Epitaxial Susceptor Underpressure Substrate Clamping
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Solution Overview
Problem
In epitaxial deposition reactors, substrates undergo deformation and thermal stresses due to temperature differences, leading to crystallographic and electrical defects, particularly when in contact with disc-shaped susceptors with shaped pockets that do not maintain uniform heating.
Innovation Solution
A susceptor with flat-bottomed pockets and an intake system that creates a pressure difference to grip substrates uniformly, preventing edge contact and maintaining substrate flatness during heating, deposition, and cooling, thereby minimizing thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If substrates are placed in shaped pockets of disc-shaped susceptors, then substrates can be supported during epitaxial deposition, but substrates undergo deformation and thermal stresses due to temperature differences
Solution Approach 1:
Instead of shaping the pocket to match the deformed substrate shape (convex bottom), the invention inverts the approach by using a flat-bottomed pocket and applying underpressure to grip the substrate from below. This reverses the conventional wisdom and achieves uniform contact and heating without substrate deformation.
Solution Approach 2:
The invention changes the pressure parameter by introducing a pressure difference (underpressure) between the substrate backside and the pocket. This pressure parameter change enables uniform substrate gripping and contact with the flat pocket bottom, preventing thermal deformation while maintaining stable support during epitaxial deposition.
2Productivity
If substrates are heated from low temperature to high temperature, then epitaxial deposition can be performed, but substrates undergo thermal deformation and take non-planar shapes
Solution Approach 1:
The invention applies underpressure to grip the substrate before and during heating, as a preliminary action. This pre-applied constraint prevents the substrate from deforming into non-planar shapes during the temperature transition, while still allowing epitaxial deposition to proceed at the required high temperatures.
Solution Approach 2:
The invention uses pressure as a controlling parameter to counteract thermal effects. By maintaining a pressure difference (underpressure) during the heating process, the substrate is constrained to remain planar despite the temperature increase required for epitaxial deposition.
3Power
If substrates contact the susceptor only in a central area, then heating can be concentrated, but radial temperature differences increase and deformation worsens
Solution Approach 1:
Instead of concentrating heating in the center through shaped pockets, the invention inverts the approach by using a flat-bottomed pocket with underpressure to distribute contact uniformly across the substrate. This reverses the conventional heating concentration strategy and achieves radial temperature uniformity.
Solution Approach 2:
The invention creates equipotential contact conditions by using a flat pocket bottom with underpressure, ensuring uniform pressure distribution and contact across the substrate surface. This eliminates radial temperature differences by establishing uniform thermal contact potential, preventing edge-related heating issues.
4Ease of operation
If pocket edges contact substrate edges, then substrate positioning is constrained, but temperature non-uniformity occurs at substrate edges
Solution Approach 1:
Instead of using shaped pocket edges to constrain the substrate, the invention inverts the approach by using a flat-bottomed pocket with underpressure. The substrate is gripped uniformly from below without edge-to-edge contact, reversing the conventional constraint method and eliminating edge temperature non-uniformity.
Solution Approach 2:
The invention changes the constraint mechanism from geometric (shaped pocket edges) to pressure-based (underpressure). This pressure parameter change allows substrate positioning without edge contact, preventing the temperature non-uniformity that would result from edge-to-edge contact while maintaining operational ease.
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
Ensures regular and uniform contact between the substrate and susceptor, reducing thermal stresses and crystallographic defects, and maintaining substrate flatness throughout the process.
Implementation Method 1
an intake system adapted to create a pressure difference to grip the substrate uniformly
Implementation Method 2
gripped on the susceptor by means of underpressure
Data Source
AI summary
The susceptor for an epitaxial deposition reactor comprises a disc-shaped portion (11, 12) which is adapted to be placed horizontally and which at the top has at least one cylindrical pocket (200) where a substrate (100) to be subjected to an epitaxial deposition process is placed; the pocket (200) has a bottom; one or more conduits (13) fluidically connected to an intake system (300) open on the bottom of the pocket (200); when a substrate (100) is placed on the bottom of the pocket (200) and the intake system (300) is active, the substrate (100) remains adhering to the bottom of the pocket (200). In particular: the upper body 12) superiorly has the pocket (200), the conduits (13) vertically cross only the upper body (12), the conduits (13) are fluidically connected to a plenum (14) located between the lower body (11) and the upper body (12) below the pocket (200), the plenum (14) is fluidically connected to the intake system (300); whereby when a substrate (100) is placed on the bottom of the pocket (200) and the intake system (300) is active, the lower body (11) and the upper body (12) remain united.