Below is Glew Engineering’s 14th article in the series on ICs and semiconductor processing. These articles are written for those that are not technical specialists in the semiconductor field. Below we highlight some of the crucial inventions that lead to the common integrated circuit.
Many of the devices that make up today’s integrated circuits were invented long before the technology was available to mass-produce them. Rectification, photoconductivity, and other basic semiconductor properties were discovered prior to 1900, although they were not fully understood at that time. By the mid 1930s, simple devices based on these properties were available. During this time the physics behind the behavior of metal/semiconductor contacts began to be understood. Much of this understanding was based on the work done by William Shockley and Nevill Mott. World War II put much of the initial semiconductor work on pause, particularly at Bell Telephone Laboratories where an effort was underway to find a solid-state device for switching telephone signals. Shortly after the end of the war work resumed and a major breakthrough was seen in December 1947 when a point contact transistor was demonstrated. The work that followed resulted in the bipolar transistor and resulted in the Nobel Prize in physics for John Bardeen, Walter Brattain, and William Shockley in 1956.
Renewed interest in semiconductors was seen in the 1950s, when it became apparent that the reliability issues associated with the new transistor structures were related to surface effects. In an experiment performed in 1953, Brattain and Bardeen found that the surface properties of semiconductors could be controlled by exposure to oxygen, water, or ozone ambient. Other experiments over the next few years led to the first high-quality SiO2 layers grown on Silicon (Si) substrates.
The first point contact transistors in 1947 were built in polycrystalline germanium. Shortly after that, the device was demonstrated in silicon and in single-crystal material. These developments had significant impacted on integrated circuit of the future. Single crystals provided uniform and reproducible device characteristics, leading to the ability to integrate millions of identical components side by side on a chip. Many of the developments associated with developing single crystal source material belong to Gordon Teal of Bell Labs.
By the mid 1950s, both grown junction and alloy junction bipolar transistors were commercially available. Germanium was still the dominant material used at this time. While these junctions were useful components, the technologies used to build them were not extendible to multitransistor integrated circuits. Exposed junctions were present on the semiconductor surface but no way to interconnect multiple devices was available. Part of the solution was provided by the invention of gas phase diffusion processes at Bell Labs. This led to the commercial availability of diffused mesa bipolar transistors by 1957.
The next major breakthrough came with the invention of the planar process by Jean Hoerni of Fairchild Semiconductor. This process relied on the gas phase diffusion of dopants to produce N- and P-type regions, as well as the ability of SiO2 to mask these diffusions. This major advancement was largely responsible for the switch from germanium to silicon. One final invention was necessary to allow for modern IC technology. That was the ability to integrate multiple components on the same chip and to interconnect them to form a circuit. Jack Kilby of Texas Instruments and Robert Noyce of Faichild Semiconductor invented the integrated circuit in 1959. By combining P- and N-type diffusions and SiO2 passivation layers, many types of devices including transistors, resistors, and capacitors are possible in modern IC structures.
Since 1960, the basic technologies used to manufacture integrated circuits have not changed. There have however been significant improvements to depositing, etching, diffusing, and patterning. While these changes have been evolutionary, they have not necessarily been revolutionary. The rapid evolution over the last 50 years has been enormous and we should expect many more developments in the years to come.
Jim Plummer, one of the co-authors of the text Silicon VLSI Technology: Fundamentals, Practice and Modeling, earned his PhD degree in Electrical Engineering from Stanford University in 1971.