Deep Trench Via Metallization to Mitigate Threshold Voltage Shift
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Solution Overview
Problem
The implementation of deep trench vias for backside power delivery in IC devices causes undesirable shifts in transistor threshold voltages due to the presence of titanium on the sidewalls of the vias during conventional metallization processes.
Innovation Solution
Implementing selective titanium deposition during metallization of deep trench vias and source/drain contacts to reduce or eliminate titanium presence on the via sidewalls, using controlled and precise deposition techniques to mitigate the deep trench via proximity effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional metallization process is used for deep trench vias, then titanium is deposited on via sidewalls providing structural support, but transistor threshold voltages shift undesirably
Solution Approach 1:
The patent extracts titanium from the via sidewalls by using a selective removal process that eliminates titanium deposition in the via region while maintaining it in other critical areas. This is achieved through selective etching or deposition masking that targets only the via sidewalls, thereby removing the harmful titanium presence that causes threshold voltage shifts while preserving structural integrity through alternative materials or processes.
Solution Approach 2:
The patent applies local quality by creating non-uniform titanium distribution across the device structure. Titanium is selectively present in regions where structural support is needed (such as source/drain contacts) but deliberately absent from via sidewalls where it causes harmful effects. This spatially selective material distribution resolves the contradiction by tailoring material presence to local functional requirements.
2Strength
If titanium is present on via sidewalls, then via structural integrity is maintained, but proximity effects cause threshold voltage shifts
Solution Approach 1:
The patent converts the harmful proximity effect into a beneficial outcome by using the absence of titanium on via sidewalls to protect adjacent transistors from threshold voltage shifts. The selective removal of titanium, which would normally be present for structural support, is compensated by alternative via filling materials or process modifications that maintain via integrity while eliminating the harmful electromagnetic or chemical interaction with nearby transistors.
3Reliability
If selective titanium deposition is implemented, then titanium presence on via sidewalls is reduced, but additional process complexity is introduced
Solution Approach 1:
The patent applies preliminary action by preparing the via structures and surrounding regions before titanium deposition in a way that prevents unwanted titanium accumulation. This may involve pre-deposition masking, selective surface treatment, or preliminary etching steps that create conditions where titanium naturally deposits only in desired locations. By preparing the structure in advance, the need for complex post-deposition removal processes is reduced.
Solution Approach 2:
The patent introduces intermediary layers or materials that mediate between the titanium deposition process and the via sidewalls. These intermediaries may be temporary masking layers, barrier films, or surface treatments that prevent titanium from adhering to via sidewalls during deposition. The intermediary is subsequently removed or integrated into the final structure, providing a relatively simple mechanism to achieve selective titanium placement.
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
Reduces or eliminates the undesirable shifts in transistor threshold voltages by minimizing titanium on the sidewalls of deep trench vias, thereby improving the performance and reliability of IC structures.
Implementation Method 1
Implementing selective titanium deposition during metallization of deep trench vias and source/drain contacts
Data Source
AI summary
Disclosed herein are IC structures and devices that aim to mitigate proximity effects of deep trench vias. An example IC structure may include a device region having a first face and a second face, the second face being opposite the first face, and further include a conductive via extending between the first face and the second face, wherein the conductive via includes an electrically conductive material, and wherein a concentration of titanium at sidewalls of the conductive via is below about 1015 atoms per cubic centimeter.