Effect Of Spreading Resistance Research Articles

STLM: A Sidewall TLM Structure for Accurate Extraction of Ultralow Specific Contact Resistivity

We propose a very large scale integration compatible, modified transfer length method (TLM) structure, called sidewall TLM, to minimize the effect of spreading resistance and thus improving the resolution of the TLM method. This is achieved by allowing uniform current collection perpendicularly through the sidewall of the contact. We demonstrate statistically significant specific contact resistivity (ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) extraction of 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> Ω cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> Ω cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for n-type and p-type NiSi contacts, respectively, on a 300-mm wafer, which are about 50% less than those extracted using the conventional TLM structure. The proposed structure also shows a tighter distribution in the extracted ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> values. The results show the importance of such test structures to accurately extract ultralow ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> values relevant to sub-14-nm technology nodes.

Ideal FET doping profile

Using variational calculus it is possible to show, for each MOSFET voltage and device topology, that there exists an ideal drain region doping profile which yields the optimum resistance versus breakdown voltage tradeoff. Because of the inclusion, in the resistance, of the effects of spreading resistance this profile tends to have a higher doping concentration (lower resistivity) at the blocking junction, this point being at or near the point of maximum spreading resistance, a minimum in doping partway into the drain and then asymptotically approach a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(1 - X/W)^{-1/2}</tex> form as derived by Hu [1] at the edge of the depletion layer. The theory and calculations in this paper compare the Hu profile, a constant profile and our optimum profile for various practical geometries over a range of breakdown voltages. It is shown that the higher the device voltage and the less important the spreading resistance effects, the closer the ideal profile approaches that of Hu. The ideal profile concept applies equally well to other FET or majority carrier (resistive) devices.

The germanium microwave crystal rectifier

The characteristics of the commercial germanium microwave mixer crystal are reviewed. The conventional theory for these devices is discussed and criticized on the grounds that minority carrier storage phenomena are completely ignored. A model which includes this effect is proposed, and conversion loss calculations which include the effect of spreading resistance are presented for a highly idealized version of this model. Some possible explanations for the dc characteristics and for the success of the conventional fabrication techniques are offered.