Indirect adaptive control of reactive ion etching using neural networks

Stokes, D.; May, G.S.

doi:10.1109/70.964665

Cited by 7 publications

(3 citation statements)

References 21 publications

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“…In [102], the control system is extended to include the control of . Etch rate of GaAs, measured using spectroscopic ellipsometry, is also controlled in [103].…”

Section: ) Control Of Etch 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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“…In [102], the control system is extended to include the control of . Etch rate of GaAs, measured using spectroscopic ellipsometry, is also controlled in [103].…”

Section: ) Control Of Etch 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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“…Real-time control of plasma etch rate has been reported by a number of researchers, but typically requires the use of bulky, expensive, or invasive measurement techniques. For example, Sarfaty et al [6] use laser reflectance interferometry (LRI), Stokes and May [7] use data from LRI, laser interferometry (LI), residual gas analysis (RGA), and optical emission spectroscopy (OES), and Rosen et al [8] use in-situ spectroscopic ellipsometry measurements of wafer thickness to implement real-time control.…”

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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“…For example, Sarfaty et al [17] implement real-time control of etch rate using a proportionalintegral-derivative (PID) controller, model-based feed-forward action for large changes in etch rate set point, and laser reflectance interferometry (LRI) to measure the etch rate. Stokes and May [18,19] describe control of etch rate using indirect adaptive control and data from LRI Laser interferometry (LI), residual gas analysis (RGA), and optical emission spectroscopy (OES) for process feedback. Rosen et al [20] develop real-time feed-back controllers for etch processes based on in situ spectroscopic ellipsometry measurements of wafer thickness.…”

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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Indirect adaptive control of reactive ion etching using neural networks

Cited by 7 publications

References 21 publications

Estimation and Control in Semiconductor Etch: Practice and Possibilities

Estimation and Control in Semiconductor Etch: Practice and Possibilities

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

Real-time virtual metrology and control for plasma etch

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