Brian A Rashap | University of Michigan (original) (raw)

Papers by Brian A Rashap

Research paper thumbnail of Applications of control to semiconductor manufacturing: reactive ion etching

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented as well as supporting experimental results.

Research paper thumbnail of Control of semiconductor manufacturing equipment: real-time feedback control of a reactive ion etcher

IEEE Transactions on Semiconductor Manufacturing, 1995

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented. The principal ideas are to sense key plasma parameters, develop a dynamic input-output model for the subsystem connecting the equipment inputs to the key plasma variables, and design and implement a multivariable control system to control these variables. Experimental results show that this approach to closed-loop control leads to a much more stable etch rate in the presence of a variety of disturbances as compared to current industrial practice.

Research paper thumbnail of Sensor systems for real‐time feedback control of reactive ion etching

Previous efforts from our group have shown encouraging initial results in stabilizing etch rates ... more Previous efforts from our group have shown encouraging initial results in stabilizing etch rates versus time during a run by using real-time, multivariable feedback control ͑RTC͒ in an Applied 8300 reactive ion etcher. That work indicated the need for improvements in our sensor systems, both the sensors currently used in feedback control and those monitoring the effects of the control on the wafers being etched. In this article we report on our efforts in the development and improvement of two such sensor systems. The first is an optical emission spectroscopy system which simultaneously measures two emission line intensities for use in actinometry. The second sensor system uses spectral reflectometry data to determine the in situ film thickness, from which we calculate the etch rate. We show examples of RTC using the actinometry sensor system during fluorine-based polycrystalline silicon etching. The results of using these sensors for RTC are presented by comparing open loop signals with those from real-time closed loop etch runs. In situ etch rate accuracies, estimated using our reflectometry system, are discussed. Film thicknesses calculated from in situ measurements are compared with those calculated by ex situ spectroscopic ellipsometry.

Research paper thumbnail of System identification and feedback control of a reactive ion etcher

Research paper thumbnail of <title>Real-time feedback control of reactive ion etching</title>

Microelectronic Processes, Sensors, and Controls, 1994

ABSTRACT This paper explores the application of modern feedback control technology to the regulat... more ABSTRACT This paper explores the application of modern feedback control technology to the regulation of the reactive ion etching process. Currently, this process is run open-loop, except for the PID controller to regulate pressure. We investigate the utility of additional measurements for the purpose of feedback control to improve process performance and robustness. First, we compare a feedback controller that regulates Vbias and chamber pressure to one that regulates Vbias and fluorine. We show that the fluorine controller yields better control of etch rate; this result is to be expected since fluorine is more closely related to the chemical etching process than is pressure. Our second study compares various controllers that regulate Vbias and fluorine using the conductance throttle and applied RF power. We show that multivariable feedback controllers that can compensate for process coupling by coordinating control inputs have advantages over decentralized controllers consisting of two independent feedback loops.

Research paper thumbnail of Real-time feedback control of reactive ion etching

This paper explores the application of modern feedback control technology to the regulation of th... more This paper explores the application of modern feedback control technology to the regulation of the reactive ion etching process. Currently, this process is run open-loop, except for the PID controller to regulate pressure. We investigate the utility of additional measurements for the purpose of feedback control to improve process performance and robustness. First, we compare a feedback controller that regulates

Research paper thumbnail of <title>Real-time feedback control of reactive ion etching</title>

Microelectronic Processes, Sensors, and Controls, 1994

ABSTRACT This paper explores the application of modern feedback control technology to the regulat... more ABSTRACT This paper explores the application of modern feedback control technology to the regulation of the reactive ion etching process. Currently, this process is run open-loop, except for the PID controller to regulate pressure. We investigate the utility of additional measurements for the purpose of feedback control to improve process performance and robustness. First, we compare a feedback controller that regulates Vbias and chamber pressure to one that regulates Vbias and fluorine. We show that the fluorine controller yields better control of etch rate; this result is to be expected since fluorine is more closely related to the chemical etching process than is pressure. Our second study compares various controllers that regulate Vbias and fluorine using the conductance throttle and applied RF power. We show that multivariable feedback controllers that can compensate for process coupling by coordinating control inputs have advantages over decentralized controllers consisting of two independent feedback loops.

Research paper thumbnail of Real-time feedback for sidewall profile control in reactive ion etching

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1995

ABSTRACT Reactive ion etching is an important process in the fabrication of microelectronic devic... more ABSTRACT Reactive ion etching is an important process in the fabrication of microelectronic devices. This article reports on work in progress towards developing a strategy for controlling sidewall profile during this process. In this strategy, a response surface is developed between plasma characteristics and etch rate components. This is then used to determine the plasma properties necessary to achieve a desired sidewall profile. Finally, a real‐time feedback controller is used to regulate the plasma to these conditions during an etch. Presented in this article are preliminary experimental results towards implementing such a strategy. © 1995 American Vacuum Society

Research paper thumbnail of Control of semiconductor manufacturing equipment: real-time feedback control of a reactive ion etcher

IEEE Transactions on Semiconductor Manufacturing, 1995

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented. The principal ideas are to sense key plasma parameters, develop a dynamic input-output model for the subsystem connecting the equipment inputs to the key plasma variables, and design and implement a multivariable control system to control these variables. Experimental results show that this approach to closed-loop control leads to a much more stable etch rate in the presence of a variety of disturbances as compared to current industrial practice.

Research paper thumbnail of Applications of control to semiconductor manufacturing: reactive ion etching

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented as well as supporting experimental results.

