Student Projects

Our research activities focus on the study and development of NEMS/MEMS resonators. We target two main applications: sensors and communications. We follow a holistic approach so we have projects/ideas on analysis, modelling, fabrication, characterization, integration, and application of these devices.
Below you can find a list with some ideas for semester and master projects. Do not hesitate to contact us because we will likely be able to find a project that matches your motivations. 
Pour les étudiants francophones, s’il vous plaît ne pas hésiter à nous  contacter, car nous pouvons également parler en français.

ANEMS project on ISA (Beta)


Collaborations with companies

 Piezoelectric MEMS for vibrations sensing

Master Project

You will mostly do Design and Fabrication

We want to miniaturize current SoA vibration sensors

The project

Vibration sensors (aka vibrometers) are essential components to keep safety and reliability of different types of machines, e.g. plane engines. A vibrometer is able to detect very small vibrations, that coming from either acceleration caused at the clamp or by pressure variations in the environment. In the frame of aerospace industry, the extremely strict requirements for safety, resolution, endurance and lifetime have caused the technology to evolve very slowly. The idea of the project is to analyze if a MEMS based device would be of interest as the next generation vibrometers. Analysis of the different transduction possibilities, design and fabrication in the CMi clean room at EPFL will be performed.

The Company

Meggitt Sensing Systems Switzerland (MSS Switzerland) leads the market in sensing and monitoring solutions, specialising in smart engineering for extreme environments. Our 60+ years of sensor and system expertise means our solutions are trusted by original equipment manufacturers around the world. MSS Switzerland was founded as Vibro-Meter® back in 1952. This became a Meggitt company in 1998 and in 2006 was integrated in the Meggitt Sensing Systems division.

Fig. 1 Schematic drawing of one concept of piezo vibrometer. A membrane with piezoelectric material will generate charges upon vertical movement that will be collected by the electrodes. A suspended mass will amplify the effect of external vibrations. Fig. 2 Schematic drawing of another concept of piezo vibrometer. In this case, a metallic membrane will deflect upon external vibrations or changes in pressure. This movement will modify the resonance frequency of the piezoelectric acoustic resonator placed underneath.
Project Components:

The project will be carried at the Advanced NEMS group at EPFL (Lausanne), but with often visits to the Meggit-sensing site in Fribourg. The main tasks involved in the project will be:

  • Study of specifications/requirements from aerospace applications (10% of the time – 1-2 weeks)
  • Study of the State of the Art of vibrometers and microphones (20% of the time – 3 weeks)
  • Design of novel vibrometer (30% of the time – 4-5 weeks)
  • Fabrication first prototypes (40% of the time – 5 weeks)
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoys learning and facing new challenges
  • Knowledge of a simulation (FEM) software is a plus
  • Knowledge in cleanroom processes is a plus

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering; Mechanical Engineering; Electrical Engineering

Guillermo Villanueva

Micro-optomechanical systems before integration

Semester/Master Project

You will do Design and Fabrication

We want to make the optical sensor of the Industry 4.0

The project

The availability of suitable sensors becomes increasingly challenging in harsh environments , typical of many industrial settings, where e.g. high temperatures, high pressures, large electromagnetic fields or radiation hinder the use of conventional electronic transducers. Optical-based sensors provide a route towards circumventing these difficulties. In particular, micro-optomechanical systems (MOMS) combining a mechanical element with optical readout techniques can be fabricated to tolerate harsh conditions. The ability to build them into optical fibers provides ease of scalability, distribution and installation in systems requiring multiple sensors, and their integration into available optical communication networks. The project aims at designing and fabricating micro-mechanical devices and resonators to be assembled in the final product with optical readout. There will be the opportunity to participate in the overall prototypes and products development, interact with external suppliers and clients (in defense, energy, automotive, aerospace), learn new challenging techniques and discover the tech startups world. The master project will be sponsored. Possibility to join the startup after the project.

The company

The Miraex is a young startup based at the EPFL Innovation Park. Miraex unique combination of nanotechnoly, new materials, photonics and artificial intelligence provides the missing tool for predictive maintenance in harsh environments. By harnessing the power of light, Miraex products enable smarter and greener factories for the Industry 4.0 Possibility to join the startup after the project.

MEMS Wafer characterization

Fig. 1 Micro-optomechanical systems (MOMS) before integration in the prototype

Project Components:

The project will be carried out between Miraex (EPFL Innovation Park) and the Advanced NEMS group at EPFL (Lausanne). The main tasks involved in the project will be:

  • Optimize design and fabrication process flow (20% of the time – 3 weeks)
  • Fabrication of the new generation of sensors in CMi (60% of the time – 8-10 weeks)
  • Integration in the final product (20% of the time – 3 weeks)
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoys learning and facing new challenges
  • Knowledge in cleanroom processes is a plus

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering; Mechanical Engineering; Electrical Engineering

Guillermo Villanueva

Semester/Master Project

 

The project

In collaboration with Nanosurf we would like to develop a new generation of cantilevers that are compatible with AFM holders and measurement setup, so that they provide a much more reliable measurement for cell growth.

