Double Diffusion Break Strain Engineering for CMOS Carrier Mobility
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Solution Overview
Problem
In CMOS integrated circuits, the use of double diffusion breaks (DDBs) and single diffusion breaks (SDBs) in semiconductor diffusion regions leads to either reduced carrier mobility in P-type or N-type semiconductor channels due to induced strain, which can degrade the performance of transistors like FinFETs.
Innovation Solution
The strategic placement of DDBs and SDBs in different diffusion regions allows for the induction of channel strain to enhance carrier mobility in one type of semiconductor device while minimizing its impact on the other type, by forming trench isolation structures and using dummy gates to create these breaks in specific regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a double diffusion break (DDB) is formed in a diffusion region, then electrical isolation between circuits is improved, but carrier mobility in the semiconductor channel is reduced due to induced strain
Solution Approach 1:
The patent applies different diffusion break configurations (DDB vs SDB) to different diffusion regions based on the transistor type. Specifically, DDB is used in N-type diffusion regions while SDB is used in P-type diffusion regions, or vice versa. This local differentiation allows each region to have optimized properties: DDB provides better isolation for N-type devices while SDB maintains carrier mobility for P-type devices, resolving the contradiction between isolation and mobility requirements.
2Manufacturing precision
If strain is induced in the semiconductor channel to increase carrier mobility, then device performance is improved, but the same strain degrades performance in the opposite type of device
Solution Approach 1:
The patent implements local quality by applying different strain conditions to different diffusion regions. N-type diffusion regions are subjected to tensile strain through DDB configuration to enhance electron mobility, while P-type diffusion regions use SDB configuration to avoid excessive strain that would harm hole mobility. This selective strain application resolves the contradiction by optimizing each device type's performance independently.
Solution Approach 2:
The patent inverts the conventional approach of applying uniform strain to all devices. Instead of applying the same strain configuration to both N-type and P-type devices, it applies opposite strain configurations (DDB for one type, SDB for the other). This inversion strategy allows each device type to experience strain conditions optimized for its specific carrier type, resolving the performance degradation issue.
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 effectively increases carrier mobility in semiconductor channels of either P-type or N-type devices while avoiding degradation in the other type, thereby improving the performance of CMOS circuits by optimizing strain effects.
Implementation Method 1
If the dielectric material 216 expands during the fabrication of the circuit 200, the dielectric material 216 will apply a compressive stress SC to the substrate 210 that will be induced as a compressive strain in the P-type semiconductor channel structures 212P(1)-212P(4) and N-type semiconductor channel structures 210N(1)-210N(4). Compressive strain may improve carrier mobility in the N-type semiconductor channel structures 212N(1)-212N(4), but reduce carrier mobility in the P-type semiconductor channel structures 212P(1)-212P(4).
Data Source
AI summary
Aspects disclosed herein include circuits employing a double diffusion break (DDB) and a single diffusion break (SDB) in different type diffusion regions, and related fabrication methods are disclosed. In exemplary aspects disclosed herein, either a DDB or a SDB is formed in the N-type diffusion region(s) and the opposing type diffusion, either a SDB or DDB, is formed in the P-type diffusion region(s). Forming different diffusion breaks between a DDB and a SDB in different diffusion regions of the circuit can be employed to induce channel strain that will increase carrier mobility of either P-type or N-type semiconductor devices formed in respective P-type or N-type diffusion region(s), while avoiding or reducing such induced channel strain in either P-type or N-type semiconductor devices formed in respective P- or N-type diffusion region(s) that may degrade carrier mobility.