Tungsten Contact Plug Grain Size Control for High Aspect Ratio Filling
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Solution Overview
Problem
The demand for highly-integrated and high-speed semiconductor devices has led to increased challenges in fabricating reliable connections with reduced interconnection distances and increased aspect ratios of contact plugs, requiring improved processes to enhance the reliability of semiconductor devices.
Innovation Solution
The implementation involves a semiconductor device structure with a lower conductor and an upper structure featuring a connection structure that includes a first tungsten layer covering the inner surface of an opening and a second tungsten layer filling the recess region, where the grain size of the second tungsten layer in the upper portion is greater than in the lower portion, and a surface treatment process is applied to the first tungsten layer to control grain growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the aspect ratio of contact plugs is increased to achieve higher integration, then the interconnection distance is reduced, but the reliability of the connection deteriorates due to potential voids and incomplete filling
Solution Approach 1:
The connection structure is divided into multiple tungsten layers (first tungsten layer and second tungsten layer) with different grain size characteristics. The first tungsten layer has finer grains providing dense filling, while the second tungsten layer has coarser grains providing structural stability. This segmentation resolves the contradiction by combining the advantages of different grain structures to achieve both complete filling and reliable connection in high aspect ratio contact plugs.
Solution Approach 2:
Different regions of the connection structure are assigned different grain sizes locally. The lower portion (first tungsten layer) has fine grains for complete filling of the high aspect ratio opening, while the upper portion (second tungsten layer) has coarse grains for reduced resistance. This local differentiation allows the structure to simultaneously achieve reliable filling and low resistance connection.
2Productivity
If the interconnection distance is reduced to increase integration, then the device density is improved, but the manufacturing precision required to ensure complete filling without voids increases
Solution Approach 1:
The tungsten connection structure is segmented into multiple layers with different deposition characteristics. The first tungsten layer is deposited to provide fine grain structure for complete filling, while the second tungsten layer is deposited to provide coarse grain structure for low resistance. This segmentation enables complete filling of high aspect ratio openings without requiring excessive manufacturing precision in a single-step process.
Solution Approach 2:
The connection structure uses a composite of tungsten layers with different grain characteristics. By combining fine-grained and coarse-grained tungsten layers, the structure achieves both complete filling (requiring fine grains) and low resistance (benefiting from coarse grains), thereby reducing the manufacturing precision burden on any single process step.
3Device complexity
If a single-layer tungsten structure is used to simplify the process, then the device complexity is reduced, but the resistance of the connection structure increases
Solution Approach 1:
The connection structure is segmented into multiple tungsten layers with different grain sizes. The first tungsten layer provides fine grain structure for complete filling, while the second tungsten layer provides coarse grain structure for reduced resistance. This segmentation resolves the contradiction by demonstrating that the additional layer complexity is justified by the significant improvement in electrical connectivity and overall reliability.
Solution Approach 2:
The grain size parameter is changed between layers - the first tungsten layer has fine grains while the second tungsten layer has coarse grains. This parameter change allows the structure to optimize different regions for different functions (filling completeness vs. resistance reduction), thereby improving electrical connectivity while maintaining acceptable structural complexity.
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 the reliability of semiconductor devices by ensuring complete filling of the opening without voids and reduces resistance, improving the electrical connectivity and stability of the connections.
Implementation Method 1
depositing a first tungsten layer covering an inner surface of the opening and defining a recess region in the opening
Implementation Method 2
depositing a second tungsten layer filling the recess region on the first tungsten layer
Implementation Method 3
performing a surface treatment process on a portion of the first tungsten layer, the first tungsten layer having a first surface treated by the surface treatment process in an upper region of the opening and a second surface not treated by the surface treatment process in a lower region of the opening
Data Source
AI summary
A semiconductor device includes a lower structure including a lower conductor, an upper structure having an opening exposing the lower conductor on the lower structure, and a connection structure filling the opening and connected to the lower conductor. The connection structure includes a first tungsten layer covering an inner surface of the opening and defining a recess region in the opening, and a second tungsten layer filling the recess region on the first tungsten layer. A grain size of the second tungsten layer in an upper portion of the connection structure is greater than a grain size of the second tungsten layer in a lower portion of the connection structure.