Sharpening of 3D electrodes

Contacts:

Patricia Vazquez, DTU Nanotech, 45 25 68 38  (pvaz@nanotech.dtu.dk)

Maria Dimaki, DTU Nanotech, 4525 6837 (madi@nanotech.dtu.dk)

Image and close up (inset) of 3D electrodes fabricated by dry etching. Sharpening of these electrodes will be the aim of this project.

Motivation:

Measurements of electrical activity in the brain are challenging, due to the environmental noise. Since the first layers of brain slices are dead, the active areas are buried about 300 µm from the surface. This is the main motivation for developing high aspect ratio needles in silicon, which will be able to penetrate these dead layers and reach the active neuronal sites.

Project Goal:

The major goal of the project is to achieve a sharpening of the electrodes already developed within the NaBIS group. These electrodes are about 70 to 100 µm tall; the tip needs to be sharpened to a diameter of about 1 µm in order to cause the least damage to the live tissue.

Project Description:

The aim of sharpening of the electrode structures will be tackled in several ways:

1. Use of sacrificial structures to avoid underetching.

2. Combination of anisotropic/ isotropic etching 

The student will get acquainted with the clean room technology (plasma etching, photolithography) and work by optimising already developed electrodes and recipes. He/she will achieve a controlled optimization of the process and define the obtained electrodes by impedance characterization.

Depending on available time, characterization and testing of these electrodes will also take place.