Nikon boosts quality control with automated system for wafer inspection

Nikon’s Industrial Metrology Business Unit has unveiled its new solution for wafer ID code inspection. The industrial measurement, inspection, and quality solutions provider hopes its new solution will assist silicon wafer manufacturing companies with quality control levels. After ID codes have been inscribed onto the surface of a wafer with a laser, Nikon’s solution aims to complete a rapid and comprehensive inspection, with high levels of accuracy.

About the silicon wafer manufacturing industry

Silicon wafers are an important element in the manufacturing process of the world’s most commonly used electronic devices (including TVs and mobile phones). This is because these particular types of wafers are valuable semiconductors that can help the circuits within these devices run smoothly. While silicon wafers might not be the most effective of all the wafers, they are the most suited for mass manufacturing. Additionally, silicon is one of the most abundant elements on the planet and is incredibly cost-effective.

How does Nikon's new wafer ID code inspection solution work to boost quality control levels?

The new solution is based on Nikon’s NEXIV VMZ-K3040 confocal video measuring system, which features dual 2D and 3D optics for measuring the various characters that identify each wafer. Then the NEXIV is linked to an automatic wafer loader that works by transferring semiconductor wafers from a front opening unified pod (FOUP) to the video measuring system. After this process is complete, the wafers are returned without the need for any manual assistance.

The machine’s ability to reliably read the wafer ID codes throughout the hundreds of processing steps in the FAB is critical to avoid errors and waste, whilst also ensuring the overall success of the operation. Therefore, the semiconductor equipment and materials international (SEMI) optical character recognition (OCR) reader must correctly identify the unique serial code and ensure that it correlates to the correct wafer. However, over time laser marks can wear out, making this process difficult to complete. This is where Nikon’s new solution comes in, as it ensures that the laser marks are at the optimum depth and dimensions, hopefully resulting in the ID code always being able to be read, even after processing and shipment.

The inspection of the laser ID marks is completed after the inscription process to check that they meet quality standards. NEXIV completes the automated video inspection routine with high levels of accuracy, as it can capture the true position of every feature. Additionally, the high throughput of the automated procedure is also consistent with integration levels on the factory floor. With these high levels of speed, real-time information can be provided to the user displaying any deterioration in marking quality.

The Nikon inspection and reporting sequence for OCR characters follows this pattern:

• It starts with the use of a circular calliper with brightfield 2D optics, which measures the laser mark and then calculates the diameter and coordinates of the centre.
• After this, the height, width, spacing, and total line length are measured.
• Then, using confocal 3D optics, laser mark depth is determined.

The NEXIV VMZ-K3040 has the ability to switch between the brightfield and confocal modes with ease during a single inspection program, providing the user with improved accuracy, a seamless inspection process, and higher speeds. This advantage is not currently seen with similar systems.

Key features of the NEXIV VMZ-K3040:

• A multi-functional confocal video measuring system.
• Incorporates confocal technology, brightfield with a 15x zoom, and a TTL laser AF.
• Compatible with 300mm wafer measurement at semiconductor fabs.
• Ability to complete 2D and 3D geometrical measurement inspections.
• Can be used for measurements of a variety of bump heights on advanced IC packages including wafer-level CSP.
• Has the ability to complete inspections of highly complicated structures of MEMS and probe cards. 

What is the impact of Nikon's new wafer ID code measurement application?

Nikon believes that its creation of the wafer ID code measurement application has further certified its aim of raising the prevalence of real-time inspection in industrial production, with a focus on automatic feedback to ensure line control and that metrology is a driving force in the manufacturing process.

This particular approach is also known as Quality 4.0, which essentially means that all products at the end of the line are good. The alternative approach results in using measurement as an arbiter of whether a part has passed, failed or needs to be scrapped.

“This quality control solution we have developed for the semiconductor manufacturing industry has already proved successful in foundries around the world,” said Goh Wei Chen, Integrated Solutions Manager at Nikon’s centre in Singapore. “The high accuracy and throughput achieved are proving to be a compelling sales proposition for this crucial quality control function.”