thin film resistor construction, conductor/pad attachment

[metebalci]

I am trying to understand the thin film resistor construction in detail, I am not sure about a few points.

There is a ceramic base like Al2O3. Then a resistive layer of something like NiCr or TaN is deposited over the ceramic. The thickness of resistive layer corresponds to a specific sheet resistance value, for example 50 ohm/sq for NiCr. Then, a particular pattern corresponding to the nominal value of the resistor is lithographically etched. I saw the video EEVblog #730 - Thin Film Resistor Networks and a few others, and they mention the conductive layer is also lithographically etched. So basically it is like a sandwich, there is the ceramic base, then resistive layer, then the conductive layer.

Question 1: is the conductive layer always lithographically etched like this (so it stays over the resistive layer), or are there other methods ? Because in the simple figures, it does not look like there is a conductive layer over the resistive layer but only the conductive pads at the terminals, but I dont know with what other mechanism a conductive part like this can be attached there.

Question 2: if the conductive part is continuous from the end of the resistive layer (not over, not lithographically etched over the resistive layer), then all the resistance is between the conductive pads. If the conductive part/layer is also lithographically etched on the resistive layer, then, I think, there is a resistive layer under it. Then it is like there is a 90 degree bend in the resistive film construction in the normal direction to the resistive film layer. Is this bend considered in the design of the pattern or is it corrected by trimming ? or what I am saying is wrong and something else is going on.

Question 3: particularly if the resistor value is small, the required area or NiCr material is very small. Assuming a 0805 resistor, is there basically a very small resistive layer on the ceramic but a large conductive layer to the pads ? or the resistive layer is left as big as possible (although it is not needed for the power handling) and conductive layer is only close to the pads.

After the pads are there, the resistor is laser trimmed while measuring it. Then depending on the manufacturer/model I think, there is some type of plating and/or coating and finally the terminals are coated with solder.

I attached a few images from Vishay documents. The first video below shows the lithography process of both resistive and conductive (copper) layer.



Edit: The second video is from Vishay, showing a bit detailed process. It seems part of what I am asking is called metal stack or metallization. Also this page https://www.thinfilm.com/metallizations.html gives various options. Not 100% clear yet but I believe then multiple layers of metals are deposited (sputtered seems to be the technical term) on resistive layer and then etched one by one. Then a Ni plating is done before Sn/solder coating.