Deposition (CVD and PVD)
Which method is used to tune the stress of plasma CVD silicon nitride from compressive to tensile?
- ARinsing it with water after deposition
- BChanging parameters such as the ratio of high- to low-frequency RF power to adjust the strength of ion bombardment of the film
- CChanging the wafer diameter
Show answer and explanation
Answer: B. Changing parameters such as the ratio of high- to low-frequency RF power to adjust the strength of ion bombardment of the film
In plasma CVD, applying low-frequency RF power makes ions bombard the film strongly, compacting it and tending to produce compressive stress. Changing the ratio of high- to low-frequency power and similar parameters tunes the stress from compressive to tensile. This is also used for stress liner films that strain transistors.
- A. Rinsing with water cannot tune the stress.
- B. Correct. RF power conditions adjust the ion bombardment.
- C. Stress is not tuned by wafer diameter.