AlScN Plasma Etching Chemistry for Better Mo Electrode Selectivity
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Solution Overview
Problem
The etching of AlScN films with high scandium content faces challenges such as reduced etch rates, decreased selectivity to masks and metal underlayers, leading to poor sidewall angles and increased electrode loss, which impairs the performance of devices like BAW filters.
Innovation Solution
A plasma etching method using specific gas ratios and plasma conditions, including BCl3, H2, and an inert diluent gas, with controlled RF bias, to enhance selectivity to metal underlayers, particularly for AlScN:Mo interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard chlorine/argon based chemistries are used for etching AlScN films, then the etch rate decreases with increasing scandium content, but this results in lower selectivity to masks and increased critical dimension
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from standard chlorine/argon to a specific mixture containing BCl3, H2, and inert diluent gas in controlled ratios. This parameter change enables maintaining high etch rates while improving selectivity to masks and controlling critical dimensions, even for high scandium content AlScN films.
Solution Approach 2:
The patent uses a composite gas chemistry system combining BCl3 (boron trichloride), H2 (hydrogen), and inert diluent gas. This composite approach leverages the complementary properties of each gas component: BCl3 provides high etch rate and good selectivity, H2 enhances sidewall angle control, and the inert diluent optimizes the overall process, achieving simultaneous improvement in multiple etching parameters.
2Manufacturing precision
If the etch rate of AlScN is reduced to improve selectivity, then mask selectivity improves, but the etch rate becomes too slow for practical manufacturing
Solution Approach 1:
The patent modifies the gas chemistry parameters by introducing BCl3 as the primary etchant instead of using standard chlorine-based chemistries. This parameter change achieves a favorable balance where high selectivity to masks is maintained while preserving sufficiently high etch rates for practical manufacturing throughput.
3Productivity
If the etch rate of AlScN is increased to improve productivity, then manufacturing efficiency improves, but selectivity to metal underlayers decreases leading to increased electrode loss
Solution Approach 1:
The patent introduces H2 as a key component in the etching gas mixture. This parameter change modifies the etching chemistry to improve selectivity to metal underlayers while maintaining high etch rates. The H2 component helps protect the metal electrodes from excessive etching, reducing electrode loss and improving device performance.
Solution Approach 2:
The composite gas system of BCl3, H2, and inert diluent creates a synergistic effect where BCl3 provides high etch rate and H2 provides enhanced selectivity to metal underlayers. This composite approach allows simultaneous optimization of both productivity and manufacturing precision, resolving the contradiction between etch rate and underlayer selectivity.
4Device complexity
If conventional etching methods are used for high Sc content AlScN, then the process remains simple, but sidewall angles become shallower and device performance degrades
Solution Approach 1:
The patent modifies the gas composition parameters by incorporating H2 into the etching mixture. This parameter change enhances sidewall angle control during the etching process, producing steeper and more uniform sidewalls in high Sc content AlScN films, thereby improving device performance without significantly increasing process complexity.
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
Improves the etch selectivity and reduces electrode loss, maintaining device performance by optimizing the etch rate and sidewall profiles of AlScN films.
Implementation Method 1
A plasma etching method using specific gas ratios and plasma conditions
Implementation Method 2
the etch becomes increasingly physical
Implementation Method 3
standard chlorine (Cl2)/argon (Ar) based chemistries
Data Source
AI summary
Apparatus and method for plasma etching an additive-containing aluminium nitride film containing an additive element selected from scandium (Sc), yttrium (Y) or erbium (Er) by placing a workpiece upon a substrate support within a plasma chamber, the workpiece including a substrate having a metal film disposed thereon, an additive-containing aluminium nitride film deposited on the metal film, and a mask disposed upon the additive-containing aluminium nitride film which defines at least one trench, introducing BCl3 gas into the chamber with a BCl3 flow rate in sccm, introducing H2 gas into the chamber with a H2 flow rate in sccm, introducing an inert diluent gas into the chamber with an inert diluent gas flow rate in sccm, and establishing a plasma within the chamber to plasma etch the additive-containing aluminium nitride film exposed within the trench.