Chemical vapour etching of Si, SiGe and Ge with HCl; applications to the formation of thin relaxed SiGe buffers and to the revelation of threading dislocations

Abstract

We have studied the etching of silicon, SiGe and germanium layers with gaseous HCl in reduced pressure-chemical vapour deposition (RP-CVD). We have observed the occurrence of two etch regimes depending on the etching temperature. The first regime takes place at high temperatures and is characterized by low activation energies (∼7 kcal mol −1 ), this whatever the germanium content of the etched layer. The other regime occurs at low temperatures and has associated high activation energies (which strongly depend upon the germanium concentration of the etched layer: 86 kcal mol −1 for pure Si versus 28 kcal mol −1 for pure Ge). Modifying the HCl partial pressure has different effects depending on the regime. In the high temperature regime, increasing the HCl partial pressure will almost quadratically increase the etch rate (ER ∝ P HCl 1.76), this both for Si and Si 0.67 Ge 0.33 . Meanwhile, the dependence is sub-linear in the low temperature regime (Si ER ∝ P HCl 0.53 and Si 0.67 Ge 0.33 ER ∝ P HCl 0.82

In situ HCl etching of Si for the elaboration of locally misorientated surfaces

“…For 895 8C and 910 8C, some small facets ((1 1 8) or (1 1 34)) are formed, with a slightly concave shape of the Si recess. A similar concave shape with (1 1 4) facets has quite recently been observed after some HCl etching at 900 8C, 20 Torr of Si in the active area of a patterned wafer (same mask) [17]. The F(HCl)/F(H 2 ) mass-flow ratio was lower in Ref.…”

“…The F(HCl)/F(H 2 ) mass-flow ratio was lower in Ref. [17], however (1.042 Â 10 À3 versus 1.875 Â 10 À3 here), leading to lower etch rates (69 nm min À1 versus 139 nm min À1 here) and more marked facets, apparently.…”

“…We have quantified the impact of the etching temperature, the pattern size, the etching time and the shallow trench isolation (STI) thickness on the misorientation. Kreuzer et al [16] and Bogumilowicz et al [17] have shown that stress has some impact on the HCl etching rates of Si in Si/Si x Ge 1Àx / Si and Si x Ge 1Àx /Si structures and might be responsible for facets formation. Hartmann et al pointed out the existence of a loading effect (i.e.…”

Selective epitaxy growth of Si1−xGex layers for MOSFETs and FinFETs

“…The dependency of activation energy on Ge content has been also observed by the previous studies [55]. However, the dependency of activation energy in Eq.…”

“…12 deviates from the extracted equations and value to etch the bulk SiGe (after epitaxy) in Ref. [37,55]. This discrepancy in activation energies is described by the fact that the required energy to etch the bulk SiGe and during SiGe epitaxy is very different.…”