Confinement Ring Surface Area Ratio for Plasma Etch Wear Reduction
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Solution Overview
Problem
The semiconductor manufacturing industry faces challenges in maximizing throughput while minimizing the cost of maintenance in high aspect ratio contact etchers, as extremely high ion energies used in plasma etching processes lead to increased wear rates of reactor parts due to high energy ions bombarding the reactor's interior surfaces.
Innovation Solution
A small volume chamber wafer processing system with a removable C-shaped grounded confinement ring is introduced, increasing the surface area ratio between the powered electrode and grounded surfaces, which enhances wafer DC bias and ion energy while reducing plasma potential, thereby decreasing wear rates and operating costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If extremely high ion energies are used in plasma etching processes, then etching performance is improved, but wear rate of reactor parts increases
Solution Approach 1:
The confinement ring creates a localized grounded surface with increased area specifically positioned to intercept high energy ions before they reach other reactor components. This local modification of surface area distribution allows high ion energies to be maintained at the wafer while redirecting ion flux to the confinement ring, resolving the contradiction between etching performance and reactor part wear
Solution Approach 2:
The removable confinement ring acts as an intermediary component that absorbs the harmful impact of high energy ions. By introducing this intermediate grounded surface, the system protects other reactor parts from ion bombardment while maintaining the necessary high ion energies for effective etching, thus mediating between productivity and reliability requirements
2Productivity
If high energy ions are used to bombard wafer surface, then etch rate increases, but cost of maintenance of plasma reactor parts increases
Solution Approach 1:
The confinement ring is designed as a removable, replaceable component that can be easily serviced or replaced when worn. This disposable-like approach to a critical component allows the system to maintain high etch rates using high energy ions while minimizing maintenance costs, as the confinement ring itself is the sacrificial element rather than expensive reactor parts
Solution Approach 2:
By modifying the surface area parameter of the grounded confinement ring, the system changes the distribution of ion flux without altering the high energy ion generation at the wafer. This parameter change increases etch rate while directing wear to the inexpensive, easily replaceable confinement ring, thereby reducing overall maintenance costs
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 system achieves a 30% increase in maximum ion energy at the wafer surface with reduced plasma potential on grounded chamber parts, leading to higher etch rates and lower operating costs compared to conventional systems, with the added flexibility of modifying electrical properties and replacing components to optimize performance.
Implementation Method 1
When a plasma is in contact with a negatively biased surface, such as an electrode or wall, a strong localized electric field appears between the plasma and that surface. This boundary layer, called a 'plasma sheath,' is a region of very low electron density, and serves as a medium to accelerate ions from the plasma to the electrode or wall surface.
Implementation Method 2
A wafer 124 is held on ESC 106 via an electrostatic force. A voltage differential is provided between ESC 106 and grounded portions (grounded upper confinement chamber portion 102, grounded lower confinement chamber portion 104, and removable floating confinement ring 108), via RF driver 110
Implementation Method 3
The pressure within plasma-forming space 112 and the voltage differential, as created by RF driver 110, is set such that the etching material supplied into plasma-forming space 112 creates plasma 116
Data Source
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Figure 5~6
AI summary
A wafer processing system is provided for use with a driver and a material supply source. The driver is operable to generate a driving signal. The material supply source is operable to provide a material. The wafer processing system includes an upper confinement chamber portion, a lower confinement chamber portion, a confinement ring, and an electro-static chuck. The upper confinement chamber portion has an upper confinement chamber portion inner surface. The lower confinement chamber portion is detachably disposed in contact with the upper confinement chamber portion. The lower confinement chamber portion has a lower confinement chamber portion inner surface. The confinement ring is removably disposed in contact with the upper confinement chamber portion inner surface and the lower confinement chamber portion inner surface. The confinement ring has a confinement ring inner surface. The electro-static chuck has an electro-static chuck upper surface and is arranged to receive the driving signal. The upper confinement chamber portion, the lower confinement chamber portion, the confinement ring and the electro-static chuck are arranged such that the upper confinement chamber portion inner surface, the lower confinement chamber portion inner surface, the confinement ring inner surface and the electro-static chuck upper surface surround a plasma-forming space that is capable of receiving the material. The upper confinement chamber portion, the lower confinement chamber portion, the confinement ring and the electro-static chuck are operable to transform the material into a plasma when the electro-static chuck receives the driving signal. The confinement ring has a non-rectangular cross section.