Silicon Film Etching with Temperature-Switched Surface Smoothing
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Solution Overview
Problem
In semiconductor manufacturing, existing methods for selective etching of silicon films on wafers often result in surface roughness issues due to irregularities formed during the etching process, which can affect the yield and quality of semiconductor products.
Innovation Solution
A substrate processing method involving the sequential supply of a halogen-containing gas (such as F2) and a basic gas (such as NH3) to form a reaction product, followed by heat treatment to sublimate and remove this product, is used to control the etching process and suppress surface roughness. This method involves alternating between two temperature settings to ensure uniformity and prevent sublimation of the reaction product during the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional selective etching is performed using F2 gas and NH3 gas with a predetermined NH3 gas ratio, then silicon film etching is achieved, but surface roughness increases due to irregularities formed during etching
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas compositions and temperature conditions. The first step uses F2 gas at a lower temperature to perform initial etching, followed by a second step using NH3-containing gas at a higher temperature to smooth the surface. This segmentation allows each step to optimize for its specific function, resolving the contradiction between etching efficiency and surface quality.
Solution Approach 2:
The patent employs periodic alternation between different processing conditions (gas types, temperatures, and compositions) throughout the etching process. By periodically switching between F2-dominated etching phases and NH3-dominated smoothing phases, the system maintains both high etching efficiency and low surface roughness, preventing the accumulation of irregularities.
2Productivity
If the substrate temperature is increased to enhance reaction rate, then etching speed improves, but the reaction product may sublime and cause surface irregularities
Solution Approach 1:
The patent performs preliminary etching at a controlled lower temperature in the first step to form the desired pattern without excessive sublimation. Then in the second step, the temperature is increased to facilitate surface smoothing through controlled reaction with NH3-containing gas. This preliminary action at appropriate temperature prevents premature sublimation that would cause surface irregularities.
Solution Approach 2:
The patent systematically changes multiple parameters including temperature, gas composition, and pressure between different processing steps. By adjusting these parameters in a coordinated manner, the process achieves both high etching speed and surface uniformity, resolving the contradiction between productivity and manufacturing precision.
3Manufacturing precision
If the NH3 gas ratio in the etching gas is increased to suppress surface roughness, then surface quality improves, but etching selectivity and speed decrease
Solution Approach 1:
The patent segments the gas composition strategy into two distinct phases: the first step uses F2-dominated gas for high etching selectivity and speed, while the second step uses NH3-containing gas for surface quality improvement. This segmentation allows each gas composition to be optimized for its specific function without compromise.
Solution Approach 2:
The patent maintains continuous processing by seamlessly transitioning between the F2-based etching step and the NH3-based smoothing step without interrupting the overall etching action. This continuity ensures that both etching selectivity and surface quality are maintained throughout the entire process, preventing loss of productivity while achieving high surface quality.
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 effectively suppresses surface roughness of silicon films after etching, leading to improved yield and quality of semiconductor products by ensuring uniform etching and reducing irregularities, thereby enhancing the manufacturing process efficiency.
Implementation Method 1
supplying a processing gas containing a halogen-containing gas and a basic gas to a wafer, on which a silicon film is formed, at a first temperature and generating a reaction product by deforming a surface of the silicon film
Implementation Method 2
removing the reaction product by setting the wafer to a second temperature after the first step
Data Source
AI summary
A substrate processing method is provided. The method comprises a first step of supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate, which a silicon film is formed on and has a first temperature, and generating a reaction product by deforming a surface of the silicon film; and a second step of removing the reaction product by setting the substrate to a second temperature after the first step.