A simple theory to predict the threshold voltage of short-channel IGFET's

Verify and Extend VLSI Device Models

“…While accurate models for long-channel devices with ion-implanted channel doping have been reported, 7 the two-dimensional CAD short-channel MOSFET models" 8 generally use an average constant doping in the channel region. This simplification is required because it results in an analytical formulation of the problem suitable for CAD simulators such as SPICE.…”

“…The trend toward higher voltage bootstrap modes and requirements of lower diffusion line capacitance, 9 however, have necessitated the design of channel ion implants that result in a depletion region depth comparable to the implant depth in the source-to-substrate bias range of interest ( Figure 4). In these cases, the constant average doping approximation results in a serious error in the calculation of substrate sensitivities since N, eN may be determined by the implant for low V 8 .s (substrate bias) and by the background level for larger V s .…”

“…The cause for this disagreement can be traced to the parasitic conduction effects that may originate at the sidewalls resulting from complete isolation etch scheme." 8 Having poor electrical quality, the sidewall dielectric is characterized by lower threshold voltage than in the parent device. The sidewalls continue to conduct current well below the gate voltage where the parent device has shut off.…”

Investigation of the two-dimensional shape of ion-implanted regions

“…Of even greater importance is the fact that linear scaling is no longer sufficient to ensure proper device operation [7], as secondary effects such as short-channel effects [8], drain-induced barrier lowering [9], punch through [10], substrate reversebias sensitivity [7], subthreshold conduction [11], snap-back [12], and hot carrier effects [13] become the limiting factors in device performance. All of these effects are determined by the details of the electric field distribution determined by the two-dimensional interactions among the doped regions and thus demand control over not only the depth distribution of the implanted ions but their lateral spreading as well.…”

Low power microelectronics: retrospect and prospect

“…Consider a family of MOSFET's in which all parameters are held constant except effective channel length L, which is allowed to take on a wide range of values, e.g., 3.0 /xm > L > 0.03 fim. As L is reduced within this range, eventually so-called short channel effects, are manifest [27]. The source and drain depletion regions begin to capture ion charge in the central region of the channel that is strictly under gate control for longer channels.…”