Radio Frequency Diagnostics for Plasma Etch Systems

Bushman, Scott; Edgar, Thomas F.; Trachtenberg, Isaac

doi:10.1149/1.1837475

Cited by 27 publications

(11 citation statements)

References 1 publication

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“…Although the replacement components are macroscopically identical to those that are removed from the chamber, microscopic differences in the electrical connections made between components when they are replaced change the electrical characteristics of the chamber. Changes in such component connections are more influential as the applied RF frequency increases [21]. 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.…”

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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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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show abstract

“…Although the replacement components are macroscopically identical to those that are removed from the chamber, microscopic differences in the electrical connections made between components when they are replaced change the electrical characteristics of the chamber. 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 [9]. 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 [10].…”

Section: Introductionmentioning

confidence: 99%

Real-time virtual metrology and control of etch rate in an industrial plasma chamber

Lynn

MacGearailt

Ringwood

2012

2012 IEEE International Conference on Control Applications

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Abstract-Plasma 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 etch rate in the presence of disturbances to the ground path of the chamber, which are representative of maintenance events. Virtual metrology (VM) models, using plasma impedance measurements, are used to estimate the plasma etch rate in real time for control, with a view to eliminating the requirement for invasive measurements. The VM 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 openloop 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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“…The operating ranges of various matching circuits are analyzed in [11] and [12]. The RF systems described in [5], [6], and [14] use matching circuits, but no details of the control are presented. Although the primary application of RF heating considered here is the defrosting of frozen foodstuffs, RF heating is also used extensively in plastics welding, rubber curing and drying processes for textiles, paper, fiberglass, and coatings [1], [15].…”

Section: Introductionmentioning

confidence: 99%

Design of matching circuit controllers for radio-frequency heating

Cottee

Duncan

2003

IEEE Trans. Contr. Syst. Technol.

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Electromagnetic energy in the microwave and radiofrequency (RF) portions of the spectrum can be used to heat or defrost (thaw) foodstuffs. This paper considers a fixed frequency RF oven, where a matching circuit is used to ensure that the combined impedance of the oven and the food (the load) matches the impedance of the generator and the transmission line. A controller measures the reflected RF signal and adjusts the settings of components in the matching circuit. The system is highly nonlinear and there are significant sources of uncertainty in the model of the process. A variable structure controller is designed and its stability is examined in the presence of uncertainties due to stray components. The switching lines are defined in terms of the real and imaginary parts of the reflected signal, which avoids the need to estimate the states. Conditions are derived for maintaining stability in the region close to the matching point. The performance of the controller is illustrated by results from an implementation on a prototype commercial RF oven.

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Radio Frequency Diagnostics for Plasma Etch Systems

Cited by 27 publications

References 1 publication

Real-time virtual metrology and control for plasma etch

Real-time virtual metrology and control for plasma etch

Real-time virtual metrology and control of etch rate in an industrial plasma chamber

Design of matching circuit controllers for radio-frequency heating

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