Toru Kurenuma

New inline AFM metrology tool suited for LSI manufacturing at the 45-nm node and beyond

A new inline metrology tool utilizing atomic force microscope (AFM) suited for LSI manufacturing at the 45-nm node and beyond has been developed. The developed AFM is featuring both of high-speed wafer processing (throughput: 30 WPH) and high-precision measurement (static repeatability: 0.5nm in 3σ). Several types of carbon nanotube (CNT) probes specially designed for the AFM have also been developed. The combination of Advanced StepInTM mode and CNT probes realizes high precision measurement for high-aspect-ratio samples such as photoresist patterns. In Advanced StepInTM mode, a probe tip approaches and contacts a sample surface, and then moves away from the surface and toward a new measurement position. A series of these actions is performed in a short time (3.8 ms for single measurement point) full-automatically. Advanced StepInTM mode not only ensures gentle probe tip contact and precise measurement of high aspect ratio samples, but also minimum tip wear. CNT probes can provide long term performance, while eliminating the need for probe exchange. The developed AFM also realizes flatness measurement of 10-nm level in a wide area of 40x40-mm maximum. This performance is sufficient for the evaluation of CMP processes at the 45-nm node.

Dimension controlled CNT probe of AFM metrology tool for 45-nm node and beyond

Atomic Force Microscope (AFM) is a powerful metrology tool for process monitoring of semiconductor manufacturing because of its non-destructive, high resolution, three-dimensional measurement ability. In order to utilize AFM for process monitoring, long-term measurement accuracy and repeatability are required even under the condition that probe is replaced. For the measurement of the semiconductors minute structure at the 45-nm node and beyond, AFM must be equipped with a special probe tip with smaller diameter, higher aspect ratio, sufficient stiffness and durability. Carbon nanotube (CNT) has come to be used as AFM probe tip because of its cylindrical shape with small diameter, extremely high stiffness and flexibility. It is said that measured profiles by an AFM is the convolutions of sample geometry and probe tip dimension. However, in the measurement of fine high-aspect-ratio LSI samples using CNT probe tip, horizontal measurement error caused by attractive force from the steep sidewall is quite serious. Fine and long CNT tip can be easily bent by these forces even with its high stiffness. The horizontal measurement error is caused by observable cantilever torsion and unobservable tip bending. It is extremely difficult to estimate the error caused by tip bending because the stiffness of CNT tips greatly varies only by the difference of a few nanometers in diameter. Consequently, in order to obtain actual sample geometry by deconvolution, it is essential to control the dimension of CNT tips. Tip-end shape also has to be controlled for precise profile measurement. We examined the method for the measurement of CNT probe tip-diameter with high accuracy and developed the screening technique to obtain probes with symmetric tip-ends. By using well-controlled CNT probe and our original AFM scanning method called as Advanced StepInTM mode, reproducible AFM profiles and deconvolution results were obtained. Advanced StepInTM mode with the dimension- and shape-controlled CNT probe can be the solution for process monitoring of semiconductor manufacturing at the 45-nm node and beyond.

Development of Automatic Loading System for Crushed Stone Industry

In reply to the desire to automate one process in the work of crushing stones, an Automatic Loading System on the basis of a hydraulic excavator was developed. The system is constituted so as to execute automatic operation relying on a Teaching Playback function. The teaching positions are only the start position for digging and the start position for loading. All desired trajectories for the required series of motion are generated on a controller. The system was tested in the field in July 1999. The results indicated that the system was effective in stone crushing.