1 Challenge the future To do list. add extra slide about the coupling, at pressure level. Burn CD

2 Challenge the future Wafer transport and gas separation in a contact-less Spatial Atomic Layer Deposition track. Candidate: Gonzalo Ramirez Troxler Committee: Dr. ir. R.A.J van Ostayen Dr. E.H.A Granneman Prof.ir. R. Munnig Schmidt Dr. R. Delfos

3 Challenge the future Outline Introduction and motivation Solar Cells Market and challenges. Solar cells, recombination velocity and passivation. Atomic Layer Deposition Levitrack System Working principle Thesis goals: fine tuning stage. Modelling Thin Film Flow Concentration of Species Results CFD model Prototype system to measure position of wafer Conclusions and recommendations

4 Challenge the future Introduction Solar Cells Market 1,600% growth of MW installed last decade. Resources depletion. Ecological impact. Outlook

5 Challenge the future Introduction Challenge: To position Solar Cells as a major actor in the power generation scenario. Cost Reduction and Increase efficiency. Motivation Surface Passivation using aluminium oxide - Al 2 O 3

6 Challenge the future Introduction Levitrack: Contact-less transportation track Substrates levitate and layers of Al 2 O 3 are deposited (ALD). High Throughput. Low cost of construction. LEVITECH and LEVITRACK Levitech BV is a Dutch based company that develops novel solutions for the IC and Solar Cells Industry. Spin-off of ASM International.

7 Challenge the future Introduction Solar cell and passivation Surface Passivation increase efficiency of solar cell: Increase lifetime of charge carriers.

8 Challenge the future Introduction Atomic Layer Deposition (ALD) Initial surface

9 Challenge the future Introduction Atomic Layer Deposition (ALD) TMA reacts with hydroxyl groups

10 Challenge the future Introduction Atomic Layer Deposition (ALD) TMA saturates surface.

11 Challenge the future Introduction Atomic Layer Deposition (ALD) Purge using N 2.

12 Challenge the future Introduction Atomic Layer Deposition (ALD) H 2 O reacts with methyl groups and Al.

13 Challenge the future Introduction Atomic Layer Deposition (ALD) H 2 O saturates the surface forming Al 2 O 3.

14 Challenge the future Introduction Atomic Layer Deposition (ALD) Purge using N 2.

15 Challenge the future Introduction Spatial Atomic Layer Deposition (1) Single Reactor Spatial ALD N2N2 TMA H2OH2O

16 Challenge the future Introduction Spatial Atomic Layer Deposition (2) Single Reactor 12 meter Spatial ALD Track Layer height: 10 nm Time: 5 min X 5

17 Challenge the future LEVITRACK Working principle (1)

18 Challenge the future LEVITRACK Working principle (2) 0.5 mm

19 Challenge the future LEVITRACK Working principle (3) 156 mm

20 Challenge the future LEVITRACK Working principle (4)

21 Challenge the future LEVITRACK Thesis goal: fine tuning stage. The aim of this thesis is to study and improve this 4-m test setup, in order to demonstrate stable transport, while minimizing the mixing of precursor gases. Stable transport: no damage on wafers. Mixing of precursors: TMA and H2O need to be always separated on space.

22 Challenge the future Modelling Multiphysics Fluid Flow Concentration of species Surface Chemistry Heat transport Structural mechanics CFD Model

23 Challenge the future Modelling Thin film flow (1) Navier-Stokes equations + Continuity equation. Reynolds’ equation Unknowns: 3 velocities and pressure. Unknown: pressure Assumptions: Lubricant isoviscous. Low Reynolds number. (Negligible Inertia force) Negligible body forces.

24 Challenge the future Modelling Height average velocity. N 2 -O 2 model. Stationary. Concentration of species Thin Film Flow Concentration of Species. One way coupling.

25 Challenge the future Results and discussion CFD Model (1) Out Volume Top Volume Gap Bottom Volume Gap Exhaust

26 Challenge the future Results and discussion Flat surface track: benchmark Mixing requirement not fulfilled. Flat surface

27 Challenge the future Results and discussion Flat surface track: improvement to geometry 100% groove 70% groove

28 Challenge the future Results and discussion 100% grooves Mixing requirement fulfilled. 100% grooves.

29 Challenge the future Results and discussion 100% grooves: Flying height

30 Challenge the future Results and discussion 70% grooves Mixing requirement not fulfilled. Fh = 140 μ m 70% grooves.

31 Challenge the future Results and discussion Flat surface vs. 100% grooves

32 Challenge the future Results and discussion Flat surface vs. 70% grooves

33 Challenge the future Results and discussion Grooved surface track (5) No Groove70% Groove100% Groove Mixing Requirement

34 Challenge the future LEVITRACK Thesis goal: fine tuning stage. The aim of this thesis is to study and improve this 4-m test setup, in order to demonstrate stable transport, while minimizing the mixing of precursor gases.

35 Challenge the future Results and discussion Design system to measure separation of the of the wafer to the lateral wall. Lateral gap measurement system (1)

36 Challenge the future Results and discussion Lateral gap measurement system (2)

37 Challenge the future Conclusions and recommendations It was developed: Fast and accurate enough CFD model to predict the pressure profile and spread of precursors inside the track. As reference 3d NS model takes 2 day per model, while the thin film flow model minutes. System to measure the lateral gap. Submitted to be patented. It was found: Alternative geometry, which fulfils the mixing requirement. Conclusions

38 Challenge the future Conclusions and recommendations Include dynamics of the wafer in the model. Implement and study lateral stability with proposed measurement system. Integration of the deposition process to the model. Recommendations

39 Challenge the future

40 Challenge the future Back Up slides

41 Challenge the future Back up slides Solar cell and passivation (1) N-type and P-type junction together. 2.- Creation of the depletion region. 3.- Light adsorbed by the silicon. 4.- Creation of electron- holes pairs Hole->p-type. Electron->n-type Electron-hole pair tries to recombine. 6.-Electrones conducted.

42 Challenge the future P1 system Working principle (4)

43 Challenge the future Modelling Analytical model A negative pressure difference decrease the wafer velocity. 0.1 mbar 20% reduction of expected velocity. Analytical model developed in Levitech. Simple approach.

44 Challenge the future Model Validation Model validation (1) 7 mbar 3 mbar 5 mbar 10 mbar

45 Challenge the future Model Validation Model validation (2) Velocity: 0 [m/s]: Row 8: in front of the wafer. Row 10: on the edge of the wafer. Row 12: Below the wafer.

46 Challenge the future Model Validation Model validation (3)

47 Challenge the future Results and discussion Channel effect. Load asymmetry Variation of the flying height (100μm). Reduce transportation velocity. Needs to be further studied in the functional prototype. Summary of grooved geometry

48 Challenge the future Results and discussion Lateral gap measurement system (3)