Impact of Halo Implantation on the Lifetime Assessment in Partially Depleted SOI Transistors

Abstract

This paper investigates the impact of the presence of a HALO implanted region on the lifetime analysis, based on a study of drain current switch-off transients. The latter were experimentally determined and compared with two-dimensional numerical simulations for PD SOI nMOSFET devices fabricated in a 0.13 µm CMOS technology. This study investigated for different channel lengths the drain current transient in relation with devices parameters such as the body potential, threshold voltage and the current density in the source/drain junctions.In the HALO devices the hole current density through the junctions between source/drain and body were not very significant, so that the influence of the junction is only due to the capacitive coupling between source/body and drain/body channel. For the channel length range studied (from 10 to 0.2µm), the transient time of HALO devices suffers from a 56% reduction. However, in the no HALO devices, there is beyond the capacitive coupling also a significant increase in the hole current density, causing a transient time reduction of 74%, for the same channel length range.

Improved Model to Determine the Generation Lifetime in Short Channel SOI nMOSFETs

“…Figure 4 compares the τ g obtained by the improved model (Eqs. [7] and [8]) with the experimental and numerical simulation data and shows a good agreement.…”

“…A transient drain current is observed due to the decrease of the floating body potential during the transient, which causes an increase in the threshold voltage. While the body potential relaxes back to zero and the threshold voltage to its steady state value, the drain current gradually reaches the steady state value due to thermally activated carrier generation (7). The method employed here assumes that the dominant generation mechanism is the generation in the space charge region.…”

“…It is observed that for devices with smaller channel length there is a reduction in the variation of the depletion region due to the proportional reduction in the charges controlled by the front gate. The transient drain current (I D (t)) normalized to the steady state current (I D∞ ) is represented by the semi-empirical model [7].…”

“…The carrier generation lifetime (τ g ) can be calculated using Eqs. [5] and [7] resulting in equation [8], whereby the transient time (T 0 ) is defined as the time required for the drain current to reach 90% of the steady state current value.…”

Estudo teórico-experimental do transitório da corrente de dreno e do tempo de vida de geração em tecnologias SOI MOSFETs.

“…Estes fatores fazem com que o valor inicial do transitório da corrente de dreno aumente com a diminuição do comprimento de canal em ambos os dispositivos, com e sem HALO. Nos dispositivos sem a presença do HALO este aumento é acentuado devido a maior densidade de corrente de elétrons nas junções, como pode ser observado na Figura 4-15 83 .…”