Continuing the task of making the MOS capacitors (1 μm x 1 μm), you have now to choose the suitable etching method. Explain which type of etching (wet, plasma assisted, CMP, lift-off, directional, anisotropic, isotropic, chemical, physical, etc.) is preferable and why. Show all the arguments in favour for the chosen method and indicate why you didn't choose the others.
If in place of aluminium you need to etch Si3N4 on a Si wafer, describe two possible process flows, one dry and one wet, giving the etching time, gases, concentration, etc.
What if the material is copper instead of aluminium? Etching is the second part of making a structure on the wafer, after lithography. Once the pattern is transferred from mask to resist (lithography step), it needs also to be transferred from the resist to the film (etching step).
The layer can be etched by various methods: wet etching (liquids are used) or dry etching (no liquids are used), etc. These methods are described and compared. The advantages of each method are presented. The main figures of merit, such as etching rate, anisotropy, selectivity are the criteria for comparing various etching methods. The layer can be etched chemically, through reactions or physically, through bombardment or mechanical forces. |
Substrate preparation
