Through-Via Electroless Plating Uniformity
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Solution Overview
Problem
Conventional methods for forming through-vias in silicon substrates face challenges in achieving uniform step coverage of diffusion-preventive and copper seed layers using electroless plating, often resulting in poor film thickness uniformity and stacking flaws due to oxidation and dissolution of less noble metals.
Innovation Solution
A method involving the use of electroless cobalt or nickel plating solutions with specific additives, such as amino group-containing polymers, to form a diffusion-preventive layer with uniform thickness on the side walls of holes in silicon substrates, followed by stacking a copper seed layer, achieving a step coverage ratio of 30% to 300%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electroless plating is used to form diffusion-preventive layer and copper seed layer, then the method replaces PVD/CVD and simplifies the process, but the metal is easily deposited in the top part of the through-hole resulting in poor step coverage
Solution Approach 1:
The patent applies local quality by introducing a bottom-up agent that selectively modifies the plating behavior at different locations within the through-hole. The agent creates a concentration gradient that suppresses deposition at the top opening while promoting uniform deposition on the side walls, thereby achieving good step coverage specific to the hole structure without affecting the overall plating process
2Manufacturing precision
If sulfur-based bottom-up agent is used to uniformize film thickness, then step coverage is improved, but the electroless deposition of copper is suppressed and the diffusion-preventive layer is oxidized and dissolved causing stacking flaw
Solution Approach 1:
The patent applies parameter changes by carefully controlling the concentration, type, and application conditions of the bottom-up agent. By optimizing these parameters, the patent achieves uniform film thickness while preventing excessive suppression of copper deposition and avoiding oxidation/dissolution of the diffusion-preventive layer. The specific parameters include using amino group-containing polymers at controlled concentrations and timing their application to occur before copper plating
3Ease of manufacture
If electroless plating is used to form diffusion-preventive layer, then the layer can be formed on side wall, but the layer is extinct after copper seed layer formation due to oxidation and dissolution
Solution Approach 1:
The patent applies beforehand cushioning by introducing a protective mechanism that prevents oxidation and dissolution of the diffusion-preventive layer before the copper seed layer is formed. The bottom-up agent and controlled plating conditions create a protective environment that cushions the diffusion-preventive layer against chemical attack during subsequent processing steps
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the reproducible formation of diffusion-preventive and copper seed layers with improved uniformity and prevents the extinction of the diffusion-preventive layer, enhancing the stacking process and film coverage within the through-vias.
Implementation Method 1
forming an alloy film as a diffusion-preventive layer by use of an electroless cobalt plating solution or an electroless nickel plating solution
Implementation Method 2
electroless plating solution containing at least cobalt ion or nickel ion, a complexing agent, a reductant, and a pH adjusting agent
Data Source
AI summary
The present invention provides a method for forming a through-via, including the steps of (1) forming an alloy film as a diffusion-preventive layer that prevents diffusion of copper, in an area on a side wall of a hole formed in a substrate that extends from an entrance of the hole to a central part of the hole, by use of an electroless cobalt plating solution or an electroless nickel plating solution containing at least cobalt ion or nickel ion, a complexing agent, a reductant, and a pH adjusting agent; (2) forming an alloy film as a diffusion-preventive layer in an area on the side wall of the hole formed in the substrate that extends from the central part of the hole to a bottom of the hole, by use of an electroless cobalt plating solution or an electroless nickel plating solution containing at least the cobalt ion or the nickel ion, the complexing agent, the reductant, the pH adjusting agent, and an amino group-containing polymer; and (3) stacking a copper seed layer on the diffusion-preventive layer formed in each of steps (1) and (2) by use of an electroless copper plating solution.