Negative Charge in Plasma Oxidized SiO₂ Layers

Abstract

Silicon dioxide (SiO 2 ) gate dielectric layers (4-60 nm thick) were deposited (0.6 nm/min) on n-type Si by inductively-coupled plasmaenhanced chemical vapor deposition (ICPECVD) in strongly diluted silane plasmas at 150°C . In contrast to the well-accepted positive charge for thermally grown SiO 2 , the net oxide charge was negative and a function of the layer thickness. Our experiments suggested that the negative charge was created due to unavoidable oxidation of the silicon surface by plasma species, and the CVD component adding a positive space charge to the deposited oxide. The net charge was negative under process conditions where plasma oxidation played a major role. Such conditions included low deposition rates and relatively thin grown layers. Additional measurements showed that the negative charge in SiO 2 also persisted on p-type substrates. We suggest that plasma oxidation of the silicon surface results in SiO 2 layers with a surplus of oxygen. This surplus of oxygen is able to accumulate a negative charge. This assumption is addressed in this paper by a review of earlier work on silicon oxidation, and by a first series of experiments wherein oxygen is implanted into thermal SiO 2 . It is shown that the implantation can result in a negative charge to the bulk oxide layer. The effect of the negative charge on the flatband voltage can be described by the implantation profile.

Investigation of Pd/MoOx/n-Si diodes for bipolar transistor and light-emitting device applications

“…Thirdly, a significant amount of negative fixed charge may also be present in the deposited layer. Unlike in thermally grown SiO 2 layers that most often contain positive fixed charge near the Si interface, it has been shown before 33 that negative fixed charge may appear in plasma-oxidized Si surfaces. The surplus of oxygen in such layers was proposed to accumulate the negative charge.…”

Effects of Mask Material on Lateral Undercut of Silicon Dry Etching

“…The proposed explanation can explain the results of the experiment well. PECVD SiN x usually contains a positive charge of approximately 10 12 cm −2 [ 24 ], while PECVD SiO 2 usually contains a negative charge of approximately 10 12 cm −2 [ 25 ]. Some electrons will accumulate on the upper surface of the mask layer during the process [ 15 ].…”

Nanochannel-dependent power generation performance of NiAl-LDH/SiO2-based generators driven by natural water evaporation

“…Herein, the positively-charged NiAl-LDH combines with the amorphous and negatively-charged SiO 2 by a sol-gel method to assemble NiAl-LDH/SiO 2 stacks with different thicknesses, which can be used to construct tunable nanochannels in a certain range. [23][24][25][26] The NWEGs fabricated with different nanochannels from NiAl-LDH/SiO 2 stacks exhibit diverse output electrical performance. This study reveals the correlation between nanochannels and power generation performance in NWEGs.…”