The semiconductor packaging industry continues to advance, with new designs adding more layers, finer features and more I/O channels for higher bandwidth and lower power consumption. Manufacturers face an increasing need for high-precision inspection and measurement to detect defects and improve process control.
Phase shift profilometry (PSP) is widely used for 3D automated optical inspection (AOI) by electronics manufacturers assembling printed circuit boards (PCB) with surface mount technologies (SMT). PSP is also used for solder paste inspection (SPI) by PCB manufacturers, and for dimensional measurements typically performed by coordinate measurement machines (CMM) in a variety of applications. PSP measurements are highly accurate and can be orders of magnitude faster than alternative methods. However, conventional PSP measurements can be significantly degraded by inaccuracies caused by multiple reflections between shiny surfaces on the inspected object. Effective suppression of these reflections is critical for accurate measurements.
Multiple Reflection Suppression (MRS) sensor technology addresses this challenge by comparing data from multiple perspectives and fringe frequencies to identify and reject these spurious signals. The MRS sensor’s unique optical architecture and the system’s proprietary image fusing and processing algorithms provide accurate 3D characterization that is several times faster than conventional PSP.
A new, ultra-high-resolution MRS sensor has been developed for advanced packaging processes control in what has been called the “middle-end” of the manufacturing process, where traditionally front-end and back-end processes overlap. The new sensor provides sub-micrometer accuracy on features as small as 25µm. And, while retaining its ability to reject spurious multiple reflections, it adds the ability to capture and analyze specular reflections from shiny surfaces of solder balls, bumps and pillars, thus allowing accurate inspection and 3D metrology of these critical packaging features. With data processing speeds in excess of 75 million 3D points per second, it delivers production-worthy throughput greater than 25 wafers (300mm) per hour.