Ir/IrO2 Electrode Etching Sidewall Film Reduction
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Solution Overview
Problem
The existing methods for etching ferroelectric capacitors with precious metal electrodes, such as platinum (Pt) and iridium (Ir), face challenges with sidewall film formation and leakage current due to the high oxygen permeability of these metals, leading to difficulties in achieving precise patterning and high etching selectivity.
Innovation Solution
A semiconductor device with a lower electrode comprising a laminated film of Ir and IrO2, where the thickness is set to 100 nm or less, and a hydrogen diffusion barrier film, along with a precious metal upper electrode, is used to reduce sidewall film formation and leakage current by controlling the thickness of Ir and IrO2 to minimize reaction product deposition during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If physical etching (ion milling) is used to pattern precious metal films, then etching can be performed, but sidewall films are formed due to adhered etched atoms causing shorts between electrodes
Solution Approach 1:
A boron nitride (BN) film is introduced as an intermediary layer between the precious metal film and the etching mask. This BN film serves as a mediator that prevents etched atoms from adhering to the mask sidewalls, thereby eliminating sidewall film formation while maintaining effective etching of the precious metal electrode
Solution Approach 2:
The invention converts the harmful effect of etched atom adhesion (which causes sidewall films) into a beneficial process by using the BN film to capture these atoms. The etched atoms that would normally cause defects are instead directed to deposit on the BN film surface, which is subsequently removed, thus eliminating the harmful sidewall films
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 effectively reduces the amount of sidewall film formed during etching, thereby minimizing leakage current between the upper and lower electrodes, enhancing the reliability and production yield of ferroelectric memory devices.
Implementation Method 1
reaction products are less likely to adhere to a side of the etching mask
Implementation Method 2
physical etching has been heretofore used in which ion collision with a surface of the precious metal film is conducted with high kinetic energy to cause the precious metal atoms to be stripped away
Implementation Method 3
RIE is an etching method in which chlorine or chlorine-containing gas are used, and the physical effects by accelerated ions and the chemical effects between the etching gas and the etched object are used in its etching mechanism
Implementation Method 4
a thermal treatment in an oxygen atmosphere at a high temperature (e.g., 600-800 degrees Celsius) is normally required to recover properties of the ferroelectric
Implementation Method 5
the etching mask is eliminated by plasma ashing
Data Source
AI summary
A method for manufacturing a semiconductor device includes the steps of preparing a semiconductor substrate, forming a lower electrode having a laminated film of Ir and IrO2 whose thickness is 100 nm or less over the semiconductor substrate, forming a capacity insulating film comprised of a metal oxide dielectric on the lower electrode, and forming an upper electrode comprised of a precious metal film on the capacity insulating film.