Layout Dependence Modeling for 45-nm CMOS With Stress-Enhanced Technique

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Layout dependences for stress-enhanced MOSFETs including contact positioning, the second neighboring poly effect, and bent diffusion are modeled in 45-nm CMOS logic technology. It is found that the sensitivity of contact position in the channel direction is larger for PMOS with a higher stress liner than for NMOS. The effect of contact positions is modeled by using the distance of contact to gate <formula formulatype="inline"><tex Notation="TeX">$(x)$</tex> </formula> and the number of contacts <formula formulatype="inline"><tex Notation="TeX">$(N)$</tex></formula>. In terms of the gate-space effect, it is concluded that, in addition to the neighboring gates, second neighboring gates affect the channel stress. The effect of bent-shape diffusion is analyzed for NMOS and PMOS. For NMOS, the channel profile is affected by the bent shape. This can be described by the change of <formula formulatype="inline"><tex Notation="TeX">$V_{\rm th}$ </tex></formula>. For PMOS, the channel stress is modulated by the bent diffusion. The stress effect in bent-shape diffusion for PMOS is modeled with three geometrical parameters. The compact model is applied to the characterization of actual 45-nm cell libraries. It is confirmed that, with the constructed models and design flow, a saturation current <formula formulatype="inline"><tex Notation="TeX">$(I_{\rm dsat})$</tex></formula> change of <formula formulatype="inline"><tex Notation="TeX">$-$</tex></formula>12%–14% is removed from the uncertain margin in 45-nm corner libraries. </para>