A New In Situ Microscopy Approach to Study the Degradation and Failure Mechanisms of Time‐Dependent Dielectric Breakdown: Set‐Up and Opportunities

Abstract

The time dependent dielectric breakdown (TDDB) in copper/ultra‐low‐k on‐chip interconnect stacks of integrated circuits has become one of the most critical reliability concerns in recent years. In this paper, a novel experimental in situ microscopy approach using transmission X‐ray microscopy (TXM) and scanning transmission electron microscopy (STEM) is proposed to study TDDB degradation and failure mechanisms. It combines electrical testing and imaging techniques. Low‐dose bright field (BF) STEM inserting a small condenser aperture is chosen to reduce the beam damage of the dielectric material, while the electron spectroscopic imaging technique is used for the chemical analysis to detect the migration path of Cu atoms. This new experimental approach will contribute to an improved understanding of the TDDB effect.

In situ TEM study of the transitions between crystalline Si and nonstoichiometric amorphous oxide under bipolar voltage bias

“…and Si was determined by the polarity of the bias voltage. In situ transmission electron microscopy (TEM) experiments 15 were carried out on an FEI Tecnai F20 microscope operated at 200 kV. The experimental setup illustrated in Fig.…”

<em>In Situ</em> Time-dependent Dielectric Breakdown in the Transmission Electron Microscope: A Possibility to Understand the Failure Mechanism in Microelectronic Devices

“…Nevertheless, the TDDB damage mechanism observed is believed to be valid because: (1) with much less TEM beam irradiation (low-dose STEM imaging, low illumination step and recording images every 30 min/1 h), the test sample showed similar failure mechanisms as in our previous TEM observation (recording images continuously, relatively high-dose TEM mode) [16][17][18] ; (2) the electrical field was confirmed as the driving force and the origin of the migration of metal particles 17 ( Figure 5B and 6A) by reversing the electrical connection; (3) migration of metal particles and dielectric breakdown were both observed at specific locations where the tip-to-tip spacing is relatively small and the Ta/TaN barrier is relatively thin, not everywhere inside the illumination area of the TEM beam; (4) a thick layer of Pt deposition on top of the sample prevents most of the contamination from the vertical implantation of Ga ions -the test structure is believed to be mainly contamination free even if there is a slight amount of contamination on the surface of the side walls (about 60 nm) from the lateral damage of the Ga ions. Therefore, the sample preparation and the TEM observation should not affect the interpretation of the intrinsic failure mechanism to a significant amount.…”

“…Therefore, it is very crucial to minimize the influence of the beam on the experiment 18 . Several strategies can be chosen to reduce this influence, but it cannot be eliminated completely.…”

“…The options could be categorized into three approaches. One possibility is using a small condenser aperture to reduce the total amount of energy deposited in the H-bar type sample 18 . The other option is operating the TEM at low voltage (≤ 80 kV) [19][20][21] and/or low electron dose [22][23][24][25] .…”

“…Thus, the STEM mode should be prioritized if it is a possible option in the TEM used. Choosing low illumination brightness and recording the TEM images with a chosen, reasonable interval time (low dose) are also recommended 18 to result in further reduced beam damage.…”