Pattern Writing by Implantation in a Large-Scale PSII System With Planar Inductively Coupled Plasma Source
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Abstract A large-scale plasma source immersion ion implantation (PSII) system with planar coil RFI plasma source has been used to study an inkless, deposition-free, mask-based surface conversion patterning as an alternative to direct writing techniques on large-area substrates by implantation. The apparatus has a 0.61 m ID and 0.51 m tall chamber, with a base pressure in thelT0- Torr range, making it one of the largest PSII presently available. The system uses a 0.43 m ID planar rf antenna to produce dense plasma capable of large-area, uniform materials treatment. Metallic and semiconductor samples have been implanted through masks to produce small geometric patterns of interest for device manufacturing. Si gratings were also implanted to study application to smaller features. Samples are characterized by AES, TEM and variable-angle spectroscopic ellipsometry. Composition depth profiles obtained by AES and VASE are compared. Measured lateral and depth profiles are compared to the mask features to assess lateral diffusion, pattern transfer fidelity, and wall-effects. The paper also presents the results of MAGIC calculations of the flux and angle of ion trajectories through the boundary layer predicting the magnitude of flux as a function of 3-D location on objects in the expanding sheath.
Introduction High-energy ion implantation is an important surface modification technique, which causes minimal dimensional change, and avoids thermal distortion of the surface profile of the treated object [ 1, 2, 3]. Plasma source immersion ion implantation (PSII) is advantageous compared to traditional beam line implantation technique for large areas, complicated work piece shapes, and high dose applications [1, 2]. The uniformity of implantation is determined by the spatial plasma density distribution and the plasma sheath distribution. It does not require beam rastering to achieve dose uniformity over large implantation areas. There is also no need for tilting or rotating of the work piece to treat all the surfaces. This greatly simplifies the mechanical construction of the implantation chamber and reduces the cost of building the system. Different plasma sources for PSII have been used, such as hot filament [2, 3, 4], cylindrical coil RF inductively coupled plasma [5], rf capacitively coupled plasma [2, 6], microwave plasma [7], and glow discharge [2]. To realize PSII technique s potential of treating large work pieces, several large-scale PSII systems have also been built, including PSII systems at Los Alamos National laboratory [6], Hughes Research Laboratories [3], and the University of Wisconsin [2]. None of these large-scale PSII systems takes advantages of the planar coil rf inductively (RFI) coupled plasma source, which is widely used to generate low-pressure, high-density discharge and demonstrates the potential for large area processing and improved spatial uniformity [1, 8]. Since rf power is coupled to the plasma inside the vacuum chamber usually through a quartz window, there are no electrical connections or suppo
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