Integration of amorphous silicon photodiodes to

microfluidic scintillation detectorsMaster Project

Intermediate presentation – 03/07/14

Cindy Wiese

Goal of the projectMicrochannels:

Vertical sidewallsTilted tipsContains the liquid scintillatorAluminium coating for light reflection

Photodiodes:p-i-n structure (in reverse voltage) to optimize

electrons collection in the depletion zoneAmorphous silicon to avoid radiation damages

Silicon

Reflective coating

PhotodiodePyrex

Channels roughnessEtching process

Etching profil along the channel width

Roughness at the middle of the channel

40% KOH etching,

60°C

40% KOH etching,

60°C + 3µm wet ox +

BHF etching

40% KOH + IPA etching,

60°C

Notching effectChannels length = 5 mm

Etching

process

Etching profil along the channel

lengthD

40% KOH

etching, 60°C

4.88 µm

40% KOH

etching, 60°C +

3µm wet ox + BHF etching

6.13 µm

40% KOH +

IPA etching,

60°C

1.26 µm

Conclusion on roughness improvement processesKOH etching + Wet ox + BHF etching:

Improve microscopic roughness

KOH + IPA etching:Improve macroscopic roughness (smoothed

profil, low notching)

Notching effect40% KOH etching

Channel

length

Etching profil along the

channel lengthD

5 mm 4.88 µm

8 mm13.34 µm

13 mm 11.9 µm

50 mm 14.6 µm

Wafers inventoryMicrofluidic tests:

Wafer n°

KOH etching

Al sputtering Bonding

1 Channels perforated

2 Wafer broken

3 Wafer broken in SPTS after TM

4 Wafer damaged by TM

5 Waiting for Anodic Bonding

Wafers inventoryScintillation detectors:

Wafer n°

KOH etching

Al sputteri

ngBonding Grindin

g

1

HCl decontamination after bonding Al etched

2 Pyrex broken

3

4

5

6 Used for measurements