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MEMS 5-in-1 RM Slide Set #9: Thickness Measurements for RM 8096

This reference material set provides a comprehensive guide for thickness measurements in MEMS devices. It includes detailed instructions, calibration procedures, and measurement techniques. The set is designed for use in physical measurement laboratories and is part of the Nanoscale Metrology Group's MEMS Measurement Science and Standards Project.

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MEMS 5-in-1 RM Slide Set #9: Thickness Measurements for RM 8096

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  1. MEMS 5-in-1 RM Slide Set #9 Reference Materials 8096 and 8097 The MEMS 5-in-1 Test Chips – Thickness Measurements (for RM 8096) 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 Thickness Measurements (for RM 8096)

  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 8, pp. 137-156) 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 MS2-1113, “Test Method for Step Height Measurements of Thin Films,” November 2013. (Visit http://www.semi.org for ordering information.) • Thickness article 6. J.C. Marshall and P.T. Vernier, “Electro-physical technique for post-fabrication measurements of CMOS process layer thicknesses,” NIST J. Res., Vol. 112, No. 5, pp. 223-256, 2007. • Fabrication 7. 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.

  5. 2a. Thickness (for RM 8096) Overview • Definition: The height of one or more thin-film layers • Purpose: Used in the determination of thin film material parameters, such as Young’s modulus • Test structure: Step height test structures • Instruments: Interferometric microscope and stylus profilometer or comparable instruments • Method: Calculated using the results of six step height measurements taken from four different step height test structures

  6. t4 = t(gl) t3 = timd(gl/pmd) t2 = tpmd(imd/fox) t1 = tfox(pmd/sub) toxide = t1+ t2+ t3+ t4 2b. Thickness Equations (for RM 8096) where t4glass thickness t3deposited oxide after the m1 deposition [between the pmd (poly-to-metal dielectric) layer and the glass layer] t2deposited oxide before the m1 deposition [between the field oxide and the imd (inter-metal dielectric) layer] t1field oxide thickness (between the substrate and the pmd layer) toxidecomposite oxide thickness

  7. 2b. Thickness Equations (for RM 8096) • Consult the thickness article reference for the nomenclature where and where Y=Y1, Y2, Y3, or Y4

  8. 2c. Data Sheet Uncertainty Equations • Composite oxide thickness combined standard uncertainty, ucoxide, equation • The data sheet (DS) expanded uncertainty equation is where k=2 is used to approximate a 95 % level of confidence

  9. 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

  10. 3. Location of Structure on RM 8096(The RM 8096 Chip) • 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

  11. 3. Location of Structure on RM 8096 Top view of a step height test structure Locate the step height test structure in this group given the information on the NIST-supplied data sheet

  12. z z x x 4. Test Structure Description (For RM 8096)

  13. 5. Calibration Procedure • Calibrate instrument in the z-direction • As specified for step height calibrations

  14. 6. Measurement Procedure • Obtain a step height measurement (according to SEMI MS2 and using Data Sheet SH.1.a) for the 6 steps pointed to in the figure below. • Step 1 [i.e., step1AB] • Step 2 [i.e., step2rA] • Step 3 [i.e., step1EF] • Step 4 [i.e., step1GH] • Step 5 [i.e., step3AB(n)] – use a stylus profilometer (or comparable instrument) due to the top layer being non-reflective • Step 6 [i.e., step3BC(0)] – use the NIST-supplied value since this is a measurement taken before the post-processing. • Record the step heights and uncertainties in Data Sheet T.1

  15. 7. Using the Data Sheet • Find Data Sheet T.1 • 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 T.1 • Click “Reset this form” • Supply INPUTS to Tables 1 through 3 • Using Data Sheet SH.1.a results for Table 1 inputs • 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

  16. 8. Using the MEMS 5-in-1To Verify RM 8096 Thickness Measurements • If your criterion for acceptance is: where Doxide positive difference between the thickness value of the customer, toxide(customer), and that appearing on the ROI, toxide Uoxide(customer) thickness expanded uncertainty of the customer Uoxide thickness expanded uncertainty on the ROI, UROI • Then can assume measuring the composite oxide beam thickness according to SEMI MS2 according to your criterion for acceptance if: • Criteria above satisfied and • No pertinent “wait” statements at the bottom of your Data Sheet T.1

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