Paper PS1-WeA1
ECR Plasma Etching Characterization using a Retarding Field Energy Analyzer

Wednesday, October 31, 2012, 2:00 pm, Room 24

Dry etching technology was introduced to integrated circuit manufacturing due to its unique ability to do anisotropic removal of material to create high aspect ratio structures. Dry etching tools in the semiconductor industry use plasma to generate electrons, bombarding ions and free radicals. These radicals are chemically reactive and highly efficient at removing material from substrate surfaces, so the etch profiles depend on ion density and ion energy.

Electron cyclotron resonance (ECR) plasma etching reactors are widely used in wafer production. They use a low pressure, high density plasma source that has resonant magnetic field coils and two independently controlled microwave and radio frequency (RF) sources. ECR plasma etching is a very complex process and most of the progress with ECR etching tools up to this time has been accomplished empirically. Introducing new and adapted plasma diagnostic techniques is essential for further characterization and better understanding of plasma and etching processes.

In previous work we presented electrical measurements obtained using a retarding field energy analyzer (RFEA) installed in an commercial ECR etching reactor. RFEAs are generally used for charged particle flux and energy distribution measurements at electrically grounded surfaces. We demonstrated that an electrically isolated RFEA can be successfully used for measuring ion energy distribution functions (IEDFs) at the surface of RF driven electrodes in the presence of strong DC magnetic fields.

In this work we present further achievements in plasma diagnostics and ECR etching characterization. The original experimental setup is expanded for additional diagnostic tools. Phase resolved optical emission spectroscopy (PROES) measurements are taken at three different discharge locations simultaneously with RFEA measurements. Electrical and optical measurements show strong correlation in comparable aspects which proves their validity and together they provide more information about plasma in complementary aspects. The RFEA has also been used to measure the electron energy distribution function (EEDF) with the aim of electron temperature and density estimation in the bulk plasma. For validating EEDFs obtained with the RFEA, we performed similar measurements of EEDFs in a capacitively coupled plasma (CCP) reactor using the RFEA and the Langmuir probe. Results of this validation and estimations made from EEDFs are presented and discussed. Experimental and theoretical plasma etching characterization has been done through the analysis of spatially resolved data sets obtained from RFEA and spectroscopic ellipsometry at various radial locations.