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1 Physical Measurement Laboratory Semiconductor and Dimensional Metrology Division Nanoscale Metrology Group MEMS Measurement Science and Standards Project MEMS 5-in-1 RM Slide Set #3 Reference Materials 8096 and 8097 The MEMS 5-in-1 Test Chips – Young’s Modulus Measurements Photo taken by Curt Suplee, NIST

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2 List of MEMS 5-in-1 RM Slide Sets Slide Set #Title of Slide Set 1OVERVIEW OF THE MEMS 5-IN-1 RMs 2PRELIMINARY DETAILS THE MEASUREMENTS: 3 Young’s modulus measurements 4 Residual strain measurements 5 Strain gradient measurements 6 Step height measurements 7 In-plane length measurements 8 Residual stress and stress gradient calculations 9 Thickness measurements (for RM 8096) 10 Thickness measurements (for RM 8097) 11REMAINING DETAILS

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3 Outline for Young’s Modulus Measurements 1References to consult 2Young’s modulus a. Overview b. Equation used c. Data sheet uncertainty equations d. ROI uncertainty equation 3Location of cantilever on RM chip a. For RM 8096 b. For RM 8097 4Cantilever description a. For RM 8096 b. For RM 8097 5Calibration procedure 6Measurement procedure 7Using the data sheet 8Using the MEMS 5-in-1 to verify measurements

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4 Overview 1. J. Cassard, J. Geist, and J. Kramar, “Reference Materials 8096 and 8097 – The Microelectromechanical Systems 5-in-1 Reference Materials: Homogeneous and Stable,” More- Than-Moore Issue of ECS Transactions, Vol. 61, May 2014. 2. J. Cassard, J. Geist, C. McGray, R. A. Allen, M. Afridi, B. Nablo, M. Gaitan, and D. G. Seiler, “The MEMS 5-in-1 Test Chips (Reference Materials 8096 and 8097),” Frontiers of Characterization and Metrology for Nanoelectronics: 2013, NIST, Gaithersburg, MD, March 25-28, 2013, pp. 179- 182. 3. J. Cassard, J. Geist, M. Gaitan, and D. G. Seiler, “The MEMS 5-in-1 Reference Materials (RM 8096 and 8097),” Proceedings of the 2012 International Conference on Microelectronic Test Structures, ICMTS 2012, San Diego, CA, pp. 211-216, March 21, 2012. User’s guide (Section 2, pp. 32-50) 4. J.M. Cassard, J. Geist, T.V. Vorburger, D.T. Read, M. Gaitan, and D.G. Seiler, “Standard Reference Materials: User’s Guide for RM 8096 and 8097: The MEMS 5-in-1, 2013 Edition,” NIST SP 260-177, February 2013 (http://dx.doi.org/10.6028/NIST.SP.260-177).http://dx.doi.org/10.6028/NIST.SP.260-177 Standard 5. SEMI MS4-1113, “Test Method for Young’s Modulus Measurements of Thin, Reflecting Films Based on the Frequency of Beams in Resonance,” November 2013. (Visit http://www.semi.org for ordering information.)http://www.semi.org Fabrication 6. The RM 8096 chips were fabricated through MOSIS on the 1.5 µ m On Semiconductor (formerly AMIS) CMOS process. The URL for the MOSIS website is http://www.mosis.com. The bulk- micromachining was performed at NIST.http://www.mosis.com 7. The RM 8097 chips were fabricated at MEMSCAP using MUMPs-Plus! (PolyMUMPs with a backside etch). The URL for the MEMSCAP website is http://www.memscap.com.http://www.memscap.com 1. References to Consult

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5 Definition: A measure of the stiffness of a material Purpose: To use in the design and fabrication of MEMS devices and ICs Test structure: Cantilever Instrument: Optical vibrometer or comparable instrument Method: Calculated using the average resonance frequency of a cantilever oscillating out-of-plane 2a. Young’s Modulus Overview

