Selective wet etching in fabricating SiGe nanowires with TMAH solution for gate-all-around MOSFETs

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

“…For a selective removal of Si to Si 0.7 Ge 0.3 , the wet etching approach using an alkaline solution is still a better choice. For example, the conventional TMAH solution, after the co-optimization of concentration and temperature, can be chosen to selectively remove the Si to Si 0.7 Ge 0.3 with a selectivity of ~17.3 [ 13 ]. To further enhance the selectivity of the wet etching process, a novel ACT@SG-201 solution is employed to verify the release process of four-levels vertically stacked Si 0.7 Ge 0.3 NW channel.…”

“…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. [ 11 , 12 , 13 , 14 , 15 ]. These processes are critical for the preparation of the stacked SiGe channel NW/NS device.…”

“…Prior to this work, there are several reports on the preparation of SiGe/Si fin in terms of the epitaxial growth and dry etching process of stacked SiGe/Si [ 11 , 12 , 16 , 17 ]. In addition, the releasing technologies of SiGe nanowire by highly selective removal of Si have been investigated in the last years using the dry etching with CF4-based plasma [ 18 ], in situ HCl gaseous thermal etching [ 19 ] and wet chemical etching [ 13 , 20 ]. However, the former two methods are normally conducted using specific tools to avoid damages or selectivity issues.…”

Epitaxial Growth of Ordered In-Plane Si and Ge Nanowires on Si (001)

“…The in-plane and site-controllable epitaxial NWs hold promise as the platform for the next generation of devices that require addressability and scalability. The Si and SiGe NWs have potential applications for high-perform transistors [ 7 , 23 ]. Moreover, the [110]-oriented Ge/Si core/shell NWs are expected to have a high mobility and a strong spin-orbit coupling [ 37 , 38 ] for the manipulation of hole spin qubits.…”

“…For instance, IMEC has previously reported the vertically stacked horizontal Si NWs with selective etching of Si/SiGe multilayer fin structures [ 1 ]. Moreover, by selectively etching Si, stacked SiGe NWs were obtained to improve the channel mobility [ 7 ]. However, the top-down fabrication introduces atomic surface roughness and damages, which deteriorate the carrier mobility of the NWs [ 8 ].…”