T-Shaped Contacts for Semiconductor Devices
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Solution Overview
Problem
As semiconductor device sizes shrink, the filling process of V-shaped openings in non-planar devices often results in 'pinch-off' gaps, increasing resistance and potentially leading to open connections due to the challenges in filling small contact sizes effectively.
Innovation Solution
A method of fabricating T-shaped contacts using a multi-layer etching stack with a dielectric layer between hard mask layers, allowing for T-shaped contacts to be created with a single fill of bulk conductive material, which reduces the aspect ratio and prevents pinching during the filling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If V-shaped openings are filled with conductive material in non-planar devices, then contact connectivity is achieved, but pinch-off gaps form in the center of the fill resulting in increased resistance and potential open connections
Solution Approach 1:
The patent transitions from filling a simple V-shaped opening to filling a T-shaped contact structure. The T-shape introduces a horizontal dimension at the top that widens the opening, allowing conductive material to flow in from multiple directions and preventing pinch-off in the center during the filling process.
Solution Approach 2:
The T-shaped contact structure is asymmetric in geometry, with a wider top portion and a narrower bottom portion. This asymmetric shape is specifically designed to prevent the symmetric pinch-off that occurs in V-shaped contacts, as the material flow pattern is fundamentally changed by the asymmetric geometry.
2Length of moving object
If contact sizes are reduced to maintain shrinking semiconductor device sizes, then device scaling is achieved, but the filling process becomes more difficult resulting in increased resistance and open connections
Solution Approach 1:
By introducing the T-shape geometry with its widened top portion, the patent effectively adds a lateral dimension to the contact opening. This dimensional change allows material to access the contact hole from a broader area, making the filling process more reliable even as the overall contact size decreases with device scaling.
Solution Approach 2:
The patent changes the geometric parameters of the contact structure by transitioning from a V-shape to a T-shape. This parameter change specifically modifies the opening geometry to have a wider top and narrower bottom, which fundamentally alters the material flow dynamics during filling and prevents pinch-off even in miniaturized contacts.
3Ease of manufacture
If T-shaped contacts are created with a single fill of bulk conductive material, then manufacturing complexity is reduced, but the etching process requires a multi-layer stack increasing process steps
Solution Approach 1:
The etching process is segmented into multiple stages using a multi-layer etching stack with different hard mask layers. This segmentation allows precise control over the T-shaped contact formation, enabling the complex T-shape to be created through controlled etching steps while maintaining a single fill operation for the conductive material.
Solution Approach 2:
The multi-layer etching stack with dielectric and hard mask layers acts as an intermediary structure that enables precise T-shaped contact formation. These intermediate layers facilitate controlled material removal to create the T-shape without requiring complex direct patterning, ultimately simplifying the overall manufacturing by enabling single-fill contacts.
Data Source
AI summary
A transistor, planar or non-planar (e.g., FinFET), includes T-shaped contacts to the source, drain and gate. The top portion of the T-shaped contact is wider than the bottom portion, the bottom portion complying with design rule limits. A conductor-material filled trench through a multi-layer etching stack above the transistor provides the top portions of the T-shaped contacts. Tapered spacers along inner sidewalls of the top contact portion prior to filling allow for etching a narrower bottom trench down to the gate, and to the source/drain for silicidation prior to filling.