CMP Pad Polyurethane Blocked Isocyanate Warping
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) pads face challenges in achieving a stable and effective polishing layer without warping, cracking, or surface deposits of blocking agents, particularly when using faster reactive amines as chain extenders, which are ruled out due to minimum gel time requirements.
Innovation Solution
A CMP pad with a polishing layer composed of a polyurethane reaction product from a mixture of diisocyanate, partially blocked diisocyanate, and aromatic diamine curative, with a controlled gel time and residual blocking agent content, ensuring stability and homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If faster reactive amines are used as chain extenders to reduce gel time, then productivity is improved, but manufacturing precision deteriorates due to warping and cracking
Solution Approach 1:
A blocked isocyanate compound is introduced as an intermediary substance in the reaction mixture. This blocked isocyanate acts as a mediator that moderates the reaction between diisocyanate and diamine, preventing excessive reactivity that causes warping and cracking while still achieving adequate gel time for the casting process. The blocking agent controls the release of isocyanate groups, creating a more manageable reaction profile.
Solution Approach 2:
The invention changes the chemical parameters of the reaction mixture by incorporating blocked isocyanate compounds with specific deblocking temperatures. This parameter change modifies the reaction kinetics and thermodynamics, allowing the system to achieve both fast enough gel time for productivity and controlled enough reaction to prevent defects. The deblocking temperature parameter is specifically selected to balance these competing requirements.
2Manufacturing precision
If blocked isocyanate is used to control reaction rate, then manufacturing precision is improved, but device complexity increases due to additional components
Solution Approach 1:
The blocked isocyanate compound serves multiple functions simultaneously: it acts as a chain extender like the diamine, provides steric hindrance to control reaction rate, and its blocking group serves as a leaving group that can be removed under processing conditions. This multi-functionality reduces the need for separate additives and simplifies the overall formulation despite the added complexity of the blocked structure.
Solution Approach 2:
The reaction mixture creates a composite polyurethane structure where blocks of polymer formed from blocked isocyanate alternate with blocks formed from diamine chain extenders. This composite structure at the molecular level provides both the controlled reaction characteristics needed to prevent defects and the mechanical properties required for polishing pad performance.
3Productivity
If aromatic diamine curative is used to achieve high removal rate, then productivity is improved, but object-generated harmful factors increase due to potential surface deposits
Solution Approach 1:
The invention converts the potential harm of aromatic diamine reactivity into a benefit by using the blocked isocyanate as a buffer. The blocked isocyanate temporarily suppresses the reactivity during mixing and casting, preventing surface deposits, then releases the aromatic diamine's high reactivity at the appropriate time to achieve the desired high removal rate during polishing. The harmful reactivity is transformed into a controlled, beneficial property.
Solution Approach 2:
The blocking agent performs a preliminary action by temporarily deactivating the isocyanate groups before the casting and initial curing stages. This preliminary deactivation prevents premature or uncontrolled reactions that would cause surface deposits. After the pad structure is formed, the blocking groups are removed (deblocked), enabling the aromatic diamine to fully react and provide the high removal rate characteristic of aromatic diamines without the harmful side effects.
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 solution provides CMP pads with high removal rates and good planarization efficiency, preventing warping and cracking, and maintaining a stable morphology for consistent performance.
Implementation Method 1
one or more blocked diisocyanate, polyisocyanate or polyisocyanate prepolymer which contains a blocking agent having a deblocking temperature of 80° C. or higher, or up to 160° C.
Implementation Method 2
a polyurethane reaction product of a reaction mixture comprising (i) one or more diisocyanate, polyisocyanate or polyisocyanate prepolymer... and (iii) one or more diamine curative
Implementation Method 3
wherein the reaction mixture has a gel time of from 2 to 15 minutes when mixed at a stoichiometric 1:1 ratio of total isocyanate groups to total amine groups
Data Source
AI summary
A chemical mechanical polishing pad for polishing a semiconductor substrate is provided containing a polishing layer that comprises a polyurethane reaction product of a reaction mixture comprising (i) one or more diisocyanate, polyisocyanate or polyisocyanate prepolymer, (ii) from 40 to 85 wt. % based on the total weight of (i) and (ii) of one or more blocked diisocyanate, polyisocyanate or polyisocyanate prepolymer which contains a blocking agent and has a deblocking temperature of from 80 to 160° C., and (iii) one or more aromatic diamine curative. The reaction mixture has a gel time at 80° C. and a pressure of 101 kPa of from 2 to 15 minutes; the polyurethane reaction product has a residual blocking agent content of 2 wt. % or less; and the polishing layer exhibits a density of from 0.6 to 1.2 g/cm3.