photochemical etching of silicon nitride surfaces and freestanding membranes

INV-18084

 

Silicon nitride is a widely used material as a component in solid-state devices for many applications such as biotechnology, electronics, photonics, and other areas. Processing silicon nitride films in order to provide defined topographical features is a major part of the silicon industry, and it has been a routine practice for micro and nanostructure fabrication. Lithography in silicon nitride typically requires aggressive dry or wet chemical treatment, which can be accomplished using a photolithography or electron beam mask layer followed by chemical processing.

 

In this invention, Northeastern researchers propose a novel idea for a photochemical method for etching either deposited silicon nitride films or freestanding silicon nitride membranes with control over the thickness achieved by optical feedback. Detailed research shows that there is a deterioration of a silicon nitride membrane after a high power visible laser beam (in the intermediate portion of the visible spectrum, blue to orange) is focused on a membrane. Recent observation shows some insight into the chemical mechanism responsible for the etching, which seems to be promoted by chloride ions. 

The following demonstrated methods are:

- Etching on freestanding membranes using a focused laser to form a thinned region that is sub-µm in size

- Locally etching the silicon nitride film off of a glass substrate

 

- Can directly write a pattern of nitride etching without the need of a lithographic mask

- No hazardous gases or liquids are needed for processing

- Can perform single step micro-nano fabrication 

- Useful to polish rough surface of silicon materials 

 

- Biotechnology

- Electronics

- Photonics

 

- Licensing

- Research collaboration

- Partnering