Table 4.

Error budget for an average diameter measurement of 3 μm spheres, using MEM^a

Category	Error source	Error contribution (μm)
		Systematic	Random
Microsphere sensing	Imperfect scan conditions: scan direction unequal-size spheres		0.0011 0.0002
	E-beam exposure	0.0009
	SEM resolution and E-beam wander		0.0008
Row length measurements	Stage travel sampling interferometer least count		0.0009 0.0005
Microsphere grouping	Sphere flattening on contact air gaps between spheres	0.0020 0.0020
Sample size (N=120)	Small sample with non-zero σD		0.0055
	Totals	0.0030	0.0057

^aUncertainty in $\overline{D}:0.0030+0.0057=0.009$ μm. Measured $\overline{D}$ (after corrections, see Sec. 4.2.5): 2.990 μm.