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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 8097The MEMS 5-in-1 Test Chips

– Young’s Modulus Measurements

Photo taken by Curt Suplee, NIST

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List of MEMS 5-in-1 RM Slide SetsSlide Set # Title of Slide Set

1 OVERVIEW OF THE MEMS 5-IN-1 RMs

2 PRELIMINARY 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)

11 REMAINING DETAILS

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Outline forYoung’s Modulus Measurements

1 References to consult

2 Young’s modulus a. Overview b. Equation used c. Data sheet uncertainty equations d. ROI uncertainty equation

3 Location of cantilever on RM chip a. For RM 8096 b. For RM 8097

4 Cantilever description a. For RM 8096 b. For RM 8097

5 Calibration procedure

6 Measurement procedure

7 Using the data sheet

8 Using the MEMS 5-in-1 to verify measurements

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• Overview1. 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).

• Standard5. 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.)

• Fabrication6. 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.

1. References to Consult

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• 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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2b. Young’s Modulus Equation

fcorrection corrects for deviations from the ideal cantilever (and beam support) geometry and composition

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42330.38

t

LfE cancan

where E Young’s modulus densityLcan length of cantilevert thickness of cantileverfcan average undamped resonance frequency of cantilever,

which includes a correction term such that

correctioneundampedavcan fff

• 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, ucE, equation

2c. Data Sheet Uncertainty Equations

22

2

2

2

2

2

242

tLfEu thick

can

L

can

fcancE

cEEDS uUU 2

where ucE=E andE standard deviation of a Young’s modulus measurement (E) standard deviation of density ()L standard deviation of length of cantilever (Lcan)thick standard deviation of thickness of cantilever (t)fcan standard deviation of average undamped resonance

frequency of cantilever (fcan), which includes a correction term such that

22nfcorrectiovefundampedafcan

2c. Data Sheet Uncertainty Equations

wherefundamped standard deviation of the undamped resonance frequency

measurementsfresol standard deviation of the frequency measurements (used

to obtain fcan) that is due to the frequency resolutionfreqcal standard deviation of the frequency measurements (used

to obtain fcan) 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/or composition

22nfcorrectiovefundampedafcan

222freqcalfresolfundampedvefundampeda

22cantileversupportnfcorrectio

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Effective value reported for RM 8096 due to:1. Debris in the attachment corners2. Undercutting of the beam3. Multiple SiO2 layers

Effective value reportedfor RM 8097 due to:1.Kinks in cantilevers2.Undercutting of the beam3.Non-rigid support

2c. Data Sheet Uncertainty Equations

22cantileversupportnfcorrectio

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UROI expanded uncertainty recorded on the Report of Investigation (ROI)

UDS expanded uncertainty as obtained from the data sheet (DS)

Ustability stability expanded uncertainty

2d. ROI Uncertainty Equation

22stabilityDSROI UUU

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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

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3a. Location of Cantilever on RM ChipFor RM 8096

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For RM 8096

Structural layer composite oxide

Wcan (µm) 28

Lcan (µm) 200, 248, 300, 348, and 400

t (µm) ≈2.743

Orientation 0º and 180º

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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3b. Location of Cantilever on RM ChipFor RM 8097

Locate the cantilever in this group given the information on the NIST-supplied data sheet

For RM 8097

Structural layer poly1 or poly2

Wcan (µm) 20

Lcan (µm) 100, 150, 200, 250, 300, 350,400, 450, and 500

t (µm) ≈2.0 (for poly1) and ≈1.5 (for poly2)

Orientation 0º and 90º

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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4a. Cantilever DescriptionFor RM 8096

Top view of a cantilever

ce 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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4b. P1 Cantilever Description (For RM 8097)

nitridenitride

anchor1

double stuffed anchor

p0

p2

p1

p1-p2 via

c

L

p1 cantilever

opening for etch

x

y

600 nmanchor1

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 used2.Anchored “tabs” are included

4b. P1 Cantilever Description (For RM 8097)

x

z

anchor1

p1-p2 via

p2

p1nitride

p2

p1

Si

5 m to 30 m

nitridenitride

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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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 viap2

double stuffed anchor p2

c

anchor2

nitride

x

y

For a more rigid beam support:1.Double stuffed anchors are used2.Anchored “tabs” are included

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 viap2

double stuffed anchor p2

f

anchor2

nitride

x

y

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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.

22certfmetercmeteru

instrument

meterf f

fcal

• 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.

• 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:

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6. Measurement Procedure

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42330.38

t

LfE cancan

See SP260-177 Tables 3 and 4 for the values of fcorrection

used for RM 8096 and 8097

µ=viscosity of ambient

Q=oscillatory quality factor

Wcan=width of cantilever

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2

330.38 can

initcaninit L

tEf

fmeasndampedn calff )4/(11 2Q

ff dampednundampedn

2

24

can

initcan

L

tEWQ

33undamped2undamped1undamped

eundampedav

ffff

correctioneundampedavcan fff

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• 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 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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• If your criterion for acceptance is:

whereDE positive difference between the Young’s modulus value

of the customer, E(customer), and that appearing on theROI, 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

8. Using the MEMS 5-in-1To Verify Young’s Modulus Measurements

22)()( EcustomerEcustomerE UUEED

• 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