Trench Gate Semiconductor Source Layout for Gate Oxide Reliability
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Solution Overview
Problem
Conventional semiconductor devices with trench gate field effect transistors face reliability issues due to gate insulating film damage from high-dose impurity ion implantation, leading to leak currents and threshold voltage variations.
Innovation Solution
A semiconductor device design featuring a source region with distinct impurity concentration zones, where a first region with a lower concentration is located on the first surface side of the gate electrode and a second region with a higher concentration is on the second surface side, along with a sidewall insulating film to prevent impurity ion implantation into the gate insulating film, enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-dose impurity ion implantation is performed to form the source region, then the impurity concentration in the source region is sufficiently high for proper transistor operation, but the gate insulating film is damaged leading to leak currents and threshold voltage variations
Solution Approach 1:
The source region is divided into two distinct regions with different impurity concentrations: a first region with lower concentration and a second region with higher concentration. This segmentation allows the higher concentration region to be positioned away from the gate electrode, providing sufficient overall impurity content while protecting the gate insulating film from damage.
Solution Approach 2:
Different regions of the source are given different impurity concentrations tailored to their specific functional requirements. The first region (lower concentration) is positioned closer to the gate electrode to minimize damage, while the second region (higher concentration) is positioned farther away to ensure proper transistor operation with sufficient impurity content.
2Ease of operation
If uniform high concentration impurity is distributed throughout the source region, then proper transistor operation is achieved, but threshold voltage variations and reliability issues occur due to gate insulating film damage
Solution Approach 1:
The source region employs non-uniform impurity distribution with two distinct concentration zones. The lower concentration first region near the gate electrode minimizes threshold voltage variations, while the higher concentration second region ensures proper transistor operation, achieving both ease of operation and reliability.
3Productivity
If the source region is formed with sufficient impurity concentration for proper operation, then transistor performance is adequate, but implantation damage to the gate insulating film causes leak currents
Solution Approach 1:
By segmenting the source region into two concentration zones, the invention achieves sufficient overall impurity content for proper transistor performance while positioning the higher concentration region away from the gate electrode, thereby preventing implantation damage and eliminating leak currents.
Solution Approach 2:
The differentiated impurity concentrations in different source regions allow optimal transistor performance to be achieved while localizing the higher concentration away from the gate electrode, preventing the harmful effect of implantation damage and associated leak currents.
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 design improves the reliability of the gate insulating film by reducing implantation damage and maintaining long-term performance while preventing threshold voltage fluctuations.
Implementation Method 1
a gate insulating film interposed therebetween
Implementation Method 2
high-dose impurity ion implantation
Data Source
AI summary
A semiconductor substrate has a first surface, a second surface opposing the first surface, and a trench extending from the second surface toward the first surface. A gate electrode is arranged in the trench and has a lower end located at a bottom of the trench and an upper end opposing the lower end. The upper end is located in a first surface side with respect to the second surface. An n-type source region has a first region having a first concentration, and a second region having a second concentration higher than the first concentration. The first region has a portion located in the first surface side with respect to an upper end of the gate electrode. The second region is located in the second surface side with respect to the upper end of the gate electrode.