Research paper thumbnail of System identification and feedback control of a reactive ion etcher

Research paper thumbnail of Applications of control to semiconductor manufacturing: reactive ion etching

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented as well as supporting experimental results.

Research paper thumbnail of Control of semiconductor manufacturing equipment: real-time feedback control of a reactive ion etcher

IEEE Transactions on Semiconductor Manufacturing, 1995

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented. The principal ideas are to sense key plasma parameters, develop a dynamic input-output model for the subsystem connecting the equipment inputs to the key plasma variables, and design and implement a multivariable control system to control these variables. Experimental results show that this approach to closed-loop control leads to a much more stable etch rate in the presence of a variety of disturbances as compared to current industrial practice.

Research paper thumbnail of Sensor systems for real‐time feedback control of reactive ion etching

Previous efforts from our group have shown encouraging initial results in stabilizing etch rates ... more Previous efforts from our group have shown encouraging initial results in stabilizing etch rates versus time during a run by using real-time, multivariable feedback control ͑RTC͒ in an Applied 8300 reactive ion etcher. That work indicated the need for improvements in our sensor systems, both the sensors currently used in feedback control and those monitoring the effects of the control on the wafers being etched. In this article we report on our efforts in the development and improvement of two such sensor systems. The first is an optical emission spectroscopy system which simultaneously measures two emission line intensities for use in actinometry. The second sensor system uses spectral reflectometry data to determine the in situ film thickness, from which we calculate the etch rate. We show examples of RTC using the actinometry sensor system during fluorine-based polycrystalline silicon etching. The results of using these sensors for RTC are presented by comparing open loop signals with those from real-time closed loop etch runs. In situ etch rate accuracies, estimated using our reflectometry system, are discussed. Film thicknesses calculated from in situ measurements are compared with those calculated by ex situ spectroscopic ellipsometry.

Research paper thumbnail of System identification and feedback control of a reactive ion etcher

Research paper thumbnail of <title>Real-time feedback control of reactive ion etching</title>

Microelectronic Processes, Sensors, and Controls, 1994

ABSTRACT This paper explores the application of modern feedback control technology to the regulat... more ABSTRACT This paper explores the application of modern feedback control technology to the regulation of the reactive ion etching process. Currently, this process is run open-loop, except for the PID controller to regulate pressure. We investigate the utility of additional measurements for the purpose of feedback control to improve process performance and robustness. First, we compare a feedback controller that regulates Vbias and chamber pressure to one that regulates Vbias and fluorine. We show that the fluorine controller yields better control of etch rate; this result is to be expected since fluorine is more closely related to the chemical etching process than is pressure. Our second study compares various controllers that regulate Vbias and fluorine using the conductance throttle and applied RF power. We show that multivariable feedback controllers that can compensate for process coupling by coordinating control inputs have advantages over decentralized controllers consisting of two independent feedback loops.

Research paper thumbnail of Real-time feedback control of reactive ion etching

This paper explores the application of modern feedback control technology to the regulation of th... more This paper explores the application of modern feedback control technology to the regulation of the reactive ion etching process. Currently, this process is run open-loop, except for the PID controller to regulate pressure. We investigate the utility of additional measurements for the purpose of feedback control to improve process performance and robustness. First, we compare a feedback controller that regulates

Research paper thumbnail of <title>Real-time feedback control of reactive ion etching</title>

Microelectronic Processes, Sensors, and Controls, 1994

ABSTRACT This paper explores the application of modern feedback control technology to the regulat... more ABSTRACT This paper explores the application of modern feedback control technology to the regulation of the reactive ion etching process. Currently, this process is run open-loop, except for the PID controller to regulate pressure. We investigate the utility of additional measurements for the purpose of feedback control to improve process performance and robustness. First, we compare a feedback controller that regulates Vbias and chamber pressure to one that regulates Vbias and fluorine. We show that the fluorine controller yields better control of etch rate; this result is to be expected since fluorine is more closely related to the chemical etching process than is pressure. Our second study compares various controllers that regulate Vbias and fluorine using the conductance throttle and applied RF power. We show that multivariable feedback controllers that can compensate for process coupling by coordinating control inputs have advantages over decentralized controllers consisting of two independent feedback loops.

Research paper thumbnail of Real-time feedback for sidewall profile control in reactive ion etching

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1995

ABSTRACT Reactive ion etching is an important process in the fabrication of microelectronic devic... more ABSTRACT Reactive ion etching is an important process in the fabrication of microelectronic devices. This article reports on work in progress towards developing a strategy for controlling sidewall profile during this process. In this strategy, a response surface is developed between plasma characteristics and etch rate components. This is then used to determine the plasma properties necessary to achieve a desired sidewall profile. Finally, a real‐time feedback controller is used to regulate the plasma to these conditions during an etch. Presented in this article are preliminary experimental results towards implementing such a strategy. © 1995 American Vacuum Society

Research paper thumbnail of Control of semiconductor manufacturing equipment: real-time feedback control of a reactive ion etcher

IEEE Transactions on Semiconductor Manufacturing, 1995

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented. The principal ideas are to sense key plasma parameters, develop a dynamic input-output model for the subsystem connecting the equipment inputs to the key plasma variables, and design and implement a multivariable control system to control these variables. Experimental results show that this approach to closed-loop control leads to a much more stable etch rate in the presence of a variety of disturbances as compared to current industrial practice.

Research paper thumbnail of Applications of control to semiconductor manufacturing: reactive ion etching

This paper describes the development of real-time control technology for the improvement of manuf... more This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented as well as supporting experimental results.

Research paper thumbnail of System identification and feedback control of a reactive ion etcher