Pulse reverse plating

Pulse and Pulse reverse plating experiments have been performed on 0.5pm, 2 1 aspect ratio features. The resistivity of the copper deposits was measured using a four-point probe. Pre- and post-anneal measurements were takea The resistivity values of the deposits before annealing ranged from 2.2 to 2.5 pfi cm, as shown in Fig.3. A 5% reduction in resistivity was observed upon annealing. 

Figure 2. SEM pictures of pulse plated and pulse reverse plated features. Notice that void size decreases with decreasing pulse period. No voids are observed for pulse reverse plated specimens.

B.N. Popov, M. Ramasubramanian, S.N. Popova, R.E. White, K.M. Yin, Galvanostatic pitlse and pulse reverse plating of zinc-nickel alloys firom sulfate electrolytes on a rotating disc electrode, Trans. 

Chandrasekar MS, Pushpavanam M (2008) Pulse and pulse reverse plating—conceptual, advantages and applications. Electrochim Acta 53 3313-3322... 

PopovN, Yin K, White R. (1993) Galvanostatic pulse and pulse reverse plating of nickel-iron alloys from electrolytes containing organic compounds on a rotating disc electrode. JElectrochem Soc 140 1321-1330. 

Table 5.3 Process parameter used for nano nickel deposition by pulse reverse plating...

Swaminathan V, Murali KR (2000) Influence of pulse reversal on the PEC performance of pulse-plated CdSe films. Sol Energy Mater Sol Cells 63 207-216... 

Fig. 15. SEM micrographs of Cu-Al deposits containing 5 a/o A1 that were prepared with different plating techniques at zavg = 0.70 mA in the 60.0 m/o AlCl3-EtMeImCl melt at room temperature (a) DC plating (b) superimposed-pulse current plating, ip = 1.254 mA, ton = 1 s, is = 0.509 mA, ts = 3 s, and (c) reverse-pulse current plating, ip = 1.254 mA, ton = 1 s, ir = 0.43 mA, tr = 0.5 s. The thickness of each deposit is approximately 5 pm based on a compact layer of pure copper. Reproduced from Zhu et al. [103]...

Bulk phase formation by current or voltage pulses results in different nucleation and crystal growth conditions compared to dc deposition and depends on the electrolyte and the pulse regime (unipolar, bipolar, pulse reverse, etc.) itself [6.98]. Several effects, which are of significance for the pulse plating process, can be distinguished. 

As the degree of part complexity continues to increase, new innovative plating solutions are being put into place. Periodic pulse reverse (PPR) is an example of this, and another major development is the advent of horizontal add copper plating. 

In this plating system, the bath is engineered to respond to a periodically pulsed reverse current. The required Tafel slope shift is accomplished through rectification (see Fig. 29.13). The rectifier prodnces a pulsed wave with a forward cathodic current that is perturbed by short anodic pnlses.The forward current at IX (e.g., 30 ASF) is maintained for 10 ms and the reversed at 3X (e.g., 90 ASF) for 0.5 ms, for example. The duty cycle may vary (e.g., 20 ms forward with 1.0 ms reverse). 

Pearson, T. and Dennis, J.K. (1990) The effect of pulsed reverse current on the polarization behaviour of acid copper plating solutions containing organic additives. /. Appl. Electrochem., 20 (2), 196-208. 

Yin K. M. (1996), Duplex diffirsion layer model for pulse with reverse plating . Surf. Coat. TechnoL, 88,162, doi 10.1016/80257-8972(96)02904-0. 

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