Chemical nickel solution applied to wafer-level packaging chemical nickel-gold process

Abstract

The invention discloses a chemical nickel solution applied to a wafer-level packaging chemical nickel-gold process. Water is adopted as the dissolvent of the solution. The solution comprises, by concentration, 20-40g/L of nickel salt, 20-40g/L of a reducing agent, 20-50g/L of a complexing agent, 1-5mg/L of a stabilizing agent and 2-200mg/L of an impurity removing agent. The impurity removing agentcontains at least one pyridine type compound, and impurity metal ions can be chelated by the pyridine type compound in the impurity removing agent so as to reduce the influence of impurities in the solution on the performance of a plating solution. The pyridine type impurity removing agent is adopted by the chemical nickel solution to eliminate the influence of impurity heavy metal in the solution on the plating solution without any side effect brought to the plating solution by the pyridine type impurity removing agent. Therefore, even if the content of impurity ions in the plating solutionis very low or zero, the performance of the plating solution is not influenced by the added pyridine type compound.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, in particular to an electroless nickel solution used in a wafer-level packaging chemical nickel-gold process. Background technique [0002] The chemical nickel-gold process is a common process in the wafer-level packaging process. It is mainly used in the field of RDL (rewiring) or UBM (under-bump metallization). Generally, electroless nickel-gold is plated on copper lines or pad patterns, which can The function of soldering and wire bonding, and the nickel layer can be used as a barrier layer for copper and tin to prevent the diffusion of copper and tin. [0003] With the miniaturization, precision, and intelligent development of electronic products, the circuits inside the chip are becoming more and more precise and small. Taking the field of wafer-level packaging and testing as an example, the current line width and line spacing are mostly concentrated at the level of tens of micr...

AI Technical Summary

Problems solved by technology

[0004] First, the risk of missing plating is likely to occur

That is, some lines are not plated with nickel, so that the copper wires are exposed. The reason for this problem is not only insufficient activation and insufficient palladium deposition, but also the low activity of the nickel bath.

Under normal production parameter conditions, the main factor causing the low activity is that the plating solution contains some heavy metal ion impurities, and these ions tend to act as stabilizers for the nickel bath, greatly reducing the activity of the nickel solution

For the chemical nickel process of general products, the impact of these impurities is not obvious, which can be solved by increasing the load or raising the nickel tank parameters a little, but for such fine lines as chips, this method will bring other risks

[0005] Second, it is easy to cause the risk of seepage plating. If the activation process is strengthened to prevent missing plating, it will generally result in more palladium residues between the lines, or deliberately increase the load or increase the nickel tank parameters to forcibly increase the nickel plating activity. In this way, nickel plating will cause nickel deposits between the lines that do not need nickel plating, causing a short circuit between the two lines

[0006] The above two situations will lead to component failure. In order to solve the problem fundamentally, it is necessary to start from the source of the problem

The source of the problem is the impurities mixed in the raw materials, which are the main factors causing the low activity of the nickel layer. For example, some impurities in the nickel sulfate raw material, when the solution contains 1mg / L of heavy metal ions such as lead ions and cadmium ions, will seriously affect the activity of nickel plating solution

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