Processes for producing fcc metals

Details Processes for producing fcc metals Processes for producing fcc metals

1999-09-29

2001-03-06

Ip, Sikyin (Department: 1742)

Metal treatment

Process of modifying or maintaining internal physical...

Heating or cooling of solid metal

C148S684000, C148S685000

Reexamination Certificate

active

06197134

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to fcc metals, or metals having a face-centered cubic lattice, which are controlled in crystal orientation to be suitable for use as target materials. The invention also relates to a process for producing such fcc metals.
With the recent development of the electronic industry, the use of sputtering target materials has increased and there is also a demand for improving their characteristics.
To provide metallization films on substrate wafers by sputtering, fcc metals are conventionally employed and required to have the following characteristics.
(1) They should have controlled specific crystal orientations, which depend on the property to be possessed by the fcc metal to be sputtered:
(i) In order to assure uniformity in the sputter film, it is particularly desired that the fcc metal have random orientations;
(ii) In order to assure high directivity in sputtering, it is particularly desired that the fcc metal be dominantly (110) oriented.
(iii) In order to assure high sputtering rate and uniformity in the sputter film, it is particularly desired that the fcc metal be dominantly (100) oriented.
(2) The fcc metal should also have good electromigration characteristics. As the line width of metallization or conductor films formed by sputtering on substrate wafers decreases, electromigration which is a kind of “breaking of wire” phenomenon has become a problem. It has been established that the phenomenon of electromigration is largely affected by the composition of the sputter film and, therefore, sputtering target materials which determine the compositions of sputter films in an almost unique way should also have good electromigration characteristics.
(3) The fcc metal should have minimum levels of impurities. The reliability of conductors formed of sputter films is largely affected by their microstructure which, in turn, is largely affected by impurities including gaseous components. It is therefore desired that sputtering target materials should also have minimum levels of impurities other than specified components.
(4) The fcc metal should have fine average crystal grain sizes. In order to enhance the uniformity of sputter films, as well as to improve the sputtering rate and directivity, it is desired that sputtering target materials have fine average crystal grain sizes.
Aluminum and any other materials that have heretofore been used to form metallization films by sputtering on substrate wafers do not satisfy the required characteristics to the fullest extent.
SUMMARY OF THE INVENTION
An object, therefore, of the invention is to provide fcc metals that are controlled to have desired crystal orientations and which possess all of the characteristics required for sputtering target materials.
Another object of the invention is to provide processes for producing such improved fcc metals.
The present inventors conducted intensive studies with a view to attaining the stated objects and found that when fcc metals, particularly those having a Cu matrix, were subjected to appropriate working and heat treatments such that they were controlled to have optimal crystal orientations in accordance with a specific object, they could be rendered to be satisfactory as sputtering target materials. The present invention has been accomplished on the basis of this finding.
Thus, according to a first aspect of the invention, there is provided a fcc metal having random orientations which satisfies the relations:
I
(200)
/I
(111)
≦2.3 and
I
(220)
/I
(111)
≦1.0
where I
(200)
and I
(220)
are the integral intensities of (111), (200) and (220) faces, respectively, of crystal faces as measured by X-ray diffractiometry.
According to a second aspect of the invention, there is provided a fcc metal according to the first aspect which is a metal having a copper matrix.
According to a third aspect of the invention, there is provided a fcc metal according to the second aspect, wherein the copper has a purity of at least 99.9999% (6 nines).
According to a fourth aspect of the invention, there is provided a fcc metal according to the second aspect which has an average crystal grain size of no more than 200 &mgr;m.
According to a fifth aspect of the invention, there is provided a fcc metal having random orientations which has a copper matrix with a purity of at least 6 nines and an average crystal grain size of no more than 200 &mgr;m and which further satisfies the relations:
I
(200)
/I
(111)
≦2.3 and
I
(220)
/I
(111)
≦1.0
where I
(200)
and I
(220)
are the integral intensities of (111), (200) and (220) faces, respectively, of crystal faces as measured by X-ray diffractiometry.
According to a sixth aspect of the invention, there is provided a process for producing a fcc metal having random orientations comprising the steps of cross rolling which is performed to achieve a total draft of at least 20%, with the rolling axis being offset at 15° or more in each pass to a total offset of at least 90°, and subsequent full annealing which is accompanied by recrystallization, said fcc metal satisfying the relations:
I
(200)
/I
(111)
≦2.3 and
I
(200)
/I
(111)
≦1.0
where I
(111)
, I
(200)
and I
(220)
are the integral intensities of (111), (200) and (220) faces, respectively, of crystal faces as measured by X-ray diffractiometry.
According to a seventh aspect of the invention, there is provided a process for producing a fcc metal having a copper matrix and random orientations comprising the steps of cross rolling which is performed to achieve a total draft of at least 20%, with the rolling axis being offset at 15° or more in each pass to a total offset of at least 90°, and subsequent heat treatment which is performed at 493-823 K for 60-7,200 seconds, said fcc metal satisfying the relations:
I
(200)
/I
(111)
≦2.3 and
I
(220)
/I
(111)
≦1.0
where I
(111)
, I
(200)
and I
(220)
are the integral intensities of (111), (200) and (220) faces, respectively, of crystal faces as measured by X-ray diffractiometry.
According to an eighth aspect of the invention, there is provided a process for producing a fcc metal according to the seventh aspect, wherein the copper has a purity of at least 6 nines.
According to a ninth aspect of the invention, there is provided a process for producing a fcc metal according to the seventh aspect, said fcc metal having an average crystal grain size of no more than 200 &mgr;m and random orientations, said process comprising the steps of performing hot working at 623-873 K to a reduction ratio of at least 20%, performing at least twice each of cold working to a reduction ratio of at least 10% and a heat treatment at 493-823 K for 60-7,200 seconds followed by cross rolling which is performed to achieve a total draft of at least 20%, with the rolling axis being offset at 15° or more in each pass to a total offset of at least 90° and subsequent heat treatment which is performed at 493-823 K for 60-7,200 seconds.
According to a tenth aspect of the invention, there is provided a target material comprising a fcc metal having random orientations which is defined by any one from the first aspect to the fifth aspect.
According to an eleventh aspect of the invention, there is provided a target material comprising a fcc metal having random orientations which has been produced by the process of any one from the sixth aspect to the ninth aspect.
According to a twelfth aspect of the invention, there is provided a fcc metal having a dominant (110) orientation which satisfies the relation:
I
(220)
/I
(111)
≧2.0
where I
(111)
and I
(220)
are the integral intensities of (111) and (220) faces, respectively, of crystal faces as measured by X-ray diffractiometry.
According to a thirteenth aspect of the invention, there is provided a fcc metal according to the twelfth aspect which is a metal having a copper matrix.
According to a fourteenth aspect of the invention, there is provided a fcc metal according to the thirteenth aspect, wherein the copper has a purity of at least 99.9999% (6 nines).
According to a fifteenth aspect of the inven

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