A physical model for boron penetration through thin gate oxides from p/sup +/ polysilicon gates

Abstract

A physical model for boron penetration through thin gate oxides from p+ polysilicon gates is presented. Based on numerical device and process simulation, it is shown that enhancement of the boron diffusivity by as much as 300x in the thin gate oxide results in a very shallow exponential p-type profile in the underlying silicon substrate. The effect of fluorine and phosphorus co-implantation into the p-type polysilicon gate is modeled by changes in the boron diffusivity in the gate oxide and segregation at the polysilicon/oxide interface, respectively. An inverse PMOS short-channel behavior in which the threshold voltage becomes more negative with decreasing channel length is modeled by twodimensional boron segregation effects caused by the poly gate oxidation.

Suppression of boron transport out of p+ polycrystalline silicon at polycrystalline silicon dielectric interfaces

“…An effective way to suppress B atom transport out of the p ϩ poly-Si gate electrodes is to interpose a dielectric barrier layer such as Si 3 N 4 , or an oxynitride alloy ͓(SiO 2 ) x (Si 3 N 4 ) 1Ϫx ͔ between the SiO 2 dielectric and the poly-Si gate electrode. [2][3][4] In contrast, the formation of oxynitride layers at the Si-SiO 2 interface leads to decreased reliability, since B can diffuse through the oxide layer and pile up at the Si-SiO 2 interface. 5 The diffusion of B through SiO 2 has been studied experimentally and modeled ͑Ref.…”

Atomic scale study of the degradation mechanism of boron contaminated hafnium oxide

“…4-6 Boron penetration into gate dielectrics has been a problem since the introduction of traditional p-type polysilicon gate. 7 However, the diffusion coefficient of boron in HfO 2 is even higher than that of silicon dioxide. 8 As a result, boron penetration effect is more severe than that of silicon dioxide.…”

Indium penetration through thermally grown silicon oxide

“…When the geometries of MOSFETs become small, the thickness of the gate oxide is also reduced. Boron penetration through the gate oxides affects the threshold voltage of p-type MOSFETs [1]. Therefore, the thermal budget during device fabrication must be modified to compensate the change of dopant profiles due to boron penetration.…”