Metrology and inspection equipment maker Lasertec Corp of Tokyo, Japan has launched the GALOIS defect inspection and review system series, designed specifically for the inspection and analysis of gallium nitride (GaN) wafers. The firm is already accepting orders.
The GALOIS Series uses bright-field confocal optics, enabling high-speed inspection of various kinds of GaN wafer defects and high-resolution observation of defect images.
Lasertec says that its SICA88 system is widely used as the de-facto standard SiC inspection tool, enjoying strong market recognition due to its high throughput and high accuracy of defect classification and its high-resolution defect review. GaN, on the other hand, lags behind in device usage, hindered by the high cost of GaN wafer manufacturing and the presence of numerous crystallographic and process defects in wafers, requiring further efforts in wafer quality improvement. The GALOIS Series, which offers the high-speed, high-sensitivity detection and classification of crystallographic and process defects, combined with high-resolution defect image review, has been launched to assist these efforts.
GALOIS uses a combination of confocal optics and differential interferometry optics - both of which are Lasertec core technologies - with a sophisticated algorithm based on advanced imaging technology. This eliminates the effect of noise from the backside of a transparent substrate, or from surface morphology, enabling the high-sensitivity detection of various kinds of defects in GaN wafers.
GALOIS employs a high-speed processing computer system and a model based on machine learning (including advanced deep learning) for defect classification. It uses the high-resolution review images captured by the firm’s core technologies and accurately classifies indeterminately formed defects, in parallel with other inspection processing. All review images captured during inspection of whole wafers are saved to computer storage, and can be used for the analysis of unclassified defects. GALOIS achieves an inspection speed of 6 minutes per 6-inch wafer, which is fast enough for future application in the production phase.
In addition to inspection for GaN wafers, GALIOS can also act as a process and yield improvement tool. It helps in identifying the root cause of defects, acting as a wafer, epitaxy and device process monitor.
