Through-Substrate Via Fabrication via Segmented Front-and-Back Processing

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Solution Overview

Problem

The existing methods for through-substrate via (TSV) fabrication in integrated circuit (IC) manufacturing face challenges such as cracking due to thermal expansion mismatch between metal TSVs and the substrate during high-temperature processing, and alignment issues when TSVs are fabricated after IC component fabrication.

Innovation Solution

A method involving front-side processing to form and fill TSV openings with a solid fill material, followed by back-side processing to expose and fill the TSVs with an electrically conductive material, ensuring alignment with metal interconnects and minimizing thermal stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If TSVs are filled with electrically conductive material during front-side processing, then alignment with metal interconnects is improved, but substrate cracking occurs due to thermal expansion mismatch during high-temperature processing

Engineering Contradiction:

Improvealignment precisionVSAvoidsubstrate integrity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The TSV fabrication process is segmented into two independent stages: front-side processing to form openings and apply initial filling, followed by back-side processing to complete the via formation. This segmentation allows alignment to be established during front-side processing while avoiding the thermal stress of high-temperature conductive material filling during this stage, thus preventing substrate cracking.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The method performs preliminary actions of forming TSV openings and applying initial fill material during front-side processing before IC component fabrication. This preliminary alignment is then preserved during subsequent high-temperature processing, and the conductive material filling is completed later during back-side processing after the substrate has been fabricated, avoiding thermal expansion mismatch issues.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If TSVs are fabricated after IC component fabrication, then substrate cracking is avoided, but alignment issues with metal interconnects occur

Engineering Contradiction:

Improvesubstrate integrityVSAvoidalignment precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

An intermediary solid fill material is used during front-side processing to establish the TSV structure and alignment. This intermediary material can withstand high-temperature processing without causing substrate cracking, and serves as a placeholder that is later replaced or supplemented with the final electrically conductive material during back-side processing, thus mediating between the conflicting requirements of early alignment and late conductive filling.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If high-temperature processing is performed with metal-filled TSVs, then IC component fabrication is completed, but substrate cracking occurs due to thermal expansion mismatch

Engineering Contradiction:

Improvefabrication efficiencyVSAvoidsubstrate integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The fabrication process is segmented so that TSV openings are formed and initially filled during front-side processing, but the final conductive material filling is deferred to back-side processing after IC component fabrication is complete. This segmentation ensures that high-temperature processing occurs without metal-filled TSVs that would cause thermal expansion mismatch, while still achieving the desired TSV structure ultimately.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The method changes the physical state and material parameters of the TSV filling process. Instead of using electrically conductive material during high-temperature processing, an electrically insulating solid fill material is used during front-side processing. The transition to conductive material occurs later during back-side processing after the substrate has been fabricated, thus avoiding thermal expansion mismatch while maintaining fabrication efficiency.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8987137B2Method of fabrication of through-substrate vias

Publication Date: 2015.03.24 BELL SEMICONDUCTOR LLC

AI summary

A method of manufacturing a through-substrate-via structure. The method comprises providing a substrate having a front-side and an opposite back-side. A through-substrate via opening is formed in the front-side of the substrate. The through-substrate-via opening does not penetrate an outer surface of the back-side of the substrate. The through-substrate-via opening is filled with a solid fill material. Portions of the substrate from the outer surface of the back-side of the substrate are removed to thereby expose the fill material. At least portions of the exposed fill material are removed to form a back-side through-substrate via opening that traverses an entire thickness of the substrate. The back-side through-substrate via opening is filled with an electrically conductive material.