Trench Oxide Film Selective Removal for Semiconductor Voltage Resistance

Solution Overview

Problem

Existing semiconductor device manufacturing methods face challenges in forming a p-type floating region with improved voltage resistance, as the oxide film on trench surfaces interferes with ion implantation, making it difficult to selectively remove the oxide from the bottom surface while maintaining a thick layer on the sides to prevent impurity implantation into the side surfaces.

Innovation Solution

A method involving the formation of a thick oxide film on the side surfaces and a thin or completely removed oxide film on the bottom surface of the trench using reactive ion etching with CF-based gas, oxygen, and argon, allowing deeper ion implantation of conductive impurities through the bottom surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the oxide film is formed to be relatively thick on the side surfaces of the trench, then implantation of p-type impurities into the side surfaces is suppressed, but the oxide film interferes with ion implantation into the semiconductor substrate through the bottom surface

Engineering Contradiction:

Improveprevention of impurity implantation into side surfacesVSAvoiddepth of floating region formation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The oxide film thickness is made non-uniform: thick on the side surfaces to prevent impurity implantation, and thin or completely removed on the bottom surface to allow ion implantation. This local differentiation of oxide film properties resolves the contradiction between protecting side surfaces and enabling bottom surface implantation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The oxide film removal process is segmented by direction: the bottom surface oxide film is selectively removed while the side surface oxide film is preserved. This segmentation allows different regions of the trench to have different oxide film conditions, enabling both side surface protection and bottom surface implantation.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the oxide film is formed to be extremely thin or is not present on the bottom surface of the trench, then ion implantation into the semiconductor substrate is improved, but p-type impurities are implanted into the side surfaces of the trench

Engineering Contradiction:

Improvedepth of floating region formationVSAvoidprevention of impurity implantation into side surfaces

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The oxide film thickness is made non-uniform: thick on the side surfaces to prevent impurity implantation, and thin or completely removed on the bottom surface to allow ion implantation. This local differentiation of oxide film properties resolves the contradiction between protecting side surfaces and enabling bottom surface implantation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The oxide film removal process is segmented by direction: the bottom surface oxide film is selectively removed while the side surface oxide film is preserved. This segmentation allows different regions of the trench to have different oxide film conditions, enabling both side surface protection and bottom surface implantation.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the oxide film is uniformly formed on the side surfaces and the bottom surface of the trench, then the oxide film protects the side surfaces, but it is difficult to selectively remove the oxide film from the bottom surface

Engineering Contradiction:

Improveprotection of side surfacesVSAvoidselective oxide film removal

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

A pad oxide film is formed in advance on all surfaces (side surfaces and bottom surface) before trench formation. This preliminary oxide layer serves as a sacrificial layer that can be selectively removed later, facilitating the selective removal of bottom surface oxide while preserving side surface oxide.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The oxide film thickness is made non-uniform: thick on the side surfaces to prevent impurity implantation, and thin or completely removed on the bottom surface to allow ion implantation. This local differentiation of oxide film properties resolves the contradiction between protecting side surfaces and enabling bottom surface implantation.

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 enables the formation of a p-type floating region with enhanced voltage resistance by preventing impurity implantation into the side surfaces and allowing deeper ion implantation, improving the semiconductor device's properties.

Implementation Method 1

The CF-based gas is gas that supplies radicals, and chemically reacts with oxygen and atoms constituting the semiconductor substrate to produce a reaction product.

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

argon is gas that supplies ions needed for an ion assisted reaction.

Methodology Applied

Scientific EffectIon bombardment: Ion Beam

Implementation Method 3

The reaction product is volatilized from the bottom surface of the trench and then deposits on the oxide film positioned on the side surface of the trench to form a protective film that protects the oxide film.

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 4

ion-implanting conductive impurities into the semiconductor substrate through the bottom surface of the trench after the dry etching

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentUS10263071B2Method of manufacturing semiconductor device

Publication Date: 2019.04.16 TOYOTA JIDOSHA KK

AI summary

A method of manufacturing a semiconductor device includes: forming a trench on a surface of a semiconductor substrate; forming an oxide film on side surfaces and a bottom surface of the trench; removing at least a part of the oxide film by dry etching from the bottom surface of the trench; and ion-implanting conductive impurities into the semiconductor substrate through the bottom surface of the trench after the dry etching. The dry etching is reactive ion etching in which etching gas including fluorocarbon based gas having a carbon atom ring structure, oxygen gas, and argon gas is used.