Maintaining etch uniformity from the center to the edge of the wafer during the etching process is a critical challenge. In particular, the edge of the wafer poses difficulties due to changes in the angle of ion incidence caused by the curvature of the sheath, making it challenging to achieve the desired etch pattern. Therefore, identifying and monitoring key factors that significantly impact center-to-edge uniformity is essential.
As semiconductor devices have become increasingly miniaturized, the ability to control very small Critical Dimensions (CDs) during the etching process has become crucial through controlled plasma processes. Consequently, diagnosing plasma and reflecting this in the process to enhance yield is of paramount importance. Typically, an invasive sensor like a Single Langmuir Probe (SLP) is utilized for plasma diagnostics. However, using this sensor can affect the plasma, necessitating the use of non-invasive diagnostic methods.
As semiconductor devices have become increasingly miniaturized, the ability to control very small Critical Dimensions (CDs) during the etching process has become crucial through controlled plasma processes. Hence, diagnosing plasma and reflecting this in the process to enhance yield is of paramount importance. Typically, a Single Langmuir Probe (SLP) is utilized for plasma diagnostics.
Recent semiconductor devices have embraced structural modifications, including vertical stacking, to overcome the limitations of miniaturization. Particularly, memory devices have seen improvements through the transition to 3D stack structures. To address the challenges of etching high aspect ratio contact holes, the Bosch process, which alternates between deposition of a passivation layer on the pattern wall to prevent sidewall etching and etching steps, has been utilized. This method commonly employs SF6 and CxFy gases with an addition of O2 to form patterns with very high aspect ratios.
