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Method for Compact Modeling of Stress Effects

IP.com Disclosure Number: IPCOM000239622D
Publication Date: 2014-Nov-19
Document File: 4 page(s) / 177K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for incorporating the influence of stress on semiconductor mobility in a compact model using an efficient algorithm to generate local mobility at each point in the device. This local mobility is then averaged to find the net effective mobility in the device.

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Method for Compact Modeling of Stress Effects

Over the last decade, the semiconductor industry has greatly used mobility-enhancing stressors to increase device performance. These stressors induce high stress levels

with complex, three-dimensional (3D) geometry. In addition, Local Layout Effects also lead to large unintentional stress variations between nominally identical devices.

Circuit designers require the capability to capture these stress effects through compact models that map the spatially dependent stress profile of a device to an effective mobility that can be utilized in a circuit simulation.

Present art for compact modeling greatly simplifies this picture by first performing a stress averaging throughout the device and then converting the averaged stress to effective mobility by linearized piezoresistance coefficients. In present art, the stress averaging may be done by using analytic models of stress vs. position for each stressor.

The proposed method greatly improves on present art, acting in place of averaging stress over a device, which is highly inaccurate if the stress profile has high spatial variation.

The novel contribution is a method for incorporating the influence of stress on semiconductor mobility in a compact model. The method uses an efficient algorithm to generate local mobility at each point in the device. This local mobility is then averaged to find the net effective mobility in the device. Experimental verification shows that the mobility-averaging technique is superior to stress-averaging technique.

The novel method enables superposition of multiple stressors and layout effects in a device and allows for the calculation of a net effective mobility from all such sources of stress. The method allows for stress fields with high spatial variations. The analytic expression includes Sxx, Syy, and Szz and therefore fully accounts for 3D character of stress field.

The method can be executed by using analytic expressions for the spatial dependence of each stressor, superimposing the stress fields due to each stressor to generate spatially dependent Sxx, Syy, and Szz, and then converting to s...