Laser-Assisted Direct Bonding for Wafer Hermeticity
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Solution Overview
Problem
Direct wafer bonding techniques often result in thermal damage and warping due to elevated temperatures and thermal expansion mismatches between substrates, weakening the bond and reducing hermeticity in component packages.
Innovation Solution
Laser-assisted direct bonding techniques that apply localized heating to strengthen the bond between substrates without the need for bulk heating, using a laser to enhance the direct bond formed between substrates, which can be either transparent or opaque to the laser wavelength, thereby reducing thermal stress and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bulk heating is used to strengthen the direct bond between substrates, then bond strength is improved, but thermal damage to temperature-sensitive components and warping due to thermal expansion mismatch increase
Solution Approach 1:
The patent applies localized heating at the bond interface rather than bulk heating of the entire substrate assembly. The laser beam is focused specifically on the contact location between substrates, creating a localized thermal field that strengthens the bond while leaving the bulk substrates and enclosed components at ambient temperature, thus avoiding thermal damage and warping
Solution Approach 2:
The patent introduces a transparent substrate as an intermediary that allows laser energy to pass through to the bond interface. This transparent substrate acts as a mediator that enables selective heating of the bond region without directly heating the opaque substrate or components enclosed within the package
2Reliability
If conventional direct bonding is used to form hermetic packages, then substrate bonding is achieved, but hermeticity is reduced due to thermal stress fractures and warping
Solution Approach 1:
By confining heating to the immediate bond interface region, the patent avoids thermal stress fractures in the bulk substrates. The localized thermal field only affects the contact area where bonding occurs, preserving the structural integrity and hermeticity of the complete package
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 laser-enhanced direct bond exhibits increased mechanical strength and chemical resistance, with tensile strength exceeding 95% of the individual substrates' strengths, and reduced thermal defects, maintaining hermeticity and stability in component packages.
Implementation Method 1
a laser may be directed on at least a portion of the contact location where the direct bond was initially formed... This may result in localized heating proximate to where the direct bond was initially formed
Implementation Method 2
one of the substrates may be substantially transparent to a wavelength of the laser while another of the substrates may be substantially opaque to the wavelength of the laser. In these examples, laser energy may pass through the substrate substantially transparent to the wavelength of the laser and may be absorbed by the substrate substantially opaque to the wavelength of the laser
Data Source
AI summary
Techniques are described for directly bonding different substrates together. In some examples, a technique includes placing a first surface of a first substrate in contact with a second surface of a second substrate to directly bond the first substrate to the second substrate at a contact location. The contact location is defined where at least a portion of the first surface of the first substrate contacts at least a portion of the second surface of the second substrate. The technique may also include directing a laser beam on at least a portion of the contact location to strengthen the direct bond between the first substrate and the second substrate. In this manner, a direct bond may be heated with localized laser energy to strengthen the direct bond. Localized laser energy may create a strong direct bond while minimizing thermal defects in regions proximate the direct bond.