Browse Prior Art Database

Doped Cathode Shield Shutter

IP.com Disclosure Number: IPCOM000050746D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Brosious, PR: AUTHOR [+2]

Abstract

Coating a clam-shell shutter with a desired impurity permits the shutter to act as a cathode shield during system DC plasma preclean and as a parallel plate opposite to the cathode for the RF oxidation tunnel barrier growth, and then the shutter opens down the middle for evaporation of the counterelectrode.

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Doped Cathode Shield Shutter

Coating a clam-shell shutter with a desired impurity permits the shutter to act as a cathode shield during system DC plasma preclean and as a parallel plate opposite to the cathode for the RF oxidation tunnel barrier growth, and then the shutter opens down the middle for evaporation of the counterelectrode.

The tunneling current of a Josephson junction is, in principle, determined by such physical parameters as the energy gap of superconductors, thickness, barrier height and energy gap of the barrier oxide. However, in practice, Josephson junctions are found to be very sensitive to the growth process of the tunnel barrier oxide. Foreign atoms which are originally sputtered off from cathode surfaces (see the figure) have a non-zero probability of being scattered back onto junction windows and are incorporated into the oxide during RF oxidation. Those foreign atoms can create trapping centers, which result in variations in the barrier height, depending on the species and the number of foreign atoms within the oxide. Since the amount of the backscattered species depends on the position of the junction on the cathode, the environment surrounding a junction and the junction area, the backscattered species leads to non-uniform spread in the tunnel current across a chip and a wafer as well as a variation in the current due to junction area. Also, the thermal stability of a junction varies, depending on the diffusivity of the foreign atoms in the oxide. Therefore, it is important to identify an impurity desired and to find a way of doping this impurity uniformly across a wafer. Those species sputtered off a photoresist surface thin film yield a thermally stable junction for the lead alloy based electrodes. Backsc...