Wafer-Level Micro-Device Bonding Using Distancing Elements
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Solution Overview
Problem
Current wafer-level manufacturing of optical devices faces challenges in achieving precise vertical distancing and control of bonding material thickness and spreading, especially for small devices with tight tolerances and complex geometries.
Innovation Solution
A method involving a distancing element to define the thickness of the bonding material layer between wafers, utilizing capillary forces and designed member shapes to steer the spreading of the bonding material, ensuring precise vertical distancing and preventing unwanted bonding on specific surfaces, thereby allowing for high-precision wafer stacking and small-footprint device production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bonding material is applied between wafers to bond them together, then the wafers are securely attached, but the thickness and spreading of the bonding material layer becomes difficult to control precisely
Solution Approach 1:
A distancing element is introduced as an intermediary component between the first and second wafers. This distancing element has a defined height that physically limits the thickness of the bonding material layer, ensuring precise control of the bonding material thickness without requiring complex process control mechanisms.
Solution Approach 2:
The distancing element is pre-positioned on one of the wafers before the bonding material is applied. This preliminary positioning establishes the exact thickness of the bonding material layer in advance, allowing for precise control of the bonding material thickness before the actual bonding process occurs.
2Reliability
If the bonding material is allowed to spread freely between wafers, then complete coverage is achieved, but bonding material may reach and damage critical surfaces
Solution Approach 1:
The wafer surface is segmented into different functional zones: a central portion containing critical surfaces that must remain free of bonding material, and a peripheral region where the bonding material is allowed to spread. This segmentation is achieved through the distancing element geometry and capillary channel design, ensuring complete bonding coverage in the peripheral region while protecting the central critical surfaces.
Solution Approach 2:
Different regions of the wafer interface are given different properties: the peripheral region allows bonding material spreading for complete coverage, while the central region surrounding critical surfaces prevents bonding material access. The distancing element creates local variations in gap geometry that control the bonding material distribution, providing complete coverage where needed while protecting critical areas.
3Manufacturing precision
If spacer wafers are used to maintain vertical distance between wafers, then precise vertical distancing is achieved, but the control of bonding material thickness and spreading is limited
Solution Approach 1:
The distancing element serves multiple functions simultaneously: it maintains the vertical distance between wafers, controls the thickness of the bonding material layer, and guides the spreading of the bonding material through integrated capillary channels. This multi-functionality eliminates the need for separate spacer components while providing comprehensive control over both vertical distancing and bonding material behavior.
Solution Approach 2:
The distancing function and bonding material control function are merged into a single distancing element structure. The capillary channels are integrated directly into the distancing element, combining the mechanical spacing function with the fluid transport function, thereby providing both precise vertical distancing and versatile bonding material control in one component.
4Manufacturing precision
If capillary forces are used to steer bonding material spreading, then precise control of bonding material distribution is achieved, but the device geometry becomes more complex
Solution Approach 1:
The distancing element with integrated capillary channels autonomously controls the bonding material spreading through capillary forces without requiring external control mechanisms. The capillary channels self-regulate the bonding material flow based on the pressure differential and channel geometry, providing precise control of bonding material distribution while avoiding complex active control systems.
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 enables high-precision vertical distancing and accurate bonding of optical components, preventing bonding material from reaching critical surfaces, thus maintaining device functionality and allowing for stable, high-yield mass production of optical devices with precise dimensions.
Implementation Method 1
utilizing capillary forces and designed member shapes to steer the spreading of the bonding material
Data Source
Figure 1~3
Figure 4~5
AI summary
The device (10) comprises a first member (1) and a second member (2) which are stacked upon each other in a direction vertical direction. The first and second members comprise a central portion (C1; C2) each, and the first member (1) comprises at least a first distancing element (4) abutting the second member (2). The device (10) comprises a gap zone (G) and a bonding material (3), wherein the gap zone is peripheral to the central portions (C1; C2), and in the gap zone (G), a gap (5) is present between the first and second members. A portion of the gap (5) is filled by the bonding material (3) bonding the first and second members to each other in a bonding zone (B) comprised in the gap zone. A height (h) of the gap (5) is defined by the first distancing element (4).