Abstract: A novel dual-directional silicon controlled rectifier(DDSCR) device with embedded PNP structure(DDSCR-PNP) is proposed for electrostatic discharge(ESD) protection, which has greatly reduced latch-up risk owing to the improved holding voltage(V_h). Firstly, the working mechanism of the DDSCR-PNP is analyzed. The theoretical analysis indicates that the proposed device possesses good voltage clamp ability due to the embedded PNP(PNP_2). Then, experimental devices are fabricated in a 0.35μm bipolar-CMOS-DMOS process and measured with a Barth 4002 transmission line pulse testing system. The results show that the V_h of DDSCR-PNP is much higher than that of the conventional DDSCR, and can be further increased by adjusting the P well width. However, the reduced leakage current(I_L) of the DDSCR-PNP shows obvious fluctuations when the P well width is increased to more than 12μm. Finally, the factors influencing V_h and I_L are investigated by Sentaurus simulations. The results verify that the lateral PNP_2 helps to increase V_h and decrease I_L. When the P well width is further increased, the effect of the lateral PNP_2 is weakened, causing an increased I_L. The proposed DDSCR-PNP provides an effective and attractive ESD protection solution for high-voltage integrated circuits.

Key words: electrostatic discharge, dual-directional silicon controlled rectifier, trigger voltage, holding voltage, leakage current