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Laser triangulation technique
CLASS: QSI Laser Diode      DATE:2016-3-23    SOURCE:www.longstartech.com.cn

In laser triangulation were detected, with a finely focused laser beam to scan on the surface of the wafer, optical system will be reflected laser focus to detector (Fig. 1). 3D laser triangulation is used to detect the morphology of micro bumps, and it has obvious advantages in precision, speed and detection. The detection technology is currently facing challenges including the interval between the bump size and convex points are very small, and in the whole wafer littered with millions of bump.

Fig. 1 laser triangulation of the convex point is calculated by the reflection of the laser beam.

Laser triangulation was detected in the probe laser beam scanning process to obtain the silicon substrate and the bump at the top of the data, because of it of the convex surface and the periphery of the substrate only a single scan, so that you can to eliminate multiple scans of the error and the uncertainty inherent in different height. Single sweep method can detect the Z direction with high accuracy and high precision. The performance of the method can reach the theoretical resolution of the detector, which is smaller than the current size of the salient points.

Laser triangulation was detected except with very high detection accuracy and precision, it also has the detection speed and production capacity, the data acquisition rate enough to meet the needs of production process of the whole wafer detection. In the full wafer detection mode, the system through a series of similar line scanning to cover the entire wafer and scanning a single for 600 mu m wide strip region, the typical data generated by density for 40000 data points / mm2 (Figure 2). Transform sampling density to optimize the detection process, to maximize meet the requirements of some special application of resolution, accuracy and yield, but also can easily meet future bump diameter and section from further reduced after the detection requirements. The data density can be increased or reduced according to the required feature size and output. The system can realize the whole wafer detection in high output, and it is possible to increase the detection output by the implementation of the sampling plan which only detects the specified chip.