Detect the invisible

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Standard operation process for our 300mm wafer (particle) defect lab tool

1) The user inserts the test wafer into the UNISERS nanocoating module manually.
2) The UNISERS-nanocoating module automatically coats the wafer (full or selected areas) for the signal-enhancement.
3) After coating, the user inserts the test wafer in the UNISERS optical inspection module.
4) The user selects the area of interest for scanning. Area of interest can be selected automatically based on a wafer map generated by another full-wafer particle inspection tool, randomly, with specific conditions, or manually.
5) The optical scanning is automated. The module provides particle size distributions, particle coordinates, and high-resolution UNISERS particle images (for physical classification) on scanned areas.

Optional Raman inspection

6) The particle defects for the enhanced Raman inspection are selected. The selection can be from the user, randomly, or with specific conditions.
7) The Raman signal acquisition is automated. The tool provides the Raman spectra for the selected particles, true-size, and high-resolution UNISERS images. UNISERS can provide additional analysis tools to detect Raman bands (peaks) and analyze the spectra.
8) The user takes the test wafer out of the inspection tool.
9)The test wafer is cleaned (reclaimed) with standard semiconductor cleaning processes for recycling.

Example Application-1: Defect classification with high resolution particle scanning on the area-of-interests

Many laboratories have access to a full wafer particle scanner. However, most of the scanners in laboratories do not have particle detection sensitivities required for high-end nodes. In addition, existing scanners can not make classification of particle defects. UNISERS can accept the defect map generated by another full wafer particle scanner and perform high-resolution scans down to 8nm on the area of interest. UNISERS scan also provides a physical classification of defects based on high-resolution UNISERS images.

Defect classification down to 8nm:
-Particle agglomerates

Example Application-2: Optimization of CMP-post cleaning process

Post chemical mechanical polishing (CMP) cleaning is a critical process that can lead to yield drop for several potential defect mechanisms. Process optimization or monitoring for post-CMP cleaning is generally performed on blanket wafers coated with dielectric or metallic thin films. Such thin films increase the background signal (haze) for existing wafer scanners based on optical scattering. Therefore, it is challenging to detect small particles, especially on metallic films.

The UNISERS nanocoater enhances the signal-to-noise. Therefore,  particles down to 8nm – 30nm (surface roughness dependent) are detected. Furthermore, the true-size distribution of the particles enables the detection of post-CMP slurry residues.

Understanding particle contamination mechanism by true-size detection capability

Example Application-3 : Full-wafer inspection of 1- to 4 inch wafers for R&D or witness wafers

Working with  1-inch to 4-inch wafers can simplify various tests in laboratories or is necessary for witness wafers. Contamination levels on these small wafers are assessed either by indirect methods (chromatography) or microscopes with limited particle detection efficiency.

UNISERS provides a particle size distribution for very low to very high defect densities. Eventually, enabling to speed up laboratory duties and provide unmatched sensitivity.

UNISERS can discriminate two particles (20nm) if they are 2 microns apart from each other. Therefore, UNISERS can inspect highly contaminated witness wafers providing particle size distributions.

Example Application-4: Chemical classification of defects with enhanced Raman

Material characterization of particle defects is an important task to identify the source of defects and improve yields. SEM-EDX can provide elemental spectra, which are used to quantify the metallic content in defects. Molecular spectroscopy like Raman is needed to speciate organic particles.

UNISERS provides Raman spectra for particles down to 50nm, facilitating speciation of organic particles of wafers. This technology helps to detect corrosion or anti-corrosive layer residues on post-CMP wafers.