Excited State Etching for DRAM Silicon Selectivity
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Solution Overview
Problem
Existing dry etching techniques for silicon portions in semiconductor manufacturing fail to achieve both high etching rates and selectivity, particularly with respect to silicon nitride and silicon oxide films, and titanium-based films, which are critical for DRAM capacitor fabrication.
Innovation Solution
An etching method involving the use of a fluorine-containing gas, such as hydrogen fluoride, and an inert gas, like nitrogen or argon, in an excited state, is employed to selectively etch silicon portions on a substrate, achieving high etching rates and selectivity with respect to silicon nitride, silicon oxide, and titanium-based films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing dry etching techniques (HF gas+F2 gas or F2 gas+NH3 gas) are used to etch silicon portions, then etching can be performed, but the etching rate and selectivity with respect to silicon nitride and silicon oxide films cannot be achieved at required levels
Solution Approach 1:
The patent applies parameter changes by using fluorine-containing gas in an excited state (plasma) instead of ground state gas, and by optimizing the ratio of fluorine-containing gas to inert gas. This changes the chemical reactivity and physical state parameters to achieve both high etching rate (100 nm/min or greater) and high selectivity (500 or greater) simultaneously, resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent uses a composite gas system combining fluorine-containing gas (HF or SF6) with inert gas (N2 or Ar) in specific volume ratios (10:1 to 1:10). This composite approach creates a plasma environment that provides both the chemical reactivity needed for high etching rates and the controlled conditions needed for high selectivity, addressing the contradiction between speed and precision.
2Manufacturing precision
If existing dry etching techniques are used for DRAM capacitor manufacturing, then silicon portions can be etched, but extremely high selectivity with respect to titanium-based films cannot be achieved
Solution Approach 1:
The patent changes the chemical parameters by selecting HF gas as the fluorine-containing gas when titanium-based films are present. HF gas provides extremely high selectivity for silicon etching while sparing titanium-based films, and when used in excited state with inert gas, maintains high etching rates. This parameter change resolves the contradiction between selectivity and productivity for DRAM capacitor manufacturing.
3Productivity
If wet etching is used to etch silicon portions, then high etching rates can be achieved, but patterning occurs during drying after etching
Solution Approach 1:
The patent substitutes wet etching (liquid-based) with dry etching using fluorine-containing gas in excited state. This replacement eliminates the drying step that causes patterning, while the plasma environment provides sufficiently high etching rates (100 nm/min or greater), thus resolving the contradiction between productivity and patterning accuracy through mechanism substitution.
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 method enables etching rates of 100 nm/min or greater with selectivity of 500 or more for silicon nitride and silicon oxide films, and maintains high selectivity for titanium-based films, ensuring precise patterning and efficient manufacturing of DRAM capacitors.
Implementation Method 1
supplying a fluorine-containing gas and an inert gas maintained in an excited state to the target substrate
Implementation Method 2
selectively etching the silicon portion with respect to the silicon nitride film and the silicon oxide film by supplying a fluorine-containing gas and an inert gas maintained in an excited state
Data Source
AI summary
There is provided an etching method which includes: preparing a target substrate having a silicon portion, a silicon nitride film and a silicon oxide film; and selectively etching the silicon portion with respect to the silicon nitride film and the silicon oxide film by supplying a fluorine-containing gas and an inert gas which stay in an excited state to the target substrate.