Previous slide
Next slide


What is the difference between Enlitech SG-A quantum efficiency measurement and traditional CIS defect detection?


Conventional methods for detecting non-destructive defects in CIS imaging wafers :

  1. AOI inspection
  2. Image quality inspection

Principle of AOI inspection

     AOI inspection (Automatic Optical Inspection), which uses optical imaging technology method of defect detection for CIS image wafers. The system consists of an active light source that shines light onto the surface of the CIS image wafer, which is reflected by the light and collected by the camera lens to form a CIS surface image. The image can be analyzed and processed by the software, which can automatically identify defects on the CIS wafer surface. The pros of AOI, are that we could efficiently and quickly detect defects on the CIS wafer surface, including blemishes, contamination, particles, etc.
     Despite, AOI has many advantages in mass-production of CIS wafers, it also with limitations. Due to the variety of surface characteristics and defect types of CIS wafers, it’s affected by environmental factors such as lighting, different optical parameter settings, and algorithm adjustments. Moreover, the AOI system needs to be constantly calibrated and maintained throughout the production line to ensure the accuracy and stability of the inspection.
     The most important limitation is that AOI is limited to the surface features of the CIS wafer and the process parameters inside the wafer, such as the characteristics of the light-to-electric process, cannot be observed through AOI, so AOI cannot provide a complete reference for CIS performance evaluation and improvement.

Principle of Image Quality Inspection:

Method and Importance of Image Quality Inspection for CIS Imaging Chips:

     Image quality inspection for CIS imaging chips is a method for evaluating the imaging performance of CIS imaging chips, aiming to determine whether the imaging chips can meet the design specifications and to detect any defects in the manufacturing process of CIS imaging chips. This inspection method is based on observing the images of standard color cards and standard image cards and analyzing them through mathematical models to determine whether the image resolution, contrast, color accuracy, noise, and other indicators meet the requirements. The image quality inspection of imaging chips is an important step in the production process, which can help ensure the quality and performance of the imaging chips and improve the stability and reliability of the products.

Standard color cards and standard drawing cards used for imaging quality inspection

Standard color cards and standard drawing cards used for imaging quality inspection

Imaging quality test set-up

Setup for image quality testing (from Imatest Inc.): Place the CIS imaging chip to be tested on a track and place the standard image card at a suitable imaging distance from the CIS imaging chip. Illuminate both sides with high uniformity light sources, and project the light onto the standard image card. The image on the standard image card is reflected by the light and projected onto the CIS imaging chip, which is then captured. The obtained image is then analyzed and compared for image quality calculation according to mathematical models and formulas.

The shortcomings of the image sensor chip detection method:

      The two commonly used CIS image sensor chip detection methods mentioned above can only detect surface defects or imaging quality during CIS image sensor chip testing, and cannot detect the important parameters inside the image sensor chip. These parameters include quantum efficiency, spectral response, system gain, sensitivity, etc., which are more detailed and crucial to the performance of the image sensor chip. Therefore, in addition to imaging quality testing, other detection methods are needed to comprehensively evaluate the performance of the image sensor chip. This can provide a more comprehensive understanding of the performance of the image sensor chip and provide better reference and support for the design and manufacturing of CIS image sensor chips.

Important parameters of CIS image sensor chips:

Here are some important parameters that have a significant impact on the performance of CIS image sensor chips, but traditional optical inspection methods cannot test some key parameters, such as:

  1. Quantum Efficiency Spectrum
  2. Spectral Response
  3. System Gain
  4. Sensitivity
  5. Dynamic Range
  6. Saturation Capacity
  7. Linearity Error (LE)
  8. Chief Ray Angle (CRA)

Compared to traditional optical defect detection methods for CIS, SG-A optical inspection solution can:

1. Provide more comprehensive defect detection information than traditional non-destructive optical inspection methods.

2. Help users gain a more comprehensive understanding of the performance of CIS image sensor chips.

This solution can test issues such as crosstalk between pixels, brightness uniformity, color consistency, and pixel tilt, and provide parameter and analysis information to manufacturers to help them develop high-quality CIS image sensor chips during the design and manufacturing process.