Silicon Interposer Thinning with Temporary Carrier

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Solution Overview

Problem

Current processes for forming 3D IC chip packages with vertically stacked chips and direct electrical interconnects face challenges in minimizing the height of interposers to achieve thinner die packages with efficient TSV integration, as existing methods are inefficient and may damage existing metallization structures during thinning.

Innovation Solution

A method involving a silicon interposer thinning process where TSVs are formed after front side RDL metallization, using a temporary carrier and mechanical or chemical-mechanical grinding to reduce substrate thickness without interfering with existing metallization, followed by back side RDL interconnect formation to create a thin, efficient semiconductor structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If mechanical or chemical-mechanical grinding is used to thin the substrate, then the substrate thickness is reduced, but the existing metallization structures may be damaged

Engineering Contradiction:

Improvesubstrate thicknessVSAvoidmetallization structure integrity

Core Design Contradiction:

Length of stationary objectVSReliability

Solution Approach 1:

A temporary carrier is attached to the front side of the substrate before the thinning process. This carrier serves as a protective support structure that prevents damage to the metallization structures during mechanical or chemical-mechanical grinding. The carrier is removed after thinning is complete, having fulfilled its protective function throughout the critical thinning operation.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If TSVs are formed before substrate thinning, then the TSV formation process is simplified, but the substrate cannot be thinned to the desired thickness without damaging existing structures

Engineering Contradiction:

ImproveTSV formation processVSAvoidsubstrate thickness

Core Design Contradiction:

Ease of manufactureVSLength of stationary object

Solution Approach 1:

The conventional sequence of operations is inverted: instead of forming TSVs before thinning the substrate, the substrate is thinned first using mechanical or chemical-mechanical grinding with a temporary carrier for protection. After thinning, TSVs are formed through the thinned substrate. This reversed sequence enables achievement of the desired thin substrate thickness while maintaining processability for subsequent TSV formation.

Inventive Principle:

Principle #13The other way round (Inversion)

3Length of stationary object

If the interposer is made thinner to minimize package height, then the die package form factor is reduced, but the process complexity increases

Engineering Contradiction:

Improveinterposer thicknessVSAvoidfabrication process complexity

Core Design Contradiction:

Length of stationary objectVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The temporary carrier acts as an intermediary element that facilitates the thinning process. It provides mechanical support and protection during grinding operations, enabling the substrate to be thinned to very thin dimensions without damage. The carrier is temporarily introduced, performs its mediating function during thinning, and is then removed, having enabled the achievement of thin interposer dimensions.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 results in a thinner semiconductor structure with reduced TSV protrusion costs and enhanced reliability, allowing for more compact die packages with improved electrical connectivity and reduced risk of damaging existing metallization.

Implementation Method 1

A temporary carrier may be attached to a front side of the substrate prior to thinning the second portion of the substrate

Methodology Applied

Scientific EffectMechanical support:

Implementation Method 2

thinning the second portion of the substrate using a mechanical or chemical-mechanical process

Methodology Applied

Scientific EffectMechanical grinding: Abrasion

Data Source

PatentUS8975183B2Process for forming semiconductor structure

Publication Date: 2015.03.10 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method for forming a semiconductor structure. A semiconductor substrate including a plurality of dies mounted thereon is provided. The substrate includes a first portion proximate to the dies and a second portion distal to the dies. In some embodiments, the first portion may include front side metallization. The second portion of the substrate is thinned and a plurality of conductive through substrate vias (TSVs) is formed in the second portion of the substrate after the thinning operation. Prior to thinning, the second portion may not contain metallization. In one embodiment, the substrate may be a silicon interposer. Further back side metallization may be formed to electrically connect the TSVs to other packaging substrates or printed circuit boards.