​Hackers are getting better every day. And backsides of secure chips have become one of their favorite targets. The chip backside lets hackers go around the protections implemented on the front side of the chip to access the circuit. Researchers at Leti drew on their expert knowledge of packaging technologies to provide additional backside protection at the packaging level.

The patented shield leverages several different means of protection. These include a metal serpentine between two polymers; one is opaque to infrared radiation to block focused ion beam (FIB) attacks. In addition, through silicon vias are used to make the electrical connections between the chip frontside and serpentine so that any anomalies can be detected. Finally, deep cavities randomly dispersed across the surface would cause the chip to break in the event of an attempted physical attack. The shield is covered with a 3D-structured metal screen for additional protection against laser attacks.

The prototypes built underwent chemical, ion beam, and infrared laser attacks. And the shield appears to be effective, especially given the difficulty of successfully carrying out these attacks and the extremely sophisticated equipment required to do so. The next step will be to improve the fabrication processes to achieve an optimal ratio between cost and protection.