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Tham khảo tài liệu 'nanotechnology and nanoelectronics - materials, devices, measurement techniques part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 7.2 Etching of Nanostructures 153 Fig. 7.12 RIE-etched crystalline silicon structure of 800 nm height and 80 nm width at the tip masked with 100 nm silicon nitride quently used. An example of a crystalline silicon structure etched by the RIE method with a 100 nm thick Si3N4 mask layer is shown in Fig. 7.12. 7.2.2 Progressive Etching Techniques Further developments in reactive ion etching are inductively coupled plasma etching ICP and electron cyclotron resonance plasma etching ECR . With reference to the energy of the excited radical ions the independently controllable dissociation rate of the reaction gas via two separated high frequency generators is common to both procedures. By this separation high densities of reactive radicals can be produced despite a small operating pressure in the reactor because a high dissociation degree of the gas is achieved by means of a large excitation RF power of the plasma source. There is no influence on the particle energy. This is only determined by the bias voltage placed at the substrate electrode via a second RF generator. Fig. 7.13 Schematic cross section of the ICP a and ECR etching device b according to 224 154 7 Nanostructuring Thus very high etching rates of up to about 10 pm min can be achieved due to the attainable high radical densities. Simultaneously extremely high selectivity is given as a result of the small particle energy. Additionally almost completely anisotropic material removal takes place due to the large mean free path of the radicals at the small process pressure. The ICP etching technique finds increasing applications for micromechanical and deep silicon trench etching with high aspect ratios. The acceptance of this equipment also increases in the area of required high selectivities such as the structuring of polysilicon on thin gate oxide. In the case of ECR etching technique inhomogeneities occur in the plasma distribution due to resonance shifts in the source. This technique does not find much .
