Tunnel Oxynitride Research Articles

Tunnel silicon oxynitride phase transformation for n-type polysilicon passivating contacts in crystalline silicon solar cells

The study investigates the fabrication and characterization of tunnel oxynitride (TON) layers produced using Plasma-Enhanced Chemical Vapor Deposition (PECVD) at different pressure and power variations. The aim is to explore TON layers as potential substitutes for conventional SiO2 in Tunnel Oxide Passivated Contact (TOPCon) solar cells. Foe this purpose, an effective oxide thickness (EOT) of 1.1–1.2 nm and 1.5–1.6 nm has been achieved by treating the TON samples with NH3 and N2 gas plasma, respectively. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed critical variations in the chemical bonding within TON layers, which exhibit different properties based on the deposition conditions. The presence of nitrogen-nitrogen and nitrogen–hydrogen bonds is prominently influenced by changes in the PECVD parameters, directly affecting the layer’s optical and electronic properties. Notably, the presence of hydroxyl (O–H) and amino (NH2) groups within the TON structure suggests an improvement in surface passivation, essential for optimizing solar cell performance and durability. A lifetime of 737 and 823 μs has been recorded for N2 and NH3 samples, compared to the NAOS 710 μs reference sample. NH3 plasma-treated samples show an improved iVoc of 736 mV, indicating better phase transformation and passivation quality than N2 plasma treatment and the NAOS reference sample.

Performance Enhancement of Silicon Nanowire Memory by Tunnel Oxynitride, Stacked Charge Trap Layer, and Mechanical Strain

Heavily doped silicon nanowires (SiNWs) are adopted to fabricate a memory device composed of an AlON tunnel layer and a HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /HfAlO charge trap bilayer, which exhibits a large memory window of 4.6 V when operated in the program/erase phases, i.e., +12 V for 100 μs and -12 V for 10 ms, along with excellent 70% extrapolated ten-year data retention and good endurance up to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cycles. Strain effects on SiNW memory characteristics have also been investigated. It is demonstrated that the tensile strain increases the program window and the compressive strain improves the data retention. The underlying mechanism is attributed to the incorporation of nitrogen in the AlON tunnel layer.

Improved Retention Characteristic in Polycrystalline Silicon–Oxide–Hafnium Oxide–Oxide–Silicon-Type Nonvolatile Memory with Robust Tunnel Oxynitride

In this paper, we present a simple novel process for forming a robust and reliable oxynitride dielectric with a high nitrogen content. It is highly suitable for n-channel metal–oxide–semiconductor field-effect transistor (nMOSFETs) and polycrystalline silicon–oxide–hafnium oxide–oxide–silicon (SOHOS)-type memory applications. The proposed approach is realized by using chemical oxide with ammonia (NH3) nitridation followed by reoxidation with oxygen (O2). The novel oxynitride process is not only compatible with the standard complementary metal–oxide–semiconductor (CMOS) process, but also can ensure the improvement of flash memory with low-cost manufacturing. The characteristics of nMOSFETs and SOHOS-type nonvolatile memories (NVMs) with a robust oxynitride as a gate oxide or tunnel oxide are studied to demonstrate their advantages such as the retardation of the stress-induced trap generation during constant-voltage stress (CVS), the program/erase behaviors, cycling endurance, and data retention. The results indicate that the proposed robust oxynitride is suitable for future nonvolatile flash memory technology application.

Improved Retention Characteristic in Polycrystalline Silicon–Oxide–Hafnium Oxide–Oxide–Silicon-Type Nonvolatile Memory with Robust Tunnel Oxynitride

Improved Retention Characteristic in Polycrystalline Silicon–Oxide–Hafnium Oxide–Oxide–Silicon-Type Nonvolatile Memory with Robust Tunnel Oxynitride

Retention Reliability Improvement of Silicon–Oxide–Nitride–Oxide–Silicon Nonvolatile Memory with N2O Oxidation Tunnel Oxide

The reliability characteristics of silicon–oxide–nitride–oxide–silicon (SONOS) devices with different thin tunnel oxides are studied. The device with the tunnel oxynitride grown in pure N2O ambient at a high temperature has better performance, including better leakage current, programming speed, read-disturb, and retention characteristics, than that with a tunnel oxide layer grown by dry oxidation with N2 annealing treatment. Moreover, the properties of two-bit operation are also displayed by a reverse read method. Furthermore, the surface roughness and interface states between a tunnel oxide layer and a Si substrate are also observed by atomic force microscopy (AFM) and charge-pumping method to evaluate interfacial nitrogen incorporation. The results show that data retention reliability attained a significant improvement while maintaining good programming/erase performance and two-bit operation. This work can provide a straightforward way of reliability improvement for future flash memory application.

Effect of Nitrogen Profile on Tunnel Oxynitride Degradation with Charge Injection Polarity

The relationship between nitrogen profiles and polarity dependence of wearout and breakdown in oxynitride films was investigated. With positive bias stress, higher concentration of nitrogen atoms near an oxynitride/Si interface (∼2 at.%) and in the oxynitride bulk (∼0.3 at.%) reduce charge trap and interface state generation, and produce greater charge-to-breakdown (Q bd). In contrast, with negative bias stress, nitrogen atoms near an interface decrease the number of charge traps, but, cannot reduce interface state generation, and thus give smaller Q bd. Furthermore, nitrogen atoms near an oxynitride surface (over 1.5 at.%) cause undesirable results for both bias stresses. Optimum nitrogen profile in an oxynitride film is discussed the viewpoint of reliability for both bias stresses.