Hydrogen-Containing Fluorocarbon Etch Chemistries for TSV
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Solution Overview
Problem
The Bosch etch process for deep silicon etching faces challenges such as non-uniform etching rates between structures of different aspect ratios, known as RIE lag or aspect ratio dependent etching, and difficulties in removing polymer residue, which hinder the formation of high aspect ratio apertures essential for 3D-IC, MEMS, and power device manufacturing.
Innovation Solution
The use of hydrogen-containing polymer deposition fluids with specific formulas, such as CxHyFz, where 1≤x<7, 1≤y≤13, and 1≤z≤13, in a cyclic process that alternates between plasma etching and polymer deposition, allows for the etching of apertures with higher aspect ratios and more consistent etching rates across varying aperture sizes, reducing RIE lag and facilitating easier polymer removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Bosch etch process is used for deep silicon etching, then high etch rates and selectivity are achieved, but non-uniform etching rates occur between structures of different aspect ratios (RIE lag)
Solution Approach 1:
The patent changes the chemical parameters of the etching process by replacing cC4F8 with hydrogen-containing fluorocarbon gases (CHF3, CF3H, CF2H2) that have different molecular structures and reactivity. This parameter change modifies the polymer deposition characteristics, leading to more uniform sidewall protection across different aspect ratios while maintaining high etch rates through SF6 chemistry.
Solution Approach 2:
The patent employs composite gas chemistry by combining SF6 (for etching) with hydrogen-containing fluorocarbons (for polymer deposition). This composite approach creates a synergistic effect where the hydrogen content enhances polymer formation and sidewall protection, while the fluorine content maintains aggressive silicon etching, resolving the RIE lag issue.
2Manufacturing precision
If the Bosch etch process is used for deep etching, then high aspect ratio structures can be formed, but polymer residue removal becomes difficult
Solution Approach 1:
The patent modifies the polymer composition parameters by introducing hydrogen-containing fluorocarbons instead of pure fluorocarbons. The hydrogen content changes the polymer's chemical structure, making it less cross-linked and more soluble, which facilitates easier removal while still providing adequate sidewall protection for high aspect ratio structures.
Solution Approach 2:
The patent uses polymers that are designed to be temporary and easily removable. By selecting hydrogen-containing fluorocarbons that produce less persistent polymer residues, the process treats the polymer as a disposable protective layer that can be efficiently removed after serving its purpose, reducing manufacturing complexity.
3Area of moving object
If smaller opening sizes are used for deep etching, then device density increases, but etching becomes more difficult due to physical access limitations
Solution Approach 1:
The patent changes the etching chemistry parameters to enable effective polymer deposition in narrow openings. The hydrogen-containing fluorocarbons produce polymers with different rheological properties that can better penetrate and coat the sidewalls of small openings, maintaining protective coverage even when physical access is limited, thus preserving etch rate uniformity in dense structures.
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 enables the etching of apertures with aspect ratios from 2:1 to 100:1, reduces RIE lag, and allows for deep silicon etching without the need for an etch stop layer, improving processing efficiency and preventing notching, while maintaining consistent etching rates across different aperture sizes.
Implementation Method 1
A polymer is deposited on the etched silicon-containing substrate by plasmas of a hydrogen-containing polymer deposition fluid
Implementation Method 2
The silicon-containing substrate is plasma etched by an etching fluid containing fluorine to form an etched silicon-containing substrate
Data Source
AI summary
Replacement chemistries for the cC4F8 passivation gas in the Bosch etch process and processes for using the same are disclosed. These chemistries have the formula CxHyFz, with 1≤x<7, 1≤y≤13, and 1≤z≤13. The replacement chemistries may reduce RIE lag associated with deep silicon aperture etching.