Polyimide Packaging for Thinned Silicon Wafers
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Solution Overview
Problem
Current packaging materials for semiconductor devices face challenges such as high cure temperatures, residual stress, moisture absorption, and thermal mismatch, which are not adequately addressed by conventional polyimides, epoxies, and BCB materials, leading to issues like warpage and delamination in next-generation 3D integration applications.
Innovation Solution
Development of novel polyimide polymers formed through specific reaction products of diamines, tetracarboxylic acid dianhydrides, and compounds with reactive functional groups, which are cured at low temperatures, exhibit low coefficient of thermal expansion, and are soluble in environmentally friendly solvents, allowing for flexible application methods like inkjet coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyimides are used for packaging, then excellent electrical, mechanical and thermal properties are achieved, but high cure temperatures (>350°C) and high post-cure shrinkage occur
Solution Approach 1:
The patent modifies the chemical structure of polyimide by incorporating specific diamine components ( Structures (Ia), (Ib), and (II)) and tetracarboxylic acid dianhydride components to fundamentally change the curing behavior. This structural parameter change enables the material to cure at low temperatures (below 200°C) while maintaining excellent electrical, mechanical, and thermal properties, thus resolving the contradiction between reliability and cure temperature.
Solution Approach 2:
The invention creates a composite polyimide system by combining multiple diamine components and tetracarboxylic acid dianhydride components in specific ratios. This composite approach allows the material to achieve both low cure temperature and high reliability by leveraging the synergistic effects of different molecular structures within the polyimide network.
2Reliability
If conventional polyimides are used for packaging, then excellent electrical, mechanical and thermal properties are achieved, but high post-cure shrinkage occurs leading to high residual stress
Solution Approach 1:
The patent changes the molecular parameters of polyimide by introducing specific diamine structures with flexible spacers and cyclic groups that reduce chain rigidity. This parameter change decreases post-cure shrinkage and residual stress while preserving the material's excellent electrical, mechanical, and thermal properties, effectively resolving the contradiction between reliability and stress levels.
3Reliability
If conventional polyimides are used for packaging, then excellent electrical, mechanical and thermal properties are achieved, but high levels of moisture absorption occur
Solution Approach 1:
The patent applies local quality modification by incorporating hydrophobic groups and dense crosslinking structures at specific locations within the polyimide molecular chain. This localized structural optimization reduces moisture absorption pathways while maintaining the overall excellent electrical, mechanical, and thermal properties of the bulk material, resolving the contradiction between reliability and moisture resistance.
4Productivity
If thinned silicon wafers are used for 3D integration, then vertical integration requirements are satisfied, but the wafers become extremely fragile
Solution Approach 1:
The patent provides beforehand cushioning by developing a packaging material with exceptionally low residual stress and low modulus characteristics that acts as a protective cushion for thinned wafers. This material compensates for the wafer's fragility by absorbing mechanical stresses during processing and operation, enabling vertical integration while protecting the fragile thinned wafers from damage.
5Stress or pressure
If packaging materials with low residual stress are used, then thinned wafers are protected, but the materials are only soluble in polar, aprotic solvents (NMP, DMAc) that are not acceptable to semiconductor manufacturers
Solution Approach 1:
The patent changes the chemical parameters of the packaging material by incorporating specific diamine and dianhydride components that create a molecular structure soluble in non-polar or weakly polar solvents. This parameter change enables the material to maintain low residual stress for wafer protection while achieving solubility in semiconductor-friendly solvents, resolving the contradiction between stress reduction and ease of manufacture.
6Reliability
If packaging materials with low CTE are used, then thermal mismatch with substrate is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent employs composite material design by formulating polyimide with specific ratios of multiple diamine components and tetracarboxylic acid dianhydride components. This composite approach achieves the target low CTE (50-70 ppm/°C) to minimize thermal mismatch while managing formulation complexity through systematic component selection and standardized manufacturing procedures.
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 new polyimide polymers provide low residual stress, reduced thermal mismatch, and improved processability, enabling reliable packaging for thinned silicon wafers in advanced semiconductor devices without warpage or delamination, meeting the stringent requirements of next-generation WLP and 3D integration.
Implementation Method 1
condensation, imidization, and endcapping reactions
Implementation Method 2
condensation, imidization, and endcapping reactions
Implementation Method 3
baking the coated substrate to form a coated substrate having a dried film
Data Source
AI summary
This disclosure relates to a polyimide polymer that includes the reaction product of: (a) at least one diamine selected from the group consisting of a diamine of Structure (Ia) and a diamine of Structure (Ib),(b) at least one diamine of Structure (II),(c) at least one tetracarboxylic acid dianhydride, and (d) at least one compound containing a first functional group reactive with an amine or an anhydride and at least a second functional group selected from the group consisting of a substituted or unsubstituted linear alkenyl group and a substituted or unsubstituted linear alkynyl group. Each variable in the above formulas is defined in the specification.