Cu-Cu Thermocompression Bonding using Ultra Precision Cutting of Cu Bumps for 3D-SIC

2011 ◽  
Vol 2011 (DPC) ◽  
pp. 001316-001341 ◽  
Author(s):  
Taiji Sakai ◽  
Akamatsu Toshiya ◽  
Nobuhiro Imaizumi ◽  
Miyajima Toyoo ◽  
Masataka Mizukoshi
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Crystal Orientation ◽  
Solid Diffusion ◽  
Single Crystal Diamond ◽  
Thermocompression Bonding ◽  
Ultra Precision ◽  
Kirkendall Voids ◽  
Solid Liquid ◽  
Bonding Technique

We have developed a new Cu-Cu thermocompression bonding technique by using cut Cu bumps in order to achieve high density 3D-stacked IC (3D-SIC). Currently, Sn layer is formed between Cu bumps, and then solid-liquid bonding is made by tin melting to connect Cu bumps. But using Sn layer can cause undesirable issues, such as electro-migration and Kirkendall voids formation between Cu/Sn interfaces, which could decrease bonding reliability. Therefore we believe that Cu-Cu thermocompression bonding is an essential technology especially in 3D interconnection. In the present study, cut Cu bumps were obtained by ultra-precision cutting using a single crystal diamond bite that would give a highly smooth Cu surface (Ra:7nm). A major advantage of cut Cu bumps is that they have an amorphous-like layer on the surface. In TEM observation, it was found that about 120nm thick amorphous-like layer was formed after cutting of Cu bumps. This layer has a potential to connect bumps each other at a low temperature similar to solder bonding because amorphous-like layer accelerates a recrystallization reaction of Cu crystal. Cut Cu bumps on both sides of LSI and substrate have been successfully bonded at 250 degrees C condition. From the analysis of crystal orientation by EBSD, it was found that the bonding interface had disappeared, which means solid diffusion was occurred and crystal grain grew across the interface.

Hybrid Bonding Methods Using Ultra Precision Cutting for 3D-SIC

2012 ◽  
Vol 2012 (DPC) ◽  
pp. 001701-001730
Author(s):  
Taiji Sakai ◽  
Nobuhiro Imaizumi ◽  
Masataka Mizukoshi ◽  
Masayuki Kawase ◽  
Ryoji Tanimoto ◽  
...  
Keyword(s):  
Narrow Gap ◽  
Oxidation Layer ◽  
Solid Diffusion ◽  
Fine Pitch ◽  
Single Crystal Diamond ◽  
Thermocompression Bonding ◽  
Ultra Precision ◽  
Lower Height ◽  
Cu Oxidation ◽  
Bonding Technique

We have developed Cu-Cu/adhesives hybrid bonding technique by using collective cutting of Cu bumps and adhesives in order to achieve high density 3D-SIC. It is considered that progression of fine pitch interconnection leads to lower height of bonding electrodes, resulting in narrow gap between 3D-SICs. Therefore, it is difficult to fill in adhesive to such a narrow gap 3D-SICs after bonding, so we consider that hybrid bonding of pre-applied adhesives and Cu-Cu thermocompression bonding must be advantageous, in terms of void less bonding and minimizing bonding stress by adhesives and also low electricity by Cu-Cu solid diffusion bonding. In the present study, we adapted the following process; at first adhesives were spin coated on the wafer with Cu post and then pre-baked. After that, pre-applied adhesives and Cu bumps were successfully cut by single crystal diamond bite. Typical adhesives may cause bite damage with continuous cutting, but in this research, we selected low damage adhesive against continuous cutting, which is important properties to commercial uses. Then, chips with adhesives were attached to substrates and Cu oxidation layer was removed by exposing formic acid atmosphere. Finally permanent bonding was done at 225 degree C for 30 minutes. We concluded that solid diffusion between bonded Cu bumps could be achieved and no adhesive residue could be seen between bonded interfaces by TEM/EDX analysis.

scholarly journals B07 Ultra Precision cutting with single crystal diamond end mill

2008 ◽  
Vol 2008.7 (0) ◽  
pp. 39-40
Author(s):  
Naoto ISHIDA ◽  
Toshiro SHIBASAKA ◽  
Hirofumi SUZUKI
Keyword(s):  
Single Crystal ◽  
End Mill ◽  
Single Crystal Diamond ◽  
Ultra Precision

