Angled Implant Shadowing for Transistor Gate Doping

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Solution Overview

Problem

Conventional transistor fabrication methods face challenges in achieving sufficient gate doping without excessive doping in source/drain regions, leading to issues like poly depletion and punchthrough, which are difficult to address without additional masking steps.

Innovation Solution

A method involving the formation of a shadowing structure to block dopant from an angled implant, allowing for sufficient gate doping while preventing excessive doping in the source/drain regions, using a separate source/drain implant process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If additional masking steps are introduced to control doping distribution, then doping precision is improved, but manufacturing complexity and process time increase

Engineering Contradiction:

Improvedoping distribution controlVSAvoidmasking steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent utilizes the existing lateral offset geometry of the gate structure relative to the active area as a self-formed shadowing mask. The gate structure itself blocks the dopant flux during the angled implant, eliminating the need for additional external masking steps. This self-service approach achieves precise doping distribution control while avoiding the added manufacturing complexity and process time associated with traditional masking methods.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent transitions from planar (2D) doping to angled (3D) doping by performing the implant at an angle rather than perpendicular to the substrate. This dimensional change exploits the lateral offset between the gate structure and active area, allowing the gate to naturally shadow the active area during doping. This approach achieves precise doping control without requiring additional masking layers or steps.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 effectively reduces poly depletion in transistors by ensuring adequate gate doping without adversely affecting the source/drain regions, improving transistor performance without requiring additional masking steps.

Implementation Method 1

performing an angled implant into the gate structure, wherein the shadowing structure substantially blocks dopant from the angled implant from implanting into the active area

Methodology Applied

Scientific EffectShadowing: Shadow

Implementation Method 2

performing an angled implant into the gate structure

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Implementation Method 3

performing a source/drain implant into the gate structure and the active area

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentUS7727838B2Method to improve transistor Tox using high-angle implants with no additional masks

Publication Date: 2010.06.01 TEXAS INSTRUMENTS INC

AI summary

A method of forming an integrated circuit includes forming a gate structure over a semiconductor body, and forming a shadowing structure over the semiconductor body laterally spaced from the gate structure, thereby defining an active area in the semiconductor body therebetween. The method further includes performing an angled implant into the gate structure, wherein the shadowing structure substantially blocks dopant from the angled implant from implanting into the active area, and performing a source/drain implant into the gate structure and the active area.