Physical Measurement Laboratory Semiconductor and Dimensional Metrology Division

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

2. List of MEMS 5-in-1 RM Slide Sets

3. Outline for Young’s Modulus Measurements

4. 1. References to Consult • 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). • 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.) • Fabrication 6. The RM 8096 chips were fabricated through MOSIS on the 1.5 µm On Semiconductor (formerly AMIS) CMOS process. The URL for the MOSIS website is http://www.mosis.com. The bulk-micromachining was performed at NIST. 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.

5. 2a. Young’s Modulus Overview • 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

6. 2b. Young’s Modulus Equation where E Young’s modulus  density Lcan length of cantilever t thickness of cantilever fcan average undamped resonance frequency of cantilever, which includes a correction term such that fcorrectioncorrects for deviations from the ideal cantilever (and beam support) geometry and composition

7. 2c. Data Sheet Uncertainty Equations • Young’s modulus combined standard uncertainty, ucE, equation where ucE=E and Estandard deviation of a Young’s modulus measurement (E) standard deviation of density () Lstandard deviation of length of cantilever (Lcan) thickstandard deviation of thickness of cantilever (t) fcanstandard deviation of average undamped resonance frequency of cantilever (fcan), which includes a correction term such that • The data sheet (DS) expanded uncertainty equation is where k=2 is used to approximate a 95 % level of confidence.

8. 2c. Data Sheet Uncertainty Equations where fundampedstandard deviation of the undamped resonance frequency measurements fresolstandard deviation of the frequency measurements (used to obtain fcan) that is due to the frequency resolution freqcalstandard deviation of the frequency measurements (used to obtain fcan) that is due to the time base calibration supportresonance frequency uncertainty due to non-ideal support or attachment conditions cantilever resonance frequency uncertainty due to non-ideal geometry and/or composition

9. 2c. Data Sheet Uncertainty Equations Effective value reported for RM 8096 due to: 1. Debris in the attachment corners 2. Undercutting of the beam 3. Multiple SiO2 layers • Effective value reported • for RM 8097 due to: • Kinks in cantilevers • Undercutting of the beam • Non-rigid support

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

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 µm CMOS process followed by a bulk-micromachining etch • Material properties of the composite oxide layer are reported • Chip dimensions: 4600 µm x 4700 µm Lot 95 Lot 98

12. 3a. Location of Cantilever on RM ChipFor RM 8096 Top view of a cantilever Locate the cantilever in this group given the information on the NIST-supplied data sheet 12

13. 3b. Location of Cantilever on RM ChipFor RM 8097 Top view of a cantilever Locate the cantilever in this group given the information on the NIST-supplied data sheet

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

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

16. -5 mm to 30 mm y p1-p2 via x anchor1 opening for etch p0 p1 p2 p2 p1 z double stuffed anchor p1 cantilever nitride x Si f L nitride nitride anchor1 p1-p2 via p2 p1 4b. P1 Cantilever Description (For RM 8097) Top view of a cantilever Cross section along Trace f

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

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

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

20. 6. Measurement Procedure • Estimate the fundamental resonance frequency of a cantilever, fcaninit (found in Table 5 of the data sheet) using • Take measurements at frequencies which encompass fcaninit • using a minimal frequency resolution, fresol • Obtain an excitation-magnitude versus frequency plot • Record the resonance frequency, fmeas1. • Repeat to obtain fmeas2 and fmeas3. Input the values to the data sheet. • The data sheet performs the following calculations: µ=viscosity of ambient Q=oscillatory quality factor See SP260-177 Tables 3 and 4 for the values of fcorrection used for RM 8096 and 8097 Wcan=width of cantilever

21. 7. Using the Data Sheet • 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” • 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 1and 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

22. 8. Using the MEMS 5-in-1To Verify Young’s Modulus Measurements • If your criterion for acceptance is: where DE positive difference between the Young’s modulus value of the customer, E(customer), and that appearing on the ROI, E UE(customer) Young’s modulus expanded uncertainty of the customer as obtained from the data sheet UE Young’s modulus expanded uncertainty on the ROI, UROI • 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