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6 2b. Young’s Modulus Equation f correction corrects for deviations from the ideal cantilever (and beam support) geometry and composition where EYoung’s modulus density L can length of cantilever tthickness of cantilever f can average undamped resonance frequency of cantilever, which includes a correction term such that

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The data sheet (DS) expanded uncertainty equation is where k=2 is used to approximate a 95 % level of confidence. 7 Young’s modulus combined standard uncertainty, u cE, equation 2c. Data Sheet Uncertainty Equations where u cE = E and E standard deviation of a Young’s modulus measurement (E) standard deviation of density ( ) L standard deviation of length of cantilever (L can ) thick standard deviation of thickness of cantilever (t) fcan standard deviation of average undamped resonance frequency of cantilever (f can ), which includes a correction term such that

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2c. Data Sheet Uncertainty Equations where fundamped standard deviation of the undamped resonance frequency measurements fresol standard deviation of the frequency measurements (used to obtain f can ) that is due to the frequency resolution freqcal standard deviation of the frequency measurements (used to obtain f can ) that is due to the time base calibration support resonance frequency uncertainty due to non-ideal support or attachment conditions cantilever resonance frequency uncertainty due to non-ideal geometry and/orcomposition

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9 Effective value reported for RM 8096 due to: 1. Debris in the attachment corners 2. Undercutting of the beam 3. Multiple SiO 2 layers Effective value reported for RM 8097 due to: 1.Kinks in cantilevers 2.Undercutting of the beam 3.Non-rigid support 2c. Data Sheet Uncertainty Equations

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10 U ROI expanded uncertainty recorded on the Report of Investigation (ROI) U DS expanded uncertainty as obtained from the data sheet (DS) U stability stability expanded uncertainty 2d. ROI Uncertainty Equation

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11 3. Location of Cantilever on RM Chip (The 2 Types of Chips) RM 8097 –Fabricated using a polysilicon multi-user surface- micromachining MEMS process with a backside etch –Material properties of the first or second polysilicon layer are reported –Chip dimensions: 1 cm x 1 cm RM 8096 –Fabricated on a multi-user 1.5 µ m CMOS process followed by a bulk-micromachining etch –Material properties of the composite oxide layer are reported –Chip dimensions: 4600 µ m x 4700 µ m Lot 95Lot 98

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12 3a. Location of Cantilever on RM Chip For RM 8096 12 For RM 8096 Structural layercomposite oxide W can ( µm) 28 L can ( µm) 200, 248, 300, 348, and 400 t ( µm) ≈2.743 Orientation0 º and 180 º Quantity of beams 3 of each length and of each orientation (making 30 cantilevers) Top view of a cantilever Locate the cantilever in this group given the information on the NIST- supplied data sheet

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13 3b. Location of Cantilever on RM Chip For RM 8097 Locate the cantilever in this group given the information on the NIST-supplied data sheet For RM 8097 Structural layerpoly1 or poly2 W can ( µm) 20 L can ( µm) 100, 150, 200, 250, 300, 350, 400, 450, and 500 t ( µm) ≈2.0 (for poly1) and ≈1.5 (for poly2) Orientation0 º and 90 º Quantity of beams 3 of each length and of each orientation (making 54 poly1 and 54 poly2 cantilevers) Top view of a cantilever

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14 4a. Cantilever Description For RM 8096 Top view of a cantilever c e x y x z x z etch stop (n-implant encompassing active area) exposed silicon to be etched (design layers include active area, contact, via, and glass) m2 dimensional marker that also helps to keep the beam support rigid amount the beam is undercut composite oxide Si m2 dimensional marker n-implant Trace c Trace e

