3D Source-Drain Contacts Using Sacrificial Diffusion Regions
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Solution Overview
Problem
As integrated circuits continue to scale to smaller feature dimensions and higher transistor densities, maintaining large and uniform source and drain contact areas becomes challenging due to the reduction in gate pitch and contact pitch, leading to increased external resistance.
Innovation Solution
A three-dimensional (3D) contact architecture is developed by removing a sacrificial core region of the source or drain region, with remnants of the core region remaining, allowing for the formation of large and uniform source and drain contacts that extend within the diffusion region, utilizing etch-selective compositional differences between the core and main regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gate pitch and contact pitch are reduced to increase transistor density, then transistor density is improved, but source and drain contact area decreases leading to increased external resistance
Solution Approach 1:
The patent transitions from planar (2D) contacts to three-dimensional (3D) contacts by forming contacts that extend vertically into the source and drain regions. This dimensional change allows the contact area to increase in the vertical dimension while the horizontal pitch remains small, thereby maintaining low external resistance despite reduced contact pitch and achieving high transistor density.
Solution Approach 2:
The 3D contacts are formed by nesting conductive material within trenches that extend into the source and drain regions. The contact structure is nested within the diffusion region, with the conductive material filling the trench and making contact with the doped semiconductor region, effectively creating a nested configuration that maximizes contact area within limited space.
2Area of moving object
If 3D contacts are formed by removing sacrificial core region, then contact area is increased, but manufacturing complexity increases
Solution Approach 1:
The sacrificial core regions are formed during the epitaxial growth of the source and drain regions, before the contact formation process. This preliminary action creates the necessary structural features (trenches where core regions will be removed) in advance, simplifying the subsequent contact formation process by pre-defining the contact geometry and location.
Solution Approach 2:
The patent utilizes compositional differences between the core region and the main source/drain region, which are created through different doping concentrations or material compositions during epitaxial growth. These parameter changes enable selective removal of the core region through etching processes that exploit the compositional contrast, thereby simplifying the contact formation process.
3Manufacturing precision
If etch-selective compositional differences are used to form 3D contacts, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent implements local quality by creating compositional variations specifically in the core regions of the source and drain, while the rest of the device structure remains relatively simple. The core regions have different doping concentrations or material compositions compared to the main source/drain regions, enabling selective etching without requiring complex compositional structures throughout the entire device.
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 results in relatively large and uniform 3D source and drain contacts, maintaining reasonable external resistance and consistent contact trench depths across the die or wafer, suitable for various transistor devices and vertical stacks.
Implementation Method 1
utilizing etch-selective compositional differences between the core and main regions
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An integrated circuit structure includes a device including a source region (104a, 105a, 133a), a drain region (104b, 105b, 133b), a body (103) laterally between the source and drain regions, and a source contact (118a, 135) coupled to the source region. The source region includes a first region (105a), and a second region (133a) compositionally different from and above the first region. The source contact (118a, 135) extends through, and is in direct contact with, the second region (133a) and extends within and is in direct contact with the first region (105a). In an example where the device is a p-channel metal-oxide-semiconductor (PMOS) device, a concentration of germanium within the second region is different (e.g., higher) than a concentration of germanium within the first region. In another example where the device is a n-channel metal-oxide-semiconductor (NMOS) device, a doping concentration level of a dopant (e.g., an n-type dopant) within the second region is different (e.g., higher) from a doping concentration level of the dopant within the first region.