Flowable Polysilicon Chips for Czochralski Crucible Recharging
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Solution Overview
Problem
The Czochralski-type process for semiconductor chip production faces inefficiencies in crucible recharging due to irregularly shaped polycrystalline silicon pieces causing incomplete melting, contamination, and short crucible lifespan, leading to increased costs and reduced crystal quality.
Innovation Solution
The development of flowable chips with controlled particle size distribution, nonspherical morphology, and low impurity levels, prepared by comminuting and sorting polycrystalline silicon rods, which can be added to the crucible during or after ingot pulling to efficiently recharge and minimize contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If granular polycrystalline silicon is added to recharge the crucible, then the crucible can be efficiently topped up, but the hydrogen released causes granules to burst and splash molten silicon damaging the crucible
Solution Approach 1:
The patent changes the physical and chemical parameters of the silicon charge material by converting granular silicon into flowable chips with controlled morphology, size distribution, and reduced hydrogen content. This parameter transformation allows the material to be added to the crucible without causing explosive reactions while maintaining efficient recharging capability.
Solution Approach 2:
The patent converts the harmful effect of hydrogen release from granular silicon into a beneficial process by using flowable chips with controlled hydrogen content and morphology. The chips melt smoothly without bursting, transforming what would be a dangerous splashing event into a controlled melting process that extends crucible life.
2Productivity
If granular polycrystalline silicon is added during ingot pulling, then the crucible is recharged, but the small particle size makes it difficult to melt in sufficient time requiring additional heat
Solution Approach 1:
The patent optimizes the size and morphology parameters of the silicon material to create flowable chips that melt more efficiently than granular silicon. The controlled particle size distribution and chip morphology enable complete melting within the available process time without requiring excessive additional heating, thus reducing energy consumption.
3Productivity
If granular polycrystalline silicon is added at high rate, then recharging is efficient, but the granules do not melt sufficiently causing damage to the ingot surface and reducing crystal quality
Solution Approach 1:
The patent transforms the physical parameters of the silicon charge material into flowable chips with optimized morphology and size distribution. This transformation enables the material to melt completely at high addition rates without causing surface damage or compromising crystal quality, thus resolving the contradiction between recharge efficiency and ingot quality.
4Ease of operation
If polycrystalline silicon pieces are broken into smaller sizes for crucible recharge, then the material can be added easily, but contamination with impurities makes the silicon unsuitable for use
Solution Approach 1:
The patent changes the physical form of polycrystalline silicon from broken pieces to flowable chips with controlled morphology and size. This parameter transformation maintains ease of addition while preserving silicon purity, as the chip formation process avoids the contamination issues associated with breaking silicon into smaller fragments.
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
This method allows for efficient crucible recharging with reduced contamination and extended crucible lifespan, improving crystal quality and reducing production costs by ensuring complete melting and minimizing surface damage.
Implementation Method 1
When the granular polycrystalline silicon is added to the heel, the hydrogen is released, causing the granules to burst. This causes splashing of molten silicon
Implementation Method 2
Four heaters surrounding the crucible are used to heat the crucible and source melt to an equilibrium temperature
Implementation Method 3
withdrawing the seed crystal as the source melt crystallizes on the seed to form a single crystal ingot
Implementation Method 4
Melting occurs at a temperature of 1420° C. in an inert gas environment
Data Source
AI summary
A method for recharging a crucible with polycrystalline silicon comprises adding flowable chips to a crucible used in a Czochralski-type process. Flowable chips are polycrystalline silicon particles made from polycrystalline silicon prepared by a chemical vapor deposition process, and flowable chips have a controlled particle size distribution, generally nonspherical morphology, low levels of bulk impurities, and low levels of surface impurities. Flowable chips can be added to the crucible using conventional feeder equipment, such as vibration feeder systems and canister feeder systems.