Spin-On Temporary Wafer Bonding for High-Temperature Processing
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Solution Overview
Problem
Current methods for mounting active wafers to carrier substrates for thinning and processing face challenges such as time-consuming chemical removal of bonding compositions, limited thickness uniformity, and inability to withstand high processing temperatures, particularly in ultra-thin wafer handling and high-temperature processing steps.
Innovation Solution
A novel wafer bonding method using a thermoplastic bonding composition layer composed of imide, amideimide, or amideimide-siloxane polymers and oligomers, which can be softened at high temperatures for separation, applied via spin-coating and baked to form a uniform layer capable of withstanding high processing temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cured bonding composition is used to mount an active wafer to a carrier substrate, then the wafer can be held securely during processing, but the bonding composition must be chemically removed by dissolving in a solvent which is time-consuming and reduces throughput
Solution Approach 1:
The bonding composition utilizes phase transitions between solid, liquid, and gas states. The composition is applied as a liquid or paste, cures to a solid bonding state, and is removed by heating to vaporize the carrier solvent without chemical dissolution. This phase change mechanism eliminates the time-consuming solvent dissolution step while maintaining secure bonding during processing.
Solution Approach 2:
The invention replaces the chemical dissolution mechanism (using solvents to chemically break down and remove the bonding composition) with a thermal vaporization mechanism. The carrier solvent is heated to its boiling point and evaporates, leaving no residue and eliminating the need for chemical removal processes, thereby increasing throughput.
2Ease of operation
If a thermal release adhesive tape is used for mounting, then separation can be achieved by heating, but the adhesive softens at low temperatures making it unable to withstand high processing temperatures
Solution Approach 1:
The bonding composition is a composite material consisting of an inorganic polymer matrix (providing high-temperature stability) combined with an organic carrier solvent (enabling thermal release). The inorganic polymer maintains structural integrity at high processing temperatures while the carrier solvent allows for controlled thermal separation at lower temperatures, achieving both temperature resistance and ease of separation.
Solution Approach 2:
The invention changes the temperature parameter at which separation occurs by using an inorganic polymer with a high decomposition temperature rather than a conventional organic adhesive. This allows the bonding composition to remain stable during high-temperature processing (withstanding temperatures above 200°C) while still enabling separation by heating to a controlled temperature where the carrier solvent vaporizes.
3Ease of manufacture
If conventional bonding compositions are used, then bonding can be achieved, but chemical removal requires time-consuming dissolution processes adding cost and complexity
Solution Approach 1:
The invention replaces complex chemical dissolution processes with a simple thermal vaporization process. The carrier solvent is heated to evaporate and leave no residue, eliminating the need for chemical solvents, dissolution steps, and associated safety and environmental controls. This reduces process complexity while maintaining effective bonding capability.
Solution Approach 2:
The carrier solvent acts as a temporary, disposable component that serves its purpose during bonding and processing, then vaporizes completely without requiring recovery or disposal procedures. This eliminates the complexity of chemical removal systems while maintaining bonding effectiveness throughout the manufacturing process.
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 method enables efficient and uniform bonding of wafers, allowing for high-temperature processing without the need for hazardous solvents, and facilitates easy separation by softening the bonding layer, thereby improving throughput and reducing costs.
Implementation Method 1
The stack is subjected to a temperature sufficiently high to soften the bonding layer
Data Source
AI summary
New compositions and methods of using those compositions as bonding compositions are provided. The compositions are preferably thermoplastic and comprise imides, amideimides, and/or amideimide-siloxanes (either in polymeric or oligomeric form) dispersed or dissolved in a solvent system, and can be used to bond an active wafer to a carrier wafer or substrate to assist in protecting the active wafer and its active sites during subsequent processing and handling. The compositions form bonding layers that are chemically and thermally resistant, but that can also be softened to allow the wafers to slide apart at the appropriate stage in the fabrication process.