This Test Method covers the measurement by ellipsometry of the thickness and refractive index of an insulator grown or deposited on a silicon substrate.
This Test Method uses monochromatic light.
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.
Two procedures for computing the results are provided. If the graphical procedure is used, the measuring wavelength shall be either 546.1 nm or 632.8 nm, and the angle of incidence shall be 70° ± 0.1°.
When this Test Method was developed in the mid-1970’s, manual-null ellipsometers, which are the basis of this Test Method, were in routine use. Since that time, faster, automated instruments have replaced manual-null ellipsometers for all common use in the semiconductor industry. There are two basic types of such automated instruments commonly used: the rotating element null ellipsometer and the rotating element photometric ellipsometer. For each of these, microprocessors or microcomputers are used to operate the instrument and to analyze the data. Details of the procedures utilized in these instruments are usually considered proprietary by the instrument manufacturers.
Two major changes have occurred since this Test Method was initially adopted. First, reference materials certified for the thickness of silicon dioxide layers on silicon are available both from the National Institute of Standards and Technology and from commercial sources. These can be used to evaluate the performance of automated ellipsometers. Second, significantly improved materials and procedures have been developed for storage of reference wafers needed for long term testing of baseline performance of ellipsometers. It is not uncommon for reference wafers simply to be stored ‘clean’ with no further wafer cleaning utilized. If cleaning steps are in fact, utilized, they are not those described in this Test Method. The cleaning steps detailed in this Test Method are retained, however, to provide background information on procedures used for the first of the interlaboratory tests.
Referenced SEMI Standards (purchase separately)
SEMI C19 — Specification for Acetone
SEMI C31 — Specification for Methanol
SEMI M59 — Terminology for Silicon Technology
Revision History
SEMI MF576-0812 (Reapproved 1023)
SEMI MF576-0812 (Reapproved 0718)
SEMI MF576-0812 (technical revision)
SEMI MF576-0706 (Reapproved 1111)
SEMI MF576-0706 (technical revision)
SEMI MF576-01 (first SEMI publication)
