Helen R. Armer

A comparison of data mining methods for yield modeling, chamber matching and virtual metrology applications

Statistical modeling methods have become a key tool in yield analysis and chamber matching. As the transition to 45nm and below increases it is becoming difficult to maintain yield and avoid excursions. Generalized and accurate models of process behavior to predict yield can quickly give insight into the cause of yield loss and process excursion. Here we simulate linear and nonlinear models of yield from process data and evaluate the performance of methods like partial least squares, support vector regression, and rules ensemble in predicting these yield models.

Metrology Delay Time Reduction in Lithography with an Enhanced AMHS using Local FOUP Buffering

An enhanced automated material handling system (AMHS) that uses a local FOUP buffer at each tool is presented as a method of enabling lot size reduction and parallel metrology sampling in the photolithography (litho) bay. The local FOUP buffers can be integrated with current OHT AMHS systems in existing fabs with little or no change to the AMHS or process equipment. The local buffers enhance the effectiveness of the OHT by eliminating intermediate moves to stockers, increasing the move rate capacity by 15-20%, and decreasing the loadport exchange time to 30 seconds. These enhancements can enable the AMHS to achieve the high move rates compatible with lot size reduction down to 12-15 wafers per FOUP. The implementation of such a system in a photolithography bay could result in a 60-74% reduction in metrology delay time, which is the time between wafer exposure at a litho tool and collection of metrology and inspection data.

Metrology delay time reduction in lithography via small-lot wafer transport

A small lot Automated Material Handling System (AMHS) is presented as a method to reduce the time between wafer exposure at a photolithography tool and collection of metrology / inspection data. A new AMHS system that is capable of the move rates required by small lot wafer transport is described, its implementation in a photolithography bay is explained, and the resulting reduction in metrology delay time is quantified. In addition, a phased implementation approach is described in which some, but not all, components of the new AMHS would be installed in existing fabs to enhance the move rate capability of traditional overhead transport (OHT) AMHS systems. This partial implementation would enable a partial lot size reduction and corresponding metrology delay time reduction of 60-70%. The full AMHS solution would be installed in new fabs and enable true small lot manufacturing in the litho area and would result in the maximum delay time reduction of 75-85%.