What’s Inside an Array of Transistors?

ZeptoBars recently broke down a 7-transistor ULN2003 Darlington driver chip and analyzed what each component does, identifying the resistors, diodes, and transistors by peering at the chip through a microscope.

P and N-type silicon have slightly different colors. This difference is quite small, but after cranking up saturation and contrast almost to the maximum we can clearly distinguish between them. Don’t worry about dual emitters – they work just like 1 with combined area.

In order to avoid aluminum interconnect shorting wrong parts of the transistor – it is covered by a layer of insulating transparent glass. This glass has holes right above places where interconnect is supposed to contact the transistor. You can clearly see this on the following photo made with a lens that has narrower depth of focus: base contact is out of focus as it’s laying higher, on the transparent glass.

[via EMSL]