Resistivity Stabilization for High Resistivity Silicon Ingots
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Solution Overview
Problem
The Czochralski process for producing single crystal silicon ingots faces challenges in achieving precise resistivity control due to variability in impurity profiles and oxygen levels, leading to inaccuracies in resistivity measurement, especially for high resistivity applications like advanced wireless communication and insulated gate bipolar transistors.
Innovation Solution
A method involving growing a sample rod with a diameter less than the product ingot, slicing a center slab, annealing to annihilate thermal donors, lapping, and irradiating with infrared light to expedite resistivity relaxation, allowing for more accurate and rapid resistivity measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional resistivity measurement methods are used on high resistivity silicon materials, then measurement can be performed, but measurement accuracy deteriorates due to increased error in resistivity measurement for high resistivity applications
Solution Approach 1:
The patent applies preliminary action by performing an infrared irradiation treatment on the silicon sample before resistivity measurement. This pre-treatment step accelerates the relaxation of thermal donors and stabilizes the resistivity value, ensuring that the subsequent measurement is performed on a stabilized sample. The irradiation is conducted for a specific duration (e.g., 1-24 hours) to achieve complete stabilization, thereby eliminating measurement errors caused by unstable resistivity in high resistivity materials.
2Measurement precision
If sufficient time is allowed for resistivity stabilization in high resistivity materials, then measurement accuracy improves, but processing time increases significantly
Solution Approach 1:
The patent employs periodic action through infrared irradiation to periodically stimulate and accelerate the relaxation process of thermal donors in the silicon lattice. Instead of waiting for natural, slow stabilization over extended periods, the periodic infrared energy input drives the system toward equilibrium much faster. This irradiation can be applied in continuous or intermittent cycles, achieving complete stabilization within 1-24 hours compared to conventional methods that require much longer waiting periods.
Solution Approach 2:
The patent changes the physical parameter of energy input by introducing infrared radiation to the system. This external energy parameter modifies the relaxation kinetics of thermal donors, transforming a slow natural process into a rapid irradiation-driven process. By controlling the infrared irradiation intensity and duration, the stabilization time is precisely controlled to achieve accurate measurements in a significantly reduced timeframe.
3Manufacturing precision
If conventional measurement procedures are used, then standard processing can be maintained, but resistivity control precision deteriorates due to variability in impurity profile and oxygen levels
Solution Approach 1:
The infrared irradiation treatment serves as a preliminary action that standardizes the sample state before measurement. By accelerating thermal donor relaxation and achieving complete stabilization, the method eliminates variability caused by incomplete relaxation. This ensures that measurements reflect the true impurity concentration and oxygen levels without being confounded by transient resistivity changes, thereby improving the reliability of impurity profile determination and resistivity control in high resistivity silicon production.
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 enables precise control of resistivity in single crystal silicon ingots by reducing the stabilization time required for accurate resistivity measurements, improving the accuracy of dopant concentration determination and reducing impurity build-up, thus enhancing the production of high resistivity ingots.
Implementation Method 1
irradiating the slab with infrared light
Implementation Method 2
annealing the slab to annihilate thermal donors
Data Source
AI summary
Methods for forming single crystal silicon ingots with improved resistivity control are disclosed. The methods involve growth of a sample rod. The sample rod may have a diameter less than the diameter of the product ingot. The sample rod is cropped to form a center slab. The resistivity of the center slab may be measured directly such as by a four-point probe. The sample rod or optionally the center slab may be annealed in a thermal donor kill cycle prior to measuring the resistivity, and the annealed rod or slab is irradiated with light in order to enhance the relaxation rate and enable more rapid resistivity measurement.