Magnesium oxide sputtering target and method of making same

Abstract

A sintered compact magnesium oxide target for sputtering having a purity of 99.99 wt % or higher, a density of 3.58 g/cm.sup.3 or higher, and a transparency 10% or more. A sintered compact magnesium oxide target for sputtering having a purity of 99.99 wt % or higher, a density of 3.58 g/cm.sup.3 or higher, and an average crystal grain size of 50 m or more.

Claims

1. A method for producing a sintered compact magnesium oxide target for sputtering, the method comprising: obtaining a raw material by the milling of magnesium oxide (MgO), wherein said raw material include powders comprising magnesium oxide (MgO) having a purity of 99.99 wt % or higher and an average grain size of 0.5 m or less, said raw material being devoid of MgCO.sub.3; and hot pressing said milled powder at a temperature of 1700 C. or less and an applied pressure of at least 200 kgf/cm.sup.2 or more in a uniaxial direction, to obtain a sintered compact magnesium oxide target, thereby said sintered compact magnesium oxide target is not hot isostatic pressed, wherein said sintered compact magnesium oxide target for sputtering has a density of 3.58 g/cm.sup.3 or higher; wherein a variation of a transparency of said target is within 1%.

2. The method for producing a sintered compact magnesium oxide target as in claim 1, wherein said sintered compact magnesium oxide target comprises a purity of 99.99 wt % or higher.

3. The method for producing a sintered compact magnesium oxide target as in claim 1, wherein said applied pressure is 300 kgf/cm.sup.2 or more.

4. The method for producing a sintered compact magnesium oxide target as in claim 1, wherein said variation in said transparency is within 0.75%.

5. The method for producing a sintered compact magnesium oxide target as in claim 1, wherein said variation in said transparency is within 0.50%.

6. The method for producing a sintered compact magnesium oxide target as in claim 1, wherein said method does not include any additional sintering steps after said hot pressing in a uniaxial direction.

7. The method for producing a sintered compact magnesium oxide target as in claim 1, wherein said method does not use any electromelted powders.

8. A method for producing a sintered compact magnesium oxide target for sputtering, the method comprising: obtaining a raw material by the milling of magnesium oxide (MgO), wherein said raw material include powders comprising magnesium oxide (MgO) having a purity of 99.99 wt % or higher and an average grain size of 0.5 m or less, said raw material being devoid of MgCO.sub.3; and hot pressing said milled powder at a temperature greater than 1500 C. and less than or equal to 1700 C. and an applied pressure of at least 200 kgf/cm.sup.2 or more in a uniaxial direction, to obtain a sintered compact magnesium oxide target, thereby said sintered compact magnesium oxide target is not hot isostatic pressed, wherein said sintered compact magnesium oxide target includes: a purity of 99.99 wt % or higher; a density of 3.58 g/cm.sup.3 or higher; a variation of a transparency of said target is within 1%; a transparency of 10% or more; and an average crystal grain size of 50 m or more.

9. The method for producing a sintered compact magnesium oxide target as in claim 8, wherein said variation in said transparency is within 0.75%.

10. The method for producing a sintered compact magnesium oxide target as in claim 8, wherein a variation in said transparency is within 0.50%.

11. The method for producing a sintered compact magnesium oxide target as in claim 8, wherein said method does not include any additional sintering steps after said hot pressing in a uniaxial direction.

12. The method for producing a sintered compact magnesium oxide target as in claim 8, wherein said method does not use any electromelted powders.

Description

DETAILED DESCRIPTION

(1) The present invention provides a sintered compact magnesium oxide target for sputtering. The sintered compact magnesium oxide target for sputtering includes a purity of at least 99.99 wt % or higher. The sintered compact magnesium oxide target of the present invention further includes a density of 3.58 g/cm.sup.3 or higher, and a transparency 10% or more.

(2) In some embodiments, the sintered compact magnesium oxide target includes a density of 3.58 g/cm.sup.3 or higher. In other embodiments, the sintered compact magnesium oxide target for sputtering includes a density of at least 3.5805 g/cm.sup.3 or higher, in other embodiments, at least 3.581 g/cm.sup.3 or higher, and in other embodiments, at least 3.5815 g/cm.sup.3 or higher.

(3) In some embodiments, the sintered compact magnesium oxide target for sputtering includes a transparence of 10% or more. The term transparence or transparency should also be understood to mean the quality of allowing light to pass through a material. In some embodiments, the sintered compact magnesium oxide target for sputtering includes a transparence of at least 15% or more, in some embodiments, a transparence of at least 20% or more, and in other embodiments, at least 30% or more.

(4) In some embodiments, the variation in the transparence is within 1%. In other embodiments, the variation in the transparence is within 0.75%, and in other embodiments, within 0.50%.

(5) In some embodiments, the sintered compact magnesium oxide target for sputtering further includes raw material of pure MgO powder. In some embodiments, the MgO powder includes a particle size of less than 10.sup.6 m and specific surface area of less than 15 10.sup.3 m.sup.2/kg.

