Dynamic in-situ temperature profile monitoring of a deep-UV post-exposure bake process

Cohen, Barney M.; Renken, Wayne; Miller, Paul A.

doi:10.1117/12.473441

Cited by 6 publications

(4 citation statements)

References 2 publications

(2 reference statements)

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“…PEB is the process step that allows the photo acid catalyst created during exposure to render the resist soluble in developer chemistry. Individual mechanisms are the acid catalyzed deprotection of the polymer chains, diffusion of acid within the resist film and a loss of acid catalyst to the environment [3]. In all three cases, a temperature as well as time -dependency is observed.…”

Section: Introductionmentioning

confidence: 96%

ArF processing of 90-nm design rule lithography achieved through enhanced thermal processing

Kagerer¹,

Miller²,

Chang

et al. 2006

SPIE Proceedings

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As the lithography community has moved to ArF processing on 300 mm wafers for 90 nm design rules the process characterization of the components of variance continues to highlight the thermal requirements for the post exposure bake (PEB) processing step. In particular as the thermal systems have become increasingly uniform, the transient behavior of the thermal processing system has received the focus of attention.This paper demonstrates how a newly designed and patented thermal processing system was optimized for delivering improved thermal uniformity during a typical 90 second PEB processing cycle, rather than being optimized for steady state performance. This was accomplished with the aid of a wireless temperature measurement wafer system for obtaining real time temperature data and by using a response surface model (RSM) experimental design for optimizing parameters of the temperature controller of the thermal processing system.The new units were field retrofitted seamlessly in <2 days at customer sites without disruption to process recipes or flows. After evaluating certain resist parameters such as PEB temperature sensitivity and post exposure delay (PED) -stability of the baseline process, the new units were benchmarked against the previous PEB plates by processing a split lot experiment. Additional hardware characterization included environmental factors such as air velocity in the vicinity of the PEB plates and transient time between PEB and chill plate.At the completion of the optimization process, the within wafer CD uniformity displayed a significant improvement when compared to the previous hardware. The demonstrated within wafer CD uniformity improved by 27% compared to the initial hardware and baseline process. ITRS requirements for the 90 nm node were exceeded.

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Section: Introductionmentioning

confidence: 96%

ArF processing of 90-nm design rule lithography achieved through enhanced thermal processing

Kagerer¹,

Miller²,

Chang

et al. 2006

SPIE Proceedings

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“…Chemically amplified resists are sensitive to temperature ramp rate and temperature uniformity of the wafer during post-exposure bake, transfer and chill cycles [1,2]. This sensitivity is due mainly to the temperature dependence of acid diffusion and acid-catalyzed deprotection reaction rates [3].…”

Section: Introductionmentioning

confidence: 99%

Performance evaluation and analysis of a novel 300-mm combination bake-chill station

Narasimhan¹,

Ramanan²,

Williams³

2003

Advances in Resist Technology and Processing XX

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DUV resists are extremely sensitive to temperature variations on the wafer during bake and chill cycles. In resistprocessing tracks today, the wafer is moved by a robot or transfer arm, from the bake to chill plate. During this move, since the resist is still above the activation temperature, the wafer temperature is uncontrolled until it is placed on a chill plate. In the new station design presented here, the wafer is heated to the desired bake temperature and chilled back to room temperature before being moved by the robot, resulting in a tight temperature control of the wafer, throughout the process. Two models, axi-symmetric and three-dimensional (geometrically similar to the new station), are generated for analyzing the thermal performance of the above station. The numerical simulations, solving the momentum and energy equations in the computational domain, are performed using the commercial CFD software Fluent ® . The simulated temporal evolution of temperature from the beginning to the end of the bake-chill process is verified with the experimental data as measured by a 42-point OnWafer TM temperature sensor wafer on the new station. Methods to improve wafer surface temperature uniformity, in light of bake-chill-station mechanical and thermal design losses are discussed. Higher throughput of the cluster, a major productivity improvement contribution of this new design, is also highlighted.

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“…4 A highly accurate and stable constant temperature control is essential for the lithography system, and the temperature stability requirement of the projection lens and the laser interferometer in the lithography is at least within the range of 60.01°C. 5 Generally, the problem of large inertial constant, time delays, and multiple disturbances are the main challenges faced by temperature control system. The combination of control algorithms, such as fuzzy control, 6,7 genetic algorithm, 8 neural network control, 9,10 feedforward control, 11,12 and Smith predictor 13 with PID control algorithms, is a common used approach at present.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A temperature control algorithm for lithography machine based on generalized predictive control and BP neural network PI control

Lan,

Chen,

Xue

et al. 2024

Measurement and Control

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Temperature stability is a critical factor affecting the performance of the most subsystems in the lithography system, due to the high precision and sensitivity of system components to temperature variations. The temperature control system of the lithography machine is characterized by its large inertial constant, time delay characteristics, as well as susceptibility to multiple disturbances. The temperature control system of the lithography machine chiefly requires response speed, high accuracy, and stable and constant temperature control. The contribution of this study is not only avoiding complex precision modeling processes based on real-time parameter estimation and neural network self-tuning but also improving the performance of temperature control in real time under external disturbances. A novel adaptive algorithm with a cascade structure based on generalized predictive control (GPC) and backpropagation (BP) neural network proportional-integral (PI) control is successfully proposed for high accuracy temperature control of lithography machine with a large inertial constant, time delay, and multiple disturbances. In this study, firstly, the liquid circulating temperature control system is developed based on heat exchanger and heater. Secondly, an adaptive controller composed of GPC and BP neural network PI control is successfully proposed. A BP neural network is employed to enable the parameters of the PI controller to adjust in real time, and the mathematical model parameters of the control system are identified in real time by the least square method. Also, the performance of the proposed controller is evaluated comparing with conventional PI controller and GPC controller in terms of robustness and quantitative study of error analysis. Finally, the temperature stability and robustness of the temperature control system controlled with the proposed adaptive GPC-PI algorithm has been investigated by the simulation results carried out in different working scenarios. The simulation results show that the steady-state error from the proposed algorithm is less than 0.01°C under the action of disturbance input. It can effectively counteract the influence of environmental interference and time-varying system parameters. The results of the simulation experiment indicate that the proposed adaptive GPC and PI control algorithm exhibits significant advantages in terms of control accuracy, anti-interference ability, and robustness compared to the conventional control method.

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Dynamic in-situ temperature profile monitoring of a deep-UV post-exposure bake process

Cited by 6 publications

References 2 publications

ArF processing of 90-nm design rule lithography achieved through enhanced thermal processing

ArF processing of 90-nm design rule lithography achieved through enhanced thermal processing

Performance evaluation and analysis of a novel 300-mm combination bake-chill station

A temperature control algorithm for lithography machine based on generalized predictive control and BP neural network PI control

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