Role of Cuprous Ion in Copper Electrodeposition Acceleration

Abstract

We have previously reported that the cuprous ion concentration inside the via increases during the reverse portion of a periodic reverse pulse waveform. The void decreases and bottom-up via filling is achieved by increasing this reverse current during copper electrodeposition. Acceleration occurs at the via bottom by increasing the reverse current for cathodic polarization. J. R. White's work showed a low cuprous ion concentration during cathodic polarization without additives. During cathodic polarization, the current density is high for copper dissolution and nitrogen gas bubbling with bis-(3-sulfopropyl) disulfide (SPS) and chloride, using the through-mask electrode trench. We have measured the increases in cuprous ion production with SPS and chloride additives using a rotating ring disk electrode. Copper electrodeposition is accelerated with SPS and chloride. An acceleration complex forms, which is based on the cuprous ion; i.e., Cu(I)-thiolate, a high cuprous ion concentration is observed at the through-mask electrode trench bottom. From a mass transfer study, therefore, the Cu(I)-thiolate complex accumulates in the through-mask electrode trench bottom. The current density increases at the through-mask electrode trench bottom and bottom-up filling then occurs.

Optimization of the Copper Plating Process Using the Taguchi Experimental Design Method

“…As a result, the copper deposition rate at the via bottom becomes greater than that in other areas of the via, which leads to bottom-up copper deposition and copper bump formation. Kondo et al [14][15] demonstrated that cupric ions react with sodium 3-mercapto-1-propanesulfonate (MPS) or bis-(3-sulfopropyl)-disulfide (SPS) to form Cu(I)-thiolate. The Cu(I)-thiolates accumulate in the microvia to locally accelerate the copper electrodeposition and achieve bottomup filling.…”

Effect of External Factors on Copper Filling in 3D Integrated Through-Silicon-Vias (TSVs)

“…Cuprous ion plays an important role in copper electrodeposition acceleration. 33 During the copper deposition process, the sulfone group of the MPS responds the cupric ion and produces the Cu(I)-thiolate complex. 33,34 This Cu(I)-thiolate complex floats in the via and releases the cuprous ion through oxidization reaction.…”

“…33 During the copper deposition process, the sulfone group of the MPS responds the cupric ion and produces the Cu(I)-thiolate complex. 33,34 This Cu(I)-thiolate complex floats in the via and releases the cuprous ion through oxidization reaction. The released cuprous ion is rapidly deposited as metallic copper on the electrode and the copper electrodeposition is accelerated.…”

“…The cuprous ion concentration inside the via is more than that in the bulk electrolyte. 33 The higher flow rate of the electrolyte causes the dramatical mass transportation between in and outside of the via, which causes the reduction of the Cu(I)-thiolate complex in via. So the acceleration effect in via bottom decreases with an increase of the flow rate of the electrolyte, resulting in the decreased filling efficiency, as shown in Figure 3b and 3c.…”

High Accuracy Concentration Analysis of Accelerator Components in Acidic Cu Superfilling Bath

“…Owing to the merits of high throughput, low process cost, and good film quality, Cu electroplating has a wide application, from traditional Cu foil production to state-of-the-art semiconductor metallization processes. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The Cu plating solution typically contains small amounts of organic additives, 1-16 which enhance the uniformity, 13 brightness, 14 and mechanical properties of the Cu film. 15 In addition, for particular application to damascene Cu plating, the additives enable bottom-up filling at trenches or vias by controlling the relative deposition rates of Cu at the top and bottom of the features.…”