Discovering the Scanning Electron Microscope (SEM) and Microelectronics

Measure the width of date and D on a dime

SEM provides greater depth of field Imaged with optical microscope imaged with SEM

Imaging with any instrument is limited by the wavelength

Scanning Electron Microscope (SEM) A Hitachi 4700 SEM

How the SEM Works The SEM uses electrons instead of light to form an image. A beam of electrons is produced at the top of the microscope by heating of a metallic filament. The electron beam follows a vertical path through the column of the microscope. It makes its way through electromagnetic lenses which focus and direct the beam down towards the sample. Once it hits the sample, other electrons (backscattered or secondary) are ejected from the sample. Detectors collect the secondary or backscattered electrons, and convert them to a signal that is sent to a viewing screen similar to the one in an ordinary television, producing an image.                                 

Zooming in with the SEM Mint mark D measure approximately 0.635mm (635,000 nanometers)

Zooming in further This is the top left corner of the D (notice the “crud” inside the D – money is dirty!)

A closer look at the dirt This dirt particle measures 0.02288mm (22,880 nanometers)

Now a look at the surface of the D These are scratches in the metal of the dime on the letter D. The width of the picture is 6/1000th of a millimeter!

Microelectronic circuit wires These lines are only 45nm wide – impossible to view with visible light! (this is a cross-sectional view)

Try making your own lines and spaces A circuit layout done with Computer Aided Design