Method of detecting radicals using mass spectrometry

Inventors

Mueller, Norbert

Assignees

Inc Inficon • Inficon Inc

Abstract

A method for detecting radicals in process gases in a semiconductor fabrication assembly is provided where the semiconductor fabrication includes a plasma source and a mass spectrometer with an ion source. The method includes separating ions from the process gases and determining a fixed electron energy in which to measure the process gases. Process gases in the semiconductor fabrication assembly are continuously sampled. A first measurement is performed on the sampled process gases at the electron energy using the mass spectrometer, where the first measurement is performed with the plasma source off. A second measurement of the sampled process gases is performed at the fixed electron energy using the mass spectrometer, where the second measurement is performed with the plasma source on. An amount of a radical present in the sampled process gases is determined as a difference between the second measurement and the first measurement.

Core Innovation

The disclosure describes a semiconductor process gas radical detection method using a mass spectrometer having an electron-impact ion source. Process gases are continuously sampled in a semiconductor fabrication assembly and are supplied to the mass spectrometer through a gas-tight connection. Ions are separated from the process gases, and ion responses are measured at a selected electron energy.

Two measurements are performed at the selected electron energy: a first measurement with the plasma source off and a second measurement with the plasma source on. An amount of a radical present in the sampled process gases is determined as a difference between the second measurement and the first measurement at the target mass number / mass spectrum peak. Ion separation and filtering are performed so that ion intensities are obtained for the comparison.

The disclosure further emphasizes appearance-potential behavior at low electron energies and use of an online evaluation based on a small data set. Measurement data are output to a controller and displayed on a graphical user interface. Examples described include CF4 radicals (CF+, CF2+, CF3+) with electron-energy selection based on maximizing differentiation between plasma-off and plasma-on measurements, including multi-radical / multi-energy measurement possibilities.

Claims Coverage

The document includes two independent claims. Both independent claims cover the core measurement concept of continuously sampling semiconductor process gases, taking two mass-spectrometer measurements at a fixed or set electron energy with the plasma source alternately off and on, and determining the radical amount as the difference between those measurements. Additional claims refine electron-energy selection and output or use of the results.

Across both independent claims, the inventive coverage centers on using a mass spectrometer to continuously sample semiconductor fabrication process gases, measuring at a fixed or set electron energy with the plasma source off and on, and determining radical amount from the difference between the two measurements. Dependent claims further specify electron-energy selection by greatest on/off differentiation across a range, an electron-impact ion source, controller and graphical user interface output, and adjustment of semiconductor manufacturing process variables.

Stated Advantages

Documented Applications