HF Gas Oxide Etching at Low Temperature for Nitride Selectivity
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Solution Overview
Problem
Conventional etching technologies struggle to isotropically etch silicon oxide films with high accuracy and selectivity relative to silicon nitride films in three-dimensional semiconductor structures, leading to issues such as pattern collapse, non-uniform etching, and difficulty in balancing etching rates, which affects the controllability and yield of microfabrication processes.
Innovation Solution
A dry etching method using hydrogen fluoride gas is employed without plasma, maintaining the wafer temperature at or below −42.0°C and adjusting the partial pressure of hydrogen fluoride gas between 50 Pa to 1000 Pa to achieve a high etching rate for silicon oxide films while maintaining a low etching rate for silicon nitride films, thereby enhancing the selection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wet etching with medicinal solution is used for isotropic etching, then etching can be performed isotropically in vertical and lateral directions, but pattern collapse occurs due to surface tension and etching residue accumulates in minute gaps
Solution Approach 1:
The patent replaces wet etching (liquid-based) with dry etching using hydrogen fluoride gas. This substitution eliminates surface tension effects that cause pattern collapse while maintaining isotropic etching capability through gas-phase chemical reactions that uniformly remove silicon oxide in both vertical and lateral directions.
Solution Approach 2:
The patent uses hydrogen fluoride gas in a controlled atmosphere to perform etching without the harmful effects of liquid medicinal solutions. The gas-phase environment prevents pattern collapse and residue accumulation while achieving the desired isotropic etching effect on silicon oxide films.
2Loss of substance
If conventional dry etching with plasma is used, then medicinal solution consumption is reduced, but balancing etching rates between silicon oxide and silicon nitride films becomes difficult
Solution Approach 1:
The patent changes the fundamental parameter from plasma-based dry etching to non-plasma hydrogen fluoride gas etching. This parameter change enables independent control of etching rates for different materials, achieving high selectivity between silicon oxide (fast etching) and silicon nitride (slow etching) without the constraints of conventional plasma chemistry.
Solution Approach 2:
The patent substitutes plasma-based etching mechanisms with direct hydrogen fluoride gas chemistry. This replacement eliminates the complex plasma interactions that make selective etching difficult, allowing precise control over etching rates for different film types through gas flow and temperature parameters alone.
3Productivity
If temperature is increased to improve etching rate, then productivity increases, but selectivity between silicon oxide and silicon nitride films decreases
Solution Approach 1:
The patent identifies and exploits the differential temperature dependence of etching rates for silicon oxide versus silicon nitride in hydrogen fluoride gas. By operating at optimized temperatures, the process achieves both high productivity through fast silicon oxide etching and high selectivity by maintaining slow silicon nitride etching rates.
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 allows for precise and uniform etching of silicon oxide films relative to silicon nitride films, ensuring high etching rates and selectivity, thus improving the accuracy and yield of three-dimensional semiconductor manufacturing processes.
Implementation Method 1
a first gas for process containing fluorine is supplied into the process chamber to perform etching on the silicon oxide film
Implementation Method 2
maintaining the wafer temperature at or below −42.0°C
Data Source
AI summary
A method for etching a silicon oxide film at a high selection ratio with respect to a silicon nitride film while a high etching rate of the silicon oxide film is balanced with a low etching rate of the silicon nitride film. The etching processing method is a dry etching processing method for etching a film without using plasma by supplying gas into a process chamber, the film having a side wall of a groove or a hole constituted by respective end parts of laminated film layers formed on a wafer, the laminated film layers including silicon oxide films each sandwiched between silicon nitride films, and in which the silicon oxide films are etched laterally from the end parts with the wafer being set to a low temperature equal to or less than (0.040x−42.0° C.) when a partial pressure of hydrogen fluoride gas is taken as x (Pa).