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what is exactly process?

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bradyue

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what is process? how does it take effect timing analyze? could anyone give a example? thanks
 

ashish_chauhan

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Putting it simple terms...

process is like a cooking receipe ... for a particular dish you have some basic ingredients... you vary the quantity and the temprature at wich you cook the taste changes accordingly.

Similarly in chip fabrication... you have a receipe(method) to make a resistor...(for example)

you change the amount of doping... effective mobility changes ... you change the temprature.... mobility varies and hence the value of resistor...

This value of resistor directly effects the timing arcs...

Hope I made my point ...!!
 

bradyue

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i think i totally understand you!
thanks for your vivid explaination!
 

santuvlsi

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Process means

Not my own words i got it somewhere dont mind

This variation accounts for deviations in the semiconductor fabrication process. Usually process variation is treated as a percentage variation in the performance calculation. Variations in the process parameters can be impurity concentration densities, oxide thicknesses and diffusion depths. These are caused bye non uniform conditions during depositions and/or during diffusions of the impurities. This introduces variations in the sheet resistance and transistor parameters such as threshold voltage. Variations are in the dimensions of the devices, mainly resulting from the limited resolution of the photolithographic process. This causes (W/L) variations in MOS transistors.

Process variations are due to variations in the manufacture conditions such as temperature, pressure and dopant concentrations. The ICs are produced in lots of 50 to 200 wafers with approximately 100 dice per wafer. The electrical properties in different lots can be very different. There are also slighter differences in each lot, even in a single manufactured chip. There are variations in the process parameter throughout a whole chip. As a consequence, the transistors have different transistor lengths throughout the chip. This makes the propagation delay to be different everywhere in a chip, because a smaller transistor is faster and therefore the propagation delay is smaller


Santu
 

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