WHOLE NEW NVM TECHNOLOGY
The conventional Complementary-Metal-Oxide-Semiconductor (CMOS) logic process for all the digital Integrated Circuit (IC) fabrication has only one single gate and gate dielectric to form the gates of MOSFET devices. Both P-type and N-type MOSFET devices provide the basic active elements for switching, amplification, and volatile static memory in digital circuit design.
LGNVM (Logic Gate Non-Volatile Memory) Introduction
To incorporate the popular and reliable floating gate NVM devices in the conventional CMOS logic process without adding extra process for the double gate stacks is very desirable in digital IC fabrication for reducing the manufacturing cost and serving the need for non-volatile memory in digital circuitries. Our solution to this challenging subject is the Scalable Logic Gate Non-Volatile Memory (LGNVM) as shown in Fig. 2. The LGNVM device is a semiconductor non-volatile memory fabricated by the conventional CMOS logic process. The floating gate of LGNVM device for non-volatile charge storage is formed by the same gate layer of MOSFET devices in the CMOS logic process.
Instead of depositing extra layers of the control gate and coupling dielectrics on the floating gate to form the conventional floating gate NVM device, the control gate of the NVM device is formed by an opposite impurity semiconductor electrode embedded in the semiconductor substrate.Since the floating gate channel length of the LGNVM device is limited by the minimal gate length of a CMOS logic process node the LGNVM device sizes are scalable according to the process technology.
For examples, Fig. 3 shows the short channel margins of LGNVM devices (threshold voltage roll-off) for 40nm CMOS logic process nodes provided by a foundry, respectively. The LGNVM devices are equivalent to the core N-MOSFET devices with equivalent physical oxide thickness of 217 Å. Fig. 4 shows the 32nm LGNVM NOR array SEM. In principle the LGNVM can be further scaled down to the FinFet technology node (1x nm) as shown in Fig. 5. Without adding extra process in the conventional CMOS logic fabrication process LGNVM device can meet the non-volatile memory requirement in digital circuitries.
Meanwhile the semiconductor Non-Volatile-Memory (NVM) devices for the non-volatile data storage are required for initializing or recovering digital circuitries after power off or interrupted. Among the semiconductor NVM devices, the floating gate Metal-Oxide-Semiconductor-Field-Effect-Transistor (MOSFET) structure Fig. 1 is the most popular and reliable semiconductor NVM device.The double gate stacks (control gate / coupling dielectrics / floating gate/tunneling oxide / semiconductor) are applied for fabricating the floating gate NVM devices.