To address security concerns and supply chain weaknesses, microchip clocks have been reused

To address security concerns and supply chain weaknesses, microchip clocks have been reused ...

Second Bay Studios provides a novel approach for fabricating the "clock" required for all microprocessors from a specialized set of transistors in a standard chip factory.

The ability to fit billions of data processing transistors onto a tiny silicon chip is huge, but a critical device, in essence, a "clock," that operates each transistor must be built separately, posing a security threat and requiring improved integration. A new approach involves commercial chip fabrication techniques and materials to fabricate special transistors that act as the foundation of this timing device, address the weakness and enabling new functionality.

Dana Weinstein, a Purdue University professor of electrical and computer engineering, is working on acoustic resonators for fin field effect transistors (FinFETs), which are used in manufacturing national security devices. New functionality such as acoustic fingerprinting of the packaged chip is also required.

FinFETs are a voltage-activated on/off gate, like all transistors. The fin is not capable of transferring electricity in the open or off state, as the name implies.

But transistors must be synchronized in order to operate all electronic devices. This is due to sound and the resonant frequency that some structures produce, such as a glass bowl may sound a certain note when pinged. This so-called acoustic resonator serves as a cadence that is integrated into a larger microelectromechanical system and used later for use.

Weinstein's goal is to use the existing materials and fabrication techniques available at a standard complementary metal oxide semiconductor chip manufacturing facility. Their most recent proposal is presented in the journal Nature Electronics.

The elegant technique basically transforms data processing transistors into a timing device.

Jackson Anderson, a Purdue graduate student in electrical and computer engineering, is the first author on the Nature Electronics paper. "It doesn't have to undergo further fabrication or be sent elsewhere for integration with a separate microprocessor chip."

With arrays of "drive" transistors, Weinstein's team processes and releases a thin layer of dielectric material between the fin and the gate.

Jackson said, "We're compressing those layers between the gate and the semiconductor, pushing and pulling on that thin region between the gate and the fin," and "we do this alternately on adjacent transistors - one compressing, one stretching - causing vibrations laterally in the device."

The drive transistors are designed to guide and amplify vibrations into forming upon themselves into a specific resonant frequency. This stretching and compresses the semiconductor material in an adjacent group of "sense" transistors, altering the characteristics of a current across those transistors into an electrical signal.

Weinstein said that FinFETs are used in every single high-performance electronic product. "Integrating these functions increases our microelectronics capabilities beyond digital microprocessors."

Jackson Anderson, Yanbo He, Bichoy Bahr, and Dana Weinstein, "Integrated acoustic resonators in commercial fin field-effect transistor technology," Nature Electronics. DOI: 10.1038/s41928-022-00827-6

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