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/Job opportunities/Investigating interactions between plasma and ultra-thin materials for high-throughput atomic etching in future nodes

Investigating interactions between plasma and ultra-thin materials for high-throughput atomic etching in future nodes

PhD - Leuven | More than two weeks ago

Explore the frontiers of atomic-level processing with our extensive know-how on plasma and materials for nanoelectronics applications and state-of-the-art process equipment.

With the exponential growth of data generation, the storage and processing capabilities must scale at a similar pace within constrained space, cost, and power budget. The reduction of the dimensions of the memory and processing elements has been maintained until now by a combination of improvements in lithography, etching and the introduction of new materials. The next generation of conventional lithography, called High Numerical Aperture Extreme Ultraviolet Lithography (“High NA EUV”), will force the use of extremely thin layers, typically a dozen atom thick, whose main purpose is to be used as a protection layer of the material underneath. Two major issues arise from it. The most obvious one is the extreme etch resistance these few atom-thick films will need to have to the plasma used to transfer the patterns defining the device to the underlying materials. Also, at such extreme thickness, materials can become transparent to plasma, thereby failing in their purpose as a protection from the areas which should not be etched. For many combinations of materials, this is the final physical limit of plasma etching as it used to be performed for the last five decades.


Thankfully, some alternative ways of etching at such dimensions have already been worked on, among which atomic layer etching (ALE). This approach is based on the difference in the amount of energy needed to induce desorption of volatile molecules from a surface, and is usually introduced as a two-step cyclic process: saturate a surface with some defined molecule and then trigger desorption by ion bombardment with adequate energy. The choice of the correct molecule to desorb from the surface of the material to be etched and not from the protection material, along with a fine control of the energy of the incoming plasma species, is defining the good performance of an etch process. The main drawback of such an approach is its very poor throughput: each step of every cycle is several second long and each cycle etches few Angstroms, making atomic layer etching a slow and costly process. Increasing the efficiency of each step quickly becomes bottlenecked by the time needed to replace one gas with another in the entire volume of the etch chamber. Improving the throughput of atomic layer etching will therefore require a deep understanding of the plasma/ material interactions both during the steady and the transient states of gas switching as the later will represent most of the process time.

In the framework of this PhD activity:

  1. The candidate should get a thorough understanding of the fundamentals of the physic of the plasmas used in nanofabrication, by the means of comprehensive literature study, performing its own experiments to test hypothesis and interaction with the members of the etch team at IMEC and etch community in general.
  2. The candidate must also become familiar with the plasma/ material interaction at the nanometer scale. Getting a clear idea of what is happening at the atomic level will help the candidate visualize the actual impact of the plasma characteristics at the surface level and choose its own experiments accordingly.
  3. IMEC possesses several etch reactors with a large range of capabilities in terms of process and plasma control. Through morphological and material analysis by techniques such as transmission electron microscopy (TEMs), X-ray photo electron spectroscopy (XPS), atomic force microscopy (AFM), etc., the candidate will be able to determine which of these capabilities are the most desirable for optimal control of ALE processes.
  4. This study will bring the candidate to the limits of what the current generation of most advanced etch reactors can bring. The need to work around these limits will eventually appear, helping the candidate develop its flexibility and adaptation skills to push the study further.
  5. Any process flow is the combination of many different steps asking for many different skills and disciplines. IMEC regroups most of these on one site and the candidate is expected to use this aspect to improve its understanding of many disciplines other than plasma and etching. This subject is an interaction between lithography, plasma physics, material science, simulations, electrical characterization, and many others. It is therefore key that the student is open-minded and able to absorb any new knowledge and constructive criticism from his/her peers and colleagues.

Required background: Enthusiastic experimentalist with a strong interest in materials chemistry and physics.

Type of work: 60% experiments, 25 % interpretation, 15% literature study and writing

Supervisor: Stefan De Gendt

Daily advisor: Philippe Bezard

The reference code for this position is 2021-129. Mention this reference code on your application form.