Tung-Yang Chen

Investigation of the gate-driven effect and substrate-triggered effect on ESD robustness of CMOS devices

The gate-driven effect and substrate-triggered effect on electrostatic discharge (ESD) robustness of CMOS devices are measured and compared in this paper. The operation principles of gate-grounded design, gate-driven design, and substrate-triggered design on CMOS devices for ESD protection are explained clearly by energy-band diagrams. The relations between ESD robustness and the devices with different triggered methods are also explained by transmission line pulsing (TLP) measured results and energy-band diagrams. The turn-on mechanisms of nMOS devices with triggered methods are further verified using the emission microscope (EMMI) photographs of the nMOS devices under current stress. The experimental results confirm that the substrate-triggered design can effectively and continually improve ESD robustness of CMOS devices better than the gate-driven design. The human body model (HBM) ESD level of nMOS with a W/L of 400 /spl mu/m/0.8 /spl mu/m in a silicided CMOS process can be improved from the original 3.5 kV to over 8 kV by using the substrate-triggered design. The gate-driven design cannot continually improve the ESD level of the device in the same deep-submicron CMOS process.

ESD protection design on analog pin with very low input capacitance for high-frequency or current-mode applications

An electrostatic discharge (ESD) protection design is proposed to solve the ESD protection challenge to the analog pins: for high-frequency or current-mode applications, By including an efficient power-rails clamp circuit in the analog input/output (I/O) pin, the device dimension (W/L) of an ESD clamp device connected to the I/O pad in the analog ESD protection circuit can be reduced to only 50/0.5 (/spl mu/m//spl mu/m) in a 0.35-/spl mu/m silicided CMOS process, but it can sustain the human body model (HBM) and machine model (MM) ESD level of up to 6 kV (400 V). With such a smaller device dimension, the input capacitance of this analog ESD protection circuit can be significantly reduced to only /spl sim/1.0 pF (including the bond-pad capacitance) for high-frequency applications.

Analysis on the dependence of layout parameters on ESD robustness of CMOS devices for manufacturing in deep-submicron CMOS process

The layout dependence on ESD robustness of NMOS and PMOS devices has been experimentally investigated in details. A lot of CMOS devices with different device dimensions, layout spacings, and clearances have been drawn and fabricated to find the optimized layout rules for electrostatic discharge (ESD) protection. The main layout parameters to affect ESD robustness of CMOS devices are the channel width, the channel length, the clearance from contact to poly-gate edge at drain and source regions, the spacing from the drain diffusion to the guard-ring diffusion, and the finger width of each unit finger. Non-uniform turn-on effects have been clearly investigated in the gate-grounded large-dimension NMOS devices by using EMMI (EMission MIcroscope) observation. The optimized layout parameters have been verified to effectively improve ESD robustness of CMOS devices. The relations between ESD robustness and the layout parameters have been explained by both transmission line pulsing (TLP) measured data and the energy band diagrams.

Novel input ESD protection circuit with substrate-triggering technique in a 0.25-/spl mu/m shallow-trench-isolation CMOS technology

A substrate-triggering technique, to increase the ESD robustness and to reduce the trigger voltage of the ESD protection device, is proposed to improve the ESD protection efficiency of the input ESD protection circuit in deep-submicron CMOS technology. Through suitable substrate-triggering design on the device structure, this proposed input ESD protection circuit can successfully protect the thinner gate oxide (50 /spl Aring/) of the input stage in a 0.25 /spl mu/m CMOS technology and sustain an ESD level above 2000 V without extra process modification.

