Recycling method for tantalum coil for sputtering and tantalum coil obtained by the recycling method

Abstract

The present invention relates to a method for recycling a tantalum coil for sputtering that is disposed between a substrate and a sputtering target. The method for recycling a tantalum coil for sputtering is characterized in that the whole or partial surface of a spent tantalum coil is subject to cutting (cutting is performed until a re-deposited film and knurling traces are eliminated) so as to eliminate the re-deposited film that was formed during sputtering, and knurling is newly performed to the cut portion. While sputtered grains are accumulated (re-deposited) on the surface of the tantalum coil disposed between the substrate and the sputtering target during sputtering, by eliminating the sputtered grains accumulated on the spent coil by way of cutting after the sputtering is complete, the tantalum coil can be efficiently recycled. Thus, provided is technology capable of lean manufacturing of new coils, improving productivity, and stably providing such coils.

Claims

1. A method for recycling a used tantalum coil of a sputtering apparatus, having a surface formed with knurling traces, wherein the surface of the used tantalum coil is cut to eliminate the knurling traces together with re-deposited films or eroded areas or both formed during sputtering on the surface of the used tantalum coil and obtain a flat and smooth surface having a surface roughness Ra of 1.6 m or less, and thereafter the flat and smooth surface is knurled to form a new surface of the used tantalum coil provided with newly formed knurling traces.

2. The method for recycling a used tantalum coil of a sputtering apparatus according to claim 1, wherein the surface of the used tantalum coil is cut under conditions including a cutting depth of 0.4 to 0.8 mm, a feed of 0.05 to 0.2 mm/rev, and a rotation speed of 20 to 80 rpm.

3. The method for recycling a used tantalum coil of a sputtering apparatus according to claim 2, wherein the new surface of the used tantalum coil provided with the newly formed knurling traces has a roughness, Ra, of 15 m or more.

4. The method for recycling a used tantalum coil of a sputtering apparatus according to claim 3, wherein the new surface of the used tantalum coil provided with the newly formed knurling traces has a variation in thickness of 0.5 mm or less, the variation in thickness being defined as a thickness difference between a maximum thickness and a minimum thickness of the tantalum coil as recycled.

5. A recycled tantalum coil for sputtering produced by the method according to claim 4, characterized in that the recycled tantalum coil has a surface provided with newly formed knurling traces and has a variation in thickness of 0.5 mm or less, and that the surface provided with the newly formed knurling traces has a roughness, Ra, of 15 m or more.

6. The method for recycling a used tantalum coil of a sputtering apparatus according to claim 1, wherein the new surface of the used tantalum coil provided with the newly formed knurling traces has a roughness, Ra, of 15 m or more.

7. The method for recycling a used tantalum coil of a sputtering apparatus according to claim 1, wherein the new surface of the used tantalum coil provided with the newly formed knurling traces has a variation in thickness of 0.5 mm or less, the variation in thickness being defined as a thickness difference between a maximum thickness and a minimum thickness of the tantalum coil as recycled.

8. A recycled tantalum coil for sputtering produced by the method according to claim 1, characterized in that the recycled tantalum coil has a surface provided with newly formed knurling traces and has a variation in thickness of 0.5 mm or less, and that the surface provided with the newly formed knurling traces has a roughness, Ra, of 15 m or more.

9. A method for recycling a used tantalum coil of a sputtering apparatus, consisting of the steps of: cutting a surface of the used tantalum coil to eliminate a re-deposited film formed during sputtering on the surface of the used tantalum coil and until irregularities produced by the re-deposited film or an erosion part and knurling traces are eliminated and a smooth surface having a surface roughness Ra of 1.6 m or less is obtained; and after said cutting step, subjecting the surface to knurling to provide the surface with the surface roughness Ra of 15 m or more; wherein the cutting step and the knurling step have no intervening processing step therebetween.

10. The method according to claim 9, wherein conditions for said cutting step include cutting depth of 0.4 to 0.8 mm, feed of 0.05 to 0.2 mm/rev, and rotating speed of 20 to 80 rpm.

11. The method according to claim 10, wherein a variation in thickness of the tantalum coil, defined as a difference between maximum thickness and minimum thickness of the tantalum coil, after said knurling step is 0.5 mm or less.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 This is a photograph of the appearance of the coil.

DETAILED DESCRIPTION

(2) With a sputtering device in which a tantalum coil is disposed so as to surround a space between a substrate and a sputtering target, the grains that are sputtered from the tantalum target will become deposited and accumulated on the surface of the tantalum coil around the target (formation of re-deposited film), other than on the wafer. Moreover, the coil is exposed to heat and expands during sputtering.

(3) When the thickness of accumulation of the sputtered grains on the coil surface increases, the film will peel due to stress increase, and such film reaches and adheres to the substrate, and causes the generation of particles or arcing. In order to prevent the foregoing problem, generally speaking, knurling is performed to the coil so as to roughen the surface and increase the peeling resistance. Knurling is a process of forming irregularities by strongly pressing a knurling tool against the work or cutting the work with a knurling tool. The present invention can recycle the knurled coil. A representative example of the knurled coil is shown in FIG. 1.

(4) As described above, grains that scattered due to sputtering adhere to the spent tantalum coil. Generally speaking, this is referred to as a re-deposited film. Cost reduction can be achieved by recycling the tantalum coils.

