Dummy Cell Pattern for Thermal Uniformity in Semiconductor Devices
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Solution Overview
Problem
Conventional dummy fill patterns in semiconductor fabrication lead to temperature variations and deteriorate device performance, specifically the ON current range between MOS transistors within an integrated circuit die, due to non-uniform thermal absorption and emission across different film stacks and pattern densities.
Innovation Solution
A dummy cell pattern is introduced, comprising a dummy diffusion pattern surrounded by a trench isolation pattern, with specific gate patterns extending above and overlapping with the trench isolation, forming defined overlapping areas that occupy about 5%-20% of the region, to unify device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional dummy fill patterns are used to maintain uniform pattern density, then CMP dishing effects are prevented, but temperature variations increase and device performance deteriorates
Solution Approach 1:
The dummy cell pattern applies local quality by creating regions with different thermal characteristics. The pattern includes dummy diffusion regions with gate patterns that have different thermal absorption and emission properties compared to conventional dummy fills, allowing localized thermal management to reduce overall temperature variations across the die.
Solution Approach 2:
The invention changes the thermal parameters of the dummy fill by introducing gate patterns over dummy diffusion regions. This modifies the thermal absorption and emission characteristics, transforming the dummy fill from a thermal liability into a thermal management tool that reduces temperature variations while maintaining pattern density uniformity.
2Manufacturing precision
If conventional dummy fill patterns are used to ensure uniform oxide removal, then manufacturing uniformity improves, but ON current range between MOS transistors increases
Solution Approach 1:
The dummy cell pattern creates localized regions with gate structures that have different electrical and thermal properties. These local variations are strategically designed to compensate for global temperature gradients, ensuring that MOS transistors across the die experience more uniform operating conditions and thus more consistent ON current characteristics.
Solution Approach 2:
The dummy cell patterns are prepared in advance during the fabrication process, before the actual device operation. By pre-establishing these thermal management structures, the system proactively compensates for anticipated temperature variations, ensuring uniform device performance from the outset rather than attempting to correct variations after they occur.
3Reliability
If RTA processing is used to activate dopants and diffuse dopants, then device activation is achieved, but temperature non-uniformity increases
Solution Approach 1:
The dummy cell patterns act as intermediary elements during RTA processing. These structures serve as thermal mediators that absorb and redistribute thermal energy, creating a more uniform temperature distribution across the die during dopant activation and diffusion processes, thereby reducing temperature non-uniformity while maintaining effective dopant activation.
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 proposed dummy cell pattern significantly reduces temperature variations and unifies the ON current range between MOS transistors, enhancing device performance by minimizing the impact of thermal non-uniformity and pattern density differences.
Implementation Method 1
RTA processes are typically performed by utilizing halogen lamp-based heating equipment or lasers which direct radiation onto a wafer surface in order to change the wafer temperature
Implementation Method 2
Temperature variations within a die are due primarily to differences in thermal absorption and emission caused by different film stacks at different locations
Data Source
AI summary
A dummy cell pattern includes a dummy diffusion pattern disposed within a predetermined region A; a trench isolation pattern encompassing the dummy diffusion pattern in the predetermined region A; a first dummy gate pattern disposed on the dummy diffusion pattern with two ends of the first dummy gate pattern extending above the trench isolation pattern, thereby forming overlapping areas C1 and C2; and a second dummy gate pattern directly on the trench isolation pattern forming an overlapping area C therebetween, wherein the combination of C1, C2 and C is about 5%-20% of the predetermined region A.