Detection and formation mechanism of micro-defects in ultrafine pitch Cu–Cu direct bonding

doi:10.1088/1674-1056/25/1/018103

中国物理B ›› 2016, Vol. 25 ›› Issue (1): 18103-018103.doi: 10.1088/1674-1056/25/1/018103

• INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY • 上一篇下一篇

Detection and formation mechanism of micro-defects in ultrafine pitch Cu–Cu direct bonding

Zi-Yu Liu(刘子玉), Jian Cai(蔡坚), Qian Wang(王谦), Yu Chen(陈瑜)

1. Institute of Microelectronics, Tsinghua University, Beijing 100084, China;
2. Tsinghua National Laboratory for Information Science and Technology, Beijing 100084, China

收稿日期:2015-05-07 修回日期:2015-07-29 出版日期:2016-01-05 发布日期:2016-01-05
通讯作者: Jian Cai E-mail:jamescai@tsinghua.edu.cn
基金资助:
Project supported by the National Natural Science Foundation of China (Grant No. 61274111) and the National Basic Research Program of China (Grant No. 2015CB057205).

Detection and formation mechanism of micro-defects in ultrafine pitch Cu–Cu direct bonding

Zi-Yu Liu(刘子玉)¹, Jian Cai(蔡坚)^1,2, Qian Wang(王谦)¹, Yu Chen(陈瑜)¹

1. Institute of Microelectronics, Tsinghua University, Beijing 100084, China;
2. Tsinghua National Laboratory for Information Science and Technology, Beijing 100084, China

Received:2015-05-07 Revised:2015-07-29 Online:2016-01-05 Published:2016-01-05
Contact: Jian Cai E-mail:jamescai@tsinghua.edu.cn
Supported by:
Project supported by the National Natural Science Foundation of China (Grant No. 61274111) and the National Basic Research Program of China (Grant No. 2015CB057205).

摘要/Abstract

摘要： In this paper, Cu-Cu interconnects with ultrafine pad pitches of 6 μ m, 8 μ m, and 15 μ m are implemented on the 12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive (NDT) c-mode scanning acoustic microscopy (c-SAM). However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO₂ bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel “defect-enlarged approach” is proposed. The bonded dies are first annealed in an N₂ oven at 300 ℃ for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO₂ bonding interface, especially near Cu pads with an ultrafine pitch of 6 μ m. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the “defect-enlarged approach” results from the combination of intrinsic micro seams and “weak” bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.

关键词: nondestructive testing of materials, microscopy acoustical, surface and interface

Abstract: In this paper, Cu-Cu interconnects with ultrafine pad pitches of 6 μ m, 8 μ m, and 15 μ m are implemented on the 12 inch wafers by a direct bonding process. Defects are not found by traditional non-destructive (NDT) c-mode scanning acoustic microscopy (c-SAM). However, cross sectional observation of bonding interfaces reveals that micro-defects such as micro seams are located at SiO₂ bonding interfaces. In order to examine the micro-defects in the ultra-fine pitch direct bonding process by the NDT technology, a novel “defect-enlarged approach” is proposed. The bonded dies are first annealed in an N₂ oven at 300 ℃ for a few hours and then cooled quickly in air. The c-SAM scanning images show large defects at the place where nothing can be detected by c-SAM before this treatment. Cross sectional observation of the bonding interfaces indicates that these defects consist of large size micro seams at the SiO₂ bonding interface, especially near Cu pads with an ultrafine pitch of 6 μ m. However, these large defects disappear after several hours at room temperature, observed by c-SAM. It is inferred that the disappearance of these defects inspected by the “defect-enlarged approach” results from the combination of intrinsic micro seams and “weak” bonds in the silicon oxide layer. Then the underlying physical mechanism of these micro-defects is proposed, which is influenced by Cu pad surface topology and bonding models.

Key words: nondestructive testing of materials, microscopy acoustical, surface and interface

中图分类号: (Methods of materials testing and analysis)

81.70.-q

43.58.Ls (Acoustical lenses and microscopes) 73.20.Hb (Impurity and defect levels; energy states of adsorbed species)

刘子玉, 蔡坚, 王谦, 陈瑜. Detection and formation mechanism of micro-defects in ultrafine pitch Cu–Cu direct bonding[J]. 中国物理B, 2016, 25(1): 18103-018103.

Zi-Yu Liu(刘子玉), Jian Cai(蔡坚), Qian Wang(王谦), Yu Chen(陈瑜). Detection and formation mechanism of micro-defects in ultrafine pitch Cu–Cu direct bonding[J]. Chin. Phys. B, 2016, 25(1): 18103-018103.

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Detection and formation mechanism of micro-defects in ultrafine pitch Cu–Cu direct bonding

Detection and formation mechanism of micro-defects in ultrafine pitch Cu–Cu direct bonding

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