TSV Testing via Conductive Adhesive Interposer

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Solution Overview

Problem

Existing methods for testing through-silicon vias (TSVs) in interposers are impractical and can damage thinned silicon bodies, as they require probing both sides simultaneously, which is not feasible for interposers with thicknesses of 25 μm to 100 μm.

Innovation Solution

A method involving the formation of conductive adhesive layers on the front-side of the interposer to couple contacts, attaching a carrier for support during thinning and testing, and forming contact arrays on both sides to test conductivity between contacts, allowing for mechanical simplification and reduced risk of damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If both front-side and back-side contacts are probed simultaneously to test TSV continuity, then testing completeness is improved, but the risk of damaging the thinned substrate increases

Engineering Contradiction:

Improvetesting completenessVSAvoidsubstrate damage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention extracts the front-side probing operation from the testing process by using conductive adhesive to electrically couple the front-side contacts together. This eliminates the need to probe the front-side while maintaining testing completeness, as only back-side contacts need to be probed to detect TSV opens and front-side contact failures.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The conductive adhesive serves as an intermediary that electrically connects the front-side contact array elements together. This mediator allows the testing system to infer the status of front-side contacts and TSVs by measuring electrical properties at the back-side contacts only, without physically probing the fragile front-side surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If the substrate is thinned to less than 100 μm to enable fine-pitch interconnections, then interposer performance is improved, but mechanical strength during testing deteriorates

Engineering Contradiction:

Improveinterconnection precisionVSAvoidsubstrate mechanical strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The invention performs preliminary action by depositing the conductive adhesive layer on the front-side contact array before the thinning and testing operations. This preliminary electrical coupling of front-side contacts enables subsequent testing to be performed on the thinned substrate without requiring front-side probing, thereby protecting the mechanically weakened substrate.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If TSV spacing is increased to reduce manufacturing complexity, then manufacturing ease is improved, but electrical performance deteriorates

Engineering Contradiction:

ImproveTSV fabrication easeVSAvoidelectrical connection reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention replaces the mechanical probing system with an electrical measurement system. Instead of using physical probes to contact both front-side and back-side surfaces (mechanical approach), the solution uses electrical measurements through the conductive adhesive and back-side contacts to infer TSV and front-side contact status, enabling effective testing of fine-pitch TSVs without increased spacing.

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

Enables effective and non-damaging testing of TSVs and associated wiring and contact arrays by probing only the back-side contacts, ensuring continuity and reducing the risk of substrate damage during the testing process.

Implementation Method 1

A layer of conductive adhesive is deposited over the first contact array on the front-side of the substrate. The conductive adhesive electrically couples contacts of the first contact array.

Methodology Applied

Scientific EffectConductive adhesive: Conduction (electrical)

Implementation Method 2

A carrier is bonded to the front-side of the substrate with the conductive adhesive.

Methodology Applied

Scientific EffectBonding: Adhesive

Data Source

PatentUS8802454B1Methods of manufacturing a semiconductor structure

Publication Date: 2014.08.12 XILINX INC

AI summary

A method for testing TSVs is provided. A plurality of TSVs is formed in a semiconductor substrate. Wiring layers and a first contact array are formed on the front-side of the substrate. The wiring layers couple each of the TSVs to a respective contact of the first contact array. Conductive adhesive is deposited over the first contact array. The conductive adhesive electrically couples contacts of the first contact array. A carrier is bonded to the front-side of the substrate with the conductive adhesive. After bonding the carrier to the substrate, the back-side of the substrate is thinned to expose each of the TSVs on the back-side of the substrate. A second contact array is formed, having a contact coupled to each respective TSV. Conductivity and connections of the TSVs, wiring layers, and contacts are tested by testing for conductivity between contacts of the second contact array.