Control of Ion Energy in a Capacitively Coupled Reactive Ion Etcher

Park, H. M.; Garvin, Craig; Grimard, Dennis S.; Grizzle, Jessy W.

doi:10.1149/1.1838945

Cited by 21 publications

(12 citation statements)

References 6 publications

(7 reference statements)

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“…An increase of negative bias at the inner electrode leaves the plasma potential unchanged, but it can be changed significantly if a positive dc bias is applied. [3][4][5][6] The dc coupling allowed a dc current to flow to the powered electrode and to expand the plasma structure to the whole chamber. In the case of low rf power without dc bias, the plasma is confined to the inner electrode, as similarly observed for planar geometry.…”

Section: Methodsmentioning

confidence: 99%

“…The change in plasma potential and, in turn, the change in ion energy by applying a positive dc voltage was repeated. [3][4][5][6] The theoretical model for sheath voltage ratio between two electrodes for these discharges and its dependence on their surface area is also provided in Refs. 7 and 8 and the relation between the self-bias and the etching rate in Si and SiO 2 was studied.…”

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confidence: 99%

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Effect of self-bias on cylindrical capacitive discharge for processing of inner walls of tubular structures—Case of SRF cavities

et al. 2018

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Cylindrical capacitive discharge is a convenient medium for generating reactive ions to process inner walls superconductive radio-frequency (SRF) cavities. These cavities, used in particle accelerators, presents a three-dimensional structure made of bulk Niobium, with axial cylindrical symmetry. Manufactured cavity walls are covered with Niobium oxides and scattered particulates, which must be removed for desired SRF performance. Cylindrical capacitive discharge in a mixture of Ar and Cl2 is a sole and natural non-wet acid choice to purify the inner surfaces of SRF cavities by reactive ion etching. Coaxial cylindrical discharge is generated between a powered inner electrode and the grounded outer electrode, which is the cavity wall to be etched. Plasma sheath voltages were tailored to process the outer wall by providing an additional dc current to the inner electrode with the help of an external compensating dc power supply and corrugated design of the inner electrode. The dc bias potential difference is established between two electrodes to make the set-up favorable for SRF wall processing. To establish guidelines for reversing the asymmetry and establishing the optimal sheath voltage at the cavity wall, the dc self-bias potential and dc current dependence on process parameters, such as gas pressure, rf power and chlorine content in the Ar/Cl2 gas mixture was measured. The process is potentially applicable to all concave metallic surfaces.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Effect of self-bias on cylindrical capacitive discharge for processing of inner walls of tubular structures—Case of SRF cavities

et al. 2018

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“…A Hammerstein model component was also added in [91] and [92] to allow static actuator nonlinearities to be accounted for; [92] also addresses the issue of spatial uniformity on the wafer. A control system that regulates the ion energy (measured using a Langmuir probe) in a capacitively coupled RIE is reported in [93].…”

Section: ) Control Of Plasma Variablesmentioning

confidence: 99%

Estimation and Control in Semiconductor Etch: Practice and Possibilities

Ringwood

Lynn

Bacelli

et al. 2010

IEEE Trans. Semicond. Manufact.

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Abstract-Semiconductor wafer etching is, to a large extent, an open-loop process with little direct feedback control. Most silicon chip manufacturers rely on the rigorous adherence to a "recipe" for the various etch processes, which have been built up based on considerable historical experience. However, residue buildup and difficulties in achieving consistent preventative maintenance operations lead to drifts and step changes in process characteristics. This paper examines the particular technical difficulties encountered in achieving consistency in the etching of semiconductor wafers and documents the range of estimation and control techniques currently available to address these difficulties. An important feature of such an assessment is the range of measurement options available if closed-loop control is to be achieved.Index Terms-Closed-loop control, plasma etch, run-to-run control, semiconductor wafer, state estimation, virtual metrology.

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“…At the high frequencies in use during plasma processing (∼13.56 MHz), changes in impedance, stray capacitances, and stray inductances cause considerable changes to the electrical behaviour of the chamber and hence the etching plasma properties. The electrical path between the powered chamber electrode and ground (the ground path) influences plasma variables such as the ion flux to the etching wafer and the DC bias of the wafer in the chamber [22]. Hence, changes in the impedance of the ground path brought about by PM events can cause the etch performance of the chamber to vary dramatically across maintenance cycle events.…”

Section: Introductionmentioning

confidence: 99%

Real-time virtual metrology and control for plasma etch

Lynn¹,

MacGearailt

Ringwood³

2012

Journal of Process Control

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a b s t r a c tPlasma etch is a semiconductor manufacturing process during which material is removed from the surface of semiconducting wafers, typically made of silicon, using gases in plasma form. A host of chemical and electrical complexities make the etch process notoriously difficult to model and troublesome to control. This work demonstrates the use of a real-time model predictive control scheme to control plasma electron density and plasma etch rate in the presence of disturbances to the ground path of the chamber. Virtual metrology (VM) models, using plasma impedance measurements, are used to estimate the plasma electron density and plasma etch rate in real time for control, eliminating the requirement for invasive measurements. The virtual metrology and control schemes exhibit fast set-point tracking and disturbance rejection capabilities. Etch rate can be controlled to within 1% of the desired value. Such control represents a significant improvement over open-loop operation of etch tools, where variances in etch rate of up to 5% can be observed during production processes due to disturbances in tool state and material properties.

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Control of Ion Energy in a Capacitively Coupled Reactive Ion Etcher

Cited by 21 publications

References 6 publications

Effect of self-bias on cylindrical capacitive discharge for processing of inner walls of tubular structures—Case of SRF cavities

Effect of self-bias on cylindrical capacitive discharge for processing of inner walls of tubular structures—Case of SRF cavities

Estimation and Control in Semiconductor Etch: Practice and Possibilities

Real-time virtual metrology and control for plasma etch

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