Aqueous Etching Solution for Silicon Oxide Pattern Loading
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Solution Overview
Problem
Existing etching technologies face challenges in minimizing pattern loading during the etching of silicon oxide, particularly in narrow gaps, especially when the silicon oxide density varies between gaps and surrounding areas, as seen in FinFET processing and Flowable Chemical Vapor Deposition (FCVD) applications, where dry etching is expensive and wet etching is prone to pattern loading.
Innovation Solution
An aqueous solution comprising an anion F− in a concentration of 2 to 4 mol/l and a cation of formula RR′R″R′″N+ in a concentration of 1.5 to 2 mol/l, with specific alkyl chain lengths and molar ratios, is used to reduce pattern loading while maintaining a good etching rate, and the pH can be adjusted with acids like HF or HCl to enhance etching speed and solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet etching is used to etch silicon oxide, then the etching rate is improved, but pattern loading increases
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by incorporating specific organic additives (ammonium fluorosulfonate and/or ammonium bisulfonate) alongside traditional HF and NH4F components. This parameter change enables the solution to achieve both high etching rates and reduced pattern loading by altering the etching mechanism to be less sensitive to confinement effects while maintaining efficient silicon oxide removal.
2Manufacturing precision
If dry etching is used to avoid pattern loading, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the complex dry etching system (which requires sophisticated plasma generation and control equipment) with a chemically optimized wet etching solution. The substituted chemical system achieves comparable pattern loading control through molecular-level interactions between the organic additives and silicon oxide, eliminating the need for expensive dry etching equipment while maintaining manufacturing precision.
3Volume of moving object
If FCVD is used to deposit silicon oxide, then the filling capability of narrow gaps is improved, but density variations between gaps and surrounding areas occur
Solution Approach 1:
The patent applies local quality by designing an etching solution with differentiated chemical components that respond differently to local oxide density variations. The organic additives (ammonium fluorosulfonate and/or ammonium bisulfonate) specifically target and compensate for density differences between FCVD-deposited oxide in gaps and thermal oxide in surrounding areas, enabling uniform etching rates across regions with different oxide densities and confinement 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
The solution effectively reduces pattern loading and maintains a high etching rate, even in narrow gaps, by optimizing the composition and pH of the etching solution, thereby addressing the density variations and confinement issues associated with FCVD silicon oxides.
Implementation Method 1
aqueous solution for etching silicon oxide
Implementation Method 2
Pattern loading is typically more severe when the gaps are smaller because it mostly results from a difference in how the etching species interact with silicon oxide under different confinement conditions
Data Source
AI summary
An aqueous solution for etching silicon dioxide and method of use are provided. The aqueous solution includes the anion F− in a concentration ranging from 2 to 4 mol/l and a cation of formula RR′R″R′″N+ in a concentration ranging from 1.5 to 2 mol/l, wherein each of R, R′, R″, and R′″ are independently selected from hydrogen and C1-5 alkyl chains with the proviso that the total number of carbon atoms in R, R′, R″, and R′″ combined equals from 8 to 16.