Cyclic Recess Etching for Smooth Silicon Sidewalls
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Solution Overview
Problem
Existing substrate processing methods for semiconductor wafers face challenges in achieving uniform etching and reducing surface roughness while maintaining the rectangular shape of recesses formed in the silicon film.
Innovation Solution
A substrate processing method involving multiple cycles of supplying processing gases, including a halogen-containing gas and a basic gas, to alter the silicon film surface, followed by heating to sublimate reaction products and widen the recesses. The method employs different processing conditions in the former and latter cycles to optimize etching results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a halogen-containing gas and basic gas are supplied to etch the silicon film, then the etching rate increases, but the surface roughness increases
Solution Approach 1:
The etching process is divided into multiple cycles, each consisting of a first step (etching with halogen-containing gas and basic gas) and a second step (heating to remove reaction products). This segmentation allows the process to achieve both high etching rate and low surface roughness by alternating between etching and surface recovery phases
Solution Approach 2:
The patent employs periodic cycling between etching conditions and heating conditions. During the first step, etching gases are supplied to remove silicon material. During the second step, heating is applied to remove reaction products and smooth the surface. This periodic action enables control over both etching rate and surface roughness
2Productivity
If the etching process is performed to widen the recess, then the productivity increases, but the rectangular shape of the recess deteriorates
Solution Approach 1:
The etching process is segmented into multiple cycles with different processing conditions. Former cycles use one set of conditions to establish the recess shape, while latter cycles use different conditions to maintain rectangularity while continuing to widen the recess
Solution Approach 2:
The patent dynamically adjusts processing conditions between former cycles and latter cycles. By changing parameters such as gas flow rates, pressure, or temperature between cycle stages, the process adapts to maintain optimal etching performance and shape control throughout the widening process
3Manufacturing precision
If multiple cycles of etching are performed, then the uniformity of etching improves, but the processing time increases
Solution Approach 1:
Multiple cycles are performed with periodic alternation between etching steps and heating steps. This periodic action ensures uniform etching across the substrate by allowing reaction products to be removed and surfaces to be reset between cycles, while the cumulative effect achieves the desired uniformity
Solution Approach 2:
The patent maintains continuous useful action by seamlessly transitioning between etching cycles and heating cycles within the same processing system. The cycles are designed to be efficient, minimizing idle time while ensuring complete removal of reaction products for uniform etching
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 reduces surface roughness, maintains a rectangular shape of the recesses, and achieves uniform etching across the substrate, thereby enhancing the yield of semiconductor products.
Implementation Method 1
supplying processing gases including a halogen-containing gas and a basic gas to a substrate having a recess with side walls formed of a silicon film and an inner wall formed of a germanium-containing film to alter a surface of the silicon film and produce a reaction product
Implementation Method 2
a second step of removing the reaction product to widen a width of the recess
Data Source
AI summary
A substrate processing method includes a first step of supplying processing gases including a halogen-containing gas and a basic gas to a substrate having a recess with side walls formed of a silicon film and an inner wall formed of a germanium-containing film to alter a surface of the silicon film and produce a reaction product, a second step of removing the reaction product to widen a width of the recess, a step of performing a cycle including the first step and the second step multiple times, and a step of performing the first step of a former cycle under a first processing condition and performing the first step of a latter cycle under a second processing condition different from the first processing condition.