Bottom Coverage of Cu Deposit for 200-nm-Class Circular Vias with High Aspect Ratios Investigated by Magnetron Sputtering Activated Using Superconducting Bulk Magnet

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We have investigated the bottom coverage effect of circular vias with different aspect ratios patterned on Si substrates by depositing Cu using a magnetron sputtering apparatus equipped with a superconducting bulk magnet. The superconducting SmBa2Cu3O7-δ bulk of 60 mm diameter was magnetized up to 4.5 T at 52 K and cooled to 40 K in a refrigerator. It served as a permanent magnet producing magnetic fields about 10 times as strong as that obtained from a conventional Nd–Fe–B permanent magnet, resulting in a marked enhancement in plasma density on the Cu target. Indeed, the present magnetron sputtering apparatus was capable of sputtering under Ar gas pressures of at least $3.33 \times 10^{-3}$ Pa with a throw distance $D_{\text{st}}$ of 300 mm when a Cu target of 150 mm diameter was employed. Practical sputtering was possible under $2.66 \times 10^{-2}$ Pa even when $D_{\text{st}}$ was extended to 500 mm. Under this condition, a uniform Cu film with a bottom coverage of 58% was successfully deposited at the bottom of a circular via of 250 nm diameter and 1.15 μm depth with an aspect ratio of 4.6 within a circle of 120 mm diameter on the substrate.
2004-09-15