Influence of the Structural and Compositional Properties of PECVD Silicon Nitride as a Passivation Layer for AlGaN HEMTs

Meng

ACS Appl. Mater. Interfaces

et al. 2018

Correlations between physical properties linking film quality with wet etch rate (WER), one of the leading figures of merit, in plasma-enhanced atomic layer deposition (PEALD) grown silicon nitride (SiN x ) films remain largely unresearched. Achieving a low WER of a SiN x film is especially significant in its use as an etch stopper for technology beyond 7 nm node semiconductor processing. Herein, we explore the correlation between the hydrogen concentration, hydrogen bonding states, bulk film density, residual impurity concentration, and the WERs of PEALD SiN x using Fourier transform infrared spectrometry, X-ray reflectivity, and spectroscopic ellipsometry, etc. PEALD SiN x films for this study were deposited using hexachlorodisilane and hollow cathode plasma source under a range of process temperatures (270–360 °C) and plasma gas compositions (N2/NH3 or Ar/NH3) to understand the influence of hydrogen concentration, hydrogen bonding states, bulk film density, and residual impurity concentration on the WER. Varying hydrogen concentration and differences in the hydrogen bonding states resulted in different bulk film densities and, accordingly, a variation in WER. We observe a linear relationship between hydrogen bonding concentration and WER as well as a reciprocal relationship between bulk film density and WER. Analogous to the PECVD SiN x processes, a reduction in hydrogen bonding concentration arises from either (1) thermal activation or (2) plasma excited species. However, unlike the case with silane (SiH4)-based PECVD SiN x , PEALD SiN x WERs are affected by residual impurities of Si precursors (i.e., chlorine impurity). Thus, possible wet etching mechanisms in HF in which the WER is affected by hydrogen bonding states or residual impurities are proposed. The shifts of amine basicity in SiN x due to different hydrogen bonding states and the changes in Si electrophilicity due to Cl impurity content are suggested as the main mechanisms that influence WER in the PEALD processes.

Section: Introductionmentioning

confidence: 99%

Investigation of the Physical Properties of Plasma Enhanced Atomic Layer Deposited Silicon Nitride as Etch Stopper

Meng

ACS Appl. Mater. Interfaces

et al. 2018

Journal of Physics and Chemistry of Solids

“…PECVD-SiNx b USPD stands for ultrasonic spray pyrolysis deposition. DI off related to different SiOx roughnesses since a larger roughness may lead to larger densities of the gate leakage related interface traps [51,52]. Moreover, oxygen vacancies in the SiOx films may act as the current leakage paths.…”

Section: Resultsmentioning

confidence: 99%

Reactive evaporation of SiOx films for passivation of GaN high-electron-mobility transistors

Zhu

Liang

Zhi‐Jian

et al. 2019

The surface passivation effects of silicon suboxide (SiOx) prepared by the reactive evaporation of silicon monoxide in oxygen atmosphere on the performance of AlGaN/AlN/GaN high-electron-mobility transistors (HEMTs) have been investigated. SiOx films with different oxygen contents (1.10 ≤ x ≤ 1.71) and root-mean-square (RMS) roughnesses (0.55 ≤ RMS ≤ 1.01 nm) were prepared under residual pressures from 1 × 10-6 to 6 × 10-4 Torr. Hall measurements revealed obvious increases in the product of sheet carrier concentration and electron mobility after the passivation. Accordingly, increases in drain current and transconductance were observed for all the SiOx passivated HEMTs. Both the gate and drain leakage currents first decreased and then increased with the increase of oxygen content. The lowest gate leakage current was observed in the devices with SiO1.23 passivation, and it was almost 20 times lower than that of the unpassivated devices. The same devices also exhibited the lowest current collapse and off-state drain current. The variations in leakage currents as a function of the residual pressure were found to correlate with the surface roughness of the passivation layer. Finally, the breakdown voltage of the SiO1.23 passivated HEMTs increased to 151 V, up from 99 V in unpassivated devices.

“…There are numerous dielectric film deposition methods: PECVD, LPCVD, ICP CVD, ALD etc. [14]. Inductively coupled plasma chemical vapour deposition (ICP CVD) is an improved modification of conventional plasma enhanced chemical vapor deposition (PECVD).…”

Section: Introductionmentioning

confidence: 99%

Optimization of passivation in AlGaN/GaN heterostructure microwave transistor fabrication by ICP CVD

Sleptsova¹,

Черных²,

Podgorny³

et al. 2020

MoEM

We have studied the effect of silicon nitride (SiN) dielectric passivating film deposition by inductively coupled plasma chemical vapor deposition (ICP CVD) on the parameters of AlGaN/GaN heterostructure high electron mobility transistors (HEMT). Study of the parameters of the dielectric layers has allowed us to determine the effect of RF and ICP power and working gas flow ratio on film growth rate and structural perfection, and on the current vs voltage curves of the passivated HEMT. The deposition rate changes but slightly with an increase in RF power but increases with an increase in ICP power. Transistor slope declines considerably with an increase in RF power: it is the greatest at minimum power RF = 1 W. In the beginning of growth even at a low RF power (3 W) the transistor structure becomes completely inoperable. Dielectric deposition for HEMT passivation should be started at minimum RF power. We have developed an AlGaN/GaN microwave HEMT passivation process providing for conformal films and low closed transistor drain–source currents without compromise in open state transistor performance: within 15 and 100 mA, respectively, for a 1.25 and 5 mm common T-gate (Ug = –8 V and Ud-s = 50 V).