Four-Period Vertically Stacked SiGe/Si Channel FinFET Fabrication and Its Electrical Characteristics

Abstract

In this paper, to solve the epitaxial thickness limit and the high interface trap density of SiGe channel Fin field effect transistor (FinFET), a four-period vertically stacked SiGe/Si channel FinFET is presented. A high crystal quality of four-period stacked SiGe/Si multilayer epitaxial grown with the thickness of each SiGe layer less than 10 nm is realized on a Si substrate without any structural defect impact by optimizing its epitaxial grown process. Meanwhile, the Ge atomic fraction of the SiGe layers is very uniform and its SiGe/Si interfaces are sharp. Then, a vertical profile of the stacked SiGe/Si Fin is achieved with HBr/O2/He plasma by optimizing its bias voltage and O2 flow. After the four-period vertically stacked SiGe/Si Fin structure is introduced, its FinFET device is successfully fabricated under the same fabrication process as the conventional SiGe FinFET. And it attains better drive current Ion, subthreshold slope (SS) and Ion/Ioff ratio electrical performance compared with the conventional SiGe channel FinFET, whose Fin height of SiGe channel is almost equal to total thickness of SiGe in the four-period stacked SiGe/Si channel FinFET. This may be attributed to that the four-period stacked SiGe/Si Fin structure has larger effective channel width (Weff) and may maintain a better quality and surface interfacial performance during the whole fabrication process. Moreover, Si channel of the stacked SiGe/Si channel turning on first also may have contribution to its better electrical properties. This four-period vertically stacked SiGe/Si channel FinFET device has been demonstrated to be a practical candidate for the future technology nodes.

4-Levels Vertically Stacked SiGe Channel Nanowires Gate-All-Around Transistor with Novel Channel Releasing and Source and Drain Silicide Process

“…In other words, the thickness of bottom Si 0.7 Ge 0.3 is ~2 nm thicker than that of others. It is known that the epitaxial rate is strongly dependent on the crystallization of the under-layer, that is, the epitaxial rate might be decreased if multi-crystallization occurs in the under-layer [ 9 ]. At the same time, the thickness of Si is measured as 13.5, 12.7, 12.0 and 12.3 nm from top to bottom for the better release of Si 0.7 Ge 0.3 NW channel.…”

“…Among them, SiGe materials, especially those with Ge concentration between 20% and 40%, have been considered as the channel material of GAA devices. This is because they have higher electron and hole mobility, better negative bias temperature instability (NBTI) reliability [ 8 , 9 ] than Si and are more compatible with present Si platform [ 9 , 10 , 11 ]. However, the fabrication of stacked SiGe nanowire/nanosheet (NW/NS) GAA devices still face many challenges, such as a high-quality stacked SiGe/Si fin structure preparation, high selectively SiGe NW/NS release, inner spacer, source/drain (S/D) epitaxial process, etc.…”

Process Corresponding Implications Associated with a Conclusive Model-Fit Current-Voltage Characteristic Curves

“…On the other hand, the mobility of silicon channel may be promoted by even 2.5 to 4 times as SiGe is technically and sophisticatedly introduced stack by stack. The above advanced techniques and other options are definitely promising and achievable, making FinFET continuously popular as currently [6][7][8][9][10][11][12].…”

Optimization of SiGe interface properties with ozone oxidation and a stacked HfO2/Al2O3 dielectric for a SiGe channel FinFET transistor

“…Among the present passivation methods, such as thermal oxidation [8][9][10][11] and plasma treatment (O 2 , N 2 or NH 3 ) [12][13][14][15][16], in-situ ozone oxidation is considered the most promising strategy [17][18][19][20]. This is because it not only achieves a high-quality IL with an in-situ low thermal budget, but it is also more suitable for advanced three-dimensional devices, such as fin field effect transistors (FinFETs) or gate-all-around field effect transistors, due to its isotropic characterization [19,21]. So far, studies have been carried out on low-temperature ozone oxidation in SiGe material under different oxidation process conditions [17,18].…”