Highly Selective Cu Electrodeposition for Filling Through Silicon Holes

Abstract

In this work, a copper plating formula that can directly and selectively fill the through silicon holes (TSHs) for 3D chip stacking packaging was developed. The copper plating technology reduced and simplified the process steps for fabricating through silicon vias (TSVs) and TSHs. The highly selectivity of copper fill in the TSHs also reduced the manufacture cost of 3D chip stacking packaging, because the copper plating technology reduced the loading of a post-copper chemical mechanical polishing (CMP) and did not need a post-thermal annealing treatment. The copper plating formula was very simple, just containing single organic additive

Characterization of Through-Hole Filling by Copper Electroplating Using a Tetrazolium Salt Inhibitor

“…2h, exhibiting a butterfly-shaped filling mode. [19][20][21]23 Effect of acid concentration.-According to a previous work, the adsorption of tetrazolium salt on a copper surface is dependent on the acid concentration, which means that its inhibiting effect on copper deposition is related to the electrochemical reduction reaction of NTBC in the presence of acid. 24,26,27 The filling performance at different acid concentrations is shown in Fig.…”

“…[8][9][10][11][12][13][14][15][16] These physical issues have been overcome by the use of chemical additives in the copper plating solution, which changes the secondary current density distribution due to the adsorption, consumption and desorption of these chemical additives inside the TH during copper electroplating. [18][19][20][21][22] Two typical chemical additives are nitrotetrazolium blue chloride monohydrate (NTBC) 19,23 and tetranitroblue tetrazolium chloride (TNBT), 20,21 and their molecular structures are illustrated in Fig. 1.…”

“…Precipitation of copper ion complex takes place at high NTBC and TNBT concentrations. [19][20][21]23 These properties enable both NTBC and TNBT to alter the secondary current density distribution inside the TH; the largest current density is located at the hole center rather than the hole mouth due to the decrease …”

High-speed metal-filling of through-silicon vias (TSVs) by parallelized magnetic assembly of micro-wires

“…By using electrodeposition of copper, very shallow TSVs with a depth of just 70 μm can typically be filled in about 35 min [8], while deeper TSVs of 390 μm depth may take as much as 12 h to fill [9]. Substrates with shallow TSVs have to be thinned after the filling, which drastically increases fabrication costs and further reduces the throughput.…”

“…Electrodeposition and CVD processes are well established in the semiconductor industry and are widely available. However, these kinds of processes typically suffer from long processing times and are limited in the achievable aspect ratios of the TSVs [8,9]. Especially electrodeposition of copper has proven to be challenging for implementing void-free filling of highaspect ratio TSVs [5,10,11].…”