Microelectronic Packaging with Diffusion Barrier Layer

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Solution Overview

Problem

Existing microelectronic device packaging technologies face challenges in achieving hermeticity at specific pressure ranges (above 100 mbar or less than 10^-3 mbar) without high temperatures and with controlled gas composition, and often result in RF coupling or short circuits due to metallic sealing layers.

Innovation Solution

A packaging structure using a non-metallic diffusion barrier layer with metallic plugging of release holes, avoiding diffusion paths and parasitic coupling effects, and allowing for a controlled atmosphere compatible with various microelectronic devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a metallic sealing layer is used to achieve hermeticity, then gas permeability is reduced, but RF coupling and short circuits occur

Engineering Contradiction:

ImprovehermeticityVSAvoidRF coupling

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The sealing structure is segmented into two functional parts: a non-metallic diffusion barrier layer that provides hermeticity and blocks gas permeation, and a metallic plugging material that fills the release holes. This segmentation allows each material to perform its optimal function without the harmful effects of a complete metallic sealing layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sealing structure has different material properties at different locations: the diffusion barrier layer uses non-metallic material (such as oxide or nitride) to prevent RF coupling, while the release hole plugs use metallic material to provide hermetic sealing. This local differentiation of material quality resolves the contradiction between hermeticity and RF coupling.

Inventive Principle:

Principle #3Local quality

2Reliability

If high temperature curing is used to reflow PSG layer for hermetic sealing, then gas permeability is reduced, but thermal budget is exceeded for some MEMS devices

Engineering Contradiction:

ImprovehermeticityVSAvoidthermal budget

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The sealing approach changes from high-temperature thermal curing (900°C for PSG) to low-temperature deposition processes (such as PECVD or sputtering) that form diffusion barrier layers at temperatures compatible with MEMS thermal budgets, while still achieving hermetic sealing through the barrier layer's intrinsic low permeability properties.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If polymer layer is deposited to close release holes, then manufacturing is simplified, but gas permeability increases preventing low pressure

Engineering Contradiction:

Improvesealing processVSAvoidpressure control

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The sealing structure uses a composite approach combining a non-metallic diffusion barrier layer (such as oxide or nitride) with metallic plugging material. This composite structure provides both ease of manufacture through standard deposition processes and low gas permeability to enable pressure control, overcoming the limitations of polymer-only sealing.

Inventive Principle:

Principle #40Composite materials

4Reliability

If cap report technology is used with controlled atmosphere bonding, then hermeticity is achieved, but high temperature and large area are required

Engineering Contradiction:

ImprovehermeticityVSAvoidbonding temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The invention extracts the hermetic sealing function from the bonding process itself. Instead of relying on high-temperature bonding to create hermeticity, the patent uses a separate diffusion barrier layer deposited on the cap and support structures, allowing hermetic sealing to be achieved independently of the bonding temperature and area.

Inventive Principle:

Principle #2Taking out (Extraction)

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

The solution provides high reliability hermetic cavities with controlled atmospheres, avoiding RF coupling and short circuits, and is compatible with a wide range of microelectronic devices, including MEMS and RF switches, while maintaining low package height and cost.

Implementation Method 1

a cap provided with a diffusion barrier layer improving the hermeticity, or tightness, of the sealing

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

metallic plugging of release holes, avoiding diffusion paths

Methodology Applied

Scientific EffectPhysical plugging: Physical Containment

Data Source

PatentEP3077326B1Packaging structure of a microelectronic device having a hermeticity improved by a diffusion barrier layer

Publication Date: 2022.10.26 TDK ELECTRONICS AG

Figure 1~3
Figure 4A~4C
Figure 4D~5

AI summary

Packaging structure (100) comprising: -at least one hermetically sealed cavity (102) in which at least one microelectronic device (104) is arranged, the cavity being formed between a substrate (106) and at least one cap layer (108) through which at least one release hole (110) is formed, -at least one portion of metallic material (120) arranged on the cap layer and hermetically plugging the release hole, -at least one diffusion barrier layer (114) comprising at least one non- metallic material, arranged on the cap layer and forming a diffusion barrier against an atmosphere outside the cavity at least around the release hole.