Ta sputtering target and method for producing the same

Abstract

A method for producing a Ta sputtering target including the following steps: (a) a step of forging a Ta ingot, comprising subjecting the Ta ingot to a forging pattern over at least 3 times, wherein each forging pattern is “a cold forging step comprising stamp-forging and upset-forging operations alternatively repeated over at least 3 times; (b) an in-process vacuum heat-treating step carried out between every successive two forging patterns to thus prepare a Ta billet; (c) a step of rolling the Ta billet to obtain a rolled plate; and (d) a step of vacuum heat-treating the rolled plate to obtain a Ta sputtering target. A sputtering target produced by the above method.

Description

TECHNICAL FIELD[0001]The present invention relates to a sputtering target which is subjected to a sputtering processing which is a thin film forming technique, and to a method for the production thereof and, more particularly, to a Ta sputtering target having a uniform crystalline microstructure and a method for the production of the same.BACKGROUND ART[0002]Up to now, in the field of semiconductors, a barrier metal film layer has been formed. Such a barrier metal film layer has conventionally been formed, in the form of a thin film between a wiring films and insulating films. Such a barrier metal film layer has conventionally been formed in the form of a thin film according to, for instance, the sputtering technique. It has therefore been required for the barrier metal film layer to be formed with a thinner and more uniform thickness. For this reason, it has correspondingly been required for the sputtering target used for forming a barrier metal film layer to make the grain size of...

AI Technical Summary

Benefits of technology

[0027]According to the present invention, the uniformity in the crystalline microstructure of the billet can be improved without lowering the yield in the forging. In addition, by optimizing the conditions for combining the total draft percentage and the vacuum heat treatment during the forging of the billet, Ta sputtering target having a fine and uniform microstructure, as well as the method for producing the same can be provided.

Problems solved by technology

Ta sputtering targets were produced by way of experiments according to these methods, but these methods are not always sufficient for the preparation of a Ta sputtering target having sufficiently fine crystalline microstructure with small scattering of the average grain size.

(1) the forging conditions thereof were inadequate and thus the crystalline microstructure of the billet (slab) was not uniform;

(3) the heat-treating conditions of the plate to be rolled were inadequate.

As a result, the resulting product has a crystalline microstructure insufficient in the uniformity between the outer peripheral portion and the central portion.

If this non-uniformity is more conspicuous, the concave area in the central portion would remain depending on the thickness of the billet even if the subsequent upset-forging operation is carried out and this would become a cause of a considerable reduction in the production yield of such billets.

In other words, in case the aspect ratio (diameter / length) is inadequate with the ingot or at the time of deformation by forging, a stable production by cold forging cannot be made.

As a result, there arises a problem in that the uniformity in the crystalline microstructure cannot be attained, i.e., in that the yield is lowered.

Even if a billet which is high in uniformity in the crystalline structure is prepared, the subsequent lower draft percentage at the time of rolling will result in a failure to obtain, in the subsequent heat treating, a uniform and crystalline microstructure.

On the other hand, even if a billet which is high in uniformity in crystalline microstructure is prepared, too high a draft percentage will give rise to a problem in that the growth into too coarse a grain size of the crystalline microstructure is likely to be accelerated in the subsequent heat treating.

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