Correlating Microscopic and Macroscopic Variation With Surface-Potential Compact Model

Abstract

Variation analysis of n-MOSFETs fabricated by different manufacturers at three technology nodes (180, 100, and 65 nm) demonstrates that surface-potential compact models are capable to bridge the gap between circuit simulation and TCAD by enabling extraction of microscopic MOSFET-parameter variation from measured macroscopic V th and I on variations. Considering only the four microscopic variations of substrate doping, pocket-implantation doping, carrier mobility degradation due to gate-interface roughness, and channel-length change, is found sufficient to reproduce within-wafer V th and I on variations of wide MOSFETs (W g = 10 μm) for all L g and all three technology nodes. Extracted microscopic variation reductions between 180-and 65-nm nodes range from 25% for pocket doping to 70% for carrier mobility degradation. However, V th and I on variations at shortest L g remain approximately constant for all three technologies, in spite of the substantial variation reductions at the microscopic level.

Within-Die/Wafer Variation Analysis of Basic CMOS Circuits based on Surface-Potential-Model HiSIM2

“…From the measurement results of single MOSFETs in 180-nm CMOS technology, the within-wafer variations have been determined (see Table II) and are verified to reproduce the drain saturation current (I on ) and threshold voltage (V th ) variation for all gate-length (L) [3]. In the following sections, these MOSFET-parameter variations are used for the variation analysis of basic CMOS circuits.…”

Analysis of Within-Die Complementary Metal–Oxide–Semiconductor Process Variation with Reconfigurable Ring Oscillator Arrays Using HiSIM

“…This provides improved physical modeling properties for the variation analysis, namely, more physical model parameters, the correct implementation of parameter corrections, one parameter set for all MOSFET dimensions, and consistent current and capacitance modeling. 9) To correlate the macroscopic threshold voltage (V th ) and the drain-saturation current (I on ) variations to the microscopic MOSFET model parameters of HiSIM, it is necessary to determine the parameters which most sensitively affect the MOSFET's V th and I on characteristics. It is found that only four key microscopic model parameters of HiSIM are sufficient for reproducing the variation of V th and I on measurement results in the technology range from 180 to 65 nm.…”

“…It is found that only four key microscopic model parameters of HiSIM are sufficient for reproducing the variation of V th and I on measurement results in the technology range from 180 to 65 nm. 9) The parameter extraction method for a single transistor is described by the following steps: STEP 1: The nominal die is selected from measured V th -I on variation plots as a function of MOSFET dimensions. STEP 2: All nominal model parameters of HiSIM are extracted from the I-V characteristics of MOSFETs on the nominal chip by fitting the simulated data to the measurement data.…”

“…As a result, the HiSIM data can reproduce the variations of the electrical properties by only considering the changes of the most sensitive physical parameters. 9) For the simulation performed here, data extracted from single devices and small circuits, obtained using a different wafer fabricated by the same technology process, are used. [14][15][16] The Monte Carlo simulation with about 1000 runs is performed using the HiSIM and the data for WID parameter variation [14][15][16] shown in Table III.…”

“…Consequently, the conventional BSIM model, which also calculates the MOS drain current based on a threshold voltage parameter, does not provide a sufficient physical correlation. 9) A WID variation analysis method using ring oscillator measurements and a surface potential MOS model, the Hiroshima University STARC (Semiconductor Technology Academic Research Center), IGFET Model (HiSIM) 10,11) is presented here. A two dimensional (2D) WID variation analysis, supported by some experimental data, over the 1:69 Â 1:59 mm 2 area covered by the ring oscillators was performed to determine the nature of WID variation.…”