PEALD Air Gap Formation for Lower Intra-Level Capacitance
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Solution Overview
Problem
Existing methods for forming air gaps in semiconductor devices face challenges in achieving low-k dielectric materials that effectively reduce parasitic capacitance without requiring etch or inhibition operations.
Innovation Solution
A method involving plasma-enhanced atomic layer deposition (PEALD) with a dilute reactant flow is used to form air gaps by preferentially depositing dielectric material at the top of features, utilizing a high dilution ratio of dilution gases to co-reactants, thereby creating closed air gaps without etch or inhibition operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional PEALD processes are used to form dielectric material in gap structures, then uniform conformal deposition is achieved, but air gaps cannot be formed without etch or inhibition operations
Solution Approach 1:
The patent changes the gas flow parameters by introducing a highly diluted co-reactant flow (e.g., 5% O2 in He at 10 sccm) during the plasma conversion step. This parameter change transforms the deposition pattern from uniform conformal growth to preferential top-side deposition, enabling air gap formation without etch or inhibition operations while maintaining process simplicity
2Manufacturing precision
If etch or inhibition operations are used to form air gaps, then air gap formation is achieved, but process complexity and potential defects increase
Solution Approach 1:
The patent extracts and removes the etch and inhibition operations from the air gap formation process. By using a diluted co-reactant plasma that naturally preferentially deposits material at the top of features, the process achieves air gap formation through deposition alone, eliminating the need for separate etch or inhibition steps and reducing overall process complexity
Solution Approach 2:
The deposition process itself performs the air gap formation function that would traditionally require separate etch or inhibition operations. The diluted co-reactant plasma automatically creates the non-conformal deposition pattern needed for air gaps, making the process self-sufficient and eliminating additional process steps
3Manufacturing precision
If high dilution ratio of dilution gases to co-reactants is used in PEALD, then preferential deposition at top of features is achieved, but reactive ion supply to bottom of feature is reduced
Solution Approach 1:
The patent creates local quality differences in the plasma distribution by using a highly diluted co-reactant flow. This results in preferential deposition at the top of features where reactive species are most concentrated, while the bottom of features receives insufficient reactive ions for significant deposition. This local variation in deposition rate is exactly what is needed to form air gaps, and the effect is enhanced by feature geometry such as overhangs
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 results in air gaps that occupy a significant portion of the original gap volume, reducing intra-level capacitance and improving device performance by minimizing defects during planarization.
Implementation Method 1
performing multiple plasma enhanced atomic layer deposition (PEALD) cycles, each cycle including: exposing the structure to a dose of a silicon-containing precursor to allow the silicon-containing precursor to adsorb on sidewall and bottom surfaces of the open gap; and exposing the adsorbed silicon-containing precursor to a plasma generated from a process gas including a co-reactant and one or more dilution gases, to react the co-reactant with the adsorbed silicon-containing precursor and form a dielectric material
Implementation Method 2
exposing the structure to a dose of a silicon-containing precursor to allow the silicon-containing precursor to adsorb on sidewall and bottom surfaces of the open gap
Data Source
AI summary
Methods of forming air gaps in hole and trench structures using plasma enhanced atomic layer deposition (PEALD) are disclosed. The methods may be used to form buried voids, i.e., voids for which the top is below the top of the adjacent features. In some embodiments, the methods are to reduce intra-level capacitance in semiconductor devices.