Aerial imaging for FABs: productivity and yield aspects

The economy of wafer fabs is changing faster for 3x geometry requirements and below. Mask set and exposure tool costs are almost certain to increase the overall cost per die requiring manufacturers to develop productivity and yield improvements to defray the lithography cell economic burden. Lithography cell cost effectiveness can be significantly improved by increasing mask availability while reducing the amount of mask sets needed during a product life cycle. Further efficiency can be gained from reducing send-ahead wafers and qualification cycle time, and elimination of inefficient metrology. Yield is the overriding die cost modulator and is significantly more sensitive to lithography as a result of masking steps required to fabricate the integrated circuit. Thus, for productivity to increase with minimal yield risk, the sample space of reticle induced source of variations should be large, with shortest measurement acquisition time possible. This paper presents the latest introduction of mask aerial imaging technology for the fab, Aera2TM for Lithography with IntenCTM, as an enabler for efficient lithography manufacturing. IntenCD is a high throughput, high density mask-based critical dimension (CD) mapping technology, with the potential for increasing productivity and yield in a wafer production environment. Connecting IntenCD to a feed forward advance process control (APC) reduces significantly the amount of traditional CD metrology required for robust wafer CD uniformity (CDU) correction and increases wafer CD uniformity. This in turn improves the lithography process window and yield and contributes to cost reduction and cycle time reduction of new reticles qualification. Advanced mask technology has introduced a new challenge. Exposure to 193nm wavelength stimulates haze growth on the mask and imposes a regular cleaning schedule. Cleaning eventually causes mask degradation. Haze growth impacts mask CD uniformity and induce global transmission fingerprint variations. Furthermore, aggressive cleaning may damage the delicate sub-resolution assist features. IntenCD based CDU fingerprint correction can optimize the regular mask cleaning schedule, extending clean intervals therefore extending the overall mask life span. This mask availability enhancement alone reduces the amount of mask sets required during the product life cycle and potentially leads to significant savings to the fab. This mask availability enhancement alone reduces the amount of mask sets required during the product life cycle and leads to significant savings to the fab. In this paper we present three case studies from a wafer production fab and a mask shop. The data presented demonstrates clear productivity and yield enhancements. The data presented is the outcome of a range of new applications which became possible by integrating the recently introduced Applied Materials Aera2TM for Lithography aerial imaging inspection tool with the litho cluster.