Stresses in a Buried-SiGe Strained-Silicon MOSFET. Part 1.

anstex02.in : Stresses in a Buried-SiGe Strained-Silicon MOSFET. Part 1.

Requires: SSuprem 4 Minimum Versions: Athena 5.21.2.R

This example demonstrates the simulation of stresses in a test MOSFET structure with embedded anSiGe layer. The simulated process includes epitaxial growth of thin compressed SiGe and relaxed silicon layers. The standard gate stack is then emulated by gate oxide and poly deposition and oxide spacer formation. All important geometrical characterisics of the test structure, including thicknesses of different layers, spacer width, gate length, etc., are parametrized. This allows us to investigate the effects of parameter variations on important device characteristics using either DBInternal capability of Deckbuild or Virtual Wafer Fab (VWF). The set values of all parameters approximately correspond to those used to simulate Figs. 2. and 3 in [1] .

The most important step of this test process is etching of the source/drain areas because it creates free surfaces on the sides of the buried SiGe layer. This step results in elastic expansion of the buried layer, reducing the compressive stress inside the layer and generating tensile stress in silicon above, i.e. under the gate. This enhanced tensile stress affects carrier transport and effectively improves device characteristics. The stresses in the whole structure are calculated before and after the S/D etch.

The results of the calculation are plotted using TonyPlot to display 2D contours of the XX component of stress in the final structure. The second plot compares stress profiles (obtained by Extract ... curve statements and measured in MPa) through the center of the gate before and after the S/D etch step.

The series of Extract statements calculate the average stresses under the gate. The first 2 extract statements estimate average stress at specified depth under the gate. Next 2 extract statements estimate average stress inside a box under the gate.

The last extract statement calculates the important figure of merit of this process, i.e. the stress transfer efficiency (STE) specified as absolute value of the ratio between the average stresses under the gate and initial stress in the SiGe buried layer.

[1] J.G. Fiorenza, et.al. "Detailed Simulation Study of a Reverse Embedded-SiGe Strained-Silicon MOSFET", IEEE Trans. on Electron Devices, v.55, No.2, p. 640, (2008).

To load and run this example, select the Load example button. This action will copy all associated files to your current working directory. Select the DeckBuild run button to execute the example.