In situ Wafer Monitoring For Plasma Etching

Grimard, Dennis S.; Terry, Fred L.; Elta, Michael E.

doi:10.1117/12.978063

Cited by 5 publications

(4 citation statements)

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“…yW = A x + xO (2) where A is a 2x2 transformation matrix, x is the stage position vector (x,y), xOis the stage position for wafer position (0,0) and yW is the position of the beam on the wafer. Each element of the series can be found by using geometric models for the corresponding optical components and the equation of a line for each of the system beams.…”

Section: Critical Dimension Measurementmentioning

confidence: 99%

<title>Diffraction image processing algorithms for in-situ monitoring of submicron polysilicon linewidths</title>

Chapados

1993

Machine Vision Applications in Industrial Inspection

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A technique using diffraction grating test patterns has been used to monitor in situ the pre and post etch linewidths on a polysilicon etch chamber. The technique is capable oflinewidth measurements to 0.25 microns with pitches as small as 0.7 microns. A comparison of in situ polysilicon linewidth measurements with off-line SEM measurements shows measurement differences ofless than 10% indicating a measurement precision on that order. The repeatability of the diffraction technique is shown to be -0.01 micron in comparison to the typical SEM repeatability of 0.025 micron.The implementation of this technique on a production etch chamber required the design of specialized optics and image processing systems. The optics system allows the monitoring of one and a half dimensions of the diffraction pattern. It consists of a CCD camera and some reflective optics for the focusing of the diffraction patterns. The image processing system uses a commercially available frame grabber and several image processing algorithms to record these patterns and extract the linewidth information. Algorithms unique to this application include an image indexing scheme used to store the diffraction images, a blob classification scheme based on a rigorous examination of the three dimensional vector field problem, and a non-line& iterative modeling algorithm used to fit the data to Fourier theory predictions. The resulting system is capable of linewidth measurements on each wafer with an overall reduction in product cycle time relative to the previously used SEM aid pilot monitoring schemes.

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Section: Critical Dimension Measurementmentioning

confidence: 99%

<title>Diffraction image processing algorithms for in-situ monitoring of submicron polysilicon linewidths</title>

Chapados

1993

Machine Vision Applications in Industrial Inspection

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“…Therefore, an in-situ monitoring technique which obtains topographical data about the wafer structure in real time would be highly useful as a feedback signal for process control. A Fourier imaging system(FIS) based on Fraunhofer diffraction theory addressing this need in the alltomation of semiconductor manufacturing was developed [2,3,4]. The Fourier imaging system contains two major components: an mmagmng system, including an irradiation subsystem, a micromechanical subsystem, and a detection subsystem, and a machmne vision system.…”

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

<title>Efficient Fourier image analysis algorithm for aligned rectangular and trapezoidal wafer structures</title>

Shu

Jain

1992

SPIE Proceedings

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We present an efficient algorithm to compute the critical dimensions of aligned rectangular and trapezoidal wafer structures using images generated by a Fourier Imaging System (FIS) [2,3]. We show that the Fourier images of aligned rectangular and trapezoidal structures are separable functions. This allows us to project them onto x and y coordinates and simplifies the computation process. We compute the critical dimensions of rectangular structures by estimating the distance between either peaks or zeros, or by estimating the distance between zeros for trapezoidal structures. For each projected 1-dimensional signal, we apply a zero-crossing technique to find the peaks or zeros, and then compute the critical dimensions at sub-pixel resolution.

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“…showed that diffraction from isolated structures could be used to distinguish between relatively large ( 20 X 20 .um) rectangular and trapezoidal structures. 8 Giapis et a/. measured the scattered light intensity from large pitch grating test patterns and showed how this correlated with sidewall angle, etched depth, and surface composition.…”

mentioning

confidence: 99%

Latent image diffraction from submicron photoresist gratings

Yoon¹

1992

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Light scattering from latent images in photoresist is useful for lithographic tool characterization, process monitoring, and process control. In particular, closed-loop control of lithographic processes is critical for high yield, low cost device manufacturing. In this work, we report use of pulsed laser diffraction from photoresist latent images in 0.24 μm pitch distributed feedback laser gratings. Gated detection of pulsed light scattering permits high spatial resolution probing using ultraviolet light without altering the latent image. A correlation between latent image and etched grating diffraction efficiencies is demonstrated and shows the value of ‘‘upstream’’ monitoring.

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In situ Wafer Monitoring For Plasma Etching

Cited by 5 publications

References 0 publications

<title>Diffraction image processing algorithms for in-situ monitoring of submicron polysilicon linewidths</title>

<title>Diffraction image processing algorithms for in-situ monitoring of submicron polysilicon linewidths</title>

<title>Efficient Fourier image analysis algorithm for aligned rectangular and trapezoidal wafer structures</title>

Latent image diffraction from submicron photoresist gratings

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