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Semiconductor Manufacturing Inspection with Smart 3D Line Confocal Sensors from LMI

Updated: Aug 21, 2023

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 LMI’s highest-resolution 3D laser line or snapshot sensors have trouble resolving them.


For these types of challenging applications, LMI offers the Gocator 5500 Series. Shown in Figure 1 is a Gocator 5512 sensor, which leverages line confocal imaging technology to accurately measure and inspect these 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.



Fig. 1: Gocator 5512 Smart 3D Line Confocal Sensor (Copyright LMI Technologies Inc., 2023)


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 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.


That’s why semiconductor manufacturers need to inspect every wafer at every stage of the process using advanced metrology and inspection tools.


Fig. 2: Gocator 5500 Series line confocal sensors are used for wafer sorting and dimensioning, in addition to many other essential applications in semiconductor manufacturing inspection (Copyright LMI Technologies Inc., 2023)


Let’s take a look at some semiconductor manufacturing quality control applications that are solved with Gocator Smart 3D Line Confocal sensors:


Wafer Inspection


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.


Fig. 3: Semiconductor Wafer Inspection with Gocator 5500 Series Line Confocal Sensors (Copyright LMI Technologies Inc., 2023)


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 visit our Clusterpartner website.

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