Epitaxial Shield Surface Irregularities for SiC CVD
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Solution Overview
Problem
In epitaxial wafer manufacturing, the deposition of SiC layers on the ceiling of CVD devices leads to particles falling onto wafers, impairing film quality and requiring frequent and time-consuming cleaning, while using large SiC single crystal ceilings is prone to warping and cracking, and expensive.
Innovation Solution
An epitaxial wafer manufacturing device with a shield having fine surface irregularities on its lower surface, which prevents deposits from falling off and allows for simple maintenance by replacing the shield, and a concentrically divided shield structure to alleviate thermal stress and prevent warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceiling is used in CVD devices for epitaxial wafer manufacturing, then high-temperature heating and epitaxial growth can be achieved, but deposits accumulate on the ceiling surface causing particles to fall onto wafers and impair film quality
Solution Approach 1:
A shield is introduced as an intermediary component between the ceiling and the wafers. The shield captures deposits that would otherwise fall onto the wafers, protecting the epitaxial layers from contamination. The shield acts as a sacrificial element that accumulates deposits instead of the ceiling, thereby preventing particles from reaching the wafer surfaces.
Solution Approach 2:
The shield is designed as a replaceable, relatively inexpensive component compared to the ceiling. It is intentionally allowed to accumulate deposits until it needs to be replaced, rather than requiring cleaning of the ceiling or risking wafer contamination. This disposable approach eliminates the need for frequent cleaning operations and prevents particle generation.
2Object-generated harmful factors
If frequent cleaning of the ceiling is performed to remove deposits, then particle generation can be reduced, but production time is significantly lost and productivity decreases
Solution Approach 1:
The shield serves as a removable intermediary that captures deposits, eliminating the need to clean the ceiling itself. By replacing the shield rather than cleaning the ceiling, the system avoids lengthy cleaning operations while still preventing particle generation. The shield can be quickly swapped out when deposits accumulate.
Solution Approach 2:
Instead of cleaning and reusing the ceiling surface, the deposit-prone shield is discarded (removed and replaced) when it becomes contaminated. This approach prioritizes rapid replacement over time-consuming cleaning, thereby maintaining high productivity while still preventing particles from reaching the wafers.
3Object-generated harmful factors
If large-sized SiC single crystal materials are used for the ceiling to improve adhesion and reduce particles, then particle generation decreases, but the ceiling becomes susceptible to warping and cracking under high-temperature heating
Solution Approach 1:
The shield acts as a mediator that assumes the role of capturing deposits, allowing the ceiling to be made from materials optimized for thermal stability rather than deposit adhesion. The shield handles the deposit accumulation function, freeing the ceiling from this burden and enabling the use of thermally stable materials that resist warping and cracking.
4Ease of repair
If the shield has a smooth surface, then deposits can be easily removed, but deposits tend to fall off onto wafers during thermal deformation
Solution Approach 1:
The shield surface is given a specific roughness profile tailored to the local requirement of preventing deposit detachment during thermal cycling. The controlled surface roughness creates mechanical interlocking with deposits, ensuring they remain anchored to the shield even when thermal deformation occurs, thereby preventing them from falling onto the wafers.
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
Reduces particle and downfall issues, simplifies maintenance, and stabilizes the deposition of high-quality epitaxial layers by preventing deposits from falling and extending the lifespan of the shield components.
Implementation Method 1
a method is used in which the susceptor on which the wafers are mounted and the ceiling (top plate) arranged opposing the upper surface of this susceptor are heated by high-frequency induction heating
Implementation Method 2
the wafers are heated by radiant heat from the susceptor and ceiling
Implementation Method 3
when the shield has undergone thermal deformation as a result of being heated by the heating means, deposits deposited on the lower surface of the shield are inhibited from falling off by the shape of the surface irregularities
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A shield (12), which in addition to being removably attached inside a chamber, is arranged in close proximity to the lower surface of a top plate (3) so as to prevent deposits from being deposited on the lower surface of the top plate (3), has a substrate (12a) having an opening (13) in the central portion thereof that forces a gas inlet (9) to face the inside of a reaction space (K), and a thin film (12b) that covers the lower surface of this substrate (12a), the surface of the thin film (12b) is in the shape of surface irregularities corresponding to fine surface irregularities formed in the lower surface of the substrate (12a), and when the shield (12) has undergone thermal deformation as a result of being heated by heating means (8), deposits deposited on the lower surface of the shield (12) are inhibited from falling off by the shape of the surface irregularities.