Ferrara & LNL Crystal farm and validation procedure Geneva,9-10 March 2006 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

Outline Crystal fabrication: dicing, lapping and polishing techniquesCrystal fabrication: dicing, lapping and polishing techniques Sample characterizationSample characterization Film with internal stressFilm with internal stress Zeolities: A novel materials for channelingZeolities: A novel materials for channeling Multilayered crystal mirrorMultilayered crystal mirror ConclusionsConclusions

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

Crystal Dicing: examples of CU mm

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

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

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

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

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). 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,HNO 3,CH 3 COOH).Removal of such layer by wet planar etching (HF,HNO 3,CH 3 COOH). Planar etching removes crystalline planes one by onePlanar etching removes crystalline planes one by one Planar etching

Chemical polishing enhances the standard roughness (R a ), which tends to decrease for longer etching times (right down). 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

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

Morphological characterization Chemical polishing enhances standard roughness (R a ) As diced Chemicaletching Chemical etching

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

A method to control of bending is obtained by a thin layer (or strips) of high stress intrinsic coating Si 3 N 4. Our goal was to identify the optimal parameters of Si 3 N 4 film deposition via low-pressure chemical vapour deposition (LPCVD). Samples with internal stress: deposition of tensile thin films

NH 3 /SiCl 2 H 2 = 1:5 HIGH STRESS Uniformity To obtain a high residual stress the NH 3 /DCS ratio must be higher than the unity, but... a good film thickness uniformity requires a NH 3 /DCS ratio lower than the unity. A trade-off is needed

Pressure: 300 mTorr Temperature: 825°C Temperature: 825°C NH 3 /SiCl 2 H 2 : 0.2 NH 3 /SiCl 2 H 2 : 0.2 Film thickness: 187 nm Film thickness: 187 nm Residual stress = 400 MPa Residual stress = 400 MPa Our LPCVD Parameters LPCVD reactor (LP-Thermtech) at Sensors and Semiconductor Laboratory Silicon nitride provides a tensile film with adjustable stessSilicon nitride provides a tensile film with adjustable stess It does not alter crystal quality like with microindentationsIt does not alter crystal quality like with microindentations

Deposition of Si 3 N 4 layers Si 3 N 4 4” (111) oriented silicon wafer with thickness h=200  m is started 200-nm-thick Si 3 N 4 coating is deposited by LPCVD on both sides of the wafer SiO 2 masking layer is subsequently deposited onto the Si 3 N 4 by LPCVD SiO 2

Selective etching of SiO 2 on the bottom by HF using the polymer as a selective mask removal of the photoresist in acetone and removal of the Si 3 N 4 in H 3 PO 4 removal of SiO 2 on the top by HF. The tensile residual stress in silicon nitride (Si 3 N 4 ) film induce a bending to the Si substrate Deposition of a photoresist on the top

Optical characterization Laser lens screen wafer slide h d  Image of the wafer holder

From Stoney equation: Values of radius and residual stress : AxesAxes wafer thickness (  m) h (mm)  (mm) d (mm) Radius R (m) Young modulus Es (GPa) Poiss on Film thickness (nm) Residual stress (GPa) x ,271300, ,82 y ,561300, ,91 mean value 0,87 x ,091800, ,24 y ,931800, ,34 mean value 1,29

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). Samples with internal stress: deposition of tensile thick films

Crystal bending through screen printing technique: preliminary samples

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

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

Example of RBS-channeling analysis 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 A SIDE B

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

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

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).

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

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

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 Zeolites for channeling?

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

Zeolites: first sample 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 Pre- process After dicing 200 micron 500 micron

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

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

Conclusions Fabrication of silicon samplesFabrication of silicon samples Morphological, structural and optical characterizationsMorphological, structural and optical characterizations Search for novel materialsSearch for novel materials First zeolite prototipe realizedFirst zeolite prototipe realized Multilayered crystal mirrorMultilayered crystal mirror