Semiconductor Substrate Bonding via In-Situ Mechanical Scrubbing
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Solution Overview
Problem
The high temperature and pressure required for thermo-compression bonding of semiconductor substrates, particularly Cu—Cu bonding, lead to stress-related failures and increased manufacturing costs, limiting its adoption in volume production and applications like memory chips.
Innovation Solution
A method involving in-situ mechanical scrubbing to remove oxides and contaminants from metal contact structures before bonding, reducing the temperature and pressure needed for effective bonding, using a bonder tool with controlled X-Y plane movement and low pressure scrubbing, combined with fly cutting for planarization, allowing for low temperature and low pressure thermo-compression bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature and high pressure are applied during thermo-compression bonding to break through oxides and contaminants on Cu surfaces, then bonding effectiveness is improved, but stress-related failures occur in the bonded semiconductor substrates
Solution Approach 1:
The patent applies preliminary mechanical scrubbing action to the Cu surfaces before thermo-compression bonding to remove oxides and contaminants. This pre-cleaning step prepares the surfaces in advance, allowing the subsequent bonding process to proceed at lower temperatures and pressures, thereby avoiding stress-related failures while achieving effective bonding.
Solution Approach 2:
The patent replaces part of the thermal-mechanical bonding mechanism with a mechanical scrubbing system. Instead of relying solely on high temperature and pressure to remove oxides, a mechanical scrubbing tool with abrasive elements is used to physically remove contaminants before bonding, reducing the thermal and mechanical stress requirements.
2Reliability
If high temperature and high pressure are used for Cu—Cu bonding, then oxide and contaminant removal is achieved, but manufacturing cost increases and productivity decreases
Solution Approach 1:
The mechanical scrubbing step is performed as a preliminary action before bonding, enabling the use of lower temperature and pressure parameters during the actual bonding process. This reduces the bonding time and energy consumption, thereby increasing manufacturing throughput while maintaining bond quality.
Solution Approach 2:
The patent changes the process parameters by introducing mechanical scrubbing, which allows the bonding process to be conducted at lower temperatures (reducing thermal budget) and lower pressures. This parameter optimization reduces manufacturing costs and increases productivity while achieving reliable bonds.
3Temperature
If conventional chemical cleaning steps are used to minimize Cu oxidization, then bonding temperature and pressure can be reduced, but process complexity increases and compatibility with high volume manufacturing decreases
Solution Approach 1:
The patent replaces chemical cleaning methods with a mechanical scrubbing system. This mechanical approach directly removes oxides and contaminants through physical abrasion, eliminating the need for complex chemical cleaning steps and inert atmosphere requirements, thereby simplifying the overall process while enabling lower bonding temperatures.
Solution Approach 2:
The mechanical scrubbing tool performs the cleaning function directly at the bonding interface, providing a self-contained solution that does not require separate chemical cleaning steps or controlled atmosphere environments. This self-service approach simplifies the process flow and improves compatibility with high volume manufacturing.
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 reduces stress-related failures, lowers manufacturing costs, and enables bonding in applications with stringent requirements, such as memory ICs, by minimizing the thermal budget and pressure required during bonding, while being compatible with high-volume semiconductor processes.
Implementation Method 1
a mechanical scrubbing action, preferably performed by the bonder tool that is subsequently used in TC-bonding
Implementation Method 2
The mechanical scrubbing action is performed at very low frequency, while the X-Y plane movement of the semiconductor substrates ranges from a few nanometers to around a few micrometer
Implementation Method 3
TC-bonding, whereby the Cu surfaces of the semiconductor substrates are brought into contact applying force (pressure) and heat simultaneously
Implementation Method 4
applying force (pressure) and heat simultaneously
Data Source
AI summary
A method is provided for bonding a first semiconductor substrate to a second semiconductor substrate using low temperature thermo-compression. The bonding method comprises the step of in-situ mechanically scrubbing the metal contact structure surfaces prior to thermo-compression bonding step, thereby planarizing the removing the oxides and/or contaminants from the metal contact structure surfaces. The thermo-compression bonding step is followed by a thermal annealing step for creating interface diffusion between the metal contact structure of the first and second semiconductor substrates