Pushing the Limits

For the past 30 years, transistor performance and density have doubled every 3 years, but now fundamental thermodynamic limits are being reached in critical areas, and unless new, innovative solutions are found, the current rate of improvement cannot be maintained. Exceeding the maximum thermodynamically stable concentration of dopant atoms in silicon leads to diminished performance as dopant atoms cluster; electron tunneling prohibits reductions in gate oxide thickness; and the transistor dimensions have become so small that small changes in the exact number and distribution of dopant atoms can cause appreciable changes in the device behavior. There are currently no known solutions to these problems, providing a serious challenge for the semiconductor industry.