Single CMP Gate Contact Integration for SAC Cap Preservation

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Solution Overview

Problem

The existing fabrication methods for semiconductor devices face challenges in preventing shorts between middle of line (MOL) contacts and gates due to thin self-aligned contact (SAC) caps, which are limited by multiple metal chemical mechanical planarization (CMP) steps, leading to non-uniformity and reduced space for SAC cap formation.

Innovation Solution

The process merges two metal CMPs into one, allowing SAC cap formation after the trench silicide process, decoupling gate metal recess from the top, and enabling selective etch/RIE between gate and source/drain regions, thereby increasing SAC cap thickness and reducing shorts by offsetting the replacement metal gate metal top and CA-TS boundary with more insulator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If multiple metal CMP steps are used for gate formation, then manufacturing precision is improved, but SAC cap thickness is reduced and non-uniformity increases

Engineering Contradiction:

Improvegate formation precisionVSAvoidSAC cap thickness

Core Design Contradiction:

Manufacturing precisionVSLength of stationary object

Solution Approach 1:

The patent combines multiple metal CMP steps into a single CMP operation by integrating the gate metal formation with the source/drain contact formation process. This merging eliminates sequential CMP steps, preserving SAC cap thickness while maintaining manufacturing precision through a unified process that forms both gate and contact metals in one planarization cycle.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent performs preliminary patterning and material deposition to prepare the structure before the single CMP step. By pre-configuring the gate and contact regions with appropriate materials and geometries, the single CMP operation can achieve both gate formation and contact planarization without requiring multiple sequential CMP steps that would consume SAC cap thickness.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If multiple metal CMP steps are used, then gate metal recess is controlled, but space for SAC cap formation is reduced

Engineering Contradiction:

Improvegate metal recess controlVSAvoidSAC cap formation space

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

The patent merges the gate metal recess control function with the SAC cap formation process by performing both operations in a single CMP cycle. The unified process simultaneously planarizes the gate metal and preserves the SAC cap, eliminating the space consumption that would occur with multiple sequential CMP steps.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent modifies process parameters including CMP slurry composition, down pressure, and rotation speed to optimize the single CMP step for both gate metal recess control and SAC cap preservation. By adjusting these parameters, the process achieves precise gate formation while maintaining adequate SAC cap thickness and formation space.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If SAC cap thickness is increased, then insulation between MOL contacts and gates is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveinsulation between MOL contacts and gatesVSAvoidfabrication process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple fabrication operations into a single integrated process that forms the gate, source/drain contacts, and preserves the SAC cap in one CMP cycle. This merging reduces the number of process steps and equipment interventions, thereby decreasing manufacturing complexity while enabling thicker SAC caps for improved insulation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single CMP process performs multiple functions simultaneously: it planarizes the gate metal, forms the source/drain contact metals, and preserves the SAC cap structure. This multi-functional approach eliminates the need for separate process steps for each function, reducing overall process complexity while achieving the desired thick SAC cap for enhanced insulation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11309221B2Single metallization scheme for gate, source, and drain contact integration

Publication Date: 2022.04.19 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A technique relates to a semiconductor device. One or more N-type field effect transistor (NFET) gates and one or more P-type field effect transistor (PFET) gates are formed. Source and drain (S/D) contacts are formed, at least one material of the S/D contacts being formed in the PFET gates. Insulating material is deposited as self-aligned caps above the NFET gates and the PFET gates, while the insulating material is also formed as insulator portions adjacent to the S/D contacts. Middle of the line (MOL) contacts are formed above the S/D contacts.