Wafer Processing Layer Stack with Sacrificial Region

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Solution Overview

Problem

The processing of thin wafers is challenging due to the mechanical barrier effect of the rear-side support ring, which impedes liquid flow and leads to inhomogeneous material removal and stringent thickness control requirements, necessitating additional stabilization and protection measures.

Innovation Solution

A method involving a layer stack with a support layer, a useful layer, and a sacrificial region, where the sacrificial region has lower mechanical and chemical resistance than the support and useful layers, allowing for the formation of a depression and channels that facilitate liquid flow and processing without compromising the stiffening effect of the support ring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the edge of the wafer is left intact to form a support ring for mechanical stiffening, then the wafer stability is improved, but the liquid flow is impeded and processing becomes more difficult

Engineering Contradiction:

Improvewafer stabilityVSAvoidprocessing ease

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The support ring is segmented by forming slots or grooves that divide the continuous ring structure into sections. This segmentation allows liquid to flow through the support ring while maintaining the overall mechanical stability of the wafer during processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The support ring is modified locally by creating slots or grooves at specific positions where liquid flow is needed, while maintaining the intact structure in other regions to preserve mechanical stiffening. This localized modification allows simultaneous achievement of stability and processing ease.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If slots are sawn into the support ring to reduce barrier effect, then liquid flow is improved, but the stiffening effect is greatly reduced and damage risk increases

Engineering Contradiction:

Improveliquid flowVSAvoidstiffening effect

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

Instead of completely removing material to create open slots, the invention uses partial action by forming shallow grooves or slots that are sufficient to allow liquid penetration without completely compromising the structural integrity of the support ring.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The invention uses a sacrificial layer deposited on the support ring that can be selectively removed by liquid. This sacrificial layer acts as a temporary barrier that facilitates controlled liquid flow while the underlying support ring maintains its stiffening function throughout the process.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of operation

If a more curved saw blade is used to reduce barrier effect, then liquid flow is improved, but more material must be removed and the distance between chips and support ring must be greater

Engineering Contradiction:

Improveliquid flowVSAvoidmaterial removal

Core Design Contradiction:

Ease of operationVSLoss of substance

Solution Approach 1:

The invention replaces the mechanical approach of using curved saw blades to cut deep slots with a chemical or deposition-based approach. A sacrificial layer is deposited and selectively removed, achieving liquid flow improvement without the material loss and mechanical complexity of deep curved slot cutting.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach enables more efficient processing of thinned regions by liquids, reducing the barrier effect of the support ring, allowing for improved resist coating, development, cleaning, and etching while minimizing the risk of damage to components and providing greater flexibility in process variations.

Implementation Method 1

said sacrificial region having, vis-à-vis a processing fluid, a lower mechanical and/or chemical resistance than the support layer and than the useful layer

Methodology Applied

Scientific EffectSelective etching:

Data Source

PatentUS10796914B2Method for processing a wafer, and layer stack

Publication Date: 2020.10.06 INFINEON TECHNOLOGIES AG

AI summary

In various embodiments, a method for processing a wafer is provided. The method includes forming a layer stack, including a support layer and a useful layer and a sacrificial region between them, said sacrificial region having, vis-à-vis a processing fluid, a lower mechanical and/or chemical resistance than the support layer and than the useful layer. The support layer has a depression, which exposes the sacrificial region. The method further includes forming at least one channel in the exposed sacrificial region by means of the processing fluid. The channel connects the depression to an exterior of the layer stack.