Yoshihiko Fujimori

New methodology for through silicon via array macroinspection

Abstract. A new methodology for inspection of through silicon via (TSV) process wafers is developed by utilizing an optical diffraction signal from the wafers. The optical system uses telecentric illumination and has a two-dimensional sensor for capturing the diffracted light from TSV arrays. The diffraction signal modulates the intensity of the wafer image. The optical configuration is optimized for TSV array inspection. The diffraction signal is sensitive to via-shape variations, and an area of deviation from a nominal via is analyzed using the signal. Using test wafers with deep via patterns on silicon wafers, the performance is evaluated and the sensitivities for various pattern profile changes are confirmed. This new methodology is available for high-volume manufacturing of future TSV three-dimensional complementary metal oxide semiconductor devices.

A new methodology for TSV array inspection

A new methodology for inspection of TSV (Through Silicon Via) process wafers is developed by utilizing an optical diffraction signal from the wafers. The optical system uses telecentric illumination and has a two-dimensional sensor in order to capture the diffraction light from TSV arrays. The diffraction signal modulates the intensity of the wafer image. Furthermore, the optical configuration itself is optimized. The diffraction signal is sensitive to via-shape variations, and an abnormal via area is analyzed using the signal. Using the test wafers with deep hole patterns on silicon wafers, the performance is evaluated and the sensitivities for various pattern profile changes were confirmed. This new methodology is available for high-volume manufacturing of the future TSV-3D CMOS devices.

Macroinspection methodology for through silicon via array in three-dimensional integrated circuit

Abstract. We are developing a new macroinspection technology for through silicon via (TSV) process wafers. We present new simulation results obtained with a fine TSV model and new optics. The optical system includes not only diffraction optics, but also polarization optics, by which we can detect changes in the profile (cross-sectional shape) of repeated patterns by detecting changes in the polarization status of reflected light. We confirmed the performance of the methodology by optical simulation using a model of via patterns with 1 μm diameter and 10 μm depth as a typical intermediate-interconnect-level TSV.

New exposure tool management technology with quick focus measurement in half pitch 22nm generation

We have developed the new technology to measure focus variations in a field or over the wafer quickly for exposure tool management. With the new technology, 2-dimensional image(s) of the whole wafer are captured with diffraction optics, and by analyzing the image signal(s), we are able to get a focus map in an exposure field or over the entire wafer. Diffraction-focus curve is used instead of a CD-focus curve to get the focus value from the image signal(s). The measurements on the production patterns with the production illumination conditions are available. We can measure the field inclination and curvature from the focus map. The performance of the new method was confirmed with a test pattern and production patterns.

Two-dimensional dose and focus-error measurement technology for exposure tool management in half-pitch 3x generation

As design rule of semiconductor device is shrinking, pattern profile management is becoming more critical, then high accuracy and high frequency is required for CD (Critical Dimension) and LER (Line Edge Roughness) measurements. We already presented the technology to inspect the pattern profile variations of entire wafer with high throughput [1] [2]. Using the technology, we can inspect CD&LER variations over the entire wafer quickly, but we could not separate the signal into CD and LER variations. This time, we measured the Stokes parameters, i.e., polarization status, in the reflected light from defected patterns. As the result, we could know the behavior of the polarization status changes by dose & focus defects, and we found the way to separate the signal into CD&LER variations, i.e. dose errors and focus errors, from S2 & S3 of Stokes parameters. We verified that we were able to calculate the values of CD&LER variations from S2 & S3 by the experiments. Furthermore, in order to solve the issue that many images are needed to calculate S2 & S3 values, we developed the new method to get CD&LER variations accurately in short time.

Design-Data Based Inspection Of Photomasks And Reticles

A New automatic design-based inspection system called Nikon RMX has been developed. With its unique algorithm of comparing photomasks and reticles with their design data, good defect detection sensitivity and low false-defect detection are achieved. Firstly, the design data are converted into Nikon Format Data and stored in a magnetic disc device. At this time, more than one files can be merged together. A magnified image of the sample on the X-Y stage is converted to a bit-pattern image. Synchronized to the image of sample, Nikon Format Data are transferred from the disc, and a bit-pattern image of design data is generated on the frame memory. The window moves pixel by pixel in both design and sample bit-patterns. Each minute character (corner, step & isolated pattern) at the same window position is extracted by using so called Template-matching method, and compared. If the characters of the two bit-patterns are different, it means that the sample has a defect. Many kinds of templates are provided for defects on pattern edge (of 0°, 45°, 90° & any angle), defects at corner and isolated defects. Another unique point of this system is automatic resizing function (enlarging or shrinking of pattern). With this function, design-image can be matched to the sample-image precisely. All of defect analysis is performed by hardware-logic, so very fast inspection is possible.