ASTM International - ASTM F576-00
Standard Test Method for Measurement of Insulator Thickness and Refractive Index on Silicon Substrates by Ellipsometry
|Publication Date:||10 June 2001|
|ICS Code (Semiconducting materials):||29.045|
1.1 This test method covers the measurement by ellipsometry of the thickness and refractive index of an insulator grown or deposited on a silicon substrate.
1.2 This test method uses monochromatic light.
1.3 This test method is nondestructive and may be used to measure the thickness and refractive index of any film not absorbing light at the measurement wavelength on any substrate (1) not transparent to light at the measurement wavelength, and ( 2) of a material for which both the refractive index and the absorption coefficient are known at the measurement wavelength.
1.4 The precision of this test method is reduced by variations, over regions smaller than the light-beam spot size, in substrate flatness, insulator thickness, and index of refraction.
1.5 Film thickness measurements determined by ellipsometry are not unique. When the film thickness is greater than that calculated from the expression N/[2(n 2 sin 20)1/2], where N is an integer, the measurement wavelength, n the index of refraction, and 0 the angle of incidence, the thickness value determined by this expression must be added to the thickness value determined by ellipsometry to obtain the correct film thickness. The value of N must be obtained by another procedure.
1.6 Two procedures for computing the results are provided. If the graphical procedure is used, the measuring wavelength shall be either 546.1 or 632.8 nm, and the angle of incidence shall be 70 ± 0.1o.
1.7 This test method may be used for referee measurements with computer calculations.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 9.