Diffusion resistors are made with n- or p- diffusions in the substrate. Poly resistors are made with the poly layer. Poly resistors tend to have much higher sheet resistivity than diffusion resistors.
Maybe , the common poly sheet resistor is smaller than the diffusion resistor.
and , from the accuracy aspect, the poly resistor is beteer than the diffusion resistor.
and for the temperatur coeffecient, the voltage coeffecient, the two types resistor is not the same. Generally, in most aspects, the poly resistor is beter than diffusion with exception of silicon Area.
The resistors are made from doped polysilicon (all poly) or different diffusions in the process. The three diffusions that are used for resistors are N+, P+, and N-Well. The N+ and P+ diffusions are used for the drain/source of NChannel/PChannel transistors respectively. The N-well is the body of a PMOS transistor. The N+ and P+ are shallow lower sheet resistance resistors. They would be best for lower value of resistors. the N-Well is a deeper junction and would be better for middle values of resistors.
The addition of silicide to all of these effictively puts a metalic layer over the resistor significantly reducing the sheet resistance. Silicide is made by reacting a metal with exposed silicon forming a silicide. There are a number of metals that will form a silicide with silicon. TSMC could tell you which one they are using.
Silicided resistors would be ones that need small resistance values.
Temperature changes the characteristics of silicon; and the number of carriers available for conduction. Think resistor!
Now if they have salicided these N+ and P+ areas, the resistance becomes smaller since they are introducing metal, but it is like creating an alloy, and the temperature doesn't affect is so much any longer.
Still, poly resistors are better-behaved with temperature.