Ion Transport to a Photoresist Trench in a Radio Frequency Sheath

We present a model which is used to study ion transport in capacitively coupled plasma(CCP) discharge driven by a radio-frequency(rf) source for an etching process.The model combines a collisional sheath model with a trench model.The sheath model can calculate the ion energy distributions(IEDs) and ion angular distributions(IADs) to specify the initial conditions of the ions incident into the trench domain(a simulation area near and in the trench).Then,considering the charging effect on the photoresist sidewalls and the rf-bias applied to the substrate,the electric potentials in the trench domain are computed by solving the Laplace equation.Finally,the trajectories,IEDs and IADs of ions impacting on the bottom of the trench are obtained using the trench model.Numerical results show that as the pressure increases,ions tend to strike the trench bottom with smaller impact energies and larger incident angles due to the collision processes,and the existence of the trench has distinct influences on the shape of the IEDs and IADs.In addition,as the bias amplitude increases,heights of both peaks decrease and the IEDs spread to a higher energy region.     

Characteristics of a Collisional Sheath Biased by a Dual Frequency Source

A hybrid model is used to simulate the characteristics of a collisional sheath in a capacitively coupled plasma （CCP） driven by a dual frequency source includin...     

Fe-Cr-V-Ti系永磁体在机械力作用下的稳定性

研究了冲击和振动对四种Fe-Cr-Co-V-Ti系永磁体磁性的影响。结果发现:退磁率在冲击开始时比较大,随着冲击次数的增加逐渐减小,以致趋于稳定状态。磁稳定性的大小与冲击力大小有关。退磁率随振动频率的增加呈波动式变化;实验曲线的振幅随振动频率增加而渐减,最后都趋于稳定状态。退磁率在振动初期变化的比较快,随着时间的增长而趋于稳定状态。但含Mo的合金在2.5h附近有增磁现象。     

Two-Dimensional Self-Consistent Kinetic Model for Solenoidal Inductively Coupled Plasma

A two-dimensional self-consistent kinetic model was developed to study the influence of the various factors on the electron energy distribution function. These factors include gas pressure the driving frequency, the radius and length of the inductively coupled plasma equipment, the amplitude of the radio-frequency coil current, and the number of turns of rf coils. The spatial profiles of the rf electric field and power density have also been calculated under the same parameters. Numerical results show that the electron energy distribution functions are significantly modified and the spatial profiles of the rf electric field and rf power density are also demonstrated.     

Simulations of Ion Behaviors in a Photoresist Trench During Plasma Etching Driven by a Radio-Frequency Source

Ion’s behavior plays an important role in plasma etching processes and is determined by the local electric potential in the etched trenches.In this study,with the trench powered by a radio frequency(rf) source,the Laplace equation is solved to obtain the electric potential.The ion trajectories and the ion energy distribution(IED) at the bottom of the trench are obtained self-consistently by tracking the ions in the trench.The results show that the aspect ratio of depth-to-width of the photoresist trench and the voltage amplitude of the rf source applied to the electrode are important parameters.The larger the aspect ratio and the smaller the amplitude are,the more ions hit the sidewalls,which results in a notching phenomenon.Meanwhile,there are a higher high-energy peak and a lower low-energy peak in the IED with the increase in aspect ratio.     

Dislocation Behaviour near the Crack Tip in Bulk Fe-3% Si Single Crystal

An investigation has been made of the disloca-tion distribution and dislocation free zone near thecrack tip in bulk Fe-3% Si single crystal duringdeformation in SEM.It has been found that anumber of dislocations were emitted from the cracktip during deformation.After that,the dislocationsmoved rapidly away from the crack tip,which indi-cated that they were strongly repelled by the stressfield at the crack tip.Between the crack tip and theplastic zone there is a region of dislocation-free,which is referred to as dislocation-free zone (DFZ).The length of DFZs is roughly estimated 100μm which is much longer than that found in thinfoil specimen.The variation of dislocation densityas a function of the distance from the crack tip wasmeasured,which showed that the dislocations areinversely piled up in the plastic zone.The length ofDFZs increased with both the length of pre-crackand the amplitude of applied stress.     

Feature Profile Evolution During Etching of SiO2 in Radio-Frequency or Direct-Current Plasmas

We have developed a plasma etching simulator to investigate the evolution of pattern profiles in SiO2 material under different plasma conditions. This model focuses on energy and angular dependent etching yield (physical sputtering in this paper), neutral and ion angular distributions, and reflection of ions or neutrals on the surface of a photoresist or SiO2 . The effect of positive charge accumulation on the surface of insulated mask or SiO2 is studied and the charge accumulation contributes to a deflection of ion trajectory. The wafer profile evolution has been simulated using a cellular-automata-like method under radio-frequency (RF) bias and direct-current (DC) bias, respectively. On the basis of the critical role of angular distribution of ions or neutrals, the wafer profile evolution has been simulated for different variances of angles. Observed microtrenching has been well reproduced in the simulator. The ratio of neutrals to ions has been considered and the result shows that because the neutrals are not accelerated by an electric field, their energy is much lower compared with ions, so they are easily reflected on the surface of SiO2 , which makes the trench shallower.