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DLC Film Thickness |
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Film thickness measurement with the NanoTest requires a specimen in which a small area of substrate is exposed such that, ideally, a sharp step occurs between the film surface and the substrate. Such steps may be produced either by using a selective etching process after film deposition, or by masking the substrate during deposition. The thickness is determined by monitoring the displacement of a probe as it "falls" over the edge of the step.
After specimen alignment using the NanoTest high resolution microscope, automatic contact with the profilometry probe occurs at very low velocity in order to minimise contact damage. For soft specimens (such as plastics) the contact load applied to the probe can be set to less than 10 µN. |
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For very thin films, it may be necessary to use the NanoTest automatic levelling stage to prevent the background slope of the specimen from masking the step itself. Here, after contact with the film surface, the specimen angle and the required tilt correction are automatically determined by moving the specimen and monitoring the probe displacement.
Case Study: DLC film on Si
The results shown were obtained from a 51 nm DLC film deposited on silicon using a small radius ceramic probe with the following measurement procedure:
1.After automatic specimen levelling, manually position two moveable cursors at the ends of a "flat" portion of the film surface. These are used to eliminate in software any residual specimen tilt.
2. Manually position two moveable cursors at the ends of a "flat" portion of the substrate surface. These are used to calculate the step height relative to the mean displacement defined by the first two cursors. The step height is given together with an error based on the topographies at the top and bottom of the step. |
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