A New Method for the Channel-Length Extraction in MOSFETs With Sub-2-nm Gate Oxide

Abstract

A simple method to extract the effective channel length in deep-submicrometer devices with sub-2-nm gate oxide thickness is presented. The method uses the measured gate current from accumulation to strong inversion. It is easy to implement, fast, and accurate.

Method of extracting effective channel length for nano-scale n-MOSFETs

“…This causes the estimated L eff values to increase. Marin's method [10] is straightforward without the need to separate I gb from the measured I g , and has no need for additional parameter extraction; this is in contrast to Langevelde's method. When the substrate is in strong inversion with a large enough positive voltage V g > V T , I g is given by I g = DL Á W Á J gsd + (L g À DL) Á W Á J gb where J gsd is tunneling current density between the gate and source/drain and J gb is tunneling current density between the gate and substrate.…”

“…Various methods of measuring or extracting L eff have been proposed [1][2][3][5][6][7][8][9][10][11][12]. Of these, methods that use the relationship of gate voltage V g to drain current I d [5][6][7][8], gate current I g [9,10], or gate capacitance C g [11] have been most widely adopted.…”

“…Of these, methods that use the relationship of gate voltage V g to drain current I d [5][6][7][8], gate current I g [9,10], or gate capacitance C g [11] have been most widely adopted. All methods that use the I d -V g relationship assume that the effective channel mobility l eff is independent of L g , which is not guaranteed for nano-scale MOSFETs.…”

“…However, it is difficult to separate I gb accurately from the measured I g -V g curves. Marin et al [10] used two straight lines obtained by plotting measured I g at accumulation and strong inversion versus L g , while keeping |V g | constant. The lines intersect at L g = DL if constant |V g | guarantees constant |V ox |, where V ox is gate oxide voltage.…”

“…For nano-scale MOSFETs, the process-dependent variations of MOSFET characteristics with L g are major obstacles for extraction of an accurate L eff [2,3,13,14]. In addition, the methods that exploit the I d -V g and C g -V g relationships are difficult to apply to a MOSFET with ultra-thin gate oxide because of the gate tunneling current [10].…”