Trench Gate Semiconductor Doping Profile for Threshold Voltage Stability

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Solution Overview

Problem

Conventional semiconductor devices with a trench gate structure experience significant fluctuations in threshold voltage due to variations in the depth of the impurity region, which affects the effective concentration and electrical performance.

Innovation Solution

A semiconductor device with a trench gate structure featuring a base layer with a specific impurity concentration profile, including a low concentration peak and two high concentration peaks, and an impurity region boundary positioned between these peaks, is designed to minimize the impact of depth variations in the impurity region, thereby stabilizing the threshold voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the depth of the impurity region is varied to adjust device characteristics, then the effective concentration can be tuned, but the threshold voltage becomes unstable and fluctuates

Engineering Contradiction:

Improveadjustment of effective concentrationVSAvoidstability of threshold voltage

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The base layer is designed with a specific impurity concentration profile featuring two peak positions at different depths. By positioning the impurity region boundary between these two peaks, the system creates a region where small variations in boundary depth do not significantly change the effective concentration, thus stabilizing the threshold voltage while still allowing for adjustment through larger boundary position changes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The base layer exhibits non-uniform impurity distribution with high concentration regions (peaks) and intermediate concentration regions. The impurity region boundary is strategically placed in an intermediate zone between peaks, where the local impurity concentration gradient provides insensitivity to depth variations, enabling stable threshold voltage despite manufacturing tolerances.

Inventive Principle:

Principle #3Local quality

2Reliability

If the impurity region depth is precisely controlled to maintain stable threshold voltage, then threshold voltage stability is improved, but manufacturing complexity and difficulty increase

Engineering Contradiction:

Improvestability of threshold voltageVSAvoidcomplexity of impurity region depth control

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of requiring precise control of the impurity region boundary depth, the invention changes the parameter being controlled to the impurity concentration profile shape of the base layer. By creating a profile with two distinct peaks, the system transforms a precision-depth-control problem into a more robust profile-shaping problem, where the boundary can be placed in a region of reduced sensitivity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The base layer is pre-engineered with a specific double-peak impurity concentration profile before forming the impurity region. This beforehand preparation creates a cushioning effect where the inherent structure of the base layer absorbs and compensates for variations in impurity region depth, reducing the need for ultra-precise manufacturing control.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the impurity region boundary is positioned to avoid high concentration areas, then threshold voltage stability is improved, but the effective concentration adjustment range is reduced

Engineering Contradiction:

Improvestability of threshold voltageVSAvoidrange of effective concentration adjustment

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The base layer is designed with spatially varying impurity concentration, creating distinct zones: high concentration peak regions and intermediate concentration regions. The impurity region boundary is positioned in the intermediate zone, which provides a compromise location that avoids the high sensitivity of peak regions while still allowing effective concentration modulation through boundary position adjustments.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of adjusting effective concentration solely by changing impurity region depth in one dimension, the invention utilizes the depth dimension of the base layer's impurity concentration profile. By positioning the boundary between two peaks in the depth dimension, the system creates a two-dimensional design space (profile shape + boundary position) that provides both stability and adjustability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS12622026B2Semiconductor device and method for manufacturing the same

Publication Date: 2026.05.05 DENSO CORP

AI summary

A base layer has a low concentration peak at a position between a portion located at a same depth as a lower end portion of a gate electrode and a portion located at a same depth as an upper end portion of the gate electrode in a concentration profile of an impurity concentration in a depth direction. An impurity region has a boundary with the base layer in the depth direction at a position between a first peak position, at which the impurity concentration of the base layer is maximum between the portion located at the same depth as the lower end portion and the position of the low concentration peak, and a second peak position, at which the impurity concentration of the base layer is maximum between the position of the low concentration peak and the portion located at the same depth as the upper end portion.