Circuit Edit using FIB
A: FIB Cut to Metal 1
- FIB milling using Gas Assisted Etching (GAE) is used to create a high aspect ratio hole through Metal 1. The GAE increases the aspect ratio of the milled hole and improves "end-point detection," making it easier to recognize when the desired metal line has been reached.
- The FIB is then used to cut Metal 1, and then again to clean the area, ensuring that no stray material is left over from the procedure, greatly reducing the possibility of shorts.
B: FIB Via to Metal 1
- FIB milling with GAE to reach Metal 1 with good end-point detection.
- The hole is then filled with conductive tungsten deposited by the FIB, creating a via to the surface.
C: FIB Via to Metal 2
- FIB milling using GAE yields a high aspect ratio hole through the middle of Metals 5 and 4, leaving sufficient metal in each layer to allow the lines to remain conductive.
- The hole is then filled with FIB deposited Silicon Dioxide to insulate against shorts to Metals 5 and 4 from the via that will be added afterwards.
- GAE is used to mill through this deposited Silicon Dioxide. A high aspect ratio hole will have been opened down to Metal 2 with good end-point detection. GAE increases the rate of milling and improves the ability to recognize when you have reached the desired metal line.
- The high aspect ratio hole is then filled with FIB deposited tungsten, creating a conductive via all the way to the surface.
D: FIB Strap Joining Vias
- The FIB is then used to lay down a well defined conductive strap of tungsten across the surface of the device. This strap connects the two vias that have been created.