Schottky Contact Integration in Power Switching Circuits

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Solution Overview

Problem

Power switching circuits experience dead time periods where charge accumulation leads to voltage spikes exceeding the breakdown voltage of insulated gate field-effect transistors (IGFETs), compromising circuit performance.

Innovation Solution

Integration of Schottky contacts within the existing process flow to reduce charge accumulation during dead time, formed by metal silicide structures contacting N-type epitaxial layers, which help in reducing voltage spikes and improving circuit performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a Schottky contact is formed using a metal silicide structure contacting an N-type epitaxial layer, then charge accumulation is reduced and voltage spikes are minimized, but the device area increases and manufacturing complexity increases

Engineering Contradiction:

Improvevoltage spike reductionVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The Schottky contact structure is merged with the existing power switching device structure. The metal silicide layer is formed over the N-type epitaxial layer in integration with the IGFET structure, combining the Schottky diode function with the power switch device to reduce area while maintaining voltage spike protection

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The Schottky contact structure is nested within the existing device architecture. The metal silicide layer is positioned to contact the N-type epitaxial layer in a configuration that utilizes the existing vertical structure, effectively nesting the Schottky diode within the power switching device footprint

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

Engineering Contradiction:

Improvecharge accumulation reductionVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The Schottky contact formation process is merged with the existing metal silicide formation steps in the manufacturing flow. The same metal silicide deposition and annealing processes used for other contacts are utilized to form the Schottky contact, combining multiple functions into a single process sequence to reduce manufacturing complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The metal silicide formation process is made universal to serve multiple functions: forming ohmic contacts to heavily doped regions and forming the Schottky contact to the N-type epitaxial layer. This multi-functionality reduces the number of separate manufacturing steps while achieving both charge reduction and voltage spike protection

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of manufacture

If the Schottky contact is integrated with minimal changes to the existing process flow, then manufacturing complexity is reduced, but the effectiveness of charge reduction may be compromised

Engineering Contradiction:

Improveprocess integrationVSAvoidcharge reduction effectiveness

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The metal silicide layer is formed with different local properties: in contact with heavily doped regions it forms ohmic contacts, while in contact with the N-type epitaxial layer it forms a Schottky contact. This local differentiation is achieved through selective positioning and doping profiles, maintaining charge reduction effectiveness while using the same overall process flow

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The doping concentration parameter is changed locally to achieve different contact types. The N-type epitaxial layer has a specific doping profile that enables Schottky contact formation, while heavily doped regions have higher doping concentrations for ohmic contacts. This parameter variation within the same process flow maintains manufacturing simplicity while ensuring effective charge reduction

Inventive Principle:

Principle #35Parameter changes

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 Schottky contacts effectively minimize charge accumulation and voltage spikes, enhancing the operational stability and efficiency of power switching circuits by integrating them with minimal changes to the existing process flow and occupying a small area.

Implementation Method 1

a Schottky contact can be formed where a metal silicide structure contacts an N-type epitaxial layer. Current flows vertically from an N+ semiconductor substrate through the N-type epitaxial layer to the metal silicide structure

Methodology Applied

Scientific EffectSchottky contact:

Data Source

PatentUS8928050B2Electronic device including a schottky contact

Publication Date: 2015.01.06 SEMICON COMPONENTS IND LLC

AI summary

An electronic device can include a semiconductor layer having a primary surface, and a Schottky contact comprising a metal-containing member in contact with a horizontally-oriented lightly doped region within the semiconductor layer and lying adjacent to the primary surface. In an embodiment, the metal-containing member lies within a recess in the semiconductor layer and contacts the horizontally-oriented lightly doped region along a sidewall of the recess. In other embodiment, the Schottky contact may not be formed within a recess, and a doped region may be formed within the semiconductor layer under the horizontally-oriented lightly doped region and have a conductivity type opposite the horizontally-oriented lightly doped region. The Schottky contacts can be used in conjunction with power transistors in a switching circuit, such as a high-frequency voltage regulator.