Effect of Plasma Treatment on Metal Oxide p–n Thin Film Diodes Fabricated at Room Temperature

Funder: Cambridge Trust; Id: http://dx.doi.org/10.13039/501100003343Abstract: There is a need for a good quality thin film diode using a metal oxide p–n heterojunction as it is an essential component for the realization of flexible large‐area electronics. However, metal oxide‐based diodes normally show poor rectification characteristics whose origin is still poorly understood; this is holding back their use in various applications. A systematic study of the origins of the poor performance is performed based on bias‐stress measurements using a cuprous oxide (Cu2O)/amorphous zinc‐tin oxide (a‐ZTO) heterojunction as an example. This suggests that multiple carrier trapping and thermal release of carriers in defect states stemming from oxygen vacancies at the heterojunction interface is the primary cause of poor rectification. It is demonstrated that a plasma treatment is an effective way to optimize the population of oxygen vacancies at the heterojunction interface based on extensive material analyses, allowing a significant improvement in the diode performance with a much‐enhanced rectification ratio from ≈20 to 10 000, and a consequent facilitation of the next‐generation of ubiquitous electronics

Reduced boron diffusion under point defect injection in fluorine implanted silicon

This thesis reports the results of experiments aimed at understanding the behaviour of fluorine under various device processing conditions and hence aims to identify the mechanisms responsible for the reduced boron diffusion. Point defect injection studies are performed to study how the injection of interstitials and vacancies from the surface influences the fluorine SIMS peaks and the diffusion of boron marker layers which are placed to coincide with major fluorine peaks of the fluorine profile.  SIMS analysis of a sample implanted with 185keV, 2.3 x 1015 cm-2 F+ and annealed at 1000°C shows fluorine peaks at depths of 0.3Rp and Rp and a shoulder between 0.5-0.7Rp.  The shallow fluorine peak at a depth of 0.3Rp­ is smaller under interstitial injection than inert anneal and it decreases in size with anneal time.  The presence of this shallow peak correlates with the suppression of boron diffusion in a boron marker located at the same depth. In fluorine implanted samples, less boron diffusion is surprisingly observed under interstitial injection than inert anneal for boron marker layers located in the interstitial-rich region (at Rp) of the fluorine damage profile. A systematic study is made of the effect of device processing on the V-F clusters.  SIMS analysis shows that the V-F clusters are stable for anneals of 1.5 hours at 820°C or 45s at 1050°C.  The clusters are stable in the presence of a low dose dopant co-implant (1x1013 cm-2), but are eliminated by a high dose dopant co-implant (2x1015 cm-2).  Investigation of the effect of decreasing fluorine implant energy on the V-F clusters shows that a low thermal budget anneal gives a better retention of the V-F clusters and allows a reduction of the fluorine implant energy for application in junction depths down to ~20 nm. Finally, this thesis reports the implementation of a fluorine implant in production silicon bipolar technology at STMicroelectronics, Sicily, Italy.  A novel approach was used and it was demonstrated that fluorine dramatically suppresses boron diffusion in the base and leads to a world record fT of 110GHz in an appropriately optimised device.</p

Reduced boron diffusion under point defect injection in fluorine implanted silicon

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Doping density extraction of plasma treated metal oxide thin film diodes by capacitance–voltage analysis

Abstract High quality thin film p‐n junction diodes with high rectification ratios and low ideality factors have been fabricated from metal oxides, such as amorphous oxide semiconductors (AOSs), and characterized. Plasma treatment of interfaces has been demonstrated to improve devices made from AOSs, using current–voltage (I–V) measurements. However, capacitance–voltage (C–V) measurements of the devices have been scarcely reported in the literature. Therefore, the focus of this work is characterization of cuprous oxide (Cu2O)/amorphous zinc‐tin oxide (a‐ZTO) thin film heterojunction diodes using C–V analysis. Performance differences of plasma‐treated and untreated diodes that are difficult to observe in I–V analysis are more prominent in C–V analysis. Moreover, C–V analysis allows extraction of charge density profiles, which is a measure of the defect state density that led to intrinsic doping. The variation of doping densities of the untreated diode across the full range of applied reverse bias is shown to be up to 2 orders of magnitude, while those of the treated diodes are within a factor of 10 only. Junction charge profiles, interfacial charge depletion, and accumulation that are key features of rectifying diodes are shown to be clearly distinct between untreated, nitrogen‐treated, and oxygen‐treated diodes, thus explaining why oxygen‐treated diodes are superior

Effect of Plasma Treatment on Metal Oxide p–n Thin Film Diodes Fabricated at Room Temperature

Funder: Cambridge Trust; Id: http://dx.doi.org/10.13039/501100003343Abstract: There is a need for a good quality thin film diode using a metal oxide p–n heterojunction as it is an essential component for the realization of flexible large‐area electronics. However, metal oxide‐based diodes normally show poor rectification characteristics whose origin is still poorly understood; this is holding back their use in various applications. A systematic study of the origins of the poor performance is performed based on bias‐stress measurements using a cuprous oxide (Cu2O)/amorphous zinc‐tin oxide (a‐ZTO) heterojunction as an example. This suggests that multiple carrier trapping and thermal release of carriers in defect states stemming from oxygen vacancies at the heterojunction interface is the primary cause of poor rectification. It is demonstrated that a plasma treatment is an effective way to optimize the population of oxygen vacancies at the heterojunction interface based on extensive material analyses, allowing a significant improvement in the diode performance with a much‐enhanced rectification ratio from ≈20 to 10 000, and a consequent facilitation of the next‐generation of ubiquitous electronics