Research & Development

Confocal Group

  • Line chromatic confocal profilometer

  • Diffraction Image Microscopy (DIM)

3D Group

  • Key technologies and modules for automatic online pose estimation of 6-axis robotic arms

  • PCB multi-dimensional optical precise measuring system

  • Automatic Precision measurement system for Semiconductor components

Nano Group

  • The ultra-precise 3D Abbe-error free wafer inspection stage


Confocal Group：Line chromatic confocal profilometer

  • Light's dispersion property is the using principle in conventional point-type chromatic confocal microscopy.

  • While an illumination pinhole is employed to provide a point light source, a designed dispersion module focuses the broadband light that passes through the pinhole onto a detected object, thus forming a particular dispersion range.

  • After the light been reflected by the detected object, a detection pinhole performs as a spatial filter that only allows the wavelength just focuses on the object's surface to pass through. And next a spectrometer is used to analyze the spectrum of the filtered light.

  • By a prior calibration, the relationship between the spectrum and the object's surface position can be acquired. This relationship is then used to precisely position the object's surface and reconstruct its profile.

  • A point-type chromatic confocal microscope can be upgraded to a line-type one by replacing the pinholes with slits and required optical design. By doing so, a higher measurement speed can be achieved.

  • Due to the inherent axial parallelization, the top surface and bottom surface of a thin film can be measured simultaneously and its thickness is determined at the same time.

▲ Principle of point/line chromatic confocal microscopy

Thin film measurement example

▲ Thin film measurement example

▲ Thin film measurement example

▲ Thin film measurement example

Confocal Group：Diffraction Image Microscopy (DIM)


  • A diffraction image microscopy (DIM) first projects a point-like source onto a detected object. Then the reflected light is focused onto an image sensor to form a diffraction image. This image is then analyzed to determine the object's surface height.

  • The principle is based on the truth that the diffractive images vary with the height of the detected object. Therefore with proper prior calibration, the object's surface height can be inferred by analyzing the detected diffractive image, and precision of sub-micrometer can be achieved.

  • This technique can be parallelized using a digital micromirror device (DMD) and necessary optical design. With the assist of DMD, a compact measurement device with a programable measurement point-array can be realized and thousands of measurement points can work together for high-speed surface profile reconstruction.

  • A measurement module based on the above-mentioned principle had been developed and integrated with our ultra-precise Abbe-free wafer stage.

  • Thus providing the function of large-area scanning and stitching, applicable to the high-speed wafer metrology in the semiconductor industry.

▲ Configuration of a diffraction image microscope integrated with DMD

▲Internal view of the developed
diffraction image microscope


▲ Mechanical design of the developed diffraction image microscope

▲ Diffraction Image Microscopy
& the ultra-precise 3D Abbe-error free
wafer inspection stage

3D Gruop： Key technologies and modules for
automatic online pose estimation of 6-axis robotic arms

  • Our Lab is aimed to develop an advanced intelligent optical precise measuring module to be integrated with 6-axis robots for achieving the goals set in Vision 4.0 -- Smart Vision for Smart Factories.

  • This system has the functions of spatial positioning and pose estimation of robot’s end effectors. The developed system has a novel featureless object recognition and positioning algorithm for detection of accurate orientation and positions of the robot end effector, in which the measurement accuracy of three-dimensional positioning can be better than 100 μm and angular resolution (Rx/Ry/Rz) better than ±1.5° in in-line detection. Most importantly, it can be used for online inspection without any additional target wafer disc like other existing systems.

▲ Probe Design layout-1

▲ Probe Design layout-2

▲ Internal view of the probe

▲ External view of the probe

▲ Key technologies and modules for automatic online
pose estimation of 6-axis robotic arms

▲ Captured vs. Measurement result

▲6 degrees of freedom pose variance of robot arm end-effector

3D Group：PCB multi-dimensional optical precise measuring system

  • This developed system can be used to perform intelligent and accurate automatic optical surface scanning and profilometry on work-pieces with complicated surface geometry.

  • Capable of automated optical inspection (AOI) for high precision 3D profilometry and 2D dimension extraction, detecting form error distribution of the workpiece, as well as critical dimension and profilometric features.

  • The measurement specification: depth resolution is 2 m and the measurement repeatability is up to 5 m @ 2σ of a 10 mm depth range.

▲ External view of the PCB multi-dimensional optical precise measuring system

▲ External view of the PCB multi-dimensional optical precise measuring system

▲The Object to be measured & the measurement result

▲ The flow chart of PCB multi-dimensional
optical precise measuring system

3D Group：Automatic Precision measurement system for Semiconductor components

▲ External view of the Automatic Precision measurement system for Semiconductor components

  • Using the structured light phase shifting method, combined with the 6-axis robot to control the movement of the measurement module, high-precision and high-flexibility profile detection can be achieved by this system. This system also transfers technology with With Vision Inspection System Co., Ltd., and can be applied to the inspection part in the semiconductor manufacturing process.

  • Capable of automated optical inspection (AOI)　of micro bumps or other microstructures in the subsequent packaging process of the semiconductor industry.

  • High accuracy 3D measurement, with 0.5 µm depth resolution, 1.0 µm @ 2σ for repeatability, and the accuracy error is less than 0.03% of the full depth.

Nano Group：The ultra-precise 3D Abbe-error free wafer inspection stage

The ultra-precise 3D Abbe-error free 12” wafer inspection stage and key optical measurement probe modules developed in this laboratory are intended for use in precision measurement or defect detection in the pre-production process of wafers.

The inspection stage can be integrated with vibration-resistant optical measurement probe modules to develop equipment and techniques for flatness inspection of wafer surfaces.

This project will integrate the experience and technology of the three laboratories of precision measurement, precision positioning control and precision mechanism design in the Department of Mechanical Engineering at NTU, in the areas of Micro-CMM precision measurement, nano-level precision positioning control and precision platform and mechanism design.

The development of inspection stage with an accuracy specification of 300 mm × 300 mm × 5 mm, a scanning speed of 40 m/min and a spatial volume positioning error of 50 (±3s) are the objectives of this study.

▲ The design layout of the ultra-precise
3D Abbe-error free wafer inspection stage

▲ Exterior design of the ultra-precise
3D Abbe-error free wafer inspection stage