Shave-off Depth Profiling Research Articles

Evaluation of Focused Ion Beam for Shave-off Depth Profiling

Shave-off depth profiling is one of the powerful methods that can be applied to the analysis of pin point and small region devices. However, acquired shave-off depth profile is affected by a long tail of the FIB because shave-off scanning mode has the distinctive position of the primary ion beam against the sample. In this study, we evaluated the influence of the long tail of the FIB in detail by the simulation method we newly proposed. The evaluation was carried out from the point of view of mainly two factors. One is thickness of the protection film. The other is the scanning speed toward the depth direction. In addition, we newly proposed the notion of ‘shave-off sputtered atom yield’, the important factor of shave-off depth profiling. As a result, it became possible that the determination of optimized experimental condition for the achievement of the ultimate depth resolution.

Improvement and evaluation of the nano-beam SIMS control system

Shave-off depth profiling with nano-beam SIMS, our own technique, achieves the highly precise depth profiling with nanometer-scale depth resolution by utilizing a Focused Ion Beam (FIB) micro-machining process to provide the depth profile. This method is to acquire depth profiling by the shave-off scanning mode. However, we could obtain the signals as a function of time because the FIB scanning system and the signal acquisition system were working independently. Therefore, we developed a new system to obtain the signals as a function of two-dimensional position of the FIB. As a result, we could divide a shave-off profile up to 256 along lateral direction. We defined these lateral areas “lanes” and named this new method “multilane shave-off profiling”.

An Introduction of Shave-off Depth Profiling

Shave-off depth profiling achieves depth information by reconstructing accurate elemental distributions even for a roughed surface and a hetero interface. In this paper, we will demonstrate two examples using shave-off depth profiling. One example is a memory chip on semiconductor, which is consisted of thousands of via-holes on the surface. Shave-off depth profiling reconstructed the sample as a manufacturing process. Useful yield on shave-off depth profiling was discussed on the same sample. The other example is focused on hetero interface, which might cause failure on circuit board. Shave-off depth profiling visualized the electro-chemical migration process ; diffusion from Cu anode to resign. We concluded that the shave-off depth profiling is powerful to samples with roughed surface and hetero interface.

Development of Reconstruction Method for Highly Precise Shave-Off Depth Profiling

Shave-off depth profiling utilizes a focused ion beam (FIB) micro-machining process to provide the depth profile. This method is a very unique depth profiling for acquiring a depth profile by the shave-off scanning mode (The fast horizontal sweep of FIB is combined with the very slow vertical sweep). Shave-off depth profiling has its own features, absolute depth scale, pin point depth profiling and application for rough surface and hetero interface. However, the shave-off depth profile is affected by the long tail of FIB because shave-off scanning mode has the distinctive position of the primary ion beam against the sample. In this study, we acquired the different shave-off depth profiles by changing the speed of shave-off scan. Then, we estimated the approximate intensity profile of FIB by the change of the depth resolution of experimental depth profiles. By using this estimated intensity profile of FIB, we carried out the deconvolution to remove the influence of the long tails of FIB. As a result, this new data analysis method enables us to reconstruct highly precise calculated depth profile that reflects not the intensity profile of FIB but the true elemental distribution. [DOI: 10.1380/ejssnt.2010.237]

Multilane shave-off profiling for build-up circuit

Shave-off depth profiling by nano-beam secondary ion mass spectrometer (nano-beam SIMS), our own unique technique, achieves the highly precise depth profiling with nanometer-dimensional depth resolution. This method is a very unique depth profiling for acquiring a depth profile by the shave-off scanning mode (a fast horizontal sweep of an FIB is combined with a very slow vertical sweep). Shave-off depth profiling has its own features: absolute depth scale, pin point depth profiling and application for rough surface and hetero interface. However, conventional shave-off depth profiling provided only depth information by integrating lateral information. Therefore, we newly developed multilane shave-off profiling. In this new method, we can divide some lateral information precisely by synchronizing signal acquisition with FIB control. In this study, we demonstrate the example of new multilane shave-off profiling by analyzing build-up circuit.

