Gas Shroud Pressure Control for Localized Wafer Plasma Etching
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Solution Overview
Problem
Semiconductor fabrication processes face challenges with wafer and film thickness non-uniformity, etch damage, and contamination during plasma etching, particularly as patterns become smaller and tolerances become more constrained, necessitating improved control and uniformity in plasma etching processes.
Innovation Solution
A plasma processing apparatus and method utilizing a gas shroud with a pressure differential to control the plasma plume's lateral width and focus it on a smaller area, while directing etch by-products and unused radicals out of the chamber, preventing contamination of surrounding regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a localized or partial plasma etch is used to remove material in a first region of a wafer, then material can be selectively removed from specific areas, but etch damage occurs from unused etch radicals and contamination occurs from etch by-products and unreacted neutrals to surrounding regions
Solution Approach 1:
The plasma chamber is divided into multiple pressure regions: a first pressure region where the plasma etch is performed and a second pressure region surrounding it. This segmentation allows selective etching in the first region while protecting surrounding regions in the second region from contamination by maintaining pressure differentials that prevent by-products and unreacted neutrals from migrating to adjacent areas.
Solution Approach 2:
A pressure differential is introduced as an intermediary mechanism between the etch zone and surrounding regions. By maintaining higher pressure in the etch region compared to surrounding areas, the pressure gradient acts as a barrier that directs gas flow and prevents the migration of harmful species to surrounding regions, thereby reducing contamination while preserving selective etching capability.
2Productivity
If plasma processes are used for film etching during pattern transfer, then material removal can be achieved, but wafer and film thickness non-uniformity causes issues in maintaining consistent etching across different regions
Solution Approach 1:
Different pressure conditions are applied to different regions of the wafer: a first pressure region directly over the wafer surface where etching occurs, and a second pressure region in the surrounding chamber. This local quality differentiation in pressure allows optimization of etching performance in the target region while controlling plasma distribution to compensate for wafer thickness variations, thereby achieving both high productivity and improved thickness uniformity.
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 high-resolution etching with improved uniformity across the wafer surface, reducing unintended etch damage and contamination, and allowing for better control of the etching process.
Implementation Method 1
A pressure differential is used to control a lateral width of the plasma plume
Implementation Method 2
generating a plasma from a plasma source
Implementation Method 3
distributing an inert gas from the gas plenum to the first region
Data Source
AI summary
An embodiment plasma processing apparatus includes a plasma generation source, a nozzle in a plasma chamber, the nozzle being able to direct plasma from the plasma generation source to a wafer that is to be processed, the plasma having the form of a plasma stream at an exit of the nozzle, a gas shroud disposed in the plasma chamber and over the wafer, the gas shroud including a first circular opening in a top surface of the gas shroud, a second circular opening in a bottommost surface of the gas shroud, the nozzle being disposed in the first circular opening and the second circular opening, and a gas plenum configured to be maintained at a first pressure, a first region between the second circular opening and a top surface of the wafer being configured to be maintained at a second pressure, the first pressure and the second pressure being different.