Kazuhiko Fukazawa

Novel inspection technology for half pitch 55 nm and below

In the automatic macro inspection, a diffraction light method is very effective. However, this method needs a shorter wavelength illumination for finer wafer patterns. A wavelength of 193 nm will be needed for half pitch 55 nm. Light source and optics for such shorter wavelength is large and expensive, and chemical clean environment is needed. Therefore, the equipment size and costs will increase dramatically. In order to solve this problem and to comply with the process of half pitch 55 nm and below, we have developed the breakthrough technology. The key is the image of polarization fluctuation caused by a wafer pattern structure. The polarized light is affected by the variation of the wafer pattern structure due to a dose or focus shift. The new technology converts the polarization fluctuation into the gray level of the image. At a result, the sensitivity for the dose or focus shift was enough to detect process errors.

Novel technology of automatic macro inspection for 32-nm node and best focus detection

As the semiconductor design rules shrink down, process margins are getting narrower, and thus, it is getting more important than ever to monitor pattern profile and detect minor structure variation. A breakthrough technology has been introduced as a solution to this concern. The new technology converts the fluctuation of polarization ingredient, which is caused by form birefringence, into light intensity variations as an optical image. This technology, which is called Pattern Edge Roughness (PER) inspection mode, is proved to be effective for 55nm production process. We also studied the possibility of the macro inspection method for half pitch 32nm technology node through FDTD method.

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.