Plasma Doping for Fin-Shaped FET Impurity Uniformity

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Solution Overview

Problem

Conventional methods for producing fin-shaped FETs fail to achieve desirable transistor characteristics due to uneven impurity region implantation doses and junction depths, leading to localized current flow and suboptimal performance.

Innovation Solution

A semiconductor device and method where the implantation dose in the side portion of the fin-shaped semiconductor region is made substantially equal to or greater than that in the upper portion, using a plasma doping method with specific conditions to control the sheet resistance and resistivity, ensuring the side impurity region has a low sheet resistance comparable to the upper region.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional ion implantation methods are used to form impurity regions in fin-shaped semiconductor regions, then the upper portion receives sufficient impurity doping, but the side portion receives insufficient doping resulting in uneven implantation doses and poor transistor characteristics

Engineering Contradiction:

Improveuniformity of impurity region implantation doseVSAvoidtransistor characteristics

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies local quality by using plasma doping to selectively enhance impurity concentration in the side portions of fin-shaped semiconductor regions. The plasma doping process targets specific areas (side surfaces) that require additional doping, creating non-uniform local properties that compensate for the insufficient side portion doping from conventional ion implantation. This resolves the contradiction by making the doping uniformity acceptable through localized enhancement where needed.

Inventive Principle:

Principle #3Local quality

2Area of moving object

If the aspect ratio of fin-shaped semiconductor regions is increased to reduce substrate area, then device integration density improves, but uneven current distribution and performance degradation occur due to insufficient side portion doping

Engineering Contradiction:

Improvesubstrate area occupied by transistorVSAvoidtransistor performance

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

By applying plasma doping specifically to enhance side portion impurity concentration, the patent enables higher aspect ratios to be used effectively. The local enhancement of side portion doping ensures that even with increased height (higher aspect ratio), the current distribution remains uniform, allowing substrate area reduction without sacrificing transistor performance.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If plasma doping is performed with high implantation dose to ensure sufficient doping in side portions, then side impurity region achieves low sheet resistance, but the upper portion receives excessive doping

Engineering Contradiction:

Improvesheet resistance of side impurity regionVSAvoidimpurity concentration in upper portion

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The patent segments the doping process into two distinct stages: conventional ion implantation for the upper portion and plasma doping for the side portions. This segmentation allows each method to be optimized for its target area, with plasma doping parameters specifically tuned to enhance side portion doping without significantly affecting the already adequately doped upper portion, thus resolving the dose distribution contradiction.

Inventive Principle:

Principle #1Segmentation

4Productivity

If conventional doping methods are used, then the doping process is simple and fast, but the junction depth varies unevenly across the fin structure leading to localized current flow

Engineering Contradiction:

Improvedoping process efficiencyVSAvoiduniformity of junction depth

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent maintains high productivity by using plasma doping, which is inherently faster and more uniform than conventional ion implantation for three-dimensional structures. The plasma doping process naturally provides more uniform junction depth across both upper and side portions of the fin structure, eliminating the need for complex multi-step ion implantation sequences while maintaining or improving doping uniformity.

Inventive Principle:

Principle #3Local quality

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 improves transistor characteristics by ensuring uniform current distribution across the fin-shaped FET, enhancing performance and reducing degradation, even with increased aspect ratios.

Implementation Method 1

a plasma doping method is carried out under a first condition such that an implantation dose is equal to a first dose, and then a plasma doping method is carried out under a second condition such that the implantation dose is equal to a second dose smaller than the first dose

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS8105926B2Method for producing a semiconductor device by plasma doping a semiconductor region to form an impurity region

Publication Date: 2012.01.31 GODO KAISHA IP BRIDGE 1

AI summary

A semiconductor region having an upper surface and a side surface is formed on a substrate. A first impurity region is formed in an upper portion of the semiconductor region. A second impurity region is formed in a side portion of the semiconductor region. The resistivity of the second impurity region is substantially equal to or smaller than that of the first impurity region.