The Next Generation of Germanium Substrates: Expoger^TM

Umicore Electro-Optic Materials, Watertorenstraat 33 – B2250 Olen (Belgium)

Email: pieter.arickx@eu.umicore.com

Abstract

Umicore has been the leading Germanium substrate manufacturer over the last 20 years. We are only able to maintain that position by constantly improving the quality of our product. In this work, Umicore wants to present how it will continue this tradition by adding even more value to its product.

In the beginning of 2014 we proposed to our customers to help them in achieving their yield improvement goals. Two main concerns were expressed: the breakage rate in their production line and non-uniform epi-growth. After two years of development, Umicore has bundled these two improvements into a new product. The ExpoGer^TM wafer combines a better mechanical yield with a uniform, epi-ready surface enabling a narrower distribution of the electrical performance.

The breakage rate of the customers is related to the wafers that suffer from early failure. The percentage of early failures is related to its thickness. With the trend towards even thinner substrates, it is important to add features that reduce the percentage of early failures. Two features are crucial: the shape of the substrate edge and the stress relief etch, which influences the wafer strength.

Just as for the strength, two distinctive aspects define the surface quality. On the one hand, there are the number and size of surface defects, which have an important influence on the metal-organic chemical vapour deposition (MOCVD) growth performed at Umicore’s customers. On the other hand, drying marks, which are invisible to the naked eye, may lead to a local, non-uniform growth and they can be a precursor to time dependent haze issues.

Umicore is able to demonstrate the impact of the ExpoGer^TM processes on the strength and surface quality of its wafers and thus on the production yield of its customers.