MEMS 5 in1 RM Slide Set 10 Reference

MEMS 5 -in-1 RM Slide Set #10 Reference Materials 8096 and 8097 The MEMS 5 -in-1 Test Chips – Thickness Measurements (for RM 8097) Physical Measurement Laboratory Semiconductor and Dimensional Metrology Division Nanoscale Metrology Group MEMS Measurement Science and Standards Project 1 Photo taken by Curt Suplee, NIST

List of MEMS 5 -in-1 RM Slide Sets Slide Set # Title of Slide Set 1 OVERVIEW OF THE MEMS 5 -IN-1 RMs 2 PRELIMINARY DETAILS THE MEASUREMENTS: 11 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) REMAINING DETAILS 2

Outline for Thickness Measurements (for RM 8097) 1 References to consult 2 Thickness for RM 8097 a. Overview b. Equation used c. Data sheet uncertainty equations d. ROI uncertainty equation 3 Location of test structure on RM chip 4 Test structure description 5 Calibration procedure 6 Measurement procedure 7 Using the data sheet 8 Using the MEMS 5 -in-1 to verify measurements 3

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. Mc. Gray, 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. 179182. 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 MS 2 -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, “New Optomechanical Technique for Measuring Layer Thickness in MEMS Processes, ” J. of Microelectromechanical Systems, Vol. 10, No. 1, pp. 153 -157, March 2001. • Fabrication 7. The RM 8097 chips were fabricated at MEMSCAP using MUMPs-Plus! (Poly. MUMPs with a 4 backside etch). The URL for the MEMSCAP website is http: //www. memscap. com.

2 a. Thickness (for RM 8097) Overview • • • Description: 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: Cantilever exhibiting stiction Instrument: Interferometric microscope, stylus profilometer, or comparable instrument(s) Method: Calculated from step height measurements of: a) the height of the anchor to the underlying layer (A), b) the height of the stuck portion of the cantilever to the anchor (B), and/or c) the height of the stuck portion of the cantilever to the underlying layer (C) C 5

2 b-2 c. P 1 or P 2 Thickness Equations and Data Sheet Uncertainty Equations (for RM 8097) where A B Ccalc H J height from the underlying layer to the anchor height from the anchor to the top of the stuck portion of the cantilever calculated height from the underlying layer to the top of the stuck portion of the cantilever anchor etch depth height from the top of the underlying layer to the bottom of the stuck portion of the cantilever that takes into consideration the roughness of the surfaces, any residue present between the layers and a tilting component 6

2 b-2 c. P 1 or P 2 Thickness Equations and Data Sheet Uncertainty Equations (for RM 8097) • Determine thickness, α, three different ways: • Choose the value for α (i. e. , αii, or αiii) that has the smallest uncertainty unless the value for α has been preselected The data sheet (DS) expanded uncertainty equation is • where k=2 is used to approximate a 95 % level of confidence 7

2 d. ROI Uncertainty Equation UROI UDS Ustability expanded uncertainty recorded on the Report of Investigation (ROI) expanded uncertainty as obtained from the data sheet (DS) stability expanded uncertainty 8

3. Location of Cantilever on RM 8097 (The RM 8097 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 9 Lot 95 Lot 98

3. Location of Cantilever on RM 8097 For RM 8097 Layer poly 1 or poly 2 W (µm) 20 L (µm) Thickness cantilevers: 600 (poly 1 only), 650, 700, 750, and 800 In-plane length cantilevers: 24, 80, 200, 500, and 1000 Orientation Thickness: 0º In-plane length: 0º (poly 1 only) and 90º Quantity of cantilevers 3 of each length for each orientation Thickness: 15 poly 1 and 12 poly 2 In-plane length: 30 poly 1 and 15 poly 2 Top view of thickness test structure Locate the cantilever in one of 10 these groups given the information on the NIST-supplied data sheet

4. Test Structure Description (For RM 8097) Top view of thickness test structure 11

4. Test Structure Description For RM 8097 p 1 p 2 Top view of thickness test structures p 2 Unconventional anchor design Top view of cantilevers in inplane length group Same anchor design as in thickness test structures p 1 12

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

6. Measurement Procedure • Measure A (using a stylus profilometer) – optional – – – Obtain 3 data traces Level the data with respect to the poly 0 layer From plat. X • • – C From plat. Y • • • Obtain plat. Xa 1, plat. Xb 1, and plat. Xc 1 Obtain splat. Xa 1, splat. Xb 1, and splat. Xc 1 Obtain plat. Ya 1, plat. Yb 1, and plat. Yc 1 Obtain splat. Ya 1, splat. Yb 1, and splat. Yc 1 Measure C (using an optical interferometer) – – Use a high magnification objective Obtain 3 data traces (typically perpendicular to the beam and crossing the pegged portion of the beam) Level the data with respect to the poly 0 layer From plat. Z – – • • – Obtain plat. Za 2, plat. Zb 2, and plat. Zc 2 Obtain splat. Za 2, splat. Zb 2, and splat. Zc 2 From plat. X • • Obtain plat. Xa 2, plat. Xb 2, and plat. Xc 2 Obtain splat. Xa 2, splat. Xb 2, and splat. Xc 2 14

6. Measurement Procedure (continued) • Obtain – From the NIST-supplied data sheet: • • • – – • repeat(samp)N H H Jest uc. Jest srough. X srough. Y = relative step height repeatability standard deviation anchor etch depth range of the anchor etch depth estimated value for the dimension J estimate for the combined standard uncertainty of Jest smallest of all the values obtained for splat. Xt 1 and splat. Xt 2 srough. Z smallest of all the values obtained for splat. Yt 1 and splat. Zt 2 Typically, choose – – – Fate of A = 1 Fate of B = 1 Fate of C > 0 C to disregard i as a possible thickness to disregard ii as a possible thickness if > 0, to force the selection of iii (calculated using C and Jest) as the thickness if = 0, to let the software determine thickness by the smallest uncertainty value 15

7. Using the Data Sheet • Find Data Sheet T. 3. a – – • 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. 3. a – – – Click “Reset this form” Supply INPUTS to Tables 1 through 4 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-1 To Verify RM 8097 Thickness Measurements • If your criterion for acceptance is: where Dα Uα(customer) Uα positive difference between the thickness value of the customer, α(customer), and that appearing on the ROI, α thickness expanded uncertainty of the customer thickness expanded uncertainty on the ROI, UROI • Then can assume measuring the poly 1 (or poly 2) thickness according to SEMI MS 2 according to your criterion for acceptance if: 17 – Criteria above satisfied and – No pertinent “wait” statements at the bottom of your Data Sheet T. 3. a