Silicon Wafer Etching via Oxide Removal and Chlorine Desorption
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Solution Overview
Problem
Existing atomic layer etching (ALE) techniques for silicon face challenges such as difficulty in horizontal processing due to ionic environments, potential roughness from ion sputtering, and a narrow ALE window with self-limiting properties, which affects the accuracy and efficiency of etching silicon layers, especially in three-dimensional structures.
Innovation Solution
A wafer processing method that involves forming modified layers on a silicon film using a combination of hydrogen, nitrogen, and fluorine gases, followed by desorption steps to remove the natural oxide film and subsequent chlorine gas treatment to achieve precise etching, allowing for controlled etching of silicon with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If atomic layer etching is performed using chlorine gas and argon ions, then silicon etching is achieved, but surface roughness occurs due to ion sputtering
Solution Approach 1:
The invention changes the fundamental parameter of the etching environment from ionic to radical-based. By using a carbon disulfide gas mixture that generates reactive radicals instead of ions, the process achieves silicon etching without the damaging sputtering effects that cause surface roughness, while maintaining atomic-layer precision
Solution Approach 2:
The invention substitutes the mechanical ion sputtering mechanism with a chemical radical-based etching mechanism. Instead of using charged particles that physically bombard and damage the surface, the process uses neutral reactive radicals that chemically react with silicon atoms, enabling precise material removal without mechanical damage
2Ease of manufacture
If natural oxide film is removed before silicon etching, then etching can proceed, but isotropic etching occurs reducing horizontal processing capability
Solution Approach 1:
The invention eliminates the need for separate oxide removal and etching steps by implementing a continuous single-step process. The carbon disulfide gas mixture simultaneously removes oxide films and etches silicon through radical reactions, maintaining anisotropic etching characteristics throughout the continuous process without transitioning to isotropic behavior
Solution Approach 2:
The carbon disulfide gas mixture serves multiple functions simultaneously: it acts as both an oxide removal agent and a silicon etching agent. This multi-functional gas system enables the process to perform both oxide film removal and anisotropic silicon etching in a single step, eliminating the need for separate processing stages
3Manufacturing precision
If ALE window with self-limiting property is used, then atomic layer etching is achieved, but the window is narrow limiting process flexibility
Solution Approach 1:
The invention broadens the process window by changing from a narrow bias-voltage-controlled ALE regime to a more robust radical concentration-controlled regime. The carbon disulfide gas system provides a wider range of stable operating conditions for achieving atomic-layer precision, increasing process flexibility and reducing sensitivity to parameter variations
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
The method enables high-accuracy etching of silicon by effectively removing natural oxide films and controlling the etching process at an atomic layer level, improving processing efficiency and reducing surface roughness, thus enhancing the manufacturing of semiconductor devices.
Implementation Method 1
a step of forming a first modified layer by supplying particles of hydrogen, nitrogen, and fluorine gases to an oxide film formed on a surface of the silicon film
Implementation Method 2
a first desorption step of heating and desorbing the first modified layer
Implementation Method 3
a step of forming a second modified layer by supplying particles of a chlorine gas to the silicon film
Implementation Method 4
a second desorption step of heating and desorbing the second modified layer
Data Source
AI summary
An object of the invention is to provide a technique capable of etching silicon with high accuracy by removing a natural oxide film. One wafer processing method according to the invention is a wafer processing method for providing a semiconductor wafer formed with a silicon film on an upper surface in a processing chamber and processing the silicon film. The wafer processing method includes: a step of forming a first modified layer by supplying particles of hydrogen, nitrogen, and fluorine gases to an oxide film formed on a surface of the silicon film; a first desorption step of heating and desorbing the first modified layer; a step of forming a second modified layer by supplying particles of a chlorine gas to the silicon film after the first desorption step; and a second desorption step of heating and desorbing the second modified layer.