Segmented Metal Contact Structure for IC Metallization

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Solution Overview

Problem

Integrated circuits face challenges in forming high aspect ratio metal contacts that reduce capacitance and contact resistance, while ensuring device reliability and signal performance, particularly as feature sizes shrink and operational speeds increase.

Innovation Solution

The implementation of conductive interconnect structures with multiple substructures at different levels, where each substructure is electrically coupled and strategically sized to maintain a consistent volume of conductive material, optimizing contact configuration and metallization layers to address the need for reduced capacitance and improved signal performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the ILD/PMD layer thickness is increased to reduce capacitance, then capacitance between metallization layer and active region is reduced, but high aspect ratio contacts are required which increase contact resistance and open yield

Engineering Contradiction:

ImprovecapacitanceVSAvoidcontact reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The contact structure is divided into multiple segments: a first contact portion extending through the thicker ILD/PMD layer to the active region, and a second contact portion extending through the metallization layer to the gate electrode. This segmentation allows each portion to be optimized independently, maintaining reliability while achieving the required thickness for capacitance reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The contact structure transitions from a simple vertical contact to a multi-dimensional configuration with portions at different levels and orientations. The first contact portion has a first orientation relative to the substrate, while the second contact portion has a second orientation, creating a three-dimensional contact architecture that addresses both capacitance and reliability requirements.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Speed

If feature sizes are reduced to increase operational speed, then operational speed increases, but contact resistance and open yield increase due to higher aspect ratios

Engineering Contradiction:

Improveoperational speedVSAvoidcontact reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The contact is segmented into multiple portions that can be formed using different process conditions optimized for each segment. This allows the first contact portion to be optimized for penetrating the thicker dielectric layer while the second contact portion is optimized for connecting to the metallization layer, maintaining reliability despite reduced feature sizes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the contact structure have different local properties: the first contact portion has dimensions and material characteristics optimized for penetrating the ILD/PMD layer, while the second contact portion has properties optimized for connecting to the metallization layer. This local optimization maintains reliability across the entire contact structure despite overall feature size reduction.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If high aspect ratio contacts are formed to achieve thicker ILD/PMD layer, then capacitance is reduced, but contact resistance and open yield increase

Engineering Contradiction:

ImprovecapacitanceVSAvoidcontact formation difficulty

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The contact formation process is segmented into multiple steps, each forming a specific contact portion under optimized conditions. This allows the first contact portion to be formed with parameters optimized for penetrating the dielectric layer, while the second contact portion is formed with parameters optimized for metallization layer connection, making the overall process easier to manufacture despite the thick ILD/PMD layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first contact portion is formed in advance through the ILD/PMD layer before forming the second contact portion through the metallization layer. This preliminary action creates a prepared structure that guides subsequent processing, making the formation of high aspect ratio contacts through thick dielectric layers more manageable and manufacturable.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10074606B2Via, trench or contact structure in the metallization, prematallization dielectric or interlevel dielectric layers of an integrated circuit

Publication Date: 2018.09.11 STMICROELECTRONICS INT NV

AI summary

A semiconductor substrate includes a doped region. A premetallization dielectric layer extends over the semiconductor substrate. A first metallization layer is disposed on a top surface of the premetallization dielectric layer. A metal contact extends from the first metallization layer to the doped region. The premetallization dielectric layer includes sub-layers, and the first metal contact is formed by sub-contacts, each sub-contact formed in one of the sub-layers. Each first sub-contact has a width and a length, wherein the lengths of the sub-contacts forming the metal contact are all different from each other.