Electron Beam Assisted Etching of Single Crystal Diamond Chips

1994 ◽  
Vol 354 ◽  
Author(s):  
Jun Taniguchi ◽  
Iwao Miyamoto
Keyword(s):  
Electron Beam ◽  
Single Crystal ◽  
Applied Voltage ◽  
Beam Current ◽  
Diamond Surface ◽  
Machining Time ◽  
Chip Surface ◽  
Single Crystal Diamond ◽  
Ultra Precision ◽  
Oxygen Gas

AbstractIn order to fabricate ultra-precision diamond tools and delineate ultra-fine patterns into diamond chips without adding radiation damage, machining characteristics of diamond chips with electron beam assisted etching (EBAE) has been investigated. This processing mechanism is considered as follows: Oxygen atoms or molecules activated by electron beam bombardment on or near the chip surface react with carbon atoms of the diamond surface, resulting in formation of volatile products such as CO or C02 . An EBAE system composed of a scanning electron microscope (SEM) which has an oxygen introduction system was used to etch synthetic single crystal diamond chips. When a diamond chip was etched at an applied voltage of 10 kV and an irradiation beam current of 1.7nA, the depth of the holes increased with an increase of machining time and the diameter of the holes also increased with an increase of machining time. When a diamond chip was etched at an applied voltage of 10 kV and an irradiation beam current of 1.3nA, the depth and diameter of the etched holes merely increased with an increase of flow rate of oxygen gas ranging from 5 cc/min to 30 cc/min, then the depth decreased rapidly with an increase of oxygen gas. With this processing method, very small holes with a diameter of about 0.5 ∼ 2 /xm, and a depth of about 0.01 ∼ 0.7 fim were obtained. Line and rectagular patterns with several /xm and sub-μum depths were also fabricated.

Study on Ultra Precision Polishing of Single Crystal Diamond Substrates under Ultraviolet Irradiation

2009 ◽  
Vol 407-408 ◽  
pp. 355-358 ◽  
Author(s):  
Satoru Anan ◽  
Mutsumi Touge ◽  
Akihisa Kubota ◽  
Junji Watanabe
Keyword(s):  
Surface Roughness ◽  
Single Crystal ◽  
Uv Irradiation ◽  
Ultraviolet Irradiation ◽  
Experimental Results ◽  
Single Crystal Diamond ◽  
Ultra Precision

The ultraviolet irradiation-assisted ultra precision polishing was performed on single crystal diamond substrates. This polishing method has been newly developed in our laboratory. The change of polishing performances was investigated by the presence of the UV irradiation. The polished surfaces were evaluated by the observation with WYKO. The experimental results are as follows; Surface roughness of diamond substrates polished under UV irradiation has become clearly smoother than that without UV irradiation. The surface roughness by this polishing method was reached to be 0.19 nm Ra on (100) surface of single crystal diamond. The equivalent surface was obtained on (110) surface by the UV-polishing.

Ultra-Precision Machining of Stainless Steel and Nickel with Single Crystal 4H and 6H Boule SiC

2010 ◽  
Vol 645-648 ◽  
pp. 853-856 ◽  
Author(s):  
Wolfgang J. Choyke ◽  
B. D'Urso ◽  
Fei Yan ◽  
Robert P. Devaty
Keyword(s):  
Stainless Steel ◽  
Single Crystal ◽  
Cutting Tools ◽  
Precision Machining ◽  
Average Roughness ◽  
Flat Surfaces ◽  
Diamond Cutting Tools ◽  
Single Crystal Diamond ◽  
Single Crystal Sic ◽  
Ultra Precision

Ultra-precision machining is dominated by single-crystal diamond cutting tools, and is typically applied to a narrow range of materials, particularly aluminum and copper. Single-crystal SiC can be comparable to some diamonds in hardness and thermal conductivity, while potentially having superior chemical and thermal stability, yet it has not been explored as a cutting tool for ultra-precision machining. We made two cutting tools with single-crystal SiC, one with sharp corners and one with a large circular radius, and used them to cut flat surfaces on two materials, 316 stainless steel and nickel. These materials generally cause unacceptably rapid diamond tool wear. We report the average roughness of the resulting surfaces cut with single-crystal 4H and 6H SiC tools.

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