Nanosurf was founded in 1997 in Liestal, Switzerland, and has since become one of the most trusted and established AFM brands in the market today. Nanosurf has a vast knowledge base in scanning probe microscopy, with an average of more than 15 years of AFM experience in our sales, service and development teams.

In this project we will design, simulate, fabricate and characterize a novel type of cantilever that is compatible with Nanosurf equipment and that allows a more stable measurement for cell growth. We will adapt the load depending whether you are a semester or a master student.

Fig. 1: Schematic of the detection scheme of the AFM

Fig.2: Cell interaction with AFM

Project components

  • Design, simulation, fabrication

Desired skills

  • Comsol, Fab experience would be welcome

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Electrical and Microengineering; Mechanical Engineering;

Guillermo Villanueva

Semester/Master Project

The project

The goal of the project is to develop cleanroom processes for micromachining refractory ceramic materials. This ability will enable new, high performance micro-electromechanical elements that can operate in harsh environments and extreme temperatures to perform specialized functions. An initial target application is in portable spectroscopy enabled by micro-NIR emitters.

The student is expected to familiarize themselves with typical cleanroom facilities and procedures and will learn standard process flows.  Starting with wafers coated with a thin-film refractory the student will need to develop an optimized process flow though systematic trial and evaluations. The four major steps include: An-isotropic etching of refractory a ceramic, mask development, optical lithography, and isotropic etching. While some steps are standard, the majority will need to be developed by the student.

Depending on rate of progress the student will also have the opportunity to be involved in device testing.

The Company

4K-MEMS is an early-stage start-up founded to create custom broadband near-infra red emitters for portable applications. By leveraging the refractory ceramic properties and the novel MEMS designs we will enable a new class of IR sources that are smaller and have higher energy density than any other thermal source existing today.

Fig. 1: Example of RIE instrument at CMi used for micro-fabrication.

Fig.2 : Intense light from micro NIR emitters.

Project components

The project will be carried out at in the ANEMS lab at EPFL Lausanne, and will reqquire significant cleanroom time at CMi. The main stats involved in the project will be:

  • Process development planning (2 week)
  • RIE recipe development (4 weeks)
  • Mask development (4 weeks)
  • Optical Lithorgaphy (4 weeks)
  • Other clenaroom processes (evaluation, metrology, etc, throughout the project)

 

Desired skills

  • Strong English, verbal and written
  • Self-motivated and Independent
  • Interest in industrial applications
  • Knowledge in cleanroom processes is a plus

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Electrical and Microengineering; Mechanical Engineering

Guillermo Villanueva

Matthias Imboden


Resonators with Microchannels

 PMUTs for acoustic spectroscopy

Master Project

You will mostly do Design and Fabrication

We want to analyze biosamples via acoustic waves

The project

Piezoelectric micromachined ultrasound transducers (PMUTs) are suspended composite membranes capable of both sensing and sending sound waves that can interact with the environment of interest. They are used in a wide variety of everyday applications, from radar/sonar to non-destructive material testing and medical imaging. One emerging area of interest is in measuring acoustic spectroscopy. We want to do that in microfluidic channels by placing PMUTs above and below the channels. In this way, there is no influence on the sample as it flows along the channels and measurements are incredibly sensitive. In this project, the student will design and fabricate PMUTs with integrated microchannels.

Fig. 1 Schematic and working principle of PMUTs. Image taken from Qiu et al. Fig. 2 SEM images of AlN PMUT from Lu et al.
Project Components:

The main tasks involved in the project will be:

  • Literature review of PMUTs and microfluidics (30% of the time – 3 weeks)
  • Design and Fabrication of the resonators in CMi (50% of the time – 7-8 weeks)
  • Microfluidic integration (20% of the time – 3 weeks)
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoys learning and facing new challenges
  • Knowledge of cleanroom processes would be welcome

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering; Mechanical Engineering; Electrical Engineering

Guillermo Villanueva

Daniel Moreno

Semester/Master Project

  • Fabrication of the channels in the clean room (involves Deep-UV lithography with stepper, dry and wet etching, electron microscopy)
  • Design and fabrication of the integrated piezoelectric electrodes (standard lithography, sputtering, dry etching)
  • Design and fabrication of the release (standard lithography, etching)
  • Characterization of the devices in the lab
  • Design and carrying out of calorimetry experiments

The project

Suspended microchannel resonators (SMRs) consist of microfluidic channels embedded in vibrating structures (Fig. 1). Their configuration allows for a wide range of applications, from the rheology of homogeneous samples to the study of single biological analytes’ physical attributes.

So far, we have only fabricated SMRs in silicon nitride (SiNx, Fig.1 and 2), and we would like to shift our focus towards devices made of glass (SiO2). The main reason is the lower thermal conductivity of SiO2, which could help us achieve better sensitivity for calorimetry applications.

