The kSA MOS Ultra-Scan is a flexible, high-resolution scanning curvature and tilt measurement system. Based on the proven technology of our standard in situ kSA MOS system, the Ultra-Scan uses a laser array to map the two-dimensional curvature of semiconductor wafers, optical mirrors, lenses - practically any polished surface. The system provides up to 200mm x,y scanning range with 2 µm resolution. Optionally, larger scanning stages (up to 300mm x,y scanning range with 4 µm resolution) are available. Scans are fully programmable for selected area, line scan, or full area map. The system also provides quantitative film stress analysis with full area map for 50-200mm wafers by first scanning the bare substrate and then re-scanning the sample post-process.
Figure 1. The kSA MOS Ultra Scan from k-Space Associates.
Applications for the kSA MOS Ultra-Scan
Applications kSA MOS Ultra-Scan include:
• Semiconductor Wafers (Si, SOI, Compound Semi)
• High Performance Optical Coatings (mirrors, lenses, glass)
Examples of Use on Advanced Silicon Materials
Figure 2. 10 consecutive wafer line scans showing excellent reproducibility from MOS technology.
Figure 3. 2D curvature mapping of SiN4 dielectric thin film deposited on bare silicon wafer. Curvature can be compared with bare substrate to determine stress induced by the thin film.
How The kSA MOS Ultra-Scan Works
Figure 4. Schematic of how the kSA MOS Ultra-Scan works.
Stress in thin films induces curvature in the substrate. The kSA MOS Ultra-Scan system measures localized curvature by monitoring the deflection of parallel beams of light. Curvature mapping of the entire sample surface is performed by 2D iteration via high precision, servo motor controlled x-y stage.
Figure 5. Stress in thin films induces curvature in the substrate. The kSA MOS Ultra-Scan system measures localized curvature by monitoring the deflection of parallel beams of light. Curvature mapping of the entire sample surface is performed by 2D iteration via high precision, servo motor controlled x-y stage.
Benefits of Using The kSA MOS Ultra-Scan
Benefits of Using the kSA MOS Ultra-Scan include
• Map the 2D curvature of semiconductor wafers, optical mirrors, lenses, or virtually any polished surface
• Patented Multi-beam Optical Sensor (MOS) technology
• 200mm x,y scanning range with 2 µm spatial resolution
• Quantitative film stress analysis map
Features of The kSA MOS Ultra-Scan
The kSA MOS Ultra-Scan features:
• Real time plotting of curvature, radius of curvature, stress-thickness product, and tilt
• Vibration controlled environment
• Scans fully programmable for selected area, line scan, or full area map
Standard Specifications of the kSA MOS Ultra-Scan
Any surface with >2% reflectivity
Max Scan speed
Spatial Scan Resolution
User scalable, up to 2µm (with higher resolution stages available)
Up to 100km (1 sigma)
Average Tilt Repeatability
<1 microradian (1 sigma)
Average Curvature Repeatability
<2x10-5 1/m (1 sigma)
Patented 2D Array Technology
2D laser array directly measures curvature without using rotating mirrors or complex optics.
A single laser is used to generate a two-dimensional array. Changes in the beam spacing are used to determine curvature and subsequent stress via pre and post-mapping. In this way, the MOS Ultra-Scan measures a true physical property in two dimensions that other systems, which use point/line scan with mechanical restoring technique, cannot capture.
The ability to directly image and view the entire reflected laser array greatly simplifies use and alignment compared with other position-sensitive detectors. Simultaneous detection of the array makes the measurement inherently less sensitive to sample vibration compared with scanning-laser systems, leading to increased curvature resolution capability (10x). And because all the laser spots move together at the same frequency, movement or tilt is not detected as a change of curvature. Through the use of simple image processing and data analysis algorithms, the Ultra-Scan can easily detect micron-sized changes in spot position.