Light Emitting Device Stacking via Transmissive Conductive Bonding
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Solution Overview
Problem
The existing light emitting devices with vertically stacked LED chips face a challenge in maximizing the formation area of the active layer per unit area due to the need for electrode formation for each chip, leading to reduced light emission efficiency.
Innovation Solution
A method for manufacturing a light emitting device involves preparing multiple wafers with semiconductor layers and active layers, bonding them using a light-transmissive conductive layer, and removing substrates to expose semiconductor layers, allowing for the stacking of light emitting portions while maintaining electrical connectivity through light-transmissive conductive layers, thereby increasing the active layer formation area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive or negative electrode is provided for each light-emitting diode chip, then electrical connectivity is ensured, but the formation range per unit area of the active layer becomes smaller
Solution Approach 1:
The patent merges the electrode formation process across multiple stacked wafers by bonding wafers with light-transmissive conductive layers. This allows a single continuous electrode to span across multiple active layers vertically, eliminating the need for separate electrodes on each wafer surface and thereby increasing the active layer formation area.
Solution Approach 2:
The patent transitions from planar electrode formation on individual wafer surfaces to three-dimensional electrode formation that extends vertically across stacked wafers. By bonding wafers in the vertical dimension and forming electrodes that penetrate through the stack, the effective electrode formation area is increased without sacrificing horizontal active layer area.
2Productivity
If multiple wafers are stacked vertically, then light emission efficiency per unit area is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the manufacturing process into distinct stages: preparing multiple wafers with active layers independently, bonding them together with light-transmissive conductive layers, and then forming electrodes across the stacked structure. This segmentation allows each stage to be optimized independently, reducing overall manufacturing complexity while achieving high light emission efficiency.
Solution Approach 2:
The patent performs preliminary actions by pre-forming active layers and light-transmissive conductive layers on each wafer before stacking. This preliminary preparation simplifies the subsequent bonding and electrode formation processes, as the structures are already in place and only require alignment and connection, thereby reducing manufacturing complexity.
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 enables the easy manufacturing of light emitting devices with enhanced light emission efficiency by increasing the active layer formation area per unit area, improving light extraction and emission properties.
Implementation Method 1
bonding the first semiconductor layer exposed at the surface of the second wafer and a second semiconductor layer of another first wafer of the m first wafers together using a light-transmissive conductive layer
Data Source
AI summary
A method of manufacturing a light emitting device includes: a first wafer preparation step including preparing, on a first substrate, m first wafers (where m≥2), each of the first wafers comprising a first semiconductor layer, an active layer, and a second semiconductor layer; a second wafer preparation step including bonding a second substrate with the second semiconductor layer of a first of the m first wafers and then removing the first substrate from the first wafer, so as to form a second wafer in which the first semiconductor layer is exposed; and a first bonding step including bonding the first semiconductor layer exposed at the surface of the second wafer and the second semiconductor layer of a second of the m first wafers together using a light-transmissive conductive layer, and then removing a first substrate of the second of the m first wafers.