Silicon Recess Etching with Two-Phase Radical Oxidation
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Solution Overview
Problem
Existing etching methods for silicon on deep recesses in substrates, particularly those with high aspect ratios, face challenges in achieving uniform thickness and good surface roughness due to uneven oxidation and etching, leading to top-bottom loading issues.
Innovation Solution
A two-phase radical oxidation process is employed, first oxidizing the upper portion of the silicon film with an oxygen-containing plasma and then etching the lower portion using a fluorine-containing gas, followed by chemical processing to remove the reaction product, repeated multiple times to achieve uniform etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching is used to etch silicon on deep recesses, then the etching process can be performed, but uniform thickness and good surface roughness cannot be achieved due to uneven oxidation and etching
Solution Approach 1:
The etching process is divided into multiple sequential steps including oxidation step, first etching step, second etching step, and stripping step. Each step targets specific portions of the silicon film at different locations, systematically addressing the top-bottom loading issue by treating upper and lower portions separately and repeatedly until uniform thickness is achieved
Solution Approach 2:
The patent employs periodic repetition of the oxidation and etching cycles. The oxidation step and etching steps are performed repeatedly multiple times, with each cycle reducing the thickness non-uniformity. This periodic application continues until the silicon film achieves the desired uniform thickness across the recess depth
2Manufacturing precision
If conventional etching methods are used on deep recesses with high aspect ratios, then etching can proceed, but top-bottom loading issues occur leading to poor surface roughness
Solution Approach 1:
Different etching conditions and gases are applied to different locations of the silicon film. The first etching step uses specific gases to target the upper portion, while the second etching step targets the lower portion. This localized treatment ensures that each region receives appropriate etching conditions to achieve uniform surface roughness throughout the recess
Solution Approach 2:
The oxidation step is performed as a preliminary action before etching to form an oxide layer on the silicon film surface. This oxide layer serves as a protective and uniform base that enables subsequent etching steps to proceed uniformly, preventing direct uneven etching of the silicon and thereby addressing top-bottom loading issues
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 ensures uniform thickness and good surface roughness of the silicon film on the recess sides, even in deep recesses, by controlling the oxidation and etching phases to address top-bottom loading issues.
Implementation Method 1
forming an oxide film on a surface of the silicon by performing a radical oxidation processing on the substrate
Implementation Method 2
a first phase of performing a radical processing with a plasma of an oxygen-containing gas
Implementation Method 3
performing a chemical processing with a gas on the oxide film
Data Source
AI summary
An etching method of etching silicon formed on a side surface of a recess that exists in a substrate includes: forming an oxide film on a surface of the silicon by performing a radical oxidation processing on the substrate; performing a chemical processing with a gas on the oxide film; and removing a reaction product produced by the chemical processing, wherein the forming the oxide film includes: a first phase of performing a radical processing with a plasma of an oxygen-containing gas; and a second phase of performing a radical processing with a plasma of the oxygen-containing gas and an etching gas, and wherein the forming the oxide film, the performing the chemical processing, and the removing the reaction product are repeated multiple times.