(5) Upon performing this recycle, the whole or partial surface of the spent tantalum coil is subject to cutting so as to eliminate the re-deposited film that was formed during sputtering. Cutting in the foregoing case refers to performing cutting until the irregularities of the re-deposited film or the erosion part and knurling traces are eliminated; that is, until a smooth surface is obtained.

(6) As described above, the re-deposited film that adhered to the uneven portion of the tantalum coil that was subject to knurling can be effectively eliminated. The cutting conditions in the foregoing case are as follows; namely, cutting depth of 0.4 to 0.8 mm, feed of 0.05 to 0.2 mm/rev, and rotating speed of 20 to 80 rpm.

(7) Subsequently, knurling is newly performed to the cut portion in order to recycle the tantalum coil for sputtering. In the foregoing case, desirably, variation in the coil thickness (difference between maximum thickness and minimum thickness) of the tantalum coil after the newly performed knurling is 0.5 mm or less. This is because, if the variation in the coil thickness is large, when the coil is reused, there are problems in that the coil may be subject to the thermal effect of sputtering and deform into an irregular shape, and the thickness of the re-deposited film or the erosion part of the coil may also become varied easily.

(8) The cutting amount can be adjusted based on the thickness of re-deposited film or the thickness of the eroded part of the coil. The present invention can provide a tantalum coil for sputtering obtained based on the method for recycling a tantalum coil for sputtering described above. A tantalum coil that is recycled based on the conditions of the present invention can ensure quality that is equivalent to the quality of a new tantalum coil.

EXAMPLES

(9) The Examples are now explained. Note that these Examples are described for facilitating the understanding of the present invention, and are not intended to limit the present invention in any way. In other words, other examples and modifications within the scope of the technical concept of the present invention are covered by the present invention.

Example 1

(10) With regard to a Ta coil in which the whole area of the coil was subject to erosion, the inner surface, the upper and lower edge parts, and the outer surface were cut based on the following cutting conditions; namely, cutting depth of 0.6 mm, feed of 0.1 mm/rev, and rotating speed of 25 to 63 rpm. In other words, cutting was performed until the erosion parts and knurling traces were eliminated, and a smooth surface was obtained. Subsequently, additional knurling was newly performed to the cut portion.

(11) The surface roughness after knurling was Ra=18.5 m, and variation in the coil thickness (difference between maximum thickness and minimum thickness) was 0.25 mm. It was thereby possible to obtain a like-new coil.

Example 2

(12) With regard to a coil in which a re-deposited film had adhered to a part of the coil and half of the coil was subject to erosion, the inner surface, the upper and lower edge parts, and the outer surface were cut based on the following cutting conditions; namely, cutting depth of 0.8 mm, feed of 0.2 mm/rev, and rotating speed of 20 to 50 rpm. In other words, cutting was performed until the re-deposited film and knurling traces were eliminated, and a smooth surface was obtained. Subsequently, additional knurling was newly performed to the cut portion.

(13) The surface roughness after knurling was Ra=17.6 m, and variation in the coil thickness (difference between maximum thickness and minimum thickness) was 0.31 mm. It was thereby possible to obtain a like-new coil.

Comparative Example 1

(14) With regard to a Ta coil in which the whole area of the coil was subject to erosion, the inner surface, the upper and lower edge parts, and the outer surface were cut based on the following cutting conditions; namely, cutting depth of 1.0 mm, feed of 0.2 mm/rev, and rotating speed of 65 to 80 rpm. In other words, cutting was performed until the re-deposited film and knurling traces were eliminated. The surface roughness was Ra=2.5 m, and a smooth surface was not obtained. Subsequently, additional knurling was newly performed to the cut portion.

(15) While the surface roughness after knurling was Ra=17.8 m, since the control of cutting was insufficient, variation in the coil thickness (difference between maximum thickness and minimum thickness) was 0.51 mm, and it was not possible to obtain a suitable coil.

Comparative Example 2

(16) With regard to a Ta coil in which the whole area of the coil was subject to erosion, the inner surface, the upper and lower edge parts, and the outer surface were cut based on the following cutting conditions; namely, cutting depth of 0.6 mm, feed of 0.3 mm/rev, and rotating speed of 25 to 60 rpm. In other words, cutting was performed until the re-deposited film and knurling traces were eliminated. The surface roughness was Ra=2.1 m, and a smooth surface was not obtained. Subsequently, additional knurling was newly performed to the cut portion.

(17) While the surface roughness after knurling was Ra=18.3 m, since the control of cutting was insufficient, variation in the coil thickness (difference between maximum thickness and minimum thickness) was 6.3 mm, and it was not possible to obtain a suitable coil.

(18) While sputtered grains are accumulated (re-deposited) on the surface of the tantalum coil disposed between the substrate and the sputtering target during sputtering, the spent coil is subject to cutting after the sputtering is complete to trim off the sputtered grains accumulated thereon so that the tantalum coil can be efficiently recycled. The present invention yields a superior effect of achieving lean manufacturing of new coils, improving productivity, and stably providing such coils.

(19) Since the present invention can recycle coils with ease and high accuracy, the present invention can provide technology capable of improving the quality and productivity of electronic components, and stably providing semiconductor elements and devices. Also with this recycled coil, as with a new coil, the present invention can prevent the generation of particles, which is caused by flaking of the sputtered grains accumulated on the surface of the coil and the adhesion of the scattered flakes to the substrate surface, and can prevent the generation of arcing; and thereby effectively inhibit the flaking of the sputtered grains accumulated on the surface of the coil. Thus, the present invention is useful in a sputtering device that uses tantalum coils.