Etched silicon wafers are possibly the most difficult product to manufacture at scale. Inevitably a certain number of wafers will not pass initial inspection due to manufacturing defects, but it would be impossible to identify many of these defects with the naked eye. In fact, semiconductor defects are usually so small and challenging to detect, that even the highest-resolution 3D laser line or snapshot sensors have trouble resolving them.
For these types of challenging applications, LMI offers the Gocator 5500 Series which leverages line confocal imaging (LCI) technology to accurately measure and inspect challenging silicon wafers at every stage of the semiconductor manufacturing process.
With a patented dual-axis design, a Gocator 5500 Series sensor can measure microscopic-scale dimensions and tomographic structures with high accuracy and speed. It works by projecting a thin line of light onto a target surface and capturing the reflected light with a line-shaped confocal aperture. The confocal aperture filters out any out-of-focus light and only allows the in-focus light to reach the sensor. By scanning the line of light across the target, the sensor’s built-in software can create a 3D point cloud of the scanned surface.
LCI technology has several advantages over conventional optical measurement methods such as laser triangulation or structured light. For example, LMI’s smart 3D line confocal sensors can measure transparent, translucent, curved, and shiny objects and are insensitive to factory light conditions.
Gocator 5500 (G5) sensors can also inspect layers within transparent materials such as glass or plastic, and provide high-contrast intensity images that can detect surface defects such as scratches, cracks, stains, and foreign materials within individual layers. All this with sub-micron resolution and repeatability at high scan rates up to 16 kHz with PC acceleration.
Semiconductor manufacturing is extremely complex. It involves hundreds of steps that require precise control of temperature, pressure, chemical reactions, and light exposure. Any deviation from the optimal conditions can result in defects or variations that affect the functionality and reliability of the final product.
Semiconductor manufacturers need to inspect every wafer at every stage of the process using advanced metrology and inspection tools including:
Sorting: G5 sensors are used to measure the thickness, flatness, bow, warp, and notch alignment of silicon wafers with sub-micron accuracy and repeatability. This enables fast and efficient sorting of wafers according to their quality and specifications.
Polishing Pad Inspection: Scanning the surface profile and texture of wafer polishing pads with nanometer resolution. This allows monitoring of pad wear and condition, as well as the detection of defects such as scratches, cracks, or foreign particles.
Dimensional Measurement and Defect Detection After Scribing: After laser dicing and/or scribing is complete, G5 Sensors are used to measure the accuracy of the groove placement, groove depth, and kerf width of the wafer scribing to prevent defects such as die chipping. This allows for more usable die per wafer and ensures maximum quality and processing speeds for the highest production throughput.
Inspection of BGA and PGA Position, Height, and Radius During Assembly and Test IC
Gocator 5500 sensors can accurately measure ball height, ball position, and other dimensional information of the ball with a diameter of less than 50 microns. They can also inspect the height and position of the PGA pins to ensure that there are no poor contacts created during the subsequent insertion and removal process, and to prevent defects such as pin damage caused by positional errors. The flatness and height of joint position before welding is also inspected, to minimize the breakage of each solder joint after welding is completed.
Inspection of Silver Epoxy During Die Application
Gocator 5500 sensors accurately measure the surface area of coated silver epoxy in each lead frame area, as well as the height or thickness of the epoxy glue bead. For example, the can detect bubbles and measure the thickness of the glue bead.
Defect Inspection During Wire Bonding Process
Gocator 5500 sensors provide high-accuracy measurement of the arch height and position of the wire whether it be gold, copper, or aluminum. In addition, these line confocal sensors can detect defects such as breaks or bends in the wire.
Dimensional Measurement During Ball-Bumping Process
Gocator 5500 sensors accurately capture the diameter and height or thickness of the ball down to 2.5 microns. The sensors are also used to inspect the coplanarity between all ball bumps, detecting any height variation that can cause uneven distribution of force, die fractures, and open circuits.
Dimensional Measurement and Defect Inspection after Final Packaging
Gocator 5500 sensors capture the length, width, and height of the chip after final packaging. These sensors can also output high-resolution 2D grayscale images to detect defects such as pits and scratches.
Today there is a growing list of applications that LMI has solved using Gocator 5500 sensors in the semiconductor industry. Gocator 5500 sensors are the industry’s first to combine LCI technology with a web-based interface, fast scan rates, onboard software, and multi-layer surface scanning ability. These sensors also run GoPxL, LMI Technologies’ latest IIoT vision inspection software that comes with smart features such as built-in measurement tools, smart filters, and a custom HMI builder.
For more information: www.lmi3d.com