OP - S

Microscope operation and Line Width Measurements

We use a variety of microscopes in our lab to allow us to examine the small features made using the photolithography equipment. The primary inspection microscope used is the Nikon metallurgical scope connected to the color video monitor. A Polaroid camera can also be attached to the microscope for photography, but this switch should only be performed by a TA. Other instructions related to the use of the microscope are given on the following pages.

The primary tool used to measure line widths is a video micrometer. Once properly calibrated, this instrument can make measurements accurate to about the third significant digit (mainly limited by the resolution of the video scan lines). You will use this instrument to measure photoresist lines, and the resulting etched features, as well as junction groove parameters. The micrometer display is controlled by the joystick; the various menu options are accessed by depressing the red button next to the joystick. Feature measurements are made by positioning the lines displayed on the monitor at the edges of the feature. The actual dimensions are then displayed as the distance between the horizontal lines (the "y" value) and the distance between the vertical lines (the "x" value). In addition, the diagonal length of the rectangle formed by the lines is also displayed (the "d" value). To convert from arbitrary units to microns, a calibration factor is used; the cal set (1 through 4) is displayed as a number after the x, y and d display. It is critical that the cal set you use matches the objective lens selected on the microscope. See posted information in lab. Also note that due to image blooming with the CCD camera, the level of illumination affects the apparent image size; thus it is very important to set the illumination so the brightness of the calibration slide and the chip to be measured are approximately the same.

The menu selections you will use the most are described below. To open the menu depress the red button, then use the joystick to move up or down to the menu item desired. Depress the red button again to activate the selection.

Menu Item	Description
SPAN	under joystick control, moves the right and top lines
DATUM	under joystick control, moves the left and bottom lines
BLANK	turns video micrometer display completely off
LINE TYPE	sets either dashed lines or solid lines
MATT	sets line color: joystick up for white, down for black

The other menu items should be used only with the supervision of a TA.