Shave-off vector profiling for TEM samples

This study aims to cross-check the same sample, the same part and the same piece by shave-off profiling and scanning transmission electron microscope (STEM) imaging. For cross-check analysis, a piece was picked up from a failed IC package which might cause electrochemical migration. Critical disagreement on each result was gradient curve on shave-off depth profiling from anode to cathode. In the same piece, shave-off profiling visualized a faint gradient of migrated ions which could not be observed by STEM imaging.

Charge neutralization using secondary electron shower for shave-off depth profiling by focused ion beam secondary ion mass spectrometry

It is very important problem for microbeam analyses to neutralize charge-up phenomenon. In our previous study, the charge-up phenomenon occurred during the shave-off depth profiling in the case of insulated samples. We developed a new neutralization method to improve the accuracy of the shave-off depth profile by FIB-SIMS. By using new method, ripples on secondary ion signals were suppressed and the shave-off depth profile reflected the precise layered shape of insulator samples without charge-up problems.

Highly accurate shave-off depth profiling by simulation method

Shave-off depth profiling, our own unique technique, utilizes a focused ion beam (FIB) micro-machining process to provide the depth profile. It is known that the FIB has long tails outside of the beam. The long tails affect the shape of depth profile and make depth resolution worse. The influence of long tails can be minimized by depositing a protection film on the sidewall or changing the speed of shave-off scan. In this study, we discussed about shave-off scanning speed toward depth direction by using simulation method and accomplished highly accurate shave-off depth profiling.

Reduction of Memory Effect in Shave-off Depth Profiling

Reduction of Memory Effect in Shave-off Depth Profiling

Precise analysis on shave-off depth profiling

An epoch-making flood gun system, which can be biased on high voltage itself, was developed to minimize charge-up problem during the shave-off depth profiling. By using the flood gun system, ripples on ion induced secondary ion signals were disappearing and a measured shave-off depth profile reflected the precise spherical shape of a silica particle without charge-up problems.

Shave-off depth profiling: Depth profiling with an absolute depth scale

Shave-off depth profiling provides profiling with an absolute depth scale. This method uses a focused ion beam (FIB) micro-machining process to provide the depth profile. We show that the shave-off depth profile of a particle reflected the spherical shape of the sample and signal intensities had no relationship to the depth. Through the introduction of FIB micro-sampling, the shave-off depth profiling of a dynamic random access memory (DRAM) tip was carried out. The shave-off profile agreed with a blue print from the manufacturing process. Finally, shave-off depth profiling is discussed with respect to resolutions and future directions.

Shave-Off Depth Profiling for Nano-Devices

Shave-off depth profiling completely differs from ultra shallow depth profiling and has an absolute depth scale and a 50 µm wide dynamic range. In this paper we report on shave-off depth profiling of a nano-device with a complex nano-structure consisting of dynamic random access memory and introduces an analytical tool for advancing of nano-devices.

Improvement on the Shave-off Depth Resolution in a Submicron SIMS Analysis.

The shave-off depth profiling is one of the most powerful techniques to obtain accurate elemental depth distributions from small particles and samples with rough surfaces. In order to clarify the factors determining the depth resolution and to estimate the ultimate depth resolution by the shave-off depth profiling, simulations of shave-off process and experiments on a model multilayer sample were performed. The simulation revealed that the key factors to realize the best depth resolution were alignment of the primary beam and the sample, and the shave-off speed. The simulation showed the best depth resolution of 3nm with precise alignment of the primary beam and the sample under the current experimental setup. From the measured depth profile of a TiN thin layer, the depth resolution of 21nm was determined. When the state-of-the-art focused ion beam is used as the primary beam, the practical depth resolution of 1.4nm is expected for the analysis of the sample with 1μm2 cross section.