Continuous Czochralski Silicon Ingot Growth with Nitrogen Doping

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Solution Overview

Problem

The Continuous Czochralski method for growing single crystal silicon ingots faces challenges in maintaining uniform defectivity and oxygen concentration across the ingot length, leading to variations in intrinsic point defects and microdefects, which affect the quality and yield of semiconductor materials.

Innovation Solution

The method involves adding a source of nitrogen to the initial charge of polycrystalline silicon, maintaining a constant melt elevation level through continuous replenishment, and controlling the pull rate to achieve uniform nitrogen and oxygen concentrations across the ingot, ensuring a substantial portion of the ingot meets specifications for defect-free silicon.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If continuous replenishment of polycrystalline silicon is performed to maintain melt level, then productivity is improved, but uniformity of defect distribution deteriorates

Engineering Contradiction:

Improvecontinuous crystal growthVSAvoiduniformity of defect distribution

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by systematically varying the pull rate during different growth stages (neck formation, seed cone, main body) to control defect distribution. By adjusting the pull rate parameter in response to changing melt conditions during continuous growth, the method maintains uniform defect characteristics throughout the ingot while enabling continuous production.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If pull rate is varied to control defect distribution, then manufacturing precision is improved, but productivity deteriorates

Engineering Contradiction:

Improveuniformity of nitrogen and oxygen concentrationVSAvoidgrowth rate

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent implements dynamics by continuously adjusting the pull rate based on the growth stage and melt conditions. The pull rate is dynamically optimized to maintain uniform nitrogen and oxygen concentration while maximizing productivity. This dynamic control allows the system to adapt to changing conditions without sacrificing either precision or speed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses parameter changes by systematically varying the pull rate during different growth stages (neck formation, seed cone, main body) to control defect distribution. By adjusting the pull rate parameter in response to changing melt conditions during continuous growth, the method maintains uniform defect characteristics throughout the ingot while enabling continuous production.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If nitrogen source is added to initial charge, then uniform nitrogen concentration is improved, but device complexity increases

Engineering Contradiction:

Improveuniformity of nitrogen concentrationVSAvoiddoping process complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by incorporating the nitrogen source into the initial polycrystalline silicon charge before melting. This preliminary doping approach ensures uniform nitrogen distribution throughout the ingot without requiring complex in-process doping equipment or procedures, thereby maintaining process simplicity while achieving compositional uniformity.

Inventive Principle:

Principle #10Preliminary action

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 enables the growth of single crystal silicon ingots with reduced agglomerated defects and uniform nitrogen and oxygen distribution, meeting industry standards for perfect silicon over a significant portion of the ingot length, thereby enhancing the yield and quality of semiconductor wafers.

Implementation Method 1

heating the crucible comprising the initial charge of polycrystalline silicon and the source of nitrogen to cause a silicon melt to form in the crucible

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

withdrawing the silicon seed crystal to grow a neck portion... withdrawing the silicon seed crystal to grow an outwardly flaring seed-cone... withdrawing the silicon seed crystal to grow a main body of the single crystal silicon ingot

Methodology Applied

Scientific EffectCrystallisation: Crystallisation

Data Source

PatentUS11680336B2Methods for growing a nitrogen doped single crystal silicon ingot using continuous Czochralski method

Publication Date: 2023.06.20 GLOBALWAFERS CO LTD

AI summary

A method for growing a single crystal silicon ingot by the continuous Czochralski method is disclosed. The melt depth and thermal conditions are constant during growth because the silicon melt is continuously replenished as it is consumed, and the crucible location is fixed. The critical v/G is determined by the hot zone configuration, and the continuous replenishment of silicon to the melt during growth enables growth of the ingot at a constant pull rate consistent with the critical v/G during growth of a substantial portion of the main body of the ingot. The continuous replenishment of silicon is accompanied by periodic or continuous nitrogen addition to the melt to result in a nitrogen doped ingot.