Bias dependent response reversal in chemically sensitive metal oxide semiconductor capacitors

Abstract

NO 2 sensitive Au gate metal-oxide-semiconductor capacitorsEffects of anneals in ammonia on the interface trap density near the band edges in 4H-silicon carbide metaloxide-semiconductor capacitors Current oscillations in thin metal-oxide-semiconductor structures observed by ballistic electron emission microscopy J.Conditions for reversal of the voltage shift in chemically sensitive metal oxide semiconductor capacitors are surveyed with the pulsed illumination technique in Si/ SiO 2 / Me 0 capacitors, with annular Pd and Au gates under controlled H 2 in N 2 and NO 2 in synthetic air stimuli, respectively. The polarity of the response is bias dependent. Above the threshold voltage, negative voltage shifts ensue from positive charges accumulated on the gate-dielectric interface for donor stimuli such as H 2 , whereas positive shifts indicate negative charge accumulation for acceptors such as NO 2 . Below the threshold voltage, the necessary charge compensation can be satisfied by proportional changes in the semiconductor-gate interface state population, which induce chemical shifts of opposite polarity.

MOS device chemical response reversal with temperature

“…Since direct access to the dielectric surface may enhance [3] response to non-hydrogenated species, discontinuous gates were investigated [4] with limited success, consistently with prior reports on porous gate applications [5][6][7], due to poor stability at the required operating temperature [8,9]. Thick film gold gates intended to remove this deficiency revealed sign reversals of response [10], which could be subsequently attributed to polarization dependence [11]. Device polarization is in turn strongly influenced by operating temperature, which motivates this investigation by pulsed illumination techniques.…”

“…Photocurrent signals (u) diminished by chemical stimulation imply positive bias displacements ( V), whereas increased u corresponds to negative V. With due accounting for the MOS operating regime, a single value for the sign and magnitude of the chemically induced charges may be obtained, regardless of applied bias, within experimental uncertainty (2%) [11].…”

“…( 7) may be evaluated independently. Chemical response, measured by the voltage shifts of u, is bias dependent [11]. Above the threshold voltage (V T ), H 2 in N 2 stimuli on Pd gates induce negative responses ( V), whereas positive shifts are characteristic of NO 2 in air on Au gates.…”

“…Above V T , negative voltage shifts ensue from positive charges (H + ) accumulated on the gate-dielectric interface for donor stimuli such as H 2 , whereas positive shifts indicate negative charge accumulation for acceptors such as NO 2 . Below V T , under depletion conditions, the necessary charge compensation can be satisfied by proportional changes in the semiconductor-gate interface state population, which induce opposite chemical shifts [11]. Consequently, the bias dependence of the photocurrent u, is not merely displaced along the voltage abscissa by chemical stimulation, but altered instead, to intersect at the threshold voltage (V T ).…”

“…Consequently, the bias dependence of the photocurrent u, is not merely displaced along the voltage abscissa by chemical stimulation, but altered instead, to intersect at the threshold voltage (V T ). Total device capacitance, in terms of the fixed dielectric (C 0 ) in series with the parallel circuit of bias dependent semiconductor (C D ) and interface state capacitances (C SS ), modeled across the gate window by a distributed capacitive-resistive network, in accordance with the lateral current model [11,13,16], is…”