With semiconductor technology moving to ever smaller feature sizes, enabling the continuation of Moore’s law, there is an increasing demand for innovative key components. Thin film membranes are examples of such key components. These are used in systems which employ high-energy beams for improving the spectral content or spatial distribution of such beams, or for providing transparent gas, pressure or particle barriers between different parts of a system.
Philips MEMS foundry has been leading in process development and manufacturing of ultra-thin membranes for over 10 years. Already back in 2012 it laid the basis for the current state of art EUV lithography membranes. Working with leading companies in the field ever since, important steps have been made in membrane technology. For example, 50 nm freestanding polysilicon-based membranes have been developed and manufactured for EUV applications, featuring transmission values in the range 80-90 % and sizes over 100 cm2. Process development is ongoing for even lower thicknesses. These membranes are multi-layer structures with precisely engineered stress levels. Material and design choices provide added functionalities, tailored to customer requirements.
The colorful picture below shows a collection of prototype membranes of 1 cm2 size and a thickness of a few tens of nanometer. The color variations are caused by differences in thickness and material.
Other examples of enhanced membranes are shown in the next picture. Top left: 5 cm2, 50 nm thin membrane with a reinforced grating on top. Top right: SEM image (80 µm x 80 µm) of the reinforced grating. Bottom left: 130 mm circular honeycomb grid membrane. Bottom right: SEM image of the honeycomb grid membrane of 6 µm diameter.
