Characteristics of silicon nitride deposited by very high frequency (162 MHz)-plasma enhanced atomic layer deposition using bis(diethylamino)silane

Silicon nitrides, deposited by capacitively coupled plasma (CCP)-type plasma enhanced atomic layer deposition (PEALD), are generally applied to today's nanoscale semiconductor devices, and are currently being investigated in terms of their potential applications in the context of flexible displays, etc. During the PEALD process, 13.56 MHz rf power is generally employed for the generation of reactive gas plasma. In this study, the effects of a higher plasma generation frequency of 162 MHz on both plasma and silicon nitride film characteristics are investigated for the purpose of silicon nitride PEALD, using bis(diethylamino)silane (BDEAS) as the silicon precursor, and N₂ plasma as the reactant gas. The PEALD silicon nitride film deposited using the 162 MHz CCP exhibited improved film characteristics, such as reduced surface roughness, a lower carbon percentage, a higher N/Si ratio, a lower wet etch rate in a diluted HF solution, lower leakage current, and higher electric breakdown field, and more uniform step coverage of the silicon nitride film deposited in a high aspect ratio trench, as compared to silicon nitride PEALD using 13.56 MHz CCP. These improved PEALD silicon nitride film characteristics are believed to be related to the higher ion density, higher reactive gas dissociation, and lower ion bombardment energy to the substrate observed in N₂ plasma with a 162 MHz CCP.

Surface degradation mechanism during the fluorine-based plasma etching of a low-k material for nanoscale semiconductors

The degradation of a low-k material surface during the exposure to plasma etching is one of the most serious problems to be solved for the realization of high speed semiconductor devices. In this study, the factors causing the degradation of a low-k material surface during the etching using fluorine-based plasma etching have been investigated by using XPS. As the plasma factors, active radicals, bombardment energy, and charge of the ions were considered and, as the low-k material, methyl silsesquioxane (MSQ) has been used. The XPS results showed that the ion bombardment during the plasma etching of MSQ affects the breaking of MSQ bone structure by changing the Si-O bonds and Si-C bonds to Si-F mostly, while fluorine-based radicals in the plasma mostly affect the change of Si-CH3 bonds to Si-CH(x)F(y). By removing the charge of the ions during the bombardment, the MSQ properties were further improved. When F intensity which is related to the damage of the MSQ surface is estimated, the bombardment energy, reactive radical density, and charge of the ions were responsible for -18%, -53%, -19% of the F intensity in the MSQ. Therefore, by using the neutral beam etching instead of a conventional ICP etching, the degradation on the MSQ surface estimated by the F intensity remaining on the MSQ surface could be decreased to 10%.

Study of the electronic structure of the interfaces between 2-TNATA and MoOx

In order to understand the characteristics of ohmic hole-contacts for the inverted/conventional organic light emitting devices, a hole-only device with all ohmic contacts, which is composed of glass/ITO/MoOx/4,4,4-tris[2-naphthyl-phenyl-amino]triphenylamine (2-TNATA)/MoOx/Al, the elements of the electronic structures of MoOx-on-2-TNATA interface and 2-TNATA-on-MoOx interface were investigated by photoemission spectroscopy, with regards to interface energetics, formative mechanism, and a potential charge carrier injection. The electronic structures revealed that the behavior of the interface between MoOx and 2-TNATA was different whether MoOx was deposited on (2-TNATA) or vice versa. The bottom interfaces of 2-TNATA-on-MoOx in this hole-only devices showed no hole-injecting barrier height (Phi(h)B) when the thickness of 2-TNATA was deposited in the range of 0.1 to 5.0 nm on the 10.0 nm-thick MoOx thin films. This has been explained to be attributed to both metal-induced gap states and a chemical reaction at the interfaces. The top interfaces of MoOx-on-2-TNATA in this hole-only device structure also showed no Phi(h)B when a hole was injected from the MoOx-on-2-TNATA interfaces to cathode. The hole-ohmic property in the top interfaces depends on interface dipole by the formation of charge transfer complexes as well as interdiffusion of MoOx into the 2-TNATA film in these interfaces.

Low damage atomic layer etching of ZrO2 by using BCl3 gas and ar neutral beam

This study examined the etch characteristics of ZrO2 etched using an atomic layer etching (ALET) system with BCl3 gas for adsorption and an Ar neutral beam for desorption. The effect of the BCl3 gas pressure and Ar neutral beam dose on the etch characteristics was examined. The results showed that the ZrO2 etch rate was maintained at a constant etch rate of 1.07 angstroms/cycle at a BCl3 gas pressure > 0.15 mTorr and an Ar beam flux > 1.485 x 1016 atoms/cm2 x cycle. Under these constant etch rate conditions, the surface roughness of the etched ZrO2 was similar to that of the as-received ZrO2. The surface composition of ZrO2 etched by ALET was compared with that etched by BCl3 inductively coupled plasma (ICP). The surface composition of ZrO2 etched by ALET showed a similar composition to that of the as-received ZrO2 while that etched by BCl3 ICP showed a Zr-rich surface.

Refractive sapphire microlenses fabricated by chlorine-based inductively coupled plasma etching

We have fabricated refractive sapphire microlenses and characterized their properties for what we believe to be the first time. We use thermally reflown photoresist lenslet patterns as a mask for chlorine-based dry etch of sapphire. Pattern transfer to the mechanically hard and chemically inert sapphire substrate is made possible by an inductively coupled plasma etch system that supplies a high-density plasma gas. Processed sapphire microlenses exhibit properties close to the ideal and operate nearly in the diffraction limit.