Ming-Ching Huang oral presentation (OA3-Tue1-3-5)
Quantifying The Ge Concentration of Si-Ge Epitaxy Grown at P-MOSFET by SIMS Calibrated TEM/EDX
1 03-6116678, Li-Hsin Rd, 300 Hsinchu, Taiwan, Province of China
2 Materials Analysis Technology Inc., 1B9, No. 1, Lihsin Road 1, 300 Hsinchu, Taiwan, Province of China
3 MA-tek, 1B9, 1F, No.1, Lising Rd. I,, 300 HsinChu, Taiwan, Province of China
Conventionally, the Ge concentration of Si-Ge epitaxy is measured by the secondary ion mass spectrometer (SIMS) from the large monitoring area. However, the epitaxial growth shows loading effect which is area sensitive. This results in the thickness of the epitaxial layer is thinner in the wide area. The actual MOSFET area is smaller and smaller as the technology scaling. It is crucial to have the capability to quantify the Ge concentration in the very localized area. TEM is the most powerful tool to reveal the image of the small structure. Also the nano-beam diffraction (NBD) has been utilized to obtain stress information from the channel region routinely. TEM/EDX provides chemical information from very localized area with sub-nano-meter resolution, however, the chemical composition data is semi-quantitative. Those EDX data cannot reliably be used for sample to sample or lot to lot comparison. In order to obtained more correct composition information of Ge from a very localized area, a calibration procedure of TEM/EDX by SIMS was conducted. After this calibration procedure, TEM/EDX data of Ge concentration can be quantified more correctly.
Three blanket SiGe epitaxial layers (SG1, SG2 and SG3) with different Ge concentration were prepared by ultrahigh vacuum chemical vapor deposition (UHVCVD) as standard samples. Ge concentrations of these three standard samples were determined to be 20.7, 30.7, and 41.9 at% by Rutherford back scattering (RBS), respectively. The RBS results were utilized to calibrate the SIMS measurements. The relative sensitivity factors (RSF) of Ge for SIMS were calculated from these three samples. Another five blanket SiGe epitaxial samples (#1, #2, #3, #4 and #5) with different Ge concentration were prepared and analyzed by SIMS to determine the Ge concentration. The Ge concentrations of the these five samples analyzed by SIMS were determined to be 7.3 at%, 14.7 at%, 18.8 at%, 30.2 at% and 37.2 at%, respectively.
Energy-dispersive X-ray spectroscopy (EDX) was utilized to measure the Ge concentration of these five samples from the TEM lamellas. Based on the quantification results of SIMS, a calibration curve of EDX was obtained to quantify the concentration of Ge as shown in Fig. 1.
Finally, Ge concentration of the SiGe epitaxy in a PMOS of a SRAM cell manufactured by 16 nm technology was analyzed by the SIMS calibrated TEM/EDX as shown in Fig. 2.