Measurement technology allows for rapid process monitoring in diode production

Optical measurement technology supports quality control at the laser diode manufacturer Lumics GmbH...

The measurement technology specialist Confovis GmbH, Jena uses detailed measurement data to provide comprehensive information concerning the process and product quality for the laser diode manufacturer Lumics GmbH from Berlin. Lumics GmbH needed a measurement system for the measurement of microstructures which is able to analyse a wide variety of samples quickly, reliably and non-destructively. With the CLV150 confocal measurement system, surface features which are in the micrometre and nanometre range can be precisely specified, manufacturing processes can be significantly improved and the quality of the diodes produced can be monitored more accurately — entirely in favour of the end customers who benefit from the improved performance and service life of the diodes.

Lumics GmbH develops and produces high-performance laser diodes and diode laser modules. It is one of few companies in the industry to have in-house chip manufacturing. “We are able to deal individually with customer requests and develop and supply appropriate diodes,” says Alexander Kaebe, Process Manager at Lumics. One of the company’s major markets is the medical sector. Here, the modules are integrated as OEM products into complex devices. In addition, Lumics also handles applications in material processing and in the field of sensor technology. When it comes to quality, the customers expect reliable and long-lasting products. To achieve this, consistent quality must be guaranteed even with large delivery volumes over long periods of time. Quality control extends across all processes right through to the finished product. The diodes from Lumics are tested individually and undergo a 100% quality control.

Measurement technology with a decisive advantage

Not least as a result of the construction of a new production area, lithography, the company needed to procure the corresponding measurement technology to support both quality control and process troubleshooting. For this, the Berlin-based company relied on high-precision measurement technology from Confovis GmbH. With its patented confocal measurement process based on structured illumination microscopy (SIM), Confovis offers a clear alternative to a multitude of common processes and systems. “Above all, the possibility of being able to take measurements quickly, precisely and non-destructively was a crucial factor in the decision to go with the measurement system from Confovis,” Mr Kaebe continues. “Previously many different measurement systems such as REM, AFM, microscopes, etc. were needed in order to obtain the necessary information. Now we can do everything with a single measurement system.” The measurements with the REM were previously very time-consuming owing to sample preparation and were not non-destructive. When measuring the structures using the available microscopes, the resolution was not sufficient to carry out depth and thickness measurements. It was possible to solve both problems through the procurement of the Confovis measuring device.

High-resolution, quick and ideally suited to transparent coatings

With the ConfoSurf CLV150, Lumics is now able to measure microstructures, in particular structure dimensions, surface properties and thicknesses, precisely and analyse them. The optical measurement system is particularly useful in the optimisation of the coating process since transparent coatings need to be applied here. Owing to the patented measurement technology, Confovis is able to reliably measure reflective materials and transparent coatings. For Lumics, this makes it possible to analyse the coating thickness and quality of the coating sidewalls with little effort and in a non-destructive manner.
With a vertical resolution of less than 3 nm, in accordance with VDI 2655, the CLV150 asserts itself as a measurement device for demanding measuring tasks. Depending on the application, the confocal measurement process provides the option of measuring and analysing a wide variety of surface structures with high precision. This is required if, for example, the roughness needs to be measured and analysed on the basis of profiles in accordance with DIN EN ISO 4287/4288 or in accordance with DIN EN ISO 13565 or on the basis of surfaces in accordance with DIN EN ISO 25178.

Non-destructive measuring within the process

Lumics monitors etching depths and coating thicknesses, for example, easily and quickly using the Confovis measurement system. “This, especially, is what allows us to determine the depth during the etching process very precisely without stripping the coating from the wafer completely before measurement and re-coating it again after the measurement,” says Alexander Kaebe. The parameters measured are compared with the calculated target values. These are heavily dependent on the epitaxy of the substrates and must to some extent be adjusted very individually. It is therefore useful to measure the etching depths or coating thicknesses again precisely between the process steps with the CLV150.
The measurement system offers very intuitive operation and thus also facilitates training on the device. The measurement data recorded with the ConfoVIZ® measurement software is subsequently transferred into the MountainsMap© analysis software. There, among other things, it is possible to quickly and simply set up and create protocols for error analysis. Confovis thus supports customers in the course of development and in the monitoring of production processes.

“We are already noticing a significant improvement in process analysis thanks to the new measurement technology,” says Kaebe. The quality is improved as a result, which is beneficial to the end customers particularly with regard to service life and performance. Lumics also states, that they were able to continuously increase the process yields. The processes can be actively optimised for the newly created lithography division. The company also sees a clear benefit with the measurement system for other future applications such as testing surface quality for materials which are purchased.