Critical dimension & overlay measurement
Optical scatterometry or optical critical dimension (OCD) is a common in-line metrology method for process control in semiconductor production. In addition to imaging techniques such as CD-SEM, OCD has developed as a fast, precise and non-destructive metrology, giving information about CD, height or side wall angles of the observed pattern structures. The relevant profile shape parameters are determined by illuminating a small area on the wafer under a certain angle and observing the scattered light via a spectrometer within the UV-NIR spectral range. To determine pattern profile information, model-based machine learning techniques are applied to wafer training spectra as a reference. ZEISS supplies OEM high-performance spectrometers like the MCS-CCD (190 - 980 nm) or custom configurations for CD and overlay OCD-metrology.
High end optical plane gratings enable you to measure cutting edge parameters in your metrology and are designed to specific customer requirements, such as the lowest levels of stray light, high efficiency and lowest wavefront aberration.
Thin film measurement / ellipsometry
Within semiconductor front-end manufacturing processes such as etching, deposition or cleaning, the thickness of thin films and complex layer stacks must be measured. Spectroscopic ellipsometry (SE) and spectral reflectometry (SR) allow for the in-line, non-contact measurement of optical thickness ranging from a few nm to several tens of microns. SE is is based on the change in the polarization state of light as it is reflected obliquely from a thin film probe. It utilizes a model-based approach to determine film thickness, surface & interface roughness as well as various optical/material properties. In addition to SE, normal-incidence spectral reflectometry (SR) is a well established inspection method for fast characterisation of thin film thickness. ZEISS MCS series (190 - 1015 nm) and CGS series (190 - 1100 nm) spectrometers have unmatched SNR, high UV-sensitivity, minimized stray light and high-volume supply. We support the custom design and manufacture of specific spectrometers with numerous plane gratings and mono- & polychromator gratings. ZEISS gratings provide high dynamic range in the spectrometers due to the lowest levels of stray light.
Plasma monitoring & endpoint detection
The production of semiconductor devices relies heavily on plasma etching processes. When patterns are etched on a wafer, the in-line control of etching progress is vital to avoid over and under-etch and ensure optimized process parameters, high yield and productivity. Optical metrology, such as optical emission spectroscopy (OES), spectral reflectometry (SR) and laser interferometry are common for plasma etch endpoint control. ZEISS MCS-CCD (190 - 1015 nm) and CGS series (190 - 1100 nm) is ideal for optical emission spectroscopy where concentrations of plasma reactants are monitored during etching in real-time. MCS-CCD feature high resolution, broad spectral coverage, good wavelength accuracy and fast readout. For spectral reflectometry the spectrometers of the MCS series and CGS series provide the required high dynamic range and good signal-to-noise ratio. ZEISS offers plane gratings, which are used in single or multichannel spectrometers from VUV to NIR for customer-specific spectrometer developments for plasma monitoring and endpoint detection. Plane gratings with a wide range of line densities between 30 l/mm and 3600 l/mm provide well adapted resolution and signal-to-noise ratios due to the lowest levels of stray light.
Wet process control
The monitoring of heated chemical baths in semiconductor wet processes requires tight control of chemical mixtures. Constant bath conditions have to be maintained during production to insure uniform process stability. Compared to standard conductivity analyzers, fiber-coupled NIR spectrometers enable remote placement and multi-constituent analysis, preventing costly yield losses due to suboptimal chemistry. ZEISS PGS NIR (960 - 2500 nm) offer a broad choice of NIR analyzers for the real-time, multi-point concentration monitoring of chemicals such as SC1, SC2, SPM, BOE or DHF. PGS NIR spectrometers have a small footprint, robust design, high SNR ratio and fast readout.