Non-Contact Electroplating for SOI Wafer Metal Deposition
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Solution Overview
Problem
Conventional contact-type electroplating methods are unsuitable for SOI wafers with buried oxide layers thicker than 500 Å, as they risk electrically breaking the oxide, and existing electrodeposition techniques require physical attachment of electrodes to the wafer, limiting their application.
Innovation Solution
A non-contact electroplating apparatus and process where the wafer is positioned between two chambers with electrodes in each chamber, connected to an electric power source but not physically touching the wafer, using an electrolytic solution and an electron source, such as illumination, to facilitate electrochemical reactions without passing current through the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If contact-type electroplating is used on SOI wafers with thick buried oxide layers, then metal deposition can be achieved, but the oxide layer risks electrical breakdown
Solution Approach 1:
The patent introduces a liquid electrolyte as an intermediary medium between the electrode and the wafer surface. The electrolyte enables ionic conduction for metal deposition while the non-contact configuration prevents direct current flow through the buried oxide layer, thus avoiding oxide breakdown while achieving quality metal deposition.
Solution Approach 2:
The patent replaces the conventional mechanical contact between electrode and wafer with a non-contact electrochemical system. Instead of direct electrical contact through the substrate, the system uses electrolytic solution-mediated electron transfer at the wafer surface, substituting mechanical/electrical contact with a chemical interface.
2Manufacturing precision
If conventional electrodeposition techniques are used, then metal can be deposited on seed layers, but physical attachment of electrodes to the wafer is required
Solution Approach 1:
The patent extracts the requirement for physical electrode attachment from the electroplating process. By using a non-contact configuration where the electrode hovers above the wafer surface separated by an electrolyte layer, the system eliminates the need for mechanical bonding or direct contact while maintaining deposition control through electrical field management.
Solution Approach 2:
The electrolyte serves as an intermediary that enables the electrochemical reaction without requiring direct contact between the electrode and wafer. The ionic conduction through the electrolyte layer allows current flow necessary for metal deposition while the physical separation simplifies the device structure by eliminating attachment mechanisms.
3Manufacturing precision
If through-mask plating is used for selective metal deposition, then area-selective plating is achieved, but multiple plating operations are required for different metal gates
Solution Approach 1:
The patent employs periodic or sequential application of different electrolyte solutions containing various metal ions. By cycling through different plating solutions in a single non-contact setup, the system can deposit different metals (such as TiN, TaN, WN for n-FET and PL, PR, PF for p-FET) without requiring multiple separate plating tools or repeated mask alignment operations.
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
Enables effective electroplating on SOI wafers with buried oxide layers of varying thicknesses, including high-k oxides, without damaging the oxide layer, and allows for selective metal deposition on semiconductor wafers, comparable to traditional backside contact methods, suitable for high-performance CMOS devices and field effect transistors.
Implementation Method 1
An electrochemical process is carried out on a semiconductor wafer. The electrochemical process involves electrodeposition of a metal layer on the semiconductor wafer
Implementation Method 2
providing electrons to a surface of the semiconductor wafer opposite the face on which the metal layer is to be electrodeposited
Data Source
AI summary
An electroplating apparatus and method for depositing a metallic layer on the surface of a wafer is provided wherein said apparatus and method do not require physical attachment of an electrode to the wafer. The surface of the wafer to be plated is positioned to face the anode and a plating fluid is provided between the wafer and the electrodes to create localized metallic plating. The wafer may be positioned to physically separate and lie between the anode and cathode so that one side of the wafer facing the anode contains a catholyte solution and the other side of the wafer facing the cathode contains an anolyte solution. Alternatively, the anode and cathode may exist on the same side of the wafer in the same plating fluid. In one example, the anode and cathode are separated by a semi permeable membrane.