A Method for Rapid Specimen-Setup in Wafer Inspection Systems

Physical Sciences : Materials and Compounds

Available for licensing


  • Michael Cullinan, Ph.D. , Mechanical Engineering, Cockrell
  • Tsung-Fu Yao , Nascent
  • Andrew Duenner, BBA , Mechanical Engineering

Background/unmet need

Probe-based metrology techniques such as atomic force microscopy (AFM) are widely used in nano-technology due to their extremely high imaging resolution. In industrial fabrication, manufacturers require in-line inspection systems to monitor the quality of products and to minimize scrap rates. Current AFM systems are too slow to set up and to make measurements in a production setting. Furthermore, current AFM inspection systems are complicated and cannot be easily integrated into other fabrication systems. These limiting factors make it difficult and impractical to utilize AFM for inline semiconductor manufacturing metrology using existing technology.

Invention Description

The invention consists of a positioning stage for an atomic force microscope (AFM) on a chip. The device sits on top of a sample stage via a highly repeatable coupling mechanism. Actuators are used to move the AFM chip to a position of interest on the sample. Flexural bearings couple the actuators to the stage containing the AFM chip. The device allows for translation on the order of millimeters with repeatability on the order of micrometers. An auto-approach algorithm has been developed to allow the stage to rapidly approach the sample without sensors other than the AFM. The system allows for rapid and precise AFM setup and scanning and supports true in-line wafer-scale metrology. Due to its simplicity it can be easily integrated into existing manufacturing processes.


  • Positioning repeatability within scanning range of AFM chip allows for automated alignment of AFM chip and wafer stage without additional sensors.
  • Setup time on the order of 1 minute--significantly faster than competing technologies.
  • Potential to enable true in-line metrology in nano-technology manufacturing.
  • Sub μm positioning repeatability over a travel range exceeding 2mm.


  • Flexure-based translation stage allows for precision positioning and a large travel range in the X-Y plane.
  • Kinematic coupling mechanism perfectly constrains degrees of freedom of translation stage relative to sample stage.
  • Rapid auto approach and step size less than 100 nanometers in z-direction.
  • Precision couplers allow for the sample to be replaced with a minimum of recalibration and setup required.

Market potential/applications

Semiconductor manufacturers; semiconductor metrology device manufacturers  

Development Stage

Proof of concept

IP Status

  • 1 U.S. patent application filed