Plasma Doping Method for Uniform Boron Distribution
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Solution Overview
Problem
The existing plasma doping methods face challenges in achieving uniform impurity distribution and preventing substrate etching during the formation of shallow extension regions in semiconductor devices, leading to high sheet resistance values and non-uniformity in impurity concentration.
Innovation Solution
A plasma doping method that separates the deposition of radicals and ion radiation steps, allowing independent control of their distributions, and adjusts the deposition and etching speeds to prevent substrate etching, ensuring uniform impurity introduction and low resistance extension regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma doping method is used to introduce impurities into substrate, then impurity introduction is achieved, but uniform in-plane distribution of radicals and ions cannot be simultaneously secured leading to non-uniform impurity distribution
Solution Approach 1:
The plasma doping process is segmented into two distinct steps: (1) radical deposition step where radicals are deposited on substrate surface without ion acceleration, and (2) ion radiation step where ions are accelerated to radiate onto the deposited radicals. This segmentation allows independent control of radical and ion distributions, solving the contradiction between achieving uniform impurity distribution and managing plasma control complexity.
2Productivity
If ions are accelerated to draw into substrate faster than radicals deposit, then impurity introduction speed increases, but substrate surface is etched leading to high sheet resistance
Solution Approach 1:
Radicals are deposited on the substrate surface in advance during the first step before ion acceleration occurs. This preliminary deposition creates a protective layer of impurities on the surface that prevents subsequent ion etching of the substrate, while still allowing fast ion introduction into the substrate during the second step.
Solution Approach 2:
The harmful etching action of accelerated ions is converted into a beneficial process by having ions radiate onto already-deposited radicals rather than directly onto the substrate. The ions still provide rapid impurity introduction but their etching effect is neutralized because they are acting on a layer of deposited impurities rather than the substrate surface itself.
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 uniform impurity distribution and low sheet resistance values by controlling the in-plane distribution of radicals and ions, preventing substrate etching and achieving a low resistance extension region.
Implementation Method 1
a plasma doping method of introducing impurities into a substrate by exposing the substrate to plasma containing the impurities
Implementation Method 2
a phenomenon in which radicals in the plasma deposit on a surface of the substrate
Implementation Method 3
a phenomenon in which ions accelerated by the bias potential are radiated onto the substrate to be drawn into the substrate
Data Source
AI summary
A plasma doping method capable of introducing impurities into an object to be processed uniformly is supplied. Plasma of a diborane gas containing boron, which is a p-type impurity, and an argon gas, which is a rare gas, is generated, and no bias potential is applied to a silicon substrate. Thereby, the boron radicals in the plasma are deposited on the surface of the silicon substrate. After that, the supply of the diborane gas is stopped, and bias potential is applied to the silicon substrate. Thereby, the argon ions in the plasma are radiated onto the surface of the silicon substrate. The radiated argon ions collide with the boron radicals, and thereby boron radicals are introduced into the silicon substrate. The introduced boron radicals are activated by thermal processing, and thereby a p-type impurity diffusion layer is formed in the silicon substrate.