 to 40
C / hr is preferred.

In the present invention, the raw material preparation from the MgO powder is not performed by spray dry granulation as described above,
The calcined powder may be used. The method of forming the sintered body is not particularly limited, and a conventionally known method, for example, a method such as uniaxial pressure forming, rubber press forming, or casting may be employed.

[0033]

The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Examples 1 to 5 A high-purity MgO powder ("MJ-30" manufactured by Iwatani Chemical Co., Ltd., average particle size 0.3 μm, MgO purity 99.9%) was fused to a fused MgO powder (Mitsubishi Materials Corporation). "FMR-P"
C ”325 mesh pass product with stirring mill, average particle size 1μm
Pulverized) and MgO fine powder (“1000A” manufactured by Ube Chemical Industry Co., Ltd., average particle diameter 0.1 μm, MgO purity 9)
9.99%) at the compounding ratio shown in Table 1, and a binder (“PEG-200” manufactured by Sanyo Kasei Co., Ltd.)
gO powder, electrofused MgO powder and MgO fine powder were added in an amount of 2% by weight, ethanol was added as a dispersion medium, and the mixture was wet-mixed with a stirring mill for 2 hours to prepare a slurry having a concentration of 70%. Dry granulated. This granulated powder is placed in a mold (inner diameter 60 mm or 155 mm and thickness 8 m).
filled into m), it was uniaxially pressed at 75 kg / cm ^2, and CIP molding at 1500 kg / cm ^2. The obtained molded body was placed in an electric furnace (manufactured by Hirokisha Co., Ltd.) and
Primary sintering at 1600 ° C. for 1 hour, and then secondary sintering at 1600 ° C. for 2 hours. The temperature rise from 1000 to 1600 ° C. is 30
The temperature was lowered from 1600 ° C./° C. at 50 ° C./hr.

A diameter 5 obtained by molding a mold having an inner diameter of 60 mm
0mm sintered body is cut out, ground and polished,
The size of a 3 × 4 × 40 mm three-point bending test piece according to IS R1601 was measured, and the density and the breaking strength were examined. The results are shown in Table 1. The density was measured by the Archimedes method in toluene. The breaking strength was measured by a three-point bending test.

The MgO sintered body obtained in Example 4 was analyzed for impurities, and the results are shown in Table 2.

Further, in Examples 1 and 4, the inner diameter is 155 mm.
Was bonded to a copper back plate, and a sputter test was performed. The deposition conditions were T / S 5 cm, substrate temperature 300.
℃, gas pressure is 10mm to reduce the recoil Ar effect
Torr was set and RF1500W was sputtered. The thickness of the formed film was measured by an ellipsometer using a He-Ne laser (6328A). The refractive index and the absorption coefficient were determined at the same time, and the results are shown in Table 3.

Comparative Examples 1 to 3 The amounts of the electrofused MgO powder and the MgO fine powder were set to the ratios shown in Table 1.
O powder was added only), and an MgO sintered body was manufactured in the same manner as in Example 1 except that the sintering was performed in one-step at 3650 ° C. for 3 hours, and the relative density and flexural strength were examined in the same manner. Are shown in Table 1.

For Comparative Example 1, impurities were analyzed in the same manner as in Example 4, and the results are shown in Table 2.

Further, for Comparative Example 1, a sputtering test was conducted in the same manner as in Example 1, and the results are shown in Table 3.

Comparative Examples 4 and 5 In Comparative Example 3, MgO sintering was carried out in the same manner as in Comparative Example 3, except that the amount of the MgO fine powder was set to the ratio shown in Table 1 and high-purity MgO powder having an average particle size of 5 μm was used. The body was manufactured, and the relative density and the bending strength were similarly examined. The results are shown in Table 1.

For Comparative Example 4, a sputtering test was performed in the same manner as in Example 1, and the results are shown in Table 3.

Comparative Examples 6 and 7 An MgO sintered body was produced in the same manner as in Example 2 except that the amount of the electrofused MgO powder was changed to the ratio shown in Table 1, and the relative density and bending strength were similarly measured. Investigation and the results are shown in Table 1.

Comparative Example 8 An MgO sintered body was manufactured in the same manner as in Example 2 except that the sintering was performed in one-step at 1650 ° C. for 3 hours.
Similarly, the relative density and bending strength were examined, and the results are shown in Table 1.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

As is clear from Tables 1 to 3, the M
The gO target has a purity of 99.99% and a relative density of 99.99%.
It is a dense sintered body of 0% or more and has a bending strength of 300 to 4
It shows a high strength of 00 MPa. The film formation rate by the sputtering method was about six times or more higher than that of the MgO sintered body of the comparative example. The obtained MgO film was oriented to the (111) plane, and the film characteristics were good. In contrast, in Comparative Examples 1 and 4,
The diffraction peak intensity of the (111) plane was low, and the crystallinity was not good.

[0049]

As described above in detail, according to the MgO target made of the high-purity and high-density MgO sintered body of the present invention,
An MgO film having good orientation, crystallinity, and film characteristics as an MgO protective film of an AC PDP can be formed at a high film formation rate by a sputtering method.

According to the method of manufacturing an MgO target of the present invention, a large-sized MgO target made of such a high-purity and high-density MgO sintered body can be manufactured at low pressure by normal-pressure sintering.

Claims (2)

[Claims] 1. An MgO purity of 99.9% or more and a relative density of 9
An MgO target composed of a MgO sintered body of 9.0% or more, and capable of supporting a sputtering film forming rate of 600 ° / min or more.
gO target. 2. The method for producing an MgO target according to claim 1, wherein the high-purity MgO powder is added to a fused MgO powder.
10 to 60% by weight of powder and M having an average particle size of 100 nm or less
1-5% by weight of gO fine powder and a binder are added, mixed and molded, and the obtained molded body is degreased.
A method for producing an MgO target, comprising performing primary sintering at 50 ° C. and then secondary sintering at 1500 ° C. or higher.