Preparation method of planar TEM sample

Abstract

The invention provides a preparation method of a planar TEM sample. The method comprises the steps of: preparing a sample, enabling the cross section of a fracture surface of the sample to be close to a target area, cutting the sample to expose a Poly layer, carrying out wet method corrosion, removing Poly, preparing a first cutting surface, cutting the sample, preparing a second cutting surface in a substrate, and finally completing the planar TEM sample. The new method based on the prior art is provided by the invention for TEM analysis which is carried out for observing gate oxide defects and silicon substrate dislocation below polycrystalline Poly, the influences of Poly crystal lattices to TEM observation are removed by means of Poly corrosion, and the detects in the gate oxide can be accurately positioned by the corrosion of a corrosive agent to the substrate. By adopting the method, the quality and the success rate of failure analysis in the type are improved.

Description

technical field [0001] The invention relates to a preparation method of a transmission electron microscope (TEM) plane sample in integrated circuit failure analysis (FA). Background technique [0002] Today, with the continuous development of integrated circuit IC manufacturing processes, due to the continuous reduction in device size, it is becoming more and more difficult to analyze the cause of its failure, because physical failure analysis (PFA) is often difficult to find obvious failure characteristics or failure points. At this time, it is necessary to use a variety of failure analysis tools comprehensively, such as optical emission microscope (EMMI), light-induced resistance change (OBRICH), transmission electron microscope (TEM), scanning electron microscope (SEM), focused ion beam microscope (FIB), Energy Spectrometer (EDS), etc. Find the real failure cause of the device through a combination of multiple tools. Among many PFA tools, TEM has sub-nanometer high-reso...

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Problems solved by technology

[0008] However, in the sample preparation method of the prior art, the first cutting plane is usually located at the position of the poly layer, so the TEM observation will be affected by the masking of the lattice image on the polycrystalline poly

As we all know, the ability of TEM high-resolution observation is through electron penetration imaging. Since Poly is a polycrystalline material, its composition is displayed as a disordered arrangement of different sizes and shapes, and different grain directions bring different diffractions. Contrast makes the imaging effect of TEM poor, so it is difficult to find the failure point located in the gate oxide layer, as well as defects such as dislocations in the active region AA, and it is also impossible to distinguish the defects from the covered Poly lattice boundary

This results in a low success rate for this type of failure analysis work

[0009] If you try to remove a cut sample and observe the gate oxide layer by removing the entire Poly, the failure or abnormal points contained in it will be destroyed by the damage caused by cutting, making this type of analysis impossible.

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