(6) In some embodiments, the present invention exhibits a magnesium oxide target having a higher purity and a higher density. This higher purity and higher density can be obtained with inexpensive processing conditions in comparison to conventional methods based on the selection of raw material powders and the optimal setting of sintering conditions.

(7) The sintered compact magnesium oxide target of the present invention exhibits larger average crystal grain size. In some embodiments, the larger average grain size results in low particle emission from the target. By having a larger average crystal grain size, less particles are located or exposed on the silicon wafer, as opposed to those targets which provide a smaller average crystal grain size. In some embodiments, the larger average crystal grain size results in better sputtering performance.

(8) In some embodiments, the sintered compact magnesium oxide target comprises an average crystal grain size of 50 m or more. In other embodiments, the sintered compact magnesium oxide target comprises an average crystal grain size of 60 m or more, in other embodiments, an average crystal grain size of 70 m or more, and in other embodiments, an average crystal grain size of 80 m or more.

(9) The present invention further provides a method for producing a sintered compact magnesium oxide target for sputtering. The method comprises obtaining a raw material by the milling of magnesium oxide (MgO), and hot pressing the milled powder to obtain a sintered compact magnesium oxide target.

(10) In some embodiments, the step of obtaining a raw material by the milling includes magnesium oxide (MgO) comprising a purity of 99.99 wt % or higher and an average grain size of 0.5 m or less.

(11) In some embodiments, the step of hot pressing the milled powder occurs at a temperature of 1700 C. or less. In some embodiments, the step of hot pressing the milled powder occurs at a temperature range between 1400-1700 C., in other embodiments, a temperature range between 1500-1700 C., and in other embodiments, a temperature range between 1600-1700 C.

(12) In some embodiments, the step of hot pressing the milled powder occurs at an applied pressure of at least 200 kgf/cm.sup.2 or more. In other embodiments, the step of hot pressing the milled powder occurs at an applied pressure of at least 300 kgf/cm.sup.2 or more.

(13) With respect to the occurrence of color shading, in some embodiments, the method of the present invention produces a sintered compact magnesium oxide target for sputtering which includes a uniformly translucent oxide target. In some embodiments, the translucent oxide target of the present invention is free of or substantially free of color shading. In other embodiments, the translucent oxide target of the present invention comprises a moderate oxygen defect.

(14) In some embodiments, the sintered compact magnesium oxide target for sputtering and methods disclosed herein do not require the addition of additives. Such additives include, for example, MgCO.sub.3 or Mg(OH).sub.2. In some embodiments, the sintered compact magnesium oxide target for sputtering and methods disclosed herein do not require any electromelted powders.

(15) In some embodiments, the sintered compact magnesium oxide target for sputtering and methods disclosed herein do not require any additional sintering steps after hot pressing. The present invention provides for good particle performance without the additional sintering steps. One benefit that can be realized from the elimination of additional sintering steps is that the present invention allows for a reduction in production costs.

(16) In a specific embodiment, a method for producing a sintered compact magnesium oxide target for sputtering is provided. The method comprises obtaining a raw material by the milling of magnesium oxide (MgO), wherein the raw material includes powders comprising magnesium oxide (MgO) having a purity of 99.99 wt % or higher and an average grain size of 0.5 m or less, and hot pressing the milled powder at a temperature of 1700 C. or less, and at an applied pressure of at least 200 kgf/cm.sup.2 or more, to obtain a sintered compact magnesium oxide target. In such embodiments, the sintered compact magnesium oxide target includes a purity of 99.99 wt % or higher, a density of 3.58 g/cm.sup.3 or higher, a transparency of 10% or more, and an average crystal grain size of 50 m or more.

EXAMPLES

(17) The following examples are included as being illustrative of the invention and shall not be construed as limiting the scope thereof.

Example 1

(18) Magnesium oxide powder of specific surface area of 8 10.sup.3 m.sup.2/kg and mean particle size of 0.5 10.sup.6 m and purity of 99.99% was hot pressed at a temperature of 1500 C. at an applied pressure of 300 kgf/cm.sup.2. Thus a magnesium oxide sputtering target produced of this invention was sintered to a density of 3.581 g/cm.sup.3 and a transparency of 16% and a grain size of 70 m. For comparison, a magnesium oxide sputtering target of purity 99.99% and density 3.576 g/cm.sup.3 and transparency in the center of 0.8% and grain size of 15 m was produced. Both the inventive sintered body and the comparative sintered body were sputtered under the same conditions. The performance of the two is shown in Table 1. We see that the particle performance of the exemplary magnesium oxide target is far superior to the comparative target. It is desirable to have lower particles on the silicon wafer to increase yield.

(19) TABLE-US-00001 TABLE 1 Average Density crystal grain Particle (g/cm.sup.3) size Transparency Performance Inventive 3.581 70 m 16% 150 Sintered Body 1 Comparative 3.576 15 m 0.8% 300 Sintered Body 1

(20) While the present invention has been described with respect to particular examples, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims and this invention should be construed to cover all such obvious forms and modifications.