While the technology is mature for the fabrication of channels in silicon nitride, using glass as a structural material is more challenging. Indeed, the chemicals we use in our standard fabrication are not necessarily all compatible with glass, potentially requiring adjustments in the process flow.

Fig. 1: SEM picture of an array of 2 SMRs made of silicon nitride at the end of the fabrication process (they are released).

Fig.2 : SEM cross-sectional views of a silicon nitride channel after fabrication. The lateral walls are only about 260 nm thick.

Project components

  • Fabrication of the devices in CMi
  • Characterization and inspection of the devices with the Scanning Electron Microscope (SEM)
  • Design of lithography masks
  • Fabrication of the piezoelectric electrodes and release
  • Characterization and experiments

Desired skills

  • Autonomy
  • Cleanroom experience is welcome but by no means a necessity!

Type of Project:

Section(s):

Contact(s):

Semester Project / Master Project

Microengineering; Mechanical Engineering

Guillermo Villanueva

Damien Maillard

Semester/Master project

  • Literature review of the existing vacuum encapsulation methods
  • Fabrication and characterization of the method chosen in cleanroom
  • Design and carrying out experiments

The project

Microfluidic devices require appropriate packaging for the efficient delivery of fluidic samples. In particular, suspended microchannel resonators (SMRs, Fig. 1) need to be operated in a vacuum to boost their sensitivity. The combination of both vacuum encapsulation and fluidic delivery makes the packaging of such devices particularly challenging (see Fig. 2). Furthermore, our devices are driven and detected piezoelectrically, adding to the requirements and complexity of the packaging. At the moment, we are using a reversible in-lab modular interface for our experiments.

In this project, we would like to investigate a means to encapsulate those devices directly after the end of the fabrication. Before taking the devices out of the cleanroom, the devices should be sealed at wafer-level, before being diced into chips. We are looking for the most integrated possible solution.

Fig. 1: SEM picture of an array of 2 SMRs at the end of the fabrication process. The electrode tracks are depicted in orange and cyan and extend further away from the beams for wire-bonding.

Fig.2: Schematic cross-section of the devices at the end of the fabrication. The vacuum is made around the devices on the top side, while the fluidic delivery is provided from the back-side.

Project components

  • Literature review of the existing wafer-level packaging methods
  • Selection, fabrication, and characterization of a packaging method
  • Experiments with the packaged SMRs

Desired skills

  • Autonomy
  • Cleanroom experience is welcome but by no means a necessity!

Type of Project:

Section(s):

Contact(s):

Semester Project / Master Project

Microengineering; Mechanical Engineering

Guillermo Villanueva

Damien Maillard

Semester project

  • Design of the microchannels with CAO software (SolidWorks, Inventor, etc…)
  • Fabrication of the microchannels with the Nanoscribe nano printer in CMi
  • Inspection of the structures with the Scanning Electron Microscopy (SEM)
  • Development of a dedicated packaging for the operation of the devices with fluidic samples

The project

The Center for MicroNanoTechnology (CMi) has installed a Nanoscribe Photonic Professional GT+ nano printer (https://www.epfl.ch/research/domains/cmi/cmi-home-page/equiment/photolithography/nanoscribe-photonic-professional-gt/). This tool works on the principle of two-photon absorption and can achieve features with resolution below 200nm.

We have already started to investigate the fabrication of microchannels with this nano-printer, with promising results (Fig. 1). The objective of this project is to optimize the fabrication of microchannels with thin walls and to develop a process flow in which we could create suspended structures. In addition, we would like to improve the fluidic network communicating with the channels, for fluidic delivery and experiments (Fig. 2).

Fig. 1: SEM picture of 3D printed microchannels directly on silicon. Picture from Lénaïc Frehner’s semester project report.

Fig.2: SEM picture of microchannels. Here, we attempted to print the fluidic network connecting the channels, but unsuccessfully. Picture from Lenaïc Frehner’s semester project report.

Project components

  • Design of microchannels with CAO software
  • Fabrication and inspection of the microchannels in the cleanroom
  • Development of a process flow allowing for the release of the devices

Desired skills

  • Autonomy
  • Cleanroom experience is welcome but by no means a necessity!

Type of Project:

Section(s):

Contact(s):

Semester Project / Master Project

Microengineering; Mechanical Engineering

Guillermo Villanueva

Damien Maillard

Semester project

  • Design and fabrication of the microchannels in silicon (involves optical lithography and dry etching)
  • Inspection of the cross-section of the channels (involves Scanning Electron Microscopy)

The project

Since they are the first building block of all microfluidic devices, microchannels are of critical importance and interest and their design and fabrication require great care.

