Wafer-Level Optical Sensor Package With Through-Silicon Vias

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Solution Overview

Problem

Existing camera modules face challenges in reducing height for thinner devices while avoiding obstructions that interfere with optical sensor operation, and they are prone to light leaks and fragility issues during the thinning process.

Innovation Solution

A wafer-level camera sensor package with through-silicon vias (TSVs) for I/O contact, embedded in a molding compound layer with a transparent cover, and a redistribution layer for compact mounting, along with anisotropic conductive adhesive for lens assembly coupling, to enhance structural integrity and reduce light leaks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If wirebonds are used to couple the sensor circuit to the substrate circuit, then electrical connection is achieved, but the housing height and width increase, limiting device thinness

Engineering Contradiction:

Improvedevice thicknessVSAvoidhousing structure complexity

Core Design Contradiction:

Length of moving objectVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the wirebonds from the camera module structure, replacing them with through-silicon vias that are integrated directly into the semiconductor die. This removal of the wirebonding process and associated housing requirements directly reduces device thickness and simplifies the overall structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent transitions from planar wirebond connections to three-dimensional through-silicon via connections that penetrate the die thickness. This dimensional change allows electrical connections to be made through the substrate rather than around it, enabling thinner device profiles while maintaining connectivity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Length of moving object

If the semiconductor die is thinned to reduce module height, then device thinness is achieved, but the die becomes fragile and prone to damage

Engineering Contradiction:

Improvedie thicknessVSAvoiddie mechanical strength

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The patent employs a composite structure where the thinned semiconductor die is bonded to a support substrate through the through-silicon vias. This composite construction provides mechanical reinforcement to the thin die, distributing stresses and preventing fragility issues that would otherwise result from extreme thinning.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The support substrate acts as a pre-established protective structure that cushions and supports the thinned die before damage can occur. This reinforcement is built into the structure during manufacturing, providing inherent protection against the fragility that accompanies die thinning.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Length of moving object

If through-silicon vias are used for I/O contact, then device height is reduced, but light leaks may occur through the vias

Engineering Contradiction:

Improvemodule heightVSAvoidlight leaks

Core Design Contradiction:

Length of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent converts the potential harmful effect of light leaks through the through-silicon vias into a beneficial feature by filling the vias with reflective material. This transforms the via structures from light-leak pathways into light-reflecting elements that actively prevent stray light from reaching the sensor, turning a potential defect into a functional advantage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Ease of operation

If the optical sensor is positioned on the substrate with the sensor facing outward, then optical image reception is enabled, but circuit coupling becomes difficult without interfering with optical operation

Engineering Contradiction:

Improveoptical image receptionVSAvoidcircuit coupling complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent inverts the traditional approach by routing all electrical connections through the back of the semiconductor die via through-silicon vias. This allows the front surface of the die to be completely dedicated to optical functions without any wirebonds or circuit elements interfering with light reception, while all circuit coupling is accomplished through the inverted back-side connection approach.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8890269B2Optical sensor package with through vias

Publication Date: 2014.11.18 STMICROELECTRONICS INT NV

AI summary

A wafer-level camera sensor package includes a semiconductor substrate with an optical sensor on a front surface. Through-silicon-vias (TSV) extend through the substrate and provide I/O contact with the sensor from the back side of the substrate. A glass cover is positioned over the front surface, and the cover and substrate are embedded in a molding compound layer (MCL), the front surface of the MCL lying coplanar with the front of the cover, and the back surface lying coplanar with the back of the substrate. Surface-mount devices, electromagnetic shielding, and through-wafer-connectors can be embedded in the MCL. A redistribution layer on the back surface of the MCL includes bottom contact pads for mounting the package, and conductive traces interconnecting the contact pads, TSVs, surface-mount devices, shielding, and through-wafer-connectors. Anisotropic conductive adhesive is positioned on the front of the MCL for physically and electrically attaching a lens array.