Bernard A Yurash

Bernard A Yurash (February 17, 1921 – January 25, 2007) was a significant contributor to the creation of the first commercially viable CMOS integrated circuits by finding the sources of mobile sodium ions coming from the manufacturing process. Today, virtually all digital electronics use CMOS circuitry. Bernard worked at Fairchild Semiconductor in Silicon Valley from 1958 ( he was employee number 158 ), through the buyouts of the company by Schlumberger and National Semiconductor, and finally retiring in 1990. In the 1960s Fairchild Semiconductor, a division of Fairchild Camera and Instrument Corp., and Texas Instruments, revolutionized electronics by employing the first integrated circuit technology. Fairchild's Robert Noyce ^[1][2] filed for this patent using deposited (printed) metal lines and Jean Hoerni's Planar Process^[3] ( patent also filed by Jack Kilby of Texas Instruments but with using bonding wires ). At the time virtually all the devices were of the bipolar type which were used to construct RTL and DTL type circuits ( Resistor-Transistor-Logic, Diode-Transistor-Logic), which unfortunately drew more power than was desired, and eventually lost ground to Texas Instruments' TTL (Transistor-Transistor-logic). The next great technological leap in computer chips would be CMOS transistors, which promised significantly lower power and greater circuit density than the Bipolar circuitry. Although Frank Wanlass first filed for the CMOS patent in 1963,^[4] Fairchild could not produce the devices for commercial output for many years because of the mystery of the mobile ions degrading their performance. Much research time and money was expended in 1967 and 1968 at Fairchild on trying to manufacture the highly promising technology, the MOS SGT ( Metal Oxide Semiconductor Silicon Gate Technology ) circuits utilizing the field effect from the "gate" on the conducting "channel" from source to drain.

Fairchild Semiconductor^[5][6]

Fairchild Semiconductor and the companies started by former Fairchild employees put the silicon in "Silicon Valley". "They (Bob Noyce and Gordon Moore ) left Fairchild to found Intel in 1968 and were soon joined by Andrew Grove and Leslie L. Vadász, who took with them the revolutionary MOS Silicon Gate Technology (SGT), recently created in the Fairchild R&D Laboratory by Federico Faggin who also designed the Fairchild 3708, the world’s first commercial MOS integrated circuit using SGT. Fairchild MOS Division was slow in understanding the potential of the SGT which promised not only faster, more reliable, and denser circuits, but also new device types that could enlarge the field of solid state electronics — for example, CCDs for image sensors, dynamic RAMs, and non-volatile memory devices such as EPROM and flash memories. Intel took advantage of the SGT for its memory development."

Difficulty in manufacturing MOS transistors

In 1967 and 1968 the MOS SGT transistors had good operating characteristics demonstrated by the C-V (capacitance-voltage) curves when first fabricated and tested, but then became degraded over time or when they were stressed under voltage or temperature, thus rendering them unusable. Gordon Moore,^[7][8] then head of Fairchild's R & D, assigned Andy Grove^[9][10] to the task of finding out why this promising technology was not working.^[11] The number of processing steps and types of solvents and materials used in processing of the semiconductor devices was quite large and any and all of them were suspects in giving off the contaminants, found eventually to be the mobile sodium ions,^[12] that might cause transistor C-V degradation because the concentration of the contaminants only had to be in the parts per billion (ppb) range. In order for Fairchild Semiconductor to effect the investigation of the source of the contaminants at such low concentrations they had to send many chemical and source samples to Union Carbide which had the type of equipment to detect such small amounts (neutron activation or mass Spectrography)^[13] but this was prohibitively expensive and slow to do with the many samples they had, frustrating and delaying the investigation. As the manager of Fairchild R & D's Chemical Analysis Lab, Bernard invented special techniques and modifications to use less expensive equipment (Flame Spectrophotometer ) to perform the necessary analysis of the many samples ( down to 1 ppb or less ) and published this work in the paper titled "A Method for Determining Sodium Content of Semiconductor Processing Materials" in the Journal of the Electrochemical society^[14] in 1968. This work lead to significant changes in the manufacturing process of the devices including a significant increase in the purity of the water used for oxidation and the use of pure quartz tubes and accessories to hold the device wafers instead of pyrex or other less pure glasses.

Earlier life

Bernard worked at the Botany Mills in Passaic N.J. after High School. He joined the Navy late in WWII and became a chief machinist's mate on a floating dry dock. Bernard graduated from Hope college with a degree in Chemistry after the war using G.I. bill funding. After working on a master's degree in Chemistry at the University of Kansas for a year he took a job at the Royal Dutch Shell corporation on the island of Aruba for 5 years and then the Exxon Corporation on the Maracaibo Peninsula, Venezuela for one year where he specialized in water purity analysis at the oil refineries there.

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