CN-116334703-B - Silver deposition layer with full nanometer twin crystal structure and high {111} preferred orientation and preparation method thereof

Abstract

The invention discloses a silver deposition layer with a full nanometer twin crystal structure and a preferred orientation {111}, wherein nanometer twin crystal layers are contained in crystal grains, no transition layer exists between the deposition layer and a substrate copper material, and the crystal grain size and the orientation are the same as those of the substrate copper material. During preparation, the electro-displacement deposition technology is adopted, and the control of the nano twin wafer layer and the orientation in the silver deposition layer is realized by optimizing the solution composition, the deposition parameters and the tissue structure of the substrate copper material in the electro-displacement deposition technology. The method overcomes the defects that the prior method needs an extra photoetching process, cannot avoid the formation of a transition layer in a silver layer, has low deposition rate and the like, can selectively deposit on the surface of a substrate copper material at a high deposition rate, has no transition layer, good binding force, strong thermal stability, uniform thickness and high {111} preferred orientation, is simple and easy to implement, is perfectly compatible with the prior copper process and has lower cost.

Inventors

• ZHAN XIAOFEI
• ZHU ZENGWEI

Assignees

• 南京航空航天大学

Dates

Publication Date

20260505

Application Date

20230105

Claims (6)

1. 1. The preparation method of the silver deposition layer with the full-nanometer twin structure with the preferred orientation of {111} comprises the steps that in the microstructure of the silver deposition layer with the full-nanometer twin structure with the preferred orientation of {111} the interior of crystal grains contains a nanometer twin layer, no transition layer exists between the deposition layer and a substrate copper material, and the crystal grain size and the orientation are the same as those of the substrate copper material; the substrate copper material adopts copper with a preferred orientation of {111} height; the ratio of the crystal plane diffraction intensity of the {111} orientation to the {200} orientation in the substrate copper material is not lower than 10:1; The crystal face of {111} orientation in the substrate copper material accounts for not less than 80%; The preparation method of the silver deposition layer with the full nanometer twin crystal structure with the preferred orientation of {111} is characterized in that the silver deposition layer with the full nanometer twin crystal structure with the preferred orientation of {111} is deposited on the surface of a substrate copper material by utilizing an electric replacement technology, and comprises the following steps: The method comprises the steps of a), preprocessing a substrate copper material, namely firstly, degreasing the surface to be deposited of the substrate copper material, flushing with deionized water, then immersing in preprocessing solution to remove a surface oxide film, and finally, drying by nitrogen; Step b), preparing an electrodisplacement solution and adjusting the pH; step C), regulating the temperature of the electrodisplacement solution to be 30-60 ℃; step d), immersing the substrate copper material in the electro-displacement solution in a flowing state for 10-300 seconds; And e), taking out the substrate copper material subjected to the electric replacement from the electric replacement solution, putting the substrate copper material into flowing deionized water for thorough cleaning, drying by clean nitrogen, and sealing and preserving.
2. 2. The method for producing a silver deposit of all-nano-twin structure having a preferred orientation of {111} as claimed in claim 1, wherein the thickness of the silver deposit of all-nano-twin structure is 15 to 400nm, and/or The thickness of the nanometer twin crystal layer in the silver deposition layer with the full nanometer twin crystal structure is 2-150 nanometers, and/or The ratio of {111} orientation to {200} orientation of the silver-deposited layer with the full nano-twin structure to the crystal face diffraction intensity of the silver-deposited layer is not lower than 10:1, and/or The silver deposition layer with the full nano twin crystal structure has thermal stability, the nano twin crystal layer cannot completely disappear after annealing for 2 hours in a 400-DEG vacuum atmosphere, and the ratio of the {111} orientation to the {200} orientation of the silver deposition layer is not lower than 10:1.
3. 3. The method for preparing the silver deposition layer with the full nano-twin structure with the preferred orientation of {111} according to claim 1, wherein the substrate copper material is nano-twin copper with the preferred orientation of {111 }.
4. 4. The method for preparing a silver deposit layer with a full nano twin structure having a highly {111} preferred orientation according to claim 1, wherein the temperature of the electro-substitution solution is adjusted to 45-55 ℃ in the step C).
5. 5. The method for preparing the silver deposit layer with the full nano twin structure with the preferred orientation of the {111} is based on the method of claim 1, wherein the electro-substitution solution comprises silver ions, complexing agents, additives, pH regulators and pure water.
6. 6. The method for preparing the silver deposit layer with the full nano twin structure with the preferred orientation of the height {111}, as set forth in claim 1, characterized in that in the step d), the electric displacement solution is made to be in a flowing state by one or more of the following means, such as controllable flow rate flushing, ultrasonic disturbance, magnetic stirring, pumping, spraying, substrate rotation or reciprocating motion, and/or The substrate copper material pretreatment solution in the step a) adopts one or more of dilute hydrochloric acid aqueous solution, citric acid aqueous solution and copper material chemical polishing solution.

