Silicon Nitride HF Gas Etching for Oxide Shape Preservation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing etching methods for silicon nitride films in semiconductor devices face challenges such as pattern collapse due to surface tension of chemical solutions, etching residue in fine gaps, and difficulty in achieving high selectivity and precision in dry etching processes, particularly in 3D-NAND structures and FinFET gate regions.
Innovation Solution
A dry etching method using hydrogen fluoride gas at controlled temperatures and pressures, combined with infrared heating, to form and remove a reaction layer on silicon nitride films without plasma, allowing for selective and precise etching of silicon nitride films relative to silicon oxide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wet etching using chemical solutions is used for isotropic etching, then etching in lateral direction is achieved, but pattern collapse occurs due to surface tension and etching residue remains in fine gaps
Solution Approach 1:
The patent replaces wet chemical etching with a dry etching process using hydrogen fluoride gas. This substitution eliminates the surface tension effects of liquid chemicals that cause pattern collapse, while maintaining the isotropic etching capability needed for lateral direction removal of silicon nitride films.
Solution Approach 2:
The patent controls etching precision by adjusting temperature parameters (wafer temperature between 60-200°C) and pressure parameters in the dry etching process. These parameter changes optimize the etching rate and selectivity, preventing residue accumulation in fine gaps while achieving complete lateral etching.
2Ease of manufacture
If dry etching processes using HF gas are used for silicon nitride film removal, then wet processing is replaced, but achieving high selectivity and precision in 3D-NAND structures and FinFET gate regions becomes difficult
Solution Approach 1:
The patent achieves high selectivity in dry etching by precisely controlling multiple parameters: wafer temperature (60-200°C), chamber pressure, and hydrogen fluoride gas flow rate. These parameter optimizations enable selective removal of silicon nitride films while preserving silicon oxide films, even in complex 3D-NAND and FinFET structures.
Solution Approach 2:
The patent applies preliminary heating to the wafer surface before and during the etching process. This pre-heating action activates the silicon nitride film surface, making it more reactive to HF gas while silicon oxide remains relatively inert, thereby establishing the required selectivity before the actual etching begins.
3Productivity
If higher temperature is used in HF gas etching to increase etching rate, then productivity improves, but selectivity with respect to silicon oxide films decreases
Solution Approach 1:
The patent identifies and controls the optimal temperature window for HF gas etching of silicon nitride films (60-200°C). Within this range, the etching rate is sufficiently high for productivity while maintaining selectivity against silicon oxide films. The patent avoids temperatures above 200°C where selectivity deteriorates.
Solution Approach 2:
The patent dynamically adjusts the etching process by controlling gas flow rates and temperature profiles during different stages of etching. This dynamic control allows the process to maintain high productivity through optimized etching rates while preserving selectivity by preventing excessive temperature effects on silicon oxide 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
The method enables high selectivity and precision in etching silicon nitride films, preventing degradation of the silicon oxide film shape and improving the desired structure in semiconductor devices.
Implementation Method 1
forming, as a first process, a reaction layer on the silicon nitride film by reaction of hydrogen fluoride gas at 30° C. or higher and 55° C. or lower
Implementation Method 2
removing, after the first process, as a second process, the reaction layer, which has been formed in the first process, through volatilization by performing heating at 70° C. or higher and 110° C. or lower without causing the hydrogen fluoride gas to flow
Data Source
AI summary
Provided is a method that allows for the etching of a silicon nitride film with respect to a silicon oxide film with high selectivity and high precision while preventing a degradation in the shape of the silicon oxide film portion during etching. The etching method of dry etching a film structure which is formed in advance on a wafer disposed in a processing chamber and in which an end portion of a film stack including a silicon nitride film and silicon oxide films vertically sandwiching the silicon nitride film forms a sidewall of a trench or hole, by supplying a gas for processing into the processing chamber, without using plasma includes: forming, as a first process, a reaction layer on the silicon nitride film by reaction of hydrogen fluoride gas at 30° C. or higher and 55° C. or lower; removing, thereafter, as a second process, the reaction layer having been formed in the first process, through volatilization by performing heating at 70° C. or higher and 110° C. or lower without causing the hydrogen fluoride gas to flow; and etching the silicon nitride film from the end portion in a lateral direction by performing the first and second processes a plurality of times.