Semiconductor Die Bonding Without BSM for Laser Solder Reflow
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Solution Overview
Problem
The semiconductor industry faces challenges in integrating complex electronics with efficient heat dissipation, as existing thermal solutions like heat sinks and TIM cannot be used in conjunction with laser-assisted bonding (LAB) techniques due to reflection or absorption issues with back side metallization (BSM) layers.
Innovation Solution
A method is developed where a semiconductor die without a BSM layer is used, allowing a laser beam to directly irradiate and reflow solder between the die and substrate, followed by the formation of a thermal interface material (TIM) layer for improved heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser-assisted bonding (LAB) is used to reflow solder bumps, then bonding efficiency and precision are improved, but thermal interface material (TIM) cannot be formed after LAB due to reflection or absorption issues with back side metallization (BSM) layers
Solution Approach 1:
The patent applies preliminary action by forming the TIM layer on the substrate before performing laser-assisted bonding. This sequence allows the laser to reflow solder bumps through the TIM layer without interference from BSM layers, as the TIM is already in place and the laser parameters can be optimized for solder reflow without causing reflection or absorption issues.
Solution Approach 2:
The patent inverts the conventional sequence by placing the TIM layer before the solder bumps and BSM layers. Instead of the traditional TIM placement after bonding, the TIM is deposited first, allowing it to serve as both a thermal interface material and a laser-transparent layer during the LAB process.
2Reliability
If BSM layer is present on semiconductor die, then electrical connectivity is improved, but laser beam cannot effectively reflow solder due to reflection or absorption
Solution Approach 1:
The patent introduces the TIM layer as an intermediary between the laser beam and the solder bumps. The TIM layer is selected to be transparent or translucent to the laser wavelength used, allowing the laser energy to pass through and effectively reflow the solder without being reflected or absorbed by the BSM layers underneath.
Solution Approach 2:
The patent changes the optical parameters of the system by selecting specific TIM materials with appropriate laser transmission properties and optimizing laser wavelength and power parameters. This allows the laser to penetrate through the TIM layer and effectively heat the solder bumps without excessive reflection or absorption from underlying metal layers.
3Temperature
If conventional thermal solutions (heat sinks, TIM) are used, then heat dissipation is improved, but they cannot be used with LAB technique
Solution Approach 1:
The patent merges the TIM layer formation with the LAB process by depositing the TIM layer before bonding and using it as part of the laser processing pathway. This integration allows the TIM to serve dual purposes: providing thermal management functionality and enabling laser energy transmission during LAB, thus combining thermal solutions with advanced bonding techniques.
Solution Approach 2:
The TIM layer is designed to perform multiple functions simultaneously: it provides thermal interface functionality for heat dissipation, serves as a laser-transparent window for energy transmission during LAB, and acts as an adhesive layer for bonding. This multi-functionality resolves the contradiction between thermal management requirements and LAB process compatibility.
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
This approach enables the use of LAB for reflowing solder while allowing the subsequent formation of a TIM layer, enhancing heat dissipation and reducing the risk of BSM layer peeling, thus improving the reliability and performance of semiconductor devices.
Implementation Method 1
irradiating the second die surface with a laser beam, wherein the laser beam passes through the semiconductor die and reflows the solder of the interconnect structure
Data Source
AI summary
A semiconductor device and a method for forming the same are provided. The method includes: providing a substrate; providing a semiconductor die having a first die surface and a second die surface opposite to the first die surface; attaching the first die surface to the substrate via an interconnect structure comprising solder; and irradiating the second die surface with a laser beam, wherein the laser beam passes through the semiconductor die and reflows the solder of the interconnect structure. In the method, laser-assisted bonding can is used to reflow solder bumps, and thermal interface material can be formed after the laser-assisted bonding.