Bond Pad Protection for Harsh Media via Composite Layers
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Solution Overview
Problem
Standard semiconductor devices are unsuitable for harsh media conditions due to corrosion issues, particularly with bond pad metals like aluminium and copper, which can corrode when exposed to chemicals such as sulfuric or fuming nitric acids or iodine, and existing protective measures like gold layers lack a strong mechanical connection to passivation layers.
Innovation Solution
A method involving the formation of a refractory metal contact layer with an adhesion and diffusion barrier, followed by a noble metal layer that extends over the edges to establish a strong mechanical connection with the passivation layer, ensuring protection against corrosive environments and preventing intermetallic alloy growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gold layer is deposited on the bond pad to protect against corrosion, then corrosion resistance is improved, but mechanical connection to the passivation layer deteriorates
Solution Approach 1:
The patent applies composite materials by creating a multi-layer structure consisting of a noble metal layer (gold, palladium, or platinum) combined with a refractory metal adhesion layer (titanium, tungsten, or tantalum). This composite structure provides both corrosion resistance from the noble metal and strong mechanical adhesion from the refractory metal layer that extends onto the passivation layer, thereby resolving the contradiction between protection and mechanical connection.
2Device complexity
If aluminium and gold are placed in direct contact to simplify structure, then device complexity is reduced, but intermetallic diffusion increases
Solution Approach 1:
The patent introduces a refractory metal adhesion layer as an intermediary between the aluminium bond pad and the noble metal protective layer. This intermediate layer prevents direct contact and intermetallic diffusion between aluminium and gold, while still allowing for a relatively simple overall structure. The adhesion layer acts as a mediator that maintains compositional stability without significantly increasing device complexity.
3Manufacturing precision
If electroless plating is used to deposit gold on the bond pad, then manufacturing precision is improved, but mechanical connection to passivation layer deteriorates
Solution Approach 1:
The patent merges two deposition techniques: electroless plating is used to deposit the noble metal layer with high precision and uniformity, while sputtering is used to deposit the refractory metal adhesion layer that provides mechanical connection. By combining these two methods in sequence, the patent achieves both manufacturing precision in the gold layer deposition and strong mechanical connection to the passivation layer through the sputtered adhesion layer.
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 solution effectively prevents corrosive chemicals from reaching internal layers, maintains bond pad integrity, and ensures reliable electrical connections even at elevated temperatures, providing a cost-effective and high-volume production method for semiconductor devices suitable for harsh media applications.
Implementation Method 1
providing the noble metal layer comprises sputtering the noble metal onto the continuous part of the contact layer and onto the exposed at least one passivation layer around the edge of the continuous part such as to establish a mechanical connection by atomic bonding between the sputtered noble metal layer and both the contact layer and the at least one passivation layer
Implementation Method 2
providing the noble metal layer comprises plating the noble metal onto the noble metal seed layer
Data Source
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AI summary
The present invention relates to methods for fabricating a semiconductor device and to the related semiconductor devices for use in harsh media. The semiconductor device comprises a silicon die (420) comprising a metal contact region (422) and, at least one passivation layer (421) covering the semiconductor die (420) and patterned such as to form an opening to the metal contact region (422) of the semiconductor die (420). The device also comprises a continuous part of a contact layer comprising a refractory metal. This continuous part overlaps and completely covers the opening in the at least one passivation layer (421), contacts the metal contact region (422) in the opening and adheres to the at least one passivation layer (421) along the entire edge of the continuous part. The contact layer comprises at least an adhesion layer (529) and at least a diffusion barrier layer. The device further comprises a noble metal layer (524) arranged over the contact layer and completely covering the continuous part, in which the noble metal layer (524) extends over the entire edge of the continuous part to adhere to the at least one passivation layer (421) around the edge of the continuous part.