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 Data Analysis Sheet SG.1

Data analysis sheet for strain gradient measurements

Top view of cantilever test structure used to measure strain gradient.

Figure SG.1.1.  Top view of cantilever test structure used to measure strain gradient.

To obtain the following measurements, consult ASTM standard test method E 2246 entitled
"Standard Test Method for Strain Gradient Measurements of Thin, Reflecting Films
Using an Optical Interferometer."


date data taken (optional) = / /
identifying words (optional)   =   
instrument used (optional)   =   
fabrication facility/process (optional)   =   
test chip name (optional)   =   
test chip number (optional)   =   
filename of 3-D data set (optional)   = 
filename of 2-D data traces (optional) =
     
     
 

Table 1 - Preliminary ESTIMATES

Description

1 material =        
       
    
   
 

    
    

material

2 design length = μm

design length

3 design width = μm design width
(needed for test structure identification purposes only)
4 which cantilever?         
   
       
              
       

     
which cantilever on the test chip, where "first" corresponds to the topmost cantilever in the column or array that has the specified length? 
5 magnification = × magnification
6 orientation =           
       
    
     
 
orientation of the cantilever on the chip
7 calx = x-calibration factor (for the given magnification)
8 interx = μm maximum field of view (for the given magnification)
9 σxcal = μm one sigma uncertainty in a ruler measurement (for the given magnification)
10 xres = μm uncalibrated resolution of the interferometer in the x-direction
11 calz = z-calibration factor (for the given magnification)
12 cert = μm certified value of double-sided physical step height used for calibration
13 σzcal = μm standard deviation of step height measurements (on double-sided physical step height)
14 zres = μm calibrated resolution of the interferometer in the z-direction
15 Rtave = μm calibrated peak-to-valley roughness of a flat and leveled surface of the sample material calculated to be the average of three or more measurements, each measurement of which is taken from a different 2-D data trace
16 aligned? Yes      No alignment ensured ?
17 leveled? Yes      No data leveled ?
18 stiction? Yes      No Is this cantilever exhibiting stiction ?  
(
If it is exhibiting stiction, do not fill out the remainder of this form.)


                                     



Table 2 - INPUTS (uncalibrated values from Trace "a" or "e")

Notes

19 x1max (i.e., x1upper) = μm  
20 x1min (i.e., x1lower) =   μm  (x1min > x1max)


Table 3 - INPUTS (uncalibrated values from Trace "b")

Notes

21 x1 = μm z1 = μm  (x1ave < x1 calx)
22 x2 = μm z2 = μm  (x1ave < x2 calx)
23 x3 = μm z3 = μm

(x1ave < x3 calx)



Table 4 - INPUTS (uncalibrated values from Trace "c")

Notes

24 x1 = μm z1 = μm (x1ave < x1 calx)
25 x2 = μm z2 = μm (x1ave < x2 calx)
26 x3 = μm z3 = μm (x1ave < x3 calx)


Table 5 - INPUTS (uncalibrated values from Trace "d")

Notes

27 x1 = μm z1 = μm  (x1ave < x1 calx)
28 x2 = μm z2 = μm (x1ave < x2 calx)
29 x3 = μm z3 = μm  (x1ave < x3 calx)


                                  


OUTPUTS (calibrated values):

           x1ave μm

            s               from Trace "c"
                    s = 1 (for downward bending cantilevers or
                             
if data was taken from the bottom of an upward bending cantilever)
                    s = −1 (for upward bending cantilevers unless

                                data was taken from the bottom of an upward bending cantilever
)

                      Rint μm    from Trace "b"
                        a   μm    from Trace "b"
                        b   μm    from Trace "b"

            sg m1    from Trace "b"

                      Rint μm    from Trace "c"
                        a   μm    from Trace "c"
                        b   μm    from Trace "c"

             sg
m
1    from Trace "c"                            (USE THIS VALUE)
                      uW m1       from two or three traces
                      usamp m
1   from Trace "c"
                      uxcal
m
1     from Trace "c"
                      uzcal m
1     from Trace "c"
                      uzres
m
1     from Trace "c"
                      uxres
m
1     from Trace "c"
             
ucsg =  SQRT[uW2 + usamp2 + uxcal2 + uzcal2 + uzres2 + uxres2]
                 
   (Each of the standard uncertainty components is obtained using a Type B analysis.)
             ucsg m1   from two or three traces

                      Rint μm    from Trace "d"
                        a   μm    from Trace "d"
                        b   μm    from Trace "d"
            sg m
1    from Trace "d"

Report the results as follows:  Since it can be assumed that the estimated values of the uncertainty
components are approximately uniformly or Gaussianly distributed with approximate combined standard
uncertainty ucsg, the strain gradient is believed to lie in the interval sg ± ucsg (expansion factor k=1)
representing a level of confidence of approximately 68 %. 


Modify the input data, given the information supplied in any flagged statement below, if applicable, then recalculate:
1. Please fill out the entire form.
2. The value for the design length should be between 0 μm and 1000 μm.
3. The value for the design width should be between 0 μm and 60 μm.
4. Is the magnification appropriate given the design length ?
5. Magnifications at or less than 2.5× shall not be used.
6. Is 0.95 < calx < 1.05 but not equal to "1"?  If not, recheck your x-calibration.
7. The value for interx should be between 0 μm and 1500 μm.
8. The value for σxcal should be between 0 μm and 4 μm.
9. The value for xres should be between 0 μm and 2.00 μm.
10. Is 0.95 < calz < 1.05 but not equal to "1"?  If not, recheck your z-calibration.
11. The value for cert should be greater than 0 μm and less than 25 μm.
12. The value for σzcal should be between 0 μm and 0.050 μm.
13. The value for zres should be greater than 0 μm and less than or equal to 0.005 μm. 
14. The value for Rtave should be between 0 μm and 0.100 μm.
15. Alignment has not been ensured.
16. Data has not been leveled.
17. x1min should be greater than x1max.
18. The calibrated values for x1min and x1max are greater than 10 μm apart.
19. In Trace "b," the calibrated values of x1, x2, and x3 should be > x1ave.
20. In Trace "c," the calibrated values of x1, x2, and x3 should be > x1ave.
21. In Trace "d," the calibrated values of x1, x2, and x3 should be > x1ave.
22. In Traces "b," "c," and "d," the value for s is not the same.

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Email questions or comments to mems-support@nist.gov.

NIST is an agency of the U.S. Commerce Department.
The Semiconductor and Dimensional Metrology Division is within the Physical Measurement Laboratory.
The MEMS Measurement Science and Standards Project is within the Nanoscale Metrology Group.

Date created: 12/4/2000
Last updated: 4/26/2013