Laminar Gas Flow for Semiconductor Substrate Bonding
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Solution Overview
Problem
The number of bonding defects in substrates increases with the number of substrates bonded in a fabrication line, despite existing methods like surface heating to minimize water presence, which can lead to edge void defects and non-transferred zones in silicon-on-insulator wafers.
Innovation Solution
A method involving a laminar gaseous flow over the bonding surfaces of substrates before contact, which removes water and prevents re-entry, using gases like nitrogen or argon with high thermal conductivity, and optionally heated to enhance convective heating, until the substrates touch, thereby reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If surface heating is applied to remove water from substrates before bonding, then bonding defects are minimized, but the number of defects increases with the number of substrates bonded in a fabrication line
Solution Approach 1:
The patent introduces a flow of inert gas (such as nitrogen or argon) over the bonding surfaces of substrates before bonding. This inert gas flow creates a controlled atmosphere that prevents water vapor from contaminating the bonding interface, thereby maintaining consistent bonding quality across multiple substrates processed in sequence. The inert atmosphere replaces the ambient environment that would otherwise allow moisture accumulation and re-contamination during the bonding process.
2Productivity
If multiple substrates are bonded in sequence, then productivity increases, but bonding defects increase with each additional substrate
Solution Approach 1:
The patent implements a continuous flow of inert gas over the bonding surfaces throughout the entire bonding process, from the first substrate to the last. This continuous protective action ensures that each substrate interface is consistently protected from moisture contamination, regardless of how many substrates are being bonded in sequence. The uninterrupted gas flow maintains a stable, dry environment at the bonding zone for the duration of the multi-substrate processing.
Solution Approach 2:
By maintaining a continuous inert gas atmosphere during sequential bonding operations, the patent prevents cumulative moisture contamination that would otherwise occur with each additional substrate. The inert gas flow rate and timing are optimized to ensure adequate protection for each bonding interface while enabling high-volume processing.
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 method effectively reduces bonding defects by maintaining a dry interface, improving bonding quality and consistency, especially in the SMARTCUT process, by ensuring a repeatable and reliable water removal process without additional heating devices.
Implementation Method 1
providing a flow of a gas over the bonding surfaces of the substrates... water that otherwise might saturate the atmosphere of a tool used for bonding, can be removed from the bonding surfaces
Implementation Method 2
the gaseous flow can be heated such that the heat treatment is at least partially carried out using the heated gaseous flow. Thus, in addition to heating the substrates via radiation or conduction means, an additional convective heating can be provided
Implementation Method 3
the gaseous flow can be heated such that the heat treatment is at least partially carried out using the heated gaseous flow. Thus, in addition to heating the substrates via radiation or conduction means, an additional convective heating can be provided
Implementation Method 4
heating the substrates via radiation or conduction means
Implementation Method 5
bonding by molecular adhesion is a technique during which two substrates are brought in close contact to each other and wherein the surface properties of the substrates are such that they stick to one another, without the application of further adhesives
Data Source
AI summary
The invention relates to a method for bonding two substrates, in particular, two semiconductor substrates that, in order to be able to improve the reliability of the process, provides the step of providing a gaseous flow over the bonding surfaces of the substrates. The gaseous flow is preferably a laminar flow that is essentially parallel to the bonding surfaces of the substrates, and has a temperature in a range of from room temperature up to 100° C.