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Sze’s theory has been the dominating theory regarding the Schottky emission effect (image force barrier lowering). The author noticed that the older and almost forgotten Krömer’s theory can frequently give a much better fit to experimental data especially for higher reverse bias voltage. In order to explain Krömer’s theory, it is necessary to apply the concept of velocity overshoot and quasi-ballistic transport to the depletion region in Schottky diodes. In this paper, the author will propose a unified theory for reverse leakage current in Schottky diodes.

One possible mechanism of reverse leakage current in Schottky diodes fabricated on large bandgap semiconductors like Ga2O3or diamond is Schottky emission (image force barrier lowering) at the metal-semiconductor interface. Historically, there were 2 theories regarding the image force barrier lowering effect. The author’s new idea is that the older and almost forgotten Krömer’s theory can frequently give a much better fit to experimental data for large bandgap semiconductors like Ga2O3or diamond Schottky diodes. It is possible to define an effective dielectric constant Keffin the reverse leakage current equation and quite frequently 1 ≥ Keff≥ ¼ for some large bandgap semiconductors like Ga2O3or diamond. Peripheral surface passivation is important.

In this paper, the author points out that Poole-Frenkel (P-F) saturation can be experimentally observed in ultrathin tantalum oxide capacitors. Factors why P-F saturation has been difficult to observe experimentally will be discussed. P-F saturation has not been successfully observed in thick tantalum oxide capacitors. Using an annealing process at a temperature just below the crystallization temperature seems to be helpful. In addition, TiN gate seems to be much better compared to Al gate. N2O is superior to O2as the annealing ambient.

In this paper, the author points out that the Poole-Frenkel (P-F) and Schottky emission mechanisms actually can happen simultaneously and a unified Schottky-Poole-Frenkel model can be used to explain a lot of existing experimental data. However, sometimes, the basic unified Schottky-Poole-Frenkel model fails and an extended unified Schottky-Poole-Frenkel model is required to explain experimental data. In this paper, an example of using the basic unified Schottky-Poole-Frenkel model to explain the I-V characteristics of high-k capacitor structures used in analog integrated circuit technology will be presented. Then an example of high-k capacitor structures used in analog integrated circuit technology which require the extended unified Schottky-Poole-Frenkel model will also be provided.

Experimental data show that the polysilicon gate length tends to be smaller in the middle of the silicon wafer and also at the silicon wafer edge. This can be seen from electrical measurement data of MOS transistors in a row along a diameter of the wafer. In-line CD (critical dimension) data will also be presented to support the above claim. Physical mechanisms responsible for the experimental observation will be provided. Possible existence of plasma instability during the polysilicon gate etch process will also be discussed.

It is expected that the leakage current can be reduced by nitridation of silicon before high-k dielectric deposition. In reality, it is not so simple because the nucleation of high-k dielectric on nitrided silicon may be different from the nucleation on silicon. In addition, the interfacial layer between the high-k dielectric becomes thinner because of the nitridation. Furthermore, the bandgap of the interfacial layer becomes smaller due to the nitridation. However, there may be less defect states in the high-k dielectric because of the nitridation. More in-depth study is needed to clarify whether leakage current is really reduced by nitridation. Experimental observation indicates the leakage current can be increased or decreased by nitridation depending on the details of the processing conditions. However, the capacitance is usually increased by nitridation; reduction of capacitance due to RTN is an unusual observation but it is possible.

Historically, there is a controversy regarding the current-voltage (I-V) characteristics of thin film MIM (metal-insulator-metal) capacitors, which is quite frequently modeled by either the Schottky model or the Poole-Frenkel model. In this letter, the author points out that the two models actually can be unified. The physics underlying this model involves a non-uniform distribution of defect states such that a very large quantity of defect states exist at the two interface of the MIM capacitor while the density of defect states in the insulator bulk is relatively low, resulting in an M/n-i-n/M structure. This unified Schottky-Poole-Frenkel model can be further extended to include other effects like space charge limited current, tunneling, etc. Evidence supporting this theory will be provided.

Mechanical stress sensors based on silicon piezoresistance have limited sensitivity. Mechanical stress sensors based on the on-current or off-current or threshold voltage of silicon MOS transistors also have limited sensitivity. In this paper, we report that the sensitivity of a silicon-based mechanical sensor can be significantly improved by simply monitoring the gate-induced-drain leakage (GIDL) current of an n-channel MOS transistor with tensile mechanical stress bias and the underlying principle will also be discussed.