C. J. Kircher

The circuit and physical design of the POWER4 microprocessor

The IBM POWER4 processor is a 174-milliontransistor chip that runs at a clock frequency of greater than 1.3 GHz. It contains two microprocessor cores, high-speed buses, and an on-chip memory subsystem. The complexity and size of POWER4, together with its high operating frequency, presented a number of significant challenges for its multisite design team. This paper describes the circuit and physical design of POWER4 and gives results that were achieved. Emphasis is placed on aspects of the design methodology, clock distribution, circuits, power, integration, and timing that enabled the design team to meet the project goals and to complete the design on schedule.

Thermal strain in lead thin films IV: Effects of multiple cycling to 4.2 K

Abstract Using scanning electron microscopy and X-ray diffraction, strain, surface morphology and grain rotation were investigated in lead thin films which were deposited onto oxidized silicon wafers at room temperature and then thermally cycled up to 400 times between room temperature and liquid helium temperature. The strains measured at 4.2 K for films cycled 400 times were observed to have the same dependence on film thickness as that observed the first time the films were cooled to 4.2 K. In the films greater than 0.2 microm thick many discolation slip lines and hillocks were observed inside grains and on grain boundaries respectively after multiple cycling. The densities of the dislocation lines and the hillocks increased with the number of cycles. It was observed that repeated cycling caused rotation of (111)-oriented grains such that the (111) planes of different grains became more nearly coplanar and parallel to the substrate surface. The amount of grain rotation increased with the logarithm of the accumulated amount of plastic strain induced by the thermal cycling.

Lead alloy Josephson junctions with Pb‐Bi counterelectrodes

An experimental investigation has indicated that the e‐phase Pb‐Bi alloy is an attractive alternative to Pb–1.7 wt.% Au for use as a counterelectrode for Josephson tunneling devices containing Pb–12 wt.% In–4 wt.% Au alloy films as base electrodes and control lines. Use of this Pb‐Bi alloy as a counterelectrode results in a significant improvement in junction quality; the normalized subgap single‐particle tunneling current is ∼2× lower at 2 mV. In addition, devices with the Pb‐Bi counterelectrodes exhibit ∼3× fewer failures after repeated thermal cycling between 300 and 4.2 °K. Out ot a total of 72 such devices having large area (6.2×10−6 cm2) junctions, 94% survived 1000 thermal cycles with negligible change.

Hillock growth kinetics in thin Pb-In-Au films

Abstract Hillock growth has been studied in films 100–500 nm thick of Pb-12wt %In-4wt%Au deposited onto oxidized Si substrates at room temperature. Overlying SiO layers were used to suppress hillock formation everywhere except within 4μ × 4μm size openings in the SiO where hillock growth could be observed. Hillock growth was initiated in these openings by heating the samples in a scanning electron microscope. The dependence of hillock growth on time, temperature and sample geometry were investigated. In addition, an X-ray technique was used to determine the elastic strain in the Pb-alloy films. Analysis of the results indicates that the driving force for hillock formation is the compressive stress generated in the film during heat treatment produced by the thermal expansion coefficient difference between the Pb-alloy film and the Si substrate. A one-dimensional stressdriven diffusion model has been developed to analyse the hillock growth behaviour. By fitting the model to the data, values of an effective ...

Thermal stability of Pb‐alloy Josephson junction electrode materials. VIII. Effects of Au addition to Pb‐Bi counterelectrodes

In previous studies, strain‐relaxation‐induced changes in film microstructure, such as grain rotation, hillock formation, and dislocation slip bands, were observed after repeated thermal cycling between 298 and 4.2 K in 0.4‐μm‐thick e‐phase Pb‐Bi films that are used as the counterelectrode material of experimental Pb‐alloy Josephson junction devices. In the present paper, the effects of small additions of Au (1–8 nm thickness) to the Pb‐Bi films on the changes in the film microstructure were studied by using x‐ray diffraction, and scanning and transmission electron microscopy. It was found that the changes in microstructure observed in the Pb‐Bi films were significantly reduced by the Au addition, although the average level of strain relaxation in the Pb‐Bi alloy films upon thermal cycling between 298 and 4.2 K was not influenced by the Au addition. Experimental junctions were made using fine‐grained Pb‐In‐Au films prepared at 77 K as the base electrode material, and Pb‐Bi or Pb‐Bi‐Au films prepared at 27...