Thin Semiconductor Dice Handling via Dielectric Tether Layer
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Solution Overview
Problem
Conventional methods for handling and processing thin semiconductor dice are prone to damage, contamination, and yield loss due to excessive handling and residual adhesion issues, particularly in high-volume applications requiring automated techniques for thin die fabrication and separation.
Innovation Solution
The use of fusion bonding, anodic bonding, and adhesive bonding techniques to form wafer stacks with silicon or silicon-on-insulator wafers, where a dielectric tether layer is formed to support the thin dice, allowing for precise thinning and separation with reduced risk of damage and contamination, using methods like deep reactive ion etching and vacuum picking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dicing and wafer sawing methods are used to separate thin dice, then separation can be achieved, but the thin die are damaged causing device failure or sensor performance degradation
Solution Approach 1:
A support structure is formed on the wafer before dicing to provide mechanical reinforcement during the separation process. This preliminary structural enhancement prevents die damage during cutting while maintaining manufacturing precision.
Solution Approach 2:
A support structure acts as an intermediary element between the dicing blade and the thin die. This mediator absorbs and distributes cutting forces, preventing direct stress concentration on the fragile die and thereby maintaining both separation precision and die integrity.
2Productivity
If conventional ejector pins are used to eject thin die from tape, then ejection can be achieved, but excessive stress damages the thin die causing cracking and device failure
Solution Approach 1:
Support structures are formed on the wafer before ejection to provide mechanical reinforcement. This preliminary reinforcement allows the die to withstand ejection forces without cracking, maintaining both ejection efficiency and die integrity.
Solution Approach 2:
The support structure serves as a cushioning element that absorbs and distributes ejection stresses before they reach the thin die. This beforehand cushioning prevents stress concentration that would cause cracking while maintaining productive ejection.
3Ease of operation
If multiple carrier transfers and tape transfers are used in the fabrication process, then thin dice can be separated and handled, but yield loss increases due to die contamination on both sides of the die
Solution Approach 1:
Multiple operations (support structure formation, dicing, and ejection) are merged into a single integrated process flow. This eliminates intermediate transfer steps that cause contamination while maintaining ease of automated handling through the unified process.
Solution Approach 2:
The support structure enables the wafer and die to be self-sufficient during processing, eliminating the need for external carrier wafers and transfer tapes. This self-service approach prevents contamination from multiple handling interfaces while maintaining operational ease.
4Strength
If organic adhesive is used to mount thin die for sensor applications, then bonding can be achieved, but residue is left on the die surface causing poor bonding with the surface being measured
Solution Approach 1:
The support structure is selectively removed after dicing and ejection, leaving the thin die free of organic adhesive residue. This extraction of the temporary support element eliminates contamination that would interfere with sensor bonding while maintaining bonding strength during the process.
Solution Approach 2:
The support structure functions as a disposable temporary element used only during fabrication. It provides necessary mechanical support during processing then is removed, leaving no harmful residue on the die surface for the final sensor application.
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
This approach enhances the yield and reduces damage to thin dice by enabling precise control over the separation process, minimizing residual adhesion and contamination, and allowing for the production of thin dice with improved mechanical and electrical properties for applications like pressure sensors.
Implementation Method 1
a dielectric tether layer is formed to support the thin dice
Implementation Method 2
The use of fusion bonding, anodic bonding, and adhesive bonding techniques to form wafer stacks
Implementation Method 3
The use of fusion bonding, anodic bonding, and adhesive bonding techniques to form wafer stacks
Implementation Method 4
The use of fusion bonding, anodic bonding, and adhesive bonding techniques to form wafer stacks
Implementation Method 5
using methods like deep reactive ion etching and vacuum picking
Data Source
AI summary
Ultra-thin semiconductor devices, including piezoresistive sensing elements can be formed in a wafer stack that facilitates handling many thin device dice at a wafer level. Three embodiments are provided to form the thin dice in a wafer stack using three different fabrication techniques that include anodic bonding, adhesive bonding and fusion bonding. A trench is etched around each thin die to separate the thin die from others in the wafer stack. A tether layer, also known as a tether, is used to hold thin dice or dice in a wafer stack. Such as wafer stack holds many thin dice together at a wafer level for handling and enables easier die picking in packaging processes.