Postdoctoral Researcher on Scalable Transfer of Extremely Thin Layers

Leuven - PostDoc
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Meer dan twee weken geleden

Extending the class of materials used in CMOS fabrication.

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Postdoctoral Researcher on Scalable Transfer of Extremely Thin Layers

What you will do

An ever-increasing number of materials are grown at temperatures that are too high for direct material integration in CMOS production lines. Other materials are grown on substrates that are incompatible with CMOS processing (e.g. sapphire). Examples of these materials are 2D materials like graphene or h-BN grown on metal catalysts, or MX2 materials (e.g. MoS2, WS2, WSe2...) grown on SiO2 or sapphire at high temperatures (>>500oC). But the class of materials that can benefit from a layer transfer is much larger than only 2D materials. Other examples are topological insulators (e.g. Bi2Se3 grown by MBE on sapphire), or even III/V materials [1]. A few commercial examples of film transfers exist today. An often-stated example is the laser lift off transfer of stacks like InGaN/GaN grown on sapphire for LED fabrication, but here, very thick (micron sized) layers are usually deposited.

In order to find a possible integration path for this class of new materials in the semiconductor industry, it is essential to find pathways to overcome the adhesion between the deposited material and the growth substrate. This might be possible by using laser lift off layers, intercalation effects (e.g. using supercritical fluids) or possibly by electrically changing the Van der Waals force between the deposited material and the growth substrate. Once the material is delaminated from the growth wafer, it needs to be laminated on a target (device) wafer. The interaction of the material with the target wafer often strongly changes the properties of the material itself. In that respect, it is demonstrated that the bandgap of a material like WS2 or MoS2 does change by only changing the dielectric environment. Furthermore, the material can become (un)intentionally doped just by laminating it on a different surface. Therefor, it is of prime importance that the interaction between the transferred material and the target wafer is understood, and that cleaning steps on the target wafer are developed in order to achieve the desired properties of the transferred layer (e.g. controlled doping level, specific bandgap, high mobility...). Such a pre-transfer clean is somewhat like a pre-epi clean. Without knowledge of the wanted passivation of the target wafer, it will be impossible to achieve the needed properties of the transferred layer.

The transfer of a thin layer will likely be implemented with a carrier wafer and a polymer support. Therefore, the final step of a transfer procedure will include a cleaning step of the transferred layer in order to be able to remove any polymer contamination, as not only the bottom interface but also the top interface is of prime importance to control the properties of the transferred layer. Possible cleaning steps include wet cleans, but also the more advanced remote plasma cleans come into the picture. The effect of those cleaning steps on the transferred layer need to be assessed in order to achieve the desired device behaviour.

[1] Y. Kim et al., Nature 544,  340 (2017)

Promotor: Stefan De Gendt (KU Leuven)
Mentor: Steven Brems and Dennis Lin (imec)
Manager: Steven Brems (imec)

What we do for you

We offer you the opportunity to join one of the world’s premier research centers in nanotechnology at its headquarters in Leuven, Belgium. With your talent, passion and expertise, you’ll become part of a team that makes the impossible possible. Together, we shape the technology that will determine the society of tomorrow.
We are proud of our open, multicultural, and informal working environment with ample possibilities to take initiative and show responsibility. We commit to supporting and guiding you in this process; not only with words but also with tangible actions. Through imec.academy, 'our corporate university', we actively invest in your development to further your technical and personal growth.
We are aware that your valuable contribution makes imec a top player in its field. Your energy and commitment are therefore appreciated by means of a competitive salary.

Who you are

  • You have a PhD degree in Chemistry, Physics or Materials Science.
  • We are looking for your background in (de)bonding technologies.
  • As the topic is about understanding interfaces, a deep knowledge of characterization techniques (X-ray techniques, scanning probe techniques, optical techniques (Raman, FTIR) etc..) is needed.
  • A proven track record with thin film transfer, 2D materials or surface passivation is considered as a plus.
  • You are a self-motivated and handy team player with good communication skills.
  • Given the international character of imec, good knowledge of (spoken and written) English is a must.

This postdoctoral position is funded by imec through KU Leuven. Because of the specific financing statute which targets international mobility for postdocs, only candidates who did not stay or work/study in Belgium for more than 24 months in the past 3 years can be considered for the position (short stays such as holiday, participation in conferences, etc. are not taken into account).

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