Etching Method Using Halogen Compounds for Mask Selectivity
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Solution Overview
Problem
The etching of semiconductor wafers with silicon nitride films under low-temperature conditions faces challenges in maintaining the shape of high-aspect-ratio holes and achieving adequate mask selectivity due to the formation of reaction products that disrupt the etching process and increase the etching rate of mask films.
Innovation Solution
The etching method involves using a compound containing a halogen element like chlorine, bromine, or iodine, such as chloroform, to decompose reaction products like ammonium fluorosilicate salts, which are formed during the etching of silicon nitride, thereby improving the shape of the etching holes and enhancing mask selectivity by depositing carbon on the mask film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If etching is performed under low-temperature conditions to maintain hole shape, then the shape of high-aspect-ratio holes is improved, but the mask selectivity deteriorates due to increased etching rate of mask films
Solution Approach 1:
A carbon-containing compound is introduced as an intermediary substance during the etching process. This compound deposits carbon on the mask film surface, forming a protective layer that reduces the etching rate of the mask film. The carbon deposit acts as a mediator between the plasma environment and the mask film, preventing direct reaction between etching species and the mask material, thereby improving mask selectivity while maintaining low-temperature etching conditions for good hole shape.
2Productivity
If etching is performed to remove silicon nitride, then the etching rate is improved, but reaction products like ammonium fluorosilicate salts are formed that disrupt the etching process
Solution Approach 1:
The carbon-containing compound transforms the harmful reaction products into beneficial carbon deposits on the mask film. The carbon deposits serve multiple functions: they protect the mask film from excessive etching, improve hole shape control, and facilitate the removal of reaction products. By converting the problematic by-products into a useful protective layer, the process maintains high etching rates while eliminating the disruptive effects of accumulated reaction products.
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 by-products attached to the wafer surface, improves the shape of the etching holes, and increases mask selectivity, while maintaining a high etching rate.
Implementation Method 1
decompose reaction products like ammonium fluorosilicate salts, which are formed during the etching of silicon nitride
Implementation Method 2
enhancing mask selectivity by depositing carbon on the mask film
Data Source
AI summary
An etching method includes: preparing a compound in a processing space in which an etching target is accommodated; and etching the etching target with a mask film formed thereon, under an environment where the compound exists. The etching of the etching target includes etching the etching target under an environment where hydrogen (H) and fluorine (F) exist when the etching target contains silicon nitride (SiN), and etching the etching target under an environment where nitrogen (N), hydrogen (H), and fluorine (F) exist when the etching target contains silicon (Si). The compound includes at least one halogen element selected from a group consisting of carbon (C), chlorine (Cl), bromine (Br), and iodine (I).