Stacked Semiconductor Package Curing Layers for Fine-Pitch Bump Reliability
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Solution Overview
Problem
Existing semiconductor packages face challenges in reliably stacking high-density semiconductor chips due to issues with solder bump expansion and interconnect reliability, particularly in fine-pitch designs, which can lead to short failures and reduced package reliability.
Innovation Solution
A semiconductor package design incorporating a double-layered curing system, where a first photo-curing layer is in contact with the upper portion of the solder bump and a second thermo-curing layer is in contact with the lower portion, with the first layer being cured before the second to prevent lateral expansion of solder bumps and enhance interconnect reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer curing material is used between semiconductor chips, then the manufacturing process is simple, but solder bumps expand laterally causing short failures between adjacent bumps
Solution Approach 1:
The curing layer is divided into two distinct layers: a first curing layer containing a photo-curing agent that cures at lower temperature, and a second curing layer containing a thermo-curing agent that cures at higher temperature. This segmentation allows each layer to perform its specific function - the first layer prevents solder bump expansion while the second layer provides strong bonding, thereby resolving the contradiction between simple structure and high reliability.
Solution Approach 2:
The patent utilizes different curing temperatures as key parameters to differentiate the two curing layers. The photo-curing agent cures at a lower temperature range, preventing lateral expansion of solder bumps during the curing process. The thermo-curing agent then cures at a higher temperature to provide strong mechanical bonding. This parameter-based differentiation enables the system to achieve both structural simplicity and interconnect reliability.
2Volume of moving object
If high-density fine-pitch semiconductor chips are stacked, then the package size is reduced, but solder bumps are prone to lateral expansion and short failures
Solution Approach 1:
The first curing layer with photo-curing agent is applied before the solder bumps are fully positioned and cured at lower temperature. This preliminary curing action constrains the solder bumps in place, preventing lateral expansion during subsequent high-temperature processing. This preliminary constraint enables high-density fine-pitch stacking while maintaining precise solder bump positioning.
Solution Approach 2:
The patent employs a two-stage temperature parameter strategy: first, lower temperature photo-curing to prevent solder bump expansion and maintain positioning precision; second, higher temperature thermo-curing to achieve strong bonding. This parameter change approach enables high-density stacking by maintaining precision during the critical curing phases.
3Speed
If a photo-curing agent is used alone, then the curing process is fast and occurs at low temperature, but it cannot provide sufficient bonding strength for high-density stacks
Solution Approach 1:
The curing function is segmented into two parts: the first curing layer with photo-curing agent provides fast, low-temperature curing to prevent solder bump expansion; the second curing layer with thermo-curing agent provides high-temperature curing for strong bonding. This segmentation allows each curing mechanism to optimize for its specific function, achieving both speed and strength.
Solution Approach 2:
The patent uses a composite curing system where two different curing agents (photo-curing and thermo-curing) are combined in separate layers. This composite approach leverages the advantages of both curing mechanisms - the rapid response of photo-curing and the strong bonding of thermo-curing - to achieve both fast curing speed and sufficient bonding strength for high-density semiconductor stacks.
4Strength
If a thermo-curing agent is used alone, then strong bonding is achieved, but the high temperature causes solder bumps to expand laterally
Solution Approach 1:
The first curing layer with photo-curing agent performs a preliminary curing action at low temperature before the high-temperature thermo-curing process. This preliminary action constrains the solder bumps and prevents lateral expansion during the subsequent high-temperature bonding process. This sequential approach allows strong bonding to be achieved without compromising positioning precision.
Solution Approach 2:
The first curing layer acts as a protective cushioning layer that prevents solder bump expansion before the high-temperature thermo-curing process occurs. This beforehand protection ensures that when the strong bonding is achieved through thermo-curing, the solder bumps maintain their precise positions without lateral expansion, thus preserving manufacturing precision while achieving strong bonding.
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 double-layered curing system effectively prevents short failures between adjacent solder bumps, improving the reliability and robustness of the semiconductor package by controlling the curing process to maintain precise contact and reduce lateral expansion.
Implementation Method 1
The first curing layer may include a first photo-curing agent
Implementation Method 2
The second curing layer may include a first thermo-curing agent
Data Source
AI summary
A semiconductor package includes a lower semiconductor chip having a lower semiconductor substrate and upper pads on a top surface of the lower semiconductor substrate, an upper semiconductor chip stacked on the lower semiconductor chip, the upper semiconductor chip including an upper semiconductor substrate and solder bumps on a bottom surface of the upper semiconductor substrate, and a curing layer between the lower semiconductor chip and the upper semiconductor chip, the curing layer including a first curing layer adjacent to the upper semiconductor chip, the first curing layer including a first photo-curing agent, and a second curing layer between the first curing layer and the top surface of the lower semiconductor substrate, the second curing layer including a first thermo-curing agent.