Description

Silver deposition layer with full nanometer twin crystal structure and high {111} preferred orientation and preparation method thereof Technical Field The invention relates to the technical field of microelectronic materials and preparation thereof, in particular to a silver deposition layer with a full nanometer twin crystal structure and a high {111} preferred orientation and a preparation method thereof. Background In recent years, with the continuous emergence of emerging application fields such as 5G, artificial intelligence, unmanned driving, metauniverse and the like, the conventional copper pillar bump welding process has difficulty in meeting the requirement of high interconnection density of microelectronic devices in the future. Copper-copper direct bonding technology has been attracting attention due to its high conductivity, high electromigration resistance, and low cost, and is considered one of the most promising approaches for achieving ultra-high density interconnects. While copper-copper bonding is advantageous, copper is so readily oxidized that the high thermal budget and stringent processing environmental conditions of copper-copper bonding processes requiring bonding temperatures in excess of 400 ℃ or chemical pretreatment （H. Hu, K. Chen, Development of low temperature CuCu bonding and hybrid bonding for three-dimensional integrated circuits (3D IC), Microelectronics Reliability, 127, 2021, 114412）. in a particular environment have limited its wide acceptance by the industry. Various attempts have been made to reduce the bonding temperature of copper-copper bonding. One promising solution is to use nano-twin copper with a highly {111} preferred orientation. Thanks to the fastest surface diffusivity and the lowest oxidation rate of the {111} oriented surfaces, the copper-copper bonding temperature can be reduced to 150-250℃（Y. Liu, Y. Lu, K. Tu, Low temperature interfacial reaction in 3D IC nanoscale materials, Materials Science and Engineering: R: Reports, 151, 2022, 100701）. under vacuum and air atmosphere conditions, and in addition, the nano twin crystal structure can be found to enhance the transmission of copper atoms and can further enhance copper-copper bonding. However, although the oxidation rate of nano-twinned copper with a high {111} preferred orientation is particularly low, oxidation of copper from pretreatment to bonding is still not completely avoided. Metal passivation is considered a promising technological approach to address the above challenges. Silver has better oxidation resistance (little oxidation at room temperature and decomposition of surface oxides occurs at 180 ℃) than copper, and has the highest electrical/thermal conductivity among metals. By sputtering a silver passivation layer on the electroplated copper surface, the entire interior electroplated copper area can be effectively protected from oxidation and has good compatibility （T. Chou, S. Huang, P. Chen, et al., Electrical and Reliability Investigation of Cu-to-Cu Bonding With Silver Passivation Layer in 3-D Integration, IEEE Transactions on Components, Packaging and Manufacturing Technology, 11, 2021, 2156-3985）. with existing copper processing techniques, however, silver is generally soft and therefore its use in microelectronic devices is always limited. For this reason, researchers have attempted to introduce nano-twin structures with a highly {111} preferred orientation in order to improve the mechanical properties of silver and further reduce the bonding thermal budget. In 2022, researchers （L. Chang, J. Wang, T. Hung, K. Chen, F. Ouyang, Direct metal bonding using nanotwinned Ag films with {111} surface orientation under air atmosphere for heterogeneous integration,Applied Surface Science, 576, 2022, 151845） from university of taiwan bloom and taiwan university of catming traffic prepared nano twin silver with highly {111} preferred orientation by magnetron sputtering technique. The direct bonding of silver in the air atmosphere is successfully realized within 3-60 minutes at the temperature of 150-250 ℃. The shear test result shows that the bonding strength is up to 70MPa, which is 2-3 times of that of the traditional welding spot. Despite these advantages, mass production of highly {111} preferred orientation nano-twin silver deposits by sputtering techniques remains a challenge. Compared to the mainstream electroplating technology, magnetron sputtering requires advanced and expensive equipment and relatively low deposition speed, while additional photolithography processes are introduced to accommodate the existing copper process (sputtering silver on copper). More importantly, the formation of a randomly oriented non-twin transition region at the bottom of sputtered silver material is still not avoided in the current industry. These transition layers may induce abnormal growth of grains in the silver layer during subsequent bonding, resulting in changes in silver orientation and grain mo