Semiconductor Test Structure for Silicide Spike Detection
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Solution Overview
Problem
The increasing sheet resistance and contact resistance in MOS transistors due to silicide layer formation on semiconductor devices lead to junction breakdown and increased leakage current, degrading the electrical characteristics and reliability of the devices.
Innovation Solution
A test structure is designed with electrically isolated active regions, silicided junction regions, and pads formed on the same level as the semiconductor substrate or metal layer, allowing for the detection of silicide spike by measuring junction leakage current, which includes connecting portions to connect pads to junction regions and wells with different conductivity types to minimize leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicide layer is formed on the source/drain region to reduce contact resistance, then electrical conductivity is improved, but junction breakdown occurs due to silicide spike penetration
Solution Approach 1:
The invention divides the source/drain region into multiple segments with different silicide formation characteristics. By forming silicide layers on separated active regions rather than continuous source/drain regions, the silicide spike penetration is prevented while maintaining low contact resistance in each segment.
Solution Approach 2:
The invention applies different treatments to different regions: silicide layers are formed on specific active regions to reduce contact resistance, while other regions are left without silicide to prevent junction breakdown. This localized approach optimizes both conductivity and reliability.
2Reliability
If a silicide layer is formed on the gate electrode to reduce sheet resistance, then electrical conductivity is improved, but manufacturing complexity increases due to additional process steps
Solution Approach 1:
The invention combines the silicide formation for gate electrode and source/drain regions into a single integrated process step. The silicide layers are formed simultaneously on both gate and source/drain regions through one deposition and annealing cycle, reducing manufacturing complexity while achieving the desired conductivity improvement.
3Measurement precision
If conventional test structures with additional metallization are used to detect silicide spike, then measurement precision is improved, but fabrication cost and process time increase
Solution Approach 1:
The invention extracts the detection function from the main device structure by creating separate test structures that are electrically isolated from functional transistors. These test structures contain only the necessary components (gate electrode, source/drain regions, and measurement contacts) to detect silicide spike, eliminating the need for additional metallization layers in the main device.
Solution Approach 2:
The invention performs silicide spike detection before final device assembly and packaging. By incorporating test structures that can be measured early in the manufacturing process, silicide spike defects are identified promptly, preventing defective devices from proceeding to costly subsequent processing steps.
Data Source
AI summary
A test structure of a semiconductor device with improved test reliability is provided. The test structure includes first and second active regions which are electrically isolated from each other and on which silicided first and second junction regions are formed, respectively, a semiconductor substrate or a well which is formed on lower parts of the first and second junction regions and has a conductivity type different from the first and second junction regions, and first and second pads through which an electrical signal is applied to the first and second junction regions and detected, and which are formed on the same level as a lower part of a metal layer or on the same level as the semiconductor substrate.