What is Selectivity?

Selectivity in the explanations

• Selectivity is the ratio of the etch rate of the film being removed to that of a film that should remain (mask or underlying layer).

  Which correctly describes 'selectivity' in etching?

• Selectivity is the etch rate of the target film divided by that of the mask (or underlayer): 100 ÷ 20 = 5.

  If the oxide etch rate is 100 nm/min and the mask is consum…

• Ceria (cerium oxide) bonds chemically with oxide and removes it efficiently, while additives such as amino-acid surfactants adsorb on nitride and suppress its polishing, giving oxide-to-nitride selectivity of tens to over 100.

  Which abrasive particles are often used in STI CMP to achie…

Questions that mention Selectivity (15)

1. Which correctly describes 'selectivity' in etching?
2. If the oxide etch rate is 100 nm/min and the mask is consumed at 20 nm/min, what is the selectivity to the mask?
3. Which abrasive particles are often used in STI CMP to achieve high polishing selectivity of oxide to silicon nitride?
4. In manufacturing nanosheet GAA transistors, why is only the SiGe selectively removed from stacked alternating Si and SiGe layers?
5. Which is a general characteristic of wet etching?
6. What is the aspect ratio of a hole or trench formed by etching?
7. Which gases are commonly used for dry etching of polysilicon gates?
8. Which solution is commonly used for wet etching of silicon nitride?
9. After the etch endpoint is detected, what is it called to continue etching for a set time to ensure the film is removed across the whole wafer?
10. What is needed to etch oxide and stop on the nitride underneath?
11. Which gas can etch silicon isotropically without a plasma, for example to remove sacrificial layers in MEMS?
12. In gate electrode etching, what is commonly done to preserve the thin gate insulator underneath?
13. What is the general effect of adding a little oxygen to fluorine-based etching gas?
14. What is the main purpose of placing a cap layer such as cobalt on top of copper wiring?
15. In oxide etching, why are carbon-rich fluorocarbon gases such as C4F8 used?

Related terms

Overetch STI (shallow trench isolation) Wet etching Dry etching 3D NAND Plasma Erosion Hard mask CMP Ceria (cerium oxide)