The Challenge of Measuring Strain in FDSOI Device Structures – HRXRD as a Potential Method of Resolution

Abstract

The strain state of Si1‐xGex/SiO2 dummy structures on FDSOI wafers is non‐destructively characterized by HRXRD reciprocal space mapping. A transition from biaxial to uniaxial strain is detected on narrow condensed Si1‐xGex lines with shallow trench isolation (STI), revealing an increasing in‐plane elastic strain relaxation perpendicular to the trenches with decreasing line width, but no strain relaxation parallel to the trenches. The degree of crystallinity of Si1‐xGex lines degrades with increasing annealing temperature and time. An additional elastic strain reduction appears in the direction parallel to the STI trenches after deposition of source‐drain Si1‐yGey islands between dummy gates. The separation of the Si1‐xGex peaks from Si1‐yGey remains unresolved if x and y are close to each other.

Atomic‐scale strain analysis for advanced Si/SiGe heterostructure by using transmission electron microscopy

“…58 Si, Ge, and SiGe alloy materials all possess a diamond cubic structure with the space group Fd3m. 59 The lattice constants (a) of the Si 1-x Ge x alloys do not precisely adhere to the commonly used Vegard's rule and can be derived by using the following Dismukes formula: 60,61 a Si…”

“…Si, Ge, and SiGe alloy materials all possess a diamond cubic structure with the space group Fd3m 59 . The lattice constants ( a ) of the Si 1‐ x Ge x alloys do not precisely adhere to the commonly used Vegard's rule and can be derived by using the following Dismukes formula: 60,61 $$$a({\mathrm{Si}}_{1-x}{\mathrm{Ge}}_{x})={a}_{0}(\mathrm{Si})+{C}_{1}\bullet x+{C}_{2}\bullet {x}^{2}$$$ where x is the atomic fraction of Ge, a 0 = 0.5431 nm, C 1 = 0.01992 nm, and C 2 = 0.002733 nm. When the Si 1‐ x Ge x film is epitaxially grown on a Si substrate, the epitaxial layer will incur lattice distortions due to the difference in lattice constants 62 .…”