Device Characteristics and Aggravated Negative Bias Temperature Instability in p-Channel Metal–Oxide–Semiconductor Field-Effect Transistors with Uniaxial Compressive Strain

Abstract

P-channel metal–oxide–semiconductor field-effect transistors (PMOSFETs) featuring poly-SiGe gates and compressive strain channels were investigated. The compressive strain in the channel was deliberately induced in this study by a plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (SiN) capping layer over the gate. Our results indicate for the first time that, while strain channel engineering serves as an effective method to enhance drive current for scaled complementary metal–oxide–semiconductor (CMOS) devices consistent with literature reports, it also simultaneously aggravates the negative bias temperature instability (NBTI) of scaled devices. The aggravated NBTI behavior is ascribed to a higher amount of hydrogen incorporation during SiN deposition as well as a higher strain energy stored in the channel. Saturation phenomena in the shift of threshold voltage and generation of interface states are observed at high stress temperatures and long stress times. Moreover, transconductance degradation in devices with SiN capping is greatly aggravated under high temperature stress.

Impacts of Low-Pressure Chemical Vapor Deposition-SiN Capping Layer and Lateral Distribution of Interface Traps on Hot-Carrier Stress of n-Channel Metal–Oxide–Semiconductor Field-Effect-Transistors

“…It should be noted that such performance improvement is related to device dimensions, a unique feature associated with the uniaxial channel strain. 5,6) To illustrate this point, Fig. 4 shows the percentage increases in the transconductances of the SiN-capped and SiN-removal samples with respect to those of the control samples, as a function of channel length.…”

“…Channel-strain engineering has emerged as one of the most effective remedies for boosting the drive current in the scaled devices. [1][2][3][4][5][6][7] This could be performed by either applying a high biaxial tensile strain to a channel region with a SiGe virtual substrate, 1,2) or by uniaxially straining a channel with strain boosters. [3][4][5][6][7] However, the approach of using a SiGe virtual substrate suffers from a number of drawbacks, such as Ge up-diffusion and a high defect density.…”

“…[1][2][3][4][5][6][7] This could be performed by either applying a high biaxial tensile strain to a channel region with a SiGe virtual substrate, 1,2) or by uniaxially straining a channel with strain boosters. [3][4][5][6][7] However, the approach of using a SiGe virtual substrate suffers from a number of drawbacks, such as Ge up-diffusion and a high defect density. In contrast, the approach of uniaxially straining the channel is essentially free from the aforementioned drawbacks.…”