In recent developments, we have been exploring 2 different fabrication methods for the realization of those channels. The first method consists of using a sacrificial layer of poly-silicon that we etch to create trenches (Fig.1). After that, we deposit the structural material (usually silicon nitride) around the poly-silicon to encapsulate it, and we proceed to empty the channel. The second method is more straight forward, as we etch directly inside the silicon wafer before redepositing the structural material in the grooves (Fig. 2).

We are interested in learning more about the fabrication of the channels etched directly in silicon. We could focus on two aspects: the profile of the trenches when they are exposed to different chemistries and the effect of the crystallinity of the silicon wafer used.

Fig. 1: SEM picture of a trench etched in poly-silicon (about 800nm wide). This is the first step in the fabrication of microchannels with the sacrificial material method.

Fig.2: SEM cross-sectional views of a silicon nitride channel after fabrication. The channels were etched directly in the silicon. After the deposition of silicon nitride to close the channels, the lateral walls were only about 260 nm thick.

 

Project components

  • Design and fabrication of the microchannels
  • Inspection of the channels with Scanning Electron Microscopy

Desired skills

  • Autonomy
  • Cleanroom experience is welcome but by no means a necessity!

Type of Project:

Section(s):

Contact(s):

Semester Project / Master Project

Microengineering; Mechanical Engineering

Guillermo Villanueva

Damien Maillard

Master Project / Internship

  • You will mostly do literature review and simulations.

The project 

Suspended microchannel resonators (SMRs) consist of microfluidic channels embedded in vibrating structures. This configuration allows operation of the devices in a vacuum environment instead of immersed in the fluidic sample to analyze. Thanks to this, the damping losses are drastically reduced (increased quality factor) and the detection sensitivity is enhanced. Theoretical and experimental results have demonstrated that the energy dissipation is non-monotonic with respect to the viscosity of the fluid flowing in the resonator. In addition to that, a significant variation in the quality factor was discovered when the microfluidic channel axis was placed away from the beam neutral axis. The objectives of the project first consist in getting familiar with the literature, the results already obtained, and understand the Comsol model. Then, the project will be continued in order to complete the study (in particular, the behavior the devices with high-viscosity fluids needs to be investigated). 

 

Fig. 1: simulation of the first 2 modes of vibration of a Suspended Microchannel resonator.

Fig. 2: non-monotonic behavior of the quality factor with respect to the viscosity of the fluid.

 

 

Project Components: 

The main tasks involved in this project will be: 

  • Literature review 
  • Comsol modelling and simulations 

 

Desired Skills: 

  • Autonomy 
  • Comsol knowledge would be welcome 

 

Type of Project:

Section(s):

Contact(s):

Master Project / Internship

Microengineering; Mechanical Engineering

Guillermo Villanueva


Acoustic mode resonators

 FEM model of LAMB resonator

Semester Project

You will mostly do Simulations

We want to find the optimal parameters to make the best LAMB wave resonators

The project

LAMB wave resonators have the potential to be used as passive RFID tags for identification and tracking of small biological molecules. Electromechanical coupling (kt^2) and quality factor (Q) are the two most important factors for improving the performance of the resonator. The idea behind the project is to improve kt^2 and Q by optimizing different geometrical parameters through COMSOL simulations. FEM model (Fig. 1) has already been designed and optimize to match the state-of-the-art but it requires further optimization for highly miniaturize resonators (6×4 μm). Student’s job will be to sweep important geometrical parameters (Fig. 2) such as anchor length (La), anchor width (Wa), bus with (Wb), finger gap (Wg) and electrode coverage to study their impact on the performance of the resonator.

Fig. 1: FEM model of LAMB resonator. Fig. 2: Design geometry showing important parameters. [Ref] G.Piazza et al, Journal of Microelectromechanical systems, 2018
Project Components:

The main tasks involved in the project will be:

  • Literature and theory review on electromechanical acoustic resonators (in particular SH0 resonators), acoustic waves and piezoelectricity (20% of the time, 2-3 weeks). 
  • Introduction to Comsol and the existing models (10% of the time, 1-2 weeks)
  • Optimization of Comsol model (70% of the time, 10 – 11 weeks) 
  • (Optional) Development of Matlab toolbox (time: variable) 
Desired Skills:
  • Fluency in English 
  • Autonomy 
  • Interest in Comsol simulations 
  • Knowledge in MEMS is desirable 
  • If choosing to contribute to the custom Matlab toolbox: Proficient with Matlab and familiarity with Git/Github 

Type of Project:

Section(s):

Contact(s):

Semester Project

Electrical and Microengineering; Mechanical Engineering

Guillermo Villanueva

Silvan Stettler

 SEM image of a µTag internalized by the cell.       [Ref] H. Wong et al, PhysRev Applied, 2017

Master Project

You will do mostly Design and Fabrication

We want to probe cell properties from the inside

Master project

Recently, a number of cell probing techniques have been developed to study the behaviour and properties of a single cell. Most of them are invasive or require optical detection. The goal of the project is to develop a wireless cell-probing system similar to an RFID system that will identify and track the movement of an individual cell in real time. Fig. 1 shows the insertion of such small device in a mouse macrophage (white blood cell). The idea is to use a piezoelectrically actuated acoustic resonator as an RFID tag that should be small enough to easily internalized and be efficient enough to send back the data from inside the cell. However, little work has been conducted to realize the full potential of acoustic devices with critical dimensions less than a few microns. The main goal of the student will be to fabricate LAMB wave resonators on thin film lithium niobate (Fig. 2). The student will get hands on experience with different microfabrication tools related to e-beam lithography, wet/dry etching and metrology.

