Plasma Etching Selectivity Using Fluorocarbon Gas Mixtures
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Solution Overview
Problem
Current plasma etching methods for silicon-containing dielectric layers face challenges in achieving high selectivity and etching rate, particularly when forming high aspect ratio contact holes using organic layers as masks, requiring a method that balances productivity and mask thickness reduction.
Innovation Solution
A plasma etching method using a processing gas mixture of unsaturated and aliphatic saturated fluorocarbon gases, along with oxygen, and applying high frequency powers to both the upper and lower electrodes in a capacitively coupled plasma etching apparatus, optimizing the flow rate ratios and frequencies to enhance etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching methods are used with standard processing gases, then the etching process can be performed, but the selectivity of the silicon-containing dielectric layer against the organic mask is insufficient and the etching rate is limited
Solution Approach 1:
The patent changes the chemical composition parameters of the processing gas by introducing a specific mixture containing unsaturated fluorocarbon gas (C4F6), aliphatic saturated fluorocarbon gas (C5F12 or C6F14), and oxygen gas in optimized flow rate ratios. This parameter change transforms the plasma chemistry to achieve both high etching rate and high selectivity simultaneously, resolving the contradiction between manufacturing precision and productivity
Solution Approach 2:
The patent uses a composite processing gas system combining three different types of fluorocarbon gases with distinct chemical properties. The unsaturated fluorocarbon provides etching capability, the aliphatic saturated fluorocarbon enhances mask protection and selectivity, and oxygen gas optimizes the plasma chemistry. This composite gas system achieves synergistic effects that simultaneously improve both selectivity and etching rate
2Productivity
If the mask layer thickness is reduced to improve productivity, then more contact holes can be formed per unit time, but the selectivity requirement becomes more stringent and harder to maintain
Solution Approach 1:
By optimizing the flow rate ratios of the composite processing gas (C4F6:C5F12:O2 = 2:1:2.0 to 2.4 or C4F6:C6F14:O2 = 2:1:2.2 to 2.6), the patent creates a plasma environment that provides enhanced selectivity. This allows the use of thinner mask layers while maintaining adequate protection, thereby improving productivity without sacrificing selectivity
3Productivity
If high frequency power is applied to both upper and lower electrodes, then the etching rate can be enhanced, but the control complexity and energy consumption increase
Solution Approach 1:
The patent employs dynamic control of high frequency powers applied to both electrodes, where the lower electrode receives power at a frequency lower than the upper electrode. This dynamic power application scheme optimizes ion bombardment and plasma density distribution, achieving enhanced etching rates while maintaining controllable process conditions through frequency differentiation
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 achieves a high etching rate and selectivity for silicon-containing dielectric layers, as demonstrated by increased etching rates and maintained selectivity compared to comparative examples, while maintaining the integrity of the organic mask layer.
Implementation Method 1
a plasma generating unit for converting the processing gas supplied from the processing gas supply unit into a plasma, thereby plasma-etching the substrate
Implementation Method 2
by applying high frequency powers between the upper and the lower electrode
Data Source
AI summary
A plasma etching method includes the step of performing a plasma etching on a silicon-containing dielectric layer formed on a substrate to be processed by using a plasma, while using an organic layer as a mask. In addition, the plasma is generated from a processing gas at least including a first fluorocarbon gas which is an unsaturated gas; a second fluorocarbon gas which is an aliphatic saturated gas expressed by CmF2m+2 (m=5, 6); and an oxygen gas. Further, a computer-readable storage medium for storing therein a computer executable control program is provided where the control program, when executed, controls a plasma etching apparatus to perform the above plasma etching method.