Local interconnect etch characterization using AFM

A method of determining presence of a trenching phenomenon after performing a local interconnect etch, comprising:

• scanning a local interconnect etched portion of a wafer with an atomic force microscope having a flared probing tip;
• generating surface profile data including sidewall profile data of the local interconnect etched portion from the atomic force microscope;
• and
• evaluating the generated surface profile data including sidewall profile data of the local interconnect etched portion to determine whether the surface profile data indicates the presence of the trenching phenomenon within the local interconnect etched portion, and
• further processing the wafer if the trenching phenomenon is not present or reprocessing or discarding the wafer if the trenching phenomenon is present.

A method of determining a value of poly gate corner selectivity after performing a local interconnect oxide etch and nitride etch on a wafer, comprising:

• scanning a local interconnect etched portion of the wafer with an atomic force microscope having a flared probing tip;
• generating surface profile data including sidewall profile data of the local interconnect etched portion from the atomic force microscope;
• calculating the value of corner selectivity S based on equations S = T ox - T 1 N loss
• wherein
• Tox=TA−Tnitride thickness
• T1=TB−Tnitride thickness
• N loss = T nitride ⁢ ⁢ thickness - [ t - Δ ⁢ T ox ER ox ] ⁢ ⁢ ER nit
• and ERox is an oxide etch rate during the nitride etch;
• ERnit is a nitride etch rate during the nitride etch;
• ΔTox is the oxide loss at an oxide spacer during the nitride etch;
• Tnitride thickness is the thickness of the nitride layer;
• t is a total nitride etch time;
• and TA, TB and ΔTox are measured by the atomic force microscope;
• and
• further processing the wafer if the corner selectivity S indicates etching of the oxide spacer does not exceed an amount or reprocessing or discarding of the wafer if the corner selectivity S indicates etching of the oxide spacer exceeds an amount, based on the calculated value of corner selectivity S.