Polyimide Packaging Material for 3D IC Thermal Mismatch
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Solution Overview
Problem
Current semiconductor packaging materials 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, leading to issues like warpage and delamination in next-generation 3D integrated circuits.
Innovation Solution
Development of novel polyimide polymers and compositions that include specific reaction products of diamines, tetracarboxylic acid dianhydrides, and reactive functional compounds, which can be processed at lower temperatures with reduced shrinkage and stress, and exhibit improved mechanical and thermal properties.
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 aromatic diamine units with flexible alkyl chains and cyclic structures. This structural parameter change enables the polymer to achieve comparable thermal and mechanical properties to conventional polyimides while reducing the cure temperature to below 350°C, as the modified molecular architecture allows for lower energy activation during curing
Solution Approach 2:
The invention creates a composite polyimide system by combining multiple diamine components (including rigid aromatic units and flexible aliphatic units) with dianhydride components. This composite approach at the molecular level allows the material to exhibit both the high-performance properties of rigid structures and the low-shrinkage characteristics of flexible segments, achieving reliable packaging performance at reduced cure temperatures
2Reliability
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 introduces hydrophobic alkyl chains and cyclic structures at specific positions within the polyimide backbone. These local hydrophobic segments create regions that resist moisture penetration, while the overall polymer matrix maintains its excellent electrical, mechanical and thermal properties. The localized modification of chemical composition selectively addresses moisture absorption without compromising performance
Solution Approach 2:
By changing the chemical composition parameters of the polyimide—specifically incorporating diamines with hydrophobic character and adjusting the ratio of aromatic to aliphatic units—the material achieves lower moisture absorption. The modified molecular structure reduces polar groups that attract water molecules while maintaining the structural integrity needed for reliable packaging performance
3Strength
If conventional polyimides are used for packaging, then material strength is achieved, but high residual stress occurs leading to bowing of the silicon wafer
Solution Approach 1:
The patent modifies the polyimide molecular structure by incorporating flexible spacers and cyclic units that reduce chain rigidity. This structural parameter change allows the material to maintain adequate mechanical strength while exhibiting lower post-cure shrinkage. The reduced shrinkage directly translates to lower residual stress on the silicon wafer, preventing wafer bowing during and after the packaging process
Solution Approach 2:
The invention employs a composite diamine system combining rigid aromatic units (for strength) with flexible aliphatic units and cyclic structures (for low shrinkage). This molecular-level composite creates a balanced polymer that delivers the material strength needed for packaging while minimizing residual stress through the flexible segments that accommodate dimensional changes during curing without transmitting excessive stress to the wafer
4Ease of manufacture
If packaging material has high CTE, then processing flexibility is maintained, but thermal mismatch with substrate occurs leading to warpage and delamination
Solution Approach 1:
The patent adjusts the thermal expansion parameters of the polyimide by incorporating rigid aromatic units and crosslinkable functional groups into the molecular structure. These structural modifications increase the thermal stability and reduce the coefficient of thermal expansion (CTE) of the cured material. The lower CTE brings the packaging material into better thermal match with the silicon substrate, preventing warpage and delamination while the uncured material remains processable
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 compositions provide a solution by meeting the stringent requirements for advanced packaging materials, including low cure temperature, minimal residual stress, and compatibility with semiconductor substrates, enhancing the reliability of 3D integrated circuits.
Implementation Method 1
a polyimide polymer containing the reaction product of components (a), (b), and optionally (c), in which components (a), (b), and (c) are: (a) at least one diamine of Structure (I)... (b) at least one tetracarboxylic acid dianhydride
Implementation Method 2
the reaction product of components (a), (b), and optionally (c)... (b) at least one tetracarboxylic acid dianhydride
Implementation Method 3
Development of novel polyimide polymers and compositions that include specific reaction products of diamines, tetracarboxylic acid dianhydrides, and reactive functional compounds, which can be processed at lower temperatures with reduced shrinkage and stress
Implementation Method 4
high post-cure shrinkage... processed at lower temperatures with reduced shrinkage
Data Source
AI summary
A polyimide polymer that includes the reaction product of: (a) at least one diamine selected from the group consisting of a diamine of Structure (I)(b) at least one tetracarboxylic acid dianhydride, and optionally (c) at least one compound containing a first functional group reactive with an amine or an anhydride and at least one second functional group selected from the group consisting of an unsubstituted alkenyl group and an unsubstituted alkynyl group. Each variable in the above formula is defined in the specification.