Concern about the layout of the bipolar transistors

[RTimothyEdwards]

The only visibility I have for the bipolar transistor layouts is in the primitive device library (pycells). (i.e., there is no QA library layout for these devices, and the documentation shows only a cross section view.)

I have a few concerns about these devices, especially related to the inconsistencies between the layouts of the device types.

The base type of NPN transistor npn13G2 does not have a contact over the emitter window. Both of the other NPN transistor types have a contact over the emitter window.

The base type npn13G2 has no diffusion under the base. There is only an nSD.block layer, with the contact otherwise sitting over nothing but substrate. This may be intentional (since parts of the device are obfuscated in the the open source PDK view) but looks odd.

The npn13G2L has square contact cuts over the base but a contact bar over the collector, whereas the npn13G2V has square contact cuts over both the base and the collector. This may be intentional but seems odd.

[hpretl]

Probably the IHP folks are better suited to answer this, but I had the same confusion before: My understanding is that the NPN layouts are not what is going directly onto the masks, but are somewhat abstracted representations to protect IHP's IP as to how exactly the NPN layouts look.

[RTimothyEdwards]

@hpretl : Thus my side remarks. But my response to that is that if it is obfuscated on the user side then it is critically important to double-check and triple-check that the devices will be correctly manufactured. Using my best independent judgement, a contact over the emitter does not seem like something that would be "obfuscated out" of the user design, and seems more like an accidental omission (and, if so, it is an omission that is fatal to the device).

[hpretl]

@RTimothyEdwards With that I totally agree 😀