Improving Ion Control for Semiconductor Processing with Repetitive Pulsed Power

The ability to use plasma etching to produce high aspect ratio (HAR) features is becoming increasingly important as the market demands solid-state non-volatile memory storage. In order to minimize bowing and twisting defects in HAR features, precision control of the ion energy distribution function (IEDF) is required. Additionally, HAR etching requires longer processing time and higher etch rates are needed to reduce overall cost, which requires higher power systems. Eagle Harbor Technologies (EHT), Inc. has previously developed a Rapid Capacitor Charger (RCC) that can charge capacitance to high voltage (6 kV) in tens of nanoseconds and operate at 400 kHz. This power system can charge the wafer and stray capacitance in an etch chamber to produce sheath voltage waveforms that are flatter than those produced with standard sinusoidal radio-frequency generators. These waveforms should produce narrower IEDFs and allow for greater process control. Additionally, this system can operate at up to 20 kW continuously when water cooled, potentially allowing higher etch rates. EHT also has produced a pulsed RF power system for plasma generation that when combined with the RCC allows for further increased control of the IEDF. These power systems have been demonstrated at the prototype level, and initial work is underway to develop industrial-use power systems. However, a physics-based approach for experimental verification and optimization of the IEDF using these bias techniques is still required. In the Phase I program, EHT will use these power systems with an existing plasma processing chamber. EHT will build the electronics to use with an existing high voltage retarding field analyzer (RFA). The RFA will be used to make precision measurements of the IEDF to demonstrate the efficacy of the new bias approach. Sandia National Laboratories will provide simulation support to help guide the experimental program. The market for solid-state non-volatile memory storage is driving the demand NAND FLASH, which requires precision etching of HAR features with aspect ratios approaching 100:1. To overcome some of the challenges with manufacturing 2D NAND, the semiconductor processing industry is moving to 3D NAND. One of the major challenges with the production of HAR features for 3D NAND is controlling bowing and twisting of the holes. Improved control of the IEDF improve the quality of HAR features. Additionally, HAR etching requires longer processing time and higher etch rates are needed to reduce overall cost. EHT pulsed power systems have the potential to improve IEDF control while operating at the high power required to increase etching rates thereby reducing production time and lowering costs.