Innovative imaging technology opens new horizon to wafer inspection for advanced DRAM products

Automated optical wafer inspection was introduced in the beginning of 90´s when wafer fabrication entered the 200 mm wafer and sub-micron processing era in order to perform yield monitoring during ramp-up and volume production. Two technologies, Brightfield (BF) and Darkfield (DF) were adapted by the semiconductor industry. However, their evolution rapidly lagged behind the stringent demand for increased sensitivity at higher throughput and lower cost. More than 10 years after the introduction of Brightfield and Darkfield wafer inspection technology the transition towards the 90 nm and 65 nm nodes is creating new and critical needs for process monitoring and yield ramp-up. Increased device and process complexity combined with the transition to 193 nm lithography and the utilization of 300 mm wafers represents a major yield challenge. An appropriate inspection technology is critical to detect a very large variety of sub 100 nm defects at a high throughput, while lowering the cost of wafer inspection. In cooperation Negevtech, Infineon Technologies Unit Process Development Group has introduced and evaluated the Negevtech 302 new inspection technology on its most advanced DRAM products.