Hydrofluorocarbon Polymer Sidewall Protection for Deep Trench Etching
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Solution Overview
Problem
The Bosch process for deep silicon etching in semiconductor substrates suffers from sidewall scalloping and undercutting, which limits the formation of high aspect ratio structures and introduces voids in through substrate via structures, affecting the reliability of three-dimensional semiconductor stacks.
Innovation Solution
An anisotropic etch process using a hydrofluorocarbon gas as a polymer deposition gas, alternating with an etchant gas, to generate a thick carbon-rich and hydrogen-containing polymer that protects sidewalls, minimizing undercut and maintaining etch rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the Bosch process is used for deep silicon etching, then high aspect ratio structures can be formed, but sidewall scalloping and undercutting occur
Solution Approach 1:
The patent changes the chemical composition parameter of the passivation gas from conventional fluorocarbon (CF4, C4F8) to hydrofluorocarbon (C5HF7, C6HF9), which contains hydrogen atoms. This parameter change fundamentally alters the polymer deposition mechanism, enabling the formation of thick carbon-rich and hydrogen-containing polymer layers that effectively protect sidewalls during etching, thereby eliminating scalloping and undercutting while maintaining high aspect ratio structure formation
Solution Approach 2:
The patent creates a composite protective layer on the trench sidewalls consisting of carbon-rich and hydrogen-containing polymer material deposited from hydrofluorocarbon gas. This composite polymer structure provides superior sidewall protection compared to conventional fluorocarbon polymers, simultaneously achieving smooth sidewall profiles and preventing undercutting of the hard mask
2Manufacturing precision
If increased amounts of passivation gas are employed to reduce sidewall scalloping and undercutting, then sidewall protection improves, but etch rate significantly reduces
Solution Approach 1:
The patent changes the chemical composition parameter of the passivation gas to hydrofluorocarbon containing hydrogen, which fundamentally alters the polymer deposition characteristics. This enables the formation of thick protective polymer layers at lower gas flow rates compared to conventional fluorocarbon gases, thereby achieving effective sidewall protection without significantly reducing the etch rate
Solution Approach 2:
The hydrofluorocarbon gas creates a localized thick polymer layer specifically on the trench sidewalls and top surface, providing concentrated protection where needed. The carbon-rich and hydrogen-containing polymer deposits preferentially on horizontal surfaces and sidewalls, forming a protective barrier that prevents undercutting while allowing vertical etching to proceed at high rates
3Manufacturing precision
If conventional fluorocarbon gas is used for polymer deposition, then sidewall protection is provided, but undercutting of hard mask still occurs
Solution Approach 1:
The patent changes the chemical composition parameter of the passivation gas from fluorocarbon to hydrofluorocarbon, introducing hydrogen atoms into the polymer structure. This parameter change enables the formation of thick carbon-rich and hydrogen-containing polymer layers that provide superior sidewall protection, completely preventing hard mask undercutting while maintaining effective etching
Solution Approach 2:
The patent creates a composite protective polymer layer with carbon and hydrogen elements from hydrofluorocarbon gas deposition. This composite material structure provides enhanced protection compared to conventional fluorocarbon polymers, forming a robust barrier that prevents both sidewall scalloping and hard mask undercutting during the etching process
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 hydrofluorocarbon polymer deposition effectively reduces undercut and maintains or enhances the etch rate, improving the formation of high aspect ratio trenches with reduced voids and increased reliability in three-dimensional semiconductor structures.
Implementation Method 1
the deposition process deposits a hydrofluorocarbon polymer on the bottom surface and sidewalls of the trench that is generated from a plasma containing ions of a hydrofluorocarbon gas
Implementation Method 2
The Bosch process employs alternating cycles of etching employing a SF6 gas
Data Source
AI summary
A hydrofluorocarbon gas is employed as a polymer deposition gas in an anisotropic etch process employing an alternation of an etchant gas and the polymer deposition gas to etch a deep trench in a semiconductor substrate. The hydrofluorocarbon gas can generate a thick carbon-rich and hydrogen-containing polymer on sidewalls of a trench at a thickness on par with the thickness of the polymer on a top surface of the semiconductor substrate. The thick carbon-rich and hydrogen-containing polymer protects sidewalls of a trench, thereby minimizing an undercut below a hard mask without degradation of the overall rate. In some embodiments, an improvement in the overall etch rate can be achieved.