SiGe device architectures synthesised by local area Ge implantation; structural and electrical characterisation

SiGe device islands have been synthesised by Ge+ ion implantation of doses of 0.45 x 1016 Ge+/cm2 to 4.05 x10 Ge+/cm2 at 100keV or 200keV into patterned (100) bulk silicon wafers. The control of 'mask edge defects' and 'end of range' defects has been achieved by applying Si+ post-amorphisation, where the ions are implanted into a wider window, and by using solid phase epitaxial regrowth. Defect free SiGe alloy islands with a peak Ge concentration of ~6at% and minority carrier generation lifetimes comparable to bulk silicon (~ms) have been successfully produced. The integration of this synthesis process into CMOS and bipolar technologies is discussed. Realization of shallower islands, with dimensions more consistent with future generations of advanced devices and with higher Ge contents, is in hand

A comparison of pnp and npn SiGe HBTs fabricated by Ge implantation

A study is made of npn and pnp SiGe HBTs produced using Ge implantation. The Ge is implanted into a complementary bipolar process after active area definition. Increased collector currents are observed in both npn and pnp transistors due to the presence of the Ge. The implanted Ge has opposing effects on the emitter dopant diffusion: increasing the arsenic diffusion coefficient in the npn devices and decreasing the boron diffusion coefficient in the pnp devices

Experimental evidence of B clustering in amorphous Si during ultra shallow junction formation

The authors have investigated ultrashallow p+ /n-junction formation by solid-phase epitaxy, by using x-ray absorption near-edge spectroscopy measurements on the B K edge. A clear fingerprint of B\u2013B clusters is detected in the spectra. The authors demonstrate that B clustering occurs during the very early stages of annealing-induced Si recrystallization, i.e., when B is still in an amorphous matrix. After complete regrowth the local structure around B remains the same as in the amorphous phase, implying that B clusters are transferred to the crystalline structure

B diffusion and activation phenomena during post-annealing of C co-implanted ultra-shallow junctions

In order to meet the technological requirements for the next generations of p-n junctions, highly promising methods consist of B and C ultra-low energy co-implantation in Ge pre-amorphized Si. We investigated the B diffusion and the activation phenomena occurring during post-annealing of ultra-shallow junctions (USJ) obtained by spike annealing Si samples pre-amorphized by 20 keV Ge and co-implanted with C at 4 keV and B at 500 eV. Isochronal (60 s) post-annealing processes were performed in inert atmosphere (N-2) by rapid thermal annealing (RTA) in the 500-1050 degrees C temperature range. We show that, contrary to what reported in the literature about C-free USJ, no B diffusion occurs up to 900 degrees C, and further B clustering is completely suppressed over the whole investigated temperature range. Moreover we observed an increase of the sheet resistance by increasing the temperature up to 900 degrees C followed by a subsequent decrease, that can be easily interpreted on the basis of B diffusion and segregation in native SiO2 and B cluster dissolution. Finally, we show that C significantly reduces up to two orders of magnitude the diffusion coefficient of B, that in our experiments is present in highly extrinsic conditions