Non-contact, non-destructive characterization of Ge content and SiGe layer thickness using multi-wavelength Raman spectroscopy

Abstract

Design and performance of a newly developed multi-wavelength, micro Raman spectroscopy system for non-contact and non-destructive characterization of semiconductor materials are introduced. The thickness and Ge content of Si 1-x Ge x /Si were estimated from the multiwavelength Raman measurement results and compared to those values obtained from X-ray diffraction (XRD) and Xray reflectance (XRR) measurements for cross-reference. Both the thickness and Ge content of Si 1-x Ge x /Si measured by Raman spectroscopy and X-ray techniques are in excellent agreement. In addition to the non-contact and nondestructive nature of Raman spectroscopy, the multiwavelength excitation capability of the system, with high spectral and spatial resolution, are very attractive and powerful for characterization of advanced semiconductor materials, such as Si 1-x Ge x /Si and strained Si, and process optimization.978-1-4244-3815-0/09/$25.00 ©IEEE

Noncontact, in-line measurement of boron concentration from ultrathin boron-doped epitaxial Si1–xGex layers on Si(100) by multiwavelength micro-Raman spectroscopy

“…content in the Si 1-x Ge x layer and has been well studied. 1,[4][5][6][7]13 From the position of the Si-Si peak of Si 1-x Ge x (i.e., shift of the Si-Si peak of Si 1-x Ge x from the Si-Si peak for a Si wafer), Ge content can be estimated. For accurate Ge content measurement, high spectral resolution (~0.1 cm À1 before curve fitting) is required.…”

“…For accurate Ge content measurement, high spectral resolution (~0.1 cm À1 before curve fitting) is required. [4][5][6][7] For thin Si 1-x Ge x epitaxial layers, shorter excitation wavelength Raman measurement results in stronger Raman signals from the Si 1-x Ge x epitaxial layers due to the shallower probing depth. Thus, for thorough and complete analysis, high spectral resolution and multiwavelength Raman measurement capability are necessary.…”

“…For proper characterization and monitoring of high quality crystalline semiconductor materials, very high spectral resolution (typically ,0.1 cm À1 before curve fitting), measurement repeatability, and long-term stability of better than ,0.1 cm À1 are required. The requirements of such a Raman system for Si-based semiconductors, and the necessity of designing a polychromator-based, long focal length (2.0 m) multiwavelength Raman spectroscopy system are reported by Yoo et al [4][5][6] and Tzeng et al 7 A multiwavelength imaging Raman spectroscopy (MRS-300) system was designed to overcome the aforementioned deficiencies in commercially available conventional micro-Raman systems. [4][5][6][7]11 Schematic illustration of the MRS-300 system is shown in Fig.…”

“…1,2 Si 1-x Ge x epitaxial layer thickness and Ge content (x value) are typically measured by Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), secondary ion mass spectrometry (SIMS), photoluminescence (PL), high-resolution x-ray diffraction (HRXRD), and spectroscopic ellipsometry (SE). 1,[3][4][5][6][7] Destructive analysis techniques such as AES, RBS, and SIMS are not suitable for use as a production monitoring technique. Proper characterization of the optical properties of Si 1-x Ge x layers using PL requires measurement at very low (cryogenic) temperatures, a very time-consuming process, and is not practical for in-line monitoring.…”

“…[8][9][10] Micro-Raman spectroscopy of Si 1-x Ge x /Si would be capable of providing accurate information on Ge content and strain in the Si 1-x Ge x layer if an imaging monochromator system was used to improve the common problems (measurement repeatability and stability) in conventional monochromator-based Raman systems with rotating grating(s). [4][5][6][7] Additionally, micro-Raman has some ability for depth profiling by selecting excitation wavelengths. The probing depth (penetration depth) of ultraviolet (UV) Raman spectroscopy is less than 10 nm, whereas the probing depth of visible Raman spectroscopy can extend to~2.5 μm.…”