Poly-emitter Bipolar Transistors Research Articles

Effect of Interfacial Oxide Thickness on 1/f Noise in Polysilicon Emitter BJTs

The role of the interfacial oxide (IFO) between the polysilicon and monosilicon emitter regions on the noise behavior of n-p-n poly-emitter bipolar transistors was investigated through 1/f noise measurements. Bipolar junction transistors with different IFO thickness, and emitter geometry were utilized. Measurements with variable external base bias resistance (R/sub S/) were used to investigate the relative contribution of each individual noise source from the base current (S/sub IB/), the collector current (S/sub IC/) and, the internal emitter and base series resistances (S/sub Vr/). When the voltage noise power spectral densities S/sub VC/ and S/sub VB/ were measured across resistances in series with the collector and base, respectively, using a relatively large R/sub S/ (/spl sim/1 M/spl Omega/), S/sub IB/ was found to have the dominant noise contribution at lower bias currents. On the other hand, when the voltage noise power spectral densities S/sub VC/ and S/sub VE/ were measured across resistances in series with the collector and emitter, respectively, in a different experimental setup with a low R/sub S/ value, S/sub Vr/ was found to have the dominant noise contribution at higher bias currents. IFO was found to increase S/sub IB/, S/sub IC/, and S/sub Vr/. S/sub IB/ was modeled as a combination of tunneling and diffusion fluctuations of the minority carriers in the emitter; whereas S/sub IC/ was modeled as a combination of number and diffusion fluctuations of the minority carriers in the base. S/sub Vr/ was attributed to the internal emitter resistance noise originating from the fluctuation in the majority carrier flow through the IFO.

The base current degradation of poly-emitter BJTs under AC stress

A simple model for the analysis of the ac stress effect in poly-emitter bipolar transistors is presented. Apart from the reverse-bias induced hot-carrier effects, the forward-bias recovery effect is a key factor under ac stress, it obviously suppresses the base current degradation of the device which is caused during the reverse-bias periods. In this work, we derived the relationship between the excess base current and the stress time for different ac stress conditions. This model is verified with experimental results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

1/f noise characterization of base current and emitter interfacial oxide breakup in n-p-n polyemitter bipolar transistors

We propose using base 1/f noise to characterize the distribution of diffusion and tunneling components of base-current (I/sub b/) at the emitter poly/monosilicon interface in n-p-n polyemitter transistors. A noise model is constructed to interpret the I/sub b/ 1/f noise (S/sub iEB/) dependence on these combined currents. Measured I/sub b/ dependences of S/sub iEB/ increase progressively from I/sub b//sup 1.2/ to I/sub b//sup 2.0/ for transistors having emitter structures concomitant with increasing current gains and series emitter resistances ranging between 115-1800 and 7-33/spl Omega/, respectively. This is indicative of tunneling components in I/sub b//sup 2.0/ that increase with higher interfacial oxide continuity, and persist in epitaxially realigned emitters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Base etched selfaligned transistor technology foradvanced polyemitter bipolar transistors

The authors report the fabrication of double selfaligned advanced bipolar transistors using base etched selfaligned transistor technology (BESTT). The main feature of these transistors is that the base and emitter contacts are self-aligned although using only a single poly layer. The fabrication and DC electrical measurements are discussed.

Effect of Interfacial Oxide on Static and High-Frequency Performance in Poly-Emitter Bipolar Transistors Under High-Level Injection

We report on a theoretical investigation of the effect of interfacial oxide on both static and dynamic performance in polycrystalline silicon emitter bipolar transistors. The calculation is carried out up to 0.9 V, before the onset of the Kirk effect. From the model, it is found that the current gain increases and the forward transit time decreases as interfacial oxide thickness increases. Furthermore, both the current gain and the forward transit time decrease as recombination velocity increases. In addition, the intrinsic base resistance remains almost constant as interfacial oxide thickness increases, and increases as recombination velocity increases. Compared with the conventional low-level injection model, the improved model provides much more accurate expressions for electrical characteristics of bipolar transistors operating under high-level injection.

Reliability imposed design aspects of submicrometer polysilicon-emitter bipolar transistors

The device reliability of narrow poly-emitter bipolar transistors with very shallow junctions is studied experimentally. The excess base current due to nonuniform poly doping, which is typically seen in such devices, is found not to accelerate device degradation. The lower doping at the emitter edge due to known perimeter depletion and emitter plug effects (PPEs) leads to a reduced increase in base current per perimeter length with stress. The results show that bipolar device scaling can probably be pursued to a point where PPEs start to appear, and that lateral emitter grading is effective in improving the device reliability. >

Observation of electromigration of hydrogen in polycrystalline silicon using poly emitter bipolar transistors

Electromigration of hydrogen inside polycrystalline silicon (polysilicon) has been observed for the first time. Experiments were conducted on polysilicon emitter (poly emitter) n-p-n transistors with and without atomic hydrogen inside polysilicon. The current gain (β) of n-p-n was selected to monitor electromigration of hydrogen during current stress because of its high sensitivity to hydrogen passivation of dangling bonds. The major characteristics of hydrogen electromigration are shown in this letter.

Effect of reactive ion etching on the electrical characteristics of poly-emitter bipolar transistors

Effect of reactive ion etching on the electrical characteristics of poly-emitter bipolar transistors