Flashcards in 100S travler Deck (11):
What are the two main purposes of the 20 photo pattern?
1) to pattern the active area in the periphery for the future c-mos devices.
2) To chop the 21, array, active area in to individual active area.
what is the purpose of the 21 photo pattern?
to pattern the arry active area
What purpose does the RELACS process serve? (during the 20 photo level)
To reduce the CD of small open features (contacts, trenches)
What 2 films are used to fill the trenches ?
we use 2 films to fill the trenches ----FCVD (flowable CVD) Oxide--- and __HDP (high density Plasma) Oxide.
What is the purpose of the poly liner (20 STI si Liner)
To reduce the active area silicon loss during the STI oxide densification? (oxidation of side wall)
How and what happens during the trench oxide densification?
at 1000 degree si liner completely turns in to oxide and both FCVD and HDP oxides densifies.
Why do we use 2 types of oxide to fill the trenches?
FCVD is necessary oxide that is more dense and suitable in narrow trenches but it is expensive. It stops when array trenches are filled and let the HDP oxide fill the rest ie Periphery trenches.
What is the difference between MOSFET and AF?
Anti Fuse, there is no pn junction beneath Gate poly. It is more like 2 different layers stacked with thin gate oxide in between. Which is a capacitor. in MOSFET there will be no active area beneath gate poly.
What is Nitride rail?
To better define the opening for the 49 contact. Contact profile is all defined by nitride rail