Semiconductor Sidewall Plasma Smoothing for Bosch Etch Scallops
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Solution Overview
Problem
Conventional Bosch etching processes produce large scallops on semiconductor substrates, which are undesirable in applications requiring smooth surfaces for subsequent processing steps such as through silicon vias and hybrid bonding, leading to defects and reduced process windows.
Innovation Solution
A method involving a plasma treatment using Ar, O2, and per-fluorocarbons in an RF-powered etch chamber to deposit a protective layer and etch the sidewalls, reducing scallop size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a longer isotropic etch step duration is employed to achieve faster etch rates, then productivity is improved, but scallop size increases leading to poor manufacturing precision
Solution Approach 1:
The etching process is segmented into multiple cycles of isotropic etching followed by anisotropic over-etching steps. This segmentation allows the isotropic etch to progress rapidly while the subsequent anisotropic step removes the scallops formed, thus maintaining both high productivity and sidewall smoothness
Solution Approach 2:
The process employs periodic alternation between isotropic etching and anisotropic over-etching. The isotropic etch step deposits material and forms scallops, while the anisotropic over-etch step removes these scallops. This periodic action enables continuous progress through the substrate while maintaining smooth sidewalls
2Device complexity
If conventional Bosch processing is used to maintain process simplicity, then device complexity is reduced, but scallop size remains large requiring additional smoothing steps
Solution Approach 1:
The smoothing function is merged into the existing Bosch etching process by incorporating anisotropic over-etching steps within the same process sequence. This combines the scallop-forming isotropic etch with the scallop-removing anisotropic over-etch in a unified process, eliminating the need for separate smoothing equipment or steps
3Manufacturing precision
If low etch rates are used to reduce scallop size, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The process dynamically changes etching parameters between different steps: using high isotropic etch rates for rapid material removal, then switching to anisotropic over-etching conditions that preferentially remove scallops. This parameter switching enables both high overall etch rates and smooth sidewalls
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 effectively reduces scallop height by up to 90%, enabling smoother sidewalls for conformal deposition and improving process reliability.
Implementation Method 1
performing a treatment step by generating a plasma in a gaseous atmosphere comprising Ar, O 2 and at least one per-fluorocarbon while applying an RF signal having an RF power to the substrate support, wherein the plasma (i) causes a protective layer formed at least partially from the per-fluorocarbon to be deposited on the sidewall
Implementation Method 2
performing a treatment step by generating a plasma in a gaseous atmosphere comprising Ar, O 2 and at least one per-fluorocarbon while applying an RF signal having an RF power to the substrate support, wherein the plasma (ii) etches the sidewall so as to smooth the scalloped profile of the sidewall
Data Source
Figure 1~2b
AI summary
According to the invention there is provided a method of treating a semiconductor substrate, the semiconductor substrate having an etched feature comprising a sidewall with a scalloped profile, the method comprising the steps of: placing the semiconductor substrate on a substrate support in an etch chamber, the semiconductor substrate having an etched feature comprising a sidewall with a scalloped profile; and performing a treatment step by generating a plasma in a gaseous atmosphere comprising Ar, O2 and at least one per-fluorocarbon while applying an RF signal having an RF power to the substrate support, wherein the plasma (i) causes a protective layer formed at least partially from the per-fluorocarbon to be deposited on the sidewall and (ii) etches the sidewall so as to smooth the scalloped profile of the sidewall.