Conical Crucible for Near-Net Shape Silicon Casting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for producing near-net shape silicon ingots using square quartz crucibles are costly and inefficient due to multiple processing steps and material wastage, as they often result in ingots that are prone to cracking during solidification and cooling.
Innovation Solution
A crucible design featuring inner and outer conical walls with a specific acute angle, coated with silicon nitride, which accommodates the thermal expansion and contraction of silicon, preventing cracking and allowing for the production of longer ingots without defects, and a method for easily releasing the ingot by disengaging the inner element from the outer element after formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard square quartz crucibles are used to cast multi-crystalline silicon, then the ingots can be produced, but the ingots are prone to cracking during solidification and cooling
Solution Approach 1:
The patent changes the geometric parameters of the crucible from a standard square shape to a shape with conical walls having a specific acute angle (α). This parameter change in the crucible geometry directly prevents cracking during solidification and cooling, improving ingot reliability while maintaining manufacturability.
Solution Approach 2:
The crucible employs a composite structure combining quartz material with a silicon nitride coating layer. This composite material approach provides both the structural integrity of quartz and the crack-prevention properties of silicon nitride, resolving the contradiction between ingot reliability and ease of manufacture.
2Productivity
If multiple processing steps are used to shape chamber parts from squared Mc-Si ingots, then the parts can be manufactured, but the process is costly and time-consuming
Solution Approach 1:
The crucible is designed with conical walls that pre-form the desired shape of chamber parts during the casting process itself. This preliminary action eliminates the need for subsequent machining and shaping operations, significantly improving productivity and reducing material wastage.
Solution Approach 2:
By changing the crucible geometry to have conical walls with acute angles, the ingot emerges with a near-net shape that requires minimal post-processing. This parameter change in crucible design directly reduces both processing time and material loss.
3Strength
If the inner conical wall and outer conical wall are made of quartz, then the crucible provides structural integrity, but the ingot may still crack during solidification
Solution Approach 1:
The crucible uses a composite material system where quartz provides structural integrity and strength, while the silicon nitride coating layer provides crack prevention during solidification. This composite approach resolves the contradiction between structural strength and ingot reliability.
Solution Approach 2:
The silicon nitride coating acts as an intermediary layer between the quartz crucible wall and the molten silicon. This intermediary prevents direct contact that causes cracking, while the quartz structure maintains its structural integrity.
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 design enables the production of longer, defect-free near-net shape silicon ingots, reducing material wastage and processing costs by preventing cracking and facilitating easy removal of the ingot, thus improving the efficiency of the ingot formation process.
Implementation Method 1
The acute angle prevents the ingot from cracking
Implementation Method 2
at least one heater arranged around the outer conical wall to heat pieces of the solid material loaded in the hollow mold
Implementation Method 3
a cooling apparatus arranged near the bottom end of the hollow mold to cool a melted liquid formed in the hollow mold
Data Source
AI summary
A crucible includes an outer element and an inner element. The outer element includes a first portion that is horizontal at a bottom end of the crucible and a second portion that ascends radially outwardly from the bottom end of the crucible to a top end of the crucible at a first acute angle to a vertical axis. The inner element includes a conus with a cylinder at a base of the conus. The conus descends radially outwardly from the top end of the crucible to the bottom end of the crucible at a second acute angle to the vertical axis. The inner element includes a base portion of the cylinder attached to the first portion of the outer element using a sealant to form a hollow mold between an inner portion of the outer element and an outer portion of the inner element.