Dimensional measurements made with an optical microscope are made on the optical image of the specimen and not directly on the specimen itself. The method of illuminating the specimen affects the image content, including the appearance of edges which are used in defining the size of the specimen.

This Practice includes adjusting the microscope for Kohler illumination, which provides uniform illumination of the specimen, reduces stray light, and results in bright images with good contrast.

This Practice provides an image with steep edge gradients by setting the ratio of condenser numerical aperture to objective numerical aperture equal to approximately two thirds. As a result, the repeatability of edge settings used in measurement eyepieces and photometer line profiles is improved.

Many different types of microscopes and micrometer attachments are used for dimensional measurements. This Practice reduces the effects of image-contrast variation on measurements with these different systems.

This Practice is particularly useful for preparing the microscope to measure the width of lines on hard-surface photomasks and processed silicon wafers. These linewidths are used for comparison with design values and to help determine the quality control of the processes used to fabricate the photomasks and wafers. These linewidths are useful for materials acceptance purposes or for other matters relating to the sale or purchase of materials.

This Practice is intended primarily as a guide in preparing an optical microscope for dimensional measurements and is used in conjunction with the instruction manual provided by the manufacturer.

This Practice covers the preparation of an optical microscope for dimensional measurements. It is intended for preparing an optical microscope to measure the width of lines, in the range from 0.5 µm to 12 µm, inclusive, on hard surface photomasks and processed silicon wafers.

This Practice is applicable for a microscope equipped with a micrometer attachment, such as an optical filar, video filar, optical image-shearing with optical or video display, optical image-scanning, or video image-scanning micrometer. Adjustment and calibration of the micrometer attachment is not included in this practice.

This Practice is intended for observing optically transparent specimens in bright-field transmitted illumination or optically opaque specimens in bright-field reflected illumination. It is not intended for dark-field illumination.

This Practice is limited to an optical microscope with an illumination system that is an integral part of the microscope body and includes a condenser lens.

No useful figure capable of showing the arrangement of components for all microscope designs is available; therefore, this Practice does not contain illustrations and procedures that would suggest a specific microscope.

Referenced SEMI Standards (purchase separately)
None.

Revision History
SEMI MF728-1106 (Reapproved 0622)
SEMI MF728-1106 (Reapproved 0317)
SEMI MF728-1106 (Reapproved 1111)
SEMI MF728-1106 (technical revision)
SEMI MF728-81 (Reapproved 2003) (first SEMI publication)