Alfamation Announces Functional Tester for Diffractive Optical Elements (DOE)

DOE_wafer_level_optics
Publication date: 3 December 2018 12:00 AM

Lissone, Italy – December 03, 2018 - Alfamation, a leading provider of state-of-the-art turnkey test and measurement solutions, has launched its Wafer Level Tester for Diffractive Optical Elements (DOE), for high-volume micro-optics testing in a production line. This gives manufacturers quick and precise feedback to optimize and monitor their processes, as well as full wafer mapping and quality control to identify defective elements.

A DOE is as an optical structure on a glass substrate acting as a lens, such as in the camera module in a smartphone. DOEs are increasingly used today, for example for facial recognition in a phone. This machine is meant to test optical properties mainly at wafer level, although diced parts loaded on a tray can be tested too. Wafers up to a diameter of 400 mm with thousands of DOEs can be tested and qualified in one fully-automatic test run at high speed.

“The new system uses an innovative measurement method, with a custom-designed ‘relay optic’ that collects all light coming out from the DOEs over a wide field of view and focuses it on a large camera sensor” said Mauro Arigossi, CEO of Alfamation. “With this methodology, the sensitivity is higher than competitor’s ATE based on a projection screen, because all light to be measured goes directly into the sensor, which enables faster tests and higher throughput in production.”

The DOE tester includes a custom-made wide angle conoscope lens coupled to a high-resolution camera. A collimated laser beam with controlled diffraction optical system is used to stimulate the DOE, which creates a diffractive pattern made of numerous output beams. The laser source is a super stable fiber-coupled laser diode paired with a series of beam-shaping optical elements that allow flexible beam shape and polarization state to meet customer-specific requirements.

The output image sensed is then transferred to the computer to be processed by a fast algorithm which applies on the diffraction pattern different metrics like single spot uniformity error and total power efficiency of the DOE. The system provides a maximum field of view (FOV) of 90° by 90°, with resolution over the whole FOV of 0.25°.

The new ATE is based on a high-end wafer handling system, with robust design and a flexible architecture. An automated wafer loading/unloading feature is optional, helping to save time and reduce labour costs on the production line.

The machine can achieve a testing speed above 3000 UPH (Units Per Hour), with an average measurement time of 1 second per sample. This is a key factor in shorten production time and reduce the testing cost per unit over the machine’s lifetime 

The DOE tester can be customized under specific requirements, improving the design flexibility. It is based on a high repeatability positioning table equipped with alignment tools and an automated visual inspection system that can fulfil the most demanding optical tests. Additionally, an automated tip/tilt correction of the chuck can fix, module by module, the wafer tilt and height variation due to process issues like wafer warpage. Lastly, a barcode/OCR reading system allows the traceability of each module of the wafer.

The ATE has a small footprint to be cleanroom-friendly, measuring 1350 mm (height) by 1330 mm (width) by 675 mm (depth). It is compliant with CE/UL safety standards and offers ISO 5 cleanroom compatibility.

Alfamation’s SuperNova software solution, based on NI TestStand, allows an easy integration with a database for result storage and analysis, the management of test diversities and the test sequence development and customization.

Alfamation has long experience in this market, and has been a supplier to major telecom and micro optics companies since 2000, including supplying test equipment for wafer-level optics for smartphones. It has the necessary mix of expertise in optics, electronics, software, integration and automation   required to develop such a complex ATE and it is a strategic partner for all the players of this market