Selective Lateral Germanium Growth for Local GeOI Fabrication

Abstract

High quality local Germanium-on-oxide (GeOI) wafers are fabricated using selective lateral germanium (Ge) growth technique by a single wafer reduced pressure chemical vapor deposition system. Mesa structures of 300 nm thick epitaxial silicon (Si) interposed by SiO2 cap and buried oxide are prepared. HCl vapor phase etching of Si is performed prior to selective Ge growth to remove a part of the epitaxial Si to form cavity under the mesa. By following selective Ge growth, the cavity was filled. Cross section TEM shows dislocations of Ge which are located near Si / Ge interface only. By plan view TEM, it is shown that the dislocations in Ge which direct to SiO2 cap or to buried-oxide (BOX) are located near the interface of Si and Ge. The dislocations which run parallel to BOX are observed only in [110] and [1–10] direction resulting Ge grown toward [010] direction contains no dislocations. This mechanism is similar to aspect-ratio-trapping but here we are using a horizontal approach, which offers the option to remove the defective areas by standard structuring techniques. A root mean square of roughness of ∼0.2 nm is obtained after the SiO2 cap removal. Tensile strain in the Ge layer is observed due to higher thermal expansion coefficient of Ge compared to Si and SiO2.

Reduced-Pressure Chemical Vapor Deposition Growth of Isolated Ge Crystals and Suspended Layers on Micrometric Si Pillars

“…9(b)). The average strain measured on two independent SUB1(SUB2) samples is  = +0.05% (+0.14%), in good agreement with the XRD determination, with a full-width at half maximum of the strain distribution over the whole patch equal to FWHM= 0.09% (0.045%), as can be derived from 60 min Ge deposition by RPCVD (c) using a standard two-step process at 300°C/550°C without cyclic annealing 25 , (d) using a one-step process at 650°C with HCl gas as etchant 26 , and (e) using a one-step process at 650°C with HCl gas but without SiO2-covered sidewalls.…”

“…One possible explanation for this additional Ge growth on the SiO 2 -covered sidewalls of the pillar, which is not observed on “flat” SiO 2 hard mask layer, could be the presence of local imperfections in the SiO 2 layer, like for instance the presence of residual Si and carbon particles after the Bosch lithographic process. To remove potential local imperfections in the SiO 2 layer and to increase the selectivity of the Ge growth, we were forced to modify the process condition by eliminating the low-temperature deposition and increasing the subsequent deposition temperature from 550 °C, that is, close to the one used in LEPECVD, to 650 °C, with the addition of HCl gas to the H 2 –GeH 4 gas mixture . The role of the HCl is to etch away low-quality material, thus favoring the selective growth of the material on the top pillar opening, as can be seen in Figure d.…”

“…To remove potential local imperfections in the SiO 2 layer and to increase the selectivity of the Ge growth, we were forced to modify the process condition by eliminating the low-temperature deposition and increasing the subsequent deposition temperature from 550 °C, that is, close to the one used in LEPECVD, to 650 °C, with the addition of HCl gas to the H 2 −GeH 4 gas mixture. 26 The role of the HCl is to etch away low-quality material, thus favoring the selective growth of the material on the top pillar opening, as can be seen in Figure 1d. Here we point out that deposition carried out on pillars featuring bare Si sidewalls (i.e., not covered by SiO 2 ), the growth resulted in being nonselective even when HCl was employed, as can be seen in Figure 1e.…”

Characterization of Hetero-Epitaxial Ge Films on Si Using Multiwavelength Micro-Raman Spectroscopy

“…The peak position shifts under the presence of strain/stress and isotopic variations. 4,5,9,[27][28][29][30][31] Alloys of Si and Ge (Si 1-x Ge x ) typically show three Raman peaks of Ge-Ge (∼300 cm −1 ), Si-Ge (∼400 cm −1 ) and Si-Si (∼500 cm −1 ). The position and intensity of the three peaks depends on the composition of the alloys.…”

(Invited) Advanced Germanium Epitaxy for Photonics Application

“…By the P4ALD process, P concentration of quarter of ML in a two dimensional plane is realized. By multiple P4ALD process with shallow spacer, it is possible to obtain heavy P concentration (10,17). Figure 9 shows SIMS depth profiles of P doped Ge without and with Si delta layers (12).…”