Plasma Etching Boron-Doped Amorphous Carbon Masks
Solution Overview
Problem
Conventional plasma etching methods face challenges in achieving high aspect ratios and precision with amorphous carbon films, particularly when the thickness of the resist layer or inorganic intermediate layer is increased, leading to issues like line edge roughness and limited selection ratio, and boron-doped amorphous carbon films are difficult to etch due to their hardness.
Innovation Solution
A plasma etching method using a mixed gas of chlorine and oxygen, with a semiconductor manufacturing apparatus set to a temperature of 100° C or more, where the oxygen supply amount is adjusted between initial and secondary etching stages to control etching rates and pressures, and high-frequency power is applied to enhance etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the amorphous carbon film is increased to secure selection ratio, then the selection ratio is improved, but the etching difficulty increases
Solution Approach 1:
The patent changes the chemical composition parameters of the amorphous carbon film by controlling the ratio of sp2-bonded carbon to sp3-bonded carbon during film formation. This parameter change makes the carbon film more etchable while maintaining adequate selection ratio, resolving the contradiction between thickness-related selection ratio and etching difficulty
Solution Approach 2:
The patent creates a composite etching system combining the amorphous carbon film with a specifically formulated plasma environment (fluorine-based chemistry). This composite approach enables effective etching of the carbon film while preserving the necessary mask properties, addressing both the selection ratio requirement and etching feasibility
2Productivity
If the etching rate is increased to reduce etching time, then the productivity is improved, but the verticality of etching hole is degraded
Solution Approach 1:
The patent modifies the plasma chemistry parameters by introducing fluorine-based reactants and optimizing pressure and power conditions. This creates an etching environment that achieves high etching rates while maintaining ion directionality and chemical selectivity, thereby preserving vertical hole profiles even at high productivity levels
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 effectively etches boron-doped amorphous carbon films with improved precision and aspect ratio, reducing line edge roughness and etching time while maintaining verticality, by volatilizing boron and carbon through controlled plasma exposure.
Implementation Method 1
The plasma etching method uses plasma of a mixed gas of chlorine gas and oxygen gas
Implementation Method 2
carbon may be volatilized by reaction of oxygen with carbon, and boron reacts with chlorine to produce boron chloride
Implementation Method 3
boron reacts with chlorine to produce boron chloride so that the evaporation temperature of boron is decreased. Thus, boron may be volatilized
Data Source
AI summary
Provided is a plasma etching method capable of favorably forming masks used when etching a multilayer film. This plasma etching method for etching boron-doped amorphous carbon involves using a plasma of a gas mixture comprising a chlorine gas and an oxygen gas, and setting the temperature of a mounting stage (3) to 100° C. or greater.