在透射电子显微镜原位时间相关的介质击穿：一种可能性，了解微电子器件的失效机理

Summary

The time-dependent dielectric breakdown (TDDB) in on-chip interconnect stacks is one of the most critical failure mechanisms for microelectronic devices. This paper demonstrates the procedure of an in situ TDDB experiment in the transmission electron microscope, which opens a possibility to study the failure mechanism in microelectronic products.

Abstract

The time-dependent dielectric breakdown (TDDB) in on-chip interconnect stacks is one of the most critical failure mechanisms for microelectronic devices. The aggressive scaling of feature sizes, both on devices and interconnects, leads to serious challenges to ensure the required product reliability. Standard reliability tests and post-mortem failure analysis provide only limited information about the physics of failure mechanisms and degradation kinetics. Therefore it is necessary to develop new experimental approaches and procedures to study the TDDB failure mechanisms and degradation kinetics in particular. In this paper, an in situ experimental methodology in the transmission electron microscope (TEM) is demonstrated to investigate the TDDB degradation and failure mechanisms in Cu/ULK interconnect stacks. High quality imaging and chemical analysis are used to study the kinetic process. The in situ electrical test is integrated into the TEM to provide an elevated electrical field to the dielectrics. Electron tomography is utilized to characterize the directed Cu diffusion in the insulating dielectrics. This experimental procedure opens a possibility to study the failure mechanism in interconnect stacks of microelectronic products, and it could also be extended to other structures in active devices.

Introduction

由于铜互连首次被引入超大规模集成电路（ULSI）技术在1997年^1，低k和超低k值（ULK）电介质被采纳到后端-的线（BEOL）片上的互连之间的绝缘材料。新材料， 例如结合，铜以降低电阻和低k / ULK电介质为低电容，克服增加的阻容（RC）的影响引起的延迟由互连尺寸收缩^2,3，但是，这样做的好处是侵占通过微电子器件近年来持续侵略性缩放。使用低k / ULK材料导致在制造过程中和产品的可靠性的各种挑战，尤其是当在互连间距达到约100纳米或更小^4-6。

TDDB是指一种介电材料的物理失效机制作为时间的函数下的电场。的TDDB​​可靠性试验通常进行加速条件（高架电场和/或升高的温度）下。

的TDDB​​在片上互连堆叠是用于微电子装置，它已经提出在可靠性社区强烈的关注的最关键的失效机制之一。它将继续在可靠性工程师，因为ULK电介质的聚光灯更弱的电气性能和机械性能被集成到先进技术节点的设备与。

专用实验已经进行调查TDDB失效机理^7-9，和一个显著量的努力已投入到开发其描述电场的装置^10-13和寿命之间的关系的模型。现有的研究有利于可靠性工程师微电子的社区;然而，许多查林GES依然存在，许多问题仍需要进行详细的解答。例如，成熟的....

Protocol

1.准备样品的聚焦离子束（FIB）变薄（图1）

1. 切割全晶圆成小片（约10毫米×10mm）的用金刚石划线。
2. 纪念“针尖对针尖”结构对芯片的位置。
3. 锯切割机芯片2毫米尺寸，以获得60微米的酒吧。酒吧包含了“针尖对针尖”结构的中心。
4. 胶水使用强力胶铜半环上的目标吧。下一步，胶水在Cu样品台的酒吧还使用强力胶。然后，用银膏来设置半环和铜样品台之​​间的导通。

Discussion

在TDDB实验成功的前提是良好的样品制备，特别是在SEM FIB研磨过程。首先，一个厚的Pt层上的“尖到尖的”结构的顶部具有待沉积。的厚度和Pt层的尺寸可以通过SEM操作者进行调整，但必须遵循三个原则：（1）厚度和尺寸是足够的，以保护从在整个研磨过程中可能的离子束损坏的目标区域; （2）还有一个比较厚的Pt层（≥400纳米）上的研磨后留下的样品的顶部，它保护从内部和外部的应力的微妙样?.......

Materials

Name	Company	Catalog Number	Comments
Automatic Dicing Saw	DISCO Kiru-Kezuru-Migaku Technologies
Scanning Electron Microscope	Zeiss	Zeiss Nvision 40
Picoindentor	Hysitron	Hysitron Pi95
Keithley SourceMeter	Keithley	Keithley 2602/237
Transmission Electron Microscope	FEI	FEI Tecnai F20
Transmission Electron Microscope	Zeiss	Zeiss Libra 200