A test structure for spectrum analysis of hot-carrier-induced photoemission from mosfets

Abstract

Hot-carrier-induced photoemission of subquarter-micron n-MOSFETs is analyzed using a specially designed test structure, which has a wide channel width of 2.0 mm for sufficient photoemission intensity. Since the test structure consists of parallel-connected unit MOSFETs and photoemission images are uniform, it can be estimated that measured spectra are the same as those from unit MOSFETs. The relation between photon counts and photon energy suggests that photon energy has a Boltzman distribution; exp( ). The electron temperature calculated from photon emission spectrum takes minimum value at the channel length of 0.23 m. If is related to the device reliability, it suggests the possibility that the device structure optimized for a certain channel length may not be optimum for other channel length devices.

A Test Structure for Spectrum Analysis of Hot-Carrier-Induced Photoemission from Scaled MOSFETs under DC and AC Operation

“…8 shows a logarithmic plot of photon counts versus photon energy of DC operation at various VD. Linear relations below 2.5 eV are similar to the published data [1], and suggest that photon energy has a Boltzman distribution; exp(-h V/kTe), where T, is the electron temperature. Although the photon counts for the energy range over 2.5 eV tends to be saturated, the photon counts were small and it needs more precise measurements.…”

“…Since the hot carriers emit photons, analyses using a photoemission microscope become useful to study the high electric fields in MOSFETs [1][2][3]. Several models of hot-carrierinduced photoemission are proposed, such as recombination of hot electrons with holes generated by the impact ionization, bremsstrahlung radiation of hot carriers.…”

A test structure to separately analyze CMOSFET reliabilities around center and edge along the channel width

“…The test devices were fabricated by a dual-gate and triple-well CMOS process with shallow trench isolation [15][16][17][18][19]. The n-wells were formed in psubstrate with deep and shallow P + -implantations, while p-wells were formed with B + -implantation.…”

“…CoSi 2 salicidation was performed to reduce resistances of both polysilicon-gates and source/drain regions. The distance between the gate edge and the source/drain electrodes was designed 1.5 µm to avoid distortion of the photoemission intensity due to the reflectance and/or interference effects of the electrodes in case of photoemission measurements [12][13][14][15][16][17][18][19]. The saturation current I S is approximated by I S =WC OX (V G -V T )v s [20], where C OX and v s are the gate capacitance and the saturation velocity, respectively.…”

“…On the other hand, as the photoemission and its intensity closely relate to the electric field near the drain region [11], the hot-carrier-induced 2-D photoemission analyses have been useful to study such 2-D hot-carrier effects along the channel-width direction [12,13] or along the channel-length direction [14][15][16][17][18]. It was reported that the photoemission intensities and the emitted photon energies were dependent on LOCOS-and trench-isolation technology [12,13].…”