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Electrochemical Method for Evaluating Pd Sn Activators for Electroless Deposition

IP.com Disclosure Number: IPCOM000045336D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Horkans, WJ: AUTHOR

Abstract

The fabrication of many types of microelectronic components (as well as other kinds of products) entails the use of electroless metal deposition. When the part to be plated is a nonconductor, the surface must first be activated with a catalyst that will initiate the electroless deposition process. In the past, the activation was achieved in a two-step process, in which the surface was first sensitized with a SnCl(2) solution or colloidal suspension, and then activated by a PdCl(2) solution. The two-step activation has now been largely supplanted by a one-step procedure, in which the surface is immersed in a suspension of a mixed colloid of Pd and Sn. The one-step activation is often followed by an acceleration step, which removes some of the tin from the activated surface.

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Electrochemical Method for Evaluating Pd Sn Activators for Electroless Deposition

The fabrication of many types of microelectronic components (as well as other kinds of products) entails the use of electroless metal deposition. When the part to be plated is a nonconductor, the surface must first be activated with a catalyst that will initiate the electroless deposition process. In the past, the activation was achieved in a two-step process, in which the surface was first sensitized with a SnCl(2) solution or colloidal suspension, and then activated by a PdCl(2) solution. The two-step activation has now been largely supplanted by a one-step procedure, in which the surface is immersed in a suspension of a mixed colloid of Pd and Sn. The one-step activation is often followed by an acceleration step, which removes some of the tin from the activated surface.

Products using these processes typically undergo a large number of steps (photolithography, cleaning, oxidation, plating, etc.), and when failure occurs, it can be difficult to isolate which of these steps is responsible. Thus, it would be extremely useful to have an independent evaluation of the activator. An electrochemical method to characterize various activating processes is described here.

The method uses Cu test electrodes, but other metal test electrodes could also be selected. The Cu electrode is sensitized or activated using the procedure to be evaluated. It is then thoroughly rinsed and mounted in an electrochemical cell. Standard potentio-dynamic procedures are used to measure the cyclic voltammetry of the activated surface in 0.01 M HC10(4). The method is not limited to this electrolyte, but the solution in which the study is done should be chosen to be as non-reactive as possible.

There are superficial resemblances between this technique and a previously published measurement (T. F. Osaka, H. Takematsu and K. Nihei, J. Electrochem. Soc., 127, 1020 11980). These authors use an Au test electrode and measure the linear sweep voltammetry in 1M HC1. The currents during the anodic sweep give a measure of the Sn and Pd coverage on the surface. The 1M HC1 solution can react chemically and electrochemically with the...