Concave Susceptor with Central Opening for Epitaxial Wafer Support
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Solution Overview
Problem
Conventional susceptors used in chemical vapor deposition processes cause wafer back surface defects and slip dislocations due to thermal gradients, and they take a long time to heat up and cool down, also blocking hydrogen and dopant outdiffusion.
Innovation Solution
A susceptor design with a recess structure that includes a central opening and multiple lift pin openings, featuring a specific geometry to minimize wafer-susceptor contact and facilitate uniform heating, allowing hydrogen to reach the back surface and dopants to escape, while reducing processing time through improved thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the susceptor has a more concave floor to increase distance between wafer back surface and susceptor, then wafer back surface defects are reduced, but radial temperature gradients form causing slip and dislocations at wafer edge
Solution Approach 1:
The susceptor floor is designed with different concavity levels in different regions: a first concave region with greater depth to prevent wafer back surface contact and defects, and a second concave region with lesser depth near the edge to maintain uniform temperature distribution and prevent slip dislocations. This local differentiation resolves the contradiction between preventing back surface defects and maintaining manufacturing precision.
2Stability of the object's composition
If the susceptor is solid beneath the entire wafer to provide support, then structural stability is improved, but hydrogen and dopant outdiffusion are blocked
Solution Approach 1:
The susceptor is segmented into solid regions for structural support and open regions (first and second concave regions) that allow hydrogen and dopant to pass through. The solid portions provide mechanical stability while the segmented open areas enable necessary chemical transport, resolving the contradiction between structural stability and harmful blocking effects.
3Reliability
If the susceptor has deep recess to prevent wafer contact, then wafer back surface defects are reduced, but processing time increases due to slower heating and cooling
Solution Approach 1:
The susceptor implements localized deep concavity only where needed to prevent wafer back surface contact, while maintaining shallower regions elsewhere. This selective depth variation prevents defects in critical areas without excessively increasing overall thermal mass, thereby balancing reliability improvement with acceptable processing time.
4Ease of manufacture
If the susceptor has uniform depth recess to simplify manufacturing, then ease of manufacture is improved, but radial temperature gradients cause slip and dislocations
Solution Approach 1:
The susceptor features a non-uniform depth recess with a first concave region of greater depth and a second concave region of lesser depth. This deliberate depth variation addresses radial temperature gradients and prevents slip dislocations, prioritizing manufacturing precision over fabrication simplicity.
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 susceptor design reduces wafer back surface defects and slip dislocations, enables faster heating and cooling, and ensures effective hydrogen and dopant exchange, enhancing the epitaxial deposition process efficiency.
Implementation Method 1
The susceptor, which supports the semiconductor wafer in the deposition chamber during the epitaxial deposition, is rotated during the process to ensure the epitaxial layer grows evenly
Implementation Method 2
introducing a cleaning gas, such as hydrogen or a hydrogen and hydrochloric acid mixture, to a front surface of the wafer to pre-heat and clean the front surface of the wafer. The cleaning gas removes native oxide from the front surface
Implementation Method 3
The susceptor, which supports the semiconductor wafer in the deposition chamber during the epitaxial deposition, is rotated during the process to ensure the epitaxial layer grows evenly
Implementation Method 4
block outdiffused dopant from the wafer back surface from escaping
Data Source
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AI summary
A susceptor for supporting a semiconductor wafer in a heated chamber having an interior space. The susceptor includes a body having an upper surface and a lower surface opposite the upper surface. The susceptor also has a recess extending downward from the upper surface into the body along an imaginary central axis. The recess is sized and shaped for receiving the semiconductor wafer therein. The susceptor includes a plurality of lift pin openings extending through the body from the recess to the lower surface. Each of the lift pin openings is sized for accepting lift pins to selectively lift and lower the wafer with respect to the recess. The susceptor has a central opening extending through the body along the central axis from the recess to the lower surface.