CVD Reactor Floor Rising in Feeder Zone
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Solution Overview
Problem
In CVD reactors, parasitic coatings form in the feeder zone due to process gas decomposition, which is not effectively prevented by existing cooling measures, leading to inefficiencies and substrate contamination.
Innovation Solution
The design features a non-uniform process chamber floor with a first floor portion that rises in the flow direction from the gas inlet element, transitioning into a second floor portion, creating a gradual height reduction and minimizing vortex formation, thereby reducing the formation of parasitic coatings. This design includes a conical or inclined first floor portion that extends over at least 10% to 30% of the feeder zone length, ensuring a smooth gas flow and effective cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the process chamber floor has a uniform level, then the structure is simple and easy to manufacture, but parasitic coatings form due to vortex formation and gas decomposition
Solution Approach 1:
The first floor portion is designed with a conical shape that rises in the flow direction, creating a curved surface that guides gas flow smoothly and prevents vortex formation. This curved geometry eliminates the sharp edges that cause parasitic coatings, while the conical structure can be manufactured as a single integrated component.
Solution Approach 2:
The floor is divided into two distinct portions: a first floor portion with a conical rising surface in the feeder zone, and a second floor portion with a uniform level in the process zone. Each portion is optimized for its specific function - the conical first portion prevents coating formation by eliminating vortices, while the uniform second portion maintains simple manufacturing and provides stable substrate positioning.
2Object-generated harmful factors
If the first floor portion rises significantly, then parasitic coating formation is reduced, but the process chamber height becomes non-uniform
Solution Approach 1:
The height variation is localized only to the first floor portion in the feeder zone, while the second floor portion maintains a uniform level. This localized approach allows the conical rising surface to prevent parasitic coatings without affecting the overall chamber uniformity, as only the feeder zone experiences the height variation necessary to eliminate vortices.
Solution Approach 2:
The floor is segmented into two distinct portions with different geometric characteristics. The first floor portion has a conical rising surface optimized for preventing parasitic coatings, while the second floor portion has a uniform level optimized for maintaining chamber consistency. This segmentation allows each portion to be optimized independently for its specific function.
3Object-generated harmful factors
If the first floor portion extends over a longer feeder zone length, then gas flow becomes more laminar and coating formation is reduced, but the feeder zone occupies more space
Solution Approach 1:
The conical shape of the first floor portion creates a gradual change in flow parameters as gas moves through the rising surface. This geometric parameter change promotes laminar flow and prevents vortex formation over the extension length, effectively reducing parasitic coatings while maintaining a compact feeder zone design.
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 solution effectively reduces parasitic coating formation in the feeder zone by minimizing gas decomposition products' deposition on the first floor portion, maintaining a consistent process chamber height and ensuring a laminar gas flow, thus enhancing the reactor's efficiency and substrate quality.
Implementation Method 1
The gas inlet element is cooled by means of a cooling agent, in particular a liquid cooling agent, in order to prevent the process gases from decomposing within the gas inlet element or reacting with one another, respectively
Implementation Method 2
The susceptor, which consists of graphite or another electrically conductive and/or thermally conductive material, is heated from below by means of a heating device. The substrates located on substrate carriers are heated to a process temperature by means of the heat supplied by the heating device
Implementation Method 3
ensuring a smooth gas flow and effective cooling
Data Source
AI summary
A CVD reactor comprising a gas inlet element which has a cooling device and gas outlet openings which lead into a process chamber. The process chamber has a feeder zone directly adjoining the gas inlet element and a process zone with one or more substrate holders. The process zone follows the feeder zone in a flow direction of a process gas entering the process chamber from the gas outlet openings. The feeder zone has a first floor portion directly adjoining the gas inlet element and a second floor portion located between the first floor portion and the process zone. In order to prevent the formation of parasitic coatings during deposition of, for example, silicon carbide at the start of the feeder zone, the first floor portion rises in the flow direction, so that the height of the process chamber initially decreases starting from the gas inlet element.