The Challenges of Ge-Condensation Technique

Abstract

Ultra-thin SiGe films on insulator with high Ge fraction were fabricated through Ge condensation. To achieve that strained Si 0.75 Ge 0.25 layers were grown epitaxially on SOI wafers and oxidized in O 2 at 1150 o C for various times. Raman measurements and X-TEM revealed the importance of purity of oxidation ambient for the oxidation process. Traces of moisture in the oxygen flux accelerate the process causing a switch from dry to wet oxidation mechanism, leading to complete oxidation of the starting layer in only 1 hour. The crystal quality and overall uniformity of such layers however is poor. The use of 100% dry oxygen provides the necessary control over the oxidation process. This allowed relaxed SiGe layers with concentration of Ge up to 45% and higher to be obtained. X-TEM indicated good crystalline quality and uniform layers with no threading dislocations or other defects introduced during oxidation.

High-Hole-Mobility Silicon Germanium on Insulator Substrates with High Crystalline Quality Obtained by the Germanium Condensation Technique

“…Among the many techniques that have been proposed for production of GeOI wafers ͑layer transfer, 8 wafer bonding and grinding, 9 wafer bonding and etchback, 10 liquid phase epitaxy, 11 fully epitaxial growth using crystalline and lattice matched oxide, 12 etc.͒, the Ge condensation technique ͑also referred as thermal mixing͒ is an interesting approach ͑wafer scalability, ultrathin GeOI, etc.͒. [13][14][15] This method is based on the epitaxial growth of a Si-rich SiGe layer on a silicon-on-insulator ͑SOI͒ substrate followed by high-temperature selective oxidation of Si atoms to condense the Ge atoms in a thinner, Ge-rich SiGe layer. The peculiarity of this technique is the concomitance of two phenomena which are, namely, the selective oxidation of Si at the top SiO 2 /SiGe interface and the diffusion of Ge through the SiGe and the top Si layer of the SOI.…”

(Invited) Identification of Intrinsic Point Defects at GexSi1-x/Oxide Interfaces by ESR Probing

“…A first one concerns SiO 2 /(100)Ge x Si 1-x /SiO 2 / (100)Si entities with atomic Ge fraction x in the range 0.27 ≤ x ≤ 0.93, fabricated using the condensation technique (16,17). Briefly, this essentially implies a three-step process.…”

“…In addition, monitoring of the in plane lattice constant by high-resolution x-ray diffraction measurements reveal that the SiGe film relaxes as the condensation proceeds, the data being supported by Raman observations, pointing to a remaining strain in the -0.9 to -1.2% range. More details can be found elsewhere (17,19).…”

Molecular beam epitaxy and defect structure of Ge (111)/epi-Gd2O3 (111)/Si (111) heterostructures

“…Several techniques have been investigated and established for preparation of GeOI substrates, the most notable amongst them being the Smart Cut TM technology, which involves transfer of Ge layers onto a Si/SiO 2 surface, from a Czochralski-grown Ge wafer [4,10,11]. Other techniques include Ge condensation [4,12] and liquid phase epitaxy (LPE) [4]. While the Smart Cut TM technology is costintensive, the two other techniques suffer from high thermal budget and limited lateral extent of GeOI (~ 20 m), respectively [4].…”