In this work, a novel diagnostic tool was developed in order to provide a measurementtechnique for sidewall charging in high aspect ratio features exposed to a plasmaenvironment. Currently, high aspect ratio features, holes which are very deep but not verywide, on semiconductor chips are used in order to create the cutting edge computermemory that is used in everyday computers. However, during creation of these features byplasma etching, charge build-up occurs on the sidewalls due to the plasma exposure and itcan divert the etch path. The result is that instead of finishing as strictly vertical features,the holes have twists and are therefore defective, as they cannot make the correct electricalconnections. In order to study this behavior and its causes, a series of Diagnostics forEtching and Charging (DECs) were created that can simulate high aspect ratio featuresand record in-situ, real-time current measurements along the etch path. Using these DECs,a complete view of the charging behavior inside the feature was accomplished and itsbehavior as a function of chamber pressure, RF power and aspect ratio was explored.These experiments were conducted in an Applied Materials oxide-etch chamber which isused in industry for plasma etching of high aspect ratio features. This chamber, donatedfrom the Micron Technology Foundation, was capable of reproducing actual etch conditionsused in memory manufacturing but only inert argon gas was used during testing for safetyreasons. Using the inductively-coupled plasma source, the DECs were immersed directlyinto the bulk plasma in order to receive a high flux of current which was subsequentlymeasured. The DECs were able to detect the incoming flux to the top, middle and bottomof the simulated holes in order to determine the behavior of sidewall charging.
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