On-chip ESD protection design by using polysilicon diodes in CMOS process

A novel on-chip electrostatic discharge (ESD) protection design by using polysilicon diodes as the ESD clamp devices in CMOS process is proposed in this paper. Different process splits have been experimentally evaluated to find a suitable doping concentration for optimizing the polysilicon diodes for both on-chip ESD protection design and the application requirements of the smart-card ICs. The secondary breakdown current (It2) of the polysilicon diodes under the forward- and reverse-bias conditions has been measured by the transmission-line-puIse (TLP) generator to investigate its ESD robustness. Moreover, by adding an efficient VDD-to-VSS clamp circuit into the IC, the human-body-model (HBM) ESD robustness of the IC with polysilicon diodes as the ESD clamp devices has been successfully improved from the original /spl sim/300 V to become /spl ges/3 kV. This design has been practically applied in a mass-production smart-card IC.

Experimental investigation on the HBM ESD characteristics of CMOS devices in a 0.35-/spl mu/m silicided process

In this paper, the layout dependence on ESD robustness of NMOS and PMOS devices in a 0.35-/spl mu/m silicided CMOS process has been experimentally investigated in details. Six 40-pins testchips including 78 different devices with different device dimensions, layout spacings, and clearances have been drawn and fabricated in a 0.35-/spl mu/m silicided CMOS process to find the optimal layout rules for the ESD protection devices. The gate-driven effect and substrate-triggered effect on the ESD performance of CMOS devices are also measured and compared. The experimental results show that the substrate-triggered effect is much better than the gate-driven effect to improve ESD robustness of the CMOS devices.

ESD protection design on analog pin with very low input capacitance for RF or current-mode applications

An ESD design is proposed to solve the ESD protection challenge to the analog pins for high-frequency or current-mode applications. By including an efficient power-rails clamp circuit into the analog I/O pin, the device dimension (W/L) of ESD clamp devices in the analog ESD protection circuit can be reduced to only 50/0.5 (/spl mu/m//spl mu/m) in a 0.35-/spl mu/m silicided CMOS process, but it can sustain the HBM (MM) ESD level of up to 6 kV (400 V). With such smaller device dimensions, the input capacitance of this analog ESD protection circuit can be significantly reduced to only /spl sim/1.0 pF (including the bond pad capacitance) for high-frequency applications.

Substrate-triggered ESD protection circuit without extra process modification

A substrate-triggered technique is proposed to improve electrostatic discharge (ESD) protection efficiency of ESD protection circuits without extra salicide blocking and ESD-implantation process modifications in a salicided shallow-trench-isolation CMOS process. By using the layout technique, the whole ESD protection circuit can be merged into a compact device structure to enhance the substrate-triggered efficiency. This substrate-triggered design can increase ESD robustness and reduce the trigger voltage of the ESD protection device. This substrate-triggered ESD protection circuit with a field oxide device of channel width of 150 /spl mu/m can sustain a human-body-model ESD level of 3250 V without any extra process modification. Comparing to the traditional ESD protection design of gate-grounded nMOS (ggnMOS) with silicide-blocking process modification in a 0.25-/spl mu/m salicided CMOS process, the proposed substrate-triggered design without extra process modification can improve ESD robustness per unit silicon area from the original 1.2 V//spl mu/m/sup 2/ of ggnMOS to 1.73 V//spl mu/m/sup 2/.

Design of cost-efficient ESD clamp circuits for the power rails of CMOS ASIC's with substrate-triggering technique

Four new device structures for power-rail ESD clamp circuits by using the substrate-triggering technique are investigated in submicron CMOS technology to improve ESD level of the protection device within a smaller silicon area. Experimental results in a 0.6-/spl mu/m CMOS process have verified that the ESD clamp circuit with the double-BJT structure can provide 200% higher ESD robustness in per unit layout area as comparing to the previous design with the NMOS device.

ESD buses for whole-chip ESD protection

A novel whole-chip ESD (electrostatic discharge) protection design with multiple ESD buses has been proposed to solve the ESD protection issue in the CMOS IC which has more separated power pins. The ESD current in the CMOS IC is diverted into the ESD buses, therefore the ESD current is conducted by the ESD buses away from the internal circuits and quickly discharged through the ESD protection devices. By using the ESD buses, the CMOS IC with separated power pins can be safely protected against the ESD damage which is located in the internal circuits.