Quartz Buffer Members for Low-Void Continuous Czochralski Silicon Growth
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Solution Overview
Problem
Existing continuous Czochralski methods for growing single crystal silicon ingots result in high void counts and inert gas bubble formation in wafers, which are not adequately addressed by current technologies.
Innovation Solution
Control the ratio of buffer member mass to time between addition and ingot growth (M/T) to be greater than a threshold, using quartz cullets to reduce inert gas bubble entrapment and enhance dissipation, thereby minimizing void counts in wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If solid polycrystalline silicon is continuously added to the melt to replenish it during ingot growth, then the productivity is improved by enabling multiple ingots to be grown from the same melt, but inert gas bubbles form in the melt which increases the void count in wafers
Solution Approach 1:
A buffer member (quartz or ceramic component) is introduced as an intermediary between the solid polycrystalline silicon feedstock and the molten silicon. The buffer member absorbs the impact of the solid silicon as it enters the melt, preventing direct violent mixing that generates inert gas bubbles. The buffer member dissolves gradually, releasing silicon into the melt in a controlled manner rather than all at once, thereby reducing bubble formation while maintaining continuous replenishment capability
Solution Approach 2:
The buffer member acts as a cushioning element that is placed in the melt beforehand to prepare for the incoming solid silicon feedstock. This cushioning effect mitigates the harmful impact of solid silicon addition before it can generate excessive inert gas bubbles, allowing continuous production while controlling void counts
2Manufacturing precision
If the ratio of buffer member mass to time between addition and ingot growth (M/T) is increased to reduce void counts, then the manufacturing precision is improved by reducing defects in wafers, but the duration of the process increases
Solution Approach 1:
The invention controls the M/T ratio as a key parameter to optimize both defect reduction and process efficiency. By adjusting the mass of buffer members added and the timing relative to ingot growth start, the process achieves effective inert gas bubble management without excessive delays. The buffer member mass and addition timing are optimized to provide sufficient bubble dissipation time while maintaining production schedule
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 void counts in wafers to less than 30 defects per wafer by effectively managing inert gas bubbles, improving the quality of silicon ingots produced by continuous Czochralski processes.
Implementation Method 1
a batch of quartz buffer members is added to the melt... to reduce void counts in wafers sliced from the single crystal silicon ingot
Data Source
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AI summary
Methods for producing single crystal silicon ingots by Continuous Czochralski (CCz ) are disclosed. A batch of buffer members (e. g., quartz cullets ) is added to an outer melt zone of the crucible assembly before the main body of the ingot is grown. In some embodiments, the ratio of the mass M of the batch of buffer members added to the melt to the time between adding the batch of buffer members to the melt and when the ingot main body begins to grow is controlled such that the ratio of M/T is greater than a threshold M/T.