PZT Thin Film Edge Bead Removal Using Non-Solvent
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Solution Overview
Problem
The use of solvents like butanol for edge bead removal in spin-coated PZT or PLZT thinfilms leads to swelling and delamination during subsequent bake and anneal steps, resulting in particle defects and reduced yield in integrated circuit capacitors.
Innovation Solution
Employing a non-solvent such as deionized water or an aqueous solution with greater than 50% DI water for edge bead removal, which physically removes the film edge without swelling or chemical dissolution, and adding a solvent like acetone, methanol, or isopropyl alcohol to the coater reservoir to prevent clogging, reduces defect formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solvent such as butanol is used for edge bead removal, then the PZT or PLZT thinfilm can be cleaned at the edge, but the solvent is adsorbed into the exposed edge causing swelling and subsequent delamination
Solution Approach 1:
The patent changes the chemical parameter of the edge bead removal fluid from a solvent (butanol) to a non-solvent (deionized water or aqueous solution with >50% DI water). This parameter change prevents the fluid from being adsorbed into the PZT or PLZT thinfilm, thereby eliminating swelling and subsequent delamination while maintaining edge bead removal capability
Solution Approach 2:
The patent uses deionized water or aqueous solutions as the edge bead removal fluid, which are inexpensive and environmentally friendly compared to organic solvents like butanol. These aqueous solutions can be disposed of without hazardous waste disposal requirements, reducing both cost and environmental impact while achieving the same cleaning function
2Reliability
If deionized water or aqueous solution is used for edge bead removal, then swelling and delamination are eliminated, but the coater reservoir may clog
Solution Approach 1:
The patent introduces a second fluid (solvent such as acetone, methanol, or isopropyl alcohol) as an intermediary substance added to the coater reservoir. This solvent acts as a mediator that prevents clogging of the reservoir and dispensing system when using aqueous edge bead removal fluids, by maintaining appropriate fluid flow properties without compromising the non-solvent action at the wafer edge
Solution Approach 2:
The patent applies different fluid properties at different locations: deionized water or high-percentage aqueous solution is used at the wafer edge for non-solvent cleaning (where non-swelling is critical), while a solvent is added to the coater reservoir (where clogging prevention is critical). This local differentiation of fluid properties resolves both requirements simultaneously
3Ease of manufacture
If organic solvents are used for edge bead removal, then effective cleaning is achieved, but hazardous waste disposal is required
Solution Approach 1:
The patent replaces expensive and hazardous organic solvents with inexpensive deionized water or aqueous solutions for edge bead removal. These aqueous solutions can be disposed of without hazardous waste disposal requirements, eliminating the harmful factor while maintaining effective edge bead removal capability
Solution Approach 2:
The patent uses deionized water or aqueous solutions as an inert, non-reactive environment for edge bead removal that does not create hazardous waste. This inert aqueous environment effectively removes edge beads without the environmental and safety concerns associated with organic solvents
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 eliminates swelling and delamination, decreases particle defects, and enhances the yield of PZT or PLZT thinfilms by using a cost-effective and environmentally friendly method that avoids hazardous waste disposal.
Implementation Method 1
a non-solvent such as deionized water or an aqueous solution with greater than 50% DI water is used for the edge bead removal and does not cause the exposed edge of the PZT or PLZT thinfilm to swell
Implementation Method 2
adding a solvent like acetone, methanol, or isopropyl alcohol to the coater reservoir to prevent clogging
Implementation Method 3
The wafer 106 is then spun at high speed to distribute the PZT or PLZT containing solution across the wafer to form a thinfilm of PZT or PLZT with uniform thickness
Implementation Method 4
A low temperature bake is then performed to remove some of the solvent and to convert the metal alkoxides to a gel
Implementation Method 5
A final high temperature anneal may be performed to cause chemical reactions converting the metal alkoxides to metal oxides
Data Source
AI summary
Use of a non-solvent for the edge bead removal of spin-coated PZT or PLZT thinfilms, eliminates swelling of the exposed edges of the PZT or PLZT thinfilms and eliminates delamination and formation of particle defects in subsequent bake and anneal steps.