 Fig 1: SEM image of a µTag internalized by the cell.    [Ref] H. Wong et al, PhysRev Applied, 2017 Fig 2: SEM image of a fabricated miniaturize acoustic resonator.
Fig 1: SEM image of a µTag internalized by the cell [Ref] H. Wong et al, PhysRev Applied, 2017. Fig. 2: SEM image of a fabricated miniaturized acoustic resonator.
Project Components:

The main tasks involved in the project will be:

  • Literature review of LAMB wave resonators including S0 and SH0 modes (10% of the time – 1-2 weeks)
  • Related cleanroom trainings at CMi (10% of the time – 1-2 weeks)
  • Design and fabrication (60% of the time – 8-9 weeks)
  • Characterization of fabricated devices (20% of the time – 2-3 weeks)
Desired Skills:
  • Fluency in English
  • Autonomy
  • Interested in microfabrication
  • Knowledge of MEMS is desirable

Type of Project:

Section(s):

Contact(s):

Master Project

Microengineering; Mechanical Engineering; Electrical Engineering

Guillermo Villanueva

Muhammad Faizan

SAW-based acoustic spectrometer

Master Project

You will mostly do Simulation and Fabrication

We want to analyze bio samples via acoustic waves

The project

Acoustic spectroscopy is being increasingly used to characterized different bio-materials and for the detection of biomolecules. The idea is to design and fabricate a miniaturized platform for the detection and characterization of cancerous cells by using Surface Acoustic Waves (SAW). The proposed platform consists of a pair of Interdigital electrodes (IDTs) for the generation and reception of SAW waves with an embedded microchannel in between for the trapping of cells or other biological entitiesas shown in Fig. 1. Information such as the elasticity of the sample, can be determined by measuring the phase change of the resultant SAW waves after passing through the sample.

Fig 1: (a) 3D simulation model. (b) Cross-sectional image from the central axis of a microcavity. Ref.: R. J. Cote and O. Tigli, Lab on a Chip interrogation of single tumour cells in Lab Chip, vol. 16, pp. 163-171, 2016.
Project Components:

The main tasks involved in the project will be:

  • Literature review of SAW-based acoustic spectroscopy (25% of the time – 3-4 weeks)
  • Design and FEM modelling of the proposed platform (25% of the time – 3-4 weeks)
  • Fabrication of the resonators in CMi (40% of the time – 5-6 weeks)
  • Preliminary characterization of the resonators (10% of the time – 1-2 weeks)
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoys learning and facing new challenges
  • Knowledge in cleanroom processes is a plus

Type of Project:

Section(s):

Contact(s):

Master Project

Microengineering; Mechanical Engineering; Electrical Engineering

Guillermo Villanueva

Muhammad Faizan

Master/Semester Project

For this project you will be focusing on fabrication and design/optimization of process flows.

In this project, we would like to develop a fabrication method for making thickness mode resonators that are small enough (1-10 um) to be inserted inside of cells. These resonators will be then used as RFID tags to identify and track the movement of individual cells.

A simulation of the device to fabricate is shown in the figure. It consists of Lithium Niobate (a piezoelectric material), sandwiched between two metal electrodes. When an RF signal is applied to the electrodes, it drives the piezo material in specific vibration modes. The resonance frequency of this device is set by the width of the piezo (wavelength), such that by sweeping the width it is possible to obtain RFID tags at different resonance frequencies. This resonance frequency will be used as unique ID for identifying cells.

By developing a method to fabricate such devices, we want to make thickness mode resonators frequency scalable on chip and explore the performance of these devices in new orientations of Lithium Niobate.

For this project you will be focusing on fabrication and design/optimization of process flows.

Project components

  • Design of process flows [Semester/Master]
  • Fabrication of devices [Semester/Master]
  • Characterization of devices and Measurements [Master]

Desired skills

  • Cleanroom experience is welcome but by no means a necessity!

Type of Project:

Section(s):

Contact(s):

Master Project

Microengineering; Mechanical Engineering; Electrical Engineering

Guillermo Villanueva

Rebecca Leghziel

In previous simulations performed in ANEMS, we have studied the behavior of PAW resonators in vacuum, however we would like to explore the possibility of using these devices for different biological applications where liquid environments are inevitable. With this project we aim to study how the viscous damping affects the QF, and assess the viscous losses in different biological mediums such as: cell medium, blood, phosphate buffer solution etc. Furthermore, we want to learn how the design can be improved and optimized to minimize the dissipative effect caused by the surrounding fluid.

