Process Gas Monitoring and Control

Sensitive, Real-Time Monitoring and Diagnostics of Semiconductor Manufacturing Processes


Process Gas and Plasma Monitoring in Semiconductor Manufacturing

Advances in material technology are closely connected to the development of in-line metrology tools.   Research and development teams build knowledge based on reliable and non-destructive measurements and pass this knowledge on to large-scale manufacturers for cost-effective production.  The semiconductor industry relies on these interconnected advances with focus on three main areas: (1) materials deposition, (2) materials etch and (3) materials patterning/lithography.  While process characterization and monitoring are standard requirements for both deposition and etch processes, the need for control in the lithography sector is becoming more critical.   With the advent of more complex EUV lithography tools and smaller features from one node to the next, lithography now depends on monitoring to ensure quality and maximize throughput and yield.

Mass spectrometry and optical spectroscopy metrology techniques are most effective for in-depth process analysis (E.g. Which species are present? What is their relative abundance?).  Although optical techniques are desirable in production settings due to their non-invasive nature, they are applicable only in specific cases and cannot address all chemistries and materials. By contrast, mass spectrometry is a powerful technique for analysis of any process gas, but it needs careful system integration that considers differences in process flow, pressure and times. These constraints have previously been addressed using quadrupole mass spectrometers (residual gas analyzers, RGAs), but as the semiconductor industry incorporates more materials in highly complex stacks for design of the next-generation chips, quadrupole mass spectrometers are no longer able to meet all the challenges of integration.

The pgaTOF simultaneously detects all precursors, byproducts, and trace species to guide immediate process control action and to inform analytics and process intelligence.  This electron ionization time-of-flight mass spectrometer (EI-TOF) has been developed specifically to overcome the limitations of RGAs and to keep up with the material technology advances in the semiconductor industry.


  • Sensitive, Real-Time Monitoring of Etch Processes Using the pgaTOF

    • Real-time monitoring of the evolution of etch gases and all reaction products
    • Plasma diagnostics based on traces of plasma species
    • High dynamic range to monitor both abundant and trace-level compounds
    • Sub-monolayer sensitivity for accurate end-point detection
    • Detection of etch rate changes and fluctuations due to malfunction or instabilities (i.e., O2 flow meter oscillations)
    • High mass resolution, high mass accuracy, and accurate isotopic distribution measurement provides accurate spectral assignment for complex and rich mass spectra

    pgaTOF for Plasma Etching

    Reactive Ion Etching of Si in a CF4/O2 Plasma Chemistry

    real-time monitoring of etch processes

    Time evolution of plasma and etch product species during a CF4 RIE process showing the effect of O2 addition on the Etch rate (Power: 400 W, 100 sccm CF4)


  • Multi-Elemental Analysis for Atomic Layer Deposition (ALD) Process Optimization Using the pgaTOF

    • Analyze saturation of gas precursors to optimize the pulsing and purging times in hours/days
    • Determine optimal temperature of precursors’ bubbler and reaction chamber
    • Detect a variety of process anomalies

    pgaTOF for Atomic Layer Deposition

    ALD Process Monitoring during Deposition of Al2O3 Using Trymethyl Aluminium and Water

    ALD Process Monitoring

    An in situ TOFMS integrated within an ALD chamber gives a unique opportunity of monitoring the signal’s time evolution of all elements and molecules participating in an ALD process, including products and by-products. The H2O (blue line) and Al (red line) signals represent the gas precursors, while N (green line) and Ar (violet line) signals provide information on the vacuum status of the deposition chamber. The time evolution of the entire deposition process (a) and magnification of the first three TMA and the first H2O cycles (b) are shown. The TOFMS data were normalized to 1 for better visualization.



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