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METHOD OF MAKING RARE EARTH TRANSITION METAL ALLOY SPUTTERING TARGETS

IP.com Disclosure Number: IPCOM000025457D
Original Publication Date: 1985-Aug-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 125K

Publishing Venue

Xerox Disclosure Journal

Abstract

W e have discovered that if molten TbFe alloy is cast directly into an iron mold (iron being one of the constituents of the resultant alloy) having a disk shape of the sputtering target to be molded and the mold is allowed to cool, the resultant ingot has a very fine grain and homogeneous alloy composition in the bottom portion or region of the coated ingot. This bottom portion of the target ingot has good flatness and good mechanical integrity. The fine grain and good homogeneity is the result of rapid cooling during the liquid-solid phase transition after casting. The bottom portion of the mold, for up to several millimeters thickness from the bottom surface of the ingot, has an excellent bulk fine grain, homogeneity and integrity desirable for a sputtering target in the fabrication of magnetic or magneto-optic recording media. Also, the bottom surface is very flat which is excellent for a sputtering target. To use this bottom surface for the sputtering target surface, one need only to remove the TbFe target ingot from its mold, flip over the target ingot and reinsert the ingot in the mold. The removal of the ingot from the mold is easily accomplished because of thermal shrinkage of the ingot from the inner surfaces of the mold during cooling.

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IXEROX DISCLOSURE JOURNAL

METHOD OF MAKING RARE EARTH Proposed Classification TRANSITION METAL ALLOY U.S. CI. 204/192R SPUTTERING TARGETS Int. C1. C23c 15/00 Tu Chen
G. Bruce Charlan

We have discovered that if molten TbFe alloy is cast directly into an iron mold (iron being one of the constituents of the resultant alloy) having a disk shape of the sputtering target to be molded and the mold is allowed to cool, the resultant ingot has a very fine grain and homogeneous alloy composition in the bottom portion or region of the coated ingot. This bottom portion of the target ingot has good flatness and good mechanical integrity. The fine grain and good homogeneity is the result of rapid cooling during the liquid-solid phase transition after casting. The bottom portion of the mold, for up to several millimeters thickness from the bottom surface of the ingot, has an excellent bulk fine grain, homogeneity and integrity desirable for a sputtering target in the fabrication of magnetic or magneto-optic recording media. Also, the bottom surface is very flat which is excellent for a sputtering target. To use this bottom surface for the sputtering target surface, one need only to remove the TbFe target ingot from its mold, flip over the target ingot and reinsert the ingot in the mold. The removal of the ingot from the mold is easily accomplished because of thermal shrinkage of the ingot from the inner surfaces of the mold during cooling.

To ensure good thermal and electrical contact and good mechanical stability of the ingot in the mold, indium, gallium or other low melting solder is placed in the bottom of the mold prior to replacement of the flipped target ingot back into the mold. Then, the whole structure (ingot, solder and mold) is placed in an inert atmosphere and heated up to about 50 to 100 degrees C. above the melting point of the solder to form a good bond between the target ingot and the mold. This method will insure that the curved surface of the original top surface of the casted target ingot makes good electrical, thermal and secure contact within the mold.

With this method, good films with reproducible composition having the desired constituent proportions have been obtained for over ten hours of continued target sputtering using the same target. The "cast and flipped over" target provides a flat surfaced and good purity sputtering target for producing alloy thin films of rare earth transistion metals, such as TbFe, GdFe, GdCo, TbCo, HoCo, HoFe, as well as many other binary and trinary alloys which include at least one rare earth metal element.

The conventional manner of making alloy sputtering targets of rare earth transition metals for RF or DC...