1. EOS
Elettronica Organica per
Strumentazione Innovativa di Ricerca

2. Outline Introduction PDIF-CN2: n-type behaviour and good properties
Flexible n-type and p-type OTFTs
Performances & Reliability
Circuit Simulations
Conclusions

3. Introduction
Reliable Organic CMOS Circuits requires p- and n-type devices with:
Comparable performances
Stability of electrical characteristics
Exploitation in flexible electronics:
Plastic substrates (devices must keep high performances)
P-type devices (developed, evaporated and solution-processed semiconductors, stability)
N-type devices (development of evaporated materials, perylene-diimide based)
PDIF-CN2 interesting performances:
High crystalline films mobility (up to 6cm2/Vs)
Transistor models:
DC model (developed)
AC model (under testing)
Transient model (under testing)

4. Fabrication p-type channel PEN (100μm) Cytop
P-type developed transitor (100 um channel length)
First batch of transistors
Al-Gate
Cytop
The molecule for p-type is under patent agreement!!
SAM
channel
SAM
Source-Au
Drain - Au
PEN (100μm)
Transistor architecture

5. Fabrication n-type Au S/D contact
HMDS treatment before perylene-diimide evaporation to increase chemical stability
No patent on this tipology!
PEN flexible substrate
Bottom-Contact/Top-Gate
Au- S/D contacts, no SAM
PDIF-CN2 evaporated (SPIN)
(Tsub=100 °C)
Gate dielectric: Cytop (550nm)
Metal gate: Al
Source-Au
Al-Gate
Drain - Au
PDIF-CN2
channel
Cytop
PEN (100μm)

6. ToF-SIMS Time of Flight Secondary Ions Mass Spectrometry
Ion gun
Elements (ppm/ppb)
Information obtained
Detection of all elements and isotopes(1 – uma)
Chemical information via molecular and cluster ions
Detection Limits
ppm of a monolayer for elements sub-fmol for molecules
Spatial Location
high lateral resolution (< 60 nm)
high surface sensitivity (< 1 nm)
high depth resolution (< 1 nm)
Mass resolution
Bi+
Molecules (sub-fmol)
Bi3+

7. ToF-SIMS – Spectra and Imaging
PDIF-CN2 is homogeneously distributed.
PDIF-CN2 molecular
peak is present.

8. ToF-SIMS – Depth Profiling
29 nm

9. TFTs On Bare PEN Substrates
Electrical Characteristics
L=100 μm
W=245 μm
Long Channel
High Ioff
Good Linearity
L=10 μm
W=230 μm
Short
Channel
High Ioff
Contact Effects

10. Sample N03 HMDS treatment before PDIF-CN2 evaporation
TFTs On HMDS-treated Substrates
Electrical Characteristics
Sample N03 HMDS treatment before PDIF-CN2 evaporation
Higher mFE
More negative Vth
Lower Sub-Threshold Slope
Higher Ion/off
Still Good Linearity when channel length is scaled down

11. Gate-bias Stress on bare and HMDS-treated substrate devices
Electrical Stability
Gate-bias Stress on bare and HMDS-treated substrate devices
Vgs-stress=+30V
Bare
Substrate
Comments:
Both TFTs on bare substrate and HMDS-treated substrate show very good stability with only small variation of the transfer characteristics
HMDS-treated
Substrate

12. P-type experimental characterization

13. P-type model

14. NOT in PMOS technology Standar NOT design
It could be a PMOS active load

15. Dedicated NOT design
EOS NOT design

16. Simulation In
INV 1
INV 2
INV 3

17. OR Port with pass transistor approach
W=120u L=5u
W=120u L=5u
W=10u L=100u
W=10u L=100u
W=10u L=100u
W=10u L=100u
W=10u L=100u
W=10u L=100u

18. Conclusions
N-type OTFT was analyzed with TOF-SIMS technic to improve processes and performances
P-type OTFT was modelized and different logic port solutions was tested
At the moment p-type OTFT circuits are under production at CNR-IMM (Rome)

19. Thank you!!!

20. Contact Resistance
Contact resistance
by TLM-method
Rc: influence of contact resistance on characteristics of devices with different L
Deviation from linear behavior
Bare
HMDS
TLM method
In both bare and HMDS-treated substrates, devices show contact resistance Rc of the same order (30 kW*cm)
No SAM treatment of S/D contacts has been performed
HMDS-treatment can improve the interface between PEN and PDIF-CN2 but it does not induce any improvement on contact characteristics

21. Chemical side ongoing OTFTs on Flexible Substrate:
N-type OTFTs with evaporated PDIF-CN2 active layer have been fabricated on bare and HMDS-treated PEN substrates
Devices show good performances and stability
Effects of HMDS-treatment on PEN substrate:
Improvement of morphological properties of evaporated PDIF-CN2
Devices made on treated-PEN show better performances with higher mFE and lower SS
Rc keep the same order in the two cases
Reliability:
Both devices show good stability after prolonged bias stress with smaller variations of the curves at high Vgs
Good stability is due to the top-gate structure and hydrophobic properties of fluoropolymer acting as gate dielectric, preventing by water/gas diffusion
Future work:
Future efforts will be devoted to minimize the contact resistance effects through proper functionalization of the S/D electrodes (use of SAM)