Fliss_presentation

04/17/2023 Oussama Fliss Master thesis 1

Master thesis presentation: Silicon micro-fluidic devices for high energy physics applications: Testing procedure and failure analysis

Student:

Oussama Fliss

Supervisor:

Alessandro Mapelli

Professor:

Philippe Renaud


Table of contents

• Introduction • Objectives• Fracture in Single Crystal Silicon• Protocol development for the pressure tests• Analysis of pressure test samples• Analysis of fracture mechanics samples• Conclusion • Outlook


Introduction: CERN• European

Organization for Nuclear Research

• High Energy Physics

• Colliding particles

• Accelerators and detectors

[1]

[1] https://cds.cern.ch/record/1621583

https://cds.cern.ch/record/1621583


Introduction: Silicon micro-fluidic devices

• PH-DT[1]: development, construction and operation of detectors• Recently: cooling systems and detectors based on micro-fluidic devices

[1] http://ph-dep-dt.web.cern.ch/

• Advantages:• Minimize material budget• Optimized heat transfer• No CTE* mismatch• Commonly used micro-

fabrication methods

•Requirements:• Minimum thickness• Internal pressure

*Coefficient of Thermal Expansion

http://ph-dep-dt.web.cern.ch/

http://ph-dep-dt.web.cern.ch/


Introduction: Micro-channel pressure tests

• Design optimization and safety factor Building a fracture prediction tool

Significant amount of fracture data

• Final devices are complex to study Samples with simpler geometry are

fabricated and tested Water is injected with a pump and

pressure is increased until fracture

• High scattering in previous tests A protocol is needed for higher

repeatability


Aims and objectives• Develop a protocol for the pressure tests

• Design of a test bench• Development of a procedure for data analysis

• Investigate the etching process effect• Identify the fracture planes


Fracture in Single Crystal Silicon

• Prediction tool based on Fracture Mechanicso Fracture toughness (Kc) data required as inputo Anisotropic behavior of ScSi

[1] M.J. Madou. Fundamentals of Microfabrication: The Science of Miniaturization, Second Edition. Taylor & Francis, 2002.p80

[1]

Fracture toughness experimental data must be correlated to corresponding fracture plane


Pressure test samples

• Variables:• Design • Bonding• Etching processes

• Water is injected through the inlet

• Pressure increased until rupture


Test bench design

Air

Automatic Pump

Connector

Sample

H2O

Pressure sensor

DAQ + Control

Water


Connector design• Requirements:

• High pressure proof (>600 bar)• Uniform clamping pressure• Accurate sample alignment • Free of constraints

• Solutions:• Sealing O-rings• Two bolts and counter balance pieces• Alignment pins and accurately

machined groove • One side clamping


Pressure test procedure1. Align the sample in the slot of the bottom part

2. Put counterbalance pieces

3. Align the top part of the connector on the bottom part

4. Bolt the two parts together until the O-ring is compressed at 30%

5. Attach the connector to the pump through the fluidic connector

6. Start the LabVIEW program and verify the sensor is working

7. Start the pump

8. Apply pressure cycle

9. Stop the program and save the files

10.Recover the sample, label it and store it for observation

Counterbalanceslots

Clampingbolts

Fluidic connector

Sample holder


Sample observation

• Samples are diced at CMi [1]

• Observations are done under SEM at CMi

• Color code and schematics

[1] https://cmi.epfl.ch/

https://cmi.epfl.ch/


Pressure tests: Pyrex-Si samples

Sample number

channel Width (µm)

Backside thickness (µm)

Failure pressure (bar)

1 200 15 200

2 200 22 190

3 100 16 325

4 100 21 265

Sample 2

Sample 3


SEM observations

What do these images show?


SEM observations with color code


ChannelSEM observations


Fracture mechanics samples

3 pts and 4 pts bending

• Simpler geometries tested under different conditions*• Samples observed under SEM• Identify fracture planes/weak points• Evaluate influence of different

etching methods• DRIE• KOH

*C. Gabry’s master thesis (CERN-LMIS4)


Fracture mechanics: SEM analysis

• Investigated areas•Interface channel/fracture•Straight fracture angles



• Samples etched with Deep Reactive Ion Etching (DRIE)



• Samples etched with KOH wet etchingPotential surface finish effect



3D fracture planes



0

1

2

3

4

5

6

{3,2,2}

{3,2,3} {2,1,2}

{1,1,3}

{3,1,1} {2,1,1} {3,2,13}

Family of fracture planes (occurrence)

• Angle measurements on both sides of the sample Scattering in the results Results do not match the theoretical predictions


Conclusions• A protocol was developed to improve the

repeatability of the pressure tests• Test bench and procedure for the pressure tests• Color code for the observations

• SEM observations suggest a potential effect of the etching method on the fracture initiation

• Further investigations are required to draw definitive conclusions regarding the fracture planes


Outlook• The pressure tests should continue

The developed protocol should greatly improve the repeatability of the results

• The surface finish effect requires further investigation Correlation to the load/pressure

• The fracture angle measurements should continue with more details Knowing the initiation point will improve the results


Connector

Several iterations

2nd version1st version


Scattering in pressure tests

15.00 17.00 19.00 21.00 23.00 25.00 27.00 29.00 31.00 33.00 35.000

50

100

150

200

250

300

350

400

Pressure VS backside thickness for200µm channel width

Thickness (µm)

Pre

ssu

re (

bar

)

15.00 20.00 25.00 30.00 35.00 40.000

20

40

60

80

100

120

140

Pressure VS backside thickness for500µm channel width

Thickness (µm)P

ress

ure

(b

ar)


Angle measurement equations

• For each side

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