Double-Side Metal Pillar Packaging for TSV Crack Reduction
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Solution Overview
Problem
The increasing demand for local communication and interconnection in integrated circuit packages is challenging due to varying thicknesses of neighboring device dies, leading to issues like TSV cracking and bubble trapping during thermal processes.
Innovation Solution
The formation of metal pillars on both sides of LSI dies compensates for thickness differences, reducing TSV cracking and bubble risk by using double-side metal vias and redistribution layers to ensure even thickness and reliable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal pillars are formed only on one side of LSI dies, then the manufacturing process is simpler, but thickness differences cause TSV cracking and bubble trapping
Solution Approach 1:
The patent divides the metal pillar formation into two separate segments: first metal pillars are formed on the front side of the LSI die, then after thinning the die, second metal pillars are formed on the back side. This segmentation allows each side to be independently optimized and prevents the complexity of forming all pillars simultaneously through the entire die thickness.
Solution Approach 2:
The patent performs preliminary actions by forming the first metal pillars before thinning the LSI die. This preliminary formation ensures that the front-side interconnect structure is established and protected before the die is thinned, preventing damage to the pillars during the thinning process and eliminating the need for pillars to span the entire original die thickness.
2Length of stationary object
If LSI die thickness is reduced to accommodate thinner profiles, then package size is minimized, but TSV cracking risk increases
Solution Approach 1:
Metal pillars are formed on the front side of the LSI die before the thinning process. This preliminary formation ensures that the pillars are established when the die is still thick and structurally supported, preventing cracking during subsequent thinning operations. The pillars do not need to span the entire original die thickness, reducing stress concentration.
Solution Approach 2:
The interconnect structure is segmented into front-side metal pillars formed before thinning and back-side metal pillars formed after thinning. This segmentation allows the die to be thinned to the desired thin profile while maintaining structural integrity, as the front-side pillars are formed when the die provides adequate mechanical support.
3Reliability
If double-side metal pillars are formed, then TSV cracking and bubble trapping are reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The manufacturing process is segmented into distinct stages: front-side metal pillar formation, die thinning, and back-side metal pillar formation. Each stage is independently optimized and can be performed with standard equipment and processes, making the overall complex outcome achievable through simple, sequential steps rather than a single complex operation.
Solution Approach 2:
The front-side metal pillars are formed as a preliminary action before die thinning. This preliminary formation simplifies the overall process because the pillars are created when the die structure provides natural mechanical support, eliminating the need for complex support structures or specialized equipment that would be required if pillars were formed after thinning.
Data Source
AI summary
A method includes forming a die, which includes forming a first metal pillar on a first side of a first semiconductor substrate of the die, polishing the first semiconductor substrate of the die to reveal a first through-via in the first semiconductor substrate, and forming a second metal pillar on a second side of the die. The first side and the second side are on opposite sides of the first semiconductor substrate. The method further includes encapsulating the die in an encapsulant, forming a first conductive feature on the first side of the first semiconductor substrate and electrically connecting to the first metal pillar, and forming a second conductive feature on the second side of the first semiconductor substrate and electrically connecting to the second metal pillar.