3D Source and 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 tight pitch, leading to increased external resistance and reduced contact efficiency.
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 regions, utilizing etch-selective compositional differences between the core and main regions to achieve consistent contact trench depths across the die or wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If traditional planar contact architecture is used, then manufacturing process is simple, but contact area becomes small and non-uniform due to tight pitch scaling
Solution Approach 1:
The patent transitions from a two-dimensional planar contact architecture to a three-dimensional contact structure 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 maintaining compatibility with the scaled horizontal pitch, thereby achieving larger and more uniform contact areas without compromising manufacturing precision.
Solution Approach 2:
The source and drain regions are segmented into a core region and a main region with different compositions. The core region is selectively removed to form the contact trench, while the main region remains to provide structural support and electrical connection. This segmentation enables precise control over the contact geometry and ensures uniform contact formation across the device.
2Productivity
If contact area is reduced to fit tight pitch, then device density increases, but external resistance increases and contact efficiency decreases
Solution Approach 1:
By extending the contact structure vertically into the source and drain regions, the patent increases the effective contact area without increasing the horizontal footprint. This allows device pitch to be reduced for higher density while maintaining sufficient contact area to keep external resistance low and contact efficiency high.
3Area of moving object
If sacrificial core region is removed to form 3D contact, then contact area increases and uniformity improves, but process complexity increases
Solution Approach 1:
A sacrificial core region is introduced as an intermediary structure during fabrication. This core region is formed with a composition different from the main source and drain regions, allowing it to be selectively removed later. The sacrificial core enables precise definition of the contact trench geometry and ensures uniform contact formation, while its removal simplifies the overall process by providing a self-aligned etch stop.
4Manufacturing precision
If etch-selective compositional differences are used, then consistent contact trench depths are achieved, but manufacturing precision requirements increase
Solution Approach 1:
The source and drain regions are given different local compositions: the core region has a composition that is etch-selective relative to the main region. This local quality difference allows the etch process to automatically stop at the desired depth when encountering the main region, ensuring consistent contact trench depths across all devices without requiring precise depth control during etching.
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, reducing external resistance and enhancing contact efficiency, while maintaining consistent contact trench depths across the integrated circuit, suitable for both vertical stacks and various transistor configurations.
Implementation Method 1
utilizing etch-selective compositional differences between the core and main regions to achieve consistent contact trench depths across the die or wafer
Data Source
AI summary
An integrated circuit structure includes a device including a source region, a drain region, a body laterally between the source and drain regions, and a source contact coupled to the source region. In an example, the source region includes a first region, and a second region compositionally different from and above the first region. The source contact extends through the second region and extends within the first region. 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.