Integrated circuit (IC) manufacturing involves two distinct processes—the formation of circuits on bare wafers and packaging.
Slicing semiconductor cylinders.
Forming circuits involves the use of cylindrical pieces of semiconductor material. These cylinders are sliced into thin, circular pieces known as bare wafers. The bare wafers are then oxidized before a complex, microscopic circuit pattern is added via photoresist coatings, etching, pattern printing, planarization, and impurity diffusion.
Once circuits are formed, the dicing process begins. The circular wafer is divided into small squares using a laser or metal blade. During the packaging process, the diced chips are securely attached to a metallic plate known as a lead frame, before being packaged with ceramic or plastic components to create an integrated circuit. Eventually, these IC chips are mounted onto printed circuit boards (PCBs).
The dicing process requires each wafer to be cut along predetermined dicing lines. The edges of the chips will ideally be smooth, but weak laser power or worn or slow cutting blades can cause surfaces to be too rough. This is known as chipping.
Some roughness is always present since the chips are physically cut, but the amount of allowable roughness is carefully controlled. If there is too much roughness, it can cause the electronic device that the chip is part of to fail.
Many manufacturers employ an automated inspection system with low-resolution optics to check for chips’ roughness. Should potential defects be discovered, chips are taken off the manufacturing line to check the amount of roughness with a digital microscope. This solution is not ideal, however, as the physical properties of IC chips often prove challenging for digital microscopes.
IC chip manufacturing.
Challenges of Inspecting IC Chips with a Digital Microscope
Low-magnification digital microscope lenses generally operate with low resolutions, meaning that chipping may be obscured by flare and shading during observation. Additionally, chipping inspection often requires users to measure the distance between the wafer’s edge and the deepest chipping point.
Issues arise, however, in the fact that many digital microscopes do not provide guaranteed measurement repeatability and accuracy, meaning that data may not be exact.
An example of shading.
An example of flare.
Advantages of IC Chipping Inspection Using the DSX1000 Digital Microscope
DSX objective lenses provide high resolution at low magnification, reducing flare and shading. This enables inspectors to better see chipping during low-magnification observations. The DSX1000 microscope also offers an accuracy and repeatability guarantee in installations where calibration work is undertaken by Olympus service technicians, allowing inspectors to be confident in their data.
Olympus LEXT objective lenses.
An IC chip captured with a conventional microscope.
An IC chip image captured using the DSX1000.
Measurement accuracy and repeatability are both important.
High-precision measurement at 2500X magnification.
Products Used for This Application
The DSX1000 digital microscope.
DSX1000 Digital Microscope – The DSX1000 digital microscope offers improved images and results, allowing for quicker failure analysis while helping ensure accuracy and repeatability.
This information has been sourced, reviewed and adapted from materials provided by Olympus Scientific Solutions Americas - Industrial Microscopy.
For more information on this source, please visit Olympus Scientific Solutions Americas - Industrial Microscopy