研究雙粒子聚焦離子束對三維構形電晶體製作穿透式電鏡試片之可靠性

Abstract

半導體結構製備穿透式電子顯微鏡試片方法主要有手磨試片製備與聚焦離子束試片製備兩種方式，手磨穿透式電子顯微鏡試片優點為試片薄區大，試片品質較聚焦離子束為佳。在半導體發展進入奈米尺寸後，由於手磨試片製備因光學顯微鏡解析度已無法分辨如此微小的半導體結構，而以雙粒子聚焦離子束進行試片製備為主。雙粒子聚焦離子束機台具有掃描式電子顯微鏡進行分析目標定位，並利用聚焦離子束顯微鏡進行精準切割，雙粒子聚焦離子束成為主要的穿透式電子顯微鏡試片製備技術。 在半導體製程不斷微縮，立體結構電晶體發展為為主要的半導體結構，穿透式電子顯微鏡試片也必須能夠切割出更小的結構，才能夠達到分離出可被分析的目標；一般穿透式電子顯微鏡試片製備技術在立體電晶體結構上製備超薄試片容易因為應力容易產生變形，以及試片表面因離子束試片切割損傷嚴重的問題，而使穿透式電子顯微鏡試片因疊影或非晶化造成分析品質不佳，及試片製備良率低落等問題。本研究將研究能夠提升試片製備良率降低重工率，並對如何控制試片變形與試片非晶化做進一步的探討。

Hand polishing and FIB shaping are two main methods for TEM sample preparation among various semiconductor foundry industries. In general, hand polishing on TEM sample exhibits large thin area and high sample quality in comparison with FIB technique. Once semiconductor structure is shrunk to nanometer scale, resolution of conventional optical microscope cannot afford for vision to target site of interest. Hence, hand polishing on TEM sample is not available. The only effective mean to treat nanometer scale sample is dual beam FIB. Dual beam FIB in together with scanning electronic microscope can accurately identify various target sites. Therefore, FIB can precisely apply to slice target of interest. As the importance of next-generation device structure is toward 3D, the invention of new semiconductor material and complicate 3D structure becomes main stream. The most challenge issue for such TEM sample preparation requires new technique for the slice of ultrathin lamella across device gate region. Sample stress in miniature region can cause serious bending problem during FIB preparation, and results in serious ion damage effect for crystal silicon. This issue deteriorates the sample quality, and increase the time and cost of sample preparation in prior to TEM inspection. How to increase the success and yield of TEM sample preparation is the most important item for future device fabrication. This research aims to address sample preparation yield and minimize rework rate in term of controlling bending lamella and avoiding sidewall amorphous layer.