Selective SiGe Etching by Germanium-Dependent Pre-Oxidation
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Solution Overview
Problem
Conventional etching processes struggle to selectively remove one silicon-and-germanium-containing material relative to another in semiconductor manufacturing, particularly in the context of complementary field-effect transistors (CFETs), leading to undesirable etching of critical materials like gate structures.
Innovation Solution
A method involving pre-oxidation of silicon-and-germanium-containing materials with varying germanium concentrations, followed by a controlled etching process, where materials with higher germanium concentrations are preferentially oxidized, allowing for selective etching of one material over another.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used, then etching of material layers can be achieved, but selective removal of one silicon-and-germanium-containing material relative to another cannot be achieved
Solution Approach 1:
The patent applies preliminary oxidation to the silicon-and-germanium-containing materials before etching. By oxidizing the materials in advance, a oxide layer is formed that etchants remove at different rates depending on germanium concentration. This preliminary action creates the selectivity needed to differentiate between materials with varying germanium concentrations, enabling selective removal of dummy materials while preserving gate structures.
Solution Approach 2:
The patent exploits parameter changes in oxidation behavior based on germanium concentration. Materials with higher germanium concentrations oxidize at different rates compared to materials with lower germanium concentrations. By controlling oxidation conditions (temperature, time, atmosphere), the process creates distinct oxide layer characteristics that enable selective etching, achieving up to 40:1 selectivity between dummy materials and gate structures.
2Ease of manufacture
If wet etching is used, then easy removal of silicon oxide is achieved, but penetration into constrained trenches and deformation control are compromised
Solution Approach 1:
The patent uses oxidation as an intermediary step between the material structure and the etching process. By forming oxide layers through oxidation, the process creates a intermediate state that is more amenable to selective removal. This intermediary oxidation step enables subsequent etchants to selectively remove oxidized regions while leaving non-oxidized or less-oxidized regions intact, achieving both ease of removal and selective control.
3Ease of operation
If dry etching with local plasma is used, then penetration into constrained trenches and deformation reduction are improved, but substrate damage from electric arcs occurs
Solution Approach 1:
The patent performs preliminary oxidation before etching, which modifies the material surface properties. This preliminary action creates oxide layers that can be selectively removed by etchants without requiring aggressive plasma conditions. By preparing the surface in advance through oxidation, the subsequent etching can be performed under milder conditions that avoid substrate damage from electric arcs while still achieving effective material removal.
Solution Approach 2:
The patent replaces direct mechanical/plasma etching of silicon-and-germanium materials with a chemical oxidation-etching sequence. Instead of using plasma to directly remove material (which causes arc damage), the process uses chemical oxidation to form oxide layers that are then removed by liquid or vapor etchants. This substitution of the etching mechanism eliminates the harmful electric arcs while maintaining effective material removal capability.
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 achieves selective etching with a selectivity ratio of up to 40:1, effectively removing dummy silicon-and-germanium-containing materials while preserving other materials, such as gate structures, by exploiting differences in germanium concentration.
Implementation Method 1
The contacting may remove the native oxide from the first layer of silicon-and-germanium-containing material and the second layer of silicon-and-germanium-containing material
Implementation Method 2
The contacting may oxidize at least a portion of the first layer of silicon-and-germanium-containing material and at least a portion of the second layer of silicon-and-germanium-containing material
Implementation Method 3
The contacting may selectively etch the first layer of silicon-and-germanium-containing material
Data Source
AI summary
Exemplary semiconductor processing methods may include providing a pre-treatment precursor to a processing region of a semiconductor processing chamber. A substrate may be housed having a first layer of silicon-and-germanium-containing material and a second layer of silicon-and-germanium-containing material may be housed within the processing region. A native oxide may be present. The methods may include contacting the substrate with the pre-treatment precursor to remove the native oxide. The methods may include contacting the substrate with an oxygen-containing precursor to oxidize at least a portion of the first layer of silicon-and-germanium-containing material and at least a portion of the second layer of silicon-and-germanium-containing material. The methods may include contacting the substrate with an etchant precursor to selectively etch the first layer of silicon-and-germanium-containing material.