In-situ AFM Tensile Testing Micron Scale Mechanical Properties Advantages of In-Situ Testing Similar Works Testing stage

In-situ AFM Tensile Testing Micron Scale Mechanical Properties Advantages of In-Situ Testing Similar Works Testing stage www.phwiki.com

In-situ AFM Tensile Testing Micron Scale Mechanical Properties Advantages of In-Situ Testing Similar Works Testing stage

Rose, Frank, Contributing Editor has reference to this Academic Journal, PHwiki organized this Journal In-situ AFM Tensile Testing ME 395 Professor Horacio D. Espinosa Chris Biedrzycki, Matthieu Chardon, Travis Harper, Richard Neal Micron Scale Mechanical Properties Once structures enter microscale, laws of macro mechanics no longer dominate mechanical response Samples approach size scale of grains in addition to dislocations, also dominated by surface effects Multimaterial interfaces, sharp corners in MEMS devices require in-situ characterization Devices in market require a high amount of reliability, necessitating direct fatigue testing methods Advantages of In-Situ Testing Model entire range of behavior Differentiate elastic in addition to plastic regimes Underst in addition to more than ultimate tensile strength (UTS)

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Similar Works 1 2) Microtensile Tests with the Aid of Probe Microscopy as long as the Study of MEMS Materials, Knauss, Chasiotis 1) Mechanical Measurements at the Micron in addition to Nanometer Scales, Knauss, Huang =2 m 2 3 3) MEMS Fatigue Testing to Study Nanoscale Response, Fisher, Labiossiere No testing results 1 Testing stage Polysilicon specimen Integrated during fabrication Pulled by mass Actuators move mass when voltage applied Force measured by capacitive sensor Strain measured by DIC From Zhu et. al., 2003 ANSYS Modeling of System From Zhu et. al., 2003 The maximum load deliverable by the loading device is ~100 mN

Polysilicon Sample 10m 4m From Prorok, et al. Vol 5, 2004. Integrated in Chip Yong’s Chip Chris’s Quarter Testing Setup Difficult to l in addition to the cantilever on the test specimen without repeatedly breaking tips

Atomic Force Microscopy (AFM) Benefits Very fine resolution (~0.02nm) Variable scanning size/rate Risks Noise sensitivity, drift Constraints on sample size/mass From Espinosa, “Introduction to AFM in addition to DPN”, ME395 Winter 2004 AFM Resolution Resolution Dimension 3100: 512×512 pix JEOL: 256×256 pix Digital Image Correlation (DIC) can interpret change in position of a pixel by change in grayscale pixel strength (from 1=black to 255=white). Ideally, DIC can underst in addition to a resolution of 1/255th of a pixel AFM Resolution Scan size (say, 1.0 m) corresponding to 512 pixels DIC resolution: 1/255th of a pixel Theoretical (maximum) displacement resolution (a) If length of sample is 10m, theoretical resolution of strain is (b) (a) (b)

AFM Imaging Types Amplitude Topography Polysilicon pad imaged using D3100 AFM AFM Imaging Types Amplitude Topography Polysilicon pad imaged using JEOL AFM AFM Problems Adjustment of voltage, frequency as long as tip Sensitivity to dust/scratches Breakage of tip Crash of tip into sample Sensitivity of feedback control system

Digital Image Correlation No automatic compensation as long as drift Correlation on stationary samples Drift strain is only strain Used to generate correction factor Digital Image Correlation (DIC) Example Illustrates DIC Capabilities X-X Tensile Strain Y-Y Tensile Strain Shear Strain Sample Prior to De as long as mation Error DIC Problems Out-of-plane De as long as mation Displacement Gradients Scanning Noise

DIC Resolution Displacement resolution of DIC is 1/255pix, much smaller than the 0.512 pix minimum displacement in pixels as long as the polysilicon at failure. AFM/DIC should be able to display 0.512/(1/255), or 130 images as long as the range of displacement to failure based on ideal resolution/largest scan area. Note: actual resolution smaller than ideal, fewer images result. Smaller scan areas will provide more images, in addition to thus finer underst in addition to ing of the change in strain over time. Digital Image Correlation (DIC) Sample DIC images from 10x10m sample using D3100 AFM Digital Image Correlation (DIC) Sample DIC images from 10x10m sample using JEOL 5200 AFM

AFM Comparison The EPIC AFM, scanned in amplitude mode, yields the best results Experimental Design Optimal Designs Computer generated Best with respect to a particular criterion D-Optimal minimizes l(X’X)-1l Places points at regions of greatest st in addition to ard error Experimental Design H0: 1 = 2 H1: 1 2 = P(type I error) = P(reject H0 l H0 true) = P(type II error) = P(fail to reject H0 l H0 is false) Power = 1 – Robust Design All relevant in as long as mation obtained using less than half the required experiments in a full factorial study

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Experimental Design St in addition to ard Order 19 Removed (Above 3.5) Outliers distort the analysis of variance Outlier when residuals +/- 3 Experimental Results Significant Factors: A, B, AB R-Squared: .776 Experimental Results

In Conclusion Optimal testing conditions as long as drift reduction: JEOL 5200 AFM (Forced Feedback) Amplitude Scan Tapping Mode High Scan Area Sample choice in addition to scan rate effect drift rate very little In Conclusion Optimized drift condition remains too large to distinguish polysilicon strains from error 1% Strain at failure as long as polysilicon – minimized drift remains 100% of experimental strain With current minimized strain values, brittle samples cannot be assessed Future Work Drift Effects Reduction Opportunities Appraiser Variation in DIC Analysis Environmental Effects Electromechanical Noise Temperature, Pressure, Humidity Variation Feedback Mechanism – Consider Image Repeatability Sample Ductility

Thank You For Your Time Questions In-Situ AFM Tensile Testing Group Chris Biedrzycki, Matthieu Chardon, Travis Harper, Richard Neal

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