resistor,capacitor,inductor fabrication

[sachinmaheshwari]

how do we fabricate a resistor,inductor n capacitor in an IC?

 

[A.Anand Srinivasan]

resistor and capacitor are fabricated generally using MOS but that is a pretty much space consuming process and hence they are avoided in ICs as much as possible... as for the case of inductor much research is going on.... some use the bond wire to make inductors....

 

[sachinmaheshwari]

i know it is made using mos..but how...can u explain me how?

 

[A.Anand Srinivasan]

for the case of resistor the MOS is biased in the ohmic region..... for the case of capacitor the gate is used as one plate, bulk as the other plate and the insulator is used as dielectric....

 

[sachinmaheshwari]

why resistor is biased in ohmic region?
n how we can have different values of resistor ?

 

[rowokii]

Resistor: Different material as certain resistivity, so depending on how big you want your resistor to be(talking in terms of resistance) you use different materials. Metal has the lowest resistance, while unsilicided poly has the highest resistance. You draw a long thin line of a given material to make a resistor.

Capacitor: Well, you should already know that capacitor is basically two conductive material with an insulator in the middle. So, in the IC chip, this is what they go for. MIM cap is metal-insulator-metal cap. Gate cap is basically a MOS gate (poly, sio2,bulk). If you remember your device physics, you know PN junction can create depletion region(an insulator), so you can have a voltage varying capacitor using reversed biased PN junctions (Junction cap.)

Inductor: Well, you have inductance when you make loops of conducting meterial. Think about a regular inductor... it's just magnet wire wrapped around something. So, this is what you do in the IC world as well. You make loops of metal material and you have an inductor.

 

[xenox]

Resistors can be fabricated on various metals;depends what the technology allows and the R value you are after.
Capacitors can be mim (metal-insulator-metal) but you can also create varactors i.e capacitors varying C value with voltage (mos type devices wit h2 shorted terminals)
Inductors are loop of metal(s).Stacked inductors can also be fabricated in order to reduce in-series resistance; best performance of course is usually when they are fabricated in top layers.

 

[mdcui]

resistor:
N-well resistor -- using the N-diff bulk resistance, relative high resitance, but tempco is big.
Poly resistor -- MOS gate poly, better tempco, resistance value is not so good as N-well resistor.
Metal resistor -- very small resistance, unless you make is long and thin enough.


capacitor:
mos gate cap -- if you have advanced process with small Tox, than the mos gate cap can be made fairly big.
metal cap -- two overlapped metal pieces with insulator between, basically two layers of metal.
line2line cap -- the side wall metal between the adjacent metal routings (same layer), rarely used.

inductor:
I only know the metal folding around, the Q value is fairly low, 5~6 maybe.

 

[ameed]

resistor:
N+&P+ well resistor -- using the N-diff bulk resistance, relative high resitance, but tempco is big.
Poly resistor -- MOS gate poly, better tempco, resistance value is not so good as N-well resistor.
Metal resistor -- very small resistance, unless you make is long and thin enough.


capacitor:
mos gate cap -- if you have advanced process with small Tox, than the mos gate cap can be made fairly big.
metal cap -- two overlapped metal pieces with insulator between, basically two layers of metal.
line2line cap -- the side wall metal between the adjacent metal routings (same layer), rarely used.

inductor:
I only know the metal folding around, the Q value is fairly low, 5~6 maybe.