Self-Limiting Lateral Atomic Layer Etch for Uniform Semiconductor Processing
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Solution Overview
Problem
Conventional etching methods for semiconductor materials often result in non-uniformly etched features, bowed or curved trench edges, and re-deposition of etched materials, leading to loading problems and pattern distortion in subsequent fabrication processes, while also risking apparatus damage from ammonia gas.
Innovation Solution
A method involving a self-limiting etch process using alternating cycles of oxidation and fluorine-containing gas exposure, with heating to remove non-volatile byproducts by sublimation, and the use of a patterned hard mask to achieve uniform etching across substrates without breaking vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching methods are used, then etching speed is improved, but etching uniformity deteriorates resulting in bowed or curved trench edges
Solution Approach 1:
The etching process is divided into multiple sequential steps: oxidation step to form silicon oxide layer, followed by fluorine-based etching step. This segmentation allows each step to be optimized independently, achieving both high speed and uniformity that cannot be achieved in a single conventional etching step.
Solution Approach 2:
The invention changes the chemical state of the semiconductor surface by oxidizing it before etching. This parameter change (from silicon to silicon oxide) enables the use of fluorine-based etching chemistry which provides both high etching speed and excellent uniformity, resolving the contradiction between productivity and manufacturing precision.
2Length of moving object
If conventional etching methods are used, then etching depth is improved, but re-deposition of etched materials occurs leading to loading problems
Solution Approach 1:
By changing the chemical composition of the etched layer through oxidation, the etched material becomes silicon oxide which etches via fluorine chemistry. This parameter change produces volatile fluorosilicate byproducts that can be easily removed, preventing re-deposition even at high etching depths.
Solution Approach 2:
The etching process utilizes phase transition of the etch byproducts from solid/liquid to gas phase. The fluorosilicate byproducts formed during fluorine-based etching of oxidized silicon are highly volatile and transition to gas phase, being removed by vacuum pumping, thus preventing re-deposition on the substrate.
3Reliability
If ammonia gas is used in the etching process, then cleaning capability is improved, but apparatus damage risk increases
Solution Approach 1:
The invention extracts ammonia gas from the etching process and replaces it with fluorine-based chemistry (NF3, CF4, SF6). This removal of the harmful substance (ammonia) eliminates the risk of apparatus damage while maintaining effective cleaning capability through the fluorine-based etching chemistry that produces volatile byproducts.
Solution Approach 2:
The invention uses disposable, easily removable fluorine-based etchants (NF3, CF4, SF6) that produce volatile byproducts which are immediately pumped away. This replaces the need for ammonia which requires careful handling and can cause apparatus damage, using instead short-lived gases that leave no harmful residue.
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 approach enables uniform, lateral etching with minimal re-deposition, maintaining feature shape and size independence, and reduces apparatus damage by separating ammonia flow, resulting in high aspect ratio trenches with linear edges and improved process reliability.
Implementation Method 1
exposing the substrate to a fluorine-containing gas to etch an oxidized surface of the substrate in a self-limiting reaction selective to non-oxidized semiconductor material
Implementation Method 2
heating the substrate to remove non-volatile solid etch byproducts by sublimation
Implementation Method 3
exposing the substrate to an oxidant to oxidize a surface of the semiconductor material to form the oxidized surface
Data Source
AI summary
Methods of and apparatuses for laterally etching semiconductor substrates using an atomic layer etch process involving exposing an oxidized surface of a semiconductor substrate to a fluorine-containing etch gas and heating the substrate to remove non-volatile etch byproducts by a sublimation mechanism are provided herein. Methods also including additionally pulsing a hydrogen-containing gas when pulsing the fluorine-containing etch gas. Apparatuses also include an ammonia mixing manifold suitable for separately preparing and mixing ammonia for use in various tools.