Graphite Wafer Carrier with Concave Step for LED Epitaxy
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Solution Overview
Problem
Traditional graphite wafer carriers for LED epitaxial wafer processes result in uneven heating, low yield, and wavelength uniformity issues due to direct contact and airflow interference, leading to defects like warping and poor epitaxial slice quality.
Innovation Solution
A graphite wafer carrier with a concave step and inward-extended support portions at the inner edge of the wafer pocket profiles, which transitions from direct to indirect contact heating and reduces airflow interference, improving thermal radiant heating efficiency and preventing turbulent flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the epitaxial wafer substrate is directly carried on the graphite wafer carrier, then the structure is simple and easy to manufacture, but the heating is uneven and the wavelength uniformity is poor
Solution Approach 1:
The patent introduces an air gap as an intermediary between the graphite wafer carrier and the epitaxial wafer substrate. The wafer is held above the carrier surface by this gap, preventing direct contact. This intermediary layer enables thermal radiant heating instead of contact heating, which resolves the contradiction by providing uniform heating (improving wavelength uniformity) while maintaining a relatively simple carrier structure with just a gap and support portions.
2Manufacturing precision
If airflow is injected into the reaction chamber during epitaxial growth, then the material distribution is improved, but turbulent flow causes warping and hollow defects
Solution Approach 1:
The patent extracts or removes the harmful turbulent flow effect by creating a controlled environment above the wafer. The air gap and support portions are designed to minimize airflow interference and prevent turbulent flow from reaching the wafer surface. This allows material distribution to be improved through controlled airflow while eliminating the harmful warping and hollow defects caused by turbulence.
3Use of energy by moving object
If the wafer substrate is in direct contact with the graphite carrier, then the heat transfer is efficient, but the epitaxial slice quality is poor due to contact heating
Solution Approach 1:
The air gap acts as an intermediary that changes the heat transfer mechanism from contact conduction to thermal radiation. This maintains efficient heat transfer (thermal radiant heating) while preventing the quality issues associated with direct contact heating, such as uneven temperature distribution and contact-related defects. The support portions provide minimal contact points that suffice for mechanical support without compromising heating uniformity.
4Productivity
If the support portions are added to the wafer pocket profile, then the airflow interference is reduced and yield is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the continuous wafer pocket profile into discrete segments with support portions. These support portions are periodically distributed along the inner edge of the pocket profile. This segmentation approach reduces airflow interference by creating a structured pattern that guides flow, thereby improving wafer edge yield while adding only moderate complexity through the periodic support structures rather than a completely redesigned profile.
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 design enhances epitaxial wavelength evenness and yield by over 10% compared to traditional carriers, reducing production costs and improving epitaxial product quality.
Implementation Method 1
transferring the original contact heating of the epitaxial slice into thermal radiant heating, which effectively improves uneven heating of the epitaxial slice
Implementation Method 2
Many LED epitaxial wafers are obtained from the metal-organic chemical vapor deposition (MOCVD) process
Implementation Method 3
After high-temperature pyrolysis, rejoin the LED epitaxial layer on the wafer substrate
Data Source
AI summary
A graphite wafer carrier for LED epitaxial wafer processes, having a plurality of wafer pocket profiles above the carrier for carrying the epitaxial wafer substrate. The inner edge of the wafer pocket profile is a concave step with a plurality of inward-extended support portions; and also has a graphite wafer carrier edge and an axle hole at the center of the graphite wafer carrier. The pocket profiles of different quantities and sizes can be arranged on the basis of different process parameters. The disclosed structure can reduce or eliminate airflow interference and improve the wafer edge yield.