Gate Contact Structure With Etch-Back Fill for Void-Free Contacts
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in filling conductive materials into high-aspect-ratio openings for gate contacts and source/drain contact vias, as existing methods often result in unsatisfactory metal fill, leading to increased resistance and device failures due to voids or gaps in the contact structures.
Innovation Solution
A multi-stage metal fill process is introduced, where a first metal fill layer is deposited and etched back before a second metal fill layer is deposited, reducing the aspect ratio of the openings and ensuring satisfactory metal fill by breaking down the single-stage high-aspect-ratio metal filling into multiple lower-aspect-ratio steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-stage metal fill process is used to fill high-aspect-ratio openings, then the manufacturing process is simple, but the metal fill is unsatisfactory with voids or gaps leading to increased resistance
Solution Approach 1:
The patent divides the single-stage metal fill process into multiple stages: forming a first metal fill layer, etching it back to reduce aspect ratio, then forming a second metal fill layer. This segmentation transforms the difficult high-aspect-ratio filling into easier lower-aspect-ratio steps, eliminating voids and gaps while ensuring complete contact opening filling.
2Area of moving object
If the contact opening dimensions are scaled down, then the device density increases, but the metal fill becomes more difficult with higher aspect ratios
Solution Approach 1:
The patent applies segmentation by dividing the metal fill into multiple layers (first and second metal fill layers) formed at different stages. The first layer is etched back to reduce the effective aspect ratio before forming the second layer, making the filling process feasible for scaled-down contact openings while maintaining complete fill quality.
Solution Approach 2:
The patent performs preliminary action by forming and etching back the first metal fill layer before forming the second metal fill layer. This preliminary step modifies the contact opening geometry to have a lower aspect ratio, preparing it for successful completion of the metal fill process in the second stage.
3Reliability
If existing metal fill methods are used, then the manufacturing process is straightforward, but contact resistance increases due to unsatisfactory metal fill
Solution Approach 1:
The patent segments the metal fill into multiple stages with intermediate etching back, which transforms the straightforward but defective single-stage process into a multi-stage process that achieves satisfactory metal fill without voids or gaps, thereby reducing contact resistance and improving reliability.
4Length of moving object
If high-aspect-ratio openings are formed, then the device dimensions are scaled down, but voids or gaps appear in the contact structure
Solution Approach 1:
The patent segments the filling of high-aspect-ratio openings into multiple stages. The first metal fill layer is formed and then etched back to reduce the remaining depth, transforming the high-aspect-ratio opening into a lower-aspect-ratio opening that can be completely filled by the second metal fill layer without voids or gaps.
Solution Approach 2:
The patent performs preliminary action by forming the first metal fill layer and etching it back before forming the second metal fill layer. This preliminary modification of the opening geometry ensures that the final metal fill completes the contact structure integrity without defects.
Data Source
AI summary
Semiconductor structures and methods of forming the same are provided. In one embodiment, a semiconductor structure includes an active region over a substrate, a gate structure disposed over the active region, and a gate contact that includes a lower portion disposed over the gate structure and an upper portion disposed over the lower portion.