Atomic Layer Etching of Silicon Germanium Films
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Solution Overview
Problem
Current substrate processing systems face challenges in achieving isotropic etching with nano-scale control, as existing methods like wet chemical etching cause structural damage, and dry chemical etching increases surface roughness and ion directionality, limiting the isotropic removal of materials such as silicon and germanium.
Innovation Solution
A method involving the use of a sacrificial layer and oxidant-containing plasma with rapid thermal heating and controlled pressure and temperature conditions to perform atomic layer etching, allowing for selective and isotropic etching of films with reduced surface roughness, using a combination of fluorine, chlorine, and bromine etch gases and oxidant gases like oxygen and hydrogen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet chemical etching is used, then isotropic removal of material is achieved, but structural damage due to pattern collapse occurs
Solution Approach 1:
The invention changes the chemical parameters by using specific etch gases (CF4, SF6, NF3 for fluorine-based; CCl4, Cl2 for chlorine-based) and controlling plasma power, pressure, and temperature to achieve isotropic etching without structural damage. The etch chemistry is optimized to prevent pattern collapse while maintaining precision.
Solution Approach 2:
The invention uses an inert plasma environment created by introducing etch gases into a vacuum chamber. The plasma provides a controlled inert atmosphere that enables isotropic etching without the harmful effects of wet chemicals, preventing structural damage while achieving precise material removal.
2Object-affected harmful factors
If dry chemical etching is used, then structural damage is reduced, but surface roughness increases
Solution Approach 1:
The invention optimizes plasma parameters including power density, pressure, and gas flow rates to control the etching process. By adjusting these parameters, the process achieves smooth surfaces while maintaining the structural integrity benefits of dry etching, preventing excessive roughness.
Solution Approach 2:
The invention replaces traditional mechanical or chemical-mechanical polishing steps with a plasma-based chemical process. The plasma etching mechanism naturally produces smooth surfaces through controlled chemical reactions, eliminating the need for additional surface finishing operations.
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 precise, fast isotropic etching with reduced surface roughness and thermal stress, allowing for the removal of a monolayer of the target material in each cycle, suitable for small feature sizes and materials like silicon and germanium, while maintaining low thermal budgets.
Implementation Method 1
increasing a surface temperature of the substrate for a predetermined period using rapid thermal heating
Implementation Method 2
cooling a lower portion of the substrate includes maintaining a predetermined temperature of a substrate support in a range from −80° C. to 20° C.
Implementation Method 3
one of creating or supplying an oxidant-containing plasma in the processing chamber
Implementation Method 4
oxidant-containing plasma
Implementation Method 5
striking plasma in the processing chamber
Implementation Method 6
etching the sacrificial layer and the film by supplying an etch gas mixture and striking plasma
Data Source
AI summary
A method for isotropically etching film on a substrate with atomic layer control includes a) providing a substrate including a material selected from a group consisting of silicon (Si), germanium (Ge) and silicon germanium (SiGe). The method includes b) depositing a sacrificial layer on the material in a processing chamber by: cooling a lower portion of the substrate; one of creating or supplying an oxidant-containing plasma in the processing chamber; and increasing a surface temperature of the substrate for a predetermined period using rapid thermal heating while creating or supplying the oxidant-containing plasma in the processing chamber. The method includes c) purging the processing chamber. The method includes d) etching the sacrificial layer and the material by supplying an etch gas mixture and striking plasma in the processing chamber.