An Extended Kalman filtering-based method of processing reflectometry data for fast in-situ etch rate measurements

Vincent, Tyrone L.; Khargonekar, Pramod P.; Terry, Fred L.

doi:10.1109/66.554482

Cited by 36 publications

(13 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Etch rates at each port were modeled using the following form ER ϭ ␣ 1 ϩ ␣ 2 Pressure ϩ ␣ 3 Power ϩ ␣ 4 Power ϫ Flow [3] where ␣ 1 , ␣ 2 , ␣ 3 , ␣ 4 are constant coefficients that depend on the location of the optical port. These coefficients were obtained by solving a least-squares regression.…”

Section: Andmentioning

confidence: 99%

Real-Time Reactive Ion Etch Metrology Techniques to Enable In Situ Response Surface Process Characterization

Klimecky

Garvin

Galarza

et al. 2001

J. Electrochem. Soc.

View full text Add to dashboard Cite

The industrial semiconductor community widely accepts that new process development is both costly and time consuming. In particular for plasma etch processing, multiple plasma input parameters such as gas flow, pressure, and radio frequency (rf) forward power directly affect desired wafer output parameters such as etch rate, uniformity, and material selectivity. Therefore, a high number of etch experiments must be performed to accurately quantify these input and output (I/O) relationships for each process. Moreover, in situ wafer monitoring in general is not currently widely pursued in the industry. 1 Therefore, the typical characterization procedure can only obtain data for a single given set point per process run, where a process set point refers to the nominal input parameters used for a particular plasma condition. Thus, money and time are spent etching only one wafer for each set point required to build the input/output response surface models for a typical design of experiments (DOE). With increasing process demands and the increasing cost of larger and larger individual wafers, these test wafer costs for model design continue to become more and more acute.This project leverages expertise from four primary research fields to achieve our results. Semiconductor process knowledge is needed to formulate the problem of new process characterization. Optical metrology background is used to obtain accurate material refractive index properties and to measure film thickness changes during processing. The thin-film properties help determine accurate film thickness and etch-rate information, which are used as inputs to the empirical process models. Nonlinear systems theory techniques are used to filter real-time optical data and estimate high speed thickness and etch-rate information. The high-speed filtering allows multiple set points to be explored per process run. Finally, response surface modeling is employed to generate empirical I/O predictions using plasma generation parameters as the model inputs, and film thickness, etch rate, and wafer uniformity as model outputs.The goal of this research is to maximize the number of set points one can observe during a single run of the etching process by monitoring output data in real-time. This decreases the number of runs required for a complete response surface mapping, effectively reducing the number of wafers and development time required to model a new process. We show accurate and instantaneous etch-rate information (on the order of tens to hundreds of milliseconds time scales) requiring less than 100 Å of etched material; 2 therefore, we obtain empirical I/O relationships at multiple set points in a short amount of time and on a single test wafer.In this paper, we demonstrate this in situ characterization mapping concept on two reactive ion etch (RIE) test-beds to show the versatility of the concept. One is an RIE chamber designed for flat panel display processing, where large area etch uniformity of an amorphous silicon (a-Si) film on metal and glass is the chosen m...

show abstract

Section: Andmentioning

confidence: 99%

Real-Time Reactive Ion Etch Metrology Techniques to Enable In Situ Response Surface Process Characterization

Klimecky

Garvin

Galarza

et al. 2001

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…In order to determine the poly-Si thickness variation accurately under poor measurement resolution, we built a simple model based on the assumption that the etch rate of poly-Si is a constant, but unknown [20], [21]: etch rate constant (3) where is the actual poly-Si thickness. Then, the model is (4) where white gaussian noise; measurement noise; measured poly-Si thickness.…”

Section: A Kalman-bucy Filter Development and Implementationmentioning

confidence: 99%

Etch profile control of high-aspect ratio deep submicrometer α-Si gate etch

Park

Grimard

Grizzle

et al. 2001

IEEE Trans. Semicond. Manufact.

Self Cite

View full text Add to dashboard Cite

Abstract-The well-acknowledged etch profile drift problem in chip production was investigated with a more accurate means of measuring actual etch thickness to monitor and correct this drift. Using a high-aspect ratio, 0.1-m -Si gate structure, the investigation was specifically focused on the control of transition timing in the critical interval from main etch (ME) to over etch (OE). This required reliable endpoint detection of -Si which was achieved through the development of a method employing a Kalman-Bucy filter with a real-time spectroscopic ellipsometer (RTSE). The robustness of our endpoint detection technique was tested and demonstrated under the actual physical and chemical disturbance environments of the etching process. Application of this endpoint detection technique to the etch of a 0.1-m patterned -Si gate also achieved a significant improvement on the etch profile repeatability.

show abstract

“…Those that do consider the wafer surface typically consider only planar processes [29], [50]. Earlier work of the first author and co-workers focused on developing techniques for real-time feature-level estimation and control of plasma etching [6]- [8].…”

Section: Introductionmentioning

confidence: 99%

Shape-based optimal estimation and design of curve evolution processes with application to plasma etching

Berg

Zhou

2001

IEEE Trans. Automat. Contr.

View full text Add to dashboard Cite

This paper considers the problem of determining a finite number of discrete parameters appearing in a nonlinear partial differential equation describing a curve evolution process. The method is applied to the plasma etching of thin films for semiconductor manufacturing. Results are obtained within the mathematical framework of level set methods. Here, the evolution of the curve under study is captured through the evolution of a level set function. The underlying physics of the process are completely contained in a scalar function called the speed function. The degree of difficulty of treating the evolution equation depends on the functional dependencies of the speed function. This paper presents optimal estimation and design techniques based on analytical gradient computations for a class of position and orientation dependent speed functions. The technique is demonstrated on a plasma etching model taken from the literature. Only simulation results are presented here, but the model under study has been shown to reproduce experimental data with reasonable accuracy. In the estimation problem, parameters in the model are fit to best match the feature shape measured in experiments. In the optimal design problem, parameter values are selected to most closely attain a desired feature shape.

show abstract

An Extended Kalman filtering-based method of processing reflectometry data for fast in-situ etch rate measurements

Cited by 36 publications

References 12 publications

Real-Time Reactive Ion Etch Metrology Techniques to Enable In Situ Response Surface Process Characterization

Real-Time Reactive Ion Etch Metrology Techniques to Enable In Situ Response Surface Process Characterization

Etch profile control of high-aspect ratio deep submicrometer α-Si gate etch

Shape-based optimal estimation and design of curve evolution processes with application to plasma etching

Contact Info

Product

Resources

About