Ferrara & LNL Crystal farm and validation procedure

1. Ferrara & LNL Crystal farm and validation procedure Vincenzo Guidi • Ferrara • Alberti Alberto • Antonini Andrea • Benvenuti Elena • Butturi Mariangela • Cruciani Giuseppe • Dalpiaz Pietro • Fiorini Massimiliano • Guidi Vincenzo • Martinelli Giuliano • Milan Emiliano • Rizzoni Raffaella • Ronzoni Alessandro • Tralli Antonio • Legnaro • Della Mea Gianantonio • Milan Riccardo • Quaranta Alberto • Vomiero Alberto • Carturan Sara • Negro Enrico • Pieri Ugo • Carnera Alberto Geneva,9-10 March 2006

2. Outline • Crystal fabrication: dicing, lapping and polishing techniques • Sample characterization • Film with internal stress • Zeolities: A novel materials for channeling • Multilayered crystal mirror • Conclusions

3. #2000 #320 Crystal Dicing-1 Samples are achieved by dicing a Silicon wafer: 0.250 mm Dicing at various speed and with different grain size of the diamond powders results in samples with diverse features

4. Crystal Dicing: examples of CU 0.250 mm

5. New lapping-polishing facility Logitech six-inch bonding station Logitech lapping-polishing machine PM5 Lapping-polishing machine (LOGITECH) at Sensors and Semiconductor Laboratory

6. Sample fabrication: the crystals stack glass Wax The stack bonder crystal ....assembling.... Wafer dicing..... Paper filter It has been found the correct process parameters: Plate type, speed plate, jig load, abrasive and process time. ....mechanical treatment...

7. Sample fabrication: the modified jig Stack clamping of pp5 jig The modified pp5 jig Right pre-process crystals stack. Left, the crystals stack after lapping and polishing process

8. Sample fabrication: the results A photo of an 2-crystals stack. The sample has been treated with lapping-polishing machine Pre Process: as cut Lapping process Polishing process

9. Planar etching • Defects are induced by the dicing saw (a surface layer estimated to be as thick as 30m is rich in stratches, dislocations, line defects and anomalies). • Removal of such layer by wet planar etching(HF,HNO3,CH3COOH). • Planar etching removes crystalline planes one by one

10. 1000 b) (nm) 100 a R sample M 10 0 10 20 30 40 etching time (min) Planar etching: the results Measurements at IHEP-2: Surface treatment proved to be useful to improve the quality of extracted beam (measurements at 70 GeV). Left :mechanically polished and right chemically polished Chemical polishing enhances the standard roughness (Ra), which tends to decrease for longer etching times (right down).

11. Chemical etching appears to be not suitable to remove the surface damage SEM and AFM- measurements Sample 2M 200x Sample 0.5/30C 1000x AS-cut Chemical etching AS-cut Chemical etching

12. Morphological characterization Chemical etching As diced As diced Chemical etching Chemical polishing enhances standard roughness (Ra)

13. Structural characterization As diced Rough and highly defected surface • RBS channeling results • Successful correlation between surface crystalline perfection and post-dicing surface treatments • Precise tailoring of sample preparation for crystal channeling Chemical etching Inhomogeneous surface BUT high crystalline degree (Baricordi et al. APL 2005).

14. Samples with internal stress: deposition of tensile thin films A method to control of bending is obtained by a thin layer (or strips) of high stress intrinsic coating Si3N4. Our goal was to identify the optimal parameters of Si3N4 film deposition via low-pressure chemical vapour deposition (LPCVD).

15. To obtain a high residual stress the NH3/DCS ratio must be higher than the unity, but... HIGH STRESS a good film thickness uniformity requires a NH3/DCS ratio lower than the unity. A trade-off is needed NH3/SiCl2H2 = 1:5 Uniformity

16. Our LPCVD Parameters • Pressure: 300 mTorr • Temperature: 825°C • NH3/SiCl2H2: 0.2 • Film thickness: 187 nm • Residual stress = 400 MPa • Silicon nitride provides a tensile film with adjustable stess • It does not alter crystal quality like with microindentations LPCVD reactor (LP-Thermtech) at Sensors and Semiconductor Laboratory

17. Deposition of Si3N4 layers 4” (111) oriented silicon wafer with thickness h=200m is started Si3N4 200-nm-thick Si3N4 coating is deposited by LPCVD on both sides of the wafer SiO2 masking layer is subsequently deposited onto the Si3N4 by LPCVD SiO2

18. Deposition of a photoresist on the top Selective etching of SiO2 on the bottom by HF using the polymer as a selective mask removal of the photoresist in acetone and removal of the Si3N4 in H3PO4 removal of SiO2 on the top by HF. The tensile residual stress in silicon nitride (Si3N4) film induce a bending to the Si substrate

19. Optical characterization d wafer slide h lens Image of the wafer holder Laser D screen

20. From Stoney equation: Values of radius and residual stress:

21. Samples with internal stress: deposition of tensile thick films Screen printing machine SMTECH 100 MV at S&SL A technique based on: first deposition of allumina paste (70%), a drying process then a firing (950°C) process. It is possible to deposit a thick layer of alumina film (larger than ten microns).

22. Crystal bending through screen printing technique: preliminary samples

23. Screen printing technique: preliminary results Film thickness permits to obtain a radius of curvature even smaller than 1 m

24. Labs IHEP (Russia) PNPI (Russia) Samples O-shaped Simple thin rod Thick rod Characterization of samples from other labs

25. Example of RBS-channelinganalysis SIDE A • Different degree of crystalline perfection between SIDE A (nearly amorphous) and SIDE B • SIDE B presents a highly defected surface with respect to perfect reference crystal SIDE B

26. Example of RBS-channeling analysis • Investigation on 2D spatial defect distribution: nearly perfect overlap of the spectra indicates homogeneous spatial distribution of defects • The minimum yield is slightly higher than reference silicon, indicating low defects concentration and high crystalline order

27. Novel crystals for channeling: zeolites High acceptance for channeling in natural and artificial zeolites Simulation of potential candidates and characterization of samples

28. What a zeolite is? Zeolite was the name given by the svedish mineralogist Cronstedt in 1756 to identify a class of natural minerals. Under heating, desorption was so strong as it appeared as it were boiling (zein = to boil, lithos = rock).

29. Zeolite is… Smith (1963): aluminosilicate with open three-dimensional tetraedric framework, containg cavities partly occupied by ions and water molecules

30. More technically speaking… The primary building unit is a coordination tetraedron

31. Zeolites for channeling? • Selection of candidates with rectilinear channels, availability in nature or in commerce as relatively wide crystals • Simulation of efficiency for channeling with existing codes • Tests for channeling with MeV protons

32. Zeolites Dicing First samples are achieved by dicing a zeolite: 0.250 mm The sample has been diced with a 30 microns high-performance NBC-Z blade. The speed was 2 mm/s 2 mm

33. Zeolites: first sample Pre- process 200 micron 500 micron After dicing SEM image of a zeolite sample treated: Left just cut from a rock, right after cutting process. In the microscope image shown below, particular of the sample after cut 1 mm

34. New proposal: Multilayered crystal mirror Designed by Institute for High Energy Physics, Protvino, Russia

35. Multilayered crystal mirror A photo of 8-fingers multilayered crystal mirror. 1.5 mm A microscope image of 2 fingers. The gap between fingers is about 30 microns 1.5 mm Cross section of the sample

36. Conclusions • Fabrication of silicon samples • Morphological, structural and optical characterizations • Search for novel materials • First zeolite prototipe realized • Multilayered crystal mirror