As I discussed in part one of this series, electrical power and lighting was débuted at the 1893 World’s Columbian Exposition by Westinghouse and Nicola Tesla. Now, a little over 100 years later we carry in our pockets technology so advanced that the Victorian era population would not even recognize it as such - in fact, it may have been considered magic or supernatural.
But what is the next stop beyond the current generation of digital and analog semiconductor devices? I recently had a chance to talk with National Semiconductor’s Chief Technology Officer and Director of NS Labs, Dr. Ahmad Bahai. I asked him what he thought of today’s high performance processes and the never ending progress to smaller geometries. He said, “Analog scaling doesn’t buy you any performance advantage” – primarily due to the way the transistors are used. Analog functions still require isolation and moving things closer only complicates the issue.
Digital processes use transistors as switches avoiding the “in-between” or linear regions of the devices. Analog semiconductors actually take advantage of the linear region to provide amplification and accurate control of voltage and current. In mixed signal semiconductors such as Analog to Digital Converters (ADCs), there is a percentage of digital logic, but it is usually such as a small percentage of the function that shrinking it doesn’t provide great benefit.
I also asked him what he thought about digital process nodes below 22nm. He made an interesting comment, “below 22nm is it (the semiconductor) electrical or mechanical?” This raises an interesting question… at these tiny geometries is it easier to build switches from mechanical functions? With so much research going on with carbon nano-tubes, it may remain in the realm of electrical for the near term. This along with the ability to stack circuits may continue to raise the transistor count to give Moore’s law another 10+ years.
For now the move in analog semiconductors will be to enhanced processes such as Silicon Nitride (SiN), Silicon Carbide (SiC), Gallium Nitride (GaN) and other familiar materials to increase the power handling capability – a property very important to energy management and technologies such as the Smart Grid. Beyond that, you’ll have to wait until part III… till next time…