Appendix A

Metrology Techniques for

MEMS

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	Spot Size or Probe Area	Resolution/Magnification	Thickness Range	Applications	Remarks (n = Refractive Index)
Reflection spectroscopy (visible: 400-900 nm)	3.5-50 µm		40 Å-5 µm	Nonabsorbing films.	Lim. meas. below 100 Å, n meas. only above 700 Å. Fast.
Reflection spectroscopy (UV: 200-400 nm)	10 µm		25 Å-2 µm	Transparent very thin films on metals.	Lim. meas. below 50 Å, n meas. only above 100 Å.
Ellipsometry (632.8 nm standard), 790 nm, 830 nm, 1300 nm and 1500 nm (optional)	12-100 µm	1-2 µm	10-1000 Å	Nonabsorbing films.	Automated, highest accuracy. Thickness and n meas.
Optical microscopes		Magnification 10 to 1000.	0.3 0 5 µm	Universal tool for all dimensions > 0.29 µm.	Poor depth of field.
Scanning electron microscope (SEM)	Spots down to 10-30 Å	Lateral: -35 Å (standard SEM); -9 Å (field-emission SEM); -150 Å (low-voltage SEM); magnification is 20 to 150,000.		SEM pictures, CD meas. below 0.8 µm..	Good for surface topography. Large depth of focus. Needs vacuum. Can be destructive
Transmission electron microscope (TEM)	10 Å	1-2 Å (resolving power 10^4 times better than optical microscope). Magnification is 500 to 500,000.	10 Å-1 µm	Atomic structure defect analysis nanoprobe.	Requires thin sample preparation.
Scanning acoustic microscopy	1.3 mm (50 MHz)	Lateral: 10 nm - 2 mm Depth: 10 nm - 5 mm	Signal penetrates 1 l	Inspection inside a ceramic packaged IC. Interface inspection, wide range of samples.	Nondestructive. Subsurface information. Needs liquid medium.
Stylus Profilometer	Tip size limits bandwidth.	Resolution of better than 1 Å and lateral resolution of ~0.03 mm		Meas. sharp steps from a few Å to several micrometers. Materials & Process R & D Low volume QC.	Meas. surf. profile using a contact stylus. May damage soft samples.
Nomarski microscope (differential interference contrast-DIC)	0.3 µm			Separation of images of different layers. Sample roughness inspection.	Pseudo three-dimensional image.
Confocal Scanning optical microscope (CSOM)	0.3 µm	0.3 µm	< 1 µm	Cross sectioning. Independent layer imaging.	Nondestructive. No vacuum. Diffraction lim. resol.
Atomic force microscope (AFM)	Radius of curvature of probe tip: 50-100 Å	Atomic imaging (one atom)	< 1 Å	Surface roughness. Tribology.	Slow scan. Probe tip wear. Nondestructive.

	Spot Size or Probe Area	Resolution/Magnification	Thickness Range	Applications	Remarks (n = Refractive Index)
Total integrated scattering		With visible light 0.15 mm is possible		Lithography control, etch structure monitoring and metal grain size determination.	Nondestructive, rapid quantitative process monitor.
Scanning Tunneling Microscope (STM)	50 - 100 Å	Lateral: 0.1 - 1 nm Depth: 0.1 nm		Atomic resolution. Measurement of chemical properties.	Sample must be conduct. Slow scan. Probe wear. Cannot meas. surfaces larger than a few µm^2.
Optical Interference Microscope		Lateral: 0.2 - 2 µm. Depth: 400 µm - 2 cm.		Cross sectioning.	Lateral resolution limited by diffraction.
Near-Field Scanning Optical Microscope	0.02 - 4 µm	Lateral: 1 - 200 nm. Depth: 10 nm.		General imaging. Lithography.	No vacuum.

See also: WWW Directory of Microscopy and Microanalysis Products and Services: http://www.mwrn.com/product/product.htmt

Guide to Microscopy and Microanalysis on the Internet: http://www.mwrn.com/guide.htm