Simulations will be performed on COMSOL: you will set up the coupling between the solid-liquid interface and carry out parametric sweeps to optimize the design.

Project components

  • Familiarize with COMSOL and the existing FEM model of PAW resonator
  • Familiarize with coupling solid-liquid interface in COMSOL
  • Literature review on properties of the different biological mediums
  • Optimization of device performance for different biological environments

Desired skills

  • Experience using COMSOL is welcome but by no means a necessity!

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering, Mechanical Engineering, Bioengineering, Electrical Engineering

Guillermo Villanueva

Rebecca Leghziel

DUV Lithography

Deep Ultraviolet (DUV) Stepper lithography relies on a system of demagnifying lenses to be put between the mask (in this case called a reticle) and the wafer to be exposed. This allows to scale down wafer features 4 times compared to the size of the same features on the reticle, bringing resolution down to 180nm, a size that previously was only covered by electron beam (E-beam) lithography. Stepper lithography, compared to E-beam, allows for a much quicker processing (100 of wafer per hour) at the expense of requiring a reticle to be previously written.

Figure 1 ASML DUV Stepper from CMi
Figure 2 Scale-down of CMR resonators (from https://ieeexplore.ieee.org/document/8540088/)

Our project

Contour-mode resonators (CMRs) are a type of MEMS resonator where the resonance frequency depends on the pitch between fingers of an interdigitated array of electrodes (IDT). A smaller pitch results in a smaller wavelength and therefore a higher frequency, allowing to move from MHz range to GHz range, to tap in 5G usage bands. The project objective is to optimize the fabrication of electrodes using DUV stepper lithography, which requires an optimization of both the reticle fabrication with direct laser writing and optimization of exposure parameters in a ASML PAS 5500 DUV Stepper.

Project components

The main tasks involved in the process will be:

  • 10% of time Review of stepper lithography
  • 10% of time for cleanroom trainings
  • 30% of time in mask design
  • 50% of time in fabrication

Required skills

  • Fluency in English or French
  • Interest in microfabrication

Desirable skills

  • Knowledge of basic lithography processes
  • Knowledge of scripting tools

Type of project: Master/Semester

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering, Electrical Engineering

Guillermo Villanueva

Marco Liffredo

 


Thin Film Optimization

 SEM image of released cantilever array

Semester/Master Project

You will do Fabrication and Characterization

We want sensors with a high k-material to investigate actuation at the nanoscale

The project

There is immense interest in fabricating nanoelectromechanical systems for creating extremely sensitive sensors or highly efficient actuators for measurement of temperature, mass, radiation, etc. or creation of nanoelectromechanical relays. Current systems are largely based on piezoelectric or capacitive mechanisms, but there is an emerging field in utilizing second order or dielectric mechanisms to reduce fabrication cost and difficulty while maintaining high sensitivity/actuation. However, producing sensors from dielectric materials have many unanswered questions and often large discrepancies between theory and experiment. In this project, the student will study the theory behind NEMS and different electromechanical transduction methods, then can help design, simulate, fabricate or conduct experiments of sensors with a high k-material to investigate actuation at the nanoscale.

Close-up SEM image of a released cantilever with 100-nm thickness, comprised of molybdenum and hafnium oxide. Alignment of laser on released cantilever for optical measurements of resonance frequency and deflection.
Fig 1 Close-up SEM image of a released cantilever with 100-nm thickness, comprised of molybdenum and hafnium oxide. Fig. 2 Alignment of laser on released cantilever for optical measurements of resonance frequency and deflection.
Semester Project Components:

The main tasks involved in the project will be:

  • Understand theory of NEMS, electromechanical transduction
  • Introduction to electrical and optical measurements of resonators
  • Measurements of beams fabricated in CMi
Master Project Components:

The main tasks involved in the project will be:

  • Understand theory of NEMS, electromechanical transduction
  • Introduction to CMi and prepare design/process flow
  • Fabrication of dielectric beams
  • Electrical and optical measurements of resonators
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoys learning and facing new challenges

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering

Guillermo Villanueva

Daniel Moreno

 cross-sectional SEM image of PLD-grown PZT

Semester/Master Project

You will do Theoretical study and Fabrication

We want to obtain the best PZT layers

The project

Piezoelectric materials, such as lead zirconate titanate (PZT) and aluminum nitride (AlN), are the mainstay materials in MEMS for efficient actuation and sensing applications. When moving from the established MEMS fabrication to NEMS, consistent deposition of highly piezoelectric, nanometer-thick films becomes increasingly important. Several different deposition methods are possible for PZT, including sol-gel processing, sputter deposition and pulsed laser deposition (PLD). Of the three, PLD offers the opportunity to deposit epitaxial, stoichiometric PZT at high temperature. PLD is a physical vapor deposition, using a pulsed laser to vaporize the material of interest off a target onto a substrate in an ultra-high vacuum chamber. Depositing high-quality PZT thin films requires heavy optimization of the deposition parameters, high purity targets and proper substrates for epitaxial growth. In this project, the student will study PLD, piezoelectricity and PZT and contribute to the deposition and fabrication of PZT in CMi.

