Contact Window Structure for Enlarged Via Bottom Contact
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Solution Overview
Problem
The increasing depth-to-width ratio of vias in semiconductor manufacturing leads to compromised circuit performance due to shrinkage during the etching process, resulting in a smaller bottom size of the via compared to the top, which increases contact resistance and reduces the contact area with the target metal layer.
Innovation Solution
A contact window structure and forming method involving the creation of an annular pad on a target layer, followed by the formation of a dielectric layer and an etch hole connected to a central via, where the annular pad is removed to enlarge the via size, reducing the depth-to-width ratio and enhancing the contact area and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the depth-to-width ratio of vias is increased to meet scaling requirements, then the via can connect deeper metal layers, but the via bottom size shrinks during etching, increasing contact resistance and reducing contact area
Solution Approach 1:
The via formation process is segmented into two distinct stages: first forming a shallow central via through the pad layer, then forming a deeper etch hole through the dielectric layer. This segmentation allows each via to be optimized independently - the central via maintains its size and connection quality, while the etch hole provides the necessary depth for accessing deeper metal layers.
Solution Approach 2:
The central via is nested within the etch hole structure. The central via is formed first, then the dielectric layer is deposited around it, and finally the etch hole is formed through the dielectric layer to connect to the central via. This nested configuration allows the shallower central via to maintain its critical dimensions while the deeper etch hole provides the necessary depth.
2Manufacturing precision
If conventional via etching is used to maintain via size, then the etching process is simplified, but the via bottom size is still greater than the critical size, compromising circuit performance
Solution Approach 1:
The etching process is segmented into two sequential steps with different objectives. The first step forms the central via through the pad layer with precise size control. The second step forms the etch hole through the dielectric layer to connect to the central via. This segmentation allows each etching step to be optimized for its specific purpose, achieving both precision and depth requirements.
Solution Approach 2:
The central via is formed in advance before the dielectric layer is deposited. This preliminary action establishes a precise reference structure that guides the subsequent dielectric deposition and etch hole formation, ensuring that the final via structure meets the critical size requirements.
3Area of moving object
If the via size is reduced to meet critical dimensions, then the contact area is sufficient, but the via bottom size becomes smaller than the critical size, increasing contact resistance
Solution Approach 1:
The contact structure is segmented into two functional parts: the central via that provides the primary contact area with the metal layer, and the etch hole that provides the depth connection through the dielectric. This segmentation allows the central via to be optimized for contact area while the etch hole is optimized for depth, preventing the trade-off between size reduction and contact resistance increase.
Solution Approach 2:
The central via is nested within the etch hole structure, allowing the shallower central via to maintain its critical dimensions and contact area, while the deeper etch hole provides the necessary depth for connecting to lower metal layers without compromising the contact quality at the via bottom.
Data Source
AI summary
A contact window structure, a metal plug and a forming method thereof, a method of forming the contact window structure and a semiconductor structure are provided. In the method of forming the contact window, an annular pad is formed on a surface of a target layer. A central via, from which partial surface of the target layer is exposed, is formed in the middle part of the annular pad. A dielectric layer covering a substrate, the target layer and the annular pad is formed. The dielectric layer is etched to form an etch hole connected to the central via in the dielectric layer. The annular pad is removed along the etch hole and the central via to enlarge a size of the central via, so as to form the contact window structure by the etch hole and the central via with the enlarged size.