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 #6 Reference Materials 8096 and 8097 The MEMS 5-in-1 Test Chips – Step Height Measurements Photo taken by Curt Suplee, NIST

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

3 Outline for Step Height Measurements 1References to consult 2Step height a. Overview b. Equation used c. Data sheet uncertainty equations d. ROI uncertainty equation 3Location of test structure on RM chip a. For RM 8096 b. For RM Step height test structure a. For RM 8096 b. For RM Calibration procedure 6Measurement procedure 7Using the data sheet 8Using the MEMS 5-in-1 to verify measurements

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 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 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 , March 21, User’s guide (Section 5, pp ) 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 , February 2013 ( Standard 5. SEMI MS2-1113, “Test Method for Step Height Measurements of Thin Films,” November (Visit for ordering information.) 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 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 1. References to Consult

5 2a. Step Height Overview Definition: The distance in the z-direction between an initial, flat surface and a final, flat surface Purpose: To determine the thin film thickness values, which can be used in the determination of thin film material parameters, such as Young’s modulus Test structure: Step height test structure Instrument: Interferometric microscope or comparable instrument Method: Obtained from multiple measurements taken along the width of a step height test structure x z

6 where stepN XYt step height measurement from trace “t” stepN XY average of the step height measurements platNYtheight measurement of platform “Y” from trace “t” platNXtheight measurement of platform “X” from trace “t” cal z z-calibration factor 2b. Step Height Equation (for one trace)

7 Step height combined standard uncertainty, u cSH, equation where u Lstep due to measurement uncertainty across length of step u Wstep due to measurement uncertainty across width of step u cert due to the uncertainty of the value of the step height standard used for calibration u cal due to the uncertainty of the measurements taken across the step height standard u repeat(shs) due to repeatability of measurements taken on step height standard u drift due to the amount of drift during the data session u linear due to the deviation from linearity of the data scan u repeat(samp) due to the repeatability of similar step height measurements 2c. Data Sheet Uncertainty Equations

8 The data sheet (DS) expanded uncertainty equation is where k=2 is used to approximate a 95 % level of confidence 2c. Data Sheet Uncertainty Equations Effective value reported? (RM 8096) Effective value reported? (RM 8097) Step HeightNo

9 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

10 3. Location of Structure 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

11 3a. Location of Structure on RM 8096 Locate the step height test structure in this group given the information on the NIST-supplied data sheet Top view of a step height test structure For RM 8096 StepFor the first structure: a m2 over poly1 step from active area to field oxide Reference platform layer m2 atop active area Orientation0º0º Quantity4 distinct step height test structures (with 3 occurrences of each structure)

12 3b. Location of Structure on RM 8097 Locate the step height test structure in this group given the information on the NIST-supplied data sheet Top view of a step height test structure For RM 8097 Stepfrom poly1 to poly2 (or vice versa) Reference platform layer poly0 Orientation0 º, 90 º, 180 º, and 270 º Quantity3 small quads and 2 large quads, where each quad has 4 step height test structures each with a different orientation

13 4a. Step Height Test Structure (For RM 8096) Top view of a step height test structure Cross section along Trace a, b, or c

14 4b. Step Height Test Structure (For RM 8097) Top view of a step height test structure Cross section along Trace a, b, or c

15 5. Calibration Procedure Calibrate instrument in the z-direction Before the data session Record height of step height standard at 6 locations = mean value of the 6 measurements  before = standard deviation of the 6 measurements Record height of step height standard at same location for 6 measurements = mean value of the 6 measurements  same1 = standard deviation of the 6 measurements After the data session Record height of step height standard at 6 locations = mean value of the 6 measurements  after = standard deviation of the 6 measurements Record height of step height standard at same location for 6 measurements = mean value of the 6 measurements  same2 = standard deviation of the 6 measurements

Determine the following: if, then and Calibration Procedure (continued)  cert = certified uncertainty of the step height standard z lin = maximum relative deviation from linearity over the total scan range of the instrument cert = certified value of the step height standard if, then and Supply the following inputs to the data sheet: cert,  cert  6ave,  6same, z drift, cal z, and z lin

17 Obtain 3 2D data traces Obtain the platform heights (and standard deviations) from each 2D data trace 6. Measurement Procedure (for one trace) All measurements are with respect to the height of the reference platform (used to level and zero the data)

18 Find Data Sheet SH.1.a –On the MEMS Calculator website (Standard Reference Database 166) accessible via the NIST Data 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 SH.1.a –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

19 If your criterion for acceptance is: where D SH positive difference between the step height value of the customer, step 1 AB(customer), and that appearing on the ROI, step 1 AB U SH(customer) step height expanded uncertainty of the customer U SH step height expanded uncertainty on the ROI, U ROI 8. Using the MEMS 5-in-1 To Verify Step Height Measurements Then can assume measuring step height 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 SH.1.a