 Example of PLD system capable of depositing PZT  cross-sectional SEM image of PLD-grown PZT
Fig 1 Example of PLD system capable of depositing PZT Reference: D. H. A. Blank, M. Dekkers, and G. Rijnders, “Pulsed laser deposition in Twente: from research tool towards industrial deposition,” J. Phys. D. Appl. Phys., vol. 47, no. 3, p. 34006, 2014. Fig. 2 Above, cross-sectional SEM image of PLD-grown PZT on an SRO/YSZ electrode. Below, SEM image of released PZT-based cantilever. Reference: M. D. Nguyen et al., “Characterization of epitaxial Pb(Zr,Ti)O 3 thin films deposited by pulsed laser deposition on silicon cantilevers,” J. Micromechanics Microengineering, vol. 20, no. 8, p. 85022, 2010.
Semester Project Components:

The main tasks involved in the project will be:

  • Theoretical study of piezoelectricity, PZT, PLD
  • Introduction to CMi and installed PLD machine
  • Optimizing PZT deposition and dry etching in cleanroom
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoys learning and facing new challenges
  • Knowledge in cleanroom processes is a plus

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering

Guillermo Villanueva

Daniel Moreno

Reactive-Ion Etching

Topic

One of the main steps of every microfabrication process is the removal of the unwanted parts of a film to transfer the pattern of the mask on the substrate. Etching procedures can be divided in two main groups: wet etching and dry etching. Wet etching uses an aggressive chemical liquid solution to remove the substrate parts, while dry etching employs either a gas or a plasma. Plasma etching allows for a mixed chemical and physical action, called Reactive Ion Etching. The chemical action is strengthened by a physical bombardment of ions on the substrate to improve the verticality of the etching process.

Figure 1 PTSA ICP SI 500

Project

Between all the semiconductor materials used in MEMS Aluminum Nitride is interesting because of its piezoelectric effect and compatibility with standard IC production processes. AlN filters are widespread in RF frontends since the end of 20th century. To comply with the requirements of bandwidth in 5G it is necessary to increase the piezoelectric coefficient of AlN, which is achievable with alloying with Sc. One of the downsides in shifting from AlN to AlScN it is that Sc is much more resistant to etching, requiring to optimize the process shifting towards more aggressive chemistries and higher power.

The most widespread plasma etching of AlN is done with an inductively coupled plasma (ICP) with Chlorine chemistry. EPFL Centre of microtechnology (CMi) employs such a standard process, but more modern machines are to be tested.

The PTSA ICP SI 500 etcher from Sentech allows for control of chemistry, power, and temperature of the chamber, allowing for exotic recipes to be developed. Aim of the project is to investigate the etch rate, selectivity, and sidewall verticality of the etched AlN and AlScN.

Project components

The main tasks involved in the process will be:

  • 10% of time review of ICP
  • 10% in training for machines
  • 30% in process develpment
  • 50% of time in measurements

Required skills

  • Fluency in English or French
  • Interest in microfabrication

Desirable skills

  • Knowledge of basic microfabrication processing

Type of project: Master/Semester

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering, Electrical Engineering, Physics

Guillermo Villanueva

Marco Liffredo

 

 

Lithium niobate (LiNbO3) is an important material that is being used for optical waveguides, piezoelectric sensors and optical modulators. Thin-film lithium niobate, or lithium niobate-on-insulator (LNOI), have become commercially available in the last decade and this opens new avenues into applications such as on-chip integrated optics. However, processing of lithium niobate remains challenging, especially etching.

Etching of lithium niobate has been done in CMI using either reactive-ion etching or ion-beam etching techniques. Standard processes with these devices result in sidewall contamination and other undesirable etch effects (Fig. 1). We would like to mitigate these problems.

This project would require a study into etching of lithium niobate in the context of tools available in CMI. Main aim is to optimize the etching of lithium niobate for deep etches and minimal sidewall contamination.

   

Fig. 1: Cross-section view of a thin-film lithium-niobate substrate after etching

Fig. 2: Veeco Nexus IBE350 Ion-Beam Etching (IBE) system at CMI

 

Project components

  • Studying different approaches for etching of lithium niobate,
  • Adaptation and optimization of etching process for lithium niobate,
  • Introduction to CMI and etching equipment.

Desired skills

  • Fluency in English,
  • Desire for cleanroom work,
  • Reporting skills,
  • Basic understanding of microfabrication processes,
  • Cleanroom experience is a plus.

