Effects of Dielectric Roughness on Texture of Both PVD Seed Layers and EP Copper

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The ability to control the crystallographic orientation of both the seed layer and the electroplated copper grains is important in obtaining highly reliable Cu interconnects for ultra-large scale integration (ULSI) circuitry. One of the factors controlling film texture is the roughness of the deposition surface. In this paper the effects of dielectric roughness on the crystallographic texture of physical vapor deposited (PVD) copper seed layers and, subsequently, on the texture of electroplated (EP) copper have been investigated. Six relevant interlevel dielectric materials were examined: tetraethyloorthosilicate (TEOS), borophosphosilicate glass (BPSG), silane oxide, silicon nitride, SiLKTM (from the Dow Chemical Corporation), and polysilicon were deposited on 200 mm (001) Si wafers. The RMS surface roughness of these dielectric layers, measured by AFM, ranged from 0.32 nm to 20.51 nm. Texture was analyzed on a dedicated x-ray diffractometer equipped with a two dimensional detector collecting incomplete pole figures with a 1.0 degree resolution in pole figure space. The orientation distribution functions (ODF) were calculated using the arbitrary defined cells method and the volume fractions of major fiber texture components were derived from the ODF. The predominant texture components of the PVD and EP copper were (111) and (511) fiber. It was found that the volume fraction of (111) fiber decreased as the dielectric surface roughness increased. One exception was with the SiLKTM dielectric, which produced significantly weaker texture than other dielectrics with similar surface roughness. The copper films deposited on polysilicon, which possessed the roughest deposition surface of all the dielectric films had a random texture. Finally, a mixture of strong (111) and (511) fiber textures of EP copper was achieved on dielectric underlayers with smoother surfaces. The results demonstrate that the deposition surface roughness plays an important role in establishing the texture in overlying PVD and EP Cu films. The texture of PVD and EP copper may serve as a useful indicator of the underlayer roughness.

Info:

Periodical:

Solid State Phenomena (Volume 105)

Edited by:

C. Esling, M. Humbert, R.A. Schwarzer and F. Wagner

Pages:

391-396

DOI:

10.4028/www.scientific.net/SSP.105.391

Citation:

K. J. Kozaczek et al., "Effects of Dielectric Roughness on Texture of Both PVD Seed Layers and EP Copper ", Solid State Phenomena, Vol. 105, pp. 391-396, 2005

Online since:

July 2005

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$38.00

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[5] [10] [15] [20] [25] 0 10 20 30 40 50 60 70 80 90 Polar angle psi (degrees) (111) Cu pole density EP Cu 1000A PVD Cu 500A PVD Cu TEOS.

[5] [10] [15] [20] [25] 0 10 20 30 40 50 60 70 80 90 Polar angle psi (degrees) (111) Cu pole density EP copper 1000A PVD Cu 500 A PVD Cu SiLK TM.

[5] [10] [15] [20] [25] 0 10 20 30 40 50 60 70 80 90 Polar angle psi (degrees) (111) Cu pole density EP Cu 1000A PVD Cu 500A PVD Cu Silicon Nitride.

[5] [10] [15] [20] [25] 0 10 20 30 40 50 60 70 80 90 Polar angle psi (degrees) (111) Cu pole density EP Cu 1000A PVD Cu 500A PVD Cu SILANE OXIDE.

[5] [10] [15] [20] [25] 0 10 20 30 40 50 60 70 80 90 Polar angle psi (degrees) (111) Cu pole density EP Cu 1000A PVD Cu 500A PVD Cu PolySilicon.

[5] [10] [15] [20] [25] 0 10 20 30 40 50 60 70 80 90 Polar angle psi (degrees) (111) Cu pole density EP Cu 1000A PVD Cu 500A PVD Cu Figure 4. Line plots of (111) pole density of copper films deposited on six types of dielectric layers 396.

[2] [4] [6] [8] [10] [12] 140. 1 1 10 100 RMS (nm) (511) Cu Volume fraction (%) 500 A seed 1000A seed RT Rec EP Cu Figure 5. Volume fractions of (511) fiber in Cu films as a function of dielectric roughness. Error bars represent one standard deviation from three measurements across each wafer. Volume fractions were calculated with a 5 degree tolerance around the ideal (511). A random film would have approximately 1. 6% of (111) oriented grains. 0. 5 0. 55 0. 6 0. 65 0. 7 0. 75 0. 8 10 100 1000 10000 Film Thickness (nm) FWHM of (111) Cu peak 500 A PVD Cu 11000 A EP Cu 1000 A PVD Cu Figure 6. Full Width Half Maximum (FWHM) of (111) reflection of Cu. Higher values of FWHM correspond to smaller grain size. The error bars show a standard deviation from measurements on six films of each particular thickness.

DOI: 10.1109/impact.2016.7800027

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