A GUIDE

Wafer Surface
Analysis
Detecting the defects withlaser solutions
The Challenge
Semiconductors need to be inspected for defects during every part of the manufacturing process.
Accurate and precise results are critical in order to prevent unnecessary product wastage andcost to the manufacturer. Many of the inspection processes associated with electronics inspection
utilise lasers, due to the inherent levels of measurement precision and resolution that these
inspection applications demand. Whilst the measurement and inspection value of laser based
technology is unsurpassed, deploying such technology often presents a number of key challenges
for the manufacturer:• Requirement for reliable, long-lifetime lasers• Maintenance free
• Passive, water-free cooling• Unique laser speckle patterns• Exceptional beam quality• Zero laser power fluctuations• Requirement to image smaller features.

What is Electronic Inspection?
Electronic inspection involves the detailed examination of critical components for surface defects
or identifying marks. This technique is particularly prevalent in silicon wafer manufacturing,where the wafers are used in the manufacture of semiconductor microchips. At each stage ofthe semiconductor wafer process, detailed inspection needs to be performed to ensure that themanufactured product meets specification, and to identify even the smallest surface defects. Thesilicon wafer is inspected at least three times throughout the wafer manufacturing process:•••Upon creation of the semiconductor wafer
Incoming Quality Control at the chip plant
During and after development of the microchips

Schematic of Semiconductor Wafer Inspection

Photograph of Semiconductor Wafer Inspection©2021 Novanta Corporation. All rights reserved.

Wafer Surface Analysis

Any surface defect renders the chip unusable and is a cost to the manufacturer. If too many
defects are detected, it is often more economical to stop production of that wafer early in theprocess and scrap it rather than let a defective wafer continue through the process.
Lasers play a key role in semiconductor wafer inspection. During this process, laser light is rapidly
scanned across the surface or edge of the silicon wafer using a high speed polygon scanner(such as those from Cambridge Technology); with any changes or deviation in the reflected lightindicating a defect on the wafer.

The Solution
In order to meet the demanding requirements of this application lasers need to be carefully
selected. This ensures that their properties can be leveraged in such a way as to balance highthroughput with accuracy, and can be rapidly scanned whilst ensuring absolute compliance toclean operating environments.
The axiom LE, is a new type of laser designed by Laser Quantum to precisely address thisapplication. Axiom LE is a high power, air-cooled laser delivering 12 W of power without the needfor liquid cooling – a feature which is widely prohibited in this application.
As with many mission-critical applications, 24/7 reliability together with long service lifetimes arerequired. Laser Quantum has a long heritage in developing lasers for mission-critical industrial
applications, following a design philosophy that delivers the very highest performance andreliability over the longest lifetimes.
Designed with the semiconductor system builder in mind, Laser Quantum has designed the axiom
LE laser specifically to address the requirements of wafer inspection, and is able to offer OEMs
involved in wafer inspection a series of features that are unique to this application. Thanks to itsnovel cavity design, the axiom LE laser can be supplied with a customized bandwidth profile thatis able to deliver a speckle pattern dedicated to the specifics of the inspection application, alongwith exceptional beam quality and active noise suppression.
Advanced integrated power feedback is a defining feature of all Laser Quantum products. With
this feature, the laser is able to intelligently maintain and optimize its own power levels in orderto maintain beam specification with no power fluctuations, making it truly the laser of choice forhigh reliability 24/7 wafer inspection applications.
With its strong focus on OEM integration, Laser Quantum understands the importance of handsfree, remote maintenance and service. For this reason, every Laser Quantum laser can be securely
accessed from any location on the globe in order to optimize performance or to troubleshoot.

axiom LE laserfrom Laser
Quantum

Novanta Advantage
Through our photonics technologies, we deliver finely tuned laser sources and beam delivery
systems that enable customers to improve their process, increase productivity and achieve
breakthrough performance. We bring unprecedented value to our customers through engineerto-engineer collaboration, a wide range of application expertise, and state-of-the-art applicationlabs.
Contact us - photonics@novanta.com©2021 Novanta Corporation. All rights reserved.