Thermal ALE of ZrO2 and HfO2 for Precise Plasma-Free Etching
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Solution Overview
Problem
Current etching methods for ZrO2 and HfO2 films in semiconductor manufacturing often require plasma or corrosive halogenating chemistries, which can damage substrates and lead to contamination, and lack the precision needed for sub-nanometer film removal in high aspect ratio features.
Innovation Solution
A process for isotropic thermal atomic layer etching (ALE) of ZrO2 and HfO2 using fluorinating agents like WF6, followed by ligand exchange with DMAC to produce volatile chlorinated species, and oxidation to remove impurities, without plasma or halogens, ensuring precise control over film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma or corrosive halogenating chemistries are used for etching ZrO2 and HfO2 films, then etching capability is improved, but substrate damage and contamination occur
Solution Approach 1:
The patent replaces plasma-based physical/chemical etching with a purely thermal chemical process. The mechanical/energy-intensive plasma system is substituted with a thermal field-based ligand exchange process using WF6 and DMAC, achieving etching without substrate damage or contamination.
Solution Approach 2:
The patent changes the etching mechanism from plasma-driven to thermally-driven ligand exchange. By adjusting temperature parameters (heating to reaction temperature and maintaining it), the process achieves controlled etching with improved selectivity and reduced harmful effects on the substrate.
2Manufacturing precision
If conventional etching methods are used, then material removal is achieved, but precision for sub-nanometer film removal is insufficient
Solution Approach 1:
The patent segments the etching process into discrete sequential steps: (1) exposure to WF6 for fluorination, (2) exposure to DMAC for ligand exchange, and (3) heating for volatile byproduct removal. This segmentation enables precise control over each step, achieving sub-nanometer thickness control.
Solution Approach 2:
The patent employs periodic cycling of precursor exposure and heating steps. Each cycle removes a controlled amount of material, and by repeating the cycle, precise sub-nanometer removal is achieved. The periodic nature allows for self-limiting reactions and excellent thickness control.
3Reliability
If thicker films are grown to achieve desirable properties (high k, low leakage, ferroelectricity), then film quality is improved, but additional material removal steps are required
Solution Approach 1:
The patent performs preliminary thermal treatment of the thicker film to establish desirable properties (high k, low leakage, ferroelectricity) before the ALE process. This preliminary action ensures the film quality is optimized before thinning, and the subsequent ALE process preserves these properties while achieving the target thickness.
Solution Approach 2:
The patent utilizes the self-limiting nature of the thermal ALE process, where the etching rate is controlled by temperature and precursor exposure time. By carefully controlling these parameters, the process removes material precisely while preserving the film's desirable electrical and dielectric properties established during thermal treatment.
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 process achieves precise, contamination-free etching of ZrO2 and HfO2 films, maintaining desirable properties and enabling the production of metal-insulator-metal capacitors with higher dielectric constants and lower leakage currents.
Implementation Method 1
a first surface modification comprising exposing the surface of the metal oxide substrate to one or more fluorinating agent to produce a fluorinated surface
Implementation Method 2
a ligand-exchange comprising exposing the fluorinated surface to one or more chlorine ligand-supplying agent to produce a volatile chlorinated species
Implementation Method 3
a second surface modification comprising exposing the surface of the metal oxide substrate to one or more oxidants to oxidize metal byproducts
Implementation Method 4
isotropic thermal atomic layer etching (ALE) of ZrO2 and HfO2 using fluorinating agents like WF6
Data Source
AI summary
The disclosed and claimed subject matter relates to (1) a process for performing thermal atomic layer etching (ALE) of films that include ZrO2, HfO2, (Hf—Zr)O2 alloy or similar materials which does not require the use of plasmas or corrosive halogenating chemistries and (2) a metal-insulator-metal capacitor (MIMcap) with unique properties enabled by a unique dielectric processing method.