MEMS Cap Bonding via Eutectic Pumping Cycle
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MEMS devices face reliability issues due to oxide layers on bonded surfaces, which affect the bonding process and the integrity of the caps used for protection.
Innovation Solution
A method involving eutectic bonding with a pumping cycle, where a first bond layer and a second bond layer are heated to a temperature above their eutectic temperature, and a varying force is applied in cycles to facilitate a reliable eutectic reaction, removing oxide layers and ensuring strong bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If eutectic bonding is performed to bond caps to MEMS devices, then bonding strength is improved, but oxide layers on bonded surfaces adversely affect bonding reliability
Solution Approach 1:
The patent applies preliminary action by performing oxide removal treatment on the bonded surfaces before the eutectic bonding process. This preliminary step eliminates the harmful oxide layers that would otherwise prevent reliable bonding, ensuring that the subsequent bonding operation achieves both high strength and high reliability.
Solution Approach 2:
The patent converts the harmful effect of oxide layers into a beneficial process by using the oxide removal treatment. The controlled removal of oxides through chemical or mechanical means transforms what would be a bonding obstacle into a preparatory step that enhances bonding quality, turning a potential failure mode into a quality assurance mechanism.
2Reliability
If oxide layers are removed before bonding, then bonding reliability is improved, but additional process steps are required
Solution Approach 1:
The patent merges the oxide removal treatment with the existing bonding process flow by integrating it as a preparatory step within the same manufacturing sequence. This combination approach consolidates multiple functions (surface preparation and bonding) into a unified process, reducing the need for separate handling steps and minimizing additional process complexity.
Solution Approach 2:
The patent applies self-service by designing the oxide removal process to be automatically integrated into the bonding workflow. The process uses in-situ treatments that occur within the bonding chamber or immediately preceding it, eliminating the need for separate manual intervention or additional equipment, thereby reducing process complexity while maintaining reliability.
3Productivity
If pumping cycle with varying force is applied during eutectic bonding, then bonding yield is increased, but process complexity increases
Solution Approach 1:
The patent applies periodic action by implementing a pumping cycle with varying force applied during the eutectic bonding process. The force is cycled between different levels (e.g., high force to remove oxides, low force to allow bonding) in a repeating pattern, which enhances bonding yield by ensuring complete oxide removal while maintaining effective bonding contact throughout the process.
Solution Approach 2:
The patent applies dynamics by transitioning from a static constant-force bonding approach to a dynamic varying-force approach. The force applied during bonding is continuously adjusted according to a predetermined pumping cycle, allowing the system to adapt to different stages of the bonding process (oxide removal phase vs. bonding phase), thereby increasing bonding yield through optimized force management.
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 method results in more reliable bonding, with increased bonding yield and the formation of dendrite structures in the eutectic alloy, significantly improving the structural integrity of the MEMS device caps.
Implementation Method 1
heating the first bond layer and the second bond layer to a temperature higher than a eutectic temperature of the first bond layer and the second bond layer
Implementation Method 2
a first force to press the first bond layer and the second bond layer against each other
Data Source
AI summary
A method includes bonding a first bond layer to a second bond layer through eutectic bonding. The step of bonding includes heating the first bond layer and the second bond layer to a temperature higher than a eutectic temperature of the first bond layer and the second bond layer, and performing a pumping cycle. The pumping cycle includes applying a first force to press the first bond layer and the second bond layer against each other. After the step of applying the first force, a second force lower than the first force is applied to press the first bond layer and the second bond layer against each other. After the step of applying the second force, a third force higher than the second force is applied to press the first bond layer and the second bond layer against each other.