Die Charge Protection in Stacked Silicon Formation

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Solution Overview

Problem

During the formation of stacked silicon devices, dies are exposed to charge during process steps like mold encapsulation and carrier wafer removal, leading to potential damage and undesirable behavior, such as poor readback yield from memory cells.

Innovation Solution

A method involving bonding dies to an interposer, encapsulating with a mold compound, grinding to expose the die, forming a protective component over the die, bonding a carrier wafer, and removing the carrier wafer and protective components to shield the die from charge exposure, while ensuring adequate heat dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If dies are left exposed during formation of stacked silicon device, then subsequent processing steps can be performed, but dies may be exposed to charge leading to damage and poor readback yield

Engineering Contradiction:

Improveease of processingVSAvoiddie integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A protective component is formed over the top surface of the die before subsequent processing steps are performed. This preliminary protective action ensures the die is shielded from charge exposure during mold encapsulation, carrier wafer bonding, and other processing steps, while still allowing easy access to the interposer for subsequent operations.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a protective component is formed over the die, then charge exposure is prevented, but additional processing steps and complexity are introduced

Engineering Contradiction:

Improvecharge protectionVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective component acts as an intermediary element between the die and the charge-generating processing environment. It provides charge protection while being removable or permeable to allow subsequent processing steps to proceed. The component can be applied and removed using standard processing techniques, minimizing additional complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If mold compound is ground to expose die top surface, then die becomes accessible, but die is exposed to charge during grinding and subsequent steps

Engineering Contradiction:

Improvedie accessibilityVSAvoidcharge exposure

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The protective component is applied to the die top surface before the mold compound is ground away. This preliminary protective measure counteracts the harmful charge exposure that would occur during grinding and subsequent processing steps. The protective component remains in place throughout these operations, preventing charge damage while allowing the die to be accessed.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS9385106B1Method for providing charge protection to one or more dies during formation of a stacked silicon device

Publication Date: 2016.07.05 XILINX INC

AI summary

A method for providing charge protection to a die during formation of an integrated circuit, includes bonding the die to an interposer to form an unprotected stacked silicon component; encapsulating the unprotected stacked silicon component with a mold compound to cover at least a top surface of the die; grinding the mold compound to reduce a thickness of the mold compound; bonding a carrier wafer to the mold compound; removing the carrier wafer from the mold compound; and removing the mold compound from the top surface of the die after the carrier wafer is removed from the mold compound, to expose the top surface of the die.