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Estimation of Temperature Distribution in Silicon

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Estimation of Temperature Distribution in Silicon during MicroLaser Assisted Machining Presented byKamlesh SutharJohn Patten*Western Michigan UniversityManufacturing Engineering Department Kalamazoo, MI-49008, USALei DongCondor USA, Inc.8318 Pineville-Matthews Road, Suite 276Charlotte, NC-28226Hisham Abdel-AalDepartment of General EngineeringUniversity of Wisconsin at PlattevillePlatteville, WI- 53818, USAOutline2ObjectiveExperimental work• Tool Modification• Measurement of laser power• Characterization• AFM• Thermal imagingAnalytical Modeling• Point heat source• Plane Heat source • Gaussian Beam Laser Heat SourceFinite Element Analysis• Gaussian Profile heat sourceSummaryMSEC-2008 ASME Conference, Evanston, ILMotivation• Semiconductor and ceramic materials are highly brittle and plastic deformation at room temperature is difficult and they prone to fracture during machining• Brittleness has detrimental effect on tool• Therefore, the challenge is to develop a cost effective machining process which can produce ultra fine surface finish3MSEC-2008 ASME Conference, Evanston, ILObjective• Silicon is highly brittle at room temperature and the hardness is the function of temperature• High Pressure Phase Transformation (HPPT) is one of the process mechanisms involved in ductile machining of semiconductors and ceramics.• Preferentially heat the HPPT material to increase ductility through thermal softening– Reduce tool wear – Minimize surface and subsurface damage.• Thermal Softening temperature for silicon is 600-800 oC4MSEC-2008 ASME Conference, Evanston, ILEffect of Temperature on Hardness of Silicon 5(Trefilov,1963)Schematic of -LAM of Silicon 6MSEC-2008 ASME Conference, Evanston, ILDiamond Tip AttachmentAttachment was done at Digital Optical Company (Charlotte, NC) by Jay Matthews250 um90 Conical Tip5 μm radius7MSEC-2008 ASME Conference, Evanston, ILDeliverable Power After Attachment of Diamond & Laser ParameterIR LaserWavelength1480nmLaser Power (max)400mWPower at Diamond Tip140mWPhoton energy~0.9 eVTransitivity of Si-II80-90 %Absorbance in Si-II10.0 %Diamond toolDiameter of tip5-6 μmThermal conductivity900-1200W/m/KSiliconSpecific heat0.7J/g/KDensity2.33 g/cm38MSEC-2008 ASME Conference, Evanston, IL0501001502002503003504000 500 1000 1500Output Laser Power (mw)Laser Driving Current (mA)Laser (0~400mw,1480nm) Power Loss Power After the AttachmentPower Before the AttachmentIR Softens Metallic SiliconIndent depths at different laser powerSi WaferWeightsFiberScratching Speed Test (Load 25mN)Speed1: 0.305 mm/sec; Speed 2: 0.002 mm/sec; Speed 3:.0002mm/secScratch and stay test (load 25mN)9MSEC-2008 ASME Conference, Evanston, ILAFM Groove Depth Measurement10MSEC-2008 ASME Conference, Evanston, ILThermal Imaging : Different Stages of HeatingStage :111MSEC-2008 ASME Conference, Evanston, ILThermal Imaging : Different Stages of HeatingStage :212MSEC-2008 ASME Conference, Evanston, ILThermal Imaging : Different Stages of HeatingStage :313MSEC-2008 ASME Conference, Evanston, ILThermal Imaging : Different Stages of HeatingStage :414MSEC-2008 ASME Conference, Evanston, ILThermal Imaging : Different Stages of HeatingStage :515MSEC-2008 ASME Conference, Evanston, ILThermal Imaging : Different Stages of HeatingStage :616MSEC-2008 ASME Conference, Evanston, ILEstimation of Physical properties of Si-II and their use in modelingTemperature (K)Thermal Conductivity of metallic Si-IIW/cm/K3000.002540000045000.00556000.00757000.01258000.01659000.02517MSEC-2008 ASME Conference, Evanston, IL1. Analytical modelingThe thermo-physical properties are taken at intermediate temperature. 2. FEM formulationThermo physical properties of si-I and Si-II are taken as function of Temperature•MatLab is used for programming analytical model •COMSOL 3.4 is used for FEAAnalytical Modeling1. Moving point heat source ( scratch test) 2 2 24332202 (1 )4x y zttpq r dTeC:Thermal Diffusivity (cm2/s)r : ReflectivityΡ : Density (g/cm3)k : Thermal Conductivity W/cm/K18MSEC-2008 ASME Conference, Evanston, ILAnalytical Modeling….2. Moving Plane Heat Source:Thermal Diffusivity (cm2/s)r : ReflectivityΡ : Density (g/cm3)k : Thermal Conductivity W/cm/K22422332202 (1 )16tvuXvaaaq r v dT e ek19MSEC-2008 ASME Conference, Evanston, ILAnalytical Modeling….3. Gaussian Beam profile Moving Plane with Laser as heating source (scratch test)22, expoxyxyI x y Irr3201( , , ) ( )QrT x y z f u duk12222222222exp1()1X V uYZuuufuuuxXryYrzZrvVr24rqQr1222 tur20Gaussian ProfileTemperature ProfileTemperature functionNon-dimensional parameterMSEC-2008 ASME Conference, Evanston, IL3. Gaussian Beam profile Moving Plane…….Temperature Profile21MSEC-2008 ASME Conference, Evanston, ILFinite Element Analysis22MSEC-2008 ASME Conference, Evanston, ILSummary• Thermal images: the absorptivity of the Si-II is different than the Si-I and therefore the temperature rise occurs is due to HPPT• The temperature rise for the stationary point heat source is 778oC. • For the moving plane heat source T at 0.0002 mm/sec, is 468oC, • The COMSOL result, for a stationary heat source temperature rise of 631oC. The COMSOL results are in good agreement with the previous estimated temperature23MSEC-2008 ASME Conference, Evanston, ILFuture Work• Numerical Analysis of the Moving laser with varying laser power with varying absorption with the depth.• Investigate the possibility of other wavelength. • Machining using chemical etching• Investigation of acoustic emission of the machining process24References[1] Abdel-Aal, H. A., Y. Reyes, et al. (2006). "Extending electrical resistivity measurements in micro-scratching of silicon to determine thermal conductivity of the metallic phase Si-II." Materials Characterization 57(4-5): 281-289. [2] Carslaw, H. S. and J. C. Jeager (1953). Conduction of Heat in Solids. Clarendon, UK, Oxford. [3] Dong, L. (2006). In-situ detection and heating of high pressure metallic phase of silicon during scratching. United States -- North Carolina, The University of North Carolina at Charlotte., PhD Dissertation, Mechanical Engineering Dept.[4] Hanfland, M., M. Alouani, et al. (1988). "Optical properties of metallic silicon." Physical Review B 38(18): 12864. [5] Hou, Z. B. and R. Komanduri (2000). "General solutions for stationary/moving plane heat source problems in manufacturing and tribology." International Journal of Heat and Mass Transfer 43(10): 1679-1698. [6]


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