New wafer shape measurement technique for 300mm blank vertically held silicon wafer

Trujillo-Sevilla, Juan M.; Casanova-González, Óscar; Roqué-Velasco, Alex; Pardo, Javier González; Ramos-Rodriguez, J.M.; Gaudestad, J.

doi:10.1117/12.2651981

Cited by 4 publications

(4 citation statements)

References 3 publications

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“…To image the wafer on both sides, the silicon wafer holder is held on a rotational stage that allows for accurate wafer inversion (See Fig. 2b) 10 .…”

Section: The Wave Front Phase Imaging Systemmentioning

confidence: 99%

New wafer shape measurement technique for 300mm blank vertically held silicon wafers

Trujillo-Sevilla,

Abrante,

Jiménez

et al. 2023

Optical Measurement Systems for Industrial Inspection XIII

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The shrinking depth of focus of high numerical aperture immersion microlithography optics requires a tight wafer flatness budget. Bare wafer surface topography variation is a significant part of the focus budget for microlithography. Thus, as the wafer surface quality becomes increasingly important, the metrology to control the surface quality is increasingly challenged 1 . Advanced lithographic patterning processes require a detailed map of the free, non-gravitational, wafer shape, to avoid overlay errors caused by depth-of-focus issues 2 . The semiconductor industry has been using interferometry-based techniques for measuring the free form wafer shape of blank silicon wafers for several years 1 .In this paper we introduce a new measurement technique, Wave Front Phase Imaging (WFPI), that can measure the free form wafer shape of a silicon wafer by acquiring only the intensity of the reflected light. In the WFPI system, the wafer is held vertically to avoid the effects of gravity during measurements. The wave front phase is then measured by acquiring the 2-dimensional intensity distribution of the reflected, non-coherent, light at two or more distances along the optical path. This method allows for very high data acquisition speed and a high number of data points equal to the number of pixels available in the CMOS imaging sensor used. In the measurements presented in this paper, we acquired 16.3 million data points on the full 300mm blank silicon wafer, generating a lateral resolution of about 65µm per pixel. Blank silicon wafer manufacturers need to acquire such metrics as bow, warp, and flatness among other parameters, to provide with the silicon wafer when sent to the device maker fabs. These metrics are easily derived by generating a free form wafer shape map of both the front and the back surfaces.

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“…To image the wafer on both sides, the silicon wafer holder is held on a rotational stage that allows for accurate wafer inversion (See Fig. 2b) 10 .…”

Section: The Wave Front Phase Imaging Systemmentioning

confidence: 99%

New wafer shape measurement technique for 300mm blank vertically held silicon wafers

Trujillo-Sevilla,

Abrante,

Jiménez

et al. 2023

Optical Measurement Systems for Industrial Inspection XIII

View full text Add to dashboard Cite

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“…The surface phase map is proportional to the relative surface height map 13 . A WFPI system acquires wafer shape maps with spatial resolution of 65µm with an optical limitation of 3.2µm if higher pixel image sensor arrays are added 14 . To test for max slope the system can handle, a very flat, high quality reference wafer is rotated until vignetting, a reduction of the intensity on the periphery of the wafer, starts to show in the intensity images.…”

Section: Wave Front Phase Imaging (Wfpi)mentioning

confidence: 99%

“…These intensity images are acquired around the conjugated plane P′ in equidistant planes along the z-axis. Choosing focal lengths of lens L1 and lens L2 appropriately allows for adjusting the sample size to the image sensor size 14 .…”

Section: Wfpi System Setupmentioning

confidence: 99%

New wave front phase sensor used for 3D shape measurements of patterned silicon wafers

Ivanov Kurtev,

Trujillo-Sevilla,

Jiméneza

et al. 2023

38th European Mask and Lithography Conference (EMLC 2023)

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“…The surface phase map is proportional to the wafer slope 13 . A WFPI system acquires wafer shape maps with spatial resolution of 24µm-96µm with an optical limitation of 3.2µm if higher pixel image sensor arrays are added 14 .…”

Section: Wave Front Phase Imaging (Wfpi)mentioning

confidence: 99%

New patterned silicon wafer shape metrology system

Kurtev,

Trujillo-Sevilla,

Castro Luis

et al. 2023

Novel Optical Systems, Methods, and Applications XXVI

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On-product overlay (OPO), with its continually shrinking overlay budget, remains a constraint in the continued effort at increasing device yield. Overlay metrology capability currently lags the need for improved overlay control, especially for multi-patterning applications. The free form shape of the silicon wafer is critical for process monitoring and is usually controlled through bow and warp measurements during the process flow 1 . As the OPO budget shrinks, non-lithography process induced stress causing in plane distortions (IPD) becomes a more dominant contributor to the shrinking overlay budget 2 . To estimate the wafer process induced IPD parameters after cucking the wafer inside the lithographic scanner, a high-resolution measurement of the freeform wafer shape of the unclamped wafer is needed. The free form wafer shape can then be used in a feed-forward prediction algorithm to predict both intra field and intra die distortions, as has been published by ASML, to minimize the need for alignment marks on the die and wafer and allows for overlay to be performed at any lithography layer 3 . Up until now, the semiconductor industry has been using Coherent Gradient Sensing (CGS) interferometry or Fizeau interferometry to generate the wave front phase from the reflecting wafer surface. The wave front phase is then used to calculate the slope which again generates a shape map of the silicon wafer. However, these techniques have only been available for 300mm wafers 3,4 .In this paper we introduce Wave Front Phase Imaging (WFPI), a new technique that can measure the free form wafer shape of a patterned silicon wafer using only the intensity of the reflected light. In the WFPI system, the wafer is held vertically to avoid the effects of gravity during measurements. The wave front phase is then measured by acquiring only the 2dimensional intensity distribution of the reflected non-coherent light at two or more distances along the optical path using a standard, low noise, CMOS sensor. This method allows for very high data acquisition speed, equal to the camera's shutter time, and a high number of data points with the same number of pixels as available in the digital imaging sensor. In the measurements presented in this paper, we acquired 7.3 million data points on a full 200mm patterned silicon wafer with a lateral resolution of 65µm. The same system presented can also acquire data on a 300mm silicon wafer in which case 16.3 million data points with the same 65µm spatial resolution were collected.

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New wafer shape measurement technique for 300mm blank vertically held silicon wafer

Cited by 4 publications

References 3 publications

New wafer shape measurement technique for 300mm blank vertically held silicon wafers

New wafer shape measurement technique for 300mm blank vertically held silicon wafers

New wave front phase sensor used for 3D shape measurements of patterned silicon wafers

New patterned silicon wafer shape metrology system

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