Selective Atomic Layer Etching Using Helium and Fluorocarbon Plasma
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Solution Overview
Problem
Existing etching processes for semiconductor devices face a trade-off between SiO2/FinFET epitaxial material etch selectivity and SiO2 etch front roughness, leading to compromised device performance, with traditional Ar-based atomic layer etching causing either high epitaxial material loss or rough etch fronts.
Innovation Solution
A method involving cyclical deposition and activation phases in an etch chamber using helium and hydrofluorocarbon or fluorocarbon gases to deposit and activate a fluorinated polymer layer, with a thiol treatment to form a passivation layer on germanium or metal-containing layers, selectively etching the dielectric layer while improving surface roughness and reducing epitaxial material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional Ar-based atomic layer etching is used to etch SiO2, then etch selectivity is improved, but etch front roughness increases and epitaxial material loss occurs
Solution Approach 1:
The patent changes the carrier gas from argon to helium, which fundamentally alters the deposition and activation processes. Helium's lower mass and different reactivity lead to improved polymer deposition quality and controlled activation, simultaneously achieving smooth etch fronts and high selectivity without the material loss associated with argon-based processes
Solution Approach 2:
The patent uses a composite gas mixture comprising helium as the carrier gas combined with hydrofluorocarbon or fluorocarbon etch gases. This composite approach allows helium to provide smooth polymer deposition while the fluorocarbon components enable controlled etching, achieving both smooth etch fronts and high etch selectivity
2Productivity
If etch selectivity is increased, then dielectric layer removal is improved, but surface roughness of the etch front deteriorates
Solution Approach 1:
The patent employs periodic alternating cycles of deposition and activation phases. During deposition, fluorinated polymer is deposited smoothly on the dielectric surface; during activation, controlled ion bombardment activates the polymer for etching. This periodic action enables progressive dielectric removal while maintaining surface smoothness through the alternating gentle deposition and controlled activation steps
3Productivity
If ion bombardment is increased to activate fluorinated polymer for etching, then etch rate is improved, but epitaxial material loss increases
Solution Approach 1:
The patent changes the ion bombardment parameters by using helium as the carrier gas, which results in lighter ions with different bombardment characteristics. This parameter change allows for effective polymer activation at lower ion energies, achieving sufficient etch rates while minimizing the physical sputtering and material loss from excessive ion bombardment
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 breaks the trade-off between etch selectivity and roughness, achieving improved SiO2 etch front smoothness and reduced epitaxial material loss, enhancing electron mobility and contact resistivity, with a balanced F/C ratio in the hydrocarbon layer optimizing the etching process.
Implementation Method 1
forming the deposition gas into a plasma, to effect a fluorinated polymer deposition
Implementation Method 2
flowing a deposition gas into the etch chamber, wherein the deposition gas comprises helium and a hydrofluorocarbon or fluorocarbon, forming the deposition gas into a plasma, to effect a fluorinated polymer deposition
Implementation Method 3
providing an activation bias in the etch chamber to cause ion bombardment of the fluorinated polymer deposition, wherein the ion bombardment activates fluorine from the fluorinated polymer deposition to etch the dielectric layer
Implementation Method 4
flowing an activation gas comprising an ion bombardment gas into the etch chamber, forming the activation gas into a plasma
Implementation Method 5
flowing a treatment gas comprising a thiol containing gas into the etch chamber, selectively forming a passivation layer from the thiol containing gas on the germanium containing layer or the metal containing layer
Data Source
AI summary
A method for selectively etching a dielectric layer with respect to an epitaxial layer or metal-based hardmask is provided. The method comprises performing a plurality of cycles. Each cycle comprises a deposition phase and an activation phase. The deposition phase comprises flowing a deposition gas, wherein the deposition gas comprises helium and a hydrofluorocarbon or fluorocarbon, forming the deposition gas into a plasma to effect a fluorinated polymer deposition, and stopping the flow of the deposition gas. The activation phase comprises flowing an activation gas comprising an ion bombardment gas, forming the activation gas into a plasma, providing an activation bias to cause ion bombardment of the fluorinated polymer deposition, wherein the ion bombardment activates fluorine from the fluorinated polymer deposition to etch the dielectric layer, and stopping the flow of the activation gas.