A diffraction grating is found at the heart of every modern spectrophotometer and yet, despite being used for over 60 years, a practical and efficient characterization tool has proven to be elusive. Part of the challenge can be attributed to the unique angular dependent geometry, or off axis dispersion, of gratings. Here we demonstrate automated grating efficiency measurements of four reflection gratings (300, 1200, 1800 and 3600 grooves per mm). Total measurement time was less than 2 hrs at a maximum of 161 wavelengths per grating. This approach can reduce test times or assist expand quality assurance, or design verification, programs. Automated measurements are performed in hours demonstrating efficiency and ease-of-use advantages when compared to equivalent manually operated systems.
Automated spectroscopic profiling (mapping) of a 200 mm diameter near infrared high reflector (centered at 1064 nm) are presented. Spatial resolution at 5 mm or less was achieved using a 5 mm × 1.5 mm monochromatic beam. Reflection changes of 1.0% across the wafer diameter were observed under s-polarized and p- polarized conditions. Redundancy was established for each chord by re-measuring the center of the wafer and reproducibility of approximately <0.1% was demonstrated by duplicate measurements. These measurements demonstrate informative spatial spectroscopic information can be obtained on large diameter samples. Multi-angle Photometric Spectroscopy (MPS) was used to measure the reflectance and transmittance of a sample across a range of angles (θi) at near normal angles of incidence (AOI). A recent development by Agilent Technologies, the Cary 7000 Universal Measurement Spectrophotometer (UMS) combines both reflection and transmission measurements from the same patch of a sample’s surface in a single automated platform for angles of incidence in the range 5°≤|θi|≤85° (i.e. angles on either side of beam normal noted as +/-). We describe the use of MPS on the Cary 7000 UMS with rotational (Φ) and vertical (z) sample positioning control. MPS(θi,Φ,z) provides for automated unattended multi-angle R/T analysis of at 200 mm diameter samples with the goal to provide better spectroscopic measurement feedback into large wafer manufacturing to ensure yields are maximized, product quality is better controlled and waste is reduced before further down-stream processing.
Spectral reflection (R) and transmission (T) are the fundamental measurements for characterizing the optical properties of materials and optical coatings. Historically the complete characterization of optical materials and coatings for precision optics has been largely accomplished on the basis of normal and near normal incidence measurements due to the experimental simplicity of such an approach. This simplicity, however, is not without compromise. Normal incidence transmission measurements are typically conducted within the sample chamber of a spectrophotometer whilst near normal reflectance measurements require the use of a suitable reflectance accessory. A consequence of this approach is that there is never any guarantee that reflectance and transmission measurements are made from exactly the same patch on the sample due to sample repositioning during the significant changes in instrument configuration between R and T measurements. Multi-angle Photometric Spectroscopy (MPS) measures the reflectance and/or transmittance of a sample across a range of angles (θi) from near normal to oblique angles of incidence (AOI). A recent development by Agilent Technologies, the Cary 7000 Universal Measurement Spectrophotometer (UMS) combines both reflection and transmission measurements from the same patch of a sample’s surface, without sample repositioning, in a single automated platform for angles of incidence in the range 5°≤|θi|≤85° (i.e. angles on either side of beam normal noted as +/-). In this paper we describe the use of MPS on the UMS with rotational (Φ) and radial (ζ) sample positioning control. MPS(θi,Φ,ζ) provides for automated unattended multi-angle R/T analysis of multiple individual samples (up to 32 pieces, 1 inch diameter) or mapping of single larger diameter samples (of up to 8 inch diameter). Examples are provided which demonstrate reduced cost-per-analysis in high volume multiple sample testing as well as spatial spectroscopic information obtained on large diameter samples.