Localised Electron-induced Laser absorption (LEILA)

• Applicant: Dr. Kristian Cvecek
• Subject Area: Joining and Separation Technology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504166000

The ability to create surface structures the size of few nanometers on dielectric materials is important for many modern applications in optics and electronics. Typical processes for this are EUV- and electron beam lithography. However, due to high complexity or low efficiency these processes are very expensive or very slow. Using direct laser structuring is more efficient and very flexible for creating surface structures, but its achievable resolution is limited due to the diffraction limit of the used wavelength.In this project a method for surface structuring will be developed that enables the fabrication of smallest structures with resolutions achievable by electron beam lithography combined with the efficiency of a direct laser ablation process. An electron beam from a Scanning Electron Microscope (SEM) creates a locally increased plasma density in a dielectric material, e.g. fused silica, via inelastic scattering. The electron beam has such low energy that it does not damage or otherwise modify the material. A laser pulse with fluence below the modification threshold of the target material interacts with the localised plasma density so that the plasma density is increased via avalanche ionisation significantly to the point that the material is ablated or otherwise modified. The high resolution of the electron beam and the resulting localised electron density allow for process resolutions on the order of few nanometers without using complex lithographic- or chemical etching processes. The proof of principle of this process will be studied experimentally using fused silica and a ultra short pulsed laser at 1064 nm. To this end an experimental setup based on a SEM as electron beam source will be set up to study the various effects of parameters such as the delay between electron-injection and laser pulse, the acceleration voltage of the electrons and laser pulse energy on the process using fused silica as sample material. The process characteristics such as achievable ablation resolution, efficiency, speed as well as process stability will be analysed for single and multiple LEILA-process applications to the work piece.

• DFG Programme: Research Grants