An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

This paper reviews the basic physical mechanisms of the interactions of ionizing radiation with MOS oxides, including charge generation, transport, trapping and detrapping, and interface trap formation. Device and circuit effects are also discussed briefly.

/pdf/total-ionizing-dose-effects-in-mos-oxides-and-devices-4ndco1w6sd.pdf

Total ionizing dose effects in MOS oxides and devices

Electronic devices in space environments can contain numerous types of oxides and insulators. Ionizing radiation can induce significant charge buildup in these oxides and insulators leading to device degradation and failure. Electrons and protons in space can lead to radiation-induced total-dose effects. The two primary types of radiation-induced charge are oxide-trapped charge and interface-trap charge. These charges can cause large radiation-induced threshold voltage shifts and increases in leakage currents. Two alternate dielectrics that have been investigated for replacing silicon dioxide are hafnium oxides and reoxidized nitrided oxides (RNO). For advanced technologies, which may employ alternate dielectrics, radiation-induced voltage shifts in these insulators may be negligible. Radiation-induced charge buildup in parasitic field oxides and in SOI buried oxides can also lead to device degradation and failure. Indeed, for advanced commercial technologies, the total-dose hardness of ICs is normally dominated by radiation-induced charge buildup in either parasitic field oxides and/or SOI buried oxides. Heavy ions in space can also degrade the oxides in electronic devices through several different mechanisms including single-event gate rupture, reduction in device lifetime, and large voltage shifts in power MOSFETs.

Radiation Effects in MOS Oxides

The outstanding properties of SiO2, which include high resistivity, excellent dielectric strength, a large band gap, a high melting point, and a native, low defect density interface with Si, are in large part responsible for enabling the microelectronics revolution. The Si/SiO2 interface, which forms the heart of the modern metal–oxide–semiconductor field effect transistor, the building block of the integrated circuit, is arguably the worlds most economically and technologically important materials interface. This article summarizes recent progress and current scientific understanding of ultrathin (<4 nm) SiO2 and Si–O–N (silicon oxynitride) gate dielectrics on Si based devices. We will emphasize an understanding of the limits of these gate dielectrics, i.e., how their continuously shrinking thickness, dictated by integrated circuit device scaling, results in physical and electrical property changes that impose limits on their usefulness. We observe, in conclusion, that although Si microelectronic devices...

Ultrathin (<4 nm) SiO2 and Si-O-N gate dielectric layers for silicon microelectronics: Understanding the processing, structure, and physical and electrical limits

This review paper discusses several key issues associated with deep submicron CMOS devices as well as advanced semiconductor materials in ionizing radiation environments. There are, as outlined in the ITRS roadmap, numerous challenges ahead for commercial industry in its effort to track Moore's Law down to the 45 nm node and beyond. While many of the classical threats posed by ionizing radiation exposure have diminished by aggressive semiconductor scaling, the question remains whether there may be unknown, potentially worse threats lurking in the deep submicron regime. This manuscript provides a basic overview of some of the materials, devices, and designs that are being explored or, in some cases, used today. An overview of radiation threats and how radiation effects can be characterized is also presented. Last, the paper provides a detailed discussion of what we know now about how modern devices and materials respond to radiation and how we may assess, through the use of advanced analysis and modeling techniques, the relative hardness of future technologies

Total-Ionizing-Dose Effects in Modern CMOS Technologies

The transconductance of SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) is typically much lower in devices fabricated on the 4H-SiC polytype compared to 6H. It is believed that this behavior is caused by extreme trapping of inversion electrons due to a higher density of traps Dit at the SiC/SiO2 interface in 4H-SiC. Here we present an approach for profiling Dit versus energy in the band gap using a modified capacitance–voltage technique on large-area MOSFETs. We find that Dit increases towards the conduction band edge Ec in both polytypes, and that Dit is much higher in 4H- compared to 6H-SiC for devices fabricated in the same process lot.

Interface trap profile near the band edges at the 4H-SiC/SiO2 interface

The creation of interface states Dit by ionizing radiation is investigated in MOS capacitors as a function of oxide thickness in the range 6-50 nm A comparison of the thickness dependence in etchback and asgrown oxides supports the idea that the number of defects at the Si-SiO2 interface increases with oxidation time For relatively thin oxides (tox<12 nm), the rate of increase in Dit is significantly smaller than would be extrapolated from the behavior of thicker oxides for both oxide types This effect is probably caused by tunneling of trapped holes near the oxide interfaces

/pdf/generation-of-interface-states-by-ionizing-radiation-in-very-2xdfxanhqq.pdf

Generation of Interface States by Ionizing Radiation in Very Thin MOS Oxides

The formation of interface traps, N/sub it/, was studied in MOSFETs during isochronal annealing up to 350 K, following exposure to ionizing radiation at 78 K. Two distinct N/sub it/ formation processes are observed. A small (1-10% of total) process occurs at 100-150 K, which is caused by neutral atomic hydrogen, and a second, higher-temperature (200-300 K) process that accounts for most ( >90%) of the N/sub it/ formation also occurs. The characteristics of the high-temperature process support the proton (H/sup +/) model of N/sub it/ formation and are not in agreement with several other common models. Charge pumping and inversion layer mobility techniques for determining N/sub it/ are compared. It is found that the mobility cannot be used to determine N/sub it/ at 78 K (in contrast to its successful use at 295 K), probably because of lateral uniformities in the large radiation-induced fixed oxide charge. >

Formation of interface traps in MOSFETs during annealing following low temperature irradiation

The time dependence of changes in the oxide trapped charge during interface trap formation is investigated. Changes in MOSFET threshold voltage V/sub th/ and number of interface traps N/sub it/ are measured in the same sample as a function of time following pulsed irradiation. When the gate bias during irradiation V/sub gl/ is positive, the initial mod Delta V/sub th/ mod is large due to trapping of radiation-induced holes at the Si-SiO/sub 2/ interface and the postirradiation time dependence of Delta V/sub th/ is dominated by hole detrapping, as expected. When V/sub gl/ is negative, interfacial hole trapping is minimized. In this case, an unusual peak in the Delta V/sub th/ vs. time curve provides evidence of the involvement of H/sup +/ ions in the N/sub it/ formation process. >

Observation of H/sup +/ motion during interface trap formation

Generation of fast interface states D11 by ionizing radiation has been measured in MOS transistors at 80K and 295K using charge pumping and subthreshold slope techniques. Using charge pumping, the more sensitive and reliable technique, we find that D11 are not formed by radiation at 80K. In contrast, subthreshold slope measurements appear to show an increase in D11 in MOSFETs irradiated at 80K. This is shown to be an artifact caused by lateral non-uniformities (LNU) in the radiation-induced fixed charge.

Generation of Interface States by Ionizing Radiation at 80K Measured by Charge Pumping and Subthreshold Slope Techniques

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