Most early microprocessors were manufactured in PMOS technology: 40 from Intel IMP-16, PACE and SC/MP from National Semiconductor TMS1000 from Texas Instruments PPS-4 and PPS-8 from Rockwell International. A number of companies followed Intel's lead. Intel introduced its first PMOS microprocessor, the Intel 4004, in 1971. The 1103 was a commercial success an quickly began replacing magnetic core memory in computers. : 13-bit dynamic random-access memory Intel 1103 followed in 1970. Intel introduced its first PMOS static random-access memory with a capacity of 256 bit, the Intel 1101, in 1969. They were shortly afterwards joined by other Fairchild engineers, including Federico Faggin and Les Vadasz. : 1302 Two of them, Gordon Moore and Robert Noyce, decided in 1968 to found their own startup instead – Intel. : 89įor various reasons Fairchild Semiconductor did not proceed with the development of PMOS integrated circuits as intensively as the involved managers wanted. Because of the lower power supply voltage, silicon gate PMOS logic is often referred to as low-voltage PMOS in contrast to the older, metal-gate PMOS as high-voltage PMOS. 16 V : 1-13 ), reducing the power consumption. The polysilicon gate material not only made the self-aligned gate possible, it also resulted in a reduced threshold voltage and consequently in a lower minimum power supply voltage (e.g. For instance, for PMOS memories this technology delivered three to five times the speed in half the chip area. The self-aligned gate process allowed tighter manufacturing tolerances and thus both smaller MOSFETs and reduced, consistent gate capacitances. Tom Klein and Federico Faggin at Fairchild Semiconductor improved the self-aligned gate process to make it commercially viable, resulting in the release of the analogue multiplexer 3708 as the first silicon-gate integrated circuit. Other companies continued to manufacture PMOS circuits such as large shift registers ( General Instrument) or the analogue multiplexer 3705 ( Fairchild Semiconductor) which were not feasible in bipolar technologies of the day.Ī major improvement came with the introduction of polysilicon self-aligned gate technology in 1968. The attempt by General Microelectronics in 1965 to develop a set of 23 custom integrated circuits for an electronic calculator for Victor Comptometer proved to be too ambitious given the reliability of PMOS circuits at the time and ultimately led to the demise of General Microelectronics. General Microelectronics introduced the first commercial PMOS circuit in 1964, a 20-bit shift register with 120 MOSFETs – at the time an incredible level of integration. The high threshold voltage of early MOSFETs led to a higher minimum power-supply voltage (-24 V to -28 V ).The switching speed was considerably lower, due to large gate capacitances.Since there is no static gate current for a MOSFET, the power consumption of an integrated circuit based on MOSFETs can be lower.ĭisadvantages relative to bipolar integrated circuits were:.A MOSFET requires fewer process steps and is therefore simpler and cheaper to manufacture (one diffusion doping step : 87 compared to four for a bipolar process : 50 ).: 87 The main reason is that the MOSFET is self-insulating and does not require p–n junction isolation from neighboring components on the chip. Given semiconductor device fabrication processes of similar precision, a MOSFET requires only 10% of the area of a bipolar junction transistor.It would be more than a decade before contaminants in the manufacturing process (particularly sodium) could be managed well enough to manufacture practical NMOS devices.Ĭompared to the bipolar junction transistor, the only other device available at the time for use in an integrated circuit, the MOSFET offers a number of advantages: They fabricated both PMOS and NMOS devices but only the PMOS devices were working. Mohamed Atalla and Dawon Kahng manufactured the first working MOSFET at Bell Labs in 1959. See also: Depletion-load NMOS logic § History and background
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