Search

This paper describes the design, fabrication and test results of a high-performance IGFET circuit made by combining electron-beam technology for all masking steps and ion implantation for the diffusion steps. The circuit consists of an eleven stage ring oscillator with two FET devices per stage. The enhancement mode device is the switching element and the depletion mode is used as load. The aluminum gate length of the devices is 1 μ and the width is 5 μ. The aluminum metallization, defined with electron-beam exposure of PMMA resist, also serves as a self-aligning mask for the ion implantation of source and drain in the gate region. The average delay per stage was determined by measuring the periodicity of the circuit oscillation and dividing by 22. Test results on several circuits indicate that the average delay per stage is approximately 295 psec.

For high-speed performance as well as high packing density, it is desirable to make the components in integrated circuits as small as possible. One of the fundamental problems in making smaller components is that of limitations in the optical technology. This paper describes an experimental process and the results obtained by using an electron-optical system to fabricate small transistors. Planar bipolar transistors with emitter and base contact windows one micron wide have been fabricated, with the electron beam exposure system used to open all the diffusion windows as well as to expose the metallization patterns. Conventional etching techniques are unable to provide 1-µm wide metal paths in half-to one-micron thick metal layers; therefore the lift-off process is used. The dc and ac characteristics presented compare favorably, for the first time using this fabrication process, with the best bipolar transistors produced by optical masking processes. These characteristics provide a guide for refinement in future micron transistor design.

Self-regulating ceramic heating systems that operate without conventional thermostatic controls are now being designed into heated appliances. The result is longer life, lower cost, and more streamlined appliance packaging. The development appropriately comes at a time when end of life safety is receiving increased attention, cost reductions in heater-thermostat systems are producing diminishing returns, and the volume of heated portable appliances for personal care and food warming is growing rapidly. The Semiconducting barium titanate heaters undergo a crystalline phase change and resultant resistivity increase in the vicinity of the ferro-electric curie temperature. This characteristic provides high initial power at which point the sharply increasing heater resistance reduces power to the required steady-state level. Positive temperature coefficient (PTC) barium titanate has been used since the 1950's for low voltage sensors, but was only made available for appliance heaters by the recent development of line voltage materials for a different segment of industry?color television. One third of all color sets now use 120-V PTC degaussing elements. The paper discusses the complex thermal design considerations involved in the development of a PTC heater for 10-200 W appliances and reviews the application of a PTC heater to a food warmer.

The temperature dependence of the effective diffusion coefficient D of Zn in GaAs has been measured at fixed temperatures between 600° and 1000°C. The isoconcentration diffusion technique was used throughout this investigation. It was found that D is essentially temperature independent over the entire range. The relationship is revealed only when the total zinc concentration is held constant since D is strongly concentration dependent. At a fixed Zn concentration of 2×1019 cm−3 the measured value was 9.0×10−10 cm2sec−1 with a standard deviation of 1.15. This experimental result is interpreted in terms of the interstitial‐substitutional diffusion model.

The possibility that the mass spectrum and pharmacological activity of a compound may be directly related has been explored with the help of various computer-based pattern-recognition techniques. The relationship appears to hold at least for tranquilizers and sedatives, and compounds with one or the other of these two pharmacological activities can thus be classified from their mass spectra with a high degree of accuracy.

The diffusion profiles of under a concentration gradient have been determined as a function of diffusion time for diffusions at 600° and 750°C. Pure radioactive Zn65 is used as the diffusion source. It is found that local equilibrium is not reached for these diffusions since the diffusion profiles can not be expressed in terms of a single variable . When the diffusion depth is plotted against the square root of diffusion time, a linear relationship is not obtained. The deviation from linear relationship is found to be quite pronounced at lower diffusion temperatures, and less so at higher diffusion temperatures. These observations indicated that the diffusion process can not be described by Fick's second law (with a concentration‐dependent effective diffusion coefficient, . Under this condition, the Boltzmann‐Matano analysis which has been used quite extensively to obtain values of the effective diffusion coefficient of from the diffusion profiles of is not valid. Results are discussed in terms of nonequilibrium in the interstitial‐substitutional diffusion. Complications due to the presence of diffusion‐induced defects are also described.