Integrated Transformer Fabrication via BEOL Merging

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Solution Overview

Problem

The existing methods for fabricating transformers integrated with semiconductor structures are complex, costly, and prone to poor electrical performance due to exposure of metal layers to moisture and particles, requiring additional processes for protection.

Innovation Solution

A method where a primary winding layer and top interconnection metal layer are simultaneously formed on a substrate, followed by a passivation layer with openings, and then a secondary winding layer and bonding pad are formed, with the secondary winding layer being fully covered by a protection layer to prevent moisture and particle exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the transformer is fabricated after completing the metal pad fabrication in BEOL, then the transformer can be integrated with the semiconductor structure, but the processes become complicated and manufacturing cost increases

Engineering Contradiction:

Improveintegration reliabilityVSAvoidfabrication process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the transformer fabrication process with the existing BEOL process by forming the primary winding layer simultaneously with the top interconnection metal layer using the same copper deposition and patterning steps. This integration eliminates separate fabrication sequences and reduces overall process complexity while maintaining reliable integration.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The copper deposition and patterning processes are designed to serve dual functions: creating both the top interconnection metal layers for semiconductor routing and the primary winding layers for transformer functionality. This multi-functionality reduces the number of dedicated process steps and simplifies the overall fabrication sequence.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of manufacture

If the primary winding layer and secondary winding layer are exposed to the environment, then the fabrication process is simplified, but the metal layers are affected by moisture and particles resulting in poor electrical performance

Engineering Contradiction:

Improvefabrication easeVSAvoidelectrical performance reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies a protection layer over the primary winding layer and via structures before completing the secondary winding layer fabrication. This preliminary protective action prevents moisture and particle contamination during subsequent processing steps, ensuring reliable electrical performance without adding significant process complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A thin film protection layer is deposited over the exposed copper structures (primary winding layer and via) to create a barrier against environmental contaminants. This thin film approach provides effective protection while maintaining process simplicity and not significantly increasing manufacturing complexity.

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If a protection layer is formed to entirely cover the primary winding layer and secondary winding layer, then the electrical performance is improved, but another PEP process is required to expose the metal pad increasing process complexity

Engineering Contradiction:

Improveelectrical performanceVSAvoidprocess steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protection layer is strategically deposited only where needed (over the primary winding layer and via structures) before the secondary winding layer is formed, rather than applying a complete coverage layer that would require subsequent removal. This preliminary, targeted approach provides necessary protection without requiring additional PEP processes to expose metal pads.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If the transformer is fabricated in BEOL after metal pad completion, then integration is achieved, but additional processes are required to protect exposed metal layers

Engineering Contradiction:

Improveintegration reliabilityVSAvoidmanufacturing simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The protection layer formation is merged with the existing BEOL process sequence by depositing the protection layer over exposed copper structures before completing the secondary winding layer. This integration provides necessary protection without requiring separate, dedicated protection steps, thereby maintaining manufacturing simplicity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS7367113B2Method for fabricating a transformer integrated with a semiconductor structure

Publication Date: 2008.05.06 MARLIN SEMICON LTD

AI summary

A substrate is provided and a top interconnection metal layer and a primary winding layer are formed thereon. Then a passivation layer having a plurality of via exposed parts of the top interconnection metal layer is formed on the substrate. A secondary winding layer and at least a bonding pad are formed on the passivation layer. The bonding pad electrically connects to the top interconnection metal layer through the via.