Die-to-Wafer Bonding Heads for Warpage Gap Reduction
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Solution Overview
Problem
The increasing complexity of integrated circuit packages, which include multiple device dies, poses challenges in bonding devices with different technologies and functions, leading to manufacturing costs and performance optimization issues due to warpage and gaps between semiconductor dies and wafers.
Innovation Solution
A device bonding apparatus employing a two-stage pre-anneal bonding process using a first bond head with a vacuum channel and a second bond head with an elastic head to apply different downward forces, reducing or eliminating gaps caused by warpage and improving bonding yield and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple device dies are packaged in the same package to achieve more functions, then the device performance and manufacturing cost are optimized, but warpage and gaps between semiconductor dies and wafers occur during bonding
Solution Approach 1:
The patent applies a pre-anneal bonding process before final bonding to reduce warpage and gaps. The pre-anneal step heats the semiconductor die to a first temperature to relax internal stresses and reduce warpage, creating better bonding conditions for subsequent steps. This preliminary action addresses the warpage issue that would otherwise compromise bonding precision and reliability.
Solution Approach 2:
The patent employs different temperature parameters at different bonding stages. The pre-anneal process uses a first temperature range, while the final bonding uses a second temperature range. By changing temperature parameters appropriately at different stages, the patent optimizes both warpage reduction and bonding quality, resolving the contradiction between bonding reliability and precision.
2Device complexity
If a single bonding process is used for all device dies, then the process is simple, but bonding yield and reliability are reduced due to warpage and gaps
Solution Approach 1:
The bonding process is segmented into multiple distinct stages: pre-anneal bonding, intermediate processing, and final bonding. Each stage has specific temperature ranges and objectives. This segmentation allows the patent to address warpage reduction separately from final bonding, improving reliability without creating an overly complex monolithic process.
Solution Approach 2:
The pre-anneal bonding stage serves as a preliminary action that prepares the semiconductor die for final bonding by reducing warpage and improving surface flatness. This preliminary step enhances bonding reliability while keeping the overall process structure manageable through clear stage differentiation.
3Reliability
If downward force is applied during bonding to reduce gaps, then bonding reliability improves, but warpage of the semiconductor die increases
Solution Approach 1:
The pre-anneal bonding process is performed as a preliminary action before applying significant downward force for final bonding. This preliminary heating and stress relaxation reduces the die's susceptibility to warpage when force is later applied, allowing gap reduction without severe shape distortion.
Solution Approach 2:
The patent changes temperature parameters between stages - using elevated temperature during pre-anneal to reduce warpage sensitivity, then adjusting temperature and force parameters during final bonding. This parameter optimization allows gap closure while minimizing warpage effects through appropriate thermal-mechanical conditioning.
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 two-stage pre-anneal bonding process enhances the process yield and reliability of semiconductor die-to-wafer bonding by minimizing gaps and ensuring stable electrical connections, thereby improving the overall performance and efficiency of the package manufacturing process.
Implementation Method 1
a first bond head configured to carry the die to the wafer, the first bond head including a first rigid body and a vacuum channel in the first rigid body for providing an attaching force for collecting the die to the wafer
Implementation Method 2
a second bond head configured to press the die against the wafer, the second bond head including a second rigid body and an elastic head disposed over the second rigid body for pressing the die, the elastic head including a center portion and an edge portion surrounding the center portion
Data Source
AI summary
In an embodiment, a device bonding apparatus is provided. The device bonding apparatus includes a first process station configured to receive a wafer; a first bond head configured to carry a die to the wafer, wherein the first bonding head includes a first rigid body and a vacuum channel in the first rigid body for providing an attaching force for carrying the die to the wafer; and a second bond head configured to press the die against the wafer, the second bond head including a second rigid body and an elastic head disposed over the second rigid body for pressing the die, the elastic head having a center portion and an edge portion surrounding the center portion, the center portion of the elastic head having a first thickness, the edge portion of the elastic head having a second thickness, the second thickness being greater than the second thickness.