Exploration 1C:

How is Chemistry used to build ICs?: Making a Capacitor

This animation illustrates the processes involved in building a capacitor on top of a doped silicon wafer. The movie is designed for easy click through of the frames individually.

Process Steps for a Discrete Capacitor

Clicking on the text links will take you to the Glossary for more information about the term.

  1. Begin with Doped Silicon Substrate
  2. Grow Oxide Layer
  3. Apply Photoresist Polymer
  4. Place Mask over Chip
  5. Expose Areas to be Removed to Light
  6. Remove Mask
  7. Wash Away Exposed Photoresist
  8. Etch Oxide
  9. Deposit Conductors
  10. Remove Remaining Photoresist

Back to Contents


Doped Silicon Substrate
Silicon's conductivity for the capacitor substrate is enhanced by "doping" or inserting other atoms into the crystal matrix. In p-doped silicon, atoms such as boron with 3 valence electrons are inserted into the crystal. The "p" designation comes from the holes (or missing electrons) resulting from having atoms present with 3 valence electrons instead of silicon's four valence electrons. In n-doped silicon, atoms with five valence electrons, such as phosphorus, are added resulting in extra electrons present relative to when all the atoms were silicon. Back
Oxide Layer
The most common insulator used in microelectronics is silicon dioxide glass. Silicon dioxide is a very poor conductor and can be grown on the wafer simply by heating it in oxygen. Back
Photoresist Polymer
The photoresist polymer is a very thin coating of polymer (similar to nail polish) applied to the wafer surface which will react with light to create areas which are soluble in different solvents. By removing selected areas of the photoresist, those areas of the wafer are available for reactions and modifications while the rest of the wafer is protected. Back
The mask is a very elaborate template which shields the areas of the photoresist that are needed for protection and allows light to penetrate to the photoresist to be removed. Back
The light used to initiate transformations in the photoresist polymer is usually ultraviolet light. For the type of photoresist polymer illustrated here, the light initiates bond-breaking so that the exposed areas can be easily washed away. Back
The conductors in microelectronics are generally formed from deposited conducting metal such as aluminum. Back

Back to Contents

Back to Contents