SBIR-STTR Award

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.

Statement of the Problem or Situation that is Being Addressed: 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.General Statement of How This Problem is Being Addressed: Eagle Harbor Technologies (EHT), Inc. has previously developed a Rapid Capacitor Charger (RCC) that can rapidly charge the wafer and stray capacitance to high voltage in tens of nanoseconds and operate at 400 kHz. This system can produce sheath voltage waveforms that are flatter than those produced with standard sinusoidal radio-frequency generators, which can improve control over the 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 is conducting an experimental and computational program to improve the understanding of the interaction between bias waveforms and plasma properties to commercialize this power system technology.What was Done in Phase I? In the Phase I, EHT operated the RCC on a small test chamber with an inductively coupled plasma source. EHT constructed a retarding field analyzer (RFA) and the associated electronics. EHT measured the source parameters with a Langmuir probe and RFA. Initial investigations with the RFA were conducted with the RCC operating. In parallel, Sandia National Laboratories (SNL) used a 1D particle-in- cell code to model the plasma with the applied bias voltage.What is planned in Phase II? EHT plans to modify the chamber to a capacitively coupled source, which is more relevant to the semiconductor tool industry and closer to the system that SNL is modeling. EHT will continue to develop the high-voltage RFA and investigate other energy analyzers. These analyzers will be used with even higher-voltage bias waveforms. SNL will continue to provide computational support to better understand the experimental results.Commercial Applications and Other

Benefits:
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.