Interposing Shield for Alpha Particle Absorption in Flip-Chip Packaging

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Solution Overview

Problem

Alpha particles emitted from ceramic substrates and solder bumps in flip-chip technologies cause soft errors in integrated circuit chips, necessitating a method to reduce particle entry.

Innovation Solution

A semiconductor interposing shield with exposed electric conductors on the top side and buried on the bottom side is used, bonded to the integrated circuit, and polished to expose conductors, allowing solder bumps to be formed in electrical contact, effectively sandwiching the shield between the chip and ceramic substrate to absorb alpha particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a ceramic substrate is used in flip-chip technology, then the substrate provides structural support and electrical insulation, but alpha particles are continuously emitted from the substrate causing soft errors in the chip

Engineering Contradiction:

Improvechip reliabilityVSAvoidalpha particle emission

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An interposing shield structure is introduced between the ceramic substrate and the integrated circuit chip. This shield includes a first portion bonded to the chip and a second portion bonded to the substrate, with a space between them. The shield acts as an intermediary barrier that absorbs or blocks alpha particles emitted from the substrate before they can reach and cause soft errors in the chip circuits.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If solder bumps containing 210Pb are used to connect the chip to the substrate, then electrical and mechanical connection is achieved, but alpha particles are generated from 210Pb in the solder bumps

Engineering Contradiction:

Improvesolder bump connectionVSAvoidalpha particle generation

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The interposing shield structure is positioned to block alpha particles generated from 210Pb in the solder bumps. The shield's strategic placement between the solder bumps and the chip creates a protective barrier that intercepts alpha particles before they can penetrate into the chip and cause soft errors, while still allowing the solder bumps to fulfill their electrical and mechanical connection function.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If the interposing shield is made thick enough to block alpha particles, then alpha particle shielding is improved, but the overall package size and complexity increase

Engineering Contradiction:

Improvealpha particle blockingVSAvoidpackage structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The interposing shield is segmented into two distinct portions: a first portion bonded to the integrated circuit chip and a second portion bonded to the ceramic substrate, with a space between them. This segmentation allows the shield to provide adequate alpha particle blocking capability while maintaining a compact overall structure. Each portion can be optimized independently for thickness and material properties, reducing the need for a single thick shield that would increase package complexity.

Inventive Principle:

Principle #1Segmentation

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 interposing shield significantly reduces alpha particle entry from both the ceramic substrate and solder bumps, enhancing chip reliability by preventing most alpha particles from reaching the integrated circuit.

Implementation Method 1

Methodology Applied

Scientific EffectAlpha particle absorption: Absorption (physical)

Implementation Method 2

polishing the bottom side of the interposing shield so as to expose the N electric conductors to the surrounding ambient at the bottom side of the interposing shield

Methodology Applied

Scientific EffectMechanical polishing: Abrasion

Data Source

PatentUS8247271B2Formation of alpha particle shields in chip packaging

Publication Date: 2012.08.21 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A structure fabrication method. First, an integrated circuit including N chip electric pads is provided electrically connected to a plurality of devices on the integrated circuit. Then, an interposing shield having a top side and a bottom side and having N electric conductors in the interposing shield is provided being exposed to a surrounding ambient at the top side but not at the bottom side. Next, the integrated circuit is bonded to the top side of the interposing shield such that the N chip electric pads are in electrical contact with the N electric conductors. Next, the bottom side of the interposing shield is polished so as to expose the N electric conductors to the surrounding ambient at the bottom side of the interposing shield. Then, N solder bumps are formed on the polished bottom side of the interposing shield and in electrical contact with the N electric conductors.