 

 

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Electrical and Microengineering

Furkan Ayhan


Complex Dynamics

PCB and circuit design for NEMS characterization

Semester/Master Project

You will mostly do Circuit Design

We want to find the best platform to characterize NEMS

The project

NEMS have a large potential for sensing applications due to their size. However, at the same time, NEMS are difficult to integrate with electronics due to huge impedance mismatching and poor amplification. In this project, a circuit will be designed with background cancellation capabilities and/or impedance matching. Then, in collaboration with the Electronics Workshop, a PCB will be modelled, designed and fabricated that can be used to make measurements of a NEMS device. For the modelling, an equivalent circuit will be created to analyze the impedance matching network and amplification stage for the best integration with NEMS.

 Schematic of two measurement circuits PCB with Camipro for scale
Fig. 1 Equivalent Circuits with NEMS Resonator and (top) a balancing bridge and (bottom) a LC-tank. Fig. 2 PCB with NEMS device in center. Camipro card for scale.
Project Components:

The main tasks involved in the project will be:

  • Literature review of existing methods (20% of the time – 3 weeks)
  • Design of circuit, including resonator model (40% of the time – 6 weeks)
  • Fabrication of the PCB (20% of the time – 3 weeks)
  • NEMS characterization (20% of the time – 3 weeks)
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoy learning and facing new challenges
  • Knowledge of analog circuit design is a plus (even a must)

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Electrical Engineering, Microengineering; Mechanical Engineering

Guillermo Villanueva

 Piezoelectric

Semester/Master Project

You will do Simulations, Fabrication and Characterization

We want to understand the most complex devices.

The project

Coupling phenomena can be found in most of physical systems in nature. Coupling increases the systems’ dimensionality (making the systems more complex) and, in some cases, also the functionality (making the “whole greater than the sum of its parts”). In Nano-electromechanical Systems (NEMS), coupling between neighboring devices can be achieved, for example, via mechanics. A common ledge (support) for different devices will effectively couple them, and therefore collective dynamics might emerge. It is necessary, however, that this coupling is strong enough so that the devices actually “coupled”. It is the purpose of this project to analyze how the strength of this linear coupling depends on the physical constraints that act on adjacent devices. This will be studied using directly as well as parametrically driven responses.

Fig. 1: Coupled piezoelectric NEMS using the overhanging ledge in one of the anchoring points. Individual dimensions are 9µm*450nm*210nm.
Project Components:

The main tasks involved in the project will be:

  • Simulation and analytical calculation of coupling coefficients (30% of the time – 4-5 weeks)
  • Design and fabrication of a battery of devices (50% of the time – 7-8 weeks)
  • Characterization of the frequencies, quality factors and coupling rates (20% of the time – 3 weeks)
Desired Skills:
  • Fluency in English
  • Autonomy
  • Enjoy learning and facing new challenges
  • Knowledge of Finite Element Modelling is a plus

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

Microengineering; Mechanical Engineering; Electrical Engineering

Guillermo Villanueva

The project

Reconfigurable Silicon Integrated Photonic Circuits (PICs) enable the construction of increasingly complex optical networks on a chip. Of particular interest are non-volatile photonic components [1]: a finite actuation pulse toggles their state, with no further action required to maintain the desired state. Integrating chalcogenide phase change materials (PCM) on silicon photonic can provide this functionality, since these alloys have extremely different optical properties in crystalline or amorphous solid states, with state transitions possible with nanosecond-duration heat pulses.

Our recent research has aimed at designing PCM optical integrated components and developing a process flow for their fabrication at the CMi using the DUV Stepper as the only lithography method. This will allow demonstrating scalable PCM-PICs, apt for reliable and straightforward production with integrated electrical actuation.

A crucial step for the manufacture of PCM PICs is the careful design of the exposure reticle, the mask used by the DUV Stepper. In this project you will contribute to the construction of a complex multi-layer DUV Stepper reticle layout for the realization of a wide range of prototype optical components and their parametric variations. Optical and thermals aspects of some components may still need to be evaluated using 2D/3D COMSOL models.

Fig. 1: Simulated modes for coupled silicon waveguides with PCM in amorphous and crystalline state.

Project components

  • Study of a fabrication process flow for integrated photonics with PCM on the DUV Stepper (10% 1-2 weeks).
  • Realization of a DUV stepper reticle layout for a PICs prototype, using dedicated software. (60%, 8-9 weeks)
    • Automatic generation of individual components and chip layout assembly.
    • Writing of a reticle at CMi (photolithography).
  • Modelling and analysis of photonic components with PCM materials. (30%, 3-4weeks)
    • Thermal transient simulation
    • Optical simulation

 

Desired skills

  • Basic programming skills (Matlab is a plus).
  • Knowledge in optics/photonics is a plus.
  • Experience with COMSOL modelling is a plus.
  • Motivated, autonomous, problem-solver.

Type of Project:

Section(s):

Contact(s):

Semester/Master Project

MT, MNIS, others possible

Hernán Furci