Polysilicon Resistor Formation in Replacement Metal Gate Process

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Solution Overview

Problem

In semiconductor manufacturing, the replacement metal gate (RMG) process typically removes polysilicon from resistor areas, preventing the formation of polysilicon resistors, which have higher resistive properties and can operate at slower speeds compared to metal gates.

Innovation Solution

A method is developed to form polysilicon resistors during the RMG process by selectively removing polysilicon layers from gate stack portions while preserving polysilicon in resistor areas, using etching and ashing processes, and subsequent metal deposition and chemical mechanical polishing to planarize the substrate, allowing for the integration of polysilicon resistors with metal gates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polysilicon is removed from resistor areas during RMG process, then metal gates can be formed on transistor areas, but polysilicon resistors cannot be formed

Engineering Contradiction:

Improvegate performanceVSAvoidresistor formation capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The substrate is divided into distinct transistor areas and resistor areas. Photoresist is selectively applied to cover resistor areas during the polysilicon removal process, ensuring that polysilicon is removed only from transistor gate areas while being preserved in resistor areas. This segmentation allows both metal gates and polysilicon resistors to coexist in the same device.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the substrate are given different treatments: transistor areas undergo complete polysilicon removal and metal gate formation, while resistor areas maintain their polysilicon layers. The photoresist masking enables local differentiation, allowing each region to have the appropriate material composition for its intended function.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If polysilicon is preserved in resistor areas, then polysilicon resistors can be formed, but metal gate formation is prevented in those areas

Engineering Contradiction:

Improveresistor formationVSAvoidgate structure

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Photoresist serves as an intermediary masking layer that temporarily protects resistor areas during the polysilicon removal process. This intermediary enables selective removal, allowing the process to differentiate between transistor areas (where polysilicon should be removed) and resistor areas (where polysilicon should be preserved).

Inventive Principle:

Principle #24Intermediary (Mediator)

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 polysilicon resistors within semiconductor devices, maintaining high resistive properties while integrating with metal gates, enhancing operational speed and efficiency.

Implementation Method 1

removing respective first portions of the first and second polysilicon layers from the first and second gate stack portions

Methodology Applied

Scientific EffectChemical etching:

Implementation Method 2

removing respective remaining portions of the first and second polysilicon layers from the first and second gate stack portions may comprise performing an ashing process

Methodology Applied

Scientific EffectAashing:

Implementation Method 3

depositing a first metal on the high-K dielectric layer

Methodology Applied

Scientific EffectPhysical vapor deposition:

Implementation Method 4

performing a chemical mechanical polishing to remove the high-K dielectric material, the first metal and the second metal from a top surface of the substrate, and to planarize the top surface of the substrate

Methodology Applied

Scientific EffectChemical mechanical polishing:

Data Source

PatentUS8685827B2Method of forming polysilicon resistor during replacement metal gate process and semiconductor device having same

Publication Date: 2014.04.01 SAMSUNG ELECTRONICS CO LTD

AI summary

A method for manufacturing a semiconductor device, comprising forming a first gate stack portion on a substrate, the first gate stack portion including a first gate oxide layer and a first polysilicon layer on the first gate oxide layer, forming a second gate stack portion on the substrate, the second gate stack portion including a second gate oxide layer and a second polysilicon layer on the second gate oxide layer, forming a resistor portion on the substrate, the resistor portion including a third gate oxide layer and a third polysilicon layer on the third gate oxide layer, covering the resistor portion with a photoresist, removing respective first portions of the first and second polysilicon layers from the first and second gate stack portions, removing the photoresist from the resistor portion, and after removing the photoresist from the resistor portion, removing respective remaining portions of the first and second polysilicon layers from the first and second gate stack portions.