Single Crystal FZ Heating for Temperature Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The Floating Zone (FZ) method for producing single crystals often results in dislocations and uneven dopant distribution due to temperature gradients, particularly in crystals with diameters of 200 mm and above, leading to unusable single-crystal semiconductor wafers and varying electrical resistance.
Innovation Solution
An additional heating device is used to selectively heat colder positions on the circumference of the single crystal, compensating for non-uniform temperature distributions and dopant concentrations by employing a laser light source directed via optical devices, with a control system to adjust heating based on temperature measurements or crystal rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-frequency coil is used to melt polycrystalline semiconductor material in the FZ method, then single crystals can be produced, but temperature gradients occur in the circumferential direction leading to dislocations and uneven dopant distribution
Solution Approach 1:
The patent applies local quality by using multiple independent heating zones with individually controllable heating elements arranged around the circumference of the single crystal. Each heating zone can be independently controlled to compensate for local temperature variations, ensuring uniform temperature distribution across the entire crystal while maintaining the ability to produce high-quality single crystals without dislocations
Solution Approach 2:
The heating system is segmented into multiple independent heating zones distributed around the circumference of the single crystal. This segmentation allows each zone to be controlled separately, enabling precise compensation of temperature gradients in different circumferential positions, thereby eliminating the temperature non-uniformity caused by the single high-frequency coil
2Productivity
If the single crystal diameter is increased to 200 mm and above, then production capacity is improved, but dislocations occur more frequently making the crystals unusable
Solution Approach 1:
The heating system is divided into multiple independent heating zones that can be individually controlled, allowing precise temperature management across large-diameter crystals (200 mm and above). This segmentation enables uniform temperature distribution even in larger crystals, preventing dislocation formation and maintaining high manufacturing precision while increasing production capacity
Solution Approach 2:
Multiple independently controllable heating elements are distributed around the circumference to provide localized temperature control. This allows each region of the large-diameter crystal to receive appropriate heating, preventing temperature-induced dislocations and maintaining crystal quality even as crystal size increases for higher productivity
3Temperature
If additional heating devices are used to compensate for temperature non-uniformity, then temperature distribution is improved, but device complexity increases
Solution Approach 1:
The heating system serves multiple functions: it provides overall heating of the single crystal, compensates for circumferential temperature gradients, and enables independent control of different heating zones. This multi-functionality justifies the increased device complexity by delivering comprehensive temperature control that eliminates dislocations and ensures uniform dopant distribution
Solution Approach 2:
The system changes the heating parameters (temperature, heating power distribution) in different circumferential zones to compensate for temperature non-uniformity. By dynamically adjusting heating parameters in each zone, the system achieves uniform temperature distribution across the single crystal, resolving the temperature uniformity issue despite increased system complexity
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 approach reduces temperature gradients and dopant concentration variations, achieving a uniform electrical resistance within 2% across the single crystal's cross-sectional area and maintaining uniformity around the drawing edges, making the single crystals suitable for semiconductor wafer production.
Implementation Method 1
electromagnetic energy can be coupled into the polycrystal, which is brought close to the RF coil, by excitation using high frequency
Implementation Method 2
A high-frequency coil (HF coil or induction heating coil) is typically used for melting
Implementation Method 3
an additional heating device, in particular with a laser light source, by means of which a selective heating of the single crystal at colder positions on its circumference is possible
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Method and apparatus for growing a single crystal (103) according to the FZ method, in which a rod of polycrystalline semiconductor material (101) is melted by means of an electromagnetic melting device (210) and subsequently crystallized as a single crystal, wherein an uneven distribution of the temperature of the single crystal (103) occurring in the circumferential direction (Ru) of the single crystal (103) is at least partially compensated by means of an additional heating device (230), characterized in that the single crystal (100) is selectively heated additionally at colder positions of its circumference by means of the additional heating device (230).