Dependence of low frequency noise in SiGe heterojunction bipolar transistors on the dimensional and structural features of extrinsic regions

Технологічні та конструктивні методи зниження рівня низькочастотного шуму в n-p-n транзисторах

“…З самого початку появи транзисторів для зниження рівня шумів постійно проводяться дослідження різних видів шумів і їх джерел [1,2]. Після початку промислового виробництва біполярних транзисторів, частину з них випускали як малошумливі, -з вимірюванням рівня шумів [3,4] [5] для зменшення низькочастотних шумів можуть бути застосовані зміни в конструкції напівпровідникових приладів і в технології їх виготовлення.…”

Low-frequency noise in downscaled silicon transistors: Trends, theory and practice

“…The second factor for deviation of noise level around the trend in Figure 2 can be attributed to differences in the fabrication of BJT. The impact of several technology steps on the low-frequency noise in polysilicon emitter BJTs was reviewed several times, for example in [31], and extensively analyzed in the past [18,19,20,21,32,33,34,35,36,37,38,39,40]. From these studies, it is found that among the many sources that can contribute to the low-frequency noise, such as fluctuation in diffusion, surface recombination and charge trapping, the major noise source is associated with or located in the interfacial oxide (IFO) between poly and monosilicon layers in the emitter of BJT.…”

“…Typical types of cross-over in the noise in BJT are between areal and peripheral noise sources in the emitter region [14,21,35,36,42,60], noise from tunneling through IFO and series resistances (carrier number fluctuation, or coupled noise to the injection process, precisely) and diffusion noise (mobility fluctuation, or intrinsic noise of the current flow in emitter and base regions) [10,19,21,32,42,61,62], surface and bulk noise sources [14,21,24,36,37,42,60], and for very small-area BJTs (A E ≤0.1µm 2 ), the extension length of the base to the contact via becomes an issue for the low-frequency noise [36,37], since that extension is with large area compared to A E , and it is vulnerable to the surface noise from the oxide on the top of the structure. Also, in small-area BJTs, the crossover between generation-recombination (GR), random telegraph signal (RTS) and 1/f noise becomes apparent [11,12,17,18,30,35,63].…”

“…It is well established that the low-frequency noise in the base and collector currents are strongly correlated. Their normalized cross-correlation spectrum, called often coherence (and corresponding to correlation coefficient for random quantities), is close to one [19,32,37,60]. The coherence between two noise spectra is given by ( )…”

“…Then, the measured noise is attributed to each noise source, and one of them usually fits the data well, which is consistent with the assumption that one noise source practically dominates in the total noise. The approach of the dominant noise source is used several times and it identified that the dominant noise source can be presented as current noise source in the base current [19,32,37,61], although the actual physical process can be in the emitter, e.g. IFO, or at the surface above base-emitter junction.…”