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The dimensions of semiconductor devices are shrinking towards the nanometer range. More accurate surface reaction control is thus required in plasma etching on this scale. Time modulation (TM) of the radio-frequency (RF) bias, discharge, and gas injection processes has been investigated to improve both directional profiles and etch selectivity. Microwave electron cyclotron resonance (ECR) plasma was also shown to have affinities to pulse modulation and low ion energy processing. As examples, wiggling was improved using a pulsed discharge in a directed selfassembling (DSA) mask etch, and directionality was improved using gas pulsing technology in fin etching. In future MOS device fabrication, higher etch selectivity and more directional etch profiles are expected to be required and their accuracy requirements will reach the atomic level. A combination of pulsing technology (tri-time modulation, Tri-TM) and low bias power control at low pressure condition is considered as candidate technology for future device fabrication.

The model-based library (MBL) matching technique was applied to measurements of photoresist patterns exposed with a leading-edge ArF immersion lithography tool. This technique estimates the dimensions and shape of a target pattern by comparing a measured SEM image profile to a library of simulated line scans. In this study, a double trapezoid model was introduced into MBL library, which was suitable for precise approximation of a photoresist profile. To evaluate variously-shaped patterns, focus-exposure matrix wafers were exposed under three-illuminations. The geometric parameters such as bottom critical dimension (CD), top and bottom sidewall angles were estimated by MBL matching. Lithography simulation results were employed as a reference data in this evaluation. As a result, the trends of the estimated sidewall angles are consistent with the litho-simulation results. MBL bottom CD and threshold method 50% CD are also in a very good agreement. MBL detected wide-SWA variation in a focus series which were determined as in a process window by CD values. The trend of SWA variation, which is potentiality to undergo CD shift at later-etch step, agreed with litho-simulation results. These results suggest that MBL approach can achieve the efficient measurements for process development and control in advanced lithography.

The effect of Push–Pull bias (phase-controlled bias) on the plasma potential and sputtering at the chamber-wall was investigated. It was found that the plasma potential could be controlled unrelated to the geometrical configuration of the chamber by using phase-controlled bias. The reason is that by using phase-controlled bias in the plasma with a magnetic field, the earth function of both electrodes facing each other can be controlled. Specifically, with the phase difference set to 180 degrees, the plasma potential was minimized and the decreased energy of incident ions to the chamber-wall reduced sputtering at the chamber-wall. Therefore, a stable process performance without particles caused by a sputtering at the chamber-wall, was expected by using Push-Pull bias in the dielectric UHF-ECR etching system.

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