Square Contact Vias Using Crystal-Plane Selective Etching
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Solution Overview
Problem
Conventional methods for forming contact vias in semiconductor devices result in rounded corners, leading to reduced contact area with source/drain elements, which affects electrical performance and thermal conductivity.
Innovation Solution
A wet ammonia etching process is applied to transform round contact via holes into square-shaped via holes, selectively etching along (100) crystal planes while minimizing etching along (110) planes, thereby increasing the contact area and improving electrical and thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional round contact via hole is formed, then the manufacturing process is simple, but the contact area with source/drain elements is reduced
Solution Approach 1:
The etching process is segmented into two distinct stages: first a conventional isotropic etch to create a round via hole, then a wet ammonia etch to selectively reshape the sides. This segmentation allows each etching step to have a specific function, transforming the simple round hole into a complex shape with larger contact area without requiring complete process redesign
Solution Approach 2:
The patent changes the etching parameters by introducing wet ammonia etching with specific chemical composition and temperature control. This parameter change enables selective etching of silicon along different crystal planes, transforming the via shape from round to square-like with larger contact area while maintaining manufacturing feasibility
2Area of stationary object
If the contact via shape is changed to square, then the contact area increases, but the etching process becomes more complex
Solution Approach 1:
The wet ammonia etch creates local quality differences by selectively etching the silicon at the corners and sides of the round via hole at different rates. This local variation in etching behavior transforms the uniform round shape into a non-uniform square-like shape with enhanced contact areas at specific locations, achieving both shape precision and area increase
3Reliability
If conventional round contact vias are used, then the manufacturing process is straightforward, but the electrical conductivity and thermal conductivity are reduced
Solution Approach 1:
The conventional isotropic etch is performed first to create the basic round via hole structure, establishing the preliminary shape. Then the wet ammonia etch is applied as a subsequent action to refine and transform this preliminary shape into the final square-like structure with enhanced electrical and thermal performance characteristics
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
The square-shaped contact vias enhance electrical contact resistance and thermal conductivity by increasing the contact area with source/drain and backside power rails, compared to conventional round contact vias, improving overall semiconductor device performance.
Implementation Method 1
performing the wet ammonia etching process on the round contact via hole transforms the round contact via hole to a rectangular-shaped contact via hole
Data Source
AI summary
An approach provides a semiconductor structure with one or more rectangular or square-shaped contact vias in a semiconductor material. The semiconductor device includes one of the first element of the semiconductor device element under the square-shaped contact via or the second element of the semiconductor device element above the square-shaped contact via. The semiconductor structure includes the square-shaped via in the semiconductor material that has straight edges that are parallel to one or more of the (110) crystal planes of the semiconductor material and the square-shaped contact vias has corners pointing in a direction orthogonal to one or more of the (100) crystal planes of the semiconductor material. The square-shaped contact via provides a larger contact area that a conventional round-shaped contact via with a diameter matching the width of the square-shaped contact via.