Image Sensor Lens Protection Using Temporary Layers

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Solution Overview

Problem

Conventional image sensor packages face challenges in preventing the mold compound from contacting the lenses during the molding process, which can interfere with light entry and affect image sensing properties, especially in stacked configurations where the keep-out zone (KOZ) is smaller, increasing the likelihood of mold compound interference with the lenses.

Innovation Solution

The implementation includes a semiconductor wafer with a pixel array and a color filter array, where an encapsulation layer with a height of at least 10 microns is used to prevent the temporary protection layer and mold compound from depositing over the lenses, and a dam structure is formed at the edge of the encapsulation layer to further prevent the temporary protection layer from crossing the lens area, ensuring the mold compound does not contact the lenses during application.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the keep-out zone (KOZ) is reduced in stacked configurations, then device integration is improved, but the risk of mold compound contacting lenses increases

Engineering Contradiction:

Improvedevice integrationVSAvoidmold compound interference with lenses

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a temporary protection layer as an intermediary substance applied over the lenses before molding. This layer acts as a mediator that prevents direct contact between the mold compound and lenses, allowing reduced KOZ while protecting the lenses during the molding process. The protection layer is subsequently removed to restore lens functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies the temporary protection layer to the lenses before the molding process begins. This preliminary action ensures that when the mold compound is later applied, the lenses are already protected, enabling tighter packaging without compromising lens integrity.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If the encapsulation layer height is increased to prevent mold compound contact, then lens protection is improved, but package height increases

Engineering Contradiction:

Improvelens protectionVSAvoidpackage height

Core Design Contradiction:

Object-affected harmful factorsVSLength of stationary object

Solution Approach 1:

Instead of increasing the encapsulation layer height, the patent uses a temporary protection layer applied directly over the lenses as an intermediary barrier. This approach provides effective lens protection during molding while maintaining a compact package height, as the protection layer is a thin coating rather than a thick structural layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The temporary protection layer is a disposable, thin coating that serves its protective function only during the molding process. It is applied, serves its purpose, and then removed, providing effective protection without permanently increasing package dimensions.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Object-affected harmful factors

If a temporary protection layer is applied over lenses, then lens protection during molding is improved, but process complexity increases

Engineering Contradiction:

Improvelens protection during moldingVSAvoidmanufacturing process complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The temporary protection layer uses a simple, disposable coating material that can be applied using standard semiconductor fabrication techniques. The layer performs its protective function and is then removed, adding minimal permanent complexity to the device while providing necessary protection during molding.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The process involves applying a temporary protection layer, using it to prevent mold compound contact with lenses, and then removing the layer. This discard-and-recover approach provides effective protection during the critical molding step without permanently complicating the device structure or requiring complex removal mechanisms.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS11728360B2Image sensor packages formed using temporary protection layers and related methods

Publication Date: 2023.08.15 SEMICON COMPONENTS IND LLC

AI summary

An image sensor package may include a semiconductor wafer having a pixel array, a color filter array (CFA) formed over the pixel array, and one or more lenses formed over the CFA. A light block layer may couple over the semiconductor wafer around a perimeter of the lenses and an encapsulation layer may be coupled around the perimeter of the lenses and over the light block layer. The light block layer may form an opening providing access to the lenses. A mold compound layer may be coupled over the encapsulation layer and the light block layer. A temporary protection layer may be used to protect the one or more lenses from contamination during application of the mold compound and/or during processes occurring outside of a cleanroom environment.