High-Voltage Transistor Graded Dopant Profile for Kirk Effect Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-voltage transistors experience increased body current due to the Kirk effect, limiting their safe operating area, and existing methods to reduce this effect are complex and difficult to control, requiring additional processing steps or specific production processes.
Innovation Solution
A high-voltage transistor design featuring doped wells with a graded dopant concentration increasing toward the drain contact, utilizing a substrate with a top-side isolation area and a gate dielectric, where the dopant concentration is controlled through masked implantation and diffusion, allowing for a simple and economical production process without additional masks or complex processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dopant concentration is increased toward the drain contact to reduce the Kirk effect, then the body current is reduced and safe operating area is improved, but the manufacturing process becomes more complex and difficult to control
Solution Approach 1:
The patent applies preliminary action by forming the isolation area before dopant implantation. This pre-formed isolation structure serves as a mask during subsequent dopant implantation, automatically creating the desired graded dopant profile without requiring additional masking steps. The isolation area is prepared in advance to guide the dopant distribution toward the drain contact, reducing body current while simplifying the overall manufacturing process.
Solution Approach 2:
The isolation area serves a dual function: it provides electrical isolation and simultaneously acts as a self-aligning mask for dopant implantation. This self-service approach eliminates the need for separate masking processes, as the isolation structure itself guides the dopant distribution. The system uses its own structural elements to control the doping profile, reducing process complexity while achieving the desired graded concentration toward the drain.
2Reliability
If a graded dopant profile is created to reduce body current, then the Kirk effect is mitigated, but additional processing steps and field oxide are required
Solution Approach 1:
The isolation area performs multiple functions simultaneously: it provides electrical isolation between devices, serves as a mask for dopant implantation, and defines the region for graded dopant concentration. This multi-functionality eliminates the need for separate field oxide structures and additional processing steps, as the isolation area accomplishes what would otherwise require dedicated components and processes.
Solution Approach 2:
The patent merges the isolation function and the dopant masking function into a single structural element. Instead of having separate isolation regions and separate masking layers, the isolation area itself is used as the masking structure during implantation. This consolidation reduces the number of processing steps and simplifies manufacturing while achieving both electrical isolation and controlled dopant distribution.
3Productivity
If the dopant concentration increases toward the drain, then current load capacity is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating a spatially varying dopant concentration profile within the drift region. The dopant concentration is locally adjusted to increase toward the drain contact, with different concentrations at different positions along the drift region. This localized variation optimizes current load capacity near the drain while maintaining appropriate characteristics elsewhere, achieving enhanced performance without requiring uniform high precision throughout the entire structure.
Solution Approach 2:
The patent changes the dopant concentration parameter as a function of position, creating a graded profile rather than a uniform distribution. By varying this critical parameter spatially, the device achieves enhanced current load capacity where needed (near the drain) while maintaining manufacturability through the self-aligning mask approach, which naturally produces the desired parameter variation without requiring extreme precision control.
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 solution effectively reduces body current, enhances current load capacity, and increases the safe operating area of high-voltage transistors, improving their performance in standard processes with minimal thermal budget, especially in sub-micron CMOS processes.
Implementation Method 1
the dopant concentration is controlled through masked implantation and diffusion
Implementation Method 2
the dopant concentration is controlled through masked implantation and diffusion
Implementation Method 3
a gate electrode arranged on the gate dielectric, wherein this gate electrode forms a field plate on the isolation area
Data Source
AI summary
An isolation area (10) is provided over a drift region (12) with a spacing (d) to a contact area (4) provided for a drain connection (D). The isolation area is used as an implantation mask, in order to produce a dopant profile of the drift region in which the dopant concentration increases toward the drain. The implantation of the dopant can be performed instead before the production of the isolation area, and the later production of the isolation area (10) changes the dopant profile also in a way that the dopant concentration increases toward the drain.