Plasma Doping Method for Uniform Impurity Distribution
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Solution Overview
Problem
The challenge in plasma doping is achieving high precision and uniformity of impurity dose distribution across large-diameter semiconductor wafers, as existing methods struggle to maintain dose uniformity, especially with increasing wafer sizes, leading to reduced productivity and low throughput.
Innovation Solution
A plasma doping method where the initial dose distribution is set with higher doses in the central portion of the substrate compared to the peripheral portion, and then reversed, allowing for a predetermined plasma doping time to achieve uniformity by adjusting gas flow rates, concentrations, or source power, ensuring a stable and precise impurity distribution across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If ion implantation is used to implant impurities at low energy to achieve shallow depth, then the implantation depth is reduced, but the throughput decreases due to beam loss and difficulty in beam delivery
Solution Approach 1:
The patent replaces the mechanical ion beam system with a plasma-based system. Instead of using an ion source, analyzing magnet, and acceleration electrode to deliver ion beams, the invention uses plasma generation to create a cloud of ions that are accelerated by electric fields toward the substrate. This substitution eliminates beam loss issues and enables efficient low-energy implantation with high throughput.
Solution Approach 2:
The patent changes the energy parameter by using plasma potential rather than acceleration voltage. By controlling the plasma potential and bias voltage, the system achieves low implantation energy (shallow depth) without the beam loss problems that occur in traditional ion implantation when acceleration energy is reduced. The plasma state allows ions to be delivered efficiently at low energies.
2Productivity
If plasma doping is used to increase throughput with low-energy ions, then the dose rate increases, but the dose uniformity across the substrate surface deteriorates
Solution Approach 1:
The patent applies local quality by creating non-uniform plasma density or ion flux distribution across the substrate surface. By controlling plasma parameters locally (through gas flow distribution, electrode geometry, or bias voltage variation), the system compensates for natural dose non-uniformity and achieves uniform doping across the entire substrate while maintaining high throughput.
Solution Approach 2:
The patent implements feedback control to monitor and adjust plasma parameters in real-time. By measuring the actual dose distribution and adjusting plasma generation parameters accordingly, the system maintains dose uniformity across the substrate surface while operating at high throughput conditions.
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 enhances dose control precision and uniformity across the substrate surface, increasing throughput and productivity, particularly for large-diameter wafers, by utilizing the reversal point of the dose distribution gradient as the process window.
Implementation Method 1
a plasma generation source for inducing a plasma
Implementation Method 2
ions in the plasma are accelerated and introduced into the wafer by the potential generated between the plasma and the wafer
Data Source
AI summary
An impurity region is formed in a surface of a substrate by exposing the substrate to a plasma generated from a gas containing an impurity in a vacuum chamber. In this process, a plasma doping condition is set with respect to a dose of the impurity to be introduced into the substrate so that a first one of doses in a central portion and in a peripheral portion of the substrate is greater than a second one of the doses during an initial period of doping, with the second dose becoming greater than the first dose thereafter.