Thermal Cyclical Etching of Ta Layers for Plasma-Free Selectivity
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Solution Overview
Problem
Current etching methods for integrated circuit manufacturing, such as the damascene process and plasma-based reactive ion etching, face challenges in miniaturization due to plasma damage, anisotropic etching limitations, and the need for selective etching of non-line-of-sight features, particularly with materials like Ta and TaN, while thermally activated gas phase etching methods face issues with selectivity and aggressive fluoride-based etchants.
Innovation Solution
A cyclical etching process using conversion and volatilization reactants, such as metal halides like niobium pentachloride, is employed to selectively etch etchable layers like Ta and Mo, with alternating reactant pulses and purges, avoiding plasma and maintaining minimal damage to underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma-based reactive ion etching is used, then etching speed and anisotropy are improved, but plasma damage to unetched layers and surrounding materials occurs
Solution Approach 1:
The patent replaces plasma-based reactive ion etching with a thermal field-based etching method. Instead of using plasma and ion bombardment, the invention employs thermally activated chemical reactions at controlled temperatures (200-450°C) to achieve etching through self-limiting chemical modification followed by volatilization, thereby eliminating plasma damage while maintaining etching efficiency
Solution Approach 2:
The patent changes the fundamental etching parameters by operating in the thermal regime rather than plasma regime. By controlling temperature, pressure, and reactant partial pressures, the method achieves etching through thermal activation of chemical reactions, fundamentally altering the etching mechanism to avoid plasma-related damage while preserving productivity
2Manufacturing precision
If reactive ion etching is used, then anisotropic etching capability is improved, but ability to etch non-line-of-sight features is worsened
Solution Approach 1:
The patent inverts the etching approach by using isotropic thermal etching instead of anisotropic plasma etching. By employing vapor-phase reactants that can diffuse and condense on surfaces from all directions, the method achieves etching of non-line-of-sight features through the same thermal chemical mechanism that provides conformal coverage
Solution Approach 2:
The patent transitions from line-of-sight plasma etching to omnidirectional vapor-phase etching. By introducing volatile reactants in the gas phase that can reach all surfaces including non-line-of-sight features through diffusion and condensation, the method adds dimensional accessibility while maintaining controlled etching through thermal activation
3Productivity
If fluoride-based etchants are used for thermal etching, then etching capability is improved, but selectivity and equipment protection are worsened
Solution Approach 1:
The patent applies local quality by using metal halide reactants that selectively react with specific metal oxides based on thermodynamic principles. The etching selectivity is achieved through controlled chemical affinity between the halide reactant and target oxide, allowing selective etching of desired materials while leaving other layers intact, thereby improving reliability without sacrificing etching capability
Solution Approach 2:
The patent changes the chemical nature of the etchant from aggressive fluoride-based compounds to more selective metal halide compounds. By adjusting the thermodynamic parameters and chemical composition of the reactants, the method achieves both sufficient etching capability and improved selectivity, reducing equipment damage while maintaining productivity
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 conformal and highly controlled etching of materials with improved selectivity, reducing plasma damage and enabling isotropic etching of non-line-of-sight features, suitable for advanced integrated circuit manufacturing.
Implementation Method 1
at least one of the plurality of etching cycles comprises a conversion reactant pulse that comprises exposing the substrate to a conversion reactant
Implementation Method 2
at least one from the plurality of etching cycles comprises a volatilization reactant pulse that comprises exposing the substrate to a volatilization reactant; wherein the volatilization reactant comprises a metal halide
Implementation Method 3
Thermal atomic layer etching is an isotropic gas phase etching method, which avoids plasma damage by using thermally activated chemical reactions for the etching
Data Source
AI summary
Methods and related systems for etching are disclosed for etching an etchable layer by executing a cyclical etching process comprising a plurality of etching cycles. Ones from the plurality of etching cycles comprise a volatilization reactant pulse that comprises exposing a substrate to a volatilization reactant.