Substrate Treatment for Shallow Doping via Chemical Adsorption
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Solution Overview
Problem
Current methods for introducing impurities into semiconductor wafers, such as ion implantation, struggle to accurately and efficiently dope extremely shallow regions, especially for complex concavo-convex patterns, and existing techniques for forming dopant monolayers are time-consuming, limiting throughput.
Innovation Solution
A substrate treatment method that removes the native oxide film with hydrofluoric acid and immediately applies a dopant solution without hydrogen-termination, allowing for the formation of a dopant-containing thin film in a short period by continuously supplying hydrofluoric acid, a rinse solution, and a dopant solution, either separately or as a mixture, in a non-air atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ion implantation is used to introduce impurities, then implantation depth and concentration can be easily controlled, but it is difficult to accurately implant impurities into extremely shallow surface layers (depth not greater than several nm)
Solution Approach 1:
The patent replaces the mechanical ion implantation system with a chemical system. Instead of using high-voltage ion collision to introduce dopants, the invention uses wet chemical treatment to form a dopant-containing monolayer on the substrate surface, followed by thermal diffusion. This chemical approach enables precise control of dopant depth at the nanometer scale, achieving shallow junctions that mechanical implantation cannot accomplish.
Solution Approach 2:
The patent changes the fundamental parameter of dopant introduction from physical ion bombardment to chemical adsorption and thermal diffusion. By controlling the chemical composition, concentration, and thermal processing parameters, the method achieves precise depth control in the range of several nanometers, overcoming the limitations of ion implantation for ultra-shallow doping.
2Reliability
If ion implantation is used for doping, then impurity introduction is effective, but it is difficult to introduce impurities uniformly into complex concavo-convex patterns
Solution Approach 1:
The wet chemical treatment method provides universal coverage across complex three-dimensional patterns. The liquid dopant solution can access and treat all surface areas uniformly, including concave and convex regions, whereas ion implantation from a single direction cannot achieve uniform doping in complex patterns. This makes the chemical method universally applicable to various pattern geometries.
3Stability of the object's composition
If hydrogen termination is performed to stabilize the surface state before forming a dopant monolayer, then surface stability is improved, but the process time increases to 2.5 hours, reducing throughput
Solution Approach 1:
The patent extracts and eliminates the hydrogen termination step from the conventional process. By removing this time-consuming stabilization step, the invention directly forms the dopant-containing monolayer on the as-prepared surface, reducing the process time from 2.5 hours to a much shorter duration while maintaining the ability to form stable dopant layers through direct chemical adsorption.
Solution Approach 2:
The invention performs preliminary surface preparation through oxide removal and direct chemical treatment, eliminating the need for subsequent hydrogen termination. The dopant-containing monolayer is formed directly on the prepared surface, and the capping film formation and heat treatment steps subsequently stabilize and activate the dopants, achieving the same stabilization effect without the time-consuming intermediate hydrogen termination step.
4Manufacturing precision
If a dopant-containing monolayer is formed by wet treatment to enable shallow doping, then extremely shallow region doping is achieved, but the process takes an extremely long period of time (2.5 hours)
Solution Approach 1:
The patent implements continuous processing by eliminating idle time between steps. The oxide removal, dopant solution application, and subsequent processing steps are performed in a continuous sequence without the long waiting period required for hydrogen termination. This continuous action maintains the shallow doping capability while dramatically reducing the total process time from 2.5 hours to minutes.
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 rapid formation of a dopant-containing thin film on semiconductor wafers, significantly reducing processing time from hours to seconds, allowing for uniform doping of complex patterns without the need for hydrogen-termination, thereby enhancing semiconductor manufacturing efficiency.
Implementation Method 1
a native oxide film is removed with a hydrofluoric acid
Implementation Method 2
a dopant solution is supplied to the surface of the substrate to form a dopant-containing thin film
Implementation Method 3
to replace the hydrogen termination with a dopant, thereby forming a monolayer containing the dopant
Implementation Method 4
subjected to a light-emission and heat treatment, thereby diffusing the dopant into the substrate surface
Data Source
AI summary
A hydrofluoric acid is supplied to a surface of a substrate, and a native oxide film formed on the surface is corroded to be removed, exposing silicon in the surface of the substrate. Then, a rinse solution such as alcohols is supplied to the surface of the substrate, and then, the hydrofluoric acid is washed off from the surface. After that, a dopant solution, which is a dopant-containing chemical solution, is supplied to the surface of the substrate. The dopant solution comes into contact with the surface of the substrate, which is not hydrogen-terminated and has silicon exposed, thereby forming a dopant-containing monolayer thin film on the surface in a short period of time.