Optical Profilometer

Optical profilometers and step-height measurement systems both characterize a surface's physical topography optically, without the point-by-point contact a stylus profiler needs, measuring exactly how tall a feature's step or edge rises relative to its surroundings.

Non-contact measurement matters here for exactly the reason it matters anywhere else in the fab: a physical probe risks damaging or contaminating a delicate feature the way light never can. A stylus profilometer's tip drags across the surface under slight physical pressure, which works fine for robust films but can scratch, deform, or pick up material from a soft or fragile feature; optical profilometry measures height through interferometric or focus-based optical techniques instead, getting the same topographical information without ever touching the surface — the right choice whenever the feature being measured can't tolerate physical contact.

Step-height measurement specifically isolates one number from a full topographical map, which matters because many process specifications care about exactly that single value rather than a whole surface profile. An etch depth specification, a CMP planarization target, or a deposited-film step coverage requirement is usually written as a single height number across a specific feature edge, not a full topographical description — step-height measurement systems are built to extract that one precise, repeatable number efficiently, rather than requiring the fuller (and slower) 3D mapping a general profilometer scan provides.

Optical profilometry and step-height measurement both avoid the physical contact a stylus technique requires, and the choice between mapping a broad surface area versus quantifying one specific feature's height comes down to whether the process question is "what does this surface look like" or "exactly how tall is this one step."