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15 4b. P1 Cantilever Description (For RM 8097) nitride anchor1 double stuffed anchor p0 p2 p1 p1-p2 via c L p1 cantilever opening for etch x y 600 nm anchor1 p1-p2 via p2 p1 L nitride p2 p1 Si 5 m to 30 m x z Top view of a cantilever Cross section along Trace c For a more rigid beam support: 1.Double stuffed anchors are used 2.Anchored “tabs” are included

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4b. P1 Cantilever Description (For RM 8097) x z anchor1 p1-p2 via p2 p1 nitride p2 p1 Si 5 m to 30 m nitride anchor1 double stuffed anchor p0 p2 p1 p1-p2 via f L p1 cantilever opening for etch x y Top view of a cantilever Cross section along Trace f

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17 4b. P2 Cantilever Description (For RM 8097) Top view of a cantilever Cross section along Trace c anchor1 p1-p2 via p2 p1 L nitride p2 p1 Si 5 m to 30 m x z 600 nm opening for etch nitride L anchor1 p1 p1-p2 via p2 double stuffed anchor p2 c anchor2 nitride x y For a more rigid beam support: 1.Double stuffed anchors are used 2.Anchored “tabs” are included

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4b. P2 Cantilever Description (For RM 8097) Top view of a cantilever Cross section along Trace f anchor1 p1-p2 via p2 p1 nitride p2 p1 Si 5 m to 30 m x z opening for etch nitride L anchor1 p1 p1-p2 via p2 double stuffed anchor p2 f anchor2 nitride x y

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19 5. Calibration Procedure In most cases, only the maximum frequency (from which all other signals are derived) needs to be measured. We will only consider this case. Before each data session, calibrate the time base of the instrument For the maximum frequency, f instrument Take at least three measurements Record the average value f meter Record the standard deviation meter Given f meter, record the certified one sigma uncertainty of the frequency meter, u certf, obtained from the frequency meter’s certificate The following calculations are performed on the data sheet with the supplied inputs f instrument, f meter, meter, and u certf : The one sigma uncertainty of a frequency measurement, u cmeter The calibration factor, cal f The frequency measurements are multiplied by cal f to obtain calibrated values.

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Estimate the fundamental resonance frequency of a cantilever, f caninit (found in Table 5 of the data sheet) using Take measurements at frequencies which encompass f caninit using a minimal frequency resolution, f resol Obtain an excitation-magnitude versus frequency plot Record the resonance frequency, f meas1. Repeat to obtain f meas2 and f meas3. Input the values to the data sheet. The data sheet performs the following calculations: 20 6. Measurement Procedure See SP260-177 Tables 3 and 4 for the values of f correction used for RM 8096 and 8097 µ=viscosity of ambient Q=oscillatory quality factor W can =width of cantilever

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21 Find Data Sheet YM.3 –On the MEMS Calculator website (Standard Reference Database 166) accessible via the NIST Data Gateway (http://srdata.nist.gov/gateway/) with the keyword “MEMS Calculator”http://srdata.nist.gov/gateway/ –Note the symbol next to this data sheet. This symbol denotes items used with the MEMS 5-in-1 RMs. Using Data Sheet YM.3 –Click “Reset this form” –Supply INPUTS to Tables 1 and 2 –Click “Calculate and Verify” –At the bottom of the data sheet, make sure all the pertinent boxes say “ok.” If a pertinent box says “wait,” address the issue and “recalculate.” –Compare both the inputs and outputs with the NIST-supplied values 7. Using the Data Sheet

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22 If your criterion for acceptance is: where D E positive difference between the Young’s modulus value of the customer, E (customer), and that appearing on the ROI, E U E(customer) Young’s modulus expanded uncertainty of the customer as obtained from the data sheet U E Young’s modulus expanded uncertainty on the ROI, U ROI 8. Using the MEMS 5-in-1 To Verify Young’s Modulus Measurements Then can assume measuring Young’s modulus according to SEMI MS4 according to your criterion for acceptance if: –Criteria above satisfied and –No pertinent “wait” statements at the bottom of your Data Sheet YM.3

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