Hot carrier aging and its variation under use-bias: Kinetics, prediction, impact on Vdd and SRAM

Abstract

As CMOS scales down, hot carrier aging (HCA) scales up and can be a limiting aging process again. This has motivated re-visiting HCA, but recent works have focused on accelerated HCA by raising stress biases and there is little information on HCA under use-biases. Early works proposed that HCA mechanism under high and low biases are different, questioning if the high-bias data can be used for predicting HCA under use-bias. A key advance of this work is proposing a new methodology for evaluating the HCA-induced variation under use-bias. For the first time, the capability of predicting HCA under use-bias is experimentally verified. The importance of separating RTN from HCA is demonstrated. We point out the HCA measured by the commercial SourceMeasure-Unit (SMU) gives erroneous power exponent. The proposed methodology minimizes the number of tests and the model requires only 3 fitting parameters, making it readily implementable.

Insight Into Electron Traps and Their Energy Distribution Under Positive Bias Temperature Stress and Hot Carrier Aging

“…C-V measurement gives a 1.2 nm equivalent oxide thickness (EOT). For nanometer MOSFETs, it has been reported that HCA is higher under Vg=Vd, rather than the conventional worst condition of Vg=Vd/2 [14][15][16]. Vg=Vd was used for HCA, therefore.…”

“…In addition to PBTI, such as the access transistors in a SRAM cell, also suffer from hot carrier aging (HCA) [14]. As channel length down-scales, HCA scales up and has attracted many attentions recently [14][15][16][17].…”

Interaction between hot carrier aging and PBTI degradation in nMOSFETs: Characterization, modelling and lifetime prediction

“…Characterization and modelling Interacted HCA-PBTI Degradation (IHPD) have become a crucially challenging task in industry [7]. Previous research [8][9][10][11] predicted device lifetime at operation Vdd of HCA (Fig.1) or PBTI ( Fig.2) separately, based on the accelerated-voltage method (HCA under Vg=Vd and PBTI under Vg are used in this paper), where unique power-law time and voltage exponents can be observed, respectively. However, this is not the case if PBTI stress is followed by HCA, or HCA stress is followed by PBTI (Fig.3a&4a), where the degradation does not follow a unique power law.…”

“…In short channel device (Fig.3), HCA is more severe than PBTI at the same stress voltage [9,15], so that the generation of AND and GCET during HCA dominates, and 3 rd HCA ('') can largely follow 1 st HCA ('') after removing the 2 nd PBTI. In contrast, 3 rd PBTI ('') cannot follow 1 st PBTI (''), because the corresponding precursors are consumed by the heavier 2 nd HCA stress.…”

Hot carrier aging of nano-meter devices

“…As the downscaling of operation bias is approaching its limit, HCA becomes more severe than NBTI in some CMOS processes [7,8] and one example is given in Fig. 1, so that HCA remerges as a major challenge for modern CMOS technologies.…”