Capacitance-Voltage Characteristics of Buried-Channel MOS Capacitors with a Structure of Subquarter-Micron pMOS

Masayasu MIYAKE  Yukio OKAZAKI  

IEICE TRANSACTIONS on Electronics   Vol.E79-C   No.3   pp.430-436
Publication Date: 1996/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Semiconductor Materials and Devices
C-V characteristics,  buried-channel MOS capacitor,  subquarter-micron pMOS,  doping profile,  thin gate oxide,  

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High-frequency capacitance-voltage (C-V) characteristics of buried-channel MOS capacitors with a structure of subquarter-micron pMOS have been measured and analyzed, emphasizing transient behavior. The C-V characteristics, including transient behavior, of buried-channel MOS capacitors that have a counter-doped p layer at the surface of n substrate are very similar to those of surface-channel MOS capacitors of n substrate if the counter-doped layer is shallow enough to be fully inverted at large positive bias. As gate voltage is decreased, equilibrium capacitance for inversion (accumulation for the counter-doped layer) reaches a minimum value and then slightly increases to saturate, which is peculiar to buried-channel capacitors. The gate voltage for minimum capacitance, which has been used to estimate the threshold voltage, changes dramatically by illumination even in room light. Net doping profiles of n-type dopant can be obtained from pulsed C-V characteristics even for buried-channel capacitors. For MOS capacitors with thinner gate oxide (5 nm), steady-state C-V curve is not an equilibrium one but a deep depletion one at room temperature. This is because holes are drained away by tunneling through the thin gate oxide.