FinFET Gate Isolation via Mandrel-Based Etching
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Solution Overview
Problem
Conventional finFET manufacturing processes, particularly those using sidewall-spacer techniques, often result in angled fin sidewalls, which can lead to conductive residue formation between adjacent gates, causing short circuits and reducing yields due to the narrowing of the process window and thickening of conductive films in gaps between fins.
Innovation Solution
A manufacturing process that forms insulating fins between adjacent gates using a single etch to define furrows, which separates the gates and prevents conductive residue formation by creating a more reliable isolation between gates, thereby avoiding the issues associated with angled sidewalls and conductive residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If sidewall-spacer process is used to form gates, then narrower gates can be formed relative to photolithography, but angled fin sidewalls cause conductive film thickening in gaps and create stringers that short adjacent finFETs
Solution Approach 1:
Mandrel structures are introduced as intermediary elements to define the gate pattern. The mandrels serve as a template that enables precise gate width control through photolithography while eliminating the need for angled sidewall etching. The mandrel-based approach acts as a mediator between the photolithography process and the final gate structure, allowing narrow gates to be formed without creating the conditions that lead to stringer formation.
Solution Approach 2:
The gate formation process is segmented into distinct steps: mandrel formation, spacer deposition, and gate material deposition. This segmentation allows each step to be optimized independently - the mandrels provide precise spatial definition, the spacers ensure uniform thickness, and the gate material is deposited only where needed. This breaks the coupled problem of gate width control and stringer prevention into manageable stages.
2Ease of manufacture
If angled sidewalls are present on fins, then the process window for sidewall spacer process narrows, but this leads to thicker conductive film in gaps between adjacent fins
Solution Approach 1:
Mandrel structures serve as intermediaries that decouple the fin sidewall angle from the gate width definition. Instead of using the fin sidewalls as the reference for gate patterning, the mandrels provide a separate, controlled reference structure. This eliminates the sensitivity to sidewall angle variations and opens up the process window for manufacturing.
Solution Approach 2:
The invention changes the reference parameter for gate width definition from fin sidewall position to mandrel position. By controlling the mandrel dimensions and spacing rather than relying on fin geometry, the process becomes less sensitive to variations in fin sidewall angle. This parameter substitution enables better film thickness control in the gaps between structures.
3Quantity of substance
If conformal conductive film is deposited over angled fin sidewalls, then the film thickens in the gap between adjacent fins, but this prevents complete removal by sidewall-spacer etch
Solution Approach 1:
Mandrel structures act as intermediaries that control the spacing and positioning of gate structures. By defining the gate pattern through mandrels rather than through sidewall spacers on angled fins, the conformal film deposition occurs on vertically oriented mandrel sidewalls. This geometry ensures uniform film thickness that can be completely removed by the spacer etch, preventing stringer formation while maintaining proper gate isolation.
Solution Approach 2:
Instead of using the fin sidewalls as the basis for gate definition (which leads to thickening problems), the invention inverts the approach by using separately formed mandrels as the basis. This reversal of the patterning reference eliminates the geometric coupling that causes film thickening in gaps, allowing complete etch removal while maintaining gate isolation.
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 enhances gate isolation, reduces short circuits, and improves yield by maintaining a consistent process window, ensuring that gates are reliably formed without the issues of conductive residue, leading to more reliable and efficient transistor production.
Implementation Method 1
a single etch to define furrows between the insulating fins and semiconductor fins
Implementation Method 2
covering a fin with a conformal, conductive film
Data Source
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AI summary
Disclosed are methods, systems and devices, including a system, having a memory device. In some embodiments, the memory device includes a plurality of fin field-effect transistors (190) disposed in rows (164), a plurality of insulating fins (154) each disposed between the rows (164), and a plurality of memory elements each coupled to a terminal (192, 194) of a fin field-effect transistor (190) among the plurality of fin field-effect transistors (190).