Equipment feature: MEMS Plasma Asher Microwave Plasma System 210 This page is also available in printer friendly format (pdf) - click here

Membrane MEMS device requiring a far reaching under etch

Introduction
The National Access Programme Committee last year approved the purchase of 3 new pieces of equipment to further enhance the facilities already available to NAP users.
One of these purchases was a new plasma asher and was installed in June 2009 at Tyndall.

 

PVA-TePla Microwave Plasma System 210

A plasma asher is a type of plasma etching system. Micro and nano fabrication uses different kinds of plasma etching systems for most of their etching steps. Plasma etch systems etch material by atoms, radicals, and ions created in a plasma.  A plasma asher differs from other plasma etching systems in that the charged particles are minimized and isotropic etching is preferred, or the same etch speed in every direction. The system is designed to minimize ion-bombardment and have the reactive species transport to the surface solely by diffusion.  Plasma ashers can be used for photoresist stripping, wafer cleaning, sacrificial layer etching of MEMS devices, surface activation, and low temperature ashing of polymers. Formerly, most plasma ashing was performed in systems build for resist stripping which did not allow for much process control. A new plasma asher was needed that could be optimized for different applications.  The PVA-TePla microwave plasma system 210 was chosen with three aspects in mind: versatility, automated process control with data logging, and cleanliness.

New Plasma Asher installed at Tyndall (June 09)

Features
• The plasma is created by a 600 Watt microwave generator at 2.45 GHz. 
• Three different process gasses can be pumped into the chamber.
• Pressure, temperature and plasma intensity are measured in the chamber and logged.
• Cooled platten for low temperature processing.
• Industrial PC for automated processing operations.
• A clean quartz chamber that can accommodate a wafer boat of 25 200mm wafers as well as wafer chips.

Examples of applications

The intentional use of the Plasma asher is for sacrificial layer etching of MEMS devices. The sacrificial etch step releases the suspended structures of MEMS devices. This step greatly influences the mechanical properties of the suspended structures. With the new plasma asher we hope to be able to underetch farther and minimize variations in the mechanical properties of MEMS devices.  Another application is plasma activation of materials before bonding. This requires low temperature processing and a very clean chamber. The third application this system is intended for is for plasma oxygen ashing of dissimilair polymers for pattern transfer. We hope to be able to improve the etch selectivity by improved process control and data-logging. The microwave plasma source should also reduce ion bombardment which is important when processing delicate polymers. With the National Access Programme, we hope we can increase the number of applications further. If you are interested in using the plasma asher for your field of work, please let us know.

Nano structured films by plasma etching of self-aligned block copolymers

For further information and to discuss your technical requirements please contact:
Jaap Verheggen (NAP engineer) at +353 (0)21 4904039 and jaap.verheggen@tyndall.ie

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