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High Aspect Ratio Surfaces

Surfaces with steep slopes or high aspect ratio features including channel grooves (Figure 1) are difficult to characterize with commonly used measuring instruments such as a triangulation sensors, which require an angle between their sensor and light projection. In contrast, Novacam’s low coherence profilometers emit and pick up light with a single non-contact probe, allowing high aspect ratio surfaces to be measured and imaged as any other surface feature – with micron precision, at high-speed (2-20 kHz per second or higher), providing real-time process feedback.

Compared to triangulation sensors and color confocal systems, low coherence profilometers:

• Provide much higher sensitivity (resolutions under 1µm).
• Can access and scan surfaces inside hard-to-reach spaces.
• Operate in difficult environments (e.g. plasma, reflective surfaces, hostile environments).
• Deliver cross-section imaging and measurements of multilayer film thickness.

Industries requiring high-precision measurements of high aspect ratio surfaces are many: aerospace (cooling holes), automotive(fuel injectors), medical device production(tool edges), electronics, fuel and solar cell production, micro-machining, cutting tool fabrication and quality control (Figures 2, 3 & 4), etc.

In the electronics industry for example, the surface condition of Chemical Mechanical Polishing (CMP) pads, patterned with high aspect channels, affects the pad’s polishing performance. Low coherence profilometers are used in process to measure the roughness parameters of this surface and thus to optimize the timing of pad conditioning or replacement.

• For more details on surface characterization with low coherence profilometry, see application note Surface Characterization and Roughness Measurement [PDF, 0.3 MB].
• For our products, see Novacam’s profilometers.

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