Capacitance Modulation in Trench MOSFETs Induced by TID Radiation Charge

This article investigates the modulation of total ionizing dose (TID) radiation charge on the capacitance of trench power MOSFET. A radiation charge modulated capacitance model is proposed to effectively characterize the degradation of input (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {iss}}\text {)}$</tex-math> </inline-formula> and output capacitance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {oss}}\text {)}$</tex-math> </inline-formula> under TID radiation. The mechanism of TID-induced capacitance degradation is revealed. At low drain voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{D}\text {)}$</tex-math> </inline-formula>, the gate–drain capacitance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {gd}}\text {)}$</tex-math> </inline-formula> and drain–source capacitance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {ds}}\text {)}$</tex-math> </inline-formula> increase after irradiation, while the gate–source capacitance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {gs}}\text {)}$</tex-math> </inline-formula> decreases. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {gd}}$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {ds}}$</tex-math> </inline-formula> are almost unchanged at high drain voltage, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{C}}_{\text {gs}}$</tex-math> </inline-formula> remains to decrease. The radiation charge equivalently modulates the doping concentration in the silicon layer, which alters the depletion width and leads to capacitance variation. The proposed model fits well with both experimental and simulation results. Measured gate charge results indicate that gate–drain charge (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {gd}}\text {)}$</tex-math> </inline-formula> increases and gate–source (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {gs}}\text {)}$</tex-math> </inline-formula> decreases after irradiation, providing further support for mechanistic explanations.