11.2 A 1Mb embedded NOR flash memory with 39µW program power for mm-scale high-temperature sensor nodes

Miniature sensor nodes are ideal for monitoring environmental conditions in emerging applications such as oil exploration. One key requirement for sensor nodes is embedded non-volatile memory for compact and retentive data storage in the event that the sensor power source is exhausted. Non-volatile memory also allows for near-zero standby power modes, which are particularly challenging to achieve at high temperatures when using SRAM in standby due to the exponential rise in leakage with temperature, which rapidly degrades battery life (Fig. 11.2.1). However, traditional NOR flash requires mW-level program and erase power, which cannot be sustained by mm-scale batteries with internal resistances >10kΩ To address this issue, we propose an ultra-low power NOR flash design and demonstrate its integration into a complete sensor system that is specifically designed for environmental monitoring under high temperature conditions: such as when injected into geothermal or oil wells.