Contactless bottom-up electrodeposition of nickel for 3D integrated circuits

Abstract

Packaging applications in the semiconductor industry rely on electrodepositing metals into high aspect ratio (HAR) vias without the formation of any defects or voids. The process and economic efficiency of conventional methodologies are limited by the ability to achieve high deposition rates along with uniformity of the deposited metal layer. In this work, a contactless and scalable electrodeposition technique has been developed to deposit metallic nickel onto p-doped silicon wafers. The effect of various process variables such as deposition and etchant solution composition and concentration, solution temperature and stirring on nickel deposition rates have been investigated. The importance of backside silicon oxidation and subsequent oxide etching on the kinetics of nickel deposition on frontside silicon has been highlighted.

The formation mechanism of gradient porous Si in a contactless electrochemical process

“…30 The possible reactions of fluorine species occurring in HF based etchant solution along with the mass balance equation are given in (R1) through (R4). 31 The pore formation is initiated by the valence band holes which are driven to the silicon surface due to applied electric field and diffusion. 32 At this initiation stage, the charge carriers are collected by the pore tips with an enhanced electric field.…”

Electrodeposition of Silver Nanoparticles on Indium-Doped Tin Oxide Using Hydrogel Electrolyte for Hydrogen Peroxide Sensing

“…Nanostructured metals deposited on diverse substrates have played a pivotal role in the development of technological applications, including microelectronics [ 1 , 2 ], sensing [ 3 , 4 ], electroplating [ 5 ], energy storage [ 6 , 7 ], and the enhancement of Raman scattering [ 8 ] and electrocatalysis [ 9 , 10 ]. Metal nanoparticles have a high surface-to-volume ratio, with the capability to interact with target molecules, good electrical and catalytic properties, and a large number of active sites [ 11 ].…”

Application of Process Simulation for Comparison of Contactless and Conventional Electrodeposition Methods for 3D Packaging

“…A nickel seed layer was deposited onto the bottom of the via using a method discussed elsewhere but without the use of surfactant. 20 The electrodeposition experiments were carried out in the two-chamber cell system, [4][5][6] where the front side of the wafer (via side) was in contact with 1 M CuSO 4 and 0.2 M H 2 SO 4 deposition solution and the back side of the wafer contacted a SiO 2 etchant solution (e.g. dilute HF).…”

“…This ion concentration gradient causes preferential deposition at the mouth of the via leading to a pinch-off effect where the bottom of the via is closed to the electrolyte before being completely filled with metal. [4][5][6] The formation of these voids increases the via resistance and results in reliability issues in ICs.…”

“…4 The effect of various processing parameters and solution variables using this technique has been examined and discussed elsewhere. 5,6 In this process, the top surfaces of the wafer (regions outside the via) and the via sidewalls were coated with SiO 2 , while a conductive Ni layer was deposited at via bottom. Therefore, Cu ions were reduced and deposited at via bottom only by accepting electrons resulting from electrochemical oxidation and etching occurring on the silicon back side.…”